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NON DISRUPTIVE ROAD CROSSINGS

MANUAL

DRAFT DOCUMENT

J ANUARY 2013


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NON DISRUPTIVE ROAD CROSSINGS M ANUAL

Page i January 2013

January 2013

Draft Edition

Abu Dhabi Department of Transport

Al Bateen Towers

PO Box 20

Abu Dhabi, United Arab Emirates

© Copyright 2012, by the Abu Dhabi Department of Transport. All Rights Reserved. This

manual, or parts thereof, may not be reproduced in any form without written permission of

the publisher.


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Page ii January 2013

TABLE OF CONTENTS

List of Figures .................................................................................................................................. v

List of Tables .................................................................................................................................. vi

1 Introduction .............................................................................................................................. 7

1.1 Overview ............................................................................................................................. 7

1.2 Purpose and scope .............................................................................................................. 7

1.3 Application of this manual .................................................................................................... 7

2 Non Disruptive Road Crossings Methods .............................................................................. 8

2.1 Non-steerable soil displacement methods ........................................................................... 8

2.2 Non-steerable soil removal methods.................................................................................... 9

2.3 Horizontal directional drilling (HDD) ................................................................................... 11

2.4 Micro tunnelling ................................................................................................................. 13

2.5 Pilot pipe jacking ............................................................................................................... 15

2.6 Manned pipe jacking methods ........................................................................................... 16

2.6.1 Open front pipe jacking techniques ..................... ........... ........... .................................. 16

2.6.2 Closed front (full face excavation) pipe jacking techniques ......................................... 17

2.7 New NDRC Techniques..................................................................................................... 19

2.7.1 Easy Pipe ................................................................................................................... 19

2.7.2 Direct Pipe .................................................................................................................. 20

3 General .................................................................................................................................... 22

3.1 Overview ........................................................................................................................... 22

3.2 Standards and Codes of Practice ...................................................................................... 22

3.3 Roles and responsibilities .................................................................................................. 22

3.3.1 Client .......................................................................................................................... 23

3.3.2 Consultant .................................................................................................................. 23

3.3.3 Contractor/Sub Contractor .......................................................................................... 23

3.3.4 Road Authority ............................................................................................................ 23 3.3.5 Abu Dhabi Town Planning ........... ........... ............ ........... ........... .................................. 23

3.3.6 Utility Agencies ........................................................................................................... 23

3.4 Process Map ..................................................................................................................... 23

3.5 Health and Safety .............................................................................................................. 26

3.5.1 At Concept Stage ............................ ....................................................................... .... 26


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Page iii January 2013

3.5.2 Preliminary Design Stage ........................................................................................... 26

3.5.3 At Pre-Construction Stage ........... .................................................. ........... .................. 27

3.5.4 During Construction Stage .......................................................................................... 27

3.6 Environmental requirements .............................................................................................. 30

3.7 Site condition survey ......................................................................................................... 31

3.8 Geotechnical Investigation .................................................................... ............................. 32

3.8.1 Minimum requirements of the exploratory boreholes .................................................. 33

3.8.2 Borehole Positions...................................................................................................... 33

4 Procedures for undertaking non disruptive road crossings ............................................... 35

4.1 Overview ........................................................................................................................... 35

4.2 Concept Stage ................................................................................................................... 35

4.3 Preliminary Design Procedures ......................................................................................... 35

4.3.1 Method selection ........................................................................................................ 35

4.3.2 Design drawings ......................................................................................................... 58

4.3.3 Hand excavation ......................................................................................................... 59

4.4 Pre-construction stage ....................................................................................................... 59

4.4.1 Design calculations..................................................................................................... 59

4.4.2 Design drawings ......................................................................................................... 60

4.4.3 Ground Surface Movement ......................................................................................... 60

4.4.4 Groundwater Control .................................................................................................. 77

4.4.5 Materials and equipment ............................................................................................ 77

4.4.6 Method of statements ................................................................................................. 78

4.4.7 Risk Assessment and Risk Register ........................................................................... 80

4.4.8 Procedure and logistics for obtaining No Objection Certificates .................................. 81

4.5 During Construction ........................................................................................................... 81

4.5.1 Monitoring of Surface Movement ................................................................................ 81

4.5.2 Instrumentation Requirements .................................................................................... 83

4.5.3 Equipment Performance Requirements ...................................................................... 84

4.6 After Construction ............................. ................................................................................. 85 4.6.1 Inspection and testing ................................................................................................. 85

4.6.2 Site clearance and decommissioning ......................................................................... 86

4.6.3 Monitoring/inspection for long term (latent) defects .................................................... 86

4.6.4 QA/ QC Methodology ................................................................................................. 86

Appendix A: Checklists for submittals ........................................................................................ 88


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Page iv January 2013

Appendix B: Forms and examples of letters for applying for NDRC works .............................. 92

Appendix C: Suggested minimum safe distances between utilities .................... ........... ......... 106

Appendix D: Checklists for monitoring during and after construction .......... ........... .............. 107

Cited References ......................................................................................................................... 112

Other References ......................................................................................................................... 113

Glossary ....................................................................................................................................... 114


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Page v January 2013

LIST OF FIGURES

Figure 1: Impact moling/soil displacement hammer ........................................................................... 8

Figure 2: Pipe ramming diagram (Earth Tool Company, LLC) ................................................. ........... 8

Figure 3: Impact moling ..................................................................................................................... 9

Figure 4: Auger head ....................................................................................................................... 10

Figure 5: Auger boring ..................................................................................................................... 10

Figure 6: Process of the horizontal directional drilling (HDD) ........................................................... 12

Figure 7: Micro tunnelling ................................................................................................................ 13

Figure 8: Slurry shield micro tunnelling (Iseki Poly-Tech, Inc.-japan) ............................................... 14

Figure 9: Stages of pilot pipe jacking with auger soil removal .......................................................... 15

Figure 10: Backactor shield ............................................................................................................. 16

Figure 11: A cutter boom shield ....................................................................................................... 17

Figure 12: Open front pipe jacking ................................................................................................... 17 Figure 13: A slurry shield (full face excavation) pipe jacking machine ................... ........................... 18

Figure 14: Earth Pressure Balance Machine (EPBM) ...................................................................... 18

Figure 15: Easy pipe Method ........................................................................................................... 20

Figure 16: Direct Pipe Method ......................................................................................................... 21

Figure 17: Process map of NDRC.................................................................................................... 25

Figure 18: Pipe jacking worksite and shaft ....................................................................................... 26

Figure 19: The different cutting heads ............................................................................................. 39

Figure 20: Principles of a hydraulic mucking boring machine (Herrenknecht documents) ................ 40

Figure 21: Locating systems ............................................................................................................ 45

Figure 22: Basic components of rig ......................................................... ......................................... 46

Figure 23: Slanted face Drill Bits ...................................................................................................... 49 Figure 24: Modified Slanted face Drill Bits ....................................................................................... 49

Figure 25: Modified Slanted face Drill Bits ....................................................................................... 50

Figure 26: Rock Drill Bits ................................................................................................................. 50

Figure 27: Tri-Cone Rock Bits .......................................................................................................... 51

Figure 28: Experience guidelines for the application of different NDRC methods ............................. 55

Figure 29: Working shafts ................................................................................................................ 56

Figure 30: Stability Vs Volume Loss ................................................................................................ 66

Figure 31: Typical Settlement Profile for a Soft Ground Tunneling ................................................... 70

Figure 32: Assumptions for width of settlement trough (adapted from Peck, 1969) .......................... 71

Figure 33: Example of Finite Element Settlement Analysis for Twin Circular Tunnels under Pile

Foundations ..................................................................................................................................... 72


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Page vi January 2013

LIST OF TABLES

Table 1: Parameters to be considered in relation to each soil type .................................................. 34

Table 2: NDRC methods related to soil types .................................................................................. 37

Table 3: Different applications of NDRC .......................................................................................... 38

Table 4: NDRC methods with typical pipe size, length and accuracy .................... ........................... 42

Table 5: Rigs types and specification ............................................................................................... 47

Table 6: Drill Bit Types and Application Guidelines (Courtesy DCCA) ............................................. 48

Table 7: Operational risks in HDD installations (Baumert and Allouche 2003) ................................. 54

Table 8: Design of working shafts in Dry ground .............................................................................. 56

Table 9: Design of working shafts in wet ground .............................................................................. 57

Table 10: Shaft Dimensions ............................................................................................................. 58

Table 11: Shaft sizes ....................................................................................................................... 58

Table 12: Relationship between Volumes Loss and Construction Practice and Ground Conditions . 68 Table 13: Risk summary for typical NDRC methods ........................................................................ 80

Table 14: Type of records for NDRC projects .................................................................................. 83


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Page 7 January 2013

1 INTRODUCTION

1.1 OverviewIn 2010, the Abu Dhabi Department of Transport commenced with the “Unifying and Standardizing of

Road Engineering Practices” Project. The objective of the project was to enhance the management,

planning, design, construction, maintenance and operation of all roads and related infrastructures in

the Emirate and ensure a safe and uniform operational and structural capacity throughout the road

network.

To achieve this objective a set of standards, specifications, guidelines and manuals were developed

in consultation with all relevant authorities in the Abu Dhabi Emirate including the Department of

Municipal Affairs (DMA) and Urban Planning Council (UPC). In future, all authorities or agencies

involved in roads and road infrastructures in the Emirate shall exercise their functions and

responsibilities in accordance with these documents. The purpose, scope and applicability of each

document are clearly indicated in each document.

It is recognized that there are already published documents with similar objectives and contents

prepared by other authorities. Such related publications are mentioned in each new document and

are being superseded by the publication of the new document, except in cases where previously

published documents are recognized and referenced in the new document.

1.2 Purpose and scopeThe purpose of this Manual is to provide specific procedural guidance on Non Disruptive Road

Crossings (NDRC) for staff of the Abu Dhabi Department of Transport and other concerned

government highway agencies (Municipalities), designers, Contractors and utility agencies.

However, due to the specific technical nature of this type of construction, the Manual also providesguidelines for the specialized Contractors experienced in the utilization of plant and equipment

fabrication, in order to select the most appropriate method for such operations.

The Manual is specifically aimed at recognizing local conditions related to the present legal

framework, existing geotechnical conditions and practices presently employed by the local

construction industry which perform successfully. However, global best practices are studied and

improvements recommended as appropriate.

The overall objective of this Manual is to provide guidelines for the construction of NDRC which do

not result in either short term or long term surface movement, nor in road collapse due to drilling

mistakes or obstacles.

1.3 Application of this manualThe Manual is intended for use by the Abu Dhabi Department of Transport and other road agencies

of the Emirate (Municipalities) in specifying the requirements and approval procedures for NDRC

work.

It is however also to be used by utility agencies, designers and Contractors in selection and design

of NDRCs.


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Page 8 January 2013

2 NON DISRUPTIVE ROAD CROSSINGS METHODSIn this Chapter more detailed information is given on various methods of NDRC.

2.1 Non-steerable soil displacement methods A number of soil displacement methods exist. Impact moling or sometimes called soil displacement

hammer is one of the more common methods. The method involves driving a moling or hammering

tool with a tapered head through the ground (see Figure 1). The hammering tool can either work with

compressed air or hydraulically and it displaces the soil as it moves through the ground.

The piping or cable material is either pushed directly behind the tool or, in stable soil conditions it

may be pulled in afterwards through the cavity made by the tool.

Pipe ramming with a closed pipe is another soil displacement method often used. Like impact moling

or soil displacement hammer it uses compressed air or hydraulically activated ramming device to

push a closed steel pipe through the soil (see Figure 2).

Figure 1: Impact moling/soil displacement hammer

Figure 2: Pipe ramming diagram (Earth Tool Company, LLC)


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Page 9 January 2013

Advantages and disadvantages of the non-steerable soil displacement technique are briefly set out

below.

Advantages

• Generally very quick and easy to use and thereby also very cost effective. Moles orhammering tools are available for many soil conditions and can penetrate soft rock.

• The methods require relatively small entry and exit pits. When installing the pipe or cable

directly behind the hammering tool, surface settlements are minimised.

Disadvantages

• The methods require that the soil is displaceable and surface heave may occur if sufficient

soil cover is not available above the tunnel.

• A minimum cover of 10 times the outer pipe or hammer diameter is recommended.

• Pipelines installed in this manner are necessarily straight as there is no steering mechanism.

• The alignment of the tunnel can be influenced by the soil conditions, especially obstructions

or stratifications that may alter the direction of the tool or pipe.

• Installation of pipelines that require a precise alignment should not be undertaken using non-

steerable methods.

• The poor alignment accuracy also reduces the typical lengths for which the methods are

appropriate, and safe distances to other structures or utilities must be maintained.

Figure 3: Impact moling

2.2 Non-steerable soil removal methods

Pipe ramming can also be carried out with an open pipe end and thereby without soil displacement.Instead the soil is either removed during the driving of the pipe or afterwards. Soil removal is typically

undertaken using water jetting, flushing, compressed air or mechanically, for example with an auger.

These are some points to consider with this method:

• With the use of an auger, a cutting head can be attached to the head giving an improved

method for application in harder soils. Examples of pipe ramming and auger boring are

shown in Figures 8 and 9.


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Page 10 January 2013

• The pipe material is usually a steel casing or sleeve pipe inside which the product pipe or

cables can be pulled or pushed after soil removal.

• Entry and exit pits are required for this method, where the entry pit may need to be very long

in order to accommodate the pipe and auger sections along with the ramming or jacking

device.• Below ground water levels the methods must be used with caution or dewatering must be

initiated.

• Pipe ramming may be achieved if the pipe can be driven completely through before soil

removal and the soil "plug" inside the pipe is sufficiently stable to withstand the ground water

pressure while ramming.

When auger boring, the auger may become flooded underground water levels giving way for

excessive soil loss and major surface settlement. Some manufacturers have designed a sluice

system for the auger to counter this effect.

Figure 4: Auger head

Figure 5: Auger boring


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Advantages

• These methods, like the other non-steerable methods, are generally less expensive than

similar sized steerable methods due to the need for fewer and simpler equipment and

machinery.

• The method can be used for significantly larger pipe sizes compared to displacement

techniques (2000 mm diameter or larger). The larger diameter pipelines are typically stiffer

and less susceptible to altering direction during installation.

Disadvantages

• In swelling or very plastic soils the methods may not be possible.

• Pipe ramming cannot be done in rock. However with the use of an auger, a cutting head can

be attached to the head giving an improved method for application in harder soils.

• Loss of face stability when tunnelling below groundwater level can lead to construction

difficulties and even failure to complete the tunnel. The same difficulties with directional

control exist as for the non-steerable methods.

2.3 Horizontal directional drilling (HDD)Horizontal direction drilling is likely to be the most widely used NDRC method, due to the extreme

versatility in uses. The method can be conducted from the ground surface without the need of deep

entry and exit shafts.

• The installation size can be anywhere from small diameter single cable crossings up to 1200

mm diameter pipes. Drilling distances can reach as much as 1500-1800 m in a single drill -

longer drills have been achieved using intersecting methods.

• The method requires a HDD rig capable of applying torque and thrust to drill a drilling pipe

through the ground. A steerable drilling head, specially designed for the soil conditions, is

situated at the front end of the pipes.

• Directly behind the drill head is a probe or transmitter sending signals through the ground.

These signals can be tracked from the ground surface, thereby determining the position and

depth of the drill. The direction of the drill can be altered by the asymmetrical steering face of

the drill head.

• After completing the drill, the bore hole is expanded to the required size by attaching reamers

to the drill pipe and pulling back in one or more steps. The desired pipeline is typically

attached directly behind the final reamer.

• Drilling fluid (typically a bentonite suspension) is continuously pumped into the borehole in

order to remove the spoils and support the borehole. An example of a HDD setup is shown in

Figure 6.

• The reamer is generally larger than the pipeline being installed creating an overcut or annular

space surrounding the pipeline through which the soil and drilling fluid mixture can escape.


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Figure 6: Process of the horizontal directional drilling (HDD)

Advantages

• The wide size range and the ability to undertake HDD without large entry and exit pits and

without groundwater lowering are very clear advantages of this method.

• The direction of the drill can be altered while drilling making it possible to install a curved

pipeline. This can be a great advantage when manoeuvring around existing structures or

other utilities.

Disadvantages

• The achievable alignment accuracy may be insufficient for pipelines that require high

precision alignment.

• Maximum pipe diameters are limited to about 1200mm.


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• Sudden changes in soil type from say clay to sand can lead to loss of control of fluid

pressure which in turn can lead to collapse of the soil annulus around the pipe.

• In certain situations, the pipe may become stuck leading to loss of the HDD string.

2.4 Micro tunnellingMicro tunnelling is a name generally associated to unmanned pipe jacking methods for pipes smallerthan 1000 mm diameter. However larger diameter machines and equipment are readily used and it

would be more appropriate to use the term micro tunnelling for any unmanned pipe jacking using a

steerable tunnelling machine.

Figure 7: Micro tunnelling

In micro tunnelling the pipeline is installed by pushing (jacking) the pipes forward from the starting

shaft as the tunnelling machine excavates the soil at the front of the pipeline. The excavated soil can

be removed through the already laid pipes by various methods. Examples of this are auger soil

removal or slurry shield micro tunnelling as shown in Figures 7 and 8.

In the auger method the excavated soil is removed mechanically with the continuous line of augers.

In the slurry shield method the excavated soil is mixed with a bentonite slurry suspension and

pumped out of the pipeline. After being pumped out the soil is settled or separated from the slurry in

a tank or separation unit and the slurry is reused.

When working below ground water levels the auger soil removal may pose the same problems,

where the auger may flood and give way for excessive soil loss. The slurry shield micro tunnelling

machine is typically designed with a pressurized bulkhead, where slurry is pumped at a sufficient

pressure to stabilizes any loose soil and balance ground water pressure.

The tunnelling machine can be controlled by an operator outside the pipeline. The alignment is

usually controlled by laser or by gyroscope and water level. The line is typically straight, but using


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gyroscope or specialized surveying equipment and short pipe lengths, curved tunnels can be

constructed.

Piping materials must be designed to withstand the jacking forces acting on them under installation.

Concrete is often used as piping material along with fibreglass or composites with concrete and

fibreglass. Polymer materials especially polymer concretes are becoming more common due to there

strength and corrosion resistance.

Figure 8: Slurry shield micro tunnelling (Iseki Poly-Tech, Inc.-japan)

Advantages

• Micro tunnelling works in almost all soil conditions and cutting heads can be modified to deal

with weak rocks.

• Pipes of up to 2000mm diameter can be installed and can be constructed to a high degree of

accuracy which makes the technique suitable for pipelines that require precision in alignment

or gradient.

Disadvantages

• Obstacles (large rocks/boulders or other materials) may stop machines not designed for

cutting through these materials. In such cases there may be no other solution, than to

excavate from the surface to remove the obstacle. If this is not possible, the tunnel and

machine may have to be abandoned.


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• Working in mixed face conditions can be problematic, particularly where slurry support is

used below groundwater as the slurry pressure may be difficult to control. Loss of slurry/face

support can lead to instability and ravelling leading to large surface settlements and, in the

extreme case, abandonment of the pipe and machine.

•

Micro tunnelling is generally more expensive than many of the other NDRC methods,requiring relatively large entry and exit shafts and more advanced equipment and materials.

2.5 Pilot pipe jackingThis method is basically a variation of the non-steerable auger boring method. In this method

however a steerable pilot pipe is initially jacked or drilled through the soil. The alignment of the pilot

pipe is controlled by laser and a small camera at the head of the pipe.

After installing the pilot pipe an open steel pipe with an auger for soil removal is attached to the pilot

pipe and pushed/jacked through. The steel pipe is usually just used as a sleeve for the product pipe

which is pulled in afterwards.

Variations of the method include attaching a reamer followed by a plastic pipeline and pulling thesethrough in a similar manner as HDD.

Figure 9: Stages of pilot pipe jacking with auger soil removal


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Advantages

• The method is very accurate (unlike the non-steerable auger boring method). The pilot pipe

can generally be installed to an accuracy of +/- 20 mm and the steel sleeve pipe will typically

follow this line with litt le deviation.

• The technique is a relatively cheap method of achieving a pipeline to a high precision in

alignment and gradient.

Disadvantages

• Large rocks or differences in soil structure surrounding the pilot pipe can give problems.

• Ground water may give some of the same problems described in sections on non-steerable

auger boring and micro tunnelling.

2.6 Manned pipe jacking methodsManned pipe jacking methods are very similar to the techniques given as micro tunnelling – the

difference is basically that the manned methods are sufficiently large in diameter to accommodateworkers inside the pipeline.

A wide range of tunnelling machines designed for varying types of soil and groundwater conditions

exist. The machines can generally be divided into open or closed face machines – the selection is

dependent on the soil conditions and the required support necessary for stability of the soil.

2.6.1 Open front pipe jacking techniquesOpen faced pipe jacking can be done in stable soil conditions with little or no ground water inflow.

The method consists of a tunnelling machine with an open front, where soil is excavated

mechanically and transported with conveyor belt and/or buckets out of the pipeline. Examples of

open front pipe jacking are shown in Figure 10 and Figure 11.

Figure 10: Backactor shield


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Figure 11: A cutter boom shield

Figure 12: Open front pipe jacking

Working below ground water levels, pressure may be applied to the front using a chamber lock

system as shown in Figure 12. The pressurized front allows excavation without losing soil stability

due to ground water infiltration. This will generally only work in cohesive soils or rock - in very loose

soils, an open front is very questionable.

2.6.2 Closed front (full face excavation) pipe jacking techniquesIn loose soils or conditions with high ground water levels, a closed front machine may be used.

Closed front machines can be of the slurry shield type as described in Section 4.5 on micro

tunnelling or alternatively an earth pressure balance machine.

The slurry shield tunnelling machine works as described previously with a bentonite slurry

suspension that is mixed with the excavated soil and pumped out of the pipeline. An example of thistype of machine is shown in Figure 16.


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Figure 13: A slurry shield (full face excavation) pipe jacking machine

Figure 14: Earth Pressure Balance Machine (EPBM)

Advantages

• Manned pipe jacking methods have the general advantage that access to the driving front is

relatively easy - making it possible to remove obstacles (larger rocks/boulders etc.) with

manual methods.

• Open front machines obviously have the most direct access, where closed front machines

may need to be designed with access gates.

Disadvantages

• There are many health and safety issues associated with manned pipe jacking, not least the

need to work in confined spaces with the dangers of face collapse and groundwater

inundation.

• Detailed and robust health and safety procedures dealing specifically with the hazards

related to this construction method need to be implemented for all manned pipe jacking

operations.


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• Tunnelling equipment is large and expensive and requires relatively large site areas for the

launch and reception pits.

2.7 New NDRC Techniques

NDRC techniques continue to evolve and new techniques are constantly being trialled andimplemented to overcome some of the disadvantages of conventional techniques or provide faster,

cheaper installations. Two such techniques are the “Easy Pipe” and the “Direct Pipe” methods

2.7.1 Easy PipeThis technique combines conventional micro tunnelling with an innovative method of using the

jacking pipes to help install the permanent pipe. Once the tunnel has been bored, the micro

tunnelling machine is removed and the permanent pipe is attached to the installed jacking pipes.

The jacking pipe segments (which are bolted together) are pulled back through the tunnel, pulling the

permanent pipe with them. In this way, the permanent pipe is installed quickly and easily and the

jacking pipe segments can be re-used for the next project.

Easy Pipe installation requires a micro tunnelling unit to be prepared and assembled in the launch

pit. The cutter head is launched and guided in the conventional micro tunnelling way along a planned

alignment.

The difference between the jacking pipes used by Easy Pipe and conventional ones is that the

special design allows them to be used as jacking pipes in the forward direction while allowing them

to be retracted from the completed bore to pull in the product pipe.

This is because the joints between the jacking pipe sections bolt together with a design that will

withstand thrust and pullback forces of up to 6,300 kN (630 tons).The close proximity of the jacking

pipes' outer wall to the bore wall also avoids the potential for collapse of the bore in unstable ground

formations.

After the cutter head has reached the target pit, it is separated from the jacking pipe string and

replaced by a specially designed connection pipe that also connects to the product pipe. The jacking

pipes are then pulled back using the bi-directional jacking frame, simultaneously pulling the product

pipe into position. In the launch pit the individual jacking pipes are successively removed along with

all other equipment until the product pipe arrives at the launch shaft.

The connection pipe and jacking frame are removed from the pit leaving the product pipe in place to

be finally connected to the remainder of the pipeline on either side of the obstacle(s) crossed.


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Figure 15: Easy pipe Method

2.7.2 Direct PipeThe direct pipe technique is a hybrid of the HDD and micro tunnelling methods. In this technique, the

micro tunnelling machine is pushed in to the ground using a jacking frame that grabs directly on to

the final production pipe and uses this to push the micro tunnel machine forward. In this way, once

the tunnel is bored, there is no need for a secondary production pipe installation process as the

production pipe is installed directly as part of the tunnelling operation. Installation of the pipe is

limited by the thrust that can be applied to the pipe without causing damage and the need for

sufficient space to lay the pipe out behind the micro tunnel machine prior to commencing boring.


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Figure 16: Direct Pipe Method

Advantages

• Single-step method leads to rapid installation of product piping and pipelines

• No time needed for coupling pipes (Micro tunneling) or drill rods (HDD)

• Pipeline can be installed pre-welded and already tested

• Costly shaft construction unnecessary - instead, only simplified surface entry and exit pits are

required

• One-pass work phase of operation for excavation and pipeline installation

•

Inclines and gradients as well as curved drilling profiles can be negotiated precisely• Ideal method for sea outfalls with access from one side only

• Pipe Thruster enables both tunneling machine and pipeline to be withdrawn, for example for

cutting tool retooling operations in inaccessible, low-diameter areas

• Cone crusher removes obstacles as they occur

Application options

• Pipeline laying from construction pit to construction pit

• Pipeline laying from construction pit to shaft

• Pipeline laying from construction pit to destination point, for example water course beds

Range of application

• Pipeline diameter: - 28” - 36” 38” - 44” 46” - 52” 54” - 60”

• Excavation diameter 805 / 990 mm 1,140 mm 1,325 mm 1,540 mm

• Maximum pipeline / drilling length 300 m 700 m 1,200 m 1,400 m

• Geology: - Clay, Silt, Sand, Gravel, Cobbles, Boulders, Rock (up to 150 Mpa = 21,750 psi)

• Pipe material: - Steel

• Coating material: - . PE, PP, GRP, FBE


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3 GENERAL

3.1 OverviewThis chapter provides general information for undertaking Non Disruptive Road Crossings including

an overview of the parties involved and their roles and responsibilities.

The chapter further covers the general requirements for environment, health and safety along with

requirements for site survey and geotechnical investigations.

3.2 Standards and Codes of Practice A number of local and international Standards and Codes of Practice along with guidelines and

specifications have been sourced during the process of creating this manual. The documents and

information listed below were chosen as they are typically viewed as being ‘best practice’

internationally, in the field of NDRC and trenchless technology. Particular reference can be made to

the following existing key documents:

• Abu Dhabi Municipality Road Department - Requirements and Recommendations for Non -

disruptive Road Crossings

• Abu Dhabi Municipality Sewerage Projects Committee - General specifications for civil works,

Pipeline construction by Non disruptive method (2003)

• The Pipe Jacking Association (UK) - "An introduction to pipe jacking and micro-tunnelling

design" (1995)

• Horizontal Directional Drilling Good Practices Guidelines - 2008 (3rd Edition) USA

• Standard DWA-A 125E Pipe Jacking and Related Techniques, German Association for

Water, Wastewater and Waste. (2008)

•

Microtunneling and Horizontal Drilling Recommendations, FSTT, French Society ofTrenchless Technology (2006)

• Euronorm EN 12889: Trenchless Construction and Testing of Drains and Sewers.

• There is a wealth of globally available documentation about 'trenchless' or 'no dig' technology

and the list above covers some of the more important ones. Additional information on

methods and equipment can be found in these or from technical associations such as:

• International Society of Trenchless Technology, ISTT - www.istt.com

• Pipe Jacking Association (UK) - www.pipejacking.org

• North American Society for Trenchless Technology, USA - www.nastt.org

3.3 Roles and responsibilities

This section describes typical roles and responsibilities of the parties involved in undertaking NDRCworks. The specific responsibilities and authorities of the different parties involved can vary from

project to project depending on the contract agreements between the parties.

Road crossings and in particular NDRC works are typically contracted as part of a main project

involving installation of utility lines in an area, along roads, etc.


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3.3.1 ClientThe Client is the owner of the pipeline or cable to be installed. The overall responsibility for the

installation and operation of the pipeline or cable is that of the Client.

The Client can delegate certain responsibilities such as design and calculations along with the

responsibility for safeguarding of the road to others through contract agreements.

3.3.2 ConsultantThe Consultant is typically hired by the Client to design, tender and supervise the overall project.

The Consultant will typically undertake preliminary site and soil investigations to collect information

on existing utilities, surface and sub-surface constructions during the design stage. The consultant

will supervise the installation and NDRC work during construction.

3.3.3 Contractor/Sub ContractorThe Contractor or, if delegated, the specialist Sub Contractor is responsible for the correct

installation of the pipeline or cable in accordance with the specifications.

The Contractor/Sub Contractor is responsible for obtaining approval from the Road Authority prior to

commencement of the NDRC work. Approval is only given after Submitting a complete and

acceptable method statement including all required information in accordance with this manual.

3.3.4 Road AuthorityThe Road Authority (Abu Dhabi Department of Transport or any Municipality) is responsible for

giving approval of any NDRC work. The Road Authority's main interest is in protecting their assets -

the road, footpaths, structures, etc. from any harm, settlement or heave resulting from the NDRC

work which lies within the highway Right of Way.

3.3.5 Abu Dhabi Town Planning Abu Dhabi Town Planning will give initial approval and assign a corridor that the Client may use. Thisis done only after checking with, and obtaining NOCs from the Road Authority, other Utility Agencies

and any other relevant authorities.

After giving approval and assigning a corridor Abu Dhabi Town Planning will refer to the Road

Authority for final approval of the NDRC work.

3.3.6 Utility AgenciesOther utilities agencies may be affected by the NDRC if their pipelines or cables are located near the

proposed NDRC. The Contractor will need to obtain No Objection Certificates (NOC's) from all the

concerned utilities agencies. These may be accompanied with certain requirements or restrictions

concerning the NDRC.

3.4 Process MapWhen following the procedure below, it is imperative that the Consultant follow the guidance

contained in this Manual, and if any of the processes are not completed to the DoT’s satisfaction,

then the relevant stage will not be approved.


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The process of undertaking NDRC work involves a five part approval process. Important points for

the Consultant to consider:

• The stages are illustrated in Figure 17 below showing the main activities and responsibilities

in each stage.

• Detailed information and requirements of the various activities can be found the subsequent

sections of this manual.

• Check lists of required submittals to the Road Authority are given in Appendix A.

• The estimated processing times in the approval stages are based on complete and full

submittals. Any missing information may result in prolonged processing times.

• Anywhere along the process factors may arise that will require the planned NDRC to be

revised and the process to be returned to an earlier stage.

• All applications for approval with the DoT must be submitted using the No Objection

Certificate - Right of Way (NOC-ROW) online system. Please refer to the DoT website for

the latest information on this subject.


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Figure 17: Process map of NDRC

Responsible Activity Details and information to be acquired

PHASE 1 Concept Stage

Client/Consultant

Map of intended NDRC Location/vicinitySize (diameter) and level

Approval process - part 1

Submit to Abu Dhabi Town Planning for approval of corridor and NOC Expected processing time:4-6 weeks

PHASE 2 Preliminary design

Client/Consultant

Geotechnical Geotechnical Assessment (Key stage 2) according to Manual forGeotechnical Investigation and Geotechnical Design includingGround Investigation Factual and Interpretative Reports.

Site investigation Surface and underground structures

Other utilities Location and type

Drawings Line, level, diameterWork area with working shaft locations and sizes

Method selection Suggested method and equipmentRequirements for accuracy, material, etc.


Submit to Road Authority for preliminary approval of designCheck list of submittals required is given in appendix A.

Expected processing time:2-3 weeks

PHASE 3 Pre-construction Stage

Contractor/Sub Contractor

Design calculations Pipe strengthWorking shaftsJacking and friction forcesSurface settlement/heave

Design drawings Plans and profiles of the intended lineWorking area plans showing placement of equipment andmaterials.Traffic diversion plansDetails of working shaftsDe-watering system design

Materials and equipment Lists of all in use

Method statement Contractor nameList of personnel with qualificationsSequencing and procedure of workGround water control and dewateringSafety proceduresEnvironmental assessmentRisk assessment

NOC From all relevant utilities and authorities

Letters of undertaking From Client and Consultant


Submit to Road Authority for approval of constructionList of submittals required is given in Appendix A

Expected processing time:3-4 weeks

PHASE 4 Construction

Contractor/

Sub Contractor

Site condition survey Surrounding surfaces and structures

Pre construction photosMonitoring Setup and monitoring of surface movement

QA/QC Documentation in accordance with QC plan

PHASE 5 After construction

Monitoring Surface movement - monthly reports


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3.5 Health and Safety All parties involved in NDRC work have an important role in establishing safe working conditions.

During planning and design all foreseeable health and safety risks likely to arise shall be identified

and taken into consideration in the design. All health and safety information known to the Client,

Consultant or designer must be given to the Contractor prior to undertaking the NDRC work.

Figure 18: Pipe jacking worksite and shaft

The Contractor must ensure that prior to commencement of any project, a Health and Safety Plan is

prepared which covers the specific requirements of the project. This plan shall be submitted prior to

approval of construction along with the Method Statement, and approved by the relevant Consultant

(usually the Engineer).

General requirements for Environment Health and Safety must comply with the EHS Manual for

Road Projects. All issues relating to EHS must be raised and addressed along all stages of the

project.

3.5.1 At Concept StageDuring this phase, it is important for the design team to establish the route of the NDRC to minimise

the risks to safety for any persons working on the construction.

When submitting the relevant design information to Abu Dhabi Town Planning, the Consultant must

take into account the safety impacts of the size and material used in the NDRC works, if they are

available at this stage.

3.5.2 Preliminary Design StageDuring this phase, the designer must take into account:

• The specification of materials

• The location of the crossing – to minimise the safety impact on pedestrians, motorists and the

general public

• The diameter – to minimise the impact of construction works for construction personnel

• The ground conditions – to establish the risks of stability of the surrounding soils.


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3.5.3 At Pre-Construction StageThis is an important phase for safety considerations as it maps out the construction processes and

methods via the Method Statement. The appointed Contractor should submit:

• A Method Statement which should detail all the construction methods and programme

• A Risk Assessment highlighting ALL risks to safety, rating each in terms of probability and

severity

• A Site Emergency Plan to show evacuation procedures in an emergency

• A Traffic Management Plan to set out the specific requirements for the site.

3.5.4 During Construction StageDuring this stage there are many considerations for the Contractor to consider.

• A daily checklist for inspection of the works is included in the Appendix and this is to be

checked back and corroborated with the Method Statement.

The worker should take the following general precautions:

• Do not take chances that may lead to injury

• Either use tight sheet shoring to guard against the caving in of sandy soil or loose material

when the depth of the excavation exceeds 5 ft, or cut back the bank to the proper slope.

Keep shoring at or near the bottom of the ditch as it is excavated and follow with bracing to

ensure safety. Trench shields are also acceptable as a protective system. A trench shield

does not protect the environment, only the worker.

• The placement of shores will depend on the type (classification) of soil encountered. Local,

state or provincial, and federal laws man - date the distances and sizing of shoring support

systems.

• Extend shoring of any type below the excavation bottom whenever possible, and brace it

thoroughly using timbers, wedges, and cleats, or a pipe/screw-jack combination. Place all

bracing at right angles to the sheeting or uprights and rigidly wedge, bolt, or cleat it to prevent

movement. Hydraulic units are being used in many types of utility-trench construction

• Use only full-sized lumber that is assessed to be sound and straight.

• Install the upper braces or screw jacks first, and remove them last for best protection.

• Also consider excavation dimensions, soil stability, variable weather and moisture conditions,

proximity of other structures, weight and placement of soil and equipment used on the job,

and sources of vibration when choosing the type of shoring to use, if any. The decision must

rest with the engineer or foreman in charge.

• Use hydraulic jacks temporarily only, and replace them with properly sized screw jacks or

solid bracing.

• Personnel should not be required to do heavy lifting that may cause injury; use mechanical

lifting devices to raise, lower, or suspend heavy or bulky material when working in trenches,

manholes, or vaults.

• Use ladders where required. Do not jump into an excavation.


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• Provide an adequate means of trench exit, such as a ladder or steps. Locate it so no more

than 25 ft of lateral travel is required. Extend the ladder from the bottom of the excavation to

at least 3 ft above the ground surface.

• Do not place excavated material closer than 2 ft from the edge of an excavation.

•

Keep all tools, working materials, and loose objects orderly and away from the excavationshoulder.

• Keep tools, equipment, and excavated material out of open traffic lanes.

• Take work breaks, rests, etc. at designated locations away from the excavation.

• When resuming excavation after heavy rains or freezing weather, inspect all banks for

cracks. These may indicate earth movement and the probability of cave-in.

• Frequently inspect the sides and rim of all open excavations to guard against cave-in.

Operate earth-moving equipment from a position that will not imperil personnel or property by

a cave-in due to vibration, stress, or dead weight.

• If it is absolutely necessary to work above an overhanging bank, use a safety belt and a

lifeline. Have a helper nearby to assist in an emergency.

• To avoid striking electric or telephone conduits, gas lines, or other sub-structures, locateother utility installations before starting work.

• Require workers to wear adequate eye, ear, and foot protection when using a jackhammer or

when exposed to flying particles or falling objects.

• Workers should always be aware of locations of running machines (back–hoes, trenching

machines, etc.). Workers should keep clear of the sweep path and try never to turn their

backs toward the working machine(s).

3.5.4.1 Pipe storage• Keep pipe yards and walkways clean and orderly.

• Always block pipe to prevent it from rolling or falling.

• Arrange and block each row of stacked pipe to prevent it from rolling from the pile.• Store small pipe in racks according to length and size.

• Store pipes larger than 2inch diameter by stacking them with spacing strips placed between

each row.

• Withdraw pipe from the top rows.

3.5.4.2 Shoring and bracing

• Use proper shoring and bracing to prevent cave-ins while vaults or similar openings are

under construction.

• Proper shoring cannot be reduced to a standard formula.

• Each job is an individual problem and must be considered under its own conditions.

3.5.4.3 Posting barricades and warning signs• Place advance warning, instructional signs, barricades, and delineators well ahead of the

construction area to warn motorists and pedestrians of the area and safely take them through

or past it.


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• Protect the work area with barricades, barriers, or planks to provide a safe working space. If

necessary, use flaggers to direct and slow down traffic. When used, place trucks or air

compressors between the work and the traffic.

• During periods of reduced visibility, use adequate lighting on all barricades.

•

When no work is in progress, place adequate barriers, barricades, flashing lights, and signsto warn and divert traffic. Use reflecting tape on all barricades.

• All personnel should wear protective clothing including hard hats and high visibility traffic

vests.

3.5.4.4 Trenching machinesThe following rules apply equally to all mechanical devices used to dig trenches and/or make

excavations including various types of trenchers, buckets, scoops, and similar pieces of equipment:

• Operators should always wear hard hats.

• Never attempt to oil or grease a mechanism or repair or adjust any moving part of a trenching

machine while it is in operation. Only qualified personnel should operate a trenching

machine.

• Guard all moving parts. Before starting the conveyor, make sure that no person is

endangered by it.

• To remove obstructions from the conveyor mechanism or buckets, stop the machines.

• Be alert for falling material that might roll from the conveyor.

• When practicable, drop dirt between the excavation and the high-way to act as a barrier.

• Cautiously fill gasoline or diesel tanks. Keep spout in metallic contact with the machine to

prevent static sparks from bridging the gap and igniting the vapours. Do not smoke. Keep

proper fire extinguishers available when refuelling construction equipment. Use only

approved containers when storing flammables on the job site; clearly mark and define

storage areas.

• Use flags by day and flashing lights or flares by night to warn the public of the trenching

machine and its operations. Liberally use these precautions on all highway or street work.

Plan the warning system before the work is started.

• Operate the machine vertically to prevent undercutting the trench wells.

• When loading or unloading trenching machines or other heavy equipment from truck beds,

lowboys, or other conveyances, provide suitable skids and ample blocking to prevent

movement of the conveyance

• When manually lifting or lowering pipe in an excavation, use two or more rope slings looped

under the pipe and handle from each side of the excavation. To prevent a heavy pipe from

pulling workers into the excavation, anchor one end of each rope sling to a massive object

such as a truck.

• When aligning pipes in the excavation, either manually or mechanically, keep hands and

fingers away from ends of pipe and other substructures that could crush.

• Govern crane operations only by the signals of a qualified worker.

• Never try to catch and hold a length of pipe that slips from a crane or hoist sling.

• Be alert to unsafe excavation sides when measuring, testing, or inspecting pipe in place on

an excavation bottom.


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• When cutting sections of pipe, keep feet in the clear and use adequate blocking, chocks, etc

to prevent pipe movement.

• Wear safety goggles

• Keep tools and appliances in good condition for handling, cutting, threading, or treating pipe.

Always use the right tool for the job.• Do not let tools or materials become stumbling hazards where pipe is being handled.

• Avoid shortcuts and makeshift methods that may increase the hazards of handling pipe.

Accidents and risks that may be particularly related to NDRC work will include, but are not limited

to:

• Falling accidents (deep excavations and shafts)

• Materials falling from a height

• Collapse of excavation or shaft

• Road collapse or failure

• Flooding from broken pipelines or groundwater

• Striking other utilities (power, gas, oil, water, etc.)

• Suffocation due to inadequate fresh air supply (manned pipe jacking or micro-tunnelling)

• Dangerous gasses

• Rotating and moving machinery and equipment

These along with any other risks must be assessed in the

Health and Safety plan including mitigation measures.

Employment of workers inside pipe jacking or micro tunnelling

pipelines shall not be permitted for pipelines with an internal

diameter smaller than 1.2 m.

The Contractor shall develop an emergency plan that describes

actions to be taken in the event of any sudden surface

settlement or collapse. This plan shall be included in the

Contractors method statement.

3.6 Environmental requirementsGeneral environmental requirements for any construction works in connection with main roads,

including undertaking of NDRCs, can be found in the EHS Manual for Road Projects.

Prior to commencing any projects an environmental permit must be acquired from The Environment

Agency - Abu Dhabi (EAD). Points that will need to be addressed for the environmental permit may

include:

• Soil or spoil removal including slurry handling and disposal.

• Dewatering including discharge.

• Waste management.

• Handling and storage of any hazardous materials.

• Activities creating dust, air pollutants or odours.

• Noise or vibrations.


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• The Contractor is responsible for establishing, operation and decommissioning of the work

site in an environmentally safe way and this can be controlled by using a daily checklist

report which will be followed in line with the Method Statement. Such details will be included

in the Contractor's Method Statement.

•

All waste materials shall be collected and disposed of in an appropriate manner, and the siteshall be cleared and void of any waste matter after the construction is completed.

• All materials and equipment shall be stored in accordance with manufacturer's guidelines and

in a way so that spills or emissions are avoided.

• Drilling fluids (slurry, bentonite, etc.) shall be recovered for

reuse or disposal at an approved location in accordance

with the environmental permit.

• The environmental issues that typically concern HDD

include:

- Access restrictions due to wetlands, streams,

endangered plant or animal life, endangered

habitat, and potential erosion

- Oil and fuel spills from construction equipment

- Drilling-fluid surface spills that endanger animal and

plant life

- Drilling fluid returns in water bodies

- Groundwater contamination from drilling-fluid

additives

- Drilling-fluid disposal locations (The contractor must obtain approval to dispose of the

drilling fluid at an approved disposal location. Bentonite is a good product for sealing

drainage ditches, irrigation reservoirs, and livestock ponds.

• However, approval must be obtained from EAD permit received for the works.

3.7 Site condition survey A site condition survey shall be conducted during both the preliminary design and construction

stages of the proposed NDRC. All surface and subsurface construction within a minimum of 30 m

from the proposed centreline and any shafts must be identified and the exact location determined.

These will include, but are not necessarily limited to:

• Cables, pipelines, sewers and manholes

• Pavements, footpaths, etc.

• Buildings

• Foundations, retaining walls, etc.

• Artificial cavities

• Constructional systems that have remained in the area along with any other structures or

systems that may have impact or be influenced by the intended NDRC.

A building and structure assessment plan documenting the condition and including photographs of

any existing damage must be included in the site condition survey. This shall be submitted for

approval of both the preliminary design and final design. In connection with the final design the site


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survey must be reviewed and approved by the DoT road maintenance consultant and approved by

the DoT.

Immediately prior to construction the site survey shall reviewed by the Contractor and any changes

in the condition of buildings, structures, roads, footpaths and other paved areas shall be recorded

and photographed.

3.8 Geotechnical InvestigationThe geotechnical investigation shall be conducted in accordance with the Manual for Geotechnical

Investigation and Geotechnical Design including determining the projects geotechnical category and

the procedures for managing geotechnical risk as described.

Evaluation of soil conditions on NDRC projects is critical, but often under-emphasized. Success or

failure is intricately tied to correctly matching equipment and methods to soil Conditions. It is the

designer's responsibility to ensure that sufficient geotechnical information is available for the

complete design and safe installation of the NDRC.

For all NDRC work, a minimum requirement of a desk study shall be carried out, assessing the

available literature, maps, aerial photographs, utility plans and existing site investigations. The aerial

photographs must encompass as much historical information as possible, that show for example

lowlands swamps which have since been backfilled. Existing geotechnical investigations may be

acquired from the road department, adjacent building owners or structures and other utilities

agencies.

If insufficient geotechnical information is available for the area where an NDRC is proposed, then a

thorough geotechnical investigation must be conducted.

The soil investigation analysis is necessary for:

• Selecting the appropriate NDRC method, jacking technique and jacking works

• Selecting and designing the supports for launch and reception shafts

• Selecting and designing jacking pipes

• Planning measures for soil improvement in unstable soils

• Planning of soil disposal (landfill, treatment, recycling)

• Planning of measures for the control of groundwater

The field exploratory techniques selected should be appropriate to the type of ground and the

planned depth of the NDRC. The laboratory testing programme should include tests relevant to the

ground conditions and the NDRC techniques likely to be

employed. Table 1 below suggests parameters to be

considered in relation to each soil type.

The soil conditions shall be investigated and documented in

accordance with the Manual for Geotechnical Investigation

and Geotechnical Design. The investigation should result in

information on reliable soil parameters which are necessary

for the adequate design of the drives, shoring, and

dewatering details. Analysis and design (calculations for


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jacking forces, stress analysis on the pipeline, ground surface settlement and heave analysis, etc.)

should be based on such parameters.

3.8.1 Minimum requirements of the exploratory boreholesNumber of boreholes:

• 2 exploratory holes for crossings less than 25 m (one

at each end)

• 3 exploratory holes for crossings greater than 25 m

(each end and centre)

• Additional holes for long crossings or in areas with

difficult soil conditions (layered)

Depth of boreholes:

• Down to 2 m below pipe invert in groundwater free

soils• Down to 3 m below pipe invert in groundwater bearing soils

• Down to the planned bottom edge of sheeting in the area of launch and reception shafts.

3.8.2 Borehole PositionsExploratory borehole positions should be chosen to provide information on the nature of the ground

that will be encountered by the NDRC. Under no circumstances should boreholes be sunk on the

line of the NDRC.

All boreholes should be properly backfilled and sealed. Piezometers should be installed where

recommended. Boreholes should always extend sufficiently far below the invert level to identify

changes in the strata below the NDRC that could affect both the construction and long term impact

of the NDRC. Boreholes should be sunk adjacent to shaft locations. Additional boreholes should beconsidered, if required, to identify the location of significant changes in geology or to resolve other

geotechnical uncertainties.

All geotechnical investigations shall be carried out by qualified personnel and in accordance with The

Manual for Geotechnical Investigation and Geotechnical Design.


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Table 1: Parameters to be considered in relation to each soil type

TestNon-

CohesiveSoils

CohesiveSoils

MixedSoils

FillMaterial

Rock

Unit weight and moisturecontent X X X X X

Angle of friction X X X

Particle size distribution X X X X

Abrasivity X X X X X

Cohesion X X X

Types and proportions ofminerals

X X X X X

Standard penetration tests X X X X

Permeability and nature ofground water level andflows (seasonal/tidalchanges)

X X X X

Toxic/hazardous

constituents in theground/groundwater X X X X X

Frequency and physicalproperties of boulders,cobbles or flints

X X X X X

Pump down tests X X X X

Presence of gases X

Compressive strength X

Rock quality designation(RQD)

X

Core logging (TCR, SCR,FI)

X

Tensile strength X

Specific energy

(excavatability)

X

Slake durability X

Geological description X X X X

Plasticity indices (LL, PL,PI)

X X

Source: An Introduction to pipejacking and microtunnelling design


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4 PROCEDURES FOR UNDERTAKING NON

DISRUPTIVE ROAD CROSSINGS

4.1 OverviewThis chapter contains the general procedures and requirements for undertaking any NDRC works

under DOT roads. It is divided into sections relating to the process map described in Chapter 1.

4.2 Concept Stage At this early stage, the concept of each project will be considered by the Designer, and as per the

stage gateway process, the options will be considered from a financial and environmental impact

point of view before progressing to the next stage. This will be in line with the requirements of Town

Planning as detailed in Chapter 2.

For NDRC, if applicable the impacts will be established and examined, and put forward into the

report generated by the Consultant. Depending on the project, it may be the case that different

routes for the NDRC are considered.

4.3 Preliminary Design Procedures

4.3.1 Method selectionIn this section more detailed information about the guidelines requirements and criteria related to the

two major NDRC methods are currently used in emirate of Abu Dhabi are given in order to help

select a method appropriate for the given project. More information on the various methods can be

found in Chapter 2.

The Client/Consultant should, before tender, determine which methods may or may not be used for

the NDRC works. The selection should be appropriate for the intended installation and meet the

requirements of this Manual. Method and equipment should be selected to avoid ground loss and

minimize settlement or heave. Also, a geotechnical section along the drive path shall be provided

with the ground surface and groundwater elevations shown. This will assist in determining the

method.

The selection of route and method shall be based on the information gathered during the site

investigation and geotechnical survey along with all other relevant information. The line and level of

the route shall be selected so as to avoid driving through weak/strong soil boundaries, weathering

interfaces and groundwater surfaces.

The methods presently available are many and diverse and new techniques are continually being

developed. Existing methods and equipment are becoming more advanced and variations or

combinations of different methods are also being developed.

The selection of method is also dependant on the:

• Cost – The cost of construction can vary dramatically depending on the method, materials,

and route chosen.


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Table 2: NDRC methods related to soil types

◙

◙

& ◙ ◙

/

◙

&

◙ ◙

◙ ◙

◙ ◙ ◙

& ◙ ◙

◙ ◙

/ ◙ ◙ ◙ ◙

◙ ◙ ◙

X – Not Suitable • - Suitable ◙ - May be Suitable (depends on specific circumstances)


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Table 3: Different applications of NDRC

Micro tunnelling and Horizontal Directional are the most used methods in Emirate of Abu Dhabi, so

more discussion will be explained.

4.3.1.1 Micro tunnelling Method All types of Micro tunnelling boring machines have the following functions in common.

Mechanized ground excavation and stabilization of the face

• The head of the machine is equipped with a cutting wheel whose tools are used to last the

soil under the combined action of rotation and thrust. A crushing cone located behind the

cutting wheel and intended to reduce the size of larger elements to allow their mucking, is

present on most machines. There exist different cutting heads for various types of soil. (see

figure below). They can be distinguished by their cutting tools.

• For sandy or gravely soil, the cutting wheels are equipped with teeth (figure –a). In ruggedsoil, these teeth dislodge the blocks, which are then crushed.

Suitable at appropriate diameters and lengths ® - Small diameter only ø - Small diameter only U –Typically for Crossings only S – Siphon crossings only


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- less than the passive earth pressure so as to avoid facing back the soil at the face

,leading to elevations of the surface or lateral movements likely to create disorder for

already –existing networks(Stein et al.,1994)

• In the case of hydraulic mucking ,this pressure is ensured by the slurry injected into the

chamber located at the back of the felling cone.it can be controlled more easily than the

pressure exerted by the soil mixed in the stpe of the scew type boring machines(Bennett et al

.1994).

Disposal of rubble (mucking)

There are three types:

• Hydraulic mucking – Removing the earth in suspension in a freely flowing fluid to the outside.

That fluid can be water or pressurised bentonite slurry.(See Figure 20)

• Mucking with a screw conveyor – The rubble is extracted from the stope using a spiral

conveyor (see Figure 20)

• Pneumatic mucking – This is a system that is rarely used and consist of mucking by suction

where the rubble is extracted from the face into an airtight vacuum container.

Figure 20: Principles of a hydraulic mucking boring machine (Herrenknecht documents)

Monitoring and correction of trajectory

• Controlling the actual trajectory of the boring machine in relation to its theoretical position ,is

done using a laser beam with the sensor located in the start shaft whose impact on a target

placed in the machine helps visualize the deviations in trajectory with the help of a camera on

board the boring machine

• When the deviation s become excessive it is possible to correct the direction of the machine

whose head is articulated by moving the three cylinders placed 120 c apart.

• 4-installation of pipelines by jacking.


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• This is done by successive jacking of pipes behind the boring machine ,this pipejacking is

ensured by a thrust frame equipped with hydraulic cylinders and located in the starting shaft.

Pipes Materials

Many types of materials are used :-

• Concrete pipes represent the majority of pipelines that are currently laid .

• Pipes made of composite materials, known as “glass fibre reinforced plastic “offer very good

resistance to corrosion and thus are efficient in transporting corrosive fluids or for carrying

chemically aggressive soil, moreover they offer a high resistance at a lower weight the

external diameters available are between 400 and 2400 mm.

• Steel pipes have the major advantage of offering strong resistance but they are sensitive to

corrosion.

• Clay pipes available in diameters of 150 to 1200 mm offer greater resistance than the

concrete pipes at the same thickness .when their surface is vitrified ,it is extremely resistant

to water absorption and chemical attacks.

In terms of corrosion resistance the jacking pipes and their joints can be subject to internal corrosioncaused by the transported substances or to external corrosion caused by the surrounding soil or

ground water.

If the materials used are insufficient ly resistant ,measures of corrosion protection have to be taken

and approved by Dot.

For steel and ductile cast iron pipes the internal protection shall not be damaged during the jacking

process.

The methods vary in size, length and accuracy as shown in Table 4. Due to the limitations in

accuracy, non-steerable methods should only be used over short distances and where suThe soil

conditions and groundwater levels are of great importance in determining the most suitable methodfor a given NDRC. In Table 2 a number of the common methods are shown with their respective

application in various soil types.

Some methods can be used in almost any soil conditions as long as the equipment and tools are

appropriate for the present soil types. Horizontal directional drilling (HDD) is an example, where drills

and reamers are available for nearly any soil type. HDD can however have limitations in coarse non-

cohesive soils where the cavity created by the reamer can have a tendency to collapse. This is


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especially the case in very uniform soil particle size efficient clear distance to other utilities can be

guaranteed.

Table 4: NDRC methods with typical pipe size, length and accuracy

External pipediameters, De

Maximumlength

Accuracy Minimumground cover

Non-steerable:

Impact moling/soildisplacement hammer,Pipe ramming with closed pipe

Up to 200 mm 25 m 1-2 % of length 10 x DeMin. 3.0 m

Pipe ramming with open pipe, Auger boring

Up to 2000 mm 80 m 1-2 % of length 3.0 x DeMin. 3.0 m

Steerable:

Horizontal Directional Drilling(HDD)

40 - 1200 mm 1800 m 2-5 % of depth

Micro tunnelling 400-4500 mm 1000 m +/- 20 mm 3.0 x De Min. 3,0 m

Pilot pipe with auger spoilremoval

100 - 1200 mm 100 m +/- 20 mm 3.0 x De Min. 3.0 m

Manned steerable:

Pipe jacking 1500 - 4500mm

1000 m +/- 20 mm 3.0 x De Min. 3.0 m

Hand excavation:

Hand dig + Mechanicalexcavator

Min 1500mm 125m Varies 3.0 x De Min. 3.0 m

.

Micro tunnelling or pipe jacking with closed front can also be applied in nearly any soil condition with

the suitable bore heads and spoil removal systems. However, in very loose non-cohesive soils, with

high groundwater levels, there is a risk of removing excessive soil in front of the bore head, which

may lead to immediate or future surface settlement.

In very loose soils or areas where soil investigations have indicated subsurface cavities, a decision

must be made either to construct deeper in an attempt to find suitable soil conditions or to apply

ground treatment methods prior to undertaking the NDRC.

In Figure 2 a number of grout types are indicated for use as ground treatment methods.

The final selection of an NDRC system should be developed using available factual and reliable soildata and surrounding constraints. The system should include the recommended route (line and

level), boring size, NDRC method, pipeline details, equipment, and operational variables, all of

which, in combination, will achieve the required tolerances. The proposed system should then be

analyzed for:

• Jack

Non Disruptive Road Crossings-1 DOT

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