Alireza Mahdizadeh - Jamaledin Borzouie

Perforating the masonry walls in rehabilitation of masonry

Buildings using center core method

Center core method is the good suggestion for retrofitting of

Historical masonry buildings due to non-destructive

construction.

Importance of Historical Buildings

Cultural Importance

Economic Impacts

Life loss ( Historical schools)

Economy of tourists

Large cost of renovation after earthquake

Arg-e-Bam and Bam earthquake,2003

The largest adobe building in the worldThe origins of Bam : 6th to 4th centuries BC

Before Bam Earthquake,2003 After Bam Earthquake,2003

Before Bam Earthquake,2003 After Bam Earthquake,2003

Time needed for rebuild of this structure after damage of Bam earthquake :12 years

Total cost for rebuild : 120 million $

others1% concrete

2%

steel8%

Masonry89%

Solution

Retrofitting of these buildings

Center core

....

....

Why Center core?

Large number of masonry buildings

Non-destructive method

Without Evacuation

Perforating the

masonry walls

Placing bars in holes

Placing grout in holes

Steps Problems

How to perforate masonry walls without any cracks

on wall surface

Area, Distance, Number of bars

Properties of grout

the building was studied under the critical conditions

Very weak mortar

Strong bricks

Loose finishing of the wall

Wall thickness is at most 30 centimetres

The building has 3 stories

The selected school: Do ShahidAged about 50 years

Drilling Machine

Parts of Drilling systems

Rotary

Hydraulic

Rod

Drilling machine produces the energy for rotation of the bit

Rod transmits the rotating force to the stabilizer and bit

Drilling Machine

Parts of Drilling systems

Rod

Stabilizer

Stabilizer reduces the lateral movements and bit shaking along the drilling path

Drilling Machine

Parts of Drilling systems

Rod

Stabilizer

Bit penetrates through the depth and determines the drilling path

Bits

Principle of design

4 boreholes (total 28 m height) were perforated in

this project. In each borehole, drilling technique,

equipments and bits were changed or design

according to the damage in the wall surface . After

observation of these cracks the wall surface was

destructed; moreover, a new bit or stabilizer was

designed according to movement of bit on surface

of bricks and other observations ( air pressure,

rotation of bit ...) to obtain the most suitable ones.

Step 1: changing available Bits and Stabilizers in drilling to obtain general vision for next stepBit

propertiespicture Damage

DiamondNon coringD: 76 mm

Bit deviation due to large contact surface with cement

Cracks were observed In the weakest part of the wall due to high air pressure and lack of mortar in the gap between two bricks, the air flow pushes the finishing and damages it such that cuttings were dispersed.

DiamondCoringD: 76 mm

TCCoringD: 93mm

How we deal with this new problem?

Bit properties

picture Damage

TCNon coringD: 93 mm

Cracks appear due to weak bricking

Finishing remains unhurt

TCNon coringD: 66mm

Good Suggestion for next step

TC Non coringD: 76 mmTC 6 mm×6mm

Step 2: Designing new bits and stabilizers by result of past drillings

New changes:

Increaseof TC dimension: 6 mm×6mm

New ways for exist of cuttings

Step 2: Designing new bits and stabilizers by result of past drillings

Increase dimension of cuttings

A Cutting act as a

base

Spiral motion of drilling system

Crack in wall

surface

To prevent spiral motion and lateral motion Special stabilization was

designed

Adding this type of stabilization decrease lateral movement; however, these holes do not supply enough area for escape of cuttings

These holes were considered for escape of cuttings

……Other bits and a stabilizer were designed and cracks that appeared in each step led to development of final drilling system and technical drilling….

Final Bit

Final Bit

Final Bit

Final Bit

Coring part of bitguide the bit way

Non-Coring partMain Drilling part

How the new designed bit act?

Masonry Wall

Masonry Wall

Rod

Coring part of bitguide the bit way

Non-Coring partMain Drilling part

Escape lineOf cuttings

Conclusion

1. Rate of penetration with non-coring bits is high. However, these bits are not as precise as coring bits. In spite of high precision coring bits are not so fast due to several pull out of the bits for emptying the cores.

2. If non-coring bits are used, as the size of TCs increases, the deviation of the hole will increase. Larger cuttings lead to asymmetric engagement of TC and cuttings and make a permanent change in the axis of rotation.

Conclusion3. Stabilizers are used to increase the accuracy and decrease the deviation in drilling path. Although, it must be noted that they increase air pressure on the surface of the holes and crack the finishing.

4. The most important result of this study is the combination of coring and non-coring bits. To stabilize the drilling path and decrease the deviation, a guide is installed on the TC-Non-Coring bit instead of stabilizers. On the whole, this drilling bit contains a TC Coring bit which cores from the masonry walls. This bit penetrates through the wall as a guide and prevents the bit from deviation and out of axis rotation. In a short distance from the TC-Coring bit, TC Non-Coring bit is installed. This bit crushes the cores and makes the cuttings ready for being removed from the hole as dust. The smaller the cuttings are, the lower air pressure is needed to remove them.

Conclusion5. This newly invented bit could use for mining, oil and other excavations as well.

6. Hydraulic drilling machines have a better performance compared to SGZ Rotary machine because they are larger.7. The drilling technique must be such that the bit pressure would be minimum.

Conclusion8. The brick type, mortar and the quality of bricking are determining factors for setting the drilling speed and air pressure. It seems that we can’t have exact quantities of such factors now; however, an expert drilling operator may achieve this.9. During drilling operation, the speed of rotation and air pressure could be set by observing the size of cuttings. An expert can minimize the size of cuttings by paying attention to it.

Thanks for your kind Attention