DEPARTMENT OF MINERALS AND ENERGY

BUREAU OF MINERAL RESOURCES, GEOLOGY AND GEOPHYSICS

SMR Record 1974/13

c.4

Record 1974/ 13

GEOLOGICAL OBSERVATIONS AT SEVERAL CONSTRUCTION SITES, AT CANBERRA (NORTHSIDE ) AND PHILLIP, ACT. 1967-68

by

D.E. Gardner

The information contained in this report has been obtained by the Department of Minerals and Energy as part of the policy of the Australian Government to assist in the exploration and development of mineral resources. It may not be published in any form or used in a company prospectus or statement without the permission in writing of the Director, Bureau of Mineral Resources, Geology and Geophysics.

Record 1974/13

GEOLOGICAL OBSERVATIONS AT SEVERAL CONSTRUCTION SITES, AT CANBERRA (NORTHSIDE) AND PHILLIP, ACT. 1967-68

by

D.E. Gardner

SUMMARY

INTRODUCTION

CONTENTS

BUILDING SITES AT THE INTERSECTION OF NORTHBOURNE

AVENUE WITH MACARTHUR AND WAKEFIELD AVENUES

PAGE

1

1

Introduction 1

Topography and general geology 1

Site investigation 2 Foundation materials 2

Clay and limestone 2

Distribution of the limestone 3

Origin of the clay 3

Foundations 3

General 3

Block 9, Section 7 4

Block 12, Section 50 4

DRILL CORE FROM SITE OF PROPOSED BRIDGE OVER SULLIVANS 5

CREEK, BOLDREWOOD STREET, ACTON AND TURNER, A.C.T.

Introduction Geology

Drilling results

Foundation level TRENCH IN FRONT OF DRILL HALL, KINGSLEY STREET,

ACTON, A.C.T.

Introduction

Geology

East of excavation

EXCAVATION FOR SECOND ARTS BUILDING, AUSTRALIAN

NATIONAL UNIVERSITY, CANBERRA, A.C.T.

Introduction

Geology

5

5

5

6

6

6

6

7

7

7

7

BUILDING SITES ON BLOCKS 2 AND 1, SECTION 5, DARWIN

PLACE, CANBERRA CITY

Introduction

Site geology

Soil

Bedrock

_ ;rqinting .

Cleavage

Faulting

BUILDING SITE, BLOCK 1, SECTION 12, CANBERRA CITY

Introduction

Site geology

Soil and decomposed bedrock

Bedrock

Jointing

Cleavage

Faulting

Foundations

BUILDING SITE, BLOCK 2, SECTION 33, REID

Introduction

Geology

Unconsolidated deposits

Bedrock

Foundations

BUILDING SITES, BLOCK 17b AND 17a, SECTION 8, PHILLIP,

A.C.T.

Introduction

Topography

Geology

8

8

8

8

8

9

9

9

10

10

10

10

11

11

11

11

13

13

13

13

13

14

14

14

14

15

15

Soil

Bedrock

Thickness of weathered bedrock

Description of weathered bedrock

Lithological note: Shale fragments in Welded Tuff

Description

possible origin

Jointing

Faulting

Foundations

15

16

16

16

18

18

18

18

19

19 Weathered bedrock: Load-bearing capacity 19

Suggested foundations

General 21

Block l7b 21

Block l7a 21

Actual foundations 21

Load-bearing capacity of soil, including 22 decomposed bedrock

REFERENCES 23

APPENDICES

Both appendices refer to the Boldrewood Street Bridge Site report.

1. Geological logs of diamond-drill holes Nos. 2 and 5

2. Metric conversion charts: Feet to metres and inches to centimetres

TABLES

l. Standard penetration tests, Biock 12, Section 50, Lyneham

2. Soil-pile friction, Block 12, Section 50, Lyneham

3. Attitudes of minor thrust faults Block 1, Section 12, Canberra Ci ty

4

4

12

FIGliRES

PLATES

Page

4. Attitudes of minor faults or joints that 12 are associated with alteration of bedrock, column C10, Block 1, Section 12, Canberra City

5. Weathering of bedrock, Blocks 17b and 17 17a, Section 8, Phillip

6. Classification of weathered bedrock, 19 Blocks 17b and 17a, Phillip, with reference to ease of excavation and to load-bearing capacity

7. Standard penetration tests in colluvial soil 22 and decomposed dacite welded tuff, Blocks 17b and 17a, Section 8, Phillip

1. General locality map, Scale 1:250,000

2. Boulders and large blocks of, residual limestone in clay, in excavation for lift well, Block 12, Section 50, Lyneharn Approx. scale 1 inch: 3 feet.

1. Detailed Locality Maps

Scale 1 inch: 4 miles (1:253,440) Scale 1 inch : 2,000 feet (1:24,000)

2. Building Site, Block 12, Section 50, Lyneham

Plan showing positions of boreholes and of excavation at site of lift well. Scale 1 inch: 80 feet (1:960)·

Sections of boreholes Scale 1 inch : 20 feet (1:240)

Excavation at site of lift well: Sketch plan and vertical sections, floor and walls, scale 1 inch : 16 feet (1:192)

3. Site Excavation, Block 9, Section 7, Braddon

Locality map. Scale 1 inch: 400 feet (1:4,800) Locations of test holes. Scale 1 inch : 40 feet

(1:480) . Logs of bore holes. Scale 1 inch: 8 feet (1:96)

4. Proposed New Bridge, Bo1drewood St., Acton and Turner, A.C.T.

Locality sketch Scale 1 inch : 400 feet (1:4,500)

Plan and Section Scale 1 inch ': 20 feet (1: 242)

5. Trench in Front of Drill Hole, Kingsley St., Acton, A.C.T.

Locality map Scale 1 inch : 400 feet (1:4,800)

Sketch plan of floor of trench, se~i-diagrammatic, Scale 1 inch : 8 feet (1:96)

Sketch section of part of north-west face, semi-diagrammatic. Scale 1 inch : 8 feet (1:96)

6. Excavation at Site of Second Arts Building, Australian National University, Acton, A.C.T.

Locality sketch, Scale 1 inch : 400 feet (1:4,800)

Plan and sections of excavation, Scales 1 inch 40 feet (1:480)

1 inch 4 feet ( 1 : 4 8 )

7. Building Sites, Blocks 2 and 1 Section 5, Darwin Place, Canberra City

Locality sketch, Scale 1 inch : 400 feet (1:4,800)

Excavation for lift well on Block 2, Scale 1 inch : 8 feet (1:96)

Excavation for basement on Block 1, Scale 1 inch : 20 feet (1:240)

8. Building Site, Block 1, Section 12, Canberra City

Locality map, Scale 1 inch .: 400 feet (1: 4,800) Map showing bedding, fainting and cleavage at

some of the pier excavations, Scale 1 inch : 40 feet (1:48)

Diagrammatic geological sections of excavations at pier sites. Scale 1 inch: 20 feet (1:240)

9. Building Site, Block 3, Section 33, Constitution Avenue, Reid

Locality map, Scale 1 inch: 400 feet (1:4,700) Vertical section on north-east face of excavation,

Scale 1 inch : 20 feet (1:240) Plan showing locality of vertical section,

Scale 1 inch: 20 feet (1:240)

10. Building Sites, Section 8, Blocks 17b and 17a, Woden District Centre, Phillip, A.C.T.

Locality map. Scale 1 inch ~ 400 feet (1:4,800)

Map of eastern part of building site on Block 17b. Scale 1 inch: 20 feet (1:240)

Vertical sections through excavations for footings. Scale 1 inch : 20 feet (1:240)

Logs of auger holes and diamond-drill hole (Augered in overburden) Compiled from drillers logs. Vertical scale 'l inch : 20 feet (1:240)

GEOLOGICAL OBSERVATIONS AT SEVERAL CONSTRUCTION SITES

AT CANBERRA (NORTHSIDE) AND PHILLIP, A.C.T., 1967-68

SUMMARY

Most of the sites discussed are in or near the Civic Centre area of Canberra (the City Division), which is underlain by Silurian sedimentary rocks (Opik, 1958). The bedrock at the sites includes the Turner Mudstone, the Riverside Formation, the City Hili Shale and the St Johns Church Beds. One site is at the Woden District Centre, where the bedrock consists of dacite welded tuff.

In Northbourne Avenue, deep clayey soil contains boulders and large blocks of residual limestone which pass downwards to solid limestone. Moderately weathered Turner Mudstone provides solid foundations for a bridge where Boldrewood Street, crosses Sullivans Creek, but it increases the cost of trenching nearby in Kingsley Street. Fairly deep weathering of the bedrock and seams of clay are associated with faulting, mainly on a minor scale in mudstone and silty mUdstone on both the northwestern and the eastern sides of London Circuit. The St Johns Church Beds near the church are situated beneath ancient alluvium; they are highly to completely weathered down to the bottoms of the foundation excavations. In the Woden District Centre, major buildings are founded on weathered dacite welded tuff, some of which contains angular shale fragments.

Foundations include piles, piers with belled conventional footings placed bedrock.

cast-in-place rammed concrete ends, spread footings, and on fairly strong, weathered

35·15'

\ ....

F ig.l

149·00'

'~4

~/

f~ ".1t kwkid: , ~ . .

149'00'

GENERAL LOCALITY MAP.

• • • •• •• Approximate bouncJtJry o f Conaflrra Urban 4r//o-/970149'15 '

J ~~ . '" . !' . - l... -' ;H('~ . . 2'lI)..:..,...., ·

. / I t. ' 1! , ,/ . .,,-.

" IInl , "''''' ''!. . I ~- f '-1 uU I , ',s r h lt. ) •

149'15 '

Boundary of area shown To accompany Record 1974/13

Map 1 of Plate1 155/AI6/1120

-<:

35"1:"

INTRODUCTION

This report gives a record of scattered geological observations made during brief inspections of several sites for buildings and other structures during 1967 and 1968.

Localities are shown in a general locality map (Fig. 1) and detailed locality maps (Plate 1).

Sites that were investigated in greater detail are described separately. These include the Secretariat Building Site, Parkes (Best & Henderson, 1968), the Camp Hill area, Parkes, (Henderson, 1969a), the CSIRO Headquarters site, Campbell (Henderson, 1969b), and a proposed Conference Centre site, Yarra1um1a (Buchhorn, 1968). Other sites which were investigated before 1967 are described by Gardner (1969); they include the sites of Kings Avenue and Commonwealth Avenue bridges; the Canberra Community Hospital, the northern suburbs main outfall sewer, Acton; a proposed weir site at the former Lennox Crossing (of the Mo1ong10 River), Acton; and the National Library site, Parkes.

BUILDING SITES AT THE INTERSECTION OF NORTHBOURNE AVENUE WITH

MACARTHUR AND WAKEFIELD AVENUES

INTRODUCTION

In 1966-67 buildings were scheduled for construction at the northwest corner of the intersection (Block 12, Section 50, Lyneham) and at the southwest corner (Block 9, Section 7, Braddon). Two buildings were to be provided at each site, one of eight or nine storeys and the other of two storeys.

The site on Block 12, Section 50 was inspected when the foundations were being prepared to gain geological information; additional information is available in a report on the site investigation (Press, 1967). The site on Block 9, Section 7 was not examined geologically; howev.er, information on foundation conditions is available in a report by Coffey & Hollingsworth (1965).

TOPOGRAPHY AND GENERAL GEOLOGY

The area is flat-lying and soil-covered; and rises gently towards the northeast. Bedrock consists of Lower Silurian shale and mUdstone and lenticular masses of limestone; it is deeply weathered. Formerly, a shallow quarry was worked for limestone in gently rising ground a few hundred feet (about a hundred metres) northeast of the intersection.

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SI~E INVESTIGATION

At Block 12, Section 50 (Plate 2, and locality 1 of Plate 1), in a preliminary investigation, eight 'Pengo' auger holes were drilled to depths that ranged from 9 to 16 feet (2.7 to 4.8 m). In a subsequent more detailed investigation, eight 'Gemco' auger holes were drilled, and two of them were deepened by diamond drilling. Standard penetration tests were carried out in three holes, using an automatic 140 Ib (45 Kg) hammer and split tube.

On Block 9, Section 7 (Plate 3, and locality 2 of Plate 1), in a preliminary assessment of the site (Coffey & Hollingsworth, 1965), ten initial test holes and three additional holes were drilled 'to refusal' with a 4-inch (10 cm) diameter continuous flight auger. Subsequently, two test holes were diamond drilled to greater depths. A few disturbed samples were identified in the laboratory and tested for moisture content.

FOUNDATION MATERIALS.

Clay and limestone

The auger holes were drilled 'to refusal' at 15.8 to 26 feet (4.8 to 7.9 m) in Block 12, and 2.6 to 15.3 feet (0.8 to 2.6 m), with an exceptional hole to 35 feet (10.6 m) in Block 9. All holes passed through stiff, highly plastic clay, and those in Block 12, which were the deeper holes, passed through limestone boulders in the clay. Two holes in Block 12 were diamond drilled to 33 and 49.8 feet (10 and 15.1 m), at which depths they had each penetrated 10 feet (3 m) of hard, solid limestone. Vertical sections of these holes are given in Plate 2.

Two holes in Block 9 were deepened by diamond drilling; one of them passed through 13 feet and 6 feet (4 and 1.8 m) of hard limestone, separated by 13.5 feet (4.1 m) of silty clay, and entered silty clay again at 37 feet (11.3 m). The other passed through solid limestone from 9.6 to 30 feet (2.9 to '9.1 m). Vertical sections are given in Plate 3.

An excavation for a lift well on Block 12 exposed an irregular mass of limestone that appeared to be the eroded upper part of a thick bed or lens; it was surrounded and overlain by clay that contained isolated masses and irregular pinnacles of the same rock (Plate 2 and Fig. 2). The largest body of exposed limestone measured about 18 feet by 10 feet (5.5 by 3 m) in the floor of the excavation and rose to a crest or rounded pinnacle about 9 feet (2.7 m) above the floor (Plate 2). A sketch map of part of the north wall shows the following section, from the surface downwards:-

Fig. 2. Boulders and large blocks of residual limestone in clay, in excavation for lift well, Block 12, Section 50, Lyneham, A.C.T. Approx. scale 1 inch : 3 feet.

Depth in feet (metres)

o - 4.5

(0 - 1.4)

4.5 - 7.5 (1.4 - 2.3)

7.5 -13 (2.3 - 4)

-3-

Description

Red or red-brown tenacious clay, mottled by a ferruginous staining or coating; contains some ferruginous pisolites.

Pale brown and yellow tenacious clay.

White, red and yellow tenacious clay, and irregular masses of limestone.

The irregular masses of limestone below a depth of 7.5 feet (2.3 m) are roughly rectangular and lenticular and range in width from less than 1 foot (0.3 m) to 2.5 feet (0.8 m); they rise from the bottom of the excavation to a maximum height of about 5 feet (1.5 m). One limestone mass was inspected after cleaning the dust from the surface. It was surrounded by an envelope of deep red, plastic, very tenacious clay 2 to 5 inches (5 to 13 cm) thick, which appears to possess a cleavage or fissility parallel to the surface of the limestone.

Distribution of the limestone

The irregular distribution of limestone near the surface - in the lift well and in the auger holes at both sites - and the presence of solid limestone at depth, suggests that extensive solution has taken place in thick limestone beds. These probably are interbedded with· calcareous shale and mUdstone.

Origin of the clay

The dark brown clay that occurs from the surface to a depth of 3 or 4 feet (0.9 to 1.2 m) is probably colluvial in origin. The red-brown, pale brown, and yellow clay is probably residual and resulted from decomposition of calcareous shale and mudstone. Through the process of weathering, limestone in contact with ground water is removed in solution, leaving a space or cavity; this is soon filled by settling of adjacent clay. The deep red clay with a fissile appearance that coats the limestone probably represents a small amount of argillaceous impurity in the original limestone. It has been pressed against the surface of the residual solid limestone.

FOUNDATIONS

General

For the two-storey building at each site, shallow footings were provided: the following paragraphs refer to the sites for the eight and nine storey buildings.

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Block 9, Section 7

For the nine-storey building at this site., where apparent large masses of limestone occur at shallow depths, the site investigation engineers recommended that the column loads be taken to the limestone by means of bored pier foundations. They recommended testing of each major footing prior to its excavation. Spread footings were used.

Block 12, Section 50

Because of the irregular or random distribution of the limestone, the site investigation engineers decided that pile foundations would be appropriate. Table 1 (Press, 1967) gives the results of standard penetration tests that had been carried out.

Table 1. Standard Penetration Tests, Block 12,

Section 50, L~neham

Depth in feet Hole D Hole F Hole H Strata (metres)

8 (2.4) 17 25 21 Hard dry clay

15 (4.6) 20 25 25 Hard moist clay

It was suggested that composite end-bearing and friction piles could be founded at depths between 20 and 25 feet (6.1 and 7.6 m); these are the depths of auger refusal in most holes.

Table 2 (after Press, 1967) gives an estimate of anticipated friction.

Table 2. Soil-Pile Friction, Block 12, Section 50,

Lyneham

Depth in feet Friction in p.s.f.

(g/cm2)

(metres) Meyerhoff Challis Recommended

0 - 10 840 1500 + 400 1000

(0 3) (410) (233 + 195) (490 )

10 - 22 900 250 +1000 1250

(3 6.7) (440 ) (1220 + 490) (610)

Value

the lift limestone positions

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Rammed, cast-in-place concrete piles were used. At well, one column footing was founded on solid and seven concrete piles were emplaced at the

shown in Plate 2.

DRILL CORE FROM SITE OF PROPOSED BRIDGE OVER SULLIVANS

CREEK, BOLDREWOODSTREET, ACTON AND TURNER, A.C.T.

INTRODUCTION

A new bridge is to be built over Sullivans Creek, Boldrewood Street, immediately south of an existing bridge (Plate 4, and locality 3, Plate 1). The depth to bedrock at the site was tested by augering, and core samples of the bedrock were obtained from two diamond-drill holes. A map showing the positions of the hoies and generalized geological sections is given in Plate 4. Geological logs of the cores are attached to this report (Appendix 1).

GEOLOGY

Bedrock at the site consists of Turner Mudstone (Opik, 1958). At a locality 500 feet southeast of the site,

where it was exposed in a trench late in 1967, the bedrock consists of thick beds of fairly hard slaty mudstone, which strike roughly northwest and dip about 30 northeast.

DRILLING RESULTS

Weathered slaty mudstone occurs at a depth of 2 feet (0.6 m) in hole 2 and 4.7 feet (1.4 m) in hole 5 (see Appendix 1, Geological logs of core). With small increases in depth, to 6.7 feet (2 m) in hole 2 and 6.2 feet (1.9 m) in hole 5, the bedrock is little-weathered, is fairly hard and is capable of sustaining a heavy load. The mudstone is thick-bedded or massive; an indistinct banding which is assumed to be parallel ~o the bedding dips 30 near the bottom of hole 2 and 450 to 50 in the upper part of hole 5.

The most common joints. dip 600 to 700 (with reference to a plane normal to the core length). In the upper two or three feet (half to one metre) of bedrock, the modal spacing of the joints is 4 to 5 inches (10 to 13 cm). In the deeper, fresher bedrock, the modal spacing increases to a range of 6 to 7 inches (15 to 18 cm) in hole 2, and 6 to 9 inches (15 to 20 cm) in hole 5. The bottom lift from hole 2, depth 17 to 20.5 feet (5.2 to 7.6 m) consists of two lengths of fresh core.

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Most joints are tight and smooth; some are stained dark, probably with a manganiferous coating, and others appear to be chloritic. Clay, 0.25 inch (5 mm) thick, coats a joint in hole 2.

A few of the joints dip less steeply, commonly at about 50 degrees. Fracturing of the core, probably during drilling, tends to take place at the intersections of these joints with the common more steeply dipping joints.

Zones or bands of brecciated core 1 to 3 inches (3 to 8 cm) thick, in some of which the core is partly decomposed to clay, occur in hole 2 from 16 to 16.3 feet (4.9 to 5 m) and at four places in hole 5, one at 12.7 to 13 feet (3.9 to 4 m) and three between 16.9 and 18.5 feet (5.1 and 5.6 m). The brecciated zones occur at minor thrust joints or thrust faults.

FOUNDATION LEVEL

Foundations suitable for heavy loading can be found at 6.6 feet (2 m) in hole 2 and 6.2 feet (1.9 m) in hole 5.

TRENCH IN FRONT OF DRILL HALL, KINGSLEY STREET, ACTON, A.C.T.

INTRODUCTION

A trench in front of the Drill Street, Acton (Plate 5, and locality 4 inspected in October, 1967.

Hall in Kingsley of Plate 1) was

The general area, though flat-lying and without appreciable topographic relief, slopes gently northwestwards, towards Sullivans Creek. In Kingsley Street and in front of the Drill Hall the surface has been levelled.

GEOLOGY

The trench exposed soil 7 feet (2.2 m) thick; it consists of an upper 2 feet (0.6 m) of red-brown sandy (?) clay with some ferruginous pisolites, and 5 feet (1.5 m) of pale brown and buff sticky clay.

The bedrock in the area (Opik, 1958) consists of Lower Silurian Turner Mudstone. In the trenches, the bedrock strikes northwest and dips northeast at an angle of 30 0

• It is thick-bedded, moderately weathered, grey in colour, and fairly hard. It is cut by two sets of closely spaced joints - interval of 4 to 8 inches (10 to 20 cm) - which have the following attitudes:-

Field designation

JO

J3

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Strike (magnetic)

040 - 0450

0050

Dip

65-680

south-east

600 east

These joints form the face of the lower part of the trench (the upper part is in soil).

Three other sets of joints were mapped:-

Jl 1000 850 south 0 0 J2 345 25 north-east

0 0 J4 0 70 west

The J4 joints are strong and through-going within the limits of the trench dimensions.

EASE OF EXCAVATION

Although the mudstone is fairly hard and very thick bedded, the numerous joints facilitate excavation, which was readily accomplished with a jackpick. The moderately weathered mudstone is not effectively excavated with a trenching machine.

EXCAVATION FOR SECOND ARTS BUILDING, AUSTRALIAN NATIONAL

UNIVERSITY, CANBERRA, A.C.T.

INTRODUCTION

In October, 1967, a site was levelled for a new Arts Building within the grounds of the Australian National University at Acton, A.C.T. (Plate 6, and locality 5 of Plate 1). Weathered bedrock was exposed at four places in a low bank along the southwestern edge of the site, where gently sloping ground had been excavated.

GEOLOGY

Beds of highly to completely weathered silty mudstone and fine-grained sandstone 2 to 12 inches (5 to 30 cm) thick were exposed at intervals along the bank, beneath two to three feet (half to one metre) of soil. The exposed bedding grades laterally into decomposed bedrock in which texture and structure are not recognizable. The bedding strikes 0550 to 0700 and dips 45 to 500 towards the southeast. Near the western corner of the site, the beds are disturbed,

-8-

apparently through dragging along minor reverse or faults. The strike of the faults was not observed; the bedding indicates that an eastern block moved relative to, or was thrust over, a western block.

thrust drag of upwards

BUILDING SITES ON BLOCKS 2 AND 1, SECTION 5, DARWIN PLACE,

CANBERRA CITY

INTRODUCTION

These two building sites are situated on adjoining blocks in Section 5, Canberra City (Plate 7, and locality 6 of Plate 1). Inspections were made of an excavation for a lift well in Block 2 and a basement excavation in Block 1. The area is flat-lying and slopes gently southwards. BedrQck consists of sediments of the Riverside Formation (Opik, 1958).

SITE GEOLOGY

Soil

The excavations exposed 3 of clay, which is mottled brown and well and is red in the basement generalized section was exposed, measured in feet (and metres).

o - 3 feet (0 - 1 m)

3 - 6 feet (1 - 2 m)

to 4.5 feet (0.9 red or purple in excavation. The

from the surface

to 1. 4 m) the lift following downwards

Clay; brown red and mottled

Clayey decomposed bedrock

Below 6 feet (2 m) Weathered bedrock

Bedrock

The bedrock consists of thick-bedded and massive slaty banded mudstone and silty mudstone; beds range in thickness from 2 inches (5 cm) to more than 5 feet (1.5 m); the common range is from 1 to 3 feet (0.3 to 1 m). Strike is northwest, and dips measured 26 to 350 to the northeast.

The bedrock is weathered but firm or fairly hard, except where it is strongly jointed and fractured near faults. At such localities it is very weathered and soft. An example is seen in the excavation in Block 2 above a minor thrust fault exposed in the southeast wall and southeast corner of the floor.

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In Block 1 a low angle minor thrust fault forms a broadly horizontal trace, but in detail an undulating trace, on the northwest face of the excavation. Above the fault plane the bedrock is decomposed; below, it is firm and hard. The bedrock is thoroughly decomposed in a fault zone about 10 feet (3 m) wide in the northeastern face of this excavation. The decomposition of jointed and fractured bedrock near faults is expected to decrease and become quite insignificant at moderate depths, say of the order of 10 feet (3 m) deeper than the site excavation. In the shear zone, decomposition could persist to much greater depths; for example, it has been proved to depths much greater than 100 feet (30 m) in the vicinity of Commonwealth and Kings Avenue Bridge foundations (Gardner, 1969, Appendix 2).

Jointing

The only joint sets recorded are a prominent platy jointing, and a steep cross jointing that cuts the platy joints in the northwest face of the excavation in Block 2. The platy joints are tight, clean and in Block 2 they are spaced at intervals of 1 to 6 inches (2 to 15 cm); the mode is about 3 inches (7 cm). In Block 1 the joint interval is about the same; locally it widens to a range of 1 to 15 inches (2 to 40 cm) with a mode of 5 or 6 inches (12 or 15 cm), and in the southeastern corner of the excavation it narrows to a range of 1 to 4 inches (2 to 10 cm). The northwest face of the basement excavation in Block 1 is formed by smooth surfaces of the platy joints, terminated by tight, clean, cross joints that strike 075 0 and dip 320 southeast.

Cleavage

The beds show well-developed slaty cleavage strikes between 150 west and 150 east of north, and 70 0 east.

Faulting

that dips

Minor thrust faults seem to be common, as is apparently the case throughout the Canberra area; they are illustrated in the plan of the excavation in Block 2 and the section of its southeast face, and in the section of the northwest face of Block 1. The fault surfaces are curved and usually dip at low angles (35 0 in Block 2 and apparently less than 20 0 in Block 1). They are commonly marked by a seam of white clay one or two inches (about 2 to 5 cm) thick; similar white clay may line small faults which branch off from the larger fault, cut across the bedding, and disappear by merging into the bedding within a distance of a few feet (about a metre). In the southeast face of the excavation in Block 1 (Plate 7) the bedrock between the thrust planes is pinkish red, decomposed and clayey; it is brecciated and locally

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hardened through silicification. visible in the crushed bedrock. over-riding block of a minor more jointed and weathered than

Narrow veins of quartz are The hanging-wall rock, in the

thrust fault is commonly much the rock in the footwall.

A normal fault and associated zone of shearing and brecciation occurs over a width of 11 to 12 feet (about 3.5 m) in the northeast face of the basement excavation (Block 1). This fault was covered by rubble elsewhere in the excavation and its attitude is not accurately known. The strike is about 020 0 magnetic and the dip 75 0 east. Over a width of 6 feet (2 m) the bedrock is decomposed to white, cream, and pale brown clay (band Al in Plate 7), and for another 1.5 feet (0.4 m) to clay stained dark brown by hydrated iron oxides (band A2 in Plate 7). Over another 3 to 4 feet (0.9 to 1.2 m) it is locally brecciated, sheared and decomposed (band A3 in Plate 7) •

BUILDING SITE, BLOCK 1, SECTION 12, CANBERRA CITY

INTRODUCTION

A 12-storey building was to be erected at this site. Column loads were to be taken down to sound bedrock by means of piers. A tentative foundation level was determined at a depth of about 17 feet (5 m), by means of drilling during preliminary site exploration. Excavations for footings were taken down to this depth, or deeper where bedrock conditions were unsatisfactory. A hole was drilled at the base of each footing to ensure a thickness of at least 10 feet (3 m) of sound bedrock.

Maps of the site and sections exposed in excavations are given in Plate 8 and locality 7 of Plate 1. Th in Plate 8 and locality 7 of Plate 1. The site is below the eastern edge of City Hill, where the ground surface slopes gently east and southeast. Bedrock consists of calcareous City Hill Shale (Opik, 1958).

SITE GEOLOGY

Soil and decomposed bedrock

A section from the surface downwards shows, typically:

Feet

0-2

2 - 4

4 - 6

(metres)

(0 - 0.6)

(0.6 - 1.2)

(1.2 - 1.8)

Clay soil

Clay, representing decomposed bedrock

Very weathered bedrock

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Bedrock

The bedrock consists of slaty mudstone, calcareous where fresh, in beds that have a common thickness of 4 to 12 inches (10 to 30 cm) and a range of 1 inch to 2 feet (2 to 60 cm). At a depth of 6 feet (2 m) below the original surface, the bedrock is weathered, and partly clayey and plastic. The plastic or clayey material tends to be localized along joints which have allowed entry of groundwater. The weathered rock is leached of soluble constituents, including calcium carbonate; it is coloured greyish yellow and creamy yellow. Deeper down in the holes it tends to be greyer and harder, but can generally be scratched with the finger nail. Near the bottoms of some holes it is fairly fresh, calcareous, blue-grey, and very hard.

The beds strike about north and nor~hwest; they dip to the east and northeast at an angle of 20 in three of the four pier excavations and 120 in the fourth.

Jointing

A platy jointing in which the spacing ranges from 1 to 6 inches (2 to 15 cm) strikes 075 to 0900 magnetic and dips 750 south. The joint surfaces are commonly hard, silicified, covered with a veneer of vein quartz, and stained with iron oxide.

Note: oA platy jointing in S3ction 7, Darwin Place, strikes 45 to 50 magnetic and dips 75 southeast.

Cleavage

A prominent slaty cleavage which tends to obscure the bedding is gisible ~hroughout the site: .Its.stri~e ranges frgm 335 to 355 magnetlc; at three localltles lt dlPS 65 to 73 east and at a fourth locality (site of column ClO) it dips 800 west.. The regional dip of the cleavage is to the east; the reversal of the direction of dip is possibly due to tilting of a block of bedrock along one of the thrust faults that occur within the area, or to drag of the bedding along a fault.

Faulting

Minor thrust faults were mapped in four of the five footing excavations that were inspected; their locations and attitudes are summarized in Table 3. One of them, at the site of column C3l is a bedding plane fault. The others cut across the bedding, and the fault surfaces are curved. Although the strikes and dips change in a short distance, two pairs of faults, each characterized by a particular attitude, are designated Set A and Set B in Table 3.

-12-

Table 3. Attitudes of minor thrust faults, Block 1,

Section 12, Canberra City

Location

C31

CS

C10

CS

C27

Strike o

273 o

020

0150

29!?o

33So

o 12 north

400

east-southeast)

SOo.. .. ~ 100 north-northeast)

) 730 east-northeast )

Remar~s

Bedding ~lane fault

Set A

Set B

C10 070 0 3S o north-northwest

* Where measured; the fault surfaces are curved

The minor thrust faults are lined with white clay, which has a conunon thickness range of 0.2S to 2 inches (S to 50 nun). Some of them are coated with hydrated iron oxide; for example, at column C31 an inch (3 cm) of soft rock and clay occurs in the hanging wall and a thin skin of hydrated iron oxide in the footwall. The two faults below column CS are lined with 3 to 6 inches (8 to lS 'cm) of white clay. In the first fault encountered in this excavation, at a depth of 13. feet (4 m) , the clay is accompanied by a black, friable substance, probably hydrated oxides of iron and manganese. Water constantly seeped from the fault, at a rate of perhaps 50 gallons (about a quarter of a cubic metre) per hour, and the excavation was kept dry by intermittent pumping. The white clay in the lower of the two faults extends vertically along adjacent joints to 2 feet (60 cm) above and 3 feet (90 cm) below the fault.

Locally, the bedrock around the intersection of joints, forms wedge-shaped brecciated and clayey masses up to several inches (some ten cm). A typical example of this local brecciation, on a slightly larger scale than usual, occurs below column C10i it is illustrated in Plate 8. There the bedrock is jointed or fractured between three curving minor faults or joints which have lengths of 10, lS, and 24 inches (2S, 3S, and 60 cm). Attitudes are given in Table 4.

Table 4. Attitudes of minor faults or joints that are

associated with alteration of bedrock, Column C10,

Block 1, Section 12; Canberra City

Strike Dip

2900 600

south-southwest (steepens upwards)

320 0 0 25 southwest

0150 0 75 east-southeast

-13-

Adjacent to the joints or fractures, irregular and wedge-shaped areas of bedrock are silicified, brecciated, and altered to white clay. The silicification occurs in irregular and narrow veins, up to 0.25 inch (6 rom) wide but lensing out over a distance of a few inches (the order of 10 cm). The white clay occurs in seams 0-25 to 0.5 inch thick (5 to 12 mro). The brecciated rock is coated with iron oxide which is commonly granular and friable.

FOUNDATIONS

The design load for the2 foundations was about 12 tons per square feet (13 Kg per cm). At most pier sites, the bedrock at foundation level was considered to be too weathered to be able to support this loading, and spread footings were provided at the bases of the piers.

BUILDING SITE, BLOCK 2, SECTION 33, REID

INTRODUCTION

The site is on the southwestern slope of a flat-topped area on which st Johns Church is situated. It is a few hundred feet (a hundred metres or so) distant from the crest and 15 to 20 feet (4.5 to 6 m) below it in elevation. The site is shown in Plate 9 and locality 8 of Plate 1.

The site was levelled by cutting in the northeast and filling in the southwest. A vertical section through soil was obtained in the low bank formed by cutting in the northeast. Some information on the bedrock was obtained from the excavations for footings, which went down through the soil into very weathered bedrock. No definite information was obtained on the load-bearing capacity of the weathered bedrock.

GEOLOGY

formed, alluvium resting exposed is:

Unconsolidated deposits

The flat-topped area on which the church is built is from the surface downwards, of soil, ancient river in the form of a gravel-bed, and decomposed bedrock on highly weathered bedrock. The section (Plate 9)

in the low bank at the northeastern edge of the site

-14-

Depth Description Feet (metres

o - 2.5

2.5 - 5

5 - 6.5

(0 - 0.75)

(0.75- 1.5)

(1.5 - 2.0)

Fill recently placed and compacted

Brown and red sandy and silty clay with a few pebbles near the bottom

Brown clay

The brown clay is probably decomposed bedrock and the soil above it is probably colluvial. The pebbles near the bottom of the soil were probably not deposited there by the river, but instead worked their way down a sloping land surface from the edge of the gravel bed higher up.

Bedrock

Bedrock in the area consists of Middle Silurian sedimentary and volcanic rocks of the St Johns Church Beds (Opik, 1958). Near the northeastern edge of the site, very weathered and decomposed sedimentary orange, yellow, cream, and bright red beds, were exposed beneath 6.5 feet (2 m) of soil. They appear to represent shale and mudstone, in part silty. The strike is 3500 magnetic and the dip 35 east.

FOUNDATIONS

Foundations suitable for light loadings were found at depths ranging from 3 to 7 feet (0.9 to 2.1 m) below the bottom of the gravelly colluvium. Footings and combined footings were placed in holes about 4 feet (1.2 m) square in the weathered bedrock at about 10-foot (3 m) centres. Of four samples taken at random from the bottoms of the excavations, two consist of plastic clay and two are non-plastic.

BUILDING SITES, BLOCKS 17b AND 17a, SECTION 8,

PHILLIP, A.C.T.

INTRODUCTION

Brief inspections were made of the foundation excavations for two buildings in Section 8, Phillip, during November and December 1967; one site is on Block 17b and the other on Block 17a. Each of the proposed buildings is to be of nine storeys, and would place fairly heavy loadings on the foundations. The sites are shown in Plate 10 and locality 9 of Plate 1.

-15_

A site investigation had already been carried out by Ground Test Australia who used a Gemco soil sampling and drilling rig for subsurface exploration. Twenty-six holes were drilled with spiral flight augers to the level of auger refusal. In four of the holes, standard penetration tests were taken in soils at depths of 5.5, 9.5 and 12.5 feet (1.7, 2.9 and 3.8 m), and the holes were continued 6 to 20 feet (1. 8 to 6.1 m) into the underlying rock by diamond drilling.

TOPOGRAPHY

The area was levelled during the preparatory stages of development, and now has a flat surface that slopes gently northwards. Previously, it formed a low rounded spur or divide that ran approximately north between Yarralumla Creek, nearly 1000 feet (300 m) to the east, and a shallow tributary creek 300 feet (90 m) to the west.

GEOLOGY

Soil

The area is covered by soil that ranges in thickness from 15 to 20 feet (4.5 to 6 m), where tested by augering (Gardner, 1963), at sites 600 feet (180 m) north of Block l7b, to 5 feet (1.5 m) at a site 150 feet (45 m) south of Block l7a. In the basement excavation of Block l7b (Plate 10) the soil is 9 feet (2.7 m) thick; it consists of sandy, silty clay with rock fragments.

Logs of auger holes compiled by the driller during the site investigation describe the soil as hard brown sandy clay with gravel and rock fragments. The drillers logs give the following range of thickness:-

Range of soil thickness shown in drillers logs, in feet (m)

16 - 19 (4~9 - 5.8)

12 - 15 (3.7 - 4.6)

8.5 - 11.5 (2.6 - 3.5)

Number of holes within this thickness range

Block l7b Block l7a

2 3

14 2

2 3

-16-

The soil thickness shown is greater than that obtained in the basement excavations. The drillers log state that the soil rests on decomposed bedrock; presumably the bottom three feet or so logged as soil consists of decomposed bedrock. The depth of weathering is very erratic in Block l7a. Shallower weathering along the western side of the excavation is men·tioned under Bedrock.

Bedrock

Thickness of weathered bedrock. The soil rests on weathered and decomposed dacite welded tuff. At the auger sites of Gardner (1963), mentioned previously, the .. Gemco auger penetrated thickness of 4 to 7 feet (1.2· to 2.1 m) of weathered bedrock before 'refusal'. The Gemco auger used by Ground Test for the site investigation penetrated 2 to 15 feet of weathered bedrock before refusal. The greater depth of perietration is due to the use of a carbide-tipped cutting bit. The greater apparent range in thickness is due partly to this, and presumably partly to the inclusion of a few feet of decomposed bedrock as soil in the drillers log; this was suggested in the paragraph on Soil to account for an exces·sive thickness of soil shown in the logs, in comparison with that observed in the excavation. Following .is a summary of the thickness of decomposed and weathered bedrock reported by the driller:-

Range of thickness of decomposed and weathered bedrock, driller's log in feet (m)

2 - 5 (0.6 - 1. 5)

5.5 - 8.5 (1. 7 - 2.6)

9 -12 (2.7 - 3.7)

12.5 -15.5 (3.8 - 4.7)

Number of holes with this thickness range

Block l7b Block l7a

6

6

3

3

6

o 1

1

Description of weathered bedrock. Three stages of weathering recognized in the building slte excavations are described in Table 5.

-17-

Table 5. Weathering of bedrock, Blocks l7a and 17b

Section 8, Phillip

Stage of Description Weathering

Completely Clay, enclosing granular mineral fragments (mainly quartz) of sand size and silt size

Highly Clayey products of rock weathering enclosed in a matrix of more coherent or harder material. The structure of the bedrock is retained to some extent; for example, jointing is visible throughout the mass.

Moderately Resembles the highly weathered bedrock, but the proportion of clayey material is much lower. The texture of the bedrock is recognizable, i.e., mineral grains can be distinguished, and they remain attached to one another. However, the mineral grains are weathered, and most of them are surrounded by films of weathered material. This has reduced the cohesion between grains, with the result that when the rock is broken, the fracture always passes around the grains, instead of through many of them.

This subdivision can be broadly recognized in the results of the site investigation. The completely and highly weathered were probably logged as decomposed (except that some of the completely weathered was included with the soil) and the moderately weathered was logged as moderately weathered.

In Block l7b, the material excavated was highly to completely weathered, except in the deeper excavation in the south-west corner, where the bedrock was only moderately weathered. In Block l7a the bedrock exposed beneath the soil down to basement level was completely and highly weathered except that, in two 3~foot (0.9 cm) lengths and one 5-foot (1.5 cm) length in the western wall, the bedrock is only moderately weathered from the floor to a height of two or three feet (0.6 to 0.9 m).

-18-

Lithological note: Shale fragments in welded tuff

Description. The weathered dacite-welded tuff at the eastern end of Block l7b (Plate 10) contains angular fragments of silty shale or mudstone, which range in dimensions from less than one inch (2 cm) up to at least 6 inches (15 cm). The fragments form abrupt contacts with the enclosing dacite welded tuff. Their sharp edges and corners are preserved, and thus the fragments must have been consolidated or indurated when they were caught up in the ash flow.

Possible origin. To account for these inclusions, three possibilities are considered:- (I) They are fragments from the wall of the vent or fissure from which the ash flow was extruded. (2) They occurred as damp mud on a mud flat that lay in the path of the ash flow; the surface layer became baked and indurated, and then was explosively disrupted by steam which formed beneath it. (3) The material from which the fragments were derived occurred as an outcrop of mudstone on a land surface over which the incandescent .ash flowed.

The first hypothesis is not a likely one. The inclusions show no evidence of hornfelsing, which might be expected if they came from a vent or fissure and they show no sign of attrition during passage through a vent or fissure. The second hypothesis would envisage the ash flow passing over say, a tidal mud flat, or a mud flat in a dried-up lake in the volcanic terrain. It seems unlikely that recently-deposited mud could become sufficiently indurated to remain on the form of fairly large angular fragments in the ash flow sheet. The third hypothesis involves the extrusion of the ash flow onto a land surface formed on well consolidated and indurated sedimentary rock. This would imply disconformity and probable unconformity between the ash flow and the sedimentary rock.

The tuff with the by dacite welded tuff fre~ appears to strike about 11 This is much steeper than sedimentary rocks mapped in

Jointing

argillitic inclusions is covered from inclusions. The bgundary

magnetic and dig about 80 west. the common 30 to 40 dip of the same general area.

Nearly all the exposed bedrock is closely jointed; the size of the rock mass bounded by joint planes is generally less than a foot (30 em) and commonly less than 6 inches (15 cm). Locally, the jointing is not so close, and blocks of bedrock bounded by joints are up to 3 feet (1 m) in dimensions.

-19-

Faulting

The site is intersected by numerous minor thrust faults, to which, probably, the close jointing is related. Slickensided surfaces are common; some are probably joint planes on which some movement has taken place. A fault exposed in an excavation for a footing is shown in Plate 10. It was visible in the walls of excavation A and would clearly pass beneath excavation B at a shallow depth.

FOUNDATIONS

weathered bedrock: load-bearing capacity

The three classes of weathered bedrock under GEOLOGY, Bedrock, are roughly classified in with reference to difficulty of excavating load-bearing capacity in foundations.

described Table 6

and to

Table 6. Classification of weathered bedrock in blocks l7b andl7a, Phillip, with reference to ease of excavation

and to load-bearing capacity

Degree of Weathering

Completely

Highly

Hoderately

Classification of material to be excavated

For engineering purposes this is essentially a soil. Excavated with shovel and blade type of equipment.

More resistant to disruption than a soil, but is easily excavated by bulldozer and ripper

To be classified asa soft rock (weathered rock). Can be excavated by jack-pick, making use of joints. Excavated by bulldozer and ripper with difficulty where joint spacing is wide (say a foot (30 cm) or more)

Load-bearing capacity in foundations

Suitable for light loading. Some settle­ment likely.

Suitable for moderate loading

Suitable for heavy loading. The foundations in Blocks 17a and 17b went down to about the transitional zone between highly and moderately weathered bedrock; this was considered adequate for loading of 12 tons per square foot (13 Kg per square cm)

-20-

Weathered bedrock was during the site investigation; information given in the report engineers:-

recovered as drill core following is a summary of by the site investigation

Drill hole

Block 17b

Hole 13

15

18

Block 17a

Hole 22

Core recovered Depth in feet(m}

From

19 (5.8)

23.5 (7.2)

22.5 (6.9)

14 (4.3)

To

25 (7.6)

29.6 (9.0)

28.5 (B.9)

34 (10.4)

Remarks

Generally hard;

grey; moderately

fractured; core

·.lengths 2 to 6

inches (5 - 15 cm)

Core very much more weathered with sUbstantial bands of almost complete decomposition inter­spersed with 1 to 2-foot bands of harder, less weathered rock. Sounder rock from 32 to 34 feet (9.8 to 10.4 m) - 2-inch (5 cm) core lengths, and fragments

Where core drilling was not undertaken, the level of auger refusal was regarded as the probable level of harder weathered bedrock.

The core recovered was described in the driller's log as generally slightly weathered; in the terminology of engineering geology, rock that is slightly weathered is discoloured but not noticeably lower in strength than fresh rock. At this site (and slightly weathered) fresh bedrock - dacite welded tuff - would have an unconfined compressive strength probably greater than 10 000 lb per sq.

-21-

The site investigation engineers considered that the rock that was cored in drill holes 13, 15 and 18 would be able to iupport foundation bea2ing pressures of 20 to 30 tons per ft (22 to 33 Kg per cm). They pr~ferred a more c02servative design pressure of 12 tons per ft (13 Kg per cm), which would reduce the effect of possible weathered zones and limit the need for extensive proving of the rock below the excavated level.

Suggested foundations

For Block l7b a nine storey building was proposed with an eleven storey tower at the western end, having basements at about 15 feet below ground level; for Block l7a, a three storey building was proposed, having a ground floor at about the existing surface level. The design of each building included relatively heavy structural sections which could not tolerate differential settlements. Because of the fairly shallow depth to rock, particularly below the basement of the major building, the site investigation engineers suggested that the foundations of all the buildings should be taken down to rock. At the sites of the cored holes, rock level was known accurately; elsewhere it would presurqably be the level of auger refusal, making an allowance of 2 to 3 feet (0.6 to 0.9 m) to cover the possiblity of boulders or weathered layers underlying harder rock.

Block l7b. The site investigation showed that the rock surface was 1 to 6 feet (0.3 to 1.8 m) below basement excavation level, with a maximum of 11 to 12 feet near one hole (hole l4). The site investigation engineers suggested after excavated pad footings ~earing dirictly on rock, using design pressures of 12 ton/ft (13 Kg/cm ).

Block l7b. Rock level was at a depth of 14.5 to 71 feet (4.4 to 9.4 m) below ground floor level. Bored piers were recommended for the three storey building, belled if necessary to provide a2equate bea2ing area, using a design pressure of 12 tons/ft (13 Kg/cm). A Williams or similar auger was suggested rather than a conventional Pengo, which would not be able to penetrate to rock level; a minimum diameter of 3.5 feet (1.1 m) was sugg~sted to allow hand excavation, if necessary, of a small thickness of material overlying rock.

Actual foundations

The foundations used were substantially those suggested in the site investigation report. They were modified locally to allow for excessive weathering and other defectsQ For example, the bedrock at the preliminary design level for footing B (Plate 10) was closely jointed and weathered. This was due presumably to fracturing associated

-~. "

-22-

with the fault that was visible in the excavation for Footing A. To provide a better foundation the north-western half of the floor at Footing B was deepened below the fault plane.

Load-bearing capacity of soil, including decomposed bedrock

Since the bedrock was fairly close to the surface, parameters relating to foundations in soil were not needed, and figures for the load-bearing capacity of the soil were not determined. It would be possible to make a qualitative assessment of the soil properties from the results of the standard penetration tests (Korol, 1960; Scott, 1969) i the results are summarized in Table 7; they could.be compared with the results of the same tests in clay in Northbourne Avenue, Lyneham (Table 1).

Table 7. Standard penetration tests in colluvial soil and

decomposed dacite welded tuff, Blocks l7b and l7a,

Section 8, Phillip

Description of Block: l7b l7a Depth ft (m) material penetrated __________________________________ ___

(based on driller's log) Hole 13 15 18

5.5 (1.7) Colluvial soil(2)

9.5 (2.9) very gravelly in hole 15 and below 6 ft (1.8 m) in hole 13

18

48

54

N(l) Value

12

28

21

21

More than

22

12

16

12.5 (3.8) Bedrock, decomposed in holes 15 and 18; weathered and decomposed in holes 13 and 22

23* 29* 16* *

6 in 3 in

Refusal to penetrate after (15 cm) 8 in (20 cm) (7.6 cm)

Footnotes: (1) Blows of a 140 lb hammer falling 30 inches (76 cm) to drive a 2 inCh (5.1 cm) sampling tube 12 inches (30.5 cm)

(2) Hard crumbly slightly moist to moist brown sandy clay with gravel and rock fragments.

-23-

The figures of Table 7 indicate that the colluvial soil is poorly compacted and would be capable of'supporting only light loadings. The decomposed bedrock, on the other hand, appears to be dense and compact and probably it would support moderate loadings. It is suggested that some experimental work would be worth while on the strength of the soils that result from in situ decomposition of the acidic volcanic rocks that are so widespread in the A.C.T.

REFERENCES

BEST, E.J. & HENDERSON, G.A.M., 1968 - Geology and· foundation conditions at the Secretariat building site, Canberra. Bur. Miner. Resour. Aust. Rec. 1968/11 (unpub1.)

BUCHHORN, P.A., 1968 - Geological and geophysical investiga­tion of the site of a proposed Conference Centre, Yarralumla, A.C.T. In Gardner, 1969, Geology of the Central area of Canberra. BUr. Miner. Resour. Aust. Rec. 1919/11.

COFFEY, D.D. & HOLLINGSWORTH, P.C., 1965 - Site investigation of proposed Braddon offices, Canberra, A.C.T. Foundation and Engineering Services pty Ltd, Report (No. 1592) to Civil & Civic pty Ltd.

GARDNER, D.E., 1963 - Soil augering at the Woden District Centre. Bur. Min. Resour. Aust. (Report, unpubl.) •..

GARDNER, D.E., 1969 - Geology of the Central Area of Canberra. Bur. Min. Resour. Aust. Record 1969/11 (unpubl.).

HENDERSON, G.A.M., 1969(a) - Geology of the Camp Hill Area, Parkes, A.CDT. Bur. Min. Resour. Aust. Rec. 1969/41 (unpubl. ) •

HENDERSON, G.A.M., 1969(b) - Geological investigation of proposed CSIRO site, Campbell, A.C.T. Bur. Min. Resour. Aust. Rec. 1969/65 (unpubl.).

KAROL, R.H., 1960 - SOILS AND SOIL ENGINEERING. Prentice-Hall. New Jersey.

OPIK, A.A., 1958 - The geology of the Canberra City District. Bur. Miner. Resour. Aust. Bull. 32.

PRESS, M.J., 1967 - Foundation investigations for proposed building at Northbourne Avenue, Lyneham, A.C.T. Monier Drilling Co. pty Ltd Report (No. 262.67) to Civil and Civic pty Ltd.

SCOTT, C.R., 1969 .. AN INTRODUCTION TO SOIL MECHANICS AND FOUNDATIONS. Maclaren & Sons, London.

APPENDIX 1

GEOLOGICAL LOGS OF DIAMOND-DRILL HOLES NOS 2 AND 5, BOLDREWOOD STREET BRIDGE SITE

British units of length in the logs may be converted to metric by r~ference to the charts given in Appendix 2

BUAfAU Of MINERAL RESOURCES. LOCATION 3S-S- lat .tovn. o.f" GEOLOGY AND GEOPHYSICS ~~;'fI;"! IUieIJB

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BUA£AU OF MINERAL RESOURCES, GEOLOGY AND GEOPHYSICS

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ANGLE r __ 'lONTAL __ 9:I...!::O~· ___________ _ DIRECTION _____ -::-

II.L 1,1k7S' GEOLOGICAL LOG OF DRILL HOLE

ISHEET / Of L COORIItNATES

OUCtiIPTION ~ or.:TH ~RAC_I~ ll,!' I~ STRUCTuRES

"hiOtOG .... COlOUR, 5TREMGTH, HIItOtiIIESS, He I LUll 15~r I LOG 1'% CORfII JOI-.", YU..s, SUIIIS, FAULTS,CAUSMEO tOHU

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APPENDIX. 2

METRIC CONVERSION CHARTS

[.

__ ,.'._.-.~.:-__ -,::.-:--'~.' .. "._'.~:.~ ..•. ~I~,:.~.;_:i:.:.:~~. " ... :-~.:::r._·.·:.~,,~: .. i':'i~,'_-t-.=_::':.:._ .. '=-.,-.:~~.'.'.~.'._~-~-~~,'_=.'~_::~i·_".·,~:,:.:-~~_'_~.~_~.:"_~~-:-~· •. _._~~:.-~=.~-::.-:=_:-"~'-_~_"~:.-,'.-_' .. ~~ .. ~.'.,,~ .. ~ _.,_-._. ~_'-_,~_=_.,' =-~',-",·_~ .. L.~_'-_~~:--_~:.'_~,'_·.:-:_:~::::_=-_,'.--. -_ ..•.• _~~-.-~._' .. -.-_.:-.::.':..-_.:. '.':·,i:,.~.~:_,,_L "._._

:

.,' ~,:~:.,"'--I------_ ".·_-_:-~·:r:;=¥::~jt~--=:~:~--=~:::~~:=:I-· ..... . -,,_~~ ... -

--. -

.. -• .~ ~'-

~-~=: -s~~}E~-:=~~~=~:t-=~:~fHl~~

,

DE TAILED LOCALITY MAPS FOR PLATE 1

GEOLOGICAL OBSERVAT IONS AT SEVERAL CONSTRUCTION SITES

WEST BASIN

. -Map2 Lo caLities 1 t o 8

To accompany Record 1974 /13

CANBERRA, A.C.T.

o 1 2 3 4

5 6 7 8 9

Site locality Block 12, section 50, Lyneham Bloc~ 9, section 7, Braddon. Proposed bridge over Sullivans Creek. Tren~h in front of drill halL, KingsLey Acto h.

st.

Arts \ building, Australian National BLoc~s 2 and 1/ section 5, Canberra BLock 1/section 12/ Canberra City. Bloc 2, section 30 ~ Reid.

University. City.

Bloc 5 17b and 17a, Phillip.

A I 8 J--- H7 -

Note: To identify sheet add suffix A,B"C or

D indicated In di agram e.g. H 7 A. C 0

1/1.

So le o

o

(Based on maps of the Interior:

published by the Department

Map 1 - based on sca le 1: 100,000 .

index 1:2[,00 Detail Maps 2 an d 3 - based

scale 1 inch: 1000 feet . ) of Canberra,

Map 3 b.ocal ity 9 , "1l les 1/2 a 1

1/1. !

1/1.. 1/2 K ILOMETRE

Series, on map

DRIVE

. .

155/AI6/IIIO

IJ1 o 8 N

" ,."

I

PLATE 2

BUILDING SITE, BLOCK 12, SECTION 50, LVNEHAM.

LOCALITY MAP

I

MACARTHUR AVE,

,

WAKEFIELD AVE.

PLAN SHOWING POSITIONS OF BOREHOLES AND OF EXCAVATION AT SITE OF LIFT WELL

60

70 r-(:j , -., t...: ,

1 8 --I .... r-J

G 0

" " PENGO AUGER DRILL HOLES. SECTIONS OF BOREHOLES

1 2 3 4 5 6 7 8 67-9 67·5 73'8 75'6 70'6 69'2 67'S 69·8

~ D d 1 Excavated 4 · f.R .Br:4 Dr.RdBr. 4 : Dr. &crumbly 4 ,: Dr.RdBr 35 ' Dr. Rd Br. Dr: Rd S . .., : . r: , Dr. Rd. Br.

. . Rd. WIth 5 7 : Rd.Br: S.5·~ RdBr: '. Sf.Yll. . Dr.Rd.B[ Ironstone. • YLl. g: Dk.Sr.

10 • ReI.Br. 9'5 Sf.YLL 9'7' Wh. '. 9·5 g 9'7 DRILLING REFUSAL REFUSAL 14 .- Rd. & Yll.12 Rd.&Yll.

STOPPED 1 6 ' REFUSAL REFUSAL REFUSAL

REF15AL

DRILLING STOPPED VERTICAL SCALE 9 10, FEET

0~--'-2 -.l METRES

"GEMCO" AUGER AND DIAMOND DRILL HOLES

Based on sheet J5D of AustraLian Cap"t~l Terr',tory, Deta',l Series, Survey Branch, Dept. of Interior, Canberra, A. C.1

A

R L 67r'5

C

75'5 o

72·4

E

68·5 F

68'5 G

68'5 H

67'9

SCALE o , o

200 400 FEET , , i : I

50 100 METRES

L..

F o

6 10

-

3 ,; Rd. Sr. 5 ; Gr. Hd.Dr. 8 •

3 .. Dr. Dk.Br. ': Dr. DkBr. 3 , IX.RdBr.

. ' Ylt. 9 ;., L' . ; Ight Sr. :: moist. 12 ~ med.mst. 15 ~ -FL .

~ Lt. Gr. :~ Light Br.

, Yll. N= 17

" mOist. 12

t· N=20 18 ': . 18

Dr.Dk.Sr. 3 . JRd .. Br. I moist "l1)earum : strength .

Yll.Mst. 15 ~ stiff .

; Dr: stiff. : Dr. Hd.

: Yll.Dr. 6 ~ Dk.Br:

2 . 5 : Dr. Stiff. • Sr:

N=21 ; N=25 6-5. BL. mottled . ! 8 : Yll Mst. Dk..5flff . . sfltf. '! moist.

~ Wh'dMst.1 5· N .. 13 15·5 ' N=25 . me - 15-8 B ttl d

3 ,Bt. Dr. Hard. Bl.Mst.

7 medium. 1 0 . Yll. stiff.

=

. moist. 22: . moist.

- - ______________ -! : 22'7 d Fl. 23 ~: • a; 22'5 7. HARD fS" ," 0

o 2 6 ~ CORE :'. Br. stiff. REFUSAL. - ~...J ~ rORE 2'0" ,~Cl

8r. most. 22·5

Yll.Mst·19 stiff. 20

22 25

REFUSAL. 26

• Fl. , REFUSAL. 19'5, r. mo e. Who 21.5' Brown.

Yll. soft satur .ated. REFUSAL.

REFUSAL.

4'5

• Dk. Sr.

: Mottled .- Hard.

REFUSAL.

- - - BOUNDARY OF EXCAVATION AT SITE OF LIFT WELL

SCALE 0 .. 0 80 FEET , - .-" , ' .......... ' -'i-I""'"""'-: ,1 ....... _, r" --Jl ,II"

o 1'0 20 METRES

x= 2 9 ~ - ~. z ~g ~ HARD 34·3 I ~A. o 33 ~ 35: ~ Br.stiff

39'8 0 . .

HARD 49·ca fa

RL REDUCED LEVEL.lN FEET. TO CONVERT TO CANBERRA DATUM ADD 1800

N = NUMBER OF BLOWS OF A 140Lb. HAMMER FALLING 30iocbes TO

PENETRATE 12'lDcbes BY A 2iocb DIAMETER SPLIT TUBE SAMPLER

EXCAVATION AT SITE OF LIFT WELL. SKETCH PLAN

AND VERTICAL SECTIONS FLOOR AND WALLS. PART OF NORTH FACE AT POSITION A-a ON FLOOR PLAN.

REFERENCE FOR SECTIONS 1=:=.1 CLAY

SCALE ~~--""I-Q---i ..;J1 p- FEET o 2 4 METRES

REFERENCE

o LIMESTONE

13'0 SITE OF COMPRESSED OR

RAMMED CONCRETE PILE AND DEPTH

TO WHICH PILE WAS DRIVEN BELOW

FL OOR OF EXCAVATION.

,..-, L _J FOOTING PLACED ON LIMESTONE

r~ '/ ... \ FILL

To accompany Record 1974/13 ..

PLAN OF FLOOR 2 a' 11'

,- -1 , , '-_J

SOUTH WALL

o;r.....--........ RED TENACIOUS CLAY WITH BLACK FERRUGINOUS MOTTLING AND OCCASIONAL PlSOLITES;

CRUMB STRUCTURE. 4·5 - -- - - --

PALE BR.QWN OR YELLOWISH TENACIOUS CLAY.

7·5 ~f-DEEP RED PLASTIC VERY TENACI OUS CLA~ , ,

WHITE RED YELLOW AND YELLOWISH TENACIOUS CLAY. , I

• FOOTNOTE: SHOWS A CLEAVED OR LAYERED STRUCTURE PARALLEL TO SURFACE OF LIMESTONE, •

~ PEBBLES & CLAY

~ LIMESTONE

Dr. DRY Flo FLOATER Rd. RED Gr. GREY Sr. BROWN Bl. BLACK VlL. YELLOW Who WHITE Ok. DARK Mst. MOIST Hd. HARD Sf. SOFT

NOTE: "GEMCO" AUGER REFUSAL AT 23' IN HOLE 'AN AND 22' IN HOLE "B"

~~/fll~/1111

J

\ \

SCALE~

lU ;z Ct: :J o en :r ~ Ct: o ;Z SECTION 7

AVENUE

~a

200 4QO 6pO FEET 6b 1:20 180 METRES

LOCALITY MAP Based on Sheets J 5 D dnd J 6 B of the Survey Branch of the Department of the Interior. Canberra. A.C.T.

4 I --

N

LOCATIONS OF TESTHOLES

3 , I

I

13 , I

1 ! 1n 17 \; --0-- --E)-----fN+' _

I f \;:r;J -, I •

I

12 I --0--I I • •

-0--i2

I

---0-­i8

2 STOREY BUILDI~G

5

@-----Q) :

9 STOREY 6/ DFi2------Ef)g--· , ,

BUILDING !

SCALE o 40 eo 120 FEET I iii I , '

o 10 20 30 METRES

LOGS OF BORE HOLES

4' 1"

17' 3"

DH1

~

*"

- VB (sil ty) and = fragments of =_ siltstone

3 0' 9" =

37' 7" => - VB (silty)

To accompany Record 1974/13

DH2

:W I 19'4" 19'8"

3 0' 0"

35' 0"

VERTICAL SCALE o 4 B I I ' i' I

o 1 2 3

7 8

P+

P+

9

0'10" =

= = DB P+

12 FEET I I

4 METRES

0' 7"

5'8"

7' 9"

10 0'8"

c RB 2'0" " = = DB == = and P+

- LB

7' 1"

- =LB P-(siLty)

15 'a" ==

15' I."

FOOTNOTES

1 = = - -- -- -==

= ~=

==:

-

-

RB

DB

LOGS OF BORE HOLES

P+

2 l' 0" ..

~-=-

= == --== --==-=

5'2" - -

6'4" :.==

00 00 000

9'6" 000

I

5 0'3"

= '='

RB

DB p+

: LB(silty)

VERTICAL SCALE 4 ~ 1f FEET

I

8'3"

6 0'10" ':

7'9" =

9' 0,,0-- DB P+ 9' 8" ...:. LB P+

10' 2"

o i I 2 :3 4 METRES

11 1 ' 0" I 6fo

=

~~ = RB (silty)

0° 4' 0" . 4'2"

P+

10' 6" = 10'6"

13 oro 00

P+

* Well interlocked jointed dipping 300 NW with a

3/Bin sedm of red clay and weathered limestone

:w Well interlocked joints dipping 40° W

I"' T

===

== ==-= ===

O.

RB

DB

LB

YB

P+

p-

DH

SITE INVESTIGATION BLOCK 9 I

SECTION 7 I BRADDON I A.C.T.

REFERENCE

Top Soil

Clay

Gravel

Limestone or Rock

Diamond drill hole

Auger Q.,Al, .. !, , , "; I I ~ d II!:,,. , I ' ,";' : : : !: : Ii' , 1 :' , i '; Ii, ' , . ,

Red Brown

Dark Brown

Light Brown

Yellow Brown

High Plasticity

Low Plasticity

Didmond drill Hole

PLATE 3

''"'',,",;

f

I 55/AIS/1I12

LOCALITY SKETCH of Austra-

the

2ll2,---+-9 50 0

/

r--------------------i/

STRIKE AND DIP ,,<0 OF BEDDING IN TRENCH 600 FEET SOUTH OF THIS LOCAL I TV.

SKETCH HOLE 2

PLA TE 4

PROPOSED NEW BR I DGE I BOLDREWOOD STREET, ACTON AND TURNER , A.C.T.*

/

* Now built; forms southern bridge of Barry

Drive Crossing of Sullivan's Creek

/ /

/

~/////

SCALE

/

x c/

/

10 0 10 20FEET ~I ~l~--~I ~~i--~I~,~i~1 3 2 0 2 3 4 5 6 ME TRES

SECTION, DIAMO~D DRILL HOLES

: HOLE 5

/ /

/

/ /

LEGEND

TN fvtN

o Diamond driLLhoLe

Auger hoLe o SuLLivans Crk.

Dip and strike of bedding.

RL 1850FT

COLLAR 1646.7

---- ------ --

1840

/

/ / I HARD ROCK 1830

/

1826.7 / / / /

/ I I I /

/ 1623.2 1820

To accompany Record 1974/13

155/AI6/1113

, I

~

'-.

Based on Sheet J6A of A. C . T . Detail Series Survey Branch; Department of the Int~rior

Canberra, A . C . T.

TRENCH IN FRONT OF DRILL HALlI KINGSLEY STj ACTON, A.C. T.

PLATE 5

a Feet O~ _________ ~J1~ ____ -. ____ ~I ____ ~_:: Scale 1- r . i ~ Metres o 1 2

\ \

"'/ .' /;/~' . ~ \

/ ; -"

./ 65 I ./ ./ / i

!

-oj

i

Sketch Plan of FLoor of Trench/

Semi - Diagrammatic. ", rid

tjQIES Qtj JQI~IS

Strike Dip Comment

JO ;. 0400

to045 654E Numerous; 4 t08 inches apart; form much of face of excavtlon

• • J1)s 100 855 Not numerous

• 0

J2 ~5 345 25NE Not numerous

~ 0 0

Numerous) for J3 005 60E much of face of excavation

J4 7i • • strong joints, 360 70W not numerous

To accompany Record 1974/13

l

5~ I / ',---

I I I

J f I

Semi - Diagrammatic Section of part of

North-West Face

---

1 Red-brown s~ndy clay I some ferruginous pisolites I

PaLe brown and buff sticky cl~y

71

- - - - - ~ Weathered slaty mudstone; I~\ \J2 '\ \ ~ fairly hard; t~ick.bedded ~ ~~ ',\ '\ \--- ~~ exc~v~ted With J~ck-plck L\ JO \, :J3 \

9 _ \ u-:s: \ ,

REFERENCE

"< Strike and dip of bedding

o Strike and dip of jointing

/ Strike and dip of cleavage

\ Trace of joint

1 55/AI6/1 14

200 0 SCAl 400 FEE T

EXCAVATION AT SITE OF SECOND ARTS BUILDING (A.N.U.) CANBERRA, A.C.T

SCALE 40 0 40 80 FEET

L' ~,-----rl -----,~'---,,~' 10 o 10 20 METRES

PLATE 6

N

REFERENCE

'60 6 60 120' METRES lOCALITY SKETCH 6r Dip and strike of bed-

Base-d on sheet J6C of AustraLi~n Capihl Territory Detail Series Survey Branch

/ /

Department of the Interior/Canberra, A.C. T A-B Sect ion line

SKETCH DIAGRAM OF BUILDING

B

DECOMPOSED BEDROCK (OBSCURED BY RUBBLE)

TRENCH (A.N.U. )

'--------,------, - ... ~---

AT SITE OF SECOND ARTS CANBERRA A.C.T.

~ DECOMPOSED BEDROCK

DECOMPOSED BEDROCK " ...... - ... ~ --, ."...,...." ,.' - -::::;--- - -, ;'" ---' ...... ---, ". , .... ; -- ---

/ ,.,~ ------, ."., .,,*"'--, ~~ ----I IT JfC--------::M~ .... -... -]f~~~-:----------- - -------------A SCALE

2p OJ 2p L.OFEET ~, ----~-----r,L---~I~I·

5 0 5 10 METRES

To accompany Record 1974/13

8

ding

155/AI6/1115

S K ETC H Based on Sheet J 6C of Austr;!llan C;:lpital

Territory Detail Series, Survey Branch,

Department of the Interior, Canberra, A_C.T.

200 , I

50

o I o

SCALE 400 FEET --._-,-_.--' -- H) 0 1M ETR ES

TN MN

I I f !

EXCAVATION FOR

SCALE

4 8 FEET 4 0 <--r--_.- ... - . -+ ._ ... 1 0

,.L .. -----r'METERS

Sketch pLin of floor ,

Small block e excaval~

b.twe.n joint and fau l t. Small block A .xcavated down to fault.

Beds not m,apped

LIFT WELL ON BLOCK 2 North -west w.LL Looking north-west sw shows bedding NW

= = I

'Y' = ,...,-: ~ """'r'i = 'J' = "'f' - I '"Y' = --r = 'I"'

NE

South-east waLL Looking south-east

Minor fault; marked by _-..: clay seam 1 to 2 inches ""

SE

ry-' = '\' = I =---r=-y" ry-'="Y'=

II II Ii 1/ /-~, f.- II

_1/ ~1 ~'! _ !~ So f t WE'a thE'_ rE'd bE'drock

'" thick_ Below f.\Ult, bedrock "'" less weathered and firm or ~"" fairly hard _ ""~

1"

South- west face looking north- east SW SE

. , , ! j ,

ILLustrates diagrammaticaLly platy jointing, mapped in part of south-west face . This jointing extends across the entire face Strike 050°, dip 750 east. Spacing of joints 1 to 6 inches, mode about 3 inches. Tight Joints; stained bLack.

PLATE 7

6UILDING SITES/ BLOCKS 2 AND 1, SECTION 5, DARWIN PLACE, ¢ANBERRA CITY/ A.C.T.

I=_T :1

h~~~~1

REFERENCE

CLayey soiL, mottled

Clayey decomposed

Shear zone

brown and red or purpLe.

bedrock

Strike and dip of bedding

Strike and dip of joint

Strike and dip of cleavage

Fau l t, pOSit 1011 approximate

EXCAVATION FOR BASEMENT ON BLOCK 1

\

/ /

To occompany Record 1974/13

/ /

/ --... " " / "

/ '"

/ Not excavated /

/ I

/ /

I

/

, "

/

Sketch

\

, I

\

/ /

pLan of floor

10 0 1--,- • -- I 3 0

70

25

.... ..

s

SCALE

10 , . ~-J -,

20 FEET ~ 6 Mt:TR'::S

SE

Part of north- east bce

Al A2

A3 A4

8 J P

Part

Sheared Sheared

Locally Weathed

and decomposed- } ~nd decomposed Fault brecciated and decomposed

bedrock.

Trace of bedding Trace of joints Trace of pLaty joints

of south-wes~ face showing pLaty jointing and s.lear zones

I

mn~mnmrr~~"TII~~~~mm~~mr,1 c o --

B Trace of bedding

Zone

Part of ~outh- east face NE thrust faults

showing minor SE

~= -, =T=

'AL tered \ and crushed bedrock between thrust ipLanes of reverse fauLt. Stri ke about hormaL to face, dip where observed ranges ifrom 400 to 600 .

Part! of "orth-west face showing minor DEPTH t t·

Feet metres SW hrus fault that dips gently westwards. NW

:5 ,: ~- --~~~ .. :-~':;~C,~ 7 21 I >:.-... '- I': -. ----r - -~' .. ~ -----"'" .. Thrust fault

16 49 __ L ~ ---

I 55/AI6/!!IE

PLATE 8 LOCALITY MAP

I I I

I

490 FEET

1io METRES

BUILDING SITE, BLOCK 1, SECTION 12, CANBERRA CITY.

I I

I '\~\o,

I -L..].O

MAP SHOWING BEDDING. JOINTING AND CLEAVAGE AT SOME OF THE PIER EXCAVATIONS.

Based on sheet J6D of· AustrCllian Capital Territory Detail Series I Survey Branch) Department of I nte ri or I Canberra I A.C.T.

18';5 .. CONTOUR SHOWI NG ~ -~

HEIGHT ABOVE SEA LEVEL.

I

. ~ .~. ",' .... ~..ili,fililim~_Itli!Wiiljlll!!II'*lhj_.If~

[7S y 30 STRIKE AND DIP OF BEDDING •

_F2 ,-~-

7'5 Pl ...... 76 STRIKE AND DIP OF JOINTING . I

[ 65 STRIKE AND DIP OF CLEAVAGE.

Pl PLATY JOINTING.

... ---1850

C5

TOPOGRAPHIC CONTOUR I APPROXIMATE .

I '\sl.~ I

I I

I

Of __ ~2 oL:......-----,--.:.I4P~-,-----=..L6,0~:__-----I.80. FEET SCALE 0'- • - . 1 ~ 15 1§ 20 METRES ~rv

o I

I.. /1 "0

SITE OF EXCAVATION FOR PIER AT COLUMN NUMBER C 5.

FAULT SHOWING ANGLE OF 01 P.

DIAGRAMMATIC GEOLOGICAL SECTtONS OF EXCAVATJONS AT PIER SITES

BEDROCK IS SLATY MUDSTONE WEATHERED CREAM AND CREAM-YELLOW. FAIRLY FRESH AND HARD AT BOTTOMS OF C31 AND C27. PLATY JOINTS , ARE COMMONLY SMEARED WITH IRON OXI DE AND COATED WITH QUARTZ.

VERTICAl SECTION AT cal AND IN BANK 5EEET NORTH OF C31. .. C 32 LOOKI NG NORTH-WEST

C 27

Depth in Feet. 0--........

Bedding is 6to18 inches thick.

"",.,. PLaty joi nting spaced 1 to 6 inches.

O.() LOOK I NG NQRTH-W E ST. (}S BLeached horizon gf SQjl.

LOOKING NORTH-WEST

~ iN~1~,I!:=1n~'2:t~\~c!~::f.;~::1i.etjons. 0

4·0 - Decomposed bedroCk grid i~!f r9rOCK!irudstonel ~epth SO ,........------,r---~..Bitblllll1..J:D.K\5itgOL In feet.

W~thered. bedrock buf~low and whitish; fairly finn.

Weathered slaty mudstone in beds

Beds 3to12 inches (plus)) indistinct. Platy jointing spaced 1to 6 inches. ~1'O 1-Tr-'[7""'T'~ 1 inch to 2feet.hcommonLy 4 to 12 inches F

thick. Greyis -yeLLow} fairly hardl .BEoowG bottom 2 feet ~rtLy rresher and Dluish- ~~

grey. Platy Joints spaced 1to6 inches# lined witfi quartz 0-2 mm thick.

F F High angle reverse faUlti attitude in floor of shaft 33~ 7fEAST.

t"";t~~ Zonet-to 2inches of ($ ~

f> 21'5~~~-

Bedding plane fault. 1" of clay in hanging W31.l; Skin d iron adele on footwaLL.

bl7"'~~~ ..BEQQING.. shearing, crushing J

F and clay.

C 5 LOOKING NORTH-WEST Depth in feet. 0,.-----,

C 10 LOOK I NG NORTH-WEST Platy jointing and cleavag~as in other excavations. Fault F1:29:> 1(fN. Lined by' band of clay and black iron oxide 3toS inches thick.

Depth in feet. o r-------,

Af3,C: Minor fauLts along which the bedrock is siLicified,brecciated and decomposed to white clay.

A:290060oS0UTH (but steepens upwards.)

8 : 3200 2SoS0UTH WEST.

C : 015° 7SOEAST.

To accompany Record 1974/13

F

17 F

~& " ~ ~

tJ~~ (j ~' )a: PLaty joints spaced 1toS inches.

Fault FF at 3feet above fLoor F2 .. ~...u

01SoS0°Eastj Lined withtto t inch white clay. Fault F2 at 2'6" above floor in south-east strikes

BErnlN 070~ dips 3So NW lined with t ~ inch wh ite clay. F1 :: ~!:::;::::==='J

26 1.-_------1

.. F2

-=. F1

Water seeps slowLy from fault. Bedrock decomposed to clay along joints adjacent to fault.

FauLt F2: 0200 400 EAST Lined with white clay 3 to 6 inches thick. White cLaytto 1 inch thick on joints adjacent to the fauLt.

I 55/ A16/1117

PLATE 9. BUI LDING SITE., BLOCK 3., SECTION 33., CONSTITUTION AVENUE, REID A.c.r

LOCALITY MAP o 200 400 Feet

S~le t-I ---+-f ...... ' --"T"j---' a 50 100 Metres

, " "- ,

Based on sheet J6D of Australian

Capi t~l Terri tory Detai l Series,

Sur v e y 8 r tl n c h" De part men t 0 f

the I nteri or, Canberra" A.C. T. ~ Proposed building site,

~ Levelled elrea

N

VERTICAL SECTION ON NORTH WEST- FACE OF

EX CA V A T ION.

Depth Metres Feet

o 0 r' O.S 2.5 -~ --

Floo r ot l'revell ~~ 5 ~>-area --2 - 6.51

Exc~v~tion -3- 10 (for drain pipe) -

FiLL, recent ly placed and c om pact ed

Brown and red sdndy Ind silty clay some pebbles

Bra Nn ela y -- .!:---

Sedimentary beds, very deeply weathered

At 9·5 feet bed ro c k w eat her e d but reelsonably firm and suitable for Ugh~ lo~djng

SCelle °1--1 ___ -.....L~-..-a 1 2 Met re s

PLAN SHOWING LOCALITY OF

VERTICAL I SECTION

/ Part of bou ndary

as building site

of area levelled

\ Locality of / h Vertical Section 35

11~ ..<)

1>0 ~ \ ~

o 20 40 Feet SCCll e It-----rj--IL....-.-.,..j ---JI

o 5 10 Met re 5

\

To accompany Record 1974/13 15S/AI6/1118

LOCALITY MAP

BASED ON MAP TP 97/68 OF THE

SCALE

NATIONAL CAPITAL 0 EVELO PMEN T COMMISSION

o ~O 400 FEET 0 .... ' ---";'60~---1';";'£O METRES

o LOGS OF AUGER HOLES AND DIAMOND DRILL HOLES (AUGERED IN OVERBURDEN)

HOLE DEPTH ft

o

(Compiled from dri llers logs.)

m o

A3

o . o

=

A'

o

= o .

A10

= o

=. o

=

ft m o 0 1'0 0·3

5·5 1-7 6'() '·8

013

H ~ 0·5 0·15 .3:(j'i).'g'

5·5 ',7

015

013 o

N 12

M.N.

--+ ----- -~

1\ 1\

. --+---REFERENCE

I;''T . I 'Lnm, topSOil

Sandy cl;;!y. with gr;;!vel and rock fragments

/I

/ /

I ,

/

/ /

/ /

-+-

/

1\

015 o

-+---

J\

---

-- +

\

/I \ \

\ , +

.-­-+ ---

+

--~ -- \ \ -\-

.-­+---

\ \

PLATE 10

MAP OF EAS TERN PART OF BUILDING SITE ON BLOCK 17 b

I

Y strike and dip of bedding. I

I I

I

GeoLogical boundary, position approximate.

- - FauLt

\1\ A 1\ \ Dacite weLded tuff

fi\YI Dacite welded tuff with inclusions ~ of .1nguLar shale fragments

~ +

Section line

Site footing

_. - S'ite boundary

OA Excavation tor footing descr'lbed in text

o Auger hole

D15 o Diamond drill hole

10·0 3<l o o =0 o '0

12·0 3-7

15'0 4-6

-o

= o

14·0 4·3 =

9,5 2·9

12·5 3·8 13-5 4·1 v I 54

9·5 2·9 no 3·4

13·5 4·1

0= 0, 28 v' I~ '0

0.1 Very gr;;!velly s;;!ndy

~ ~ f~eursa~inches Bedrock (Dacite tuff)

clay BUILDING SITES, SECTION 8, v v 14·5 4·4 v

18.0 5.5 v -v

v = "

17·0 5·2

200 6·1 V II I~ ~ I Decomposed

v =

v v 20·0 6·1

v 22·0 6·7 Auger refusal

22·5 6·9 Auger refusal

= v

v

27·0 8·3 Auger refusal

v , 25.0 7.6 v

End of hole

23·5 7·2

v v , V I v

29·5 9·0 I End of hole

VERTICAL SECTIONS THROU GH EXCAVATIONS FOR FOOTINGS

SECTION

X-V

o

9

16

SCALE q 10 20 FEET 0~--~2~'~l--~6METRES

x AI,

(Proj. ) v CoLLuvium. I I r I I

I I

Trac~ of J,fault

"' " •

~

---

(sandy SILty cLay and rock fragments.)

Weathered and decomposed tu ff.

Weathered tuff.

A3 (Proj.) V

N

Moder;;!tely weathered

Slightly weathered

standard penetration test -number of blows of 11,0 lb

(63·5 kg) hammer falling 30 inches ( 76 cm) to drive a 2-inch (S.1cm) sampling tube 12 inches (30.5 cm ).

W Section V-W showing calculated pos dian of fault below footing B.

.

!J

E 5 mall block of bed rock to be ex ca vat ed and rep lac e d by con ere t e ,

1/

'. "- Be-d rock is weathered tuff, containing angular shale fragments, 26

30

FOOTING A

" \, "l "-"

" " 'lEI i .i ...

"

FOOTING 8

BLOCKS 17a AND 17b

WODEN DISTRICT CENTRE,

PHI LLI P, A.C.T.

SCALE

NOTE: SEE

o o

10

i 2 -------

C.D.W. DRAWING

20

NO. CS 67/119 8.

I ~~/AI5/1119