Geological studies for the planning and construction of Tumut 2 underground power station

b-.lrá¿

CEOLOGICAL ^STUDIES FOR THE PLANNING AND CONSTRUCTION OF TUMUT ² UNDERGROUND

POWER STATION

By David

H.

Stapledon, B.Sc.

Engineering Geologist, Snowy Mountains Hydro -Electric

Authority,

Australia ^.

Thesis for the Degree

^of

Master

of

Science, submitted

to the University of

^Adelaide

Ec onomic G eology Department.

This Thesis

is

^{eubmitted with the} kind permission of the Snowy Mountains Hydro-Electric

Authority.

The views expressed ^are those of the Author, ^and not necessarily those of the Authority.

AUTHORTS STATEMENT

Ttris tJlesie contains no material previously

submitted by me for a degree at

^any

University.

To

the best of my knowledge i.t contains no

materíal previously writteu

or

^{published by} another per6on, except when due reference

is

made in the text.

D.H.

Stapledon Z?nd Auguat, 1961.

TABLE OF. CONTENTS

SUMMARY INTRODUCTION

ACKNOWLEDGEMENTS

SCOPE OF. GEOLOGICAL V/ORK REGIONAL GEOLOGY

Snowy Mountains Tumut ? A.tea

Rock Types and

Their

Occurrence Geological Structure

PRELIMINARY INVESTIGATIONS AND SITE SELECTION DESIGN

Prelirninary Layout of the Power Station Objectives of Geological \dlork

Detailed Exploration Exploratory Tunnel

Detailed Geology from Deeign Stage Work Rock Types

Jointing Minor Faults

Final

Layout of the Power Station Orientation of t,l-e Machine Hall Prediction of Rock Behaviour

Application of Rock Behaviour Studies Gr oundwate

r

Observations

Goncrete Aggregates CONSTRUCTION

Scope and Objectives of Geological ^'.li[ork Geological ^Logging

GeoLogy of the Completed Excavations Granitíc Rocks

Primary Structuree in the Granitic ^Rocks Porphyry Dykes

Primary Structures in the Porphyry Dykee

Dolerite Dykes

Pgge

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CONSTRUCTION (cont. ₎ Geological Structures Set

(i)

Structures Set

(ii)

Structuree Age Relationships

Groundwater Inflowe During Constructic¡n Excavation

Machine Hall Roof

Deepening of Machine Hall to

RL.

¹⁸⁰⁰

Completion of the Excavation

t:tÁ

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42 44 47

DISC USSION CONC LUSION REFERENCES APPENDIX I.

APPENDIX

II.

APPENDIX

lil.

ILLUSTRAÎIONS Figure

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DESCRIPTIONS OF MAIN ROCK TYPES PHYSICAL PROPERTIES OF' ROCKS ROCK BOLT SUPPORT

AT

THE POÏIIER

SlATION

48 48 49

53 58

6l

65 ó8

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73

7ï

5 6

?

I

9

Title

Location and Project Layout Regional Geology

Turnut 2 Power Station, Surface Geology Sections showing Geology and Groundwater Observations

Design Stage Geological Investigations

Typical Summarized Logs of Diamond

Drill

^Holes

Rock Behaviour

Geology of Completed Excavatíon

Control Building Access Gallery and Machine Hall Crown

Drive,

Geological Log, Sheet

l.

Machine Hall Roof, Geological Log.

l0

-lb-

ILLUSTRATIONS ^(Cont. ₎ Figure_

ll

T2

l3

PLATES

Title

Machine Hall Upstream

Wall,

Geological Log.

Machine Hall Downstream Vï¡all, Geological ^Log.

(t)

f,ine

'ttrall;

_{(20) Line}

Wall;

^lüorkshop.

Geological ^Log.

View of Tumut 2 Power Station

site,

^looking north along the valley of the Tumut River.

Painted cardboard model, used during design stage exploration

for

Tumut 2 Power Station.

Drill

Holes 5703 and 5?06, sealed off by rneans of rubber packers and fitted with valves and pressure gauges.

Core from

Drill

Hole 5704 between 210 and 350 feet.

Schlieren in Happy Valley Granite near its contact rx,ith Bocmerang Creek Granitic Gneiss, exposed in the Tailwater Tunnel.

Intrusive contact between porphyry dyke and Happy Valley Granite, exposed

in

Penetock Tuunel

No.

6.

Face cf typical slickensided

joint

in granitic

gneis s .

Typical joints in a porphyry dyke.

Relative movernent of adjacent

jcint

blocks in

granite,

indicated by the displacement of ^a xenoLith,

Relative moveñrent clf adjacent joint _blocke in granitic gneise, indicated by the 0.5 to 0.75 inch displacernent of a prominent elickensided joint.

I

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4

5

6

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PLATES ^(Cont. ₎

II

- lc

-

Sheared ^zone

in

granitic gneiss, exposed in wall of the Transformer Hall.

Intersection of three crushed searns, ranging from 0.1 to 0.5

in.,

^exposed

in

Tumut ² Tailwate

r

Tunnel ^.

Tumut

2,

Excavation of Machine Hall.

Excavation of Machine Hall (continued).

Granite in the central portion of the Machine

Hall downstream

wall,

showing breakage along

line-drill

holes and across the rock fabric.

Granitic gneiss at the Control Building end

of the downstream

wall.

The rock has broken along joints and minor faulte.

Crack open ae much as 0.05 inch developed in the reinforced concrete

collar

of Penstock Tunnel No.

6,

^during excavation of the ^Machine Hall.

Title

Primary

Comprçssive Stresses at Tumut 2 Power Station Site

Weathering Products of Granitic ^Rocks Rock Condition Clas sification

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TABLES Table No.

I

Page

24

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