Discontinuum Modeling of Underground Power House Excavation - A Case Study

7/23/2019 Discontinuum Modeling of Underground Power House Excavation - A Case Study

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Stress Analysis using 3DEC

A case Study

Dr. R. Venugopala RaoScientist & Head

Numerical Modeling

National Institute of Rock Mechanics

Kolar Gold Fields - 56 !!"


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Stress Analysis and Design ofUG Powerhouse using

Discontinuum Modeling

Introduction

#$%ectie

'escri(tion of the )ro$lem

Geolog* and Rock Mass +lassification

+om(utational Model

Results and 'iscussion

,ack nal*sis & Su((ort .aluation

Summar* and +onclusions


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Objective

State of stresses around the e/caations

'is(lacement distri$ution

./tent of failure 0ones

Interaction of multi(le e/caations

'esign of su((ort s*stem

.fficac* of Su((ort S*stem through ,ack

nal*sis


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Description of the Problem

Machine Hall 206x20.4x45.5m

Transformer Hall 191x16x24mPS Manifolds 4.5x5.5m, 6x6m

Passage Dc!s ".1x"m, 4.6x5.5m

#s Dc!s 11x".5mT$T Manifolds 6.6x"m


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Geology and oc!mass"lassi#cation

1 ranges from !234 to !2"

5 discontinuities

* Joint Sets cutting the powerhouse crown at Y=538.5 X=109.5

jset dip Aount dd !irection org "

# $ spacing eters nu

* !ip !irection with respect to %owerhouse A"is

jset dip &5 dd 11' org 109.5 538.5 &'

spacing ' nu 3

Insitu Stresses

SH !26 S

Sh !2 S


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"omputational Model

' 'iscrete .lement Model 75/7/5

.lasto-(lastic +onstitutie Model

Mohr-+oulom$ 8oint +onstitutie Model

Su((ort S*stems

Shotcrete 9+ured )late .lement

Ri$s .:uialent liner

Rock ,olt-.lement ;ith /ial and Shear

Stiffness


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Physico$mechanicalProperties


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Physico$mechanicalProperties

8oint )ro(erties

Shear Stiffness JKs = 0.97 GPa/m

Normal Stiffness JKn = 10 GPa/m

Cohesion = 0.0 MPa

Friction = !

"ensile Stren#th = 0


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%&cavation Se'uence (Support installation

Central G$llet an% si%e slashin# &ith '.!m

(ench hei#ht for )o&erho$se

*$s %$cts to (e e+ca,ate% in ! sta#es

Press$re shafts -"" manifol%s to (e

e+ca,ate% lea,in# a le%#e of !m till !00m

of P

F$ll2 #ro$te% 32&i%a# (olts of !7t

ca)acit2 &ith resin en% anchore% an% )re

tensione% to 1t


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)ac! Analysis ( %valuationSupports

oc4 *olt Fail$re

7 (olts at %ifferent ele,ations faile% &hen

Press$re shaft manifol% 5 &as o)ene%

*ac4 anal2sis6 re,ie& of s$))ort s2stem

Ca$ses of roc4 (olt fail$re


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Summary ( "onclusions

"he mo%el co$l% )re%ict the (eha,ior satisfactoril2

*olt fail$re mechanism co$l% (e e+)laine%

% The ex!en!s of roc& mass failres ha'e (een

redced )i!h !he *ro'ision of ri(s in !he cross

o*enings

% +i!h o! !he ri(s in !he cross o*enings, en!ire *illar

(e!)een !he MH and TH ca'erns exhi(i!s failre

% The *ro'ision of ri(s in !he cross o*enings ha'e

redced !he horion!al deforma!ion of !he d-s )all.


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% Maximm redc!ion of !he order 40 and 55 is o(ser'ed a!

/ /525M and / 510m res*ec!i'el

% The redc!ion in !he horion!al deforma!ions in !he -s )all is

lo)er com*ared !o !hose on !he d-s )all

% The maximm redc!ion of 40 is o(ser'ed a! / 510. The

redc!ion in deforma!ion a! /525M on !he -s )all is marginal

% The effec! of ri(s is no! seen in ser'ice (a area as !he cross

o*enings do no! exis! !here.

% The ri(s *ro'ide immedia!e and-or rigid s**or! allo)ing li!!le

deforma!ion, !here( con!rolling !he dila!ions arond !he

o*enings


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% The exis!ing s**or! ss!em in !he machine hall )as

adea!e

% 3r!her s!reng!hening measres )ere sgges!ed as follo)s

1. "m long d)idag (ol!s in *lace of 6m long (ol!s in (s dc!s * !o10m from T

2. $i( s**or! of SM# 250 a! 50mm c-c in PS manifolds

7. $i( s**or! of SM# 150 a! 1.0m c-c in D8 from $D 20"0 and

$D 170155 in -s )all of machine hall

4. $i( s**or! of SM# 150 a! 1.0m c-c in D8 from $D 090 and

$D 125145 in d-s )all of machine hall

Discontinuum Modeling of Underground Power House Excavation - A Case Study

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