Page 94 - Water Standards

thickla y er , thesurroundin grockp ressurema ybedeterminedac-
cordin gtotheactin gforcesb ytheunstableblocksinthesur-
roundin grocks.
3 Forshallowburiedcavernsunabletoformstablearch,
thesurroundin grockp ressureshouldbedeterminedaccordin gto
theg ravit yofoverl y in grockmassabovethecavernroof ,and
shouldbeu p datedaccordin gtothesu pp ortin gmeasuresactuall y
usedinconstruction.
4 Ifcomp ositesu pp ortisused, thesurroundin grockp res-
sureactin gonthelinin gshouldbereducedp ro p erl yconsiderin g
theunloadin gp rocessofsurroundin grocks.
5 Forsurroundin grockswiths p ecialp ro p ertiessuchas
,
rheolo gyorswellin g etc., thesurroundin grockp ressureshall
bedeterminedthrou g hs p ecialstudies.
7.2.17 Theexternalwaterp ressureactin gonthelinin gshall
beanal y zedanddeterminedthrou g hen g ineerin ganalo gyorsee p -
a g ecalculationbasedontheg roundwaterconditions , thep erme-
abilit yofsurroundin grocksandthesee p a g econtrolanddraina g e
measuresado p tedinthep ro j ect.Forcavernsofunder g round
p owerhousesub j ecttoabundantg roundwater , reliabledraina g e
s y stemandwater p roofg routin gcurtainsshallbearran g eda-
roundandontheto pofthecavernsinordertoreduceorelimi-
natetheexternalwaterp ressure.
7.2.18 Backfillg routin gshallbeconductedontheto pofcrown
concretelinin g.Forsurroundin grockswithp oorinte g rit yand
develo p edfissures , consolidationg routin gma ybeconsideredand
carriedoutafterconstructionofconcretelinin g.Backfillg routin g
andconsolidationg routin gshouldconformwiththefollowin g s :
1 Thebackfillg routin gshouldcoveraran g ealon gthe
crownina60°120°centralan g le.Groutin gp ressureshallbede-

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