Page 91 - Water Standards

beimp lementedbeforetheexcavationofmaincaverns ,and
shouldbearran g edincombinationwiththecavernsexcavatedin
advance.
3 Theg eolo g icalma pp in gshallbemadeintime , andthe
p otentialunstablewed g esorblocksshallbeforecasttimel y.
4 Theg roundwaterinsurroundin grocksshallbemoni-
tored.
7.2.9 Thesha p esofunder g roundcavernsformainp owerhouse ,
maintransformer , hi g hvolta g eswitch y ard, etc.shouldmeetthefol-
lowin g s :
1 Thecrosssectionwithverticalle g sandcurvedroofshouldbe
ado p tedforcavernsinstron gandsoundsurroundin grockswithsmall
insitustresses.
2 Thecrosssectionofhorseshoe-sha p eore gg -sha p eshouldbe
usedforcavernsinweakandfracturedsurroundin grocksormedian
q ualit ysurroundin grockswithhi g herhorizontalinsitustresses.
3 Thep rofileofcavernshaouldbefreeofabru p tchan g e
andacutean g le.
7.2.10 Inthesu pp ortdesi g nofunder g roundp owerhouse, the
bearin gca p acit yofsurroundin grocksthemselvesshallbeutilized
full y.Pro p ersu pp ortt yp eshallbeselectedaccordin gtotheg eo-
lo g icalconditionsofsurroundin grocks ,thesha p eanddimen-
sionsofcrosssectionofcavernsandtheconstructionmethod.
,
Thesurroundin grocksshallbesu pp ortedtimel y andtemp orar y
su pp ortdurin gconstructionshallbeusedasap artofp ermanent
su pp ortasfarasp ossible.
7.2.11 Forlocationssuchasthep ortalsectionofcavet yp e
p owerhouse, intersectionp ortionofcaverns , rockmassorrock
p illarbetweencaverns ,etc.,withunfavorablestabilit ycondi-
tions , su pp ortmeasuresshallbeintensifiedandp ro p erconstruc-

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