地质岩土英文文献翻译Word格式文档下载.docx

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tensile

stresses.Flexuraltopplingfailureoccursbytensilestresscausedbythemoment

dueto

the

weight

ofthe

inclined

superimposed

cantilever-like

rock

columns.

Hence,

geo-structuraldefectsthatmaynaturallyexistinrockcolumnsaremodeledbya

series

of

cracks

inmaximumtensile

stress

plane.

Themagnitudeandlocation

maximumtensile

inrock

columns

with

potential

flexural

toppling

determined.

Then,the

minimumfactor

safety

for

columnsare

computedbymeans

ofprinciples

solid

andfracture

mechanics,

independently.

Next,

anewequation

isproposedtodeterminethelengthofcriticalcrackinsuchrockcolumns.Ithas

beenshownthat

if

length

ofnatural

crackis

smaller

thanthelength

ofcritical

crack,thentheresultbasedonsolidmechanicsapproachismoreappropriate;

otherwise,

result

obtained

basedonthe

principles

offracture

mechanics

is

more

acceptable.

Subsequently,

stabilization

oftheprescribed

slopes,

somenew

analyticalrelationshipsaresuggestedfordeterminationthelengthanddiameter

oftherequiredfully

groutedrockbolts.Finally,forquick

designof

rockslopes

againstflexuraltopplingfailure,agraphicalapproachalongwithsomedesign

curves

arepresented

by

whichanadmissibleinclinationofsuchrockslopesand

or

all

required

fully

grouted

rockbolts

In

addition,

acase

studyhasbeenusedforpracticalverificationoftheproposedapproaches.

KeywordsGeo-structuraldefects,In-siturockstructuralweaknesses,Critical

cracklength

...

1.

Introduction

Rockmassesarenaturalmaterialsformedinthecourseofmillionsofyears.

Sinceduringtheirformationandafterwards,theyhavebeensubjectedtohigh

variablepressuresbothverticallyandhorizontally,usually,theyarenot

continuous,andcontainnumerouscracksandfractures.Theexertedpressures,

sometimes,producejointsets.Sincethesepressuressometimesmaynotbe

sufficientlyhightocreateseparatejointsetsinrockmasses,theycanproduce

microjointsandmicro-cracks.However,theresultscannotbeconsideredas

independentjointsets.Althoughtheeffectsofthesemicro-cracksarenotthat

pronouncedcomparedwith

large

sizejointsets,yet

theymaycauseadrasticchange

ofin-situgeomechanicalpropertiesofrockmasses.Also,inmanyinstances,due

todissolutionofin-siturockmasses,minutebubble-likecavities,etc.,are

produced,whichcauseaseverereductionofin-situtensilestrength.Therefore,

oneshouldnotreplacethisin-situstrengthbythatobtainedinthelaboratory.

Ontheotherhand,measuringthe

in-situ

strength

interaction

complexparametersis

impractical.

anappropriate

approach

estimation

ofthetensilestrengthshouldbesought.Inthispaper,bymeansofprinciplesofsolidandfracturemechanics,anewapproachfordeterminationoftheeffectofgeo-structuraldefectsonflexuraltopplingfailureisproposed.

2.Effectofgeo-structuraldefectsonflexuraltopplingfailure

2.1.Criticalsectionoftheflexuraltopplingfailure

Asmentionedearlier,MajdiandAmini[10]andAminietal.[11]haveprovedthattheaccurate

factorofsafetyisequaltothatcalculatedforaseriesofinclinedrockcolumns,which,by

analogy,isequivalenttothesuperimposedinclinedcantileverbeamsasshowninFig.3.According

totheequationsoflimitequilibrium,themomentMandtheshearingforceVexistinginvarious

cross-sectionalareasinthebeamscanbecalculatedasfollows:

（5）

（6）

Sincethesuperimposedinclinedrockcolumnsaresubjectedtouniformlydistributedloads

causedbytheirownweight,hence,themaximumshearingforceandmomentexistattheveryfixed

end,thatis,atx=Ψ:

（7）

（8）

IfthemagnitudeofΨfromEq.

（1）issubstituted

ofshearingforceandthemaximummomentofequivalent

intoEqs.（7）and（8）,thenthemagnitudesbeamforrockslopesarecomputedasfollows:

（9）

（10）

whereCisadimensionlessgeometricalparameterthatisrelatedtotheinclinations