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Chapter1
DETERMINATIONOFSTRENGTH
PROPERTIESOFGRANULARANDBRITTLE
MATERIALS
JanMaciejewski,PawełCiężkowski
1.1.Theoreticalintroduction
1.1.1.Testingofsoilandrock
Inviewofthecapabilitiesofconstructionmachinery,weareinterestedintheme-
chanicalcharacteristicsofsoilandrockmaterialsthatdefinethelimitstate,i.e.the
stateofstressinthesoilmaterialforwhichthematerialisstable.Whenthelimit
stateisreached,stabilityislostandtheprocessofplasticdeformationofthemate-
rialbegins.Atthecriticalload,theshearstressesalongthefailuresurfacereach
theshearstrengthlimits.Thismechanismisatypicalfailuremechanismoccurring
insoilandrockexcavationprocesses[12].Examplesofdeformationmechanisms
inprocessesoftoolinteractionwithcohesivesoilareshowninFigure1.
Fig.1.Deformationmechanismsincohesivesoil:a)wallthrust,b)excavatorbucketexcavation
Todate,thereisnocompletedescriptionofthesoilexcavationprocessgiving
ananswertohowtheforceonthetoolchangesandhowtheconfigurationofthe
excavatedmaterialchangesduringtheprocess.Todate,plasticitytheorysolutions
arelimitedtostaticsolutionsthatdeterminethevalueanddistributionofstresson
thestructureforagivenconfigurationandparametersofthematerial.Thistype
ofapproachintheanalysisofsoilexcavationprocessesisquitedifferentfrom
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