For excavation case: f:BW{Cij;y
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1) Clay: low permeability, undrained condition. In this type of soil, Y#rao:I
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for example, in PLAXIS, you can have three options: Li7/pUq>}!
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A) analysis in terms of effective stresses (undrained material with E', v', g/T` 4"p[H
c', phi' and psi') ]p$fEW g
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B) analysis in terms of effective stresses with undrained strength q|Ga
parameters (undrained material with E', v', but with c_u, phi=0) Pu}2%P)p
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C) analysis in terms of total stresses (material is drained and dry, or non EnfSVG8kB8
porous, E_u, v_u, c_u and phi = 0) 7ZJYT#>b
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If you want to know the detail, please see the PLAXIS MANUAL. t/y0gr tm6
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2) Sand: drained condition because it has high permeability. The effective poisson's ratio should be input. Cu=0, and phi=some value. Undrained strength for sand should be zero. T T29 LC@
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Currently: Hardening soil model can not model the undrained condition for clay(total stress analysis). R2r0' Yx
Duncan-Chang model is best model due to the modulus depending on the stress level that is more suitable for excavation and backfill. )FgcNB 1|7
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Mohr-Coulomb model is quick for trial. The parameters are easy to get and the result can give you overview. I used this model, the results are good compared to the measure data. X\flx~
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To geofem: v/CXX<^U(
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"对于强透水性土", if the soil is clay, whatever the permeability is high, please use undrained condition, because it is the most unsafe status. If it is sand, use drained condition. zR]l2zL3
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To:daniellb1023: i5:fn@&
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"固结不排水": 1)固结, of course it is under drainage. Can you imagine soil can consolidate without water drainage. [,l BY-Kz+
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2)不排水, that means the after using confining stress, adding more deviator stress causing failure is under undrained(without pore pressure dissipate)
