Undisturbed piston samples of grey silty Chicago clay were obtained from a depth of -9 m as shown in the soil profile in Fig. P13.70a, for laboratory testing. Different types of strength tests as well as a consolidation test were conducted, and the results of the consolidation test are shown in Fig. P13.70b. Unconfined compression (UCC) tests on adjacent specimens from that depth had an average unconfined compressive strength of about 100 kPa.

(a) An additional specimen was trimmed and consolidated hydrostatically in a triaxial cell to 300 kPa; then it was sheared un-drained (CU test). Estimate the compressive strength of this specimen.

(b) A companion specimen of the same clay was also consolidated to 300 kPa, but then it was sheared drained (CD test). Estimate the compressive strength of this specimen.

(c) Estimate the water content at failure for both the CD and CU triaxial specimens.

(d) Estimate ∅’  and ∅_T for the two specimens.?

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1.00 Soil Description Dopth, m Brown silty clay (CL) W, - 22%, Ym = 19.7 kN/m 0.95 GWT 0.90 -3 Brown silty sand (SM) Wn- 30%, Yat= 18.9 kN/m 0.85 -6 • 0.80 Groy silty clay (CL) Wn= 34%, Ysat = 18.6 kN/m LL = 36, PL = 22 0.75 = wGs = 0.34 (2.70) = 0.92 0.70 -12 - 0.65 0.60 Vory denso "hand pan" til 10 100 1000 -15 oic (kPa) FIGURE P13.70a FIGURE P13.70b