Question

The following results were obtained from an undrained shear box test carried out on a set of undisturbed soil samples. 0.2 0.8 Normal Load (N) Strain (%) 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 0 21 46 70 89 107 121 131 136 138 138 137 136 0.4 Shearing force (N) 0 33 72 110 139 164 180 192 201 210 217 224 230 234 237 236 0 45 101 158 203 248 276 304 330 351 370 391 402 410 414 416 417 417 415 The cross-sectional area of the box was 3600mm and the test was carried out in a fully instrumented shear box. Determine the strength parameters of the soil in terms of total stress. (You may use the xls Direct.xls to (under direct shear test on Week 2) populate your data and present your results, or you can draw the plots on a graph paper, or a piece of paper).

Answer 1

CASE 1: Considering Normal load interms of "N"
From the given table :
Ultimate shear force values with respect to normal forces are 138N, 237N and 417N.

Since angle of internal friction value is more than usual. We have considered normal stress in kN

Normal Load Shear Load Normal Stress Shear Stress (N) (N) (kN/m2) (kN/m2) 0.2 138 0.06 38.33 0.4 237 0.11 0.22 65.83 115.83 0.8 417 140 Case - 1 120 100 80 Shear Stress (kPa) C= 13kPa 4 = 89.9° 60 40 20 0 0 0.05 0.2 0.25 0.1 0.15 Normal Stress (kPa)

CASE 2: Normal load in "kN"
Normal Load Shear Load Normal Stress Shear Stress (kN) (N) (kN/m2) (kN/m2) 0.2 138 55.56 111.11 38.33 65.83 0.4 237 0.8 417 222.22 115.83 140 Case-2 120 100 80 Shear Stress (kPa) 2 60 C= 13kPa = 24.8° 40 20 0 0 50 100 150 200 250 Normal Stress (kPa)