A consolidation test (Taylor, 1948) was conducted on a sample of soft Chicago silty clay. The specimen had a dry weight of 343.57 g and a density of solids of 2.65 Mg/m3. The area of the ring was 93.31 cm2. A displacement transducer was used, which has a precision of one ten thousandth of an inch (1 x 10-4 in), and the incremental stresses applied to the specimen were recorded in kgf/cm2. Direct measurements of the thickness of the specimen were as follows:

1.254 in when under 1/8 kg/cm2

1.238 in when under 1/2 kg/cm2

1.215 in when under 1 kg/cm2

Deformations to the nearest 10-4 in recorded during the test are listed in Table P9.14. Required:

(a) Use a spreadsheet to plot the e versus log σ' and/or the e versus log σ' curve for this test.

Determine the pre-consolidation stress and the appropriate compression index.

(b) Use a spreadsheet to plot dial reading versus (t) 1/2 for each increment and determine cv. Plot cv versus log σ'.

(c) Same as part (b) only use the Casagrande log time-fitting method.

(d) For two increments, one before and one after the pre-consolidation stress, compare the values of cv as determined by the two fitting procedures

TABLE P9.14 Converted Transducer Deformation Readings in 10 in. Loading Increment (kg/cm) 1 to 2 8 to 16 /s to 4 to to 1 Elapsed Time (min) 2 to 4 4 to 8 1343 47 149 385 -2 63 179 422 1392 53 60 1435 14 75 196 464 101 115 1489 19 214 506 154 169 204 4 23 92 233 555 1539 227 6 4 26 101 251 604 1595 259 278 267 30 108 653 1646 309 332 12 4 32 114 281 701 1700 357 372 119 1750 399 16 34 290 745 410 20 35 123 297 799 1800 440 442 470 498 25 36 126 303 830 1844 464 30 4 128 874 1887 37 310 36 1921 38 130 314 906 525 498 42 44 938 39 1951 133 134 326 1006 2013 575 532 60 40 137 335 1103 2078 563 100 41 604 200 42 350 2121 629 582 141 1203 365 1258 2150 654 400 44 144 601 47 385 1343 2201 701 632 1440 149 -2 (reset to) reset to 0