1.254 in when under 1/8 kg/cm2 — consolidation test Taylor 1948 was conducted sample soft Chicago silty clay The — 1/8 kg/cm2

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

SOLUTION

Adjust loads to stresses:

Determine e:

Vs = Ms / ps = 0.34357 kg / 2650 kg/m3 * (100 cm)3 / m3 = 129.649 cm3

Vt = area * height = (93.31 cm2) (1.254 in) * 2.54 cm / in = 297.207 cm3

Vv = Vt – Vs = 297.207 cm3 – 129.649 cm3 = 167.53 cm3

eo = Vv / Vs = 167.56 cm3 / 129.649 cm3 = 1.292

Determine strain, Ɛ: % strain = (deformation reading) * 10-4 / 1254 in * 100

Determine e (e1) at each load:

∆e = Ɛ(1 + eo); ei = eo – ∆e

ei = eo – Ɛ(1 + eo) (refer to table and plot for solutions)

Transducer

Load Effective Stress Reading Vertical Strain Void Ratio

(kg/cm2) (kPa) (10-4 in) (%) e

0.125 12.263 -- -- 1.292

0.25 24.525 47 0.3748 1.283

0.5 49.050 149 1.1882 1.265

1 98. 100 385 3.0702 1.222

2 196.200 1343 10.7097 1.047

4 392.400 2201 17.5518 0.890

8 784.800 2902 23.1419 0.762

16 1569.600 3536 28.1978 0.646