Back Pressure Saturated Constant Rate of Strain Consolidation Device With Bender Elements: Verification of System Compliance
A back pressure saturated, constant rate of strain (BP CRS) consolidation device was modified to incorporate bender elements (BE) A series of laboratory tests were conducted on a dummy brass sample and on kaolinite soil samples, using the BP CRS and BP CRS BE devices, to determine the amount of system compliance for the BP CRS BE device, as compared to the BP CRS device. The amount of machine deflection was determined for both the BP CRS BE device and BP CRS device. Two approaches (quick and slow) were evaluated for determining the machine deflection. The machine deflection results, as obtained from both methods, were comparable; therefore, the use of the quick method is recommended. The respective average amount of maximum machine deflection (brass sample) and maximum corrected vertical deformation (kaolinite sample) for the BP CRS and BP CRS BE devices were 0.78 mm and 0.88 mm (machine deflection) and 3.15 mm and 3.43 mm (soil deformation) respectively. Consolidation parameters were determined by subtracting the amount of respective machine deflection from the amount of vertical deformation that was measured during the tests that were performed on kaolinite soil samples. The consolidation parameters, as obtained from both devices, were also comparable. The average values of recompression index (Cr) compression index (Cc) swell index (Cs) and coefficient of consolidation (Cv) for the kaolinite samples that were tested in the BP CRS and BP CRS BE devices were 0.07 and 0.08, 0.19 and 0.21, 0.08 and 0.07, and 9.3E 8 m2/s and 9.6E 7 m2/s, respectively. Because similar values were obtained for the consolidation parameters, as obtained by using wither the BP CRS device or the BP CRS BE device, the use of the newly designed BP CRS BE device is advocated because the BP CRS BE device also enabled collection of shear wave velocity measurements while the sample was being subjected to various stress levels.