A Refined True Triaxial Apparatus For Testing Unsaturated Soils Under Suction-controlled Stress Paths

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Title: A Refined True Triaxial Apparatus For Testing Unsaturated Soils Under Suction-controlled Stress Paths
Author: Perez-Ruiz, Diego D.
Abstract: A novel , computer -driven , true triaxial (cubical ) apparatus has been developed to test unsaturated soil specimens under suction -controlled multi -axial stress paths that are not achievable in a conventional cylindrical apparatus . The cubical cell implemented in this research work is a considerably refined version of those previously reported by Hoyos (1998 ) and Laikram (2007 ) . The refined version is a servo -controlled , mixed boundary type of cell that allows for full control and real time measurements of matric suction , net principal stresses and soil deformations along a wide range of simple -to -complex stress paths induced on cubical specimens of unsaturated soil . The specimen seats on top of a high -air -entry ceramic disk with a 5 -bar entry value .A comprehensive series of drained (constant -suction ) hydrostatic compression (HC ) , conventional triaxial compression (CTC ) , triaxial compression (TC ) , triaxial extension (TE ) , and simple shear (SS ) tests were conducted on compacted , 3 in (7 .62 cm ) per side , cubical specimens of clayey sand (SP -SC ) under constant suction states . Target suction levels are induced and kept constant during testing using the axis -translation technique . Results from suction -controlled tests under axisymmetric conditions were used for a thorough calibration of the elasto -plastic , critical state -based frameworks previously postulated by the Barcelona Basic Model (Alonso et al . , 1990 ) , the Modified Barcelona Basic Model (Josa et al . , 1992 ) , and the Oxford Model (Wheeler and Sivakumar , 1995 ) .Results from suction -controlled conventional triaxial compression (CTC ) and triaxial compression (TC ) tests were used for the validation of these models in predicting stress -strain response of compacted clayey sand under 50 , 100 , and 200 kPa suction states . Results were also used to validate the modifications proposed under the Refined Barcelona Basic Model framework developed in the present work .
URI: http : / /hdl .handle .net /10106 /1764
Date: 2009-09-16

Citation

A Refined True Triaxial Apparatus For Testing Unsaturated Soils Under Suction-controlled Stress Paths. Available electronically from http : / /hdl .handle .net /10106 /1764 .

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