Undrained Shearing Properties of Sand Permeated with a Bentonite Suspension for Static Liquefaction Mitigation

The undrained shearing properties of sand permeated with bentonite suspensions are studied to investigate the use of bentonite suspensions for static liquefaction mitigation. Rheological tests are performed to evaluate the penetrability and the thixotropic strength recovery of the suspensions. The results show that the initial viscosity and the yield stress are reduced significantly by adding 2% sodium pyrophosphate (SPP) to 10% bentonite suspensions. Moreover, the yield stress and the viscosity gradually increase with time due to the thixotropic nature of the bentonite suspensions. The shearing response of the permeated soil is observed by consolidated undrained triaxial tests on loose Ottawa sand specimens permeated with bentonite suspensions. The stress-strain response of the permeated specimens shows no drop in stress after the undrained instability state as compared to the response of clean sand specimens. Additionally, the undrained shear response of the permeated sand specimens displays no cohesion and the same friction angle as clean sand. This indicates that the sand fabric is relatively unaffected by the pressures applied to permeate the bentonite suspension. It is concluded that the permeation of bentonite suspensions could be an effective method of soil improvement for static liquefaction prevention in loose saturated sands.