Published Online: 19 September 2008
Page Count: 11
Cox, Brady R.
Assistant Professor, Department of Civil Engineering, University of Arkansas, Fayetteville, AR
Stokoe, Kenneth H.
Jennie C. Graves and Milton T. Graves, Chair and Professor, Department of Civil, Architectural, and Environmental Engineering, University of Texas, Austin, TX
Rathje, Ellen M.
Assosiate Professor, Department of Civil, Architectural, and Environmental Engineering, University of Texas, Austin, TX
(Received 15 October 2007; accepted 4 August 2008)
An in situ test method for evaluating the coupled response between excess pore water pressure generation and nonlinear shear modulus behavior has been developed. This technique is an active, strain-based method that may be used to directly evaluate the liquefaction resistance of soils in place. The test is based on the premise of dynamically loading a native soil deposit in a manner similar to an earthquake while simultaneously measuring its response with push-in sensors. Dynamic loading is performed via a large, buggy-mounted hydraulic shaker (vibroseis) that is used to generate vertically propagating (downward), horizontally polarized shear waves (Svh-waves) of varying amplitude within an instrumented portion of a liquefiable soil deposit. The newly-developed, push-in sensors consist of a three-component (3D) MEMS accelerometer and a miniature pore water pressure transducer. The new test method has been used to conduct field experiments in liquefiable soil deposits approximately 3 to 4 m below the ground surface. These tests were successful at measuring: (1) excess pore water pressure generation, and (2) nonlinear shear modulus behavior in native silty-sand deposits as a function of induced cyclic shear strain and number of loading cycles. These accomplishments represent a large step forward in the ability to accurately evaluate the susceptibility of a soil deposit to earthquake-induced liquefaction. While typical test results are presented herein, this paper primarily focuses on the equipment, field testing practices, and data analysis procedures for the new test method.
Paper ID: GTJ101484