Comparison of Measured Cyclic Resistance of Sand in Simple Shear Tests under Constant Volume versus Constant Total Vertical Stress Conditions

摘要

The simple shear test has been the preferred element testing method of choice for researchers and practitioners when it comes to laboratory evaluation of liquefaction and cyclic resistance of soil. The simple shear setup provides a close simulation of vertically propagating horizontal shear waves while providing a simple configuration to apply Ko effective confining stresses on the soil element. To better simulate field conditions, undrained conditions during shear is achieved by fully saturating the specimen and closing the drainage, preventing movements of pore fluid in and out of the specimen. However, this condition can be simulated by keeping the height of the specimen (and therefore, volume) constant during the test. The paper presents results from cyclic simple shear tests performed on Nevada sand. Undrained response to cyclic loading under the different testing conditions (constant volume versus constant total vertical stress) are compared at two different relative densities. The results show that the constant volume testing can result in lower cyclic strength if volumetric dilations occurred. This reduction in measured strength is particularly noticeable in denser sands.