Self-boring in situ shear pressuremeter testing of clay from Dalian Bay, China

Abstract

A new geotechnical in situ test technique using a self-boring in situ shear pressuremeter (SBISP) is developed to evaluate the initial state (horizontal at rest pressure Ph), deformation (yield pressure Pf and pressuremeter modulus EP) and strength characteristics (cohesion C and internal friction angle φ) of soil. The SBISP possesses a self-boring drilling functionality that can greatly reduce the disturbance of the tested soil. The multistage compound loading method, which applies normal stress incrementally to the soil in the test hole while repeatedly applying shear stress, was adopted.Relying on the investigation of the cross-sea traffic engineering of Dalian Bay, three sites in the sea area of Dalian Bay were selected for SBISP testing of clay. The field vane shear test (FVT), pressuremeter test (PMT) and unconsolidated-undrained triaxial compression test (UU) were also evaluated at each testing site to compare with the SBISP test. The results measured by the SBISP and comparative tests (FVT, PMT and UU) showed the same trends with an increase in depth and change in strata. The differences in the test results were discussed in terms of the disturbance effect, anisotropy of undrained shear strength, differences in loading methods and instrumentation used in the different tests. A comparison between the results measured by the SBISP and in comparative tests shows that the engineering characteristics of Dalian Bay clay evaluated by SBISP are fairly accurate and can provide reference for the investigation and design of the cross-sea traffic engineering of Dalian Bay.