An analysis of the influence of clay structure on piezocone penetration test results

The effect of clay structure on the piezocone penetration test results and its mechanism are not very clear, the structured Cam-clay model is firstly program-implemented in the ABAQUS software. Then, the numerical model of piezocone penetration into structured clay is established, and the effect of clay structure on piezocone penetration test results is analyzed through numerical simulation. The numerical calculation results show that (1) the clay structure causes the increase of deviatoric stress of the soils surrounding the cone tip, and the maximum deviatoric stress appears at the lower right at some distance from the cone tip due to the structural damage of the soils near the cone tip. (2) The larger the parameter p\text'_ \rmyi representing structural strength is, the larger the cone tip resistance q_c, and the larger the parameter w representing structural damage speed, the smaller the q_c value. (3) The larger the p\text'_ \rmyi value is, the larger the excess pore water pressure u when the penetration stops, and the larger the w value is, the smaller the u value when the penetration stops. (4) The value of the empirical cone factor N_kt decreases obviously with the increasing p\text'_ \rmyi , and decreases slightly with the increasing w . Therefore, the structural strength of clay and its damage will obviously affect the measurement results of the piezocone penetration test, and the empirical cone factor N_kt considering the structural effect should be used to estimate the undrained shear strength s_u of the structural clay based on the cone resistance q_c, otherwise, the s_u of the structural clay will be underestimated. The research results can provide reference for the analysis and application of piezocone penetration test results.