Abstract

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Title:: Characteristics of 3D Pore Structure Evolution of Nanjing Silty Sand During the Triaxial Compression

Author(s):: CAO Jian-qiu; ZHANG Wei; XIAO Rui; LIANG Xiao-long; XU Lin; LI Heng-zhen; 1. School of Earth Sciences and Engineering, Nanjing University, Nanjing 210023, Jiangsu, China; 2. Nanjing University (Suzhou) High Technology Research Institute, Suzhou 215123, Jiangsu, China

Keywords:: geological engineering; Nanjing silty sand; microCT; triaxial shear test; pore structure; 3D reconstruction; representative elementary volume

Abstract:: A close relationship exists between the evolution of micro pore structure and macro mechanical properties of sand during the triaxial shear test. The micro-triaxial shear apparatus developed by Nanjing University was used to perform the triaxial shear test on Nanjing silty sand; micro-CT scanning was used to obtain the evolution features of 3D pore structure of the specimen during the loading. The results show that the specimen exhibits strain softening-hardening-type characteristic of stress-strain curve; the friction at both ends of the sample impedes the specimen’s volume expansion, causing the drum type zone destruction occurring in the specimen; the porosity of specimen decreases from 46.3% to 40.9%, then increases to about 43.0%, and the porosity of failure zone increases obviously; according to the pore parameters of representative elementary volume of zone destruction area, the pores are compressed before failure, causing a decrease of the pore number by 32.4% and a decrease of the average pore radius by 48.8%, so that there are a concentration of the distribution of pore radius, and a good amount of pores with large pore radius occur in the post-failure zone; the dislocation of particles makes the edges of the particles broken, causing the pore shape tends to be regular.