MECHANISM BEHAVIOURS OF SANDS WITH FINES BASED ON INTERGRANULAR STATE VARIABLES

This paper is based on the discussion of the framework of sands with fines and the interaction between coarse and fine particles. It shows the intergranular state variables for a particular host sand mixed with different amounts of nonplastic fines. It presents large strain undrained shear strength (S_us) data and steady state line in triaxial compression for the samples. Results indicate that when D_rs >>0 (which is defined as intergranular relative density), the undrained shear strength of the composited soil of sand-silt is similar to that of homogeneous sand with e=e_c, which is high. When D_rs→0, the undrained characteristic of the samples is uncertain, but it is obvious that the undrained shear strength of the composited soil is lower than that of the homogeneous sand. When D_rs < 0, the composited soil exhibits the contractive behaviour caused by shear stress, and the S_us is lower than the others. In this research, the particular host sand mixed with nonplasitc fine is from Nanjing sand. The comparison between the test result and the predicted situation is done, and both of them is anastomose. The steady state lines in e_c-logS_us increases with the amount of the fines, and are parallel. The intergranular state variables can reflect the interaction between sand and fine particles, defined as force chain in cohesionless soil. This research is presented for the choice for the microstructure of sand mixed with fines.