Vol18 No.10: 2776-2790
【Title】Influence of grain segregation on the behavior of sand in triaxial tests
【Author】YU Fang-wei1,2,3,4,5; PENG Xiong-zhi6; SU Li-jun1,2,3,4*
【Addresses】1 Institute of Mountain Hazards and Environment, Chinese Academy of Sciences, Chengdu 610041, China; 2 Center for Excellence in Tibetan Plateau Earth Sciences, Chinese Academy of Sciences, Beijing 100101, China; 3 China-Pakistan Joint Research Center on Earth Sciences, CAS-HEC, Islamabad 45320, Pakistan; 4 University of Chinese Academy of Sciences, Beijing 100049, China; 5 Department of Civil Engineering, The University of Tokyo, Tokyo 113-8656, Japan; 6 Department of Civil Engineering, Southwest Jiaotong University, Chengdu 610031, China
【Corresponding author】SU Li-jun
【Citation】Yu F, Peng X, Su L (2021) Influence of grain segregation on the behavior of sand in triaxial tests. Journal of Mountain Science 18(10). https://doi.org/10.1007/s11629-021-6709-3
【Abstract】As a common phenomenon in granular flow, grain segregation plays a great role in affecting the behavior of granular soil by causing a great change of grain-void distribution in granular soil. This paper presents an experimental study on the influence of grain segregation on the behavior of sand, by a number of triaxial tests to interpret the characteristic behavior, friction and dilatancy behavior, excess pore water pressure behavior and critical state behavior of sand incorporating grain segregation. An index - grain segregation index was proposed to quantify grain segregation. Grain segregation affected greatly the characteristic behavior of sand, causing the movement of void ratio-dilatancy relation of sand towards the increase of void ratio and dilatancy of sand. In the drained tests, the mobilized friction angle of sand showed a decrease followed by an increase but the mobilized dilatancy angle of sand increased, with increasing grain segregation index. An increase in grain segregation index impaired the basic friction of sand. In the undrained tests, the mobilized friction angle of sand showed an increase followed by a decrease with increasing grain segregation index. However, grain segregation caused an increase of the mobilized dilatancy of sand followed by a different development. An increase in grain segregation resulted in a higher summit of the dilatancy of sand but with a faster decrease along axial strain. In the q-p′ plane, grain segregation caused a reciprocating rotation of the dilatancy line and failure line of sand. Grain segregation resulted in enhancement of the peak-state dilatancy of sand, affecting greatly peak-state friction angle and peak-state basic friction angle of sand as well as the normalized excess pore water pressure. The excess friction angle of sand showed an increase followed by a decrease in the drained tests but increased linearly in the undrained tests, with increasing grain segregation index. The excess friction angle-over-maximum dilatancy angle of sand decreased in up convexity while increasing grain segregation index. Grain segregation resulted in rotation and translation of the critical state line of sand in the e-p′α=0.7 plane. However, in the q-p′ plane, the critical state line of sand showed an anticlockwise rotation followed by a clockwise rotation with increasing grain segregation index.
【Keywords】Critical state; Dilatancy; Friction; Grain segregation; Landslides; Soil behavior; Triaxial tests