The Simple Shear Test Of Carbonate Sand And Macroscopic And Microscopic Mechanical Analysis

Calcareous sands are located widely in Taiwan Strait and the southern seas of China.Since the high void ratio,crushability and angularity of soil grains,the character of calcareous sands is quite different from that of quartz sands.In this paper,to provide technical supports for the construction in the area covered by calcareous sands,a series of simple shear tests were conducted,and the discrete element PFC was used to simulate the whole process of them.The tests described here were performed by a new generation of GCTS simple shear test system,which can simulate the actual stress state and analyze the change of dilatancy under the condition of fragmentation better.The main works and results are shown as follows:1?The simple shear test is carried out to study the relationship of stress-strain for calcareous sand.The influence of initial relative density,overburden pressure and stress path on dry and saturated calcareous sands are also researched.For comparison,the quartz sands with similar gradation are also introduced.2?During these tests,the crushing mode of calcareous sands is obtained by soil dyeing.The crushability of calcareous sand was quantified using Hardin and Marsal model.Based on the test results,the relationship between overburden pressure and crashing ratio are established.3 ?The change of dilatancy of calcareous sands under low and high stress is studied.At the same time,the stress condition and strength composition of calcareous sands under simple shear test were analysed.Then a strength composition relationship was established by combining the strength with the critical state.4?The discrete element analysis results reveal the law of evolution for particle crushing in consolidation and shear process;By studying the effects of particle crushing on shear strength;The characteristics of displacement field,the formation of shear band and the change of force chain in shear process were analyzed.