Study on the Shear Strength of Carbonate Sand by Single Shear Test

The carbonate sand is the main soil material in the underground space of island reef soil. The shear strength of carbonate sand is studied by direct simple shear tests under constant volume and constant stress conditions on two kinds of carbonate sand with different relative density and by contrast tests on quartz sand with the same particle distribution gradation. The test results show that for the same particle size distribution, carbonate sand has a critical friction angle higher than that of quartz sand, its phase angle and maximum dilation angle lower than that of quartz sand. At the same time, the maximum dilation angle, phase angle and critical friction angle of carbonate sand are affected by particle breakage, of which the maximum dilation angle and critical friction angle decrease with the increase of breakage, while the phase angle increases with the increase of breakage. In this study, the critical friction angle and dilation angle are considered as the "effect angle" of particle breakage. By introducing the relative density that affects particle breakage, a calculation model for the maximum internal friction angle of carbonate sand based on the existing evaluation methods is proposed.