Study On Macro- And Micro-mechanical Properties Of Sandstone-concrete Composite Interface Under Dry-wet Cycle

Under the condition of heavy rainfall,the variation of water level of the bank slope of the reservoir forms a frequently changing wet and dry cycle environment,which affects the stability of the bank slope of the rock or concrete reservoir.In this paper,by making sand-concrete samples,the basic wet and dry cycle test simulated the natural environment,the macroscopic drawing mechanics test and shear mechanics test,and the microscopic test and nuclear magnetic resonance test were conducted.To explore the macro and micro mechanical characteristics changes of sandstone-concrete interface under the action of dry and wet cycling,and draw the following conclusions:1)Through the drawing mechanical test,it is concluded that there are two forms of failure force of sandstone-concrete samples.The low-strength samples are sandstone expansion and extrusion failure,while the high-strength samples are shear failure.The failure is mainly divided into three stages: elastic deformation stage,concrete failure and extrusion stage and concrete sliding and falling.2)Through the shear mechanics test,it is concluded that the shear strength of sandstone-concrete samples gradually presents a linear decline trend under the action of dry and wet cycling.The shear stress is mainly provided by the sandstone-concrete interface bonding strength and friction force,and the failure can be divided into three stages.3)The distribution and development of internal pores of the sample can be more clearly observed through the meso-mechanics test from T2 spectrum and NMR,and the law of strength changes of drawing mechanics and shear mechanics is verified.4)The sandstone-concrete interface cracks were observed from the optical microscope magnification.The degree of pore development of the samples in different regions could be obtained by the GR sequence measurement.The change results of macroscopic mechanical parameters were verified from the micromechanical characteristics,and the failure mode and mechanical strength of sandstone-concrete samples in the drawing test and shear test were explained.