Expansion Mechanism Of Weathering Front Of Rock Blocks With Low Permeability In Slope Unsaturated Zone

This thesis focuses on the expansion mechanism of weathering front of rock blocks with low permeability in slope unsaturated zone,to elucidate the expansion process of weathering front and the effects of different humidity on the expansion of weathering front.Using chemical analysis,rock thin section identification,electronic scanning microscope and other test methods,combined with theoretical research and numerical simulation.Results shown that the rock mineral structure near the weathering front of rock structure was mainly dominated by physical weathering,but less chemical weathering,and there were obvious differences in the structure of rock mineral in different weathering zones.In the initial stage of weathering,the water vapor got into the rock under the concentration gradient and atmospheric pressure,weathering front formed by the effect of preferential weathering.Water vapor began to diffusion inside the rock under the effect of concentration gradient.The numerical simulation results shown that the through-pole was the storage place and the mainly diffusion channel of the water vapor in the low permeability rocks.Water vapor diffused along the normal direction in rocks,in the form of convection-diffusion on both sides and caused by the edges of rock passivated.The completely weathering time of the rock and the diffusion rate of the weathering front were affected by the change of relative humidity.In ideal circumstances,the diffusion rate of the weathering front was gradually decreased and then increased rapidly.The research results have a certain practical significance for engineering problems and geological hazards such as rock avalanche,debris flow and etc.Specific works and main results were as follows:(1)Micro sandy fine feldspathic quartz sandstone was analyzed by the sandstone casting thin-section image processing under an electron microscope,and therefore two-dimensional sandstone pore diffusion model was established.(2)In the natural state,the storage and flow of the water vapor mainly occurred in the through-pole that the ccement being corroded and the flow of water vapor in the through-pole was in accordance with the general law of fluid flow.(3)The influence of relative humidity on rock weathering was mainly shown that the higher relative humidity the shorter time required for the complete weathering of rocks.Under the condition of low humidity,the change of the weathering front expansion rate was controlled by the actual water pressure in the air.Under the condition of high humidity,the change of the weathering front expansion rate was controlled by the concentration gradient.