Mechanism Of Strength Deterioration Of Silty Mudstone In Acidic Environment And Stability Analysis Of Cutting Slope

Silty mudstone is mainly distributed in Hunan,Guangdong,Guangxi and other southern regions of China.It mainly contains clay minerals such as quartz,illite and montmorillonite.Its mineral particle size is very small,cracks are easy to develop,and it is easy to shrink and crack when water is lost,and it is easy to expand and soften when water is met.At present,some acid rain still exists in southern China,and the acid solution can cause chemical corrosion of silty mudstone.There are a large number of initial pores,micro-cracks,joints and other defects in the silty mudstone rock mass,which will accelerate the corrosion of acid rain.Under the influence of acid rain,the internal microstructure of the rock mass changes,resulting in the continuous deterioration of rock mass strength,posing a threat to the long-term stability of the silty mudstone slope.In this paper,the basic physical parameters of silty mudstone are obtained by laboratory test and numerical simulation.The macroscopic mechanical properties and pore changes of silty mudstone under acidic environment were investigated.Uniaxial compression test,triaxial compression test,scanning electron microscope test and energy spectrum analysis test were carried out on the silty mudstone samples with different PH values and different corrosion time.The effects of different PH values and different corrosion time on the macroscopic mechanical properties and mesoscopic damage characteristics of the silty mudstone samples were obtained.Based on the above parameters,the stability of silty mudstone cutting slope is calculated by numerical simulation software.The main research contents and conclusions are as follows:(1)Standard samples were obtained by drilling and grinding the silty mudstone excavated from the slope in accordance with the test specifications,and the samples were screened by drying quality and longitudinal wave velocity;Based on laboratory tests,the basic physical parameters of silty mudstone,such as mineral and chemical composition and proportion,dry density,particle density,porosity and soil-water characteristic curve,are obtained.(2)Based on the uniaxial compressive strength and elastic modulus of silty mudstone under different conditions,it is found that the uniaxial compressive strength and elastic modulus of samples decrease significantly with the decrease of solution PH value and the increase of corrosion time;Will silty mudstone under different test conditions for triaxial mechanics test,obtains each silty mudstone under the condition of cohesive force and internal friction Angle,for subsequent provide numerical parameters and test and numerical simulation,and with the increase of triaxial confining pressure,specimen gradually reduce the damage to the main crack Angle and crack width,samples increase in the number of microcracks,integrity gradually becomes poor(3)According to the electron microscope photos and energy spectrum of silty mudstone under different conditions,the microscopic morphology and chemical element changes of silty mudstone after acid corrosion were studied,and the relationship between microscopic changes and macroscopic mechanical properties deterioration was established.It is found that the corrosion mechanism of silty mudstone samples by acid solution is mainly due to the chemical reaction between Al2O3 and H+ in acid solution,which leads to the degradation of the macroscopic mechanical properties of the samples.(4)Using the previously obtained parameters,geo-studio software was used to simulate the distribution law of slope pore water pressure under acid rain conditions to obtain the rainwater infiltration depth under acid rain conditions,and then different slope models were constructed to analyze the influence of acid rain rainfall time on slope stability.It is found that the safety factor of silty mudstone cut slope decreases with the increase of acid rain time.