Study On Shear Strength And Permeability Of Loess Improved By The Red Mud

This thesis consists of three parts.To begin with,red mud used to improve the loess which locate in Taiyuan,Shanxi Province.The shear resistance and permeability of the loess improved by red mud were studied by electrical resistivity method.The relationship between shear strength and the content of red mud,age,vertical pressure and void ratio was found.And the relationship between the permeability coefficient and the osmotic pressure,the content of red mud,the void ratio and the age was also found.At the same time,we analyzed the shear stress and electrical resistivity which changed with current frequency,the content of red mud and other factors systematically.What's more,the relationship between shear strength and electrical resistivity,permeability coefficient and electrical resistivity of red mud improved loess were established.Besides,the loess improved by red mud as engineering or impermeable material might be affected by acid rain or factory wastewater with different pH and 5 kinds of pH used in the experiment.The changes of hydration products and pore structure of loess improved red mud were described by the sulfuric acid,the electrical resistivity,shear property and permeability of loess were studied.At last,we set up the formulas between shear stress,permeability coefficient and the concentration of acid.The concentration of leachate before and after the experiment were obtained.The main research results are as follows:(1)The electrical resistivity is firstly corrected to eliminate the influence of the misalignment of the electrode pads.When the current frequency is small,the current frequency has a greater influence on the electrical resistivity.So,the current frequency takes 50 kHz for the following discussion and analysis so as to reduce the influence of the current fluctuation on the electrical resistivity.The electrical resistivity increases with the shear displacement increases in different content of red mud,vertical pressure and age.The fitting find that age and electrical resistivity close to the logarithmic function.The electrical resistivity increases with age increases.With the content of red mud increasing,the conductivity of the sample enhances and electrical resistivity decreases.(2)Hydrated calcium silicate and calcium aluminate hydration which produced by red mud and cement improve the pore structure of loess,resulting in compactness and strength of improved soil increased.The shear stress increase linearity first and then the carve becomes smoothly.The shear strength first increases slightly and then decreases slightly when the content of red mud increasing.When the content of red mud about 15%,the shear strength has its maximum.The shear strength index is obtained by the linear relationship between shear strength and vertical pressure.The shear strength increase with the increase of age,and the shear strength increase rapidly when the age is less than 14 d.The fitting find that shear strength and age close to the logarithmic function.We set up the relationship between shear stress and electrical resistivity.The shear stress increases with the increase of electrical resistivity.(3)The electrical resistivity of loess improved by red mud increases with the shear displacement under the different pH.The electrical resistivity increases with the increase of shear displacement and void ratio.The shear stress increase firstly and then tends to be constant with the shear displacement increases.The shear strength of the improved soil increases linearly with the increase of vertical pressure.When the porosity ratio increases,the density of the sample decreases and the structural performance between the particles decreases,so the shear strength decreases.The relationship between the shear strength and the acid concentration is obtained,the shear strength firstly increases and then decreases with the increase of the concentration of acid,Shear strength with the acid concentration close to the quadratic function.(4)It is found that the permeability coefficient remained unchanged with the increase of osmotic pressure.The red mud will increase the impermeability of the mixed materials.When the red mud content is 15%,the permeability coefficient is the smallest and the anti-seepage effect is the best.The permeability coefficient increases rapidly with the increase of void ratio increases,its show a good exponential relationship,the void ratio has great effect to the permeability coefficient.The age has a certain impact on the permeability coefficient,permeability coefficient decreases with age longer.We obtained the relationship between permeability coefficient and the concentration of acid under the content of red mud and the electrical resistivity of the sample increases after the permeation test and it is found that the permeability coefficient increases with the increase of the resistivity.