Study On The Rheological Properties Of Soil And Their Influences On The Stability Of Slopes

The studies on stability of slopes have always been a hot topic in engineering.The stability of slopes are closely related to the rheological properties of soil which is the constitute material of slopes.However,there are few systematic studies on the rheological properties of different soil from sandy soils to clays.In this paper,the rheological properties of five different kinds of soil which were simulated by taking shale soils and sands as the base material have been studied by theoretical analysis and laboratory tests.Numerical simulations have been conducted to analyze the relationship between rheological properties of soil and the stability of slopes.?The quantitative rules between the influencing factors and the rheological properties of soil are as follows:1)Under the same conditions,the creep deformation of soil decreases with the increase of sand ratio.While in the stress relaxation test,the initial load,final load and relaxation value increase with the increase of sand ratio,and the relaxation ratio decreases with the increase of sand ratio.Experiments show that when the water content of the soil is 0.923?L,compared with Soil B(Sandy clay with low liquid limit),Soil C(Sandy clay with low liquid limit),Soil D(Sandy clay)and Soil E(Sandy clay),the creep deformation of Soil A(Low liquid limit clay)increases by 70.90%,117.59%,198.78% and 630.62% respectively.In the stress relaxation test,compared with Soil A,the initial load,final load and relaxation of Soil E increases by 2430.45%,688.87% and172.90%,while the relaxation ratio decreased by 65.37%.2)The creep deformation of soil increases with the increase of water content.Taking Soil A as an example,the creep deformation when the water content of the soil is0.923?Lis respectively 1.21,2.35,11.10 and 20.26 times of that when its water content are 0.823?L,0.723?L,0.623?Land 0.523?L.In the stress relaxation test,the initial load,final load and relaxation decrease with the increase of water content,while the relaxation ratio increases with the increase of water content.Taking Soil A as an example,the initial load,final load and relaxation when the water content of the soil is0.523?Lincreases by 1088.85%,3002.79% and 521.82% compared with that when its water content is 0.923?L,while the relaxation ratio decreases by 47.73%;3)The creep deformation of soil increases with the increase of stresses,and non-attenuate creep will take place when the stress exceeds a critical value.The criticalcreep deformation between attenuate creep and non-attenuate creep decrease with the increase of sand ratio.From Soil A to Soil D,the critical creep deformations are46.25×104 ??,28.75×104 ??,12.12×104 ?? and 2.5×104 ?? respectively.The critical stress between attenuation creep and non-attenuation creep increase at first and then decreases with the increase of sand ratio.From Soil A to Soil D,the critical stresses are32.61 kPa,54.89 kPa,32.30 kPa and 13.68 kPa respectively.In the stress relaxation test,when the strain is relatively small,the initial stress,final stress and relaxation increase with the increase of the strain.When the strain is relatively large,the initial stress is a relatively constant value all the time because of the fracture of soil,with the increase of the stress,the final stress decreases,the relaxation and relaxation ratio decrease.4)The creep deformation of soil increases with the increase of loading rate,while in the stress relaxation test,the initial stress,relaxation and relaxation ratio increase with the increase of loading rate,and the final stress decreases with the increase of loading rate.When the loading rate increases by 5 times,the creep deformation of Soil A whose water content is 0.723?Lincreases by 20.10%.In the stress relaxation test,the initial load,relaxation and relaxation ratio increase by 3.83%,24.42% and 19.79%respectively,while the final load decreases by 9.29%.?Relationships between the rheological properties of soil and the stability of slopes:1)As the necessary condition for the deformation and damage of soil slopes,the creep deformation of soil exists among all the stages of a slope failure.2)Water content is the most important factor that influences the creep property of soil.So great attention should be paid to the design,construction and maintenance of drainage facilities in slope engineering to ensure that the water in the slope can be drained in time.3)The monitoring data and soil tests of a slope show that the creep property of the slope soil varies with different seasons.In rainy seasons,the creep property of soil is more significant than that in dry seasons,and the displacement of slope increases more quickly in rainy seasons than that increases in dry seasons.This rules are consistent with the numerical simulation results4)In the condition of high water content,the soil with low sand ratio is easy to slide(flow),because the water cannot be drained.It means that sandy soil is more suitable for filling a slope than clay if the angle of the slope is less than the repose angle of the sandy soil in the rainy areas.5)The stability of slopes can be increased by improving the rheological properties of soil.For example,by mixing a little lime,the creep deformation of soil can be greatly reduced.It's an available way to prevent the landslide or debris flow by adding some lime into the soil before the soil is used for filling a slope.