Study On Mechanical Characteristics And Slope Stability Of Expansive Soil Under Dry-wet Cycle

Expansive soils are widely distributed in China,and have encountered problems with expansive soils in engineering construction in 26 provinces.As a special climate-sensitive soil,expansive soil has the characteristics of expansibility,fissures,and strength attenuation.Under the influence of seasonal dry and wet climate cycles,the soil's periodic expansion and contraction are prone to deformation and destruction.The research on the influence of the mechanical properties of expansive soils under the action of dry and wet cycles is helpful to guide the engineering construction of expansive soil areas.In this paper,through geotechnical experiments,theoretical analysis,and numerical simulation,a more in-depth study of expansive soils in a certain area of Hebei is carried out.?1?Based on expansive soil evaporation samples used to explore the evaporation characteristics of expansive soils,the distribution of soil temperature field and water content at different depths under different sunshine hours were analyzed;the temperature difference formed by heating and cooling at the same time explained The reason why the soil stores heat;it fits the temperature relationship of the soil at different sunshine hours and different depths.Based on the expansion time-history curves of the expansive soil under different dry and wet cycles,the Knothe time function expansion model and multiple regression expansion model were used to analyze the changes of the dry and wet cycles and expansion time to the expansion rate.The residual sum of squares and the correlation coefficient were used to To evaluate the fitting degree,the fitting effect based on the Knothe time function as a criterion is better.?2?Through the study of the shear strength characteristics of expansive soil under different dry-wet cycles and different confining pressures,the failure stress of the expansive soil under dry-wet cycles is reduced,the strength indicators in the low and high confining pressure sections differ greatly,and the low confining pressure The cohesive force decreases more than the high confining pressure section.The internal friction angle at low confining pressure is greater than the internal friction angle at high confining pressure.In addition,starting from the secant modulus and secant modulus parameters of the work hardening curve,Two stress-strain curve relationships considering dry and wet times are fitted.Regarding the dynamic characteristics of expansive soils,the effects of confining pressure,different dynamic stress amplitudes,and the number of dry and wet times on it were studied.Increasing the number of dry and wet cycles and increasing the dynamic stress amplitude will cause the cumulative plastic strain to increase;the dynamic stress amplitude The value is linearly related to the elastic deformation of the soil.Under the same dynamic stress amplitude,the elastic deformation of the soil continuously increases with the increase of the number of dry and wet cycles.?3?Use FLAC^3D to establish numerical models of expansive soil slopes with different slope ratios and supporting forms,and analyze the influence law of strength reduction on expansive soil slopes under dry and wet conditions.Exceeds 40%;discusses the effect of different slope ratios and supporting forms on slope stability after dry and wet conditions.The anchor lattice beam strengthens the expansive soil slope well.The slope ratio 1:0.75reinforces the lattice beam The safety factor is increased by 21.6%under the condition of natural soil slope,while the safety factor is only increased by 5.73%at the slope ratio of 1:1.5.As the slope becomes slower,the reinforcement effect is weakened.Based on the above conclusions,it has certain guiding value for the engineering construction of the expansive land area.