Research On The Strength Attenuation And Fissures Of The Soil Under The Effct Of Atmosphere

The soil is in the Earth’s outermost layer, more sensitive to atmospheric effects. When evaporation from the soil is greater than infiltration, the soil tends to dry; especially, in the climate of the rainfall, much flow of water infiltrate in the soil, soil tends to wet. This alternating of wetting and drying under the effects of soil will occur a series of physical and chemical effects to the soil, the macroscopic manifestations is that the shear strength of the soil is reduced. In addition, the continuous evaporation can also lead to the crack in the soil. In this paper, the red clay and the expansive soil is the object of study, through this research, try to find out the law the shear strength attenuation action of the soil and how to crack under the atmosphere effects, and the findings are as follows:(1) Base on the studying of the experiment of wetting and drying in the red clay in Wuming and the expansive soils in Nanning, and from the data of the shear strength attenuation, a mathematics fitting function of the soil strength attenuation is proposed, find the function has higher fitting precision in test, it is better to describe the strength attenuation of the soil in wetting and drying cycle;(2) Basing on Water content of soil changes without rules under the atmosphere action, the rain flow count method is put forward to order the irregular history data of water content of soil, Times of wet and dry cycle in different amplitude of water content changing is counted, and through the concrete example demonstrated this method is feasible;(3) According the law of strength attenuation of the soil in wetting and drying test, combined with the rain flow count method, the soil strength cumulative attenuation model in wetting and drying cycle is set up. the red clay slope under atmospheric action is simulated in finite element numerical method, the strength attenuation of red soil under the atmospheric action is calculated by the use of established soil strength mode, and the slope stability is analyzed, found that the safety factor when considering strength attenuation in wetting and drying cycle is more smaller.;(4) To simulate the suction response of the expansive soil of Nanning under atmosphere action, found that the results of numerical calculation approaches to the field monitoring data, shows the feasibility of the numerical method. Combined with the Morris’s elastic mechanics theory about the soil crack, this paper proposes the laws of the expansive soil cracking judgment of Nanning, And weathering fracture of the expansive soil of Nanning are simulated, and found that parameters on the expansive soil is great influence on cracking, according to the difference between the soil layer, the paper using different permeability functions, this relatively solute the expansive soil cracking simulation reasonably.