On The Response Test And Disastrous Mechanism Of Expansive Soil Slope Under The Effect Of Atmosphere

With the research object of expansive soil in Nanning, Guangxi and the aim of response analysis and disastrous mechanism of expansive soil slope under the effect of atmosphere, evolvement principle of slope under the effect of atmosphere are roundly demonstrated and the disastrous mechanism is analyzed by laboratory test, field slope test and numerical analysis of interaction of atmosphere-unsaturated soil. The main outcomes are as follows:1. According to the laboratory soil-water characteristic curves, the preparation method of pre-desaturation to control suction of specimen is used to discuss the drying-and-wetting cycle effect on the strength parameters and deformation modulus of expansive soil, which behave as attenuation of strength and deformation. By the comparison of strength parameters from tri-axial specimens of different dimension, it is found that fissured expansive soil has obvious dimension effect. Also, the linear changing principle of soil and water volumes of expansive soil with suction under the iso-volumetric stress is demonstrated;2. Field monitoring systems of three slopes of a gentle slope, a steep slope and a gentle slope covered with grass in Nanning, Guangxi are established. The deformation, water content and temperature of these three slopes changing with atmosphere are measured by a six-parameter mini-environmental station, TDR system, oven-drying method, temperature sensor, inclinometer, settlement plates and double ring apparatus. Precipitation is regard as the most direct factor of outer climate to bring expansive soil slope into disaster and evaporation effect is one of important premise, while fissure due to evaporation is the internal factor for disaster. Based on the measured data, the experimental formulations of runoff of three slopes are established and experimental models of predicting the deformation of slopes are obtained;3. Based on the non-isothermal flow equation considering thermal-moisture coupling, the interaction model of atmosphere-unsaturated soil is established with different evaporation formulations. By the analysis of evaporation effect on the suction of unsaturated soil, this model is considered to be more reasonable than the traditional method considering isothermal flow and potential evaporation. This model is also incorporated with vegetation root uptake and transpiration, including the deformation behavior resulting from the changing of soil moisture. At last, the sensitive analysis of multi-parameters, including climatic factors, soil parameters and vegetation physiological parameters, controlling the calculation of evaporation, soil suction and deformation is done. It is regarded that net radiation and wind velocity have more effect on the evaporation, soil suction and deformation than other climatic parameters, while soil hydraulic and thermal parameters have limited effect. For the soil covered with grass, the key parameters are leaf area index LAI and root depth.4. Based on laboratory test and field slope test, the basic physical and mechanical parameters of inclination pipe used in the field slope are measured and the influence of inclination pipes imbedded in the slope on the displacement and stability of slope is considered to be negligible by...