| With the rapid development of China’s economy, various construction are developed with a large-scale high-speed and caused serious damage to the disturbance for native landscapes, which made serious soil erosion. Engineering spoil is one of the main source of anthropogenic soil erosion, which is Complex material composition, structure, loose, poor cohesion and proned to severe soil erosion and geological disasters, landslides, mudslides under the rainfall and runoff, and threat serious for people’s production and life. Therefore, the study of slope stability of the engineering spoil has important theoretical research and practical engineering value to reduce soil erosion and control measures.By taking the typical purple engineering spoil and coal engineering spoil in purple hilly area as the research object, a analysis of soil moisture content, porosity characteristics, soil water storage and shear strength characteristics was made under different rainfall events by the determination of physical and mechanical properties of soil indoors, and soil physical and mechanical properties of engineering spoil dynamic characteristics and differences was studied in this article. The infiltration characteristics and its influencing factors of the underlying surface of different engineering spoils was studied by using the field double-ring infiltration analysis method and the suitability model of engineering spoils underlying surface infiltration process was determined in purple hilly area. The critical slip surfaces and safety factors of various engineering spoils under different rainfall events was calculated used by GEO-SLOPE software and the slope stability influencing factors was analyzed with orthogonal design. The results provide an important scientific basis for preventing geologic catastrophes of engineering spoil, such as soil and water losses and shallow landsliding in Chongqing. The main conclusions were as follows:(1) The soil bulk density, total porosity, natural moisture content and field capacity were significantly different (P<0.05) from the purple engineering spoil and coal engineering spoil. The particle-size distributions of the various engineering spoils were mainly 2～20-mm, which was 45.61～73.79%. The particle-size distributions displayed well-developed fractal properties and the coefficient of detennination was greater than 0.85; the maximum fractal dimension was 2.692, and the minimum fractal dimension was 2.374. The natural moisture content, soil bulk density and field capacity of purple engineering spoils respectively were 4.12～16.23%,1.32～1.64 g/cm3 and 16.35～29.58%; While which of coal engineering spoils were 19.01% and 20.09%,1.19 g/cm3 and 1.15 g/cm3,33.82% and 35.66%. The cohesion force of the purple engineering spoil and coal engineering spoil were significantly different (P<0.05), which were purple engineering spoil (28.95 kpa)> coal engineering spoil (6.61 kpa). The internal frictional angles of the purple engineering spoil and coal engineering spoils were in the ranges of 9.58～57.32°and 27.71～28.76°.(2) The infiltration characteristics of the purple engineering spoil and coal engineering spoils were significantly different (P<0.05). The initial infiltration rates of the purple engineering spoil and coal engineering spoils were respectively 13.86 mm/min and 20.09 mm/min and which of the stable infiltration rates were 6.79 mm/min and 10.19 mm/min. The soil initial infiltration rate, stable infiltration rate, average infiltration rate and penetration of the total were negatively correlated with the soil bulk density and natural moisture content, while positively correlated with the soil porosity which the correlation coefficient is low. While the correlation coefficient between infiltration characteristics and gravel content was higher.The stable infiltration rates was negatively correlated with 60～40 mm gravel content and was negatively correlated with 40～20 mmã€20～10 mm and 10～5 mm gravel content significantly, which was positively correlated with 5～2 mm gravel content. The average infiltration rate was negatively correlated with 60～40 mm and 10～5 mm gravel content and was negatively correlated with 40～20 mm and 20-10 mm gravel content significantly, which was positively correlated with 5～2 mm gravel content. It is showed that the> 5 mm gravel can inhibit infiltration capacity of engineering spoils and 40～20 mm and 20～10 mm gravel were more significant.(3) The goodness of fit of infiltration model with different engineering spoils was difference and the coefficient of determination listed in decreasing order were the common empirical infiltration model (0.751～0.979)> Kastiakov infiltration model (0.724～0.956)> Philip infiltration model (0.728～0.938)> Horton infiltration model (0.689～0.936); Compared with calculated infiltration rate and measured infiltration rate, the coefficient of determination of infiltration regression equation with purple engineering spoils were Kastiakov infiltration model (R2=0.959)> common empirical infiltration model (R2=0.9586)> Philip infiltration model (R2=0.9414)> Horton infiltration model (R2=0.8954), which the coal engineering spoils were Kastiakov infiltration model (R2=0.935)> common empirical infiltration model (R2=0.9337)> Philip infiltration model (R2=0.8992)> Horton infiltration model (R2=0.8698). Kastiakov infiltration model was the suitable model for analyzing the infiltration process of engineering spoils in purple hilly area.(4) The soil moisture content of 0-50cm soil layer of the purple engineering spoil was varied from 10.28% to 20.48% under the different rainfall events, and which of the different slope positions was trended different. While the soil moisture content of 0-50cm soil layer of the coal engineering spoil was varied from 21.60% to 38.30% and the average was 28.99 which were 2.04 times greater than purple engineering spoil. Compared with the one-time rainfall events, soil moisture content was greater range of variation under intermittent rainfall events, which is mainly related to rainfall intensity, rainfall frequency, intermittent time, climatic conditions and evaporation capacity and other related. The maximum soil moisture content of the purple engineering spoil was respectively 20.48%,20.27% and 18.02% under intermittent rainfall events, which of the minimum respectively 12.90%,10.28% and 11.04%. The soil moisture content of the coal engineering spoil was respectively 25.20～31.69%,25.19～35.75% and 25.50～32.51%, which was 1.85,2.07 and 2 times greater than the purple engineering spoil, respectively. The soil moisture content of different slope positions were significantly different (P<0.05) from the purple and coal engineering spoil. The soil moisture content of the purple engineering spoil was 6.14(14.18%)> 6.5(13.51%)> 6.9(13.41%), while the coal engineering spoil was 6.9(29.26%)> 6.14(29.14%)> 6.5(28.36%). The soil moisture content of different slope positions of the purple engineering spoil were significantly different (P<0.05), which were 12.95%,14.79% and 14.95%, respectively.(5) The soil bulk density, total porosity and field capacity were significantly different (P<0.05) between the purple engineering spoil and coal engineering spoil under the same rainfall event. The soil bulk density of the purple engineering spoil was 1.11～1.69 g/cm3 and the coal engineering spoil was 0.9-1.28 g/cm3. The soil total porosity, non-capillary porosity, capillary porosity of different soil layers were were significantly different (P<0.05). The soil total porosity and capillary porosity was 0-10cm soil layer> 10-20cm soil layer, while the non-capillary porosity was 10-20 cm soil layer> 0-10 cm soil layer. The soil saturated water storage, water-holding capacity of non-capillary porosity and water-holding capacity of capillary porosity with the different slope positions were significantly different (P<0.05) between the purple engineering spoil and coal engineering spoil under the different rainfall events. The water-holding capacity of non-capillary porosity of different slope positions under the purple engineering spoil was 6.5 mm,5.75 mm and 5.58 mm, while which of the coal engineering spoil was 17.03 mm,12.47 mm and 11.84 mm. The internal frictional angles of the purple engineering spoil was 12.16～30.77°and the coal engineering spoils was 11.82～26.81°(6) The critical slip surfaces and the safety factors of engineering spoils were different under the different rainfall events. The safety factors were greater than 1.25 and which was decreased with the Increasing rainfall intensity. The safety factors of the purple engineering spoil under the different rainfall events were 2.434,1.384 and 1.275, while which of the coal engineering spoil were 3.015,2.638 and 1.408. The safety factors was positively correlated with the cohesion force, the internal frictional angles and the stable infiltration rates and was negatively correlated with the soil bulk density, soil moisture content and rainfall intensity. The safety factors was Bishop> M-P> Ordinary> Janbu with orthogonal design and the Slope Stability of engineering spoil was evaluated. The results showed that:extremely stable state was 11, stable state was 2, basically stable state was 2 and potentially unstable state was 1. Sensitivity analyzes was slope high> cohesion force> internal frictional angles> slope> gravitational density, which of slope high was 1.505 and cohesion force was 1.191. |
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