| The Loess Plateau is the world’s largest loess accumulation area,as well as the plateau with the largest loess coverage in the world.The geological environment of the Loess Plateau is fragile,and landslide and debris flow geological disasters are prone to occur under the influence of rainfall infiltration.Dongzhiyuan is the largest platform in the Loess Plateau and the most active region in politics and economy in Qingyang City.Due to its special geological and geographical conditions and fragile ecological environment,landslides and other geological disasters occur frequently around the platform,directly threatening the production and life of local residents,and becoming a bottleneck that restricts the sustainable development of politics,economy,and society in Qingyang City.Rainfall infiltration is one of the main factors that trigger geological disasters in loess slopes.As rainfall infiltrates,the soil near the slope surface gradually tends to saturation,the matric suction in the unsaturated zone decreases,and the soil shear strength decreases.The infiltration force pointing to the outside of the slope exacerbates the downward trend of the slope,leading to instability and damage of the slope.Therefore,how to effectively prevent rainfall and surface water from entering deep soil has become one of the main research directions for preventing loess slope disasters.Ecological slope protection technology is applied to the treatment of loess slopes,which can not only drain through engineering measures,but also use the joint action of root-soil composite,prevent rainfall infiltration,and improve the stability of the slope;at the same time,it can achieve the growth of plants and organisms,and improve the landscape and ecological environment.This article takes the Huangtu slope of Xiaokengtonggou in Dongzhiyuan as the research object,and carries out research on the influence of rainfall infiltration on the stability of loess slopes and ecological slope protection and control technology through field investigation,indoor geotechnical tests,indoor simulation tests,and simulation analysis.Firstly,through the self-developed artificial rainfall device,the infiltration characteristics and deformation characteristics of loess slopes under rainfall were studied,and the finite element numerical simulation method was used to simulate the influence of different rainfall intensity,duration and rainfall type on the stability of loess slopes.On this basis,the failure mechanism of loess slopes with different slopes under rainfall was analyzed.Secondly,the solidified soil planting test was carried out through indoor experiments to analyze the physical and mechanical properties of solidified soil planting samples,and the finite element software was used to evaluate the slope protection effect of different slope protection methods under rainfall.Finally,the feasibility of this technology was proven through engineering applications.The paper achieved the following results:(1)Rainfall infiltration can be described as the process in which surface water begins to seep into the soil during a rainfall event,changing the soil’s saturation status from unsaturated to saturated,with the seepage behavior following Darcy’s Law.The classic Green-Ampt(GA)model was extended to sloping terrain and validated through experimental,theoretical and numerical analysis.The improved GA model reveals that infiltration depth during rainfall is related to the infiltration coefficient,matric suction,rainfall duration and slope gradient of the loess soil.(2)The infiltration characteristics of loess slopes under rainfall conditions were studied using a self-developed artificial rainfall simulator,and the failure mechanism of different slope gradients under the influence of rainfall infiltration was investigated using finite element numerical simulation.The finite element numerical simulation took into account the effects of rainfall intensity,duration,and rainfall type on the stability of loess slopes.The study shows that:(a)under the action of rainfall,the displacement and pore water pressure of the loess slope increase with increasing rainfall intensity and duration;(b)the displacement of the rear soil mass of the slope is mainly controlled by the rainfall infiltration volume,while the displacement of the front and middle soil masses of the slope is mainly controlled by the deformation and compression of the surrounding soil and the rainfall infiltration volume;(c)during the rainfall process,the slope undergoes continuous deformation,and after the rainfall ends,the soil mass behind the slope relative to the rainfall and gravity forces,compresses the soil mass in front of the slope,resulting in a certain lag effect of the pore water pressure in the soil mass in front of the slope;(d)the time lag of the maximum pore water pressure is often related to the compression and traction effects of the surrounding soil masses.As rainfall intensity and duration increase,the compression and traction effects on the surrounding soil masses of the slope where the maximum pore pressure appears become stronger.(3)The experimental results show that soil stabilizers can improve the durability and strength of loess by working to modify its internal structure,making it a key research direction for soil and water conservation and slope protection.Bioprotection can improve the stability of shallow slopes by reinforcing soil through root systems,while the upper biomass can inhibit rainfall infiltration.The soil stabilizer used in this study is an environmentally friendly type that results in a 60% increase in shear strength and a decrease in permeability when used as a soil-plant composite compared to plain soil plant composite.(4)This paper analyzes the displacement and pore pressure variation of loess slopes under rainfall conditions when using plain soil,stabilized soil ecological protection technology,and when no protection measures are implemented,evaluating the impact of different protection measures on the stability of the loess slope.The results show that,as rainfall intensity increases,the reduction of pore pressure in the stabilized soil and plain soil ecological protection technology-intervened slopes is larger compared to the unprotected slope,while the reduction of displacement decreases with an increase in rainfall intensity.The use of stabilized material is more effective than plain soil,so it is recommended to use stronger protective materials as the rainfall intensity increases.(5)Based on field experiments,the application effect of stabilized soil vegetation on the growth of vegetation,coverage and root development was evaluated.The technology can improve the erosion resistance of the soil,and shows good ecological slope protection effect.The untreated slope surface soil is loose and has weak erosion resistance with large amounts of sediment accumulating at the bottom of the slope due to external environmental factors such as dry-wet cycles and freeze-thaw cycles.In contrast,the treated slope does not show these phenomena.Ecological protection using stabilized soil technology is feasible in the ecological governance of loess slopes,and can be considered as a new approach for slope protection and management. |
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