| In recent years,a series of major engineering construction activities have been carried out in the Loess Plateau area,and a large number of exposed slopes have been formed.Under the disturbance of rainfall and other factors,these exposed slopes are easy to produce shallow failure disease.Such diseases not only affect the appearance of the slope,but also induce potential slope stability problems.Therefore,the engineering community urgently needs good effect,low cost slope protection materials put into practice.In this paper,two kinds of slope protection materials,fiber reinforced soil A and glue mixed soil B,are applied to loess slope protection.Through field investigation,the characteristics of failure development in the shallow layer of loess slope were studied.Field slope protection monitoring tests were carried out to explore the difference of slope water transport law and surface deterioration characteristics under the conditions of two kinds of slope protection materials.According to the laboratory test,the deterioration law of physical and mechanical properties of the two protective materials under the condition of dry-wet cycle was analyzed,and the difference of protection effect of slope protection materials was explained from the perspective of material properties.The main research contents and achievements are as follows:(1)Field investigation was carried out,and 45 spalling damage sites in the test area during the rainy season were counted.By measuring the thickness of the exfoliated inner wall and observing the morphological characteristics of the inner wall,the developmental characteristics of the slope exfoliation failure were explored.The results show that the wall thickness of the exfoliation body of the loess slope around the in-situ test site is relatively thin,and the effective effect of rainfall infiltration process on the mechanical properties of the loess slope may be shallow,and the variation characteristics of the shallow surface water of the slope deserve attention.At the same time,the survey results also showed that the morphological characteristics of different parts of the exfoliated inner wall were different.The top wall showed tensile failure characteristics on the whole,and the side wall showed shear failure characteristics on the whole.When analyzing the mechanical properties of slope protection materials,attention should be paid to the characteristics of shear strength and tensile strength.(2)A soil water potential sensor and a soil water sensor were embedded in a bare slope of a gully treatment project in Yan 'an,and monitoring tests were carried out under different slope protection materials to explore the difference in water transport laws between the two types of slope protection materials.The test lasted for 13 months.The results showed that the shallow water content of slope fluctuated sharply during the monitoring period under the conditions of two protective materials.However,the water holding capacity and water permeability of the two are different.The slope protected by polypropylene fiber reinforced soil has better water holding capacity,while the slope protected by guar gum mixed soil has better water holding capacity.The permeability of Guar gum mixed soil may be related to the gradual emergence of penetrating cracks in the slope after repeated rainfall.(3)Under the condition of two kinds of slope protection materials,the regular effect of water transport in the slope not only shows the difference of travel,but also shows some similarity under the influence of seasonal factors,rainfall type and slope position.Firstly,the surface layer of the slope is generally replenished by the water inside the mountain,and the water replenishment characteristics are different in different seasons.However,water can be transported to the interior of the mountain during rainfall,thus forming a dynamic transport process of water.Secondly,the duration of rainfall affects the water infiltration process of the slope.The shorter the duration of rainfall,the less water infiltration,and almost no water infiltration into the slope in the case of short-term heavy rainfall.Finally,more water is always stored in the downslope of the slope under the conditions of two kinds of slope protection materials,and the water fluctuates sharply during rainfall.(4)Using 3D laser scanning technology,slope surface degradation monitoring experiments were carried out under two kinds of slope protection materials.During the monitoring period,a total of seven scanning operations were carried out,and quantitative calculation of slope surface failure between each scan could be realized through the steps of point cloud registration,model generation and model merging.The results show that although the two kinds of slope protection materials can slow down the failure development of slope surface to a certain extent,there are still some problems.The ability to resist the shallow damage of the slope protected by B adhesive soil is excellent in the short term,but the long-term effect is not good.Under the protection condition of this kind of slope protection material,the erosion damage amount of the slope is 2876.75 g before July 16,but after that,the erosion damage amount is 5905.25 g in a short period of time due to the influence of the upper slope surface falling off.The anti-erosion ability of the slope protected by fiber reinforced soil A is relatively poor,and the slope develops to the stage of gully erosion failure in the late monitoring period.(5)The difference of the protection effect of the two kinds of slope protection materials was explained from the perspective of material physical and mechanical deterioration characteristics through the laboratory test under the condition of dry-wet cycle.In order to be consistent with the in-situ test,the variation range of the moisture content of the soil sample during the test was set as 10%?20%,and the number of cycles was set as 0,2,4,6,9,14,16 times.The test results show that the mechanical properties of B-cement mixing soil deteriorate obviously after multiple cycles,which may be the cause of the poor long-term resistance to shallow failure ability of the protective slope.A fiber reinforced soil has poor disintegration resistance,which can explain the severe erosion damage development of this kind of protective slope.Cracks gradually appear in B-cement mixing soil during the wetting and drying cycle,which will affect the regular effect of water transport. |
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