| At present,micropiles are widely used in landslide treatment projects,and there are relatively many studies on slope fixing mechanism in the reinforcement process.However,the application time of micropiles in reinforcement projects is still relatively short,there is a lack of measured data when preventing landslide examples,and the influence of external factors such as rainfall on the role of micropiles during the application process is not fully understood.Therefore,it is of great significance to carry out on-site monitoring and numerical simulation analysis to study the force deformation and mechanism of micropiles in the actual landslide prevention and control project under rainfall.In this paper,the method of combining on-site monitoring test and numerical simulation was used to carry out the experimental research of micro-pile reinforcement of landslide in Xiangong Town,the study of micro-pile-landslide system under annual rainfall,and the study of micro-pile-landslide system of different locations and different displacements under maximum rainfall.Finally,the mechanism and deformation characteristics of the landslide-micropile system were revealed,the stress-strain characteristics of micropiles under different laying positions and the optimal layout position of the reinforced slope were obtained,and the stress-strain characteristics and force transmission mechanism of micropiles under different rows were studied.The specific research results are as follows:(1)The monitoring results of micro-pile reinforcement of landslide in Gongzhen County showed that the overall change of soil pressure after micropile pile showed the stage of soil mass compaction after pile,the stage of micro-increase of soil pressure,and the stage of soil pressure rising to stability.In the sliding direction of the landslide,the comprehensive force distribution ratio of the three rows of piles is about 1:0.87:0.77,reflecting the synergistic effect of the micropile group.The stress change of the micropile body was in the stage of rapid deformation,the stage of linear growth of deformation,and the stage of stable deformation.(2)Based on the simulation of the seepage field of loess landslide based on the rainfall infiltration process,it can be found that the shallow layer of the slope will change from unsaturated to saturated during the rainfall stage,rainwater will gather at the foot of the slope,and the unsaturated zone inside the slope will decrease.The saturation zone of the shallow slope in the unrained stage will gradually become unsaturated with rainwater infiltration,and the saturation zone will move to the interior of the slope and finally descend to the junction of rock and soil layers.The stability analysis of loess landslide based on the rainfall infiltration process shows that the maximum shear strain of the entire slope increases gradually from January to December without piling,and the deformation area can be clearly seen at the leading and trailing edges of the landslide.The maximum shear of the belt should be changed larger than that of the sliding body.(3)The stability analysis of micro-pile-loess landslide based on the rainfall infiltration process shows that the maximum shear strain of the slope after piling is significantly reduced compared with no piling,and gradually increases every month,and the deformation area can be seen on the leading and trailing edges of the landslide.During the rainfall infiltration process,the maximum shear strain of the slope behind the pile is small and almost unchanged,and the pressure of the slope is concentrated in the position of the pile,resulting in the concentration of the maximum shear strain of the slope before the pile,and the value is large.Based on the stress analysis after stability calculation,it can be obtained that the absolute value of earth pressure and bending moment after pile increases when rainfall increases,and remains stable or slightly increases when rainfall decreases,and enters the landslide stabilization stage.During the process of rainfall infiltration,the absolute value of the soil pressure and bending moment of the pile body gradually decreases along the sliding direction of the landslide.The absolute value of the earth pressure and the negative bending moment of the pile body gradually increases with the depth and reaches a maximum near the sliding belt.However,the soil pressure after the pile in the pile anchoring section is small,and the pile body bears a positive bending moment,which is the maximum near the slip belt and gradually decreases with depth.(4)When the micro piles in different positions are simulated by rainfall,the closer the position of the micro piles to the front edge of the landslide under the same depth of the load section,the greater the absolute value of the soil pressure and bending moment of the pile after the pile.Through the analysis of the stability coefficient,pile deformation,soil stress and bending moment of the micropile slope at different locations,it is best to apply the micropile in the front middle of the landslide when reinforcing the micropile in the landslide.(5)In the simulation of rainfall infiltration of micropiles with different rows of micropiles,the smaller the deformation of the pile body,the greater the absolute value of the soil pressure and bending moment of the pile body of each row of piles,and the greater the landslide thrust of the micro piles.The landslide thrust borne by the micropiles of different rows in the sliding direction decreases sequentially,and the piles in rows 1-3 bear most of the landslide thrust.When the micropile is increased to 6 rows,the landslide thrust borne by the 6th row of micropiles is only 1/20 of the total landslide thrust,and when the stability coefficient is calculated,the stability coefficient increment of 6 rows relative to 5 rows is less than 0.01,so it is not economically reasonable and practical to increase the number of micro piles. |
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