Study On Bearing Capacity Of Anchor Cable Micropile Group For Soil Landslide Reinforcement

With the in-depth development of the "One Bel t,One Road" strategy,infrastructure construction in the western region has become the top priority,resulting in a large number of landslide ge ological disasters.It seriously affects the construction of projects and the safety of people’s lives and property along the line.These landslides generally have certain premonition.When the landslide is in initial slip or potential slip,urgent measures should be taken to control it,so as to avoid casualties and huge economic property losses.Anchor cable micropile group are one of the effective measures for landslide em ergency rescue.It is very suitable for the needs of landslide emergency rescue works because of its convenient construction,small disturbance to the slope,small damage to the surrounding vegetation,economic and environmental protection characteristics.At present,there have been many research results on the internal force and deformation of the pile.Corresponding theoretical calculation models based on different assumptions are established.However,these calculation model s seldom consider the plastic deformation of soil in front of the embedded section and the continuity of deformation of soil at the side of the pile.And its p ile spacing is generally determined by engineering experience,which greatly affects the anti-skid ability of the structure.Therefore,it is of great practical significance and theoretical value to study the internal force and deformation of micropiles wi th anchor cables and its reasonable pile spacing.Based on this,this paper studies the soil slop e reinforced by micropiles with anchor cables.The main research contents are as follows:Firstly,this paper analyzes the mechanical characteristics and worki ng mechanism of anchor cable micropile group for landslide reinforcement.The Winkler foundation beam model and Pasternak two-parameter foundation beam model,which are two main analysis methods of flexible long piles under horizontal load,are summarized.Several main methods for calculating soil resistance in front of piles are described: linear elastic foundation reaction method,nonlinear elastic foundation reaction method and p-y curve method.Then,this paper analyzes the internal force and deformatio n of micropiles with anchor cables in reinforcement of soil slope.The micropile group is divided into loading section and embedded section with the potential slip surface as the boundary line.For the load section,soil between piles is simplified as hori zontal soil spring to effectively consider the transfer effect of soil force between piles.For the embedded section,the pile-soil interaction is analyzed by the ideal elastic-plastic p-y curve.Then,based on Pasternak two-parameter foundation beam metho d,a finite difference calculation model of internal force and deformation of micropiles with anchor cab les is established,which takes into account the elastic-plastic deformation of soil in front of the embedded section and the continuity of deformation of soil at the side of the pile.The model is used to calculate the engineering example,and the rationality of the model is verified by comparing with the experimental and numerical simulation results.On this basis,the influences of soil shear stiffness,anchor cable bundle and pile diameter on horizontal displacement and internal force of pile are discussed.The results show that the horizontal displacement and internal force of micropiles are greatly affected b y the plastic deformation of soil in front of the embedded section and the continuity of deformation of soil in side.Finally,the reasonable pile spacing of micro pile group is studied in this paper.Analyze the distance between individual micro piles.Fi rst,the axis of the soil arch between piles is regarded as a parabola.Then,the additional stress field of soil near the pile was deduced by using the Boussinesq solution and the height of the axis of the soil arch was determined.Furthermore,the formul a for calculating the maximum distance between piles was given under the contr ol condition that the soil at the arch top or arch foot reached the lim it state.The rationality of the method is verified by comparison with model test results.On this basis,a ccording to the stress of soil slope reinforced by micropile group with unifor m arrangement,a method to determine the reasonable pile spacing of the structure is given.The analysis of pile spacing of composite micropiles is based on the maximum pile spac ing of independent micropiles.Considering the interaction of soil arch betwee n piles and soil arch between pile groups,a simplified calculation mod el of pile spacing is established.The rationality of the calculation model is verified by comparing the calculation results with the numerical simul ation results.The influence of micr opile group spacing on reasonable pile spacing of the structure is also discussed.It is shown that the equivalent column spacing of the structure can be effectively increased by increasing the transverse clear distance between pile groups under the condition that the soil arch between pile groups works normally.