Numerical Study Of The Control Of A Backfill Slope Based On In-situ Borehole Shear Test

In order to study the strength parameters of slope soil more precisely so as to provide solid base for the subsequent design,this thesis conducts the survey on a backfill slope first,then apply in-situ borehole shear test to obtain the soil parameters of the backfill slope accurately,after that,slope stability is analyzed,and control methods were put forward.Finally,the effect of different control methods was simulated based on numerical method.The main conclusions are:(1)Aiming on the difficulty in the sampling of soil and the complexity of lab test on the soil parameters,the in-situ borehole shear test is applied to study the soil parameters of the bakfill slope precisely.Combined with lab test results and engineering experiences,the shear strength parameters ?=24° and c=12 kPa are used as the slope design parameters.(2)Based on the test parameters,the slope stability is insufficient,and the slope is easily collapsible.Then the comprehensive control measures such as "anti-slide pile gravity retaining wall" and drainage system are put forward.(3)The control measures "anti-slide pile gravity retaining wall" on this slope was simulated by finite element method,and the pile length,pile diameter and pile spacing are chosen as the design parameters of parametric study.The results show that compared with the unreinforced slope,the lateral displacement of the slope after different reinforcement can be reduced by 76.46% ~ 94.05%,respectively,and the vertical displacement can be reduced by 81.35% ~ 90%,respectively,the reinforcement effect is obvious,and the control measures is more effective on lateral displacement than on vertical displacement.(4)The bending moment of the anti-slide pile all shows such a trend: first increases,then decreases,and finally reaches the minimum in the bottom of the pile.The maximum bending moment is located at a depth of 5 m,therefore,for this slope studied,the pile body at embedded depth of 5 m is the key part in the pile design,which needs additional strengthening.(5)When the pile diameters and pile lengths maintain unchanged,but the pile spacings are varied,the bigger the pile spacing is,the bigger the deformation of the slope is,and the larger the pile deformation will be,resulting in larger bending moment of the pile.When the pile lengths and pile spacings maintain unchanged,but pile diameters are varied,the deformation of the slope gets smaller as the pile diameter increases,but the double increase of the pile diameter leads to the increase of pile bending stiffness in cubic series,therefore,a smaller pile strain can also result in significant increase of the pile bending moment.When the pile spacings and pile diameter maintains unchanged,but the pile length are varied,the deformation of the slope gets larger as the pile length decreases,but the pile length is too short,and the anchoring depth in the strongly weathered granite layer is insufficient,which leads to the minimal pile bending moment.