Study On Mechanical Characteristics And Calculation Of Bearing Capacity On Inflatable Anchor Under Red Clay Embankment Slope

Inflatable anchor is introduced into China as a new anchoring technology,and much progress has been made,however,as a new type of anchoring technology,the analysis of inflatable anchor in complex application environment is not enough.For example,the analysis of partial stress of air bag and engineering application do not go far enough;The ultimate bearing capacity and the causes of anchorage failure need to be further analyzed;And the influence of intermediate principal stress on ultimate bearing capacity has not been discussed.Therefore,in order to improve the research and analysis of inflatable anchor,this paper carries out indoor pull-out model test of inflatable anchor on red clay embankment slope,based on the research of the existing scholar,and finally studies the influence of principal stress on ultimate bearing capacity.The main contents and results are as follows:(1)On the basis of extensive reading and reference of inflatable anchor test and embankment model test,suitable test and test model box device is designed according to the test contents.(2)Experiments on the influence of transverse spacing,longitudinal spacing and balloon pressure on ultimate bearing capacity and ultimate displacement are carried out under the condition of no surplus load embankment slope.The test results show that:the ultimate bearing capacity and ultimate displacement increase with the decrease of transverse spacing of anchor,compared with 550 mm group,the ultimate bearing capacity of 400 mm group is increased by 10.38%,and the ultimate displacement is reduced by 3.39%,compared with 400 mm group,the ultimate bearing capacity of 250 mm group is only increased by 1.3%,but the ultimate displacement increases by 38%,therefore,when the transverse spacing is 400 mm,the anchorage effect is the best.Because of the need to balance the weight of overlying soil,the influence of longitudinal spacing is greater than that of transverse spacing:compared with 400 mm group,the bearing capacity of 250 mm group changes 13.43%,more than 10.38% and 1.3%,and the ultimate displacement is the same rule.The increase of air pressure increases both the ultimate displacement and the ultimate bearing capacity,when the pressure increases from 0 MPa to 0.16 MPa,the increment of ultimate bearing capacity is 14.48%,95.57%,106.81%,and the increment of ultimate displacement is 13.52%,19.1% and 54.95%,and the best air pressure is 0.11 MPa..(3)The Q-S curves can be divided into three stages: the initial stage of loading,the middle stage of loading and the later stage of loading.At the initial stage of loading,the curve changes linearly,and the drawing force increases obviously while the displacement changes slightly.The middle stage of loading curve is arc,and the soil around the bolt enters the stage of elastic-plastic change.The later stage of loading the curve changes approximately linearly,parallel to the abscissa axis,and continues to develop into the failure stage.Finally,the force characteristics of the airbag are classified.(4)In order to analyze the mechanical characteristics of inflatable anchor under the condition of increasing the height of embankment slope the pull-out test is carried out.Three groups of surcharge are set up in the test.It is concluded that increasing surcharge can increase bearing capacity;the effect on ultimate displacement is less than that of changing anchor spacing and air pressure;it has greater influence on anchor with shallow buried depth.Combining the displacement of embankment with the ultimate bearing capacity and ultimate displacement of inflatable anchor,it is found that the inflatable anchor performs well in increasing the height of slope.(5)The Q-S curve of inflatable anchor with or without overload was fitted by 1stOpt software,and the non-linear fitted Q-S curve was obtained.It is also found that the calculation formula under overloading condition needs to be modified by adding coefficients.The range of coefficients is 1.01 < ? < 1.05.Finally,the calculation formula is obtained.(6)At the end of the paper,based on the unified strength theory,the ultimate bearing capacity of inflatable anchor is deduced theoretically,and the empirical formula of bearing capacity is obtained.It is found that the calculated values based on the unified strength theory of twin shear are compared with the experimental values,the range is-5.6% to 9.5%.When the coefficient b is 0.3 will have the best fitting.Finally,it summarizes and analyses the theoretical calculation of inflatable anchor,and finds that the calculation formula based on the unified strength theory of twin shear has smaller error,which can provide reference for optimum design.