Model Test And Numerical Simulation Analysis Of Loess Slope Strengthened By Frame Anchor

With the further development of Chinese reform and opening up and the development of the western region,the economic construction in the Northwest region has made rapid progress.As an important cornerstone of the national economy and social development,the transportation industry,Most of the Northwest China is the Loess Plateau,and most of them are mountainous and hilly landforms.Therefore,slope engineering will inevitably be encountered in the engineering construction.It is of great significance to study the deformation law,influencing factors,stability and reinforcement methods of loess slope under load,which is of great significance for maintaining the stability of loess slope and promoting the infrastructure construction in Northwest China.The effect of frame bolt support on improving slope stability and reducing slope deformation is remarkable.In recent years,frame bolt anchoring has the advantages of simple manufacture,convenient construction,short construction period,low cost and so on.The method of using frame bolt to improve slope stability and control its lateral displacement is more and more used in engineering.The geographical environment of our country is complex,and the development time of frame anchor support technology in our country is relatively short.There is no detailed specification for the construction methods of many specific working conditions.Therefore,this paper,referring to a practical project,through indoor model tests,from two aspects: different anchoring methods and different anchoring angles.The ultimate bearing capacity of loess slope,stress distribution of soil,sliding displacement of slope and stress distribution of anchor rod are studied.Then the numerical simulation is carried out by using MIDAS/GTS NX finite element software,and the results are compared with the results of indoor model test.The main contents of this paper are as follows:(1)To find out the research status of frame bolt support,and summarize the characteristics of frame bolt support structure from the aspects of theoretical research,experimental research and numerical simulation.This paper analyzes the action mechanism and mechanical characteristics of frame prestressed anchor support structure.In view of the fact that scholars at home and abroad have little research on the action mechanism of frame bolt in loess slope and the problems of frame anchor support technology in slope anchoring,the scheme of indoor model test is worked out.The main contents of this paper are put forward.(2)The anchor rod used in indoor model test is an iron screw with diameter of 8 mm and length of 800 mm.The diameter of anchor hole is 25 mm,the cement used for grouting mortar is Portland 42.5 cement in Qilian Mountain,the water-cement ratio is 0.45: 1,and the ratio of ash to sand is 1: 1.The filling is Lanzhou loess,and the optimum moisture content of the soilis determined by geotechnical test.The maximum dry density,cohesive force and internal friction angle,and other soil parameters.Through model test,the loess slope with unreinforced,waist beam anchoring and frame anchor rod Anchorage is tested,and the displacement of slope body,the force of anchor rod and the force of frame beam under different roof loads are compared and analyzed.The variation of the distribution and the ultimate bearing capacity of the slope provides a reference for the engineering practice in the future.(3)Under the condition of certain slope density and moisture content,the indoor anchor drawing tests were carried out under the same roof load with different anchoring angles.Through comparison and analysis,it can be seen that with the increase of anchor angle,the anti-pull-out force of the bolt increases first and then decreases.When the anchor is inclined to 40,the anti-pulling force reaches the maximum,that is 40 is the optimal anchoring angle.(4)Under the condition of single grade slope,the bearing capacity of the slope under the anchor of the waist beam is tested,and the support effect of the different anchoring position of the waist beam on the slope is explored.Through the comparison and analysis of the test results,it can be seen that the ultimate bearing capacity of the slope increases first and then decreases during the change of the Anchorage position of the waist beam from the top to the bottom.When the waist beam is located 1/2 of the slope height,the ultimate bearing capacity of the slope is the largest and the anchoring effect is the best.By comparing and analyzing the effect of no support,waist beam bolt support and frame beam bolt support,it is found that the effect of frame beam bolt support is the best.(5)Using Midas/GTS NX finite element software,the stability coefficient of slope,the settlement of slope top,the lateral displacement of slope and the stress distribution of soil are studied under different anchoring forms during slope excavation.The mechanism of frame bolt supporting structure and the effect of waist beam anchor support are analyzed.The conclusion is basically consistent with the change trend of indoor model test,and the correctness of the model is verified.The research results can provide reference for similar loess slope reinforcement.