Study On Shear Characteristics And Road Performance Of Polypropylene Fiber Reinforced Tailings

Mining industry is one of the pillar industries of China ’s national economy and plays an important role in China ’s resource structure.In recent years,the rapid development of economy is inseparable from the support of mineral resources.However,due to the non-standard mining of minerals in the past,a large number of tailings have been accumulated,which has caused the waste of land resources,induced geological disasters,increased safety hazards,and consumed a lot of human and material resources.In recent years,the rapid development of China ’s transportation industry has led to a shortage of building materials.The problem of material shortage is solved by using the stockpiled tailings.Fibers are added to the tailings to improve the overall mechanical properties of the tailings,so that it can meet the engineering requirements of high standards.And because the fibers are randomly distributed in the tailings,the reinforced soil has approximately isotropic mechanical properties.In this paper,a series of laboratory tests were carried out based on iron tailings and polypropylene fibers,and the effects of different fiber parameters on the shear and road performance of reinforced tailings were studied.According to the results of laboratory tests,the finite element model of shear performance of reinforced tailings was established by means of reinforcement-soil separation,and the stability of subgrade slope was analyzed by means of reinforcement-soil calculation.The main research work is as follows :(1)Polypropylene fiber can significantly improve the shear strength of tailings.With the increase of fiber content,the optimum fiber content will appear.The optimum fiber content measured in this paper is 0.3 %;When the fiber content is constant,the fiber length is changed,and the shear strength of the reinforced tailings increases with the increase of the fiber length.With the increase of water content,the shear strength of reinforced tailings increases first and then decreases.When the water content is 7 %,the shear strength of reinforced tailings is the largest.(2)Through the compaction test and bearing ratio test,the influence of different fiber content and fiber length on the road index of reinforced tailings was discussed.By changing the fiber parameters,the optimal moisture content of the reinforced tailings fluctuates in the range of 6.74 %-7.25 %,and the maximum dry density generally shows a decreasing trend;The CBR value of reinforced tailings increases first and then decreases with the increase of fiber content,and continues to increase with the increase of fiber length.The road performance test provides a theoretical basis for the engineering application of reinforced tailings.(3)Based on the direct shear test conditions and data of polypropylene fiber reinforced tailings,the pre-processing of ABAQUS is redeveloped by Python language.The random distribution of fibers in the tailings matrix is realized,and the numerical model of reinforced tailings is established.The direct shear test was simulated,and the simulation results were compared with the indoor test results to verify the validity and accuracy of the model and script.(4)ABAQUS finite element software was used to study the safety and stability of subgrade slope under different fiber content,fiber length and rainfall intensity.The plastic cloud diagram of subgrade slope and the safety factor of slope stability under various factors were obtained.