Analysis Of Bearing Characteristics And Failure Mode Of Geosynthetic-encased Stone Columns Structure

With the advancement "The Belt and Road" initiative of our country,China and the countries along the Belt and Road Initiative are implementing projects linking global infrastructure,and the geological conditions of these countries along the route are extremely complicated.In addition,the distribution of soft soil in China is very extensive,and a large number of transportation infrastructure often passes through the soft soil layer,Therefore,there are a lot of foundation treatment problems.As a fast and economical foundation treatment method,geosynthetic-encased stone columns have been widely used in the new construction of highways,the widening of existing highways and the soft roadbed treatment of high-speed railways.At present,the research on geosynthetic-encased stone columns mainly focuses on the macroscopic force characteristics of its subjected to static load.Based on the above reasons,this paper,combined the existing research results,utilizes numerical simulation and theoretical analysis to investigate the bearing characteristics and failure modes of geosynthetic-encased stone columns under static and dynamic loads,and to reveal the deformation and failure characteristics of geosynthetic-encased stone columns from the perspective of macroscopic and mesoscopic,respectively.Thus,it can provide useful parameter indicators and effective calculation ideas for relevant design and construction specifications.The main research contents and results are as follows:1.The parameter sensitivity analysis of geosynthetic-encased stone columns was carried out.including six influencing parameters: the surrounding soil’s elastic modulus,internal friction angle,cohesion,the crushed stone’s elastic modulus,internal friction angle and elastic modulus of reinforcement.The bearing characteristics and failure modes of single piles with geosynthetic-encased stone columns under static load are studied from a macroscopic point of view by analyzing the law of stress-sedimentation,pile-soil stress ratio,lateral deformation of piles and stress of tendons.2.By establishing different numerical models,the effects of length and location of the reinforcement,and the bearing layer of the pile end on the bearing capacity of geosynthetic-encased stone columns are studied to obtain the influence rules of length and location of reinforcement,strength and height of bearing layer of pile end on the bearing capacity of geosynthetic-encased stone columns.3.The numerical models of pile group of geosynthetic-encased stone columns are established.The soil arching effect and its evolution process of geosynthetic-encased stone columns group are studied.The influence of net distance between columns,height of cushion layer at columns top and diameter of columns on equal sinking surface of soil arching effect is analyzed.The ratio of equal settlement height to net distance between piles is obtained.Therefore,the ratio of the height of the equal sinking surface to the net distance between the columns is obtained,and the mechanism of soil arching formation of geosynthetic-encased stone columns group is revealed.4.The numerical models of geosynthetic-encased stone columns under dynamic load are established and the mechanical response of geosynthetic-encased stone columns under cyclic loading is simulated to analyze the variation rules of displacement,acceleration,velocity and dynamic stress at different positions of columns are analyzed and to investigate the influence of the center value,amplitude and frequency of dynamic load on the bearing characteristics of geosynthetic-encased stone columns.5.The discrete-continuous coupling numerical models for the static load of a single pile of geosynthetic-encased stone columns are established.The evolution laws of load-stress,displacement of gravel particles,contact force of reinforcement,porosity and contact number at traditional gravel columns,part and full-length wrapped reinforcement materials in columns body are comparatively analyzed.In addition,the failure process and failure mode of these three kinds of columns are studied.The results show that the internal friction angle of the gravel and the elasticity of the reinforcement are most beneficial to improve the bearing capacity of the columns.The reinforced stone column with full-length wrapped is advantageous to improve the bearing capacity of the column body,while the partial wrapped reinforcement is not conducive to exert lateral restraint.Both the partially wrapped gravel column and the traditional gravel column produce bulging damage,while the full-length wrapped geosynthetic-encased stone columns appear the lacerating damaged.