Study On The Subgrade Diseases In Permafrost Of Qinghai-Tibet

For the settlement of half filled and half excavated roadbed,it is generally caused by the compression of the fill and the sliding of the slope.Therefore,to solve the uneven settlement at the top of the half filled and half excavated roadbed,it is necessary to eliminate soil compression and control the sliding of the slope.Based on this,this article aims to reduce the settlement of the top surface of the roadbed,and studies the use of grouting method to simultaneously inject grout on the top and slope of the half filled and half excavated roadbed to overcome the shortcomings of only considering soil compression settlement and not considering the stability of the fill slope when commonly used for top grouting.Taking the investigation of semi filled and semi excavated roadbed diseases in a mountainous area of Fuyuan County,Yunnan Province as the background,FLAC3 D numerical simulation was applied to study the uneven settlement of the top surface of different heights of semi filled and semi excavated roadbed,the maximum displacement of the slope,the maximum shear strain increment,plastic zone,safety factor,and other changes and influencing factors of grouting method,gravity embankment wall,and grouting method+gravity embankment wall.The following main conclusions were obtained:(1)Based on the investigation of the diseases of the semi filled and semi excavated roadbed and the form of the roadbed section,a geometric conceptual model for semi filled and semi excavated roadbed was established through FLAC3 D numerical simulation calculation.The numerical simulation calculation parameters for grouting reinforcement were determined through analysis and demonstration.(2)By establishing numerical simulations of grouting at the top of the roadbed,grouting at the top of the roadbed,and simultaneous grouting at the slope,a comparative analysis was conducted.The results showed that the smaller the spacing between grouting at the top of the roadbed,the smaller the settlement at the top,and there was no impact on the stability of the slope;When grouting at the top of the roadbed and the slope simultaneously,not only is the settlement reduction at the top of the roadbed smaller than when grouting alone at the top of the roadbed,but also the stability of the slope is significantly improved.The grouting reinforcement effect can be controlled based on the grouting spacing of the slope,and the smaller the spacing,the better the reinforcement effect.(3)The stability of half fill and half cut subgrade is analyzed by numerical simulation of grouting reinforcement of different subgrade fill widths and heights,and the strength reduction method is used to solve the safety factor of the research model.The results show that the fill width has a certain impact on the reinforcement effect,while the height has a greater impact on the reinforcement effect;After grouting reinforcement,the average safety coefficient increases by 50%,the plastic zone area decreases,and the shear strain increment shows a state of disconnection during grouting reinforcement displacement,resulting in a significant reduction in the settlement of the top of the roadbed.(4)Under the same slope height,three kinds of reinforcement measures are adopted to conduct numerical simulation analysis on the treatment of half fill and half cut subgrade,and the self compiled strength reduction method in fish language is used to solve the safety factor of the slope after different reinforcement measures.The results show that the stability of half fill and half cut subgrade is improved after the reinforcement of gravity embankment wall,but the settlement problem of the subgrade top is not solved,the plastic area is reduced,and the safety factor does not meet the specification requirements when the slope height is greater than 20m;Composite reinforcement has high slope stability,reduced plastic zone area,and significantly reduced settlement at the top of the roadbed in all studied models;Considering both economy and safety,grouting reinforcement is the most economical and reasonable reinforcement measure.