| With the rapid development of the economy,my country’s transportation construction continues to advance to the west.In the process of designing and constructing expressways,there are a large number of karst areas in Guizhou,Guangxi,Yunnan and other provinces,and the development of karsts is seriously harmful to expressways.The route is difficult to avoid because of the variety and wide distribution of karst.Therefore,how to reasonably evaluate the stability of karst roadbed has become a key problem that needs to be solved urgently in engineering construction.For this reason,this paper takes the karst roadbed project of a highway in Hunan Province as the background,considers the spatial form and roof load of the karst cave under the roadbed,and simplifies the karst roof into a parabolic arch model and a circular arch model,and establishes its theoretical analysis method.Theoretical calculation is carried out according to the engineering case,and the numerical model is established by ABAQUS finite element software,and the karst cave model with different vector heights f is established under the load of the overlying soil layer and the subgrade,and the numerical calculation results obtained are compared with the theoretical calculation results to verify the feasibility of numerical analysis.At the same time,the stability of the karst subgrade cave roof with different sag heights is analyzed,and the variation law of the safe thickness of the karst roof of the expressway with the sag height,span,and overlying soil height of the karst cave is revealed.Through the research,the following conclusions can be drawn:(1)The change of the sag height has a significant effect on the minimum safe thickness of the roof of the two simplified models,and other factors(the span of the cave and the height of the overlying soil layer on the roof)also have a greater impact on the safe thickness of the roof,indicating that the spatial shape of the cave and the The sag height is a key factor in the evaluation of the stability of the karst subgrade roof.Therefore,in the actual project,the stability evaluation of the roof needs to find out the spatial form of the karst cave and the soil parameters of the rock and soil mass,so that the evaluation results are more in line with the actual engineering.(2)By analyzing the influence of various factors in the karst area on the ultimate bearing capacity of the roof of different karst cave vector height models,the karst cave span,the thickness of the overlying soil layer,and the physical and mechanical parameters of limestone cohesion and internal friction were analyzed under the condition of a certain roof thickness.The relationship between the four factors of angle and the ultimate bearing capacity of the karst cave roof was obtained,the ultimate bearing capacity of the karst cave roof under different working conditions was obtained,and the influence rule of the above factors on the roof bearing capacity of different karst cave vector height models was obtained.(3)Orthogonal numerical test is carried out for each influencing factor,and the influence degree of each factor on the ultimate bearing capacity of the karst cave roof is systematically studied,and the primary and secondary relationship between the influencing factors is obtained by combining the orthogonal parameter analysis theory,that is,the height of the overlying soil layer>Limestone cohesion>karst cave span>limestone internal friction angle,the relevant conclusions can provide reference for similar projects in the future. |
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