Analysis And Research On Stability Of Karst Bridge Foundation Of A Expressway

With the development of economy,the construction of transportation infrastructure in China is more and more rapid.The safe operation of railway and highway must ensure the stability of subgrade and bridge foundation,and ensure that the foundation deformation is within the allowable safety range under various external factors.The karst cave joints formed by karst geomorphology develop near the surface,which have some characteristics of concealment,complexity and universality.The occurrence of collapse can not be detected by creep,which is sudden.It poses a great threat to the safe operation of traffic engineering and the safety of human life and property.This is also a major engineering problem that perplexes the construction of karst areas.Wide area and widespread distribution are the prominent characteristics of karst distribution areas in China,and their development characteristics are different.Under the background of vigorous development of Western China,it is even more important to carry out risk assessment of engineering geological conditions in Casterqi area.It is more important to evaluate the engineering geological conditions of the karst area.Therefore,it is particularly necessary to evaluate the stability of typical karst bridge foundation in the study area.Firstly,according to the research route,combining with the geographic location and climatic conditions along the project,the field geological investigation was carried out.The stratum lithology of the project,the hydrogeological conditions including aquifer rock group,groundwater type,groundwater recharge runoff and drainage were analyzed.Secondly,collecting relevant engineering data,analyzing the causes of Engineering karst collapse cases in recent years,and dividing them into five types.Combining with the investigation data analysis,the formation mechanism of collapse and the mode of karst collapse are studied.Through the existing theory,the punching,shearing and bending resistance of roof are checked.According to the properties of soil and rock strata in the bridge site area and using FLAC3 D to simulate the stress mode of the karst bridge foundation in the study area under load,the stress,displacement and interaction mechanism of collapse structure in the formation process of collapse are analyzed.According to the engineering geological conditions of bridges in the main karst areas,the karst development characteristics,geological conditions and karst hydrodynamics of the bridge site are analyzed,and the mathematical model is established by using the analytic hierarchy process(AHP)to evaluate the risk of karst collapse of the main bridge site.Finally,the corresponding suggestions for reconnaissance and construction treatment of bridge sites with different degrees of collapse risk are put forward.