Refine Detection And Safety Treatment Of Karst Cavern And Its Engineering Application

With the sustained and rapid development of national economy and the acceleration of urbanization process,the contradiction between urban infrastructure design,especially urban transport facilities and urbanization development has gradually become prominent.Rail transit has gradually become the main public transport in major cities because of its advantages of large volume,high speed,safety,reliability,punctuality and comfort.At the same time,rail transit plays an important guiding role in the process of changing the current urban structure and urban development mode.With the rapid development of rail transit,its social effects and the impact of urban development are also discussed.The economic benefit will be more obvious.Up to now,nearly 50 cities have been approved to build subway.The construction of rail transit is mainly underground engineering,which has great environmental and safety risks,but also brings risks of time limit,quality and cost.Based on Jinan Metro Project,this paper mainly studies the fine detection of karst caves in the karst area of metro tunnel and the filling treatment of new materials through the research methods of indoor test,field test,theoretical derivation and equipment development.The main research contents are as follows:(1)Starting from the forward and inversion research of resistivity method and seismic wave method,the cross gradient theory is used to organically combine the two methods.Through the joint inversion research of the results,more accurate geological model and detection results can be obtained.Finally,according to the Karst Detection situation of Jinan Metro in Jinan,a detection scheme is proposed.Based on field data acquisition,the distribution of underground structures is given by the joint inversion results of resistivity method and seismic wave method,which verifies the feasibility and effectiveness of the joint inversion theory and method.(2)The application effect of laser point cloud scanning in dry cave and water-filled cave is discussed.Aiming at the problem of fast attenuation of laser in water-filled cave detection,the influence of laser wavelength and water environment of cave on attenuation characteristics is revealed.The "blue-green window" with low turbidity and high turbidity in water environment of cave are found.The existence of near infrared window.An optimum scheme of laser maximum detection distance in complex karst cave water environment is proposed,and a method of obtaining three-dimensional point cloud of karst cave shape is formed,which realizes coordinate splicing of multi-station detection point cloud under complex karst cave,and is applied to karst cave detection along Jinan Metro.(3)For different types of karst caves,different types of filling materials are compared and selected,and the application scope,advantages and disadvantages of various filling materials are analyzed.The treatment methods of filling,semi_filling and non-filling karst caves are put forward for non-overflowing caves,and the treatment of Renla section of Jinan Metro is expounded.In this paper,a treatment method using cement-sodium silicate as filling material is proposed for overwater caverms.The relationship between setting time and water inflow time of cement-sodium silicate is studied.The results show that the effect of injecting caverns near cement-sodium silicate loss of flow is the best.