Research On The Influence Of Xuzhou Shallow Overburden Karst On The Settlement Of Tunnel Segments And Ground Surface

In this paper,the Xuzhou Metro Line 2 Normal University Station to the Central Hospital Station section of the shield tunneling project through the karst area as the engineering background,through the collection of data,field investigations,theoretical analysis and numerical simulation and other research methods The engineering geological problems were summarized and analyzed.The force,displacement and surface settlement of the lining segment structure when the subway shield tunnel passed through different karst areas were studied and analyzed in depth,and the following conclusions were obtained:(1)Analyze the basic factors of karst development in the study area,mainly from three points: groundwater,stratum lithology and geological structure.The characteristics of karst development mainly include the distribution area of soluble rock,the morphological characteristics of karst caves and the spatial distribution of karst caves.(2)There are two major engineering geological problems when the shield tunneling of Xuzhou Metro Line 2 crosses the karst area,namely,surface subsidence and water and mud inrush.The basic conditions,modes and mechanism of typical karst collapse in the study area are analyzed.The basic conditions,types,inducing factors and characteristics of karst water inrush and mud outburst are studied.(3)Based on the engineering geological background mentioned above,a numerical calculation model was established to study the structural stress analysis and surface settlement of the shield tunnel through different karst tunnels in the area and the following conclusions were obtained:a)Lining segment displacement and ground settlement displacement are negatively related to the distance d from the cave roof to the lining segment.The lining segment structure also has a negative correlation with d in terms of maximum principal stress and minimum principal stress.When d is 8m,it is the safe distance.b)The surface settlement displacement of the lining segment is negatively correlated with the degree of cave filling w,and the structure of the lining segment is also negatively correlated with w in terms of the maximum principal stress and the minimum principal stress.c)Since most of the karst caves encountered in the study area are located at the same buried depth of the tunnel,this paper simulates and calculates the influence of the different diameters D of the karst on the right side on the structure of the lining segment and the ground settlement.D is positively correlated.The paper has 80 pictures,6 tables,and 61 references.