Research For The Disease Assessment And Prevention And Control Of The Large Deep Buried And Operating Tunnel In Karst Region

Infrastructure construction has achieved rapid development in our country inrecent years. The total distance of expressway construction is increasing constantly.With the increase of highway construction, there are rich achievements in thetunnel construction, however, there also appear some problems, even a good deal oflining problems in some newly constructed tunnels. On the one hand, the emergenceof these problems is related to the fuzziness and complexity of the tunnel engineering;on the other hand, it has something to do with the construction technology andquality control of the tunnel engineering. Based on the design and testing data of ahighway in southwest China tunnel, this article analyzed the lining thickNess defect,cavity defect, and lining crack defect. The main content and the results are as follows:It analyzed the design and testing data of the tunnel in detail, classified the tunneldefect, and introduced the common testing content and methods of the tunnel defect.It analyzed the influence on the structural stability that lining defect in the gradeIII,IV and V surrounding rock had by using the finite element software ANSYS. Andthen it arrived at the relationship of lining thickNess and the structural safetycoefficient, bending moment, axial force and shearing force. It concluded that thechange rule of the lining structural safety coefficient, bending moment, axial forceand shearing force in the grade III surrounding rock is consistent with that of thegrade IV and Vsurrounding rock. Dangerous sections of the lining structure lie in thevault, haunch and the corner of the flank wall.It analyzed the influence on the structural stability that the cavity defect in thegrade III and IVsurrounding rock had through numerical calculation. And then itconcluded the change rules between the maximum tensile stress of the liningstructure and the cavity width, the cavity height, the cavity acreage. And it claimedthat the amplification of the maximum tensile stress of the lining structure that thechange of the cavity size in the grade III surrounding rock had is greater than that ofthe grade IV surrounding rock had. And the influence on the maximum tensile stressof the lining structure of the change of the cavity width is greater than that of thechange of the cavity height.By analyzing the assessment method of the tunnel lining crack, it put forwardtwo assessment methods, including a method of lining monolete which is convenient to test and distinguish on the spot, and a comprehensive assessment method “themost unfavorable principle” of the whole tunnel lining crack.It investigated the cause of the lining thickNess defect and the cavity defect fromthe perspective of tunnel construction. And it also analyzed the cause of the liningcrack from the point of surrounding rock deformation and the lining defect itself. Andit concluded that the tunnel lining thickNess defect and the cavity defect are closelyrelated to the quality control during the construction. When there exists defects in thelining structure, the bending, shear and tension of the structure often lead to thetensile fracture and the dislocation fracture in the structure. According to these, theauthor put forward the prevention and treatment measures of the tunnel disease.