Analytic solution to initial damage of cavern strata by complex function method

To analyze the stability of oval cavities in shallow strata in urban areas, taking both gravity stress and vertical uniformly distributed load into consideration, the accurate solution to the stress field of concealed oval cavity is got by means of the complex function method. Assuming that the Mohr-Coulomb yield criterion and the tensile stress of soil equal zero as the discriminate rule, the scope of plastic zone is obtained. The results reveal that: (1) Under the gravity stress field, the stability of round-shaped and slender-shaped cavities is better than that of the flat-shaped ones. The failure of the flat-shaped caverns is mainly caused by tensile stress. (2) Under the action of external load, the failure mode of cavern strata is a comprehensive tensile-shear failure. With the increment of external load, the plastic zone caused by shear stress will connect with the tensile zone, which will accelerate the failure caused by cavity destabilization. (3) Five kinds of partition patterns of cavern strata are put forward based on a great number of analyses and calculations. Therefore, the stability of cavern strata becomes the core of preventing catastrophic accidents. The results are of great significance in the prediction, evaluation and handling of catastrophic accidents caused by cavity strata.