It is difficult to solve the leakage problem of large underground structures,in which the width and quantity of cracks on concrete floor directly determine the leakage severity of the whole underground structure, but there are few studies on the distribution characteristics of cracks after cracking. In this paper, the expressions of crack location, width, and spacing of concrete floor under increasing temperature and shrinkage effect were obtained by analytic method, and the distribution characteristics of cracks were described. Under the condition that the surface of the slipping steel bar was subjected to approximately uniform friction (concrete tensile strength) and the concrete at the slipping critical point was the ultimate 100×10-6tensile strain, the relationship among the parameters of the steel bar tension, the slipping length and the deformation of the steel bar was obtained, and then the width of the first crack and the displacement and stress distribution in the new floor plate were calculated. When the location of cracks and the stiffness of slipping reinforcement were constant, the new combination stiffness and free displacement value of the floor body were obtained from the calculation of the coordinate origin and the end block to a crack, and then the crack width after stress redistribution was solved. Under the continuous increase of temperature or shrinkage strain, the assembly block stiffness and maximum tensile stress after the emergence of new cracks were calculated, and the position of existing cracks and the stiffness of slipping bar for the next step were stored. Up to the strain maximum, the final crack width and spacing of the whole block were obtained. The method of describing cracks character of concrete floor was established. Finally, 0 ~ 350×10-6temperature or shrinkage strain was continuously applied to a concrete floor with a size of 80 m×20 m×0.4 m, and the cracks distribution characteristics calculation was finished in five time cracking process.
