Abstract: Stability analysis of foundation pit support without considering the random uncertainty of soil parameters, and the uncertainty of soil physico-mechanical parameters may lead to unreasonable results. In view of this, the reliability theory is introduced. But the traditional methods of simple and quadratic of the two ranks quadrature require the transformation of basic random variables or the equivalent normalization. This transformation has also led to nonlinear performance function, thus becoming a source of error. The integration probability density function of the basic variable in the failure domain is adopted to calculate the failure probability of structure. In the maximum possible points of the failure, making the logarithm of the probability density function of basic variables into a Taylor series and taking development to the second item; the performance function is also as a Taylor series expansion. Using super tangent plane or quadratic hypersurface plane to approximate the actual failure surface, then the achievements of simple and quadratic of the two ranks quadrature methods are used to complete the asymptotic probability of failure points. A method of the asymptotic integration of reliability analysis is proposed for foundation pit support; and its application to the Hongzecheng projects of Tianjin shows that the method not only considers the randomness of the parameters, but also avoids errors of normal state changing or equivalent normalizatin. It provides an effective way for the reliability analysis of supporting structure.

Key words: foundation pit, supporting structure, stability, reliability, asymptotic integration method