Reliability Analysis for Retaining Pile in Foundation Pit Based on Bayesian Principle

Abstract

Moso bamboo has the advantages of high short-term strength and reproducibility, appropriating for temporary supporting structure of shallow foundation pit. According to the displacement of the pile top from an indoor model test, the reliability of the supporting effect of the moso bamboo pile was analyzed. First, the calculation formula of reliability index was deduced based on the mean-value first-order second-moment (MVFOSM)method and probability theory under ultimate limit state and serviceability limit state. Then, the dimensionless bias factor (the ratio of the measured value to the calculated value) was introduced to normalize the displacement. The mathematical characteristics of the displacement were estimated and optimized based on Bayesian theory. Finally, taking 2.5 as the design reliability index, the effect of safety factor, tolerable limit displacement, and the ratio of the ultimate limit displacement to the tolerable on reliability index was analyzed. The results show that the safety level of the supporting pile can be increased by 1–2 levels when the safety factor increases by 0.5. When the coefficient of variation of tolerable limit displacement is less than 0.3, the safety factor can be 2–2.5. And the ratio of the ultimate limit displacement to the tolerable has a great influence on the reliability index, when the soil conditions is well, the ratio can be 1.2–1.3.