A novel reliability-based method of calibrating safety factor: Application to the cemented sand and gravel dams

Abstract

The cemented sand and gravel (CSG) dam is newly developed. Currently, the allowable safety factors of CSG dams are not well established due to a lack of engineering experience. To meet this demand, a novel framework to calibrate allowable safety factors based on reliability theory is proposed in this study. First, a sample set of CSG dams with the same safety factor are collected. Second, the reliability indices of all dams are calculated, and the reliability index distribution is analyzed, which can reveal the relationship between the reliability index and the safety factor. Third, a 90% guaranteed rate is adopted to link the allowable safety factor with the target reliability index. Updated safety factors could be derived with consideration of the uncertainty of input parameters. Such safety factors are suitable for CSG dams with materials of large heterogeneity and dispersion. The allowable safety factors of CSG dams with structure grades I, II, and III are suggested to be 2.9, 2.6, and 2.2, respectively. Dam height and cohesion significantly have a significant impact on the allowable safety factors, with sensitivity coefficients ranging from 0.29 to 0.84 and from 0.05 to 0.25, respectively. A higher allowable safety factor corresponds to a dam with a higher dam height and lower cohesion. For the high dam (70 m < h < 200 m) with low cohesion (0.3 MPa < c < 0.7 MPa), the recommended allowable safety factor is estimated to be 3.3. The new design criterion is applied to five existing projects, which proves that the proposed method can yield reasonable results.