Study on Risk Assessment of Steel Pipe Pile Cofferdams in Geological Conditions of Water-Rich Sand Layers

As a large-scale temporary enclosure structure for bridge foundation projects, steel pipe pile cofferdams face a large number of uncertain risk factors during the construction process. In order to accurately evaluate the safety risk level of steel pipe pile cofferdams and enhance project emergency management capabilities, after a year of on-site practice and investigation, a risk assessment model based on the combination weighting-cloud model was proposed, which adopted the Lagrangian minimum entropy principle to combine the determined subjective and objective weights, and output the evaluation language with the forward and reverse generators of the cloud model. The evaluation language presented quantitative evaluation results based on the three digital characteristics of E_x, E_n and H_e mapped by various data. Taking a highway and railway combined bridge under construction as the project background, a case analysis was conducted on the steel pipe pile cofferdam project in the water-rich sand geology. The results indicated that the evaluation results were good and basically in line with the actual situation on site. In the condition of a super entropy H_e of 0.03, the numerical characteristics of the overall evaluation cloud of the steel pipe pile cofferdam were 3.543 8, 0.815 4 and 0.328 5. It was reflected the cofferdam was in a relatively low risk. The proposed evaluation model could provided effective means and scientific basis for the safety management of steel pipe pile cofferdams.