Optimization of bentonite parameters for shield tunneling based on response surface method

In order to determine the optimal parameters of bentonite improvement in the strongly weathered granite strata in Jinniu Mountain-Gongye Road shield interval of Fuzhou metro line 4, the concentration and mixing ratio of bentonite slurry and advancing speed of shield are selected as the three factors, and the slump, permeability and improvement cost of soils are taken as the response values. The central composite design (CCD) method is used to carry out 20 groups of tests, and the response surface functions of each response value are constructed respectively. The results show the concentration and mixing ratio of bentonite slurry and advancing speed of shield all have great influences on the improvement effect of soils, and there is a significant interaction among these factors. By using the response surface-satisfaction function, the optimization problem of three response values for soil improvement is transformed into that of a single response value, and the optimal improvement parameters of the strongly weathered granite strata under different advancing speeds of shield tunneling are obtained. The proposed method is scientific and reasonable, which provides a technical guarantee for the efficient construction of Jinniu Mountain-Gongye Road shield interval in the strongly weathered granite strata.