Qiwei Wan

Engineers pay more and more attention to the economic benefits of foundation pit engineering. At present, the optimal design of the foundation pit supporting structure mainly focuses on strength and functional design, and there is no mature theoretical design method for deformation control. In this paper, a method for calculating the overall deformation of a foundation pit supporting structure based on the principle of minimum potential energy is proposed. Based on this method, the optimal design of the foundation pit of Guangzhou Baiyun District Comprehensive Transportation Hub Metro Station is realized. The deformation calculation results and optimization design scheme are validated by finite element numerical simulation and field monitoring data. The results show that the proposed theoretical algorithm predicts the pile deformation curves better than the finite element method, suggesting the proposed theoretical method is reasonable and the optimization scheme of the retaining pile is feasible. In the optimized design, the deformation of the foundation pit retaining pile is controlled by its push-back effect. The proposed deformation calculation method can realize the overall deformation calculation of the foundation pit supporting structure.

Conventional methods for designing retaining structures are not applicable to asymmetric excavation or deformation-based designs. This study proposes a quadruple-line displacement-dependent earth pressure coefficient model. Based on the proposed model, an analytical solution was developed to facilitate the deformation-based design of the asymmetric length of retaining walls propped at the crest. Furthermore, the effects of the soil internal friction angle, strut stiffness, excavation asymmetry level, and deformation control value on the embedment ratio (R_e) of retaining walls were investigated. The results showed that R_e determined by the classical equivalent-beam method is unsafe due to its basis on the ultimate-state earth pressure theory. The R_e value of the shallower side exhibited greater sensitivity to asymmetric excavation than that of the deeper side. The retaining structure’s required R_e decreased with an increase in the excavation asymmetry level. The required R_e on either side of the retaining structure decreased as the deformation control values increased. The controlled deformation had a more obvious effect on the R_e value of the retaining structure on the deeper side. The proposed method can be used for the deformation-based design of asymmetric wall lengths of retaining structures propped at the crest, considering the different excavation depths on both sides.

DIC technology is widely used in civil engineering surveying technology. In order to improve the calculation speed and accuracy of DIC technology, based on the basic principle of DIC and the characteristics of SIFT algorithm, this paper extracts the feature points and improves the DIC method, which not only ensures the accuracy but also reduces the amount of calculation. Through the analysis and comparison of the control variables of the displacement calculation method before and after the improvement of the digital images of soil and concrete, it is concluded that the calculation speed can be increased by more than 12 times when the calculation accuracy is more than 90%. When the calculation accuracy is more than 99.5%, the calculation speed can be increased by 4~6 times according to the surface properties of different materials. The result shows that the deformation of other parts can be estimated by the deformation characteristics of some points, and the calculation speed can be greatly improved when the accuracy is high.