###### Abstract  
The support system is the most important part of foundation pit engineering, which mainly determines the safety of foundation pit engineering. Based on the characteristics of the foundation pit of Changsha international financial center, the original pile-anchor-beam (PAB) support system is improved into a new form of support system, the pile-anchor-ribbed-beam (PARB) support system. This study establishes a numerical simulation model to calculate the surface settlement and the deformation of the retaining structure caused by the excavation of the foundation pit by using the PAB and PARB support systems, respectively. Finally, this study analyzes the influence of pile anchorage depth, ribbed beam size and waist beam size on the support effect. The field monitoring data are in good agreement with the numerical simulation results, which verifies the validity and accuracy of the numerical calculation model. The support effect of the new PARB support system is 30% higher than that of the original PAB support system. The position of maximum surface settlement is about 0.5 times the excavation depth from the retaining structure, and the position of maximum lateral deformation of the pile is about 0.9 times the excavation depth from the pile top. The increase in pile embedded depth and ribbed beam size can significantly improve the support effect, while the change of waist beam size does not improve the support effect significantly. foundation pit; support system; deformation analysis; parameter influence +
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(pole) support is an improved support system based on the cast-in-place pile wall, in which the anchor bolt and the anti-slide pile provide anchoring force and sliding resistance force to jointly resist the sliding of the soil behind the support. The cast-in-place pile and anchor cable (pole) support system is favored by designers and scholars, because of its good support effect and stability. Many scholars have studied the disturbance effect of foundation pit excavation by the cast-in-place pile and anchor cable (pole) support system in laboratory tests, numerical simulation, on-site monitoring, etc. [PERSON], et al. [8] presented a complete case record of a deep foundation pit with pile-anchor retaining structure excavated in red sandstone stratum, and established an FEM to analyze the additional stress and deformation induced by the excavation. Both the measured and numerical simulation results show that the deformation of the pile-anchor supported deep excavation is significantly affected by the spatial effect. [PERSON] et al. [9], based on the analysis of the deformation data of a pile-anchor supporting a deep foundation pit in Harbin, obtained from monitoring during the winter, investigated the influence of freezing and thawing cycles. The results show that the horizontal displacement in the middle of the shallow layer of the foundation pit is significantly larger than that on both sides during the freeze-thaw cycles, and the spatial effect becomes noticeable. [PERSON] et al. [10] designed a large model test for a foundation pit supported by a pile-anchor with a geometric similarity ratio of 1:10 to study the force and deformation characteristics of the support structure. The test results show that for the pile-anchor support structure, the anchors have significant limiting effects on the displacement of the piles. [PERSON] et al. [11] used physical model tests to study the deformation law of the piles and the surrounding soil during the excavation of the deep foundation pit, revealing the variation law of earth pressure in time and space in the pit and then verified it by numerical simulation. The result show that the embedded depth has a significant effect on the deformation and earth pressure distribution of the foundation pit. [PERSON] et al. [12] carried out a large number of parametric studies considering all aspects of soil-structure interaction or different excavation geometries to find the optimal design.