Deformation Characteristic of a Supported Deep Excavation System: A Case Study in Red Sandstone Stratum

Abstract

A complete case record of a deep foundation pit with pile-anchor retaining structure excavated in red sandstone stratum is presented in this study. The horizontal displacement of pile top, the horizontal displacement at various depths, the axial force of anchor cable, and ground settlement during construction are measured. A three-dimensional numerical model is established to analyze the additional stress and deformation induced by the excavation and the accuracy of the FEM model is verified by comparing with field measured results. 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. The results show that the deformation in the middle of the foundation pit is greater than the pit angle and that the deformation of the long side is greater than that of the short side and gradually decreases from the middle to the pit angle. The deformation and stress in the middle of the long side of the foundation pit are the largest, which is the most unfavorable part. With the increase of vertical excavation depth, the spatial effects tend to increase, and the influence scope of spatial effects is about five times the vertical excavation depth in the red sandstone stratum. The ground settlement outside the pit is mainly distributed in a groove shape, and the maximum settlement occurs about 8.5 m away from the pit edge. Finally, parametric studies of reinforcement parameters indicated that 1.5–2.0 times the initial elastic modulus and cohesive force of soil should be used for reinforcement. It is recommended that the ranges for pile diameter, pile spacing, anchor cable prestressing and inclination angle should be selected as 0.8–1.2 m, 1.4–2.0 m, 100–150 kN, and 10°–20°, respectively.

Analysis of Slip Failure Characteristics and Support Deformation Law of Structural Planes and Rock Foundation Pits with Developed Karst Caves

“…It can be identified through the research above that conventional supporting methods have certain disadvantages in controlling the deformation of retaining piles, especially when the slip surface is uncertain. Narrowing the spacing of retaining piles will remarkably increase the supporting cost and construction period, but the greater the excavation depth of foundation pit, the more obvious the space effect [27,28]. Therefore, this paper attempts to adopt the spatial effect-based sectionalized support control technique to artificially construct a dense space to improve the engineering efficiency and support effect, avoiding the influence of weak structure on the overall stability of rock mass [29].…”

Ground Deformation Associated with Deep Excavations in Beijing, China

“…The results of hundreds of pits with different lengths, widths, and excavation depths were analyzed. The surface settlement is affected by excavation geometry [17] (i.e., length, width, and depth of excavation), and it regularly changes with the width of the foundation pit [18]. A small length-width ratio produces little ground movement [19].…”

Study on Design and Deformation Law of Pile-Anchor Support System in Deep Foundation Pit

“…The literature [11,[29][30][31][32][33][34][35] applied the theory to the monitoring data processing and inversion analysis to obtain the support structure and stratum stress, compared them with the design results to evaluate the rationality of the design, and discussed the corresponding improvement methods from a theoretical perspective. The literature [36][37][38][39] proposed a three-dimensional space effect of the foundation pit retaining structure deformation by monitoring a deep foundation pit in soft soil. The literature [40][41][42], combined with the monitoring data of the whole construction process, studied the influence of deep foundation pit excavation on an existing adjacent building structure.…”