Large Scale Model Test Study of Foundation Pit Supported by Pile Anchors

Abstract

Due to the special time–space and environmental effects of the foundation pit, there are many unstable factors in the construction process of the field test. The indoor model test can avoid many uncertainties in the construction process due to its operability, which can reduce the interference with the test results and improve the accuracy of the test. In order to further discuss the force-bearing characteristics and deformation laws of loess pits’ support structure in Northwest China, a large model test of foundation pit supported by a pile anchor with a geometric similarity ratio of 1:10 was designed and completed. The force and deformation characteristics of the support structure were systematically studied by simulating the conditions of additional load at the pit edge, soil layered excavated, and anchors tensioned. The test results show that: for the pile-anchor support structure, the anchors have significant limiting effects on the displacement of the piles. Especially, when the position of the first row of anchors is closer to the pile top, the displacement of the pile is smaller. The stress state of the piles was changed by the prestressed anchor. The passive stress state of piles is changed from one side of tension and the other side of compression to the active stress state of “S” shape, which makes the distribution of the bending moment of piles more reasonable. The measured earth pressure in the process of soil unloading has a nonlinear distribution, which is different from the classical Rankine earth pressure distribution; specifically, the passive earth pressure in front of the pile is more obvious. In addition, the prestress applied to the anchors has a more significant effect on the internal forces of the other anchors. Compared with sequential tensioning, the prestress loss caused by interval hole tensioning is significantly reduced. The greater the number of spaced holes, the smaller the prestress loss and the better the anchoring effect of the anchor. The results of the study can provide reference for similar model tests, and also for related engineering applications.

Anchor Shear Strength Damage under Varying Sand Content, Freeze-Thaw Cycles, and Axial Pressure Conditions

“…Substituting Equation (7) into Equation ( 8) yields the statistical damage constitutive model for the anchor-soil contact surface.…”

“…Chase Barnard and Cherdsak Suksiripattanapong et al [3,4] evaluated the mechanical properties of an anchor-soil interface in detail through on-site anchor pull-out testing. Aoxue Chen et al [5][6][7][8] explored the anchor support system of a deep foundation pit and obtained the force and deformation characteristics of the anchors in the foundation pit, pointing out that strengthening the shallow support of the foundation pit can effectively improve the safety reserve. Weizhi Su [9] conducted anchor pull-out tests with two different model boxes and proposed an exponential anchor-soil interface model.…”

Special Issue on the Geo-Environmental Problems Caused by Underground Construction

“…Zhang et al [2] used the GEO-Studio finite element software to explore the influence of the comprehensive slope rate on the permanent displacement when the slope rate of each grade of multi-stage loess slope changes and the stage of multi-stage slope changes. Additionally, Su et al [3] completed a large model test of a foundation pit supported by a pile anchor with a geometric similarity ratio of 1:10. In their paper, the researchers discussed the force and deformation characteristics of the support structure by simulating the conditions of additional load at the pit edge, soil layered excavated, and anchors tensioned.…”

Theoretical Study on Diaphragm Wall and Surface Deformation Due to Foundation Excavation Based on Three-Parameter Kerr Model

“…Excessive deformation caused by pit excavation leads to slope instability, which affects construction safety and is not conducive to the goal of sustainable development of a project. At present, research on the horizontal displacement of diaphragm walls caused by foundation excavation mainly includes field monitoring [1], model tests [2], theoretical calculations [3], and numerical simulations [4,5]. The existing theoretical studies mainly include the limit equilibrium method, elastic foundation beam method, and variational method.…”