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

Abstract

In this study, a deep foundation pit project of Nanlishi Road in the Xicheng District of Beijing was taken as the engineering background. Based on the monitoring method of that project and referring to its design scheme principle, this study applied advanced monitoring technology methods such as anchor axial force and deep horizontal displacement monitoring. The mechanism of pile–soil interaction, the stress change and deformation law of the three-pile and two-anchor support systems of deep foundation pits, and the stability of deep foundation pit support in an anhydrous sandy pebble stratum, were studied in depth. Results show: The axial force of the anchor rod had great loss in the early stage of prestressed tension locking; with the deepening of foundation pit excavation, the lateral pressure of stratum increased gradually, and the prestress of the anchor increased until the end of excavation, where it tended to be stable; the maximum horizontal displacement of the pile was smaller than the design value, and the maximum horizontal displacement was not at the top of the pile; the axial force of the prestressed anchor varied with the formation pressure and surrounding load; the tension of the lower anchor had a certain influence on the axial force of the upper anchor. Except for the east side of the foundation pit, the anchors of the first layer were all stabilized at about 140 kN, and the anchors of the second layer were stabilized at about 150 kN. The third row of anchors on the north side was stable at around 170 kN. By analyzing the variation law of stress and deformation of the supporting structure of the foundation pit, the timeliness of the data during the construction process was improved, and a reference is provided for the informatization construction of related working conditions.

Research on the Deformation Law of Foundation Excavation and Support Based on Fluid–Solid Coupling Theory

“…However, due to the differing geological conditions in various regions and the lag in corresponding theoretical system updates, frequent accidents during excavations have occurred [ 3 , 4 , 5 ]. Through a comprehensive analysis of various excavation accidents, two main types were identified: one is the collapse of the excavation itself, caused by the instability of the excavation support structure [ 6 , 7 , 8 ], and the other is the overturning of the excavation due to excessive settlement around the excavation [ 9 , 10 , 11 ]. A further analysis of the destruction mechanisms based on the accident type revealed that approximately 90% of excavation safety issues are attributed to the mutual influence of excavation seepage and soil consolidation [ 12 , 13 , 14 ].…”

Stability of a Deep Foundation Pit with Hard Surrounding Rocks under Different in-Time Transverse Supporting Conditions

“…The development of urbanization is bringing more and more tests of traffic in cities. In order to ease traffic pressure, governments have taken various measurements, such as widening roads, building more flyovers, and developing underground traffic systems [1][2][3]. Among these measurements, underground traffic systems are the most effective since land resources are very scarce in cities.…”

Numerical Simulation Study on Application of T-Shaped Composite Pile Support System in Super-Large Foundation Pit Support Engineering

“…The selection of support structures has a significant impact on foundation pits. Sun et al [17] studied the stress changes and deformation patterns of the three-pile and two-anchor support systems for deep foundation pits, as well as the stability of deep foundation pit supports. The results demonstrated that the lateral pressure of the formation gradually increased with the increasing excavation depth of the foundation, and the pre-stress of the anchor rod gradually increased until the excavation ended and tended to stabilize.…”