Displacement Monitoring during the Excavation and Support of Deep Foundation Pit in Complex Environment

Zhouqiang Li,Rihong Cao

doi:10.1155/2021/5715306

Abstract

Taking a super large deep foundation pit project as an example, the horizontal displacement of crown beam and driveway, surface settlement, axial force of anchor cable, and underground water level in the construction process of the foundation pit are dynamically monitored and analyzed. The excavation deformation rule of the deep foundation pit and the influence of excavation on surrounding buildings are analyzed. The results show that, with the excavation of the foundation pit, the crown beam and driveway of the foundation pit incline towards the direction of the pit and eventually tend to be stable. The variation of axial force of the prestressed anchor cable in the first layer of the foundation pit is basically consistent with the variation of horizontal displacement time history. The variation trend of the groundwater level at each side of the foundation pit is different but tends to be stable in a short time. In the whole monitoring period, the cumulative settlement value of each area of the foundation pit is within the controllable range, but the surface settlement of the north side of the foundation pit and a surrounding building has not reached stability, so it is suggested to extend the monitoring time of settlement in the relevant area.

Highlights

Combined with the engineering characteristics and site conditions, double row triple highpressure jet grouting piles are constructed around the foundation pit to strengthen the surrounding soil and cut off the seepage path of the peripheral groundwater into the foundation pit. e foundation pit support method is “double row jet grouting pile sealing curtain + artificial excavated pile + anchor cable,” which is widely used in the foundation engineering [29, 30]. e layout of foundation pit monitoring points is shown in Figure 1, where C1–C4 represent the driveway
Horizontal Displacement of Foundation Pit Crown Beam and Foundation Pit Driveway. ree reference points are set outside the influence range of building deformation, and the buried depth is 0.5 m. e monitoring points are arranged along the perimeter of the foundation pit on the concrete roof or crown beam of the foundation pit slope. e horizontal spacing of the monitoring points is less than 20 m, and the polar coordinate measurement method is adopted for horizontal displacement monitoring
The restriction of the prestressed anchor cable on the horizontal displacement of the surrounding soil is weakened, and the pile top tends to move towards the pit

Summary

Introduction

The restriction of the prestressed anchor cable on the horizontal displacement of the surrounding soil is weakened, and the pile top tends to move towards the pit.

Results

Conclusion