Effect on Stress and Strain of Surrounding Soil by Excavation of Foundation Pit

Abstract

It took the project Rainbow Boulevard (Workers Road ~ City Center Road) of Xiaoshan District as the study background and object. Through the monitoring of horizontal displacement of deep soil and the analysis of supporting axial force of steel rebar in different stages of excavation, the rules of stress-strain variation of soil and overall displacement of foundation pits after unloading in different stages of excavation were obtained, thus providing relevant basis for engineering safe design and construction. Preface During the past 20 years China's high-rise buildings have developed very quickly. The full use of underground space promotes the development of foundation pits. However the deep foundation pit engineering is still one of the heated and difficult problems in the field of geotechnical engineering. In the current field of foundation pit engineering, the semi-theoretical and semi-empirical method is still adopted. There accident not only affects the stability of the foundation pit and cause economic losses, but also affects the safety of adjacent building near the pits, because the pits may cause the surrounding buildings or underground facilities to crack, tilt or even collapse, resulting in foundation pit accident and personnel casualty. The above facts restrict the development of deep foundation pit engineering. The excavation of the deep foundation pit exerts great effect and disturbance on the soil. Due to the release of soil stress the foundation pit also has influences on the adjacent buildings [1-3]. It affects the foundation of the adjacent buildings, thus affects the upper structure of the building. Therefore, domestic and foreign scholars have carried out a lot of research into the effect on stress and strain of the soil surrounding the excavated foundation pit. This research is carried out based on the existing theory and knowledge in combination with the data of actual measurement at site. Overview of Foundation Pit This project is two-way six-lane open cut tunnel with buried section 354m long. The main structure is of single-box double-chamber reinforced concrete box. The clearance size of the tunnel’s cross section is 29.1m (width)×5.990m (height), and the passage size of the unilateral lane is 12.00m(width)×5.0m(height). The designed excavation depth of the foundation pit is 10.0m~14.20m. International Conference on Advances in Mechanical Engineering and Industrial Informatics (AMEII 2015) © 2015. The authors Published by Atlantis Press 657 Figure 1. Layout of Foundation Pit Monitoring Point of Rainbow Boulevard of Xiaoshan Monitoring data: taking the project of Rainbow Boulevard (Workers Road ~ City Center Road) Section A in Xiao District (hereinafter referred to as the XS Project) as the test point. We selected 19 inclination measurement points around the foundation pit of the XS Project, and respectively took the vertical depth direction as the Z axis and the direction close to the pit side and vertical to pit boundary as the Y axis. Daily monitoring was then carried out and inclinometer was utilized to draw the displacement of different inclinometer point in the Y direction during the last one month. At the same time the monitoring data and crack observation data of supporting axial force were collected respectively. Now we randomly select the data for example. Figure 2 Inclinometer Diagram of Inclination Figure 3 Variation of Axial Force