Characteristics of ground surface settlement associated with deep excavation in Beijing city

Abstract

As a viable means to understand the associated deformation, performance study of deep excavations has been conducted worldwide in previous studies, a scenario of ground surface settlement characteristics among different sites has been proposed since 1960s. The objective is to study the characteristics during excavation in Beijing and fill in the blank on the scenario. Thirty excavation cases with good-quality construction and field observation data are selected to quantify the relationship between settlement and excavation, and to analyze the ground surface deformation behavior. The magnitude and location of maximum ground surface settlement ($\delta vm$), the apparent influence range, development process and pattern are depicted. This study demonstrates that: (1) Concave trough pattern of final ground surface settlement is detected, slight heave was observed and $\delta vm$ located at distances about 0.5H to 0.75H from the wall. (2) Spatial difference of ground surface settlement ($\delta v$) varies greatly, great depression appeared behind each wall and maximum settlements at midspans of both sides occurs with the lowest 1-2 struts removal, especially the long side with a $\Delta \delta v$ of $2.8 \pm 0.75$ mm. Movement was least of all by the corners. (3) Final settlement generally ranges from 5mm to -20mm, less than $\delta vm$. Influence zones reach to a distance about 2.5H to 3.1H outside the excavation.