Effect of excavation on performance of adjacent buildings
Date of Issue2008
School of Civil and Environmental Engineering
Deep excavations in urban area can damage surrounding buildings. The current practice in assessing building damage is based on greenfield settlement computed from 2-D finite element analysis. This is less than satisfactory for situations where 3-D effect is prominent. In this case, a 3-D analysis is preferred. Unfortunately, the 3-D finite element analysis is a fairly complex and demanding task. A simple method has been developed to estimate 3-D settlement from 2-D analysis. The conventional method also assumed that the building would settle the same amount as the ground. This assumption is reasonable for buildings supported on individual footings without ground beams. For frame structures and buildings supported on rafts, the differences in building and ground settlements can be significant. A new method has been developed to integrate the soil-structure interaction into the analysis so that the structure stiffness can be taken into consideration. A new chart for damage assessment of frame structures has also been developed. The chart divides the damage into several categories. This study also investigated the potential causes of post-excavation settlement in deep excavations in soft clay. Results indicate that there are two major causes. The first one is leakage in the retaining wall and the base slab. The second one is under-drainage into a pervious layer that extends into the excavated area and exposed at the formation level. This research is numerical based with the aid of the computer programs ABAQUS and Sage Crisp. The proposed methods and charts have been validated against hypothetical problems and case records.