Interaction between strip footings and concrete-lined soft ground tunnels

• Main Author: Jao, Mien
• Format: Dissertation
• Language: English
• Published: ProQuest Dissertations & Theses 01-01-1995
• Subjects: Civil engineering
• ISBN: 9798641054148

When a footing is underlain by a shallow tunnel, they interact with each other. As a result, either the footing or tunnel or both may undergo structural damage. Presently, no analysis or design methodology is available to ensure the stability of such footing-lined soft ground tunnel systems. As a step toward the development of such a methodology, this study was undertaken to investigate the footing-tunnel interaction mechanism and to develop bearing capacity equations for strip footings centered above concreted-lined soft ground tunnels. In this study, a two-dimensional, plane strain, elasto-plastic finite element computer program developed by Hsieh (1991) was modified and adopted for analysis. The modified computer program was validated by comparing the predicted pressure-settlement behavior with available model test results. Three different foundation soils representing a broad range of soil conditions, including a silty clay, a commercial kaolin, and a kaolin-sand mixture were analyzed. A wide range of tunnel size, location and lining thickness were investigated. Based on the results of analysis, the mechanistic behavior of the footing-tunnel system was evaluated. The behavior studied included the footing pressure vs. settlement relation, footing pressure vs. area of yielded soil element relation, propagation of plastic yielding of soil, soil arching around the tunnel, and stress distribution both in the supporting soil and within the concrete lining. Meanwhile, the engineering significance of the analysis results was discussed and the bearing capacity of each condition analyzed was determined. From these bearing capacity values, semi-empirical equations were developed for predicting the critical depth and bearing capacity of strip footings underlain by concrete-lined soft ground tunnels. These equations were shown to be capable of predicting the bearing capacity of footings located above concrete-lined tunnels reasonably well.