Slope stability and settlement analysis of Dhaka flood protection embankment

Abstract

The severe flooding in 1987 and 1988 led to the design and construction of about 30 kIn long flood control embankment on the Western side of Dhaka city. In some of the stretches, the embankment crossed silted up channels consisting of soft subsoils. Approximately 13 kIn of the embankment suffered some sort of failure immediately after construction, including slip fui1ures and fuilure due to plastic lateral spread of the subsoils. Subsequent studies by local and foreign Consultants identified several failure zones. Based on those studies three locations ofthe embankment at Mirpur and two locations at Kellar Mohr site have been selected for this study. Detailed field and laboratory investigations were carried out. Based on the results of soil investigations, stability analysis using XST ABL at five critical sections (9500, 9900, 13925, 29930, 30000) of the embankment were performed compared with previous analysis. It has been found that stability of the embankment increased significantly within the last few years. This can be attributed to the fact that repeated dumping of soil at the top of the embankment and consequent settlement of the embankment has improved the properties of soil. The settlement analysis has performed for three critical sections (9900, 13925, 29930) of the embankment. The analysis is based on the soil parameters obtained during the construction phase of the embankment. Finite Element program CRISP has been used for modeling settlement of the embankment. Consolidation analysis with elastic-anisotropic model has been used. The loading is due to the self-weight of the body of the embankment. Loading has been transferred on the foundation of the embankment in three stages using remove-add mechanism of CRISP, to simulate embankment construction sequence. Maximum settlement estimated for the embankment top at 9900, 13925 and 29930 are 4.07 ft, 5.44 ft and 3.49 ft respectively.