Mechanically Stabilized Earth Wall Failure at Two Soft and Sensitive Soil Sites

Abstract

Two highway bridge approaches, about 10 and 12 m in height, near Kolkata (Calcutta), India constructed with mechanically stabilized earth (MSE) failed recently. These structures were founded on sensitive, soft and compressible, fine-grained soils of the intertidal flats and backswamps of the Ganges delta. One of these MSE walls, which failed in the final stages of its construction, was constructed after foundation soils were strengthened with prefabricated vertical drain installation and preloading. The second MSE wall that failed within a month of its opening for traffic was constructed on unimproved ground. Fortunately, immediate collateral damage from these incidents was small. Using pre and postconsolidation shear strengths the MSE walls were redesigned. Reconstruction involved prefabricated vertical drain installation at the second site and construction of stabilizing berms at both locations. The facilities are now operational and appear to be performing satisfactorily. Details of the failures, postfailure investigations, and monitoring, redesign, and reconstruction are presented in this paper.