27 ABSTRACT: Thick deposits of soft ground such as soft marine and estuarine clay are widespread throughout the world especially along deltas and coastal regions. Such soils possess poor geotechnical properties such as high natural moisture content (close to liquid limit), high compressibility & low shear strength. Embankments on such soft ground commonly adopted for the construction of highways, rail- ways and airport runways are often affected by edge stability and long term settlement. The earliest method or technique employed for stable construction of embankments on soft ground was the use of ver- tical drains combined with stage construction. However, with growing demand for rapid construction and associated difficulty in meeting the project deadline, column-supported embankments have emerged as an appropriate technical solution. In addition, geosynthetics in the form of basal reinforcement are exten- sively being used at present for embankments on soft ground, to improve the bearing capacity, reduce dif- ferential settlement and prevent slope instability. A broad over-view of embankments on soft ground is presented in the present paper. The review is complemented by six well documented case histories of embankments constructed over soft ground using different geotechnical techniques. The case histories presented could help the geotechnical community to understand and evaluate the benefits of the tech- niques for their adoption for the construction of embankments over soft ground. Keywords: Embankments, soft ground, pre-fabricated vertical drains, stone columns, deep cement mixed piles, basal reinforcement, soil arching 1 Introduction Embankments form the heart of the land compo- nent of the transportation sector and are necessary to bring the elevations of existing low-lying areas up to functional elevations for roadways and rail- ways. The construction of embankments over soft, compressible ground is increasing due to lack of suitable land for infrastructure and other develop- ments. When constructing an embankment over very soft subsoil of low shear strength and high compressibility, the engineering tasks are to ensure stability of the embankment against possible slope failure and to control the subsoil deformation or settlement to within allowable limits. Several methods such as stage construction with vertical drains, use of columns (such as con- crete piles, stone columns and deep soil mixed piles) extending into the soft ground, and geosyn- thetic basal reinforcement (in the form of geotex- tiles, geogrids and geocells) etc, have been devel- oped for economically and safely constructing embankments on soft ground. With such a vast variety of techniques, eventually the final choice depends upon the subsoil characteristics, project cost and time of completion, as well as the long term benefits. This paper presents a review of embankments on soft ground. The review briefly addresses the existing methods of stability analysis for unrein- forced & basal reinforced embankments, piled & basal reinforced piled embankments, embankment founded on stone columns and deep soil mixed piled embankment, over soft ground. In addition, six well documented case histories of (i) embank- ment on pre-fabricated vertical drain (PVD) im- Embankments on soft ground: an overview S.V. Abhishek Postgraduate Student, Department of Civil Engineering, A.U. College of Engineering (A), Visakhapatnam, India, <[email protected]> Madhira R. Madhav Professor Emeritus, JNT University & Visiting Professor, IIT, Hyderabad, India <[email protected]> Foundation and Soft Ground Engineering Conference Thu Dau Mot University ICTDMU-1, Binh Duong, June 5 .6, 2013
Embankments on soft ground: an overview
Jun 29, 2023
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