Very Soft Organic Clay Applied for Road Embankment




Introduction

water in the clay has to be removed as fast as possible. The time it can take to remove the water or consolidate relatively thick compressible layers can be long. Any technique, which decreases the drainage path length through the clay, would be helpful in decreasing the time required for compaction. Making layered clay-sand embankment is one of the construction methods which speed up consolidation and improve strength more rapidly as compared to a full clay fill owing to the shorter drainage path provided by the sand layers (Inada et al., 1978; Ostlid, 1981; and Tan et al., 1992). Thus, this method may be recommended too when using very soft clay as fill material for embankment. The works of Gibson and Shefford (1968), Koppula and Morgenstern (1972), Lee et al. (1987), Karunaratne et al. (1990), and Tan et al. (1992) show that engineering behaviour and workability of layered clay-sand embankments are dependent on many parameters such as the thickness, permeability, and the relative length of the flow path for two materials and there seems to be no consistent rationale for their design and construction. Thus, use of this method still needs a further study.

Above methods have been applied to construct embankments of wet clay, and the result showed the potential of applying these methods in embankment construction with wet or high water content fill material. However, it is not clear which method to use in which circumstances. How to use very soft clay economically as a fill material is not clear. Questions concern: * How large a stockpile will be used; * How long it will take for drying; * What is the proper thickness of clay for drying; * What is the proper thickness of clay and sand in a layered clay-sand embankment; * Comparison of drying and the accelerated consolidation process: which is the most

suitable method for embankment construction; * How to combine these improvement methods and yield the most beneficial

construction.


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