STUDY OF PRECOMPRESSION FOR REDUCING SETTLEMENT CHARACTERISTICS OF CLAYS

Abstract

Analyses for reducing post construction primary consolidation by precompression of different types of clays in terms of surcharge intensity ratio Ps/Pf, permanent load ratio Pf/Po, time and mineralogical composition have been studied. Various methods of finding the compression index' and coefficient of consolidation have also been studied for various types of clays. The precompression is a highly effective and economical means for improving subsoils beneath structures and embankments. Eighty consolidation tests under surcharge and eight conventional consolidation tests, have been performed on remoulded cohesive soil specimen composed of three important minerals groups (Kaolin, Illite and Montmorillonite). The analysis of the results reveals, the importance of the mineralogical composition of clay. An empirical relation has been obtained to find degree of consolidation under surcharge loading. The study also indicates that degree of consolidation under surcharge, compression index and coefficient of consolidation depend on the mineralogical composition of the soil and consolidation pressure. iii iv Only four types of soils have been studied viz. Dhanauri clay, Black cotton soil, Kaolin and Bentonite. Two mineral groups are covered i.e. Kaolin in soil Kaolin and another montmorillanite in Bentonite. There was no soil available directly for the illite group. Therefore, Dhanauri clay has been studied as an substitute of illite and Black cotton soil is a mixture of sand, sil and montmorillonite clay