Characteristics of Hardpan Calcrete of the Nyalau Formation and Impact on Design of Foundations

Abstract

Nyalau Formation, found in Bintulu Division in Sarawak, Malaysia was formed by a thick array of shallow water marine and paralic sedimentary rocks. The formation is of predominantly sandstone origin and also the lesser known ‘limestone’ which is described as hardpan calcrete in this paper. Changes of sea levels during the mid-Pleistocene epoch resulting in the formation of raised terrace wheremarine deposits sedimented and subsequently followed by depositions of the coastal alluviums and inland peat swamps. The interaction of the depositions may have contributed to the formation of the hardpan calcrete. Laboratory tests such as petrographic thin section, X-Ray Diffraction (XRD), uniaxial compressive strength, point load tests, in-situ static load tests had been carried out on the hardpan calcrete to obtain the engineering design parameters to formulate a possible detailed design methodology on shallow foundation and its as sociated construction work progress. Several practical and effective solutions had also been proposed at locations where the hardpan calcrete layer was present. Use of finite element analyses in design has also successfully provided valuable in-sights into the complex soil-structure interaction.