Effect of Tidal Fluctuation on the Stability of Estuarine Structures in Sarawak

Several incidents of lateral movement and failures of estuarine structures have been reported in Sarawak. These structures located in very soft and deep sedimentary soils are usually supported on pile foundations. There is a 4 to 7 m daily tidal fluctuation in these locations, the effect of which on the ground and the piles is usually neglected in design. A study has been undertaken to formulate improved approaches for the design of riverine and estuarine structures. The validation of a theoretical model requires data on ground movement and pore water pressure changes due to tidal fluctuation. Accordingly, piezometers and inclinometer casings were installed at the sites of two structures where a bridge and jetty are proposed to be constructed. The inclinometers measure the lateral movement of the river banks and a pile installed in the riverbed. The piezometer and inclinometer readings are being recorded periodically. The paper explains the background of the study, case histories of failures, soil conditions at the two sites, details of instrumentation, results of measurement, and the interpretations

Stabilization of Indian Fly Ashes with soils, cement, and randomly oriented fibers

Experimental studies were carried out on fly ashes from two Indian thermal power plants, namely Rajghat and Dadri, with the aim of improving the utilization of fly ash in geotechnical engineering applications. It was attempted to improve the engineering performance of fly ash by several means such as by mixing fly ash with soils, cement, and polyester fibers. The research program included the study of: a) physical properties, chemical composition and morphology of the fly ashes; b) compaction, strength, and permeability characteristics of the fly ashes and fly ash-soil mixtures; c) compaction and strength characteristics of fly ash-soil mixtures stabilized with fibers alone, with cement alone, and with both cement and fibers. Results showed that addition of fly ash to soils would result in lighter and stronger fills. Fiber inclusions increased the strength of fly ash-soil specimens significantly and altered their behaviour from brittle to ductile. Even small cement contents increased the strength of the fly ash-soil mixtures significantly. With higher cement contents of up to 18% it was possible to prepare fly ash-cement design mixes that satisfied the strength criteria for pavement base courses