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Solid waste management is a serious problem worldwide as the amounts of produced wastes are increasing annually. For example, the disposal of waste gypsum plasterboard, used as dry walling across the world, represents a serious environmental issue. Therefore, this study examines the potential for reusing plasterboard wastes as a stabiliser material for earthwork projects, especially for organic soft clay soil. Recycled plaster, mixed with cement or lime at different ratios was used as a stabiliser for tested soil. Atterberg limits, scanning electron microscopy, x-ray diffraction, compressive strength, and secant moduli tests were conducted to evaluate the improvement in stabilised soil properties. The results indicate that the inclusion of plaster-cement (B-C) or plaster-lime (B-L) admixtures improved the geomechanical properties of the stabilised soil, with higher admixture concentrations leading to greater improvement. Moreover, the soil specimens stabilised using the B-L admixture exhibited a higher strength gain rate and reduction in plasticity index and water content than those stabilised by the B-C admixture. The development of cementation compounds in a stabilised soil matrix has a considerable effect on permanent strength enhancement. It is concluded that the proposed stabilising technique can be valuable for both waste management and construction industries. [ABSTRACT FROM AUTHOR]

The interaction behaviour between a floating column and the surrounding soil, with or without a surface cement stabilised slab, has been investigated by laboratory model tests as well as finite-element analysis (FEA) using an axisymmetric unit cell model. Based on the test and the FEA results, a method for calculating the consolidation settlement-time curve of floating-column-improved soft clayey subsoil has been developed. This method has been modified from the earlier method of Chai and Pongsivasathit by treating a part of the column improved layer with a thickness of as an unimproved layer in settlement calculation to consider the effect of possible penetration of the column into the soft soil layer below the column. An explicit equation for calculating the value of has been proposed as a function of area improvement ratio (), depth improvement ratio (), load intensity () and the undrained shear strength ( ) of the soft clayey soil. The validity of the method has been checked using the laboratory model test results as well as four field case histories in Japan. [ABSTRACT FROM AUTHOR]

Ground improvement via soil stabilisation has been widely applied and proven to be an effective countermeasure for development on problematic soils. The stabilisation procedure usually involves addition and thorough mixing of hydraulic binders with in situ soils, consequently transforming the soft materials into a stronger and stiffer stratum for load bearing. Nevertheless the method can also be adopted for reusing and strengthening clayey soils, such as laterite, for the construction of road foundations. Recycling and reuse of waste materials, such as granulated rubber processed from waste tyres, should be considered for developing alternative soil stabilisers. Each new combination of stabilising agents introduced needs to be carefully examined in terms of the stabilised material's enhanced properties, especially the strength and stiffness of the targeted soil, as different soil types are known to react differently with different stabilisers. This paper presents experimental test results of a lateritic soil (clayey sand) stabilised with 0-4% cement and 0-4% rubber chips or rubber shreds. In the study, unconfined compressive strength tests were complemented by elastic (i.e. P- and S-) wave velocity measurements. The corresponding strength and stiffness of the various mixes were analysed and discussed in this paper. Correlations between the parameters investigated were also established to shed light on the improved soil properties. Both strength and stiffness of the stabilised soil were found to be predominantly controlled by cement content, although higher rubber dosages were observed to increase the ductility of the stabilised material. Furthermore, the form of the rubber addition, as either chips or shreds, did not appear to have a significant effect on the response of the stabilised material. In short, results from the unconfined test series highlighted the potential of cement-rubber as an alternative stabilising agent for similar lateritic soils, specifically in terms of strength and stiffness improvement. Long-term durability of the stabilised material however, with relevance to exposure to the elements and various site conditions, needs to be addressed in follow-up investigations to ascertain the site applicability. [ABSTRACT FROM AUTHOR]

A simplified method is proposed for the stability analysis of clayey slopes subjected to pore pressure changes. The method is based on the infinite slope model and takes advantage of an analytical solution to evaluate the changes in pore pressure at the potential (or pre-existing) failure surface directly from the pore pressure measurements at a piezometer which is installed above this surface. A case study documented in the literature is analysed as an application. [ABSTRACT FROM AUTHOR]

Stabilisation of sulphate-bearing soils with lime/cement-based binders has always been problematic, owing to excessive sulphate-induced expansion. This paper reports on investigations conducted on the consistency and compaction properties of Lower Oxford Clay (LOC), a sulphate-bearing soil that has been difficult to stabilise in the traditional manner using lime. In the investigations, LOC was stabilised both in the conventional manner using lime as the control, and also using a wide range of sustainable stabilisers incorporating industrial waste and by-product materials. The sustainable binders included wastepaper sludge ash (WSA) used on its own, as well as binary binders comprising WSA--lime, WSA--Portland cement (PC) and WSA--ground granulated blastfurnace slag. The results obtained showed that the blended stabilisers incorporating WSA were able to modify the soil by reducing the plasticity index, coupled with good compaction, strength and volume stability properties. The findings suggested that there are economic and environmental advantages of utilising WSA and similar industrial by-products in the modification and compaction of soils, including sulphate-bearing clay soils, as equal or at times superior alternatives to the traditional stabilisers of lime and/or PC. [ABSTRACT FROM AUTHOR]

The results of an experimental investigation to explore the effectiveness of coir geotextile vertical drains for ground improvement are reported. The time settlement behaviour of clayey soil, as influenced by coir geotextile drains, is summarised and the construction and installation details are also discussed. Two types of coir drains, a circular type and a rectangular type, using two varieties of coir geotextiles were tested in three configurations, namely a single drain and triangular and rectangular patterns. It was observed that the time for consolidation was very much reduced due to the installation of coir drains irrespective of the type of coir geotextile used, type of coir drain and the layout of the drains. Furthermore, in addition to ease of construction these drains are eco-friendly and will not pose any environmental problems. [ABSTRACT FROM AUTHOR]

The article discusses the results of the study concerning the behavior of compacted clay soil, as the building material that is most used in terms of volume in civil engineering. It compares the pore size distribution (PSD) curves of two samples of same water content compacted at two different void ratios. It indicates that the decrease in void ratio owing to increased static compression only affected the coarser pores with no effect on the PSD of finer pores. With decreased water content, it shows an increase in the modal entrance pore diameter of the intra-aggregate porosity, which resulted in a well-graded unimodal PSD curve.