Environmental concerns arising from the over-dredging of sand have led to restrictions on its extraction across India, with direct economic impacts on concrete construction. A suitable environmentally friendly alternative to sand must be found to match the huge demand from the concrete construction industry. At the same time, waste plastic is rarely recycled in India, with as much as 40% left in landfill. The dumping of such materials which degrade at extremely low rates meaning they persist in the environment is a long-term environmental concern. To tackle both issues, it is proposed to process waste plastic to create a partial replacement for fine sand in a novel mix for structural concrete. In this paper eleven new concrete mixes are evaluated to study five plastic material compositions, three groups of particle sizes, three different aspect ratios, and two chemical treatments and establish an appropriate choice of material to act as partial replacement for sand. The results show that replacing 10% sand by volume with recycled plastic is a viable proposition that has the potential to save 820 million tonnes of sand every year. Through suitable mix design the structural performance of concrete with plastic waste can be maintained. This preliminary work was supported through funding from the British Council under the UKIERI (United Kingdom India Educational Research Initiative) programme for the project 'Development of structural concrete with the help of plastic waste as partial replacement for sand'.

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Capacity expansion of existing landfills is the most economical alternative to constructing new landfills where cost of land is prohibitive. From the safety point of view, the stability analyses of existing landfills expanded either vertically and/or laterally are required for different stages of construction, operation and during closure of a landfill. In the present study, a pseudo-static limit equilibrium seismic stability analysis was performed for a typical side-hill type municipal solid waste (MSW) landfill expanded using an engineered berm. Seismic stability analyses were performed for the two critical cases, namely when the failure surface passes below the berm (under berm) and when the failure surface passes over the back slope of the berm (over berm). Close-form solutions were developed for the upper bound and lower bound factor of safety and the yield acceleration of such slopes under both failure conditions. From parametric analyses it was observed that as the height of the berm increased, the factor of safety for both the over-berm failure and the under-berm failure conditions also increased. The average factor of safety and yield acceleration coefficient were found and the under-berm failure condition became critical for a back slope steeper than 1.7H : 1V. The average factor of safety decreased as both horizontal and vertical seismic accelerations increased. Comparisons between the present results and those in the literature for the static case showed good agreement and the present results of the pseudo-static seismic case were found to be of particular importance.

Municipal solid waste (MSW) landfills in seismic zones are subjected to the seismic forces both in the horizontal and vertical directions. The stability of landfills against these seismic forces was evaluated by computing the factor of safety of landfills with different modes of failure among which failures of landfills due to translation are very common. Conventionally, the seismic stability of landfill is evaluated by using pseudo-static limit equilibrium method. In the present study, seismic stability of landfills is evaluated by both the conventional pseudo-static and modern pseudo-dynamic method. The pseudo-dynamic method is superior as it takes into account the effect of duration and frequency of earthquake motion and corresponding body waves in addition to the variation of earthquake accelerations along depth and time. In the present study, the effects of cohesion and fill amplification on seismic stability of landfill are also taken into account. It was noticed that, neglecting cohesion of fill material as well as liner material, results in a lower factor of safety and, hence, a very conservative/uneconomic design. Also, fill amplification is found to reduce the factor of safety values computed only by using the pseudo-dynamic method, showing its advantage. Generalized expressions are developed for factor of safety and yield acceleration against translational failure, which can be used for evaluating the seismic stability of MSW landfills. Comparisons of results under static condition with existing, similar methodology show a very good agreement. However, the present study seems to provide unique results for the seismic case.