Leachate is a hazardous liquid that poses negative impacts if leaks out into environments such as soil and ground water systems. The impact of leachate on the downgraded quality in terms of chemical characteristic is more concern rather than the physical or mechanical aspect. The effect of leachate on mechanical behaviour of contaminated soil is not well established and should be investigated. This paper presents the preliminary results of the effects of leachate on the Atterberg limit, compaction and shear strength of leachate-contaminated soil. The contaminated soil samples were prepared by mixing the leachate at ratiosbetween 0% and 20% leachate contents with soil samples. Base soil used was residual soil originated from granitic rock and classified as sandy clay soil (CS). Its specific gravity ranged between 2.5 and 2.64 with clay minerals of kaolinite, muscovite and quartz. The field strength of the studied soil ranged between 156 and 207 kN/m 2 . The effects of leachate on the Atterberg limit clearly indicated by the decrease in liquid and plastic limit values with the increase in the leachate content. Compaction tests on leachate-contaminated soil caused the dropped in maximum dry density, dry and increased in optimum moisture content, w opt when the amount of leachate was increased between 0% and 20%. The results suggested that leachate contamination capable to modify some geotechnical properties of the studied residual soils.

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Non-destructive techniques of in-situ stress measurement from oriented cored rocks have great potential to be developed as a cost cost-effective and reliable alternative to the conventional overcoring and hydraulic fracturing methods. The tangent modulus method (TMM) is one such technique that can be applied to oriented cored rocks to measure in-situ stresses. Like the deformation rate analysis (DRA), the rock specimen is subjected to two cycles of uniaxial compression and the stress-tangent modulus curve for the two cycles is obtained from the stress–strain curve. A bending point in the tangent modulus curve of the first cycle is observed, separating it from the tangent modulus curve of the second cycle. The point of separation between the two curves is assumed to be the previously applied maximum stress. A number of experiments were conducted on coal and coal measured rocks (sandstone and limestone) to understand the effect of loading conditions and the time delay. The specimens were preloaded, and cyclic compressions were applied under three different modes of loading, four different strain rates, and time delays of up to one week. The bending point in the stress-tangent modulus curves occurred approximately at the applied pre-stress levels under all three loading modes, and no effect of loading rate was observed on the bending points in TMM. However, a clear effect of time delay was observed on the TMM, contradicting the DRA results. This could be due to the sensitivity of TMM and the range of its applicability, all of which need further investigation for the in-situ stress measurement.

Authors' Contribution FG, MR, AG and HM conceived and designed study. FG executed the experiments. FG and MR analyzed the data. FG and MR prepared the manuscript. The manuscript is critically revised by all authors and approved this final version of manuscript.

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