An experimental study is undertaken to evaluate the characteristics of the sensitive Champlain Sea clay. Undisturbed samples obtained from a site in Ottawa were trimmed along both the vertical and horizontal orientations for consolidation and simple shear tests. The results of the one-dimensional consolidation tests indicate that the vertical orientation has greater preconsolidation pressures than the horizontal orientation. The ratio of the horizontal to vertical preconsolidation pressure varies from 0.71 to 0.95. Consolidation along the horizontal orientation leads to higher (1% to 23%) compression indices than those in the vertical orientation. The values of the coefficients of consolidation and permeability in the horizontal orientation are found to be larger than those in the vertical orientation, and the ratios of both coefficients of consolidation and permeability in the horizontal orientation to that in the vertical orientation evolve as the effective vertical stress increases. Generally, the at rest lateral earth pressure coefficient in the horizontal orientation was greater than that in the vertical orientation. The average ratio of the at rest lateral earth pressure coefficient throughout all tests (5.82 m to 21.55 m) ranges from 0.90 to 1.82 during the entire stress history. Based on the observation of one-dimensional consolidation tests, it is noted that sensitive Champlain Sea clay shows anisotropic behaviour with respect to the ratios of the horizontal-to-vertical coefficient of consolidation, permeability and the at rest lateral earth pressure coefficient. The undrained monotonic simple shear resistance is somewhat dependent on sample orientation. Test results indicate that samples in the vertical orientation have lower peak and residual shear strengths than those sampled along the horizontal orientation. The iii horizontal to vertical peak strength ratio varied between 1.05 and 1.42. However, the mobilized friction angle at peak and residual states appears to be not dependent on the loading orientation.

In this study, an instrumented thickened tailings deposit model was designed, built and employed to evaluate the behaviour of layered thickened tailings to dynamic loading by using a shaking table equipment. The thickened tailings were deposited subsequently in three thin layers in a flexible laminar shear box mounted on top of the shaking table. Cyclic loading with a peak horizontal acceleration of 0.13 g and a frequency of 1 Hz was applied to the layered tailings deposit. Different types of sensors were placed to monitor the accelerations, displacements, volumetric water content and pore water pressures at the intermediate depth of each layer. Results indicated that the acceleration for the bottom and middle layers were similar to that of the base of the shaking table; but, this was not the case for the top layer. The measurements of vertical displacements indicated that all layers of thickened tailings experienced initially contraction and subsequently dilation during the shaking. The excess pore water pressure ratios were found to exceed unity through all layers of thickened tailings when the shaking ended. In other words, the results showed that the layered thickened tailings are susceptible to liquefaction under the considered testing conditions. It is also found that upward pore water migration to the top layer and downward pore water flow to the bottom layer occurred in the thickened tailings deposit. This water migration generated additional pore water pressure and also impacted the vertical displacement and liquefaction susceptibility of the thickened tailings material. The results of this study give a better understanding of the dynamic behaviour of thickened tailings, which is crucial for the safety of thickened tailings systems as well as sustainable mining.

A landfill biocover system optimizes environmental conditions for biotic methane (CH4) consumption that controls the fugitive and residual emissions from landfills. Research shows that wasted compost material has more (CH4) oxidation potential than other materials. Thus, in this study, the authors investigate the engineering properties of compacted compost to test its suitability for CH4 oxidation capacity. Different laboratory and analytical approaches are employed to attain the set objectives. The biochemical tests show that the studied material indicates the presence of methanotrophs with sufficient organic contents. The compacted compost also shows adequate diffusivity potential to free air space for a wide range of water content. The data also imply that compacting compost to low hydraulic conductivity can be accomplished for a wide range of water content, according to the suggested values for a landfill hydraulic barrier. Furthermore, the low thermal properties of compost as compared to other mineral materials seem more beneficial, as specifically, during the winter season, when the atmospheric temperature is low, low thermal conductivity enables it to sustain a stable temperature for the activities of the microbial organisms, which therefore extends the CH4 oxidation process right through a long period in the winter.

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