In a probabilistic slope stability analysis, the failure probability associated with the most critical slip surface (the one with the minimum reliability index) is known to be smaller than that for the system that comprises all potential slip surfaces. The first order reliability method (FORM) targets the minimum reliability index related to the critical slip surface, and thus cannot be used to predict the system reliability of slopes, except when all possible slip surfaces are perfectly correlated. It is shown in this paper that the random finite element method (RFEM), which uses elastoplastic finite elements combined with random field theory in a Monte-Carlo framework can accurately predict the system probability of failure (p_f) of slopes.

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The paper presents the results of three full-scale tests that were carried out to investigate the influence of transient flooding on the performance of multi-anchor reinforced soil walls (MAW). The walls were constructed to a height of 6 m and flooded from the front of the structures to about mid-height and then drained in two to four stages. The walls were constructed with three different sand soils varying with respect to permeability, fines content and shear strength. Earth pressures and anchor loads were monitored during the flooding and draining stages and in-situ anchor pullout tests were performed. The analysis of results showed that the wall facings were very permeable and thus prevented unbalanced hydrostatic or seepage forces from developing during drawdown that could increase anchor loads beyond drained condition values. The accuracy of the current PWRC (2002) analytical model to estimate anchor capacity of MAW systems was demonstrated to vary widely depending on soil type and whether the soil was flooded or drained. However, on the load side, the method proposed by Miyata et al. (2009) to predict anchor loads was judged to be more accurate than the current BS8006 (2005) and PWRC (2002) methods based on the mean and spread of bias statistics where bias is defined as the ratio of measured to predicted anchor load.

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The influence of soil structure on the breakthrough of a copper contaminant plume when passing through undisturbed decomposed granite soil was studied. The copper concentration was measured in real time by means of two fibre-optic sensors with reflective-type located on either side of the undisturbed granite soil sample. The adsorption properties were also studied by the column and batch testing. It was found that the copper adsorption of both slightly and severely decomposed granite soil followed a Freundlich model, and the measured values of both samples corresponded well with the calculated values. In this paper, the experimentally obtained copper dispersion characteristics are compared with the contour and velocity vectors by FEM analysis using the advection-dispersion equation. It is shown that the copper concentration and velocity distributions in the severely decomposed granite soil are dependent on the usual parameters, such as the modified coefficient of permeability, retardation factor, dispersion length and dispersivity, which control the flow into the macro (>0.1 μm) and meso pores (0.002-0.1 μm).

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The procedure for evaluating the settlement of saturated soil deposits following liquefaction during earthquakes is examined, with the effect of grain compositions also taken into effect. The recommended procedure is described in detail, with some revisions and suggestions to the previous study by Tsukamoto et al. (2004b). The use of Swedish weight sounding tests is highlighted for estimating the extent of post-liquefaction settlement. Three case histories involving the post-liquefaction settlement of saturated soil deposits observed during the recent earthquakes are introduced. The use of maximum and minimum settlement potentials, S_max and S_min, is recommended to cover some uncertainty in making evaluations.

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A procedure based on the Janbu method for slope stability analysis and Newmark's sliding block method for displacement calculation is proposed to evaluate rationally the earthquake-induced displacement of slopes containing a weak layer. In the procedure, the effects of the irregular geometry of the sliding plane and generation of excess pore water pressure in the weak layer which forms partly the sliding plane are considered. In the computation following the proposed procedure, a negative yield seismic coefficient to induce a safety factor of unity can be obtained because of the effect of excess pore water pressure, while the residual displacement can become a finite value because the sliding plane becomes flatter in general after the slope undergoes a large displacement.

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In order to investigate liquefaction-induced ground displacement, we conducted a series of undrained cyclic torsional shear tests on saturated Toyoura sand using a modified torsional apparatus capable of applying and measuring double amplitude shear strain up to about 100%. The limiting value of double amplitude shear strain, at which strain localization appears during undrained cyclic loading tests, was evaluated from the test results with reference to the change in the deviator stress during liquefaction. The limiting strain values, which increase with a decrease in the relative density of the specimen, were found to be consistent with the maximum amounts of liquefaction-induced ground displacement observed in the previous shaking table model tests and most of the relevant case studies. This feature is reasonable considering the reduction in the mobilized cyclic shear stress in liquefied soil due to the degradation of the shear resistance. As long as the liquefied soil layer remains in uniform deformation, these limiting strain values may be used in estimating the maximum amount of liquefaction-induced ground displacement.

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This paper proposes new testing methods for evaluating the effects of freeze-thaw action on the deformation-strength characteristics and the water retention-permeability characteristics of granular materials under unsaturated conditions. A triaxial apparatus and a permeability apparatus for unsaturated soils, with cooling systems to control the temperature of soil specimens and use the pressure membrane method instead of the pressure plate method, were newly developed in order to examine the hydro-mechanical behavior of unsaturated soils subjected to the freeze-thaw sequence, as experienced by in-situ soils in cold regions. Results indicate that the proposed testing methods with these newly developed test apparatuses are highly useful in the evaluation of the effect of freeze-thaw action on the hydro-mechanical behavior of unsaturated granular materials and in the reduction of total testing time.

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The design, fabrication, and assembly of a new laboratory apparatus for the investigation of the behavior of compaction grouting in triaxial condition are presented in this paper. Using this laboratory apparatus, pressure-controlled compaction grouting tests were carried out in specimens of completely decomposed granite (CDG) in Hong Kong. Precisely controlled injection water into a specially designed latex balloon in the specimen was to simulate a compaction grouting process. In these tests, the effective confining pressure, lateral earth pressure coefficient (K), excess pore water pressure, back pressure, void ratio change, and vertical deformation of the specimen were measured. The main focus was to investigate the development of injection pressure, void ratio, and excess pore water pressure due to compaction grouting and subsequent consolidation of soils. In addition, both the compaction efficiency and the average strength enhancement ratio are defined to evaluate the effect of compaction grouting.

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