In conventional underwater coal ash disposal, the major concern is to increase the disposal capacity by increasing the density. Underwater placement of coal ash slurry is thought to be one method to achieve this. The properties of the slurry and its density compared to the conventional disposal method, however, have not been studied. In this paper, the properties of a new high density slurry, the density of which is 96% of the maximum dry density, are shown from results obtained through laboratory tests. Since the density decrease during underwater placement is less than 4%, this slurry is expected to dispose of coal ash at 92% of the maximum dry density, even underwater. That corresponds to the same density as the field compaction, and 159% of the conventional disposal. The advantage of the new slurry method with regards to strength suggests new possibilities in the utilization of coal ash for stable fills.

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The factors essential to the development of quick clay in the soft marine sediments of Ariake Bay are the same as those for the Scandinavian and Canadian quick clays. These similarities are : sedimentation in marine or brackish water, with resultant development of a flocculated microstructure; domination of the soil material by low-activity minerals; and the decrease of the liquid limit of the Na-saturated soil material as the salinity of the pore water decreases. The above factors are essential for quick clay development in both materials. Differences include : the origin of the material-glacial rock flour in Scandinavia and Canada, eroded soil containing some volcanic ash at Ariake; the mineralogy-primary minerals, illite and chlorite in Scandinavia and Canada, a low-swelling, high-iron, beidellitic smectite at Ariake. The difference in origin of minerals is unimportant as long as the dominant minerals are of low activity, and the environment of deposition assured a flocculated structure in the sediment. The upper limit of activity which allows quick clay development upon salt removal, is on the order of 1 for the low-salinity, Na-saturated soil material.

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The improvement of bearing capacity for soft purely cohesive soils reinforced by columns was studied. Using the Yield Design theory, the extreme load of an isolated column was determined based on the plane strain assumption, and then in axisymmetry. Two loading cases were considered, and the influence of gravity was investigated. In order to ensure the improvement of the soil's bearing capacity, the minimum values of the mechanical characteristics of the column material are identified. Quasi-exact values and acceptable bounds for the extreme load were compared to results presented in the literature. The method developed here is considered relevant for better performance.

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The finite element program HOT CRISP developed at Cambridge University allows the two dimensional coupled heat conduction and consolidation analysis of soil barriers subjected to temperature gradients. The analysis uses an elasto-plastic soil model based on the critical state principles. This paper presents prediction of temperature and pore water pressure changes in kaolin clay and comparison with experimental data. The experiments undertaken involved triaxial samples subjected to temperature changes at the outer boundary by a temperature controlled water circulation system. Temperature sensors and miniature pore water pressure transducers were used for the monitoring of temperature and pore water pressures at two locations in the soil samples. Tests were performed both under undrained and drained conditions. The comparison of data between experiments and analyses showed very satisfactory results.

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The topographical features of dam sites are in general, so complex that two dimensional finite element models might not be applicable in the aseismic designs of these fill dams because of limited knowledge of how the seismic responses of dams are affected by them. Three dimensional vibration modes are not even well known. In this paper, elementary dynamic response behaviors for fill dams obtained from vibration tests on a three dimensional elastic model are discussed. These tests are simulated with a computer code for three dimensional seismic response analysis developed by the authors in order to both confirm the validity of the code and distinguish the fundamental modes. Finally, regarding the topographical features influencing the seismic responses of fill dams, the valley wall slopes in abutments and the width of a riverbed are taken into consideration in order to examine how every eigenfrequency up to the 4th order should fluctuate according to the change of each factor with a number of numerical analyses using the code. The results are presented in general diagrams representing the relationships between dimensionless eigenfrequencies and dimensionless topographical features.

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The purpose of this paper is to establish a trafficability control system for a flexible tracked tractor traveling up and down a weak slope using an initial track belt tension sensor. The distribution of track belt tension and contact pressure depends on the initial track belt tension. In this paper, some analytical results are presented for a 50 kN weight tractor towing up (or down) other construction machinery on a decomposed weathered granite slope. The driving (or braking) efficiency of power decreases (or increases) remarkably with decrease in the initial track belt tension. The amount of depression of the rear sprocket increases vice versa with initial track belt tension, while the eccentricity of the resultant normal force remains almost constant. As a result, it has been confirmed that the lower limit of the initial track belt tension can be determined to be 2∼3 kN at the driving action and almost zero at the braking action, for the given vehicle and the given sloped terrain. This automation of the trafficability control system will produce a high power efficiency for a flexible tracked tractor towing up and down a weak slope.

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A procedure for limit equilibrium slope analysis based on a realistic consideration of the mobilized interslice shear forces is presented in this paper. This new approach ensures that solutions are kinematically admissible and the possibility of convergence problems, often associated with numerical solutions, is minimized. The proposed approach recognizes the importance of slip surface geometry in estimating interslice shear forces whether vertical or non-vertical slices are used in a limit equilibrium analysis. Illustrative examples are presented and the results shown to be reasonable. The calculated factors of safety based on the new method compare very well with values based on recognized methods of analysis. Yet the method is more direct and enables a proper visualization of the transfer of mobilized normal and shear forces through a sloping soil mass above a potential slip surface. The method also gives consistent results with non-vertical slices even if the shape of non-vertical slices is varied.

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This paper presents an experimental program to investigate the effect of radial strain on the friction capacity of an instrumented model pipe pile. The model was buried in a dry INAGI sand. Loads were then applied in four different ways with and without applied surcharge pressures, one compression (push-down) and three tensions (pull-out). The first pull-out load was applied at the top of the model, the second was applied at the tip and the last was applied at the tip for an axially prestressed condition. The use of these different types of loading had a significant effect on the friction capacity, that is, the friction capacity decreases in the following order; push-down, pull-out under prestress, pull-out at the tip and pull-out at the top. These decreases were interpreted to be the results of radial strain and due to the differences in arching in the sand.

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Imperfection-sensitive bifurcation of a rectangular (12 cm × 36 cm) Cam-Clay specimen emerging from a state of homogeneous in-plane compression with undrained boundaries is simulated by soil-water coupled finite deformation analysis, in which the vertical displacement at a constant rate is imposed on the top of the specimen. The analysis is carried out using a non-linear finite element method through an up-dated Lagrangean scheme, in which the bifurcation points corresponding to the first few bifurcation modes are found to be well approximated by the limit points of external load by introducing cosine-curve geometrical imperfection on both sides of the specimen. This is particularly true when a fast rate of testing is considered. Even with undrained boundaries, when the specimen includes initial imperfection, the imperfection causes the migration of pore water from the beginning. The effect of migration on the shear deformation, therefore, should be highly dependent on the rate of vertical displacement. When a slow rate of displacement (9.12 × 10^-3%/min) is applied, it is found, in this study, that the mode-switching occurs due to migration and a "peak" in the load-displacement curve occurs which naturally yields a relatively low undrained shear strength. One of the possible reasons for this rate dependency of undrained shear strength of saturated clay is ascribed to the effect of pore water migration on the imperfection-sensitive bifurcation behaviour of saturated clay.

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In this paper, the hyperbolic fitting method is extended to the case of consolidation with combined vertical and radial flow, which occurs when vertical drains are used to accelerate consolidation in clayey soils. Theoretical results indicate that the hyperbolic plots are linear between the U₆₀ and U₉₀ points for the combined flow problem. Based on detailed parametric studies, it is shown that the slope (α) of the first linear segments between U₆₀ and U₉₀ for the theoretical hyperbolic plots (T_υ/U vs T_υ) depends only on three non-dimensional parameters. These are the drain spacing ratio (n), the drainage path ratio (H/D), and the consolidation coefficient ratio (c_h/c_υ). The slope S_i of the first linear segment of the field hyperbolic plot and the slope α can be used to identify the U₆₀ and U₉₀ points on the field settlement plot. These are used to estimate the total primary settlement from field settlement data as either α/S_i, δ₆₀/0.6 or δ₉₀/0.9. In order to validate this approach for estimating total primary settlement for consolidation of clays with vertical drains, a controlled laboratory experiment using a flexible fibre drain in a clay cylinder, and several well documented case histories were examined. Estimates using the proposed hyperbolic method agree very well with actual settlements, thus, validating the method for field applications.

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In the 1993 Kushiro-oki Earthquake of Richter magnitude 7.8, simultaneous recording of earthquake motions was successfully made at the ground surface and at a depth of 77 meters in a dense saturated sand deposit. The peak horizontal acceleration was 0.47 g on the ground surface and 0.21 g at a depth of 77 meters. The acceleration record at the ground surface showed a distinctive ground response, which consisted of a cyclic motion having a period of about 1.5 seconds overlain by a spike at each peak of the motion. In order to study the mechanism of this peculiar ground response, effective stress analysis was conducted on the dense saturated sand deposit. The model used for this study was a strain space multiple mechanism model, which takes into account the effect of principal stress axis rotation. The recorded earthquake motion at a depth of 77 meters was used as the input earthquake motion for the analysis. Sampling after in-situ freezing was done in order to evaluate the properties of the sand. The results of the analysis indicated that the observed ground response was due to the effect of dilatancy of sand, which plays a significant role in the response of the dense saturated sand deposits during strong earthquake motions.

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A series of model tests on plain, reinforced and panel faced slopes were carried out. Models were prepared for two types of slope face gradient. Behavior of these models was observed from initial loading to ultimate failure. Special attention was given to the development of axial strains in the reinforcement, footing load, footing settlement and the shape of the failure surface. The linear elastic finite element method (LEFEM) and the rigid plastic finite element method (RPFEM) were used in the numerical simulations for the model test results corresponding to the first tangent slope in the footing pressure-settlement curve and the ultimate failure load, respectively. The pattern of the axial strain distributions recorded in the model test is supported by numerically calculated tensile forces. Similarly, the type of failure modes observed in the model tests are also clearly predicted from numerical analysis results. Both observed and computed results confirm that the reinforcement itself is more effective and that the addition of facing reduces the lateral movement thereby avoiding local failue near the slope face.

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This paper presents results of a study on the effects of high temperature (up to 90°C) on undrained shear characteristics of clay in both normally consolidated (NC) and overconsolidated (OC) states. The study is based on isotropically consolidated undrained triaxial tests carried out using a temperature controlled triaxial apparatus. Several sequences of heating and consolidation were used to gain insight into the effects of temperature on clay. The study reveals that : (1) in NC state, both the initial secant modulus and the shear strength increase with increasing temperature, and (2) in OC state, only the initial secant modulus increases with a temperature rise, but the shear strength is not affected by heating. This paper further explains these experiment results in terms of micro-resistance and macro-resistance of the clay structure.

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The shape of granular materials can be described by either their fractal dimension (D) or by the use of the Krumbein's angularity or roundness number (R). The concepts of fractals and fractal dimension as a shape descriptor are presented. Fractal analysis of the Krumbein's standard two dimensional particle profiles used to determine the angularity of granular materials is carried out. A relationship between the fractal dimension (D) and the Krumbein's roundness number (R) is described. The relationship between D and R is found to be : D=1.0541-0.0335R.

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