Saturated remolded specimens of peat sample were used in this investigation. After the specimens were normally consolidated and overconsolidated under an isotropic stress condition, drained triaxial compression shear tests were carried out. After the ends of shear tests, all the specimens were instantly dried on vacuum freezing and then the measurements of pore size distribution were performed by using a mercury intrusion porosimetry apparatus. Based on the measured results of pore size distribution, the relationships between change in pore structure and drained shear behavior were discussed. Furthermore, undrained triaxial compression shear tests were carried out on normally consolidated specimens and the effect of strain rate on pore structure was also investigated. It was found that the changes in pore structure of peat corresponded to the volume changes during shear and were especially influenced considerably by the degree of overconsolidation.

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Relatively little attention has been given in the past to the soil disturbance due to installation of a single pile or pile group. This paper investigates the soil (Leighton-Buzzard Sand) disturbance due to installation of a single pile and pile groups. The technique which has been previously used at Leeds University (UK) is based on the fact that changes in sand density cause changes in thermal conductivity of the sand. Model piles which have a diameter of 40mm and overall length of 1 m each were driven individually by a drop hammer into medium dense and dense air-dried sand. The effects of the initial sand density, the shape of the pile's bottom and the spacing between piles on soil disturbance are examined. These factors were found to be very significant and various zones of loosening and compaction of sand were observed in regions below and beside the pile, inside and outside the periphery of the pile group.

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Experimental investigation on stress development in sand due to installation and uplifting of helical screw anchors is presented. Five model anchors with different geometry were tested to examine the effect of screw shape on stress development in sand. The sand was placed in layers and mechanically compacted by a hand-held air hammer. The testing tank was equipped with stress transducers located at predetermined positions to allow measuring the stresses in the sand around and in the near vicinity of the installation path. Stress transducers were oriented such that vertical and lateral stresses could be measured. Anchors were installed into layers of dense, medium, and loose sands. Stress measurements indicated that the tested sands were slightly overconsolidated due to the utilized placing technique. Furthermore, measured stresses were used to determine the extent of stress field inside the sand. Deflections of sand surface, during pullout load application, were measured by displacement transducers. The stresses measured within the sand together with the recorded surface deflections were utilized to establish the extent of the mechanism of failure for shallow, transit, and deep anchors.

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The response of many geotechnical problems is governed by the development of discontinuities within the soil mass. Model tests, at one gravity and on a centrifuge at 100 gravities, on granular soils of different particle sizes, have been used to study the formation of discontinuities over a moving fault and in front of a rotating wall or blade. Discontinuities are observed as zones of localised shearing deformation and associated density decrease. The pattern of discontinuities is controlled by the changing dilation of the soil, and varies during the course of a test. The pattern of discontinuities is linked with particle size : in tests conducted at the same stress level, the same pattern of discontinuities is observed if the ratio of boundary movement to particle size is the same. Dilatancy and friction in granular soils are affected by stress level. Stress levels can be correctly reproduced in small models tested on a centrifuge and observations of continuous soil response can then be extrapolated from model to prototype scale. Kinematic effects associated with discontinuous soil masses require statements about displacements as well as strains, and care is required in predicting large scale response on the basis of the results of small model tests.

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A new neutron-moisture cone penetrometer has been designed and developed at the Kyoto University. It uses Cf²⁵² as the source for fast neutrons and He³-filled proportional tube as the detector. In the present paper the principles of neutron action with the matter is briefly reviewed and some of the test results are presented. It has been shown that this newly developed Neutron-Moisture Cone Penetrometer (hereafter NM-cone penetrometer) can measure soil strength parameters such as penetration resistance (q_c), friction ratio (f_s), pore pressure (u) as well as natural water content (w_n%) for the entire depth of the penetration. This instrument enables us to have continuous data rather than discreet data which are obtained using other types of sampling technique. It has been observed that the presence of strong neutron absorber could give erroneous results, therefore, the knowledge of the composition of the soil is necessary. One of the biggest advantages of having such a system is that it eliminates the need to procure samples which may or may not represent the actual in-situ conditions.

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The paper discusses the main aspects involved in numerical modeling of successive, large deformation, rigid body impacts in sand. The modeling was performed for the study of dynamic compaction of dry sand induced by repeated drops of a rigid tamper. Two dynamic finite element codes were used with a variety of soil models and computational algorithms. Large deformation effects and associated plastic behavior of the sand required special computational techniques of remeshing and reassignment of material properties. Consistency and stability of the formulations were evaluated based on their characteristics of convergency, accuracy, and computational efficiency. The adequacy of these models to represent actual soil behavior was evaluated by comparing computed results with available experimental data from an extensive laboratory investigation. The conclusions presented may serve as general guidelines relevant for this type of analysis.

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The paper presents results from an extensive experimental model study of response of dry sand to impact of a rigid tamper. In the laboratory tests a circular steel tamper was repeatedly dropped on sand contained in a large tank. Measurements included tamper acceleration aud soil pressure at impact, tamper settlement, aud soil densities and strains. Effects of tamper drop height, weight and contact area were investigated. A method is presented for the evaluation of global dynamic stiffness of the soil mass affected by the impact by calculating a dynamic settlement modulus (DSM). The DSM values are determined from integration of the impact acceleration record with respect to time using measured integration constants. DSM values show good correlation to soil densities and corresponding elastic moduli obtained from laboratory tests for loose sand. However, for dense sand, results indicate apparent discrepancies between elastic modulus and the higher DSM values. Analyses of normalized impact energy and the resulting densification in the sand in terms of normalized dimensions of volumetric strain (relative density) contours show unique correlations which are used for a proposed rational design method for dynamic compaction in dry sandy soils.

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A theoretical framework based on a one-dimensional wave equation model in conjunction with standard penetration test (SPT) results for the dynamic compaction analysis of loose sand deposits is presented. The wave equation model properly simulates the dynamic interaction between the pounder and the soil, the punch-through failure mechanism as well as the propagation of stress waves in the soil. Two reported case histories are analyzed and it is demonstrated that the pounder penetration, the degree and depth of soil improvement can be reasonably predicted using this model. The computed results of soil improvement are found to agree closer to those estimated based on the correlations of Skempton (1986) and Peck and Bazaraa (1969). The correlation of Gibbs and Holtz (1957) appears to lead to an over-estimation of the relative density of sand after dynamic compaction. It is believed that the theoretical framework discussed in this paper can provide a better understanding of the dynamic compaction process and may in due course lead to more cost-effective means of designing dynamic compaction work.

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A method for analyzing the uncertainties involving the use of empirical relationships in design is developed. It is applied to evaluate the reliability of the relationship s_u(mobilized)=0.22σ'_p(measured), whereby the pertinent uncertainties are analyzed using extensive laboratory and field observed data. On the average, the relationship s_u(mobilized)=0.22σ'_p (measured) is unbiased and the error implicit in the relationship is about 15%. When cone values are used to infer s'_p, additional uncertainties on the mobilized undrained strength will incur resulting mainly from the calibration uncertainty between σ'_p and the cone values. Alternatively, vane tests may be performed to infer the mobilized strength using Bjerrum correction factor. Results show that uncertainty level associated with using the vane tests is smaller than that using the cone values, provided that similar scatter is observed between measured vane and cone values at a given site. However, prediction of the mobilized strength is even more accurate if direct measurements can be made on the preconsolidation pressure. The proposed probabilistic method also assesses the benefit of additional tests besides comparing the accuracy of using various soil parameters for predicting mobilized undrained strength. Such information is essential for planning cost-effective site characterization program.

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Results from undrained cyclic triaxial tests followed by drainage on a reconstituted marine clay with high plasticity have been formulated to model the generation and dissipation process of cyclic induced excess pore pressure in clay. Through the introduction of two stress parameters in the formulation related to the relative cyclic strength and position in the effective p'-q stress space a unique relationship was found between the peak stress ratio on the extension side and the double amplitude shear strain under undrained cyclic loading. The excess pore pressure model proposed using this unique relation between the two defined parameters was then combined with the theory of axisymmetrical consolidation with radial drainage to predict the behaviour of clay under partially drained cyclic loading. The results of analyzing the behaviour during partially drained conditions were compared with the observed values of pore pressures and shear strains in drained-cyclic triaxial tests. It is suggested from comparisons that the proposed model for cyclic-induced pore pressures and shear strains should provide a practical tool for evaluating the settlements and stability of clay under partially drained cyclic loading.

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Undrained cyclic triaxial tests and drained triaxial compression tests were conducted on undisturbed samples of diluvial dense gravelly soils obtained by in-situ freeze sampling at four sites. These test results, together with test results by other researchers indicate that undrained cyclic strengths of gravelly soils depend not only on the modified blow count of penetration tests but also on effective confining pressure. By considering the effect of effective confining pressure on undrained cyclic strength, a method to evaluate undrained cyclic strength of natural gravelly deposits using the blow count of Large Penetration Test (LPT) is proposed. Furthermore, the possibility of evaluating undrained cyclic strength of natural gravelly deposits using initial shear modulus was investigated. It was found that although initial shear modulus can be used for this purpose, the accuracy is much less than that based on LPT penetration resistance.

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A three-dimensional (3D) analysis of bearing capacity of square and rectangular footings is presented by means of a slice method, assuming that sliding surfaces are composed of a set of log-spirals with different initial radii in the direction of the longer axis of the footing base. Discussions are first made on some fundamental aspects of 3D solutions, such as the effect of the number of soil columns on the accuracy of solution, the extent of 3D sliding surfaces, and the differences among solutions obtained by various slice methods. Bearing capacity factors are then calculated to investigate the effects of the ratio L/B of footing and the angle of internal friction and the accuracy of the superposition involved in the conventional bearing capacity formula. The values of shape factors obtained by the present 3D solutions are also compared with experimental and empirical formulae.

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The paper examines the role of physico-chemical factors in the consistency limits and compressibility behavior of kaolinitic soils and montmorillonitic soils of residual origin. The liquid limit, equilibrium void ratio at a given load (in the oedometer test) and compression index values of the kaolinitic soils in the remolded state correlate well with the shrinkage limit values, which in turn are a function of the clay fabric. The corresponding engineering properties of the remolded montmorillonitic soils correlate well with the exchangeable sodium content that reflects a soil's potential to develop diffuse ion layer. Oedometer tests with undisturbed samples highlight the role of clay mineralogy in the engineering behavior of residual soils; on inundation with water under a nominal pressure, the kaolinitic soils exhibit no volume change while the montmorillonitic soils exhibit a notable swell. Oedometer tests with undisturbed samples also showed that besides the physico-chemical factors, the in-situ moisture content, density and degree of saturation have an important bearing on the void ratio sustained by the soils at a given stress level.

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Plate anchors are the popular type of anchors used in civil engineering construction both on land and offshore. In this paper, the uplift capacity of plate anchor in a sloped clayey ground has been brought out with the help of an experimental programme, carried out on a 50mm diameter model plate anchor. The tests have been conducted at slopes of O°, 15°, 30°and 45°. From the test results, it is found that in the case of shallow anchor, as the slope is increasing from O°to 45°, there seems to be a reduction in uplift capacity. Simple expressions are suggested to arrive at the uplift capacities in sloped ground. The mechanisms involved in the reduction of capacity with slope are explained based on the observed behaviour.

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When a load is applied to a normally consolidated clay which has experienced secondary compression, the skeleton of soil particles can sustain a part of the load increment, before sliding of particles will be initiated at a certain pressure. This is referred to a quasi-preconsolidation effect. The quasi-preconsolidation effect can be mostly explained by Bjerrum's concept concerning the delayed compression of a clay. However, in general, there exists some difference between the observed and the estimated values of quasi-preconsolidation pressure. In the present Note, the degree of the difference and its characteristics are examined through consolidation tests on various clayey soils. As a result of these tests, it is found that the degree of difference is unchanged by consolidation pressure, but is influenced by the duration of sustained loading at a previous stage and has some relation with the properties of a clay.

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Residual granite soil occurs extensively in peninsular Malaysia. The soil has been commonly used for construction of airfields and road embankments. This paper describes the stabilization of the residual soil by adding a cementive stabilizing agent and an additive to improve the engineering properties of the soil for the above applications. Compaction and unconfined strength properties as well as durability characteristics were investigated to evaluate the effectiveness of the stabilization method.

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