Seismic damage to embankments has sometimes been found to take place at locally-limited spots even though the foundation conditions are almost the same along their axes. A few studies related to this kind of local failure have been conducted, however the reason why local failures of embankments take place is not known. This paper aims to study the influence of the three-dimensional response of embankments on their local failures. A series of shaking table tests were conducted. Test results revealed that local failures occurred despite the fact that the model base was shaken uniformly. It was also found that the interval of local failures depends on the frequency of input motion and the stiffness of the embankments. Thus, an equation to calculate the intervals of local failures was derived, and this was found to agree well with the seismic damage to the Kushiro River Dike.

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A laboratory study was conducted to evaluate the potential of 9.5mm-minus crushed glass (CG) to improve the physical and strength properties of a high plasticity soil (CH). The model soil used in this study, a kaolinite-bentonite mixture or “model” clay (MC), was chosen to represent the properties of naturally occurring fat clays, as well as to provide baseline data for future comparison of site-specific CH soils. Tests were performed on 100% MC and 80/20, 60/40, 40/60, 20/80 CG-MC (dry CG weight% reported first) blends using the CG previously evaluated by Grubb et al. (2006a). The most significant incremental increases in maximum dry density for standard (2.8 kN/m³) and modified (2.5 kN/m³) Proctor compactive effort and decreases in moisture sensitivity (14 and 12%), respectively, were observed to occur with the addition of 40% CG. By a CG content of 40%, the effective friction angle increased by about 5° while the compressibility decreased by about 33%. Similar improvements of lesser magnitude occurred with additional incremental (20%) increases in CG content.

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The naturally cemented clay preserving chemical bonds that was gradually disintegrated by weathering is a soil exhibiting a progressive failure such as a landslide. The residual strength of soil possessing cementation properties given by diagenesis has not yet been investigated. The objective of this study is to clarify the residual strength characteristics of naturally and artificially cemented clays using an improved reversal direct box shear test apparatus. Based on the test results of reconstituted Kaolin clay, undisturbed, remolded and reconstituted samples of three natural clays, this paper describes the influence of normal stress, shear displacement rate, consolidation and shear histories on the residual strength of cemented clay. Especially, to simulate the same mechanical behavior as the naturally cemented clays, the cementation was artificially reproduced by adding cementing agents to slurry clay. Consequently, 1) the residual strength of cemented clay is independent of consolidation yield stress and initial void ratio. 2) The residual strength of cemented clay as well as non-cemented clay increases with increasing the shear displacement rate. 3) The residual strength of cemented clay as well as non-cemented clay is not affected by any stress history.

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The aim of this paper is to show how to obtain the impact efficiency from a static load test performed on the standard penetration test (SPT) sampler. In a dynamic test, the maximum resisting force developed during the hammer impact depends on the displacement (static component), velocity (damping component) and acceleration (inertial component). At the instant corresponding to the dynamic test end, experimental data show that the elastic potential energy is negligible. As a consequence, the work done is almost equal to the potential energy stored in the system. Similarly, in a static load test performed on the sampler right after the dynamic test, the elastic potential energy is also negligible. As a consequence, the work done is almost equal to the potential energy stored in the system. Thus, in both tests, the maximum penetration of sampler into the soil is permanent. Additionally, it was verified that the potential energy stored in dynamic test is almost equal to the potential energy stored in static test, for the same value of sampler penetration. Thus, the efficiency can be obtained dividing the system potential energy by the SPT nominal potential energy (474 J).

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When using the substructure method for a pile-supported structure, it is common to adopt a simple element (equivalent model) to simulate the load-deflection behavior of a laterally loaded pile. Conventionally, two kinds of equivalent models, the uncoupled spring model and the equivalent cantilever model, are used to approximate the lateral pile-head response of a laterally loaded pile. These equivalent models can not work equally-well for different pile arrangements and loading conditions because the stiffness matrix (or flexibility matrix) of these equivalent models do not entirely match that of the original pile-soil model. The response obtained will never give correct displacements and forces simultaneously. To solve this problem, this study develops an exact equivalent model, in which an artificial lateral spring is added at the base of the cantilever to modify the fixed-base cantilever model so that it can completely represent the pile-head behavior of a laterally loaded pile-soil system. For verification, comparison studies between the proposed model and conventional equivalent models are conducted to show the effectiveness of the proposed model.

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Large-scale plane strain compression tests were performed to study the effect of compaction on strength and deformation properties of gravel. The specimen is rectangular prismatic with dimensions of 50 cm in height and 22 cm times 25 cm in cross-section. By employing well-graded crushed sandstone called as Chiba gravel, five sets of plane strain compression tests were conducted on partially saturated specimens having dry densities in the range of 1.80-2.15 g/cm³ that were prepared using manual or automatic compaction techniques. For each set of tests, one specimen was tested by following the conventional approach called as “passive control” of ε₂, while the second specimen was tested by following a new approach called as “active control” in which one of the two confining plates was allowed to move forward and backward for keeping the locally measured value of ε₂ almost zero. As a result, no significant effect of the active control was found on the stress-strain behavior as compared to the passive control, except for the beginning of shearing. The maximum deviator stresses in the two kinds of plane strain compression tests were about 20% larger than those in the relevant triaxial compression tests under the employed range of the compaction levels.

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Testimony from eyewitnesses of the Showa Bridge collapse was collected with the objective of pinning down the cause of the collapse. On the basis of this testimony, a chronology of events was established. The bridge collapsed about 70 seconds from the beginning of the earthquake, i.e., long after the strong shock. The liquefaction-induced flow occurred after the collapse of the bridge. By studying these times of occurrence, as well as observed earthquake records, the cause of the Showa Bridge collapse was deduced. The possibility of inertia force in the superstructure and liquefaction-induced flow is low as the main cause of the collapse of the Showa Bridge. There is a high possibility that it was due to increased displacement of the ground in circumstances where pile deformation occurred more easily due to liquefaction.

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Nakhon Nayok Province, Thailand, is located in the floodplain area and has severe problems regarding acid soil which contains sulphide bearing material resulting in soil pH below 4.0. The objectives of this study are to investigate the geochemical variation that occurs under a groundwater controlling condition above the acid materials while other field factors are maintained in natural condition and to study the groundwater controlling technique to alleviate the acidic condition. The field experiment is designed in order to control groundwater level within a time period. The effects on the chemistry of groundwater, surface water, porewater and the soil itself are also monitored. The result reveals that acidity of the soil increases initially from the soil disturbance and the acidity decreases afterwards as a result of the groundwater controlling condition. This finding is also confirmed by the water chemical changes. Several cations are released into porewater when acidity increases and these metals can be hazardous to plants, foundations, and humans. From this study, we conclude that soil disturbance from any activity can stimulate the acidity of the acid sulphate soil, and maintaining groundwater level above the parent material can help alleviate the acidity.

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Flexible pipes are traditionally used for shallow burial depth, say less than 10 m. In recent years, flexible pipes are increasingly used in the difficult terrains for infrastructures, landfills, residential, and industrial developments. Occasionally, the fill height may exceed 20 to 30 m. The existing guidelines do not address the design of flexible pipes under such high fills. In this paper, a general solution for the moment and displacements of a thin-wall ring subject to external earth pressures exerted by the high fills was derived. A finite element procedure was also used to analyze the pipe behavior under high fill. The closed-form solution and finite element results were verified with the measurements obtained from the field under a fill height of 47.1 m. The analytical and finite element results showed good agreement with the measured results. This study revealed that existing design for pipe buried under high fill could be overly conservative and uneconomical. The vertical and lateral earth pressure diagrams for design were revised.

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The effects of geosynthetic reinforcement type on the strength and stiffness of reinforced sand were evaluated by performing a series of drained plane strain compression tests on large sand specimens. The reinforcement type is described in terms of the degree of unification of the constituting components (for geocomposites) as well as the tensile strength and stiffness, the covering ratio and others (for geocomposites and geogrids). Sand specimens reinforced with different geosynthetic reinforcement types exhibited significantly different reinforcing effects. A geocomposite made of a woven geotextile sheet sandwiched firmly with two sheets of non-woven geotextile, having a 100% effective covering ratio, exhibited reinforcing effects higher than typical stiff and strong geogrids. With some geocomposite types, the reinforcing effects increase substantially by better unifying longitudinally arranged stiff and strong yarns and non-woven geotextile sheets. When fixed firm to the yarns, the non-woven geotextile sheets function like the transversal members of a geogrid by locally transmitting load activated by interaction with the backfill to the yarns. These geocomposites can exhibit reinforcing effects equivalent to those with stiff and strong geogrids. Local strain fields of the specimens are presented to show that, for reinforced sand, the peak stress state reached is always associated with the development of shear band(s) in the sand and a higher peak strength is achieved when the strain localisation starts at a larger global axial strain due to better reinforcing effects.

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Severe rainfall associated with the passage of super-typhoon “Reming” on November 30, 2006 triggered lahar flows, landslides and flash floods on the south-eastern quadrant of Mayon Volcano, resulting in extensive damage to life and property. Among the affected areas, the towns of Guinobatan, Camalig and Daraga suffered the most damage, with numerous houses, roads and other infrastructures either buried or swept away by the flowing lahar and rampaging floodwaters. This paper outlines the observations from the reconnaissance work conducted at the affected sites following the disaster, with emphasis on the hydro-geological aspects of the disaster and their impact on civil engineering structures and other infrastructures. Moreover, the properties of the lahar samples obtained near Mayon Volcano were analyzed and compared with the lahar deposits from Mt. Pinatubo.

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A system for a hybrid consolidation simulation was developed to predict more realistically the nonlinear behavior of the consolidation settlement of soft clay, including a large strain consolidation problem. The hybrid simulation method can introduce the mechanical behavior of the soils directly by combining numerical analysis and the soil element test in an online state. In this paper, a fundamental study to apply the hybrid simulation method to the consolidation settlement problem, a basic concept, and the corresponding algorithm and components are presented. Furthermore, using preconsolidated Kaolinite clays, verification studies were also conducted in the laboratory to verify the operational performance and data reliability of the system. On the basis of the test results, we concluded that the new consolidation analysis system using the hybrid simulation concept provided an adequate performance in the reproduction of the consolidation behavior of preconsolidated Kaolinite clays in the aspect of the dissipation of excess pore water pressure and corresponding consolidation settlement.

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