Accurate prediction of consolidation settlement has been one of the most important geotechnical issues in the land development with reclamation. The soil properties in reclamation ground should be estimated properly in order to predict the consolidation settlement accurately. However, they are varied spatially due to effect of their sedimentary condition. Then, the soil properties obtained through soil investigations have various errors which cannot be eliminated. Also, the number of soil investigations is not enough to estimate properly them in many cases. In this paper, the soil properties are estimated properly from the limited number of soil investigations with an artificial neural network. Also, the estimation error in soil properties and its effect on estimation of consolidation settlement is discussed stochastically. Firstly, an artificial neural network is applied to estimate spatially soil properties, including relationship between void ratio and consolidation pressure of the Holocene clay in Kobe Airport. Secondary, it is elucidated that the estimation accuracy of both void ratio and relationship between void ratio and consolidation pressure is higher than those of compression index and pre-consolidation pressure thought discussions about relative errors. Finally, the Monte Carlo simulations to consolidation settlement is carried out in order to estimate stochastically the consolidation settlement. The consolidation settlement applied practically might be estimated about 1.1 times of that estimated with an artificial neural network judging from the probability.

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In this study to assess the stratal architecture of the surface layer around the Kego fault zone, we collected and studied boring data. Approximately 17,000 boring data was collected, most of which is publicly available. The Kego fault is known for being primarily left-lateral, with one portion in the south-western direction being dip-slip. As such, this study focused on changes in the altitude at which the boring data’s bedrock appeared and investigated the locations at which the fault structure passes along. As a result, changes in the altitude at which the bedrock appeared was notable at Hakata Bay, and this gradually became hilly towards the south. Due to prominent gravel layers, the bedrock appearance altitude was difficult to ascertain, however we were able to confirm the locations at which the fault structure passed through from Hakata Bay to the southern part of Kasuga City.

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All too often in geotechnical works, slopes fail as a result of high seepage force arising from excessive rainfall or impoundment as well as poor compaction of fill material. One of the challenges facing geotechnical engineers is how to locate the high-seepage zones within slopes early during design and construction with a limited budget and time so that appropriate slope stabilization method can be arrived at. Groundwater Aeration Sound (GAS) survey technique recently developed in Japan is now being used in Thailand for studying seepage in various natural slopes. The technique involves using very high sensitivity accelerometer to pick up vibration or “sounds” of water flowing through unsaturated soil pores with air bubble bursting sounds. The device measures the Groundwater Aeration Sound (GAS) in the manufacturer’s representative index unit known as D value. GAS survey was carried out at two landslide sites in Northern and Southern Thailand and a distinct correlation was found between the locations of high D values (high GAS sounds), landslide scars and geological structures. In addition, tentative correlation between pore-water pressure and D values has been attempted and appeared to be site-specific.

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The Thomson Line (TSL) is a 30 km underground train line that is expected to be fully completed in 2021, and will be the sixth Mass Rapid Transit system in Singapore. The line will run through the north-south corridor, starting in the northern Woodlands area, passing through the industrial estate of Sin Ming, down to the residential Thomson area and the shopping districts of Orchard and Marina Bay, before ending at Gardens by the Bay. One of the key challenges is bored tunnelling through the soils and rocks of Bukit Timah Granite near to existing buildings, especially within the densely built-up regions near Orchard. Specifically, there are pockets of areas where it is not possible to conduct conventional borehole investigation method due to accessibility issues for the drilling rigs. To overcome the challenges in investigating the soil-rock interface at these locations, seismic survey methods were proposed to enhance the clarity on geological profile.The paper first explains the nuances and limitations between various seismic acquisition methods, such as 2-dimensional (2-D) methods, and 3-dimensional (3-D) methods. These have used in combination for oil and gas exploratory functions, but is uncommon to see their application in ground investigations for land infrastructure projects in Singapore. Eventually, a decision was made to make use of 3-D seismic refraction in the ground investigations for Thomson Line in Singapore.In practical sense, the paper presents an instance whereby 3-D acquisition method is scaled down to solve a civil engineering problem which in LTA’s case was determining bedrock depth that the bored tunnels will encounter during construction phase. The target depth for the soil-rock interface was between 30 m to 60 m, and is small-scale as compared to hundreds of metres of potential information that could be mapped using the acquisition method. Other than discussing the technicalities in implementing the 3-D survey, the effectiveness of the seismic acquisition in mapping the soil-rock interface of the Bukit Timah Granite Formation will be discussed. Future application of the seismic acquisition for LTA projects is also briefly included.

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Methane Hydrate (hereafter referred to as MH) is being researched and developed in order to prepare for production in the Nankai Trough of Japan. The grain size distribution and the degree of MH saturation of MH bearing sand varies based on location with varying fines content. Also, the shear behaviour is affected by particle shape. In order to investigate the effect of the characteristics of host sand on the shear behaviour of MH-bearing sands, MH was artificially produced in specimens composed of four kinds of materials with varying particle shape, fines content and degree of MH saturation. In this study, a high stress and low temperature triaxial plane strain testing apparatus was used. A marked increase in stiffness and strength was observed in all MH-bearing materials. In the case of glass beads, higher peak stress appeared in MH-bearing material than that without MH and the softening behaviour of MH bearing sand after peak strength was most predominant. In the case of MH-bearing sand, an increase in fines content leads to an increase in strength. An increase in degree of MH saturation leads to an increase of the angle of the shear band and the width of shear band becomes narrower.

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Particle image velocimetry (PIV) is a widely used image processing technique for mapping deformation in centrifuge models. One of the problems associated with PIV is the occurrence of incorrect or ‘ wild vectors’. A ‘ wild vector’ is defined as a vector that does not follow the general directional trend of the other vectors surrounding it, which if present in large numbers, can affect the accuracy of the deformation plot. This problem is particularly important in clay model, the surfaces of which often do not have inherent texture. The paper examines some possible enhancements to PIV images by fine tuning three parameters, namely type of texture material, method of texture placement and the use of high resolution colour imagery. The trials were conducted on centrifuge models of tunnels. The desired outcome is to minimize the percentage of wild vectors that is attained from the PIV analyses of the recorded images. The results show that with the use of colour model terrain, the likelihood of clay obscuration can be reduced significantly, Furthermore, by the use of an appropriate method of scatter will offer favorable image contrast for PIV based experiments involving the use of saturated clay. Finally the advantage of colour imagery is that it is able to capture the difference in color as the coloured camera is able to detect the hue, saturation and luminance of the texture used. These lead to a corresponding improvement in image contrast and hence, PIV analysis results.

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Energy pile foundation technology has received increasing attention as a means for reducing energy requirements for space heating and cooling and cutting down the emission of carbon dioxide. Energy piles provide a means for efficiently transferring heat to and from the soil underlying a structure, providing a heat source for heating and a heat sink for cooling of spaces within the structure. Currently the design of energy foundations relies heavily on empirical methods, owing to a limited understanding of coupled cyclic thermo-mechanical effects on pile behavior, particularly long-term performance in clay. Moreover, there is lack of field data since it is expensive and time-consuming to carry out field trials. Based on theoretical derivation, geotechnical centrifuge modelling permits the simulation of heat diffusion phenomena at a rate N² times (where N is scaling factor) than in prototype. It is thus beneficial to assess long-term behaviour of energy piles by the use of centrifuge modelling technology. In this study, a new heating and cooling system developed for centrifuge modelling at the Hong Kong University of Science and Technology (HKUST) is described. The heating and cooling system is comprised of an array of thermoelectric coolers and an electrical-resistance heating coil. Ethylene glycol is used as a heat exchanger fluid to transfer the thermal energy from the heating and cooling system to tubular aluminum model piles via insulated piping with the help of a pneumatic pump. The heating and cooling system is able to control the temperature of the pile over the range from 3°C to 90°C. To assess the long-term serviceability of energy piles in stiff clay, a centrifuge model test was carried out where five cycles of heating and cooling were applied to a single energy pile under a sustained working load at 40g. Test results revealed that a ratcheting settlement pattern was induced after cyclic thermal operation.

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