In recent years, the utilization of geothermal energy for buildings has increased significantly. Especially in growing urban areas, there is a need for supplementary research to maximize the efficiency of heat exchange in geothermal energy systems on space-restricted sites. There is currently a little research about improving the heat exchange by choice of pipe materials. Circular pipes of high-density polyethylene (HDPE) and polybutylene (PB) are commonly used as ground heat exchangers (GHEs) for convenience and cost benefit, but PB pipes, in particular, have thermal properties that do not have a favor in the heat exchange. Therefore, this paper presents the results of an experimental study on the use of annular stainless steel (STS) pipe as a GHE. Thermal response tests (TRT) were conducted to measure heat exchange rates in circular PB pipe and annular STS pipe installed in a steel box with the dimension of 5 m × 1 m × 1 m. Dry Joomunjin standard sand was used to fill the box and TRTs were performed for 30 hours to reach a steady state. As a result, the annular STS pipe showed about 9% higher heat-exchange rate (per pipe length) than did the circular PB pipe. Compared to the length of heat exchanger required under the same conditions, the annular STS pipe needed was shorter than the circular PB pipe. It is concluded that the STS pipe could be used as an efficient GHE.

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In Japan, the construction of social infrastructure has been increasing since the high economic growth in the 1960s. Right now it is a problem in Japan that these infrastructures are deteriorating. It is expected that further deterioration will occur in the future and the maintenance and the effective operation for these infrastructures are now emerging the significant subjects. Under these circumstances, a managing method named as an infrastructure asset management is beginning to be employed recently. Infrastructure asset management is a strategic management of physical assets during their life in the organization, which enables us to manage physical assets effectively and efficiently. The goal is to conduct a mid and long term efficient maintenance and operation plan for the subway tunnels and to decide the proper budget for rehabilitation.

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To date, Shanghai has built an intensive network of metro tunnel system. In the operation of such a complex tunnel system, the vulnerability and the recovery of the segmental linings subjected to unexpected disruptions are badly concerned by the engineers and owners. In this respect, the analysis of segmental lining resilience, i.e., the ability to absorb the disruption caused by the hazards and then the ability to recover to the acceptable level of the functionality, is necessary for the safety of the tunnels. In Shanghai, from time to time, some dumped soils from construction site elsewhere are found to be disposed without permission at the ground surface above the operated tunnels. When the volume of these dumped soils are significantly large, e.g., a height of 5-8m, it will inevitably do threats to the safety of the underlying operated tunnels. In this paper, the resilience of the segmental lining system subjected to this unexpected extreme surcharge loads will be characterized with a real field case in Shanghai. The convergence deformation is regarded as the functionality of tunnels. The functionality curve is described using the measured data from a detailed monitoring program. The unloading of the dumped soils above the surface and the grouting around tunnel from surface are the two recovery measures both implemented in this field case. The calculated metric of resilience indicates that the functionality of the tunnels can be bounced back significantly using these two recovery measures. Besides, the rapidity of the recovery of these two measures is compared. Finally, some discussion and concluding remarks on the resilience of operated tunnels subjected to this extreme surcharge load are presented.

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Nowadays, articulated shield becomes popular to construct tunnels with curved alignments. To steer the articulated shield, it is necessary to determine the operation on jack, copy cutter and articulation mechanism. But since these three functions have a high co-linearity to shield behaviour, it is difficult to obtain unique operational parameters at once. Therefore, the authors developed a numerical method to determine the copy cutter length and the articulation angle uniquely, based on geometric conditions under some constraint conditions. This paper shows an example of the application of the proposed method to a 3 dimensional compound alignment and discusses the validity of the proposed model. As conclusions, the followings were found: 1) the articulation angle depends on shield dimension, tunnel alignment and operation rules of shield rotation; 2) the copy cutter length distributes across the major normal direction of the tunnel about a half of the skin plate area; and 3) the analysis results demonstrate that the proposed method can provide articulation angle and copy cutter length and range reasonably from the view point of geometric conditions.

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This paper reports the field monitored surface settlements due to the construction of 161 kV power-cable shield tunnels in Hsinchu. The soils encountered during tunneling were mostly cobble and gravelly soils. Four earth-pressure-balance shield machines with outside diameters 6.24 and 6.70 m were used for tunnel excavation. When driven through gravelly soils, significant cutter head wearing was observed. Base on field observation data, the following conclusions were made. The maximum surface settlement was reached at approximately 30 days after the passage of the face. The maximum surface settlement achieved was only 5 to 6 mm. The field monitored settlement-time data were in fairly good agreement with the curves estimated with the hyperbolic model. The maximum surface settlements induced in cobble and gravelly soils were significantly less than those induced in clayey and sandy soils. This is most probably due to the high stiffness and shear strength of the gravelly soil, which reduced the ground deformation due to subsurface excavation. The induced settlement trough was wider than those induced in stiff clay, soft to hard clay, and sand above ground water table.

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The existing Bangkok MRT Blue Line has been operating almost 10 years and its extension is now under construction. It is the first highlight underground construction project in Bangkok involving many excavations and tunnelling works. The long-term tunnel behaviour is identified by many influential factors such as the magnitude and distribution of excess pore pressure generated during construction, compressibility and permeability of soil as well as relative soil-lining permeability. This paper focuses on the long-term behaviour of the underground tunnels based on the finite element analysis. The work deals with the deformation analyses of the Bangkok MRT tunnels. The soil constitutive models adopted herein were the hardening soil model for soft and stiff clays and the Mohr-Coulomb for sand. The parameters selected were calibrated against the laboratory testing results. The short-term analysis results were calibrated and compared with the field measuring data during the construction phase. For long-term analysis, a coupled consolidation analysis based on Biot’s theory was adopted. The long-term behaviours of the Bangkok MRT tunnels from the finite-element simulation were reported.

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Due to an increasing number of constructed tunnels in urban areas, excavation of a new tunnel may cause damage to adjacent existing tunnels. In order to assess damage on the existing tunnel, it is important to improve our understanding of the influence zone due to new tunnel excavation. The influence zone may include the location of significant tunnel settlement, tensile strain, shear stress or stress transfer acting on an existing tunnel. To investigate the influence zone of new tunnel excavation crossing beneath an existing tunnel, a series of three-dimensional centrifuge tests in dry sand was carried out. To identify the zone of substantial stress transfer on an existing tunnel, three-dimensional numerical back-analysis was also conducted using an advanced hypoplasticity constitutive model with small strain stiffness considered. The influence zone of new tunnel excavation on the existing tunnel is presented and discussed.

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