1,720,965 research outputs found
Numerical study to prevent ground settlements induced by over-excavation with EPB shield TBM
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Estimation of Gas Hydrate Saturation for Hydrate-bearing Sediments Using Shear Wave Velocity
No full textSoil-tunnel interaction for segmental linings with non-planar longitudinal joints via centrifuge modeling
No full textSegmental tunnel linings can develop uneven internal forces and excessive deformation when nearby construction or groundwater fluctuations weaken their joints, threatening long-term durability. Conventional planar longitudinal joints often slip or rotate excessively under asymmetric, multidirectional loads, yet alternative geometries to overcome this vulnerability remain underexplored. This study proposes a novel design with nonplanar, topologically interlocking longitudinal joints and evaluates its performance against a planar counterpart. A 50g geotechnical centrifuge test imposed asymmetric surcharge loading on both linings. Ground responses, including surface settlement, soil stiffness, and stress redistribution, were monitored alongside structural responses such as bending moment and hoop force. The non-planar joints promoted more uniform hoop force distribution, limited peak bending moments, and stiffened the soil-tunnel system. Correspondingly, lining displacement and ground surface settlement decreased relative to the planar case. Key metrics, such as the loadsharing ratio and the equivalent radial spring stiffness of the system, quantify these performance gains. The highfidelity dataset clarifies the load transfer mechanisms and supports the establishment of sophisticated numerical models required for comparative design optimization. These findings demonstrate that non-planar interlocking joints enhance system resilience and provide a practical pathway toward more robust segmental linings.
Numerical study on behavior of ground surrounding interface between submerged floating tunnel and subsea bored tunnel
No full textIn this paper, the behaviors of the ground-tunnel interface of submerged floating tunnels (SFTs) and traditional bored subsea tunnels are investigated through numerical analyses. The analyses consider both permanent loads (self-weight, hydrostatic pressure, buoyancy etc.) and environmental loads (currents, waves, tides etc.). In order to simulate accurate subsea conditions, the magnitude, influence factors, governing formula and characteristics of each load type are discussed and determined. The analyses show the maximum stress and maximum displacement distributions along the ground-tunnel interface. The results can be used to suggest a three-dimensional ground reinforcement scheme based on additional stiffness requirements and ground deformation ranges
Numerical study on pre-fabricated composite segment with compressible layer combined at their extrados
No full textThe development of TBM technology enables continuous tunnel excavation with limited deformation of the ground, so it is also being utilized in challenging conditions. Nevertheless, geo-risk problems, such as squeezing during tunneling in overstressed rock, like deep soft rock, cause excessive stress in the segmental lining. The conventional structural solution based on the resistance principle causes the problem of overdesigning the segmental lining. Therefore, studies have been conducted on various yielding supports to reduce support pressure by allowing some internal displacement of the tunnel wall after excavation. Pre-fabricated composite segments with a compressible layer combined at their extrados can be considered in the shield tunnel, but this design is not well established. In this study, a numerical analysis based on the finite element method was performed to investigate the effect of the compressible layer on the segmental lining and the surrounding ground during the excavation of the shield tunnel in the deep soft rock. A parametric study was conducted with the characteristics of the compressible layer, the physical properties of the rock, and the presence or absence of backfill material as the main factors
Effect of soil type on effective soil thermal conductivity for the full range of water saturation
No full textAccurate estimation of effective soil thermal conductivity is crucial for designing and managing geosystems such as underground power cables, thermally active geostructures, and nuclear waste repositories. Previous studies have examined the soil thermal response by varying soil properties and water saturation for specific soil types. However, the applicability of these methods in capturing the evolution of effective soil thermal conductivity across different soil types and fundamental soil properties is limited. This study investigates the effect of soil type and fundamental soil properties on effective soil thermal conductivity across the full range of water saturation. A predictive model is developed to describe the evolution of normalized thermal conductivity with saturation, incorporating two physically meaningful parameters that characterize the initial and intermediate thermal response with increasing water saturation. This model adequately fits the effective soil thermal conductivity data collected from the literature. Using an extensive dataset of various soil types, soils are classified into three major texture groups: coarse-textured, moderately coarse-to medium-textured, and moderately fine-to fine-textured soils. These groups exhibit distinct trends in thermal conductivity evolution with water saturation, as reflected in their model parameters. Further analysis explores the key soil properties that govern these model parameters, providing a comprehensive understanding of the mechanisms controlling thermal conductivity variation. As an engineering application, a practical reference is proposed to categorize soils based on key parameters such as the saturated and dry thermal conductivity, initial porosity, and average thermal conductivity of soil particles.
Experimental Study on the Relationship between Permeability and Gas Hydrate Saturation in Marine Sediments
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Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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