Influence of water pressure on deep subsea tunnel buried within sandy seabed
TL;DR: For a subsea tunnel, the changeable high water pressure is of great significance in the soil-water-tunnel interaction as mentioned in this paper, and a series of parametric studies were conducted to investigate th...
Abstract: For a subsea tunnel, the changeable high water pressure is of great significance in the soil-water-tunnel interaction. In this study, a series of parametric studies were conducted to investigate th...
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TL;DR: Based on the three-dimensional hydraulic head distribution model and the upper bound theorem of the limit analysis, a new model was established to calculate the limit support pressure in shield tunnel faces as discussed by the authors .
9 citations
TL;DR: In this paper , a plan of reconstruction of the collapsed metro line at its original location rather than relocation was selected finally for the post-failure rehabilitation, and extensive innovative construction plans, measures, and techniques were designed and then implemented into the reconstruction, e.g., a lightweight cofferdam and pile-supported steel platform for diaphragm walling through the existing metro line underneath the Huangpu River, unique protective solutions and construction techniques for execution of vertical and horizontal ground-freezing programs, special procedures of cleaning up the existing tunnels previously filled with water, sand and cement; innovative joints and grouting measures adopted between the reconstructed tunnel and the pre-existing intact metro line, and so on.
Abstract: The destructive failure of Shanghai Metro line 4 across underneath the Huangpu River on July 1, 2003, led to massive ground subsidence and collapse of pre-existing structures in the proximity; additionally, the failure generated large amounts of human-made rigid obstructions in the strata, which made rehabilitation of the collapsed metro line be very technically challenging. By extensive comparisons in terms of technical difficulties, economic costs, and construction durations, a plan of reconstruction of the collapsed metro line at its original location rather than relocation was selected finally for the postfailure rehabilitation. The majority of the failed metro line was replaced by a 262-m-long×23.7-m-wide×38.5–41.2-m-deep cut-and-cover tunnel bottoming out in the confined aquifer, whose two ends were connected with the existing intact metro line via two 10-m-long tunnels mined within the aquifer by the ground-freezing method. Excavation of the cut-and-cover tunnel was retained by 1.2-m-thick and 65-m-high perimeter diaphragm wall panels braced by 9–10 levels of steel-reinforced concrete struts. To ensure the project safety and mitigate potential adverse influences of field works on the urban environments, extensive innovative construction plans, measures, and techniques were designed and then implemented into the reconstruction, e.g., a lightweight cofferdam and pile-supported steel platform for diaphragm walling through the existing metro line underneath the river; unique protective solutions and construction techniques for execution of vertical and horizontal ground-freezing programs for diaphragm walling and mining; special procedures of cleaning up the existing tunnels previously filled with water, sand, and cement; innovative joints and grouting measures adopted between the reconstructed tunnel and the pre-existing intact metro line, and so on. Furthermore, the initial designs were optimized and adjusted with the progress of field construction works. Lastly, the long-term field performance data demonstrated the success of this rehabilitation project, which affected the urban environments rarely. The construction plans, measures, and techniques outlined in this paper are practical, useful references for professionals worldwide to deal with similar underground projects in the future.
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TL;DR: In this article, an analytical solution for a deep tunnel in a saturated poroelastic ground has been obtained for static and seismic loading, where linear elasticity of the liner and ground, and plane strain conditions at any cross-section of the tunnel are assumed.
185 citations
TL;DR: In this paper, a semi-analytical approach for analyzing the tunnel water inflow is proposed by using the classical ground water theory, where the groundwater problem in a finite domain is transformed to a problem in an infinite domain by the image method and the superposition principle.
141 citations
TL;DR: The highway tunnels under the Huangpu River of Shanghai are constructed at a maximum depth up to 45m, within the artesian aquifer as discussed by the authors, and the recently constructed tunnels have leaked less than 0.1 L/m2/day.
Abstract: The Quaternary deposits in Shanghai primarily consists of a phreatic aquifer group (Aq0) and five artesian aquifers (AqI–AqV) that are separated by six aquitards (AdI–AdVI). In the basin of the Huangpu River, the first artesian aquifer (AqI) is connected to the second artesian aquifer (AqII), forming a 50-m-thick artesian aquifer with a very high groundwater level. The highway tunnels under the Huangpu River of Shanghai are constructed at a maximum depth up to 45 m, within the artesian aquifer. These tunnels are lined with precast reinforced concrete segments without a second lining. Under high water pressure, it is difficult for the single shell linings to achieve water tightness. Different degrees of groundwater leakage have been observed in road tunnels under the Huangpu River. The tunnels constructed before the 1990s have had very serious groundwater leakage (e.g., >1 L/m2/day), and the recently constructed tunnels have leaked less than 0.1 L/m2/day. The factors influencing groundwater leakage include depth below groundwater level, differential settlement of the tunnel, and applied waterproof technologies. The increase in depth leads to a significant increase in groundwater leakage. The differential settlement causes gaps to open and offset between segments, as well as cracking of segments, which can also induce groundwater leakage. According to the analysis of recorded data, the number of leaking points tends to increase with the curvature of the settlement curve. In addition, inappropriate waterproofing materials and poor waterproofing design will also lead to groundwater leakage. Groundwater leakage causes deterioration of the structure, aging of the installations in the tunnels (e.g., facilities and pavements), as well as discomfort for users of the tunnels and adverse environmental impacts. Furthermore, groundwater leakage also causes structural deformation of the tunnel itself, leading to further leakage and hazards.
119 citations
TL;DR: In this paper, a rigid plate was set in front of the tunnel face to maintain stability at the initial state, by moving the plate backward from the soil, the displacement and earth pressure curve of tunnel face was obtained.
100 citations
TL;DR: In this paper, a semi-analytical method using the slope of the late-time drawdown asymptote of Stage III for determining the transmissivity is proposed.
89 citations