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A conveyance water shield tunnel under the Yangtze River, which was designed for the Jiangsu Changshu Power Plant Co., Ltd., was damaged due to water leakage and submersion. In order to complete the engineering, the shield tunnel should be repaired, and the connection between the shield and standpipes should be completed. Therefore, a deep excavati...
Citations
... The form of foundation pit supporting structure has great difference in the control of displacement and internal force of adjacent tunnel. The common supporting forms are pile-anchor supporting structure [1][2], double-row pile supporting structure [3][4], row piles (ground connecting wall) + internal bracing structure [5][6]. ...
Relying on the deep foundation pit support engineering adjacent to the subway tunnel in Lanzhou, Two support schemes of double row piles and row piles + inner bracing are designed. Through the method of numerical simulation, the three-dimensional models including tunnel are established by using MIDAS-GTS-NX software, and then compared and analyzed from two aspects: the displacement of supporting structure, deformation and internal force of tunnel lining. The results show that: (1) For the double-row pile supporting structure, the maximum displacement and stress of the row pile appear near the midpoint of the side of the excavation side; for the row pile + internal bracing supporting structure, the maximum displacement and stress appear near the left position of the midpoint of the excavation side. (2) The maximum position of the tunnel displacement is different, and the displacement decreases gradually from the maximum position of the tunnel displacement to both sides of the tunnel. Through the comparative analysis, it can be known that the row pile + internal bracing structure is much better than the double-row pile supporting structure in controlling the deformation of foundation pit and adjacent tunnel.
... When the vertical displacement or lateral convergence deformation of the shield is large, it will seriously affect the safe use and operation of the existing tunnel [1][2][3][4][5]. At present, many scholars have used theoretical calculation [6][7][8], numerical simulation [9][10][11][12], and measured analysis [13,14] to conduct in-depth analysis on the deformation of the underlying tunnel caused by foundation pit excavation under different geological conditions or construction schemes. In addition, many factors are also considered in the research on the mechanism of stress and displacement of a tunnel caused by loading or unloading. ...
... The undetermined constant C ij (i = 1,2,3) can be obtained by solving formula (9). j = 1,2,3,4 and the undetermined constants are substituted back to formula (5), that is, the theoretical solution of the static uplift of each beam section at the stress stage at that time. ...
The construction of a deep and large foundation will inevitably impose stress and deformation on the existing shield tunnel structure. Based on the two-stage analysis and the Pasternak foundation beam model, the analytical solution for the existing tunnel deformation is derived by taking the grouting pressure and water buoyancy into account in the total tunnel deformation. Using FLAC 3D software, based on the soil-structure interaction model, the variation law of the tunnel uplift value under partition excavation of the foundation pit is studied and the variation law of the stress field and displacement field of the tunnel under the MJS method is analyzed and compared. The results of this paper are worthy of reference for similar projects.
... The influence of deformation is mainly concentrated around the foundation excavation. Beyond the range of 55.0 m (1.37H e ), the influence of foundation excavation on the surrounding environment can be ignored, and the influence range is much smaller than that described in the literature, which is (2-3)H e (Sun et al., 2018). The reason proposed in this paper is that the strata of the project site are a dual structure of rock and soil, which has a great influence on the subsidence deformation and restricts the deformation of the deep rock and soil mass. ...
A 40-m-deep large excavation of a subway station is relatively rare in the world. The retaining design scheme and deformation characteristics of suspended diaphragm walls with struts in rock and soil composite ground are introduced. The excavation is numerically simulated, and the reliability of the numerical model is verified by field-testing data. Then, by changing the parameters of the numerical model, the influences of the parameters on the deformation of the excavation are analysed. Research shows that the deformation characteristics of this superdeep excavation is different from the conventional foundation excavation. The superdeep excavation has a small scope of influence on the surrounding soil, the maximum lateral deformation of the supporting structure is also small, and the maximum ground settlement point is closer to the foundation pit. The most important influence on the lateral displacement of the superdeep excavation with the dual structure of rock and soil is the prestressing. The support method of the suspended diaphragm wall is reliable.
... They compared the numerical simulation results with real projects, validating their results. The numerical simulation method has a certain applicability and reliability for the research of the water leakage disease of tunnels (Sun et al. 2018). Compared with model tests and field monitoring, simulations do not require large amounts of time and work and are more economical. ...
In this study, the water leakage susceptible areas in a loess multi-arch tunnel were examined, providing a basis for the prevention and control of water leakage disease during the operation periods of multi-arch tunnels in loess areas. Through the field investigation of the leakage in loess multi-arch tunnel, the leakage mainly focuses on three joints: construction joints, expansion joints, and settlement joints. The spatial distribution of the leaking part in the tunnel is summarized and abstractly into three types: annular cracks, longitudinal cracks and full longitudinal cracks + circumferential cracks. By setting up different number of annular and longitudinal cracks, a total of 20 combinations were designed. This paper sets three kinds of working conditions, including 40 and 60 m of reinforcement water head and 60 m of no reinforcement water head, considering groundwater lateral recharge conditions. Using the midas/GTS geo-technical analysis system software, 3D numerical simulations were conducted to determine the distributions of the total water head and water pressure in cracks for all the combinations of water leakage positions under different working conditions and to analyze the variations in the seepage field of the surrounding rock. Based on the areas where the total water head and water pressure in the cracks sharply changed, the water leakage susceptible areas were determined. The rationality and reliability of the method were verified by a comparison with the results of a field investigation.
Deep foundation pit excavation (DFPE) for metro stations in soft layers can cause strata deformation, impairing the safety and performance of nearby existing structures. This paper aims to explore the impact of DFPE on an adjacent oil pipeline using numerical simulations and field tests. Using the project of Xinxingcun Station of Tianjin Metro Line 4 in China as a case study, two approaches of layered excavation (LE) and bench excavation (BE) are proposed for DFPE. The deformation induced by the two approaches was analyzed using the FE method. The maximum vertical settlement of the oil pipeline caused by LE was 8.1 mm, compared with the maximum vertical settlement of 12.5 mm caused by BE. In practice, LE was selected as the construction scheme for the DFPE in Xinxingcun Station. Some field measurement work on pipeline deformation was conducted, and the results were in good agreement with the numerical simulation. Lastly, the change pattern in the pipeline-soil gap was studied. The angle of the position with peak gap width increased from 25° to 110°.
