A DEM-based study of the disturbance in dry sandy ground caused by EPB shield tunneling

Hu, Xiongyu; He, Chuan; Lai, Xiaohui; Walton, Gabriel; Fu, Wei; Fang, Yong

doi:10.1016/j.tust.2020.103410

Cited by 49 publications

(8 citation statements)

References 27 publications

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“…It can be also observed that the maximum displacement of each measuring line did not exactly occur at the central line of the tunnel ( Figure 10 a) and the excavation-influenced area did not have a symmetrical shape ( Figure 10 b). However, for the simulations on the ground formed by rounded particles, the ground settlement and the excavation-influenced area are almost symmetrical with respect to the central line [ 45 , 46 , 47 , 48 ]. Therefore, the particle shape-induced heterogeneity may have a negligible effect on the excavation-induced responses.…”

Section: Resultsmentioning

confidence: 99%

Role of Particle Shape on Ground Responses to a Circular Tunnel Excavation in Sandy Soil: Consequences from DEM Simulations

2022

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Due to the sensitivity of sandy soil’s mechanical behavior to the particle shape, it is thus of importance for interpreting the effect of particle shape on the ground response induced by tunnel excavation in sandy formations. We conducted a series of 2D DEM (discrete element method) simulations on a common circular tunnel excavation in sandy soil with variable-shaped particles, which are characterized as two descriptors, i.e., aspect ratio (AR) and convexity (C). The macroscopic responses and the microscopic characteristics of the sandy ground are elaborated in detail. The simulation results show obvious asymmetrical features of the excavated ground, which results from the ground heterogeneity caused by the irregular particle shape. In addition, we investigate the roles of AR and C on the ground response and find that reducing AR or increasing C will enlarge the ground settlement, i.e., the sandy ground deformation is more sensitive to the particles with more irregular shapes. However, elongated particles are beneficial for the generation of soil arching with stronger bearing capacity and thus reduce the soil pressure on the tunnel lining. Our findings have important implications for the safety assessment of the tunnel excavation, as well as other underground structure construction in sandy formations.

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Section: Resultsmentioning

confidence: 99%

Role of Particle Shape on Ground Responses to a Circular Tunnel Excavation in Sandy Soil: Consequences from DEM Simulations

2022

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“…Another main geometric factor for the calculation of tunnels is the dimension of tunnels. In these situations, conditions such as the depth, diameter, and distance of the tunnels constitute the essential parameters for this question in numerical modeling [25,26]. Initially, the excavation depth of tunnels is a decisive factor in the generation of surface settlement, and a threshold value of 16 m depth is determined for their mitigation [27].…”

Section: Introductionmentioning

confidence: 99%

Numerical Model Validation for Detection of Surface Displacements over Twin Tunnels from Metro Line 1 in the Historical Area of Seville (Spain)

et al. 2022

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In order to solve connectivity problems in metropolitan areas, the development of underground metro lines constitutes an unquestionable requirement. However, the construction work thereof encounters unfavourable circumstances when surface excavations must be carried out that cross historical areas of the city, due to the need to control surface movements. The design of the metro in the city of Seville (Spain) from 2004 to 2006 provides a representative example of this situation and triggered major upheavals that exerted repercussions on historical buildings. For these reasons, the excavation stages of Line 1 of this metro have been simulated by numerical methods using FLAC3D software and validated with the results provided by the real conditions. Consequently, various surface settlements have been evaluated by taking not only variates of the main parameters that characterise the soil of Seville, but also of the various load situations and excavation conditions. Notable results have been achieved through calibration of 54 variants of the same model corresponding to Line 1, and their comparison with the real results obtained in nine critical areas of the itinerary. The results obtained have made it possible to determine the effects of excavation on the subsoil of the city of Seville with great accuracy, since the percentage error of calculated vertical surface movements varies from 0.1% to 5.3%.

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“…The pile foundation is the most typical reinforced concrete structure in shield tunneling during the excavating process. The strongest grade of concrete is C40, the largest primary reinforcement diameter in the pile is 32 mm, the largest number of cutting piles is 137, the largest cutting pile diameter is 1500 mm, and the longest cutting pile diameter is 48 m. The pile group can essentially be removed during the operation through the transformation of the shield cutter and the reinforcement or underpinning of the pile foundation [12][13][14]. However, some problems still cannot be solved, such as excessive cutter wear or collapse, reinforced winding cutterhead, and building inclination [15][16][17][18].…”

Section: Introductionmentioning

confidence: 99%

Adaptability of a Reinforced Concrete Diaphragm Wall Cut by Disc Cutter

Chen

Peng

2022

Sustainability

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On the background of a subway project in Suzhou City of Jiangsu Province and targeting the engineering difficulty of disc cutters cutting reinforced concrete walls, this paper illustrates the adaptability of a reinforced concrete diaphragm wall cut by disc cutter through conducting related laboratory tests and numerical simulations. When cutting a reinforced concrete diaphragm wall, the cutter should use the low-penetration depth excavation pattern with the depth of the penetration kept within 10 mm/r. In order to keep the torque in a small floating range, the cutterhead driving speed and thrust should be strictly controlled during the cutting period. Three types of fracture surface after the cutting operation, namely, single-side rolling destroy, double-sided rolling destroy, and brittle destroy. The percentage of the length of the cut steel bar smaller than 60 cm can reach 44.2% when the driving parameters of the disc cutter are well regulated. The simulation results show that the deeper the penetration, the more unstable the cutting load. The relationship between the normal force of the disc cutter and the penetration depth was linear, and the trend of the simulated value was comparable with the experimental one, which ensures the rationality of this pattern. The cutter spacing had little impact on the cutting results when it was wider than 80 mm.

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A DEM-based study of the disturbance in dry sandy ground caused by EPB shield tunneling

Cited by 49 publications

References 27 publications

Role of Particle Shape on Ground Responses to a Circular Tunnel Excavation in Sandy Soil: Consequences from DEM Simulations

Role of Particle Shape on Ground Responses to a Circular Tunnel Excavation in Sandy Soil: Consequences from DEM Simulations

Numerical Model Validation for Detection of Surface Displacements over Twin Tunnels from Metro Line 1 in the Historical Area of Seville (Spain)

Adaptability of a Reinforced Concrete Diaphragm Wall Cut by Disc Cutter

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