Abstract:It is an effective approach to use Steel Tube Slab (STS) structure combined with the Pile-Beam-Arch (PBA) method to construct a large-space underground station. Traditional construction methods cannot meet the requirement of construction because of the complicated soil layers and high building densities in urban areas. The STS method can effectively increase the rigidity of the supporting system by using steel tubes. Firstly, the stress of bolts and steel tubes are investigated in the construction process base… Show more
“…However, for the numerical simulation software, c = 0 may cause some options to hardly perform, even the calculation of non-convergence. Therefore, the cohesions of sandy soils are generally assumed to be 1 kPa in the numerical analysis [37][38][39]. The segment is deemed to have a liner-elastic behavior, and the main mechanical parameters of the structure are shown in Table 5.…”
Double-O-tube shield tunneling has attracted increasing attention because it offers cost-efficiency in underground construction. Prediction of ground surface settlement and the variety of additional stresses induced by shield construction is crucial to underground construction in metropolises since excessive settlement could trigger potential damage to the surrounding environment. The additional stresses induced by the propulsion of double-O-tube shields are calculated by means of the Mindlin’s equations of elasticity. The characteristics of additional stresses are analyzed with compound Gauss-Legendre integral arithmetic, and the frontal additional thrust, the lateral friction, and the ground loss are taken into account. Subsequently, based on field measurements, the maximum settlement coefficient and width of the settlement trough coefficient of the typical Peck formula are modified. The predictive curve of the Peck formula is closer to the engineering measured data than that of the typical formula. The cut-off functions of ground surface settlement caused by double-O-tube tunnel shield construction are proposed and can predict the shape of ground surface settlement, such as single peak or double peak. The correctness of the proposed functions is verified based on an engineering project.
“…However, for the numerical simulation software, c = 0 may cause some options to hardly perform, even the calculation of non-convergence. Therefore, the cohesions of sandy soils are generally assumed to be 1 kPa in the numerical analysis [37][38][39]. The segment is deemed to have a liner-elastic behavior, and the main mechanical parameters of the structure are shown in Table 5.…”
Double-O-tube shield tunneling has attracted increasing attention because it offers cost-efficiency in underground construction. Prediction of ground surface settlement and the variety of additional stresses induced by shield construction is crucial to underground construction in metropolises since excessive settlement could trigger potential damage to the surrounding environment. The additional stresses induced by the propulsion of double-O-tube shields are calculated by means of the Mindlin’s equations of elasticity. The characteristics of additional stresses are analyzed with compound Gauss-Legendre integral arithmetic, and the frontal additional thrust, the lateral friction, and the ground loss are taken into account. Subsequently, based on field measurements, the maximum settlement coefficient and width of the settlement trough coefficient of the typical Peck formula are modified. The predictive curve of the Peck formula is closer to the engineering measured data than that of the typical formula. The cut-off functions of ground surface settlement caused by double-O-tube tunnel shield construction are proposed and can predict the shape of ground surface settlement, such as single peak or double peak. The correctness of the proposed functions is verified based on an engineering project.
“…Accordingly, the field can be classified into five layers based on the mechanical properties and formation lithology, as shown in table 8. And the soil profile was shown in figure 17 [6]. Figure 17.Geological profile of the soil.…”
Section: Description Of Engineering Project In Chinamentioning
confidence: 99%
“…A full three-dimensional model of the station construction was established using FLAC 3D software (FLAC 3D 5.0). The dimensions of the numerical model were 120 × 39 × 50 m to eliminate the boundary conditions [6], as shown in figure 20. The bottom of the model was fixed in X -, Y- and Z -directions.…”
Section: Numerical Modelling Of Engineering Applicationmentioning
This study presents a novel construction pre-supporting system for large underground space excavation with shallow depth, Steel Tube Slab system (STS), in which adjacent steel pipes are connected by a couple of flanges, bolts and concrete for flexural capacity and lateral stiffness of the whole structure. The STS method is employed for the first time for the construction of the ultra-shallow buried and large span subway station in China, during which ground settlement and structural deformation are monitored. A numerical model for the subway station is established with reliability verified by monitored data comparison from numerical results and investigation on the effect of large span underground excavation on surrounding soil surrounding soil and existing buildings in soft soils. Unlike traditional methods, the STS method can effectively control and reduce the ground settlement during construction, thereby rendering it ideally suited for application in soft soils.
“…Wu et al [11] proposed a new supporting method of shallow buried super-span tunnel based on small tunnel sheds. Jia et al [12] demonstrated that using a steel-tube-slab structure combined with the pile-beam-arch method is an effective approach when constructing a super-span underground station. Some scholars also focused on the selection of the excavation methods.…”
A super-span tunnel that has the characteristics of a large excavation area, a small high-span ratio and a significant spatial effect exhibits a complex mechanical response during the excavation process. In this paper, taking the Badaling Great Wall station in Beijing, China as the engineering background, a case study of field monitoring a super-span tunnel has been presented. A typical monitoring section was selected in the super-span transition section of the tunnel and the deformation and forces of both the surrounding rock and the support structures were systematically monitored. The dynamic evolution and the spatial distribution characteristics of the monitoring data, including the internal displacement of the surrounding rock, the tunnel displacement, the contact pressure between the surrounding rock and the primary supports, the contact pressure between the primary and secondary supports, the axial forces in the bolts and cables, the internal forces in both the steel arches and the secondary supports and the internal stresses of the surrounding rock, were analyzed. The results of the monitoring and the analyses have shown that the deformation and the forces acting on both the surrounding rock and the tunnel’s lining are directly related to the construction procedures, the geological conditions and the locations in the super-span tunnel. According to the results, a few suggestions to improve the construction of the tunnel have been proposed.
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