Impact Analysis for Safety Prevention and Control of Special-Shaped Shield Construction Closely Crossing Multiple Operational Metro Tunnels in Shallow Overburden

Abstract

With the improvement of the urban rail transit network, crossing construction has become an inevitable situation in the construction of subway tunnels. The special-shaped shield has great advantages in space utilization and the ability to cross narrow roads. However, due to its section characteristics, the special-shaped shield under construction often has a greater impact on the existing operating subway. Based on the background of quasi-rectangular shield tunneling through multiple existing tunnels, this paper proposes a two-stage safety pre-control (prevention before construction and control during construction) treatment method for large crosssection special-shaped shield construction. With three protection or auxiliary measures, the pre-reinforcement and process treatment of the crossing construction section are carried out. The effectiveness of these three measures is evaluated by establishing a 3D finite element model. Moreover, the reasonable range of construction parameters of the quasi-rectangular shield is optimized by numerical calculation. This study exposes the strata displacement law and tunnel deformation characteristics under corresponding protection or auxiliary measures and optimized construction parameters. The analysis proves that the proposed two-stage method can effectively reduce the impact of shield tunneling on the surrounding environment and existing tunnels. After applying the corresponding safety precautions, the surface uplift and tunnel uplift are reduced by about 30% on average, and the surface settlement is reduced by about 80%. Parameter optimization analysis shows that the thrust (face) pressure and grouting volume (filling rate) are more sensitive to environmental impact. It is recommended to select 100-160 kPa thrust pressure, 200% grouting filling rate, moderate grouting pressure, and slow propulsion speed in construction.

Construction and Quality Control of Subway Wet Loess in Concealed Tunnel Based on Particle Swarm Optimization Algorithm

“…In research methods and materials from the quality control process, foreign scholars have established some relatively sound theoretical systems. The whole process quality control is equally divided into five aspects: planning, experiment, construction, inspection, and overall error correction, focusing on the management function of people [8]. John Christian puts forward the concept of quality control and quality control measures, according to the requirements of users and project quality requirements, the implementation of project quality control in each stage, the implementation of project tasks in stages, the control of construction, and quality, construction, technology, and quality system improvement.…”

Analysis of the Impact of Shield Tunneling Under Existing Subway Station

“…Liu and Lu (2017) highlighted the fire safety design features of subway tunnels [9]. Further contributions include research on the mutual influence between long-span highway tunnels and urban rail transit tunnels [10], the analysis of special-shaped shield construction closely crossing multiple operational metro tunnels [11], and the study of construction technology using the freezing method for connecting passages in subways [12]. provided insights into the maximum settlement and convergence values during construction, ensuring they meet control requirements [13].…”

AHP‐FSE‐Based Risk Assessment and Mitigation for Slurry Balancing Shield Tunnel Construction

“…Research on risk control of slurry shield construction is still in its infancy. Most of existing researches are oriented to key technologies, such as ground settlement control [ 6 – 9 ], numerical simulation of tunnel excavation process [ 10 , 11 ], influence of shield tunneling that go through existing structures [ 12 – 16 ], and with less research on safety risk control [ 17 – 20 ]. In fact, it is of great significance to improve the safety of slurry shield construction to clarify the composition of safety risks and carry out safety management from the beginning of whole life cycle of project.…”