# Analysis of Shield Tunnels Undercrossing an Existing Building and Tunnel Reinforcement Measures
###### Abstract  
Research on tunnel excavation has rarely considered the effect of the tunnel excavation on a complete building. Therefore, this paper considered a building with a double basement and piles, and a three-dimensional finite-element model for shield tunnels undercrossing an existing building was established to study the effects of the excavation of double-shield tunnels on the displacement and internal forces of soil, segments, piles, and buildings. Grouting reinforcement technology was used in the model to analyze the effect of grouting reinforcement on pile displacement and building subsidence. The results showed that for every 100 kPa increase in grouting pressure, the maximum subsidence of the soil was reduced by 3.512 mm. The successive excavation of double-shield tunnels resulted in elliptical segments. The longitudinal and transverse stresses of the segments were effectively reduced by grouting pressure of 250 kPa. The excavation of tunnels had an obvious nonlinear effect on the maximum lateral displacement of the piles along the direction of excavation and the maximum subsidence of the building. When using deep-hole grouting reinforcement, the maximum lateral displacement of piles and the maximum subsidence of the building were effectively reduced by increasing the radial grouting reinforcement radius and adjusting the reinforcement range. double-shield tunnels; mathematical simulation; grouting pressure; ground surface subsidence; segment internal force; building; grouting reinforcement Article  
Analysis of Shield Tunnels Undercrossing an Existing Building and Tunnel Reinforcement Measures  
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rational selection of parameters for shield tunneling, [PERSON] et al. [16] proposed the EAIW-IPSO algorithm. [PERSON] and [PERSON] [17] summarized effect factors such as construction sequence, pillar width, and overburden depth on ground subsidence and internal force of tunnel lining by collecting a large quantity of field-measured data, experimental test data, and finite-element analysis data. [PERSON] et al. [18] developed a numerical model and concluded that shield tunnel construction with isolation pile reinforcement could abate the deformation of the tunnel lining and ground subsidence. [PERSON] et al. [19] developed a numerical model to study ground subsidence in straight and curved tunnels by shield- and pipe-jacking methods. [PERSON] et al. [20] proposed a new, simplified method of exploring the relationship between coupling resonance frequency and Young's modulus for tunnels. Using a 3D finite-difference simulation approach, [PERSON] et al. [21] evaluated the impact of shield performance factors on surface subsidence and lining reactions. [PERSON] et al. [22] proposed a deformation-analysis method for shield tunnels considering the tunnel-shear effect and tunnel depth and verified the effectiveness and feasibility of the method by using three-dimensional finite-element analysis and measured data. [PERSON] et al. [23] and [PERSON] et al. [24] used theoretical methods to study the impact of ground displacement caused by tunnel excavation on existing tunnels. [PERSON] et al. [25] developed suitability charts that can reasonably select stabilizers for improving the engineering performance of tunnels. As can be seen from the above, some scholars [8; 9; 10; 11] studied the impact of shield tunneling on soil subsidence, while others [16; 17; 25] studied the impact of shield parameters on surface subsidence. Other scholars [12; 23; 24] conducted studies on the impact of shield tunnel excavation on existing pits and tunnels. From the existing studies, most scholars have focused on the effects of shield tunnel excavation on soil, segments, existing pits, and tunnels. However, few have considered the effects of shield tunnel excavation on external buildings, especially the effect of tunnel excavation on complete buildings with basements and piles.