Investigating the damage to masonry buildings during shield tunneling: A case study in Hohhot Metro

Abstract

After prolonged service, masonry buildings constructed in the 1970s and 1980s often experienced significant deterioration in strength and stiffness. Excessive ground deformation caused by shield tunneling frequently leads to cracking in adjacent masonry buildings. Most studies have focused on the settlement and tilting caused by shield tunneling on masonry structures, failing to reflect the specific damages caused by shield tunneling. This paper employs a jointed masonry model in numerical simulations to simulate masonry buildings, considering the actual measurement data from the Hohhot Metro Line 1 project. It discusses a thorough investigation into the potential damages and cracking on masonry buildings that may occur during shield tunneling in masonry structures. It provides a detailed study of the specific forms of cracking in masonry buildings. Then, a comprehensive and in-depth analysis is conducted on the impact of bricklaying methods, mortar adhesive strength, and synchronous grouting pressure on buildings in the context of shield tunneling through structures. The results show that using the jointed masonry model can effectively reflect the cracking and damage situation of masonry structures during shield tunneling construction, providing valuable guidance for actual shield tunneling operations. The area of cracking damage caused by shield tunneling construction gradually increases from the top to the bottom of the building. It is concentrated above the doors and windows of the structure. Potential cracks around door and window openings extend from the upper-middle part of the openings towards both sides, forming a regular figure-eight distribution. With changes in the masonry construction method, grouting pressure, and mortar bond strength, the settlement and damage levels of the building also undergo alterations. Specifically, as the mortar bond strength increases from 30 kPa to 50 kPa, the maximum tensile strain of the masonry construction decreases to 0.11 %. Simultaneously, when the construction method of the building bricks transitions from A to B, the damage at the door and window openings on the west wall of the building gradually intensifies, resulting in a rise in the maximum tensile strain to 0.109 %. Furthermore, as the grouting pressure increases from 50 kPa to 300 kPa, the maximum settlement of the building walls decreases by 51 %, and the maximum tilt reduces by 48 %. However, this study did not account for the lintels and sills in the masonry building, which may lead to an overestimation of simulated strain data.