Abstract
Concrete structures after construction and commissioning exhibit various diseases with diverse characteristics and varying degrees of severity during their service life. Some of these disease problems are special, emergency, and particularly challenging to address. For instance, when large-area air cavities exist in the upper semicircle of a mined tunnel, under the action of train operation vibration loads or external water pressure, the surface concrete of the structure cracks and spalls, forming voids and cavities. Stabilizing the cracked concrete on cavity surfaces, repairing void and cavity diseases, while ensuring normal and safe train operation, presents significant difficulty and urgency. An emergency shroud was employed to stabilize the fractured concrete surfaces, combined with EAA high-permeability hydrophilic epoxy material and a cement grout—EAA high-permeability hydrophilic epoxy material composite grouting process, to perform penetration—filling—solidification—strengthening repair treatment on voids and cavities. For poor strata such as dynamic water-bearing mucky silt, silty fine sand, medium sand layers, and silty soil, operating tunnels experience differential settlement diseases due to sand loss. Based on the characteristics of such strata, a stable single-slurry cement—water glass material was adopted to overcome the problem of cement grout segregation and loss under dynamic water conditions. The grout exhibits good self-stability, drains, fills, and consolidates soil in poor strata, stabilizes the tunnel base, and controls settlement.
This paper enumerates relevant diseases in operational subway concrete structures, and according to the special, emergency, and difficult problems encountered, correspondingly developed materials and construction technologies are employed to treat damaged subway concrete diseases, achieving certain timely effectiveness in treatment.
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Problems and Treatment of Concrete Structure Defects in Operating Subway Systems
Qiu Xiaopei, Yang Yang
(Guangzhou Tailisi Consolidation Reinforcement Engineering Co., Ltd., Guangzhou 510030, China)
Abstract
After construction and commissioning, concrete structures in operating subway systems inevitably develop various defects during their service life, exhibiting diverse characteristics and varying degrees of severity. Certain defects present exceptional challenges requiring emergency responses and difficult remediation, particularly when they must be addressed without disrupting continuous safe operation. For example, large air voids in the upper crown of mined tunnels can cause surface concrete cracking and spalling under train-induced vibration loads or external water pressure, creating hazardous cavities. Stabilizing cracked concrete at cavity surfaces while repairing these voids and ensuring uninterrupted safe train operation demands highly specialized emergency solutions. This study addresses such issues through an emergency protective covering to stabilize fractured concrete surfaces, combined with composite grouting using EAA high-permeability hydrophilic epoxy material and cement-EAA mixtures. This approach achieves penetration, filling, consolidation, and reinforcement of voids and cavities. Additionally, for poor ground conditions—including silt, silty fine sand, medium sand layers, and silty soil under flowing water—differential settlement caused by soil loss presents another critical challenge. To remedy this, a stable single-slurry cement-sodium silicate material was employed, which overcomes cement slurry segregation and loss under flowing water conditions through its self-stabilizing properties. This grout effectively drains, fills, and consolidates the soil mass to stabilize the tunnel foundation and control settlement.
This paper enumerates typical defects in operating subway concrete structures and presents corresponding specially-developed materials and construction technologies tailored to address these special, urgent, and challenging problems. The implemented remediation measures have demonstrated effective and timely results in treating deteriorated subway concrete structures.
Keywords
Operation; Rail Transit; Concrete Structure; Defects; Treatment Measures