EAAI Journal 2026 Journal Article
Few-shot semantic segmentation for clearance intrusion risk detection in metro tunnel point clouds
- Wenbo Qin
- Yuxiang Wang
- Shangbin Gao
- Cheng Zhou
A wide range of mechanical, electrical, and plumbing (MEP) components are mounted along metro tunnel linings, where subtle spatial displacements caused by loosening or deformation may intrude into the train clearance envelope. Detecting such early-stage deviations is challenging due to occlusion, low illumination, and the dense arrangement of facilities in tunnel point clouds acquired using simultaneous localization and mapping (SLAM). To address this problem, this study proposes a training-free few-shot semantic segmentation framework for clearance intrusion detection. The model integrates geometry-based descriptors (linearity, planarity, verticality), a scale factor control mechanism for multi-scale feature enhancement, and a confidence-based filtering strategy to suppress uncertain predictions. Experiments were conducted on metro tunnel point clouds acquired using a backpack-mounted light detection and ranging (LiDAR) SLAM system, with segmentation performed using 1 m under a single-class few-shot setting. The proposed method achieves a mean intersection over union (mIoU) of 78. 4 %, while requiring only a small support set of 15 blocks, and the reconstructed axes of MEP facilities enable deviation detection below 1 cm relative to reference inspection epochs. These results demonstrate that the proposed framework provides a practical and robust solution for early-stage clearance intrusion risk assessment in metro tunnel environments.