Abstract
Monitoring of subgrade settlement in railway and highway helps to maintain traffic safety and reduce infrastructure losses. When an excess subgrade settlement is detected, maintenances of the unqualified subgrade will be processed in time, and early warning of constructions will be processed to prevent the occurrence of safety accident. In this article, a noncontact, real-time, and unattended system based on optical method is introduced to monitor the subgrade settlement remotely. Several high-power infrared LED targets are mounted on the subgrade and they will move as the subgrade subsides. The movements of the LED targets are detected by an optical detection device based on the principle of optical imaging. The displacement data is remotely transmitted to a server for analysis via GPRS. The remote monitoring system has been applied to the monitoring of subgrade settlement of Zhensheng highway in Guizhou province of China in 2014. This technology helped to detect the subgrade settlement that was caused by the construction of Beiyinpo railway tunnel. Four test points on road surface were monitored at a sampling rate every 20 minutes. The effectiveness of the system has been verified by the practical application.
Highlights
As an important part of railway and highway, subgrade plays a key role in traffic safety, efficiency and comfort
When an excess subgrade settlement is detected, maintenances of the unqualified subgrade will be processed in time, and early warning of constructions will be processed to prevent the occurrence of safety accident
Several high-power infrared LED targets are mounted on the subgrade and they will move as the subgrade subsides
Summary
As an important part of railway and highway, subgrade plays a key role in traffic safety, efficiency and comfort. Automatic monitoring of subgrade settlement can be realized by using multiple highly sensitive pressure sensors to detect the differential of fluid pressure in different places [11, 12] or using an inclinometer to sense the incline caused by the subgrade settlement [13]. Optical fiber sensors, such as fiber Bragg grating, are competitive candidates for remote monitoring of the subgrade settlement, but they are susceptible to ambient interference, especially temperature fluctuation [14, 15]. The successful application of the system in the real-time remote monitoring of settlement in subgrade adjacent to the Beiyinpo tunnel in Guizhou province of China verifies the effectiveness of the system
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