In-Situ Testing and Monitoring of Silty Soft Clay's Characteristics around a Subway Tunnel under Train Vibration

The uneven settlement of a subway tunnel will aggravate the tunnel defects which may threaten the safety operation of the metro and increase the maintenance cost greatly. A series of in-situ testing and monitoring works in the future two years are being conducted in the tunnel between Zuibaichi Station and Songjiangnan Station of the Shanghai No. 9 subway line. Monitoring systems are divided into two parts, the system which is for monitoring the mechanics of the tunnel structure and the system which is for measuring the characteristics of the silty soft clay during the train operation. The monitoring system for tunnel structure has been fixed on the tunnel structure, including lining, ballast and track vibration acceleration sensors. The dynamics characteristics data of the silty soft clay will be detected by some vibration acceleration sensors, displacement meters, and pore-water pressure meters which have been drilled on both sides of the tunnel. Through these measurements, the deformation characteristics and change regulation of silty soft clay under train vibration will be studied and can offer valuable information for the subway tunnel maintenance department. In this paper, the design of the monitoring solution will be discussed in detail and some typical measured data will be analyzed.