Vibrating Wire Strain Gages and Civil Structures

This paper discusses the use of vibrating wire strain gages with large civil structures. A two-hundred ft. section of tunnel liner has been instrumented with twenty-five vibrating wire strain gages. The section of liner will be monitored long term to develop a better understanding of the thermal stresses in the liner, and as part of ongoing health monitoring. The twin tunnel is bored in soft rock. The liner is a polypropylene fiber reinforced shotcrete, which, in the test section, is a minimum of 2 in. thick. The tunnel is a dedicated dual track light rail transit tunnel, and is 3.5 miles long. The test section is near an entrance portal, and temperature gradients exist between the rock subsurface and the shotcrete liner surface. The liner, the experimental program and the objectives of the study are discussed.