FIELD LOAD TEST OF COLLAPSIBLE CANVAS LINER FOR SHALLOW TUNNELS,
ARMY ENGINEER RESEARCH AND DEVELOPMENT LABS FORT BELVOIR VA
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The load test described in this report was designed to furnish data concerning the ultimate crushing strength of a collapsible, reinforced, canvas liner for shallow tunnels in loose, unconsolidated earth. A field load test using the sandbox method of loading was conducted. Vertical and horizontal field deflection measurements and laboratory tests of individual components were made. The report concludes a Based on the criterion for linear failure, a conservative estimate of the load-carrying capacity of the liner is 4,713 pounds per lineal foot or a fill height of 12 feet of sand fill. The ultimate crushing strength was never ascertained. b The bedding condition significantly affects settlement and, therefore, affects the supporting strength of the liner. c The imperfect trench method of installation would materially increase the liners load-carrying capacity. d It is desirable to have the liner fabric yarn with the least ultimate elongation oriented parallel to the longitudinal axis of the liner. Lack of knowledge of textile properties resulted in greater deformation of the canvas covering than anticipated. e Of the two types of ring joints tested, the steel insert and the pipe coupling, the latter appears to be the better. f Method of welding of the pipe coupling appears critical and should be given proper consideration. g The hollow pipe rings seem to have only a minimal advantage over the solid rod rings, but on the basis of military logistics a greater weight reduction can be achieved by the use of the pipe rings.
- Structural Engineering and Building Technology