Investigation of Instruments for Measuring Pore Pressures in Concrete. Literature Review and Preliminary. Laboratory Tests.

摘要

It is customary to design a gravity dam so that the resultant of all forces acting on it will fall within the middle one-third of the dam. Accurate and economical design, therefore, calls for advance information on the magnitude of the pore pressures that will act in the concrete and in the foundation, and from which the uplift force is to be computed. From a review of the literature relating to: (a) failures of structures, (b) the need for pore-pressure measurements, and (c) experimental techniques, it was concluded that pore-pressure theory alone is not sufficient to assure accurate and economical design; that field measurements should be made, if possible, using several types of instruments that have been found satisfactory for measuring pore pressures; and that laboratory work should be done to improve both techniques and instruments. To develop information on equipment and techniques for measuring pore pressures in concrete, four types of pressure-measuring instruments were installed in small concrete cylinders and tested at various ages of the concrete under a hydrostatic head of 200 psi. In the tests, all four instruments gave comparable readings. The tests disclosed certain precautions that should be used in installing the meters to ensure accurate readings. On the basis of these tests, three of the instruments (WES pressure cell, Carlson pressure cell, and piezometer tip) were selected for installation in Hartwell Dam, Savannah River, where results will be observed for several years. (Author)