Foundation Modulus Tests for Karadj Arch Dam

Thirty-one in situ tests were conducted in six chambers along both abutments of Karadj arch dam. The testing program, its scope and purpose, and field operations is described. Analysis of results based on the theory of elasticity resulted in an average effective modulus of 2,330,000 psi, with a range from 2,050,000 psi to 2,610, 000 psi. The modulus did not appear to change with elevation. Effects of minor and major jointing and rock alteration were evaluated. Separate tests were conducted to determine the effect of lenses of altered rock and of joints filled with highly compressible material. Analytical methods are developed to account for these effects on prototype scale. A 4-meter-thick lens would reduce the modulus from 2,330,000 psi to 1,950, 000 psi. The effect of jointing and rock alteration appeared in the considerable differences with the average laboratory result of 5,050,000 psi. No consistent relationship was found between in situ and laboratory results. An analytical method is presented to explain the low value of the in situ modulus.