[TECHNICAL NOTES] Development of in-situ triaxial test for rock masses

A new field test method was proposed for the purpose of directly measuring average stress-strain relationships and to investigate strength and deformation characteristics of rock masses. The test is conducted on a hollow cylindrical specimen prepared at the bottom of a drill-hole. Average axial as well as lateral strains can be measured in a center hole and an outer slit by a novel technique of instrumentation for cavity deformation. A set of test equipment for this test method was developed and improved at Central Research Institute of Electric Power Industry, CRIEPI, in Japan. The purpose of this paper is the technical notes of application to some rock masses in different rock type. Trial series of tests were carried out at the site of rhyolitic tuffacious rock and rudaceous rock of Neogene system. The results, similar to conventional laboratory triaxial tests, proved that the proposed test method was successful in measuring average stress-strain relationships of large rock specimens