Cyclic shear device for interfaces and joints with pore water pressure

Abstract

An improved multi degree-of-freedom direct shear device has been designed and constructed to test interfaces and joints under pore water pressure. Any two structural (concrete, steel, wood) or geologic (soil, rock) materials may be tested in the device as long as the top specimen is solid. The apparatus is designed to hold a 7.5-inch diameter 3-inch thick upper sample and a 9-inch diameter 3-inch thick lower sample. A normal stress of 400 psi (2.7 MPa) and a shear stress of 550 psi (3.9 MPa) can be developed at the interface. Test loading may be static, quasi-static, or cyclic, and constant or variable stiffness loading is available. A stiff reaction frame was designed to house the device and is described. The electro-hydraulic system is capable of supporting cyclic testing at 30 Hz. A new computer-controlled data acquisition and control system is also described.