A testing facility which includes provisions for access to a co-axial borehole in a cylindrical rock sample will provide the necessary means to study a number of engineering geomechanics problems that can not be investigated readily with presently available equipment. Examples include the stability of deep boreholes; the sealing performance of well cementing and plugging; the influence of size, shape, stress gradient and energy concentration effects on rock failure about underground openings (simulating deep shafts and tunnels in hard intact rock); influence of discontinuities and reinforcement on opening stability; ground-interaction modeling of tunnel support mechanics. Approximate ranges for desirable loading conditions (axial and laterial rock stress, fluid pressure and flow, temperature, geochemical environment) are suggested for some of these problems as well as requirements for in-hole instrumentation. A large scale laboratory testing facility will find immediate use for the study of many important rock engineering problems.