Cost and feasibility evaluation for the excavation of large hemispherical cavities in Rainier Mesa. Topical report, January-October, 1978

In order to provide necessary facilities for the fielding of experiments in support of the underground nuclear testing program, there has been an increase in interest concerning the construction of large underground caverns in Rainier Mesa. As a result, a cost and feasibility program was commissioned to evaluate hemispherical cavities between 24.4 and 91.4 m (80 and 300 ft) in diameter. The rock support designs for the cavities are based upon the use of internally installed rockbolts for the smaller cavities and tendons installed from annular galleries for the larger chamber. The evaluation program included research into past experience pertaining to the excavation and support of large underground caverns, assessment of the geological conditions which exist in Rainier Mesa, preliminary design of the cavities and their rock support system based upon the geological setting, development of mining plans for the excavation of the caverns, and estimation of the cost and manpower schedule to complete the construction of each size chamber based upon the preliminary design and mining approach. This report presents the findings of the cost and feasibility evaluation program and includes recommendations concerning the maximum practical chamber size considering schedule, dollar, and state-of-the-art constraints.