ABSTRACT
This paper presents an overview of the geomechanical studies conducted at the Large Block Test at Fran Ridge, near Yucca Mountain, Nevada, and results of geomechanical observations made during the first 10 months of heating. This test is being conducted on a block of rock that is 3m × 3m in cross-section and 4.5m high. Heaters have been placed in the rock to simulate a plane heat source, 1.75m above the base of the block. The 3-dimensional geomechanical response of the rock to the heating is being monitored using instrumentation mounted in boreholes and on the surface. Results show that thermal expansion of the block began a few hours after the start of heating. Moreover, expansion in the horizontal direction is consistent with opening of vertical fractures. Opening and sliding of fractures has been correlated with anomalous temperature behavior, indicating that fracture deformation influences the hydrothermal behavior.
