Geomechanical observations during the large block test

This paper presents an overview of the geomechanical studies conducted at the Large Block Test at Fran Ridge, near Yucca Mountain, Nevada. The 3-dimensional geomechanical response of the rock to heating is being monitored using instrumentation mounted in boreholes and on the surface of the block. Results show that thermal expansion of the block began a few hours after the start if heating, and is closely correlated with the thermal history. Horizontal expansion increases as a linear function of height. Comparison of observed deformations with continuum simulations shows that below the heater plane deformation is smaller the predicted, while above the heater plane, observed deformation is larger than predicted, and is consistent with opening of vertical fractures. Fracture monitors indicate that movement on a large horizontal fracture is associated with hydrothermal behavior