Process Of Thermal Spalling Behavior In Rocks An Exploratory Study

Abstract

Thermal spalling or spallation of rocks is defined as progressive failure caused by thermal stresses induced by a sudden application of heat from a high-temperature heat source. A theoretical explanation of the failure process is attempted on the basis of simplified engineering (phenomenological) assumptions and temperature-dependent properties. The implications of the theoretical analysis are then compared with the results of experimental measurements of thermal gradients produced during spalling and of related rock characteristics. The process of failure by thermal spalling in predominantly quartz- containing rock (Sioux Quartzite) takes place at temperatures considerably below the high-low inversion of quartz. In good spalling rocks, a thin heat layer with high thermal gradient forms during spalling. Spalling behavior in a rock appears to depend on the thermal expansion and shear-strain characteristics of the rock. Inelastic behavior of the rock inhibits failure by thermal spalling. (32 refs.)