Thermal/Mechanical Properties of Pomona Member Basalt: Full-Scale Heater Test No. 2 (Area 2)

摘要

Over 130 specimens from 21 Area 2 (Full-Scale Heater Test No. 2) boreholes were prepared. All samples were from the entablature of the Pomona flow. Pomona basalt from the entablature is hard, dark gray, and closely jointed (0.5 to 1.0 ft columns). It has a moderate porphyritic texture and is primarily composed of plagioclase and augite in a glass groundmass. Most joints and vesicles are lined with chlorophaeite or similar mineraloids. In this study, specimens which contained visible throughgoing fractures are termed jointed; specimens which contained many randomly oriented, hairline cracks were termed multifractured. Specimens with no visible cracks were termed intact or unjointed. Fourteen different thermal and mechanical tests were performed on the various specimens. In general, the thermal and mechanical properties of Area 2 specimens are consistent with the Area 1 results. However, the thermal conductivities for four test specimens were considerably less than the Area 1 thermal conductivity. This may be due to the presence of fractures in these four specimens. The apparent porosity of Area 2 specimens was also less than that of Area 1 specimens. This result can be attributed to the fact that the area to volume ratio was less for the Area 2 specimens than for the Area 1 specimens. Thermal expansion versus temperature data for Area 2 indicated that microcracks may be produced if specimens are heated above 150 exp 0 C. This result is supported by the observation that the compressive strength of heated specimens is less than the strength of unheated specimens. We recommend that additional work be undertaken to more thoroughly investigate the effects of heating on microcracking. (ERA citation 06:015372)