High-pressure mechanical properties of Kayenta sandstone
Pressure-volume, uniaxial strain loading, uniaxial stress loading to failure, and ultrasoric velocity detemninations have been performed on samples of Kayenta sandstone from the site of the Mixed Company event. Hydrostatic pressure of 3 GPa produces about 23% volume compression, with 9% permanent compaction remaining upon unloading. The pressure-volume data indicate that crush-up of porosity begins between 200 and 300 MPa. In uniaxial strain loading, the sandstone loads directly to the vicinity of the failure envelope, then parallels that envelope to the highest confining pressure (480 MPa). At strain rates of about 10/sup -4//s, the loading path in uniaxial strain up to 200 MPa is coincident in pressure-volume space with the shock-loading path (at a strain rate of about 10/sup 5//s) observed on samples from the same block. The permanent compaction, after unloading under conditions of uniaxial strain from 625 MPa mean pressure, is about 3.8%. Uniaxial stress loading indicates a brittle-ductile transition between 400 and 500 MPa mean pressure. Between 100 and 500 MPa mean pressure, the slope of the failure envelope is decreased consideably with respect to that below 100 MPa and between 500 and 900 MPa. This plateau, which is not present in the failure envelope for material subjected to a 700-MPa confining pressure before the uniaxial stress test, is interpreted as being due to pore crush-up during hydrostatic loading. As confining pressure is increased from 0.1 MPa to 1 GPa, the measured compressional velocity increases from 3.0 km/s to 5.0 km/s and the shear velocity increases from 1.5 km/s to 2.4 km/s. Small decreases in compressional velocity ( approximates 5%1 between 10 and 40 MPa are attributed to local brittle failure resulting from highly localized stress concentrations within the sample under hydrostatic loading. (auth)
- Research Organization:
- California Univ., Livermore (USA). Lawrence Livermore Lab.
- DOE Contract Number:
- W-7405-ENG-48
- NSA Number:
- NSA-29-029404
- OSTI ID:
- 4327076
- Report Number(s):
- UCRL--51526
- Country of Publication:
- United States
- Language:
- English
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