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Material Property Determinations for Alluvium in Support of Source Physics Experiment

Broome, Scott T.; Barrow, Perry C.; Jaramillo, Johnny L.

Two blocks of alluvium were extensively tested at the Sandia National Laboratories Geomechanics laboratory. The alluvium blocks are intended to serve as surrogate material for mechanical property determinations to support the SPE DAG experimental series. From constant mean stress triaxial testing, strength failure envelopes were parameterized and are presented for each block. Modulus and stress relationships are given including bulk modulus versus mean stress, shear modulus versus shear stress, Young's modulus versus axial stress and Poisson's ratio versus axial stress. In addition, P-&S-wave velocities, and porosity, determined using helium porosimetry, were obtained on each block. Generally, both Young's modulus and Poisson's ratio increase with increasing axial stress, bulk modulus increases with increasing pressure, and increases more dramatically upon pore crush, shear modulus decreases with increasing shear stress and then appears to plateau. The Unconfined Compressive Strength for the BM is in the range of 0.5-0.6, and for SM in the range of 2.0-2.6 MPa. The confined compressive strength increases with increasing confining pressure, and the BM alluvium is significantly weaker compared to SM alluvium for mean stress levels above 8 MPa. ACKNOWLEDGEMENTS The authors would like to thank Steve Bauer and Moo Lee for their critical reviews of the report. The authors acknowledge the support of the National Nuclear Security Administration Office of Defense Nuclear Nonproliferation Research and Development for funding this work. This paper describes objective technical results and analysis. Any subjective views or opinions that might be expressed in the paper do not necessarily represent the views of the U.S. Department of Energy or the United States Government.