ABSTRACT
This paper presents laboratory experiments on clay seams in-between layers of salt, and simulations of WIPP disposal rooms that include clay seams. The experiments involved two series of direct shear tests. The first test series was performed on representative core samples from a potash mine near the WIPP. These natural geologic contacts had intergrown halite crystals, and their residual shear strengths were like that of intact salt. The second test series involved artificial clay seams prepared by mixing brine with bentonite, placing the clay between two cylindrical salt specimens with grooved contact surfaces, and hydrostatically consolidating the assembled specimen. The artificial clay seam residual shear behavior was similar to that of a saturated, highly consolidated, clay. Thus, these weak and strong residual strengths likely bound the actual shear behavior of clays seams in bedded salt. The bounds were then used in simulations that probe the sensitivity of WIPP disposal room porosity to clay seam shear behavior. Weaker clay seams accelerated the decrease of room porosity within the first 300 years but had minimal impact on final room porosity.
