Sensitivity of the Residual Stress Field to Variation of the Strengths for a Weak Layer Overlaying a Strong Working Point Layer.

摘要

A parameter study using the two-dimensional TENSOR code examines the sensitivity of the residual stress field around the cavity created by an underground nuclear explosion when the shear strengths were varied for: a strong layer containing the WP and a weaker overlaying layer. The baseline calculation used materials similar to those encountered in Area 20 of the Nevada Test Site (NTS). To provide a quantitative basis for comparing the effect of the calculated residual stress fields, a product factor is introduced that combines the magnitude and thickness of the residual stress field relative to cavity size and pressure. This product factor is useful in parameter studies for comparing levels of residual stress field, and is a supplement to other judgment factors which are considered in calculational site evaluations for containment purpose. Calculational results indicate generally stronger hoop stress along the horizontal than the vertical direction. This reflects the fact the weaker material above the cavity tends to degrade hoop stress in that direction. The magnitude of the hoop stress above the cavity generally increases as the strength of the upper material increases from 2 to 20 MPa. However, the magnitude of the hoop stress decreases, when the strength of working point material increases from 17 to 68 MPa. This is due to the smaller cavity radius and higher resulting cavity pressure in combination with a characteristic lower residual stress in the weak upper material. 22 refs., 9 figs., 2 tabs.