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Mr. Max Ramey ,lone 17, 2003 page 9 for the case where the rock mass strength is reduced by 20% from the base case. The figure shows the depth of yield into the roof as a function of the number of pressure cycles. The figure also displays the stepwise decreasing temperah¢e at the top and center of the cavern during free temperature or "cool down" cycling. INTERPRETATION OF MODEL RESULTS Temperature Temperahire isotherm distributions are shown in Figure 7 for cavity temperatures of 350°F and 420°F. Isotherm plots are not provided for reduced pressure scenarios because thermal properties are independent of cavity pressure in the model. We have assumed that the cavity depressurization associated with the shape characterization study would be of short duration and, hence, the temperatures in the cavern would not change during the test. For the base model with a 350°F cavity temperature, the predicted 100°F isotherm ranges from 38 [0 88 ft from the cavity boundary. For [he elevated-temperature case with a cavern temperature of 420°F, the 100°F isotherm ranges from 40 to 90 ft from the cavity boundary A comparison of the depth of yield plots in Figures 9 and 10 reveals that depth of yield increases with increased temperature. Elevated temperatures induce thermal stresses and reduce rock mass strength properties causing an increased zone of yielding. Pressure Figures 11 and 12 are compilations of yield depths into the roof and wall at various cavern pressures and widths. Using these figures, [he predicted depth of yield into the roof and wall can be obtained for any given cavern pressure and diameter within modeled ranges. Figure 11 shows that reducing cavern pressure increases the depth of yield into the root. Cavity pressure provides resistance against inward collapse of the cavity roof and walls. A 200-ft-diameter cavity with a temperature of 350°F is expected to yield about 62 ft into the roof at 900 psi. The same cavity is expected to yield another 20 ft furdter into the roof at 100 psi. While this represents a 32% increase in yield depth, the average crown thiciatess of 251 ft would still have an uncompromised thickness of 188 and 168 ft for the respective cases. Even at a temperature of 420°F and aloes-end pressure of 100 psi, a predicted 89 ft depth of yielding into the roof would leave an intact crown pillar of 161 ft. Figure 12 shows that reducing cavern pressure also increases the depth of yield into the wall. A 200-ft-diameter cavity with a temperature of 350°F is expected to yield about 24 ft into the wall at 900 psi. The same cavity is expected to yield another l0 ft fw-ther into the wal! at 100 psi. A predicted 34 ft depth of yielding into the wall would occur at a temperature of 420°F and a pressure of 100 psi. Agapito Associates, Inc.