Thermally induced rock-mass

RESULTS AND DISCUSSIONS 3.1 Thermally induced rock-mass mechanical responses... 

Figure 3. Thermally induced rock-mass yielding.

After heating started, the rock mass began to deform in response to the thermally induced stresses. At some point of heating, a yield zone... 

Abstract As a part of the DECOVALEX 111 project—model predictions were carried out of thermomechanical (TM) rock-mass responses at the Yucca Mountain drift scale test (DST), Nevada. This paper presents model predictions of TM-induced rock displacements at the DST carried out by two independent research teams using two different approaches and two different numerical models. Displacements predicted by the two independent analyses compare reasonably well to the measured ones, both in trends and average magnitude. The analyses indicate that the rock mass behaviour is essentially elastic and that the in situ rock mass thermal expansion coefficient is well represented a temperature-dependent thermal-expansion derived from laboratory tests on intact rock. 

The most important parameter for the prediction of TM-induced displacement is the thermal expansion coefficient. Both LBNL and CEA used a temperature-dependent rock-mass thermal expansion coefficient derived from measurements on intact rock samples (Figure 2). Judging from a good general agreement in displacement average magnitude, the thermal expansion coefficient derived from core samples appears to be appropriate in this case. 

The thermal gradient induced by the heat generated from the wastes causes first a desaturation close to the heater, followed by a resaturation controlled by the rock mass permeability. For the base case, the predicted time necessary for a full re-saturation of the buffer, varies between 7 years (CEA) and 55 years (SKI) for the three dimensional models. The evolution of the degree of saturation at point B4 is plotted on Figure 4. 

We estimated from the maintenance results that the thermal loss in Gonjiam underground cold storage cavern is mostly induced from the groundwater flow and latent heat of freezing due to the poor quality of rock mass of surrounding storage cavern. 

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