Radioactive waste disposal facilities for heat generating waste are designed to maintain a compressive stress regime in the host rock. Field-scale tests have been undertaken to study how heating of the host rock can reduce the effective stress on the rock. However, it is not possible to carry out experiments at the scale of a whole repository (km-scale), so variation of host rock properties that might be encountered at this scale is not captured by the experiments.

Previous numerical modelling of field scale experiments has demonstrated that the physical processes leading to changes in the stress regime are well understood. Here those models are applied at the km-scale, considering approaches to representing a whole repository and the effect of variability in the properties of the host rock. A dataset from the Callovo-Oxfordian Claystone at the Meuse/Heute-Marne Underground Rock Laboratory is used to characterise the natural variability of a potential host rock at the scale of a disposal facility.

The modelling demonstrates that for understanding the generation of thermal stresses, considerable learning can be gained from models that employ symmetry conditions and represent a small part of the repository, hence reducing the size of the computational problem. The host rock at the mid-point between waste cells remained in vertical compression for all the parameter combinations used, which builds confidence that horizontal fracturing of the host rock between waste cells due to thermal pressurisation is unlikely for the disposal concept discussed here. Ground surface uplift was also considered and is in the range of 9–13 cm for disposal system studied.

Spatial variability in the properties of the host rock has the potential to lead to significant variability in temperature, pressure, effective stress and displacement around the facility. In particular, thermal conductivity, permeability, Young’s modulus and coefficient of thermal expansion need to be well characterised.

用于产生热废物的放射性废物处置设施旨在维持基质岩石中的压应力状态。已经进行了现场规模的测试，以研究基质岩石的加热如何减少岩石上的有效应力。但是，不可能在整个储存库的规模（千米规模）下进行实验，因此实验无法捕获在该规模下可能遇到的基质岩石特性的变化。

以前的现场规模实验数值模型表明，导致应力状态变化的物理过程已广为人知。在这里，这些模型是在km规模上应用的，考虑到了表示整个储层的方法以及母岩性质变化的影响。Meuse / Heute-Marne地下岩石实验室的Callovo-Oxfordian粘土岩数据集用于表征处置设施规模内潜在宿主岩的自然变异性。

该建模表明，为了了解热应力的产生，可以从采用对称条件并代表存储库一小部分的模型中获得大量学习，从而减小了计算问题的规模。对于所使用的所有参数组合，废料间中点处的主石保持垂直压缩，这建立了信心，即对于此处讨论的处置概念，由于热加压而导致的废料间主石的水平压裂是不可能的。还考虑了地面隆起，对于处置系统研究范围为9-13 cm。

基质岩石特性的空间变异性有可能导致温度，压力，有效应力和设施周围位移的显着变异性。特别地，导热系数，渗透率，杨氏模量和热膨胀系数需要很好地表征。