Dear Mark,
Residual stress is a real phenomenon, poorly understood in Earth Science but perhaps better understood by material scientists/engineers. It is the stress approaching equilibrium in the interior of a rock or mineral, when neither normal or shear stresses are being transmitted through its surface. Crystal-plastic deformation or phase transitions are potentially responsible for the development of residual stresses in earth materials.
It can be measured directly using synchrotron x-ray radiation. It is possibly amenable to neutron diffraction analysis as well. If you achieve some reasonable results in your research it will be a very interesting result and potentially quite high impact.
For a recent study I recommend;
Chen et al., GEOLOGY, March 2015; v. 43; no. 3; p. 219–222
Also the excellent text book;
Zang & Stephansson, Stress Field of the Earth's Crust, Springer.
I'm actively working on this and am open to discussing collaborations in the field.
Regards,