The phenomenon of roughness induced opening or slip opening is well known in rock mechanics and relates to a crack (or rock joint) behaviour under compression and shear. It has been widely utilised in tight gas and coal bed methane industries to increase the permeability of geological reservoirs during hydraulic stimulations and has recently been extended to geothermal energy technologies for successful harnessing the thermal energy from hot rocks. However, this phenomenon is still poorly understood; and only several semi-empirical equations are currently available in the literature to predict values of the slip openings. In this paper new mechanical and mathematical models of the roughness induced opening are suggested. A computational approach based on the distributed dislocation technique was implemented to analyse various coupled effects. The focus of this paper is on stress analysis of a straight crack with rough faces located in an infinite impermeable body. The crack is subjected to remote normal and shear loading and a uniform fluid pressure applied inside the crack. The developed model A. Kotousov · L. can further be extended to investigate many other interesting and practically important problems such as analysis of fracture initiation in natural faults subjected to fluid pressure, residual opening after releasing the fluid pressure or permeability changes associated with hydraulic stimulations.

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Tensile behavior of electrorheological fluids under direct current electric fields J. Appl. Phys. 94, 6939 (2003); 10.1063/1.1621051 Three-dimensional dynamics simulation of electrorheological fluids under large amplitude oscillatory shear flow SynopsisElectrorheological ͑ER͒ fluids made of starch particles in silicone fluid were studied under different electric field strength, particle concentration, water content, and shear rate. The ER fluids were sheared under constant shear rates during at least 210 min and the shear stress was measured. According to the results, the shear stress increased with time until a maximum was reached, decreased a little, and then stabilized. Some samples did not show a point of maximum, but after increasing with time, they stabilized at a given shear stress. The influence of the shear rate on the shear stress depended on the time the sample was sheared, on the electric field strength, on concentration, and on water content. The results were analyzed in terms of changes of lamellar formations in the direction of shear.