Many rock types have naturally occurring inherent anisotropic planes, such as bedding planes, foliation, or flow structures. Such characteristic induces directional features and anisotropy in rocks' strength and deformational properties. The Hoek–Brown (H–B) failure criterion is an empirical strength criterion widely applied to rock mechanics and engineering. A direct modification to H–B failure criterion to account for rock anisotropy is considered as the base of the research. Such modification introduced a new definition of the anisotropy as direct parameter named the anisotropic parameter (Kβ). However, the computation of this parameter takes much experimental work and cannot be calculated in a simple way. The aim of this paper is to study the trend of the relation between the degree of anisotropy (Rc) and the minimum value of anisotropic parameter (Kmin), and to predict the Kmin directly from the uniaxial compression tests instead of triaxial tests, and also to decrease the amount of experimental work

The awareness of the impact of high temperatures on rock properties is essential to the design of deep geotechnical applications. The purpose of this research is to assess the influence of heating and cooling treatments on the physical and mechanical properties of Egyptian granodiorite as a degrading factor. The samples were heated to various temperatures (200, 400, 600, and 800 °C) and then cooled at different rates, either slowly cooled in the oven and air or quickly cooled in water. The porosity, water absorption, P-wave velocity, tensile strength, failure mode, and associated microstructural alterations due to thermal effect have been studied. The study revealed that the granodiorite has a slight drop in tensile strength, up to 400 °C, for slow cooling routes and that most of the physical attributes are comparable to natural rock. Despite this, granodiorite thermal deterioration is substantially higher for quick cooling than for slow cooling. Between 400:600 °C is ‘the transitional stage’, where the physical and mechanical characteristics degraded exponentially for all cooling pathways. Independent of the cooling method, the granodiorite showed a ductile failure mode associated with reduced peak tensile strengths. Additionally, the microstructure altered from predominantly intergranular cracking to more trans-granular cracking at 600 °C. The integrity of the granodiorite structure was compromised at 800 °C, the physical parameters deteriorated, and the rock tensile strength was negligible. In this research, the temperatures of 400, 600, and 800 °C were remarked to be typical of three divergent phases of granodiorite mechanical and physical properties evolution. Furthermore, 400 °C could be considered as the threshold limit for Egyptian granodiorite physical and mechanical properties for typical thermal underground applications.

The current research discusses the validity of utilizing Electrical Resistivity Tomography (ERT) and Ground Penetrating Radar (GPR) for the geo-hazard assessment and the detection of the subsurface voids associated with mining activities. The presence of subsurface voids poses a significant safety challenge to any operating mine due to the associated geotechnical risks and the severe consequences for human life, the environment, and mine infrastructure if left unaddressed. Traditional subsurface investigation tools in mines are borehole and probe drilling, which are costly, time-consuming, and unable to provide a comprehensive image of subsurface structures. In contrast, geophysical techniques have demonstrated through decades of research their exceptional ability to obtain a complete subsurface image, surpassing other invasive methods. In this case study, a geophysical survey was conducted at the actively operating Sukari gold mine (SGM) in Egypt utilizing a combination of GPR and ERT to detect unknown subsurface voids. Based on the joint interpretation of both techniques, risk zones were identified and delineated. Moreover, the obtained results were validated through numerical simulations and existing borehole data. This study demonstrates the efficiency of integrating geophysical techniques with geological and mining information in active mines to enhance operational safety by minimizing the risks of subsurface subsidence and failure in a timely/cost-effective way. Additionally, It represents the first published work on identifying subsurface voids in a large-scale operating gold mine in Egypt utilizing near-surface geophysical techniques.