The traffic-induced cyclic stresses on the road base and subbase courses are usually in three-dimensional stress state, while so far most laboratory studies have focused on the deformation behavior of base and subbase layers in axisymmetric stress state. This study investigates the three-dimensional resilient behavior of coarse granular base and subbase materials based on a true triaxial apparatus. The factors of effective confining pressure, [ ], amplitude of cyclic shear stress, q^ampl, coefficient of cyclic intermediate principal stress, b_cyc, and fines content are involved. Test results indicate that the increase of either [ ] or q^ampl leads to a nonlinear growth of resilient modulus with a decreasing growth rate. b_cyc, which is proposed to represent the coupling of cyclic major and intermediate principal stresses, is found to have a promotion effect on the resilient stiffness, and the promotion effect tends to be enhanced by the increase of q^ampl. A modified model is established to predict the resilient modulus of coarse granular materials in three-dimensional stress state. There appears to exist a critical value of fines content, at which the variation trend of resilient modulus is changed from increasing to decreasing, and the critical fines content is related to both [ ] and b_cyc.

Unraveling the seepage and heat transfer coupled process between the working fluid and the fractured rocks in geothermal reservoir is of great significance to the exploitation and utilization of geothermal resources. In this study, based on the numerical modeling of fracture flow in geothermal reservoirs, the seepage and convective heat transfer behavior of fractured granite during geothermal extraction were investigated, and the effects of different fracture patterns, fluid injection temperature, and injection velocity on the temperature evolution of rock mass were comparatively analyzed. The results clearly revealed the influence of five different fracture patterns, i.e., single fracture, echelon fracture, parallel fracture, Y-shaped fracture, and crossfracture, on heat transfer capacity. Generally, the echelon fracture has the highest fluid outlet temperature, while the crossfracture has the largest total heat and shows the strongest heat transfer capacity. Besides the fracture shape, the fluid injection temperature and injection velocity also play significant roles in the heat transfer performance. The increase of fluid injection temperature would improve the total outlet heat of the crossfracture system and also benefit the system life. When the fluid injection temperature raises from 20°C to 35°C, the system life and the total outlet heat would be increased by 58.76% and 22.42%, respectively. However, higher fluid injection velocity would damage the system life of the geothermal reservoir, which obviously results in a decrease in total outlet heat. With the fluid injection velocity increasing from 0.004 m/s to 0.006 m/s, the system life could drop by 72.47%, and the total outlet heat was reduced by 55.72%. This work contributes to the preliminary understanding of the coupled seepage and heat transfer behavior in rock mass with various fracture patterns, and it could provide some practical implications for the rational exploitation of geothermal resources.

As lunar exploration missions advance, the need for safe and sustainable in situ energy systems has become increasingly critical. This study investigates the thermoelectric performance of Bi₂Te₃-based thermoelectric materials under the natural temperature variations on the lunar surface, aiming to illustrate the potential of thermoelectric generation technology in power supply for a crewed moon base. A numerical approach was employed to assess the energy conversion behavior and optimize the geometric design of a thermoelectric module couple consisting of a P-leg and N-leg. The results indicate that Bi₂Te₃-based modules exhibit promising functionality under cryogenic conditions, highlighting their potential as an in situ power source during the long lunar night. Furthermore, geometric optimization was shown to significantly enhance the overall thermoelectric performance. The present study illustrates that TEG technology offers a viable pathway toward reliable energy generation in extreme lunar environments, supporting future mission sustainability.

In the mining industry, microseismic monitoring has emerged as a crucial instrument for reducing risks related to the stability of underground rock masses. The present research conducts an analysis of dynamic hazards specifically at the 8204-2 working face in Tashan Mine. A novel monitoring framework is introduced, which integrates a nonlinear threshold curve model with a wireless microseismic monitoring system. The results demonstrate the effectiveness of the microseismic monitoring system with high-frequency sampling, utilizing the nonlinear threshold model, in detecting and providing real-time early warnings for microseismic signals, even in challenging geological environments. Practical implementation and monitoring over the past six months revealed that the microseismic monitoring system, employing the threshold curve model, achieved a monitoring and early warning accuracy exceeding 95%. This model combines the construction of a nonlinear threshold curve with dynamic conversion of confidence factors, and implements multi-level graded early warning based on the matching degree between real-time data and the hazard model, making its accuracy superior to traditional monitoring and early warning systems. Consequently, this study holds great significance in enhancing precise identification and early warning capabilities for mine microseism, as well as improving safety assessments for deep rock mining and construction practices.

Shale oil reservoirs are distinguished by their extremely low permeability and the presence of numerous natural bedding interfaces. As a typical layered sedimentary rock, shale requires hydraulic fracturing for efficient recovery, making it crucial to investigate the influence of these bedding properties on the hydraulic fracturing process. To address gaps in existing research regarding the influence of multiple bedding interface properties, this study utilizes artificially laminated specimens in conjunction with triaxial hydraulic fracturing experiments and CT imaging techniques. This approach enables a systematic investigation into the effects of bedding interface properties and horizontal principal-stress difference on hydraulic fracturing behavior. The findings reveal that the shear strength of the bedding interfaces is governed jointly by their cohesion, their friction angle, and the prevailing normal-stress condition. Under the tested conditions, specimens containing the relatively stronger bedding interfaces generally exhibited higher breakdown pressures, indicating greater resistance to hydraulic fracture initiation. Notably, specimens containing the intermediate-strength bedding interfaces exhibited greater hydraulic input work before fracture breakdown, primarily owing to the longer injection duration under these conditions. Among the representative specimens examined, the highest reconstructed fracture-network complexity was observed for the intermediate-strength bedding interface at a horizontal principal-stress difference of 6 MPa. Overall, hydraulic fracture propagation was strongly governed by the imposed principal-stress regime, whereas variations in bedding-interface properties influenced fracture deflection and the stress-dependent shear resistance of the interfaces.