High geotemperatures are encountered during tunnel construction in areas with complex geological structures, which can seriously affect personnel and equipment in the process of tunnel construction and operation. The Nige tunnel, a deep-buried extra-long tunnel, was selected to monitor the geotemperature during construction. The air, rock, and water temperatures during the tunnel construction were measured at the tunnel face, and the actual temperatures of the rock or water body at the tunnel face were measured by advanced drilling. The variation trends of the water temperature, air temperature, and flow of water with the tunnel mileage were analyzed. The differences in three measured rock temperatures in three advanced drillings were revealed. The results showed that the Nige tunnel had a maximum water temperature of 63.4 °C, maximum rock temperature (Rock T) of 88.8 °C, and maximum air temperature (Air T) of 56.4 °C. Increasing trends of the air, rock, and water temperatures with the tunnel’s horizontal distance and the buried depth (vertical depth) were obvious, and the geotemperature gradient was approximately 7.6 °C per 100 m. Additionally, the variation laws of the construction ambient temperature with time in a complete construction cycle showed four stage characteristics, and each stage presented different mathematical relationships. These findings will provide guidance for the construction of high geotemperature tunnels in future.

The initial stresses have a strong effect on the mechanical behavior of underground rock masses, and the initial stressed rock masses are usually under strong dynamic disturbances such as blasting and earthquakes. The influence mechanism of a blasting excavation on underground rock masses can be revealed by studying the propagation of stress waves in them. In this paper, the improved Mohr-Coulomb elasto-plastic constitutive model of the intact rock considering the initial damage was first established and numerically implemented in Universal Distinct Element Code (UDEC) based on the variation of the experimental stress wave velocity in the initial stressed intact rock, and the feasibility of combining the established rock constitutive model and the BB (Bandis-Barton) model which characterizes the nonlinear deformation of the joints to simulate stress waves across jointed rock masses under initial stress was validated by comparing the numerical and model test results subsequently. Finally, further parameter studies were carried out through the UDEC to investigate the effect of the initial stress, angle, and number of joints on the transmission of the blasting stress wave in the jointed rock mass. The results showed that the initial stress significantly changed the propagation of the stress waves in the jointed rock mass. When the initial stress was small, the transmission coefficients of the stress waves in the jointed rock were vulnerable to be influenced by the variation of the angle and the number of joints, while the effect of the angle and the number of joints on the stress wave propagation gradually weakened as the initial stress increased.

During blasting in deep mining and excavation, the rock masses usually suffer from high in situ stress. The initial seismic energy generated in deep rock blasting and its attenuation with distance is first theoretically analyzed in this study. Numerical modeling of the multiple-hole blasting in a circular tunnel excavation under varied in situ stress conditions is then conducted to investigate the influences of in situ stress levels and anisotropy on the blasting seismic energy generation and attenuation. The case study of the deep rock blasting in the China Jinping Underground Laboratory (CJPL) is finally presented to demonstrate the seismic energy attenuation laws under varied in situ stress levels. The results show that with the increase in the in situ stress level, the explosive energy consumed in the rock fracture is reduced, and more explosive energy is converted into seismic energy. The increasing in situ stress causes the seismic Q of the rock mass medium to first increase and then decrease, and consequently, the seismic energy attenuation rate first decreases and then increases. Compared to the condition without in situ stress, the blasting seismic energy decays more slowly with distance under in situ stress. Then the seismic waves generated in deep rock blasting are more likely to reach and exceed the peak particle velocity (PPV) limits stipulated in the blasting vibration standards. Under non-hydrostatic in situ stress, the generation and attenuation of the blasting seismic energy are anisotropic. The highest seismic energy density is generated in the rock mass in the minimum principal stress orientation. Its attenuation is dependent upon the in situ stress aligning the wave propagation orientation.

During blasting excavation in deep rock masses, the in situ stress initially exerted on blast-created free surfaces is rapidly released along with rock cracking by blasting. The rapid stress release can initiate seismic waves transmitting through the medium. In addition to explosion loading, the rapid stress release occurring on blast-created free surfaces is another excitation source of the rock vibration generated in blasting excavation of deep rock masses. In this paper, a theoretical model of seismic wave radiation from a circular blasting excavation in a deep rock mass is first developed to study the frequency differences between explosion seismic waves and stress release-induced seismic waves. Based on this, variational mode decomposition (VMD) is then introduced to separate explosion seismic waves and stress release-induced seismic waves from coupled vibration signals in the frequency domain. By utilizing the VMD separation, the composition and the amplitude and frequency characteristics of the rock vibration monitored in an actual deep tunnel blasting are investigated. The theoretical analysis and field investigation show that the vibration frequency of stress release-induced seismic waves is significantly lower than that of explosion seismic waves. Due to the existence of stress release-induced seismic waves with lower frequency, the coupled vibration amplitude is increased and vibration frequency is reduced. The monitored rock vibration in the near field is dominated by explosion seismic waves. However, in the far field, stress release-induced seismic waves become the major component due to their lower frequency and slower attenuation with distance. Extra care should be taken for the stress release-induced seismic waves in the far field. The stress release-induced seismic waves can be effectively reduced through shortening blast-created free surface sizes and increasing blasthole lengths moderately.

The rapid heat loss and corrosion of nano-aluminum limits the energy performance of metastable intermolecular composites (MICs) in aquatic conditions. In this work, superhydrophobic n-Al/PVDF films were fabricated by the cryogel-templated method. The underwater ignition performance of the energetic films was investigated. The preparation process of energetic materials is relatively simple, and avoids excessively high temperatures, ensuring the safety of the entire experimental process. The surface of the n-Al/PVDF energetic film exhibits super-hydrophobicity. Because the aluminum nanoparticles are uniformly encased in the hydrophobic energetic binder, the film is more waterproof and anti-aging. Laser-induced underwater ignition experiments show that the superhydrophobic modification can effectively induce the ignition of energetic films underwater. The results suggest that the cryogel-templated method provides a feasible route for underwater applications of energetic materials, especially nanoenergetics-on-a-chip in underwater micro-scale energy-demanding systems.