The large load and poor heat dissipation of moon rock core drilling leads to
the difficulty of rock breaking and low drilling and sampling efficiency. As
a new auxiliary rock breaking method, laser rock breaking is expected to be
applied to perturbation sampling in lunar rock drilling. Revealing the
fracture characteristics and mechanism of rock under laser irradiation is
an important basis for realizing laser-assisted lunar rock sampling. Basalt
was used as simulated lunar rock sample, and its mechanical response
characteristics under laser irradiation were analyzed from macro to micro
point of view, and the failure law under different laser power and different
irradiation time was explored. The results show that the failure of the
sample under laser irradiation is mainly characterized by local rock melting
and dynamic crack propagation, and the surface temperature of the sample
follows the characteristics of Gaussian distribution. The laser power has a
greater influence on the degree of rock weakening than the irradiation
time. Laser irradiation of rocks can significantly reduce rock strength,
and has obvious effects on improving rock breaking efficiency and reducing
in situ disturbance. It is expected to provide theoretical and technical
support for assisting lunar rock drilling and sampling in the future.
In order to understand the mechanical behavior of a stope and analyse the stress conditions of surrounding rocks after ventilation shaft excavation and the abutment stresses of the top coal mining layout. In situ uniaxial stress monitoring tests were performed to understand the field abutment pressure evolution. Furthermore, the variation of the stress concentration factor was studied using the Tongxin Mine 8309 mining face of the TongMei Group, China, as a case study. A loading model of coal rock under excavation- and mining-induced disturbances was proposed, and the stress path and experimental method were designed to investigate the high excavation-damaged zone (HDZ), excavation-damaged zone (EDZ), and undisturbed zone (UZ). Moreover, the mechanical characteristics and failure characteristics of coal rock in different zones under site disturbance were obtained and the mesoscopic analysis is carried out by acoustic emission test. The results indicated that the strengths of the UZ, EDZ, and HDZ samples declined gradually. The volume of the UZ sample continuously expanded. However, the volumes of the EDZ and HDZ samples were compressed first and then expanded. Furthermore, the shear bands presented in all three samples resulted in failure. The cubic triaxial tests performed without considering mining-induced pressure produced higher strengths and less damage compared with the results of the true triaxial tests. The stress path used in the laboratory with the mining-induced stress throughout the stope could optimally reproduce the in situ mining process, which is significantly safe and efficient for the mining of deep resources.
Mining of underground resources is generally accompanied by frequent geological disasters. To understand the mechanical behavior of a stope, the stress conditions of the surrounding rocks after ventilation shaft excavation and the abutment stresses of the top coal mining layout were analyzed. In situ uniaxial stress monitoring tests were performed to understand field abutment pressure evolution, and the variation of stress concentration factor was studied, using a case of Tongxin Mine 8309 mining face of the TongMei Group, China. The loading model of coal rock under excavation- and mining-induced disturbances was proposed, and the stress path and experimental method were designed to investigate the high excavation damaged zone (HDZ), excavation damaged zone (EDZ), and undisturbed zone (UZ). The mechanical characteristics of the coal rock in different zones under site disturbance were obtained. The results indicated that the strengths of the UZ, EDZ, and HDZ samples declined gradually. The maximum principal strains of the HDZ and EDZ sample are 2.30 times and 2.21 times that of the UZ sample at the peak stress, respectively. The intermediate principal strains of the HDZ and EDZ samples are 0.91 and 0.88 times that of the UZ sample, respectively. The volume of the UZ sample continuously expanded, whereas the volumes of the EDZ and HDZ samples expanded when the peak stress was reached. The shear bands presented in all three samples resulted in failure. The stress path used in the laboratory with mining-induced stress throughout the stope could well reproduce in situ mining process, which is of significance for safe and efficient mining of deep resources.
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