A new mistuning form, pre-twist mistuning was found in the bladed disk based on the engineering practice. Based on a continuous parameter model of bladed disk, the characteristics of bladed disk with pre-twist mistuning and natural parameters mistuning, including stiffness mistuning, mass mistuning and damping mistuning were compared and analyzed, and the effect of pre-twist mistuning on the vibration response localization of bladed disk was researched. The result shows that pre-twist mistuning can lead vibration response localization to bladed disk as well as natural parameters mistuning. The degree of vibration response localization caused by force mistuning is comparative with the natural parameters mistuning. Compared with natural parameters mistuning, the pre-twist mistuning could not change the natural characteristics of bladed disk. As a result, the pre-twist mistuning can not be detected by traditional method, such as the frequency test. The result not only completed the research content of bladed disk, but also conducted the design and manufacture of bladed disk.

In this work, a numerical study is conducted on the seismic response of deep-buried roadways in coal mines under the influence of goafs, and a 3D numerical model of the seismic response simulation of deep-buried roadways is established using the coupling model of the finite difference method and the distinct element method. This model simulates the seismic response of different coal pillar widths and the seismic conditions of the deep-buried roadways under the influence of the adjacent goafs. The deformation, stress distribution, and plastic area distribution of roadways and coal pillars are systematically studied, and the situations under the static load and the roadways, which are not affected by the goafs, are compared and analyzed. A reasonable width of the coal pillar is proposed on the basis of the stability of the roadway and the coal pillars. In the end, suggestions for the reasonable setting of coal pillars under seismic load are provided.

No abstract

Fault slip will cause a change in mining stress at the longwall face, which will cause adverse effects. In this study, on the basis of Fast Lagrangian Analysis of Continua in 3 Dimensions (FLAC3D) and Particle Flow Code in 3 Dimensions (PFC3D), the sliding of the fault fracture zone and its impact on the longwall working face were analyzed. The rock mass of the fault fracture zone with a certain thickness was constructed using rigid random model particles. The coupling between the wall element of PFC3D and the zone element of the continuous medium in the software was used to realize the transmission of force and displacement, and the interaction between the fault fracture zone and the working face was studied. The influence of the slip of different fault zone positions on the fault and working face was also explored using the method of externally disturbing the fracture zone of the fault. The numerical results showed that as the distance between the fault and the working face continued to decrease, the peak stress concentration in front of the longwall face first increased, then decreased, and gradually shifted to the vicinity of the fault zone. The stress mutation and fault slip occurred within a certain distance of the longwall face from the fault. When fault slip activation begins, the stress near the fault zone showed a sudden change of varying degrees with the advancement of the longwall face. This sudden change was caused by the influence of mining activities from the activation distance of the rock in the fault fracture zone and the rolling extrusion of the rock mass in the fracture zone. When the fault zone closer to the working face was disturbed, the influence on the fault zone and longwall face was greater. When the fault zone near the coal seam was disturbed, the rock mass and working face near the fault zone brought different degrees of dynamic responses, which were mostly instantaneous and had high frequency and amplitude. The results of this research could help in the mining of longwall mining affected by fault zones and have a certain guiding role in coal mining before crossing faults.