With the excavation of underground opening,the roof rock block may fall under external dynamic disturbance.In this paper,the roof rock mass was simplified as a rock block system composed of trapezoidal rock blocks.A s...With the excavation of underground opening,the roof rock block may fall under external dynamic disturbance.In this paper,the roof rock mass was simplified as a rock block system composed of trapezoidal rock blocks.A series of experiments and numerical simulations were performed to study the sliding process of the key block under the horizontal static clamping load and vertical impact disturbance.The propagation of stress wave in the block system were captured and analyzed by using high-speed camera and digital image correlation technique.The results reveal that a pendulum-type wave was generated due to the propagation and superposition of stress waves in the block system.Therefore,the governing mechanism of the sliding displacement of the key block was clarified based on the propagation of incident stress waves or pendulum-type waves.Meanwhile,it is found that the sliding distance of the key block decreases in a power function with the increasing friction coefficient,or decreases in a parabolic function with the increasing trapezoid internal angle.Finally,a case study on the roof block sliding of the roadway at a gold mine was conducted,and it is concluded that the sliding of the key block resulted from the coupled effects of"shear driving"and"low friction"driven by stress wave propagation,regardless of a single or multi-layer rock block system.These results may provide technical guideline for preventing rock-falling accidents caused by blasting distur-bances in underground mining.展开更多
Dynamic responses of a multi-storey building without or with a sliding base-isolation device for ground shock induced by an in-tunnel explosion are numerically analyzed. The effect of an adjacent tunnel in between the...Dynamic responses of a multi-storey building without or with a sliding base-isolation device for ground shock induced by an in-tunnel explosion are numerically analyzed. The effect of an adjacent tunnel in between the building and the explosion tunnel, which affects ground shock propagation , is considered in the analysis. Different modeling methods, such as the eight-node equal-parametric finite element and mass-lumped system, are used to establish the coupling model consisting of the two adjacent tunnels, the surrounding soil medium with the Lysmer viscous boundary condition, and the multi-storey building with or without the sliding base-isolation device. In numerical calculations , a continuous friction model, which is different from the traditional Coulomb friction model, is adopted to improve the computational efficiency and reduce the accumulated errors. Some example analyses are subsequently performed to study the response characteristics of the building and the sliding base-isolation device to ground shock. The effect of the adjacent tunnel in between the building and the explosion tunnel on the ground shock wave propagation is also investigated. The final conclusions based on the numerical results will provide some guidance in engineering practice.展开更多
An optimal active sliding mode controller with specified decay rate design is proposed to control the wave-induced offshore jacket-type platform with active mass damper （AMD）. Irregular wave loading is approximated ...An optimal active sliding mode controller with specified decay rate design is proposed to control the wave-induced offshore jacket-type platform with active mass damper （AMD）. Irregular wave loading is approximated by finite sums of Fourier series, and its dynamic characteristics are governed by an exosystem derived from the linearized Morison equation. The offshore platform system is first decomposed into two virtual subsystems based on a linear transformation. By considering the velocity of AMD as a virtual control force for the first subsystem, the optimal virtual controller is derived. Furthermore, an optimal sliding mode surface with specified decay rate is proposed. Then, the active sliding mode controller is designed to ensure that the state trajectories reach the sliding surface in finite time and remain on it thereafter. Numerical simulation is employed to verify the effectiveness of the proposed approach.展开更多
基金supported by National Natural Science Foundation of China(Grant Nos.U1906208,51874069,51904056)Liaoning Revitalization Talents Program,China(Grant No.XLYC1802031)+1 种基金Fundamental Research Funds for the Central Universities,China(Grant Nos.N180115009,N2101028)China Postdoctoral Science Foundation(Grant No.2020M670782).
文摘With the excavation of underground opening,the roof rock block may fall under external dynamic disturbance.In this paper,the roof rock mass was simplified as a rock block system composed of trapezoidal rock blocks.A series of experiments and numerical simulations were performed to study the sliding process of the key block under the horizontal static clamping load and vertical impact disturbance.The propagation of stress wave in the block system were captured and analyzed by using high-speed camera and digital image correlation technique.The results reveal that a pendulum-type wave was generated due to the propagation and superposition of stress waves in the block system.Therefore,the governing mechanism of the sliding displacement of the key block was clarified based on the propagation of incident stress waves or pendulum-type waves.Meanwhile,it is found that the sliding distance of the key block decreases in a power function with the increasing friction coefficient,or decreases in a parabolic function with the increasing trapezoid internal angle.Finally,a case study on the roof block sliding of the roadway at a gold mine was conducted,and it is concluded that the sliding of the key block resulted from the coupled effects of"shear driving"and"low friction"driven by stress wave propagation,regardless of a single or multi-layer rock block system.These results may provide technical guideline for preventing rock-falling accidents caused by blasting distur-bances in underground mining.
基金Supported by National Science Fund for Distinguished Young Scholars of China (No. 50425824)National Natural Science Foundation of China (No. 50528808)
文摘Dynamic responses of a multi-storey building without or with a sliding base-isolation device for ground shock induced by an in-tunnel explosion are numerically analyzed. The effect of an adjacent tunnel in between the building and the explosion tunnel, which affects ground shock propagation , is considered in the analysis. Different modeling methods, such as the eight-node equal-parametric finite element and mass-lumped system, are used to establish the coupling model consisting of the two adjacent tunnels, the surrounding soil medium with the Lysmer viscous boundary condition, and the multi-storey building with or without the sliding base-isolation device. In numerical calculations , a continuous friction model, which is different from the traditional Coulomb friction model, is adopted to improve the computational efficiency and reduce the accumulated errors. Some example analyses are subsequently performed to study the response characteristics of the building and the sliding base-isolation device to ground shock. The effect of the adjacent tunnel in between the building and the explosion tunnel on the ground shock wave propagation is also investigated. The final conclusions based on the numerical results will provide some guidance in engineering practice.
基金supported in part by the National Natural Science Foundation of China (Grant Nos.40776051,60874029 and 40806040)the Natural Science Foundation of Zhejiang Province (Grant No.Y107232)the Scientific Research Fund of Zhejiang Provincial Education Department (Grant No.Y200702660)
文摘An optimal active sliding mode controller with specified decay rate design is proposed to control the wave-induced offshore jacket-type platform with active mass damper （AMD）. Irregular wave loading is approximated by finite sums of Fourier series, and its dynamic characteristics are governed by an exosystem derived from the linearized Morison equation. The offshore platform system is first decomposed into two virtual subsystems based on a linear transformation. By considering the velocity of AMD as a virtual control force for the first subsystem, the optimal virtual controller is derived. Furthermore, an optimal sliding mode surface with specified decay rate is proposed. Then, the active sliding mode controller is designed to ensure that the state trajectories reach the sliding surface in finite time and remain on it thereafter. Numerical simulation is employed to verify the effectiveness of the proposed approach.
