Based on systematic experiments on the influence of air entrainment on rock block stability in plunge pools impacted by high-velocity jets,this study presents adaptations of a physically based scour model.The modifica...Based on systematic experiments on the influence of air entrainment on rock block stability in plunge pools impacted by high-velocity jets,this study presents adaptations of a physically based scour model.The modifications regarding jet aeration are implemented in the Comprehensive Scour Model(CSM),allowing it to reproduce the physical-mechanical processes involved in scour formation concerning the three phases;namely,water,rock,and air.The enhanced method considers the reduction of momentum of an aerated jet as well as the decrease of energy dissipation in the jet diffusive shear layer,both resulting from the entrainment of air bubbles.Block ejection from the rock mass depends on a combination of the aerated time-averaged pressure coefficient and the modified maximum dynamic impulsion coefficient,which was found to be a constant value of 0.2 for high-velocity jets in deep pools.The modified model is applied to the case of the observed scour hole at the Kariba Dam,with good agreement.展开更多
The paper analyses the stress characteristics in longwall face and its interaction with impact coal cutting, and puts forward the operation method for impact coal cotting. Similar material to the coal in particular mi...The paper analyses the stress characteristics in longwall face and its interaction with impact coal cutting, and puts forward the operation method for impact coal cotting. Similar material to the coal in particular mine was used to simulate the coal mass. Impact coal breaking test was performed on the test rig. The traveling pattern of the impact stress wave in coal and the dynamic response of impact parameters on coal property is analyzed.展开更多
文摘Based on systematic experiments on the influence of air entrainment on rock block stability in plunge pools impacted by high-velocity jets,this study presents adaptations of a physically based scour model.The modifications regarding jet aeration are implemented in the Comprehensive Scour Model(CSM),allowing it to reproduce the physical-mechanical processes involved in scour formation concerning the three phases;namely,water,rock,and air.The enhanced method considers the reduction of momentum of an aerated jet as well as the decrease of energy dissipation in the jet diffusive shear layer,both resulting from the entrainment of air bubbles.Block ejection from the rock mass depends on a combination of the aerated time-averaged pressure coefficient and the modified maximum dynamic impulsion coefficient,which was found to be a constant value of 0.2 for high-velocity jets in deep pools.The modified model is applied to the case of the observed scour hole at the Kariba Dam,with good agreement.
文摘The paper analyses the stress characteristics in longwall face and its interaction with impact coal cutting, and puts forward the operation method for impact coal cotting. Similar material to the coal in particular mine was used to simulate the coal mass. Impact coal breaking test was performed on the test rig. The traveling pattern of the impact stress wave in coal and the dynamic response of impact parameters on coal property is analyzed.
