Effect of Crack Propagation on Mining-Induced Delayer Water Inrush Hazard of Hidden Fault

Hidden faults in deep coal seam floor threaten the exploitation of coal resources. Under the influence of mining and water confined in the floor, the cemented filler in the hidden fault will be eroded by water flow, in order to investigate the fracture characteristics and water inrush risk of hidden faults in floors above confined aquifer. Using the 27305 working face as geological background, the influence of the seepage scouring filler on the mechanism of water inrush from hidden faults was assessed by developing a stress-seepage coupling model and employing the finite difference method to simulate the seepage process of hidden faults under the combined action of high ground stress and high confined water. The evolution of seepage, shear stress, and plastic zone was also assessed. The influence of the hydraulic pressure of the aquifer and the thickness of a waterproof rock floor on the formation of the water inrush pathway was analyzed. Results indicate that (1) under the influence of mining, the hidden fault experienced the change process of stress stability, stress concentration, and stress release. The shear stress increases first and then decreases. The compressive stress decreases gradually due to stress release. (2) Water inrush disaster will not occur immediately when the working face is above the hidden fault. The delayed water inrush occurs in the mined-out area when the working face advances to 160 m, the floor failure zone is connected with the hidden fault failure zone, and the delayed water inrush channel is formed. (3) With the mining advances, the water pressure of aquifer is the same. The larger-angle fault leads to the thinner thickness of floor aquifer. The greater the influence of hidden fault on coal seam mining, the higher the danger of water inrush.

COVID 19 and The New Normal

The world is waking up to a new reality where an invisible enemy has made human contact contagious and exposed the long-hidden fault line of verisimilitude, blurring the lines between reality and paranoia. The global reaction is unprecedented with world economy virtually at a standstill. The economic fallout of the outbreak could trigger a recession of unparalleled scale. But is economics the only challenge? The pandemic is attacking societies at their core. The author of Sapiens, Yuval Noah Harari puts it well when he writes “The biggest danger is not the virus itself. Humanity has all the scientific knowledge and technological tools to overcome the virus. The really big problem is our own inner demons, our own hatred, greed and ignorance”

SFRA, Detect of Winding Deformation in Power Transformer

The sweep frequency response analysis is extensively used technique for detect hidden fault and condition monitoring of power transformer. The operation is administered by supply a coffee voltage signal of varying frequencies to the transformer windings and measuring both the input and output signals. These two signals give the specified response of the ratio is named the transfer function of the transformer from which both the magnitude and phase are often obtained. Frequency response is change as measured by SFRA techniques may indicate a phase transition inside the transformer, then causes of fault identified and investigation is required for root cause analysis.