A study on the mechanism and control technology of strong mine pressure in parallel coal pillar and hard roof mining

In multi-seam mining, as mining ranges expand and depths increase, the strong ground pressure exerted on the lower coal-seam working faces (WFs) or roadways by coal pillars (CPs) and the hard roof between the interburdens becomes increasingly severe, leading to periodic roof-fall accidents. This study focused on the 42108 WF of the 4–2 coal seam in the Buertai Coal Mine of Shandong mining. It combined field tests, theoretical research, and numerical calculations to investigate the superposition or amplification of ground pressure as WF traversed the CP with the hard roof between interburdens. The ground pressure behavior of WF entering and exiting the CP stage progressed from strong to weak: exiting the CP > under the CP > entering the CP, with the CP stage being prone to a strong ground pressure occurrence. We proposed the influence mechanism of strong ground pressure and a seesaw structural mechanics model under the mining conditions with parallel CPs and hard roofs. The relationship between the geometric structure movement and stress evolution of the seesaw space of the overlying hard roof was analyzed, revealing the mechanism behind stress increase, evident damage, and the likelihood of dynamic disasters within 5–10 m from the CP boundary of the WF. The stress concentration factor (SCF) of the advance abutment pressure in the coal wall was the primary controlling factor determining seesaw instability, effectively ensuring safe and efficient mining practices. This research holds significant theoretical importance and practical engineering value for controlling strong mine pressure under the overlying CPs and hard roofs

Research on Roof Load Transfer by Passing Coal Pillar of Working Face in Shallow Buried Closely Multiple-Seam

The dynamic load effect of supports is mainly caused by the movement of the roof structure and the load transfer of overburden. In view of the practice issue that the phenomenon of strong ground pressure is easy to happen, when the working face of the lower coal seam passes the inclined coal pillar in shallow buried closely multiple-seam, it will lead to supprot damaged. This paper takes the mining of over-inclined coal pillars in the 22410 working face of the Bulianta Coal Mine as the background, based on the research method combining the field measurement, physical simulation experiment, and numerical calculation, the evolution law of the front abutment pressure (FAP) and roof weighting in mining under the inclined coal pillar is analyzed, and the mechanism of the stress transfer of the inclined coal pillar and the dynamic load of the support is revealed. The research shows that the concentrated stress of the coal pillar is jointly borne by the front coal wall of the working face and the interburden structure above the support. The vertical stress transmitted from the coal pillar to the floor acts on the key blocks of the interburden of the lower coal seam, which causes strong pressure and dynamic load effect, such as roof structure cut-off. The periodic breaking of the key stratum of the interburden leads to the development height and range of the cracks increasing stepwise. The partition characteristics of the mutual transformation of the interburden stress, the FAP, and the working resistance (WR) by passing the coal pillar stage are revealed, which is divided into three stages and four regions. With the working face passing through the inclined coal pillar, the influence area of the concentrated stress of the coal pillar is reduced, and the peak stress of the coal pillar is gradually transferred to the outside of the coal pillar. When the working face is 5 m away from the coal pillar, the peak of FAP and WR reaches the maximum values, the roof is cutting along the peak stress line, and the working face has a strong weighting phenomenon. The research results are consistent with the field measurement results, providing a reference for the mining of working faces under similar conditions

Liver injury in COVID-19: clinical features and treatment management

Abstract Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has spread to many countries around the world. In addition to lung disease, severe cases also displayed varying degrees of liver injury. This article will describe the latest developments regarding coronavirus and the pathogenesis of liver injury, the prone population and clinical characteristics of these patients, as well as providing some suggestions for clinical treatment

SIFSIX-3-Zn/PIM-1 mixed matrix membranes with enhanced permeability for propylene/propane separation

status: publishe