Maximal loads acting on legs of powered roof support unit in longwalls with bumping hazards

• 来源期刊: 煤炭学报（英文版）
• 学科: 工学
• 年，卷（期）: 2001,（2）
• 页码范围: 1-15
• 页数: 15页
• 分类号: TD82
• 语种: 英文

摘要

In the article the results of measurements of the resultant force in th e legs of a powered roof support unit, caused by a dynamic interaction of the ro ck mass, are discussed. The measurements have been taken in the longwalls mined with a roof fall, characterized by the highest degree of bumping hazard. It has been stated that the maximal force in the legs Fm, recorded during a dynam ic interaction of the rock mass, is proportional to the initial static force in the legs Fst,p. Th erefore a need for a careful selection of the initial load of the powered roof s upport, according to the local mining and geological conditions, results from su ch a statement. Setting the legs with the supporting load exceeding the indispen sable value for keeping the direct roof solids in balance, deteriorating the ope rational parameters of a longwall system also has a disadvantageous influence on the value of the force in the legs and the rate of its increase, caused by a dy namic interaction of the rock mass. A correct selection of the initial load caus es a decrease in the intensity of a dynamic interaction of the rock mass on powe red roof supports, which also has an advantageous influence on their life. 　　Simultaneously with the measurements of the resultant force in the legs, the vertical acceleration of the canopy was also recorded. It has enabled to prove that the exte rnal dynamic forces may act on the unit both from the roof as well as from the f loor. The changes of the force in the legs caused by dynamic phenomena intrinsic ally created in the roof and changes of the force in the legs caused by blasting explosives in the roof of the working, have been analyzed separately. It has been stated that an increase in the loads of legs, caused by intrinsi c phenomena is significantly higher than a force increase in the legs caused by blasting. It means that powered roof supports, to be operated in the workings, w here the bumping hazard occurs, will also transmit the loads acting on a unit du ring blasting. The majority of recorded force changes in the legs has been caused by a dyna mic interaction of the roof. They are characterized by a load increase coefficie nt Kd, satisfying the inequality 1.06<Kd=Fm/Fst,p<1.24. A much smaller number of cases, when the external load acted on the bases, w as recorded. Individual, recorded results of measurements indicate that changes of the force in the legs, caused by external loads of this type, run more inten sively due to roof loads (1.08<Kd<1.80),particularly in these cases when the near-the-roof layer of the seam is under mining. A determination of more precise relations among the changes of forces in the legs, caused by a dynamic interacti on of the floor and the bases and the mining and geological conditions requires a performance of additional underground tests.