Study On Falling Law And Its Application Of Magnesite Orebody And Rock With Multi-mined-out Areas

The magnesite resources in Dashiqiao area of Yingkou are rich,but most of the shallow orebodies are destroyed by the people's mining,leaving a large number of mined out areas,which seriously damaged the integrity of the ore bodies,and brought great difficulties to the recovery of resources.The magnesite deposit called Da Ling Xi Shan is one typical mine damaged by the people.The orebody and the surrouding rock are layered and the dip angle is 0?30 degrees.There are many mining areas in the ore body,and the ore mining condition is seriously damaged by the large scale and complex horizon relationship.It is difficult for the conventional mining method to solve the caving and collapse safety problems in the mined-out areas.At the same time it is difficult to guarantee the reliability of stope production and economic benefits.Therefore,the induced caving mining scheme was proposed in this paper.The load strength of rock mass structure investigation was firstly measured and the level of rock was analysed in this paper.The rock solid ?-? grade has good caving capability,which is based on the need of the layered caving law and the induced caving mining safety.Secondly,five caving failure mode was summarized according to the structure characteristics of bedded magnesite body and a single roch beam clamped mechanical model was established in this paper.Thirdly,according to the optimization of the brittle rock properties of magnesite and similar material proportion scheme,a new kind of cylindrical specimens of similar material stress and strain determination was put forward.Fourthly,according to the similarity theory and model design,the non-empty area of layered rock mass the caving process simulation experiments was completed and the trapezonidal layered rock caving space form,the critical caving span,lower dimension and falling height relations were got in this paper.Fifthly,the caving process of many mined-out areas was simulated and the concept of mine-out areas group weak plane and key-pillars was put forward referred to the mine-out areas distribution characteristics.The fracture mine-out area is the first fracture plane rock failure surface.The key-pillar is a pillar which exists between the mine-out areas group and the upper part of the undercutting space,and is the main support of the upper rock mass,and lower initial undercutting position should be selected under the weakeast key-pillar and extending the undercutting area to all sides.Sixthly,the caving process in the no mine-out areas and many mine-out areas were simulated by 3 DEC software,the distribution characteristics of the stress field simulation was analyzed,the simulation of the reasonable parameters were determined and the reasonable undercutting position and way were confirmed.Seventhly,a new method to determine a lower level was also determined in the principal of ensuring the safe thickness,that is,the space between the level of undercutting and the lowest mine-out areas should be ensure the loosen-body protection buffer can effectively prevent the harm of air blast.Finally,the results of the study will be applied in the Da Ling Xi Shan magnesite deposit.The development system and induced engineering were designed,and "Falling and Ground Mining" and "Falling and Drawing" two schemes were raised.The former is to mine after ores caving to ground and becoming dense,The latter is to draw the ore from the drift port.Through comparative analysis,the "Tailing and Drawing"scheme was finally determined.The analysis shows that the induced mining method can be adopt in the mining conditions of the Da Ling Xi Shan magnesite deposit with remarkable experimental effect.