Study On The Development Law Of Separation Layers Water Damage In Overlying Strata With Extra Thick Seam Mining

Coal is not only the largest energy source but also the cornerstone and guarantee of the national energy security strategy in China.It provides inexhaustible motivation for the continual development of national economy.With the exploitation of shallow coal resources,Coal mining is shifting to deeper parts with geological structures becoming more and more complex.Mine water damage,especially the water damage from the separation layers,affects the safety of mining seriously.However,it is difficult to study the thick seam mining under the conditions of structural combination.The middle region of the Laohutai coal mine in Fushun mining area is selected to research,where the thick seam with the thick of 96m,dip of 20°,mining location near fault,aquifer on the upper plate of the fault and the mine water damage occurrence sometimes.There are many methods such as similar material simulation experiment,numerical simulations and theoretical analysis are used to study the development of strata evolution in overburden strata and separation layers water damage with thick seam mining under certain construction conditions,based on laws of water-conducting fissure zones.The research results will be a certain theoretical significance,practical reference value.The main conclusions are showed by following:(1)The damage's characteristics of overlying strata are obvious in the study area,it mainly based on shear,tensile shear damage.The fault line and the axis of the rock formation are basically skewed at about 60o.The profile that selected in this study was divided into a tension zone,a transition zone(the region overlays like ridges prone to happenin in)and a compression zone.Among them,overlays like ridges tend to occurring in the front of the compression zone.It mainly affected by the fallen of inclined overburden rock.And it is easy to cause secondary collapse if continue excavate after formation.Due to the large thickness of the coal seam,the three regions have clearly differentiated.(2)The height of the water flowing fractured zone will continue to increasing with the mining continue.Due to the large thickness of the coal seam and the presence of faults,the water flowing fractured zone eventually developed to the maximum height,i.e.395m.The experimental records were consistent with the theoretical analysis.(3)When the thick seam is mined,the faults are obviously disturbed.When the left wing of the syncline is mined,the phenomenon of overlying strata slip to the right is obvious.Overlays like ridges oppresses the middle area of the fault.Therefore,the fault activity basically shows the development law of "steady state-dynamic-steady state".The fault is affected by the compression zone,the upper crack is more active than the lower one.The maximum sinking is 1.2m,and the maximum horizontal movement is 1.6m in the upper plate of fault F1.So,the horizontal movement is larger than the sinking value,which provides space and access for the influx of groundwater in the upper aquifer,and is consistent with the actual production of the water gushing.(4)The main aquifer being cut through by separation of layers and the fault reactivated induced by extra thick coal seam mining are the main causes of water inrush damage.The development of the separation layer is approximately upward along the inclined axis of the normal line of the roof,and the rock layer in the axial position collapses rapidly.The separation layer is less produced and lasts for a short time.The separation layers are divided into dry layer and water-filled layer.The separation layers are not obvious before the fault is disturbed.The number of the separated layer decreases and the regularity becomes worse after the fault is disturbed.However,the newly formed separation layers cutting the fault is easy to form roof water damage.