Study On Identification And Evolution Characteristics Of Overburden Rock Periodic Pressure Caused By Mining Based On Distributed Optical Fiber Sensing Technology

Coal is an important energy source in our country.With the deepening of mining depth and increasing intensity,the problems of ground collapse,ground fissures and water inrush caused by the society have attracted widespread attention.The deformation and destruction of overlying strata caused by coal seam mining is a hot issue in the field of coal mine safety.This paper uses distributed optical fiber sensing technology and based on similar principles to carry out the physical model test of the overburden rock in the 2^-2 coal seam face of Daliuta Coal Mine to study the strain response characteristics of each rock layer and the identification method of overburden deformation under coal mining conditions,And achieved the following results:(1)Introducing the average strain parameter,by calculating the average strain value of each rock layer in the coal mining process,reveals the law of strain response of each rock layer.And based on this,a preliminary identification method of the key layer and a method of determining the period of pressure are proposed.And comparing the discriminant result with the actual situation of the model test,it verifies that the discriminant result of this method has a certain reference.The key layer identification method and the periodic pressure determination method are applied to the field measured data,and the key positions are successfully identified and the periodic pressure step distance is determined.(2)Based on the rock tensile failure criterion,combined with the stress-influenced height change characteristics of the strain curve,a method to distinguish rock formation failure is proposed;in the model test,the distance between the strain mutation points of the transverse optical fiber can be a good way to determine the overburden failure With the drop width and the error-producing fiber discrimination result,the constant correction is carried out,and the relative error after correction is 2.7%.(3)Based on the rock tensile failure criterion and the optical fiber strain mutation theory,a method for identifying coal seam mining cracks is established.Based on the simulation test of similar materials in Daliuta Coal Mine,the distributed optical fiber sensing technology was used to analyze the distribution of cracks in the overburden strata caused by mining.The results show that:when the coal seam is mined 45cm,the overburden at the height of 0.27m by the B fiber appears tensile cracks;the coal seam is mined 100cm When the B fiber is 0.6m high,the overburden has a tensile crack;when the coal seam is mined 120cm,the C fiber has a tensile crack in the overburden at a height of 0.45m.The identification result is consistent with the photogrammetric result in the model test,which verifies the effectiveness of this method.accuracy.The paper has 42 pictures,13 tables,and 80 references.