Study On Height And Influencing Factors Of Water Guide Fracture Zone In Fully Mechanized Caving Mining

Fully mechanized top-coal caving mining method is widely used in thick seam,which will cause more severe overburden damage than other mining methods.When mining coal seam under water body,the damage of overlying strata after fully mechanized top-coal caving mining is the most concerned.Because there are many factors affecting the development of overburden failure height in fully mechanized top-coal caving mining,there is no effective prediction method at present.The predicted results of existing empirical formulas deviate greatly from the field measured results.In most cases,analogy method is still used to predict the height of water conducting fracture zone.Based on this,numerical simulation,similar material simulation,regression analysis and other methods are used to study the development of water conduction fracture zone height under fully mechanized caving mining conditions.The main research results of this paper include:(1)Through the analysis of measured data of overburden failure height,the main factors affecting the development of overburden failure height are mining thickness and overburden lithology.The numerical simulation method is used to study the influencing factors.The results show that under the same lithological condition,with the increase of mining thickness,the height of water conduction fracture zone presents a non-linear increasing trend,and the weak overburden can be used.In order to effectively prevent the upward development of water-conducting fracture zone,the height of water-conducting fracture zone in hard overburden is the highest.(2)Similar material simulation results of fully mechanized top-coal caving mining in Shuangshan Coal Mine show that under the condition of 10 m mining thickness,the maximum height of caving zone of overlying strata is 38 m,the maximum height of water-conducting fracture zone is 65 m,and the apex of water-conducting fracture zone is 15 m into laterite layer,which does not pass through laterite layer,and the overburden laterite layer prevents the upward development of fracture zone.(3)A regression analysis of experimental data,it is concluded that in the hard rock,hard rock,soft rock lead water crack bring height formula is expected,for very weak rock lead water crack bring height measured is difficult to realize data lack,using the practice results obtained by selecting characteristic value trend analysis its height of water flowing fractured zone is expected to formula.(4)To make thin bedrock thick soil layer in coal mine fully mechanized mining conditions,bedrock pillar thickness changes lead to larger expected when the height of water flowing fractured zone is difficult to select the appropriate level of overburden rock,put forward the exploitation conditions to determine the strata lithology level principle: according to the hard strata is expected to get the water flowing fractured zone height value,if its 50% above,the actual thickness of rock column is in accordance with the extremely weak strata type is expected;If the thickness is 35% higher than the actual thickness of bedrock column,the height of water-conducting fracture zone can be estimated according to the type of soft overburden.For the same mining thickness and different bedrock columns,the corresponding height of water-conducting fracture zone is calculated by mathematical interpolation as the predicted result.Combined with the concrete conditions of shuangshan coal mine,the height of water-carrying fracture zone is estimated,which is basically consistent with the results of mining practice.