Research On Mechanism Of Water Inrush From Floor Of Ultra-thin Waterproof Layer And Regional Remediation Technology

When mining in the lower group of coal or deep coal,coal mines often face the problem of safe mining on confined water under the condition of ultra-thin aquiclude.However,the "weak surface" area of the floor is very easy to induce water inrush.The process of damage,distribution form,water inrush mechanism under the combined action of pressure and water pressure and the effective treatment of water damage of ultra-thin aquifers floor are urgent problems to be studied.Based on the case and phenomenon of water inrush from deep ultra-thin aquifer floor,the paper quantitatively analyzes the main controlling factors of water inrush from ultra-thin aquifer floor.Systematically explore the internal mechanical mechanism of the karst confined water breakthrough along the weak zone under the condition of the ultra-thin water-resistant layer of the deep lower coal group.The dynamic characteristics of the breakthrough of the confined water weak surface are systematically studied.A risk assessment method based on fine exploration of confined water is proposed,and the safety of waterproof coal and rock pillar in floor is deeply analyzed.Finally,a set of regional remediation methods and technologies are formed.The main research results of this paper are as follows:(1)The main control factors of water inrush from the ultra thin aquifers are quantitatively studied by grey correlation analysis.The most important contribution of each factor to the water inrush of the floor is geological structure,followed by: the thickness of the bottom water barrier,the water pressure of the aquifer,the inclined length of the working face and the thickness of the coal seam.(2)A set of main control factors system for water inrush from the bottom of the ultra-thin water-proof layer has been constructed.Based on the four major control factors of geological structure,floor relative aquifer,confined aquifer and mine pressure,a set of main control factors system for mining floor water inrush on the confined water body with ultra-thin aquifer was constructed.(3)The water inrush from the floor of ultra-thin aquiclude can be divided into three types: water inrush from the complete weak plane of the floor,water inrush from the hidden weak plane of the floor and water inrush from multiple weak planes of the floor.The ultimate water pressure values of various types of bottom plates were analyzed.Based on the comprehensive analysis of rock fracture,fracture evolution and acoustic emission events,it is considered that the occurrence and development of fracture in weak mining face is a dynamic process,and the mechanical properties,thickness and position of the key compressive layer are the key influencing factors.And the mechanical judgment basis of water inrush disaster and the instability failure condition type of the weak surface were established.(4)Affected by the continuous advance of the working face,the conventional high-low switching of the stope stress between the coal wall and the goaf was realized.However,when there is a weak structural plane,because the floor is relatively thin relative to the aquiclude,the stress concentration area is first formed in the structural development area,resulting in the superposition of tectonic stress and mining stress.As the working face advances to a certain position,the mining failure zone is connected with the weak face fracture,resulting in the formation of water channel.(5)The "two exploration" geological conditions of the demonstration working face were carefully explored,and the water rich area and structural area were delineated.Based on the results of geophysical exploration and drilling refined geological exploration,the vulnerability index method is used to evaluate the exploitation of the ultra-thin aquiclude floor confined water body,and the floor vulnerability zoning is implemented.(6)The safety of mining on confined water body is judged by the reasonable retaining of floor waterproof coal pillar.The water resistance coefficient method is used to evaluate the water resistance ability of the key compressive layers,and the important effects of the mechanical strength,thickness and space position of the key compressive layers are put forward.(7)Regional grouting repair technology is used to thwart the floor,and the general treatment mode and three-dimensional detection technology of regional grouting treatment technology are put forward.In the demonstration working face,the interface of Ordovician limestone roof has been reformed by using the downhole area management technology,and the results are good.