Mechanism Of Water Inrush From Coal Seam Floor And Continuous Survey Of Fractured Zones In Coal Seam Floor

Water inrush from Coal Seam Floor(CSF)is one of the five severe disasters in coal mines, and it is a main mission in the future to study the behaviors in the deformation of CSF and Seepage flow in CSF, and to uncover the mechanism of water inrush from CSF, and to develop the technique for prevention and cure of water inrush, and to realize the safety in coal mining. In the current thesis, the mechanism of water inrush from CSF, the technique for continuous survey of fractures in CSF and the prevention and cure of water inrush are systematically studied from several respects,including test, theoretical and numerical analysis, and engineering practices. The main subjects involve as follows:(1) The permeability parameters of four kinds of rock are measured by specimens which go through a total failure process. An index, namely seepage stability index, is defined. The reason why the non-Darcy flowβfactor and the acceleration coefficient may be negative is analyzed.(2) A dynamical model which describes the interaction between the deformation of a stratum and the seepage flow of water in the stratum is established. A Fast Lagrangian Arithmetic for calculation of Response of the Model is presented. Two kinds of failure of stratum, i.e., the submit induced by shear, and the failure induced by tension, were considered in the construction of constitutive relations. A function which describes the state of stratum at a point is defined. The switch among the states is also considered.(3)"Semi-coupling"method is used to calculate the water-inrush-factor (WIF) of the floor of Tuntou 21st Coal Seam around the 21201 waking face. The mechanism for water inrush from CSF is explained by using Dynamics of Systems with Variable Boundaries. It holds that whether water inrush takes place is decided by the change process of boundaries, including the interfaces among the elastic zone, plastic zone, fractured zone and broken zone. Water inrush will take place when two conditions are satisfied, the first is that the formation of passage for water to flow, the second is that the permeability parameters and pressures within the aquifer concerns a certain condition. When the water-inrush-factor is great than one, water inrush from CSF will follow.(4) The electrical resistivity of specimens of mudstone, sandstone and limestone are measured in the total stress-strain process. Several types of stress, strain—electrical resistivity curve are summarized. Based on what mentioned above, a ground-electricity model for forward simulation of the distribution of electrical resistivity is presented; the mechanism of the failure of CSF and the law that electrical resistivity changes as the permeability parameters are uncovered.(5) A software, 3D EarthImager, is used to forward simulate the fractured zone in CSF and the change of apparent resistivity of the zone as the working face advances on. On the principle of parallel electrical survey, a system of successively monitoring the fractured zone in CSF is designed. The technical specifications and requirements for the monitoring system are presented. The monitoring system can provide efficient data for the engineering practice in coal mining.(6) The results in both test and theoretical study have been used to the integrated control of water inrush from CSF in Longgu Coal Mining and to the successive monitoring of the fractured zone of CSF in Wugou Coal Mining, Anhui.Based on the integrated geophysical exploration to the floor of Tuntou 21st Coal Seam arousing the 21201 Waking Face, a series of control measurements to prevent and cure water inrush have been formulated, such as injection grouting to the CSF, improving the technique of coal mining. By these means, the depth of fractured zone in CSF has decreased, and the realization of safe mining comes being. Economic and social benefits have been made observably.The results of successive monitoring of the fractured zone in CSF in Wugou Coal Mine show that the change of the fractured zone is very evident. Electrical resistivity method can be used to monitor the water situation in CSF and be use a supplementary means in the prevention and cure water inrush.