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Risk Assessment Of Water Inrush From Deep Coal Floor And Lagging Water Inrush From Fractures In Zhaogezhuang Mine

Posted on:2016-10-02Degree:DoctorType:Dissertation
Country:ChinaCandidate:K BianFull Text:PDF
GTID:1221330464472489Subject:Geological Engineering
Abstract/Summary:PDF Full Text Request
Our country territory is broad, limestone aquifers that under coal seam floor are widely distributed and containing an abundant supply of water, so it has been a serious threat to mine safety. By some accounts, floor water inrush occupies 50-60 percent of mine water inrush accidents. With the continuous improvement of mining technology and mining equipment, the coal development efforts are increasing and the depth of mining are deepening year by year. Under this high geostress conditions resulted from, outstanding problem of floor high-pressure water has seriously affected and restricted the construction of high-productivity and high-efficiency mines. Deep mining experience and research of typical mines in our country can expect to will play a guiding role for mines being mined to the deep.Water inrush from coal seam floor is a complicated dynamic process that real-timely varies with changes of geological and hydrogeological conditions. During this process, coal mining can bring real-time dynamic change of rock stress field, seepage field, surrounding rock permeability and rock mechanical properties, etc, and this dynamic change is a nonlinear dynamic phenomena controlled by multi-factors and with a very complex formation mechanism. So facing with such a complex dynamic process and multiple factors, Application of variable weights partitioned model is used to have solved the drawbacks of invariant right in traditional constant weight partition model, which greatly improves the accuracy of vulnerability assessment of water inrush from coal seam floor. Due to different dimensionless theories of main controlling index in coal floor water inrush can get risk assessment results with certain differences, the dimensionless theory and the variable weight theory are combined to have constructed partitioned variable weight model that reflects the data attribute characteristics of water bursting main controlling index in different hydrogeological conditions, thus make the evaluation results are more scientific and reasonable.On the basis of fluid-solid coupling theory, custom functions, variables are wrote by using fish programming language that embedded in the numerical simulation software FLAC3 D. It has achieved that elasticity modulus and permeability coefficient real-timely vary with the changes of stress and water pressure during the process of coal mining, also on this base constructs variable parameters-elastoplastic fluid-solid coupling model and variable parameters-rheological fluid-solid coupling model which regards fault materials as elastoplastic and rheological medium and reveals mechanism of deep coal-seam lagging water inrush from fault in floor.Combined with the typical deep mining mine-Zhaogezhuang mine, the paper based on the fluid-solid coupling theory, dimensionless theory and the variable weight theory to explore the deep coal mining water inrush mechanism and predict water inrush risk, the detailed research results are as follows:1. In depth analysis of the general situation of the the study area, the production level of the mine and main mining coal seam, mine drainage system, mine location, transportation, topography, hydrology and meteorology; a detailed analysis of stratum, structure, containing(separated) layer and groundwater recharge, runoff, drainage and other geological and hydrogeological conditions, determined the coal seam floor Ordovician aquifer is the main threat.2. Collecting data of geology, hydrogeology, mining design etc, which relate to water inrush from coal seam floor. Having comprehensively analyzed main controlling index influence the water inrush from coal seam floor of the deepest level of 12-2# coal in Zhaogezhuang mine. Main controlling index of aquifer in Ordovician limestone under coal seam floor is determined and have built. According to main controlling factor, building each thematic map of varies main controlling factors using GIS technology, and based on characteristics of each index, to quantify the value of each index value using a variety of dimensionless method, the results show that different dimensionless treatment methods will get different comprehensive evaluation results; Applying Spearman rank correlation coefficients to compare and prefer the comprehensive evaluation results that based on the model of dimensionless and constant weight partition model, then get a suitable evaluation model of dimensionless method, the results show that the comprehensive evaluation results drawn from varieties of dimensionless methods have a high correlation with an average ranking of "reasonable sort," and the average ranking and the "reasonable sort" have the highest correlation, the correlation coefficient was 0.998. Therefore, it can be concluded that the comprehensive evaluation results using the average process are the best; Establishing the water bursting vulnerability assessment model based on the variable weight partition model, and determine the water bursting vulnerability zoning threshold of ordovician limestone aquifer under 12-2#coal seam floor, while applying varieties of dimensionless treatment method to the variable weight partition model to evaluate the coal seam vulnerability. Finally getting the comprehensive zoning map about the risk of coal floor water bursting based on the partition threshold. By comparative analysis on variable weight partitioning model results, we can see that applying a variety of dimensionless treatment method to variable weight model not only shows the effects of comprehensive evaluation results by different dimensionless treatment methods, but also reflects effects of evaluation results by the variable weight; Thus, getting a more scientific and reasonable comprehensive evaluation final results, by comparing and preferring various dimensionless methods to choose the most suitable dimensionless method for evaluating the model, and then apply it to the variable power partition model.3. Making a thoretical analysis on influence factors of coal floor rock mechanical properties and water-physical properties, and analyzing mutual coupling action between them. Aquifers and aquicludes of coal seam floor are geological structures consists of a series of non-continuous joints and rock blocks divided by joints and fractures. There are varieties of defect structures with different scales, different directions and different characters in rock mass, such as faults, collapse columns, porosity, micro-cracks, joints and cracks, etc. As a result of these macro discontinuous surfaces exist, on the one hand,it changes the mechanical properties of the rock mass like elastic modulus and strength parameters, on the other hand also seriously affects the water physical properties of rock mass such as the coefficient of permeability and porosity. Before mining activities, most of these detect structures in a closed state in deep rock mass under high stress. Once the original stress state of surrounding rock is destructed by mining activities, some range of the rock mass’ s stability is breached, that will cause deformation and failure of surrounding rock, lead to the redistribution of stress field, at the same time create expansion of directed fracture and generation of new fractures. Caused by changes of rock fracture aperture, seepage channel changed and then changes the permeability coefficient and seepage force. While changes in pore water pressure will cause changes in effective stress and cause stress gradually increases in fracture normal and tangential stress, it significantly changes fracture aperture and new fracture generation, this forms complex coupling action between stress and seepage. The study of rock mass seepage model promotes generation of fluid-solid coupling theory. Based on the principle of effective stress of Terzaghi, combining the theory of Biot, it can realize the double field coupling in porous media. With the help of the deformation law of crack width, the coupling of seepage stress parameters in fractured rock mass can achieved, and likewise, the coupling of seepage stress parameters in porous rock mass can realized by deformation law of rock porosity.4. Hydrogeological physical conceptual model of water inrush from coal floor in the fourteen level of the first mining area.Based on fluid-solid coupling theory, custom functions and variables are wrote in fish programming language that embedded in the numerical simulation software FLAC3 D, it has realized the elastic modulus and permeability coefficient of the material vary with coal mining process while stress and pressure changes in real time, also on this base construct variable parameters-elastoplastic fluid-solid coupling model and variable parameters-rheological fluid-solid coupling model which regards fault materials as elastoplastic and rheological medium. Finally, the two model are used to simulate respectively, By observing parameters of vertical stress, vertical displacement, the maximum principal stress, the minimum principal stress and pore water pressure in coal seam floor normal location and different heights tectonic location, get the dynamic evolution rule within the process of coal mining. The simulation results prove that variable parameters-elastoplastic fluid-solid coupling model can show the dynamic regulation of seepage field of coal seam floor(Normal location and tectonic location), stress field, rock mechanics parameters, flow parameters in the process of coal mining, and variable parameters-rheological fluid-solid coupling model that can show the change of each field and parameter during process of excavation and show the possibility of lagging water inrush after the end of mining, so it can better explain the mechanism of deep fracture lagging water inrush. Through the contrast analysis of the calculation results, it has determined that the fracture zone of the most dangerous time lagging water inrush.5. Combined with the mechanical characteristics and seepage characteristics of deep rock mass, according to the fluid-solid coupling simulation results of the first mining face of research area and analysis of main controlling factors of coal floor water inrush risk of ordovician limestone aquifer as well as coal floor water inrush risk zoning results of ordovician limestone aquifer. Refer to the comprehensive prevention and control measures and experience of coal floor water inrush of ordovician limestone aquifer in northern China coal field, and put forward the comprehensive control measures and safety protection measures for the fourteen levels of development project.
Keywords/Search Tags:deep mining, floor water inrush, fluid-solid coupling, lagging water inrush, vulnerability evaluation
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