| In accidents of mine safety, water disaster is the second largest disaster restricting its healthy development, only after to the colliery gas disaster. With the increase in depth of mine, the high stress and high geotemperature may lead to significant changes of water liquidity of mine cranny, the increase of Ordovician limestone water storage and the water pressure, and the occurrence of serious pressure water outburst problems which may thus increase the water inrush probability, as well as the probability of occurrence of major water disaster accident. But in the existing technical and economic conditions, water hazard detection and prevention is faced with great difficulty. Once the occurrence of mine water disaster happens, it is the top priority to take such measures as starting the emergency plan as soon as possible, eliminating dangerous cases, rescuing workers, protecting the mine, reducing disaster losses to the least extent, and carrying out rescue, as well as making achievement, so drainage is crucial to the management measures.In the coal mine drainage process, because a serious of actions such as a sudden power failure or the rescue of the trapped personnel, blocking off water, repairing roadway series of work result in a submersible electric pump to stop the pump, the resulting water hammer is a very common phenomenon in the process of disaster relief drainage; as for the stop pump water hammer, on the other hand, improper protective measures will cause serious harm to rescue equipment, and lead to the occurrence of such secondary disasters as the breakdown of the system and trapping rescue workers in danger. Although, at present, it is seldom reported on the breakdown accident in the coal mine drainage because of the stop pump water hammer accident, but it really exists. Especially in deep mine disaster relief drainage system, which is characterized with high lift, large flow and power, fixed upper end, a latent characteristics exactly, and heavy-duty suspension, its weight bearing system and the pipe not only have to bear the entire drainage system, but also bear the weight of pipeline in the water storage and stop pump water hammer shock force, it is necessary to study its calculation and protective measures of water hammer, and analyze the structure strength check of the main load-bearing components.This thesis, through theoretical analysis, experimental study, numerical simulation and case verification method, analyzes deep coal mine drainage pumping accident limit condition of water hammer shock force and its protection measures, water hammer effect on bearing system and the check of structure strength and fatigue life. The specific contents are as follows:(1) The definition of the concept of water disaster "deep". For deep relief drainage, The "deep" concept is related not only with mining depth, but also with the drainage equipment lift. In terms of the rescue and drainage of water disasters the deep mine disaster relief drainage is defined as the rescue of vertical more than sudden flooding accident in 800 m occurred in the mine. It is proved that the drainage work to solve the problem of deep mine with shallow mining conditions of disaster relief drainage equipment and water hammer prevention and control technology of accident is certainly not enough and with high risks. In accordance with the characteristics and conditions of deep mine rescue and drainage system, hydraulic transition process is correctly calculated, water hammer is analyzed comprehensively and presciently, so as to take safe and reliable water hammer protection measures. The rational design of the derrick and bearing system, the choice of pipeline of sufficient strength, and the fatigue reliability analysis of the bearing system, are the important prerequisites to ensure the deep mine rescue drainage.(2)From different aspects such as the multi fault state of the system and mine, calculate the deep mine disaster relief drainage stop pump water hammer, simulate and compare a variety of water hammer protection measures, and determine the optimal combination of the valve protection. The engineering practice may not one by one test a variety of protective measures against water hammer, electric algorithm with feature line based global hydraulic recognized and after decades of mature water engineering validation failure calculation method, relates to the important water hammer calculation of water hammer, the hazard analysis and protection design, the characteristic line method can not only solve the problem of complex piping system and boundary conditions of subject and stop pump water hammer, high calculation accuracy, good efficiency. Firstly, in this thesis, according to the no valve inverse calculation and analysis of check valve, butterfly valve and a slow closing check valve + butterfly valve different protection measures for deep relief drainage system stop pump water hammer in submersible electric pump outlet end, it is pointed out that no valve water hammer pressure is small, but the reverse flow; quick closing check valve reverse current velocity is small, but the water hammer pressure and pump pressure pulse intense; slow closing check valve water hammer vibration is weakened, but causes the inversion velocity; butterfly valve can guarantee the flow and pressure of pump is reduced to zero, but the reverse high velocity and maximum pressure pipeline, so deep relief drainage system shall be applied to corrosion common protective measures closed check valve and the two stage control butterfly valve to eliminate water hammer. Further more, through the different tilt angle slow close check valve butterfly valve under the joint action of + water hammer protection effect comparative analysis for 90 degrees, shaft, should slow closing check valve joint to eliminate the water hammer using butterfly valve quick closing 4S, slow 16 S and synchronous time; for deviated well, should slow closing check valve to eliminate water hammer using butterfly valve quick closing 4S, slow 26 S and synchronization time. Finally, through the 800 m deep well of a coal mine water inrush wells in the East after the emergency drainage emergency case, the drainage process of four months, the start stop 40 times, stable operation, to verify the two stage optimized control butterfly valve check valve and the correctness of the close common water hammer protection measures.(3)Defining the reliability of deep relief drainage bearing system and analyzing the structure strength check of the theory include transient shock structure durability under the load of structure safety and dynamic under cyclic load. Especially the impact of water hammer accident relief drainage system of deep well pump is stopped, resulting in great passing back and forth in the pipeline pressure wave, will cause serious damage to the whole system, so it is necessary to carry out the important parts of safety check relief drainage system on the hydraulic transition process happens. Specifically, according to on-site emergency rescue drainage, fast, highly reliable, this thesis summarizes the main structural components of the existing method for strength checking of bearing system of rough relief drainage, including derrick supporting force analysis, the bearing beam, bolt, piping stress analysis and verification etc.. However, finite element analysis compared these rough checking method in the treatment of geometry, boundary conditions, material properties, loads and changeable complex structure problem, existence of high precision, good efficiency, static analysis, stability analysis and life prediction can be both advantages.(4) In this thesis, the numerical simulation is carried out on the reliability of deep relief drainage bearing system, which involves whether the structure is stable or not under both static load and dynamic load, and whether the system is fatigue or not when the water hammer shocks under extreme load, and is featured with non-stability, deformation, fatigue influence life. Based on the establishment of 3D entity model of the bearing system, the finite element analysis software is applied to simulate the stress, deformation, vibration and fatigue rules of key components under both static and dynamic operations, as well as under the impact of the water hammer. The static analysis is included as well to verify whether the conditions meet the load-bearing components of drainage requirements, stability analysis to determine the natural frequency and the work of key components of the external excitation frequency when does it lead to the occurrence of resonance, analysis to predict the component stress under the action of the service life of the cyclic fatigue strength, and find the weakness and fatigue rules, and combined with the case of drainage to further validate the necessity of finite element structure strength check of the deep well drainage bearing system for disaster relief, relief materials reserve proposed classification label management measures.(5) The numerical analysis for the design of deep relief drainage of bearing system of supporting beam: static analysis shows that, under the same load, the total deformation of supporting beam and the stress value both increase with the wellhead diameter, even at maximum water hammer force, the maximum deformation of supporting beam is within the material allowable range, which belongs to the small deformation; the maximum stress occurs at the contact position of beam and foundation, the maximum stress value less than the yield strength, the safety factor more than 3.43, thus the supporting beam is safe and reliable. The vibration mode analyzed by the stability of bearing beam shows that, its natural frequency is much larger than the excitation frequency, and resonance will not occur; but the vibration of both web sides of the beam deforms, the position of which is between the two internal stiffeners. In order to avoid stop pump water hammer and other high frequency conditions causing damage to the supporting beam, we can improve the vibration characteristics of load-bearing beams by increasing the thickness of web or increase the layout density beam internal stiffening rib; Fatigue life analysis shows that the support beam even at maximum water hammer force, can also stop pumping 1225 times, and in the slow closing check valve + two stage control butterfly valve with the water hammer protection measures, it can be accidental pump stop 3155 times. The numerical analysis of pipelines selected by the deep relief drainage bearing system: static analysis results show that the maximum water hammer in pipeline under the action of stress, the maximum deformation is small deformation, the maximum stress concentration values were less than the tensile strength and yield strength, to meet the use requirements; stability analysis shows that the natural frequency of 800 m drainage pipeline is much smaller than the excitation frequency, resonance does not occur in normal operation, the pipeline shows the main rotating pendulum, swing when the type variable to a maximum of 7.0727 mm, the value of 800 m pipeline for small deformation; fatigue life analysis show that the upper end of the drainage pipe road in the maximum water hammer force, can be accidental pump stop 49 times, must take more optimization water hammer protection measures, can after pumping accident 160 times, the lower end of the water drainage pipeline in the maximum water hammer force, can be accidental pump stop 361 times, the optimization of water hammer protection measures, can stop the pump 2073 accident. At the same time, the fatigue life analysis of the pipeline also shows that, under the same load, there is great difference between the fatigue life and frequency of use of lower drainage pipeline system and those of higher drainage pipeline system, therefore, in engineering application, each line shall be labeled: the drainage pipeline is used at the lower end, and then it is adapted to the upper end at the next drainage, and the pipeline use(using times, each use long, each time in the process of using the pump stop number) shall be recorded in detail in case that the pipeline service life is close to its fatigue life.In the emergency drainage case of a coal mine water inrush wells under 800 m deep in Eastern China, during the 4 months of emergency drainage process, single pump starts and stops 40 times. Due to its later stable operation, the emergency drainage task was finished. after the demolition, the system was sent back to the factory and warehouse to check and test of the motor, pump, pipe, flange, the bolt and the supporting beam of the key components of electric submersible pump: the performance index and the load-bearing system vice versa are good, always maintain the normal operation of the state, and thus ensure downhole plugging operation, clear the establishment of power supply system, the installation of large water pump and motor and other large engineering quantity of homework on the work, the successful completion of the. The experience of four months’ rescue and drainage under complex conditions has confirmed the high reliability, high stability of deep relief drainage system. |
PDF Full Text Request