A visco elasto plastic creep model of outburstprone coal under triaxial compression

Using self made creep seepage experimental apparatus, triaxial creep tests on outburst prone coal are carried out with coal samples taken from Songzao Coal Mine. It is found that the attenuation creep property is shown in the conditions of less than its long term strength load, while non attenuation creep property for the greater conditions. By introducing a visco elasto plastic body which can describe the deformation property of non Newtonian fluids, the visco elasto plastic creep model of outburst prone coal is put forward combined with a Poyting Thomson model. The model parameters were fitted out with Matlab programmer and validation is employed. It is found that the test results were in good agreement with those by the proposed model.     

Triaxial creep characteristics and constitutive relation of gas containing coal

The characteristics of conventional triaxial creep are obtained via a conventional triaxial creep test of gas containing coal under different stress levels. Mathematical fitting research regarding an experimental curve is done. A constitutive model of conventional triaxial creep of gas containing coal is developed by improving a generalized K B model. The results show that the characteristics of conventional triaxial creep of gas containing coal are related to the load step, and creep deformation is limited by the gas and confining pressures. Curves of the order 3 ε(t) describe the three steps of conventional triaxial creep tests of gas containing coal very well; the improved generalized K B model can represent a constitutive model of the conventional triaxial creep of gas containing coal.     

Experimental analysis of matrix shrinkage’s influence on mechanical permeability of gas filled coal

Based on the coal seam of Zhao zhuang coal mine and Si he coal mine belong to Jin cheng anthracite Mining Group in Shanxi province, by using the self developed three axial servo controlled seepage equipment for hot fluid solid coupling of coal containing methane, parallel experiments for permeability of helium and methane under different gas pressures are carried out to quantitatively study the influence of Klinkenberg effects on the permeability of coal. Meanwhile, the problem of permeability decreasing caused by fluid pressure decreasing and gas desorption is eliminated by controlling the effective stress. The results show thatthe Klinkenberg effect is obvious under low gas pressure. With the increase of gas pressure, the permeability of coal decreases at first and then increases. The inflection points of gas pressure for Klinkenberg effect are about 0.9 MPa both for coal samples in Zhao zhuang coal mine and Si he coal mine. When the effective stress is constant, with the increase of gas pressure, the permeability increment caused by Klinkenberg effect decreases, while permeability increment caused by coal matrix shrinkage increases. Coal matrix shrinkage has a close relationship with the mechanical properties of coal rock mass. For the coal sample with a poor mechanical property, coal matrix shrinkage is more obvious.     

Effect of outburst coal’s gas seepage properties under stage cyclic loading

Experiments of outburst coal’s gas seepage and deformation under cyclic loading of the stationary gas pressure and different confining pressures are made by “fluid-solid-heat coupling with axis servo seepage system of coal”. The results show that loading route has a significant effect on mechanical properties of coal sample. Although the complete stress-strain curves and one cyclic loading curve present similarity in the overall trend, the stress peak value of coal sample under cyclic loading is lower. Under cyclic loading, the stress-strain curves during loading and unloading don’t overlap. They connect to form a hysteretic loop. The permeability is in close relation with the damage deformation process of coal sample. Under cyclic loading, permeability is increasing during the unloading and decreasing during the loading. The permeability-strain curves during loading and unloading form a hysteretic loop, which is corresponding with the hysteretic loop of stress-strain curves of coal sample.     

The Catastrophic Theory Model of Instability of Coal and Rock Mass

In this paper,the stability problems of coal and rock mass exerted by horizontaland vertical forces are studied with the help of the method of catastrophic theory. The expression ofthe total potential energy function for this system is derived. This system can be described by thecusp catastrophe model. The bifurcation set which makes this system to loss its stability in the hori-zontal and vertical force control space is obtained. At the same time ,the process of Sudden statechange of coal and rock due to the changes of horizontal and vertical forces is discussed.     

Prediction of coal and gas outburst intensity with Incorporate GeneticAlgorithm Based Back Propagation Neural Network(IGABP)

For the prediction of coal and gas outburst intensity, Incorporate Genetic Algorithm Based Back Propagation Neural Network(IGABP) is proposed to solve the limitations in the traditional GABP such as time consuming, optimal stop condition of GA pretreatment indeterminacy, independency and complex task of great importance etc. IGABP addresses some improvements in adaptive crossover and mutation probability to promote GA performance. And with the introduction of BP operator in the evolution of GA operations, the standard GA optimization is from random search to self guiding search and the convergence rate of GA is upgraded, as well as the determination ability of exact solution. With a simulation as a case study, it is found that the minimum error and standard error with IGABP are 0.012 and 0.227, respectively, compared with -0.126 and 1.529 by traditional GABP.     

Regularity of the saturation lines’ change and stability analysis oftailings dam in the condition of flood

Yangtianqing tailings dam is a new dam planned for a copper mine. At the design period, test in laboratory is carried out to simulate the process of dam pile based on the design information of Yangtianqing tailings dam. And the regularity of the saturation lines’ change at the condition of flood and normal is studied, when the dam have been heaped to the about 2/3 of the total height (120 m). Based on the test data, the stability coefficients of the dam at this height in different conditions are obtained with the Slide software, and they could be served for the following test and the mine’s future safety production. It is shown that the dam is safe in the normal condition, while in the condition of flood, the stability coefficient is less than the benchmark in national standard. Thus, it is necessary to rectify the preliminary design or to take other measures to ensure the safety of the tailings dam.     

Numerical simulation of outburst prevention air door destruction by coal and gas outbursts

We explore the destruction of outburst prevention air doors by coal and gas outbursts using numerical simulation. The reflective overpressure when an outburst acts on doors is elucidated, and its formula is obtained. The destruction of outburst prevention wind doors by coal and gas outburst are simulated using ANSYS software based on data of wind door pressure obtained by similarity simulation experiment. The simulation results show that the weakest place of gate posts is where the wind tube is. Simulation results also show the first shock wave pressure that acts on an outburst prevention wind door is not the maximum one. Due to the effect of reflected overpressure, the outburst prevention wind door pressure will reach the maximum in several milliseconds. This finding is similar to the experiment result.     

Optimal allocation model and its genetic algorithms of outsourcingproduction resources in multi task

According to the characteristics of the outsourcing production such as multi task, dynamic environment, and multi objectives etc, an optimal allocation model of outsourcing in multi task is established by the linear weighted method. Outsourcing production time, outsourcing production cost and outsourcing production quality are set as its target functions. Then, genetic algorithm for solving this model is also investigated. Finally, a case study is employed for the effectiveness and the validity.