Du Changlong

Numerical Simulation of Rock Fragmentation under the Impact Load of Water Jet

To investigate the rock fragmentation and its influence factors under the impact load of water jet, a numerical method which coupled finite element method (FEM) with smoothed particle hydrodynamics (SPH) was adopted to simulate the rock fragmentation process by water jet. Linear and shock equations of state were applied to describe the dynamic characteristics of rock and water, respectively, while the maximum principal stress criterion was used for the rock failure detection. The dynamic stresses at the selected element containing points in rock are computed as a function of time under the impact load of water jet. The influences of the factors of boundary condition, impact velocity, confining pressure, and structure plane on rock dynamic fragmentation are discussed.

A theoretical model for predicting the Peak Cutting Force of conical picks

In order to predict the PCF (Peak Cutting Force) of conical pick in rock cutting process, a theoretical model is established based on elastic fracture mechanics theory. The vertical fracture model of rock cutting fragment is also established based on the maximum tensile criterion. The relation between vertical fracture angle and associated parameters (cutting parameter n and ratio B of rock compressive strength to tensile strength) is obtained by numerical analysis method and polynomial regression method, and the correctness of rock vertical fracture model is verified through experiments. Linear regression coefficient between the PCF of prediction and experiments is 0.81, and significance level less than 0.05 shows that the model for predicting the PCF is correct and reliable. A comparative analysis between the PCF obtained from this model and Evans model reveals that the result of this prediction model is more reliable and accurate. The results of this work could provide some guidance for studying the rock cutting theory of conical pick and designing the cutting mechanism.

Orthogonal Test and Support Vector Machine Applied to Influence Factors of Coal and Gangue Separation

In order to find the influence factors on coal and gangue separation, the article put forward an optimization design based on a support vector machine (SVM) and orthogonal experimental method. The crushing rates of coal and gangue were chosen as investigation target, and a comprehensive analysis was made for the coal gangue hardness relative difference value, crushing velocity, and crush frequency. According to the theory of selective crushing of coal and gangue, an impact crusher was used in crushing. The analysis showed that the relative hardness value of coal and gangue and the crushing velocity had significant effects on the coal crushing rate, while the crushing times had an insignificant influence on the coal crushing rate. The best technology scheme of coal and gangue crushing is obtained: The crushing velocity is 14 m/s, the relative hardness value of coal and gangue is 3.6, and the crushing number is 1. Relationships of various factors with crushing rate were obtained by analysis through SVM. The coal crushing rate error of experiment value and fitting value is less than 5\percent; the gangue crushing rate error of experiment value and fitting value is less than 10\percent. As can be seen, the SVM model has important guiding significance and high practical value.

A study on the remote monitoring system of hydraulic support based on 3DVR

The framework of hydraulic support remote monitoring system for fully-mechanized coalface is investigated in this paper. The three-dimensional virtual reality technology (3DVR) is applied to the control of hydraulic support and the OPC (OLE for process control) communication technology) is used to obtain the important sensing data of hydraulic support, meanwhile, by using dynamics analysis and rapid solution based on intelligent algorithm, the virtual prototyping modeling of hydraulic support is driven. As a result, the hydraulic support working conditions reappeared synchronously and truly, the hydraulic support working process is remotely controlled.

Fractal character of the impact crusher of coal

Fractal expression of the size distribution of impact crusher of coal is built according to fractal theory. Orthogonal experiment is carried out by impactive crush equipment and size distribution of the crusher of coal is linear fitted and analyzed in double logarithmic coordinates. The results indicate that regression curve in double logarithmic coordinates is straight and linear regression is favorable The fractal theory is suitable for the distribution discipline of the impact crusher of coal Among the factors which affect the fractal dimension of coal, the speed of impact is notable, hardness of materiel is secondly and impact frequency is very little; fractal dimension decreases with the increases of hardness of coal and increases with the increases of impact speed