Liu Songyong

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.

Rock Breaking by Conical Pick Assisted with High Pressure Water Jet

In the process of hard rock breaking, the conical pick bears great cutting force and wear, and the cutting efficiency is lower. Thus different combination ways of water jet and conical pick were proposed to solve this issue; for instance, water jet placed in the front of pick (JFP) and water jet through the center of pick (JCP) was researched by numerical simulation and experiments in this paper. First, the models of rock breaking were built based on SPH combined with finite element method. Then, the stress distribution of rock and the cut force of pick were analyzed when the rock broken by the conical pick assisted with the high pressure water jet. It indicates that the effect of the JCP on rock breaking is better than the JFP. At last, experiments about rock breaking with a conical pick and the JCP were conducted to verify the reliability of the simulation. It indicates that the rock breaking with the assistance of high pressure water jet cannot only reduce the pick force, but also increase the rock crushing volume.

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.