The Law Of Rock Crack Growth Under Blasting Load Superposition

Supported by the key project of Liaoning Provincial Natural Science Foundation,research on the propagation mechanism of rock damage crack and the control of fracture morphology under blasting(20170540456),this paper studies the superposition of stress wave in rock blasting load and the influence of joint on rock stress response state.Combined with theoretical analysis and numerical simulation,the superposition of stress wave is studied The simulation method is used to study the rock crack growth law and stress response characteristics under the superposition of blasting load.The main research contents and results are as follows:(1)The results show that the attenuation law of stress wave in rock mass is related to the distance between the position of rock mass and the explosion source The key word of *MAT?ADD defined by Von mises criterion can achieve the purpose of blasting crack under the condition of simulated blasting test.By analyzing the grid sensitivity,the size of simulated grid is determined to verify the rationality of parameter selection.(2)This paper studies the law of stress wave superposition and rock crack propagation under different blasting conditions,and studies the influence of charge height,blast hole spacing and blast hole number on the test results.The results show that the stress wave superposition effect of linear column charge is related to its equivalent spherical charge number,as well as its distance and angle from the blasting source.It is found that with the increase of the charge height,the peak stress at the initial stage of the vertical line of the linear column charge presents an upward trend,and the crushing effect at the end of the linear column charge is more obvious.When the distance between two blastholes is changed,the peak stress of the nodes on the vertical line of the line between two blastholes decreases with the increase of distance,which approximately satisfies the linear fitting relationship.When the distance between blastholes is increased,the proportion of damage elements increases,and the proportion of failure elements and nodes also approximately satisfies the linear fitting relationship,in which the distance is 15 m,When the distance is 20 m,the radial crack is longer.The peak stress of the monitoring node of rock mass is related to the distance between the location and the explosion source.When the location is equidistant from multiple explosion sources,the positive superposition effect of stress wave is the most obvious.When the location has certain difference in the process of stress wave propagation,the peak stress is obviously less than the equidistant node.(3)This paper studies the influence of joint conditions on the superposition of explosive stress waves and the law of crack propagation,analyzes the propagation law of stress waves in jointed rock masses,and discusses the influence of joint conditions,joint groups and joint angles on the test results.The results show that joints hinder the propagation of explosive stress waves,the peak stress of rock mass decreases by about 60%,and the reflection results in the rock mass between blastholes and joints The joint changes the direction of radial crack development,and the failure of rock grid between the blasthole and joint is more.When the number of crack groups changes,the peak stress of the rock outside the joint presents a linear downward trend.With the increase of the number of joint groups,the blocking effect of the stress wave is stronger.Although the peak stress of the monitoring points inside the joint and the blast hole has a downward trend,the overall difference is not big,the range is about 2.94 MPa.The increase of the number of joint groups has no obvious influence on the superposition effect of the stress wave.Under the condition of multiple explosion sources,the increase of peak stress is mainly caused by the superposition of stress waves generated by multiple explosion sources,and the range of peak stress of each group is about 1.74 MPa.When the joint angle is 15 °,30 ° and 45 °,it has a strong guiding effect on the development of cracks,and the effect of rock breaking at the crack is more obvious.When the joint angle is 60 ° and 75 °,the development of radial cracks is not obvious.