Study On Propagat Ion O F Explosive Stress Wave In Rock Mass With Layered Joints

There are a lot of joints,bedding,holes and other structural surfaces in natural rock mass(The following are called joints),which have great influence on the extension of explosive crack and propagation of explosive stress wave.At the joint surface,the explosive stress wave is reflected and stretched,and the damage at the joint surface is aggravated.However,it is difficult to form a better blasting profile due to the leakage of explosive gas from jointed fillers,especially in more jointed rock masses.Based on this,the propagation law of explosive stress wave in layered joints is studied.The explosive stress waves at joints with different thickness in the blasting process model were measured by embedded resistance strain gauges in the cement mortar model.The test takes the hole of the gun as the center and presents a circular cloth.Four sets of strain gauges were placed,corresponding to the thickness of the joints of 2.0 cm,1.6 cm,1.2 cm,0.8 cm,respectively,and a control group was set up in the absence of joint.The effects of different thickness and moisture content of joints on the propagation of explosive stress wave are analyzed.The relationship between the moisture content of joint thickness on the propagation of explosion stress wave and joint is analyzed,and the influence of crack length around the hole after explosion is also analyzed.The main findings are as follows(1)Based on the same moisture content of joint filling materials,the width of a sample's joints is in negative relation to the magnitude of blasting stress wave.The wider joints are,the weaker stress wave becomes.As the width of joints increases from 0.8cm to 2.0cm,the transversal stress wave declined about 66.7%~72%.joints delay the spread velocity of blasting stress wave.Every 0.4cm growth in joint width will cause 3-4?s delay in the corresponding peak value of stress wave in rocks.(2)Within the certain moisture content(25%-31%),with the increase of water content in joint fillers,the peak value of the blasting stress wave passing through joint filling materials decreases as the moisture content increases,is smaller,and the velocity of propagation increases with the increase of water content.Moreover,the former's decay rate changes with arithmetic series of numbers,i.e.,The propagation velocity of explosive stress wave increases with the moisture content,The water content increases by 1% and the peak time is 5 ?s ahead of time.(3)The duration of the blasting stress wave bears upon the width of joint filling materials.Under the experimental conditions,the duration of the peak value of blasting stress wave decreases as the width of joints and the moisture content of joint filling materials both increase.In consideration of the characteristics of joints,the rock ruptures first occur in joint planes,which could intensify the rupturess adjacent to joint planes and cause overdigging in rocks far from joint planes.