Mechanism of Rock Breakage under Pressure of Gas Explosion
Mechanism of Rock Breakage under Pressure of Gas Explosion
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瓦斯爆炸压力下岩石破碎机理
DOI：
10.2472/jsms.20.203
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发表时间：
1971
期刊：
影响因子：
--
通讯作者：
C. Tanimoto
中科院分区：
文献类型：
--
作者：
I. Ito;K. Sassa;C. Tanimoto
认为岩石爆破破碎一般是由强应力波作用下的动态破碎和瓦斯爆炸压力作用下的准静态破碎两种方式完成的。首先，在这项研究中，由随时间变化的压力在弹性介质中所引起的应力条件被计算时，它的球形空腔的工作时间，从而推断出什么是介质中的应力的影响，在空腔中的压力的上升时间的变化。结果表明，应力波在介质中引起的动应力值随压力上升时间的增加而减小，介质中的应力状态受腔内压力引起的准静态应力控制。认为低爆速炸药爆炸对岩石的破坏主要是由瓦斯爆炸产生的准静态压力来完成的。其次，采用有限元法分析了圆形钻孔在准静态压力作用下的应力状态，假定钻孔间距为10 a，钻孔呈直线排列，其中a是孔的半径。首先对每隔一个钻孔施加压力，仔细观察未施加压力的孔周围的应力状况，然后对每个孔施加压力，并根据假设的四个径向裂纹的生长来研究应力分布的可能变化，所述径向裂纹将起源于孔的内表面，因为两条裂缝沿着连接每个孔中心的线生长，另外两条裂缝沿着垂直于上述的线生长。当压力值超过材料的抗拉强度时，这些裂纹应该是从每个孔的内表面产生的。结果表明，沿各孔中心连线沿着的裂纹将进一步扩展，而垂直于上述连线扩展的裂纹则被抑制。通过将应力分析结果与材料中实测应变及瓦斯爆炸压力实际产生的裂纹形态进行比较，最终得出准静态瓦斯压力对光面爆破中光面墙的完成有很大贡献的结论。
It is believed that rock breakage by blasting is normally completed both by the dynamic breakage under intense stress waves, and by the quasi-static breakage under the pressure of gas explosion. First in this study the stress condition caused by the time dependent pressure in an elastic medium was computed from time to time as it worked on the spherical cavity, and thereby were inferred what were the stresses in the medium that were affected by the variation of the rise time of the pressure in the cavity. It is concluded that the values of the dynamic stresses in the medium caused by the stress wave decrease with increase of the rise time of the pressure, and that the stress condition in the medium is controlled by the quasi-static stress caused by the pressure in the cavity. It is considered therefore that the breakage of rocks caused by the explosion of the explosives having low velocity of defragration is completed chiefly by the quasi-static pressure of the gas explosion.Next the stress condition caused by the quasi-static pressure was analyzed by using the finite element method as it worked on the circular boreholes, assuming the cases in which the boreholes ranged linearly with constant spacing of 10a, where a was the radius of the hole. At first pressure was applied to every other borehole, and the stress condition around the hole where no pressure was applied was carefully observed, and then the pressure was applied to every hole, and probable change in the stress distribution was studied upon the assumed growth of four radial cracks that would be originated from the inner surfaces of the holes, as two cracks grew along the line which connected the centre of each hole, and two other cracks grew along the line perpendicular to the above. These cracks are supposed to have been produced from the inner surface of each hole when the value of the pressure exceeds the tensile strength of the material. It is clarified as the result that the cracks along the line which connects the centre of each hole will grow further while those which grow perpendicular to the above are repressed. By comparing the results of these stress analyses with the strain measured in the material and the pattern of the crack produced actually by the pressure of the gas explosion, it is concluded finally that the quasi-static gas pressure contributes very much to the completion of smooth wall in the smooth blasting operation.