初始地应力作用下岩石爆破裂纹扩展研究

Study on Rock Blasting Crack Growth Under Initial In-situ Stress

为了研究初始地应力作用下的岩体爆破时的裂纹扩展规律,分析了不同初始地应力情况下的裂纹扩展机理,并考虑了具有初始损伤的岩体在地应力作用下的裂隙区半径。鉴于初始地应力作用下裂隙区公式计算的复杂性,对于等向围压的岩体,引入了强度折减系数用于计算裂隙区半径,并通过ANSYS/LS-DYNA软件模拟出不同初始地应力作用下的岩体爆破时的裂纹扩展规律,并验证公式的适用性。得出结论:初始地应力作用下的岩体产生的爆破压碎区呈现类椭圆状,且随着初始地应力的增大其压碎区半径有着一定的增大趋势。单向初始地应力作用下对于爆破产生的主裂纹扩展起导向作用,裂纹的长度随着初始地应力的增大而逐渐减小,表现为抑制作用;双向等压地应力作用下主裂纹的扩展趋势为沿着最大主应力方向大致成45°角,强度折减系数的引入有效的考虑了初始地应力作用下的岩体裂隙区半径;不等向初始地应力的裂纹扩展方向为沿着岩体最大主应力方向成一定角度,当一侧围压固定不变时,该角度会随着另一侧围压的改变而逐渐增大或者减小。

In order to study the law of crack growth in rock mass under initial in-situ stress,the crack growth mechanism under different in-situ stresses is analyzed,and the radius of crack zone in rock mass with initial damage under in-situ stress is considered.In view of the complexity of the calculation of the fracture zone formula under the action of in-situ stress,the strength reduction coefficient is introduced to calculate the radius of the fracture zone for the rock mass with constant confining pressure,and the crack growth law of the rock mass under different in-situ stress is simulated by ANSYS/LS-DYNA software,and the applicability of the formula is verified.The following conclusions are drawn:the blasting crushing area of rock mass under the action of in-situ stress presents a quasi-elliptic shape,and the radius of the crushing area has a certain increase trend with the increase of in-situ stress.Under the action of unidirectional in-situ stress,the propagation of the main crack produced by blasting plays a guiding role,and the crack length decreases with the increase of in-situ stress,showing the inhibition effect.Under the action of bidirectional isobaric in-situ stress,the propagation trend of the main crack is approximately 45°along the direction of the maximum principal stress.The introduction of the strength reduction coefficient effectively considers the radius of the rock fracture zone under the action of in-situ stress.The crack propagation direction of unequal initial ground stress is a certain angle along the direction of the maximum principal stress of rock mass.When the confining pressure on one side is fixed,the angle will gradually increase or decrease with the change of the confining pressure on the other side.