基于ALE算法的隧道开挖爆破振动特性数值分析

基于ANSYS/LS-DYNA软件,分析隧道开挖过程中爆破振动对围岩及初期支护的影响.为了使数值模拟能够真正反映实际情况,采用更精确合理的爆炸数值计算方法:利用软件内置炸药模块和状态方程模拟爆破荷载的作用,并采用ALE算法模拟炸药与岩石之间的接触关系.在ALE算法中,为防止爆炸过程中网格的过分畸变给结果带来不利影响,将炸药定义成流体.分析结果表明:应力、速度均在爆炸发生的极短时间内达到峰值,而后迅速衰减,10ms后达到稳定状态.上台阶爆破在围岩拱顶处产生的水平振速峰值为下台阶爆破的6倍左右,在拱脚位置约为0.88倍;上台阶爆破在围岩拱顶处产生的竖直振速峰值为下台阶爆破的8倍左右.下台阶爆破在围岩拱顶处产生的应力峰值是上台阶爆破的1/5,在拱脚处相差不大;同一位置,初期支护结构质点振速峰值与单元应力峰值均比围岩大.

Numerical analysis for blasting vibration characteristics in tunnel excavation based on ALE algorithm

Based on ANSYS/LS-DYNA software, the influences of blasting vibration in tunnel excavation on surrounding rock and initial support structure are analyzed. In order to make the numerical simulation truly reflect the actual situation, a more accurate method of explosion simulation is adopted. The built-in explosives module in software and equation of state are used to simulate the explosive loads. In the meantime, the ALE algorithm is used to simulate the contact relationship between the structure of explosives and rocks. In ALE algorithm, explosives are defined into the fluid in order to avoid excessive grid distortion caused by explosion, which adversely affects the result of the calculation. The analytical results show that: Stress and velocity all reach a maximum within a very short period of time after the blasting, and then decay to the stable state at 10 ms. The peak value of horizontal vibration velocity at the dome roof of the surrounding rock of the upper-step blasting is about 6 times that of the lower-step blasting, and about 0.88 times at the arch foot position. The vertical vibration velocity peak value at the dome roof of the surrounding rock of upper-step blasting is about 8 times that of the lower-step blasting. The peak value of stress generated by the lower-step blasting at the dome roof of the surrounding rock is 1/5 of the upper-step blasting, and the difference is small at the arch foot. At the same position, the peak value of mass point vibration velocity and element stress of primary support structure are larger than those of surrounding rock.