基于CDEM的岩石基坑爆破效果的数值模拟

Numerical simulation of blasting effect of rock foundation pit based on CDEM

为探讨延时时间及炮孔间距对岩石基坑爆破破碎效果的影响规律,依托大连地铁五号线虎滩公园站,建立岩体二维数值计算模型,通过连续-非连续数值模拟方法(CDEM)中的JWL爆炸模型及断裂能模型,对岩石基坑开展了爆破过程的数值模拟,并通过应力、振动速度、平均破碎尺寸、极限破碎尺寸、大块率及系统破裂度等指标进行综合分析。结果显示:模型监测点处以拉应力破坏为主导,延时35 ms时应力波叠加效果较好,引起的模型监测点峰值振速较小;随着延时的增大,岩石爆破效果逐渐变差,而当延时为25 ms时,较短的延时不利于应力波的传播和衰减导致爆破效果不佳。监测点处y方向峰值振动速度随着炮孔间距L的增大逐渐减小,岩石爆破效果逐渐改善,而过大的炮孔间距会阻碍应力叠加。炮孔间距6 m时能够有效减少大块率,爆破破碎效果最佳。改变炮孔间距相对于改变延时时间大块率降低了3.2%,系统破裂度提高了3.8%,因此,改变炮孔间距优于改变延时时间的爆破效果。

In order to explore the influence of delay time and blast hole spacing on the blasting crushing effect of rock foundation pit, a two-dimensional numerical calculation model of rock mass is established based on Hutan Park Station of Dalian Metro Line 5. By using JWL explosion model and fracture energy model of the Continuous-Discontinuous Element Method(CDEM), the numerical simulation of blasting process of rock foundation pit was carried out, and the comprehensive analysis is carried out through the several indexes such as the stress, vibration velocity, average fragmentation sizes, limit fragmentation sizes, percentage of massive blocks, system fragmentation degree. The results show that the monitoring points of the model are dominated by tensile stress failure, and the stress wave superposition effect is better when the delay time is 35 ms, and the peak velocity of the model points is smaller. With the increase of time delay, the blasting effect of rock gradually becomes worse. When the time delay is 25 ms, the shorter time delay is not conducive to the propagation and attenuation of stress wave, resulting in poor blasting effect. The peak value of vibration velocity in y direction at the monitoring point decreases gradually with the increase of blast hole spacing, and the blasting effect of rock gradually improves, while the excessive spacing between holes will hinder stress superposition. When the hole spacing is 6 m, the percentage of massive blocks can be effectively reduced, and the blasting fragmentation effect is the best. Compared with changing the delay time, changing the blast hole spacing reduces the massive blocks rate by 3.2%, and the system fragmentation degree increases by 3.8%. Therefore, changing the blast hole spacing is better than changing the delay time.