城市隧道穿越复合地层的合理微差时间间隔

以莞惠城际项目的“上软下硬”复合地层条件为依托，结合现场测试数据，采用理论与数值分析相结合的手段，开展城市隧道穿越复合地层中合理微差时间间隔的研究。研究结果表明:复合地层中微差爆破效果较好，第1、2炮适宜的微差时间间隔为50~70 ms；围岩条件相同，振动波形和主震相的持续时间均随着爆心距的增加而变长；而围岩条件变差时，振动波形更易出现波形叠加现象；随着微差时间间隔增加，第1、2炮产生的主震相逐渐分离，在0~35ms间降震率波动明显且整体上小于稳定降震率；在复合地层中，两测点爆心距相同时，成洞区上方测点受空洞效应影响显著，振速明显偏大。

Optimal microsecond time interval of urban tunnel passing through complex strata

In view of seismic-wave detection, laws of waveform change, and the vibration-reducing effect that different millisecond time intervals have on millisecond blasting in underground engineering, we conducted research on optimal microsecond time interval in the underground blasting for the construction of an urban tunnel passing through complex strata through theoretical and numerical analysis based on the so-called "a soft layer on top of a hard layer" soil condition found with the Guan-Hui inter-city expressway project and the related field test data. Our results show that the effect of millisecond blasting in the complex strata is preferable, the optimal microsecond time interval of the first and second guns is 50-70 ms; under the same surrounding rock conditions, the duration of the vibration waveforms and the main shock phases increase with the distance from the center of the explosion; meanwhile under the unfavorable surrounding rock conditions, the vibration waveforms are more likely to appear superimposed; with the increase of the microsecond time interval, the main shock phases of the first and second guns gradually separate, the vibration-reducing rate fluctuates significantly between 0 and 35 ms and is less than stable; in the complex strata, with the same distances from the center of the explosion at the two measuring points, the points above the hole area have significant influences with relatively greater vibration velocity.