爆破循环对围岩松动圈的影响

INFLUENCE OF BLASTING ROUND ON EXCAVATION DAMAGED ZONE OF SURROUNDING ROCK

基于松动圈的现场测试结果,研究声波波速沿孔深的变化规律以及爆破施工对于松动圈的影响。结果表明,波速沿径向逐渐增大,经历一个波峰后又逐渐降低,最后趋于稳定。每一循环进尺,测区中都存在强化和弱化区域,分布比较复杂,与爆破前松动圈的大小以及爆破效果密切相关。而爆破循环的累积影响效应表明,弱化带位于裂隙区,其损伤是纵波和横波共同作用的结果;强化带位于应力集中区,主要得益于爆破的震实效应以及碎胀力的挤压。当测孔离掌子面达到一定距离之后,波速虽有小幅的调整但不影响松动圈的形状,应力集中区不会产生偏移,据此得出松动圈测定的原则和时机。沿着隧洞轴线方向,当测点离掌子面一定距离之后,波速趋于稳定,据此给出爆破施工影响范围的确定方法。爆破循环对于围岩松动圈影响范围的确定,可为软岩隧洞的围岩支护以及硬岩隧洞岩爆的防治提供依据。

The variation in acoustic velocity along the borehole and the influence of blasting on excavation damaged zone（EDZ） are studied based on the in-situ testing results.It is found that the acoustic velocity increases gradually,then decreases gradually after a peak and tends to be stable finally.There are reinforced and weakened zones in survey area in each blasting round.Its distribution is complex and closely related to the size of EDZ and the effect of blasting.The cumulative effect of blasting rounds illustrates that the weaken zone lies in the crack area;and its damage is attributed to the effect of longitudinal wave and transverse wave.The reinforced zone lies in the stress concentration area;and its reinforcement is contributed to the tamping effect of blasting vibration and the compression of bulking force.When the distance between the borehole and the working face is up to a certain value,the blasting does not affect the shape of EDZ in spite of some slight adjustment in acoustic velocity.In other words,it does not cause the offsets of the stress concentration zone.Accordingly,the principle and time for EDZ test are proposed.Meanwhile,along the axis direction of the tunnel,the acoustic velocity tends to be stable when the testing point has a certain distance from the working face,which can provide a method to determine the blasting influence range.It is the determination of influence range that provides significant guidance for choosing the best time for the support of soft rock tunnel and the protection scope against rock burst of hard rock tunnel.