改扩建公路岩质高边坡爆破开挖稳定性分析

Stability analysis of blasting excavation on high rock slope of reconstruction and extension highway

为研究不同爆破开挖方式对岩质高边坡稳定性的影响,依托京沪高速公路改扩建工程,建立岩质高边坡爆破荷载时程曲线,研究了边坡采用同时起爆和微差爆破两种起爆方式的动力响应特征,对比分析了两种起爆方式的安全系数以及质点速度变化规律。结果表明:采用修正的爆破荷载常量B计算等效爆破动载的方法,研究爆破作用下的岩质高边坡的稳定性是合理可靠的;采用微差爆破边坡稳定性较高,边坡的安全系数随等效爆破动荷载的施加呈现出递减的周期性变化,在等效爆破动荷载F达到最大值F_(max)和0.6F_(max)时所对应的安全系数为极小值点;各质点的速率变化与爆破动荷载的施加有同步变化,随着质点距爆破区的距离增加,规律逐渐减弱,仅在最大值附近出现峰值振动,而同时起爆的各质点的速率要大于微差爆破,不利于边坡开挖,各测点之间的峰值依次出现了递减和滞后的现象;采用微差爆破在爆破区附近出现了应力集中现象,局部剪应力大于岩体的抗剪强度,产生剪切破坏,爆破前后的位移监测差值较小,取得了良好的松动作用,岩体出现局部裂隙,应注意后期及时支护。

In order to study the influence of different blasting excavation methods on the stability of high rock slopes,relying on the reconstruction and expansion project of Beijing-Shanghai Expressway,the blasting load time history curve of high rock slopes was established.The dynamic response characteristics of the slope using simultaneous blasting and millisecond blasting methods were studied,and the safety factors of the two blasting methods and the change law of particle velocity were compared and analyzed.The results show that the method of calculating the equivalent blasting dynamic load with the modified blasting load constant B is reasonable and reliable to study the stability of the high rock slope under the action of blasting.The slope stability is high by using millisecond blasting,and the safety factor of the slope shows a decreasing periodic change with the application of the equivalent blasting dynamic load.When the equivalent blasting dynamic load F reaches the_(max)imum value F_(max)and 0.6F_(max),the corresponding safety factor is the minimum point.The velocity change of each particle changes synchronously with the application of the blasting dynamic load.As the distance between the particle and the blasting area increases,the law gradually weakens,and peak vibrations only appear near the_(max)imum value.The velocity of each particle of simultaneous blasting is greater than that of millisecond blasting,which is not conducive to the excavation of the slope.The peak values between the measuring points appear decreasing and lagging.Stress concentration occurs near the blasting area.The local shear stress is greater than the shear strength of the rock mass.The use of millisecond blasting resulted in stress concentration near the blasting area,and the local shear stress is greater than the shear strength of rock mass,resulting in shear failure.The displacement monitoring difference before and after blasting is small,and good loosening effect is achieved.Local cracks appear in rock mass,so it is necessary to pay attention to timely support in the future.