大跨隧道围岩爆破损伤特征实测及其稳定性分析

Measurement of Blast Damage Characteristics and Stability Analysis of Large-Span Tunnel Surrounding Rock

摘要:

为探究大跨隧道爆破开挖过程中围岩的累积损伤演化规律及其稳定特性,采用岩石声波测试仪及压力传感器分别对爆破开挖期间围岩的损伤特征及初期支护结构的受力进行了现场实测。基于围岩损伤实测结果,采用数值模拟方法分析了围岩存在损伤时的隧道稳定性。研究结果表明:循环爆破开挖对围岩损伤的影响深度区间为3.4~3.6 m;随着测试深度增加,岩体声波波速曲线呈"S"形分布,而围岩累积损伤曲线呈"倒S"形分布;考虑隧道围岩爆破累积损伤时,测孔不同深度范围的围岩状态存在差异,即0.0~2.0 m深度为松动区,2.0~3.4 m深度为中度损伤区,3.4~4.8 m深度为轻度损伤区。与不考虑围岩损伤条件相比,考虑损伤时围岩塑性区分布面积显著增大;在考虑围岩损伤的情况下,隧道开挖后最大拱顶沉降为24.01 mm(现场实测均值25.8 mm),最大水平收敛为14.39 mm(现场实测均值15.19 mm),而不考虑损伤时,最大拱顶沉降20.43 mm,最大水平收敛13.85 mm,考虑围岩损伤的模拟结果更接近实际监测值。

Abstract:

To explore the cumulative damage evolution law and stability characteristics of the surroun-ding rock during the blasting excavation of large-span tunnels, this study used a rock acoustic wave tester and pressure sensors to conduct on-site measurements of the damage characteristics of the surrounding rock and the stress of the initial support structure during the blasting excavation process. Based on the measured results of the surrounding rock damage, the numerical simulation method was used to analyze the stability of the tunnel when there is damage to the surrounding rock. The research results show that the influence depth range of the cyclic blasting excavation on the surrounding rock damage is 3.4 to 3.6 meters; as the test depth increases, the rock wave velocity curve shows an "S" shape distribution, while the cumulative damage curve of the surrounding rock shows an "inverted S" shape distribution; considering the blasting cumulative damage of the tunnel surrounding rock, the rock state in different depth ranges of the test holes varies, that is, the 0.0 to 2.0 meter depth is the loosening zone, the 2.0 to 3.4 meter depth is the moderately damaged zone, and the 3.4 to 4.8 meter depth is the mild damage zone. The numerical simulation results show that compared with the condition without considering the surrounding rock damage, the distribution area of the plastic zone of the surrounding rock under consi-deration of damage is significantly larger; considering the surrounding rock damage, the maximum arch top settlement after tunnel excavation is 24.01 mm (the average value measured on site is 25.8 mm), and the maximum horizontal convergence is 14.39 mm (the average value measured on site is 15.19 mm), while without considering the damage, the maximum arch top settlement is 20.43 mm and the maximum horizontal convergence is 13.85 mm. This indicates that the simulation results considering the surrounding rock damage have a higher degree of consistency with the actual monitoring data.