初始应力下岩体爆破损伤特性及破裂机理

Blast-induced damage characteristics and fracture mechanism of rock mass under initial stress

钻爆法在岩体开挖工程中应用广泛,其工作效率与岩体结构及地质环境密切相关。初始应力会显著影响岩体爆破裂纹的扩展行为及破坏特征,导致深部岩体超/欠挖等问题。本文采用理论分析和数值模拟相结合的方法研究了不同初始应力下岩体的爆破损伤特性及破裂机理。基于弹性力学建立单孔爆破动静组合理论模型,分析了静态应力分布及动态应力演化特征,揭示了初始应力作用下岩体爆破损伤机制。通过经验公式及动态力学试验对RiedelHiermaier-Thoma(RHT)模型参数进行标定与修正,并结合室内爆破实验及理论结果对数值模型进行验证。此外,在单孔爆破数值模型中分析了爆炸压力演化规律、裂纹扩展行为及分形特征,结果表明数值模拟结果可以较好地论证理论模型的合理性。研究发现:环向拉应力是影响爆破裂纹扩展的重要因素,当初始应力较大时,合理调整环向应力分布可改善岩体爆破碎裂效果,实际工程中可结合预裂技术进行地压调控改变应力分布。

The technique of drilling and blasting is widely applied in rock excavation,and its working efficiency mainly relies on the rock mass structure and geological conditions.The initial stress plays a crucial role in the blast-induced cracking behavior and failure characteristics,and troubles such as over/underbreak and insufficient fragmentation may be arisen in deep rock masses,leading to other issues related to the waste of mineral resources and production costs.In this paper,the damage features and fracture mechanism of rock blasting under various initial stresses were studied using combined theoretical analysis and numerical simulation.Considering the effect of initial stress on the mechanical response of rock blasting,a theoretical model for single-hole blasting was developed based on elastic mechanics,and then the features of static stress distribution and dynamic pressure evolution were analyzed separately,revealing the fracture mechanism of rock blast-induced damage under initial stress.In addition,the Riedel-Hiermaier-Thoma(RHT)model parameters of rock were determined and adjusted based on a series of empirical formulas as well as dynamic mechanical tests.After calibrating the numerical model against the blasting crack pattern and attenuation of peak pressure by combining test and theoretical results,the single-hole geometric model was created and meshed in the commercial software ANSYS to study the dynamic tangential stress evolution as well as cracking behavior,and the fractal features of rock blasting cracks under different initial stresses were also discussed.The results show that the rationality of the theoretical model can be proved by the numerical simulation:the tangential tensile stress is a critical factor affecting the blasting crack propagation and the rock fragmentation can be improved by adjusting the distribution of hoop stress reasonably when the initial stress is large.In practical engineering,the stress distribution can be changed by controlling the field of geo-stress with presplitting technology.