JH2模型参数的确定及动静荷载耦合作用下隧道围岩损伤研究

Determination of Johnson-Holmquist-ⅡConstitutive Model Parameters and Study on Tunnel Surrounding Rock Damage under Coupling of Dynamic and Static Loads

为了研究隧道围岩在静动应力耦合作用下的变形和损伤情况,建立地应力与爆破荷载耦合作用的隧道模型。首先依据文笔山隧道现场监测数据和岩体波速反推围岩的JH2本构参数。根据围岩等级,结合已知参数和波动方程,给出简易的JH2本构参数确定方法,并通过子程序嵌入ABAQUS中建立围岩的损伤模型;为了使仿真模型更接近现实情况,先进行地应力平衡,将此时的土体状态作为爆破模拟的初始应力状态,再采用等效爆破荷载法模拟隧道爆破,以此在宏观上实现大型岩土工程在静动应力耦合作用下的爆破仿真。仿真模型不仅考虑爆破面的爆破效果,还着重研究爆破对隧道围岩的影响情况。研究结果表明:初始地应力在隧道爆破中对围岩的损伤和变形都有不可忽视的作用。初始地应力的存在诱导损伤扩展,地应力越大,损伤越大,拱底在竖向发生2.2 m最大损伤深度;在相同进尺,地应力越小变形越大,拱顶在靠近开挖面处产生11.7 mm最大变形。围岩上下的水平收敛变形不同:上部背离隧道,下部指向隧道,围岩上下台阶分界处受剪切荷载。围岩的损伤与变形贴合实际工程,研究结果丰富隧道爆破模拟,对隧道爆破施工有现实指导意义。

In order to study the deformation and damage of tunnel surrounding rocks under the coupling action of static and dynamic stresses,a tunnel model under the coupling action of ground stresses and blasting loads is established.Firstly,the JH2 constitutive parameters of surrounding rock are deduced based on the on-site monitoring data of Wenbishan tunnel and the wave velocity of the rock mass.According to the surrounding rock grade,combined with the known parameters and wave equation,a simple method to determine the JH2 constitutive parameters is given,and the damage model of the surrounding rock is established by embedding a subprogram into ABAQUS.In order to make the simulation model closer to the reality,this research first balances the ground stress,takes the soil state at this time as the initial stress state of the blasting simulation,then using the equivalent blasting load method to simulate the tunnel blasting,so as to realize the blasting simulation for large-scale geotechnical engineering under the coupling of static and dynamic stresses on a macro level.The simulation model not only considers the blasting effect on the working face,but also focuses on the impact of blasting on the surrounding rock of the tunnel.The results show that the initial ground stress plays a significant role in the damage and deformation of the surrounding rock during tunnel excavation.The existence of the initial ground stress induces damage propagation.The greater the ground stress is,the greater the damage is.The maximum damage depth of the arch bottom in vertical direction is 2.2 m.At the same footage,the smaller the ground stress is,the greater the deformation is.The maximum deformation of 11.7mm is produced at the arch crown near the excavation face.The horizontal convergence deformation of the surrounding rock is different.The upper part is away from the tunnel,and the lower part points to the tunnel.In addition,the surrounding rock at the boundary between the upper and lower benches is subject to shear load.The damage and deformation of the surrounding rock are closely related to the actual project.