小净距隧道扩建爆破动力响应数值模拟方法研究

Numerical Simulation of Blasting Dynamic Response ofSmall Spacing Tunnel Expansion

摘要:

以国内首次施工的大帽山四车道公路隧道扩建爆破震动控制为研究背景，介绍了爆破数值模拟分析中爆破荷载的计算原理和施加方法。从炸药直接起爆的角度，采用流固耦合多物质单元技术，利用LS-DYNA3D软件建立了扩建隧道爆破荷载作用下邻近运营隧道动力响应的数值计算模型。通过爆腔半径数值模拟结果与经验公式计算结果的比较，得到围岩的合理破坏应变值；对数值模拟计算结果的影响因素进行分析，结果表明材料采用理想弹塑性模型较硬化弹塑性模型的计算结果偏大；由现场实测数据拟合的经验公式验证数值模拟方法的可靠性。可为大断面小净距隧道施工及类似问题的解决提供参考。

Abstract:

With the rapid economic development in China，an increasing number of highway tunnels require reconstruction and expansion because the road traffic volume is increasing exponentially.The original Damaoshan highway tunnel is a separated four-lane expressway located between Fuzhou city and Xiamen city，Fujian province，southeastern China.The expansion scheme of this tunnel includes new construction of a four-lane tunnel between the original two tunnels and expansion of the right hand original tunnel into a four-lane structure.Thus，the expanded Damaoshan highway tunnel will comprise a series of closely spaced tunnels.The newly constructed four-lane tunnel，22 m long and 255 m2 wide，will be merely 5.89 m from the original tunnel. Moreover，the structure safety of the nearby original tunnel must be ensured to maintain effective traffic flow during the explosions for the construction of the new tunnel.Thus，the blasting vibration must be strictly controlled.In this study，semi-empirical theory and direct initiation method are used to determine blasting loads in numerical simulation of blasting dynamic response.With the project background of the first application of the Damaoshan highway four-lane tunnel expansion，a numerical analysis model is established using LS-DYNA3D software from the direct initiation of explosives to simulate blasting effects on an adjacent operation tunnel. The numerical analysis model is based on a multi-material unit and fluid-structure interaction technique to simulate the explosive detonation and the dynamic response of the nearby structure，respectively.The element type is SOLID164，and the non-reflected boundary condition is used.Influences of the rock calculation range，mesh size，material hardening condition，and failure strain on the numerical simulation are analyzed.The rock failure strain value in this study is obtained by comparing the explosive cavity radius between the numerical simulation and experience formula.The simulation results show that the blasting effects for the ideal elastic-plastic material model are larger than that for the hardening elastic-plastic model.The maximum relative error of vibration speed is approximately 20%.Moreover，the numerical results of vibration velocity generally comply with the Sadaovsk formula fitted by on-site measured data.Therefore，the results of this study are useful for tunnel constructions and similar projects.