小净距隧道爆破开挖对既有隧道动力影响数值分析

发布时间：2018-04-17 14:30

本文选题：小净距隧道 + 有限元法　；参考：《兰州交通大学》2014年硕士论文

【摘要】：本文依托兰州枢纽新建的北环隧道上穿既有红山顶隧道为工程参考背景，两隧道交叉断面处最小净距1.365m，交叉角度为43.287度。新建隧道爆破开挖施工产生的爆炸冲击波会对围岩及既有隧道衬砌结构产生振动影响造成一定的不稳定性。本文运用动力有限元原理，采用LS-DYNA3D有限元分析程序对新建隧道爆破开挖产生的冲击波对既有隧道的影响进行数值模拟分析，得到了爆炸冲击波在围岩与既有隧道衬砌结构上的传播规律，也为数值计算分析和实际施工提供了一定的参考依据。研究方面如下: ⑴首先对空间交叉小净距隧道在爆破开挖施工过程中存在的问题进行了概述，并针对个别问题提出本文的研究方向及目的；其次详细的分析总结了国内外近10年尤其是我国学者与工程技术人员在空间交叉隧道和隧道爆破开挖领域的理论计算、数值模拟成果和工程实践积累的经验。 ⑵就岩石爆破理论阐述了岩石破坏机理与爆破地震波的产生与传播方式，并就国内外的爆破振动影响的控制标准进行了对比分析；而且还针对LS-DYAN3D动力有限元分析程序在爆炸冲击数值计算领域的应用进行了详细阐述。 ⑶从现场实际爆破施工与实际控制标准出发分析了工况1在交叉点断面处爆破开挖对既有隧道衬砌结构的振动影响，对既有隧道衬砌结构的分析从3个要素着手：①分析了典型位置处如拱顶振速的变化规律，以此为依据判断分析出既有隧道受爆破振动较危险的区域；②就爆破冲击产生的应力波既有隧道二次衬砌应力分布形式与时间历程进行了分析，提出了受爆破冲击敏感度较高的区域位置；③从即有隧道二次衬砌拉伸应力破坏角度出发分析既有隧道断面受爆破冲击波的影响沿拱顶到拱腰到仰拱处拉伸应力的传播变化规律。 ⑷对不同净距条件下既有隧道二次衬砌结构受爆破冲击的影响进行了分析，并得出了振速与应力随净距的变化规律，得出了台阶法爆破施工时的临界净距，还观测了爆炸冲击波由爆孔经过围岩到既有隧道衬砌随时间的变化图示。 ⑸在不同围岩下既有隧道二次衬砌振速与应力的变化规律进行了分析，并从实际施工的角度分析了各工况下对既有隧道造成的不安全性，，同时分析了距交叉点断面不同间距下爆破掌子面爆破时既有隧道迎爆面沿二次衬砌的移动规律。
[Abstract]:Based on the project background of the new North Ring Tunnel in Lanzhou hub, the minimum net distance at the cross section of the two tunnels is 1.365 m and the cross angle is 43.287 degrees.The blast wave produced by blasting excavation of new tunnel will cause instability to the surrounding rock and the existing tunnel lining structure.In this paper, the influence of blast wave on the existing tunnel caused by blasting excavation in a new tunnel is numerically simulated and analyzed by using the dynamic finite element principle and LS-DYNA3D finite element analysis program.The propagation law of blast wave in surrounding rock and lining structure of existing tunnel is obtained. It also provides a certain reference for numerical calculation analysis and actual construction.The research areas are as follows:Firstly, the problems existing in the construction of space crossing small clear distance tunnel during blasting excavation are summarized, and the research direction and purpose of this paper are put forward.Secondly, the theoretical calculation, numerical simulation results and engineering experience accumulated in the field of space cross tunnel and tunnel blasting excavation in recent 10 years, especially in our country, especially in China, are analyzed and summarized in detail.(2) based on rock blasting theory, the rock failure mechanism and blasting seismic wave generation and propagation mode are expounded, and the control standards of blasting vibration at home and abroad are compared and analyzed.Moreover, the application of LS-DYAN3D dynamic finite element analysis program in the field of numerical calculation of explosion shock is described in detail.3. Based on the actual blasting construction and actual control standard, the vibration effect of blasting excavation on existing tunnel lining structure at cross section is analyzed.Based on the analysis of existing tunnel lining structure, the variation law of vibration velocity at typical locations such as arch roof is analyzed from three elements: 1. Based on this analysis, the dangerous region of existing tunnel subjected to blasting vibration is analyzed.(2) the stress distribution form and time history of the secondary lining of the existing tunnel caused by blasting impact are analyzed, and the location of the region with high sensitivity to blasting impact is proposed.(3) from the angle of the secondary lining tensile stress failure of the tunnel, the propagation and variation of the tensile stress along the arch top to the arch waist to the inverted arch are analyzed by the influence of blasting shock wave on the existing tunnel section.4. The influence of blasting shock on the secondary lining structure of existing tunnel under different net distance is analyzed, and the variation law of vibration velocity and stress with net distance is obtained, and the critical net distance during step blasting construction is obtained.The time variation of blast wave from blasting hole through surrounding rock to existing tunnel lining is also observed.5. The variation law of vibration velocity and stress of secondary lining of existing tunnel under different surrounding rock is analyzed, and the insecurity of existing tunnel under different working conditions is analyzed from the point of view of actual construction.At the same time, the moving law of the blasting face along the secondary lining of the existing tunnel is analyzed under the different spacing between the cross section and the blasting face.
【学位授予单位】：兰州交通大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：U455.6

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