近距离隧道施工对既有隧道结构安全性影响研究

发布时间：2018-02-04 07:05

  本文关键词： 三台阶七步法 数值模拟 爆破振动 衬砌安全系数 敏感性　出处：《兰州交通大学》2014年硕士论文　论文类型：学位论文

【摘要】：近年来伴随着国民经济的飞速发展，对铁路运输能力的要求也在不断提升，大量单线铁路隧道需要在旁边增建二线隧道，这样既可以提高既有铁路的运输能力又可节省建设投资，但是由于新建隧道与既有隧道间距往往很小，新建隧道施工过程中有可能损伤既有隧道结构进而影响运营安全。 本文依托西康二线新建铜羊沟隧道，通过现场检测，理论分析和数值模拟来研究新建隧道施工对既有隧道结构的影响。主要工作内容和研究成果如下： (1)利用地质雷达对既有隧道衬砌质量进行检测，通过雷达波图像判别衬砌的厚度，脱空，不密实等缺陷情况，利用超声回弹综合法测混凝土强度，并且结合现场观察判定既有隧道结构的健全度为C。 (2)运用MIDAS/GTS软件建立三维模型，模拟在不同间距情况下新建隧道在三台阶七步法开挖过程中各特征测点位移变化规律、不同间距下中岩柱塑性区分布规律、既有隧道衬砌最大拉应力和最大压应力变化规律，并对既有隧道轨道变形风险和衬砌破坏风险进行了确定。通过对既有隧道各断面拱底位移值进行比较分析，将轨道风险等级确定为Ⅳ级，安全，，只需照常维护。新建隧道开挖方法安全可靠。 (3)通过现场振速监测，结果表明：既有隧道衬砌结构振速未超过允许标准，对采集的爆破振动数据，利用最小二乘法回归得到适用于该隧道Ⅳ级围岩区域的爆破振动速度传播与衰减规律的经验公式。 (4)用ANSYS模拟新建隧道爆破振动对既有隧道结构的影响。当两隧道间距为1D时，模拟得出的峰值振速值与实测值只相差0.072，速度时程曲线变化趋势相近，说明数值模拟可靠。得到间距为1D时既有衬砌各特征点峰值振速分布和主应力峰值分布，迎爆侧分布振速值大，迎爆侧特征点振速要早于背爆侧达到峰值。既有隧道的最大峰值振速和最大拉应力峰值，衬砌安全系数都在安全控制值内，说明当前新建隧道的爆破施工不会造成既有结构的破坏。 (5)用ANSYS模拟当间距变化时新建隧道在爆破施工中对既有隧道衬砌结构的影响规律，既有隧道衬砌迎爆测振速对间距的变化较敏感，通过回归分析得到间距—峰值振速曲线，当间距大于2.5D时既有衬砌峰值振速变化趋于稳定。 (6)对既有隧道结构最大峰值振速的影响因素进行敏感性分析，得到爆破荷载对峰值速度影响最大，通过控制炸药量保证既有隧道结构峰值振速在安全允许值内。
[Abstract]:In recent years, with the rapid development of the national economy, the demand for railway transport capacity is also increasing. A large number of single-track railway tunnels need to be built next to the second-line tunnels. This can not only improve the transportation capacity of the existing railway but also save the construction investment. However, because the distance between the new tunnel and the existing tunnel is often very small, the construction process of the new tunnel may damage the existing tunnel structure and affect the operation safety. Based on the construction of Tongyanggou tunnel in Xikang No. 2 Line, this paper studies the influence of the new tunnel construction on the existing tunnel structure through field inspection, theoretical analysis and numerical simulation. The main work and research results are as follows:. (1) the quality of existing tunnel lining is detected by using ground penetrating radar, the thickness, void and density of lining are judged by radar wave image, and the strength of concrete is measured by the comprehensive method of ultrasonic rebound. And combined with on-site observation, the existing tunnel structure is judged to be the soundness of C. (2) using MIDAS/GTS software to establish 3D model, simulate the displacement change law of each characteristic measuring point in the excavation process of three-step and seven-step method under different spacing, and the distribution law of plastic zone of rock column under different spacing. The variation law of maximum tensile stress and maximum compressive stress of existing tunnel lining is determined, and the deformation risk of existing tunnel track and the risk of lining failure are determined. The displacement of arch bottom of each section of existing tunnel is compared and analyzed. The risk grade of track is determined to be grade 鈪

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