浅埋大跨度公路隧道软弱围岩段集中坍塌原因分析及处置措施研究

发布时间：2018-03-05 17:01

本文选题：浅埋　切入点：大跨度　出处：《烟台大学》2017年硕士论文　论文类型：学位论文

【摘要】：随着我国社会经济的不断发展及物流运输体系的不断完善,高速公路的规模逐年扩大。伴随公路设施的设计理论及施工技术水平的巨大进步,大跨度公路隧道的技术门槛降低,建设量不断增加。对处于浅埋软弱围岩条件下的大跨度隧道来说,大跨且扁平的断面形状具有完全不同于传统圆形断面的受力特点,因而更易发生以坍塌为主的地质灾害。合理的隧道开挖支护方法是处置塌方灾害的首要手段,而双侧壁导坑法被证明是应用于浅埋大跨度隧道开挖支护的最理想方法。断面跨度处于15~18m范围内的大跨度隧道在按照双侧壁导坑法施工时,一次性开挖并支护面积较大的导坑断面具有一定困难,故采用上下台阶法进行开挖,且经验上不在该条件下的侧壁导坑施工中添加临时横支撑,这一构件的缺失会严重影响支护结构的稳定,引发坍塌事故。因此,研究添加临时横支撑的必要性及不同设置条件下临时横支撑的支护效果具有重要意义。以荣乌高速公路营尔岭隧道为工程背景,通过现场勘察和跟进隧道施工,了解隧道浅埋段工程地质特征、工程地质评价、隧道施工方法及流程。依据地层结构法,结合有限元分析原理,使用Midas GTS NX岩土通用有限元分析软件对营尔岭隧道浅埋软弱围岩段连续集中发生的坍塌事故进行了数值模拟,并对侧壁导坑开挖时导坑上台阶高度的选择及不同结构形式临时仰拱的支护效果进行了对比分析,得出以下结论:(1)侧壁导坑分上下台阶开挖时,原设计支护结构分段施作,且未添加临时支撑使支护结构封闭成环,这是引起坍塌事故在较短距离内连续发生的主要原因。添加临时仰拱可以抑制支护结构向洞内的滑动变形,控制沉降,改善围岩受力条件,控制塑性区扩展,有效防止坍塌事故集中发生。(2)针对隧道左、右线来说,导坑上台阶合理高度的选择与临时仰拱结构形式的选择是具有灵活性的,4m高的右洞右导坑上台阶及4.5m高的左洞左导坑上台阶采用素混凝土形式的临时仰拱即可满足安全需求,5m高的左洞左导坑上台阶及右洞右导坑上台阶则需要分别选择刚度较大的20b工字钢或钢筋混凝土形式的临时仰拱来满足安全需求。
[Abstract]:With the continuous development of China's economy and logistics transportation system more perfect, the highway scale has expanded each year. With the great progress of the level of design theory and construction technology of highway facilities, technical threshold of highway tunnel with large span is reduced, the construction quantity is increasing. In the shallow and large span tunnel in soft rock under the condition. Large span and flat section shape is completely different from the traditional circular cross-section stress characteristic, so it is more prone to geological disasters to collapse mainly. Reasonable tunnel excavation method is the primary means of disposal of landslide disasters, and the double side drift method is proved to be applied in large-span shallow tunnel is ideal method of supporting the excavation of a large span tunnel span section. The range of 15~18m in accordance with the method of double side construction, excavation and supporting one-time large heading off. Some difficulties, so step method used for excavation, and the experience is not in the side heading construction under the condition of adding temporary cross support, lack of this component will seriously affect the stability of supporting structure, lead to collapse. Therefore, adding the need for temporary cross support and different setting conditions under the support of the temporary cross supporting effect has important significance. In Ying'er Rong Wu highway tunnel as the engineering background, through on-site investigation and follow up the tunnel construction, understand the geological characteristics of shallow buried section of tunnel engineering, engineering geological evaluation, construction method and process of the tunnel. Based on the stratum structure method, combined with the principle of finite element analysis, the use of Midas GTS NX geotechnical finite element analysis software of Ying'er tunnel in shallow buried soft rock section of continuous collapse was simulated, and the side heading excavation step heading height Comparing and selection of different structural forms of temporary inverted arch supporting effect, draw the following conclusions: (1) the side heading on the excavation, the original design of supporting structure for supporting section, and did not add temporary support to the supporting structure into a closed loop, which is the main cause of continuous collapse in a short distance. Add temporary inverted arch support can restrain the deformation, the sliding support structure to control the settlement, improve the surrounding rock stress condition, control the expansion of plastic zone, effectively prevent the collapse accident occurred. (2) aiming at the left tunnel, the right line, heading on the reasonable height of step structure selection and temporary invert selection is flexible, the right hole heading 4m high level and high 4.5m level with the left hole left heading temporary inverted concrete arch form can satisfy the security requirements, left heading left hole 5m high level and Right right on the stage to heading hole respectively choose temporary inverted high stiffness 20b steel or reinforced concrete arch form to meet the safety requirements.

【学位授予单位】：烟台大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：U458.3

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