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| 下穿石油管道浅埋黄土隧道施工变形控制技术研究
摘 要
由于黄土具有显著的各向异性、渗透性强、多具湿陷性等特点，导致浅埋黄土隧道在施工过程中普遍存在的问题是：围岩变形量大、拱脚稳定性差、地表沉降量大、围岩裂隙广泛发育等，这给隧道建设者们带来极大困扰，也是学者们重点研究的方向之一。本文以渑淅高速公路可乐湾黄土隧道为研究背景，主要根据工程设计文件、现场试验、数值模拟分析方法，对下穿石油管道浅埋黄土隧道施工变形控制技术进行研究，以期得到最优施工参数，为今后类似工程提供参考与指导。论文主要内容如下：
（1）简单介绍论文所依托的工程背景，包括可乐湾隧道的工程地理位置、地质水文条件、设计概况，以及隧道上方既有石油管道的情况。通过大量查阅文献资料，概述了现有浅埋和深埋隧道的分界方法和适用范围。
（2）通过原状黄土物理特性试验，得知黄土的平均含水率为19.95%，平均密度为1.80g/cm3；黄土的塑限为19.15%，液限为30%。通过室内固结压缩试验，竖直方向天然压缩模量为18.22MPa，水平方向天然压缩模量为26.68MPa，竖直方向天然压缩模量小于水平方向。通过三轴抗剪试验，水平方向黏聚力118.11kPa，内摩擦角为20.81°，竖直方向黏聚力85.59kPa，内摩擦角21.65°。
（3）利用数值模拟软件，对二台阶五部法和三台阶七部法两种工况下的多项模拟结果进行对比分析。与三台阶七步法相比较，采用二台阶五步法开挖时产生的围岩位移值、地表及石油管道沉降值、喷射混凝土及石油管道应力值均比较小，说明二台阶五步法更适合该隧道的开挖。
（4）在二台阶五步法的开挖方法下，对0.75m和1.5m的开挖进尺进行对比分析，最后得出0.75m的开挖进尺能较好的控制围岩变形。在超前小导管的外插角取10°，并沿开挖轮廓120°范围布设时，对3m、4m、4.5m、6m的超前小导管进行对比分析，最后得出超前小导管的合理长度为4.5m。
（5）为减小隧道施工对既有石油管道的影响，对石油管道周围地层进行垂直注浆预加固。在隧道模型采用不同注浆宽度、不同注浆深度时，分别比较了石油管道的沉降值和应力值。对于该工程提出如下建议：①建议注浆宽度为2.44m；②建议注浆深度为4m。
关键词：黄土隧道；各向异性；数值模拟；下穿石油管道；地表垂直注浆
Abstract
Because loess has the characteristics of significant anisotropy, strong permeability,and collapsibility, the common problems in the construction of shallow loess tunnelsare: large deformation of surrounding rock, poor stability of arch toe,large surface settlement, and the widespread development of fissures in the surrounding rock, etc., which has caused great troubles to tunnel builders andis also one of the key research directions of scholars. This paper takes the Kelewan Loess Tunnel of the Mianxi Expressway as the research background, mainly based on the engineering design documents, field tests,and numerical simulation analysis methods to study the constructiondeformation control technology of the shallow loess tunnel underneaththe petroleum pipeline, in order to obtain the optimal construction parameters and provide reference and guidance for similar projects in the future. The main content of the paper is as follows:
(1) Briefly introduced the engineering background on which the thesis relies,including the geographical location, geological and hydrological conditions,design overview of the Colawan Tunnel, and the existing oil pipelines above the tunnel. Through a large number of literatures,the demarcation method and scope of application of existing shallow and deep tunnels are summarized.
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