【作者】 郭军；

【导师】 王明年；

【作者基本信息】 西南交通大学 ， 桥梁与隧道工程， 2008， 博士

【摘要】 随着国内大规模基础设施的投资建设,西部将建设一大批大断面黄土隧道。先期建设的郑西铁路客运专线包含大量黄土隧道,其单洞开挖断面达170m~2,为我国黄土历史上第一,且黄土地层具有特殊性和软弱性,工程难度大。我国目前尚无相关工程的施工与设计经验,缺少规范的指导,因此对其施工技术和支护理论的研究显得尤为迫切。本文依托该工程,率先对大断面黄土隧道的力学行为展开研究,主要开展了以下工作:1.通过调查和分析客专黄土围岩的特殊性质,指出黄土的结构性强度可概括为双线性屈服准则,而垂直节理可视为遍布节理,两者在新、老黄土中具有不同的赋存状况和发育程度。2.提出应按考虑黄土特性的双线性本构模型进行黄土隧道的力学分析,结果认为,结构强度主要影响塑性区和位移量值,对形态影响不大,而垂直节理对深、浅埋黄土隧道的位移模式与破坏形态有很大影响。3.采用三维数值仿真方法,并结合试验工点监测数据,研究了大断面黄土隧道中双侧壁、CRD、弧形导坑法的施工力学动态,揭示出深、浅埋皆为不利情况,开挖前围岩位移释放率高、支护位移量大、早期变形快、持续时间长、支护受力大等是其主要特点;给出了施工监测控制基准值,指出浅埋应按变形控制,深埋应按变形与受力双重标准控制。4.针对三种工法提出改进与优化,并进行了力学验证。5.针对黄土围岩中锚杆的拉拔试验,修正了基于剪滞理论的锚杆轴力与剪力计算式,并用于评价锚杆-围岩界面强度;基于中性点理论研究了锚杆-黄土围岩的相互作用机制,指出围岩不同部位的变形模式是锚杆作用与受力大小的决定性因素。6.采用数值分析与现场1:1原型支护试验结果,对系统锚杆在黄土隧道中的锚固效果进行了研究,指出拱部锚杆作用小,边墙锚杆有一定作用。7.根据黄土的结构性及喷射混凝土硬化,建立了支护钢架+喷混组合体的平面受力分析方法,得出快速硬化条件下格栅+喷混与型钢+喷混支护能力相当。8.采用三维分析方法,对型钢与格栅在大断面黄土隧道中的支护机制与支护能力进行了分析,指出两者的主要差别在于对水平位移的约束上,而对约束拱部的整体沉降差别不大。9.采用现场1:1原型支护试验结果对格栅与型钢的支护性能进行对比分析,发现快速硬化条件下两者差距不大,均可在断面黄土隧道中采用。更多还原

【Abstract】 With much domestic investment being used for transport infrastructure, groups of loess tunnels with large cross section will soon appear in the west of China. The railway passenger delicated line from Zhengzhou to Xi’an, which has taken the lead in building, includes a lots of loess tunnels. These tunnels have a cross section of more than 170 m~2 that broke the history record in loess region. Loess ground is so special and weak that this building project will have to encounter huge challenge. At present, there is quite a lack in relative construction & design experience and necessary guidance of criterion for large loess tunnel, for that reason the research of constructing technology and support theory seems very urgent. This dissertation firstly carries out a study on the mechanical behavior of large loess tunnel by multiform methods.1. Through the research of special loess property in passenger delicated line, it is pointed out that loess’s structural strength could be concluded into bilinear yielding rule, and that vertical joint could be treated as ubiquitous joint. Both of them have different growth environment.2. According to loess’s special property, bilinear constitutive model should be adopted for tunnel’s mechanical analysis. The results reveal that structural strength, with a little effect on displacement form, affects mainly plastic zone and the magnitude of displacement, and that vertical joint affect not only displacement mode but also breakage form of wall rock.3. By three-dimensional numerical method and monitoring data from experimental tunnel, constructing schemes that include method of double side-wall, CRD and arch lead hole, has been studied in dynamic mechanics process. It comes to the conclusion that either shallow burial or deep burial is not enough secure. Some typical characters, such as big displacement magnitude and release ratio, durative deformation and high early deformation, great support stress, etc, will occur synchronously in large loess tunnel. Monitoring method suggests support deformation should be controlled in shallow burial condition, and double control of support stress and deformation should be done in deep burial condition.4. Based on mechanical character of three methods above, countermeasure or optimization is proposed to make the tunnel construction safe. Numerical analysis validates the amendatory effect.5. To obtain cohesion strength between rockbolt and loess ground, shear-lag theory is modified to evaluate rockbolt pull-out test. On the basis of midpoint principle and data fit of numerical analysis, interaction mechanism of rockbolt-ground is studied, and finally finds that deformation mode occurring at different rock wall location will bring a critical effect to rockbolt axial force.6. Through numerical analysis and 1:1 antetype test, anchor effect of systemic rockbolt in large loess tunnel is investigated. The result shows its’ weak in the tunnel crown and work relatively well in the sidewall.7. In term of loess’ structural strength and hardening of shotcrete, plane method is created for analyzing the combined effect of steel rib and shorcrete. The outcome indicates that under fast hardening lattice girder and profiled bar have the same support effect.8. By three-dimensional numerical method, it is pointed out that the difference between lattice girder and profiled bar is in the resistance capability to horizontal displacement, not in the resistance to arch settlement.9. 1:1 antetype support experiment is used to compare lattice girder with profiled bar, detecting that under fast hardening they have a little distinction. All of them may be applied in large loess tunnel.更多还原