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121.
深埋隧洞围岩变形是一个复杂的非线性力学问题,其中岩石的蠕变全过程和扩容是两个重要的影响因素。引入扩容角考虑塑性体积变化的影响,推导Hoek-Brown屈服准则下考虑与不考虑洞周面力的深埋隧洞围岩非线性应力解。借助可描述蠕变全过程行为的河海模型,获得了围岩黏弹塑性区蠕变位移表达式。针对不同NVPB蠕变参数和不同材料参数m值情况,讨论分析了洞周面力与扩容角对隧洞洞壁蠕变位移的影响规律。结果表明:在高地应力作用下,采用非线性蠕变模型描述深埋隧洞围岩蠕变问题可获得蠕变全过程曲线;扩容角增大或洞周面力和材料参数m值减小时,相同时刻隧洞洞壁蠕变位移增大,对围岩长期稳定不利。研究结论对深埋隧洞围岩临崩预报具有一定指导意义。 相似文献
122.
Tunnels are commonly designed under seismic loading assuming “free field conditions”. However, in urban areas these structures pass beneath buildings, often high-rise ones, or are located close to them. During seismic excitation, above ground structures may cause complex interaction effects with the tunnel, altering its seismic response compared to the “free field conditions” case. The paper summarizes an attempt to identify and understand these interaction effects, focusing on the tunnel response. The problem is investigated in the transversal direction, by means of full dynamic time history analyses. Two structural configurations are studied and compared to the free field conditions case, consisting of one or two above ground structures, located over a circular tunnel. Above ground structures are modeled in a simplified way as equivalent single-degree of freedom oscillators, with proper mechanical properties. Several parameters that are significantly affecting the phenomenon are accounted for in this parametric study, namely the soil to tunnel relative flexibility, the tunnel dimensions, the tunnel burial depth and the soil properties and nonlinearities during shaking. Tunnels response characteristics are compared and discussed, in terms of acceleration, deformations and lining dynamic internal forces. Internal forces are also evaluated with analytical closed form solutions, commonly used in preliminary stages of design, and compared with the numerical predictions. The results indicate that the presence of the above ground structures may have a significant effect on the seismic response of the tunnel, especially when the latter is stiff and located in shallow depths. 相似文献
123.
The first part of this paper presents an extensive validation of four analytical solutions for the seismic design of circular tunnels. The validation is performed with a quasi-static finite element (FE) model which conforms to the assumptions of the analytical solutions. Analyses are performed for a wide range of flexibility ratios, slippage conditions at soil–lining interface, assuming both drained and undrained behaviour. Based on the numerical predictions the relative merits of the considered analytical solutions are discussed and recommendations are given for their use in design. The second part of this paper explores the use of equivalent linear soil properties in analytical solutions as an approximate way of simulating nonlinearity. The results of equivalent linear site response analyses are used as an input for the analytical solutions. The comparison of the analytical predictions with nonlinear numerical analysis results is very satisfactory. The results of this study suggest that analytical solutions can be used for preliminary design using equivalent linear properties and the corresponding compatible strain as an approximate way of accounting for nonlinear soil response. 相似文献
124.
125.
Dynamic interaction of twin vertically overlapping lined tunnels in an elastic half space subjected to incident plane waves 下载免费PDF全文
The scattering of plane harmonic P and SV waves by a pair of vertically overlapping lined tunnels buried in an elastic half space is solved using a semi-analytic indirect boundary integration equation method. Then the effect of the distance between the two tunnels, the stiffness and density of the lining material, and the incident frequency on the seismic response of the tunnels is investigated. Numerical results demonstrate that the dynamic interaction between the twin tunnels cannot be ignored and the lower tunnel has a significant shielding effect on the upper tunnel for high-frequency incident waves, resulting in great decrease of the dynamic hoop stress in the upper tunnel; for the low-frequency incident waves, in contrast, the lower tunnel can lead to amplification effect on the upper tunnel. It also reveals that the frequency-spectrum characteristics of dynamic stress of the lower tunnel are significantly different from those of the upper tunnel. In addition, for incident P waves in low-frequency region, the soft lining tunnels have significant amplification effect on the surface displacement amplitude, which is slightly larger than that of the corresponding single tunnel. 相似文献
126.
在上跨隧道的基坑工程中基坑开挖常引起下卧隧道发生结构变形,限制隧道的隆起变形成为基坑施工控制的关键。详细介绍了该类工程的特点,包括交叉形式、隧道变形特点、常见控制措施等,对近期国内发生的39例类似工程进行分类总结,分析了隧道纵向最大隆起变形与各影响因素间的关系,并提出了隧道最大隆起变形的预测模型。结果表明,该类工程中工程地质对隧道的隆起变形影响较大,工程地质条件越差隧道的隆起变形越难控制;开挖深度、基坑面积、基坑形状同样是影响隧道隆起变形的重要因素,基坑开挖面积及深度越大,形状越不规则,隧道的隆起变形越大;在软土地区,当基坑开挖面积及深度较大时设置抗拔桩能显著减小隧道的最大隆起变形。 相似文献
127.
The impact of the incident angle of earthquake motion on the seismic response of the long lined tunnels is studied. Based on the time‐domain finite element method with the viscous‐spring artificial boundary condition, the earthquake motion of oblique incidence is transformed into the equivalent nodal forces acting on the truncated boundary of finite element model. In the present work, the formulas of equivalent nodal forces for the plane P wave with arbitrary incident angle are deduced and implemented into the commercial software abaqus 1 . The effectiveness of the formulas and its implementation are demonstrated by two numerical examples with the reference solutions. The proposed method is applied to investigate the seismic responses of the long lined tunnels under the obliquely incident P waves. The numerical results indicate that the seismic responses of the long lined tunnels are highly affected by the incident angles of P waves. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
128.
This paper describes finite element procedures that have been developed to model the ground movements that occur when a shallow tunnel is installed in a clay soil. This study is part of a wider project concerned with the development of new methods to predict the likely extent of damage to surface structures caused by nearby shallow tunnelling. This particular paper, however, is concerned only with the numerical model of tunnel installation. The structural liner is an important component of this tunnel installation model; two different ways of modelling the liner (based on continuum elements and shell elements) are discussed in the paper. A test problem consisting of the installation of a lined tunnel in an elastic continuum is used to investigate the merits of these different approaches. When continuum elements are used to model the liner, the numerical results agree well with an analytical solution to the problem. When shell elements are used to model the liner, however, the results were found to be significantly influenced by the particular formulation adopted for the shell elements. Example analyses, involving incremental tunnel construction in a clay soil where the soil is modelled using a kinematic hardening plasticity model, are described. These analyses confirm that a thin layer of continuum elements may be used, satisfactorily, to model tunnel linings in a soil–structure interaction analysis of this sort. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
129.
并行隧道围岩应力的线弹性分析 总被引:3,自引:0,他引:3
间距较小的并行隧道,两洞室开挖的相互影响不能忽略。引入双圆洞室围岩应力函数的线弹性方程,并通过编程实现工程计算,探讨了间距较小的并行双圆隧道围岩的应力特点以及应力随净距改变的变化规律,为间距较小的并行隧道围岩状态的定性判断提供了依据。 相似文献
130.
Cynthia Sorrensen 《Geographical review》2014,104(3):328-345
The number of unauthorized tunnels discovered through the U.S.–Mexico border has risen dramatically since the mid‐1990s. These tunnels are problematic for the state because the subterranean border is both less visible and more difficult to monitor and control than is the surface border. In this era of heighten security, the debate on secure borders has intensified. As a result, the need to demonstrate security success at both the national and the agency level has risen. Efforts to make tunnel discoveries (and security) visible are made within border‐security agencies and within national discourse and legislation. These efforts spatially fix tunnels to the border in ways that obscure fuller a understanding of drug trafficking in general. This paper employs archival research, content analysis, and informal interviews with security‐enforcement agents to consider the material presence of tunnels within border landscapes. 相似文献