3-D seismic response analysis of long lined tunnels in half-space   总被引：4，自引：0，他引：4  

A.A. Stamos  D.E. Beskos 《Soil Dynamics and Earthquake Engineering》1996,15(2):111

The dynamic response of infinitely long lined tunnels with a uniform cross-section buried into an elastic or viscoelastic half-space to body and surface harmonic seismic waves is numerically determined by a special direct boundary element method in the frequency domain. The waves have an arbitrary direction of propagation with respect to the axis of the tunnel and this renders the problem three-dimensional. However, this problem is effectively reduced to a two-dimensional one by a coordinate transformation and appropriate integration of the full-space dynamic fundamental solution along the direction of the tunnel axis. Quadratic isoparametric boundary line elements and advanced numerical integration techniques for the treatment of singular integrals produce results of high accuracy. Numerical results are presented for the case of an infinitely long lined tunnel of circular cross-section and compared against those of a full three-dimensional boundary element analysis, as well as those of other methods. Thus the proposed method is illustrated and its merits demonstrated.  相似文献   

Pile responses to side-by-side twin tunnelling in stiff clay: Effects of different tunnel depths relative to pile     

《Computers and Geotechnics》2017

In densely built areas, the development of underground transportation systems often involves twin tunnels, which are sometimes unavoidably constructed adjacent to existing piled foundations. Because soil stiffness degrades with induced stress release and shear strain during tunnelling, it is vital to investigate the pile responses to subsequent tunnels after the first tunnel in a twin-tunnel transportation system. To gain new insights into single pile responses to side-by-side twin tunnelling in saturated stiff clay, a three-dimensional coupled-consolidation numerical parametric study is carried out. An advanced hypoplasticity (clay) constitutive model with small-strain stiffness is adopted. The effects of each tunnel depth relative to pile are investigated by simulating the twin tunnels either near the mid-depth of the pile shaft or adjacent to or below the pile toe. The model parameters are calibrated against centrifuge test results in stiff clay reported in literature. It is found the second tunnelling in each case resulted in larger settlement than that due to the first tunnelling with a maximum percentage difference of 175% in the case of twin tunnelling near the mid-depth of the shaft. This is because of the degradation of clay stiffness around the pile during the first tunnelling. Conversely, the first tunnelling-induced bending moment was reduced substantially during the second tunnelling. The most critical location of twin tunnels relative to the pile was found to be the tunnels below the pile toe. This is because the entire pile was located within the major influence zone of the twin tunnelling. Two distinct load transfer mechanisms can be identified in the pile, namely downward load transfer in case of tunnels near mid-depth of the pile shaft and next to the pile toe and upward load transfer in case of twin-tunnelling below the pile toe. These two transfer mechanisms can be useful for practitioner to assess the pile performance due to twin tunnelling.  相似文献   

水平及竖向地震共同作用下双线隧道的响应分析     

王杰  刘华北  邹炎  阮滨 《震灾防御技术》2020,15(4):670-683

基于有效的土-结相互作用有限元数值模拟方法,利用有限元软件ABAQUS对水平及竖向地震共同作用下双线盾构隧道的地震响应进行分析研究。地震动输入选取近场地震Loma、ChiChi、Mammoth和WoLong的基岩水平及竖向加速度时程记录。结果表明,不同近场地震记录对隧道结构的作用不同,隧道的地震反应与场地性质及地震动的频谱特性密切相关。对比隧道在水平及竖向地震动共同作用下的响应与单向水平地震动作用下的响应,发现隧道的最大地震附加内力及其分布均发生较大的变化,在隧道结构抗震设计中需引起重视。另外,分析中还考虑了在双向地震动共同作用下,隧道间距、土-结接触面的摩擦系数、土-结相对刚度、输入的地震记录和竖向地震动相对强度对隧道地震响应的影响等,研究结果对隧道工程的抗震设计具有一定的参考价值。  相似文献   

Diffraction of anti-plane SH waves by a semi-circular cylindrical hill with an inside concentric semi-circular tunnel   总被引：8，自引：3，他引：5  

Vincent W.Lee  罗昊  梁建文 《地震工程与工程振动(英文版)》2004,3(2):249-262

A closed-form analytic solution of two-dimensional scattering and diffraction of plane SH waves by a semicylindrical hill with a semi-cylindrical concentric tunnel inside an elastic half-space is presented using the cylindrical wave functions expansion method. The solution is reduced to solving a set of infinite linear algebraic equations. Fourier expansion theorem with the form of complex exponential function and cosine function is used. Numerical solutions are obtained by truncation of the infinite equations. The accuracy of the presented numerical results is carefully verified.  相似文献   

Making the Subterranean Visible: Security,Tunnels, and the United States–Mexico Border     

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   

A finite strain solution for the elastoplastic ground response curve in tunnelling: rocks with non‐linear failure envelopes          下载免费PDF全文

Apostolos Vrakas 《国际地质力学数值与分析法杂志》2017,41(7):1077-1090

This paper generalizes the finite strain Coulomb solution of Vrakas and Anagnostou (Int J Numer Anal Meth Geomech 2014; 38(11): 1131–1148) for the classic tunnel mechanics problem of the ground response curve to elastoplastic grounds satisfying a non‐linear Mohr's failure criterion. A linear (Coulomb‐type) plastic potential function is used, leading to a non‐associated flow law, and edge plastic flow is considered in the plastic zone. The solution for a general non‐linear Mohr's failure criterion is semi‐analytical in that it requires the evaluation of definite integrals. In the special case of the Hoek–Brown criterion, however, these integrals are calculated analytically, resulting in a rigorous closed‐form series solution. The applicability of the derived solution is illustrated through the example of the Yacambú‐Quibor tunnel, where very large deformations were observed when crossing of weak graphitic phyllites. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

A finite strain closed‐form solution for the elastoplastic ground response curve in tunnelling     

Apostolos Vrakas  Georgios Anagnostou 《国际地质力学数值与分析法杂志》2014,38(11):1131-1148

The ground response to tunnel excavation is usually described in terms of the characteristic line of the ground (also called ‘ground response curve’, GRC), which relates the support pressure to the displacement of the tunnel wall. Under heavily squeezing conditions, very large convergences may take place, sometimes exceeding 10–20% of the excavated tunnel radius, whereas most of the existing formulations for the GRC are based on the infinitesimal deformation theory. This paper presents an exact closed‐form analytical solution for the ground response around cylindrical and spherical openings unloaded from isotropic and uniform stress states, incorporating finite deformations and linearly elastic‐perfectly plastic rock behaviour obeying the Mohr–Coulomb failure criterion with a non‐associated flow rule. Additionally, the influence of out‐of‐plane stress in the case of cylindrical cavities under plane‐strain conditions is examined. The solution is presented in the form of dimensionless design charts covering the practically relevant parameter range. Finally, an application example is included with reference to a section of the Gotthard Base tunnel crossing heavily squeezing ground. The expressions derived can be used for preliminary convergence assessments and as valuable benchmarks for finite strain numerical analyses. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

A new closed‐form solution for analysis of unlined pressure tunnels under seepage forces     

Ahamad Fahimifar  Mohammad Reza Zareifard 《国际地质力学数值与分析法杂志》2013,37(11):1591-1613

In this study, a simplified analytical closed‐form solution, considering plane strain and axial symmetry conditions, for analysis of a circular pressure tunnel excavated underwater table, is developed. The method accounts for the seepage forces with the steady‐state flow and is based on the generalized effective stress law. To examine the effect of pore pressure variations and also the boundary conditions at the ground surface, the formulations are derived for different directions around the tunnel. The proposed method can be applied for analysis and design of pressure tunnels. Illustrative examples are given to demonstrate the performance of the proposed solution and also to examine the effect of seepage forces on the stability of tunnels. The simplified analytical solution derived in this study is compared with numerical analyses. It is concluded that the classic solutions (Lame's thick‐walled solution), considering the internal pressure as a mechanical load applied to the tunnel surface, are not applicable to pervious media and can result in an unsafe design. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Analytical solution of the harmonic waves diffraction by a cylindrical lined cavity in poroelastic saturated medium     

Y. S. Karinski  V. V. Shershnev  D. Z. Yankelevsky 《国际地质力学数值与分析法杂志》2007,31(5):667-689

This paper presents a model for the analysis of plane waves diffraction at a cavity in an infinite homogeneous poroelastic saturated medium, lined by a lining composed of four equal segments. An elastic boundary layer is placed between the cavity lining and the infinite porous medium. The boundary layer is simulated by ‘elastic boundary conditions’ in which the bulk matrix stress is proportional to the relative displacement between the lining and the surrounding medium matrix boundary. In addition, fluid impermeability through the intermediate layer is assumed. For the frequencies, that differ from the pseudoresonanse frequencies, the problem was reduced to the problem of an ideal elastic medium. A closed‐form analytical solution of the problem was obtained using Fourier–Bessel series, the convergence of which was proven. It was shown that the number of series terms required to obtain a desired level of accuracy can be determined in advance. The influence of the medium porosity on the medium dynamic stress concentration was studied. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

并行隧道围岩应力的线弹性分析   总被引：3，自引：0，他引：3  

胥润东  徐林生 《岩土工程技术》2005,19(3):127-129

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