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1.
在既有公路下进行浅埋隧道开挖会引起地层产生位移,导致地表沉降。为了保证施工安全,快速精确地计算地层位移及应力,有效地控制地表沉降,对浅埋隧道的设计与施工均十分重要。在镜像法原理的基础上,引入等效模量当层法,推导出了在有上覆不同材料下浅埋圆形隧道开挖引起地层位移、应力及地表沉降的解析分布规律。计算结果表明,既有路基下开挖隧道引起地层产生的位移和应力解析解能够很好地体现上层高弹性模量路基对沉降及应力的扩散作用,可以求得隧道开挖后洞周地层包括上覆路基及下卧层中任意位置处的位移、应力以及地表沉降,为在双层地基材料中开挖浅埋隧道引起地层位移及地表沉降的计算提供了一种新的解析方法。 相似文献
2.
深埋圆形隧道弹塑性位移统一解及其比较分析 总被引：1，自引：0，他引：1
基于统一强度理论和非关联线性流动法则,考虑塑性区的真实弹性应变,推导了深埋圆形隧道弹塑性位移统一解。位移统一解合理地考虑了中间主应力效应和围岩剪胀特性的影响,具有广泛的理论意义。经与文献简化位移解析解比较分析知,围岩塑性区的弹性应变对隧道位移影响显著,简化解析解所得结果偏小,简化解析解和文中统一解之间的差异与中间主应力效应和围岩剪胀特性密切相关;考虑中间主应力的影响,能更加充分发挥围岩的强度潜能;隧道支护设计应考虑围岩剪胀特性的重要影响 相似文献
3.
By applying the series expansion technique in the complex variable method established by Muskhelishvili, the plane elasticity problem for the stress and displacement field around a lined circular tunnel in conjunction with the consideration of misfit and interaction between the liner and the surrounding geomaterial is dealt with. The tunnel is assumed to be driven in a homogeneous and isotropic geomaterial. The coefficients in the Laurent series expansion of the stress functions are determined. The complex potentials in the liner and the surrounding geomaterial are explicitly derived, respectively. As an example, the case of a lined circular tunnel located in an isotropic initial stress field but subjected to uniform internal pressure is numerically considered. Numerical results indicate that the installation of tunnel liner can reduce the influences of the tunnel excavation on the in situ displacement and stress fields. However, the relative thickness and rigidity of the liner should be in an appropriate range. In addition, the effect of the tunnel excavation upon the displacement field is more significant than that upon the stress field. As far as the stress field in the surrounding geomaterial is concerned, when the ratio between the cover depth of tunnel and the tunnel radius is larger than 5, the results for the stress field in the paper are applicable. When the ratio between the tunnel depth and the tunnel radius is larger than 20, the results are applicable for the displacement field. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
4.
An analytical model which represents the behaviour of a reinforced rock mass near a circular underground opening in a homogeneous, uniform stress field has been developed. The theory adopts the concepts of elastoplasticity and considers a proper interaction mechanism between the ground and the grouted (or friction) bolts. It highlights the influence of the bolt pattern on the extent of the yield zone and tunnel deformation. A dimensionless parameter is introduced as a design tool which relates the tunnel convergence to the bolt spacing for a given bolt length. This publication contains the derivation of the analytical model and an illustration of the effect of bolts on the stress and displacement field near an opening. Its application to tunnel design is discussed briefly. The verification of the theory by laboratory simulation and field measurements will be presented, in detail, in a future publication. 相似文献
5.
地下圆形衬砌隧道对沿线地震动的影响(II):数值结果 总被引：5，自引：3，他引：5
利用地下圆形衬砌隧道对入射平面P波和SV波散射级数解答，定量分析了入射波长、入射角度、隧道直径、衬砌刚度等因素对沿线地表位移放大作用的影响。计算结果表明，当入射频率较低时，地下隧道的存在对地表位移幅值影响不大；而当入射频率较高时，地表位移幅值可以达到无隧道情况的4．5倍以上；衬砌情况下地表位移幅值可以高出非衬砌情况的87．8％。建议在地铁的规划设计中考虑地下隧道的建设对隧道沿线设计地震动的影响。 相似文献
6.
The Applicability of the Ground Response Curve to Tunnelling Problems that Violate Rotational Symmetry 总被引：1，自引：1，他引：0
The applicability limits of the closed-form solution to the problem of ground response to tunnelling are sounded out by systematically
investigating the effect of deviations from some of the important assumptions underlying the closed-form solution. The ground
response curve (GRC) expresses the relationship between tunnel support pressure and the radial displacement of the tunnel
boundary on the basis of a rotationally symmetric model. The assumptions underlying rotational symmetry are a circular tunnel,
a hydrostatic and uniform initial stress field, an isotropic and homogeneous ground and uniformly distributed support pressure.
Deviations from these assumptions generally necessitate potentially time-consuming numerical analyses. The paper revisits
the classical problem of tunnel excavation in a linearly elastic, perfectly plastic ground obeying the Mohr–Coulomb yield
criterion, and analyses the effects of non-uniformity and anisotropy of the initial stress field and of a non-circular tunnel
geometry. The results show that the GRC also provides a reasonably accurate approximation of average tunnel convergence for
a wide range of ground conditions that violate rotational symmetry. 相似文献
7.
A new closed-form solution is presented for the stress and displacement distribution surrounding circular openings with finite external radii that are subject to uniform internal and external pressures under plane strain conditions. The specific solution for a deep circular tunnel in an infinite rock mass is also provided. It is assumed that the rock mass is elastic–brittle–plastic and governed by the Unified Strength Theory (UST). In the plastic zone, the radius-dependent Young’s modulus (RDM) model and a non-associated linear flow rule were adopted to establish the radial displacement solution. The new closed-form solution obtained in this paper is a series of results rather than one specific solution; hence, it is suitable for a wide range of rock masses and engineering structures. The traditional solutions, which are based on the Mohr–Coulomb failure criterion and the Generalized Twin Shear Stress yield criterion, can be categorized as special cases of this proposed solution. This new solution agrees reasonably well with the results of a borehole collapse test, a secondary development numerical simulation and an additional closed-form solution using the generalized non-linear Hoek–Brown failure criterion. Parametric studies were conducted to investigate the effects of intermediate principal stress, RDM and dilatancy on the results. It is shown herein that the effects of intermediate principal stress and dilatancy are significant; the RDM model is recommended as the optimum approach for calculating radial displacement and support pressure. 相似文献
8.
9.
An analytical solution to the problem of a load applied to a portion of the wall of a circular tunnel installed deep in a homogeneous isotropic material has been found. The solution is obtained by taking a Fourier transform, in the axial direction, of the field quantities and then representing these as a Fourier series in the polar angle. The integration which is necessary for the inversion of Fourier transforms has to be performed numerically using Gaussian quadrature. The solution has been used to analyse the problem of uniform normal loading applied over rectangular patches of the tunnel wall. An indication of how the solution can be applied to the tunnel jacking problem is given. 相似文献
10.
横观各向同性岩体中圆形巷道反分析的惟一性 总被引：1，自引：1，他引：0
惟一性研究是位移反分析的基础工作之一。推导了横观各向同性岩体中圆形巷道的位移解析解,利用参数可辨识条件对横观各向同性岩体中圆形巷道位移反分析的惟一性进行了探讨。结果表明,无论量测多少个点的位移也不能惟一地反演出所有6个参数;必须至少已知3个参数时,才有可能惟一地反演其他参数;2个地应力分量是否相等对反分析结果有明显的影响;2个地应力分量的可辨识性最好,各向同性面上的弹性模量和泊松比次之,垂直各向同性面方向的弹性模量和泊松比最差。 相似文献
11.
This paper presents an analytical solution for the prediction of internal forces and displacements of a jointed segmental precast circular tunnel lining. The effects of joint stiffness on the performance of the tunnel lining are discussed. The ‘force method’ is used to determine the internal forces and displacements of jointed tunnel lining. Five shield‐driven tunnel cases are adopted to study the effects of joint stiffness, soil resistance, joint distribution and joint number on the internal forces and displacements of circular tunnels. Laboratory model tests are conducted to verify the proposed analytical solution. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
12.
离散单元法适合室内试验和局部小尺度问题的模拟,但在分析隧道开挖等大尺度问题时计算复杂且耗时.为拓展离散元在大尺度问题分析中的适用性,尝试将离散元与理论解分区耦合.针对深埋圆形隧道围岩开挖过程,采用离散元模拟内部近孔口处围岩,外部采用理论解,耦合边界上使用迭代算法,控制收敛以保证力与位移连续条件,在弹性阶段范围内对两区域进行耦合以分析解法的适用性和误差.针对隧洞有、无内压两类算例,采用该分区耦合方法经15步左右迭代收敛,所得边界位移与理论解分别相差1.86%、3.2%;所得离散元结果与理论解对比良好：位移误差随角度有关、最大处在13.5%以内,应力误差除在少量部位为15%左右外,其余各处在8.6%以内.据此表明,该方法具有相当的精度及可行性. 相似文献
13.
通过采用均匀化方法,研究了圆形隧洞的锚杆支护特性,将高密度支护模式下的岩石和锚杆复合体考虑成均匀、连续、强度参数增强的等效材料,简化了岩石和锚杆间复杂的力学耦合问题。通过定义锚杆密度参数来反映不同支护模式的特性,建立锚杆密度参数与Mohr-Coulomb屈服准则中主要参数之间的关系,推导出等效弹性模量、等效黏聚力和等效内摩擦角的表达式,并分析比较了隧洞在支护前后的位移情况。结合可靠性理论,采用容许极限位移量作为失稳判据,分析了隧洞在支护前后的可靠性指标与破坏概率,结果表明,文中提出的方法简单可靠,锚杆支护对隧洞的位移限制效果明显,可显著提高隧洞的可靠性。 相似文献
14.
Analytical and Numerical Study of the Mechanics of Rockbolt Reinforcement around Tunnels in Rock Masses 总被引：1，自引：0，他引：1
C. Carranza-Torres 《Rock Mechanics and Rock Engineering》2009,42(2):175-228
Summary This paper addresses the problem of quantifying the mechanical contribution of rockbolts installed systematically around tunnels
excavated in rock masses. The mechanical contribution referred to here is that of increased stress confinement and decreased
tunnel convergences as compared with corresponding stresses and displacements obtained for non-reinforced tunnels. The problem
is treated analytically first by presenting a closed-form solution for stress and displacement distributions around a circular
tunnel excavated in elastic material and reinforced by grouted or anchored rockbolts. The analytical solution assumes that
rockbolts are regularly spaced around the tunnel and that axi-symmetry conditions of geometry and loading apply. The results
obtained with the closed-form solution are shown to be equivalent to the results of the same problem solved with traditional
numerical methods. Based on the analytical and numerical results and by introducing dimensionless ratios that allow to quantify
the increase of radial stresses and the decrease of radial displacements in the reinforced region of the tunnel, the paper
shows that reinforcement can have a significant mechanical effect (i.e., increasing the confinement and decreasing the convergences)
in tunnels excavated in rock masses of poor to very poor quality. The paper analyzes then the mechanical contribution of rockbolt
reinforcement when the rock mass is assumed to behave elasto-plastically. For this case, it is shown that rockbolt reinforcement
can also have a critical effect in controlling the extent of the plastic failure zone and the convergences of the tunnel.
Correspondence: C. Carranza-Torres, Department of Civil Engineering, University of Minnesota, Duluth Campus, 1305 Ordean Court,
Duluth, USA 相似文献
15.
The interaction between twin‐parallel tunnels affects the tunnelling‐induced ground deformation, which may endanger the nearby structures. In this paper, an analytical solution is presented for problems in determining displacements and stresses around deforming twin‐parallel tunnels in an elastic half plane, on the basis of complex variable theory. As an example, a uniform radial displacement was assumed as the boundary condition for each of the two tunnels. Special attention was paid to the effects of tunnel depth and spacing between the two tunnels on the surface movement to gain deep insight into the effect of the interaction between twin‐parallel tunnels using the proposed analytical approach. It is revealed that the influence of twin tunnel interaction on surface movements diminishes with both the increase of the tunnel depth and the spacing between the two tunnels. The presented analytical solution manifests that, similar to most of the existing numerical results, the principle of superposition can be applied to determine ground deformation of twin‐parallel tunnels with a certain large depth and spacing; otherwise, the interaction effect between the two tunnels should be taken into account for predicting reliable ground movement. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
16.
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
17.
Complex variable analysis for stress distribution of an underwater tunnel in an elastic half plane 
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下载免费PDF全文 When an underwater tunnel is excavated, the groundwater may flow into the tunnel. The seepage forces consequently induced can have important effects on the effective stresses around the tunnel. Moreover, the influences of the free surface of a shallow underwater tunnel should also be considered. In this research, an analytical solution is presented to calculate the seepage‐induced effective stresses around a shallow underwater tunnel in an elastic half plane. The solution uses the complex variable method and consists of conformally mapping the half plane with a hole onto a transformed circular ring. The coefficients of the various terms in the Laurent series expansions of the stress functions in the transformed region can be obtained from the boundary conditions. The total stress distribution around a shallow underwater tunnel can be calculated by the potentials in the half plane. The effective stress can be obtained by subtracting the pore pressure from the total stress. The analytical solution is validated by numerical simulations and can be used to perform both the short‐term and long‐term analyses. By using the proposed solution, it is found that the circumferential effective stresses around the tunnel increase greatly because of seepage, and they increase with the increase of water depth in both the undrained and drained conditions. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
18.
Finite strain elastoplastic solutions for the undrained ground response curve in tunnelling 下载免费PDF全文
下载免费PDF全文 The instantaneous response of saturated low permeability grounds to tunnel excavation is important for deformations and stability close to the tunnel face. It is characterized by zero volume change in combination with the development of excess pore pressures. In tunnelling through poor quality ground under great depth of cover and high in situ pore pressure, heavily squeezing conditions (characterized by very large convergences) may occur soon after excavation. This paper presents exact finite strain analytical solutions for the undrained ground response around cylindrical and spherical openings that are unloaded from uniform and isotropic initial stress states, on the basis of the Modified Cam Clay (MCC) model and the Mohr–Coulomb (MC) model. The solution for a Drucker–Prager material is also given as it requires only a very small modification to the MC solution. The so‐called ground response curve, that is, the relationship between the support pressure and the cavity wall displacement, is derived in closed form for the MC model. The solution for the MCC problem is semi‐analytical in that it uses the trapezium rule for the computation of a definite integral. The influence of the significant parameters of the problem on the predicted deformation behaviour is shown by means of dimensionless charts. Finally, the practical usefulness of the solutions presented is illustrated by applying them to the breccia zones of the planned Gibraltar Strait tunnel – an extreme case of weak, low permeability ground under high pore pressure. The solutions can serve as a trustworthy benchmark for numerical procedures that incorporate material and geometric nonlinearities. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
19.
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
20.
An analytical solution is presented for a buoyant tunnel in an elastic half‐plane. The tunnel undergoes a prescribed displacement along its boundary, and the surface of the half‐plane is stress‐free. The solution uses the complex variable method and consists of conformally mapping the hole and half‐plane to an annular region. The complex potentials each contain two logarithmic terms due to the resultant buoyancy force acting on the tunnel, and as a result the displacements at infinity are unbounded. An example is presented for the case of a rigid buoyant tunnel in a half‐plane with gravity loading. Even though the tunnel does not deform, the buoyancy effect can be clearly seen in the contours of the displacements and stresses. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献