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1.
将围岩和衬砌分别视作均质、连续的线弹性正交各向异性和各向同性体,并充分考虑衬砌的支护滞后效应和隧洞运行时的内水压力作用,运用复变函数方法中的幂级数解法,提出了正交各向异性岩体中任意形状水工隧洞的力学解析方法。以直墙半圆拱形水工隧洞为例,所获得的解析解可精确满足衬砌内边界的应力边界条件以及围岩与衬砌接触面的应力、位移连续条件,同时还将解析结果与ANSYS数值结果对比分析,吻合良好。利用获得的解析解,讨论了围岩开挖面上不同的各向异性程度、不同的弹性对称面角度以及隧洞内不同的水压荷载对衬砌以及围岩上应力和位移分布的影响。 相似文献
2.
A numerical algorithm for simulation of 2-D (axis-symmetric) wave propagation using a multidomain approach is proposed. The method uses a cylindrical coordinate system, Chebyshev and
Fourier differential operators to calculate the spatial derivatives along the radial and vertical direction, respectively,
and a Runge–Kutta time-integration scheme. The numerical technique is based on the solution of the equations of momentum conservation
combined with the stress–strain relations of the fluid (drilling mud) and isotropic elastic media (drill string and formation).
Wave modes and radiated waves are simulated in the borehole-formation system. The algorithm satisfies the reciprocity condition
and the results agree with an analytical solution and low-frequency simulation of wave-propagation modes reported in the literature.
Examples illustrating the propagation of waves are presented for hard and soft formations. Moreover, the presence of casing,
cement, and formation heterogeneity have been considered. Since the algorithm is based on a direct (grid) method, the geometry
and the properties defining the media at each grid point, can be general, i.e., there are no limitations such as planar interfaces
or uniform (homogeneous) properties for each medium.
相似文献
3.
针对水泥环弹性模量变化对套管强度是否有帮助的讨论,采用弹性力学分析方法研究了水泥环弹性模量对不同性质地层内套管外挤荷载的影响规律。研究认为,在岩性较软的地层,应选用刚度较大的水泥环,可帮助套管抵卸一部分载荷;在地层岩性较硬时,选用刚度小的水泥环有助于提高套管抵抗外挤载荷能力。理想的水泥环特性应为高强度、低刚度。其机理是利用高强度抵御地层载荷、低刚度降低载荷传递系数,从而达到保护套管目的;单纯增加水泥环的厚度不一定能够改善套管的受力情况,只有当水泥环弹性模量大于一定值后,加大其厚度可改善套管的受力状况。因此,在实际现场中,应根据具体的地层情况,调整水泥浆特性,达到最好的固井效果。 相似文献
4.
Analytical layer element solutions for deformations of transversely isotropic multilayered elastic media under nonaxisymmetric loading 总被引：1，自引：0，他引：1
This paper presents the analytical layer element solutions for deformations of transversely isotropic elastic media subjected to nonaxisymmetric loading at an arbitrary depth. The state vectors for the nonaxisymmetric problem are deduced through the substitution of the Hu Hai‐chang solutions into the basic equations for the transversely isotropic elastic media. From the state vectors, the analytical layer element of a single layer is obtained in the Hankel transformed domain. The analytical layer element is an exact and symmetric stiffness matrix whose elements are without positive exponential functions, which can not only simplify the calculation but also improve the stability of computation. On the basis of the continuity conditions between adjacent layers, the global stiffness matrix is obtained by assembling the interrelated layer elements. The solutions for the multilayered elastic media in the transformed domain are obtained by solving the algebraic equation of the global stiffness matrix, which satisfies the boundary conditions. The actual solutions in the physical domain are further obtained by inverting the Hankel transform. Finally, some cases are analyzed to verify the solutions and evaluate the influences of the transversely isotropic character and stratified character of the media on the load–displacement responses. The numerical results show that the variations of the elastic properties between layers have a great effect on the displacements of the multilayered media. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
5.
将石油专用浮箍浮鞋用于煤矿服务钻孔的下管及固井工作中,需要解决的主要问题是如何使其在泵压达到2MPa时,阀门自动打开,容许浆液通过,否则阀门始终处于关闭状态。以清水营送料孔为例,对石油浮箍浮鞋在煤矿服务钻孔下管和固井中,如何确保浮箍浮鞋在孔底顺利打开,掌握搅拌水泥浆液的时机,从而使注浆过程一次性注完以及固井过程中采用的技术措施作了详尽说明。从实际应用来看,该方法起到了简化下管和固井施工程序,节约工程成本的效果。 相似文献
6.
桑树坪煤矿采取地面注骨料和井下注浆技术治理奥灰(奥陶纪灰岩)岩溶陷落柱时,施工的3个常规检查钻孔出现严重的水砂突涌现象,封孔难度极大,采取向孔内下入木楔、反丝止浆塞等方法均封孔失败。针对此难题,提出带压顶替注浆封孔技术,首先,向孔内注入大于套管体积的清水以确保孔内通畅,避免砂粒填充至套管内,导致封孔深度未达到套管以下稳定岩层;之后,采取低泵量向孔内多次循环注入大于套管体积的稀水泥浆;最后,待水泥浆凝固后,采取小直径钻头钻进至套管外以检查大孔径钻孔的封孔质量。该技术成功应用于3个常规检查钻孔封堵工程,实践发现:先期注浆封孔水泥浆液水灰比宜选取1︰1,单次候凝时间宜选取3~4 d,延长水泥浆候凝时间,可提高钻孔封孔质量。此技术适用于井下狭小空间作业,可防止孔口涌水涌砂,避免孔内水砂高速流动,确保封孔质量及人员安全,为封堵类似水砂突涌钻孔提供技术借鉴。 相似文献
7.
A technique is developed for the analysis of multiple underream anchor systems resting in an elastic soil. This technique may be used to consider anchor systems involving arbitrary anchor inclination and depth beneath the soil surface, as well as arbitrary number, shape, size and spacing of underreams. The approach is largely analytical in nature and involves only a fraction of the computation required for a finite element analysis. Consideration is given to the effects of anchor depth and inclination to the soil surface, and the spacing and number of underreams upon the elastic response of anchor systems. On the basis of the result from this study, a simple, approximate method for estimating the response of multiple underream anchors is proposed. This approach involves the use of several interaction charts, which are presented in the paper, and can be used as a hand method for estimating the load–displacement behaviour of quite general anchor systems to sufficient accuracy for most practical purposes. The use of the approximate approach is illustrated by an example. 相似文献
8.
Deformation of a poroelastic layer overlying an elastic half‐space due to dip‐slip faulting 
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下载免费PDF全文 An analytical solution of the plane strain problem of the deformation of a homogeneous, isotropic, poroelastic layer of uniform thickness overlying a homogeneous, isotropic, elastic half‐space due to two‐dimensional seismic sources buried in the elastic half‐space has been obtained. The integral expressions for the displacements, stresses and pore pressure have been obtained using the stress function approach by applying suitable boundary conditions at the free surface and the interface. The solution obtained is in the Laplace–Fourier transform domain. The case of a vertical dip‐slip line dislocation for the oceanic crust model of Earth is studied in detail. Schapery's formula is used for the Laplace inversion and the extended Simpson's formula for the Fourier inversion. Diffusion of pore pressure in the layer is studied numerically. Contour maps showing the pore pressure in the poroelastic layer have been plotted. The effect of the compressibility of the solid and fluid constituents on pore pressure has also been studied. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
9.
In this paper, a closed-form solution is presented for the stress and displacement distributions throughout a hollow cylinder subjected to uniform pressures acting on its internal and external boundary surfaces under plane strain conditions. The material is assumed to be elastoplastic, obeying a Mohr–Coulomb failure criterion, and exhibiting dilatant plastic deformation according to a non-associated flow rule. The newly developed analytical solution is verified through comparison with the solutions obtained from an infinite boundary problem (for which a closed-form solution exists), and numerical analyses using the program FLAC. The solution is also compared with the results of a borehole collapse test on a thick-walled hollow cylinder of synthetic shale. The analytical solution can be used to calculate the stress and displacement distributions around boreholes and other cylindrical cavities under both infinite and finite boundary conditions under both drained and undrained conditions. Copyright © 1999 John Wiley & Sons, Ltd. 相似文献
10.
The solution of static elastic deformation of a homogeneous, orthotropic elastic uniform half-space with rigid boundary due to a non-uniform slip along a vertical strike-slip fault of infinite length and finite width has been studied. The results obtained here are the generalisation of the results for an isotropic medium having rigid boundary in the sense that medium of the present work is orthotropic with rigid boundary which is more realistic than isotropic and the results for an isotropic case can be derived from our results. The variations of displacement with distance from the fault due to various slip profiles have been studied to examine the effect of anisotropy on the deformation. Numerically it has been found that for parabolic slip profile, the displacement in magnitude for isotropic elastic medium is greater than that for an orthotropic elastic half-space, but, in case of linear slip, the displacements in magnitude for an orthotropic medium is greater than that for the isotropic medium. 相似文献
11.
Richard Giot Sylvie Granet Maxime Faivre Nadia Massoussi Julie Huang 《Geomechanics and Geoengineering》2018,13(4):246-263
A transversely isotropic thermo-poroelastic constitutive law is developed and implemented in the finite element code Code_Aster (EDF, France). It is then validated using an analytic solution for an inclined borehole in a transversely isotropic medium. A strategy for identifying the parameters of the transversely isotropic thermo-poroelastic model based on an inverse method is proposed on the basis of different laboratory tests. To demonstrate the efficiency and applicability of the model, it is then applied in a three-dimensional numerical model of an underground structure in a parameter sensitivity study. The results of the modelling highlight the importance of accounting for anisotropic phenomena when determining the dimensions of underground facilities. The whole approach is presented in the paper, from model development to application to 3D numerical modelling to an engineering case study. 相似文献
12.
Neetu Garg 《Journal of Earth System Science》2009,118(6):677-687
In a pre-stressed anisotropic elastic medium, three types of quasi-waves propagate along an arbitrary direction. In general, none of the waves is truly longitudinal. The present study finds the specific directions in a pre-stressed anisotropic elastic medium along which longitudinal waves may propagate. This paper demonstrates how the propagation of longitudinal waves is affected by various pre-stresses present in the medium. The study establishes the explicit expressions defining the existence and propagation of longitudinal waves in pre-stressed anisotropic elastic medium. These expressions involve not only the direction and elastic stiffness of the medium, but also the pre-stresses present in the medium. Changes in conditions for the existence of longitudinal waves in orthotropic, monoclinic and triclinic anisotropies are discussed in detail. The most important part of the paper is a practical aspect suggested to calculate the specific directions for the existence of longitudinal waves in pre-stressed anisotropic elastic medium. In this approach, only those parameters are used that can be observed by the receiver in a geophysical experiment of wave propagation. The existence of longitudinal waves has been shown graphically using a numerical example for three types of anisotropic symmetries in elastic medium. 相似文献
13.
Existing solutions to Mandel's problem focus on isotropic, transversely isotropic, and orthotropic materials, the last two of which have one of the material symmetry axes coincide with the vertical loading direction. The classical plane strain condition holds for all these cases. In this work, analytical solution to Mandel's problem with the most general matrix anisotropy is presented. This newly derived analytical solution for fully anisotropic materials has all the three nonzero shear strains. Warping occurs in the cross sections, and a generalized plane strain condition is fulfilled. This solution can be applied to transversely isotropic and orthotropic materials whose material symmetry axes are not aligned with the vertical loading direction. It is the first analytical poroelastic solution considering mechanical general anisotropy of elasticity. The solution captures the effects of material anisotropy and the deviation of the material symmetry axes from the vertical loading direction on the responses of pore pressure, stress, strain, and displacement. It can be used to match, calibrate, and simulate experimental results to estimate anisotropic poromechanical parameters. This generalized solution is capable of reproducing the existing solutions as special cases. As an application, the solution is used to study the responses of transversely isotropic and orthotropic materials whose symmetry axes are not aligned with the vertical loading direction. Examples on anisotropic shale rocks show that the effects of material anisotropy are significant. Mandel-Cryer's effects are highly impacted by the degree of material anisotropy and the deviation of the material symmetry axes from the vertical loading direction. 相似文献
14.
This paper presents a boundary element method (BEM) procedure for a linear elastic fracture mechanics analysis in two‐dimensional anisotropic bimaterials. In this formulation, a displacement integral equation is only collocated on the uncracked boundary, and a traction integral equation is only collocated on one side of the crack surface. A fundamental solution (Green's function) for anisotropic bimaterials is also derived and implemented into the boundary integral formulation so that except for the interfacial crack part, the discretization along the interface can be avoided. A special crack‐tip element is introduced to capture the exact crack‐tip behavior. A computer program using FORTRAN has been developed to effectively calculate the stress intensity factors of an anisotropic bimaterial. This BEM program has been verified to have a good accuracy with previous studies. In addition, a central cracked bimaterial Brazilian specimen constituting cement and gypsum is prepared to conduct the Brazilian test under diametral loading. The result shows that the numerical analysis can predict relatively well the direction of crack initiation and the path of crack propagation. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
15.
In this paper a coupled finite and boundary element formulation is developed for the analysis of excavation in jointed rock. The presence of joints in the rock mass has been included implicitly by treating it as an appropriate anisotropic elastic continuum. The boundary element formulation for an anisotropic medium is briefly discussed. Good agreement has been found between numerical and analytical solutions for several example problems, demonstrating the accuracy of the present formulation. Numerical solutions are also presented for the problems of a deep circular tunnel and a basement excavated in a variety of jointed rock masses. 相似文献
16.
Elastic Solution for Deep Tunnels. Application to Excavation Damage Zone and Rockbolt Support 总被引：1，自引：1，他引：0
A. Bobet 《Rock Mechanics and Rock Engineering》2009,42(2):147-174
Summary A new formulation is presented for deep circular tunnels in rock with cylindrical anisotropy. The formulation is an exact
solution since it satisfies equilibrium, strain compatibility, and the anisotropic constitutive model. Complete solutions
have been found for two scenarios: tunnel with excavation damage zone, and tunnel with rockbolt support. The solution is based
on the assumption of a deep, circular tunnel in a medium with two homogeneous zones: an inner zone surrounding the tunnel,
which is either isotropic or anisotropic, and an outer zone, for the remainder of the medium, which is isotropic. Plane strain
conditions, elastic response of rock, rockbolts and support, and simultaneous excavation and support installation are also
assumed. For tunnels surrounded by an excavation damage zone with reduced rock properties, the tangential stresses and the
radial deformations at the tunnel wall are very sensitive to both the magnitude of stiffness reduction of the damaged rock
and the size of the damaged zone. The effect of the rockbolts on the rock is approximated by treating the rockbolt-rock composite
as a material with cylindrical anisotropy with stiffnesses related to the properties of the rock and rockbolts, and spacing
of the rockbolts. Comparisons between the analytical solution and a numerical method show small differences and provide confidence
in the approach suggested. 相似文献
17.
SummaryThe Influence of Rock Anisotropy on Stress Measurements by Overcoring Techniques A medium is anisotropic if its properties vary with direction. This is the general characteristic of many rocks, for example, schists, slates, gneisses, phyllites and other metamorphic rocks. Bedded and regularly jointed rocks also display anisotropic behavior.This paper is concerned with the influence of rock anisotropy on in-situ stress measurements. It is limited, to stress measurements by overcoring techniques for which strains and displacements are recorded either on the walls of a pilot hole at the end of one or several boreholes or within instrumented solid or hollow inclusions perfectly bonded to the surface of the pilot hole. The rock is described as homogeneous, continuous, anisotropic and linearly elastic.The following questions are answered with special emphasis on rocks that can be classed as transversely isotropic or orthotropic: the number of independent measurements obtainable in a single borehole; the number of boreholes required to determine the in-situ stress field; the influence of rock anisotropy on these numbers; the influence of the anisotropy type and the error involved by neglecting rock anisotropy.With 5 Figures 相似文献
18.
Reinhard Jung Marion Schindler Patrick Nami Torsten Tischner 《Comptes Rendus Geoscience》2010,342(7-8):636-643
The article presents a method to derive synthetic flow logs from low rate injection tests in wells, which are otherwise not accessible for logging. The tests were carried out in the 5 km deep geothermal well GPK2 in the Enhanced Geothermal System (EGS) project of Soultz-sous-Forêts (France) and were aimed at characterizing the status of the well before chemical treatments. The method consists of injecting water at constant flow rates into the well initially filled with brine. The wellhead pressure record of this test is transformed into log of the flow velocity versus depth by a technique described in the paper. Applying this method to borehole GPK2, three outlets could be detected and quantified within the cased and uncased section of this borehole. The outlet in the cased section at 3860 m absorbed 15% of the total flow. This depth corresponds to a known casing restriction, which makes the borehole inaccessible for logging operations. The two other outlets are at the casing shoe at 4420 m (15%) and at 4670 m (70%). 相似文献
19.
W. G. Pariseau 《国际地质力学数值与分析法杂志》1999,23(7):577-594
Consolidation of a poroelastic material that yields according to Drucker–Prager or Mohr–Coulomb criteria leads to a Stefan problem for time-dependent pore fluid pressure. The solution to the Stefan problem for a column of infinite depth is known and is adapted to poroelastic/plastic consolidation of a weightless material under a uniform surface load applied instantaneously and subsequently maintained constant. In this approach, the plastic potential and yield criterion need not be the same. If yielding occurs concurrently with application of load, then collapse is instantaneous. Otherwise, yielding may occur during the consolidation period. If so, then the elastic–plastic zone first appears at the surface and subsequently moves down the column. Depth to the elastic–plastic boundary is given by the simple expression Z = 2β√t where β is a constant determined from continuity conditions at the elastic–plastic boundary. Time-dependent surface displacement that occurs during consolidation is directly proportional to Z. There is little difference between elastic–plastic and purely elastic results in a numerical example because there is little difference in the respective consolidation coefficients. Elastic–plastic finite element results obtained from a column of finite depth are in close agreement with analytical results as long as the pore pressure at the bottom of the column does not change significantly from the value induced by application of the surface load. The analytical solution provides for: (1) efficient evaluation of material properties effects on consolidation, including strength and fluid compressibility, and (2) an accurate way of validating poroelastic/plastic computer codes that are based on Drucker–Prager and Mohr–Coulomb criteria. Copyright © 1999 John Wiley & Sons, Ltd. 相似文献