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1.
Local gas pipelines provide a valuable resource to urban areas and are often forced to cover unfavourable ground conditions in order to form a serviceable network. This can force pipelines through soil, which is subjected to permanent ground displacements due to faulting and strong vibrations due to earthquakes. Due to the inseparability of faulting from earthquakes it is pertinent to examine the combined effect of dynamic vibration and shear deformation of the surrounding soil on buried pipelines and a better understanding of the factors affecting pipe response to these inputs will enable more intelligent design of future pipe networks with the intention of reducing damage inflicted on pipes in extreme events. To advance understanding of this topic, a series of model experiments were performed under 1 g conditions on instrumented 20 mm diameter acrylic prototype pipes buried in dry Toyoura sand as well as a tyre derived aggregate (TDA) backfill trench surrounded by Toyoura sand crossing a vertical fault. The apparatus setup allowed faulting and dynamic input to be applied simultaneously to the model, which revealed that the simultaneous loading reduces the bending of a pipe and that installation of a pipe in a tyre derived aggregate backfill reduces the bending moment experienced by the pipe by up to 74% for small fault displacement and low levels of acceleration. 相似文献
2.
输气管道作为1种薄壁壳体结构,逆冲断层引起的管道压缩变形容易使其破坏。本文以大北南疆输气管道工程为例,探讨了穿越克孜尔逆冲断层的输气管道地震安全问题。在确定管道穿越处的断层倾角、设防断层位错量、表征管土相互作用的土弹簧参数以及钢管容许应变等参数后,采用壳有限元方法,分析了穿越克孜尔逆冲断层的输气管道变形反应。分析结果显示,管道在逆冲断层作用下以压缩应变为主,管道内的最大轴向压缩应变的幅值随着交角的减小而减小。在通过探槽等方法确定断层活动位置后,该管道若以小于或等于11°的交角通过克孜尔断裂,断层引起的最大轴向压缩应变和拉伸应变均在管道相应的容许应变范围内,满足相关规范的抗震要求。 相似文献
3.
Seismic ground faulting is the greatest hazard for continuous buried pipelines.Over the years,researchers have attempted to understand pipeline behavior mostly via numerical modeling such as the finite element method.The lack of well-documented field case histories of pipeline failure from seismic ground faulting and the cost and complicated facilities needed for full-scale experimental simulation mean that a centrifuge-based method to determine the behavior of pipelines subjected to faulting is best to verify numerical approaches.This paper presents results from three centrifuge tests designed to investigate continuous buried steel pipeline behavior subjected to normal faulting.The experimental setup and procedure are described and the recorded axial and bending strains induced in a pipeline are presented and compared to those obtained via analytical methods.The influence of factors such as faulting offset,burial depth and pipe diameter on the axial and bending strains of pipes and on ground soil failure and pipeline deformation patterns are also investigated.Finally,the tensile rupture of a pipeline due to normal faulting is investigated. 相似文献
4.
This paper deals with seismic wave propagation effects on buried segmented pipelines. A finite element model is developed for estimating the axial pipe strain and relative joint displacement of segmented pipelines. The model accounts for the effects of peak ground strain, shear transfer between soil and pipeline, axial stiffness of the pipeline, joint characteristics of the pipeline, and variability of the joint capacity and stiffness. For engineering applications, simplified analytical equations are developed for estimating the maximum pipe strain and relative joint displacement. The finite element and analytical solutions show that the segmented pipeline is relatively flexible with respect to ground deformation induced by seismic waves and deforms together with the ground. The ground strain within each pipe segmental length is shared by the joint displacement and pipe barrel strain. When the maximum ground strain is higher than 0.001, the pipe barrel strain is relatively small and can be ignored. The relative joint displacement of the segmented pipeline is mainly affected by the variability of the joint pullout capacity and accumulates at locally weak joints. 相似文献
5.
Polynikis Vazouras Spyros A. Karamanos Panos Dakoulas 《Soil Dynamics and Earthquake Engineering》2010
The present paper investigates the mechanical behavior of buried steel pipelines, crossing an active strike-slip tectonic fault. The fault is normal to the pipeline direction and moves in the horizontal direction, causing stress and deformation in the pipeline. The interacting soil–pipeline system is modelled rigorously through finite elements, which account for large strains and displacements, nonlinear material behavior and special conditions of contact and friction on the soil–pipe interface. Considering steel pipelines of various diameter-to-thickness ratios, and typical steel material for pipeline applications (API 5L grades X65 and X80), the paper focuses on the effects of various soil and pipeline parameters on the structural response of the pipe, with particular emphasis on identifying pipeline failure (pipe wall wrinkling/local buckling or rupture). The effects of shear soil strength, soil stiffness, horizontal fault displacement, width of the fault slip zone are investigated. Furthermore, the influence of internal pressure on the structural response is examined. The results from the present investigation are aimed at determining the fault displacement at which the pipeline fails and can be used for pipeline design purposes. The results are presented in diagram form, which depicts the critical fault displacement, and the corresponding critical strain versus the pipe diameter-to-thickness ratio. A simplified analytical model is also developed to illustrate the counteracting effects of bending and axial stretching. The numerical results for the critical strain are also compared with the recent provisions of EN 1998-4 and ASCE MOP 119. 相似文献
6.
地震断层作用下的埋地管道等效分析模型 总被引：2，自引：0，他引：2
地震作用下,活动断层附近的埋地管道易发生强度屈服、局部屈曲或整体失稳等形式的破坏,建立准确、高效的埋地管道在断层作用下的计算模型,对管道的抗震设计和震后安全状态评估具有重要的实用价值。本文采用非线性弹簧模拟远离断层处埋地管道的反应,基于管土之间小变形段管道处于强化阶段,提出一种改进的管土等效分析模型,进一步减小了管土之间大变形段的分析长度,从而提高了有限元分析效率。该模型采用ALA推荐的方法计算管土间的滑动摩擦力,可以考虑土体种类的影响;用Kennedy方法确定管道的计算长度。通过与精确模型比较,验证了管土等效模型的合理性和有效性。 相似文献
7.
A new shell finite element method (FEM) model with an equivalent boundary is presented for estimating the response of a buried
pipeline under large fault movement. The length of affected pipeline under fault movement is usually too long for a shell-mode
calculation because of the limitation of memory and time of computers. In this study, only the pipeline segment near fault
is modeled with plastic shell elements to study the local buckling and the large section deformation in pipe. The material
property of pipe segment far away from the fault is considered as elastic, and nonlinear spring elements at equivalent boundaries
are obtained and applied to two ends of shell model. Compared with the fixed-boundary shell model, the shell model with an
equivalent boundary proposed by the study can remarkably reduce the needed memory and calculating time.
Foundation item: National Natural Sciences Foundation of China (50078049).
Contribution No. 04FE1017, Institute of Geophysics, China Earthquake Administration. 相似文献
8.
Tarek H. Abdoun Da Ha Michael J. O’Rourke Michael D. Symans Thomas D. O’Rourke Michael C. Palmer Harry E. Stewart 《Soil Dynamics and Earthquake Engineering》2009
Seismic ground faulting is a severe hazard for continuous buried pipelines. Over the years, researchers have attempted to understand pipe behavior, most frequently via numerical modeling and simulation. However, there has been little, if any, physical modeling and tests to verify the numerical modeling approaches and assumptions. This paper presents results of five pairs of centrifuge tests designed to investigate the influence of various factors on the behavior of buried high-density polyethylene (HDPE) pipelines subjected to strike-slip faulting. Parameters considered are the soil moisture content, fault offset rate, relative burial depth (H/D), and pipe diameter. The centrifuge test results show that pipe behavior, specifically pipe strain, is nominally not affected by the soil moisture content and fault offset rate when the pipe is subjected to strike-slip faulting. On the other hand, the burial depth ratio (H/D) and pipe diameter influence peak pipe strain, and in some cases, the ground soil failure pattern. 相似文献
9.
The present paper addresses the mechanical behavior of buried steel pipes crossing active strike-slip tectonic faults. The pipeline is assumed to cross the vertical fault plane at angles ranging between zero and 45 degrees. The fault moves in the horizontal direction, causing significant plastic deformation in the pipeline. The investigation is based on numerical simulation of the nonlinear response of the soil–pipeline system through finite elements, accounting for large strains and displacements, inelastic material behavior of the pipeline and the surrounding soil, as well as contact and friction on the soil–pipe interface. Steel pipes with D/t ratio and material grade typical for oil and gas pipelines are considered. The analysis is conducted through an incremental application of fault displacement. Appropriate performance criteria of the steel pipeline are defined and monitored throughout the analysis. The effects of various soil and line pipe parameters on the mechanical response of the pipeline are examined. The numerical results determine the fault displacement at which the specified performance criteria are reached, and are presented in diagram form, with respect to the crossing angle. The effects of internal pressure on pipeline performance are also investigated. In an attempt to explain the structural behavior of the pipeline with respect to local buckling, a simplified analytical model is also developed that illustrates the counteracting effects of pipeline bending and axial stretching for different crossing angles. The results from the present study can be used for the development of performance-based design methodologies for buried steel pipelines. 相似文献
10.
An equivalent-boundary method for the shell analysis of buried pipelines under fault movement 总被引：2，自引：0，他引：2
Introduction The history of research work on the response of buried pipeline under the fault movement hasbeen about 30 years. Several simplified design methods have been proposed to obtain the maxi-mum stress or strain in pipe. These methods include the theoretical method and the finite elementmethod (FEM). In the theoretical method, the pipe is usually modeled as a cable (Newmark, Hall1975; Kennedy, et al, 1977) or a beam (Wang, Wang, 1995; LIU, ZHANG, 2002). These theoreti-cal me… 相似文献
11.
The seismic response analysis of buried pipelines at fault crossings is a complex problem requiring nonlinear 3D soil-structure and large deformation analyses. Such analyses are computationally expensive and the results are hard to evaluate. Therefore, a simple numerical model is needed for engineering and design offices to determine the seismic demand of steel pipes at fault crossings. This paper presents a simplified numerical model for buried steel pipes crossing strike-slip faults and oriented perpendicular to the fault. Two pipes with different diameter to thickness (D/t) ratios and steel grades are used in the study. The proposed model permits plastic hinge formations in the pipe due to incrementally applied fault movements, allows determination of the critical length of the pipeline and measure strains developed on the tension and compression sides in the pipe. The model also considers the effect of bending as well as axial strains due to stretching. 相似文献
12.
Structural design of buried pipelines for severe earthquakes 总被引：1，自引：0，他引：1
In order to realistically assess the seismic risk of a pipeline system, the accurate estimate of the pipe strains which depend upon structural details, pipe material, properties of the surrounding soil, the nature of the propagating wave, etc. is critical. Emphasis in this study, therefore has been placed on the analysis of a structural strain for several types of piping elements unique to the buried pipeline and also the provision of a simplified design formula which can be used practically. The purpose of this study is (a) to define the slippage factor in order to estimate the decrease in pipe strain resulting from the slippage effect, (b) to propose a simplified method to evaluate the plastic deformation of the pipeline for severe earthquakes, and (c) to derive a practical design formula for the structural strains of bent pipes. 相似文献
13.
The paper studies the performance of a typical overpass bridge, with continuous deck and monolithic pier-deck connections, subjected to strike-slip faulting. A three-dimensional (3D) finite element (FE) model of the entire bridge–foundation–abutment–soil system is developed, accounting for soil, structure and geometric nonlinearities. Soil behaviour is simulated with a thoroughly validated strain softening constitutive model. The concrete damaged plasticity (CDP) model is implemented for piers, accounting for the interaction between axial force N , bending moment M , shear force Q and torsion T (NMQT ); the model is validated against experimental results from the literature. The location of the fault rupture is parametrically investigated, confirming the vulnerability of indeterminate structural systems to large tectonic deformation. The deck is shown to sustain both in-plane and out-of-plane bending moments, as well as torsion; the piers are subjected to biaxial bending, shear and torsion. The response is highly dependent on the location of the fault rupture, emphasizing the need to develop cost-effective modelling techniques. Four such techniques are developed (with and without decoupling) and comparatively assessed using the detailed 3D FE model as benchmark. The best prediction is achieved by a coupled model, which includes the bridge superstructure, detailed 3D modelling of the soil-foundation system only for the pier directly affected by the fault, and nonlinear springs representing the foundations of all other piers. The proposed technique offers a computationally efficient means to parametrically analyse long multispan bridges subjected to faulting, for which full 3D FE modelling is impractical. 相似文献
14.
由于管道与土体的刚度相差较大,在振动荷载下,两者的运动不能相互协调,致使在研究管道破坏方面,管土之间的变形传递是一个极其重要的研究方向。目前学者对弯管的管土变形传递研究做得较少。本文通过弯管与土体的缩尺振动台试验及三维有限元模型,得出了地震作用下埋地弯管的变形传递系数的拟合公式。然后将试验结果与拟合公式的计算结果和有限元的模拟结果进行对比,证实了拟合公式的合理性,并分析了管道弯头处变形传递系数的变化规律,包括对不同管径、埋深、壁厚、土性和弯头角度的分析,证实了这些因素对管土之间的变形传递影响都很大,说明弯头处变形传递系数拟合公式对管道的抗震具有重大意义。 相似文献
15.
The performance of pipelines subjected to permanent strike–slip fault movement is investigated by combining detailed numerical simulations and closed-form solutions. First a closed-form solution for the force–displacement relationship of a buried pipeline subjected to tension is presented for pipelines of finite and infinite lengths. Subsequently the solution is used in the form of nonlinear springs at the two ends of the pipeline in a refined finite element model, allowing an efficient nonlinear analysis of the pipe–soil system at large strike–slip fault movements. The analysis accounts for large strains, inelastic material behavior of the pipeline and the surrounding soil, as well as contact and friction conditions on the soil–pipe interface. The numerical models consider infinite and finite length of the pipeline corresponding to various angles β between the pipeline axis and the normal to the fault plane. Using the proposed closed-form nonlinear force–displacement relationship for buried pipelines of finite and infinite length, axial strains are in excellent agreement with results obtained from detailed finite element models that employ beam elements and distributed springs along the pipeline length. Appropriate performance criteria of the steel pipeline are adopted and monitored throughout the analysis. It is shown that the end conditions of the pipeline have a significant influence on pipeline performance. For a strike–slip fault normal to the pipeline axis, local buckling occurs at relatively small fault displacements. As the angle between the fault normal and the pipeline axis increases, local buckling can be avoided due to longitudinal stretching, but the pipeline may fail due to excessive axial tensile strains or cross sectional flattening. Finally a simplified analytical model introduced elsewhere, is enhanced to account for end effects and illustrates the formation of local buckling for relative small values of crossing angle. 相似文献
16.
海洋地震频繁且海底土体环境复杂,当地震导致断层土体发生永久变形后,穿越断层的海底埋地管道也将受迫发生变形。为确定变形后的管道能否正常工作,需根据实际工况对其进行应变响应预测。首先通过有限元计算软件ABAQUS建立管道与走滑断层的三维实体模型,模拟管-土间的接触作用并通过等效边界方法修正模型,得到管道局部屈曲破坏形式及应变分布情况。然后,通过调整有限元模型参数对断层交角、管道工作内压、管道径厚比对管道极限塑性应变的影响进行敏感性分析,定性分析不同敏感性因素对穿越走滑断层海底管道应变响应的影响。最后,在数值模拟数据的基础上通过MATLAB软件利用基于遗传算法优化的BP神经网络实现对管道应变响应的精确预测。结果表明:穿越走滑断层管道在发生局部屈曲时,可根据轴向压缩应变突变现象确定管道局部屈曲时对应的断层位移,并且断层交角、管道工作内压和管道径厚比都会对跨断层管道应变响应产生影响。 相似文献
17.
18.
Development of faults as zones of deformation bands and as slip surfaces in sandstone 总被引：10，自引：0，他引：10
Three forms of fault are recognized in Entrada and Navajo Sandstones in the San Rafael Desert, southeastern Utah; deformation bands, zones of deformation bands, and slip surfaces. Small faults occur asdeformation bands, about one millimeter thick, in which pores collapse and sand grains fracture, and along which there are shear displacements on the order of a few millimeters or centimeters. Two or more deformation bands adjacent to each other, which share the same average strike and dip, form azone of deformation bands. A zone becomes thicker by addition of new bands, side by side. Displacement across a zone is the sum of displacements on each individual band. The thickest zones are about 0.5 m and total displacement across a thick zone rarely exceeds 30 cm. Finally,slip surfaces, which are through-going surfaces of discontinuity in displacement, form at either edge of zones of highly concentrated deformation bands. In contrast with individual deformation bands and zones of deformation bands, slip surfaces accommodate large displacements, on the order of several meters in the San Rafael Desert.The sequence of development is from individual deformation bands, to zones, to slip surfaces, and each type of faulting apparently is controlled by somewhat different processes. The formation of zones apparently involves strain hardening, whereas the formation of slip surfaces probably involves strain softening of crushed sandstone. 相似文献
19.
Permanent earthquake‐induced actions in buried pipelines: Numerical modeling and experimental verification 
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下载免费PDF全文 《地震工程与结构动力学》2018,47(4):966-987
Buried pipelines are often constructed in seismic and other geohazard areas, where severe ground deformations may induce severe strains in the pipeline. Calculation of those strains is essential for assessing pipeline integrity, and therefore, the development of efficient models accounting for soil‐pipe interaction is required. The present paper is aiming at developing efficient tools for calculating ground‐induced deformation on buried pipelines, often triggered by earthquake action, in the form of fault rupture, liquefaction‐induced lateral spreading, soil subsidence, or landslide. Soil‐pipe interaction is investigated by using advanced numerical tools, which employ solid elements for the soil, shell elements for the pipe, and account for soil‐pipe interaction, supported by large‐scale experiments. Soil‐pipe interaction in axial and transverse directions is evaluated first, using results from special‐purpose experiments and finite element simulations. The comparison between experimental and numerical results offers valuable information on key material parameters, necessary for accurate simulation of soil‐pipe interaction. Furthermore, reference is made to relevant provisions of design recommendations. Using the finite element models, calibrated from these experiments, pipeline performance at seismic‐fault crossings is analyzed, emphasizing on soil‐pipe interaction effects in the axial direction. The second part refers to full‐scale experiments, performed on a unique testing device. These experiments are modeled with the finite element tools to verify their efficiency in simulating soil‐pipe response under landslide or strike‐slip fault movement. The large‐scale experimental results compare very well with the numerical predictions, verifying the capability of the finite element models for accurate prediction of pipeline response under permanent earthquake‐induced ground deformations. 相似文献
20.
华北地震场和源地壳形变前兆研究 总被引：3，自引：1，他引：3
文中用实测资料和构造物理学观点论证了华北中、强地震前孕震形变场(断层活动系统)的存在和它的运动学与力学机制,并用有限元法加以检验;讨论了形变场、源前兆之间的关系和它们的前兆特征;给出了可操作的剪切破裂指标S(t),用断层滑动速度和剪切应变速度较好地表达了某地的地震破裂危险性;最后,提出了华北形变场活动的长期稳定性和周期性(约12年)。 相似文献