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1.
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
2.
A new remediation technique is proposed to mitigate large deformations imposed on buried pipeline systems subject to permanent ground deformation. With this technique, low-density gravel (LDG) with high porosity, such as pumice, is used as backfill in the trench containing the pipe near an area susceptible to PGD. This countermeasure decreases soil resistance, soil-pipe interaction forces and strain on the pipe as the pipeline deformation mechanism changes to a more desirable shape. Expanded polystyrene geofoam has been introduced to decrease the density of the pipeline backfill; however, LDG is more efficient regarding workability during construction, environmental effects, durability, fire safety, and cost-effectiveness. A series of centrifuge model experiments in which the pipelines were subjected to reverse faulting was conducted to evaluate the proposed method. During faulting, the axial and bending strain and pipe deflection were measured. A comparison of the responses of the remediated pipeline and the pipeline without remediation indicates that the proposed technique substantially mitigates the effects of large deformation.
相似文献3.
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
4.
In this paper, a nonlinear stochastic seismic analysis program for buried pipeline systems is developed on the basis of a probability density evolution method (PDEM). A finite element model of buried pipeline systems subjected to seismic wave propagation is established. The pipelines in this model are simulated by 2D beam elements. The soil surrounding the pipelines is simulated by nonlinear distributed springs and linear distributed springs along the axial and horizontal directions, respectively. The joints between the segmented pipes are simulated by nonlinear concentrated springs. Thereafter, by considering the basic random variables of ground motion and soil, the PDEM is employed to capture the stochastic seismic responses of pipeline systems. Meanwhile, a physically based method is employed to simulate the random ground motion field for the area where the pipeline systems are located. Finally, a numerical example is investigated to validate the proposed program. 相似文献
5.
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
6.
沉陷区域埋地管线数值模拟分析 总被引：4，自引：0，他引：4
场地的不均匀沉陷是导致埋地管线破坏的重要原因之一。本文考虑了材料非线性、几何非线性以及管土接触非线性,将管线计算分析模型模拟为四节点薄壳单元结构,周围填覆土体采用八节点六面体单元划分。管土相互作用模拟为三维刚性与柔性的面面接触单元结构,并采用线性位移加载来模拟土体的沉陷作用,对三维薄壳有限元模型进行数值计算分析。通过比较不同参数,如沉陷长度、沉陷深度、埋深、管径、径厚比、土特性等对管线的反应影响,得出管线在沉陷情况下的应力和应变的关系,通过算例分析,说明了该方法能更好地模拟管线的破坏过程,该方法将为沉陷区域埋地管线数值模拟提供理论分析依据。 相似文献
7.
An analysis procedure for seismic wave propagation effects on straight continuous buried pipelines is proposed. It shown that ground strain due to surface waves can be substantially larger than that due to body waves. An elastic model a buried pipeline surrounded by equivalent soil springs indicates that frictional slip between the pipeline and the surrounding soil springs is likely for high ground strains. A method for estimating ground strain due to surface waves, based on data from the 1971 San Fernando earthquake, reviewed. An analysis procedure, which utilizes frictional forces near the soil-pipeline interface, is proposed for surfae wave effects on straight buried continuous pipelines. The proposed procedure is illustrated with an example. 相似文献
8.
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
9.
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
10.
地下管网地震反应分析模型 总被引：1，自引：0，他引：1
建立了多点地震动激励作用下的地下管网地震反应拟静力分析模型。首先建立基于有限单元模型的地下管网系统刚度方程,接着给出考虑地震动空间相关性及场地条件等诸多因素的地震动场模拟思路及管网系统地震动施加策略,最后通过解析法验证了模型的正确性。采用本文方法对一＂十＂字形管网进行了地震反应分析,结果表明：①管线轴向应力沿着管线长度从管线端部向管线交叉点逐步增大,在管线交叉点处应力达到最大值;②与轴向应力相比,尽管管线的弯曲应力不是控制应力,但在管线端部及管线交叉点处弯曲应力值将会有较大突变。因此,对于地下管网而言,在受到地震作用时,不同布置方向的管线之间的相互影响是不容忽视的。 相似文献
11.
地震作用下土体发生液化之后,由于超静孔隙水压力的产生和土体抗剪强度的降低,管道易发生上浮破坏。为研究管道上浮动力反应的影响因素,基于OpenSees有限元软件,通过目标反应谱和谱匹配等方法选取地震波,考虑不同管土特性和地震动特性,对地震作用下管道上浮动力反应进行了二维数值模拟。结果表明:土体相对密度、管径和管道埋深对管道上浮反应的影响较大,分别给出了土体相对密度、管径、管道埋深对管道上浮位移的影响规律及对应拟合公式;长持时地震动作用下,超静孔隙水压力消散较慢,管道上浮位移可达短持时地震动作用下管道上浮位移的2倍左右;近断层脉冲地震动作用下,管道上浮破坏和横向破坏两种破坏模式同时存在,且由于速度脉冲效应,管道横向破坏风险大于上浮破坏风险。 相似文献
12.
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
13.
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
14.
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
15.
跨越断层埋地管线地震反应数值分析 总被引：9，自引：2，他引：7
跨越断层埋地管线在地震中的破坏是非常严重的,地震本身和管土相互作用体系中都存在很多不确定性因素,所以管线在断层运动过程中反应比较复杂。本文利用有限元理论和数值模拟手段,建立了管土作用模型,采用非线性接触问题研究方法详细地分析了管线由断层运动而产生的反应,对影响管线的各种因素进行了分析,包括位错量、跨越角度、断层运动形式、埋设深度、初始轴向力、断层裂缝宽度、填覆土质和管径。通过研究,得到一些初步结论。 相似文献
16.
埋地管道在断层错动作用下的内力分析及其抗震措施一直是生命线工程的一个重要问题与研究热点。对地下管道在断层错位下的响应计算,取得的成果较多,比较经典的有Newmark-Hall方法和Kennedy方法。后来又出现基于壳模型的简化方法,如高田至郎提出的简化计算方法等。相对来讲,关于管道抗震措施的研究成果较少。本文提出一种抗震措施,进行了基于壳模型的有限元动力数值模拟,并与4种松到中密场地土条件下的埋地管道断层错位响应进行对比分析。计算结果表明,本方法中三种长度管道的最大轴向拉应变远小于埋地管道的最大轴向拉应变,而且最大轴向压应变亦不大。 相似文献
17.
The behaviour of long straight buried pipelines subjected to seismic wave propagation is investigated. Well-known relationships for determining upper bounds for the axial strain and curvature in the pipeline as well as relationships for relative displacement and rotation at the pipeline joints are discussed. The assumption that the seismic excitation can be modelled as a travelling wave having a shape which remains unchanged as it traverses the pipeline is examined in detail. It is shown that this assumption is unconservative when the effective propagation velocity of the seismic waves with respect to the pipeline is such that the actual time lag (separation distance between points divided by effective propagation velocity) is less than a ‘cross-over’ time lag. Cross-over time lags for 22 pairs of ground displacements recorded during the 1971 San Fernando Earthquake are presented in this paper. Finally, methods for estimating the propagation speed of the seismic waves along or with respect to the pipeline are discussed. 相似文献
18.
Some lifelines, such as gas and oil transmission lines and water and sewer pipelines, have been damaged in recent earthquakes. The damages of these lifelines may cause major, catastrophic disruption of essential services for human needs. Large abrupt differential ground movements that result from an active fault present one of the most severe effects of an earthquake on a buried pipeline system. Although simplified analysis procedures for buried pipelines across strike-slip fault zones that cause tensile failure of the pipeline have been proposed, the results are not accurate enough because of several assumptions involved, such as the omission of flexural rigidity of the pipe, simplification of soil resistant characteristics, etc. Note that the omission of flexural rigidity cannot satisfy equilibrium conditions for pipelines across a ‘reverse’ strike-slip fault that causes compressions in the pipeline. This paper presents a refined analysis procedure for buried pipelines that is applicable to both strike-slip and reverse strikeslip faults after modifying some of the assumptions used previously. Based on the analytical results, this paper also discusses the design criteria for buried pipelines which are subjected to various fault movements. Parametric responses of buried pipeline for various fault movements, angles of crossing, buried depths and pipe diameters are presented. 相似文献
19.
D.K. Karamitros G.D. BouckovalasG.P. Kouretzis V. Gkesouli 《Soil Dynamics and Earthquake Engineering》2011
The complex problem of strength verification of a buried steel pipeline crossing the trace of a normal active fault is treated analytically, and a refined methodology for the calculation of the axial and bending pipeline strains is presented. In essence, the proposed methodology extends the analytical methodology originally proposed by Karamitros et al. [1] for the simpler case of strike-slip fault crossings. The modifications introduced to the original methodology are first identified, following a thorough examination of typical results from advanced 3D nonlinear numerical analyses, and consequently expressed via an easy to apply solution algorithm. A set of similar numerical analyses, performed for a wide variety of fault plane inclinations and intersection angles between the pipeline axis and the fault trace, is used to check the accuracy of the analytical predictions. Fairly good agreement is testified for pipeline strains up to 1.50–2.00%. It is further shown that, although the methodology proposed herein applies strictly to the case of right intersection angles, it may be readily extended to oblique intersections, when properly combined with existing analytical solutions for strike-slip fault crossings (e.g. [1]). 相似文献
20.
场地沉陷埋地管道反应分析方法 总被引：8，自引：1，他引：8
场地的不均匀沉陷是导致埋地管线破坏的重要原因之一，至今，国内外对这一问题的研究甚少。本文提出了一个新的方法，用以分析受沉陷作用的埋地管道的反应，该方法选取跨越非沉陷区和沉陷区的埋地管道为研究对象，用三次曲线模拟沉陷区管道的几何大变形，推导出沉陷区段管道在几何大变形条件下的受力平衡方程的内力递推公式，用弹性地基梁模型模拟非沉陷区的管道变形，并用学陷区和非沉陷区交界面处的变形及力学协调条件给出了交界点 相似文献