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Characterization of soil-structure interaction for seismic design of hazard-resistant pipeline systems with enlarged joints
Abstract
New segmented pipeline systems, with improved materials and jointing mechanisms , are being employed to address water distribution network vulnerability to seismically-triggered permanent ground movement such as liquefaction-induced lateral spreading and land-sliding. Contrary to their improved performance, these systems typically include connections that are larger in cross-section than standard jointing mechanisms, and therefore develop elevated levels of interaction with surrounding medium in response to the relative soil-pipeline movement needed to accommodate earthquake-induced ground displacements. This assessment builds on existing design equations and full-scale experiments to assess the non-linear resistance force that develops at enlarged pipe bells and joint restraints in response to axial soil-pipeline interaction. Several methods of calculating design values for seismic evaluation are provided and compared against test data normalized to account for pipeline depth and annulus size. Results provide needed inputs for the analysis and design of hazard-resilient pipeline systems.
... While approaches exist for estimating friction along the pipe barrel (i.e., ASCE 1984), recent studies have shown the significant contribution of enlarged projections to axial system response that has not been previously considered (Wham et al. 2017b(Wham et al. , 2018a. The additional axial force from enlarged bells, joint harness restraints, and other anchor-like components develops progressively with relative soil-pipeline displacement and includes contributions from friction, passive bearing pressure, and soil yielding/flow (Wham et al. 2019a). This nonlinear response is simplified in the present solution with a single parameter, the average resistance force, f r , along the pipe system, which is intended to include all friction force f p and axial resistance F jr components averaged per unit length of pipe. ...
... The selection of an appropriate resistance force for a pipe system is important to understanding analysis results from the following design framework. Wham et al. (2019a) review existing experimental data and propose several methods for estimating a representative f r for a pipeline given system geometry and soil type. The method can be applied generally to pipe buried in any soil type; however, for the current development the pipeline is assumed to be buried in a cohesionless sandy soil. ...
... The values presented for f j are only an initial approximation for these example calculations. Wham et al. (2019a) show how f j changes with D b and relative displacement between soil and pipe. More research is needed to determine how to evaluate f j , which may result in different values for these same examples in the future. ...
In responding to the need for improved technologies to accommodate permanent ground deformation imposed by earthquakes, landslides, and other sources, a new family of segmented pipelines has emerged employing joints that displace axially and deflect before locking up and restraining further movement. Other than employing finite-element modeling, there is no existing procedure allowing practicing engineers to efficiently evaluate displacements and strains that develop along segmented pipelines consistent with those of continuous pipelines at equivalent levels of potential ground movement. A methodology is presented that allows continuous and segmented pipelines of any defined material in the elastic range to be evaluated consistently using a single set of equations for block ground deformations moving parallel to the longitudinal pipe axis. The equations reduce to previously recognized solutions for continuous pipelines as the segmented pipe joints reach their allowable displacement. Results show how the hybrid-segmented pipelines have lower axial strains than continuous pipes for equivalent levels of block deformation. The proposed model provides a fundamental basis for engineering design selection of continuous and segmented pipelines in hazard-prone regions.
... Frictional resistance per unit length averaged along a pipe segment (fr [kips/ft]) is a function of various soil and pipe characteristics and varies depending on the methodology selected. Wham et al. (2019a) compared known axial friction estimation methods, provided in Table 2, to full-scale axial pull-out test results. They showed that various solutions can provide a reasonable estimate, but fit is highly dependent on the level of relative movement between soil and pipe. ...
... The pipe ramming solution (Meskele & Stuedlein, 2015) typically provides the highest estimate of fr and is hence the most conservative approach for seismic design, but is arguably over-conservative for some situations. Additional details and justification for these four methods can be found in Wham et al. (2019a). While other methods of calculating fr have been proposed (e.g., Rajah, 2019), these four methods were selected to reasonably bound estimated levels of axial soil resistance based on full-scale experiments. . ...
This study focuses on the development of a pipeline performance classification for Axial Connection Force Capacity (CFC) to support the ongoing efforts of developing seismic design guidelines for water and wastewater systems. The only existing seismic design standard that includes a performance classification system for pipelines is ISO 16134. While this standard recommends performance, levels based on axial CFC (referred to as joint “slip-out resistance” under axial tension loading), it only considers ductile iron (DI) pipe and does not apply to other common pipe materials, connection types, or system components. Previous studies have defined the axial CFC of segmented PVCO (molecularly oriented polyvinyl chloride) pipes relative to Earthquake-Resistant DI Pipe (ERDIP) systems that have performed well during past seismic events and associated earthquake-induced permanent ground deformations. This study expands on previous work by adapting the ISO 16134 classification system for quantifying the CFC to additional pipeline materials and connections common to water distribution and wastewater collection systems. These pipeline materials and their system characteristics, such as joint/connection geometry, burial depth, and backfill soil conditions, affect seismic demands and deformations by influencing the frictional resistance along the pipe length and joint/connection as it undergoes axial deformations. This study quantifies a ratio between the CFC of a particular system of interest and the ISO ERDIP CFC, defined as K1. The study demonstrates how this conversion factor, calculated based on analytical and experimental results, can be used to classify a pipeline systems’ CFC performance class. The enclosed evaluation of the frictional forces generated under significant ground movement (seismic demand), and the CFC required for a particular system to accommodate these various levels of potential demand, is intended to support industry guidelines for the seismic design of buried water and wastewater pipeline systems.
... 707 The approach is predicated on accurately assigning a representative 708 frictional force, f r , along the pipeline that accounts for both the pipe barrel friction, f p , and the 709 increased localized interaction of the joint restraint, F jr . Wham et al. (2019a) propose several 710 methods for estimating a representative f r given soil properties and system geometry. For the 711 approach described and implemented by , the value of F jr is estimated as 712 the axial force recorded from full-scale tests at an axial pull-out displacement of approximately 15.2 713 cm (6 in.), which is equivalent to 27.1 kN (6.1 kips) and 18.7 kN (4.2 kips) for the PVCO restraint 714 and DI joint, respectively. ...
Innovative hybrid-segmented pipeline systems are being used more frequently in practice to improve the performance of water distribution pipelines subjected to permanent ground deformation (PGD), such as seismic-induced landslides, soil lateral spreading, and fault rupture. These systems employ joints equipped with anti-pull-out restraints, providing the ability to displace axially, before locking up and behaving as a continuous pipeline. To assess the seismic response of hazard-resistant pipeline systems equipped with enlarged joint restraints to longitudinal PGD, this study develops numerical and semi-analytical models, considering the nonlinear properties of the system, calibrated from large-scale test data. The deformation capacities of two hybrid-segmented pipelines are investigated: (1) hazard-resilient ductile iron (DI) pipe, and (2) oriented polyvinylchloride (PVCO) pipe with joint restraints capable of axial deformation. The numerical analysis demonstrates that, for the conditions investigated, the maximum elongation capacity of the analyzed DI pipe system is greater than that of the PVCO pipeline. The implemented semi-analytical approach revealed that the pipeline performance strongly improves by increasing the allowable joint displacement. Comparison of the numerical results with analytical solutions reported in recent research publications showed excellent agreement between the two approaches, highlighting the importance of assigning appropriate axial friction parameters for these systems.
Buried pipelines subjected to permanent ground deformations (through, e.g., earthquake-induced liquefaction or fault rupture) often experience widespread damage. Regardless of the direction of the demands, pipelines tend to respond and experience damage axially due to their directional stiffness characteristics. In addition, case studies and previous testing have shown that damage concentrated at the pipe joints due to their lower strength compared to a pipe barrel. Previous testing has also shown that axial forces increase significantly when pipe connections have jointing mechanisms, such as coupling restraints, with larger diameters than the pipe barrel alone. These enlarged joints act as anchors along the pipe, increasing the soil resistance at these locations. Current methods for predicting the axial force along a pipe underpredict the force demands and oversimplify the mechanics of soil resistance on the joint face. This study conducts a series of 12 pipe-pull tests in a centrifuge, varying joint diameter and burial depth, to quantify the axial forces developed. A strong, linear correlation is observed between the soil resistance on a joint face and the joint surface area and burial depth. The study also proposes an analytical solution based on pullout capacity design equations for vertical anchor plates as a function of soil and pipe joint properties. The proposed solution to calculate joint resistance is in good agreement with the centrifuge tests performed for this study and previous full- and model-scale experiments. The proposed prediction equation is anticipated to have future applications to other buried structures, because it is based on mechanisms of passive resistance commonly encountered in underground structures and lifelines.
Buried pipelines are susceptible to damage from ground movements triggered by earthquakes, such as liquefaction-induced lateral spreading, landslides, and fault rupture. Given the linear characteristics of water and wastewater pipelines, failure due to ground displacement is most likely to occur at locations of weakness, which for segmented pipelines is typical at joints or fittings linking adjacent sections of pipe. Connections can be characterized as unrestrained (e.g., bell-and-spigot joints), fully restrained (e.g., continuous systems with welded/fused connections), or hybrid segmented joints, which provide the ability to displace axially in response to ground movement before locking up and behaving as a continuous system. The joint type and geometry will contribute significantly to the expected performance of a given pipe system subjected to axial and/or transverse ground movements. Furthermore, the connection force capacity of the joints is an important limit state for predicting failure of pipe systems for which the joint has less strength than the pipe barrel. To support the development of an ASCE/UESI manual of practice (MOP) on Seismic Design of Water and Wastewater Pipelines, this paper presents a framework for establishing the minimum connection force capacity (based on burial conditions and pipe/connection characteristics) required for a particular system to be classified in one of four proposed seismic demand categories defined by the MOP. To predict system response to various levels of ground movement, an analytical model is paired with a statistical approach to compare the survival rate of pipe systems that have performed well in past earthquakes to the expected survival of other systems composed of different materials and mechanical connections. Results will aid seismic capacity classification by providing a basis for establishing connection force capacity coefficients for new and existing systems.
This work is part of an extensive research program concerning the design of buried pipelines crossing unstable slopes. In these cases the most common choice is that of the pipe axis running parallel to the slope, so that longitudinal interaction is of foremost significance. Soil deformations will influence the pipe, to an extent which depends on pipe-soil interaction; it is desirable that this should be low, so that after exceeding the maximum interface shear strength the soil will deform without further stressing the pipeline. Current methods in use for quantifying shear longitudinal interaction bear some similarity to calculation methods for driven piles. Even though the majority of existing pipelines has been thus designed, these methods are in fact not satisfactory, and some recent research is dedicated to finding new more appropriate methods by means of extensive use of in-situ tests in order to quantify shear strength in soil-structure interaction. In this paper the traditional methods deriving from pile analogies are examined and their inappropriateness in the case of pipelines is shown. The results of some in-situ tests are examined, and the information that can be drawn is analysed. In addition, the results of some laboratory interface tests are presented. In the aim to create reference values valid for general design rather than for some specific case, these are examined in order to highlight the physical mechanisms responsible for the development of shear strength. Various material combinations are considered, and conclusions are drawn regarding appropriateness of these. Comparison between in situ and laboratory results in part confirms the qualitative analysis of the shear mechanisms; on the other hand, attention is drawn to some physical phenomena, occurring in situ and non reproduced in the laboratory tests.
A new family of hybrid-segmented pipes is emerging into the international market which allow the joints to displace axially and deflect a prescribed quantity before locking up and restraining further movement. These pipe systems are mainly targeting improvement to earthquake-induced ground deformations, but also apply to other types of ground-induced strain such as landslides, flooding-induced scour, and differential subsidence. As the segmented pipe joints lock up in response to ground movement, the system behaves similar to a continuous pipe along the regions where ground movement is sufficient to engage the locking mechanisms. Other than employing finite element modeling, there is no methodology allowing engineers to evaluate the stresses and strains that develop along segmented pipes consistently with those of continuous pipes at equivalent levels of potential ground movement. This paper presents an evaluation methodology based on a single set of equations that allow continuous and segmented pipes, of any defined material, to be evaluated consistently for block ground deformations moving parallel to the longitudinal pipe axis.
The expansion of urban communities around the world resulted in the installation of utility pipes near existing natural or artificial slopes. These pipes can experience significant increase in axial earth pressure as a result of possible slope movement in the pipeline direction.This research aims at utilizing the discrete-element method to investigate the response of a buried pipeline in granular material subjected to axial soil movement. To determine the input parameters needed for the discrete-element analysis, calibration is performed using triaxial and direct shear test data and the microscopic parameters are determined by matching the numerical and experimental results. The soil–pipe system is then modeled and the detailed behavior of the pipe and the surrounding soil as well as their interaction at the particle-scale level are presented. Conclusions are made regarding the suitability of the empirical approach used in practice to estimate the axial soil resistance indifferent soil conditions. This study suggests that caution should be exercised in calculating axial soil resistance to relative pipe movement in dense sand material. A suitable lateral earth pressure coefficient should be determined in these cases as a function of the soil and pipe properties.
The performance of buried steel pipelines subjected to relative soil movements in the axial direction was investigated using full-scale pullout testing in a soil chamber. Measured axial soil loads from pullout testing of pipes buried in loose dry sand were comparable to those predicted using guidelines commonly used in practice. The peak values of axial pullout resistance observed on pipes buried in dense dry sand were several-fold (in excess of 2 times) higher than the predictions from guidelines the observed high axial pullout resistance is primarily due to a significant increase in normal soil stresses on the pipelines, resulting from constrained dilation of dense sand during interface shear deformations. This reasoning was confirmed by direct measurement of soil stresses on pipes during full-scale testing and numerical modeling. The research findings herein suggest that the use of the coefficient of lateral earth pressure at-rest (K0) to compute axial soil loads, employing equations recommended in common guidelines, should be undertaken with caution for pipes buried in soils that are likely to experience significant shear-induced dilation.
The performance of buried, medium-density polyethylene (MDPE) pipes subject to movements relative to the soil in the direction of the pipe axis is investigated by full-scale physical model testing conducted using a large soil box. A new closed-form solution was developed to account for the nonlinear material response of MDPE pipes under axial loading, and the analytical results are compared with the results obtained from the full-scale pipe pullout testing. The closed-form solution provides a rational framework to estimate the response of the pipe (i.e., level of strain, force) and the mobilized frictional length along the pipe for a known relative axial pipe movement. The approach, in turn, could be used to estimate the relative axial movements needed for pipe failure, which is an important consideration in the evaluation of field-performance of pipe systems located in areas of potential ground movement. The methodology is an important initial step towards the development of representative axial soil-springs representing complex pipesoil interaction encountered in relatively extensible, buried polyethylene (PE) pipe systems subject to soil loading arising from ground movements.
This article provides a comprehensive evaluation of ductile iron (DI) pipeline response to earthquake-induced ground deformation through the results of a large-scale testing program and a fault rupture test on a 150-mm DI pipeline with restrained axial slip joints. The test is used to validate a two-dimensional finite element (FE) model that accounts for soil–pipeline interaction with axial slip, pullout resistance, and rotation of pipe joints. The maximum strike-slip fault offset sustained by push-on, restrained, and restrained axial slip joints is presented as a function of the pipeline/fault crossing angle. DI pipeline performance is controlled by one of the following limit states; tensile, compressive, rotational joint capacity, or local buckling in the pipe barrel. A systematic FE assessment shows that pipelines with restrained axial slip joints accommodate 2–9 and 2–10 times as much fault offset as pipelines with push-on and restrained joints, respectively, for most intersection angles. The results of this work can be used for simplified design and to quantify the relative earthquake performance of different DI pipelines.
Buried pipelines are susceptible to damage from ground movements triggered by earthquakes, such as liquefaction-induced lateral spreading, landslides, and fault rupture. Given the linear characteristics of water and wastewater pipelines, failure due to ground displacement is most likely to occur at locations of weakness, which for segmented pipelines is typical at joints or fittings linking adjacent sections of pipe. Connections can be characterized as unrestrained (e.g., bell-and-spigot joints), fully restrained (e.g., continuous systems with welded/fused connections), or hybrid segmented joints, which provide the ability to displace axially in response to ground movement before locking up and behaving as a continuous system. The joint type and geometry will contribute significantly to the expected performance of a given pipe system subjected to axial and/or transverse ground movements. Furthermore, the connection force capacity of the joints is an important limit state for predicting failure of pipe systems for which the joint has less strength than the pipe barrel. To support the development of an ASCE/UESI manual of practice (MOP) on Seismic Design of Water and Wastewater Pipelines, this paper presents a framework for establishing the minimum connection force capacity (based on burial conditions and pipe/connection characteristics) required for a particular system to be classified in one of four proposed seismic demand categories defined by the MOP. To predict system response to various levels of ground movement, an analytical model is paired with a statistical approach to compare the survival rate of pipe systems that have performed well in past earthquakes to the expected survival of other systems composed of different materials and mechanical connections. Results will aid seismic capacity classification by providing a basis for establishing connection force capacity coefficients for new and existing systems.
This paper reports on a series of full-scale tests to evaluate the performance of seismic resistant, oriented polyvinyl chloride (PVCO) pipe. Earthquake resilience in water distribution networks requires pipelines that can accommodate fault rupture, liquefaction-induced lateral spreading, and subsidence. The implementation of hazard-resistant pipeline systems requires a new design approach that accounts for large relative displacement between soil and pipeline joints. Reported herein are the results of a series of five full-scale tests in which 150-mm (6-in.)-diameter pipes with restrained joints were pulled axially through a dense sand backfill at various burial depths. The resulting force-displacement relationships are employed to characterize the pull-through capacity of restrained pipe joints. Results from axial tension tests performed on restrained pipe joints are also discussed, providing a maximum axial joint capacity for comparison with buried tests. The test results are important for seismic design standards covering underground water and wastewater pipelines as well as improvements in numerical modeling of soil/pipeline interaction involving large ground deformation.
Technological advances have improved pipeline capacity to accommodate large ground deformation associated with earthquakes, floods, landslides, tunneling, deep excavations, mining, and subsidence. The fabrication of polyvinyl chloride (PVC) piping, for example, can be modified by expanding PVC pipe stock to approximately twice its original diameter, thus causing PVC molecular chains to realign in the circumferential direction. This process yields biaxially oriented polyvinyl chloride (PVCO) pipe with increased circumferential strength, reduced pipe wall thickness, and enhanced cross-sectional flexibility. This paper reports on experiments performed at the Cornell University Large-Scale Lifelines Testing Facility characterizing PVCO pipeline performance in response to large ground deformation. The evaluation was performed on 150-mm (6-in.)-diameter PVCO pipelines with bell-and-spigot joints. The testing procedure included determination of fundamental PVCO material properties, axial joint tension and compression tests, four-point bending tests, and a full-scale fault rupture simulation. The test results show that the performance of segmental PVCO pipelines under large ground deformation is strongly influenced by the axial pullout and compressive load capacity of the joints, as well as their ability to accommodate deflection and joint rotation. The PVCO pipeline performance is quantified in terms of its capacity to accommodate horizontal ground strain, and compared with a statistical characterization of lateral ground strains caused by soil liquefaction during the Canterbury earthquake sequence in New Zealand.
The performance evaluation of buried extensible plastic pipelines, such as polyethylene pipes in the gas distribution industry, in areas prone to ground movement is a key consideration for many utility owners. Considering the relatively smaller deformation stiffness and nonlinear stress-strain response of these pipes compared with those of steel pipes, a good understanding of the basic soil-pipe interaction mechanisms forms a critical part in these evaluations. The increase in soil normal stress on the pipe attributable to soil dilation and gradual degradation of interface friction with axial pipe displacement was investigated. An analytical method was developed to estimate the pipe response when subject to axial frictional loads arising from soil movements, which accounts for these factors and the nonlinear stress-strain response of the pipe material. For a known relative axial soil displacement, the approach provides a convenient way to determine the axial force, strain, and length along which the friction is mobilized. The proposed analytical solution was used to model the response of five large-scale field pipe pullout tests. It is shown that the analytical solution is capable of effectively forming a framework to relate pipe displacement, pullout resistance, strain, and mobilized length. The findings also highlight the significance and need to account for soil dilation effects in describing the soil-pipe interaction in extensible plastic pipes. (c) 2014 American Society of Civil Engineers.
Installation of new buried pipes and culverts, and replacement of existing ones utilizing trenchless technologies, is increasing in popularity because these methods mitigate many of the surface disturbances associated with conventional open-cut placement. Pipe ramming is an efficient technique that allows installation of casings in soils that can present difficulties for other trenchless technologies. Despite increasing usage, little technical guidance is available to owners and engineers who plan installations with pipe ramming. This paper provides an overview of the pipe ramming technique, possible design procedures, and governing mechanics associated with pipe ramming, with the goal of providing a baseline for engineered installations and identifying areas for further research. Methods to estimate soil resistance to ramming, analysis of ground deformations, and ground vibrations are discussed and compared with measurements observed in field installations. Soil resistance predictions based on conventional jacking methods are shown to underpredict measured resistances inferred from dynamic load testing. Empirical Gaussian settlement models commonly employed in tunnel engineering were shown to result in somewhat inaccurate predictions for an observed pipe ramming installation in cohesionless soils. Field measurements of the ground vibrations resulting from ramming are presented and compared with commonly used safe vibration standards developed for residential structures; the frequencies of vibration generally range from 20-100 Hz, are considerably high for small source-to-site distances, and attenuate rapidly with radial distance. In general, the study lays a basis for planning pipe installation projects with the intent of providing technical advancement in pipe ramming.
Pipe ramming is a cost-effective trenchless pipe installation method in which percussive blows generated by a pneumatically or hydraulically powered encased piston rammer are used to advance a pipe or culvert through the ground. To evaluate the feasibility of a pipe ramming installation, engineers must be able to reliably predict the pipe drivability and installation stresses. Assessment of the drivability of the pipe and selection of the optimal hammer for pipe ramming installation requires that the static and dynamic soil resistance to ramming at the pipe face and along the casing be reliably estimated. However, pipe ramming-specific models are not currently available, and engineers often resort to the existing traditional pipe-jacking and microtunneling models for static soil resistance computations. This paper describes the results of four full-scale pipes rammed in the field and the corresponding static soil resistance to ramming in granular soils. A companion paper addresses dynamic soil resistance and pipe drivability. The accuracy of the existing pipe jacking and microtunneling-based static soil resistance models is evaluated herein and found to provide unsatisfactory estimates of the face and casing resistance. New semiempirical pipe ramming-specific models are proposed based on the field observations and are found to produce good estimates of static soil resistance for use in pipe drivability evaluations. (C) 2014 American Society of Civil Engineers.
Comparison among full-scale axial pull test results and methods of approximating frictional resistance
- T Meskele
- A W Stuedlein
Meskele, T., Stuedlein, A.W., 2015. Static Soil Resistance to Pipe Ramming in Granular Soils. J. Geotech.
Figure 6. Comparison among full-scale axial pull test results and methods of approximating frictional
resistance (Wham and Davis, 2019).
Experimental Evaluation of Ductile Iron Pipeline Response to EarthquakeInduced Ground Deformation
- C Pariya-Ekkasut
Pariya-Ekkasut, C., 2018. Experimental Evaluation of Ductile Iron Pipeline Response to EarthquakeInduced Ground Deformation. Cornell University.
Ermittlung der rohrreibung und entwicklung eines bohrgerätes
- W Weber
- G Hurtz
Weber, W., Hurtz, G., 1981. Ermittlung der rohrreibung und entwicklung eines bohrgerätes. Tiefbau,
Ingenieurbau, Straßenbau 23, 550-555.