Mechanical Behavior Analysis of the Buried Steel Pipeline Crossing Landslide Area

2016 ◽  
Vol 138 (5) ◽  
Author(s):  
Jie Zhang ◽  
Zheng Liang ◽  
Chuanjun Han
Keyword(s):  
Mechanical Behavior ◽  
Tensile Strain ◽  
Structural Integrity ◽  
High Stress ◽  
Soil Parameters ◽  
Buried Pipeline ◽  
Landslide Area ◽  
Steel Pipeline ◽  
Bending Deformation ◽  
Pipeline Crossing

Landslide movement is one of the threats for the structural integrity of buried pipelines that are the main ways to transport oil and gas. In order to offer a theoretical basis for the design, safety evaluation, and maintenance of pipelines, mechanical behavior of the buried steel pipeline crossing landslide area was investigated by finite-element method, considering pipeline-soil interaction. Effects of landslide soil parameters, pipeline parameters, and landslide scale on the mechanical behavior of the buried pipeline were discussed. The results show that there are three high stress areas on the buried pipeline sections where the bending deformation are bigger. High stress area of the compression side is bigger than it on the tensile side, and the tensile strain is bigger than the compression strain in the deformation process. Buried pipeline in the landslide bed with hard soil is prone to fracture. Bigger deformations appear on the pipeline sections that the inside and outside lengths of the interface are 30 m and 10 m, respectively. The maximum displacement of the pipeline is smaller than the landslide displacement for the surrounding soil deformation. Bending deformations and tensile strain of the pipeline increase with the increase in landslide displacement. Bending deformation and the maximum tensile strain of the pipeline increase with increasing of the soil's elasticity modulus, cohesion, and pipeline's diameter–thickness ratio. Soil's Poisson's ratio has a great effect on the displacement of the middle part, but it has a little effect on other sections' displacement.

Mechanical Behavior of Buried Pipeline Crossing Thaw Settlement Zone

2021 ◽  
Author(s):  
Rui Xie ◽  
Prof. Jie Zhang
Keyword(s):  
Mechanical Behavior ◽  
Axial Strain ◽  
Compressive Strain ◽  
High Stress ◽  
Axial Direction ◽  
Soil Parameters ◽  
Buried Pipeline ◽  
Obvious Effect ◽  
Thaw Settlement ◽  
Pipeline Crossing

Abstract Thaw settlement is one of main reason caused pipeline failure crossing cold region. Mechanical behavior of buried pipeline crossing thaw settlement zone is investigated. Effects of pipeline and soil parameters on the buried pipeline were discussed. The results show that the high stress area and the max axial strain of the pipeline is at the edge of the thaw settlement zone. The upper surface of the pipeline is tensile strain, while the lower surface is compressive strain. The max ovality of pipeline near the edge of thaw settlement zone tends to oval. The pipeline axial strain, ovality and displacement decreases with the increasing of pipeline wall thickness, while the change of high stress area is not obvious. The high stress area and ovality decrease with the increasing of pipeline diameter, while the high stress area is expanded along the axial direction, but axial strain decreases slightly. The high stress area, axial strain, ovality and displacement of pipeline decrease with the buried depth increases. With the internal pressure increases, the stress and axial strain of pipeline increase, but the ovality decreases. The soil`s elasticity modulus has no obvious effect on pipeline`s stress, axial strain and displacement, but it can affect ovality slightly.

scholarly journals Numerical simulation of buckling behavior of the buried steel pipeline under reverse fault displacement

2015 ◽  
Vol 6 (2) ◽  
pp. 203-210 ◽  
Author(s):  
J. Zhang ◽  
Z. Liang ◽  
C. J. Han ◽  
H. Zhang
Keyword(s):  
Friction Coefficient ◽  
Internal Pressure ◽  
Structural Integrity ◽  
Reverse Fault ◽  
Buried Pipeline ◽  
Buckling Mode ◽  
Steel Pipeline ◽  
Buckling Behavior ◽  
Pressure Pipeline ◽  
Fault Displacement

Abstract. Reverse fault movement is one of the threats for the structural integrity of buried oil-gas pipelines caused by earthquakes. Buckling behavior of the buried pipeline was investigated by finite element method. Effects of fault displacement, internal pressure, diameter-thick ratio, buried depth and friction coefficient on buckling behavior of the buried steel pipeline were discussed. The results show that internal pressure is the most important factor that affecting the pipeline buckling pattern. Buckling mode of non-pressure pipeline is collapse under reverse fault. Wrinkles appear on buried pressure pipeline when the internal pressure is more than 0.4 Pmax. Four buckling locations appear on the buried pressure pipeline under bigger fault displacement. There is only one wrinkle on the three locations of the pipeline in the rising formation, but more wrinkles on the fourth location. Number of the wrinkle ridges and length of the wavy buckling increase with the increasing of friction coefficient. Number of buckling location decreases gradually with the decreasing of diameter-thick ratio. A protective device of buried pipeline was designed for preventing pipeline damage crossing fault area for its simple structure and convenient installation. Those results can be used to safety evaluation, maintenance and protection of buried pipelines crossing fault area.

Numerical Analysis of Mechanical Behavior of Buried Pipes in Subsidence Area Caused by Underground Mining

2019 ◽  
Vol 141 (2) ◽  
Author(s):  
Jie Zhang ◽  
Rui Xie
Keyword(s):  
Friction Coefficient ◽  
Plastic Strain ◽  
Internal Pressure ◽  
Mechanical Behavior ◽  
Underground Mining ◽  
Axial Strain ◽  
High Stress ◽  
Soil Parameters ◽  
Buried Pipe ◽  
Subsidence Area

The buried pipe crossing the subsidence area is prone to failure. The mechanical behavior of buried pipe in subsidence area was investigated in this paper. Effects of subsidence displacement, pipe parameters and soil parameters on the mechanical behavior were investigated. The results show that high stress appears on the pipe's surface and exceeds the yield strength after the strata subsidence. As subsidence displacement increases, the ranges of high-stress area and displacement increase, and the pipe section changes from a circle to an ellipse. The maximum axial strain occurs on the pipe in no-subsidence area. The maximum plastic strain and ovality of the pipe increase with the increasing of subsidence displacement. The displacement, plastic strain, and ovality of the pipe increase with the increasing of diameter–thickness ratio and buried depth. Internal pressure and friction coefficient has a little effect on the pipe displacement. The ovality decreases as internal pressure increases. The plastic strain and ovality increase with the increasing of the friction coefficient. As the elastic modulus and cohesion of soil increase, the displacement, plastic strain, and ovality of the pipe increase. The effect of Poisson's ratio on the deformation of pipe is small.

Debonding Behaviors of CFRP Strengthened RC Beams with Weak Interfaces

2013 ◽  
Vol 351-352 ◽  
pp. 587-591
Author(s):  
Sen Li ◽  
Xiao Gang Wang ◽  
Xin Gang Zhou
Keyword(s):  
Tensile Strain ◽  
Structural Integrity ◽  
Structural Performance ◽  
Rc Beams ◽  
Test Results ◽  
Weak Interface ◽  
Premature Rupture ◽  
Loading Process ◽  
Interface Effects

Debonding behaviors of CFRP strengthened RC beams were experimentally investigated under the influence of weak interfaces, which are induced either by defective bonding of replaced cover or expansive cracks. Shown by test results, weak interfaces impaired considerably the structural integrity of strengthening systems during loading, and easily led to CFRP debonding failure. U-strips worked effectively in preventing the integral debonding and guarantee the structural performance of flexural sheets. However, local cover delamination in the loading process and premature rupture of flexural CFRP could still take place due to the weak interface effects. Therefore, allowable tensile strain of flexural CFRP should be reduced, and more strict confinement and anchorage measures should be taken in this case.

J and CTOD Based Tensile Strain Capacity Prediction for Pipelines with a Surface Crack in Girth Weld

2021 ◽  
Author(s):  
Youn-Young Jang ◽  
Nam-Su Huh ◽  
Ik-Joong Kim ◽  
Young-Pyo Kim
Keyword(s):  
Crack Initiation ◽  
Internal Pressure ◽  
Surface Crack ◽  
Driving Force ◽  
Tensile Strain ◽  
Structural Integrity ◽  
Accurate Estimation ◽  
Long Distance ◽  
Crack Driving Force ◽  
Girth Welding

Abstract Long-distance pipelines for the transport of oil and natural gas to onshore facilities are mainly fabricated by girth welding, which has been considered as a weak location for cracking. Pipeline rupture due to crack initiation and propagation in girth welding is one of the main issues of structural integrity for a stable supply of energy resources. The crack assessment should be performed by comparing the crack driving force with fracture toughness to determine the critical point of fracture. For this reason, accurate estimation of the crack driving force for pipelines with a crack in girth weld is highly required. This paper gives the newly developed J-integral and crack-tip opening displacement (CTOD) estimation in a strain-based scheme for pipelines with an internal surface crack in girth weld under axial displacement and internal pressure. For this purpose, parametric finite element analyses have been systematically carried out for a set of pipe thicknesses, crack sizes, strain hardening, overmatch and internal pressure conditions. Using the proposed solutions, tensile strain capacities (TSCs) were quantified by performing crack assessment based on crack initiation and ductile instability and compared with TSCs from curved wide plate tests to confirm their validity.

Features Testing of Stud Material Under Low Constraint Ductile Tearing

2017 ◽  
Author(s):  
P. James ◽  
M. Jackson ◽  
P. Birkett ◽  
C. Madew
Keyword(s):  
Structural Integrity ◽  
High Stress ◽  
Crack Tip ◽  
Pressure Vessels ◽  
Materials Testing ◽  
Screw Thread ◽  
Surface Point ◽  
Defect Tolerance ◽  
Material Response ◽  
Crack Tip Constraint

Defect tolerance assessments are carried out to support the demonstration of structural integrity for high integrity components such as nuclear reactor pressure vessels. These assessments often consider surface-breaking defects and assess Stress Intensity Factors (SIFs) at both the surface and deepest points. This can be problematic when there is a high stress at the surface, for example due to the stress concentration at the root of a screw thread. In the past this has led to the development of complex and costly 3D finite element analyses to calculate more accurate SIFs, and still resulting in small apparent limiting defect sizes based on initiation at the surface point. Analysis has been carried out along with supporting materials testing, to demonstrate that the increased SIF at the surface point is offset by a reduction in crack-tip constraint, such that the material exhibits a higher apparent fracture toughness. This enables a more simplistic assessment which reduces the effective SIF at the surface such that only the SIF at the deepest point needs to be considered. This then leads to larger calculated limiting defect sizes. This in turn leads to a more robust demonstration of structural integrity, as the limiting defect sizes are consistent with the capability of non-destructive examination techniques. The high SIF at the surface location, and the concomitant reduction in crack-tip constraint, meant that it was not possible to demonstrate the material response with conventional tests, such as those using shallow-notched bend specimens. Instead it was necessary to develop modified specimens in which semielliptical defects were introduced into a geometry which replicated the notch acuity at the root of a screw thread. These feature tests were used to demonstrate the principle, prior to testing with more conventional specimens to fit more accurately the parameters required to represent the material response in a defect tolerance assessment. Margins in defect tolerance assessments are usually measured against the initiation of tearing, even though the final failure for the material may occur at a higher load following stable crack extension. This work measured and assessed the benefit of reduced crack-tip constraint on both the point of initiation and on the development of the tearing resistance curve. This demonstrated that the effect of constraint was valid with tearing for this material and that there was additional margin available beyond the onset of tearing. The feature test geometry also provided evidence of the tearing behaviour at the surface and deepest points of a surrogate component under representative loading. This paper provides an overview of the range of tests performed and the post-test interpretation performed in order to provide the R6 α and k constraint parameters.

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