Failure Mechanisms of Pipelines Subjected to Loss of Support Under Deep Burial Conditions

2004 ◽  
Author(s):  
Yuri D. Costa ◽  
Jorge G. Zornberg ◽  
Benedito S. Bueno ◽  
Carina L. Costa
Keyword(s):  
Vertical Section ◽  
Failure Mechanisms ◽  
Soil Mass ◽  
Experimental Program ◽  
Rigid Base ◽  
Failure Patterns ◽  
Slip Surfaces ◽  
Deep Burial ◽  
Flexible Pipes ◽  
Adjacent Soil

This paper investigates the failure mechanisms of pipelines subjected to a localized loss of support. An experimental program was conducted, which consisted of a series of four centrifuge model tests containing an aluminum tube embedded in a pure dry sand backfill that was placed over an underlying rectangular rigid base moving downwards during the test. All models were built taking advantage of the longitudinal symmetry of the problem. The prototype pipe had a diameter (D) of 1.1 m and a soil cover height of about 5 D, characterizing deep burial conditions. Failure patterns were observed within a vertical section comprising the central axis of the pipe and also in four distinct vertical transverse sections along the length of the pipe in the region of ground loss. The influence of pipe stiffness and backfill density on the behavior of the system was assessed. The transverse sections showed fully developed slip surfaces starting in the vicinity of the edge of the void towards the adjacent soil mass. The mode of failure of the flexible pipes took the form of a severe deformation at the region of the shoulder and a reversal of curvature at the invert due to over-deflection. This situation was more critical in the central section. The damage experienced by the flexible pipes was noticeably more pronounced when using the looser backfill, whereas only negligible deflections were observed when using the denser backfill. The experimental results were compared with analytical predictions, which showed to be highly unconservative for the case loose backfill.

Soil Stresses on Carbon Steel Pipe Undergoing Uplift

2016 ◽  
Vol 835 ◽  
pp. 439-443
Author(s):  
Yuri D. Costa ◽  
Lucas S. Moraes ◽  
Carina L. Costa
Keyword(s):  
Carbon Steel ◽  
Relative Density ◽  
Numerical Study ◽  
Three Dimensional ◽  
Soil Mass ◽  
Steel Pipe ◽  
Surcharge Loading ◽  
Flexible Pipes ◽  
Stress Variations

This paper presents a three-dimensional numerical study to evaluate the variations in stresses in the soil mass surrounding a carbon steel pipe class API 5L X60 submitted to uplift due to ground elevation. Analyses were carried out for soil relative density, pipe stiffness and surficial surcharge loading. Results have shown that stress variations due to uplift are lower for looser backfill soils and flexible pipes. Stress variations in pipe invert are meaningful in the vicinity of the region between stable and unstable soil masses.

Deformation and Failure Behavior of Woven Composite Laminates

1994 ◽  
Vol 116 (2) ◽  
pp. 222-232 ◽  
Author(s):  
M. Karayaka ◽  
P. Kurath
Keyword(s):  
Composite Laminates ◽  
Failure Mechanisms ◽  
Elastic Stiffness ◽  
Experimental Program ◽  
Internal Stresses ◽  
Failure Behavior ◽  
Deformation Model ◽  
Deformation And Failure ◽  
Linear Elastic ◽  
Proposed Model

Conceptually, fabric composites have some structural advantages over conventional laminates. However, deformation and failure analyses become more complex with the additional anisotropy introduced by the weaving geometry. A micromechanistic deformation model, that could realistically be incorporated into structural finite element codes, is proposed where loading direction and weave parameters are allowed to vary. Comparisons are made to previous models and experimental results for woven materials, indicating that the proposed model provides improved estimates for the linear elastic stiffness. The model further provides predictions for internal stresses in the longitudinal, transverse, and interlace regions of the woven laminate which qualitatively correspond to the experimentally observed failure mechanisms. The experimental program investigates deformations behavior and failure mechanisms of 5-harness 0/90 weave Graphite/Epoxy laminates under tension, compression, and 3-point and 4-point bending loading. Under these conditions the woven laminates exhibit orientation dependent mechanical properties and strength.

scholarly journals Improved Shear Strength Performance of Compacted Rubberized Clays Treated with Sodium Alginate Biopolymer

Polymers ◽  
2021 ◽  
Vol 13 (5) ◽  
pp. 764
Author(s):  
Amin Soltani ◽  
Ramin Raeesi ◽  
Abbas Taheri ◽  
An Deng ◽  
Mehdi Mirzababaei
Keyword(s):  
Sodium Alginate ◽  
Clay Content ◽  
Soil Mass ◽  
Experimental Program ◽  
High Plasticity ◽  
Content Increase ◽  
Sem Images ◽  
Strength Performance ◽  
Environmentally Sustainable ◽  
Soil Clay Content

This study examines the potential use of sodium alginate (SA) biopolymer as an environmentally sustainable agent for the stabilization of rubberized soil blends prepared using a high plasticity clay soil and tire-derived ground rubber (GR). The experimental program consisted of uniaxial compression and scanning electron microscopy (SEM) tests; the former was performed on three soil–GR blends (with GR-to-soil mass ratios of 0%, 5% and 10%) compacted (and cured for 1, 4, 7 and 14 d) employing distilled water and three SA solutions—prepared at SA-to-water (mass-to-volume) dosage ratios of 5, 10 and 15 g/L—as the compaction liquid. For any given GR content, the greater the SA dosage and/or the longer the curing duration, the higher the uniaxial compressive strength (UCS), with only minor added benefits beyond seven days of curing. This behaviour was attributed to the formation and propagation of so-called “cationic bridges” (developed as a result of a “Ca2+/Mg2+ ⟷ Na+ cation exchange/substitution” process among the clay and SA components) between adjacent clay surfaces over time, inducing flocculation of the clay particles. This clay amending mechanism was further verified by means of representative SEM images. Finally, the addition of (and content increase in) GR—which translates to partially replacing the soil clay content with GR particles and hence reducing the number of available attraction sites for the SA molecules to form additional cationic bridges—was found to moderately offset the efficiency of SA treatment.

scholarly journals Residual Tensile Stress Estimation for Shear Strength of UHPC Nonprismatic Beams

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Nasser Hakeem Tu’ma ◽  
Mustafa Raad Aziz ◽  
Haider Jabbar J. Barry
Keyword(s):  
Shear Strength ◽  
Tensile Stress ◽  
High Performance ◽  
High Performance Concrete ◽  
Longitudinal Axis ◽  
Steel Fibers ◽  
Experimental Program ◽  
Residual Tensile Stress ◽  
Ultra High Performance Concrete ◽  
Failure Patterns

Abstract Estimating the shear strength of Ultra-High-Performance Concrete (UHPC), with high compressive and tensile strengths, is complicated by many variables that affecting its behavior. Residual tensile stress (RTS) plays an important role in raising the efficiency of both types of resistance, especially shear strength due to the presence of steel fibers, which makes it difficult to quantify the residual tensile stress due to the different failure patterns of these fibers and the distribution mechanism within the concrete matrix. There is no study to date in assessing residual tensile stress of UHPC structural members of the variable section. Thirteen beams were selected as an experimental program to study six main variables in determining shear strength. Stirrups ratio, flexural reinforcement ratio, the volumetric fraction of steel fibers, geometry changing, existing openings along the longitudinal axis, and shear span to depth ratio. According to on Tests results, RTS is compatible with most of the global specifications.

Plausible failure mechanisms of wildlife-damaged earth levees: insights from centrifuge modeling and numerical analysis

2017 ◽  
Vol 54 (10) ◽  
pp. 1496-1508 ◽  
Author(s):  
Gholamreza Saghaee ◽  
Ahmad A. Mousa ◽  
Mohamed A. Meguid
Keyword(s):  
Pore Pressure ◽  
Failure Mechanisms ◽  
Hydraulic Gradient ◽  
The Body ◽  
Centrifuge Modeling ◽  
Silty Sand ◽  
Failure Patterns ◽  
Animal Burrows ◽  
Wide Range ◽  
The Impact

Earth levees are subject to a wide range of wildlife intrusion patterns that cause mass removal and subsequent serious deformations. Such invasive activities leave the body of an earth embankment with burrow systems too complex to map and model using conventional techniques. This study investigates the impact of different idealized configurations of animal burrows on the geotechnical performance of levees. For this purpose, centrifuge testing was conducted on homogenous scaled-down 1 horizontal : 1 vertical (1H:1V) levee models built from silty sand material. Modeling involved introducing horizontal cylinder-shaped waterside and landside burrows at different elevations within the levee section. The reference (intact) and deteriorated levee models were subject to a centrifugal acceleration of 35g, which was kept constant as the water level behind the levee model was gradually increased. The deformation profile of the model was tracked, and the crest displacements were concurrently measured. Miniature pore pressure transducers (PPTs) embedded within the levee body provided pore pressure measurements. A three-dimensional finite element model was developed to investigate the hydraulic performance and verify the failure patterns of the deteriorated levees. Compared with an intact levee, the presence of animal intrusions was found to increase the exit hydraulic gradient for both waterside and landside intrusions. Lower animal burrows appeared to cause larger exit gradients than higher ones. Similarly, waterside burrows exhibited a notably higher pore pressure and larger hydraulic gradient. Waterside damage resulted in a quicker and more violent failure than landside burrows. The failure mechanisms for both the waterside and landside burrows are dissimilar despite their similarly abrupt nature.

scholarly journals Seismic Fragility of Chinese Light-Gauge Steel Keel Gypsum Board Partition Walls

2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Duozhi Wang ◽  
Xudong Zhi ◽  
Fangxu Zhu ◽  
Yixing Wang
Keyword(s):  
Failure Mechanisms ◽  
Seismic Damage ◽  
Basic Data ◽  
Seismic Fragility ◽  
Experimental Program ◽  
Engineering Practice ◽  
Gypsum Board ◽  
Nonstructural Components ◽  
Partition Walls ◽  
Damage States

A quasi-static experimental program of light-gauge steel keel gypsum board partition walls (LSKGBPW) was carried out to evaluate the seismic damage phenomena, failure mechanisms, and fragility. The 15 specimens in five groups were designed per current Chinese codes and engineering practice. Then, three damage states were defined based on the damage and repair measures, and the fragility data of each group were presented, providing basic data for the estimation of seismic damage and consequential loss of nonstructural components.

Evaluation of earthquake resistance of deep foundations of bridge supports, taking into account the interaction with the adjacent soil mass

1981 ◽  
Vol 18 (2) ◽  
pp. 66-70
Author(s):  
A. A. Nikitin ◽  
O. D. Tananaiko ◽  
A. M. Uzdin ◽  
M. A. Shvarts ◽  
S. A. Shul'man
Keyword(s):  
Soil Mass ◽  
Earthquake Resistance ◽  
Deep Foundations ◽  
Adjacent Soil

An Overview of Risk-Based Inspection Planning for Flexible Pipeline

2018 ◽  
Author(s):  
Hamad Hameed ◽  
Guowei Sun ◽  
Yong Bai
Keyword(s):  
Failure Mechanisms ◽  
Cost Effective ◽  
Initial Assessment ◽  
Risk Level ◽  
Pipeline System ◽  
Inspection Planning ◽  
Flexible Pipes ◽  
System Risk ◽  
Integrity Management ◽  
Detailed Assessment

There are many failure mechanisms that may occur in flexible pipes during their service life, such as external sheath damage, damage of tensile armours due to fatigue, kinks due to corrosion, and over-bending. The above mentioned defects are very common and can lead to the failure of flexible pipes. Therefore, huge operational costs have to be spent to ensure the integrity of the flexible pipeline system. Risk-Based inspection (RBI) methodology can establish a cost-effective strategy for inspection and monitoring, while maintaining the expected level of safety. However, there are some factors that can hamper the development of an optimized RBI for the integrity management of flexible pipelines, such as the complexity and variety of flexible pipes’ multi-layer structures with their interacting failure mechanisms, the somewhat poor defect capability of the existing inspection techniques and the lack of broad [1]. In this paper, RBI planning is described thoroughly to ensure the integrity management of flexible pipelines. All risk terms have been described in detail with respect to integrity management strategy. The working process of RBI, including initial assessment and detailed assessment, is introduced. Estimation and evaluation of risk level, including the development of optimized inspection planning, have been described completely.

Analysis of Failure Mechanisms during Powder Compaction

2007 ◽  
Vol 534-536 ◽  
pp. 237-240 ◽  
Author(s):  
Chuan Yu Wu ◽  
A.C. Bentham ◽  
A. Mills
Keyword(s):  
Early Stage ◽  
Failure Mechanisms ◽  
Shear Bands ◽  
Powder Compaction ◽  
Hydraulic Press ◽  
Practical Significance ◽  
Pharmaceutical Powders ◽  
Pharmaceutical Tablets ◽  
Failure Patterns ◽  
Wide Range

Powder compaction is a well-established process for manufacturing a wide range of products, including engineering components and pharmaceutical tablets. During powder compaction, the compacts (green bodies or tablets) produced need to sustain their integrity during the process and possess certain strength. Any defects are hence not tolerable during the production. Therefore, understanding failure mechanisms during powder compaction is of practical significance. In this paper, the mechanisms for one typical failure, capping, during the compaction of pharmaceutical powders were explored. Both experimental and numerical investigations were performed. For the experimental study, an instrumented hydraulic press (a compaction simulator) with an instrumented die has been used, which enable the material properties to be extracted for real pharmaceutical powders. Close attentions have been paid to the occurrence of capping during the compaction. An X-ray Computed Microtomography system has also used to examine the internal failure patterns of the tablets produced. Finite element (FE) methods have also been used to analyse the powder compaction. The experimental and numerical studies have shown that the shear bands developed at the early stage of unloading appear to be responsible for the occurrence of capping. It has also been found that the capping patterns depend on the compact shape.

Direct Visualization of the Initiation and Progression of Vertebral Fractures

2010 ◽  
Author(s):  
Amira I. Hussein ◽  
Elise F. Morgan
Keyword(s):  
Vertebral Fractures ◽  
Failure Mechanisms ◽  
Image Data ◽  
Quantitative Information ◽  
Digital Volume Correlation ◽  
Direct Visualization ◽  
Finite Element Analyses ◽  
Micro Computed Tomography ◽  
Failure Patterns ◽  
Large Size

Vertebral fractures are the hallmark of osteoporosis, yet the failure mechanisms involved in these fractures are not well understood. Failure patterns within whole vertebrae are typically estimated from finite element analyses or from images acquired after fracture has occurred. Experimental measurement of deformations sustained by vertebrae during injurious loading would enable direct visualization of vertebral failure mechanisms as well as the possibility of validating the results of numerical simulations of vertebral fracture. Time-lapsed micro-computed tomography (μCT) has been used previously to visualize failure processes in excised specimens of trabecular bone [1,2], and methods of digital volume correlation (DVC) can be applied to these types of image series to obtain quantitative information on the deformations that the bone undergoes [3]. However, application of DVC to whole bones has not been reported and involves additional challenges such as the irregular geometry of the volume and the large size of the sets of image data. The overall goal of this study was to develop a DVC-based method for quantifying deformations throughout entire vertebrae as these vertebrae are loaded to failure.

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