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.

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.

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.

Simulation of Influence of Friction Coefficient on Extrusion of TC4 Alloy

2013 ◽  
Vol 470 ◽  
pp. 244-249
Author(s):  
Chang Dong Liu ◽  
Yi Du Zhang
Keyword(s):  
Friction Coefficient ◽  
Strain Rate ◽  
Effective Strain ◽  
High Stress ◽  
Extrusion Process ◽  
Extrusion Pressure ◽  
Tc4 Alloy ◽  
Stress Zone ◽  
D Model ◽  
High Stress Zone

Based on Simufact11.0, a 3-D model of T profile extrusion is established and the extrusion process of TC4 is investigated using finite volumemethod(FVM) of Euler mesh description. Effects of different friction coefficients on the effective stress, extrusion pressure, effective strain and effective strain rate have been studied. The study shows that there is a high-stress zone at a certain distance from the entrance of the forming area and a high strain rate zone around that area. With the increase of friction coefficient, the value of the stress increased and the deformation is more uneven. The track of extrusion pressure shows that extrusion increase with the increase of friction coefficient.

Elasto-Plastic Large Deflection Analysis of a Copper Film

1992 ◽  
Vol 114 (2) ◽  
pp. 221-225
Author(s):  
J. H. Lau
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Plastic Strain ◽  
Mechanical Behavior ◽  
Effective Stress ◽  
Large Deflection ◽  
Applied Pressure ◽  
Copper Film ◽  
Engineering Practice ◽  
Deflection Analysis

The ductility of a copper film has been determined by an elastoplastic large deflection finite element method. The effective stress and incremental plastic strain and pressure-deflection curves of the copper film have also been provided for a better understanding of its mechanical behavior. Furthermore, for engineering practice convenience, the ductility and effective stress of the copper film have been plotted as functions of measurable variables, i.e., applied pressure and deflection at the center of the bulge.

scholarly journals Factors Influencing Ore Recovery and Unplanned Dilution in Sublevel Open Stopes. Case study of Shaft No.4 at Konkola Mine, Zambia

2020 ◽  
Vol Special Issue (1) ◽  
Author(s):  
Kalunga Ngoma ◽  
Victor Mutambo
Keyword(s):  
Numerical Modelling ◽  
Principal Stress ◽  
Underground Mining ◽  
Poisson Ratio ◽  
High Stress ◽  
Geological Strength Index ◽  
Total Displacement ◽  
Ground Conditions ◽  
Geological Discontinuities ◽  
Major Principal Stress

Konkola Copper Mine’s Number 4 Shaft is a trackless underground mine applying sublevel open stoping (SLOS) mining method. Number 4 shaft wants to increase ore production from 1 million metric tonnes per annum to 3 million metric tonnes per annum in the next 5 years but ore recovery is 70% or less and dilution is 20% or more. In order to achieve the desired annual target of 3 million metric tonnes ore recovery should be increased from70% to (≥85%) and dilution should be reduced from 20% to (≤10%). Despite being one of the most used underground mining methods, the current SLOS has a challenge of high unplanned dilution. This paper reviews and evaluates parameters that influence recovery and unplanned dilution in sublevel open stopes and applies numerical modelling using PHASE2 software to establish the influence of stress environment on unplanned dilution at the mine. The input parameters for numerical modelling were: Uniaxial Compressive strength (UCS=170MPa), Geological Strength Index (GSI) =55, Young’s Modulus (E) =26000MPa, Hoek-Brown constant (s) =0.0067, Hoek-Brown constant (mi) =20 and Poisson ratio (v) =0.2 major principal stress (σ1) 39MPa, intermediate stress (σ2= 18MPa) and the minor principal stress (σ3= 15MPa). Results obtained from review of mine production records indicate that the main factors that influence unplanned dilution at Number 4 shaft are: poor ground conditions, lack of compliance to recommended stope designs, poor drilling and blasting practices, presence of geological discontinuities, adopted mining sequence of extracting high ore grade first that leads to creation of high stress blocks within the orebody and delayed mucking practice. Results obtained from PHASE 2D model indicate that total displacement of 90mm is recorded in the hangingwall hence influencing stope wall instability that leads to increased unplanned dilution. After stope extraction, it was observed that 60MPa of induced stress developed at the top right corner and 45-50 MPa at the crown pillar and right bottom corner of the stope.

A Comprehensive Study on Burst Pressure Performance of Aluminum Liner for Hydrogen Storage Vessels

2021 ◽  
Vol 143 (4) ◽  
Author(s):  
Serkan Kangal ◽  
A. Harun Sayı ◽  
Ozan Ayakdaş ◽  
Osman Kartav ◽  
Levent Aydın ◽  
...  
Keyword(s):  
Internal Pressure ◽  
Axial Strain ◽  
Cylindrical Part ◽  
Pressure Vessels ◽  
Fe Analysis ◽  
Burst Pressure ◽  
Experimental Investigations ◽  
Fe Model ◽  
Stress Criterion ◽  
Analytical Approaches

Abstract This paper presents a comparative study on the burst pressure performance of aluminum (Al) liner for type-III composite overwrapped pressure vessels (COPVs). In the analysis, the vessels were loaded with increasing internal pressure up to the burst pressure level. In the analytical part of the study, the burst pressure of the cylindrical part was predicted based on the modified von Mises, Tresca, and average shear stress criterion (ASSC). In the numerical analysis, a finite element (FE) model was established in order to predict the behavior of the vessel as a function of increasing internal pressure and determine the final burst. The Al pressure vessels made of Al-6061-T6 alloy with a capacity of 5 L were designed. The manufacturing of the metallic vessels was purchased from a metal forming company. The experimental study was conducted by pressurizing the Al vessels until the burst failure occurred. The radial and axial strain behaviors were monitored at various locations on the vessels during loading. The results obtained through analytical, numerical, and experimental work were compared. The average experimental burst pressure of the vessels was found to be 279 bar. The experimental strain data were compared with the results of the FE analysis. The results indicated that the FE analysis and ASSC-based elastoplastic analytical approaches yielded the best predictions which are within 2.2% of the experimental burst failure values. It was also found that the elastic analysis underestimated the burst failure results; however, it was effective for determining the critical regions over the vessel structure. The strain behavior of the vessels obtained through experimental investigations was well correlated with those predicted through FE analysis.

scholarly journals Compression and Shear Fracture Analysis of Boundary Cracks Containing Water in Rock

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Zhensheng Yang ◽  
Fulin Li ◽  
Tianran Ma
Keyword(s):  
Stress Intensity ◽  
Friction Coefficient ◽  
Stress Intensity Factors ◽  
Underground Mining ◽  
Shear Fracture ◽  
Water Environment ◽  
Initial Crack ◽  
Open Boundary ◽  
Shear Stresses ◽  
Intensity Factors

In order to conserve the water resource during underground mining, the fracture and mechanical properties of rock are important for the stability of water-resisting layers, especially for the fracture behavior of boundary cracks containing water in rock. Considering the swelling of rock under water environment and the influence of water on rock, the stress intensity factors of modes I and II are derived for boundary cracks in rock under compressive and shear stresses. The cracks are divided into the closed and open states. The effects of the crack inclination angle, friction coefficient between crack surfaces, and initial crack length on stress intensity factors are also taken into account. The stress intensity factors for closed and open boundary cracks are verified by numerical and physical experiments, respectively, and the deviation of the results is within 5%. It is shown that pore pressure has different effects on the relationship between stress intensity factor and friction coefficient under different lateral pressures. The effect of water on crack propagation is mainly due to the deterioration of the fracture toughness of the rock. It is found that the critical coefficient λc is a key parameter to determine whether the boundary crack propagates in rock under compression-shear stress. Further studies should be performed to apply the present fracture theory to rock mass or water-resisting layers.

Strain-based fatigue life analysis of pipelines with external defects under cyclic internal pressure

2020 ◽  
pp. 030932472095756
Author(s):  
Hojjat Gholami ◽  
Shahram Shahrooi ◽  
Mohammad shishehsaz
Keyword(s):  
Fatigue Life ◽  
Stress Concentration ◽  
Plastic Strain ◽  
Internal Pressure ◽  
Oil And Gas ◽  
Isotropic Hardening ◽  
Element Simulation ◽  
Life Analysis ◽  
Fatigue Life Analysis ◽  
Pipe Geometry

Gouge and dent are common mechanical defects in oil and gas pipelines. These defects with plastic strain cause stress concentration in the pipelines. Plastic strain is dependent on initial deformation and spring-back behavior of materials. Therefore, they reduce the fatigue life of pipelines. In this paper, the strain-base fatigue life analysis is investigated in pipelines with smooth dent or combination smooth dent and gouge defects under cyclic internal pressure. For this purpose, elastic-plastic multilinear isotropic hardening finite element simulation was used to investigate the effects of various factors, such as residual stress of dent, amplitude internal pressure, pipe geometry, gouge geometry, and smooth dent geometry on stress concentration factor (SCF). Finally, a new method is proposed for predicting the fatigue life of pipelines with uniform dent and uniform dent and gouge combination defects. The model is presented based on the Smith-Watson-Topper (SWT) criterion. A set of fatigue life test specimens with various pipe materials, size and geometry were prepared and tested. The specimens carried a smooth dent, as well as a combination of smooth dent and gouge defects, results of which were collected to validate those obtained based on the proposed model. The results of the predicted tests using the developed formula showed a good correlation to practical experiments.

scholarly journals Mining-Induced Failure Criteria of Interactional Hard Roof Structures: A Case Study

Energies ◽  
2019 ◽  
Vol 12 (15) ◽  
pp. 3016 ◽  
Author(s):  
Shen ◽  
Wang ◽  
Cao ◽  
Su ◽  
Nan ◽  
...  
Keyword(s):  
Mechanical Behavior ◽  
Longwall Mining ◽  
Underground Mining ◽  
Failure Criteria ◽  
Normal Operation ◽  
Analysis Model ◽  
Plane Stress Condition ◽  
Field Case ◽  
Hard Roof ◽  
Soft Interlayer

Due to the additional abutment stress, interactional hard roof structures (IHRS) affect the normal operation of the coal production system in underground mining. The movement of IHRS may result in security problems, such as the failure of supporting body, large deformation, and even roof caving for nearby openings. According to the physical configuration and loading conditions of IHRS in a simple two-dimensional physical model under the plane stress condition, mining-induced failure criteria were proposed and validated by the mechanical behavior of IHRS in a mechanical analysis model. The results indicate that IHRS, consisting of three interactional parts—the lower key structure, the middle soft interlayer, and the upper key structure—are governed by the additional abutment stress induced by the longwall mining working face. The fracture of the upper key structure in IHRS can be explained as follows: Due to the crushing failure, lower key structure, and middle soft interlayer yield, the action force between the upper and lower key structures vanishes, resulting in fracture of the upper key structure in IHRS. In a field case, when additional abutment stress reaches 7.37 MPa, the energy of 2.35 × 105 J is generated by the fracture of the upper key structure in IHRS. Under the same geological and engineering conditions, the energy generated by IHRS is much larger than that generated by a single hard roof. The mining-induced failure criteria are successfully applied in a field case. The in-situ mechanical behavior of the openings nearby IHRS under the mining abutment stress can be clearly explained by the proposed criteria.

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