Use of Discrete Element Modeling to Capture the Effect of Backfill Particle Size on the Soil Restraints of Buried Pipelines Subjected to Lateral Ground Movement

2014 ◽  
Author(s):  
Sadana Dilrukshi ◽  
Dharma Wijewickreme
Keyword(s):  
Particle Size ◽  
Friction Angle ◽  
Discrete Element ◽  
Ground Movement ◽  
Scale Model ◽  
Discrete Element Modeling ◽  
Buried Pipelines ◽  
Ground Movements ◽  
Backfill Material ◽  
Ground Deformations

Geotechnical hazards can be a major cause of damage to pipelines, particularly as a result of unacceptable strains induced in buried pipelines due to permanent ground deformations. The common design philosophy in reducing soil restraint involves taking measures to effectively isolate the pipeline from the anticipated surrounding soil movements. One of the important engineering design considerations in this regard is the selection of suitable trench backfill material(s). Full-scale model tests have revealed that, in addition to the internal friction angle, coarseness of the backfill material is also an important parameter in controlling the lateral soil restraints on the pipes due to ground movements. It can be demonstrated that discrete element approach is suitable to study the effect of particle size on lateral soil loads of buried pipelines subjected to ground movement. This paper describes the outcome from DEM numerical modeling of the response of buried pipelines subjected to lateral ground movements, with a comparison of the findings with experimental results.

scholarly journals Effects of Axial Relative Ground Movement on Small Diameter Polyethylene Piping in Loose Sand

2021 ◽  
Vol 6 (12) ◽  
pp. 168
Author(s):  
Auchib Reza ◽  
Ashutosh Sutra Dhar
Keyword(s):  
Distribution System ◽  
Design Method ◽  
Small Diameter ◽  
Friction Angle ◽  
Design Guidelines ◽  
Ground Movement ◽  
Loose Sand ◽  
Ground Movements ◽  
Rate Dependent ◽  
Pulling Force

Small diameter (42 mm) medium density polyethylene (MDPE) pipes are widely used in the gas distribution system in Canada and other countries. They are sometimes exposed to ground movements resulting from landslides or earthquakes. The current design guidelines for evaluating the pipes subjected to ground movement were developed for steel pipes of larger diameters and may not apply to flexible MDPE pipes. This paper evaluates 42 mm diameter MDPE pipes buried in loose sand under axial relative ground movement for developing a design method for the pipes. MDPE is a viscoelastic material; therefore, the behaviour of MDPE pipes exposed to landslides would depend on the rate of ground movements. In this research, full-scale laboratory tests were conducted to investigate the responses of buried pipes under various rates of relative axial displacement. Finite element modelling of the tests was used to interpret the observed behaviour using the continuum mechanics framework. The study revealed that the pulling force on the pipe depends on the rate of relative ground displacement (pulling rate). The nondimensional pulling force possessed a nonlinear relationship with the pulling rate. A rate-dependent interface friction angle could be used to calculate the maximum pulling forces using the conventional design guidelines for the pipes in loose sand. Based on the pulling force, the pipe wall strains can be estimated using the methods available for larger diameter pipes.

Stress Analysis of Surface Pipelines Located in Regions of Differential Ground Movements

2006 ◽  
Author(s):  
Kam Deng ◽  
David J. Queen ◽  
Andreas Felber ◽  
Don W. Bergman
Keyword(s):  
Stress Analysis ◽  
Ground Movement ◽  
Analysis Program ◽  
Buried Pipeline ◽  
Buried Pipelines ◽  
Ground Movements ◽  
Load Paths ◽  
Load Effects ◽  
Stage Analysis ◽  
The Impact

Buried pipelines running through areas of large differential ground movements, such as active landslides, can be subject to severe overstress conditions. Moving these pipelines to the surface (i.e. surfacing) and resting them on timber skids reduces the impact of ground movements because slippage can occur between the pipe and the skids. This approach has been used successfully on several pipelines. Surfacing was recently considered for a 4.5 km section of a buried pipeline situated in northern British Columbia. The surfaced pipeline is supported by timber skids every 2 m and winds through mountainous terrain containing twenty different movement zones in which differential displacements range from 0 m to 3 m. Along the route, the direction of the ground movement varied with the terrain. The alignment also crossed a creek with a 45 m clear span. This paper describes the methodology used in completing the stress analysis for the surfaced pipeline. To capture various load effects, an existing construction stage analysis program was modified to facilitate the modelling of the surface pipeline under the various load paths. The evolution of the displacement and stress state of the pipeline was determined and tracked for several different load paths. For each state, a single plot that summarized the ground movement, slip distances, skid reactions and pipe stresses was produced. The results from this analysis are used to discuss the response of surface pipelines under thermal and ground movement loads.

scholarly journals An Energy-Based Discrete Element Modeling Method Coupled with Time-Series Analysis for Investigating Deformations and Failures of Jointed Rock Slopes

2021 ◽  
Vol 11 (12) ◽  
pp. 5447
Author(s):  
Xiaona Zhang ◽  
Gang Mei ◽  
Ning Xi ◽  
Ziyang Liu ◽  
Ruoshen Lin
Keyword(s):  
Time Series ◽  
Iterative Process ◽  
Discrete Element ◽  
Jointed Rock ◽  
Modeling Method ◽  
Discrete Element Modeling ◽  
Rock Slopes ◽  
Sliding Surface ◽  
Element Modeling ◽  
Displacement Based

The discrete element method (DEM) can be effectively used in investigations of the deformations and failures of jointed rock slopes. However, when to appropriately terminate the DEM iterative process is not clear. Recently, a displacement-based discrete element modeling method for jointed rock slopes was proposed to determine when the DEM iterative process is terminated, and it considers displacements that come from rock blocks located near the potential sliding surface that needs to be determined before the DEM modeling. In this paper, an energy-based discrete element modeling method combined with time-series analysis is proposed to investigate the deformations and failures of jointed rock slopes. The proposed method defines an energy-based criterion to determine when to terminate the DEM iterative process in analyzing the deformations and failures of jointed rock slopes. The novelty of the proposed energy-based method is that, it is more applicable than the displacement-based method because it does not need to determine the position of the potential sliding surface before DEM modeling. The proposed energy-based method is a generalized form of the displacement-based discrete element modeling method, and the proposed method considers not only the displacement of each block but also the weight of each block. Moreover, the computational cost of the proposed method is approximately the same as that of the displacement-based discrete element modeling method. To validate that the proposed energy-based method is effective, the proposed method is used to analyze a simple jointed rock slope; the result is compared to that achieved by using the displacement-based method, and the comparative results are basically consistent. The proposed energy-based method can be commonly used to analyze the deformations and failures of general rock slopes where it is difficult to determine the obvious potential sliding surface.

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