Effect of Drainage on Upheaval Buckling Susceptibility of Buried Pipelines

2017 ◽  
Author(s):  
Joe G. Tom ◽  
David J. White
Keyword(s):  
Soil Conditions ◽  
Soil Drainage ◽  
Buried Pipelines ◽  
Local Flow ◽  
Plane Failure ◽  
Upheaval Buckling ◽  
Numerical Predictions ◽  
The Common ◽  
Undrained Conditions ◽  
Uplift Resistance

This paper investigates the effect of soil drainage on the uplift resistance of buried pipelines, and their susceptibility to upheaval buckling. The uplift resistance of buried pipelines is considered through analytical and numerical predictions for both drained and undrained conditions. Combinations of soil strength parameters for typical soils are estimated based on common correlations. For certain ranges of typical normally consolidated soil conditions, particularly those with high critical state friction angles, the drained uplift resistance may be lower than the undrained resistance. This observation is important because in typical practice only drained or undrained behaviour is considered depending on the general type of soil backfill used. In this case, the critical or minimum uplift resistance may be overlooked. Further, the changing undrained uplift mechanism between shallow and deep conditions is investigated. It is found that the common approach of considering the minimum of either a local (flow around) or global (vertical slip plane) failure can overestimate the uplift resistance in normally consolidated soils.

Design of Buried Pipelines in Soft Clay: A Case Study

2019 ◽  
Author(s):  
Martin Gallegillo ◽  
Michele Cerulli ◽  
Ali Haghighi ◽  
Justin Kennedy
Keyword(s):  
Soft Clay ◽  
Scale Model ◽  
Design Calculation ◽  
Buried Pipelines ◽  
Local Flow ◽  
Significant Saving ◽  
Soil Response ◽  
Upheaval Buckling ◽  
Flow Round

Abstract High pressure high temperature offshore pipelines are generally buried for protection. For buried pipelines, upheaval buckling can be triggered in the presence of vertical imperfections when the pipeline compressive state is increased. One of the main uncertainties in the design calculation is the soil resistance to upward and downward movement and the displacement at which the peak resistance is mobilised. For clays the soil response will usually be undrained, certainly for most loading events, however it may also be necessary to consider the drained response (particularly if there is any long term applied uplift). In addition, local flow-round failure mechanism may occur, generally for deeply buried pipelines. If local failure dominates the design, it may not be possible to bury the pipeline. This could have significant cost implications. An experimental programme was carried out to determine the uplift resistance of buried pipelines in soft clay soils. The results of scale model testing and computational analysis (finite element limit analysis) showed that the local behaviour was not applicable. The implications of these results are illustrated in a case study upheaval buckling (UHB) analysis. The overall result was a significant saving on rockdump quantities. The implications for the case study are presented in this paper alongside a description of other backfill requirements and practical considerations for a UHB design.

UHB Design Approach for Multiple Pipelines Installed in Shared Trench

2019 ◽  
Author(s):  
M. Liu ◽  
C. Cross
Keyword(s):  
Proximity Effect ◽  
Burial Depth ◽  
Field Development ◽  
Upheaval Buckling ◽  
Resistance Reduction ◽  
Failure Angle ◽  
The Common ◽  
Uplift Resistance ◽  
Mitigation Design ◽  
Offshore Field

Abstract Upheaval buckling (UHB) mitigation for trenched and buried pipelines can constitute a substantial cost element for offshore field development. There appears to have a variety of reasons for dual or more pipelines and umbilicals to be considered for installation inside the same trench. A single shared trench has been used for multiple pipelines not only for cost saving, but especially when constrained and driven by route corridor challenges. The common practice for dual pipeline trenching and UHB design is to either perform UHB design independently without due consideration of the pipelines in the proximity, potentially resulting in a compromised UHB mitigation design, or simply combine the uplift resistance required for each individual pipeline in the proximity to obtain the overall backfill/rock dumping to account for pipeline interactions. This paper re-examines the rationale of the normal practice and some fundamental aspects of UHB design for dual pipelines installation inside the same trench. The proximity effect on the uplift resistance is investigated with respect to pipeline spacing and burial depth. Its impact on the UHB mitigation is considered by a detailed analysis and a series of parametric simulations with respect to pipeline dimensions and gaps. The sensitivity of the soil slip failure angle and the dilatancy is also performed. Based on the theoretical analysis and FEA modelling, a model solution is formulated and proposed for evaluating uplift resistance reduction for multiple lines. The formulae are extended to deal with multi-layered soil and rockdump. A number of pipeline configurations have been discussed including a piggyback arrangement. A robust UHB mitigation and reduced optimum rockdumping can be achieved by considering the proximity effect through challenging the industry norms and common approach.

Consolidation of Lumpy Clay Backfill Over Buried Pipelines

2009 ◽  
Author(s):  
Mahmoud Ghahremani ◽  
Andrew J. Brennan
Keyword(s):  
Pore Pressure ◽  
Clayey Soils ◽  
Buried Pipelines ◽  
Offshore Pipelines ◽  
Lump Size ◽  
Upheaval Buckling ◽  
Backfill Material ◽  
Centrifuge Tests ◽  
Uplift Resistance ◽  
External Loads

Offshore pipelines are usually buried to protect the pipe from external loads. When trenching is achieved by jetting or ploughing, some clayey soils can be cut into distinct lumps and this lumpy soil is then used as the backfill material under which the pipe is buried. To counter the effects of upheaval buckling, the resistance of the soil to pipe uplift must be known. There is still uncertainty about the performance of lumpy backfill in this regard. A series of centrifuge tests were performed with such soils as backfill, utilising a specially designed pore-pressure measuring pipe, to determine the influence of lump size, lump shape and pullout rate on uplift resistance Backfill comprising larger lumps consolidates quicker than if the backfill lumps are smaller. It is also observed that backfill comprising larger lumps provides greater resistance to pipe uplift after consolidation.

Numerical Simulation of Upheaval Buckling Using “Intelligent” Backfill Soil Springs

2015 ◽  
Author(s):  
Prigiarto Hokkal Yonatan ◽  
Filip Van den Abeele ◽  
Jean-Christophe Ballard
Keyword(s):  
Numerical Simulation ◽  
New Technique ◽  
Buried Pipeline ◽  
Buried Pipelines ◽  
Upheaval Buckling ◽  
Backfill Soil ◽  
Uplift Resistance ◽  
A New Technique ◽  
Force Equilibrium

Designing the cover height of buried pipelines to prevent them from buckling requires a method that can thoroughly and realistically model the phenomenon. This paper introduces a new technique to assess the risk of upheaval buckling (UHB) by using backfill soil springs (BFSS) to represent the uplift resistance provided by the backfill soil on top of a buried pipeline. This paper investigates the pre-buckling pipeline behavior related to UHB and highlights some of the key parameters governing the analysis. UHB assessment based on a case study was carried out and the results were then compared with those obtained from force-equilibrium methods generally used in the industry. The comparison shows that UHB assessment can be performed more rigorous using BFSS than using force-equilibrium methods. Therefore, using BFSS for UHB assessment improve the reliability in cover height design.

Pressuremeter Testing of Normally Consolidated Clays—The Effects of Varying Test Technique

1986 ◽  
Vol 2 (1) ◽  
pp. 125-132
Author(s):  
W. F. Anderson ◽  
I. C. Pyrah ◽  
F. Haji-Ali
Keyword(s):  
Test Methods ◽  
Time Dependent ◽  
Clay Soils ◽  
Shear Creep ◽  
Test Technique ◽  
Pressuremeter Test ◽  
Numerical Predictions ◽  
Cylindrical Cavities ◽  
Undrained Conditions ◽  
Insight Into

AbstractAlthough BS 5930:1981 describes both Menard and self-boring pressuremeter tests, little guidance is given on test methods. A number of techniques, both stress controlled and strain controlled, have been used and it has been shown that for clays the test technique has a significant influence on the derived strength and modulus parameters.When a pressuremeter test is carried out in a clay, it is assumed that shearing occurs under undrained conditions. However, in addition to immediate shear strain, some creep and local consolidation will occur in the soil around the expanding borehole. These two phenomena are time-dependent and variations in test technique will affect the test data and hence the derived strength and modulus values.To obtain a better understanding of these effects, pressuremeter tests have been studied both experimentally and numerically. Experimentally, pressuremeter tests have been simulated by expanding cylindrical cavities in samples of three clays prepared with known stress history and the results compared with numerical predictions where the effects of immediate shear, creep and consolidation can be separated. The experimental results compare well with the numerical predictions.This has given a new insight into the behaviour of clay soils during pressuremeter tests. The results indicate that any simple standardization of pressuremeter test technique should be approached with caution.

scholarly journals Influence of soil fertility on waterlogging tolerance of two Brachiaria grasses

2015 ◽  
Vol 33 (1) ◽  
pp. 20-28 ◽  
Author(s):  
Juan De la Cruz Jiménez ◽  
Juan Andrés Cardoso ◽  
David Arango-Londoño ◽  
Gerhard Fischer ◽  
Idupulapati Rao
Keyword(s):  
Soil Fertility ◽  
Nutrient Availability ◽  
Negative Impact ◽  
Nutrient Content ◽  
Soil Conditions ◽  
Soil Drainage ◽  
Waterlogging Tolerance ◽  
Waterlogged Soil ◽  
Fe And Mn ◽  
The Tropics

As a consequence of global warming, rainfall is expected to increase in several regions around the world. This, together with poor soil drainage, will result in waterlogged soil conditions. <em>Brachiaria</em> grasses are widely sown in the tropics and, these grasses confront seasonal waterlogged conditions. Several studies have indicated that an increase in nutrient availability could reduce the negative impact of waterlogging. Therefore, an outdoor study was conducted to evaluate the responses of two <em>Brachiaria</em> sp. grasses with contrasting tolerances to waterlogging, <em>B. ruziziensis </em>(sensitive) and <em>B. humidicola</em> (tolerant), with two soil fertility levels. The genotypes were grown with two different soil fertilization levels (high and low) and under well-drained or waterlogged soil conditions for 15 days. The biomass production, chlorophyll content, photosynthetic efficiency, and macro- (N, P, K, Ca, Mg and S) and micronutrient (Fe, Mn, Cu, Zn and B) contents in the shoot tissue were determined. Significant differences in the nutrient content of the genotypes and treatments were found. An increase of redoximorphic elements (Fe and Mn) in the soil solution occurred with the waterlogging. The greater tolerance of <em>B. humidicola</em> to waterlogged conditions might be due to an efficient root system that is able to acquire nutrients (N, P, K) and potentially exclude phytotoxic elements (Fe and Mn) under waterlogged conditions.  A high nutrient availability in the waterlogged soils did not result in an improved tolerance for <em>B. ruziziensis</em>. The greater growth impairment seen in the <em>B. ruziziensis</em> with high soil fertility and waterlogging (as opposed to low soil fertility and waterlogging) was possibly due to an increased concentration of redoximorphic elements under these conditions.

scholarly journals Discovery of a spatially and temporally persistent core microbiome of the common bean rhizosphere

2020 ◽  
Author(s):  
Nejc Stopnisek ◽  
Ashley Shade
Keyword(s):  
Common Bean ◽  
Spatial Scales ◽  
The United States ◽  
Plant Health ◽  
Soil Conditions ◽  
Full Potential ◽  
Core Microbiome ◽  
Starting Point ◽  
The Common ◽  
Plant Microbiome

AbstractPlants recruit soil microbes that provide nutrients, promote growth and protect against pathogens1–3. However, the full potential of microbial communities for supporting plant health and agriculture is unrealized4–6, in part because rhizosphere members key for plant health are difficult to prioritize7. Microbes that ubiquitously associate with a plant species across large spatial scales and varied soil conditions provide a practical starting point for discovering beneficial members7. Here, we quantified the structures of bacterial/archaeal and fungal communities in the common bean rhizosphere (Phaseolus vulgaris), and assessed its core membership across space and time. To assess a spatial core, two divergent bean genotypes were grown in field conditions across five major growing regions in the United States, and then also compared to eight genotypes grown in Colombian soil. To assess a temporal core, we conducted a time course of rhizosphere and rhizoplane microbiome members over bean development in the field. Surprisingly, there were 48 persistent bacterial taxa that were detected in all samples, inclusive of U.S. and Colombian-grown beans and over plant development, suggesting cosmopolitan enrichment and time-independence. Neutral models of abundance-occupancy relationships and co-occurrence networks show that many of these core taxa are deterministically selected and likely in intimate relationships with the plant. Many of the core taxa were yet-uncultured and affiliated with Proteobacteria; these taxa are prime targets in support of translational plant-microbiome management. More generally, this work reveals that core members of the plant microbiome can have both broad ranges and temporal persistence with their host, suggesting intimate, albeit possibly opportunistic, interactions.

Uplift Capacity of Suction Caissons in Sand for General Conditions Of Drainage

2021 ◽  
Author(s):  
Ragini Gogoi ◽  
Charles P. Aubeny ◽  
Phillip Watson ◽  
Fraser Bransby
Keyword(s):  
Constitutive Model ◽  
Load Capacity ◽  
System Capacity ◽  
Soil Conditions ◽  
Uplift Capacity ◽  
Soil Response ◽  
Dense Sand ◽  
Centrifuge Tests ◽  
Numerical Predictions ◽  
Suction Caissons

Abstract Suction caissons have emerged as a viable solution for the foundations of offshore wind turbines, which are gaining momentum worldwide as an alternate energy source. When used in a multi-bucket jacket system, the system capacity is often governed by the uplift capacity of the windward bucket foundation. Seabed conditions at offshore windfarm sites often comprise dense sand where the soil response may be drained, partially drained or undrained depending on the loading regime, the foundation dimensions and the soil conditions. Given the large difference in uplift capacity of caissons for these different drainage conditions, predicting the behavior of a suction caisson under a range of drainage conditions becomes a paramount concern. Consequently, this paper presents the findings of a coupled finite element investigation of the monotonic uplift response of the windward caisson of a multi-bucket jacket system in a typical dense silica sand for a range of drainage conditions. The study adopts a Hypoplastic soil constitutive model capable of simulating the stress-strain-strength behavior of dense sand. This choice is justified by conducting a comparative study with other soil models — namely the Mohr Coulomb and bounding surface sand models — to determine the most efficient soil failure model to capture the complex undrained behavior of dense sand. The numerical predictions made in this study are verified by recreating the test conditions adopted in centrifuge tests previously conducted at the University of Western Australia, and demonstrating that the capacity from numerical analysis is consistent with the test results. The Hypoplastic soil constitutive model also provides an efficient method to produce accurate load capacity transition curves from an undrained to a drained soil state.

Uplift Resistance of Buried Pipelines Enhanced by Geogrid

2014 ◽  
Vol 51 (4) ◽  
pp. 188-195 ◽  
Author(s):  
K. Faizi ◽  
D. Jahed Armaghani ◽  
E. Momeni ◽  
R. Nazir ◽  
E. Tonnizam Mohamad
Keyword(s):  
Buried Pipelines ◽  
Uplift Resistance
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