Experience with Interface Shear Box Testing for Axial Pipe-Soil Interaction Assessment on Soft Clay

2018 ◽  
Author(s):  
Z. J. Westgate ◽  
D. J. White ◽  
M. Savazzi
Keyword(s):  
Soft Clay ◽  
Interface Shear ◽  
Shear Box

Experience with Interface Shear Box Testing for Pipe-Soil Interaction Assessment on Sand

2021 ◽  
Author(s):  
Zack Westgate ◽  
Ricardo Argiolas ◽  
Regis Wallerand ◽  
Jean-Christophe Ballard
Keyword(s):  
Soil Properties ◽  
Normal Stress ◽  
Oil And Gas ◽  
Early Stage ◽  
Soft Clay ◽  
Interface Roughness ◽  
Coarse Grained ◽  
Interface Shear ◽  
Shear Box ◽  
Test Database

Abstract This paper is a companion paper to OTC 28671, titled "Experience with Interface Shear Box Testing for Axial Pipe-Soil Interaction Assessment on Soft Clay", and presents a similar range of experience and best practice recommendations for geotechnical laboratory testing to determine soil properties relevant to pipeline-seabed friction on sandy seabeds. The paper is underpinned by a new database that demonstrates the driving parameters that influence interface friction in granular materials. By accurately quantifying shear resistance along the pipe-soil interface under low normal stresses imposed by subsea pipelines, design ranges in friction can be narrowed and/or tailored to specific pipeline conditions. These improved geotechnical inputs to pipe-soil interaction can alleviate unnecessary axial expansion mitigation and lateral stabilization measures, unlocking cost savings otherwise unavailable through conventional testing. A large database is presented, compiled from both previously published research and unpublished recent industry experience with low normal stress interface shear testing using various modified direct shear box devices. The test database comprises several coarse-grained soil types of both silica and carbonate minerology tested against pipeline coatings of various material, hardness and roughness. The database populates a framework for assessing frictional pipe-soil interaction response, illuminating key trends from normal stress, interface roughness and hardness, and particle angularity, which otherwise remain elusive when examined through individual test datasets. This database and the populated framework provides guidance to pipeline and geotechnical engineers in the form of a basis for initial estimates of axial and lateral friction of pipelines on sand and an approach for improving these estimates via focused site-specific testing. The test database includes previously unreleased project data collected over the past few years for offshore oil and gas projects. Similar to its predecessor paper on soft clays (OTC 28671), this paper shares the authors’ collective experience providing guidance on the planning, execution and interpretation of low stress interface shear tests in sands. The combined databases across both papers provide a significant improvement in early stage guidance for characterization of geotechnical soil properties for subsea pipeline design.

Characterisation of Residual Shear Strength at the Sheringham Shoal Offshore Wind Farm

2014 ◽  
Author(s):  
Thi Minh Hue Le ◽  
Gudmund Reidar Eiksund ◽  
Pål Johannes Strøm
Keyword(s):  
Shear Strength ◽  
Wind Farm ◽  
Offshore Wind ◽  
Interface Shear ◽  
Residual Shear Strength ◽  
Axial Capacity ◽  
Ring Shear ◽  
Stiff Clay ◽  
Soil Units ◽  
Shear Box

For offshore foundations, the residual shear strength is an important soil parameter for the evaluation of installation resistance and axial pile capacity (for jacket foundation). Estimation of residual shear strength can be conducted in a shear box test in the conventional way, or with the introduction of an interface to evaluate the change in residual shear strength under influence of friction between soil and the interface. In addition, the residual effective friction angle can be measured in the ring shear test using the Bromhead apparatus. In this study, the three above-mentioned methods are employed to estimate the values of residual shear strength of two soil units: the Swarte Bank Formation and the Chalk Unit sampled from the Sheringham Shoal offshore wind farms. The Swarte Bank Formation is dominated by heavily over-consolidated stiff clay, while the Chalk Unit is characterized by putty white chalk which behaves in a similar manner to stiff clay if weathered, or to soft rock if unweathered. These soil units are located at the bottom of the soil profile at the Sheringham Shoal wind farm and hence are important in providing axial capacity to the foundation. Samples from the two soil units are tested and compared at different rates of shearing to evaluate the change in axial capacity and installation resistance of the offshore wind turbine foundations under various possible loading and drainage conditions. Comparison is also made between residual shear strength with and without a reconsolidation period to assess the potential for soil set-up and its influence on the soil capacity. The results show that, for both the clay and the chalk, the estimated residual shear strengths are quite similar between the conventional and interface shear tests and tend to increase with increasing shearing rate. This can be attributed to the increasing dominance of the turbulent shearing mode. Relative to the peak shear strength, the values of residual shear strength are approximately 5 to 35% lower in most cases. Reconsolidation for a period of 24 hours appears to have, if any, marginal positive effect on residual shear strength of the two soils in both shear box and interface shear box tests. The residual friction angles derived from the shear box and ring shear tests are comparable and fall in the immediate range of shear strength. The various test results imply that the pile foundations at the Sheringham Shoal would have considerably large axial capacity, assuming that the horizontal stress is similar to the normal stress used in testing. The test data however should be used with caution and combined with piling experience in comparable soils where possible. The study aims to provide a source of reference for design of pile foundations for sites with similar soil conditions.

scholarly journals The influence of saturation on the interface shear strength of clay and nonwoven geotextile

2021 ◽  
Vol 15 (1) ◽  
pp. 41-54
Author(s):  
Minh-Duc Nguyen ◽  
Minh-Phu Ho
Keyword(s):  
Shear Strength ◽  
Clayey Soil ◽  
Water Pressure ◽  
Strength Analysis ◽  
Direct Shear ◽  
Interface Shear Strength ◽  
Interface Shear ◽  
Shear Box ◽  
Nonwoven Geotextile ◽  
Adhesion Factor

The paper presents a series of modified direct shear tests to investigate the interface shear strength between clay and nonwoven geotextile under different normal stresses and degrees of saturation. The modified direct shear apparatus consists of a 60 mm × 60 mm square shear box assembly with a 60 mm × 60 mm acrylic block inserted in the bottom shear box. A woven geotextile layer was glued to the top of the acrylic block, while the top shear box was filled by the compacted clayey soil. The results revealed that the interface shear strength of clay and nonwoven geotextile reduced by 13.4-27.7% when changing from optimum moisture content (OMC) of the soil to saturation condition. The high permeability of nonwoven geotextile induced the dissipation of excess pore water pressure at the interface when shearing. As a result, the adhesion factor of the clay-geotextile interface increased from about 0.6 for the specimens at OMC to over 0.8 for consolidated saturated specimens. In contrast, for the impermeable reinforcement, the interface shear strength analysis of previous studies shows that the adhesion factor of the reinforcement and clayey soil would be reduced when increasing the water content of the clay specimens. Keywords: adhesion factor; clay; nonwoven geotextile, interface shear strength; saturation.

scholarly journals The Significant Effect of Interface Shear Strength Between Soil Liner and Geotextile with Different Percentages of Bentonite and Sodium Bentonite with Geosynthetic

2018 ◽  
Vol 150 ◽  
pp. 02009
Author(s):  
Roslizayati Razali ◽  
Nor Azizah Che Azmi ◽  
Diana Che Lat ◽  
Mazidah Mukri ◽  
Farah Hafifie Ahamad
Keyword(s):  
Shear Strength ◽  
Direct Shear ◽  
Interface Shear Strength ◽  
Interface Shear ◽  
Sodium Bentonite ◽  
Liner Material ◽  
Fine Soil ◽  
Shear Performance ◽  
Soil Liner ◽  
Shear Box

This research focuses on the interface shear performance between geotextile and soil with various percentages of bentonite and sodium bentonite for landfill stability by using Direct Shear Test. Admixtures are mixed with clay to improve its performance as a liner material due to their ability to fill the voids between soil particles and also the most effective sealants. The aim of this study is focused on evaluating the effectiveness of bentonite and sodium bentonite on improving interface shear strength of fine soil. In this study, direct shear box was used to measure the interface shear strength of soil with different percentages of bentonite and sodium bentonite at optimum moisture content. Analysis shows that the most suitable percentage is of 5 % of bentonite and 2.5 % of sodium bentonite due to the highest interface shear strength of the mixture with geosynthetic. It is clearly shown that 2.5 % sodium bentonite is the most suitable percentage to be used as admixture for landfill stability as it gives higher interface shear strength.

scholarly journals Interface shear box tests for assessing axial pipe–soil resistance

Géotechnique ◽  
2017 ◽  
Vol 67 (1) ◽  
pp. 18-30 ◽  
Author(s):  
N. Boukpeti ◽  
D. J. White
Keyword(s):  
Soil Resistance ◽  
Interface Shear ◽  
Shear Box

scholarly journals Strength anisotropy at soil-structure interfaces with snake skin inspired structural surfaces

2019 ◽  
Vol 92 ◽  
pp. 13008
Author(s):  
Hans Henning Stutz ◽  
Alejandro Martinez ◽  
Lars Heepe ◽  
Halvor Tram Tramsen ◽  
Stanislav N. Gorb
Keyword(s):  
Soil Structure ◽  
Strength Anisotropy ◽  
Shear Tests ◽  
Interface Shear ◽  
Snake Skin ◽  
Loading Direction ◽  
Potential Benefits ◽  
Shear Box ◽  
Practical Implications ◽  
Typical Soil

Typical soil-structure interfaces exhibit a response that is independent of loading direction due to the symmetry of the surfaces' profile. This study presents results from an experimental investigation on the response of sand specimens sheared against three types of surfaces bio-inspired from the skin along the underside of snakes. The results of shear box interface shear tests indicate that all three surfaces exhibit significant anisotropy in response in terms of mobilized shear resistances and corresponding volumetric changes. A discussion on the practical implications and potential benefits of implementation of the snake skin-inspired surfaces in engineering design is provided.

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