Some Observations on Soil-Pipe Interface Shear Strength in Direct Shear Under Low Effective Normal Stresses and Large Displacements

2016 ◽  
Author(s):  
Ruslan S. Amarasinghe ◽  
Dharma Wijewickreme ◽  
Hisham T. Eid
Keyword(s):  
Shear Strength ◽  
Accurate Determination ◽  
Direct Shear ◽  
Normal Stresses ◽  
Interface Shear Strength ◽  
Interface Shear ◽  
Fine Grained ◽  
Direct Shear Tests ◽  
Macro Scale ◽  
Soil Pipe

Experimental work is undertaken at the University of British Columbia (UBC) to study the soil-pipe interface shear strength at levels of shear displacements and effective normal stresses typically encountered in offshore soil-pipe interaction problems. A macro-scale interface direct shear apparatus having a test specimen footprint of 1.72 m × 1.75 m was designed and built for this purpose. The apparatus is capable of testing various soil-pipe interfaces under effective normal stresses in the range of 3 kPa to 6 kPa. A maximum shear displacement of 1.2 m is achievable at rates ranging from 0.1 μm/s to 1 mm/s. Sensors mounted at the interface enable the accurate determination of the effective normal stress at the interface when fully saturated fine-grained soils are tested. This paper presents some observations arising from a series of interface direct shear tests involving fine-grained soils of different plasticity against bare and epoxy coated steel surfaces.

Residual shear strength of fine-grained soils and soil–solid interfaces at low effective normal stresses

2015 ◽  
Vol 52 (2) ◽  
pp. 198-210 ◽  
Author(s):  
Hisham T. Eid ◽  
Ruslan S. Amarasinghe ◽  
Khaled H. Rabie ◽  
Dharma Wijewickreme
Keyword(s):  
Shear Strength ◽  
Large Strain ◽  
Laboratory Research ◽  
Normal Stresses ◽  
Interface Shear ◽  
Residual Shear Strength ◽  
Fine Grained ◽  
Solid Interface ◽  
Wide Range ◽  
Shear Area

A laboratory research program was undertaken to study the large-strain shear strength characteristics of fine-grained soils under low effective normal stresses (∼3–7 kPa). Soils that cover a wide range of plasticity and composition were utilized in the program. The interface shear strength of these soils against a number of solid surfaces having different roughness was also investigated at similar low effective normal stress levels. The findings contribute to advancing the knowledge of the parameters needed for the design of pipelines placed on sea beds and the stability analysis of shallow soil slopes. A Bromhead-type torsional ring-shear apparatus was modified to suit measuring soil–soil and soil–solid interface residual shear strengths at the low effective normal stresses. In consideration of increasing the accuracy of assessment and depicting the full-scale field behavior, the interface residual shear strengths were also measured using a macroscale interface direct shear device with a plan interface shear area of ∼3.0 m2. Correlations are developed to estimate the soil–soil and soil–solid interface residual shear strengths at low effective normal stresses. The correlations are compared with soil–soil and soil–solid interface drained residual shear strengths and correlations presented in the literature.

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 Generalized Interface Shear Strength Equation for Recycled Materials Reinforced with Geogrids

2021 ◽  
Vol 13 (16) ◽  
pp. 9446
Author(s):  
Artit Udomchai ◽  
Menglim Hoy ◽  
Apichat Suddeepong ◽  
Amornrit Phuangsombat ◽  
Suksun Horpibulsuk ◽  
...  
Keyword(s):  
Shear Strength ◽  
Interface Shear Strength ◽  
Interface Shear ◽  
Recycled Materials ◽  
Reclaimed Asphalt ◽  
Analysis And Design ◽  
Direct Shear Tests ◽  
Base Course Material ◽  
Base Course ◽  
Recycled Material

In this research, large direct shear tests were conducted to evaluate the interface shear strength between reclaimed asphalt pavement (RAP) and kenaf geogrid (RAP–geogrid) and to also assess their viability as an environmentally friendly base course material. The influence of factors such as the gradation of RAP particles and aperture sizes of geogrid (D) on interface shear strength of the RAP–geogrid interface was evaluated under different normal stresses. A critical analysis was conducted on the present and previous test data on geogrids reinforced recycled materials. The D/FD, in which FD is the recycled materials’ particle content finer than the aperture of geogrid, was proposed as a prime parameter governing the interface shear strength. A generalized equation was proposed for predicting the interface shear strength of the form: α = a(D/FD) + b, where α is the interface shear strength coefficient, which is the ratio of the interface shear strength to the shear strength of recycled material, and a and b are constants. The constant values of a and b were found to be dependent upon types of recycled material, irrespective of types of geogrids. A stepwise procedure to determine variable a, which is required for analysis and design of geogrids reinforced recycled materials in roads with various gradations was also suggested.

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