Laboratory Evaluation of Mechanical Properties of Draupne Shale Relevant for CO2 Seal Integrity

The mechanical integrity of caprocks overlying injection formations is one of the key factors for safe storage of carbon dioxide in geological formations. Undrained effects caused by CO2 injection on strength and elastic parameters should be properly considered in the operational design to avoid fracture creation, fault reactivation and unwanted surface uplift. This study presents results from eleven undrained triaxial compression tests and one oedometer test on the Draupne shale, which is the main caprock of the Smeaheia site in the North Sea, to extract parameters relevant for seal integrity. Tests have been performed on samples oriented perpendicular to and parallel with the horizontal layering of the rock to study the effects of sample orientation relative to the loading direction. Results from undrained triaxial tests showed only minor effects of sample orientation on friction and cohesion. However, when loading during undrained shearing was parallel with layering (horizontal samples), measured Young’s modulus was roughly 1.4 times higher than for the vertical samples. Undrained shearing of vertical samples generated 30–50% more excess pore pressure than for horizontal samples with similar consolidation stress owing to more volume compaction of vertical samples. With apparent pre-consolidation stress determined from a high-stress oedometer test, the normalized undrained shear strength was found to correlate well with the overconsolidation ratio following the SHANSEP (Stress History and Normalized Soil Engineering Properties) procedure.

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Strength envelope of granular soil stabilized by multi-axial geogrid in large triaxial tests

Canadian Geotechnical Journal ◽

10.1139/cgj-2019-0036 ◽

2020 ◽

Vol 57 (3) ◽

pp. 448-452 ◽

Cited By ~ 1

Author(s):

A.S. Lees ◽

J. Clausen

Keyword(s):

Triaxial Compression ◽

Triaxial Tests ◽

Compression Tests ◽

Failure Envelope ◽

Element Analysis ◽

Linear Elastic ◽

Perfectly Plastic ◽

Elastic Perfectly Plastic ◽

Triaxial Compression Tests ◽

Properties Of Soil

Conventional methods of characterizing the mechanical properties of soil and geogrid separately are not suited to multi-axial stabilizing geogrid that depends critically on the interaction between soil particles and geogrid. This has been overcome by testing the soil and geogrid product together as one composite material in large specimen triaxial compression tests and fitting a nonlinear failure envelope to the peak failure states. As such, the performance of stabilizing, multi-axial geogrid can be characterized in a measurable way. The failure envelope was adopted in a linear elastic – perfectly plastic constitutive model and implemented into finite element analysis, incorporating a linear variation of enhanced strength with distance from the geogrid plane. This was shown to produce reasonably accurate simulations of triaxial compression tests of both stabilized and nonstabilized specimens at all the confining stresses tested with one set of input parameters for the failure envelope and its variation with distance from the geogrid plane.

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Laboratory Evaluation of a Novel Real-Time Respirator Seal Integrity Monitor

Annals of Work Exposures and Health ◽

10.1093/annweh/wxy026 ◽

2018 ◽

Vol 62 (6) ◽

pp. 742-753

Author(s):

Bingbing Wu ◽

Jonathan Corey ◽

Michael Yermakov ◽

Yan Liu ◽

Sergey A Grinshpun

Keyword(s):

Real Time ◽

Laboratory Evaluation ◽

Seal Integrity

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Appraisal of Geotechnical Characteristics of Ormara Soil, Baluchistan, Pakistan

International Journal of Economic and Environmental Geology ◽

10.46660/ojs.v10i3.304 ◽

2019 ◽

Vol 10 (3) ◽

pp. 22-26

Author(s):

Abdul Jabbar Khan ◽

Naveed Ahsan ◽

Muhammad Sanaullah ◽

Gulraiz Akhter

Keyword(s):

Triaxial Compression ◽

Liquid Limit ◽

Soil Samples ◽

Engineering Properties ◽

Clay Layer ◽

Compression Tests ◽

Geotechnical Characteristics ◽

Density Values ◽

Construction Plans ◽

Triaxial Compression Tests

Ormara is located 240 km west of Karachi which is a coastal and port city (25° 16' 29N, 64° 35' 10E) ofPakistan. Present study evaluates engineering properties of soils of Ormara for future construction plans and possibleexpansions in the area. Fifty bore holes were done in study area at depths of 20m, 40m and some (10 bore holes) were60m deep. The study area was divided into three major zones i.e. Foot hills, on-shore and off-shore. Groundwater wasencountered at depths of 2.75m on onshore and offshore zones and at 3.65m depth in foothill zone. Laboratory testingi.e. moisture content (12 to 38 %), liquid limit (from 26 to 34), plasticity index (10 to 18) of soil samples indicate thatsoils are low plastic to moderate plastic in nature. Soil samples of granular soils indicate angles of internal friction (ø)varying from 260- 36ºin upper sand layers while 260 to 30º in lower silt layers (encountered after the clay layer) andCohesion ranges 0 to 0.04kg/cm2 in all three zones. Further, unconsolidated undrained triaxial compression tests on aclayey soil sample indicated an undrained cohesion value of 28 kPa. Density values ranges from 1.6 to 2.05gm/cm3.Consolidation (Cv = 0.20 to 0.40 cm2/minute, Cc = 0.149 to 0.17) has been calculated for clay layer. Chemical testscarried out on soil samples indicated that soil and water both are reactive aggressively and may cause corrosion to steeland concrete disintegration.

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Cyclic soil-root mechanical interaction

10.5194/egusphere-egu21-8127 ◽

2021 ◽

Author(s):

Anthony Leung ◽

Ali Akbar Karimzadeh ◽

Zhaoyi Wu

Keyword(s):

Triaxial Compression ◽

Reinforced Soil ◽

Plant Roots ◽

Triaxial Tests ◽

Uniaxial Tensile ◽

Mechanical Interaction ◽

Liquefaction Resistance ◽

Cyclic Stress Ratio ◽

Geotechnical Centrifuge ◽

Wide Diameter

<p>Plant roots have been considered to be effective to reinforce shallow soil slopes under rainfall conditions. Recent evidence from geotechnical centrifuge modelling shows that plant roots could improve earthquake-induced slope stability and reduce slope crest settlement. However, the underlying fundamental mechanisms of soil-root mechanical interaction against seismic loading are unclear. Although there has been a large volume of studies focusing on root reinforcement, cyclic soil-root mechanical interaction has rarely been investigated. Moreover, whether plant roots could reduce the liquefaction potential of rooted soil. This presentation will present some new test data and evidence about (1) cyclic root biomechanical behaviour and (2) cyclic responses of root-reinforced soil. In part (1), results of cyclic uniaxial tensile tests on roots of a wide diameter range will be presented, including any root hardening or softening and change in the size of hysteresis loops under displacement-controlled loading condition. Special attention will be paid on any observation of cyclic-induced root mechanical fatigue. In part (2), results of a comprehensive set of monotonic and cyclic triaxial tests on rooted soil will be presented. The cyclic behaviour observed will be interpreted through the monotonic behaviour observed along both the triaxial compression and extension paths. Any change in soil failure mechanism from limited flow failure to cyclic mobility due to plant roots, and how/when this change occurs at different root volume and cyclic stress ratio, will be discussed in detailed. A new attempt to interpret the liquefaction resistance through an energy-based approach will be made to evaluate the energy dissipation mechanism in rooted soils.</p>

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Three-dimensional numerical simulation of mechanical properties of soil-tire mixture by discrete element method

E3S Web of Conferences ◽

10.1051/e3sconf/20199214011 ◽

2019 ◽

Vol 92 ◽

pp. 14011

Author(s):

Mohsen Asadi ◽

Ahmad Mahboubi

Keyword(s):

Mechanical Properties ◽

Shear Strength ◽

Damping Ratio ◽

Strain Curve ◽

Young Modulus ◽

Engineering Properties ◽

Triaxial Tests ◽

Sand Particle ◽

Arithmetic Average ◽

Harmonic Average

Soil engineering properties can be improved employing different methods. Among them is mixing soil with tire derived additives (TDA). TDAs generally increase some parameters of mixture such as damping ratio, permeability, ductility and also in some cases shear strength. Various properties of TDAs from mechanical properties to their geometry can affect the mixture behavior. In this paper using the YADE platform, simulations of triaxial tests on sand tire mixtures are presented. To take compressibility into consideration, each rubber crumb particle is made of several spheres connected elastically to each other. For sand particle generation the clump technique was employed. Shapes of both sand and rubber particles are inspired from real grains. As properties of sand and rubber are different, especially Young modulus, rubber sand interaction is considered as soft rigid contact. Therefor harmonic average and arithmetic average was used to compute contact Young modulus (and then stiffness). The model was validated by comparison of results of triaxial tests simulation on pure rubber sample with literature ones which both exhibited linear stress-strain curve. Then triaxial tests with different sand to rubber ratio were simulated to see whether harmonic average or arithmetic average gives the best match to literature. The results show shear strength reduces by decreasing of sand to rubber ratio. This is the same as what is reported in literature.

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Microscopic Mechanism Affecting Shear Strength in Lignin-Treated Loess Samples

Advances in Materials Science and Engineering ◽

10.1155/2019/7126040 ◽

2019 ◽

Vol 2019 ◽

pp. 1-12 ◽

Cited By ~ 2

Author(s):

Wei Liu ◽

Juan Wang ◽

Gaochao Lin ◽

Li Wen ◽

Qian Wang

Keyword(s):

Shear Strength ◽

Lignin Content ◽

Axial Stress ◽

Water Pressure ◽

Excess Pore Pressure ◽

Triaxial Tests ◽

Microscopic Mechanism ◽

Valley Fill ◽

Fill Material ◽

Excess Pore

In China, engineers have worked to create additional usable land for building construction by flattening the ridges of hills and filling in the adjacent valleys. China’s Loess Plateau comprises a type of soil (loess) with a large pore structure that can collapse and become unstable when exposed to groundwater. Conventional valley fill materials include remolded loess or remolded loess treated with cement, lime, gypsum, or other stabilizing additives. These stabilizers are often detrimental to the surrounding environment. Moreover, loess treated with conventional stabilizers exhibits excessive brittleness, which is not suitable for building foundations. Adequate stability of the building foundations in the filled valleys is required to ensure public safety. In this study, we tested 50 remolded loess samples treated with a lignin polymer compound to determine its potential as a valley fill material. Triaxial tests, scanning electron microscopy (SEM), and X-ray diffraction (XRD) were used to study the mechanical characteristics of each sample, determine the effects of the lignin treatment on the loess, and identify the microscopic mechanism affecting shear stress in the lignin-treated loess. The corresponding development of excess pore pressure and volumetric responses under monotonic triaxial testing were also considered. Based on this study’s results, the optimum lignin content in the treated loess samples was 4%; lignin contents exceeding 4% decreased axial stress and increased dilation after saturation. The shear strength and strain-hardening phenomenon of the lignin-treated loess samples increased as the lignin content increased, while the excess pore water pressure decreased. Microscopically, the addition of lignin increased cohesion in the loess samples, while slightly contributing to the internal friction angle. The use of lignin as a stabilizing additive for valley fill material shows potential for controlling building foundation deformation by increasing soil strength and minimizing environmental impacts by maintaining the soil pH and limiting pollutant production.

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Deep sampling and testing in soft stratified clay

Canadian Geotechnical Journal ◽

10.1139/t03-016 ◽

2003 ◽

Vol 40 (3) ◽

pp. 575-586 ◽

Cited By ~ 5

Author(s):

Simon James Cummings ◽

Vinayagamoorthy Sivakumar ◽

Isaac Gregg Doran ◽

Jim Graham

Keyword(s):

Triaxial Compression ◽

Relevant Literature ◽

Thick Layer ◽

Site Investigation ◽

Anisotropic Elasticity ◽

Triaxial Tests ◽

Compression Tests ◽

Lower Zone ◽

A Site ◽

Triaxial Compression Tests

A 37-m thick layer of stratified clay encountered during a site investigation at Swann's Bridge, near the sea-coast at Limavady, Northern Ireland, is one of the deepest and thickest layers of this type of material recorded in Ireland. A study of the relevant literature and stratigraphic evidence obtained from the site investigation showed that despite being close to the current shoreline, the clay was deposited in a fresh-water glacial lake formed approximately 13 000 BP. The 37-m layer of clay can be divided into two separate zones. The lower zone was deposited as a series of laminated layers of sand, silt, and clay, whereas the upper zone was deposited as a largely homogeneous mixture. A comprehensive series of tests was carried out on carefully selected samples from the full thickness of the deposit. The results obtained from these tests were complex and confusing, particularly the results of tests done on samples from the lower zone. The results of one-dimensional compression tests, unconsolidated undrained triaxial tests, and consolidated undrained triaxial compression tests showed that despite careful sampling, all of the specimens from the lower zone exhibited behaviour similar to that of reconstituted clays. It was immediately clear that the results needed explanation. This paper studies possible causes of the results from tests carried out on the lower Limavady clay. It suggests a possible mechanism based on anisotropic elasticity, yielding, and destructuring that provides an understanding of the observed behaviour.Key words: clay, laminations, disturbance, yielding, destructuring, reconstituted.

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Quantifying fault reactivation risk in the western Gippsland Basin using geomechanical modelling

The APPEA Journal ◽

10.1071/aj12022 ◽

2013 ◽

Vol 53 (1) ◽

pp. 255 ◽

Cited By ~ 2

Author(s):

Ernest Swierczek ◽

Cui Zhen-dong ◽

Simon Holford ◽

Guillaume Backe ◽

Rosalind King ◽

...

Keyword(s):

Structural Model ◽

Strike Slip ◽

Fault Reactivation ◽

Fault System ◽

Co2 Injection ◽

Normal Faults ◽

Surface Geometry ◽

Northern Margin ◽

Fault Surface ◽

Gippsland Basin

The Rosedale Fault System (RFS) bounds the northern margin of the Gippsland Basin on the Southern Australian Margin. It comprises an anastomosing system of large, Cretaceous-age normal faults that have been variably reactivated during mid Eocene-Recent inversion. A number of large oil and gas fields are located in anticlinal traps associated with the RFS, and in the future these fields may be considered as potential storage sites for captured CO2. Given the evidence for geologically recent fault reactivation along the RFS, it is thus necessary to evaluate the potential impacts of CO2 injection on fault stability. The analysis and interpretation of 3D seismic data allowed the authors to create a detailed structural model of the western section of the RFS. Petroleum geomechanical data indicates that the in-situ stress in this region is characterised by hybrid strike-slip to reverse faulting conditions where SHmax (40.5 MPa/km) > SV (21 MPa/km) ~ Shmin (20 MPa/km). The authors performed geomechanical modelling to assess the likelihood of fault reactivation assuming that both strike-slip and reverse-stress faulting regimes exist in the study area. The authors’ results indicate that the northwest to southeast and east-northeast to west-southwest trending segments of the RFS are presently at moderate and high risks of reactivation. The authors’ results highlight the importance of fault surface geometry in influencing fault reactivation potential, and show that detailed structural models of potential storage sites must be developed to aid risk assessments before injection of CO2.

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