A Comparative Study Between Lateral and Upward Anchor-Soil and Pipe-Soil Interaction in Dense Sand

2016 ◽  
Author(s):  
Kshama Roy ◽  
Bipul Hawlader ◽  
Shawn Kenny ◽  
Ian Moore
Keyword(s):  
Shear Bands ◽  
Experimental Studies ◽  
Confining Pressure ◽  
Design Guidelines ◽  
Vertical Strip ◽  
Dense Sand ◽  
Progressive Development ◽  
Lateral Resistance ◽  
Strain Behaviour ◽  
Uplift Forces

Buried pipelines are extensively used in onshore and offshore environments for transportation of hydrocarbons. On the other hand, buried anchors have been used for many years to stabilize various structures. In the development of design guidelines for pipelines, theoretical and experimental studies on buried anchors are sometimes used assuming that pipeline-soil and anchor-soil interaction are similar. In the present study, finite element (FE) modeling is performed to simulate the response of pipeline and anchor buried in dense sand subjected to lateral and uplift forces. The similarities and differences between the responses of these two types of structures are examined to justify the application of anchor theory to pipeline behaviour. The stress-strain behaviour of dense sand is modeled using a Modified Mohr-Coulomb (MMC) model, which considers the pre-peak hardening, post-peak softening, density and confining pressure dependent friction and dilation angles. A considerable difference is found between the lateral resistance of pipeline and vertical strip anchor of similar size. Progressive development of shear bands (shear strain concentrated zone) can explain the load-displacement behaviour for both lateral and upward loading.

Lateral resistance of pipes and strip anchors buried in dense sand

2018 ◽  
Vol 55 (12) ◽  
pp. 1812-1823 ◽  
Author(s):  
Kshama Roy ◽  
Bipul Hawlader ◽  
Shawn Kenny ◽  
Ian Moore
Keyword(s):  
Strain Softening ◽  
Shear Bands ◽  
Fe Modeling ◽  
Vertical Strip ◽  
Buried Pipes ◽  
Dense Sand ◽  
Progressive Development ◽  
Softening Behaviour ◽  
Lateral Resistance ◽  
Peak Resistance

The response of buried pipes and vertical strip anchors in dense sand under lateral loading is compared based on finite-element (FE) modeling. Incorporating strain-softening behaviour of dense sand, the progressive development of shear bands and the mobilization of friction and dilation angles along the shear bands are examined, which can explain the variation of peak and post-peak resistances for anchors and pipes. The normalized peak resistance increases with embedment ratio and remains almost constant at large burial depths. When the height of an anchor is equal to the diameter of the pipe, the anchor gives approximately 10% higher peak resistance than that of the pipe. The transition from the shallow to deep failure mechanisms occurs at a larger embedment ratio for anchors than pipes. A simplified method is proposed to estimate the lateral resistance at the peak and also after softening at large displacements.

Compression and strength of dense sand at high pressures and elevated temperatures

2004 ◽  
Vol 41 (6) ◽  
pp. 1206-1212 ◽  
Author(s):  
James Graham ◽  
Marolo Alfaro ◽  
Gerald Ferris
Keyword(s):  
High Pressures ◽  
Elevated Temperatures ◽  
Confining Pressure ◽  
Triaxial Tests ◽  
One Dimensional ◽  
Dense Sand ◽  
Strain Behaviour ◽  
Effects Of Temperature ◽  
Canada Limited ◽  
Compression Shear Strength

The paper examines the stress–strain behaviour of densely compacted sand tested at pressures up to 80 MPa in one-dimensional compression and 7.2 MPa confining pressure in triaxial tests. Tests were performed at temperatures up to 100 °C. The testing relates to a proposal by Atomic Energy of Canada Limited to fill containers of waste nuclear fuel with a crushed quartz sand to provide additional stiffness. No significant effects of temperature were encountered in either isotropic compression or triaxial shear.Key words: sand, compression, shear strength, temperature, pressure.

scholarly journals Experimental studies on the differentiation of embryonic tissues growing in vivo and in vitro .—II. The development of the isolated early embryonic eye of the fowl when cultivated in vitro

1926 ◽  
Vol 100 (703) ◽  
pp. 273-283 ◽  
Keyword(s):  
Medical Research ◽  
Research Council ◽  
Medical Research Council ◽  
Experimental Studies ◽  
Limb Bud ◽  
Progressive Development ◽  
Embryonic Tissues ◽  
Self Differentiation

In a previous communication (Strangeways and Fell, 1926) it was shown that if the undifferentiated limb-bud of the embryonic Fowl was cultivated in vitro , it underwent a considerable amount of progressive development. This capacity for independent development in vitro possessed by an isolated organ has been further investigated, and for these later experiments the writers have employed the early embryonic eye, a structure endowed with more complex potentialities than the limb-bud. As a result of these experiments it was found that the eyes of young Fowl embryos possess, in a remarkable degree, the faculty for self-differentiation in vitro and for “organotypic” growth as defined by Maximow (1925). The previous work on organotypic growth in vitro has already been briefly outlined in the writers’ earlier paper and need not be discussed here. The expenses connected with the experiments described in this communication were met by the Medical Research Council, to whom the writers desire to express their thanks.

scholarly journals A Constitutive Model for Locally Drained Shear Bands in Globally Undrained Dense Sand

2019 ◽  
Vol 92 ◽  
pp. 16005
Author(s):  
Hansini Mallikarachchi ◽  
Kenichi Soga
Keyword(s):  
Shear Band ◽  
Constitutive Model ◽  
Bifurcation Analysis ◽  
Shear Bands ◽  
Constitutive Relationship ◽  
Excess Pore Pressure ◽  
Biaxial Compression ◽  
Compression Tests ◽  
Equilibrium Equations ◽  
Dense Sand

When saturated granular materials which are dilative in nature are subjected to the undrained deformation, their strength increases due to the generation of negative excess pore pressure. This phenomenon is known as dilative hardening and can be witnessed in saturated dense sand or rocks during very fast loading. However, experimental evidence of undrained biaxial compression tests of dense sand shows a limit to this dilative hardening due to the formation of shear bands. There is no consensus in the literature about the mechanism which triggers these shear bands in the dense dilative sand under isochoric constraint. The possible theoretical reasoning is the local drainage inside the specimen under the globally undrained condition, which is challenging to be monitored experimentally. Hence, both incept of localisation and post-bifurcation of the saturated undrained dense sand demand further numerical investigation. Pathological mesh dependency hinders the ability of the finite element method to represent the localisation without advanced regularisation methods. This paper attempt to provide a macroscopic constitutive behaviour of the undrained deformation of the saturated dense sand in the presence of a locally drained shear band. Discontinuation of dilatant hardening due to partial drainage between the shear band and the adjacent material is integrated into the constitutive model without changing governing equilibrium equations. Initially, a classical bifurcation analysis is conducted to detect the inception and inclination of the shear band based on the underlying drained deformation. Then a post-bifurcation analysis is carried out assuming an embedded drained or partially drained shear band at gauss points which satisfy bifurcation criterion. The smeared shear band approach is utilised to homogenise the constitutive relationship. It is observed that the dilatant hardening in the saturated undrained dense sand is reduced considerably due to the formation of shear bands.

Statistical evaluation of model factors in reliability calibration of high-displacement helical piles under axial loading

2020 ◽  
Vol 57 (2) ◽  
pp. 246-262 ◽  
Author(s):  
Chong Tang ◽  
Kok-Kwang Phoon
Keyword(s):  
Limit State ◽  
Axial Loading ◽  
Design Guidelines ◽  
Resistance Factor ◽  
Hyperbolic Model ◽  
Ultimate Limit State ◽  
Dense Sand ◽  
Capacity Model ◽  
Helical Piles ◽  
Two Parameters

An industry survey suggests an increasing application of high-displacement helical piles with greater shaft and helix diameters to support various structures. In this paper, a database of 84 static load tests is compiled and analyzed to evaluate the disturbance effect and characterize the model factors that can be used for reliability-based limit state design. The measured capacity is defined as the load at a pile head settlement equal to 5% of helix diameter. For similar helix configurations tested at the same site, the ratio of uplift to compression capacity indicates a low degree of disturbance for very stiff clay (0.8–1) and a medium degree of disturbance for dense sand (0.6–0.8). At the ultimate limit state, the model factor is defined as the ratio between measured and calculated capacity, where three design guidelines are considered. A hyperbolic model with two parameters is used to fit the load–displacement curves. At the serviceability limit state, the model factor can be defined with the hyperbolic parameters. Based on the database, probabilistic distributions of the capacity model factor and hyperbolic parameters are established. Finally, the capacity model statistics are applied to calculate the resistance factor in the load and resistance factor design.

scholarly journals An Experimental Study on Pile Spacing Effects under Lateral Loading in Sand

2013 ◽  
Vol 2013 ◽  
pp. 1-8 ◽  
Author(s):  
Mahdy Khari ◽  
Khairul Anuar Kassim ◽  
Azlan Adnan
Keyword(s):  
Pile Group ◽  
Experimental Investigations ◽  
Pile Groups ◽  
Dense Sand ◽  
Spacing Effects ◽  
Pile Diameter ◽  
Lateral Resistance ◽  
Model Pile ◽  
Pile Interaction ◽  
Subgrade Modulus

Grouped and single pile behavior differs owing to the impacts of the pile-to-pile interaction. Ultimate lateral resistance and lateral subgrade modulus within a pile group are known as the key parameters in the soil-pile interaction phenomenon. In this study, a series of experimental investigation was carried out on single and group pile subjected to monotonic lateral loadings. Experimental investigations were conducted on twelve model pile groups of configurations 1 × 2, 1 × 3, 2 × 2, 3 × 3, and 3 × 2 for embedded length-to-diameter ratiol/d= 32 into loose and dense sand, spacing from 3 to 6 pile diameter, in parallel and series arrangement. The tests were performed in dry sand from Johor Bahru, Malaysia. To reconstruct the sand samples, the new designed apparatus, Mobile Pluviator, was adopted. The ultimate lateral load is increased 53% in increasing ofs/dfrom 3 to 6 owing to effects of sand relative density. An increasing of the number of piles in-group decreases the group efficiency owing to the increasing of overlapped stress zones and active wedges. A ratio ofs/dmore than6dis large enough to eliminate the pile-to-pile interaction and the group effects. It may be more in the loose sand.

Glulam rivet connections under eccentric loading

1987 ◽  
Vol 14 (5) ◽  
pp. 621-630 ◽  
Author(s):  
Erol Karacabeyli ◽  
Ricardo O. Foschi
Keyword(s):  
Failure Modes ◽  
Experimental Studies ◽  
Design Guidelines ◽  
Bearing Failure ◽  
Element Analysis ◽  
Theoretical Predictions ◽  
Failure Loads ◽  
Fracture Theory ◽  
Timber Engineering ◽  
Type Of Failure

Results from theoretical and experimental studies on the strength of glulam rivet connections under eccentric loading are presented. Two failure modes are studied: (1) rivet yielding in bending with simultaneous bearing failure of the wood under the rivet's shank and (2) wood failure around the rivet cluster. The latter is studied using brittle fracture theory and a finite element analysis of the stress distribution in the wood around the rivets.Experimental results are shown to compare well with theoretical predictions for failure loads and type of failure, and design guidelines are proposed. Key words: fasteners, wood connectors, glued-laminated, nails, timber engineering.

Design Guidelines on the Ultimate Strength of Retrofitted Deep Concrete Coupling Beams by Laterally Restrained Side Plates

2012 ◽  
Vol 226-228 ◽  
pp. 942-948 ◽  
Author(s):  
Bei Cheng ◽  
Ray K.L. Su ◽  
Jian Luo
Keyword(s):  
Ultimate Strength ◽  
Experimental Studies ◽  
Design Procedure ◽  
Design Guidelines ◽  
Shear Capacity ◽  
Coupling Beams ◽  
Original Design ◽  
Group 4 ◽  
Plate Size ◽  
Flexural Resistance

Existing deep reinforced concrete (RC) coupling beams with low shear span ratios and conventionally reinforced shear stirrups tend to fail in a brittle manner with limited ductility and deformability under reversed cyclic loading. Experimental and numerical studies have demonstrated the effectiveness of laterally restrained steel plate (LRSP) retrofitting method in improving the seismic performance of deep RC coupling beams. In this way, the deformability and energy dissipation of the retrofitted beams are greatly enhanced. Based on the experimental studies and numerical simulation of LRSP coupling beams, an original design procedure on the ultimate strength of LRSP coupling beams is proposed. The proposed design guidelines consist of seven parts, which are (1) estimation of shear capacity of RC component, (2) estimation of plate size, (3) design of bolt group, (4) estimation of axial force, (5) determination of buckling effect coefficient, (6) shear resistance design of the retrofitted beam, and (7) flexural resistance design of the retrofitted beam.

scholarly journals Triaxial Testing on Geogrid-reinforced Granular Soils

2021 ◽  
Vol 1200 (1) ◽  
pp. 012030
Author(s):  
Tigo Mindiastiwi ◽  
Po-Kai Wu ◽  
Agus Bambang Siswanto ◽  
Mukhamad Afif Salim
Keyword(s):  
Shear Strength ◽  
Triaxial Compression ◽  
Confining Pressure ◽  
Reinforced Soil ◽  
Deviatoric Stress ◽  
Granular Soils ◽  
Peak Shear Strength ◽  
Compression Tests ◽  
Soil C ◽  
Dense Sand

Abstract Laboratory triaxial compression tests were carried out to investigate the mechanical behavior of dense sand and geogrid-reinforced granular soils. The tested sand having its mean particle size (D50) equal to 0.6 mm was adopted. Three geogrids with different longitudinal and transverse nominal strengths were used. The dimensions of the cylindrical soil specimen were 70 mm (diameter) × 160 mm (height). The relative density was equal to 70% for all tests. The reinforced sand specimens with one or two geogrid layers were sheared under effective confining pressures (σ′3) equal to 50 kPa. The test results of unreinforced sand indicate the general stress-strain behavior of dense sand when sheared, whereas the deviatoric stress reaches its peak value, after which it gradually decreases to ultimate value (σ1 - σ3)ult. The difference of effective confining pressure indicates that the peak of deviatoric stress Δσd = (σ1 - σ3) increases with the increase in effective confining pressure (σ′3), while the peak principal stress ratio (σ′1/σ′3) decreases with the increase (σ′3). The friction angle (ϕ′)and cohesion (c′), defined by analytical and graphical methods for unreinforced sand. Geogrid as reinforcement increasing peak shear strength. The increasing peak shear strength is more pronounced with a higher number of geogrid and the geogrid with higher stiffness. Increased in confining stress inside reinforced soil mass (Δσ3R) can be interpreted by cohesive reinforced soil (CR).

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