scholarly journals Estimation of Distribution Factor for Peak Penetration Resistance Prediction of Spudcan Foundations in Loose to Medium-Dense Sand Overlying Clay

2020 ◽  
Vol 10 (24) ◽  
pp. 8795
Author(s):  
Muhammad Asad Jan ◽  
Muhammad Bilal Adeel ◽  
Usman Pervaiz ◽  
Duhee Park
Keyword(s):  
Friction Angle ◽  
Failure Criteria ◽  
Penetration Resistance ◽  
Distribution Factor ◽  
Dense Sand ◽  
Soft Clays ◽  
Stiff Clays ◽  
Perfectly Plastic ◽  
Wide Range ◽  
Estimation Of Distribution

A series of 3D finite element (FE) analyses were performed to estimate the peak penetration resistance of spudcan foundations in sand over clay soil profiles. Elasto-perfectly plastic models following Mohr–Coulomb and Tresca failure criteria were used for sand and clay layers, respectively. The coupled Eulerian–Lagrangian (CEL) approach was used to simulate the large deformation in soil that occurs during the spudcan penetration. The performance of the numerical model was validated against centrifuge test results. A parametric study with a broad range of strength parameters for sand and clay was performed. The numerical results were used to assess the influence of sand thickness (Hs), the diameter of spudcan (D), friction angle of sand, and undrained shear strength of clay (su). A wide range of su was utilized to predict the resistance both of the soft and stiff clays. The calculated peak resistances are compared with a published analytical model. It is demonstrated that the model highly overestimates the peak resistance for stiff clays, most likely because it was developed specifically for soft clays and, therefore, does not account for the influence of su. One of the parameters of the model is revised to account both for su. Comparisons highlight that the modified model is able to capture the simulated peak penetration resistance for both soft and stiff clays.

scholarly journals Field and Laboratory-based Approach for the Determination of Friction Angle of Geological Discontinuities of Malaysian Granites

2011 ◽  
Vol 28 (2) ◽  
pp. 151 ◽  
Author(s):  
R. A Ghani ◽  
T. L Goh ◽  
A. M Hariri ◽  
Y. N Baizura
Keyword(s):  
Friction Angle ◽  
Roughness Coefficient ◽  
Average Value ◽  
Peak Friction Angle ◽  
Maximum Value ◽  
Wide Range ◽  
Discontinuity Surfaces ◽  
Geological Discontinuities ◽  
Range Of Values

The basic friction angle, Φb for artificially sawn discontinuity planes for fresh granite, as determined by tilt testing, has an average value of 30º. For the natural rough discontinuity surfaces, a wide range of values have been determined for the peak friction angle, Φpeak ranging from 47º to a maximum value of 80º, depending on the joint roughness coefficient (JRC). The average values of the friction angles for the different degrees of roughness were as follows: JRC 2–4 = 58°; JRC 6–8 = 60°; JRC 8–10 = 47°; JRC 12–14 = 60°; JRC 14–16 = 71° ; JRC 18–20 = 80°.

scholarly journals Evaluation of p-y Curves and p-multiplier of Pile Groups Corresponding to Sand Properties Change Based on 3D Numerical Analysis

2020 ◽  
Vol 20 (4) ◽  
pp. 207-217
Author(s):  
Yongjin Choi ◽  
Jaehun Ahn
Keyword(s):  
Numerical Analysis ◽  
Soil Properties ◽  
Pile Group ◽  
Friction Angle ◽  
Dominant Factor ◽  
Group Effect ◽  
Pile Groups ◽  
Dense Sand ◽  
Laterally Loaded Pile ◽  
Laterally Loaded

The <i>p-y</i> curve method and </i>p</i>-multiplier (<i>P<sub>m</sub></i>), which implies a group effect, are widely used to analyze the nonlinear behaviors of laterally loaded pile groups. Factors affecting <i>P<sub>m</sub></i> includes soil properties as well as group pile geometry and configuration. However, research on the change in <i>P<sub>m</sub></i> corresponding to soil properties has not been conducted well. In this study, in order to evaluate the effect of soil properties on the group effect in a laterally-loaded pile group installed in sandy soil, numerical analysis for a single pile and 3×3 pile group installed in loose, medium, and dense sand, was performed using the 3D numerical analysis program, Plaxis 3D. Among the factors considered in this study, the column location of the pile was the most dominant factor for <i>P<sub>m</sub></i>. The effect of the sand property change on <i>P<sub>m</sub></i> was not as significant as that of the column location of the pile. However, as the sand became denser and the friction angle increased, the group effect increased, leading to a decrease in <i>P<sub>m</sub></i> of approximately 0.1. This trend was similar to the result reported in a previous laboratory-scale experimental study.

A Novel Polyaxial Strength Criterion for Rock Materials Under General Stress Condition

2018 ◽  
Vol 10 (08) ◽  
pp. 1850082 ◽  
Author(s):  
Yugui Yang ◽  
Feng Gao ◽  
Chengzheng Cai ◽  
Peijian Chen
Keyword(s):  
Stress State ◽  
Stress Condition ◽  
Strength Criterion ◽  
Friction Angle ◽  
External Loading ◽  
Nonlinear Characteristics ◽  
Rock Materials ◽  
Wide Range ◽  
Confining Pressures ◽  
The Relationship

Yielding or failure of rocks under the action of external loading is complicated due to the dependence on pressure sensitivity and Lode angle. In this study, a generalized hyperbolic strength criterion is proposed to describe the strong nonlinear characteristics of rocks over a wide range of confining pressures. The relationship between failure stress and instantaneous friction angle of rocks is analyzed based on nonlinear Mohr strength envelope. In order to reflect the influence of intermediate principal stress on the strength of rock materials, the generalized hyperbolic criterion has further been extended to complicated stress state. The failure criterion allows the possibility of transitions from an equilateral triangle to circle, which greatly improves the durability and applicability to describe the strength characteristics of various rocks under complicated stress state. The validity of the proposed criterion is verified by comparing predictions with experimental results of rocks.

Pseudo-Dynamic Active Earth Pressure on Battered Face Retaining Wall Supporting c-Φ Backfill Considering Curvilinear Rupture Surface

2014 ◽  
Vol 5 (1) ◽  
pp. 39-57
Author(s):  
Sima Ghosh ◽  
Arijit Saha
Keyword(s):  
Wave Velocity ◽  
Retaining Wall ◽  
Pressure Coefficient ◽  
Wedge Angle ◽  
Earth Pressure ◽  
Friction Angle ◽  
Active Earth Pressure ◽  
Horizontal Shear ◽  
Rupture Surface ◽  
Wide Range

In the present analysis, using the horizontal slice method and D'Alembert's principle, a methodology is suggested to calculate the pseudo-dynamic active earth pressure on battered face retaining wall supporting cohesive-frictional backfill. Results are presented in tabular form. The analysis provides a curvilinear rupture surface depending on the wall-backfill parameters. Effects of a wide range of variation of parameters like wall inclination angle (a), wall friction angle (d), soil friction angle (F), shear wave velocity (Vs), primary wave velocity (Vp), horizontal and vertical seismic accelerations (kh, kv) along with horizontal shear and vertical loads and non-linear wedge angle on the seismic active earth pressure coefficient have been studied.

Measurement and Calibration of the Parameters of Hypoplasticity Model for an Iraqi Soil

2020 ◽  
Vol 857 ◽  
pp. 243-252
Author(s):  
Aysar Hassan Subair ◽  
Ala Nasir Aljorany
Keyword(s):  
Constitutive Model ◽  
Void Ratio ◽  
Initial Stresses ◽  
Model Parameters ◽  
State Variables ◽  
Soil Behavior ◽  
Dense Sand ◽  
Hypoplastic Model ◽  
Material Parameters ◽  
Wide Range

There are many constitutive models that have been used to model the mechanical behavior of soils. Some of these models are either unable to represent important features such as the strain softening of dense sand or required many parameters that can be hard to obtain by standard laboratory tests. Because of that, a more reliable constitutive model, which is capable to capture the main features of the soil behavior with easily obtained parameters, is required. The Hypoplasticity model is considered as a promising constitutive model in this respect. It is considered as a particular class of rate non-linear constitutive model at which the stress increment is expressed in a tensorial equation as a function of strain increment, actual stress, and void ratio. The hypoplastic model required only eight material parameters (critical friction angle critical, maximum and minimum void ratio respectively), granular stiffness hs and the model constants n, α, β). The appealing feature of the hypoplastic model is that the material parameters are separated from the state variables (void ratio and the initial stresses). This feature enables the model to simulate the soil behavior under a wide range of stresses and densities with the same set of material parameters. In this research, a brief description of the Hypoplasticity model is presented. Detailed discussions regarding the measurement and calibration of the model parameters of an Iraqi soil are then exposed. It is concluded that only Consolidated Drained (CD) triaxial test, oedometer test, and the well-known limit density tests are needed to get all the parameters of the hypoplasticity model.

Plastic Limit Loads for Piping Branch Junctions

2007 ◽  
Vol 345-346 ◽  
pp. 1377-1380 ◽  
Author(s):  
Yun Jae Kim ◽  
Kuk Hee Lee ◽  
Chi Yong Park
Keyword(s):  
Three Dimensional ◽  
Limit Load ◽  
Plastic Limit ◽  
Perfectly Plastic ◽  
Plastic Materials ◽  
Wide Range ◽  
Pipe Radius ◽  
Plastic Limit Load ◽  
The Mean ◽  
Elastic Perfectly Plastic

The present work presents plastic limit load solutions for branch junctions under internal pressure and in-plane bending, based on detailed three-dimensional (3-D) FE limit analyses using elastic-perfectly plastic materials. The proposed solutions are valid for a wide range of branch junction geometries; ratios of the branch-to-run pipe radius and thickness from 0.0 to 1.0, and the mean radius-to-thickness ratio of the run pipe from 5.0 to 20.0.

scholarly journals Relation between the Friction Angle of Sand at Triaxial Compression and Triaxial Extension and Plane Strain Conditions

Geosciences ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 29 ◽  
Author(s):  
Zenon Szypcio
Keyword(s):  
Plane Strain ◽  
Soil Mechanics ◽  
Triaxial Compression ◽  
Deformation Mode ◽  
Friction Angle ◽  
Failure Criteria ◽  
Compression Tests ◽  
Laboratory Test Results ◽  
Experimental Findings ◽  
Triaxial Extension

The strength of sand is usually characterized by the maximum value of the secant friction angle. The friction angle is a function of deformation mode, density, and stress level and is strongly correlated with dilatancy at failure. Most often, the friction angle is evaluated from results of conventional compression tests, and correlation between the friction angle of sand at triaxial compression and triaxial extension and plane strain conditions is a vital problem of soil mechanics. These correlations can be obtained from laboratory test results. The failure criteria for sand presented in literature also give the possibility of finding correlations between friction angles for different deformation modes. The general stress-dilatancy relationship obtained from the frictional state concept, with some additional assumptions, gives the possibility of finding theoretical relationships between the friction angle of sand at triaxial compression and triaxial extension and plane strain conditions. The theoretically obtained relationships presented in the paper are fully consistent with theoretical and experimental findings of soil mechanics.

scholarly journals Bearing Capacity of Ring Foundations on Sand Overlying Clay

2020 ◽  
Vol 10 (13) ◽  
pp. 4675
Author(s):  
Chaowei Yang ◽  
Zhiren Zhu ◽  
Yao Xiao
Keyword(s):  
Bearing Capacity ◽  
Friction Angle ◽  
Failure Criteria ◽  
Unit Weight ◽  
Sand Layer ◽  
Collapse Mechanisms ◽  
Internal Radius ◽  
Vertical Bearing ◽  
Vertical Bearing Capacity ◽  
Ring Foundations

The vertical bearing capacity of rough ring foundations resting on a sand layer overlying clay soil is computed in this study by using finite element limit analysis (FELA). The sands and clays are assumed as elastoplastic models, obeying Mohr–Coulomb and Tresca failure criteria, respectively. Based on the FELA results, design charts are provided for evaluating the ultimate bearing capacity of ring foundations, which is related to the undrained shear strength of the clay, the thickness, the internal friction angle, the unit weight of the sand layer, and the ratio of the internal radius to the external radius of the footing. A certain thickness, beyond which the clay layer has a negligible effect on the bearing capacity, is determined. The collapse mechanisms are also examined and discussed.

Formulation of Seismic Passive Resistance of Retaining Wall Backfilled with c-F Soil

2012 ◽  
Vol 3 (2) ◽  
pp. 15-24 ◽  
Author(s):  
Sima Ghosh
Keyword(s):  
Retaining Wall ◽  
Pressure Coefficient ◽  
Earth Pressure ◽  
Friction Angle ◽  
Wall Friction ◽  
Unit Weight ◽  
Passive Resistance ◽  
Angle Of Internal Friction ◽  
Variation Of Parameters ◽  
Wide Range

Knowledge of passive resistance is extremely important and it is the basic data required for the design of geotechnical structures like the retaining wall moving towards the backfill, the foundations, the anchors etc. An attempt is made to develop a formulation for the evolution of seismic passive resistance of a retaining wall supporting c-F backfill using pseudo-static method. Considering a planar rupture surface, the formulation is developed in such a way so that a single critical wedge surface is generated. The variation of seismic passive earth pressure coefficient are studied for wide range of variation of parameters like angle of internal friction, angle of wall friction, cohesion, adhesion, surcharge, unit weight of the backfill material, height and seismic coefficients.

scholarly journals Prediction of spudcan penetration resistance profile in stiff-over-soft clays

2016 ◽  
Vol 53 (12) ◽  
pp. 1978-1990 ◽  
Author(s):  
J. Zheng ◽  
M.S. Hossain ◽  
D. Wang
Keyword(s):  
Bearing Capacity ◽  
Soft Clay ◽  
Bottom Layer ◽  
Design Approach ◽  
Rate Dependency ◽  
Soft Clays ◽  
Perfectly Plastic ◽  
Clay Deposits ◽  
Additional Resistance ◽  
Elastic Perfectly Plastic

Spudcan punch-through during installation and preloading process is one of the key concerns for the jack-up industry. This incident occurs in layered deposits, with new design approaches for spudcan penetration in sand-over-clay deposits reported recently. This paper reports a novel design approach for spudcan penetration in stiff-over-soft clay deposits. Large-deformation finite element (LDFE) analyses were carried out using the Coupled Eulerian–Lagrangian (CEL) approach. The clay was modelled using the extended elastic – perfectly plastic Tresca soil model allowing strain softening and rate dependency of the undrained shear strength. A detailed parametric study was undertaken, varying the strength ratio between bottom and top soil layers, the thickness of the top layer relative to the spudcan diameter, and degree of nonhomogeneity of the bottom layer. Existing data from centrifuge model tests were first used to validate the LDFE results, and then the measured and computed datasets were used to develop the formulas in the proposed design approach. The approach accounts for the soil plug in the bottom layer, and the corresponding additional resistance. Where there is the potential for punch-through, the approach provides estimations of the depth and bearing capacity at punch-through, the bearing capacity at the stiff–soft layer interface, and the bearing capacity in the bottom layer. Comparison shows that the punch-through method suggested in ISO standard 19905-1 provides a conservative estimate of the bearing capacity at punch-through, with guidelines provided to improve the method.

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