scholarly journals Peak punch-through capacity of spudcan in sand with interbedded clay: numerical and analytical modelling

2017 ◽  
Vol 54 (8) ◽  
pp. 1071-1088 ◽  
Author(s):  
Shah Neyamat Ullah ◽  
Yuxia Hu
Keyword(s):  
Clay Soil ◽  
Soft Clay ◽  
Friction Angle ◽  
Analytical Models ◽  
Fe Model ◽  
Clay Layer ◽  
Dense Sand ◽  
Centrifuge Tests ◽  
Improved Performance ◽  
Sand Plug

The presence of a thin soft clay layer inside a bed of sand may significantly reduce the bearing capacity of the sand layer, imposing a risk of punch-through failure. In this paper, finite element (FE) simulations are reported using a hardening soil (HS) model for sand. The FE model has been verified against centrifuge tests involving loose and dense sand layers overlying clay soil. The effects of sand stiffness, foundation roughness, sand friction angle, undrained clay strength, clay strength nonhomogeneity, and sand and clay layer geometries on the foundation peak capacities have been studied. Punch-through failure is initiated with an inclined sand plug being sheared and pushed into the underlying soft clay. During punch-through, the clay layer fails due to significant radial squeezing. Existing analytical models do not capture the combined failure mechanism of sand shearing and clay radial squeezing. A new analytical model is developed to estimate the peak punch-through capacity of a spudcan in sand with an interbedded clay layer, showing improved performance over the current industry guidelines.

scholarly journals Numerical Study of Laterally Loaded Piles in Soft Clay Overlying Dense Sand

2021 ◽  
Vol 7 (4) ◽  
pp. 730-746
Author(s):  
Amanpreet Kaur ◽  
Harvinder Singh ◽  
J. N. Jha
Keyword(s):  
Layer Thickness ◽  
Soft Clay ◽  
Bending Moment ◽  
Layered Soil ◽  
Clay Layer ◽  
Pile Groups ◽  
Dense Sand ◽  
Lateral Capacity ◽  
Laterally Loaded ◽  
Pile Length

This paper presents the results of three dimensional finite element analysis of laterally loaded pile groups of configuration 1×1, 2×1 and 3×1, embedded in two-layered soil consisting of soft clay at liquid limit overlying dense sand using Plaxis 3D. Effects of variation in pile length (L) and clay layer thickness (h) on lateral capacity and bending moment profile of pile foundations were evaluated by employing different values of pile length to diameter ratio (L/D) and ratio of clay layer thickness to pile length (h/L) in the analysis. Obtained results indicated that the lateral capacity reduces non-linearly with increase in clay layer thickness. Larger decrease was observed in group piles. A non-dimensional parameter Fx ratio was defined to compare lateral capacity in layered soil to that in dense sand, for which a generalized expression was derived in terms of h/L ratio and number of piles in a group. Group effect on lateral resistance and maximum bending moment was observed to become insignificant for clay layer thickness exceeding 40% of pile length. For a fixed value of clay layer thickness, lateral capacity and bending moment in a single pile increased significantly with increase in pile length only up to an optimum embedment depth in sand layer which was found to be equal to three times pile diameter and 0.21 times pile length for pile with L/D 15. Scale effect on lateral capacity has also been studied and discussed. Doi: 10.28991/cej-2021-03091686 Full Text: PDF

scholarly journals Design Charts for Axially Loaded Single Pile Action

2019 ◽  
Vol 5 (4) ◽  
pp. 922-939 ◽  
Author(s):  
Anis Abdul Khuder Mohamad Ali ◽  
Jaffar Ahemd Kadim ◽  
Ali Hashim Mohamad
Keyword(s):  
Clay Soil ◽  
Skin Resistance ◽  
Soft Clay ◽  
Single Layer ◽  
Load Test ◽  
Engineering Properties ◽  
Single Pile ◽  
Dense Sand ◽  
Design Charts ◽  
Pile Length

The objective of this article is to generating the design charts deals with the axially ultimate capacity of single pile action by relating the soil and pile engineering properties with the pile capacity components. The soil and are connected together by the interface finite element along pile side an on its remote end.  The analysis was carried out using ABAQUS software to find the nonlinear solution of the problem. Both pile and soil were modeled with three-dimensional brick elements. The software program is verified against field load-test measurements to verify its efficiency accuracy. The concrete bored piles are used with different lengths and pile diameter is taken equals to 0.6 m. The piles were installed into a single layer of sand soil with angles of internal friction (20° t0 40°) and into a single layer of clay soil with Cohesion (24 to 96) kPa.  The getting results showed that for all cases study the total compression resistance is increased as pile length increased for the same property of soil, also illustrious that the total resistance of same pile length and diameter increased as the soil strength increasing. In addition, the same results were obtained for the end bearing resistance, skin resistance and tension capacity. Design charts were constructed between different types of soil resistance ratio and the pile length/diameter ratio (L/D) for all cases of study. One of improvement found from these curves that it is cheaply using piles of larger diameter than increasing their lengths for dense sand and to increasing piles lengths for loose sand. Moreover, it is inexpensively using piles of larger length in soft clay soil than increasing their diameter and piles of larger diameter in firm and stiff clay soils than increasing their length.

scholarly journals FEM Analysis of Dynamic Soil-Pile-Structure Interaction in Liquefied and Laterally Spreading Ground

2013 ◽  
Vol 29 (3) ◽  
pp. 733-755 ◽  
Author(s):  
Dongdong Chang ◽  
Ross Boulanger ◽  
Scott Brandenberg ◽  
Bruce Kutter
Keyword(s):  
Fem Analysis ◽  
Pile Group ◽  
Fe Model ◽  
Plasticity Model ◽  
Dense Sand ◽  
Structure Interaction ◽  
Centrifuge Tests ◽  
Centrifuge Models ◽  
Pressure Independent ◽  
Pressure Dependent Plasticity

A two-dimensional nonlinear dynamic finite element (FE) model was developed and calibrated against dynamic centrifuge tests to study the behavior of soil-pile-structure systems in liquefied and laterally spreading ground during earthquakes. The centrifuge models included a simple structure supported on pile group. The soil profiles consisted of a gently sloping clay crust over liquefiable sand over dense sand. The FE model used an effective stress pressure dependent plasticity model for liquefiable soil and a total stress pressure independent plasticity model for clay, beam column elements for piles and structure, and interface springs that couple with the soil mesh for soil-structure interaction. The FE model was evaluated against recorded data for eight cases with same set of baseline parameters. Comparisons between analyses and experiments showed that the FE model was able to approximate the soil and structural responses and reproduce the lateral loads and bending moments on the piles reasonably well.

scholarly journals Predicting the resistance profile of a spudcan penetrating sand overlying clay

2014 ◽  
Vol 51 (10) ◽  
pp. 1151-1164 ◽  
Author(s):  
Pan Hu ◽  
Dong Wang ◽  
Mark J. Cassidy ◽  
Sam A. Stanier
Keyword(s):  
Penetration Resistance ◽  
Clay Layer ◽  
Interface Shear ◽  
Element Analysis ◽  
Resistance Profile ◽  
Dense Sand ◽  
Geotechnical Centrifuge ◽  
Centrifuge Tests ◽  
Full Penetration ◽  
Stress Dependent

Assessment of the risk of punch-through failure of spudcan foundations on sand overlying clay requires prediction of the full penetration resistance profile, from touchdown and through punch-through to equilibrium of the vertical resistance at depth in the underlying clay layer. This study uses the Coupled Eulerian–Lagrangian approach, a large deformation finite element analysis method, to model the complete penetration resistance profile of a spudcan on sand overlying clay. The sand is modeled using the Mohr–Coulomb model, while the clay is modeled using a modified Tresca model to account for strain softening. The numerical method is then used to simulate a series of spudcan penetration tests, performed in a geotechnical centrifuge, on medium dense sand overlying clay. The punch-through behavior observed in the experiments is replicated, and the penetration resistance profiles from numerical analyses are generally a reasonable match to the experimental measurements. The influences of the sand layer height to foundation diameter ratio, sand–clay interface shear strength, and strength gradient in clay on the penetration resistance profiles are explored in a complementary parametric study. The penetration resistance in the underlying clay layer is well predicted using a simple linear expression for the bearing capacity factor for the spudcan and underlying sand plug. This expression is combined with an existing failure stress dependent model for predicting peak resistance to form a simplified method for prediction of the full penetration resistance profile. This new method provides estimates of the vertical penetration that the spudcan will run during the punch-through event. It is validated against both medium dense and dense sand centrifuge tests.

Spudcan Penetration in Clay-Sand-Clay Soils

2011 ◽  
Author(s):  
Long Yu ◽  
Hui Zhou ◽  
Wen Gao ◽  
Jun Liu ◽  
Yuxia Hu
Keyword(s):  
Yield Criterion ◽  
Soft Clay ◽  
Friction Angle ◽  
Small Strain ◽  
Clay Soils ◽  
Soil Conditions ◽  
Sand Layer ◽  
Element Analysis ◽  
Dense Sand ◽  
Flow Mechanisms

Multi-layered soil conditions often exist in offshore practice. In some sites a thin layer of medium dense sand lays between firm to stiff clay layers. In these cases the ultimate bearing capacity of foundations can be increased due to the strong sand layer by comparing with foundations in uniform clay. However, there is also a potential of reduction in foundation capacity when the foundation punches through the sand layer. The punch-through failure can occur during either pre-loading or storm loading. In this study, the continuous penetration of spudcan foundations on clay-sand-clay soils was investigated by large deformation finite element analysis. The numerical simulation was carried out using Remeshing and Interpolation Technique with Small Strain (RITSS) model. The clays obey Tresca failure criterion for undrained analysis and the sands obey Mohr-Coulomb yield criterion for drained analysis. The friction angle of the sand was taken as φ = 32° and 40° with its dilation angle ψ = 2° and 10° respectively. The effects of the relative height of the top soft clay and the relative thickness of the middle sand layer on the load-displacement responses were investigated. The soil flow mechanisms at various penetration depths were also discussed.

Uplift and Settlement Prediction Model of Marine Clay Soil e Integrated with Polyurethane Foam

2019 ◽  
Vol 9 (1) ◽  
pp. 481-489
Author(s):  
D.C. Lat ◽  
I.B.M. Jais ◽  
N. Ali ◽  
B. Baharom ◽  
N.Z. Mohd Yunus ◽  
...  
Keyword(s):  
Polyurethane Foam ◽  
Clay Soil ◽  
Ground Improvement ◽  
Soft Soil ◽  
Soft Clay ◽  
Effective Thickness ◽  
Marine Clay ◽  
Uplift Pressure ◽  
Pu Foam ◽  
Improvement Method

AbstractPolyurethane (PU) foam is a lightweight material that can be used efficiently as a ground improvement method in solving excessive and differential settlement of soil foundation mainly for infrastructures such as road, highway and parking spaces. The ground improvement method is done by excavation and removal of soft soil at shallow depth and replacement with lightweight PU foam slab. This study is done to simulate the model of marine clay soil integrated with polyurethane foam using finite element method (FEM) PLAXIS 2D for prediction of settlement behavior and uplift effect due to polyurethane foam mitigation method. Model of soft clay foundation stabilized with PU foam slab with variation in thickness and overburden loads were analyzed. Results from FEM exhibited the same trend as the results of the analytical method whereby PU foam has successfully reduced the amount of settlement significantly. With the increase in PU foam thickness, the settlement is reduced, nonetheless the uplift pressure starts to increase beyond the line of effective thickness. PU foam design chart has been produced for practical application in order to adopt the effective thickness of PU foam within tolerable settlement value and uplift pressure with respect to different overburden loads for ground improvement works.

scholarly journals Influence of Pile Diameter and Aspect Ratio on the Lateral Response of Monopiles in Sand with Different Relative Densties

2021 ◽  
Vol 9 (6) ◽  
pp. 618
Author(s):  
Huan Wang ◽  
Lizhong Wang ◽  
Yi Hong ◽  
Amin Askarinejad ◽  
Ben He ◽  
...  
Keyword(s):  
Aspect Ratio ◽  
Large Diameter ◽  
Pressure Coefficient ◽  
Offshore Wind ◽  
Fe Model ◽  
Soil Pressure ◽  
Pile Diameter ◽  
Centrifuge Tests ◽  
Aspect Ratios ◽  
Wide Range

The large-diameter monopiles are the most preferred foundation used in offshore wind farms. However, the influence of pile diameter and aspect ratio on the lateral bearing behavior of monopiles in sand with different relative densities has not been systematically studied. This study presents a series of well-calibrated finite-element (FE) analyses using an advanced state dependent constitutive model. The FE model was first validated against the centrifuge tests on the large-diameter monopiles. Parametric studies were performed on rigid piles with different diameters (D = 4–10 m) and aspect ratios (L/D = 3–7.5) under a wide range of loading heights (e = 5–100 m) in sands with different relative densities (Dr = 40%, 65%, 80%). The API and PISA p-y models were systematically compared and evaluated against the FE simulation results. The numerical results revealed a rigid rotation failure mechanism of the rigid pile, which is independent of pile diameter and aspect ratio. The computed soil pressure coefficient (K = p/Dσ′v) of different diameter piles at same rotation is a function of z/L (z is depth) rather than z/D. The force–moment diagrams at different deflections were quantified in sands of different relative density. Based on the observed pile–soil interaction mechanism, a simple design model was proposed to calculate the combined capacity of rigid piles.

SEA model for structural acoustic coupling by means of periodic finite element models of the structural subsystems

2021 ◽  
Vol 263 (1) ◽  
pp. 5301-5309
Author(s):  
Luca Alimonti ◽  
Abderrazak Mejdi ◽  
Andrea Parrinello
Keyword(s):  
Finite Element ◽  
Numerical Approach ◽  
Unit Cell ◽  
Analytical Models ◽  
Finite Element Models ◽  
Fe Model ◽  
Acoustic Coupling ◽  
Representative Unit Cell ◽  
Definition Of ◽  
Acoustic Treatment

Statistical Energy Analysis (SEA) often relies on simplified analytical models to compute the parameters required to build the power balance equations of a coupled vibro-acoustic system. However, the vibro-acoustic of modern structural components, such as thick sandwich composites, ribbed panels, isogrids and metamaterials, is often too complex to be amenable to analytical developments without introducing further approximations. To overcome this limitation, a more general numerical approach is considered. It was shown in previous publications that, under the assumption that the structure is made of repetitions of a representative unit cell, a detailed Finite Element (FE) model of the unit cell can be used within a general and accurate numerical SEA framework. In this work, such framework is extended to account for structural-acoustic coupling. Resonant as well as non-resonant acoustic and structural paths are formulated. The effect of any acoustic treatment applied to coupling areas is considered by means of a Generalized Transfer Matrix (TM) approach. Moreover, the formulation employs a definition of pressure loads based on the wavenumber-frequency spectrum, hence allowing for general sources to be fully represented without simplifications. Validations cases are presented to show the effectiveness and generality of the approach.

Characterization of a smear zone around vertical drains by large-scale laboratory tests

2000 ◽  
Vol 37 (6) ◽  
pp. 1265-1271 ◽  
Author(s):  
J S Sharma ◽  
D Xiao
Keyword(s):  
Large Scale ◽  
Soft Clay ◽  
Excess Pore Pressure ◽  
Laboratory Model ◽  
Clay Layer ◽  
Prefabricated Vertical Drains ◽  
Vertical Drains ◽  
Undisturbed Samples ◽  
Oedometer Tests ◽  
Excess Pore

Installation of prefabricated vertical drains using a mandrel causes disturbance of clay surrounding the drain, resulting in a "smear" zone of reduced permeability. In this paper, an attempt is made to characterize the smear zone using large-scale laboratory model tests. Two tests, simulating the cases of "no smear" and "with smear," were conducted. Excess pore-water pressures were monitored at seven different locations along the radial direction. In addition, undisturbed samples were collected at various locations in the clay layer for conducting oedometer tests. The distribution of excess pore pressure due to drain installation gave a clear indication of the extent of the smear zone. The effect of reconsolidation on the properties of clay was found to be much greater than that of the remoulding of the clay. The extent of the smear zone was also confirmed from the change in permeability of the clay layer in the smear zone obtained from oedometer tests. The radius of the smear zone is about four times that of the mandrel, and the horizontal permeability of the clay layer in the smear zone is approximately 1.3 times smaller than that in the intact zone.Key words: consolidation, permeability, smear zone, soft clay, vertical drains.

Sign in / Sign up

Export Citation Format

Share Document