Multi-layered Foundation Research Articles

A simulation on soil structure interaction with ABAQUS; effect on the behavior of a concrete building of soil layers and earthquake properties

In this article, the effect of soil properties and earthquakes on a structure built in a multi-layer foundation soil is studied using Abaqus/СAЕ. Single foundations are one of the most common types of foundations traditionally required to support buildings in earthquake-prone regions. Most researchers work on the dynamic interaction between the foundation and the soil, which can affect the response of the building during earthquakes due to the type of earthquake and the properties of the soil layer. In this paper, four different earthquakes were applied to a reinforced concrete building constructed in two-layer soils with very different soil properties, and a discussion on soil-structure interaction was opened using Abaqus software. In the analysis, a layered soil is simulated with 4 different models (soft-hard, hard-soft). Through these analyses, the influence of the different soil layers (soft and hard), the building displacement and the frequency content of the earthquake were studied. According to the result of the analysis, it is important to consider the earthquake characteristics, the soil properties, and the type of foundation in the dynamic soil-structure interaction.

Nonlinear consolidation finite element analysis of a layered soft soil foundation under multistage loading based on the continuous drainage boundary

To comprehensively consider the impacts of stratification, residual pore water pressure, soil nonlinearity, and boundary permeability on consolidation settlement of soft soil foundations for accurate prediction, a continuous drainage boundary condition is proposed in this study that reflects the residual pore pressure under multistage loading, and a nonlinear elastic constitutive model based on the double logarithmic model is adopted to account for the nonlinear consolidation behaviour of soils. A UMAT subroutine is developed based on the proposed boundary condition and nonlinear elastic constitutive model. Subsequently, the developed subroutine is compared with the built-in linear elastic soil constitutive model in ABAQUS and engineering examples. The application of continuous drainage boundaries in stratified foundations is analysed, as well as the influence of factors such as the loading rate and soil nonlinearity on consolidation settlement. The results indicate that, compared to the built-in model, the subroutine developed in this study can be employed to more accurately calculate the nonlinear consolidation of multilayered foundations under multistage loading. By adjusting the loading rate parameter αk, consolidation under different loading conditions can be predicted. Additionally, the proposed boundary condition simplifies the calculations for soft soil foundations with sand layers, providing a novel computational approach for the design of construction loading schemes and long-term settlement predictions in soft soil foundations.

Axisymmetric Thermoelastic Deformation of a Multilayer Foundation with Imperfect Thermal Contact of the Layers

An axisymmetric stationary problem of thermoelasticity for a multilayer foundation with imperfect thermal contact between the layers is solved by the method of compliance functions along with the Hankel transform. The recurrence relations are constructed for the auxiliary functions and the compliance functions of neighboring layers of the foundation. We analyze the influence of the coefficient of thermal resistance on the distribution of normal and tangential stresses and temperature at the points of the bottom boundary of the top layer for a two-layer foundation subjected to the action of thermal loads.

РАСЧЕТ ЭФФЕКТИВНОЙ ДЛИНЫ БУРОНАБИВНЫХ ВИСЯЧИХ СВАЙ ПРИ СЖАТИИ ПО НЕСУЩЕЙ СПОСОБНОСТИ ДВУХСЛОЙНОГО ГРУНТА ОСНОВАНИЯ

The article discusses a new method for calculating the effective length of bored hanging piles based on the bearing capacity of a two-layer foundation soil. This calculation problem is of particular importance when it is necessary to use piles of large length and large diameter. The calculation of a hanging pile according to the bearing capacity of the foundation soil adopted in regulatory documents is based on the occurrence of friction forces on the surface of the pile because of its movement (“disruption”) in the ground environment. It does not correspond to the behavior of the pile during operation. In practice, the disruption of the pile is unacceptable, therefore, for the safe operation of the pile, the coefficients of the working conditions are entered into the calculation. A new approach to the calculation of hanging piles by bearing capacity in multilayer foundation soils based on the account of friction-adhesion forces on the surface of the pile is proposed. The friction-coupling forces are caused by micro-displacements of the surface layers of the pile material because of its general deformation from the compressive load on the pile. The effective length of the pile is understood to be such a length at which the bearing capacity of the soil on its surface and under the lower end of the pile is effectively used. Due to this length of the pile, an economic effect is achieved in pile foundations. The above method of calculating the bored pile can be used in the calculations of other piles by material, method of immersion and the number of layers of the foundation soil.

Studying the consolidation settlement for multi-layered foundation concerning the change in compressibility within the settlement zones

This paper deals with the approach of predicting the consolidation settlement for a multi-layered foundation concerning the change in the compressibility of the settlement layers. This non-linear problem is preliminarily solved by using the Massachusetts Institute of Technology’s (MIT’s) suggestion of approximation, according to which every two layers are converted into a single layer having an equivalent coefficient of consolidation Cv. This paper aims to further the solution by considering the variation of the permeability in the settlement zones of each compressible layer as a change in the compressibility and coefficient of compression. During consolidation, the new value of k is updated, resulting in a new coefficient of consolidation Cv and mv simultaneously; then compressible layers are combined and converted into either equivalent properties or thickness of consolidation. In case the coefficient of volume compression mv is kept to be constant, and the change in the compressibility of the settling zone is taken into account as in this study, preliminary results on the settlement of the alternatives indicate that the consolidation settlement will be greater than that of the conventional approach of analysis and the numerical computation by Plaxis model. The results of the comparison between this study and those of the other models _that are assumed to yield the same time-dependent consolidation_ and numerical model Plaxis indicate that the consolidation for multi-layered foundation requires a more rigorous study. This is a more detailed modification for coming closer to a conservative prediction of the time of consolidation and final consolidation settlement.

A Simplified Approach for Predicting the Time of Consolidation for a Multi-Layered Foundation

Research & Development in Material Science A Simplified Approach for Predicting the Time of Consolidation for a Multi-Layered Foundation Tham H Duong* Department of Civil Engineering, Ho Chi Minh City Open University, Vietnam *Corresponding author: Tham H Duong, Department of Civil Engineering, Ho Chi Minh City Open University, Vietnam Submission: September 21, 2021;Published: September 28, 2021 DOI: 10.31031/RDMS.2021.15.000871 ISSN: 2576-8840 Volume 15 Issue 5

Research on analytical conversion method of self-balanced test pile results

An analytical conversion method of self-balanced test of foundation pile bearing capacity is proposed. First, the load transfer matrices for the elastic-plastic state of the upper and lower segment piles in a multi-layer foundation were derived under the assumption of the load transfer function of the pile side associated with the ideal elastic-plastic model. Then the internal forces and vertical displacements at each micro-element of the upper and lower segment of the pile were calculated by programming, and the results of the self-balanced test pile were converted into the load-displacement curve of the conventional static load test by substituting the accurate conversion formula, and the ultimate bearing capacity was obtained. Finally, by combining with an engineering test pile example, two groups of loading results of anchor pile method and self-balanced method were used to verify the theoretical analysis of conversion method in this work. It can be concluded that the load-displacement curves obtained by this conversion method are more consistent with the results of the conventional static pressure tests compared with the simplified conversion method. Moreover, the proposed model can be widely used in the self-balanced test engineering of pile bearing strength with sufficient accuracy.

Predicting the Time-Dependent Settlement for Multi-Layered Foundation Concerning the Coupling of Settlement Zones and Layers

The major part of this paper is on the challenges in predicting settlements in highway embankments and reclamation works in marine, deltaic and estuarine type of deposits. The emphasis is on practical aspects and the difficulties experienced in confidently estimating settlements even after a century of developments and contributions. The influence of the general geology and soil conditions is discussed in relation to the site investigation works and the establishment of soil profile models. The fundamentals of preloading techniques with and without prefabricated drains (PVD) as ground improvement measures are also included. The observational approach in evaluating PVD performance and settlement estimations is then made with emphasis on curtailing residual settlements. Finally, the latter part of the paper is devoted to the analytical and numerical solutions of the behaviour of piled supported approach embankments with transfer layers. Geogrid reinforced pile supported (GRPS) embankment system is studied with the analytical approaches of Terzaghi, BS8006 method and Hewlett and Randolph method. Additionally, numerical analyses are also made with the Plaxis software.

Temperature Correction for FWD Deflection in Cement Pavement Void Detection

The use of the falling weight deflectometer (FWD) for detecting pavement voids is based on the principle that, under the same impact load, the deflection of pavements with voids increases significantly. Under the effect of temperature, the cement pavement becomes warped, which affects the deflection detection accuracy. In order to improve the accuracy of FWD detection of cement pavement voids, a three-dimensional numerical model of cement pavement on a multilayered elastic foundation under the coupled action of temperature and load is established in this paper. In addition, under different pavement void, climatic, and load conditions, the influence of temperature difference between top and bottom of the plate on the deflection of the center point of plate angle load is studied. Considering the temperature difference between top and bottom, the temperature correction coefficient is established and experimentally verified the accuracy of the temperature correction coefficient. The results showed that, within the ranges of positive and negative temperature differences, the fitting degree of the temperature correction coefficient for the cement pavement exceeded 0.99, which was consistent with the variation trend of the temperature correction coefficient obtained through field tests. The error was lower than 7%, which verified the applicability of the temperature correction coefficient for the dynamic deflection of cement pavements based on FWD. The accuracy of the FWD method in detecting cement pavement voids was improved, and this study demonstrated theoretical reference value and practical engineering significance.

Inverse problem analysis for nondestructive evaluation of structural characteristics of multilayered foundations

The evaluation of the parameters of multilayered foundations (pavements, runway strips, etc.) plays an important role in ensuring the safe movement of vehicles. An approach of model construction for estimating the mechanical and geometric parameters of such foundations based on the solutions of inverse problems for multilayered elastic packets is proposed. As input data for such problems the measured displacements (or velocities) of certain points on the package surface are used. The proposed approach is based on informational-probabilistic paradigm for inverse problem analysis, whose task is to obtain a posteriori probability density in the space of unknown parameters. The essence of the approach is the block-parametric approximation of the a priori probability density and likelihood function in the spaces of parameters and model data of the problem. The method allows estimating the parameters of the a priori distribution of unknown variable parameters, identifying and excluding outliers of the measured data from the created model, and constructing a posteriori estimation of the unknown parameters’ probability density with acceptable resolution. Proposed method can be used to create a new generation of equipment intended for nondestructive monitoring and estimating of the condition of pavements, runways and foundations of artificial structures. The appropriate software for such high-speed scanning devices that allow on-the-fly display of the diagnosed layered foundation parameters can be developed.

The analysis of a free two-layer composite beamon the elastic foundation

Abstract
 Introduction. This article offers a methodology for the analysis of a two-layer composite beam on an elastic foundation that represents a one-parameter Winkler model. The behaviour of two-layer beams is described by A.R. Rzhanitsyn in his theory of composite rods that have rigid transverse and elastic-yielding longitudinal connections between layers. The theory of composite rods allows to study the stress-strain state (SSS) of multilayer foundation beams, having a layer featuring low thermal conductivity, and perforated beams.
 Materials and methods. However, analytical solutions to these problems involve certain difficulties; therefore, they are often inapplicable. We propose to apply a numerical method, a method of successive approximations (MSA), developed by professor R.F. Gabbasov at the Department of structural and theoretical mechanics of the Moscow State University of Civil Engineering. MSA has proven to be an effective and highly accurate method designated for analyzing static/dynamic loads, applied to beams, slabs and shells, and for making stability calculations. The difference-based variation of the MSA method has a number of advantages over difference equations of the “classical” finite difference method (FDM). The proposed methodology allows to take into account various types of boundary conditions without involving contour points. Сoncentrated forces, concentrated moments, and piecewise distributed loads can be taken into account as loading types.
 The article describes a problem solving algorithm. The system of initial differential equations is solved using difference analogs. Typical difference equations for regular and boundary points are provided.
 Results. The analysis of a composite free-lying beam on an elastic foundation illustrates the proposed approach. The qua-lity of the analysis results is controlled by performing a numerical study of the solution convergence using several nested meshes.
 Conclusions. The proposed method can be used in the engineering practice of design organizations and the educational process of higher educational institutions training civil engineering specialists.

Axisymmetric thermoelastic deformation of a multilayer foundation with imperfect thermal contact of its layers

Axisymmetric thermoelastic deformation of a multilayer foundation with imperfect thermal contact of its layers

Numerical analysis of bearing characteristics of composite foundation with variable diameter rigid pile

Variable diameter rigid pile composite foundation are proposed for the multi-layer foundation. The bearing characteristics of composite foundation with variable diameter rigid pile under vertical load are numerically calculated and analysed. The research content of this paper focuses on the variation law of load and settlement of composite foundation, pile axial force, pile lateral friction resistance and distribution law of soil internal force between piles under different diameter ratios etc. The results showed that Variable diameter of rigid pile composite foundation can effectively improve bearing capacity and control settlement and reduce the stress level of soil; negative skin friction section at the top of pile decreases with variable diameter ratio D/d increases, Zero skin friction section in diameter produced and increases with variable diameter ratio D/d increases; Optimal diameter ratio of pile in the variable diameter rigid pile composite foundation should be at about 1.75.

3D dynamic analysis of a pavement plate resting on a transversely isotropic multilayered foundation due to a moving load

A method is proposed for the 3D dynamic analysis of a pavement plate resting on transversely isotropic multilayered foundation due to a moving load. The composite laminated plate theory and the analytical layer-element method are utilized to solve the dynamic plate-foundation interaction problem. The governing equations of motion of the pavement plate in the moving system are derived with a combination of the thin plate theory and laminated plate theory, while the solutions for the transversely isotropic multilayered foundation under dynamic loadings are achieved with the use of the analytical layer-element method. Then, based on the continuity conditions at the plate-foundation interface, the dynamic behavior of the pavement plate undergoing a moving load is achieved. Finally, several examples are given to confirm the accuracy of the proposed method and to illustrate the influences of the location of rebar, the velocity of moving load, the reinforcement ratio and the elastic modulus of concrete on the dynamic behavior of pavement plates.

Optimization of multilayer rail substrate under moving load, using metamaterials.

Abstract Paper presents the optimization of linear elastic multilayer foundation of the Timoshenko beam, which can be considered as a rail model. The moving load traveling along a beam with particular velocity, which distribution is characterized by Gauss function, is implemented in the model. The displacement caused by the load is dependent on multilayer foundation parameters such as layer thickness, a type of material and load parameters such as moving velocity as well its distribution on a beam. The optimization, i.e. minimization of the total displacement sum, as the result of objective function determined regarding chosen parameters of a foundation and load, as a design variable was carried out. The Comsol Multiphysics [1], is applied in order to solve the beam and moving load problem by using the finite element method [2,3,4,5,6]. Using genetic algorithm [7,8,9] searches the minimum of objective function.

Punch-Through Risk of Jack-Up Under the Dual Uncertainty of Structure and Foundation

Abstract The preload operation of Jack-up in complex multi-layered foundation requires an enhanced understanding of its behavior in punch-through accident and suitable safety analysis tools for the assessment of their reliability in a particular site. In order to evaluate punch-through risk, a risk-consistent method is proposed based on the model of foundation hazard and structural vulnerability. Besides, foundation bearing capacity is evaluated to quantify foundation hazard. Third, to improve the solution efficiency, higher-order moment method (HOMM)-Pushover method has been developed for assessing the structural vulnerability. In addition, case studies are presented to demonstrate the advantages of these techniques and important trends are highlighted by the results of parametric sensitivity studies. More specifically, failure probability analysis has been undertaken using improved method and the punch-through risk is evaluated quantitatively in different hazard levels. The results show that the dual uncertainty of both structure and foundation is crucial for assessment of foundation hazard and structural vulnerability. The randomness of foundation parameters is the dominant factor affecting the punch-through risk, and the risk increases with the increase of preload weight. The time-varying risk in the process of preload operation can be revealed using the risk analysis method mentioned in this paper.

Experimental testing of a full-scale of group efficiency in multiple soil layers

Results of in-situ tests showed that the performance of single isolated piles and individual piles within a group is largely different. When piles are arranged in a group, the interaction between piles and the foundation depends on the pile arrangement and the pile group effect. To date, studies on the pile group effect in Vietnam have been limited to reduced-scale laboratory testing or static load testing where piles are installed into homogeneous sandy or clayey foundation. This paper presents in situ tests which were performed on both single piles and pile groups, loaded to failure, with the aim of studying the pile group effect of piles embedded in multi-layered foundation. Strain gauges were installed along the shaft of 10 m long steel pipe piles, with a diameter of 143 mm. The influence of loose sand layers on the group effect in case of friction piles was evaluated. The experimental results indicated that the influence of sand layers was evident, and the group factor was calculated to be 1.237.
 Keywords:
 group efficiency; pile groups; axial capacity; load transfer.

Plane Thermoelastic Deformation of a Multilayer Foundation with Non-Ideal Thermal Contact between its Layers

We proposed the method of the compliance function for the solution of two-dimensional stationary problem of thermoelasticity for a multilayer foundation (stack of elastic layers coupled with a half plane) with a non-ideal thermal contact between its layers. We constructed the recurrence relations for the auxiliary functions and the compliance functions of neighboring layers of the foundation. We analyzed the influence of thermal resistance on the distribution of stresses and temperature at the points of the lower boundary of the upper layer for a two-layer foundation subjected to the action of thermal loads.

A symplectic analytical approach for beams resting on multi-layered elastic foundations

Attributable to their complexity the problems of a beam resting on a multi-layered foundation (BMF) have not gain sufficient attention from researchers compared to those of a beam placing on a single-layered foundation (BSF). Although they are as significantly important in engineering disciplines, few scientific articles regarding BMF were published so far. Thus, this paper is aimed to establish an effective analytical approach to study a Timoshenko beam on a multi-layered elastic foundation. Comprehensive types of beam/foundation as well as a variety of load conditions are presented. The mathematical model of BMF is developed based on a symplectic dual equation, which is derived from the Hamiltonian principle associated with the Legendre transformation. The vertical deformations of the multi-layered foundation are assumed as the linear combination of the products of the vertical deformation at layer interface and the corresponding transverse distribution function. Variational method and iterative technique are utilized to formulate and solve for the distribution functions. Discretizing each layer in the foundation into sublayers is proposed to obtain more accurate deformation and stress responses. Compared to the finite element method, this article provides a highly reliable and effective analytical approach to investigate BMF problems.

Reliability of Jack-up against Punch-through using Failure State Intelligent Recognition Technique

The preload operation of jack-up in complex multi-layered foundation requires enhanced understanding of its behaviour in punchthrough accident and suitable safety analysis tools for the assessment of their reliability for a particular site. In this study, reliability analysis model of jack-up against punch-through is established considering structural uncertainty. In order to identify the failure state, an improved reliability solution method has been developed based on Sparse Auto-Encoder (SAE) deep learning network model. Sparse self-coding algorithm is used to the training of the deep network, and Softmax regression model is established to solve the identification and classification problem of the output layer. The first application of the technique was the study of HYSY 941 jack-up platform. More specifically, numerical calculations of structure ultimate bearing capacity have been undertaken, and the influence of model parameters on the prediction accuracy of the failure state is discussed. The results show that implicit performance function can be constructed accurately using SAE-MC method by reflecting the relationship between different critical safety state and structural vulnerability. Compared with traditional BP neural network, deep learning network has higher prediction accuracy to failure probability. The dynamic risk grade in the process of preload operation can be determined quantitatively using the reliability analysis method mentioned in this paper.