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A GWO-ML-based large deformation finite element variable mapping method: An example of RITSS large deformation finite element simulation

The mapping of variables between old and new elements is a crucial aspect of large deformation finite element simulation. However, traditional mapping methods suffer from limited applicability and complex operations. In this study, a novel Gray Wolf Optimization-Machine Learning (GWO-ML) based variable mapping method for large deformation finite element analysis is proposed. This method achieves accurate mapping results without requiring explicit determination of element-to-element positional relationships. Furthermore, it effectively integrates a wider range of integration point information during the mapping process and maintains high prediction accuracy near boundaries with sparse mesh data. The remeshing and interpolation technique by small strain is employed as an illustrative example, wherein a set of automated operations is proposed to control the commercial software ABAQUS through Python scripting for conducting small strain analysis and GWO-ML mapping process. For machine learning models, Multilayer Perceptrons, Random Forest, Extreme Learning Machine, and Support Vector Regression, are compared, where the RF model has excellent computational accuracy and efficiency in terms of performance. The application of this method is investigated in scenarios with various foundation types, motion modes, loading modes, and multi-physics coupling mappings. The results confirm that the method exhibits high accuracy and robustness in simulation processes.

Response surface method-based efficient approach for the load and resistance factors calibration of breakwater foundation considering soil spatial variability

This study aims to propose an efficient approach to calibrate the load and resistance factors (LRFs) for the limit state design of breakwater foundations. The spatial variability of soil was considered by employing the Cholesky decomposition technique. To overcome the low computational efficiency of the Monte Carlo simulation (MCS), a response surface method (RSM) was utilized. Additionally, an efficient algorithm, namely the adaptive boundary-based particle filtering algorithm (ABB-PFA), was proposed with the use of RSM to automatically and quickly search optimal nominal values of random variables in the LRF calibration process. Noticeably, the optimal number of particles and values of the modification factor used in the ABB-PFA were observed to enhance the efficiency of the calibration process. The results showed that the computational efficiency of the calibration process is significantly increased by utilizing the response surface method and the proposed ABB-PFA. The efficiency increases the most if the number of particles is one and the value of the modification factor is 0.5 or 0.6. The influences of the random field element size on the efficiency of the calibration process were also investigated. By using the appropriate size, the efficiency is significantly increased while still obtaining a high accuracy of the LRFs calibration process.

Experimental Study on the Bearing Characteristics of Rigid-Flexible Long-Short Pile Composite Foundations in Thick Collapsible Loess Areas

The bearing and deformation characteristics of embankments with rigid-flexible long-short pile composite foundations (RLPCFs) in thick collapsible loess strata are not yet accurately understood. In this study, a large-scale field experiment was conducted, and screw (long) and compaction (short) piles were employed to reinforce a section of the foundation of the Lanzhou-Zhangye high-speed railway in thick collapsible loess. The pile load transfer, foundation settlement, pile-soil stress distribution, and load sharing characteristics were analyzed to reveal the bearing properties of the composite foundation. The results show that negative friction arises along the upper part of the pile, and the neutral points of the short pile and long pile are located at 2/5 and 1/3 down the pile lengths, respectively. The short pile eliminates the collapsibility of the shallow loess and enhances the foundation's bearing capacity. The long pile transfers the load of the shallow foundation and pile top to the deep foundation through lateral friction, which reduces the settlement of the shallow foundation. When the soil arch in the embankment is fully formed, the short pile bears approximately 20% of the load, while the long pile and the soil between piles bear 80%. With the increase in embankment filling height, the load borne by the long pile rises, and the load borne by the soil between piles decreases gradually. The top settlement of the cross-section of the composite foundation is distributed in a concave basin shape, and the maximum settlement occurs in the center of the embankment. The parameters of the short pile can be obtained on the basis of the collapsibility grade and bearing capacity of the loess foundation, the length and area replacement rate of the long pile can be obtained based on the settlement control requirements of the superstructure of the composite foundation, and the lateral friction of the long pile can be increased by increasing the roughness of the pile and setting the screw.

Numerical Study of Piled Raft Foundation in Non-Homogeneous Soil Using Finite Element Method

This paper analyzes a piled-raft foundation on non-homogeneous soils with variable layer depth percentages. The present work aims to perform a three-dimensional finite element analysis of a piled-raft foundation subjected to vertical load using the PLAXIS 3D software. Parametric analysis was carried out to determine the effect of soil type and initial layer thickness. The parametric study showed that increasing the relative density from 30 % to 80 % of the upper sand layer and the thickness of the first layer has led to an increase in the ultimate load and a decrease in the settlement of piled raft foundations for the cases of sand over weak soil. In clay over weak soil, the ultimate load of the piled raft foundation was increased, and the settlement decreased by increasing the clay cohesion of the upper layer from 20 kPa to 70 kPa. It was observed that the load shared by the raft was very effective when using dense sand in the upper layer. In the case of dense sand over stiff clay, the percent of load carried by the raft is (30-40) %. Although, for the case of stiff clay over soft clay, the load percentage was almost constant (16-20) %. While for other issues, the sharing load of raft foundation was close and had the same behavior, the load carried by raft is between (8-12) %.

Numerical analysis of uneven settlement of highway subgrade based on nonlinear algorithm

Abstract In order to accurately and easily calculate the settlement of the foundation, a high-speed roadbed based on a nonlinear algorithm is proposed to broaden the uneven and uniform reduction numerical analysis. The basic loading test results of the foundation loading test results in a series of sand-bearing test results made by gear suppressive elastic Mohr–COMB were verified using general finite element procedure ABAQUS. The results show that for most original slopes of 1:1.5 highways, according to the above research results and relevant specifications, the high-wig ratio of the steps should be controlled in 1:1.2 to 1:1.5. That is, when the width is controlled in a range of about 1.2 m, the height of the step is held at 0.8–1.0 m. The larger the role of filling the top surface, the more obvious is the role of the geogrid to reduce the settlement of the road embankment. Under the conditions of the same subgraduation, the reinforced road embankment of the geotechnical grille, the settling effect that occurs in the load activity is also more obvious. This method offers a better design and construction technique for expanding the project, investigates the control of differential settlements caused by excavation step size and geogrid size, and seeks more complete, scientific programmes. It has the potential to drastically reduce the project’s investigation effort, shorten the survey cycle, and provide incalculable economic and social benefits. Therefore, the research results of this paper have improved the reliability of existing ground settlement analysis.

Study on Horizontal Loading of Large Diameter Single Pile of Offshore Fan on Soft Clay Seabed Foundation


 Vigorously developing offshore wind power is an important measure to achieve China's "dual carbon" goal. For offshore wind turbines, the foundation embedded in the seabed is directly related to the safety and stability of the wind turbine, and is the most important part of wind power design. At present, in the offshore wind power construction within 40 m, large diameter single pile foundation is the most widely used foundation form. For the design of single pile foundation, it is necessary to ensure that the ultimate load of foundation can withstand the most extreme external load. Secondly, it is necessary to ensure that during the 25-year service period of the fan, the cumulative deformation of a single pile at the mud surface under the cyclic load of wind and waves does not exceed the value specified in the code; Finally, it is necessary to ensure that the wind power structure does not occur fatigue damage under the action of reciprocating dynamic load. Such strict design criteria, coupled with the soft clay seabed with poor mechanical properties widely distributed in the sea area of China's wind farms, bring severe challenges to the design of single piles.

МАТЕМАТИЧНЕ МОДЕЛЮВАННЯ ЗА МГЕ ПРОЦЕСУ ПІДСИЛЕННЯ ФУНДАМЕНТІВ

Taking into account the presence of weak soils on the territory of Ukraine, additional vertical deformations occur in soil foundations, associated with a violation of their structure. Water saturation of such soilsleads to a change in VAT and affects the conditions for the reliable operation of construction objects. In this regard, it becomes necessary to strengthen the foundations of these building objects, to improve the bearing capacity of these foundations. Therefore, in practice, the search for new ways to strengthen the foundations, improve their bearing capacity is constantly being carried out. In difficult engineering and geological conditions, the deterioration of the physical and mechanical properties leads to a rise in deformations and a decrease in the bearing capacity of the foundations. Reinforcement of foundations is also necessary when constructing superstructures. In the robot, using the numerical method of boundary elements, the behavior under load of a shallow foundation on a natural basis reinforced with cross piles is predicted. Reinforcement of foundation structures requires determination of their bearing capacity and stress-strain state (SSS) after reconstruction. Normative design of foundations, based on subsidence and rolls, which are borderline permissible from the point of view of the operational suitability and reliability of structures, puts forward increased requirements for the accuracy of calculating the displacements of foundations. Thecomplexity of the properties of soils and the many factors that influence their mechanical behavior have long been a barrier before which the mathematical methods of continuum mechanics were de-strengthened. The emergence of modern ECM allowed algebraicizing the mathematical formulation of most problems in soil mechanics, which require taking into account a large number of nonlinear determining factors and the transition to elastic-plastic models. The use of a numerical eexperiment, as never before, closely linked the physical meaning of the problem, its mathematical formulation, numerical methods of calculation and the ECM. In the robot, to obtain a forecast of the bearing capacity of a reinforced foundation, anelastic-plastic model of a discrete soil medium and a numerical MGE are used

Dilatancy Effects on Surface Foundations on Dry Sand

This paper presents the results of finite-element analyses of rigid-surface strip foundations on dry cohesionless soil subjected to displacement-controlled vertical loading. A two-surface constitutive model with a non-associated flow rule, representing the full range of pressure-dependent drained shear strength and volume change behavior of dry sand, is employed to model the soil. A range of foundation widths and sand initial relative densities is covered. The results show that, for narrow, rigid-strip foundations, the conventional bearing-capacity calculation provides a reasonable indication of the load-carrying capacity of the foundation. However, there is no peak in the load-carrying capacity for wide foundations, and the load–deformation curve exhibits stiffening behavior, even at large settlements; this is particularly apparent at larger values of the initial relative density. Based on the results, it is observed that with the increase in vertical foundation loading, the vertical stiffness of the foundation increases with each loading increment, due to the tendency of the dense sand to become more dilatant with the increase in confining pressure. At large settlements, the state of the sand beneath the foundation approaches the critical state. Settlement vectors beneath the foundations on dense sand reveal that the displacements approximate one-dimensional compression.

Development of analytical and FEM solutions for static and dynamic analysis of smart piezoelectric laminated composite plates on elastic foundation

This paper proposes new analytical and finite element solutions for studying the effects of elastic foundations on the uncontrolled and controlled static and vibration responses of smart multi-layered laminated composite plates with integrated piezoelectric layers, acting as actuators and sensors. A non-polynomial higher-order plate theory with zigzag kinematics involving a trigonometric function and a local segmented zigzag function is adopted for the first time for modeling the deformation of a smart piezoelectric laminated composite plate supported on an elastic foundation. This model has only five independent primary variables like that of the first-order shear deformation theory, yet it considers the realistic parabolic behavior of the transverse shear stresses across the thickness of the laminated composites plates, and also maintains the continuity conditions of transverse shear stresses at the interfaces of the laminated plates. A two-parameter foundation model, namely Pasternak’s foundation, is used to model the deformation and shear interactions of the elastic foundation. The governing set of equations is derived by implementing Hamilton’s principle and variational calculus. Two different solution methods, namely, a generalized closed-form analytical solution of Navier-type, and a C0 isoparametric finite element (FE) formulation, are developed for solving the governing set of equations. The solutions in the time domain are obtained with Newmark’s average acceleration method. Comprehensive parametric studies are presented to investigate the influence of elastic foundation parameters, piezoelectric layers, loading, and boundary conditions on the static and dynamic responses of the smart composite plates with piezoelectric layers. The effects of the elastic foundations on the vibration control of the smart composite plates are also presented by coupling the piezoelectric actuator and sensor with a feedback controller. Several benchmark results are presented to show the influence of the various material and geometrical parameters on the controlled and uncontrolled responses of the smart plates, and also the significant effect of the elastic foundations on the static and dynamic responses of the smart structures. The results obtained are in very good agreement with the available literature, and it can be concluded that the proposed analytical solution and FE formulation can be efficiently used to model the static and dynamic electro-elastic behavior of smart laminated plates supported on elastic foundations.

Оценка эффективности параметров свайных фундаментов на стадии проектирования

The analysis and evaluation of the possibility of pile placement options, which took into account various combinations of foundation loading, was carried out on the example of the construction of a residential building, during the design and calculation of which there is a significant margin of safety of the most loaded pile and the difference in effort between the most and least loaded piles, as evidenced by the value of the average load per pile, which is almost two times less than the permissible value, indicate insufficient use of the bearing capacity of the pile as part of the foundation. As a result of the project adjustment, it was possible to reduce the number of piles and achieve significant cost savings of the SMR.

A Neural Network Model for Estimation of Failure Stresses and Strains in Cohesive Soils

In this article, a set of neural networks for the prediction of the stresses and the corresponding strains at failure of cohesive soils when subjected to a load of a shallow foundation are presented. The data are acquired via Monte Carlo analyses for different types of loadings and stochastic input material variabilities, and by adopting the clayey soil domain and modified Cam Clay material yield function. The mathematical functions for the estimation of the failure stresses and strains are computed with the feed forward neural network method (FNN). It is demonstrated that the accuracy of the derived relations is in the order of a maximum relative error of 10−5 in all monitored output variables. In addition, the number of training epochs required for convergence is relatively low and this means that the computational and data costs for the construction of the FNN are low. The critical input variable for the estimation of the most unfavorable situations is the Karhunen Loeve series expansion for porous analyses, while for non-porous analyses the constant distribution over depth is the one that provides more critical estimations for the monitored output variables of stresses and strains at failure. This set of functions can estimate the aforementioned variables of the footing settlement in clays with high accuracy; consequently, it can be an important tool for geotechnical engineering design, especially in providing the largest stress allowed from the foundation.

Numerical study on the bearing capacity of strip footing resting on partially saturated soil subjected to combined vertical-horizontal-moment loading

This study investigates the bearing capacity of strip footings resting on unsaturated soils subjected to combined loading using the lower-bound limit analysis coupled with the finite element discretization approach. In this regard, second-order cone programming (SOCP) is exploited to simulate the nonlinear form of the universal Mohr-Coulomb yield criterion during the process of stress field optimization. The significant influence of matric suction induced below the surface footing was accounted for by adopting the suction stress concept under the no-flow and steady-state infiltration/evaporation flow conditions. The eccentricity and inclination of the foundation loading are introduced into the equilibrium equations along the strip footing so as to render various combinations of moment (M), vertical (V) and shear (H) forces. The results stemming from the lower-bound finite element limit analysis are compared with several previous studies throughout the literature for verification of the model. The substantial contribution of suction stress to the evolution of failure loci and the distribution of subsurface stresses for the shallow foundation subjected to inclined and eccentric loadings is thoroughly discussed. A general three-dimensional failure envelope is presented for shallow foundations resting on partially saturated soils under combined vertical, horizontal and moment loadings.

Uncertainty Quantification of Failure of Shallow Foundation on Clayey Soils with a Modified Cam-Clay Yield Criterion and Stochastic FEM

In this article, a quantitative numerical study of the random distribution of the soil material parameters to the probability density functions of the failure load and failure displacements of a shallow foundation is presented. A modified Cam-Clay yield function is used for this scope into a stochastic finite element numerical formulation. Several hypotheses for the random distribution of the compressibility factor κ, of the material constitutive relation, the critical state line inclination c of the soil, as well as of the permeability k of the continuum, have been tested and assessed with Monte Carlo simulation accelerated with Latin hypercube sampling. It is validated that both failure load and failure displacements follow Gaussian normal distribution despite the non-linear behaviour of the soil. Furthermore, as the soil depth increases, the mean value of failure load decreases and the failure displacement increases. The failure mechanism of clays can be determined with accuracy using this numerical implementation, without the restrictions imposed by analytical solutions, taking into consideration the eccentricity of the load in combination with non-linear constitutive relations.

Mechanism and Prevention of Rockburst in Deep Multipillar Gob-Side Entry

Abstract Rockburst frequently occurs in deep multipillar gob-side entry in Inner Mongolia and Shaanxi, China. A case study of the Hongqinghe coal mine was analyzed to reveal the occurrence mechanism of rockburst in deep multipillar gob-side entry through theoretical and applied research. And new control methods were put forward. The results show that there is an essential difference between the surrounding rock load characteristics of multipillar gob-side entry and single-pillar gob-side entry. Within the influence area of the lateral goaf, more coal pillars will promote stress concentration, and the high stress concentration area will migrate to the coal pillar of mining roadway. The hanging roof of the working face can cause the stress concentration in the area of leading coal pillar to reach 5 times. The multipillar gob-side entry is less affected by the dynamic load of the roof of the lateral goaf. The ‘F-shaped and L-shaped’ stress source structure model of the deep gob-side multipillar entry was established, and the occurrence mechanism of rockburst is revealed. On the one hand, the static load of rockburst start foundation is formed under the superposition of lateral goaf, rear goaf, and multicoal pillar. On the other hand, the superposition of the foundation static load and the opportune static load induces the start of rockburst. Aiming at the two types of load sources, the fracturing method of kilometer bedding drilling in the roof of coal pillar area is proposed to reduce the foundation static load. The treatment method of periodic tendency blasting fracture of leading roadway roof in a working face reduces opportune static load. The field test has been carried out, and the effect was good.

Experimental Investigation of piled raft foundation on Cohesionless Soil

The combination of piles and raft foundation is known as piled raft foundation. Piled raft foundations have proven to be more cost-effective and capable of meeting safe bearing capacity and serviceability norms in the case of high-rise buildings on cohesionless soil. The behavior of a stacked raft foundation is influenced by the piles, raft, and soil. The stacked raft system’s bearing capacity is improved and settlement is minimized when the ground beneath the raft foundation bears the burden of supporting the applied loads. The piled raft foundation minimizes total settlement and improves bearing capacity more than the raft foundation. When isolated footings cover more than 70% of the building area under a superstructure, raft foundations are used, and the present study focuses on the vertical load bearing capability of piled raft foundation systems on cohesionless soil for concentric loading. The use of strategically positioned piles increases the load capacity of the raft while reducing differential settlement. The present study sheds some light on the use of piles as raft foundation settlement reducers, as well as the behavior of a piled raft in sand. A series of small-scale model experiments were carried out. The present investigation studies by varying pile length and alignment on the ultimate load of piled raft foundation. The results indicate that for a 10mm raft thickness, installing 4 piles, 6 piles, and 9 piles by varying L/D ratios of 5,10,15,20 carries significant load. In this present work for a 50mm length of pile, and the value of load improvement ratio increases by 36 percent, 60 percent, and 68 percent, respectively, when compared to plain raft.

Bearing Characteristics of Diaphragm Wall Foundation under Vertical and Combined Load

To investigate the bearing characteristics of diaphragm wall foundation under combined load, the results from elasto-plastic analyses of 3D finite element models (FEM) were presented in this study. The vertical load of the diaphragm wall foundation is borne by inner and outer side resistance, resistance of soil core and the end of wall, respectively. Moreover, the sum of end resistance and soil core resistance accounts for about 75% of the vertical load. The mobilization mechanism and distribution of side resistance of the foundation were also analyzed. It is clarified that the mobilization characteristics of inner and outer side resistance of the wall are completely opposite. Due to the combined load, the horizontal load has an amplification effect on the settlement of the foundation. Additionally, the calculation methods of the Eight-component Winkler spring model and rigid pile displacement were used for determining the vertical load-bearing capacity and the overturning stability. A comparison between results from the FEM and the theoretical calculation methods showed that the results of the numerical simulation properly coincided with that of the displacement solution of theoretical model. The conclusions obtained by the above methods all indicate that the foundation has the characteristics of overall overturning failure under the combined load.

Safety Evaluation of the Combined Load for Offshore Wind Turbine Suction Foundation Installed on Sandy Soil

Offshore wind turbine (OWT) receive a combined vertical-horizontal- moment load by wind, waves, and the structure’s own weight. In this study, the bearing capacity for the combined load of the suction foundation of OWT installed on the sandy soil was calculated by finite element analysis. In addition, the stress state of the soil around the suction foundation was analyzed in detail under the condition that a combined load was applied. Based on the results of the analyses, new equations are proposed to calculate the horizontal and moment bearing capacities as well as to define the capacity envelopes under general combined loads.

Probabilistic Failure Estimation of an Oblique Loaded Footing Settlement on Cohesive Geomaterials with a Modified Cam Clay Material Yield Function

In this work, a quantitative uncertainty estimation of the random distribution of the soil material properties to the probability density functions of the failure load and failure displacements of a shallow foundation loaded with an oblique load is portrayed. A modified Cam Clay yield constitutive model is adopted with a stochastic finite element model. The random distribution of the reload path inclination κ, the critical state line inclination c of the soil and the permeability k of the Darcian water flow relation, has been assessed with Monte Carlo simulations accelerated by using Latin hypercube sampling. It is proven that both failure load and failure displacements follow Gaussian normal distribution despite the excessive non-linear behaviour of the soil. In addition, as the obliquity increases the mean value of failure load and the failure displacement always increases. The uncertainty of the output failure stress with the increase of the obliquity of the load remains the same. The failure spline of clays can be calculated within an acceptable accuracy with the proposed numerical scheme in every possible geometry and load conditions, considering the obliquity of the load in conjunction with non-linear constitutive relations.

Rapid in situ test and determination of dam foundation weak mudstone bearing capacity

In a hydropower station project in the middle reaches of the Minjiang River, the dam foundation rock mass is the upper cretaceous Guankou formation (K2g) brick red weak mudstone. In previous investigations, the single-pipe core drilling technology was employed, which greatly disturbed the cores. Most of the cores were broken, and the mudstone cores quickly lost water, cracked, and disintegrated after being taken out, making it difficult to obtain several columnar cores. Indoor uniaxial compressive strength tests were conducted using only a few short columnar mudstone cores, but the obtained mudstone uniaxial compressive strength was extremely low, and the converted bearing capacity of the dam foundation mudstone was only 0.25 Mpa, which does not meet the dam foundation bearing capacity standard. Large-area pile foundation treatment is required for the dam foundation mudstone at a high cost, and the project construction period is delayed. To obtain the accurate bearing capacity of the dam foundation mudstone, we used a self-developed “self-anchored dam foundation rock mass bearing capacity rapid test device” and excavated the dam foundation ship lock section to the elevation of the foundation surface. In situ tests were conducted on 12 dam foundation mudstone rock masses in 15 days, and the longitudinal wave velocities of the rock masses were tested. Reliable bearing capacity parameters of the weak mudstone of the dam foundation were obtained, and the relationship between the bearing capacity of the dam foundation mudstone and the longitudinal wave velocity was established. In situ tests showed the minimum and maximum bearing capacities of 0.986 and 1.972 Mpa, respectively, for the dam foundation weak mudstone. After excavating the dam foundation mudstone, it showed high bearing capacity without obvious softening and relaxation. The in-situ-measured minimum bearing capacity (0.986 Mpa) is consistent with the recommended bearing capacity of dam foundation mudstone, which is much greater than the maximum load of the dam foundation (0.5 Mpa). The value meets the bearing capacity requirements for dam foundation rock masses without engineering treatment. This study obtained the real bearing capacity of mudstone for dam foundations, thereby overcoming the problem of the low bearing capacity of weak mudstone obtained through laboratory experiments. The method not only saves cost but also lays the foundation for scheduled pouring of dams.

Numerical Simulation Research on the Horizontal Bearing Capacity of Rock-Socketed Piles for Offshore Wind Turbines

Introduction The aim of this paper is to analyze the influence of the size and the vertical load of the pile foundation on the horizontal bearing capacity of rock-socketed piles. Method Based on a field test of the rock-socketed concrete pile under horizontal load， a 3-D finite difference numerical model was established and parametric analyses were performed. Result The results show that there is a critical rock-socketed length （ratio of length and diameter） for rock-socketed piles. Changes of the size of the pile will influence the relative stiffness of the pile and the rock， which will affect the critical rock-socketed length. With the decrease of the pile diameter， the critical socket length will increase. Within the scope of the bearing capacity of the pile and under the condition of combined vertical and horizontal load， the horizontal displacement and bending moment of the pile will have a pretty large decrease. This influence will be neglected if the vertical friction is assumed to be the same on the both sides of the pile or simplified to be at the center of the pile， which will cause error to the calculation results. Conclusion This study is supposed to provide contribution to the reasonable design and further research of the horizontal load of rock-socketed piles.