Foundation Elements Research Articles

A new grouting procedure to enhance axial response of helical piles in sand

Helical (or screw) piles are deep foundation elements consisting of a steel shaft with single or multiple helical plates (helices) attached near the base of the shaft. The helices and shaft are rotated into the ground using a torque motor located at the head of the shaft. The axial resistance of the piles is provided through bearing on the helices with some additional axial resistance derived from skin friction on the shaft. This paper examines the benefits of a variation of this foundation system in sandy soils, which involved post-installation injection of a cementitious grout in the vicinity of the helix. The intent is that the grout adds a bond strength to a volume of sand that has a larger diameter than that of the helix, thereby increasing the bearing resistance. A new set-up devised to facilitate easy and rapid grouting to take place is first described. The benefits of grouting are then examined in a series of full-scale static tension and compression tests performed at sand sites in Perth, Australia involving both grouted and un-grouted single helix piles. It is demonstrated that grouting led to doubling of axial stiffness and capacity with the addition of just 80 litres of grout to a 350mm diameter helix. The increases observed are quantifiable by combining a recently published design method with measured injected grout volumes.

Application of the finite element method for analysis of the influence of dynamic loads on a machine foundation on piles

This work presents the fundamental concepts of structural dynamics, applied to the study of machine foundations. It discusses a method of obtaining the representative parameters of the pile-soil set considering the effect of the group acting by the proximity of the piles. In addition, this monograph is dedicated to preparing a detailed case study with the aid of ANSYS®, software based on finite elements, in order to reach the displacement values incorporated by the foundation element. These results were obtained according to normative criteria in the questions of severity of vibrations, effects on people and damage to the structure, allowing for attesting the capacity of the chosen foundation to resist the dynamic loads caused by the operation of the machine.

Shear behavior at the interface of rough surfaces and cohesive soils under axial loading

Foundation elements with rough (textured) surfaces mobilize larger interface shear resistance than ones with conventional smooth or random rough surfaces when sheared against soils under monotonic loading. The overall performance of foundation elements such as piles supporting offshore wind turbines, suction caissons supporting tidal energy converters, soil nails, and soil anchors installed in cohesive soils could be enhanced through utilizing rough (textured) surfaces to resist applied static and/or cyclic loading. This paper describes the shear behavior of smooth and rough (textured) surfaces in kaolinite clay and kaolinite clay-sand mixture soils under static and cyclic axial loading. The experimental investigation presented herein consists of a series of interface shear tests performed on 3D printed rough (textured) surfaces and a 3D printed smooth reference surface utilizing the Cyclic Interface Shear Test system. The paper includes a description of the interface testing system components, cohesive soil specimens’ preparation procedure, smooth and rough (textured) surfaces details, testing procedure, and results of static and cyclic tests. Test results indicate that kaolinite clay-sand mixture soil mobilized larger static and post-cyclic interface shear resistance and volume contraction relative to kaolinite clay soil when sheared against the smooth reference surface. When tested against rough (textured) surfaces with variable asperity height, larger shear resistance was mobilized and larger soil dilation greater than that mobilized by the reference untextured surface in both soils. The results also indicate rough (textured) surfaces exhibited a prevalent frictional anisotropy increases with asperity angle and height in cohesive soils, the surfaces mobilized larger shear resistance and volume change in one direction (i.e., against the asperity right-angled side) than the other direction (i.e., along the asperity inclined side).

Field investigations on the thermo-mechanical behavior of a partially activated energy pile in Miocene sediments

The City of Vienna, as one of the largest public clients in Austria, initiated a research project to determine the load-bearing behavior of various foundation elements in typical Viennese soils. Numerous large-scale tests were carried out on bored piles, micro piles, anchors, and jet grouted columns. In addition, two energy piles were installed in different soil layers to investigate their behavior under mechanical and thermal loading in each soil layer separately. This paper discusses the energy pile in the Miocene sediments, which consist mainly of silty fine sand and some sandy silt. The energy pile – fully instrumented with strain gauges, extensometers, heat gauges and optical fiber sensors – was loaded for two and a half months. The mechanical load was kept constant throughout the thermal cycles to determine the response of the pile to thermal loads. The measured temperature data were used in numerical back-calculations to determine the thermal parameters of the soil layers and the concrete. Based on the measured strain and deformation data, the deformation behavior of the energy pile due to the thermal load was investigated. Finally, a static pile load test was carried out on the energy pile and the results are compared with those of the conventional reference piles installed in the vicinity, which have not been subjected to thermal loading. The test demonstrated that, after several weeks of cyclic thermal loading, the energy pile exhibited more favorable load-deformation behavior compared to conventional reference piles.

Recent Advancements in Geothermal Energy Piles Performance and Design

Geothermal energy piles or ground heat exchange (GHE) systems embrace a sustainable source of energy that utilizes the geothermal energy naturally found inside the ground in order to heat and/or cool buildings. GHE is a highly innovative system that consists of energy loops within foundation elements (shallow foundations or piles) through which a heat carrier fluid circulates, enabling heat extraction or storage in the ground. Despite the innovation and potential of GHE systems, there are significant challenges in harmonizing their thermal and mechanical designs due to the complex interactions involved. This review critically examines state-of-the-art design methodologies developed to address these complexities, providing insights into the most recent advancements in GHE performance and design. Key findings include innovative techniques such as advanced numerical modeling to predict thermomechanical behavior, the use of different pipe configurations to optimize heat transfer, and strategies to minimize thermal stress on the foundation. Additionally, this review identifies research gaps, including the need for more comprehensive full-scale experimental validations, the impact of soil properties on system performance, and the long-term effects of thermal cycling on pile integrity. These insights aim to contribute to a better understanding of the thermomechanical behavior of energy piles, ultimately facilitating more accurate and effective design solutions.

Об элементных фундаментах опор высоковольтных линий

Purpose: to substantiate the possibility of using the foundations of supports of high-voltage lines in the form of dispersed horizontal elements combined into a single structure for the perception of alternating loads. To determine by experimental and computational methods the effect of the mutual displacement of elements in the form of an increase in the bearing capacity of foundations and a decrease in their deformations under the influence of pressing and pulling loads. To show the possibility of replacing slab foundations of supports of high-voltage lines with structures made of prefabricated elements to reduce the volume and weight of products transported from the factory. Methods: application of the moire photogrammetric method to assess the development of soil compaction zones and angular deformations of the soil base in a tray with a glass wall under models of slab and elemental foundations. Using the method of boundary integral equations to obtain the dependence of precipitation on the step of elements for flexible and rigid foundations. Results: the effect of mutual influence of foundation elements during their convergence and dispersal in the form of a change in the stress-strain state in their base is illustrated. Differences in the depths of the distribution of compaction zones and areas of development of angular deformations are revealed. Quantitative data on the precipitation of slab and elemental foundations and the influence of the depth of the roof of the solid underlying layer on them have been obtained. Graphical dependences of the relationship of sediment elements with the distance (step) between them are presented. The effect of the division of the foundation on the rate of extinction of marginal tangential stresses in the base is shown. An illustration is made of an increase in the volume and surface area of the bulging body of the elemental foundation, which leads to an increase in its bearing capacity compared to the slab one when calculating for pulling out. Practical importance: the effectiveness of the use of an element foundation in comparison with the paid option in reducing the parameters of the stress-strain state of the base and facilitating logistical tasks during construction is shown. The experimental and computational methods used can be recommended for further refinement of the parameters of the elemental foundations.

Analysis of the effectiveness of the use of short piles as part of a columnar pile foundation

The realization of the operation of the grid and piles as a part of the columnar pile foundation, depending on the length of the piles, the method of arranging the piles, the distance between the piles and the type of soil with a constant number of piles, has been studied. The degree of implementation of the load-bearing capacity of the piles and the degree of implementation of the grid work as part of the pile foundation were analyzed. To solve the tasks set in this work, mathematical modeling by the finite element method of the joint operation of the pile foundation elements with the soil base and the separate operation of the pile and grid as a shallow foundation was performed in the "Plaxis 3D Foundation" software complex. It was established that the implementation of the load-bearing capacity of piles in the composition of the foundation with a large distance between the piles is much better. The length of the piles also affects the degree of their implementation. When the length increases, the bearing capacity of the piles is realized less. The greatest implementation of the load-bearing capacity of piles in the composition of the foundation is observed for short piles. The realization of the pressure under the sole of the grid with an increase in the pitch of the piles also improves, the realization of the load-bearing capacity of the grid is from 8 to 50%, which allows to raise the load-bearing capacity of the foundation. For sandy and clay soils, the nature of the redistribution of forces between the elements of the columnar pile foundation is similar. For foundations made of drilled piles, the degree of realization of pressure under the sole of the grate, as well as the degree of realization of the load-bearing capacity of the piles, is higher than for foundations made of driven piles. The guiding factor is the length of the piles. The economic efficiency of the transition in homogeneous soils from a bush made of long piles with a standard minimum step to a bush made of short piles with an increased distance between the piles was investigated. By taking into account the joint operation of piles and grid, a bush made of short piles with larger dimensions of the grid provides the same bearing capacity as a bush made of long piles with a compact grid. Despite the significant increase in the volume of concrete grating and the number of fittings with an increase in the pitch of the piles, cost savings on the cost of piles provide an economic effect of using bushes from short piles with wide gratings up to 35%.

Energy geo-structures: A review of their integration with other sources and its limitations

Ground Source Heat Pumps, in the framework of Shallow Geothermal Energy Systems, outperform conventional Heating Ventilation and Air Conditioning systems, even the high efficiency Air Source Heat Pumps. At the same time, though, they require considerably higher installation costs. The utilization of dwellings' foundations as ground heat exchanger components has recently demonstrated the potential to generate significant cost reductions primarily attributed to the reduction in expenses associated with drilling and backfill material (grout). These elements are referred to in the literature as Thermo-Active Structures or Energy Geo-structures (EGs). The current study employs a ‘mixed studies’ review (i.e., literature review, critical review and state-of-the-art review) methodology to comprehensively examine and assess the compatibility and integration of different renewable energy sources and environmentally friendly technologies with foundation elements deployed as EGs. These mainly include heat pumps, district heating and cooling networks, solar-thermal systems, waste heat, biomass and other types such as urban structures. Emphasis has been given on the advancement on this area, with the current study identifying and addressing two primary categories. The first category involves the integration of EG elements with sources that are able to supply green electricity, referring to renewable energy electricity obtained from on-grid or off-grid integration. The second category, involves a direct or indirect integration with sources that provide heat, or vice versa. The technical and non-technical barriers of such integrations have been discussed in detail, with the technical challenges generally involving engineering design, and system optimization, whereas non-technical challenges encompassing the economic, social, and policy domains.

Evaluation of Tangent Bearing Element Axial Load Response

Augered cast-in-place (ACIP) piles, also known as continuous flight auger (CFA) or augered pressure-grouted (AGP) piles, are a well-established method for installation of deep foundation elements. A current equipment constraint of ACIP piles is the largest practical diameter that can be constructed. To overcome this limitation, some ACIP contractors have begun offering deep foundations which in this paper will be referred to as Tangent Bearing Elements (TBEs). A TBE consists of two or more ACIP piles spaced at one diameter center-to-center. The individual pile elements form a bundle which acts as a single foundation element in axial loading. This results in an efficient foundation installation method which produces equivalent-sized elements faster than traditional large-diameter bored piles. Because of their non-traditional geometry however, design engineers may be hesitant to utilize TBEs. This paper examines the results of several bi-directional static load test programs conducted on TBEs.

METHODOLOGICAL FEATURES OF TEACHING RANDOM VARIABLES AT THE COMPREHENSIVE SECONDARY SCHOOL

In the evolving landscape of educational methodologies, the integration of complex mathematical concepts such as random variables into secondary school curriculums poses significant challenges and opportunities. As the global educational framework increasingly emphasizes the importance of a robust mathematical foundation, understanding and teaching stochastic elements within the school system has become crucial. This article delves into the nuanced methodological features essential for imparting knowledge of random variables effectively to secondary school students. We explore the historical context of mathematical education reforms in Armenia, highlighting the recent inclusion of stochastic topics in the school programs since 2004. The reformed educational standards introduced in 2020 and implemented in 2023 have further emphasized the need for a structured approach to teaching random variables, alongside other advanced mathematical topics. Through this lens, we examine the preparedness of educators, the adequacy of existing teaching methods, and the potential cognitive hurdles faced by students. Our analysis is rooted in both qualitative assessments and a theoretical framework that aims to bridge the gap between abstract mathematical theories and practical understanding, ensuring that students not only learn but also appreciate the significance of probability theory in everyday contexts .

Methodology for geometry assessment of self-drilling micropiles using distributed fibre optic sensors

Self-drilling micropiles (SDMs) are gaining popularity as bearing foundation elements, as this construction technique allows for considerable time and cost savings. However, the irregular geometry and variability in the bearing capacity present uncertainty and a significant risk that has limited SDM deployment. To date, no reliable technology has been used to measure the SDM geometry. This paper proposes a methodology that uses distributed fibre optics (DFO), heat conduction modelling and inverse analysis to measure the pile geometry, and could also be extended to assess its bearing capacity. The temperature distribution during cement hydration was measured using two DFO investigative technologies and was compared to traditional temperature measurements using point sensors. An inverse analysis of SDM geometry was subsequently carried out based on the DFO measurement of temperature, a finite-element heat conduction model and a calibration pile. Finally, the calculated pile geometry was compared to the geometry of an excavated pile in the uppermost part. The methodology presented here is not only intended as a tool for designing SDMs but can also be deployed as a structural health monitoring system to detect and monitor crack formation.

Experimental Study on the Mechanical Strength, Deformation Behavior and Infiltration Characteristics of Coral Sand

In this investigation, coral sand is presented as a sustainable substitute for conventional river and machine-manufactured sand. This study comprehensively investigated the macro-scale strength, deformation, and permeability characteristics of coral sand, alongside analyzing the mechanical behavior, deformation, and permeability under various conditions and in relation to distinct particle characteristics. It revealed that coral sand primarily consists of biotite and high-Mg calcite, featuring abundant internal pore space. Its compressive properties resemble clayey soils, displaying minimal unloading rebound and predominant plastic deformation during compression. In direct shear tests, the stress–strain relationship follows an approximate hyperbola, with no pronounced strain softening. Describing particle fragmentation in the process proves challenging, making indicators like internal friction angle less applicable in engineering. Triaxial tests indicate a rapid initial bias stress increase, followed by a gradual decrease post-stress peak, suggesting a strain softening phenomenon. As surrounding pressure rises, the axial strain needed to reach peak strength also increases. The permeability coefficient of coral sand correlates linearly with pore ratio increase, represented by 10e. The complex interaction of multiple factors influences the strength, deformation, and permeability of coral sand blown fill mixes, with specimen porosity having the greatest impact. The design and construction of high-weight foundation elements in coral sand blown fill projects should consider porosity effects.

Application-Level Caching Approach Based on Enhanced Aging Factor and Pearson Correlation Coefficient

Relational database management systems (RDBMS) have long served as the fundamental infrastructure for web applications. Relatively slow access speeds characterize an RDBMS because its data is stored on a disk. This RDBMS weakness can be overcome using an in-memory database (IMDB). Each query result can be stored in the IMDB to accelerate future access. However, due to the limited capacity of the server cache in the IMDB, an appropriate data priority assessment mechanism needs to be developed. This paper presents a similar cache framework that considers four data vectors, namely the data size, timestamp, aging factor, and controller access statistics for each web page, which serve as the foundation elements for determining the replacement policy whenever there is a change in the content of the server cache. The proposed similarCache employs the Pearson correlation coefficient to quantify the similarity levels among the cached data in the server cache. The lowest Pearson correlation coefficients cached data are the first to be evicted from the memory. The proposed similarCache was empirically evaluated based on simulations conducted on four IRcache datasets. The simulation outcomes revealed that the data access patterns, and the configuration of the allocated memory cache significantly influenced the hit ratio performance. In particular, the simulations on the SV dataset with the most minor memory space configuration exhibited a 2.33% and 1% superiority over the SIZE and FIFO algorithms, respectively. Future tasks include building a cache that can adapt to data access patterns by determining the standard deviation. The proposed similarCache should raise the Pearson coefficient for often available data to the same level as most accessed data in exceptional cases.

Switchable Two-Dimensional AND and Exclusive OR Operation Based on Dual-Wavelength Metasurfaces.

Logic operation serves as the foundation and core element of computing networks; it will bring huge vitality to advanced information processing with its adaptation in the optical domain. As fundamental logic operations, AND and exclusive OR (XOR) operations serve a multitude of purposes, such as their ability to cooperate in enabling image processing and interpretation. Here, we propose and experimentally demonstrate a wavelength multiplexed AND and XOR function based on metasurfaces. By combining two cosine gratings with distinct frequencies and an initial phase difference of π/2, we extract the similarities and differences between two input images simultaneously by illuminating them with 445 and 633 nm wavelengths. Additionally, we explore its potential in information encryption, where overall security is enhanced by distributing distinct parts of initial information and encoded keys to different receivers. This design possesses the benefits of convenient mode switching and high-quality imaging, facilitating advanced applications in pattern recognition, machine vision, medical diagnosis, etc.

Effect of soil-pile contact parameters on pile bearing capacity value

The soil and foundation elements are fundamental to the behavior of a structure. When the foundation soil has a low capacity, it is necessary to transmit the loads to a deeper and more resistant layer, using deep foundations. A pile load test is a field measurement of the bearing capacity (vertical or horizontal) of a foundation element. In addition to a physical model of a load test, the use of computational tools can bring additional understanding. In order to analyze the responses obtained by numerical models compared to field test results, tools that use Finite Element Methods (FEM) and that have a series of constitutive models become a great alternative. This paper aims to study the behavior of Continuous Flight Auger (CFA) piles, aiming to understand the soil-pile interaction regarding the effect of soil-pile contact parameters on pile bearing capacity value. In this way, experimental data from three load tests were compared with numerical simulations using the Mohr-Coulomb constitutive model. Also, a parametric study was completed based on the collected soil data from the literature of the region that most affected the settlement behavior of the load pile. It was concluded that there is a direct and significant influence of the friction coefficient on the pile bearing capacity. In addition, by incorporating more real soil data and parameters representing its actual formation, the results of the pile load test simulation can be taken as an alternative to estimate the ultimate capacity of a vertically loaded pile in the absence of the static load test, which has been widely observed in engineering practice.

Spectral analysis of cross-hole sonic logging data for pile integrity assessment

Ensuring the safety of foundations requires advanced non-destructive testing techniques. Cross-hole sonic logging (CSL) is a widely adopted method for evaluating the integrity of deep foundation elements, such as bored piles, barrettes, and diaphragm walls. This method involves analyzing the propagation time and relative energy of ultrasonic pulses transmitted and registered by probes inserted into pre-installed access tubes. However, in certain cases, standard analyses may not effectively distinguish anomalous signals arising from defects and other factors unrelated to concrete quality. Our study explores the potential of an alternative frequency-domain approach for CSL data analysis. We propose new attributes to quantify ultrasonic signal spectra, including spectrum area, normalized spectrum area, weighted mean frequency, and maximum frequency. These attributes are automatically calculated, eliminating the need for additional data processing time and minimizing the risk of human error. The proposed approach was applied to CSL data collected from two bored piles of 46 m length and successfully identified signals classified as anomalous through standard time-domain analysis. Further research is deemed necessary to fully explore the potential of the frequency-domain approach in enhancing the information content and reliability of CSL pile integrity testing

Computational Fluid Dynamics Modeling of Concrete Flows in Drilled Shafts

Drilled shafts are cylindrical, cast-in-place concrete deep foundation elements. During construction, anomalies in drilled shafts can occur due to the kinematics of concrete, flowing radially from the center of the shaft to the concrete cover region at the peripheral edge. This radial component of concrete flow develops veins or creases of poorly cemented or high water-cement ratio material, as the concrete flows around the reinforcement cage of rebars and ties, jeopardizing the shaft integrity. This manuscript presents a three-dimensional computational fluid dynamics (CFD) model of the non-Newtonian concrete flow in drilled shaft construction developed using the finite volume method with interface tracking based on the volume of fluid (VOF) method. The non-Newtonian behavior of the concrete is represented via the Carreau constitutive model. The model results are encouraging as the flow obtained from the simulations shows patterns of both horizontal and vertical creases in the concrete cover region, consistent with previously reported field and laboratory experiments. Moreover, the flow exhibits the concrete head differential developed between the inside and the outside of the reinforcement cage, as exhibited in the physical experiments. This head differential induces the radial component of the concrete flow responsible for the creases that develop in the concrete cover region. Results show that the head differential depends on the flowability of the concrete, consistent with field observations. Less viscous concrete tends to reduce the head differential and the formation of creases of poorly cemented material. The model is unique, making use of state-of-the-art numerical techniques and demonstrating the capability of CFD to model industrially relevant concrete flows.

МОДЕЛЮВАННЯ НАПРУЖЕНО-ДЕФОРМОВАНОГО СТАНУ СИЛОВОЇ ПІДЛОГИ СКЛАДСЬКОГО КОМПЛЕКСУ ДЛЯ РАЦІОНАЛЬНОГО ПРОЕКТУВАННЯ

The paper contains the methods of modeling the stress-strain state of the power industrial floor of the warehouse complex intended for storing products on multi-level racks, taking into account the operation of loading and unloading equipment in free space. Have been developed the finite-element model of stress-strain state of the floor under the action of a complex of dead and leave loads on the example of a real warehouse complex, taking into account the design soil conditions, the location of the foundation elements and the features of the installation of racking systems. Have been checked the design reinforcement, selected based on the results of classical calculations taking into account the equivalent pressure on the floor, using the deformation method for reinforced concrete structures. Have been found that the design reinforcement of the floor slab does not satisfy the strength conditions of the bearing floor under the action of concentrated influences from racking columns. Have been found a rational method of reinforcement and the optimal thickness of the bearing floor by sorting out the constructive options. Have been developed structure recommendations for mandatory cutting of seams on the floor in the area adjacent to the building's bearing columns. Have been recommended to reduce the size of the floor boards by cutting additional deformation joints to reduce the intensity of reinforcement. The rational size of the floor board should not exceed 20 × 20 m. Have been proved that the replacement of the actual concentrated influences from the columns of the racks by equivalent uniformly distributed pressures does not adequately reflect the performance of the floor structure and leads to false under-reinforcements of the bearing plate and, as a result, insufficient strength of the floor structures.

Probabilistic analysis of seasonal influence on the prediction of pile bearing capacity by CPT: A case study

In this study, we used a probabilistic approach to evaluate the probability of failure of small diameter bored piles in unsaturated sandy soils. The prediction of the bearing capacity was based on the Cone Penetration Test (CPT). We assessed the seasonal influence by analyzing CPT data from dry and wet seasons. The LCPC and Aoki-Velloso semiempirical methods were deterministically applied, and the Aoki-Velloso method was examined using reliability theory. The first-order reliability method (FORM) was used to evaluate the probability of failure and calculate the reliability index based on random variables obtained from CPT data considering the effect of season when predicting bearing capacity. A total of 8.0 m long bored piles with diameters of 0.25, 0.30, and 0.35 m were used for both deterministic and probabilistic analyses. We also evaluated the influence of load ratio variation on the reliability index and determined the pile length required to reach a target reliability index value. Reliability analyses considering CPT campaigns conducted in different seasons showed the effect of season on the prediction of bearing capacity. For example, an 8.0 m long pile with a 0.30 m diameter and 100 kN vertical load had a probability of failure of 38.7 % in the wet season and 0.01 % in the dry season. The reliability analyses provided insights into the influence of seasonal variability on in situ tests for pile bearing capacity, affecting the design of foundation elements.

EXPERIMENTAL JUSTIFICATION OF THE SOIL BASE MODEL FOR THE CALCULATION OF THE COMBINED RAFT-PILE FOUNDATION

A new design of a combined raft-pile foundation, which is devoid of the shortcomings of similar existing design solutions and installation methods are proposed. This technical solution has been implemented at one of the construction sites in Kharkiv (Ukraine). The proposed design makes it possible to efficiently use the load-bearing capacity of the soil base by involving the raft part in the response to the loading in a controlled manner with transfer of up to 50% of the total load to this without going beyond the allowable strains of the soil base. The remaining 50% of the load are taken up by piles. The article considers the improved soil base model of the combined raft-pile foundation to consider the nonlinear behavior of the elements “before” and “after” the connection between the raft and the piles (structural nonlinearity) to calculate the stress-strain state using the finite element method in present-day calculation software. Using the improved model makes it possible to qualitatively simulate the behavior of the CRPF with the structural nonlinearity in the behavior of its elements. As a result, we obtain reliable results on the stress-strain state of the base-foundation-structure system. The article presents the modeling and numerical calculation of the "soil base - combined raft-pile foundation - structure" system of a real building object by program SOFISTIK using the proposed soil base model and the method of determining its parameters. The comparison and analysis of the results of the numerical calculation and the field experiment of the settlement of the raft part and the initial settlements of the piles of the foundation confirmed the adequacy of the application of the improved soil base model in the form of a combination of two known models: a limited distribution capacity and a Fuss-Winkler and method of determining it parameters on the basis of preliminary pile test. The analysis of the stress-strain state of the combined raft-pile foundation at different stages of the interaction with the proposed soil base model helps to confirm the physical significance of this structural nonlinearity of the behavior of the foundation elements. Keywords: Soil Base, Combined Raft-Pile Foundation, Model, Modeling, Field Investigation