Bases and Foundations

Consideration of the pliability of joints panels of a precast concrete building in the analysis of forces in foundation structures

2024-12-26T18:17:42+02:00

Summary. As cities develop, there is a rising trend towards the construction of multi-storey buildings. The main reason is dense urban development and rising land prices. One of the most common materials for the construction of multi-storey buildings is monolithic reinforced concrete. Monolithic structures allow architects to freely design the interior space, as well as more evenly distribute the forces in the frame elements, and the building works as one rigid structure. At the same time, the construction of monolithic structures requires significant time for construction and highly qualified control over the quality of monolithic work. Therefore, to accelerate the pace of construction, precast concrete structures are used.

This paper presents the results of numerical modeling of the interaction of the elements of the “soil-foundation-aboveground structure” system, taking into account the stiffness of the joints between wall panels.

A comparison of numerical modeling of a panel building was conducted using two principal schemes:

A) Without considering the stiffness (pliability) of panel joints.
B) Considering the stiffness of panel joints.

Each of these schemes included three variants of panel joint interpretation (sub-schemes):

Variant 1 - without considering the operation of vertical panel seams (panels are disconnected from each other).

Variant 2 - panels are connected with hinges, meaning vertical seams only transmit horizontal forces.

Variant 3 - panels are rigidly connected.

The influence of considering the stiffness of horizontal and vertical joints on the redistribution of forces in piles during the modeling of a large-panel building was studied.

It was found that in the absence of vertical panel connections (comparison of schemes A and B under Variant 1), considering the stiffness of the horizontal joint results in up to 8% discrepancies in the outcomes.

It was demonstrated that when hinged panel connections are considered vertically (comparison of schemes A and B under Variant 2), the inclusion of appropriate stiffness in horizontal and vertical joints results in discrepancies within 10%.

It was established that for rigid panel connections (comparison of schemes A and B under Variant 3), accounting for the stiffness of horizontal and vertical joints results in discrepancies of up to 10%.

Monitoring of deformations of the deep pit wall and surrounding buildings in dense urban areas

2024-12-26T19:12:51+02:00

Summary. The construction of buildings in dense urban areas is often characterized by the presence of deep pits, with the arrangement of parking lots, technical rooms and shelters in them. The timeframe for the installation of zero-cycle structures is usually quite long and can be measured in several months, and in complex cases and with large volumes of underground structures, it can last for tens of months. Such works are accompanied by the excavation of tens of thousands of cubic meters of pit soil, changes in the stress-strain state of the soil base and the supporting structures of neighboring buildings, and thus the need to monitor the technical condition of both the pit wall and the surrounding buildings.

The paper analyzes the results of monitoring the state of the deep pit wall and the surrounding buildings in Kyiv.

The monitoring of deformations of the pit wall was carried out using the classical method (the method of direct repeated linear-angular notching) and the modern method using inclinometers. Monitoring of the deformations of the existing surrounding buildings was carried out by determining additional foundation settlements by leveling.

It is demonstrated that the modern tools used for monitoring have high accuracy, which is important when conducting observations in dense urban areas.

Based on the results of monitoring the deformations of existing nearby structures, it was determined that the additional settlements of existing buildings do not exceed the limit values according to DBN B.2.1-10:2018 Bases and foundations of buildings and structures.

This publication is the first in a series of articles on the assessment of the stress-strain state of the pit envelope and surrounding buildings, using the example of a specific construction site and includes both a description of the actual monitoring data in this article and numerical simulation of the stress-strain state in further publications.

Study of Stress-Strain State of foundation structures in determining pile vertical stiffness if various software suites

2024-12-26T19:27:44+02:00

Summary This paper presents the results of numerical modeling of the interaction between a sheet pile retaining wall and the soil foundation using the Plaxis software package. A detailed analysis of the stress-strain state (SSS) of the retaining wall was carried out for both two-dimensional (2D) and three-dimensional (3D) problem formulations. The aim of the study is to evaluate the influence of the spatial modeling approach on the distribution of forces and displacements in the retaining wall structure and to compare the results of 2D and 3D analyses.

As part of the study, the 2D calculation of the SSS of the retaining wall was performed using the Plaxis 2D software. This method provides the distribution of stresses and strains within the cross-sectional plane of the structure, offering valuable insights into the interaction between the wall and the soil foundation. However, the main limitation of this approach is its inability to account for the spatial behavior of structures, including the interaction between different structural elements such as piles, walers, and bracing components.

The 3D analysis was performed using the Plaxis 3D software, employing the Hardening Soil model for soil behavior. This approach enables a comprehensive consideration of the spatial behavior of structures, allowing for a more accurate simulation of the retaining wall's performance under load. The model takes into account the influence of walers and bracing components, ensuring a more uniform force distribution within the structure.

Three characteristic piles were selected for analysis: a corner pile (№1), an edge pile (№2), and a central pile (№3). The results of numerical modeling revealed that the bending moments and horizontal displacements for the corner and edge piles exhibit similar patterns and close values in both the 2D and 3D analyses. However, significant differences in the distribution of bending moments and displacements were observed for the central pile. This discrepancy is attributed to the inclusion of additional structural elements in the 3D model, which distribute the loads more evenly and improve result accuracy.

The findings confirm the importance of using 3D modeling for the assessment of the stress-strain state of complex engineering structures such as sheet pile retaining walls. They also demonstrate that accounting for the spatial behavior of structures significantly affects the final distribution of forces and displacements, providing a more precise representation of the wall's real behavior.

Simulation the interaction of a pile with the soil using a nonlinear mathematical model with a modified Mohr–Coulomb strength criterion

2024-12-26T19:58:01+02:00

Summary. Static pile tests allow determining the bearing capacity of a pile as accurately as possible. They should be carried out in advance, before the foundation structures are installed, because their results are used to decide on the need for adjustments. However, static tests usually require significant time, which is due to their execution technology. The main disadvantage of static tests of a full-scale pile is the cost. They are the most expensive method, but at the same time they allow the most accurate reproduction of the pile operating conditions, namely, the load on the pile from the superfoundation structures of the building or structure.

The calculated value obtained from engineering calculations allows only a preliminary and approximate assessment of the bearing capacity of the pile on the soil. This method is the simplest, but at the same time the least accurate.

Numerical simulation allows us to approximate the results of static testing of an experimental pile to the results of modeling, provided that the parameters of the soil environment for the selected mathematical model are identified.

In this work, the Midas GTS NX software package was used for numerical modeling of the experiment (computer simulation of testing a full-scale pile with a static compression load). In this case, volumetric finite elements were used to model the soil mass and the pile shaft. To describe the regularities of soil behavior under load, a nonlinear law of deformation of the soil environment with a modified Mohr-Coulomb strength criterion was used. This model combines nonlinear elastic and elastic-plastic models.

The paper investigates the nature of the formation of the stress-strain state of the soil mass under the bottom of the pile and along the lateral surface of the pile at all stages of loading during computer simulation of a full-scale pile test. The phases of pile operation mainly along the lateral surface and the inclusion of the bearing capacity component under the bottom of the pile are identified. The formation of vertical stress concentrator zones in the soil mass under the bottom of the pile is recorded. The nature of the load transfer to the soil through the lateral surface of the pile is established according to the distribution of longitudinal forces in the pile shaft.

Principles of creating numerical models for studying the impact of impulse loads on underground structures

2024-12-26T22:21:54+02:00

Summary. The current situation in Ukraine has led to new geotechnical challenges, the solution of which is aimed at protecting critical infrastructure facilities from the effects of explosive shock waves. Protective structures that are buried in the soil environment are built to protect critical infrastructure facilities. A necessary condition to ensure their safe operation is the assessment of the stress-strain state of the system “soil environment-shelter building”. It is important to choose an adequate phenomenological model of the behavior of the materials of the protective structure and the soil environment, which describes the work of materials under the impulse impacts. The paper analyses four methods of constructing numerical models for calculating the impact of impulse loads, namely:

Lagrange mesh.
Euler's mesh.
Arbitrary Lagrangian-Eulerian (ALE).
Smooth Particle Hydrodynamics (SPH).

Each of the methods has its advantages and disadvantages. The Lagrangian mesh enables to easily track the boundary between materials of different structures, both before and after the calculation, and it does not require much computational time. However, this method is not practical in cases of significant model deformations with rapid changes in time.

The Euler and Arbitrary Lagrange-Euler methods allow to model the problems with a large distortion of the model, such as an underground or underwater explosion. Their disadvantage is the size of the computational domain and the considerable labour intensity for the model setup.

Smooth Particle Hydrodynamics is a meshless Lagrangian method. The advantage of this method is the ability to work with large model deformations. The disadvantage is labour intensity and calculation time.

All of these methods of building a numerical model are available in the LS-Dyna software package. During the analysis of calculations in LS-Dyna, we found that it is advisable to use the Lagrange mesh to create a model of a structure made of reinforced concrete or steel due to their high stiffness. The Euler and ALE methods are preferable for soil, they enable a strong change in the geometry of the model under the influence of the blast. Different methods are combined to achieve adequate model performance and to obtain correct results that will closely match the actual behavior of structures, facilities and materials under impulse loads.

Research on the impact of new construction on the stress-strain state of the soil base foun-dations of existing buildings

2024-12-27T11:29:15+02:00

Summary. The trends of the modern stage of housing development, which is accompanied by an increase in the density of development of historically formed areas of large cities, are analyzed.

Engineering problems arise that are associated with the use of underground space and lead to a change in the stress-strain state of existing buildings. Many buildings, next to which construction is underway, have shallow foundations. The construction of new foundations, excavation of pits for the arrangement of underground space disrupt the balance of the stress-strain state of the soil base and, in most cases, have a negative impact on existing building structures.

Research conducted in this area indicates the significant relevance of this topic. An important role in this is played by a comprehensive system of geotechnical monitoring of the state of the surrounding development at different stages of new construction.

The practice of construction in dense development with the presence of observations of the movements of existing buildings has shown the possibility of additional settlements and damage to above-ground structures, which indicates the lack of justification for the adopted design decisions. When analyzing the stress-strain state of the “base - foundation - above-ground structures” system, it is necessary to take into account not only the physical and mechanical parameters of the soils, hydrogeological conditions, loads, but also to pay significant attention to the technology of work and the sequence of their execution.

A study of the patterns of the influence of new construction on the stress-strain state of the existing building has been conducted.

Geotechnical monitoring data are presented and compared with the results of numerical modeling. Numerical modeling was performed in two versions: in combination and without a protective screen of small-diameter piles. The soil mass was modeled using the Hardening Soil Model.

The possibility of stabilizing the stress-strain state of the soil mass during the performance of underground cycle works has been shown.

A sequence of designing buildings with underground space is proposed, which allows achieving the effect of minimizing the impact of new construction on additional subsidence of the foundations of neighboring buildings

Assessment of Building-Foundation Interac-tion Using the Finite Element Method Based on Soil Compression Test Data

2024-12-27T11:47:32+02:00

Summary. The article presents a methodology for assessing the interaction between buildings and their soil foundations based on data from soil compression tests widely available in engineering geological survey reports. The primary aim of the study is to develop an approach for accounting for soil compaction within the "Base-Foundation-Structure" system using the finite element method (FEM). This approach enables more accurate modeling of the stress-strain state of structures under pressure ranges typical for modern buildings, such as high-rise residential complexes or industrial facilities.

The methodology proposed in the article considers the specific characteristics of soil deformation under loading, particularly the compaction processes that occur due to the reduction of porosity. The dependency of the deformation modulus on soil pressure is described based on experimental data from compression tests extended to higher stress levels using mathematical models. This eliminated the need for expensive and complex tests that are rarely accessible in the context of Ukrainian engineering practice.

The study involves modeling the stress-strain state of a real-life object—a 25-story residential building in Kyiv. Two scenarios were analyzed: the traditional approach with a constant deformation modulus and the proposed methodology incorporating a variable deformation modulus. The modeling results demonstrated that considering soil compaction processes significantly reduces peak stress values in foundation structures and ensures a uniform distribution of bending moments in grillages.

Special attention is given to assessing the height of the structurally disturbed soil zone beneath the foundation. It was found that this zone could reach up to 9 meters for grillages and 12 meters for pile foundations, depending on the applied load. The results suggest the necessity of embedding piles beyond this zone to ensure structural stability.

The proposed approach is universal, as it is based on standard oedometer data and can be adapted to various soil types and structural configurations. The results demonstrate the practical value of the methodology for optimizing foundation design, reducing the material consumption of structures, and improving their reliability. Furthermore, accounting for soil compaction processes enhances the accuracy of engineering calculations and ensures the rational use of material resources in complex geological conditions.

The calculation methodology proposed in this study can be integrated into modern software packages such as ABAQUS, significantly simplifying its implementation in engineering practice. This makes it particularly valuable for the design of high-rise buildings, industrial facilities, and other structures subjected to significant foundation loads.

Theoretical studies of the installation weight of reinforced concrete structures

2024-12-27T12:02:50+02:00

Summary. The article is devoted to the study of changes in the installation weight of reinforced concrete extrusion structure depending on structural, technological and other factors. The technology of reinforced concrete extrusion structures is an innovative and important step in increasing the efficiency and speed of construction of underground structures. The essence of the technology is that a monolithic structure is made on the ground surface in a modular form, and then, under its own weight, it is lowered into the excavated trench to the design depth, where it is fixed for further work. Therefore, one of the key parameters that determines the safety and reliability of the process is the installation weight of the structure.

The article describes in detail the components that form the installation weight of a structure and analyzes the influence of design, technical and other factors on its value. The paper theoretically investigates the permissible maximum and minimum variants of the assembly weight with changes in geometric parameters: length (from 6 to 18 m), width (from 0.4 to 0.8 m) and height (from 10 to 50 m). The results show that changing these parameters significantly affects the weight of the structure both in general and during installation.

The effect of the density of the clay slurry used to stabilize the trench walls and prevent their collapse was also investigated. It was found that increasing the density of the suspension reduces the installation weight due to the buoyancy effect. For example, at a density of 1.5 t/m³, the installation weight is reduced by up to 37%, and at a minimum density of 1.03 t/m³ - by up to 25%.

The obtained results open up prospects for further research aimed at optimizing design solutions and improving the technology of reinforced concrete structures. In particular, it is important to develop methods to reduce the installation weight by using lighter materials and optimized structural shapes without losing the required strength.

Geotechnical monitoring of the hospital Chernigov

2024-12-27T11:36:01+02:00

Summary. Geotechnical monitoring is a system of observation, collection and data analysis on the condition of soils, basements and structural elements of facilities. It is a key tool for safety assurance and control during the reconstruction of structures. This is extremely important while old buildings reconstruction, where unexpected reactions to changes in loads are possible. The monitoring of emergency facilities is especially important, where even minor changes can lead to serious consequences.

Geotechnical monitoring of the Chernihiv`s hospital was conducted. The building was put into operation in 1982. Since 1984, the building began to deform. There were opening of temperature joints with displacement of transverse walls, separation of the longitudinal wall from the transverse ones, minor deformation cracks in other blocks were detected. In the early 1990s, the works for strengthening of the structures was carried out, but they were not fully completed. In 2016, a major repair of the roofing and the drainage system from the building were carried out. The deformation of the building did not stop. In 2018, the SE NIIBK conducted a study and, based on the recommendations of «Eurotechindustry» LLC, a reinforcement of the stairwell was developed. However, in 2022, during active hostilities in the Chernihiv city, the hospital was severely damaged. There were direct hits and the collapse of structure`s elements. The meticulous inspection of the facility in order to establish the residual resource and reliability of the whole structures becomes necessary. An inspection of the hospital building as well as geotechnical monitoring, particularly engineering and geodetic observations, and verification calculations of the basement were performed.

Determination of the deformation modulus of soil-cement by laboratory methods during construction site investigations

2024-12-27T09:33:37+02:00

Summary. In the modern construction of multi-storey buildings, pile foundations are becoming increasingly common in difficult conditions of weak soils. Modern engineers face the difficult task of choosing design solutions that not only meet modern construction requirements but also ensure economic feasibility in dense urban development and complex geology. One of the most promising methods of solving this problem is the use of soil-cement elements to reinforce the foundation as an alternative to pile foundations. This approach can significantly reduce the cost of constructing foundations and reduce the labor intensity of the processes associated with design and construction due to the simple technology of such elements.

The main purpose of the study is to evaluate the physical and mechanical properties of soil cement produced by the drilling and mixing method, as well as to determine its deformation modulus during the construction of a residential building.

To determine the modulus of deformation of the reinforced base of a multi-storey residential building, data from engineering and geological surveys were obtained. The geological structure of the territory to the explored depth is based on loams, sandy loams and clays. According to the data obtained, the prolific soil properties were revealed at a depth of 7.5 to 8.4 meters.

To achieve this goal, a number of preparatory works were carried out, including the preparation of equipment, in particular the MII-100 device for measuring bending strength with a working range of measurements up to 100 kgf/cm2, as well as the manufacture of prism samples measuring 40x40x160 for laboratory tests. The prepared samples made it possible to implement a full cycle of experimental studies, including strength and deformation tests.

The results obtained allowed us to conclude that the deformation modulus of the base reinforced with soil-cement elements increases by 15 times compared to conventional soils. This is an important argument in favor of using soil cement in weak clay soils.

The study confirms the high efficiency of using soil cement to strengthen foundations with a methodology for checking the deformation modulus during surveys. Particularly noteworthy is the practical significance of the work, which is to increase the reliability and durability of multi-story buildings. This method can be successfully implemented in modern construction, which will reduce material costs, optimize technological processes and improve the performance of buildings and structures.

Geotechnical calculations in the design of building foundations and building foundations in central Africa

2024-12-26T20:49:41+02:00

Summary. The main calculation methods for designing foundations and foundations in Central Africa are considered. The methodology for calculating foundations and foundations in Central Africa is analyzed and compared. Geotechnical calculations are an integral part of the design of foundations and foundations of buildings, especially in Central Africa, where geological, climatic and environmental factors can significantly affect the stability of structures. This work considers the main aspects affecting geotechnical calculations, including a detailed geological survey of the site, which allows determining the types of soils, their physical and mechanical properties and the level of groundwater.

An important stage is the assessment of the mechanical properties of soils, such as bearing capacity, water permeability and compressibility, which affect the choice of the type of foundation. The work also analyzes different types of foundations, in particular strip, slab and pile, taking into account the loads that they must withstand, as well as the specifics of soil conditions.

The article analyzes the existing methods for this region, in particular the use of drilling and laboratory soil testing. Effective approaches to the selection of foundation types for various geotechnical situations are identified.

The article also describes soil investigation methods and principles of foundation design that ensure the stability and safety of buildings in conditions typical of Central Africa.

Geotechnical calculations are a crucial component in the design of foundations for buildings, especially in regions with complex geological and climatic conditions, such as Central Africa. This region presents unique challenges for engineers due to the variety of soil types, seasonal rainfall, high temperatures and different groundwater levels. Proper geotechnical analysis ensures the stability, safety and durability of structures. The main factors affecting the design of foundations include soil properties such as strength, compressibility and shear resistance, as well as the state of groundwater, which affects soil stability.

Areas with weak or expansive soils often require deep foundations, such as piles or bored piles, while strong soils may allow for shallow foundations. Fluctuations in groundwater levels due to seasonal rains or droughts require special attention to prevent erosion, flooding, or weakening of the foundation base. Geotechnical studies also consider environmental impacts, such as the impact of construction on surrounding ecosystems and local water resources. In addition, compliance with local and international standards ensures that structures meet safety standards. Engineers must also assess climatic factors, such as thermal expansion and contraction, which can affect soil behavior over time. The use of advanced software tools such as PLAXIS and GeoStudio a vital role in modeling soil behavior and predicting potential foundation performance under different conditions. Ultimately, successful geotechnical calculations in Central Africa require a comprehensive approach that takes into account regional soil types, climate and environmental considerations, ensuring the durability and structural integrity of buildings in this challenging environment.

Foundation reinforcement is a mandatory stage in the construction of reinforced concrete structures. Its purpose is to strengthen the concrete, allowing it to resist the tensile, bending and shear forces that can act on the foundations. Reinforcement consists of inserting steel bars (rebars) into the concrete to increase its load-bearing capacity.

Foundations can be of different types, such as isolated foundations, strip foundations or slab foundations, and the reinforcement varies depending on each type and the constraints of the project. For isolated foundations, for example, the reinforcement usually consists of longitudinal bars arranged in the main direction to resist tension and bending, and transverse bars arranged perpendicularly to counteract transverse forces. This reinforcement must be carefully positioned and positioned to ensure the strength of the foundation.

Reinforcing the foundation is also crucial to prevent cracking and warping of the concrete over time. The concrete coating around the reinforcement protects it from corrosion and ensures its durability. Finally, the reinforcement is carried out according to strict standards that take into account the characteristics of the soil, the loads to be supported, and the dimensions of the foundation to ensure safety and stability.