Foundation Slab Research Articles

Field pullout test and anchorage length calculation for external anchorage of GFRP anti-floating anchors

Field pullout destructive tests of GFRP anti-floating anchors with different anchorage lengths and different anchorage forms are carried out on inverted foundation slabs. Explore the damage patterns and anchorage mechanisms of bent anchors, straight anchors and GFRP anchors with different bending configurations in relation to the concrete foundation slab. Calculate the reasonable anchorage length of anti-floating anchors. The test results show that the straight line anchor rod and bent anchor rod are mainly damaged by sliding. The displacement of anchor rod body decreases with the increase of anchorage length, bending radius and bending length. The bending treatment of anchor rods reduces the pullout bearing capacity of GFRP anti-floating anchors, but it can significantly reduce the rod displacement. The longer the length of the bent section of the anchor rod body and the larger the bending radius, the lower the strength utilization of the anchor rod body. Through the calculation of the test results of different anchorage length anti-floating anchor rods, it is found that the current calculation method for the basic anchorage length of anchor rods is too conservative. For the actual anti-floating project, a more reasonable anchorage length calculation method is proposed, and the reasonable anchorage length of anchor rods for this test condition is 370–530 mm.

Weakening characteristics of pile group foundations in clayey soil under vertical cyclic loading: Experimental and numerical investigation

Long-term cyclic loading can substantially reduce the bearing capacity of pile foundations, potentially compromising the structural integrity of offshore foundations. A small-scale model test system for vertical cyclic loading of pile foundations is independently designed. Model experiments and numerical simulations were conducted to investigate the weakening characteristics of four foundation types (i.e., slab foundation, single pile with cap, 2 × 2 pile group foundation, and 3 × 3 pile group foundation) in clayey soil under cyclic loading. The results of both methods demonstrate that 3 × 3 pile group foundations exhibit the greatest resistance to deformation, followed by 2 × 2 pile groups, single piles with a cap, and slab foundations under cyclic loading. Furthermore, a 3D numerical model was developed to simulate the real-world behavior of a pile group foundation for an offshore wind turbine. Results reveal that although the ultimate compressive bearing capacity decreases with higher cyclic loading levels, typical cyclic loads (0.1–0.2) encountered in practice do not greatly affect the long-term bearing capacity of the foundations. The proposed experimental and numerical simulation methods offer valuable insights into the weakening characteristics of pile group foundations under cyclic loading.

Centrifuge tests for earthquake response of shallow soil with locally raised bedrock

ABSTRACT Centrifuge tests were performed to study the dynamic properties of shallow soil with locally raised bedrock (i.e. variable soil depth). The test parameter was the slope of bedrock: 0° (S0), 35° (S35), and 45° (S45). In each test, accelerations were measured along the soil depth, and the results of acceleration, displacement, Fourier transform, and response spectrum were compared. Based on the results, the transfer function (TF), the ratio of response spectrum (RRS), and the site period were estimated. The ground motion and site period of specimens with raised bedrock were smaller than those of the specimen without raised bedrock (i.e. with deeper soil). Further, parametric studies using 2-dimensional finite element (FE) analysis were performed to investigate the effect of design parameters on the response of shallow soil with variable soil depths. For design parameters, the length of raised bedrock and the length of foundation slab were considered. Parametric study results indicated that when the shallow soil region is wide, the results are similar to those of a 1-dimensional soil column. However, when the shallow soil region is narrow, the 2-dimensional response is smaller than the 1-dimensional soil column response. This was also observed in the actual site model.

Implementation Of Value Engineering Using Analytical Hierarchy Process (Ahp) (Case Study: Flyover Construction Project Of Jpl 64 Km 38+897 Across Surabaya – Solo)

The development of infrastructure development in Indonesia is being intensively carried out by the government to meet the needs of the community. Infrastructure development is often faced with various obstacles that can disrupt the project. To ensure the sustainability of the project, it is necessary to apply Value Engineering to identify opportunities for cost savings and solve problems so as to get maximum value without reducing project quality. The purpose of the research is to analyze the structure, determine the alternative, types and construction methods chosen to make the project cost efficient. Value Engineering is applied to the foundation and deck slab work of the Fly Over Replacement Construction Project JPL 64 Km 38-897 Lintas Surabaya-Solo using the AHP method with the help of expert choice. Based on the results of the Value Engineering analysis, an alternative bore pile d-120 foundation was obtained in the foundation work and a change in the cantilever elbow support method in the deck slab work. The cost efficiency results obtained after Value Engineering amounted to Rp15,108,214,225 or 10%.

Multichannel GPR and multi-depth electromagnetic surveys for the study of Villa Eucheria and Aquinum at Castrocielo (Frosinone, Central Italy)

The municipality of Castrocielo (Frosinone, Italy) is a historically significant center which includes several centers of great archaeological importance, including part of the archaeological site of the ancient Roman city of Aquinum. In this work, we show the results of geophysical surveys performed in two different areas: the first area is close to the Monacato of Santa Maria al Palazzolo, built on the foundation slab of a Roman villa dating back to the 1st-2nd century BCE; the second area is close to the charging station Casilina Est, where several burials, dating back to different periods from 4th century BCE to 4th century CE, were found. The aims of geophysical investigations is to identify structures linked to the ancient Roman villa (Villa Eucheria) in Area 1, and to identify the tombs of the necropolis in Area 2. The two areas were investigated in two different days, on 27th and 28 th March 2023 respectively, through a multi-channel georadar system (GPR). In the second area, an electro-magnetometric survey was also performed. This choise is to address the heavy rain developed during the night before the acquisition. Infact the GPR survey performed during the second day of the geophysical campaign did not provide good results.Based on the geophysical results, the archaeological excavation in Area 1 confirmed the detected anomalies, documenting a section of wall and other structures and elements brought to light over a length of approximately 9 m. The results obtained in Area 2 confirmed the cropmarks visible in the aerial photo, highlighting the traces of buried structures.

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.

Interpretation of the data of modern methods of field soil research

This study examines modern in-situ testing methods for soils; it investigates the impact of interpreting these methods on the calculated strength and deformation parameters of soils and compares them with tabulated values according to the DSTU (Standard of Ukraine). In today's world, there is an urgent need for accurate and prompt soil investigations, which are crucial for design and construction. Although laboratory methods are reliable, they often require significant time and resources. The advantage of in-situ methods lies in the fact that testing is performed directly in the soil mass, meaning that the results are not influenced by the transportation and preparation of samples. Conducting tests directly in the soil massif allows for the acquisition of information about soil characteristics and their classification, providing data on soil stratification. This publication reviews modern methods of in-situ soil investigations, specifically CPTu (Cone Penetration Test) and DMT (Dilatometer Test) [1, 2]. These methods are widely used in Europe, while in Ukraine, they are relatively new and are just beginning to gain popularity. Therefore, it is relevant to compare these methods with the tabulated values provided in Ukrainian reference guides. The deformation and stress values were compared using three calculation models based on CPTu, DMT, and DSTU data. A comparative analysis of the foundation slab deformations was conducted using models with elastic and elastic-plastic model. For this purpose, a foundation slab was designed, and a finite element model of the building was developed, examining the foundation on a soil massif with inclined stratification, using both elastic and elastic-plastic soil models.

Numerical studies of the distribution capability of a continuous linear strain soil base model for largesized raft foundations

The paper examines the existing methodology for determining the main design parameters of the model in the form of a continuous linearly strained layer of finite distribution capability (the design thickness of the layer H0 and design stress-strain modulus E0) to simulate the adequate interaction between soil bases and large-size slab foundations. The aim of this work is to numerically study the stress-strain state of a uniformly loaded flexible rectangular foundation slab when the thickness of the soil base model layer is reduced in the form of a continuous linearly deformed layer of finite distribution capacity. Numerical studies of the effect of the thickness of the layer of the specified soil base model that interacts with a large-size flexible slab foundation of various rectangular shapes in plan were conducted in the SCAD package using the finite element method. The numerical study results have shown that when the ratio H0/Ha (the design thickness of the layer of the soil base model H0 to the actual compressible thickness of the soil base Ha) decreases, the maximum moment forces along the orthogonal axes of rectangular foundations decrease to 50% because of the decrease in the distribution capability of the soil base model and, accordingly, in the edge reactions R under the slab at equal average settlements of the slab saver. Numerical studies have shown interesting results on the distribution of moment forces in flexible rectangular slabs, where the maximum is outside the center of gravity of a uniformly loaded raft, which confirms the peculiarity of the interaction of flexible slabs with relatively narrow compressible layers under the sole. With an appropriate in-situ experimental justification, the use of the soil base model in the form as a continuous linearly strained layer of finite distribution capability with the design parameters (H0 and E0) rather than with the actual parameters (Ha and Ea) in calculations of large-size slab foundations can be of fundamental practical importance in their rational design, as the reinforcement can be reduced to 50%

NUMERICAL STUDIES OF THE DISTRIBUTION CAPACITY AND DEFORMABILITY OF THE SPATIAL MODEL OF THE SOIL BASE IN THE FORM OF A LINEAR-DEFORMED LAYER

The article analyses the existing approaches to modelling the interaction between a structure and a soil foundation, which consider the joint deformation of the soil and the structure. The “base-foundation-structure” models can be created in one-dimensional, two-dimensional, or three-dimensional space. Each of these models has its own set of boundary conditions and calculation methodology The advantages and disadvantages of each model, during application in engineering calculations, are presented. The purpose of research is to substantiate the methodology for assigning the geometric parameters of a three-dimensional model of a soil foundation, represented as a linearly deformed layer of finite resolution, for adequate modelling of interaction in the "base- foundation-structure" system. A finite-element model of the interaction between the soil base and the slab foundation was built using the modern SCAD software package. The modelling was performed in three dimensions. The soil base is represented by volumetric finite elements with constant deformation characteristics. The foundation is modelled by plate finite elements In context of this research, the slab model of the foundation was assumed to be rigid to neglect stress redistribution in the above-ground part of the building. Based on the analysis of modern approaches to the assignment of geometric parameters to the model of the soil base represented by a continuous linearly deformed layer with finite overall dimensions, which is created in a three-dimensional problem statement, it was shown that today there is no single approach to modelling such a “base-foundation-structure” system. Numerical studies of the effect of rigid horizontal constraints in the plan on the stress-strain state of a uniformly loaded rigid foundation interacting with a linearly deformed layer (compressible thickness) of finite distribution capacity were carried out using the SCAD program. Based on the analysis of the results of numerical calculations for a three-dimensional problem, the minimum allowable sizes in terms of the model of a linearly deformed layer of finite distribution capacity, which considers the distribution of compressive stresses along the depth at an angle of α = 25º to the vertical from the edges of the loaded foundation, are substantiated. At the same time, the overall size of the model in the plan according to the distribution angle α = 25º has practically no effect on the average settlement and maximum moment forces of the foundation compared to the angle α = 45º. Keywords: slab foundation, soil foundation, linear-deformed model, distribution angle, stress-strain state.

Determination of Temperature Stresses during the Construction of Massive Monolithic Foundation Slabs, Taking into Account the Subgrade Compliance

Background The problem of early cracking caused by the heat of concrete hardening is relevant for massive reinforced concrete structures, including foundation slabs. The purpose of this work is to develop the methodology for determining temperature stresses during the construction of foundation slabs, taking into account the interaction with the subgrade. Methods The Pasternak elastic foundation model with two-bed coefficients is used for the soil. The temperature of the foundation slab is considered a function of only one coordinate z (temperature changes only along the thickness of the slab). As a result, to determine the stress-strain state of the slab, a fourth-order differential equation for deflection was obtained. A technique for numerically solving the resulting equation using the finite difference method is proposed. The calculation of the stress-strain state is preceded by the calculation of the temperature field, which is performed by the finite element method in a simplified one-dimensional formulation. Results The solution to the test problem is presented for a constant modulus of elasticity of concrete over time. The results were compared with finite element calculations in a three-dimensional formulation in the ASNYS software. The calculation was also performed taking into account the dependence of the mechanical characteristics of concrete on its degree of maturity. In this case, the picture of the stress-strain state changes significantly. The proposed method was also successfully tested on experimental data. Conclusion The proposed approach can significantly save calculation time compared to the finite element analysis in a three-dimensional setting.

Structural analysis for a slab-on-grade cellular concrete foundation to reduce heat losses in temperate climate residential buildings

Reducing the energy requirements of buildings is imperative in the face of global warming and the imminent need to build low or zero-carbon housing in the following decades. This research proposes the design of a structural foundation to reduce heat transfer between the ground and the house to improve thermal comfort, thus reducing the incidence of low interior temperatures and lower energy requirements. The proposed foundation consists of a waffle slab system incorporating on-site cellular concrete fabrication for a residential home. The foundation proposal was evaluated over a year through simulation to quantify the heating demand reduction for four cities with temperate semi-arid and temperate sub-humid climates. The analysis shows that the prevalence of low temperatures is reduced when applying any of the proposed foundations. However, the benefits must be weighed for cities like Durango and Puebla since the reduction of hours with low temperatures is minimal, and they show an increase in energy for cooling. The city with the most significant benefit in reducing the incidence of low temperatures and the heating demand is Toluca, followed by Zacatecas, which are cities showing prevalent heating demands. Based on the results, it is observed that it is viable to apply foundations with a lower overall heat transfer coefficient, with the addition of lightened materials produced on-site. However, it is still necessary to conduct more experimental studies on these prefabricated systems applied to foundation slabs and care for their implementation in mixed climates.

Methodology for determining true temperature stresses during the construction of massive monolithic reinforced concrete structures

The purpose of the article is to develop and test a simplified method for calculating temperature stresses during the construction of massive monolithic reinforced concrete structures. The essence of the method is to calculate the stress-strain state in standard FEM complexes (ANSYS, Abaqus , etc.) with constant physical and mechanical characteristics of concrete over time, followed by recalculation to true stresses, taking into account the dependence of the elastic modulus of concrete over time. The methodology is based on the hypothesis of equality of temperature deformations for structures with a constant and time-varying modulus of elasticity of concrete. The developed methodology was tested on experimental data for a massive monolithic foundation slab. The calculation at a constant modulus of elasticity of concrete was carried out in the ANSYS software package. Conversion to true stresses was implemented by the authors in the MATLAB environment. A good agreement between the calculated stress values and the experimental values was obtained.

Optimizing Foundations: The Case for Slab Selection in Multi-Story Residential Buildings

This study investigates the optimal foundation design for multi-story residential buildings through a comparative analysis of two foundation variants under specific geological conditions. Employing the finite element method via SCAD software, we assessed the structural integrity and load-bearing capacities of the foundation options. Material consumption was quantified for each variant, and the consistency of settling calculations for the slab foundation was evaluated. The results indicated that the slab foundation not only minimizes material usage but also simplifies design complexity according to normative standards. Based on technical and economic assessments, the slab foundation is recommended as the most cost-effective and structurally efficient option for such construction projects. This research provides a pivotal foundation design perspective that could influence future architectural and engineering practices in residential building construction.
 Highlights:
 
 SCAD software validates foundation integrity via finite element analysis.
 Slab foundations offer superior cost and material efficiency.
 Simplifies design, enhancing construction process efficiency.
 
 Keywords: Structural Integrity, Slab Foundation, Reinforcement, Monolith, Building

Methodology for Calculating Additional Dynamic Settlements of the Bases of Slab Foundations of Buildings and Structures from Vibrations Propagating in the Soil Environment

The paper provides a method for calculating additional settlements of slab foundations of existing buildings and structures from vibration-dynamic influences that arise during various construction works near them (driving piles, vibra- tory driving of sheet piling beams, soil compaction with heavy rammers and vibrating hammers), as well as from industrial equipment and transport. The technique includes the following main steps. Using the finite element method, or measured existing vibration fields, the distribution of the maximum accelerations of ground vibrations under the base of the foundation along the depth is determined and the zone in which they exceed the critical accelerations at which volumetric and shear deformations of the soil begin to appear is identified. The soil at the base of the foundation is divided into elementary layers with a thickness of no more than 1/4 of the width of the foundation. Further, according to the known vibration-compression depen-dencies (the dependence of the change in the porosity coefficient e of soil samples on the acceleration of their vibrations a), which are obtained in laboratory conditions, the settlements of each layer are determined, the summation of which gives the total value of the additional dynamic settlement Sд. If it, together with the static settlement Sст, exceeds the maximum normalized settlement values, it is proposed to use three methods to reduce or eliminate Sд – drilling injection strengthening of the zone of development of additional settlements, the use of a horizontal inertial plate or a vertical barrier made of easily compressible materials in the path of vibration propagation, the use of which reduces the intensity of vibration-dynamic impacts transmitted to the foundations under consideration.

Organisational and technological reliability of pile foundation construction flow in permafrost

The construction of pile foundations in permafrost conditions is a durable and cost-effective design that shows high performance of piles in contrast to slab, block and strip foundations. In the Russian experience of construction in permafrost conditions, the most common methods of piling are the following: sinking method, driven method, drill-and-pile method, and drill-and-pile method. Descending method, where the piles are driven into thawed and liquefied soil. Pile driving method, in which piles are driven into frozen ground using percussion mechanisms. Drill-and-pile method, which combines the use of sinking and drilling piles. Drill-and-pile method, in which a borehole is drilled first and then the piles are driven into the frozen ground. Organisational and technological flow reliability involves the efficient use of resources, compliance with standards, organisation of work processes and safety. This allows the objectives to be achieved efficiently and ensures reliable process operation. The main indicators are: system uptime without failure TO, delays in information transfer HO, equipment reliability PO, material quality FO, operator errors DO. In fact, the control of these indicators affects the organisational and technological reliability of the flow and the work production system as a whole.

COMBINED SLAB-PILE FOUNDATION

Solid reinforced concrete slab foundations are commonly employed in the construction of multi-story frame and panel buildings on natural grounds, as well as in industrial structures such assilos, elevators, chimneys, steel reactors, and more.One significant advantage of monolithic foundations is their ability to be used on weak and uneven ground bases. These foundations can distribute uneven loads over a considerable area, redistributingthem to equalize the inevitable differential settlements of individual foundations. On soft and uneven soils, slab foundations are not only used to mitigate deformations but also to protect against highgroundwater, creating what is known as a "floating" foundation.It has been demonstrated that the combined slab pile foundation (CSPF) is an effective development in the field of foundation construction. CSPF constitutes a foundation system comprising a "pile field – slab grillage – soil base," where piles bear a portion of the building load, and the slab grillage functions as a foundation slab. CSPF can be interpreted as a monolithic slab supported by piles of various types arranged in the form of a pile field, strips,clusters, or individual piles. Various types of piles, including "barrette" piles, can be used for CSPF foundations.Considering the soil resistance beneath the slab grillage in the deformation calculations and loadbearing capacity of combined slab-pile foundations provides a reserve for enhancing their economic efficiency. This includes reducing the number ofpiles, lowering the consumption of steel reinforcement, and decreasing the thickness of the grillage.However, the implementation of CSPF in construction is hindered by the limited theoretical research, necessary regulatory framework, and design experience for such structures.The determination of design parameters for CSPF is carried out using the method of successive approximations. By specifying the area of the slab grillage and defining the pile length and spacing, the number of piles in the foundation, the settlement ofan individual pile, and the design load on the pile are calculated (initially assuming that all piles bear 70-80% of the total load).

Assessment of the impact of a high-rise building on the stress-strain state of the foundation and structures of existing buildings in dense development

One of the most progressive problems of modern urban planning is the gradual decrease in areas suitable for construction, especially within the historical districts of cities. This prompts developers to increasingly develop sites in difficult engineering and geological conditions, which are often located within dense buildings.
 Today, the construction of multifunctional residential complexes combines the construction of high-rise residential sections and commercial real estate buildings with multi-level parking lots, which are often located in close proximity to each other. Often, the sequence of construction of these buildings is stretched over years or even decades, for example, due to an unfavorable economic climate or the instability of the political situation in the country, which leads to the commissioning of only certain stages of construction. The subsequent resumption of construction work requires taking into account the mutual impact of new construction and observations of previously constructed buildings during the construction of new structures.
 The execution of deep pits at the stage of laying the foundations of new buildings, as well as the substantial weight of high-rise buildings, causes a change in the stress-strain state of the adjacent soil massif, so designers face the task of determining the impact of such construction on the adjacent buildings.
 This article presents the results of a study of the change in the stress-strain state of load-bearing structures and foundations an existing building, taking into account the mutual impact of an adjacent high-rise section of a residential complex.
 The calculations were performed in two independent software systems Plaxis 3D and LIRA-FEM, in the spatial formulation of tasks, for a comprehensive assessment of the SSS of the system "soil base-foundation-superstructure".
 The zone of impact of new construction on the adjacent buildings, the values and character of additional displacements of foundations of adjacent structures are determined. The regularities of changes in the calculated forces in piles are shown, which indicate a decrease in axial forces in piles up to two times at the interface with the foundations of the new building and an increase in the load on the piles of the central zone by up to 17%. The obtained results show a tendency to redistribute stresses in the foundation slab from the bearing zones to the span zones, as well as in the bearing vertical structures of the lower floor of the existing building.

Computer modeling of the limit state of a slab foundation with regard to the rigidity of the above-foundation structure

The task of this research is to determine the values of the generalized strength parameters of the foundation soil and , at which the depth D Z of the development of Coulomb areas of plastic deformation under the edges of the foundation of finite rigidity thickness Н , loaded with a uniformly distributed load of variable intensity q and foundation of the same thickness, bearing a rigid above-foundation structure of variable height H * will correspond to the closure of plastic area under the base of the foundation what is complied with the ultimate state of the foundation (according to Prandtl). To carry out computer modeling a list of variables of design parameters that influence the process of formation and development of plastic areas under the sole of the foundation, and the intervals of their change, has been established. As a result of the calculations and processing of the data obtained it was found that the numerical values of and differ significantly from each other: equations of approximating curves of dependencies of the form have different forms correspondingly and are described by the different approximating expressions. If it is given the values of the generalized strength parameters of the foundation soil and , which the soil mass should have after its fixing, then using the graphs shown in Fig. 6-10 and the table it will be possible to conclude whether the limit state of the fixed soil base will be achieved under given loads. In other words, focusing on the numerical values of and , it is possible to determine the values , which must be obtained in the process of fixing the soil base so that the specified external load does not exceed the maximum permissible value.

Influence of Parameters of the Reinforced Base on the Change of Components of the Stress-Strain State of the Transformed Base

The choice of the foundation type is a crucial issue for ensuring safety and reliability in the construction of buildings and structures of various levels of responsibility. The main advantages of the construction of man-made bases are both their operational properties and the cost-effectiveness of the construction. At the same time, in case of exceeding settlements the reinforcement of soil base allows to reduce them. The paper presents the formulation and solution of the problem of behaviour of the stress-strain state (SSS) in the system «reinforcing elements – surrounding soil» on the example of a 21-storey building with a height of 65.7 m. Finite-element modelling related to the application of reinforcement elements of various parameters such as length, stiffness and geometry, as well as conventional methods of foundation construction such as slab or pile foundation. Analysis demonstrates that reinforcement elements have significant variability and could be effectively used in cases where the installation of a slab foundation settlements exceeding ultimate values. In addition, it shows which geometry of reinforcement elements is relevant to rational application in terms of settlements and forces in such elements.

Thermal performance of wedge pile slab foundation without frost protection insulation and highly insulated slab on ground floor – first year measurements

In the Nordic countries frost insulation is necessary if the foundation is above the frost-free depth. The thermal performance of the pile foundations is between a shallow ground foundation and a frost wall foundation. The pile ends extend below the frost line to help insulate the ground beneath a building’s foundation. The ends of the piles extend below the frost line to prevent the foundation of the building from frost heaving. However, there may be a risk that the ground below the slab on ground may freeze and frost heaving may occur there. The risk of frost below the slab on ground floor and/or basement increases because increasing thickness of floor insulation remarkable influences frost insulation dimensioning. In this study a 6.5 × 17-meter size uninsulated wedge pile slab foundation with highly insulated (U=0.07 W/(m2·K)) slab on ground floor was constructed for a heated building and equipped with temperature, soil moisture, relative humidity, and heat flux sensors. Seven temperature measurement piles below the building and one for reference 8 meters far from the building reached a depth of up to 3.2 meters, which is deeper than the usual 1.4 m depth to avoid freezing in foundation design. In three places, the temperature below the insulation of slab on the ground is measured at 0.5 meters step up to 3 meters from the outer wall of the building. The first-year measurement results showed that temperature did not drop below the zero degree below the foundation and floor. Even though during winter the daily average absolute minimum temperature was -24 °C the sum of degree hours below the zero degree was -7300 °Ch. The historic 50-year absolute sum of minimum degree hours below the zero degree was -28600 °Ch. In addition to real measurement results this three-dimensional temperature sensor field helps to calibrate and validate dynamic model for temperature simulation of thermal performance of wedge pile slab foundation without frost protection insulation and highly insulated slab on ground floor.