Foundation Soil Research Articles

Failure mechanism in a highway embankment founded on a sloping tectonised flysch formation

A highway embankment founded on a slope in a tectonised flysch formation of the Apennines chain (Central Italy) has been affected for about 30 years by continuous slow movements that caused some fractures on the road paving thus requiring periodic maintenance works. Due to the relevance of the damaged infrastructure, different investigation and monitoring campaigns have been carried out to collect information about the properties of the involved soils, the groundwater regime and the displacement field. Field monitoring, in particular, revealed that the movements were the result of a failure mechanism affecting both the embankment and the foundation soils. In particular, the observed displacements showed a weather-induced seasonal trend featured by acceleration/deceleration stages during the wet/dry periods. In order to better understand the detected mechanical response, a numerical model accounting for a soil hydrological balance of the interested area has been developed allowing a reliable historical reconstruction of the displacement regime.

Different Design Aspects of L-Shaped Earth Retaining Structures

The L-shaped retaining walls (L-SRWs) are considered one of the important earth retaining structures (ERSs). The investigation of L-SRWs mainly depends on factors directly related to the design process. Reviewing these factors represents the key matter in the design of ERSs, and this is the main purpose of this paper. This review showed that, in the design of L-SRWs, there are important issues to be considered. Some of them are related to the backfill and foundation soils e.g. the dependency of soil stiffness on the state of stresses, information related to soil behavior, inclination and quality of backfill, and settlement of foundation soil. Other issues are related to the wall itself such as the wall dimensions, failure mechanism, and flexural failure mode. In the design processes of L-SRWs, structural and geotechnical design requirements should be considered. L-SRWs should be designed to be proportional in their dimensions, the width of the wall base and its height should be designed to meet a specific ratio. Considerations related to the "conjugate rupture planes", the displacement pattern, and flexural failure mode should be included in the design process of L-SRWs.

Subsoil stiffness effects on the bridge-abutment dynamic behaviour

Integral abutment bridges (IABs) are robust structures that avoid the use of bearings and expansion joints and are relatively maintenance-free compared to conventional bridges. The seismic design code of IABs is not fully developed, and the complex soil-abutment interaction is not well understood. Therefore, research was carried out at the Schofield centre, the University of Cambridge, to understand the backfill-abutment interaction under earthquake loading, aimed at developing design guidelines for the industry. Understanding the mechanics by which the foundation soil stiffness and strength govern the abutment deformation and, thus, the earth pressures generated behind the abutment is essential. Two centrifuge tests have been conducted simulating an abutment with the conventional abutment-deck connection (or semi-integral abutment bridge), where moment restraint is released. In this paper, the dynamic response of the abutment founded on dry and liquefiable sandy soil is compared. Different deformation modes have been observed depending on the relative abutmentsoil stiffness. The abutment experienced minimal base displacement in dry sands. Conversely, the abutment witnessed cyclic rotational ratcheting about the deck level in liquefiable soil. The dry soil test helped identify the zones where soil stiffness and strength loss can be critical. In the case of the saturated test, the water table level was up to one-third of the abutment height, fully saturating the foundation soil while the backfill height was dry. The comparative results highlight the vulnerability of semi-integral abutment walls to liquefaction-induced failure, as witnessed in the 2011 Christchurch earthquakes.

Reinforcement of piling platforms with geogrids over dewatered docks with very soft soils: Wood Wharf, London

Wood Wharf is a major redevelopment of 23 acres designed to provide residential and office buildings as well as public spaces for shops, restaurants, parks and community uses. The development is located on the Isle of Dogs, Canary Wharf, London. This paper describes the design and results of the piling mats required to construct the buildings in the area of the South Dock, where 14,000m2 of land had to be reclaimed. Cofferdams were installed to create a watertight retaining structure to facilitate dry construction methods in the reclaimed area behind the new quay wall. To construct the different buildings, CFA and LDA piles between 8m to 34m deep were installed for the foundations. The soil profile primarily comprised Made Ground, Dock Sediments and River Terrace Deposits with very low undrained shear strengths between 2.5 to 42 kPa. The rigs to be used on site were 225 tons with applied pressures in the range of 300 to 470kPa and loadings of more than 1500kN. A series of reinforced piling mats were required to support the heavy rigs and reduce the applied pressures over the foundation soil. The design of the working platforms reinforced with geogrids was conducted in two stages, first to improve the modulus of the platform using recycled granular material, and second to provide safe platforms to support the heavy rigs.

Статистические характеристики данных температурного мониторинга грунтовых оснований фундаментов зданий города Салехарда за 2018–2023 годы как основа для автоматизации процесса первичной обработки данных

The Arctic today is a dynamically developing territory where the construction and operation of infrastructure are complicated by the presence of permafrost. Climatic changes and anthropogenic factors have a negative impact on their condition. In this regard, studies of the current and forecast state of permafrost in natural and anthropogenic conditions are relevant, which is necessary for the formation of plans for adaptation to climate change, design and engineering surveys work, and risk ma­nagement. Monitoring the temperature regime of soils at the base of the existing infrastructure seems to be the most obvious solution for monitoring the state of permafrost. The object of the study is the soil foundation of buildings erected on permafrost. The subject of the study is data obtained using an automated soil temperature control system for the foundations of capital construction facilities in Salekhard. For the purpose of identifying negative changes in the bearing capacity of permafrost at early stages, the task of determining a set of criteria based on the analysis of temperature monitoring data and their statistical characteristics is solved. In Salekhard wells were drilled at the base of 30 buildings to the depth of the foundation, where thermometric equipment was installed. The sensors measure the soil temperature every 3 hours and transmit it to the server for analysis. As a result, the possibility of using the amplitude of annual fluctuations in the temperature of the soil base and the capacity of the seasonal melt layer under the building to assess the effectiveness of the soil thermal stabilization system is shown. By analyzing the average and maximum temperature values in the bases of objects, it is possible to identify objects with weakened zones. A set of criteria is given for identifying objects with negative changes in the frozen base, and statistical characteristics can serve as a basis for automating the process of processing monitoring data. The information obtained on the parameters of permafrost under buildings will allow us to determine the current state of the soil foundations and predict the development of the situation in order to prevent the destruction of infrastructure.

ВИБРОДИАГНОСТИКА ЗДАНИЙ НА ПРИМЕРЕ УЧЕБНО-ЛЕКЦИОННОГО КОМПЛЕКСА МГРИ

The article provides the results of vibration diagnostics of the MGRI building in order to establish the level of vibrations on the soil foundation and study the nature of the distribution of vibration levels across floors. A significant decrease in vibration acceleration amplitudes was noted with increasing distance from the source to the vibration receiver. The opposite picture is observed when studying the floor-by-floor distribution of vibration background across floors of a building. As the floor increases, the vibration components increase, and the vertical component grows faster than the horizontal one.

Dynamic properties of the sandy soil in the Red river dyke foundation

Dynamic properties of the sandy soil in the Red river dyke foundation

Using soft soil models in geotechnical engineering: a review paper

Soil is considered a complicated material as, in general, the behavior under loading is non-linear in addition it is anisotropic material and its behavior is time-dependent. Various models were developed in the method of finite element for modeling the behavior of soil under different loading cases, and it must be known that no constitutive model is available that can simulate completely the actual soil behavior under all conditions. This paper attempts to investigate the soft soil model and present a discussion about the advantages and disadvantages for the purpose of giving an overview, and discussing the main finding of the previous studies regarding using the Soft Soil model in the numerical analysis of geotechnical engineering problems and applications. In this research, it was observed from the previous studies that the relation between the modified compression index (λ*) and unloading index (κ*) is from (5 to 10). The Soft Soil model gives a stiffer stress-strain behavior compared to Hardening model. Using this model for compressible soils needs a longer calculation time than other models as the material stiffness matrix was included in each calculation step. It shows satisfactory results in the analysis of the settlement of immediate and consolidation cases of foundation in clayey soil than the model of Mohr-Coulomb.

On the dynamic response of shallow foundations in saturated soils

On the dynamic response of shallow foundations in saturated soils

Sediments of an underwater tunnel constructed by the immersed sections method

In St. Petersburg there is a necessity to build a large number of underwater tunnels for various purposes. The construction of tunnels using the method of immersed sections is the most complex and high-tech, but at the same time competitive construction method, requiring the solution of a non-standard engineering task at each stage. The aim of the study is to analyze the sediment of the immersed tunnel section depending on the deformation characteristics of the underlying sand covering and the different depth of the bedrock of the Proterozoic clays. The calculations were completed using mathematical 3D models in the MIDAS GTS NX software package based on the finite element method. The reliability of the mathematical modeling results was confirmed by high convergence with the results of field observations of section precipitation during the construction of the Kanonersky Tunnel. The obtained results were statistically processed by methods of correlation and regression analysis with the construction of functional dependence. The greatest contribution to the change in the sediment of the tunnel section was made by the thickness of the Quaternary soils at the base of the section – the depth of the Proterozoic clays, with significantly less influence of the stiffness of the underlying sand covering. The obtained functional dependence makes it possible to predict the precipitation of the section with a high degree of probability in the geological conditions of St. Petersburg. It is established that with any combination of the considered parameters, the amount of precipitation of the section of the underwater tunnel with these characteristics does not exceed the values requiring expensive additional fixing of the foundation soils.

Model Updating of different Bridge types using ambient vibration and OMA identification.

Structural Health Monitoring (SHM) to date is an increasingly crucial issue in civil engineering. Many structures like bridges and viaducts nowadays are often older than their design life and show signs of structural deterioration that can potentially affect structural safety. One of the most popular monitoring techniques is dynamic monitoring under environmental vibrations using Operational Modal Analysis (OMA) techniques.OMA needs f.e.m. models that can simulate structural behavior under the real conditions and that can be used for interpretation of monitoring data and for possible damage detection.The study proposes a model updating for two different bridges: a girder and box deck one. After an OMA identification using ambient vibration, through the modal parameter identified, modal updating is performed on f.e.m. models, changing only few essential parameters. All the f.e.m. models are made with beam elements.The study highlights that even a simple f.e.m. model of the structure can describe accurately the dynamic and in general the structural behavior of a complex structure such as bridges and viaducts. The authors also show the differences between a f.e.m. model developed for the design and or verification and a f.e.m. model intended SHM. Model updating is performed through the management of a few parameters of the structure like the stiffness of bearing devices between superstructure and substructure, the deformability of foundation soil, the mechanical properties of concrete and reinforcement and the modal masses. The variation in each of these parameters can have a different role on the behavior of the structure.A good reliability of the f.e.m. model can be achieved through the management of a few structural parameters obtaining results that are sufficient for models that have the purpose of interpreting SHM data and are used to perform damage research.

NUMERICAL ANALYSES TO OBSERVE THE PERFORMANCE OF A MONUMENTAL BUILDING AT THE UNIVERSITY OF BENGKULU, INDONESIA

The Integrated Laboratory Building of Political and Social Science Faculty, located in a seismic-prone area, has been the subject of a comprehensive study of its performance using seismic response analysis. This research has yielded significant findings, gathering crucial secondary data, such as soil layers, bedrock depth, building structure, and earthquake wave information. The seismic response analysis, conducted by referencing the synthetic earthquake wave from the Bengkulu–Mentawai earthquake in 2007, with a magnitude of Mw 8.6, has provided a comprehensive overview of the earthquake waves at the foundation soil layers. The data, analysed using the finite element method to understand the structural response, revealed that the Peak Ground Acceleration (PGA) and amplification factor at the surface soil layer are 0.220g and 1.429, respectively. The most critical PGA and amplification factors at the foundation soil layer are 0.147g and 0.955. Structural analysis has revealed internal forces and beam elements experiencing over-strength, necessitating retrofitting the affected structural elements to reduce the impact. One practical and highly effective method of retrofitting involves increasing the beam dimensions by 53.12%. With retrofitting, the impact of structural deformation can be minimised, enhancing the building’s resilience in case of an earthquake of equal or greater magnitude. These findings underscore the importance of our research and highlight the significant role of engineers, architects, and researchers in ensuring the safety and longevity of structures in seismic-prone areas.

Non-invasive characterization of particle morphology of calcareous sands from São Tomé & Príncipe

Calcareous sands of biogenic origin are widely spread throughout the world’s seabed. They are the foundation soils for many offshore geotechnical structures, and, in addition, onshore uses of this material are becoming more significant with the growing demand of backfill material for transport infrastructure. These sands comprise the remains of marine organisms such as shells and tests, and the grains can vary from platy to hollow thin-walled forms with highly angular features. Geotechnical design on calcareous sands is challenging owing to the many uncertainties related to their microscale properties. This study uses non-invasive X-ray micro-computed tomography (μCT) and advanced three-dimensional (3D) image analysis techniques to quantify the morphology of bioclastic calcareous sands from São Tomé & Príncipe. The statistics of particle shape parameters of the São Tomé sand are compared to that of the previously studied Ledge Point sand. In spite of an order of magnitude difference in particle size, São Tomé and Ledge Point sands are markedly similar and, as seen in other calcareous sand, São Tomé shows a strong correlation in 3D sphericity and convexity. The results presented here help to better understand the mechanisms of grain interlocking, and the role of intra-granular void ratio on the mechanical behaviour of calcareous sands from different parts of the world.

Geotechnical investigations of lead-silver ore processing residues at the Auzelles site, Auvergne (France)

<p>Mining operations generate a significant quantity of mining waste in the form of sterile rocks and processing residues. These mining wastes are typically placed on the surface and can cause geotechnical and geochemical disturbances, as well as contaminants in surface water (through runoff) and groundwater (through infiltration), thus posing environmental risks. This article aimed to characterize the geotechnical properties of lead-silver ore processing residues at the Auzelles site in order to assess their stability and propose recommendations for their management and rehabilitation. The adopted methodology included in situ tests (such as density measurement and permeability) and laboratory analyses (grain size distribution, moisture content, methylene blue test, direct shear test, and standard Proctor test). The results showed a wet density of 1.63 g/cm<sup>3</sup> for the residues compared with 1.65 g/cm<sup>3</sup> for the waste rock, as well as a permeability of the residues measured at 5.5 × 10<sup>-5</sup> m/s, indicating significant drainage capacity. Laboratory analyses revealed that the samples were primarily composed of very silty sands and gravel, classified as B5 according to the Guide to Road Settlements. The cohesion of the residues was found to be zero, while the internal friction angle varied between 28° for the residues and 30° for the foundation soils. These geomechanical properties, particularly density, lack of cohesion, and friction angle values, raise concerns about the long-term stability of the residues. Due to their high permeability and lack of cohesion, the residues are susceptible to mass movement and erosion, which may exacerbate contamination risks. Therefore, it is essential to integrate these parameters into any potential residue stability analysis. Proactive management, based on these results, requires the implementation of appropriate rehabilitation techniques, such as drainage optimization and incorporation of vegetation covers, to minimize environmental impacts and ensure the long-term sustainability of mining waste structures.</p>

Application and Development of Intelligent Systems in Monitoring and Early Warning of Coastal Soft Soil Foundation

In coastal areas, due to their special geological conditions, soft soil foundation has become a common form of foundation in engineering construction. Soft soil foundation has low bearing capacity and large settlement deformation, posing a serious threat to surrounding building facilities and human life and property. Therefore, monitoring it is crucial. However, the inherent characteristics of soft soil foundation make it difficult to monitor, and traditional monitoring methods have shortcomings such as poor timeliness, low manual efficiency, and difficulty in sharing monitoring data. Therefore, in practical engineering, a combination of manual and automated methods is often used for monitoring. With the advancement of technology and the development of new technologies such as artificial intelligence, applying intelligent systems to soft soil foundation monitoring, real-time monitoring and early warning have become a new research direction. This article took a coastal soft soil foundation project as an example to introduce the application of intelligent systems in this project.

Application and Research Progress of Filling Piles in Expansive Soil Foundation

Application and Research Progress of Filling Piles in Expansive Soil Foundation

Research on Engineering Characteristics of Cement Mixing Piles Strengthening Steel Sheet Pile Structure Wharf

In order to solve the technical problem of using steel sheet piles in soft soil foundations of deep water docks, the use of grid type cement mixing pile walls to reinforce the in-situ soft soil behind steel sheet pile docks is a new type of composite structure attempt. This paper combines practical engineering and uses finite element analysis software to study the vertical displacement, vertical stress, and horizontal displacement changes of reinforced soil in three layout forms: non-mixing pile structure, grid type cement mixing structure, and dispersed mixing pile structure. The results show that the grid type cement mixing pile structure can reduce soil settlement, improve the stability of reinforced soil, and reduce lateral soil pressure on steel sheet piles compared to the non-mixing pile structure and the dispersed mixing pile structure. In the practical application of steel sheet pile wharf engineering, the use of grid type cement mixing piles can improve the stability and engineering benefits of the wharf structure.

Fractional Mathieu Differential Equations in Dynamic Stability of Piles

Piles are commonly used in Civil and Mechanical Engineering to provide support to superstructures and to transmit loads to deeper ground layers. During earthquakes, pile instability can result in the collapse of the entire structure. In this paper, the pile is modeled as a column surrounded by Winkler soil foundations with fractional damping. Investigation of the axially loaded pile leads to a fractional Mathieu differential equation of motion. The Bolotin method, employing harmonic balance, is proposed to obtain the approximate instability boundaries of the pile in the stability diagrams. A practical example is presented to conduct a parametric study on pile instability concerning the fractional order. The study observes parametric resonance in the first order, representing the principal instability region, which requires special attention to maintain stability. Furthermore, increasing the fractional damping order leads to a higher critical dynamic load and a slight reduction in the critical frequency ratio in each instability region. Higher-order instability regions exhibit greater sensitivity to changes in the fractional order. These results provided insights into the stability of piles under earthquake conditions.

Calculation of the wave field in a layered soil foundation using the grid method

The article contains a solution to the problem of propagation of waves in a soil massif arising from the movement of subway trains. This problem often arises when predicting vibration levels in buildings located near metro lines. The problem is considered in a two-dimensional formulation, taking into account the actual location of soil layers with different physical and mechanical properties. The soil is modeled using the assumption of its linear deformability, which, to a first approximation, is acceptable due to small vibration displacements. To solve the problem, the finite difference method is used, which allows taking into account the various physical properties of individual soil layers and the structure of subway tunnels and at the same time is one of the simplest numerical methods. To obtain a solution, the direct integration method is used using an explicit scheme, which requires setting sufficiently small time steps. The results are presented as graphs of vibration displacements obtained at various points in time. The graphs illustrate the different nature of the wave field at different load frequencies. The dynamic load is specified in the form of vibrations of the walls of the subway tunnel.

Dynamic response analysis of layered saturated frozen soil foundation subjected to moving loads

Dynamic response analysis of layered saturated frozen soil foundation subjected to moving loads