Shallow Footings Research Articles

Numerical and experimental study of effect woven geotextile on clay soil

Structures erected on soft soil often face challenges related to uncontrollable settlement and critical bearing capacity. The footing of numerous structures is prone to failure and collapse when situated on weak soil. In geotechnical engineering, enhancing the bearing capacity of a shallow footing is imperative. Ground reinforcement techniques are employed to improve the properties of weak soils, particularly addressing issues of compressibility and bearing capacity. One method for achieving this improvement is the use of woven geotextile reinforcement, as soil is proficient in compression but lacks tensile strength. By incorporating woven geotextile, the tensile potential of the soil is increased, consequently enhancing its load-bearing capacity. This paper reviews potential benefits of woven geotextile's (WG) in improvement the bearing capacity of square footing rest on clay soil. The model footing load tests were conducted on woven geotextile layers were added at varying distances. The findings demonstrated that, in comparison to unreinforced soil, the use of a woven geotextile system for reinforcement greatly increased bearing capacity and reduce settlement beneath the square foundation. Compared with unreinforced soil the ultimate bearing capacity increased about 1.91 times when reinforced with three layers of woven geotextile. Furthermore, the study employs advanced modeling techniques, utilizing the Plaxis-3D software program, to rigorously analyze the experimental results obtained from model footing tests. The results of these tests provide valuable insights into the effectiveness of the woven geotextile, contributing to a better understanding of their influence on soil stability and foundation support.

A Study of the Effect of Reinforcement Layers on the Performance of Shallow Footing Under Machine Foundation Loads

This paper exhibits an experimental study the effect of numbers of layers of reinforcement on the behavior of shallow footing under machine foundation. A reinforcement was inserted in to the sandy soil of relative density 50% during the raining techniques with 30*30cm at distance (0.5B, B,2B,3B) in a steel container with dimensions (50*50*55) cm. The test was performed under a machine foundation at frequency 10, 15 HZ. This research aims to find the optimal number of layers of reinforcement with geogrid under the square foundation under the machine foundation. For this purpose, laboratory experiments were conducted. The factors that were studied to find the optimal number of layers of reinforcement include the optimal number of layers of reinforcement, as well as displacement amplitude, velocity, acceleration, and settlement. The results showed at frequency 10 HZ, the optimal number of layers was one layer. The percentage of improvement in displacement, velocity, and settlement was (26%,39% and 75%), while acceleration increased when using one layer. At frequency 15 HZ, the optimal number of layers was four layers. The percentage of improvement in displacement, velocity, and settlement was (34%,44% and 66%). We conclude from this research that the type of reinforcement gave good results in reducing displacement amplitude, velocity, and settlement, but does not give good results in reducing acceleration.

The behavior of geogrid-reinforced sand soil supporting shallow footing under earthquake

The behavior of geogrid-reinforced sand soil supporting shallow footing under earthquake

Upgrading the capacity of foundations by using a hybrid expanded footing-micropile system

This paper introduces an innovative approach, where a hybrid expanded footing-micropile system is utilized to improve the load-bearing capacity of shallow footings on loose sand. Finite element analyses were carried out with a validated numerical model to simulate a shallow foundation on loose sand supporting a concentric vertical load. The simulated foundation was then upgraded by expanding its area and underpinning the additional area with pressure-grouted micropiles. The micropile installation process was treated as a pressure-controlled cavity expansion problem in the numerical simulation to account for the associated increase in radial stresses in the adjacent soil. A comprehensive parametric study was conducted, focusing on the primary determining factors: number of micropiles, micropile diameter, micropile bond length, grouting pressure, width of the additional area around the perimeter of the footing, and footing aspect ratio. The results showed that the micropiles acted as excellent settlement reducers once installed. If reducing the settlement is a high priority, when designing an expanded footing, the hybrid expanded footing-micropile system should be preferred rather than expanding the footing without the use of micropiles. The load capacity of the underpinned foundations was highly dependent on the grouting pressure applied during micropile construction.

Evaluation of load-settlement behavior of shallow footings using hybrid MLP-evolutionary AI approach with ER-WCA optimization

Evaluation of load-settlement behavior of shallow footings using hybrid MLP-evolutionary AI approach with ER-WCA optimization

Developing preliminary cost estimates for foundation systems of high-rise buildings

This study provided a unique Artificial intelligence (AI) model for the cost estimation of the foundation system for high-rise buildings. First, parametric data research was conducted, including 180 examples of foundation systems for high-rise building models related to criteria such as average column spacing, floor height, slap load, overall weight, base shear, and over. In addition, moment, gravity load, seismic load, design load, various columns (mid-edge-corner), soil profile, bearing capacity, GWT, excavation depth, and foundation systems are all factors to consider (shallow and deep footing). The research encompassed column spacing (5.0, 7.0, and 9.0 m) and the number of stories from 15 to 35, with an average cost decrease of 15%. The AI model utilizes extensive machine learning algorithms to analyze structural and geotechnical parameters. It provides a predictive tool that improves decision-making in the preliminary design. The methodology includes collecting data, training models utilizing innovative neural network techniques and validating them against current cost estimation models. The findings indicate that the AI model significantly improves the accuracy of cost estimations, with a precision rate of 95%, compared to traditional methods. Moreover, the model presents a potential cost savings of up to 15%. Construction designers and decision-makers may utilize the study’s findings to increase the accuracy of foundation system selection, lower costs and construction length, and improve overall project performance. Future work may involve applying this concept to infrastructure and substructure projects and collecting more data for benchmarking and empirical study.

Assessment of Building Response Supported on Shallow Foundation Due to Tunnelling in Cohesionless Soil

The depth of foundations significantly influences the building response due to tunnelling-induced ground movement. The present study investigates the responses caused by tunnelling on buildings supported on isolated footings. The response of buildings supported on shallow foundation systems due to progressive tunnelling is investigated through experimental and numerical methods. A three-dimensional finite element analysis (3D FEM) has been developed to evaluate the response of an existing reinforced cement concrete (RCC) building underpasses a circular-shaped tunnel in cohesionless soil. The model includes soil strata, footings, super-structure, and tunnel. Different parametric studies, i.e., C/D ratios, tunnel volume losses, and eccentricity of the building, have been considered in the present study. A scale-down model of the tunnel and building is prepared in the laboratory. The scale-down model simulates the volume loss during tunnelling and evaluates the response on surface and building components due to tunnelling. The surface settlement, total and differential settlement of the foundation, and induced strain on lining and building elementals are estimated. The numerical model is benchmarked with the experimental study conducted in the laboratory. It is observed that the numerical method agrees well with the experimental investigation. The responses of buildings supported on shallow footings are compared with available literature. The findings of the present study will be useful for the hazard estimation of existing buildings situated along/adjacent to a proposed alignment of the tunnel.

Evaluating the N γ Coefficient for Shallow Strip Footings on Sloping Ground by the Method of Stress Characteristics

Evaluating the <i> N _γ </i> Coefficient for Shallow Strip Footings on Sloping Ground by the Method of Stress Characteristics

Influence of the superposition and flow rule assumptions on the bearing capacity of shallow strip footings

Influence of the superposition and flow rule assumptions on the bearing capacity of shallow strip footings

Some practical applications of shear wave velocity measurements in dense sand

Shear wave velocity (Vs) profiles were obtained using two techniques at a dense sand site in Blessington near Dublin, Ireland. It was shown that both the multichannel analysis of surface waves (MASW) and seismic CPT (SCPTU) techniques provided reliable data. Use was made of a novel approach involving a Monte Carlo inversion of the MASW output to assess the fit between the measured and theoretical surface wave data. Differences between the SCPTU and MASW data are likely to be due to a combination of natural anisotropy in the sand and to uncertainty in the two methods involved. Previous published correlations between CPTU data and Vs also work well for this site. The Vs data was also used to accurately predict (Class 3 prediction) measured settlement data from shallow footing tests at the site.

Rocking foundations on geosynthetic-improved sand

This study focuses on the load-deformation response of a heavily loaded rocking footing on geogrid-reinforced sand via centrifuge-model scale shake table tests. To mitigate issues observed with overturning failure and excessive settlement of shallow footings on unimproved ground, geogrid reinforcement can help control footing kinematics while maintaining the enhanced energy dissipation of a rocking footing. The scalemodel geogrid evaluated in this study was manufactured with 3D printing and placed at a depth equal to the footing width. Shake sequences induced controlled yielding, and the geogrid was observed to reduce settlement during rocking and preserved recentering under strong shaking.

Critical acceleration of shallow strip footings

Critical acceleration of shallow strip footings

Integration of GIS with the Generalized Reciprocal Method (GRM) for Determining Foundation Bearing Capacity: A Case Study in Opolo, Yenagoa Bayelsa State, Nigeria

This study addresses the pressing need to assess foundation bearing capacity in Opolo, Yenagoa, Bayelsa State, Nigeria. The significance lies in the dearth of comprehensive geotechnical data for construction planning in the region. Past research is limited and this study contributes valuable insights by integrating Geographic Information System (GIS) with the Generalized Reciprocal Method (GRM). To collect data, near-surface seismic refraction surveys were conducted along three designated lines, utilizing ABEM Terraloc Mark 6 equipment, Easy Refract, and ArcGIS 10.4.1 software. This methodology allowed for the determination of key geotechnical parameters essential for soil characterization at potential foundation sites. The results revealed three distinct geoseismic layers. The uppermost layer, within a depth of 0.89 to 1.50 meters, exhibited inadequate compressional and shear wave velocities and low values for oedometric modulus, shear modulus, N-value, ultimate bearing capacity, and allowable bearing capacity. This indicates the presence of unsuitable, soft, and weak alluvial deposits for substantial structural loads. In contrast, the second layer (1.52 to 3.84 m depth) displayed favorable geotechnical parameters, making it suitable for various construction loads. The third layer (15.00 to 26.05 m depth) exhibited varying characteristics. The GIS analysis highlighted the unsuitability of the uppermost layer for construction, while the second and third layers were found to be fairly competent and suitable for shallow footing and foundation design. In summary, this study highlights the importance of geotechnical surveys in Opolo’s construction planning. It offers vital information for informed choices, addresses issues in the initial layer, and suggests secure, sustainable construction options.

Numerical modelling of traffic-induced dynamic loading on a two-story residential building

BackgroundThis paper presents a numerical modelling procedure of dynamic loading due to traffic on a two-story residential building. In developing countries cities and towns, poor quality narrow road sections with high traffic density are common. In such cases, ground vibration due to traffic could be higher and lightweight buildings located closer are exposed to traffic-induced dynamic loading. Design codes require a proper assessment of such vibrations. However, a clear and definite procedure of assessment is not usually provided. This research presents an assessment procedure of dynamic loading due to traffic on a soil foundation system of light weight buildings based on numerical modeling. Traffic induced ground vibration acceleration amplitudes, frequencies and durations were measured, and the dynamic loads were calculated from measured vibration accelerations and vibrating mass of the vehicle. A two-story residential building with flexible square shallow footings was modelled together with the foundation soil using PLAXIS-2D. The dynamic load was modelled as harmonic loading considering the highest amplitude of vibration measured.ResultsOn the calculation stage, static loading analysis, dynamic loading analysis and free vibration dynamic analysis were carried out. A maximum increase in extreme total displacement of the soil to 22.03 mm was observed after the dynamic loading from 18.96 mm extreme total displacement due to static loading. Extreme effective mean stress in the soil increased to 112.81 kPa from 110.5 kPa, due to the dynamic loading. In addition, a differential settlement of 3.14 mm between two adjacent footings was observed after the traffic induced ground vibration. Furthermore, the Mohr–Coulomb plastic points were observed to be concentrated to the side of the soil-foundation system which the dynamic load was acting on.ConclusionThe regular exposure to traffic-induced vibrations may cause frequent change in stress and deformation response of the foundation-soil system. In areas where lightweight buildings are exposed to regular traffic induced vibrations, proper assessment of the effect should be carried out and measures should be taken to mitigate the problem. Improving road surfaces and limiting vehicle speed are possible remedial measures to reduce ground vibrations due to traffic.

Deterministic and probabilistic analysis of the response of shallow footings on unsaturated soils due to rainfall

Due to rainfall, footings are usually subjected to effects of water table fluctuations which results in the variation of ultimate bearing capacity in unsaturated soils. However, the conventional bearing capacity theories don’t account for the variation of suction as the water table position changes. In this paper, an equation based on Terzaghi theory is proposed to evaluate the variation of bearing capacity due to suction variations due to rainfall. The proposed equation results in higher bearing capacity values compared to the conventional Terzaghi equation. Further, a comparison of the bearing capacity obtained using the proposed equation is made with those obtained from Barcelona Basic model (BBM), Mohr-Coulomb model and Terzaghi equation. It is observed that BBM results in lower values of bearing capacity compared to Mohr-Coulomb model as the former considers the loss of suction upon infiltration. Soil properties like porosity, permeability and soil water characteristic (SWCC) influence the bearing capacity in unsaturated soils. Thus, probabilistic analysis is carried out by using an efficient kriging surrogate model in order to analyze the impact of variation of the associated parameters on the bearing capacity. The surrogate model can predict the surface displacements of footing upon infiltration with enhanced accuracy and computational efficiency. Considering the uncertainty associated with rainfall loads, it is observed that as the return period of rainfall increases, failure probability increases.

Reliability-based analysis of seismic bearing capacity of shallow strip footings resting on soils with randomly varying geotechnical and earthquake parameters

Seismic bearing capacity of strip footings is a challenging task for geotechnical engineers due to its stochastic framework instigated by the natural uncertainties incorporated into geotechnical properties and earthquake parameters. Consequently, the introduction of the random field theory into reliability analysis may provide power tools to succor designers check how reliable their designs. This paper aims to assess the seismic bearing capacity of shallow strip footings resting on soils with randomly varying parameters. Bearing capacity formulas for purely cohesive and cohesive-frictional soils are considered. The influence of the type of the autocorrelation functions (ACFs), the scale of fluctuations (SOFs) and the coefficient of variation (COV) of the random parameters are investigated. Statistical moments, probability density function (PDF) and failure probability (Pf) of the seismic bearing capacity are computed. It is shown that the Single Exponential (SNE) ACF is the most appropriate function to characterize the spatial variability of the soil properties since it provides conservative results. On other hand, the results indicate that the increase in the coefficients of variation (COV) of the cohesion or the friction angle increases the variability of the seismic bearing capacity while this variability remains unaffected when the COV of the seismic coefficient increases. The results also highlight that the effect of the vertical SOF on the PDF and the failure probability is much more significant than that of the horizontal SOF. In addition, the mean seismic bearing capacity fluctuates slightly as the horizontal or vertical SOF increases so that the increment of variation is between 0.4% and 2% for the both two soil types.

A theoretical and practical framework based on plasticity theory for the drained behavior of single and multiple shallow footings

AbstractWith the shift of the offshore wind energy sector to deeper waters, demand for the development of more complex foundation solutions, particularly suction bucket – supported tripod/tetrapod and jacket foundations, has increased. This paper is divided into two main sections. The first part comprises a comprehensive review of the performance of circular surface and shallow foundations under combined loading (VHM), and how it can principally be understood in a theoretical framework of plasticity theory. Examination of the considered data suggested that the general assumption of over‐estimated non‐association degree with constant failure surface parameters and increasing vertical load may require further investigation. This may be attributed to the complex interplay of multiple properties such as stress level, soil strength profile and foundation geometry. The existing data in the literature were also used to provide practical guidance for a successful implementation of the elasto‐plastic constitutive relationships in offshore foundation design. In second part of the paper, the suitability of the non‐associated plasticity formulation for a baseline multi‐pod system in H‐M load space was investigated using three‐dimensional (3D) finite element (FE) analyses and not verified. Furthermore, the failure envelopes and hardening law for caissons with different embedment ratios differed from those recommended in the literature were established. Parametric studies of multi‐caisson foundations revealed that the failure mechanism of multi‐bucket foundations under horizontal loading depended greatly on the bucket spacing. The horizontal bearing capacities increased with the bucket spacing until they reached a threshold. Meanwhile, analyses of the multi‐bucket foundation under moment loading confirmed the occurrence of a push‐pull failure mechanism.

Mechanical Properties of Polyamide Fiber-Reinforced Lime–Cement Concrete

Lime–cement concrete (LCC) is a type of lime-based concrete in which lime and cement are utilized as the main binding agents. This type of concrete has been extensively used to construct support layers for shallow footings and road backfills in some warm regions. So far, there has been no systematic research conducted to investigate the mechanical characteristics of polyamide fiber-reinforced LCC. To address this gap, LCC specimens were prepared with 0%, 0.5%, 1%, and 2% of polyamide fibers (a synthetic textile made of petroleum-based plastic polymers). Specimens were then cured for 3, 7, and 28 days at room and oven temperatures. Then, the effects of the fibers’ contents, curing conditions, and curing periods on the mechanical characteristics of LCC, such as secant modulus, deformability index, bulk modulus, shear modulus, stiffness ratio, strain energy, failure strain, strength ratio, and failure patterns, was investigated. The results of the unconfined compressive strength (UCS) tests showed that specimens with 1% fiber had the highest UCS values. The curing condition and curing period had significant effects on the strength of the LCC specimens, and oven-cured specimens developed higher UCS values. The aforementioned mechanical properties of the LCC specimens and the ability of the material to absorb energy significantly improved when the curing period under the oven-curing condition was increased, as well as through the application of fibers in the mix design. Based on the test results, a simple mathematical model was also established to forecast the mechanical properties of fiber-reinforced LCC. It is concluded that the use of polyamide fibers in the mix design of LCC can both improve mechanical properties and perhaps address the environmental issues associated with waste polyamide fibers.

Bearing capacity of footings on geosynthetic-reinforced soils under combined loading

In this study, the ultimate bearing capacity of shallow strip footings resting on a geosynthetic-reinforced soil mass subjected to inclined and eccentric combined loading is rigorously examined through the well-established method of lower bound limit analysis (LA) in conjunction with finite element (FE) and second-order cone programming (SOCP). Lower bound limit analysis formulation is modified to consider the ultimate tensile force of the geosynthetic layer in the soil mass so as to account for both pullout (sliding) and rupture (structural) modes of reinforcement failure. The effects of several parameters, including the embedment depth (u) and the ultimate tensile strength (Tu) of the geosynthetic layer along with load inclination angle (α) and load eccentricity (e), on the bearing capacity ratio (BCR) and failure envelopes of the overlying shallow foundation are examined and discussed. The results generally show a marked increase in the ultimate bearing capacity of the surface footing against combined loading with the inclusion of a single geosynthetic layer. Results also reveal that a second intermediate reinforcement might be required to bear a dual performance against both vertical concentric and combined loading scenarios so as to more effectively support the footing.

Strip footings for the extension of a piled building

A four-storey building in south-west London, UK is to be extended to eight storeys by introducing a system of strip footings to supplement the original foundation system, formed by displacement flight auger piles. The reuse of the original foundation piles and the implementation of the new footings were made possible by a detailed desk study, which obtained record information on the existing foundation system together with a thorough investigation of the existing foundations, which validated the record data. The strip footing solution was assessed against other options and selected on the basis of accessibility and construction practicalities. New ground beams were designed to distribute the new column loads in a manner compatible with the implemented solution. The complex interaction between the new shallow footings and the existing deep footings was assessed considering different loading scenarios and maximum and minimum displacements for each element. Simplified linear elastic geotechnical analyses and pile settlement calculations supported the structural assessment of the proposed extension.