Edge Of Foot Research Articles

2D discrete element analysis of the footing above excavated circle in soil

The bearing capacity and settlements of surface foundations located on a soil slope are the important issues that have to be considered by geotechnical engineers for the design. The presence of an underground void beneath the footing can affect the foundation stability and can lead to serious structure damages. In this study, the results of two-dimensional (2D) discrete element (DE) and finite element (FE) analyses of a surface footing on a soil slope above a void are presented. To validate the numerical model results, the DE results obtained have been compared with experimental test presented in the previous study. After validation of the DE numerical model, parametric studies were carried out to evaluate the effect of important factors on the surface footing performance. The studied parameters include the horizontal spacing of the void axis relative to the slope edge (SH), the vertical spacing of the void crown relative to the footing base (SV), the horizontal spacing of the footing edge relative to the slope edge (De) and the void diameter (Dv). The effects of these parameters on the pressure-settlement curves and the contact force distributions in the soil slope are presented and discussed. The results showed that the footing bearing pressure increases with an increase of SH, SV and De but decreases when Dv increases. The behavior of a surface footing on a soil slope above a void significantly depends on the SV value.

An Investigation into the Influence of a New Building on the Response of a Sheet Pile Wall Adjacent to an Existing Buried Pipe

This paper explores a solution to safeguard buried pipes located near constructions in the Al-Bisri region of Assiut Governorate by utilizing the concept of the characteristic damage state. This issue has escalated due to the increasing rate of construction activity near pipelines, resulting in a multitude of legal disputes. This study investigates the behavior of buried pipes when influenced by newly constructed buildings using the finite element method. The paper employs two-dimensional models of a 12-story reinforced concrete building with a raft foundation and a series of piles supporting the buried pipe. In this study, we used the PLAXIS software, a 2D plane strain program, to conduct numerical investigations. The soil was idealized using the Mohr–Coulomb model with a 15-node triangular element, while the piles and structures were idealized with a five-node isoperimetric beam element. The point of contact between the beam and the soil was represented by the interface element. Our research examined the distance between the pipe and the footing edge and the distance between the piles and the footing edge. The finite element model results provided nodal displacements and element straining actions for analysis. The results shed light on the behavior of the sheet pile wall and sewage pipe in various situations. The largest bending moment in the sewage pipe was seen in the absence of piling, in contrast, to pile support at Rx = 0.75. The bending moment in the pipe expanded and always occurred at the same location as Rx rose. The clay layer next to the pipe’s lateral deformation was significantly reduced after piling, with the greatest deformation occurring at Rx = 0.

Laser-Induced Ultrasonic Guided Waves Based Corrosion Diagnosis of Rail Foot

Rail foot corrosion is an important issue for electrified railway system. It usually initiates at the bottom of rail foot edges covered by a rail clip and is hardly accessible to conventional online inspection systems. To address this problem, this study combines air-coupled ultrasonic transducer (AUT) and laser-induced ultrasonic guided wave to detect rail foot corrosion. The corrosion sensitivity of the guided wave below 500 kHz is examined considering the impact of rail clip. The results have shown that A <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> and S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> are the dominant wave modes near the edge of rail foot. The preferred A <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> wave is insensitive to allowable rail foot corrosion below 100 kHz. It is neither sensitive above 270 kHz due to wave mode conversion and reduced wave penetration. The optimal frequency is about 200 kHz where the attenuation of A <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> wave can reflect the impact of all levels of corrosion even in the presence of a rail clip. Accordingly, an end-to-end deep learning model is employed for corrosion detection based on 200-kHz air-coupled ultrasonic signals. It can automatically extract signal features for corrosion diagnosis as well as differentiate unknown anomalous signals by environmental interference. It is tested with 8122 labeled signal samples collected from field trial and achieves a detection accuracy of 99.5%. All the anomalous signals are also correctly identified.

Bearing Capacity Factor of Shallow Foundation on Reinforced Sloped Clayey Soil

The placement of buildings and structures on/or adjacent to slopes is possible, but this poses a danger to the structure due to failures that occur in slopes. Therefore, a solution or improvement should be determined for these issues of the collapse of the structure as a result of the failure of the slopes. A laboratory model has been built to test the impact of some variables on the bearing capacity factor. The variables include the magnitude of static axial load applied at the center of footing, the depth of embedment, the spacing between geogrid reinforcement layer and the numbering of the geogrid sheet under the footing, the inclination angle of slope clayey soil (β), the spacing between the footing's edge and the slope's end (b/H). The results show that the critical case of reduction in bearing capacity is mobilized at (b/H˂ 0.25) and (β˃ 30°). A design chart has been obtained to the case of unreinforced slope soil under a footing to describe the reduction in (Nc) when increasing the inclination angle and another design chart of the case of reinforced slope soil with (N=1, 2 and 3) has been obtained to show the increase in value of (Nc) with increasing the number of the reinforced layer at different values of (β) and finally simple equations have been obtained in order to calculate the ultimate bearing capacity of foundation on sloped clayey soil at different number of reinforcement.

Comparison of Electrodermal Activity from Multiple Body Locations Based on Standard EDA Indices' Quality and Robustness against Motion Artifact.

The most traditional sites for electrodermal activity (EDA) data collection, palmar locations such as fingers or palms, are not usually recommended for ambulatory monitoring given that subjects have to use their hands regularly during their daily activities, and therefore, alternative sites are often sought for EDA data collection. In this study, we collected EDA signals (n = 23 subjects, 19 male) from four measurement sites (forehead, back of neck, finger, and inner edge of foot) during cognitive stress and induction of mild motion artifacts by walking and one-handed weightlifting. Furthermore, we computed several EDA indices from the EDA signals obtained from different sites and evaluated their efficiency to classify cognitive stress from the baseline state. We found a high within-subject correlation between the EDA signals obtained from the finger and the feet. Consistently high correlation was also found between the finger and the foot EDA in both the phasic and tonic components. Statistically significant differences were obtained between the baseline and cognitive stress stage only for the EDA indices computed from the finger and the foot EDA. Moreover, the receiver operating characteristic curve for cognitive stress detection showed a higher area-under-the-curve for the EDA indices computed from the finger and foot EDA. We also evaluated the robustness of the different body sites against motion artifacts and found that the foot EDA location was the best alternative to other sites.

Estimating the Ultimate Bearing Capacity for Strip Footing Near and within Slopes Using AI (GP, ANN, and EPR) Techniques

Numerical and computational analyses surrounding the behavior of the bearing capacity of soils near or adjacent to slopes have been of great importance in earthwork constructions around the globe due to its unique nature. This phenomenon is encountered on pavement vertical curves, drainages, and vertical infrastructure foundations. In this work, multiple data were collected on the soil and footing interface parameters, which included width of footing, depth of foundation, distance of slope from the footing edge, soil bulk density, slope and frictional angles, and bearing capacity factors of cohesion and overburden pressure determined for the case of a foundation on or adjacent to a slope. The genetic programming (GP), evolutionary polynomial regression (EPR), and artificial neural network (ANN) intelligent techniques were employed to predict the ultimate bearing capacity of footing on or adjacent to a slope. The performance of the models was evaluated as well as compared their accuracy and robustness with the findings of Prandtl. The results were observed to show the superiority of GP, EPR, and ANN techniques over the computational works of Prandtl. In addition, the ANN outclassed the other artificial intelligence methods in the exercise.

Class-A prediction of three-sided reinforced concrete culverts and numerical investigation of the supporting strip footing geometry effect

This paper presents three-dimensional finite element analyses conducted to optimise the instrumentation plan for monitoring the structural performance of reinforced concrete three-sided culverts (TSCs). Numerical models were developed for three TSCs with spans of 7.3, 10.4, and 13.5 m to establish the anticipated range of measurements. The TSCs were instrumented with 30 pressure cells and 56 strain gauges. Comparing the numerical predictions with field measurements of the 10.4-m-span TSC verified the adequacy of simulating the concrete behaviour as linear elastic for estimating the applied earth pressures. However, such simplification would lead to underestimating the induced strains in the culvert body in case cracks develop. In addition, Class-A predictions of soil pressures on the culvert were compared with the field measurements of a 7.3-m-span TSC. The calculated soil pressures agreed well with the field measurements. The measured and calculated earth pressures suggest a vertical arching factor of 1.05 at the final backfill height. The influence of the shallow foundation geometry was investigated employing the validated numerical model. It was found that the footing geometry has no influence on the applied earth pressures. However, the calculated stresses below the footing edge on the backfill side decreased as the footing flexibility increased.

Upshots of pin piles retrofitting for existing structures

The heterogeneity of soil is an advantage as well as a disadvantage at the same time. The well graded soil possesses more density and stability then uniformly graded soil, but at same time because of uneven distribution of soil underneath the foundation soil may behave differently to different soil conditions. The soil beneath the foundation cannot be accessed directly therefore methods like pin piles came into the picture. The piles having diameter less than 300 mm are termed as pin piles. Under this portion of study the gain in strength by soil under the foundation of existing structure was noted down by an experimental method. The structure and subsequent conditions were simulated in the laboratory. The quantity and spacing of pin pile are interrelated. In the analysis the pin piles are inserted in the periphery of the existing footing in one line and footing size remains constant throughout the experiments, therefore the more spacing means less number of pin piles and vice versa. The distance between pin piles is termed as pitch length as measured from center to center.The distance from the outermost edge of footing is termed as edge distance also taken as variable. The experiments were designed in MiniTab 9.0 for suitable combinations of variables. The settlement of soil at 25 mm was considered a failure and optimized quantity and spacing of pin piles were determined. The positive effects of pin piles were observed when inserted in the periphery of existing footing.

Plate load tests to analyze the load-settlement response of shallow foundations on sand beds reinforced with micropiles.

Micropiles can act as structural support for a new foundation and sustainable solution for existing foundations with advantages such as high load-carrying capacity and use in in situ conditions. Installing micropiles around the footing at some distance from the footing edge could turn out to be extremely helpful for existing distressed foundations where improvement is needed. An experimental investigation is carried out on a laboratory model square footing in the ongoing study, placed on sand, with micropiles driven around the footing. A parametric study focusing on the effect of the slenderness ratio of the micropiles, the state of sand beds, the micropile spacing ratio (S/b), and the micropile edge distance ratio (ED/d) are analyzed. The results demonstrate that the micropiles can appreciably improve the footing's settlement characteristics and load-bearing capacity when placed around it. The load-carrying capacity shows some appreciable increase by increasing the slenderness ratio of micropiles, but increasing the slenderness ratio beyond 20 is insignificant. For unreinforced footing, a denser form of sand was found more advantageous in terms of bearing capacity, while as for reinforced footing, micropiles provided maximum improvement for medium-density sand. The improvement in bearing capacity is approximately 22.2% when the spacing ratio is reduced from 0.5 to 0.3. Also, for an edge distance ratio of 3, the improvement in the bearing capacity ratio is 76% higher than that of unreinforced footing. Multivariate linear regression showed a strong correlation between the experimental and predicted bearing capacity ratio.

Behavior of Square Footing Resting on Gypseous Soil and Surrounded by a Sheet Pile Wall

Abstract Laboratory model is used in this study to investigate the behavior of centrally loaded square footing resting on gypseous soil, and surrounded by a sheet pile wall at a distance of 2B from the footing edge and extend in depth to 2B as well. During this study the soil were subjected to ten cycles of saturation and drainage at one-week interval to simulate heavy rainfalls or floods. It should be noted that the soaking water were added only outside the area surrounded by the sheet pile. Four points were chosen to detect gypsum solubility, three of them below the footing edge at different depths and one outside the sheet pile wall for comparison. It has been found that the dissolved gypsum below the footing is significantly less than the one outside the sheet pile wall. For each cycle of saturation-drainage the gypsum content is found to be reduced by 3 % and 0.8 % for the outsider point and for average of the three points respectively. Settlement during first cycle of saturation – drainage was twice as the second cycle and about four times of the third cycle. However, this first cycle settlement is about 25 % of the settlement of footing where no sheet pile wall is used. To sum up, the sheet pile wall found to be an effective protection to reduce the collapsibility of gypsum soil and to reduce footing settlement.

Influence of micropile parameters on bearing capacity of footings.

Micropiles, on account of their versatility, can serve as both a new foundation and a long-term option for prevailing foundations without disturbing the subgrade underneath. They can improve highway facilities, historically significant structures, or distressed structures. The present laboratory model study is conducted on a square footing installed with micropiles all around it and subjected to vertical concentric loading. A parametric analysis based on the impact of five micropile parameters is also performed. The results obtained from this study reveal that the inclination of micropiles has little effect on ultimate vertical load but can profoundly impact the horizontal load. As the diameter of micropiles is progressively increased from 10 to 20 mm, the bearing capacity improves by around 27%. As the micropile spacing decreases from five times diameter (5d) to three times diameter (3d), the footing system's bearing capacity increases nearly by 22.2%. The bearing capacity ratio shows a reduction beyond the value of L/b = 2. Installing micropiles nearer to the footing edge (ED/b = 0.3) provided approximately 76% improvement with respect to the unreinforced footing. The optimum value of the different parameters is equal to L/b = 2, d = 20 mm, ED/b = 0.3, and S/d = 3. There is a 98% improvement in bearing capacity at the optimum values for 30° inclined micropiles.

A Numerical Study on the Bearing Capacity of Fly-Ash Reinforced with Fine Micropiles

Soil reinforcement technology is beneficial for weak and soft subgrade soils supporting the footing loads. Vertical reinforcement to it further enhances the bearing capacity substantially. Fine micropiles as vertical reinforcement are becoming more popular. This numerical study focuses on the performance of subgrade soil (fly-ash), reinforced with fine-micropiles as the vertical reinforcement. The numerical model was developed in SIGMA/W of GeoStudio 2016 based on laboratory model tests. Analysis was carried out to study the influence of length of the reinforcement, spacing between the reinforcing bars and their lateral extent beyond the footing edge on the bearing capacity and settlement of the foundation system. The analysis shows that the bearing capacity increases and the settlement decreases with a decrease in the spacing between the reinforcing bars and increase in their lateral extent beyond the footing edge. The maximum improvement in the bearing capacity of the reinforced fly ash was obtained as 340% with a corresponding decrease in the settlement of 86%. For all spacing and lateral extent values, the bearing capacity increases by increasing the length of the reinforcement bars.

Numerical parametric study of geosynthetic reinforced soil integrated bridge system (GRS-IBS)

A 2-D finite flement model was developed in this study to conduct a FE parametric study on the effects of some variables in the performance of geosynthetic reinforced soil integrated bridge system (GRS-IBS). The variables investigated in this study include the effect of internal friction angle of backfill material, width of reinforced soil foundation (RSF), secondary reinforcement within bearing bed, setback distance, bearing width and length of reinforcement. Other important parameters such as reinforcement stiffness and spacing were previously investgated by the authors. The performance of GRS-IBS were investgated in terms of lateral facing displacement, strain distribution along reinforcement, and location of potential failure zone. The results showed that the internal friction angle of backfill material has a significant impact on the performance of GRS-IBS. The secondary reinforcement, setback distance, and bearing width have low impact on the performance of GRS-IBS. However, it was found that the width of RSF and length of reinforcement have negligible effect on the performance of GRS-IBS. Finally, the potential failure envelope of the GRS-IBS abutment was found to be a combination of punching shear failure envelope (top) that starts under the inner edge of strip footing and extends vertically downward to intersect with Rankine active failure envelope (bottom).

Experimental Investigation of Skirt Footing Subjected to Lateral Loading

Background:The skirt foundation is one of the powerful types of foundations to resist the lateral loads produced from natural forces, such as earthquakes and wind action, or from the type of structures, such as oil platforms and offshore wind turbines.Objective and Methodology:This research experimentally investigated the response of skirted footing resting on sandy soil of different states to lateral applications of loads on a small-scale physical model manufactured for this purpose. The parameters studied are the distance between the footing and the skirt and its depth.Results and Conclusion:The results show that the presence of the skirt behind the footing loads to an increase in bearing load and a reduction in the lateral movement whereas the skirt near or adjacent to the footing edge causes maximum increases in bearing load and reduction in lateral movement, for skirted footing. The ratio between the wall distance and the width of the footing has no effect when it is greater than one. On the other hand, the state of the soil influences the bearing load and lateral movement with different ratio of wall distance and wall depth to the width of the footing, especially when the wall distance to the footing width is less than one and the state of the soil has no effect on the bearing load and lateral movement when the ratio is more than one.

Stability analysis and design charts for a sandy soil slope supporting an embedded strip footing

In several field situations, especially in the hilly terrains, the construction of footings on slopes becomes essential. The factor of safety of a slope supporting a loaded footing on the crest is dependent on the position of the footing from the crest edge. Most studies in the past have focused on analysing the bearing capacity and settlement behaviour of a footing resting on a slope crest, but foundations in most infrastructure projects are usually built at some depth below the ground surface. Therefore, the availability of some form of design charts for determining the factor of safety of a slope supporting an embedded footing will be highly useful for the practising engineers. In the current work, the finite element analysis of a sandy soil slope supporting an embedded footing was carried out using the Plaxis 2D, a finite element-based commercial software, in order to examine the effect of slope geometry, soil properties, and footing locations on the stability of slope in terms of factor of safety. The results of the analysis show that the factor of safety of the slope increases with an increase in the footing edge distance, footing depth and soil relative density, but it decreases with an increase in the slope angle and applied pressure on the footing. Some design charts have been developed along with an illustrative example to explain how these charts can be used by the practising engineers.

Theoretical model and finite element analysis for restoring moment at column foot during rocking

Column usually rests directly on top of a stone base without any physical connection in traditional timber structures. When timber structure is subjected to horizontal loads, rotation around the edge of column foot may occur with or without slippage of column. Columns rock with cyclic lift and reset. Compression deformation occurs to column foot due to the heavy vertical load of the structure and it is an important factor to the loading bearing capacity of timber structure. Accordingly, the rotation behavior of column foot during rocking has to be taken into account when carrying out the structural analysis. For this purpose, rotation behaviors of column foot during rocking is studied, and theoretical model of restoring moment at column foot joint is proposed with consideration of the compression effect; finite element model is established to verify the proposed model and good agreement of the two models is found. Result shows that column foot has contributions to resist horizontal loads with rocking under lateral load.

The influence of foundation stiffness on the behaviour of surface strip foundations on sand

The objective of this study was to determine whether the contact stress distribution underneath a strip footing on dense cohesionless sand can be predicted as a function of the properties of the footing and that of the underlying sand. Together, the footing and the underlying sand form a foundation system which can be classified in terms of relative stiffness. Centrifuge model tests were conducted on seven aluminium footings of various depths and hence stiffness, and one reinforced concrete footing, during which the qualitative variation in contact stress distribution underneath the footing was captured with the use of Tekscan™ pressure sensors. It was found that, as long as the relative stiffness of the foundation classifies as "stiff", the contact stress distribution underneath the footing is approximately uniform. As the relative foundation stiffness is reduced, the contact stress underneath the footing edge as a percentage of the maximum stress occurring underneath the column, reduces. In the case of a semi-flexible footing tested, zero pressure was measured underneath the footing edge in response to loading of the footing. An expression is presented to allow the contact stress under the edge to be estimated as a function of the relative stiffness of the foundation. This allows the contact stress distribution underneath semi-stiff footings to be estimated. The stiffness of the model reinforced concrete footing tested reduced considerably due to cracking during loading. It is recommended that footings be provided with sufficient stiffness to classify as stiff. A modification of the benchmark value for the minimum relative stiffness classifying as stiff is proposed, based on the results of the centrifuge tests.

Analysis of Strip Footings on Fiber-Reinforced Slopes with the Aid of Particle Image Velocimetry

AbstractThis paper provides results of a comprehensive investigation into the use of waste carpet fibers for reinforcement of clay soil slopes. The interaction between laboratory scale model slopes made of fiber-reinforced clay soil and surface strip footing load was examined. Results for the influence of two variables, namely fiber content and distance between the footing edge and the crest of the slope, are presented and discussed. The particle image velocimetry (PIV) technique was used to study the deformation of the slope under the surface loading. The front side of the tank was made of a thick Perspex glass to facilitate taking accurate images during the loading stage. To study the stress induced in the slope under footing pressure, excess pore-water pressure and total stress increase were measured at predetermined locations within the slope. The results showed that fiber reinforcement increased the bearing resistance of the model slope significantly. For instance, inclusion of 5% waste carpet fiber ...

Bearing Capacity of Embedded Strip Footing on Geogrid-Reinforced Fly Ash

Fly ash is a pozzolanic waste from the burning of coal ash in thermal power plant which will be unchangeable in India and increasing environmental pollution. There is an urgent need of increasing bulk utilization of fly ash in geotechnical application. In this regard, a study was undertaken to investigate the bearing capacity of fly ash slopes (β) with the strip footing of width (B) 0.1 m located at different edge distances (De = 1B, 2B, 3B) from slope crest. These tests were conducted in the laboratory and the pressure-settlement behaviour of strip footing on unreinforced and reinforced fly ash slope having an angle of 45? was studied. The embedment ratio (Z/B = 0.30), and the depth of first layer of polyester geogrid reinforcement were investigated with different footing edge distances (De = 1B, 2B, 3B). From the experiment, pressure and settlements were measured and subsequently, the pressure settlement curves were drawn. It is observed from test results that the load carrying capacity is found to increase with an edge distance in both cases: unreinforced and reinforced slope. Also, a substantial increase is observed in the bearing capacity with the addition of geogrid reinforcement. It is observed that, the bearing capacity ratio (BCR) decreases with edge distance increase. These investigations demonstrate that both, the ultimate bearing capacity and settlement characteristics of the foundation, can be improved due to the inclusion of reinforcements within the fill.

Bearing Capacity and Settlement Characteristics of Sand Subgrades with Vertical Reinforcement Supporting a Square Footing

The restraining effects in the sand subgrade under the footing can be provided by inserting the vertical reinforcing bars beyond the footing base without disturbing the subgrade below the footing. This technique of soil reinforcement can be quite beneficial for the footings where improvement is necessary. This paper presents the results of model square footing tests with vertical reinforcements inserted into the sand subgrade beyond the footing base only. The variables selected for the investigation were spacing of vertical reinforcement, extent of reinforcement from the edge of footing, length of reinforcement, diameter of reinforcement, width of footing and surface characteristics of the reinforcement. The values of theoretical bearing capacity of reinforced sand subgrade were determined using the method of slices and compared with experimental results. It was found that results were comparable particularly when the length of reinforcement and extent of reinforcement were two times the footing width.