Foundation Load Research Articles

Prediction of the Nominal Side Resistance of Drilled Shafts in Dominantly Cohesive Soils using ANN

The conventional methods used in the design of drilled shafts might not fully consider the multiple sources of uncertainty in the soil such as the geometric and mechanical variability and/or the construction methods. These uncertainties can introduce nonlinearity to the analysis, leading to underestimation or overestimation of the resistance, which can be translated into expensive or even unsafe projects. Because of this, machine learning techniques such as artificial neural networks (ANNs), proven to be effective in solving nonlinear problems, are becoming popular in solving civil engineering problems. Therefore, the objective of this preliminary study is to evaluate a concept for predicting the nominal side resistance of drilled shafts with improved accuracy, using ANN. In this study, 45 load tests were collected from the extended version of the Nevada Deep Foundation Load Test Database and divided into 85% for training and 15% for testing. Then 1,638 ANN models were trained to determine the optimum model with a root-mean-squared error of 2,058 kips and an R-squared ( R2) of 85% on unseen load tests. The model was then benchmarked against the AASHTO predicted side resistance, with an average overall improvement of the prediction accuracy using ANN of 23%. This paper demonstrates that such models could be developed, improved, and used in the industry at an early stage and with limited data as supplemental tools that can help optimize designs in regard to construction safety, time, and cost.

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.

A Novel Calculate Model of Shear Deformation and Relative Displacement of Pile–Soil Interface in Warm Frozen Soil Foundation

In permafrost regions with warm frozen soil, the pile foundation is commonly used, but most currently available models for the WFS foundation pile–soil system are either highly empirical or overcomplicated, without a simplified theoretical manner in engineering. This study derives a novel and simplified calculated model of the WFS pile–soil system. The model is formulated in terms of the shear deformation theory and load transfer method based on the rigorous deformation mechanism of the WFS foundation soil around the pile. Considering the different depth soil features and the equilibrium state of the pile–soil system, dividing warm frozen soil foundation into three regions (TPPR, ER, and BPPR) to calculate the Dp and Ds can simply obtain the total displacement of pile under different loads. The results demonstrate that the present theoretical model can well predict the WFS foundation load–displacement response of the pile. The present model provides a simple, practical, and effective approach for the estimation of the load–displacement behavior of piles installed in the WFS foundation.

A Comparative Study on Load Assessment Methods for Offshore Wind Turbines Using a Simplified Method and OpenFAST Simulations

Simplified methods are often used for load estimations during the initial design of the foundations of offshore wind turbines (OWTs). However, the reliability of simplified methods for designing different OWTs needs to be studied. This paper provides a comparative study to evaluate the reliability of simplified approaches. The foundation loads are calculated for OWTs at the mudline level using a simplified approach and OpenFAST simulations and compared. Three OWTs, NREL 5 MW, DTU 10 MW, and IEA 15 MW, are used as reference models. An Extreme Turbulence Model wind load at a rated wind speed, combined with a 50-year Extreme Wave Height (EWH) and Extreme Operating Gust (EOG) wind load and a 1-year maximum wave height are used as the load combinations in this study. In addition, the extreme loads are calculated using both approaches for various metocean data from five different wind farms. Further, the pile penetration lengths calculated using the mudline loads via two methods are compared. The results show that the simplified method provides conservative results for the estimated loads compared to the OpenFAST results, where the extent of conservativism is studied. For example, the bending moment and shear force at the mudline using the simplified approach are 23% to 69% and 32% to 53% higher compared to the OpenFAST results, respectively. In addition, the results show that the simplified approach can be effectively used during the initial phases of monopile foundation design by using factors such as 1.5 and 2 for the shear force and bending moment, respectively.

Nonlinear analysis and design of high-strength concrete filled steel tubular columns under nonuniform fires

The main objective of this study is to investigate the behaviour of concrete-filled steel tubular (CFST) columns with ultra-high strength concrete (UHSC) and high strength steel (HSS) under fires through finite element method (FEM). High-strength materials can be used in CFST columns to reduce member dimensions, lowering material consumption and foundation loads. However, their fire behaviour has been insufficiently examined, especially under nonuniform fire exposure. In this study, thermal-structural models of the composite columns are developed using the SAFIR software. The numerical results are compared with published test data on temperature distribution, axial displacement, lateral displacement, failure modes and failure time. Then, parametric analyses are conducted to investigate the influence of various factors such as concrete strength, steel strength, different fire exposures, column length and load ratio on the fire performance of the CFST columns. In addition, the tabular design approach in European code EN1994–1-2 and Australian/New Zealand code AS/NZS 2327:2017 for designing uniformly exposed CFST columns is evaluated. It is observed that the prescribed design values in the table for R30 and R60 fire ratings under load ratio lower than 0.47 appear insufficient for the allowable slenderer columns. The applicability of the tabulated data for a load ratio up to 0.47 is further checked for the columns with UHSC of 120 MPa and HSS of 690 MPa, which is the strength limits recommended in AS/NZS 2327:2017.

A comparative study on the estimation of ultimate bearing capacity of rock masses using finite element and limit equilibrium methods

Most rock masses are excellent foundation materials due to their bearing capacities of MPa. However, the ultimate bearing capacity of rock masses should be accurately estimated in the design of structures with high foundation loads. In this study, the ultimate bearing capacities of a strip footing built on rock masses with different geotechnical properties are determined using the finite element method (FEM) and the failure criterion of Hoek & Brown. The results of FE-analyses are compared to those obtained from the limit equilibrium methods (LEM) in the literature. It has been shown that the FEM with associated flow rule and Terzaghi`s limit equilibrium method give similar failure surfaces for most cases, and the ratio of ultimate bearing capacities determined according to the Terzaghi´s method to FEM varies between 1.5 and 4. In cases, in which the failure surfaces obtained from both methods differ, this ratio can rise up to 11.aring capacities determined according to the Terzaghi´s method to FEM varies between 1.5 and 4. In cases, in which the failure surfaces obtained from both methods differ, this ratio can rise up to 11.

A Case Study for Stability Analysis of Toppling Slope under the Combined Action of Large Suspension Bridge Loads and Hydrodynamic Forces in a Large Reservoir Area

The foundation of a large river crossing bridge is often located on high and steep slopes in mountainous area, and the stability of the slope has a significant impact on the safety of the bridge. Not only the bridge load, but also the hydro-dynamical action in the reservoir area has a significant impact on the stability of the bank slope where the bridge foundation is located, especially for the toppling bank slope. This paper takes the stability of the toppling bank slope where the one major bridge foundation is located at on the Lancang River in China as an example. Through on-site exploration, drilling data and core conditions, and television images of the borehole, the geological structure of the on-site bank slope were conducted. Based on the development of the dumping body obtained from on-site exploration, corresponding indicators have been proposed from the perspectives of rock inclination, deformation, and rock quality to clarify the degree of dumping along the depth of the bank slope. The failure mechanism of the overturned bank slope under the action of a bridge was analyzed from a mechanical perspective. Numerical simulations were conducted using GeoStudio 2018:SEEP/W and FLAC3D 6.0 software to analyze the failure modes of bridge loads and hydrodynamic forces under different water levels and rainfall conditions. The seepage field characteristics, failure modes, and stability characteristics were analyzed from a two-dimensional perspective, while the displacement characteristics, plastic zone, and stress–strain characteristics were explored from a three-dimensional perspective, which revealed the evolution mode of overturned deformation under the action of bridge foundation loads. Finally, the stability of the wide slope was numerically calculated using the strength reduction method, and the stability calculation data was combined with the numerical simulation results to determine the optimal location of the bridge foundation.

Mobile application development for estimation of permissible load on shallow and deep foundation using SPT data

The present study demonstrates the development of an Android Application that aims to calculate the allowable bearing pressure for shallow foundations and safe load on pile foundations using the SPT data. The application was built using Android Studio 2020, utilizing XML for the User Interface and Java for the coding. The application offers support for various foundation types, including strip, square, rectangle, and circular shapes for shallow foundations and circular shape for pile foundations. The in-situ SPT data entered by the user was corrected and then processed to calculate soil properties. Subsequently, the bearing pressure for shallow foundation and safe load on the pile was computed adhering to relevant codes. The developed application was verified by comparing the results with already solved examples in the literature. The developed application may be considered under Intelligence in Geotechnics. The created application will be helpful for field engineers to estimate soil parameters and allowable bearing pressure on-site quickly. As a result, it decreases the amount of time and effort necessary for design and thus eliminates the need to refer to tables, codes, and consultants.

Non-contact model test and numerical simulation of plastic zone in sandy soil foundation

Reasonable determination of the ultimate bearing capacity of the foundation is of great significance in engineering applications. Based on the self-developed non-contact testing device for the plastic zone of shallow foundation, this paper carries out model test research on the plastic zone of sandy soil shallow foundation and analyzes the development law of plastic zone under the action of foundation load. The main advantages and functional characteristics of the foundation plastic zone test system are that it can realize the non-contact test of displacement deformation of soil, the dynamic development process of shear deformation, and the plastic zone of model foundation can be obtained intuitively. The development process, morphological boundary characteristics, and foundation failure mode of the plastic zone of the sand foundation are obtained. The plastic zone of the foundation starts from the edges of both sides of the bearing plate; with the increase of the load, the plastic zone gradually develops downward and approaches to the center line, and finally crosses through at the bottom until the local shear failure of the foundation occurs. The measured plastic zone is a symmetrical spindle shape with thin ends and a bulge in the middle; the sand on both sides of the bearing plate partially bulges, forming a “V” shaped shear failure zone, and the bottom of bearing plate forms a triangular compression zone, the foundation failure mode of sandy soil represents a typical punching shear failure mode. In order to study the distribution characteristics of the plastic zone range of foundation under different foundation loads and foundation widths, the Universal Distinct Element Code (UDEC) based on the discrete element method is used for numerical simulation research. By conducting parameterized numerical simulation test for the plastic zone of foundation and analyzing the results, with the changes in the foundation load and the foundation width, the variation law of (1) the depth of the plastic zone on the foundation bottom, (2) the width of the plastic zone on both sides of the foundation, (3) the ratio for the depth of plastic zone to the width of foundation, (4) the ratio for the width of plastic zone to the width of foundation and (5) the ratio for the width of plastic zone to the depth of plastic zone is obtained. The research has significant guiding significance for the study of the development law of plastic zone and foundation design.

Review of Jet Grouting Practice around the World

This paper aims to make a historical review of jet grouting techniques and encountered problems at different sites in several countries. This review is a good guide to understanding the performance and limitations of improved soils or lands. The basic concept of jet grouting technology is to use cement as a binder to accelerate the hardening process of an admixture of material grout and soil. The different case history was conducted in both sand soil and clay soil in the horizontal and vertical direction. Other papers on field construction showed that the grout can be gelled within 5-10 minutes. Due to different cases and studies, these will help improve soil by supporting the foundation load with a minimal settlement. The Jet grouting technology can be used in difficult situations, confined and unconfined areas, or places with light equipment. Although the jet grouting technique is an ideal modification technique compared to reinforcement and ground treatment support or serves the foundation, Dams and excavations will save time and cost and increase the bearing capacity.

Development of design typhoon profile for offshore wind turbine foundation design in Southern China

For offshore wind development in Southern China, typhoon represents the extreme environmental loading condition to be considered in the design of the turbine structures. For the geotechnical design of the foundations, it is specified by the design code that the effect of cyclic loading on the soil strength and stiffness must be considered. This necessitates the complete time history of loads on the foundation experienced during a design typhoon. Idealised storm profiles with staged mean wind speeds and significant wave heights are commonly used as input to time-domain simulations to generate the foundation load history. However, no such design typhoon profile is provided in the Chinese design standard which creates considerable difficulty and uncertainty in the design process. In this paper, the methodology and the rationale that were applied to derive the design typhoon profiles for an offshore wind project in Guangdong province are presented. The wind and wave characteristics generated by typhoon are described in detail and the implications for the foundation design are discussed. To demonstrate application of the proposed typhoon profile, a case study for the ULS design of a suction bucket jacket is presented.

Geotechnical considerations for assessing the life extension of offshore wind foundations

This paper describes the geotechnical considerations in assessing the fatigue lives of offshore wind foundations over their lifetime, including the potential for life extension.A case study is presented where a new analysis tool was used to reassess the fatigue lives of monopile foundations at a wind farm experiencing significant scour. Previous assessments using conventional modelling techniques for foundation loads and soil structure interaction predicted several locations with unacceptable fatigue lives.The fatigue reassessment was based on in-service loads calculated from an innovative monitoring system. The latest industry guidance for the geotechnical design of monopiles, as recommended by the PISA project, was used to predict the sub-mudline stiffness. Life reassessment was completed for all primary foundation steel circumferential welds in the wind farm including critical sub-mudline locations.The use of advanced soil structure modelling techniques, coupled with in-service load data and explicit modelling of scour effects, has enabled a more accurate assessment of fatigue lives. Fatigue life was demonstrated to be acceptable at all locations, with the potential for life extension. The relative effect on fatigue life of the improved geotechnical assessment and monitored loads was studied. This showed that both components were necessary to achieve the fatigue life targets.

Effect of structure-to-foundation mass ratio in analytical modeling of soil-foundation-structure interaction during earthquakes

The vertical factor of safety (FSv) of shallow foundations has been widely used for static design and seismic design. The FSv is a function of the bearing capacity of the system and the vertically applied load from the structure and foundation loads to the soil and foundation interface. However, the structure-to-foundation mass ratio (MR) can be different for the systems presenting the same FSv. The dynamic responses of the structure and foundation system depend on the MR as it develops dissimilar inertial behaviors from the structure and foundation. In this study, the effect of MR on the structure and foundation responses was evaluated using an analytical model that enables influence of the nonlinearity of the soil on the modeled foundation base and structure. For systems with the same FSv under identical input loading conditions, the inertial behavior of heavy foundations had a larger acceleration response than the lighter foundations. Consequently, MR should be considered for evaluating dynamic soil-foundation-structure interaction problems.

A predictive analytics model for designing deep underground foundations using artificial neural networks

Artificial neural networks (ANNs) are commonly used to solve nonlinear problems. ANNs are composed of parallel interconnected layers that include processing elements called neurons. These neurons use mathematical functions to process the data, mimicking the human brain. In this study, we use ANNs for designing deep underground supports. We develop a predictive model for the ultimate axial capacity of deep foundations called drilled shafts, commonly used as support for highways, bridges and high-rise buildings. Different single hidden layer ANN architectures are utilized to predict the ultimate axial capacity of drilled shafts. The data used in this study are load tests collected from the extended version of the Nevada Deep Foundation Load Test Database. This study focuses on certain difficulties in foundation engineering problems, such as the variability in the soil or construction method which, conventional methods might not fully address. This can sometimes lead to overestimation or underestimation of the capacity. Consequently, a project can be unsafe or expensive. Therefore, the objective of this study is to improve prediction accuracy which is important and can save design and construction costs and time. A total of 45 load tests were divided into 85% for training, and 15% for validation. The developed ANN model achieved good generalization and prediction accuracy with a Root Mean-Squared Error of 2807.08 Kilopounds force (kips), a Mean Absolute Error of 2380.6 kips, and an R-squared (R2) of 87% on unseen data. The results can be adapted in future studies and the industry as a first-order estimate for the architecture of an ANN predictive model and the ultimate nominal axial capacity of drilled shafts.

Evaluation of the Foundation Beds Liquidation by Using Soil Modeling for El-Burullus Power Plant Area, Kafr El-Sheikh, Egypt

In this study, the soil has been numerically modeled as the Mohr-Columb model because it is simple to capture essential features of soil behavior. Plaxis 2D software program has been used for modeling. The dynamic analyses depend on some data, such as grain size gradation for materials, stiffness and water level. This data has been used in the calculation process. Simple applications have been chosen to calculate the relations. The program computes entered data automatically. Earthquakes result in dynamic loading on soil which has a significant effect on the soil properties. The model is formed of five soil layers. Sands and mud deposits covered the area and Delta also. Some of the study results can be estimated by using the modeling method. The applied load value is 100 kN/m2. The amplification factor (S %) to the soil in the study area is 108 % when soil is without the foundation load and 150 % when soil with foundation load. Thus, the soil is classified as type – D (Moderate) and no liquefaction is expected in the results, but subduction or landslide, so piling foundations are recommended within the area of study. As well, numerical modeling is recommended in several locations in Egypt to obtain suitable areas for the foundation constructions.

The Plastic Zone of Clay under Foundation Load: an Experimental and Numerical Analysis

The Plastic Zone of Clay under Foundation Load: an Experimental and Numerical Analysis

Hygro-thermal vibration study of nanobeams on size-dependent visco-Pasternak foundation via stress-driven nonlocal theory in conjunction with two-variable shear deformation assumption

This article presents a hygro-thermal-damping vibration analysis of two-variable shear deformation beams supported by a visco-Pasternak foundation. In contrast to the majority of the literature on this subject, the hygro-thermal load, and external foundation are simultaneously presented as nonlocal, by employing the well-posed stress-driven local/nonlocal mixture formulation with a set of constitutive constraints. The Generalized Differential Quadrature Method (GDQM) is adopted to solve the complex eigenvalue problem at hand. In the numerical simulation section, we first conduct comparison studies to validate the accuracy of the present formulation and results. Then, a series of benchmark results for the vibration frequency of different bounded higher-order shear deformation beams supported by the elastic foundation are presented. Subsequently, the effects of simultaneously applying stress-driven nonlocal assumptions on the foundation and hygro-thermal load in the undamped and damping vibration of the shear deformation beams are examined.

Study of the Interaction between Regular Waves and a Wind-Fish Combined Structure

The combination of a wind turbine and fish cage (wind-fish) is able to solve the complex issue of power supply for deep-sea aquaculture. Nevertheless, the hydrodynamic coupling between the fish cage and the wind turbine foundation is increasingly complex, and there is little research on the related hydrodynamics. In this paper, the hydrodynamic research on the wind turbine foundation and fish cage structure is carried out using numerical simulation, in which the porous medium model is adopted to simulate the effects of the fish cage on the flow field. By analyzing the hydrodynamic characteristics of the combined structure of an offshore wind turbine and aquaculture cage under the action of regular waves, the load on both the cage in the combined structure and the wind turbine foundation, and the overall load on the combined structure of offshore wind turbine and cage are obtained. The effects of wave parameters, structural dimensions, cage submergence depth, and biological attachment on cage load, wind turbine foundation load, and overall load of the combined structure are analyzed. The results demonstrate that the wind turbine foundation is persistently the central part of the combined structure. The wave height, water depth, and degree of attachment of marine organisms all have different effects on the amplitude of the structural load. In contrast, the wave period, cage geometry, and cage submergence depth have no significant effects on the amplitude of the structural load. In addition to the water depth, other factors will affect the proportion of the load on the wind turbine foundation and the total load as well.

Linear Dynamic Analysis and Design of Raft Foundation considering Long-Term Deflection and Uplift Check

The Mat or Raft Foundations are widely used these days because we cannot use isolated footings and combined footings everywhere. As the spacing of the column is not uniform in the actual structures it may result in large uneven settlements at the base of the high-rise buildings. In a Mat foundation load from the superstructure is distributed evenly on the soil and uneven deflection is eliminated. Mat or raft foundation can be used with drops or without drops and with beams or without beams. For structures built on low-bearing capacity soil raft foundations, it is a good alternative as it reduces the settlement by distributing loads from super-structure to very large. In this study, the analysis and design of Mat Foundation for a G+7 story building are done by considering long-term deflection and uplift pressure accounts. For this study, Etabs v19.1.0 and Safe v20.0.0 software is used. The analysis is done by performing Response Spectrum Analysis or Linear Dynamic Analysis. After the analysis, results are collected in terms of short-term deflection, Uplift Pressure, long-term deflection, and punching shear and compared with permissible limits specified by the code IS 1904 (Part-1):1986. Results show that all values like deflection, uplift pressure and punching shear are under the permissible limits.

Observations on the Seismic Loading of Rigid Inclusions based on 3D Numerical Simulations

Rigid inclusions are increasingly being specified in seismic regions to transmit foundation loads to competent strata at depth due to their ability to provide excellent static performance and potential for cost-savings over other forms of ground improvement and/or deep foundations. Despite their widespread application in seismic regions, the seismic kinematic interaction of rigid inclusions is not well understood. This study presents a series of parametric numerical simulations specifically conducted to capture the kinematic soil-rigid inclusion interaction under seismic loading to identify key mechanisms that contribute to seismic performance. The effect of ground motion variability, area replacement ratio, surface crust thickness, embedment into a competent layer, liquefiable layer thickness, and steel reinforcement is systematically investigated. Although the rigid inclusion may not prevent liquefaction triggering, severe amplification associated with dilation spiking of transiently liquefied soil is mitigated and the onset of liquefaction delayed due to the soil-rigid inclusion interaction. The role of static arching to alter the geostatic stress state prior to and during shaking is shown to be responsible for significant and heretofore unknown coupled fluid-mechanical interaction that drives the performance of the rigid inclusion within the reinforced soil system. The kinematic flexural demand following the triggering of liquefaction and phase transformation associated with cyclic mobility is met through transient increases in axial load, which increases the confinement of the grout comprising the rigid inclusion, and therefore its moment capacity. The complex mechanisms identified in this work should be used to help identify which subsurface conditions may lead to responses, guide design decisions regarding selection of reinforcement and embedment, and provide a basis for assessments of the anticipated kinematic demands in view of the beneficial axial load-moment capacity interaction following soil liquefaction.