Behavior Of Foundations Research Articles

Seismic performance of group pile foundation with ground improvement during liquefaction

A pile foundation with ground improvement under the footing is a composite foundation with the objectives of enhancing the seismic performance and rationalizing the substructure by combining the pile foundation with ground improvement. Although the effectiveness of this method has been confirmed in previous studies for application to soft grounds, the applicability of this method to liquefiable grounds has yet to be fully investigated. In this study, therefore, centrifuge model tests and finite element analyses were conducted to clarify the effectiveness of this method and to ascertain the improvement in strength (stiffness) when the method is applied to a liquefiable ground. Firstly, in order to investigate the effect of an improved ground on the behavior of the pile foundation during liquefaction, dynamic centrifuge model tests were conducted for three cases with different strengths of the improved ground. Then, three-dimensional soil–water coupled finite element analyses of the centrifuge model experiments were performed to validate the applicability of the analytical method. After that, parametric studies, in which the strength of the improved ground and the input ground motion were changed, were conducted using the same analytical model. The results confirmed that the horizontal displacement of the pile heads was reduced by the improved ground even in the liquefiable ground, and that the effect of this reduction was more remarkable in cases of high stiffness of the improved ground. Furthermore, it was possible to reduce the bending moments at the pile heads by applying the ground improvement. However, since the bending moment at the boundary between the improved ground and the natural ground became the local maximum, there was an optimum stiffness of the ground improvement at which the maximum bending moment of the piles was reduced. This is because improving the ground around the pile heads has the same effect as extending the footing. It was thus concluded that the behavior of the pile foundation is similar to that of a composite foundation comprised of a caisson and group piles.

Experimental study on adfreezing strength at the interface between silt and concrete

The mechanical behavior of the interface between soil and structure is the key to determine freezing behaviors of pile foundations in cold regions. In order to explain the formation mechanisms of adfreezing strength at the soil-structure interface and explore its influencing factors and changing rules, orthogonal direct shear tests and orthogonal tensile tests were carried out under various conditions of moisture content, temperature, and dry density. Test data shows that: (a) The influence of moisture content and temperature on the shear and tensile strength is significant, while the influence of dry density is not. (b) The shear and tensile strength of the contact surface are positively correlated with the absolute value of the temperature and moisture content, but they exhibit different growth characteristics. (c) Under the same test conditions, when the tensile strength is less than 100 kPa, there is little difference in the shear and tensile strength of the contact surface. When the tensile strength exceeds 100 kPa, the tensile strength of the contact surface will be significantly greater than the shear strength. There is an exponential relationship between shear strength and tensile strength. Based on the experimental results, a bond-friction interface model which confirms the reliability of the model in simulating the mechanical behavior of the pile-soil interface is established. Research results clarify the mechanical behavior of the pile-soil interface at low temperatures, which can provide references for the interactive mechanisms of tapered pile-soil and the establishment of anti-freeze models.

Vertical Bearing Behavior of Monopod Caisson Foundation in Sandy Soils

Abstract This paper presents the results of numerical investigation on the vertical bearing behavior of monopod caisson foundations embedded in sandy soils and supporting offshore wind turbines. Th...

An Experimental Study on heave and Uplift Behaviour of Granular Pile Anchor Foundation System

Several innovative ground improvement techniques were presented by various researchers throughout the globe for modification of the existing poor soils. Granular Pile-Anchors (GPA) were found to be more promising in resisting the heave behavior of the expansive soils in recent times. The engineering behavior of the soil can be improved by this technique apart from resting the swell. This technique is a modification on the existing granular pile technique with an anchor plate beneath the granular pile that is connected to the foundation by means of an anchor rod or cable. Numerous scale model tests were discussed in this paper to understand the heave and pull-out behavior of Granular Pile-Anchor Foundation (GPAF) system. The effect of spacing was studied by using two granular piles at varied spacing. It was observed that the swell potential was reduced to about 68.09% for 50mm dia GPA, compared to the virgin expansive soil. The swell potential was found to be further reduced at twice the diameter of the pile spacing. The pull-out capacity was found to be increased by about 393% by providing a 50mm diameter GPA in the expansive soil.

A comparative study of bearing capacity of shallow footing under different loading conditions

ABSTRACT In the present study, the behaviour of a shallow rectangular foundation placed over the multiple layers of the geogrid reinforced sand under eccentric and oblique loads in both dimensions was studied. Various parameters were investigated in this study including the number of reinforced layers (N), eccentricity (e/B, e/L) and inclination of applied load (α). Bi-axial geogrid (Bx20/20)-reinforced sand and laboratory results were compared with PLAXIS 3D software keeping N, eccentricity ratios and angle of inclination as input parameters. The results present that the value of Ultimate Bearing Capacity (UBC) of model foundation found reduced as the axial eccentricity and inclination of applied loads increased. It also found that multiple geogrid-reinforced layers increased the UBC of about 75%. Finally, the model test results were analysed using PLAXIS 3D. A good agreement was originated between the laboratory results and numerical analysis.

Consolidation Characteristics and Bearing Behavior of Sand Pile Composite Foundation in Caisson Heightening

Consolidation Characteristics and Bearing Behavior of Sand Pile Composite Foundation in Caisson Heightening

Automated procedure to derive convex failure envelope formulations for circular surface foundations under six degrees of freedom loading

Failure envelope formulations are typically employed to assess the ultimate capacity of foundations under combined loading and for incorporation in macro-element models. However, the complex interaction between each load component, especially for six degree of freedom (6DoF) loading, means that determining satisfactory formulations is often a complex process. Previous researchers have identified this difficulty as an obstacle to the adoption of the failure envelope approach in foundation engineering applications. To address this issue, the paper describes a systematic procedure for deriving globally convex failure envelope formulations; the procedure is applied to a circular surface foundation, bearing on undrained clay, in 6DoF load space. The formulations are shown to closely represent the failure load combinations determined from finite element analyses for a variety of loading conditions, including non-planar horizontal-moment loading. An example macro-element model based on the proposed formulation is described; the macro-element model provides a close representation of the foundation behaviour determined from a separate finite element analysis. A key aspect of the paper is that it demonstrates an automated process to determine well-behaved failure envelope formulations. The automated nature of the process has considerable advantages over the manual procedures that have previously been employed to determine failure envelope formulations.

Numerical Modeling of Single Pile Behaviors Due to Groundwater Level Rising

Behaviors of the pile foundation due to groundwater level rising were analyzed by a series two-dimensional finite element analyses with fully coupled flow-deformation analysis. The different numerical models of single bore pile depth and diameter in Bangkok subsoil were represented with the parametric study. The pile–soil movement due to groundwater levels rising between numerical simulation and a previous experiment of the centrifuge test as the same condition are in good agreement. With rising groundwater level, the reduction of pile capacity can be evidently performed by the increase of pile settlement relative to soil surface. Moreover, the development of the plastic point captured by the finite element analysis revealed the mechanism behind the reduction of pile capacity. In this study, the evaluation of pile stability due to groundwater level rising for preliminary guidelines to protect existing structures are proposed.

Failure mechanism and lateral bearing capacity of monopile-friction wheel hybrid foundations in soft-over-stiff soil deposit

Experimental and numerical studies are carried out to explore the lateral load and moment resistance capacities of the monopile-friction wheel hybrid foundation in soft-over-stiff soil deposit. Model tests are firstly conducted to preliminarily investigate the soil failure mechanism of hybrid foundation under lateral eccentric load (lateral loading at a certain height above the seabed), which is followed by full model tests conducted to investigate the lateral load and moment resistance behaviors of the monopile-friction wheel hybrid foundation under static horizontal loading in soft-over-stiff soil deposit. A numerical model is then generated and validated with the laboratory testing results. Parametric study is performed to quantify the lateral bearing capacity of hybrid foundation in clay-over-sand soil deposits. Both the experimental tests and numerical simulations show that compared to conventional monopiles the hybrid system can provide a higher lateral bearing capacity and a larger lateral stiffness. The bearing capacity is found to be mainly influenced by the diameter of wheel D w, undrained shear strength of clay s u, loading eccentricity e and clay layer thickness T c. Finally, empirical design formulae are proposed to estimate the lateral bearing capacity of the monopile-friction wheel hybrid foundation system under static horizontal loading in soft-over-stiff soil deposit.

Effect of Existing Building Walls on the Geotechnical Behavior of Foundation under Earthquake Loading

— Structure’s systems are subjected to additional loads due to earthquakes that may be produces progressive failures. The building illustrates dissimilar categories of failure mechanism for the minor to major earthquake conditions. These structures categorized to the most susceptible type of building has experienced serious hazard or even full failure for the period of seismic activities, therefore their investigation is a complex thing to do. Consequently, this research aims at studying the behaviour of large-scale model of structures constructed with and without brick walls under seismic conditions. The effect of building walls on the performance of the structure during earthquake loading is investigated numerically using PLAXIS 3D software. An eight story building with basement designed on a mat foundation is simulated as three-dimensional model in case of brick walls existing and without brick walls case. The effect of existence such wall building on the stability of foundation soil system is discussed in the form of lateral, horizontal deformation, and foundation acceleration. The studied showed that the reduction of extreme horizontal displacement and bending moment for building foundation with brick walls reached to 43%, and 68% respectively compared to the building without walls. The consideration of wall as filling for super structure significantly reduce the foundation acceleration by as much as 72% of its initial value, which lead to considerable effect of increasing the foundation stability.

Effect of Existing Building Walls on the Geotechnical Behavior of Foundation under Earthquake Loading

— Structure’s systems are subjected to additional loads due to earthquakes that may be produces progressive failures. The building illustrates dissimilar categories of failure mechanism for the minor to major earthquake conditions. These structures categorized to the most susceptible type of building has experienced serious hazard or even full failure for the period of seismic activities, therefore their investigation is a complex thing to do. Consequently, this research aims at studying the behaviour of large-scale model of structures constructed with and without brick walls under seismic conditions. The effect of building walls on the performance of the structure during earthquake loading is investigated numerically using PLAXIS 3D software. An eight story building with basement designed on a mat foundation is simulated as three-dimensional model in case of brick walls existing and without brick walls case. The effect of existence such wall building on the stability of foundation soil system is discussed in the form of lateral, horizontal deformation, and foundation acceleration. The studied showed that the reduction of extreme horizontal displacement and bending moment for building foundation with brick walls reached to 43%, and 68% respectively compared to the building without walls. The consideration of wall as filling for super structure significantly reduce the foundation acceleration by as much as 72% of its initial value, which lead to considerable effect of increasing the foundation stability.

Experimental study on piled ring foundation resting on RDFS cushion overlying soft clay

The piled ring foundations offer an economic foundation system. Piled ring foundation systems can be used under structures like chimneys, OHRS, and towers. In this paper, an experimental study was carried out to understand the behavior of ring footing (with/without RDFS cushion) and piled ring foundation (with/without RDFS cushion) in soft clays. Total 57 model tests were carried out to comprehend the effect of parameters like variation of radii ratio of ring footing, spacing between piles, a diameter of pile, length to diameter ratio, RDFS cushion on the behavior of the piled ring foundations. The outcome of this study helped in understanding the effect of these factors on axial stiffness, load sharing, load improvement factor, and settlement reduction ratio. From the results of the experimental study, it was found that the ultimate load carrying capacity of the ring and piled ring foundation with RDFS cushion was significantly higher than that of ring footing and piled ring foundation without RDFS cushion. It was also observed that the behavior of ring footing with RDFS cushion resembles that of circular footing.

Thermal performance of seasonally, thermally-activated floating pile foundations in a cohesive medium

The thermal-activation of pile foundations for use within shallow geothermal energy systems has received much attention with a number of studies having reported full- and small-scale testing and/or numerical analysis. Various conditions in terms of pile type, ground profiles and thermal loading, have been considered in these studies, leading to a broad understanding of the thermo-mechanical behaviour of thermally-activated pile foundations. One area that requires further attention is the clarification of the foundation response under seasonal cyclic thermal loading. This study systematically assesses the impact of cyclic thermal loading in relation to the initial mechanical loading, for isolated floating piles and pile groups in a cohesive soil medium. For piles where the shaft resistance dominates the pile total resistance, it was found that irrecoverable movement will be small and thermal stress and pile head movements change in a cyclic and regular manner. It is shown that the effect of the coefficient of thermal expansion of the soil, is much reduced from that suggested in studies using constant thermal loads applied over long periods. The effect of the overlying building was explored and it is shown that thermal-activation of the pile foundation mitigates the effect of the imposition of a higher average temperature at the surface.

Load-settlement response of piled raft foundations in sand

ABSTRACT The load-settlement behaviour of piled raft foundations (PRFs) resting on sand subjected to vertical uniformly distributed load is studied using three-dimensional elasto-plastic finite element (FE) analyses. The unified Clay and Sand Model (CASM), based on the critical state soil mechanics, is used as the soil constitutive model. In the present study, 38 rectangular, strip, and circular raft connected to different pile configurations resting on four different types of sands in their loose, medium, and dense states are considered. The accuracy of the finite element analysis is confirmed through verification and validation with other numerical and experimental studies. A detailed parametric study is conducted, which includes soil elastic and critical state parameters as well as different dimensions of PRFs. A guideline chart is provided, which will be helpful for a design practitioner to choose the suitable PRF configurations considering serviceability limit states of safety and economical design aspect. This flow chart is based on (i) combined effects of various parameters on PRF load settlement behaviour, (ii) load sharing between the raft and the pile groups, and (iii) a preliminary cost analysis.

Studying the effects of negative skin friction on driven pile groups in Basrah governorate

The finite element method is used to simulating the behavior of deep foundations subjected to negative skin friction in Basrah soil. Pile groups are analyzed under dragforces using 3D Plaxis software. Linear elastic and Mohr–Coulomb constitutive relations are adopted for the pile and soil materials. Three sites are selected to perform the study, where the negative skin friction is developed due to fill loads. The dragforces on driven piles, within (3 x 3) square groups with spacing of (3B), are evaluated and compared to their counterparts of single piles. The dragforces are decreased on piles constituting the group, and the reduction depends on pile location within the group. Centeral piles exhibit maximum reductions of (50%). To study the effect of pile spacing, a range of [(3B) to (6B)] was adopted. Apart from pile location, it is concluded that, the dragforce is proportional to pile spacing.

A review on the effective use of Artificial Intelligence for the analysis of cyclic loading on pile foundation

A competent alternative approach to the conventional modelling techniques is artificial intelligence (AI). AI is about the computer science division that creates human intelligence machines and applications. AI-based solutions are great substitute where research is not feasible to evaluate engineering design parameters and therefore contribute to substantial human-time and effort savings in experiments. AI can also speed up the decision-making process, minimize errors and improve performance. AI can also make the decision-making process faster, reduce error rates and improve computing efficiency. Reinforced pile embankment is a useful technique used in soft soil construction, because of its advantages in reducing settlement, building time, and economic efficiency. The response of deep bottoms subjected to a uniform static surcharge was considered in most of the existing research. Very few researchers have studied the cyclical load effect or the effect of variation in depth. An experimental analysis was carried out on the impact of cyclical loading at a specific area of unreinforced and reinforced embankment of differing heights. During the initial stages of cyclical loading, soil arching, regardless of the height of the embankment, was adversely affected. However, the arching of the soil started to improve somewhat by increasing the number of cycles. The magnitude of the loads transferred to piles was increased by the reinforcement layers. But for a thinner embankment, the improvement was more obvious. The main purpose of this report is to identify the AI techniques that can be used to analyze the behaviors of pile foundation undergoing cyclic loading by making models which will help in testing different kinds of failure patterns and the solutions with which these problems can be mitigated.

Structural Design of Raft Foundation - A Case Study of Lucknow Region in Uttar Pradesh, India

In this age of rapid growth in population in India, there is a scarcity of land in prime locations, especially in metro cities of the country. To overcome this problem, we are moving towards vertical constriction. The main problem in moving towards vertical construction is the foundation system, if the foundation system in high-rise buildings is not planned and designed smartly and economically then there are different problems related to the foundation system that is going to arise, the soil in that area also plays a very important role in designing of the economical and stable foundation system. It is always beneficial to have a raft foundation on alluvial soil for high-rise buildings. But, however, it is a matter of great concern what foundation will be proposed on such types of natural soils or man-made refills. In this paper, an attempt has been made to design a raft foundation based on its geotechnical analysis. An extensive survey of research works devoted to studying the geotechnical parameters affecting the behavior of raft foundations is carried out with detailed experiments raft foundations are increasingly being recognized as an economical and effective foundation system for high-rise buildings. This paper sets out some principles of design for such foundations, including design for the geotechnical ultimate limit state, the structural ultimate limit state, and the serviceability limit state. Attention will be focused on the improvement in the foundation performance due to the raft being in contact with, and embedded within, the soil.

Numerical analysis and geomonitoring of behaviour of foundation of Abu-Dhabi Plaza in Nur-Sultan

In similarity to every civilization in history originated from the riverside, the city of Nur-Sultan, which the new capital of Kazakhstan developed around the Ishim River. During the last 25 years, many high-rise buildings supported by pile foundations are rising in Nur-Sultan. The paper presents the monitoring of development for the unique residential building of 310 m high with 4-story underground parking. The pile raft foundation (for block R) analyses had designed using Geocthenical soft, which can assess in precise of the deformations, occurs in soil. In the paper presidents, method monitoring raft foundations for block R, the height of this block R is 320 meters. Design of distributed fibre optic strain sensing system (DFOSS) has been employed for measuring the strain in civil engineering structures for over a decade. It is now harnessed worldwide for monitoring a wide range of structures slab pile foundation. Geotechnical monitoring data of adjacent building and utility systems settlement caused by the construction of presented high-rise buildings were compared to numerical modelling results, predicted, and permissible values.Finally, the raft foundation recommended for future high-rise buildings constructed of Nur-Sultan city on complex soils.

Simplified estimation of rotational stiffness of tripod foundation for offshore wind turbine under cyclic loadings

As the importance of safe and economical foundation design of offshore wind turbines has increased, suction bucket foundations have become increasingly common. A tripod suction bucket foundation consists of three individual buckets arranged in a triangular shape. The cyclic behaviour and soil-foundation-structure interaction of single suction bucket foundations has been a subject of active research. However, it is difficult to predict the behaviour of tripod bucket foundation because it is structurally complex and requires consideration of cyclic load effects. This study focuses on the behaviour of tripod suction foundations under cyclic loading. The rotational stiffness of the tripod foundation is estimated by combining equations depending on compression, pullout, and rotational stiffness of the single suction bucket with a series of centrifuge model test results. By presenting the theoretical stiffness values, it is verified that the rotational stiffness can be estimated only based on the cross-section of the foundation and the shear modulus of the soil. In addition, it is possible to predict the long-term rotational stiffness of the tripod by applying the vertical stiffness obtained from the cyclic loading test of the single bucket to the simplified method.

How US Private Foundations Change Payouts Based on Financial Shocks: Revealed Publicness or Revealed Privateness?

AbstractThis article asks what distribution behavior of private foundations in the United States reveals about their motivations and strategy. Do private foundations intentionally distribute additional money to grantees to help them manage through business cycles and maintain services during economic downturns? Such behavior would be consistent with revealed publicness with respect to distributions. Do they retrench during difficult economic times to protect their endowments? Or do they simply distribute money independent from the larger economy? The current study considers these conflicting expectations, and empirically tests whether private foundation distributions vary with endowment returns and the larger economy as suggested by competing theories. Using administrative data filed with the Internal Revenue Service, fixed effects regression models indicate that private foundations change distributions in a manner consistent with retrenchment or independently from the larger economy, depending on the sample used. The results do not support the notion that private foundations act with prosocial-countercyclical motivations about distributions—in which more money is distributed during economic downturns—despite their receiving significant public subsidies.