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By Y. C. Han

The advances in seismic design considering soil-structure interaction or soil-pile-structure interaction are described using a substructure approach. The nonlinearity of soil is considered approximately using a boundary zone model with non-reflective interface, and computer programs are available for practical applications. The validation of model is confirmed with dynamic tests on piles in the field, and the results for a single pile are used to compare with the predictions in this study. The liquefaction for sand soil layer can be accounted for, and a case of liquefaction is discussed. Two practical examples are examined, a vacuum tower structure supported on foundation of steel pile group and a table top structure supported on foundation of concrete pile group. To illustrate the effects of soil-pile-structure interaction on the seismic response of vacuum structure, different base conditions are considered, rigid base, i.e. no deformation of the foundation; linear soil-pile system; and nonlinear soil-pile system. The method introduced can be applied to the design of tall buildings, bridges, industrial structures and offshore platforms with soil-pile-structure interaction under seismic or dynamic loads.

Jan 1, 2010

By Yazn Khasawneh Ph. D. P. E., Will Tjaden, Spencer E. Ness P. E., Mohammed Nasim Ph. D. P. E.

Wind turbine components undergo many loading cycles during their operational life. Additionally, wind turbines may undergo extreme loading conditions from natural hazards, mechanical failures, or emergency stops. Current design practice for the foundations of wind turbines accounts for these complex loading conditions through a simplified pseudo-static approach based structural loading combinations. A rotational stiffness for the foundation is estimated from the pseudo-static analysis and then compared to an acceptable minimum rotational stiffness provided by the turbine manufacturer. These minimum rotational stiffnesses are based on dynamic analysis of the tower and nacelle system with the foundation represented as linear springs. This approach provides a reasonable approach to the foundation design but does not accurately capture the true dynamic performance of the entire soil-foundation-tower-nacelle system. This becomes especially important for pier-type foundations, which are being more commonly used to support modern and future generations of larger turbines. Additionally, the dynamic performance of the foundation will vary as the adjacent soil undergoes a large number of loading cycles of varying strain magnitudes. In this study, the full turbine-tower-foundation-soil system was modeled using finite element methods. An advanced non-linear soil constitutive model and dynamic loading time histories were used to investigate changes in stiffness of the soil, and the possible impact on the dynamic response of the system. Results were compared to conventional design methodologies with the goal of reducing foundation capital costs while avoiding increases in O&M costs and which can lower the LCOE of wind energy.

Oct 1, 2022

By Steven Dapp

A new hyperbolic model for generating P-Y curves is developed for use in lateral analyses of cemented soils (a ?C-F? soil with both cohesive intercept and friction angle), and includes degradation of the static loading soil response to model the effects of load cycling (repeated loading) with load cycle number. The p-y curves, for both static and cyclic loading, were derived from full-scale lateral test results conducted on a set of six drilled shafts in a loess deposit at the Kansas DOT test site. Values of the model parameters obtained from the load testing at this site are presented, as well as a discussion of the model parameters effect on the results such that the model may be rationally applied to other sites with C-F type soils. A step-by-step procedure is presented to illustrate the application of the model. Correlation of the model to the CPT cone tip resistance (qc) from CPT testing is made, as this was found to be the most reliable; However, the model is applicable to other methods, both in-situ and laboratory, of assessing the soils strength.

Jan 1, 2011

By Y. Duraisamy

This paper presents the compressibility of tropical peat reinforced with cylindrical cement column. When a cement column installed vertically in peat, its compressibility was reduced because of the hardened skeleton matrix formed by cement particles bonding with adjacent soil particles in the presence of pore water. The effects of diameter, number of columns and cement proportions in cement columns on the compressibility have been investigated in this study. The results indicated that compressibility index Cc and Ca decreased with the increase in diameter of the cement column. Specimens with 45 mm and 60 mm diameter of cement column were cured for 28 days, after which they were subjected to Rowe Cell Consolidation test. Based on the results obtained, it shows that cement columns can successfully reduce the compressibility of tropical peat.

Jan 1, 2007

By Mike Muchard

STATNAMIC load testing augmented with embedded instrumentation has been successfully used to obtain structural and geotechnical design information on large diameter spun cast concrete cylinder piles on many large marine construction projects. The paper focuses on one particularly interesting large marine project involving a new bridge to St. George Island, Florida where instrumentation and STATNAMIC load testing was used in conjunction with static load testing on high capacity piles. The information presented includes embedded instrumentation measurements taken during pile fabrication (post-tensioning), during pile driving, during static load testing, and STATNAMIC load testing. As much of this data is the first of its kind on concrete cylinder piles, it is exciting to present the foundation industry with this additional insight as to the behavior of this pile type and the accuracy of the methods used to test them.

Jan 1, 2005

By Seung-hoon Lee

The use of piled raft foundations has been considered as an economical alternative to conventional piled foundations because a portion of the applied load is carried by the raft in the design of piled raft foundation. In analyzing the behavior of a piled raft foundation as a settlement reducer, an accurate estimate of settlements of the system should be made on the basis of the understanding of nonlinear behavior of piles in layered soils as well as the interaction between the raft, soils, and piles. Although the 3-dimensional finite element method and simplified analysis methods have been used for the design of piled raft foundations, these methods were found to be inadequate for the practical purpose or could not consider the interactions properly. This study developed an approximate hybrid method of analysis to be used for the practical design of piled raft foundations considering pile-soil, raft-soil, pile-soil-pile and raft-soil-pile interactions. In the presented method of analysis, the settlements of the system are estimated satisfying the compatibility of two separate models which are the flexible raft model consisting of 2-dimensional finite elements supported by springs representing soils and piles, and the group-pile model embedded in layers of soil having different properties. Comparisons with other analytical methods as well as a 3-dimensional FEM program were made to verify the sufficient capabilities of the proposed hybrid model for application to practical design and analysis of piled raft foundations.

Jan 1, 2008

By Y. El-Mossallamy

The piled raft foundation was extensive applied in the last two decades in different soil conditions e.g. in soft to stiff clay as well as in medium to dense sand and even in highly weathered rock. The piled raft is now applied not only to control the foundation settlement but also to minimize the required raft thickness to reach the most economic foundation design. An innovative application of the piled raft is its special adjustment to cases of foundations with large load eccentricities or very different loaded parts of buildings to avoid the need of settlement joints, which are especially complex below ground water table. Recently, the piled raft is applied for foundations of highway and railway bridges with special serviceability requirements regarding the allowable total and differential settlement as well as tilting. Actually numerical analyses are the mostly used design methods for piled rafts. For all day design practice a simple and modest design method is highly needed -at least in the first design stage- to check the feasibility of the piled raft on the specific project conditions. In this paper, a general overview on the recent innovative applications of piled rafts in Germany will be presented in a short overview. The results of the simple design method will be discussed and compared with the results of more enhanced numerical methods.

Jan 1, 2006

? Hollow Stem Auger ? Drill Bits ? Leads/Torque Arm ? Hydraulic Gearbox ? Hydraulic Power Unit ? Grout Pump ? Crawler Crane

Jan 1, 2000

By P. Bermingham

A new approach to load testing of high capacity piles is presented. The method is mobile, inexpensive, repeatable and non-destructive allowing for multiple pile testing at a single site. A reaction mass is placed over a pressure chamber situated atop the pile to be tested. The test method is significant in that it can produce linearly increasing forces of high magnitude (over 5.0 MN) with durations of up to 80 milliseconds. This represents pulse durations an order of magnitude longer than achieved using a drop hammer. The accelerations the pile undergoes are less than one g, (conventional dynamic methods = 50 to 100 g). These effects combine to produce pile behaviour no longer dominated by the action of stress wave, instead the pile is under high levels of stress through its length during the force input. This is representative of the situation when static loads are applied, thus the method may be considered quasi-static. Further advances introduced with this method are that pile deflection and transmitted force are measured directly by means of a laser beam and load cell. This allows accurate correlation of event load displacement histories without the error associated with zero shift (acceleration integration) or non-homogeneous materials (strain measurement). The load displacement histories emulate those obtained for static load testing.

Jan 1, 1989

By C. Y. Liu

This paper principally deals with the application of caisson foundation in the Chinese bridge building industry, the different types of caisson foundation adopted, and their spheres of application. Caisson foundation has been used and speedily developed for bridge works in New China, and a number of new innovations have been made in its design. Especially in deep water foundation, the Nanjing Bridge over Changjiang has attained one of the deepest bridge foundations in the world. There are six types of deep caisson foundation being now in use in China, namely:

Jan 1, 2010

By Karl A. Higgins

In 1976, Prof. G. G. Meyerhof published a famous article in the Journal of Geotechnical Engineering titled ?Bearing Capacity and Settlement of Pile Foundations?. This article presents the authors opinions on calculating pile capacities in clays and sands, group capacities and pile settlement. A portion of the article presents correlations of shaft friction and end bearing to the Standard Penetration Test (SPT) N-value. Subsurface exploration via the Standard Penetration Test is the most widely used exploration tool in the United States, so correlations of pile capacity to N-value are significant to the practice of geotechnical engineering. Meyerhof?s SPT-N correlations are relatively simple calculations compared to other pile capacity computation methods presented in the article or found in other text books (such as the a-method, b-method, Nordlund, Vesic, Meyerhof?s semi-empirical, others) and therefore are popular amongst practicing geotechnical engineers. At the time these correlations were published by Prof. Meyerhof, utilization of dynamic testing with the Pile Driving Analyzer (PDA) was not widespread in geotechnical engineering practice. Prof. Meyerhof?s correlations appear to be based upon conventional static pile load testing of instrumented piles. Dynamic pile measurements to estimate a pile?s static capacity provides certain advantages over conventional static load testing, namely the determination of unit shaft friction values at discrete intervals along the pile, and the unit end bearing support value. The author has compiled a database of driven, displacement piles tested with dynamic methods (ref. ASTM D4945, Test Method for High-Strain Dynamic Testing of Piles). The data was collected between 2002-2010 and is comprised of displacement piles driven into coastal plain sediments in the mid-Atlantic states of Virginia, Maryland and the District of Columbia. In layered soils, dynamic testing in particularly helpful as it reveals the differences in unit shaft friction for varying soil types. One hundred ninety (190) piles are included in the database, with a corresponding 1,373 discrete shaft friction and 190 end (toe) bearing measurements. The pile type typically consisted of 12 and 14 inch square, prestressed, precast concrete piles; however, a significant number of piles were steel HP 12 or 14 inch sections. The database was sorted based upon soil type, and then correlations of shaft friction and end bearing were derived in the same or similar manner as Meyerhof?s original 1976 publication. The new correlations are compared to Meyerhof?s original values.

Jan 1, 2011

By Venda Oliveira P. J., Correia A. A. S., Danisi C. M.

"AbstractA laboratory study has been undertaken to establish common understanding of the creep phenomenon of a Portuguese soft soil chemically stabilised with binders. In order to study the effect of different stress levels on the strength and on the creep behavior of the stabilised soil, oedometer creep tests and unconfined compressive tests were performed at different curing times. Results show that the creep stress level does not influence the unconfined compressive strength. In addition, the creep phenomenon increases the unconfined compressive strength of the treated soil. Two different secondary compression indexes were recognized from the one-dimensional compression curve which increase with an exponential trend with the creep stress level.IntroductionConstruction on soft soils requires a mandatory soil stabilization work to improve mechanical characteristics of the natural soil. Deep mixing method is a worldwide employed ground improvement method, nevertheless the creep phenomenon hasn’t been yet thoroughly analyzed. Most of the published papers have focused on the analysis of the compressibility and the strength of the soil-binder mixtures without considering the creep phenomenon. However, numerical results (Venda Oliveira et al. 2009) have shown that although settlements that occur during the creep stage (namely creep strains) are less in case of treated columns, they are still important especially due to the high loads applied to the stabilised soil. The few published studies about creep behavior of soil-binder mixtures reveal that the stabilization of an organic soil with cement induces a reduction of creep deformations, which is related to the amount of cement used and that the increase of the organic matter of the soil has a negative impact on soil stabilization, further inducing a slight increase in the creep deformations (Venda Oliveira et al. 2012).As part of the current research the effect of different stress levels on the creep behavior of a soft clayey-silt soil was studied. The binder mixture used to enhance the properties of the soil had a specific composition and quantity. Unconfined compressive strength tests (UCS) and UCS creep tests were carried out at pre-set curing times in order to analyze the creep behavior of the soil-binder mixture. In particular five different creep stress levels were studied to understand its influence on the strength and on the compressibility of the stabilised soil. In addition, considerations about the secondary consolidation index are also presented."

Jan 1, 2014

By L. C. Reese

? Good construction and inspection presumed. ? Capacity-computation factors are independent of construction method. ? To account for variable or uncertain site conditions, anticipated construction problems, and/or minimal inspection, increase factor of safety. ? Conduct load tests and/or develop easily implemented design alternates (e.g., straight shaft in case bell can't be formed) to reduce factor of safety.

Jan 1, 1988

By R. J. Folic

Investigations of the vibrations of a pile in soil are performed on a dynamic model in the form of a prismatic bar of finite axial and flexural stifnesses with a discrete mass at its free end representing the cap. The soil is represented by a system of springs of constant and variable stiffnesses. Oscillation differential equations are derived by means of the Hamiltonian principle for non-conservative systems. The problem is reduced to a coupled system of two non-linear partial differential equations with corresponding initial-boundary conditions. Frequency equations of longitudinal and lateral linearized equations are formed. The paper determines natural frequenc­ies and oscillation modes. It separately examines longitudinal vibrations excitated by a hermonic force acting upon the pile cap, and lateral vibrations excitated by an impulse acting upon the cap. The results of the numerical processing are presented in respective diagrams in dimensionless form.

Jan 1, 2010

By JO Choi

Jet-grouting method is a useful technique to reinforce foundations on relatively soft or vulnerable soil layers such as fractured zone and stratum with cavities. Although jet-grouting has been widely applied to various field works, a reliable design standard has not been established yet. A number of model tests were performed to investigate end bearing behaviors of piles reinforced by jet-grouting. It was concluded that end bearing capacity was increased in proportion to uniaxial compressive strength of grout column. Based on the test results, the design criteria for the end bearing capacity were suggested.

Jan 1, 2006

By Andrew Malinak, William Perkins

Seattle’s Elliott Bay Seawall protects the 1½ miles of downtown waterfront between South Washington and Broad streets. The seawall supports the urban waterfront and infrastructure, including the Alaskan Way Viaduct and Alaskan Way, access to historic waterfront piers, and numerous essential buried utilities. Most of the original seawall was constructed between 1916 and 1936 over soft/loose non-engineered fill, estuary, and beach deposits. The majority of the original seawall was a pile-supported timber relieving platform that extended up to 60 feet behind the face of the wall (Figure 1). With maximum spacing between the timber piles of 3 to 5 feet, a virtual forest of timber piles were driven for the original wall.

Jan 1, 2018

By Carl D. Ealy

Work is being done to web enable the FHWA Deep foundation Load Test Database. Originally designed to function in the client server environment via modem, access to the database both for data maintenance and user queries has been upgraded to take advantage of the Internet and current and future information technology innovations. The DFLTD will be part of an Automated Geotechnical Information and Design Aid System, the object of which is to assist those involved with managing and maintaining our nation's highway infrastructure. The system will also meet the needs of university and other research institutions for a statistically meaningful source of high quality data for the development and verification of improved analysis methods, in-situ testing methods, etc.

Jan 1, 2002

By Luo Yang

A one-dimensional wave equation based algorithm for estimation of shaft and toe resistance of driven piles using High Strain Testing (HST) data is presented. The pile is represented by a uniform elastic bar, while the soil around the pile is assumed as a homogenized isotropic medium, and Smith model is adopted to represent soil-pile interaction in the wave equation analysis. In most cases, the displacement of pile particles along pile shaft is greater than recoverable soil deformation (i.e., soil quake in Smith model). Therefore, static shaft resistance could be reasonably assumed to be totally mobilized during pile driving. Smith damping factor is used to account for combined dynamic and rate effect. Force and velocity time histories measured at the pile head are used as input boundary conditions in an analytical solution of the one-dimensional wave equation. As a result, two unknown parameters, static shaft resistance and Smith damping factor, can be incorporated into the one-dimensional wave equation and determined analytically for the time duration prior to the first downward wave reaching the pile toe. Then, soil resistance and Smith damping factor at pile toe can be further determined. The advantage of the proposed analysis technique is that the Smith damping factor and the static soil resistance can be directly determined based on the closed-form solution of the one-dimensional wave equation, which is computationally efficient. Numerical examples are given to illustrate the use of the proposed method to determine the pertinent Smith model constants and the static resistances.

Jan 1, 2006

By I. Stanculescu

The consolidation of thick and very compressible soil deposits by stone columns associated with cast-in-place plain concrete columns, has been performed for shallow foundations of some heavy industrial structures. The reduction of settlements and increase of soil bearing capacity were thus ensured as a result of soft soil interaction with stone and concrete columns. The results of model tests and in situ large scale applications are presented. A calculation procedure is also suggested for foundation bases improved by the proposed method.

Jan 1, 2010

By Mostafa Mossaad, Ali Helwa, Manal Salem

Support of excavation (SOE) design practice tends to model SOE elements using two-dimensional (2D) analyses to avoid the complexity associated with three-dimensional (3D) analyses. Such practice overlooks soil arching in the horizontal plane and prevents designers from accounting for elements such as capping beams as part of the statical system. This study simulates square excavations supported by cantilever slurry walls in dry cohesionless soil using 2D and 3D finite element (FE) models. First, side support wall behavior is compared from 2D and 3D FE models for variable excavation length to depth (L/H) ratios. Second, the effect of slurry wall lateral bending stiffness on wall behavior is studied by modeling the wall using plate element with isotropic and anisotropic wall stiffness. Finally, the sensitivity of cantilever wall behavior to the presence of capping beam is illustrated. The study concludes that unbraced excavations with L/H ratios greater than 5 almost resemble plane-strain conditions. Slurry walls are better simulated in 3D FE models by dividing the plate element into discrete panels or by assigning anisotropic bending stiffness to the plate element. Finally, the presence of capping beam affects the behavior of cantilever walls resulting in reduction of deflections and redistribution of bending moments. INTRODCUTION Support of excavation (SOE) design practice ranges in complexity from conducting simple hand calculations to performing three dimensional numerical modeling depending on several factors among which is the geometry of the design problem. This paper addresses walls that are designed using numerical modeling, and discusses the factors governing the choice of the most suitable modeling approach. It has been believed for a while that modeling excavations using 2D numerical models would lead to a more conservative solution, which turned out to be incorrect in specific cases. This paper attempts to describe cases where 2D finite element modeling could be on the conservative side and other cases where it could be less conservative than the more complex 3D modeling.

Jan 1, 2018