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By F. Z. Suo

Baoahan Iron and Steel Complex is situated at lower beaches of the Yangtze River. The subsoils 50~70 M below the surface is a deposite of Yangtze River delta, consisting mainly of weak silty clay and loam, with low soil bearing capacity. Consequently, to build on such a weak soil a grant iron and steel integrated works weak soil improvement at the Complex, pile foundation is the effective type. It is estimated that at the first stage of Baoshan project 60,000 piles have been driven, of which 60% are steel pipe piles and 40% reinforced concrete piles. To provide reliable basis for pile foundation design, on-site loading tests were carried out for long reinforced concrete piles 27,45 60 M in length ,with strain gauges on the chief reinforcement of pile shaft and strain rod on pile tip. Based on loading tests, the paper discusses and analyses some issues, including determination of load transfer mechanism distribution of frictional resistance. Tests show that as far as long friction piles in soft clay are concerned, regardless of the properties of pile tip's bearing stratum, loads are mainly carried by shaft frictional resistance which it is effective to determine pile capacity in terms of P ~ S relationship.

Jan 1, 2010

By M. England

A method for the analysis and prediction of single pile displacement behaviour is described. It is the displacement in time, under constant load, based on the use of hyperbolic functions to characterise individual constituents of the displacement-time behaviour. Extensive use of this technique has confirmed its validity in a variety of soils and that consolidation and creep settlement appear to be indistinguishable. The algorithms employed are suitable to model the displacement behaviour from the onset of load to infinite time for all types of piles and surface foundations. Until the advent of computer controlled static load testing, analysis of the displacement-time characteristic during pile load tests has been hindered by the quality of the data recorded and inconsistency of loading. This has hitherto made the development of suitable behavioural models very difficult. Understanding the soil deformation within a proper time framework allows the subject of pile instrumentation and testing to be developed. The equipment required is basically a computer controlled loading and pile head displacement measuring system which allows accurate analysis of the settlement characteristic in almost every situation.

Jan 1, 1993

By Derrick D. Dasenbrock

Three piers of a new river bridge are supported on 1.067 m diameter open-end steel pipe piles. At time of drive, and after pile re-strikes, high-strain dynamic capacity values at plan tip elevations, were as low as 23% of design requirements. Pile lengths were extended 20% to 40% deeper than planned at two piers, driving to rock, impacting both the project cost and schedule. The significant discrepancy between predicted and observed capacity was investigated through a series of coordinated dynamic tests; a full-scale test pile was installed and monitored over 221 days by both dynamic and quasi-static methods. Unusually slow strength gains were observed by dynamic monitoring on all piles installed at the site. CPT soundings were advanced at the test pile and through the pile interior to investigate the soil plug. High-strain dynamic methods were found to have significant limitations in properly assessing the long-term capacity of large-diameter open-end pipe piles during driving and short-term pile re-strikes. As the benefits of large diameter high-capacity open-end pipe piles are numerous, the geotechnical community needs to address appropriate construction monitoring and control of these foundation types to take full advantage of these systems. An improved understanding of the physical effects of pile installation and the impact on soil strength assessment while driving and long term soil strength gain should be developed and incorporated into both design and monitoring procedures to avoid either unsafe or needlessly costly designs.

Jan 1, 2006

By Maurizio Siepi

The realisation of most of the civil engineering works is subordinate to the execution of consolidation works, in order to improve the soil physical-mechanics characteristics. The works classifiable with the term "Soil Improvement" can be realised using several technologies, among which the Deep Mixing Method is distinguished for his remarkable flexibility and productivity characteristics. The Deep Mixing Method is a process whereby a rotary drilling machine mechanically drills a constant diameter hole while cement slurry is injected into the soil at high pressure. The process combines state of the art construction techniques merging mechanical and hydraulic mixing energies at the tool bit. The result is a soil-cement column of engineered strength, consistency and dimension. Whereby the soil cement column formation process is controlled by a computerised device, the result is a speedy installation, thorough mixing, and a high degree of control, repeatability and documentation.

Jan 1, 2002

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 Sachihiko Tokunaga, Hirofumi Taguchi, Kenji Maruyama, Hidenori Takahashi, Yoshiyuki Morikawa

"Abstract The present study proposed a new liquefaction countermeasure to improve sandy ground and conducted a trial execution. The new method is a floating-type and lattice-shaped cement treatment method, where cement-treated soil is not fixed to a non-liquefiable stratum. A fixed structure such as treated soil should be formed at the side of the floating-type treated soil to reduce its lateral displacement. In the study, one-dimensional dynamic response analyses were first conducted to confirm the mechanism of the new method. Then, a series of centrifuge model tests were performed to demonstrate the effect under a stress condition at the prototype scale. The analyses and model tests confirmed the effect of the liquefaction countermeasure. Finally, trial executions were carried out to confirm high-quality vertical execution.INTRODUCTIONLiquefaction induced by an earthquake generates sand boiling and ground settlement. Other problems have also been reported, including a decrease in bearing capacity and an increase in the horizontal earth pressure against retaining walls. To prevent these problems caused by liquefaction of the ground, various countermeasures have been proposed, such as cement deep mixing and high-pressure jet mixing methods. These methods have the big advantage of being applicable to ground that contains soil with a fine-grain fraction. Furthermore, the unnecessary displacement caused by the construction can be reduced. In Japan, a lattice-shaped cement-treatment method has frequently been used at many construction sites to prevent liquefaction, where cement-treated piles are intersected to form a lattice, as shown in Fig. 1. The lattice-shaped walls can reduce the shear stress generated by an earthquake, restricting the liquefaction at that location. However, the construction cost of the cement treatment is relatively high compared to other methods such as the sand compaction pile (SCP) method, and needs to be reduced. In particular, the cost of the high-pressure jet mixing method, which can be applied to the liquefiable ground under existing structures, is significantly high. Therefore, decreasing the total volume of the cement treatment is necessary to reduce the construction cost."

Jan 1, 2014

By Fritz J. Klingler

From site demolition, to design, to construction, Detroit's new Tiger Stadium project is required to be completed within a short 2 ½ years from award of the design-build contract. Such extreme schedule requirements together with somewhat difficult ground conditions at the site, resulted in several challenges in the design and construction of the deep foundation system for the stadium. During the geotechnical investigation, an intermittent water bearing sand layer was encountered overlying the hardpan at the site. As a result, some concern developed regarding the potential for collapse of caisson bells within this layer, as well as the potential for flooding of the caissons during drilling. Although sand and/or ground water was encountered within about half of the caissons, standard drilling and belling methods were used, and adverse conditions were controlled in almost all cases through expeditious drilling, inspection and concreting of the caissons. This paper will present a summary of the ground conditions, design and specification requirements, and construction methods used to successfully install the caissons for this project.

Jan 1, 1999

By John N. Cunningham

Despite the wide use of micropiles for rehabilitating and retrofitting existing structures, little is known regarding the load-transfer distribution of grouted micropiles in various soil deposits. The rehabilitation of a concrete-frame warehouse in Portland, Oregon, required provisions for the seismic restraint of a new shear wall; the installation of two micropiles was specified to meet project requirements. The micropiles were uncased, 19-m (63-ft) long, 200-mm (8-in) nominal diameter, and reinforced full-length with a 64-mm (No. 20) diameter hardened steel threadbar. Due to space limitations, a sacrificial, instrumented micropile was installed near the two production piles to verify design assumptions. This paper describes the geologic setting of the project within the unsaturated Missoula Flood deposits, instrumentation, load-displacement behavior, load transfer, and Beta-coefficients for the sacrificial micropile.

Jan 1, 2011

By Bas R. Hemmen

GeoBrain is a facility at GeoDelft with the purpose to provide society with all relevant geo-engineering knowledge and experience in a structured way. On the basis of the available knowledge and experience engineers, decision makers and construction supervisors can come to a fast, reproducible and objective choice, taking into account the consequences. The paper presents examples from the GeoBrain experience databases and forecasting models developed for foundation engineering and directional drilling, or: "GeoBrain Foundations" and "GeoBrain Drilling". GeoBrain is closing the gap between theory and practice. It is aimed directly at reducing uncertainty and the costs of failure, thereby increasing the quality of profession and minimising the risk in geo-engineering works.

Jan 1, 2006

[ENGLISH active earth pressure adapter additive adhesion admixture, addition adsorbed water aggregate air air entrainment air hose allowable bearing value allowable pile bearing load]

Jan 1, 1994

By Michael J. Brown

It is often necessary to undertake some form of pile testing to verify design calculations. Historically this has been limited to static and dynamic tests. Newer rapid testing methods such as Statnamic are seeing more frequent use. This form of testing can be advantageous due to short set up time and test duration. Although the methodology suffers from a lack of formalised guidance and may prove difficult to analyse in certain soil conditions. This paper investigates the suitability of Statnamic testing and analysis for a range of soil and pile types as well as different installation methods through a number of case studies undertaken in the UK. Recommendations are made on test specification and analysis.

Jan 1, 2006

By M. Makarchian

Existing buildings sometimes experience excessive settlement under their design loads, or due to increased foundation loading, if a change of building use is required. One of the oldest and widely numerical study has been carried out of a simple idealised problem of an underpinned rigid circular foundation to better understand the behaviour of pile used for underpinning and load transfer mechanism from an existing foundation to the underpinning piles. The finite element method has been used for this analysis, with the soil treated as a two-phase elasto-plastic material. It is found that the effect of the length of the pile becomes more significant as pile length increases. As would be expected, the earlier the pile is installed, the less is the final settlement.

Jan 1, 1996

By Stan Merjan

Composite piles with precast concrete tapered pile tips (TPT Composite Piles - U.S. and foreign patents) are a new and important addition to the piling types available to the construction industry. TPT Piles were invented by Stanley Merjan, Vice President of Underpinning & Foundation Constructors, Inc.. U. F. C. installs these piles in the Northeast United States and licenses piling contractors in other parts of the country. TPT Piles have been developed for use in sandy subsoils at depths to 70 feet or greater. The TPT system (see Figure 1) is simple. A pile stem of conventional material (shell, pipe, steel, wood, precast concrete) is connected to a socket formed in a precast concrete tapered pile tip (TPT). This composite assembly is then driven as a unit by ordinary pile driving methods until adequate driving resistance (established by formula or load tests) is met in a suitable soil strata. This driving resistance develops from the displacement and densification produced by the TPT. Many combinations of tip shapes and stems are available to suit particular job requirements with respect to subsoil conditions and pile capacities. TPT Piles should be considered for use on a wide variety of jobs. The advantages offered by a TPT installation include: ? High capacity piles in marginal soils ? Minimal lengths required to produce these capacities ? The use of conventional pile driving equipment and procedures ? Pile inspection techniques that are the same as for ordinary pile driving Furthermore, TPT piles are economical due to a combination of a low cost per ton of pile capacity and high productivity, both of which lead to significant savings in foundation costs and time required to complete foundation work.

Jan 1, 1987

By H. F. Cowie

Britain's first pressurised water reactor (PWR) Nuclear Power Station is now under construction at Sizewell on the Suffolk coast. A linear cut-off wall was proposed to ensure that the drawdown of water to some 14m below sea level in the overlying sands during construction of the new power station would not affect the existing adjacent nuclear power station. The low permeability cut-off wall was constructed by diaphragm walling techniques by excavating a continuous deep trench supported by bentonite mud and then dis­placing the bentonite by a plastic concrete to form the "impermeable" membrane. The paper describes the automated digging apparatus ("Hydrofraise") with the extensive support facilities required to achieve completion within programme, control methods used to obtain the high vertical tolerances and the properties of the plastic concrete and the production plant used for its production.

Jan 1, 1989

By Hui Yongning

This paper presents a simulating test of constitutive relation of soil anchor in laboratory and puts forward a new plastoelastic mechanical model, on which a new calculating formula of elastic and plastic limit bearing capacity for soil anchor is suggested and two engineering projects verify that this method is adaptable.

Jan 1, 1991

By Chris D. Thompson

In Southern Ontario, Canada, piles are frequently driven through competent clayey soils to obtain end bearing on extremely dense till or bedrock. One reason for this is the difficulty at assessing the adhesion of the clayey soils. This is illustrated by texts, such as the Canadian Foundation Engineering Manual, which is the standard of practice in Canada, that indicate that theoretical analysis of the adhesion values of such soils are unreliable. In this paper, the results of high strain dynamic testing have been used to estimate the shaft resistance of 11 closed end pipe piles driven in overconsolidated very stiff to hard clayey tills at four sites by means of the CAPWAP wave equation analysis. More than twenty-five years of experience with bearing capacity predictions by such means have developed considerable confidence in its accuracy. The results were found to correlate reasonably with the average Standard Penetration Resistances of the clays at the sites. There was a linear relationship between an adhesion of 64 kPa at 20 blows per 300 mm and 192 kPa at 60 blows per 300 mm. At one site, 6 piles were tested and found to have a wide range of Standard Penetration Resistance and estimated adhesion in the same stratum. While there was significant scatter of the results, piles would have been safe at design loads obtained from the relationships established by the analysis carried out for this paper after applying appropriate factors of safety.

Jan 1, 2002

By Dilip Khatri

Helical pile anchors have gained acceptance over the past sixty years. Most recently they have been commonplace in the 20th century for the power utility industry in anchoring transmission towers, equipment platforms, street lighting, telephone poles, and radio tower applications. They have a strong proven industrial track record in these industries. As the cost of conventional deep pile foundations rises, the practical benefits of helical pile anchors becomes evident as a practical alternative. Noted for their uplift capacity, helical piles demonstrate equally strong compressive capacity as a structural foundation element. This paper summarizes the history, practical benefits, and technical requirements for helical piles. Significant structural testing has been completed at various universities. The practical benefits of these tests are discussed. One case example of proven performance is presented to demonstrate the advantages and disadvantages of helical pile anchors as suitable foundation elements.

Jan 1, 2003

By J. Nakayama

Construction of foundation piles or diaphragm walls through rocky or boulder containing formations has been long-standing difficulty. It has been widely understood that the down-the-hole hammer is the most capable mechanical means but is restricted in drilling diameter by the unavailability of drillhead sufficiently large diameter and the difficulty of disposal of cuttings. A great number of submersible motordrills have been used for the construction of cast-in-place piles and diaphragm walls and the reverse circulation system employed has demonstrated its advantage of the prompt removal of cuttings. The development of multi-head down-the-hole hammer drill combined with reverse circulation system presents a powerful engineering choice for those "hard-to-drill" ground formations. This paper will introduce the features of the system and some actual operation results in the foundation engineering through those hard rocky ground formation in some countries.

Jan 1, 1989

By Giuliana A. Zelada-Tumialan

Reduced workability and flowability of the concrete through the tremie tubes and drilled shaft reinforcement have been identified as the main causes of tremie-concrete drilled shaft concrete defects. This paper discusses two recent case studies of defective tremie-concrete drilled shafts. The defects (soft inclusions, aggregate segregation, and low concrete strength) were primarily caused by the combined effects of the tremie placing sequence, rapid concrete slump loss, and poor passing and blocking characteristics of the approved concrete mix design. The level of detail contained in the drilled shaft specifications varied between projects. However, even when the specifications incorporated several of the more recent recommendations for tremie-concrete placement, the case studies showed that typical provisions for concrete mix proportioning and placement can be further improved to minimize construction defects such as those described in this paper. Based on the findings of the case studies presented, recommendations for the development of more effective specifications are provided. The recommendations include requirements for mock-up testing of proposed concrete mix designs and evaluation of the tremie-concrete placement sequence. Performance of such testing and evaluation would greatly reduce the potential for drilled shaft defects and consequent time and financial burdens associated with them.

Jan 1, 2009

By Jason Weck, Alper Turan, Ali Chehadeh

"Rapid expansion of urban areas dictates the need to expand/rehabilitate the existing buried infrastructure at the same rate. The technical challenges such as variable soil and rock profiles, high groundwater tables and limitations imposed by the built environment combined with present fiscal and schedule limitations necessitates the implementation of fast and cost effective construction methods. Since drilling procedures and equipment allow the construction of overlapped pile systems in almost all subsurface conditions, the secant pile walls have become a cost-effective shoring option for such infrastructure expansion/rehabilitation projects. The secant pile walls constructed in a circular plan layout to form a vertical shaft provide unique advantages since they act as a compression ring. Secant pile walls require stringent drilling tolerances be achieved in order to provide structural support and to work as a compression ring in addition to a groundwater cut-off wall.This paper outlines design methodology, installation procedures and verification techniques used for the secant pile compression ring for the Waterloo Landfill Pumping Station No.2. The secant pile compression ring had a 6m inner diameter with over a 20m wall depth and over 18m excavation depth. The details of subsurface conditions, analytical and numerical methods used in design are presented here. The details of the monitoring system are introduced and results of monitoring are presented and compared with analytically estimated and numerically simulated quantities. The results presented in this study are considered to be of interest to those involved in design and construction of vertical circular shafts."

Jan 1, 2014