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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 Mark X. Haley

Foundation design and construction in Boston has changed dramatically during the past 10 years. Prior to 1985, the primary foundation element in Boston, where deep foundations are required, was driven end-bearing piles. Since 1985, drilled or excavated high capacity foundation elements have been utilized more frequently. This paper will provide a historic perspective of their use and a summary of design parameters for elements installed and founded in the bedrock. TOPOGRAPHY Boston was founded in 1630 by the Massachusetts Bay Company of John Winthrop and his hearty band of Puritans. The settlement was chosen for: ? its safe harbor, ? abundant source of fresh water, and ? peninsula setting offering protection of the ocean on almost all sides with high ground for fortification. These three factors were a direct result of past geologic processes that created the Boston Basin by erosion of the soft bedrock underlying this area as compared to the harder granite rock to the north, west and south. As the glacial ice sheets melted and moved northward, various soil types were deposited. During ice sheet re-advancement the hills and islands of Boston took on their precolonial shapes. The Trimont, consisting of Beacon, Mt. Vernon and Pemberton Hill, rose to 150 ft above sea level with the smaller Copps and Fort Hill to the north and south.

Jan 1, 1994

By Nuno Cruz, Saúl Rodríguez

"When executing offshore bored piles there are several specific factors and problems to consider in order to guarantee excavation stability. One of the methods employed to carry out this type of work consists in setting up a floating work platform, typically a barge, and implementing a soil stabilization system that combines a partial steel guiding casing with third generation polymeric drilling fluids. The main aspects to take into consideration when performing offshore pile boring works are soil stabilization, project design, work methodology and operational aspects. An example of a work methodology problem arises before any pile boring work takes place as the steel guiding casing contains water, sometimes salt water. What to do with this water in order to replace it by an adequate polymer fluid will determine the stabilization capacity as soon as the shaft advances below the protection of the casing. Another example of operational problem may derive from barge movements while executing boring activities. This study is the result of extensive field data collection and concrete logging analysis from marine projects using polymers in different continents. The bored pile stability target was set ranging between 2% to 15% of concrete overbreak. Values above 15% or below 2% mean that there is a stability problem. Then the off-target pile’s data is collected, analyzed and classified under categories. Thus, a direct correlation is established between the problem category and the final results. Modifying steps in the pre-established construction methods or operational variables guarantees target results without the need to replace the approved construction methods. As a general conclusion, the worldwide experience in large diameter marine works, allows to provide truthful information and solutions for these problems. In knowing how to follow a logical sequence of work and applying adequate work methodology will be the key for success.GENERALBackgroundTo carry out the drilling process of offshore bored piles there are two main options to take into consideration: drilling the pile by using full guiding casing until final depth; or using a combined system of partial steel guiding casing and support drilling fluids.The knowledge and situations described in this paper come from the experience acquired in different projects where the second method was employed. This construction method consists in installing a steel guiding casing by vibration and thus covering the water table and further stabilizing the soil below it with polymeric fluids until reaching the pile’s final depth. The Fig. 1 schematic shows an example of this method where H corresponds to the length of the steel guiding casing whereas the remainder of the shaft’s length is stabilized by polymer fluid. The entire bored length is full of slurry up to top of casing.In most cases this kind of civil works results from the need to build a bridge or executing port structures in places where the creation of temporary artificial peninsulas with fill material is impracticable or not allowed. Hence the need to use floating work platforms, commonly referred to as barges."

Jan 1, 2017

By Michael P. Balducci

Urban deep foundation projects contain unique risks that must be recognized by the parties involved. Common pitfalls must be recognized and avoided or addressed through contractual relations and corresponding insurance coverage. By understanding these pitfalls, examining the risk-apportioning clauses and corresponding insurance obligations, may the parties? desires and expectations be met.

Jan 1, 2008

By Li Huimin

In this paper the step of determining the property index and the program of mixture ratio design of stabilizing agent in deep foundation construction are presented. According to the principle of computer simulation, the model and the method of computer simulation for optimum mix design are set up. Also, the precision of simulation results has been estimated and verified experimentally.

Jan 1, 1991

Jan 1, 1985

By Mark M. Petersen

As part of the addition of eight new combined cycle generating units at the Florida Power & Light Sanford Plant, 2,129 piles were to be installed. The existing plant elements were supported on driven piles, and the variation in pile lengths during previous work, as well as available subsurface information, indicated a complex stratigraphy. At the request of the owner, the designer/construction manager developed a program to evaluate the use of pressure-grouted displacement piles. A pre-design load test program in areas that represented the apparent extremes in subsurface conditions indicated that the system was feasible; however, the presence of existing features that were to be demolished later precluded the clear delineation of subsurface conditions in advance of construction. A contract was negotiated with the pile installer based on the best estimate of potential pile lengths, with modifications to pile lengths to be set based on additional exploration. A total of 52 cone penetration soundings and five load tests were performed immediately prior to and during pile installation to establish correlations between the CPT data and pile performance. Pile depths were set based on these correlations. Pile installation was completed 6 weeks ahead of schedule and 15 percent under the original budget estimate. This paper documents the evaluation of pressure-grouted displacement piles as an emerging technology, and illustrates the benefits of a close working relationship between the owner, designer, and pile contractor at a site with variable subsurface conditions.

Jan 1, 2002

By W. D. Guo

With an experimental apparatus developed recently, model tests on piles were conducted in sand subjected to triangular soil movement profiles. Four instrumented piles tests are reported, which show the pile behavior predominantly determined by soil sliding depth. Axial load can create additional bending moment and pile deflection, which also make mode of pile-soil interaction change with sliding depth. Limiting resistance was found 1.5~3 times higher than currently used for laterally loaded piles in sand.

Jan 1, 2006

By Martin Pratt

This paper is an overview of deep foundation engineering in Hong Kong past, present and future. The enormity of the subject compared with the space available makes brevity inevitable. Issues of construction and design are covered and some examples of recent challenging projects are given. The content is aimed at those with an interest in foundations generally, but with limited knowledge of the Hong Kong scene. Reference is made to informative publications for further reading on specific topics.

Jan 1, 2000

By Richard A. Forth

During the construction of the Island Line (ISL) in Hong Kong between 1982 and 1986 piled foundations of a building were encountered in a tunnel drive. As the tunnel alignment could not be changed work was temporarily suspended whilst grouting took place beneath the pile cap. The tips of the piles were then cut off. The normal precast concrete lining segments were replaced by the "stiffer" spheroidal graphite iron segments and tunnelling resumed. Settlement of the building was found to be under 10 mm due to the tunnel drive and no damage was reported to the building.

Jan 1, 2002

By Nabil F. Ismael

The axial capacity of step tapered bored piles in sand was examined by field tests at one site in Kuwait. Two straight piles, and two step tapered piles were load tested in compression to failure. All four piles were 3 m deep. The straight piles were 0.2 m in diameter. The step tapered piles had a diameter of 0.3 m for the upper segment which extended up to 40% of the pile length changing to 0.2 m diameter for the lower section. The soil profile consists of medium to dense sand with minor cementation and no groundwater was encountered. Both the ultimate bearing capacity and the settlement at working loads were examined. The axial capacity of the step tapered piles was greater, and the settlement at working loads was less, compared with the straight shaft piles. The increase in capacity is mainly attributed to the added side friction along the larger diameter top segment of the shaft.

Jan 1, 2008

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

By Yu Zhenquan

At the construction site of Bao Shan Iron &. Steel Mill in Shanghai, lots of RC driven piles with length of 50 to 60m were applied. The most unfavourable distribution of stress along the pile shaft was known by measuring the compressive and tensive stresses. With analysing the test results a phenomenon of impact fatigue of RC pile was discovered, the range of impact fatigue and its critical zone can be distinguished. Finally some countermeasures are presented to avoid the impact fatigue of RC long pile.

Jan 1, 1991

By B. Sivarama Sarma, Biswabikash Rout

"Seepage control has to be achieved with plastic concrete cut-off diaphragm walls in dam structures. Materials selected for construction of cut-off walls must be durable, impermeable and have stiffness comparable to the surrounding soil.Plastic concrete provides a feasible and economical solution for construction of durable and impermeable cut off walls for dam structures. Plastic concrete wall should not be understood as a concrete wall with similar mechanical properties of concrete used in buildings, piles and spillways sections. Though it consists of the same materials as those of conventional concrete it has the major differences in end product due to predominant addition of bentonite slurry in the mix with very high water cement ratio. This makes the hardened concrete with very low compressive strength less than 5MPa and high failure deformations after the peak load.This technical paper examines a case study, the typical specifications on demand for construction and the issues corresponding to misunderstanding of the material as a structural grade concrete material. Conclusions were drawn based on a few project site quality data and trial mix experimental data. The anomalies in specifications on demand for construction of curtain wall in a dam structure were removed with modifications.INTRODUCTIONDiaphragm walls which are constructed in trenches made of plastic concrete basically serve the function of seepage control under confined measures. They should have the ability to sustain and undergo large plastic strains as compared to conventional concrete. The three basic mechanical properties of plastic concrete cut-off walls are to have least permeability, minimum strength to retain its shape and ability to undergo large deformations under confined loading conditions. The constituents of plastic concrete are cement, bentonite, coarse and fine aggregates, chemical additives to improve flow of concrete and sometimes to retard the setting time and water."

Jan 1, 2017

By M. Mets

Pile foundations have been used in Estonia since the beginning of 1960's. To evaluate the capacity of piles nearly 2,500 pile tests and 1,800 pile loading tests Have been carried out. The pile foundations of nearly 150 houses are under settlement observations.

Jan 1, 2000

By François G. Bernardeau

Cement-bentonite (C-B) slurry walls have been used for ground water cutoff in deep excavations, contamination containment, and other applications. Hydraulic conductivity is of great concern for cement-bentonite slurry walls. The quality control program usually specifies permeability and strength tests to be performed in a laboratory on samples cast in the field and cured for a certain time. Currently there is no widely accepted in-situ test method for the performance of the constructed slurry wall. A recently constructed cement-bentonite slurry wall in South Carolina included a 200-foot-long test section done in advance of the production of an 8,300 foot-long wall. Intensive tests and investigation were conducted during and after the test section construction: Monitoring piezometers were installed using wet insertion method and packer tests were conducted in boreholes drilled in the post-28-day-cure slurry wall. The permeability measured from the packer tests was about two orders of magnitude higher than the design and the laboratory test values. Additional investigation was performed using a video camera to inspect the borehole walls especially the packer test sections. Test pits were excavated to observe both sides of the cement-bentonite slurry wall. A thorough inspection was conducted to evaluate the integrity of the wall. The lessons learned and issues regarding the disturbance effects of in-situ testing of cement bentonite slurry walls is presented and discussed.

Jan 1, 2008

By Helen S. W. Chow

The use of piled raft foundations for tall buildings has been increasing in this decade as it is an economical alternative to conventional piled foundations. Piled rafts are composite structures comprised of the piles, raft and soil and so soil-structure interaction is important in computing the behaviour of the foundation. In this paper, the behaviour of piled rafts subjected to non-uniform loadings will be examined where the raft is supported by piles of different lengths. Finite layer techniques are used for the analysis of the horizontally layered soils and finite element techniques are used for the analysis of the raft and piles. This method accounts for the soil-structure interaction and the lateral resistance of the soil on the piles and raft. Results provided from the present method are compared with the results of a full 3D finite element analysis.

Jan 1, 2006

By Dhanaji S. Chavan, Thallak G. Sitharam

"It is well known that sites comprising of saturated loose sand undergoes large deformations, due to liquefaction, during seismic shaking. To cope with this, different mitigation techniques such as vibroflotation, deep dynamic compaction, compaction grouting, deep soil mixing etc. have been used in practice. However, as all these methods are costly, a new mitigation technique is required. Air injection has emerged as a new mitigation technique in which air is injected into the saturated loose sand. The introduced air makes the pore fluid mixture compressible and results into decrease in the generation of excess pore water pressure during seismic shaking. This paper reviews the laboratory and field studies performed to investigate the effect of air injection on liquefaction resistance. In addition to this, previous research in the direction of desaturation has evolved different techniques to generate gas in saturated sand. These techniques have also been discussed in the present paper. All the field and laboratory studies have shown that even a slight decrease in the degree of saturation increases the liquefaction resistance significantly.Keywords: desaturation, air injection, liquefaction resistance, pore pressureINTRODUCTIONEarthquake events in the past, caused liquefaction of loose saturated sands at many sites in the world. The consequence of liquefaction varied from small deformations to catastrophic failures such as flow slides, lateral spreading, sand boiling etc. (Kramer, 1996). To reduce the liquefaction potential of such soils, different mitigation techniques have emerged across the world. Some of the most widely used mitigation techniques are vibroflotation, deep dynamic compaction, compaction grouting and deep soil mixing (Idriss and Boulanger, 2008).Yoshimi et al. (1989) found that the liquefaction resistance of partially saturated sand is significantly higher than that of saturated loose sand. Further, Pietruszczak et al. (2003) proposed desaturation of the saturated loose sand as a new liquefaction mitigation technique. It is observed that the liquefaction resistance of sandy soil is enhanced significantly owing to the desaturation caused during construction of sand compaction piles (Ishihara et al. 2003). Over past few years research is being carried out on desaturation of sandy soil and its liquefaction resistance ( Ishihara et al. 2003; Okamura and Soga 2006; Yegian et al. 2006; Yegian et al. 2007; Takemura et al. 2009; Eseller-bayat et al. 2013; He et al. 2013; Marasini and Okamura 2015; Zeybek and Madabhushi 2016). As a result of this, different techniques of desaturation have also emerged. Different studies conducted in this direction and their outcome has been discussed in the section to follow."

Jan 1, 2017

By Liu Run, Jia Zhao-lin, Yan Shu-wang

"Piles with diameter larger than 2m in engineering can be defined as large diameter pile, and piles used for oil platform foundation in Bohai Gulf, are usually over 100m long and 2m in diameter. Such long piles have to be manufactured by segments before installation, because of transformation and hoisting difficulties. The segments of the pile are assembled by welding during installation one to another. Normally, assembling two pile segments takes one day or even a longer time, which mainly depends on construction conditions. After pile segment assembling, it proves to be difficult to restart the successive penetration. The mechanism of pile refusal is discussed and the process of driving a segmented pile is simulated with a finite element program. The calculating results show that, when the stick-up stability was satisfied, increasing the length of the last segment of the pile and assembling the pile segments when the pile tip penetrates into a clay layer could greatly ease the difficulty of driving the pile. Furthermore, cutting down the pile extension time is also one of the most effective measures to minimize the refusal risk.1. InstructionIn recent years, more and more oil platforms with six or eight legs have been adopted in Bohai Gulf, China. The leg piles with diameters of 2m or more have to be driven to about 100m below the sea bed. Such long piles have to be manufactured by segments before installation, because of transportation and hoisting difficulties. The segments of the pile will be assembled during installation, in which a successive segment will be attached to a formerly penetrated one by welding (Fig.1). The assembling work often takes one day or even a longer time."

Jan 1, 2014

By Robert Fernie

Demographics and Infrastructure demands have led to a significant increase in construction of: deep basements for buildings and, trough structures for Highway and Rail/Metro. Concrete embedded walls used for temporary works can be incorporated into permanent works and because of this (and geological conditions) tend to be favoured in UK. This paper considers British practice in the provision of diaphragm (slurry) walls secant (true and pseudo) piled walls contiguous piled walls Plant utilisation, construction techniques, reinforcement placement, connections, propping, water tightness, tolerances, general UK practices and their relation to design practices are discussed. [ ]

Jan 1, 2000