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By Wen-Chieh Cheng

Two bored piles with base grouting are loaded axially and the results are used to compare with numerical analyses. One compressive pile with a diameter of 2 meters is drilled through clay deposit and into bedrock to a depth of 13.7 meters. One tensile pile with a diameter of 1.5 meters is drilled through the same clay deposit and into bedrock to a depth of 17 meters. Both piles are installed with monitoring system such as rebar strain meters, concrete strain gauges and extensometers. The monitored data during pile load test are used to obtain average frictional stress (t) a displacement (z) curve, pile tip bearing (q) as well as pile head load (p) and a displacement (s) curve. FLAC3D is used to simulate the pile loading and base grouting. The soil and bedrock are modeled with Mohr-Coulomb. The parameters of the constitutive law are established from soil biaxial tests and rock bore hole deformation tests. The pile is assumed as an elastic body. The interface element is used to simulate the pile/soil interface and pile/rock interface. The numerical results are compared with the pile load test in terms of t-z curve, q-z curve and p-s curve. Finally, the pile base grouting is simulated and the uplift is analyzed. The result from this study is promising and the numerical modeling is successful.

Jan 1, 2006

By R. G. Shen

The relation curve of strain and acceleration is presented in this paper. The steel pipe pile of 609.6 mm in external diameter driven by IDH-45 diesel motor hammer on the esturial shoal of Yangtze River. The ultimate bearing capacity of pile is analyzed by one dimensional wave equation and the effect of computational parameters of the equation is discussed.

Jan 1, 2010

By Cassandra A. Wetzel

Rock socketed mini-piles are a desirable foundation alternative when design capacity is more than 40 tons and there is limited access. In this case history mini-piles were designed to support between 75 and 200 kips at 12 locations adjacent to a perimeter wall, a party wall and at cast iron column piers. Limited geotechnical information, low overhead clearance, and active building population tested the creativity of the team to get the piles installed. The key geotechnical concern during installation of the mini-piles was the presence of a glacial till layer above the bedrock surface that restricted the seating of the casing into bedrock with a track mounted drill rig. Soil loss during the advancement of the rock socket using an air hammer was excessive and increased the risk of subsidence. Over a three week period the engineer worked with the contractor to modify the design, means, methods, and materials to install piles with adequate load capacity. This paper will present the changes in design and construction methods that were required.

By Wei Zheng

A pulverized coal fired power plant is being built in Osceola, Arkansas, along the Mississippi River. The subsurface soil conditions consist of a certain amount of very soft clayey silt and clay underlain with a medium dense sand layer and a dense sand layer. The site has been raised four to five feet with fill material consisting of sand and gravel. Consolidation settlement due to the fill is expected to cause negative shaft resistance (downdrag) on the pile foundations. The site is located in a high seismic hazard area - the New Madrid Seismic Zone (NMSZ). The liquefaction analyses indicated that there is a high liquefaction potential in the medium dense sand layer. Load tests are needed to determine the shaft resistance and the end bearing of each soil layer for design purpose. Two types of pile foundations ? augered pressure grouted displacement pile (APGD) and partial augered pressure grouted displacement pile (P-APGD) were considered for this project. Ten pile load tests, including five compression tests and five tension tests, were performed for three different areas. Strain gauges were installed for the compression tests. The APGD and P-APGD piles were installed side by side for comparison. In addition, three additional dynamic tests were performed to supplement the information from the static load tests. Load deflection curves for the compression tests were predicted, and the failure loads were interpreted using four different methods. The shaft resistance and the end bearing were determined from the strain gauge data and were used to back calculate the ultimate capacity. The back-calculated capacities are in good agreement with the predicted failure loads; they were further verified with the tension load test results.

Jan 1, 2007

By Andrew Pontecorvo

The design of foundations for the tall buildings of lower Manhattan rely on the use of high capacity, rock anchors to resist overturning forces generated by lateral loads from wind, earth, water and, to a lesser degree, seismic forces. Once completed, the proposed towers at the World Trade Center (WTC) site will be among the tallest buildings in New York City. The towers are exposed to coastal winds and from several levels of below grade structure soil and water loads. The design loading required under the current New York City Building Code (NYCBC) is similar to the requirements of the building code used to design the original WTC Twin Towers. We will compare how rock anchors were deployed in the Twin Towers and how they are used in the new buildings. Changes to the building code are less significant that the changes to the design of the structure; that is how the outer skin or perimeter structure interacts with the building core. The result is a significant increase in the number of rock anchors required for the new buildings when compared to those installed in the original WTC Twin Towers.

Jan 1, 2011

By Osamu Taki

This paper presents the system, the strength of column, the design concept, and the applications with four case histories from the past project as the general aspect of Geo-Column (trade mark of single soil-cement column by SCC Technology, Inc.). In the system, it shows the installation process and drilling/mixing tool with the mixing process. In the design concept, it shows how to design Geo-Column against the vertical and horizontal load. Finally, it shows the applications with four case histories, (1) building mat foundation, (2) isolated foundation on the pedestrian bridge, (3) bridge spread footing and slope erosion control wall in the channel, and (4) cut-off wall and shoring wall in the underpass roadway to the railroad.

Jan 1, 2000

By Nuno Cruz

"The concrete overbreak estimation for bored piles provides the quantification of the shaft’s expansion beyond its theoretical volume. There are stability analysis methods that can be employed before and after concrete pour but as for the moment of decision, during pile cast, the most common method still consists in measuring the rising of the concrete level in order to compare its poured volume with the theoretical pile section volume. This is a determinant parameter to monitor, not only because it assesses the bored shaft stability but also because it represents a direct cost. When analyzing the estimation methods commonly applied on-site it becomes evident that these are often affected by human errors that lead to misleading results. The objective of this paper is to identify those errors and discuss a subject which is usually overlooked. As a general conclusion, it was ascertained that most errors derive from inaccurate volumetric data, working procedures and gauging equipment. By acknowledging these widespread practices deep foundations contractors will be in a better position to make informed decisions on how to correct and improve bored pile stability.GENERALBackgroundWhen executing bored piles, the estimation of its concrete overbreak allows a swift appraisal of the excavation stability during the drilling process. This is simply obtained from the proportion of the poured volume of concrete over the drilled shaft theoretical volume, as shown in equation [1].Where CO = concrete overbreak percentage, Vc = volume of poured concrete, Vr = pile’s theoretical volume. This calculation not only provides a general idea of the shaft’s expansion from its theoretical volume, but also the outline of the excavated column’s geometry. For the latter, the outline will be as accurate as the number of measurements taken for each partial known volume of poured concrete. This means that for each load placed inside the excavation there is a corresponding rising of the concrete level. The profile of the definite pile is then plotted (see Fig. 1) and allows inferring about how stable remained the shaft walls up to the moment of casting.The technological developments in this area have provided other methods for determining pile stability before and after pile cast, such as ultrasonic echo sensing, cross-hole sonic logging or thermal integrity profiling systems. Notwithstanding, concrete overbreak assessment remains as common practice and confers the advantage of providing stability information during the process of pile casting."

Jan 1, 2017

By D. V. Karandikar

Contiguous bored piles have been used in the past for retaining the sides of deep excavation. An innovative version of this method was adopted successfully in two prestigeous projects in Bombay in which in a very constricted and congested locality, adjoining seashore at Walkeshwar, 14 m deep excavations with vertical sides were required. 600 mm dia bored cast-in-situ piles were first installed at 1.2 m c/c and subsequently as the excavation proceeded, they were tied to cast-in-situ RCC waling beams. The shear connectors to the beams were pre-fixed to the pile reinforcing cage at specified depths. The pile / waling beam system was anchored into the ground by installing inclined prestressed cable anchors at the designed depths. The waling beams were also used to support the brickwalls, which formed the required backup wall for fixing the tiled water proofing system. Catch-drains were installed behind the brickwalls for relieving the ground water pressure and thus ensuring a very economic design. The adequacy of the system was proven in that where the system was not installed in time, failure of the sides occurred during monsoon. Whereas in the areas where the above retaining system was installed, there were no problems inspite of heavy monsoon and surcharge of construction materials and equipment. The system became a very effective and economic alternative to an anchored diaphragm wall. The paper presents the case studies of these two projects.

Jan 1, 1996

By Chu E. Ho

Jet grout column formation at large depths are prone to several uncertainties, such as inaccuracy in setting out boreholes, drilling deviation, soil variability and reduced jetting energy at the nozzle. This would result in shorter cutting distance of the jet, with potential lack of interlock between grouted columns. A design strategy for mitigating the risk should include a soil investigation program aimed at discovering potential variability in soil conditions at the locations of jetting. Determination of soil strength profiles with depth would be useful for evaluation of jetting parameters and prediction of the achievable cutting distance at any depth. Selection of design column spacing should include allowance for setting out accuracy, verticality of the boreholes and the achievable jet cutting distance. For deep jet grouting operations, it would be necessary to take into account the energy losses at the nozzle inlet; however the increase in the presiding pressure at the nozzle outlet at depth is small relative to the range of jetting pressures commonly employed and would not affect the cutting distance to any significant degree. Design column spacing should not be so close as to cause problems with ?masking? which may lead to localized ungrouted zones of soil. For effective field control, boreholes should be cased up to the top elevation of the grouted zone so that the orientation of the borehole can be measured prior to grout injection. An analytical equation for calculating the cutting distance is proposed for adjusting jetting parameters where necessary to compensate for drilling deviation and changes in soil conditions. It is preferable that jet grouting trials be executed at elevations that correspond to the actual production jet grouting depths for accurate evaluation of jet cutting performance.

Jan 1, 2008

By V. M. Troughton

Large diameter bored piles with grouted bases have been adopted for the foundations of the majority of the buildings at Canary Wharf in London's Docklands, including a deep basement car park. The piles are founded in the Thanet Sand which forms part of London's aquifer where water levels are reported to be slowly rising. A special pile test has been carried out to determine the effects of both the basement excavation and a possible long term rise in the groundwater level on the performance of base grouted piles. These effects were simulated by injecting water around the pile toe and thus reducing the vertical effective stress. In this paper the test layout and procedures are described and the results are presented. The test results showed that the reduction in pile base resistance under increased water pressures was less than predicted by conventional design methods based on vertical effective stress. The end bearing resistance was found to be proportional to the mean effective stress.

Jan 1, 1989

By Amalia Giannakou

This paper utilises 3-D finite-element modeling to study the static and dynamic lateral harmonic response of inclined piles, in a homogenous and a non-homogenous soil, modeled as a linear hysteretic medium. The results of a comprehensive parameter study are presented in the form of dimensionless plots of: (a) static and dynamic swaying and rocking stiffnesses and damping ratios, and (b) distribution of internal forces (bending moment, shear and axial force) with depth. These plots can be readily utilised in practical applications and they offer insight on the role of the inclination in the response of flexible piles.

Jan 1, 2006

By K. Viking

This article deals with some of the civil engineering related problems to be encountered when offshore wind energy projects transform from prototype offshore wind energy converter farms, developed and installed during the 1990's, to commercial farms that's currently planned to be built. The offshore wind energy converter (OWEC) installations encounter a wide range of problems, only partial of these are geotechnical. In Europe both onshore and offshore wind farms have, from a historical point of view, usually been founded by using the monopole technique, installed with traditional impact hammers, or by using gravitational foundations. However, the rapid development of bigger turbines and larger wind farms, together with increasing considerations of fatigue aspects, has lead to financial benefits of developing and exploring other foundation techniques. This paper reviews some Scandinavian experiences regarding critical components of the design phase in relation to connecting the superstructure to the ground, and some of the main considerations of how the loads applied to the structure are transferred to the surrounding soil. Keywords: Offshore Wind Turbines, Wind Farms, Foundation, Pile, Gravity Structures

Jan 1, 2005

By Harry K. Weatherbee

The paper presents a design case study for a four-story correction facility addition in south Boston, Massachusetts, supported on friction piles driven into the Boston Blue Clay. 356 mm (14-in.) square prestressed-precast (PSPC) concrete piles were selected as they were found more effective and economical. A static load test was performed where the pile was brought to "failure". The load test data were evaluated to estimate the Ultimate Pile Capacity as well as the Ultimate Unit Skin Friction (Adhesion) to serve as a design tool for friction pile projects in the south Boston Area.

Jan 1, 2003

By Brock Wallis, Steve Davidow

The following text will present the concept of rock socketed drilled shafts used to support electrical substation structures, and discuss the cost and schedule risks that traditional design responses to unforeseen shallow rock can pose to a project. Design considerations will be detailed, including rock characterization, shear strength of drilled shafts, and modeling lateral resistance of the shaft and surrounding rock. The specific case of drilled shafts installed for heavily loaded structures at the Moxie Freedom Substation will provide an example of how close collaboration between the engineer and contractor to refine designs based on site-specific feedback can provide tangible benefits to the project. In this example, value engineered designs resulted in an approximate 40% reduction in shaft/concrete volume and a 60% reduction in total rock socket depth. PROJECT OVERVIEW The Moxie Freedom Project included the construction of a new 500 kV switchyard in Berwick, Pennsylvania. The foundation contractor was selected to install both small and large diameter drilled shaft foundations to support the structures within the switchyard. The small diameter shafts were utilized to support transformers, switches, bus supports and a static mast, while the large diameter shafts were used to support one 180-foot monopole and six H-Frame structures. CHALLENGES: ROCK SOCKETED DRILLED SHAFTS Available geotechnical data at the time of bid included limited borings and seismic refraction. The borings were not located at every structure, and the contractor and design engineer were left to interpret desktop studies and geophysics to determine the probable site-specific conditions at each foundation. The data suggested substantial variability in the quality and depth to bedrock across the project area, indicating significant risk of deep embedment into bedrock at all seven large diameter shaft locations. Rock socketed drilled shafts pose unique challenges for both designers and contractors, and the topic has become a focus of national foundation organizations. Traditional design models result in deeper and/or larger diameter shafts where rock is encountered. In the case where site-specific geotechnical conditions are not clearly understood and rock is encountered at shallow depths, this can lead to significant additional rock drilling, impacting overall project cost and schedule. Rock drilling can result in more than ten times the cost of soil drilling and can easily take in excess of ten times longer to excavate.

Jan 1, 2018

By Ali Porbaha

The use of soil nailing technology as a cost effective alternative for excavation support and slope stabilization has substantially increased in the United States during the last decade. For example, in the past thirteen years, more than 185,800 square meters of soil nail walls have been constructed in California alone. The conventional soil nail systems pose difficulties when ground conditions are subject to caving, for instance for silty sand (sugar sand) or cobbles and boulders. The construction industry has developed self drilling hollow bar systems (or pressure injected bored, IBO) that combine both drilling, placing and grouting in a single operation as a solution to speed up construction. While the system is extensively used for temporary applications, nevertheless, some concerns, particularly about corrosion, has limited the use of this technology as a permanent system in North America. This study presents several issues related to self drilling soil nail systems, the results of a field investigation and a summary of the research project.

Jan 1, 2006

By G. R. Dasari

New Austrian Tunnelling Method (NATM) has been analysed by Finite Element method in two and three dimensions by Strain Dependant Modified Cam Clay (SDMCC) Model. The effects of construction sequence, stiffness of shotcrete and time dependency of shotcrete on surface settlement magnitude due to the NATM have been studied. Settlements obtained in 2D analysis, as expected, found to be more than the observations. The surface settlements obtained in 3D analysis found to be about 3 times less than equivalent plane strain analysis. This is due to mobilisation of soil strength around the tunnel face and soil-tunnel lining interaction. About 40% settlements occurred due to excavation of face at the monitor section and 60% after the excavation crossed monitor the section.

Jan 1, 1996

By S. Hardy

The paper describes state of the art non-linear analyses of the pile groups that were employed during the raising of the 133m high triumphal arch which forms the centre piece of the new Wembley stadium in North London. The deformation behaviour of these piles groups was critical during the lifting process, due to the slendemess of the arch structure. The issue was made more critical by the high profile nature of the project. The results of Class A (Lambe (1973)) predictions of the pile group movements are compared with observed displacements and rotations which were accurately measured on site. To illustrate the importance of soil non-linearity on pile group behaviour, comparison is also made with pile group analyses which assume a linear soil stiffness.

Jan 1, 2006

By M. B. Wechsler

An analysis is developed for determining the maximum loading, as well as the potential uplift of the piles on bridge pier foundations. There are considered piers supported on two through seven rows of piles, and related to two simply supported collinear superstructures of any structural material. The study leads to different types of influence lines for various load combinations. For load combinations containing vertical loads only, the related influence lines are similar to those as for the bending moments of a virtual span covering the two actual spans, as well as the gap between the two superstructures; and, in this case, the heavier loads should be positioned in the vicinity of the pier. While, in the case when vertical loads are acting together with hori­zontal forces, the related influence lines will indicate where the heavier live loads should be positioned. And they will also indicate on which portions of the spans the live load should be avoided.

Jan 1, 1989

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 Dipl. -Ing. (FH) Thomas Schmitt, Dr. Melvin England

Foundations in Geneva are difficult and expensive due a large overlayer of clay and silt above competent bearing material in the moraine. Common foundation schemes use deep barrettes or bored piles, first passing large, weak layers of soil before finally reaching acceptable, solid moraine with reasonable values of skin friction and end bearing resistance, thus requiring further deep penetration for the necessary length for load transfer in the moraine. Depths of more than 60 m (200 ft) in Geneva are common in this region. At the Onyx-Project Geneva Implenia Foundation Company also encountered these circumstances. Despite usual solutions Implenia referred to an old and well known, but still intelligent and in today’s words smart, efficient and economical solution. Using small shafts, passing the large layers of clay and silt, ending with the pile toe in the underlaying moraine with a belled or underreamed base was the technic adopted to save drilling time, reduce spoil and concrete, so finally reducing the CO2 footprint. Piles with enlarged base (“belled” or “underreamed”) are reported at the beginning of the 20th century, for example at Chicago, which has a quite similar geotechnical structure as Geneva with the need of deep foundations. The first pile base enlargements were built in hand-dug caissons with wood lagging and steel ring bracing. In the 50s and 60s piling works were more and more mechanized, driven by the development of more powerful cranes and specialized drill rigs. Additionally the first tools for mechanized base enlargement were invented around that period. This report describes the project situation at Geneva, the drilling and enlargement technique of the pile base, the verification of the design values with an in-situ bi-directional load test and the smart execution by reduction of CO2 and costs.

May 1, 2022