Search Documents

By M. Nomura

This paper describes the results and field measurements of two long-term observation tests and two short-term loading tests to confirm the effectiveness of NF piles in reducing negative skin friction. All the test piles were equipped with strain gauges, allowing measurement of the compressive axial forces in the piles. These test results prove that NF piles are effective in reducing the negative skin friction to an insignificant value. Some examples of the design procedures used in Hong Kong and Japan are also presented.

Jan 1, 2010

By D. E. Sherwood

Twelve toe grouted, and eleven ungrouted piles, founded in very dense sands have been analysed to establish how toe grouting enhances pile performance. It is shown that pile stiffness is greatly increased, and that pile bases work effectively. This is in contrast to ungrouted piles, where some milli­meters of base movement may be required before the base is mobilised. Grouting appears to recover most of the disturbance caused during construc­tion, but in general does not enhance the ultimate bearing capacity of undisturbed ground.

Jan 1, 1989

"Boston’s Central Artery passes beneath nine active railroad tracks carrying commuter and Amtrak trains into South Station, the City's busiest rail terminal. These railroad operations had to remain in service throughout the construction of the “Big Dig”. The solution was to jack the tunnel under the tracks, rather than build the tunnel by more conventional means.Jacking of utility pipes is fairly common, but jacking boxes as big as a highway had never been done in North America, until the Big Dig came along.Soil freezing was decided upon as a means of stabilizing the soil under the tracks. This allows the tunnels to be jacked into place without soil caving when the soil is excavated at the leading face of the advancing tunnel boxes. Hundreds of pipes were driven into the ground between the tracks. Inside the steel pipes were smaller plastic pipes. A freezing plant near the railroad tracks pumped refrigerated brine into the inner plastic pipes. The brine ran out the bottom of the inner pipe, flowed up to the top inside the outer pipe, and was re-circulated to the freezing plant and back again into the ground. Over several weeks the circulating brine drew the heat out of the soil little by little, and froze the ground outward from the pipes. Soil FreezingThe plan required the construction of jacking pits in which the tunnel boxes could be constructed, and from which they could be jacked forward to their final locations, as described in the accompanying article. Once the jacking pit was built and the tunnel box constructed inside the pit, crews made an opening in the headwall of the pit to allow passage of the tunnel sections, excavated about three feet of the frozen soil, pushed the tunnel box ahead, and repeated the procedure again and again."

Jan 1, 2003

By Rouzbeh Vakili, Adel M. Hanna

"The application of piled raft foundations has significantly increased during the last few years. In this system, the raft and the pile group collectively transfer the applied building load to the underlying soil layers. Determination of load sharing between the raft and the piles derives the complexity of piled raft designs due to its multi-parameter nature. These parameters are but not limited to: soil density, pile length, pile spacing, raft geometry, and piles installation technique. This study is to examine experimentally the effect of sand density and pile installation techniques on the load sharing mechanism. Experimentally, tests were conducted on a square rigid raft with a single pile in sand under three different soil densities; 30%, 45%, and 60%. The experimental results are used to determine the pile and the raft shares in non-displacement and displacement piled raft systems. The results of this study reveal that soil density changes the load sharing of displacement piled raft; the pile share increases in higher soil density. However, this is not the case in non-displacement piled raft and load sharing is independent of soil density in working loads.IntroductionThe piled raft foundation is a combination of shallow and deep foundation which transfers the superstructure load to the soil by a complex soilstructure interaction. The interacting mechanism among foundation elements and their surrounding soil is illustrated schematically in Figure 1 and could be classified into two categories: (1) pile-soil-pile and (2) pile-soil-raft. The pile-soil-pile interaction is the same as the free standing pile group and is a function of pile spacing and pile installation method. Pile-soil-raft interaction, which only involves in piled raft foundation design, could be affected by: the length, spacing, and roughness of the pile, the rigidity and dimension of the cap, soil condition, and the pile installation method. Pile-soil-raft interaction could have favourable and unfavourable effects on bearing capacity and settlement, respectively. The pressure between the cap and the soil favourably increases the horizontal stress on the pile shaft and consequently increase the shaft resistance. Whereas, this pressure induces negative skin friction on the piles which increases the settlement. The pile-soil-raft interaction mainly controls the load sharing mechanism of piled raft foundation when pile spacing (S) is more than 3.5dp."

Jan 1, 2017

By Hector Simchas

"1. BENTONITE: THE CRUCIAL CONSTITUENT OF SLURRYSuspensions of bentonite and water are used in a variety of applications in underground engineering. For the construction of underground elements like slurry walls or piles, bentonite slurries offer support to the excavation of loose soils and counter pressure against hydrostatic pressure of ground water, especially where soil permeability is high. In addition, for the construction of tunnels by the slurry-shield method or when hydromills are used for excavation, bentonite suspensions transfer the loosened soil to the surface. In applications like pipe jacking and microtunneling, or where high revolution drilling is required, bentonite also provides lubrication and cooling.To fulfill these functions, the properties of a bentonite slurry need to remain stable, or at least predictable, during the course of construction. Unfortunately, when a suspension mixes with earth, ground water and/or impurities, its properties may be compromised resulting to reduced performance, which would in turn lead to increased construction costs and the risk of the excavation collapsing. Our experience in the lab and onsite is presented herewith.2. MOST USUAL FACTORS OF PERFORMANCE FAILUREWater and soil quality are important factors defining the behavior of suspensions. In an extensive program of measurements in our technical laboratory, the effect of frequently encountered harmful substances on bentonite suspensions has been examined and the results are summarised in Table 1.Some tests show that the conductivity of water has a direct relationship with Marsh Viscosity. For example, we have seen that if the quantity of bentonite required to achieve a 40s Marsh Time ranges between 50-52 kg/m3 at water conductivity below 100 µS/cm; when conductivity is increased to 1,400 µS/cm, we need 65-68 kg/m3 in order to achieve the same property."

Jan 1, 2015

By Jorj Osterberg

550 load tests of up to 150 MN have been completed on driven and bored piles using the Osterberg Load Cell. Because the test measures side shear and end bearing separately, much can be learned about the forces on the pile as it is loaded to ultimate capacity. At working loads side shear almost always far exceeds end bearing, with the distribution of shear and bearing greatly affected by disturbance occurring during drilling operations. Since much less movement is required to mobilize side shear than end bearing, most of the bearing develops after the working load is exceeded. Thus with insufficient bottom cleaning, safety against excessive settlement can be considerably reduced. Improved methods of drilling, hole cleaning, rebar cage installation and concrete placement are discussed. For rock socket piles it has been found that the ultimate test load far exceeds the working loads in most cases. This is almost always due to greater penetration into the rock than is required for adequate safety against excessive settlement. Factors affecting rock socket capacity are discussed. Increase of side shear and ultimate capacity with time is discussed. Case histories for driven and bored piles in soil and rock sockets are described.

Jan 1, 2001

By Z. Q. Bian

The wireline sampling originates from core drilling in rocks. The authors combined the wireline sampling technique with conventional undisturbed soil samplers, including Osterberg sampler, Denison sampler and double tube barrel, and then developed the wireline samplers of WPS, WSS and WSR models. These samplers are able to sample various soils. They reserve all the advantages of the original samplers, and moreover, they are noted with quick hoisting and lowering by wire rope. Therefore, it becomes an efficient new technique of sampling undisturbed soil from deep foundation.

Jan 1, 2010

By Makarand G. Khare

Though the phenomenon of dragload is known for many decades, there is a lack of clear guidelines to evaluate the amount of dragload. The development of dragload depends on relative movement between pile and surrounding soil which is a complex phenomenon and requires a detailed numerical analysis. Bitumen layer has been used in the past with varying degree of success in reducing the dragload but the reduction appears to depend on number of parameters. No procedure is available in literature to estimate the dragload when a slip layer is applied on pile surface. This paper investigates performance of two commercially available bituminous coats to reduce the negative skin friction on pile. Direct shear test apparatus was used to model the interface friction between soil and coated pile surface. The lower half of direct shear box was replaced with either a concrete block or a mild steel block representing pile surface. Two types of bituminous coats namely Shalikote and bitumen having penetration value of 30-40 were evaluated in this study. Shearing resistance of pile material-coat-soil is found to be influenced by normal stress, coat thickness, and rate of shear. Laboratory results are compared with published field data where coated and uncoated piles have been load tested.

Jan 1, 2006

By Mitsuhiro Shibazki

I can't answer that question but I am looking at Andy, my co-author, and he says we didn't measure it. No movement. If I understand it correctly, how do we handle lateral forces in shear? The main columns were designed as pin connections so there wasn't a moment in the shear between the pile cap and the columns the steel reinforcing was used to resist that. I am not aware of how we would have installed those, it is possible to try and submerge them all if the jet grout is still fluid. They were higher than design. You are correct.

Feb 10, 2003

By Arturo Ressi di Cervia

"The Construction of the Thrust Pits for Jacking of the I-90 Tunnel for the Central Artery/Tunnel Project (Part of Contract No. C09A4) in Boston MA was nominated for DFI’s 2002 Outstanding Project Award. In the judging, the project and the specialty subcontractor, Treviicos Corporation, was chosen for a Special Recognition Award. INTRODUCTIONBoston’s Big Dig, as the construction of the underground artery became known, is undoubtedly the largest urban construction project of this century.The Central Artery/Tunnel Project, or CA/T, to call it by its proper name, runs approximately eight miles through the heart of Boston, five miles of which are built underground while maintaining traffic on the elevated existing structure, while at its southern end I-90 is extended to Logan airport under active rail lines, Fort Point Channel and Boston Inner Harbor.Since the alignment of the road closely parallels the shoreline as it existed in colonial times, the cut and cover construction had to contend with substantial portions of filled ground, not to mention existing subway lines, live utilities, building foundations and, last but not least, the irritable Boston drivers and litigious adjacent property and business owners.Consequently, while it is impossible to single out the most difficult or challenging contract, the jacking of the tunnels of I-90 under the live rails of Amtrak certainly will rank high on the list.Never before, anywhere in the world, was an attempt made to jack tunnels of this size: the South Bay Interchange consists of three 78 feet (24 m) wide by 38 feet (11.6 m) high tunnels, the shortest of which is 167 feet (51 m) long. TECHNOLOGYIn order to achieve this engineering feat it was necessary to consolidate the soil under the track to prevent it from moving or settling during the jacking process. After a detailed analysis of the geological profile to be traversed it was decided that freezing was the most suitable method, since it could be applied to the full range of soils present on the proposed alignment."

Jan 3, 2003

By Prof. Dr. -Ing. habil. Sascha Henke, Johannes Beck

The growth of Building Information Modeling (BIM) during recent years opens possibilities for integrating new digitally driven design approaches. While parametric design and algorithmic design slowly gains popularity in numerous ACE-applications, e.g. bridge design, it is rarely used by geotechnical professionals. This article presents an approach for implementation of parametric design in the BIM-based geotechnical design process. The methodology is applied to pile design and enables a real time design analysis according to DIN EN 1997-1 and EA-Pfähle 2012 considering boundary conditions such as pile position and layout, pile geometry, soil stratification and soil properties. By using intelligent attributes and scripts to control, calculate and assign them, the design analysis is directly executed in the BIM-software environment, in this case Autodesk Revit with Dynamo. This BIM integrated design approach allows multi-criteria evaluations of pile designs using aspects such as costs, environmental impact or constructability in addition to the commonly examined structural analysis criteria. As the proposed models are fully parametric, generative optimization algorithms can be applied to identify the ideal design for the entirety and each of the piles. Finally, the potential and limits of this methodology with respect to modeling, analysis, simulation and optimization are discussed.

May 1, 2022

By A. Partos

It was decided to build a fourteen-storied office building over a six-storied garage and a four-storied office building. The high vertical and horizontal loads required foundations on rock approximately 18m below street level. Drilled piers (caissons) were selected. Eight caissons (1.98m diameter) were installed through the six-storied garage and four caissons from a temporary deck at the location of a former two-storied building. Excavations were done by the slurry method. Proof testing of rock was done before construction by test borings and during construction with a core barrel of small diameter. Quality control measures included telecommunications between ground crews and the equipment operator on the garage roof; records of field observations and testing of bentonite slurry and rock; and a continuous evaluation of all information. Instruments were installed in one caisson to monitor load distributions and curing of concrete.

Jan 1, 2010

By Ruth McKeown, Gilson de F. N. Gitirana, Murray Fredlund, HaiHua Lu

The current design standards for the use of anchors in slopes is based on two-dimensional (2D) limit equilibrium analyses. Anchors are considered as discrete loads and the 2D anchor, factored based on the spacing distance, corresponds to extending anchors indefinitely in the third dimension. A three-dimensional (3D) analysis offers a more realistic representation of the problem, including the true discrete nature of the anchor point loads. This paper explores the typical differences between analyzing anchors in 2D and 3D, using four typical conceptual models. Slopes with constant cross sections were shown to be adequately represented by the traditional 2D approach. The maximum difference between 2D and 3D models was 21% and becomes negligible for lower anchor spacing values, as expected. A slope with an external load was analyzed to evaluate critical slip surfaces with lower aspect ratios. Slip surfaces with lower aspect ratios presented higher edge effects that contributed to the stability of the slope. The results indicate that optimum design requires the 3D evaluation of field conditions inducing low aspect ratios, such as concave and convex surfaces, weak layers, and external loads. INTRODUCTION Slopes may be stabilized using a variety of solutions, including anchors. When performing an analysis, geotechnical engineers often follow the traditional two-dimensional (2D), Limit Equilibrium Method (LEM). It is important to understand the consequences and limitations of the assumptions on which the 2D LEM is based. There are numerous studies on anchors that show the importance of considering the actual three-dimensional field conditions. Desai et al. (1986) proposed a three-dimensional procedure based on the Finite Element Method and considering elastoplastic behavior and interface elements, to account for stress and displacement distributions, the relative motion between the anchors and the soil mass, and nonlinear soil behavior. Several important stabilization mechanisms were explained. The role of grout injection was evaluated in terms of the produced normal stresses along the anchor-soil bounding surface. The approach was shown to reproduce adequately experimental tests on a sand, proving realistic stress distributions around the anchor. Nonlinear soil behavior influenced to a large extend relative interface motions. Michalowski (1989) applied an upper-bound limit analysis in 3D to slope stability analyses. Anchors were not specifically considered in this study, but the consideration of locally loaded conditions shed light on important modeling aspects. The manner how the slide mechanism becomes three- dimensional as the slope is locally loaded was demonstrated. This emphasizes the fact that anchors should produce field conditions that require 3D analysis approaches.

Jan 1, 2019

By R. L. Wei

The disturbing influences of pile driving on the surrounding soil mass, including the induced vibration, pore pressure and displacement of soil, were observed during the construction of pile foundations. It is shown that the effects of pile driving in saturated soft clay are tremendous and ought to be concerned attentively.

Jan 1, 2010

By D. Vanni

Constructing new infrastructure in urban areas increasingly entails the use of sophisticated techniques for soil improvement in order to minimize surface disturbances in adjacent areas and damage to existing structures. In Naples, at the new Piazza Garibaldi subway station, TREVI built a 45 m deep shaft using a hydromill, and utilized soil freezing for the excavation of the four station's tunnels, fifty meter long, located approximately 30 meters below the water table. An innovative use of directional drilling was specially developed by TREVI to successfully complete this challenging job.

Jan 1, 2006

By X. L. Chen

The diaphragm walling has been recently adopted in one of the largest excavation of deep foundation engineerings in Shanghai, China with dimension of 90m in length, 50m in width and 13m in depth to solve its stability problem. In this paper the field test for monitoring the stability of the diaphragm wall is discribed, in which the excess pore water pressure and the horizontal displacement of the clay layers were monitored during the period of the excavation. The data measured in the field test are efficient for the safety during construction.

Jan 1, 2010

By Lawrence F. Johnsen, Marc J. Gallagher

"Micropiles are small diameter, bored, grouted-in-place piles incorporating steel casing and/or reinforcements. The omission of micropiles from most United States building codes has resulted in the application of varying standards for design and installation. The ADSC/DFI Micropile Committee has developed a proposed section for the 2006 edition of the International Building Code (IBC 2006) covering micropiles. The proposed IBC 2006 micropile code section is presented, along with comparisons to existing micropile codes and guidelines. A discussion section is provided to clarify sections of the proposed code. IntroductionMicropiles, defined as small diameter (typically less than 12 inches outer diameter), bored, grouted-in-place piles incorporating steel casing and/or reinforcements, are becoming common foundation elements for new construction, retrofits, and emergency repairs. Developed in Europe in the 1950's and used in United States practice since the late 1970's, micropiles are typically not addressed in building codes, particularly in the United States. As a result, micropiles are often reviewed by building officials to a variety of standards, including drilled shafts, caissons, cast-in-place bored piles, and concrete filled pipe piles. None of these adequately address the unique design and construction aspects of micropiles. Therefore, it became apparent to the foundation design and construction community that a micropile-specific code section was required.To that end, the International Association of Foundation Drilling and the Deep Foundations Institute (ADSC/DFI) Micropile Committee appointed a subcommittee in October 2003 to develop and submit a proposed micropile code section for the 2006 IBC. The subcommittee members included the two co-authors, as well as Tom Richards (Nicholson Construction Company), Tom Armour (DBM Contractors, Inc.), John Wolosick (Hayward Baker, Inc.), Allen Cadden (Schnabel Engineering) and Matt Niermann (Schnabel Foundation Company). At the time of the writing of this paper, the proposed code section has been presented at the IBC public hearing during which it was modified slightly. Final adoption (or rejection) will be determined by the IBC at the final action hearing in September 2005. The attached code section is the revised version following the public review hearings."

Jan 1, 2005

By Charles M. Wilk

"Mass stabilization (MS) is a ground improvement technique that can prepare areas of low bearing strength soil for subsequent infrastructure development. The technique involves mixing binding agents such as portland cement, fly ash, slag, or lime into the subject soil while the soil remains in-place (insitu). The binders “cement” the soil grains together to form a cement modified soil or a soil cement. The MS-treated area now has improved bearing capacity to support infrastructure or to prevent movement of the material such as landslides.The same insitu soil mixing technique can be used to address contaminated areas. Binders or reagents are mixed into soil. The treatment protects human health and the environment by immobilizing hazardous constituents within the treated material. When used for the purpose of environmental remediation the technology is called Insitu Solidification/Stabilization (ISS).Both Mass Stabilization and ISS treatments require laboratory studies to develop a mix design of soil and binder(s) that produce the desired physical and/or chemical properties. The mix design is then transferred into the field. Successful MS and ISS treatments rely on reproduction at full-scale of the mix design and the thorough mixing attained at laboratory scale. Fifty to 70% of the cost of a MS or ISS project is in the cost of the binding agent that is to be mixed into the subject soil. Under-dosing, overdosing, non-thorough mixing, and mixing in the wrong areas all create cost over-runs.This paper will discuss recent innovations in mass stabilization systems that improve the cost effectiveness of the treatment technology. Specialized equipment can impart greater mixing shear thus improving the thoroughness of mixing. Dry powder pressure feeders can conserve the “drying capacity” of binder resulting in higher strengths at lower binder dosages. Global Positioning System (GPS)-based systems can guide the mixing operator for complete mixing coverage. An integrated tracking and feeding system can record that proper dosing and mixing was accomplished and generate construction QA/QC reports for the client.INTRODUCTIONNew or expanding infrastructure projects may encounter areas of low bearing capacity soil or areas where marginal materials such as waste, dredged material, or sediment have been placed. Mass stabilization is a geotechnical method that can be used to improve the bearing capacity or stiffness of soil. Mass stabilization involves mixing binding agents into soil subject to treatment while the soil remains in-place or insitu.Mass stabilization technique can also address contaminated soil therefore, the same technique can be used to attain both civil and environmental engineering goals. In this environmental application the technology is known as insitu solidification/stabilization (ISS). ISS protects human health and the environment by immobilizing hazardous constituents within the treated material."

Jan 1, 2015

By Han Jie

The results of full scale plate load tests on stone columns on soft clay in coastal areas are presented in this paper. Four load tests were made, two of which were performed on the ground treated with stone columns, one on an isolated stone column and the last one on the untreated ground. For a given stress range, the settlement of the rigid plate, the stress concentration factor, and the excess pore water pressure were measured. It is found that the distribution of vertical stress beneath the rigid plate supported by the composite ground of stone columns is very different in shape from the one by the untreated ground, that the stress concentration factor has a relation with the stress level and time, that the stone columns increase the bearing capacity up to by 2 times, and that the ground stabilized by stone columns is of great advantage to keep the foundation stable.

Jan 1, 1991

By Ramin Motamed, Anna Panorska``, Joseph A. W. Toth

In this study, a dataset of 145 bi-directional and static load tests was used to evaluate the load-displacement response with respect to unit side resistance for drilled shafts comprising fully and partially mobilized data. A total of 612 unit side resistance curves were calculated which included 52 fully mobilized curves showing a maximum response. A new approach using the double tangent method, is proposed in calculating the maximum unit side resistance from partially mobilized load-displacement data. The double tangent method was applied to each load-displacement response to estimate the ratio of mobilized resistance between the intersecting tangents and peak measured resistance. It is observed that as the mobilization of side shear approaches a maximum, the ratio approaches unity. Using the fully mobilized curves, regression models were developed using correlations between ratios of estimated resistance at the double tangent, peak, and maximum measured responses. Regression models are evaluated for the following factors: predominant soil type and drilled shaft construction methods. Comparisons of calculated and measured maximum values of unit side resistance are compared for each model. Although these factors each influence the load-transfer behavior, a single global regression model including all the data showed promise in yielding accurate results.