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By Gary M. Weinstein

Micropiles have seen increasing use for foundation support and slope stabilization applications over the past half century. Most often designed and installed in groups of vertical or battered elements or combinations thereof, continued applied research conducted through partnerships established between academia, government and industry has led to the recent development of practical engineering and design guidelines for such micropile systems. In contrast to a group of directly loaded micropiles, the micropile network relies on a three-dimensional array of reticulated elements to encompass and internally reinforce the soil, resulting in a network or "knot" effect. The potential for enhanced engineering behaviour of reticulated micropile network systems compared to that of a group of micropiles has been continually revealed by numerous researchers in the past. The concept is elementary - the roots of a tree interact with the soil to form a composite foundation capable of performance superior to that of the individual parts. However, given the large number of parameters which must be modelled and studied, experimental assessment and rational analysis of the soil-structure system has been difficult and therefore, in contrast to above, reliable design methods have not yet been forthcoming.

Jan 1, 2003

By Thomas M. Caruso

Construction of a new ship dock at a major Philadelphia area refinery required geotechnical design and field consultation. The new dock, which consists of a system of mooring dolphins and platforms, will be capable of docking the Stena V-MAX Oil Tanker (V-MAX). The 1100 ft long V-MAX is currently the largest tanker to travel the Delaware River and will induce significant lateral loads on the new ship dock. Lateral loads induced on the dock will be resisted by over 200 pipe piles installed on a batter. The piles used for support of the dock included 20 and 30 in. diameter reinforced, concrete filled pipe piles. Complete construction of each pile included driving of the pile to the design ultimate capacity, flushing the pipe pile casing clean of overburden materials followed by drilling rock sockets into the underlying Wissahickon Formation. Variations in depth to bedrock, rock quality and degree of weathering and presence of very hard quartzite lenses created a complex geologic environment that presented challenges for the pile/rock socket design and installation. The design of the pile system, installation methods, QA/QC and testing (Pile Dynamic Analysis), as well as the challenges that were encountered through the duration of the project are presented and discussed.

Jan 1, 2008

By Brunella Recinto

Pile loading tests are carried out with two main objectives: 1) evaluating the ultimate resistance; 2) checking the behaviour of the pile under live load. In the first case and particularly for large diameter bored piles the cost of a loading test may be very high. In the late '80s, a new method to perform static loading tests was proposed. It is based on the use of a sacrificial hydraulic jack placed at the pile toe. The device, internally pressurized, expanding applies an upward force on the pile shaft and an equal but opposite downward force on the soil beneath the pile toe. This device is well known as Osterberg's load cell, shortly O-cell. The obtained results are typically summarized in two separate load-movement curves: one for the shaft side shear resistance and another for the toe resistance. The two curves are used to build what is generally named the "equivalent head load-movement curve" relying upon two hypotheses: - the pile is rigid; - the load movement relationship for the shaft is not affected by the direction of movement. The former assumption can be easily removed, while it is not possible to remove the latter. On the validity of this latter hypothesis, comparisons between conventional head loading tests and toe loading tests could be very helpful. Unfortunately in the literature there are only a few case histories and most of them are also poorly documented. In order to explore limitations and potentialities of the new testing method, a finite element model has been set up. Results of simulations of conventional head loading tests and of O-cell tests are analyzed, discussed and compared.

Jan 1, 2003

By Wolfgang G. Brunner

In the far north of Uttar Pradesh Province in the Indian Himalayas, the 280 MW Dhauliganga hydroelectric power plant is under construction by National Hydroelectric Power Corporation (NHPC), a state- owned enterprise, and a joint venture of Kajima Corporation of Tokyo and Daewoo Corporation of Seoul. This project sets out to develop the lower section of the mountain cascade of the Dhauliganga River, a tributary of the Sarda River, with a 311 m gross head. The 1360 km2 mountainous catchment area is bounded in the north- east by the Chinese border and in the south- east by the Nepalese border. The dam project is located in a remote area north of the principal town of Darchula of the upper Sarda valley, which is one of the seismically most active regions of India. The 56 m high rock fill dam, which will be the first of its kind in India, is faced with concrete and has a 1 m thick, at its crown 270 m long and over 70 m deep cut- off wall of plastic concrete below its toe. The cut- off wall, with a total area of 7500 m2, is constructed by a combination of Bauer hydraulic grabs, assisted by chisels and a Bauer BC 40 cutter which enables the overlapping joint system to be installed, guarantees optimum verticality and enables the cut- off to be keyed into the bedrock formation.

Jan 1, 2004

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 Timothy C. Siegel, Paul J. Axtell

The Missouri Department of Transportation (MoDOT) recently replaced the Hurricane Deck Bridge that carries Highway 5 traffic across the Osage Arm of the Lake of the Ozarks in Camden County, Missouri. The former bridge was constructed in the 1920's and was supported on pneumatic caissons bearing on dolostone bedrock. The replacement structure is founded on drilled shafts socketed into the bedrock. During the design phase of this bid-build project, a baseline design was developed and Alternative Technical Concepts (ATC's) were allowed from approved contractors. Those ATC's were confidential and not shared between teams. Either the baseline design or the approved ATC design could be bid by the respective contractors. The baseline design included re-use of the 90-year old caisson foundations. Accordingly, an extensive evaluation of the caissons and underlying bedrock were conducted by coring, laboratory testing, acoustic tele-viewer (ATV), and cross-hole sonic logging (CSL) methods. The results of the investigation indicated the caissons were in excellent condition and suitable for re-use. However, a more cost-effective ATC was submitted, awarded, and constructed that did not re-use the existing caisson foundations but rather reduced the span lengths, increased the number of piers in the water, and supported those piers on drilled shafts. Interestingly, the difference in low bid price between the awarded ATC and the baseline design was less than one percent of the construction cost. This paper describes the multiple foundation designs that were necessary for this interesting project. The various foundation evaluations include the existing pneumatic caissons, large-diameter open-ended pipe piles to support the baseline design, and the design of rock-socketed drilled shafts that were successfully constructed in 2012.

Jan 1, 2017

By Farhad Elmi

In this paper, a new procedure is used to find the bearing capacity of single piles and cone penetration resistance in soils. Although the procedure is mainly applicable to clay and sand using any plasticity model, this paper deals only with steady penetration in Sand. Cylindrical cavity expansion around the probe in a calibration chamber is modeled by finite element method using the HUJEUX elasto-plastic multi-mechanism model. The penetration resistance (qc) is related to cylindrical cavity expansion pressure limit (pL) using the method of Salgado et al. (1997). This procedure is tested using the results found in 3S/IMG calibration chamber. In this article the word "penetrometer" refers to both pile and cone.

Jan 1, 2002

By Sherrill Gardner

Vibratory drivers have been used since the 1930s to drive and extract piles. Vibratory pile drivers have the capability of significantly decreasing pile installation time, especially in granular type soils. However, they have not been widely accepted because of the uncertainty in estimating the bearing capacity of the driven pile. When driving bearing piles, the industry standard method for obtaining load carrying capacity of a pile installed with a vibratory driver is to redrive with an impact hammer. The advantage of improved productivity is lost with the redrive procedure. Currently, there is no other method to predict the capacity of these bearing piles installed with a vibratory driver. The Naval Civil Engineering Laboratory (NCEL) is making progress towards being able to estimate the bearing capacity of these piles. This paper describes field testing and corresponding analytical modeling of the vibratory driver-pile-soil system. The following sections describe the development of the numerical model and techniques for collecting field data. A discussion of the prediction of the pile driving process based on field test data is followed by suggestions as to the additional work that should be done to further verify the model to a point where it can be used with confidence.

Jan 1, 1987

By E. Ulrich Klotz

It is difficult to predict accurately the capacity of driven piles in sand. In practice, this uncer­tainty either leads to conservative designs if the capacity is under-predicted, or worse, if the capacity is over-predicted, it can lead to severe foundation problems. One significant possible cause of the problem is that currently available semi-empirical design methods do not capture the fundamental mechanisms that govern the load capacity of driven piles in sands. As part of a recent research project at City University centrifuge tests on a driven model pile in sands have been undertaken. A fully instrumented model pile was constructed and pushed into samples of quartz and carbonate sand thus covering a wide range of mineralogies. Tri-axial tests were used to determine the fundamental patterns of behavior of the sands. This allowed a general framework to be established, in which the in situ stress:volume relationship is shown to govern the capacity of the pile. The paper sets out with a brief introduction of the experimental techniques used in the study. The results of the pile tests are discussed in detail with particular attention given to distribution of the radial stresses along the pile shaft. Existing design methods for piles in sand are then discussed in the light of the new understanding gained from the research, highlighting their deficiencies and suggesting an improved approach.

Jan 1, 2002

By Frank Rausche

Although Quality Control (QC) during construction is preferable for deep foundations, there are many instances when it is necessary to resort to Quality Assurance (QA) methods if, for various reasons, QC is not possible. Non Destructive Testing (NDT) methods for deep foundations are indirect approaches, i.e. in complex situations they do not provide complete information and need to be augmented by additional testing and/or analyses. While the challenges are varied for the different deep foundation types and the different test methods they are the same in many different countries. Experience of the tester is often mentioned as being most important for a successful quality assurance. In addition, reliable testing equipment for the best possible measurements and complete construction documentation for a meaningful data interpretation are minimum requirements for a successful test outcome. Another problem is the widely varying cost of the QA tests. For that reason the specifying engineer or authority has to be aware of what can reasonably be expected so that technically feasible specifications can be written for optimal cost and minimal construction delays. This paper discusses the most common NDT methods with a view on how these methods are applied world wide. It summarizes features of specifications, recommendations for test procedures and advanced analysis methods which can help to overcome uncertainty in the quality assessment of the foundation. Finally, the authors propose a decision tree for various QA methods, deep foundation types and soil properties.

Jan 1, 2008

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 Dhanvin B. Mehta

Pile testing is generally understood as static load test. It is our common experience that for high capacity, large diameter bored piles, static testing is expensive and time consuming. It is practically impossible to test large number of piles by traditional testing methods. The escalating cost in carrying out a static load test, as well as incomplete information derived therefrom compelled researchers in United States to look for an alternative method of testing for both bored and driven piles. The original research work was carried out at Case Western Reserve University in early 70's, under the funding of Federal Highway Administration as well as several State Depts. of transportation in United States. The outcome of the research was the development of a state of art field computer for capacity determination, based onOne Dimensional Wave Mechanics.

Jan 1, 1996

By H. R. Taber

The extensive subject area "Engineering Practice of Ground Improvement" will be treated within the limitations of space and the writer on the basis of personal practice and experience?largely in Northern California over a period of some thirty-six years and, in "ground improvement" work, with an emphasis on transportation facilities. The stress is on improvement of ground conditions, rather than on techniques of improving inherent earth materials characteristics. "Ground improvement" is discussed as engineering resolution of existing or emergent earth materials defects or deficiencies?that is, as the technically feasible procedures best adapted to achieving a required level of service within physical, economic, social and other constraints. A "required level of service" concept is presented as a tool in evaluation of appropriate ground improvement work.

Jan 1, 2010

By F. M. Abdrabbo

Flight auger bored piles are formed by screwing a continuous flight auger into the ground, and pumping cement/sand grout or concrete down the hollow stem of the auger as its withdrawn. The auger is driven at the top by hydraulic or electrical motor and is guided by a vertical crane leader. Loading tests on concrete piles are described. The stability plot method is used to drive the shaft friction and the end bearing load components of the pile capacity. This paper outlines features of crucial construction factors that affect the geotechnical capacity of this type of piles. These factors include, vertical speed of auger during boring, grout factor, grout pressure, number of reborings, type of material, and slump of concrete used to form the piles. Two of these factors are highlighted in this paper. It was found that, shaft resistance is independent of grout factor, whilst point resistance increases as grout factor increases. Nevertheless the engineer should decide the safe pile load associated with the most economical grout factor. High vertical speed of auger during boring of piles may cause disaster for the adjacent buildings, due to soil decompression.

Jan 1, 1993

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 Shenbaga R. Kaniraj

The pile loading tests are generally conducted to assess the safe load on piles in compression. In the Indian practice, the safe load is determined using the pile loading test data and the two criteria specified in the Indian Standard Code, IS.2911 (Part 4) -1985. For this, the test pile should have undergone a minimum displacement equal to 10% of the pile diameter. Often, the piles are not subjected loads that are sufficient to cause a displacement of this magnitude. If the settlement is at least 12 mm, then the safe load is determined based only on the first criterion. But, if the settlement is less than 12 mm, the safe load cannot be determined using the IS Code criteria. The paper presents two procedures called hyperbolic and generalized hyperbolic methods to estimate the safe load using the IS Code criteria even when the loading test data is insufficient. The data from two initial tests have been analyzed. The predicted safe loads have been compared with the actual safe loads.

Jan 1, 1996

By P. Middendorp, Gerald E. H. Verbeek

"INTRODUCTIONStatic Load Testing (SLT) is generally considered the pile testing method that provides the de-facto answers regarding pile capacity and load-deflection behavior. However, as this testing method is time consuming and costly, alternative pile testing methods are applied, such as High-Strain Dynamic Testing (HSDT), commonly referred to as Dynamic Load Testing (DLT), and Rapid Load Testing (RLT), which includes Statnamic Testing (STN) and the Fundex Pile Load Tester (PLT). Extensive descriptions of these pile testing methods as well as comparisons of the results from these two methods have been widely published, but little is written on the choice between HSDT and RLT. This article will address this issue for concrete piles by discussing five different aspects that should be considered when making a choice between HSDT and RLT for either cast-in-situ piles or precast driven piles. TIMINGThe timing of the pile load test is independent of the testing method. For cast-in-situ piles load testing is performed some time after the pile has been installed (to allow the pile to obtain the compressive strength required to withstand the test load), while for precast driven piles load testing is performed after a so-called set-up period following pile installation (to allow the soil to recover from driving induced disturbances and, at least in most cases,regain strength).In other words, the timing of the test does not affect the choice of the testing method.ACCURACY OF THE APPLIED LOADWhen a pile is tested by RLT the applied load is measured by a calibrated load cell placed on the pile head, just as it would be during SLT. This means that the error in the applied load value is less than 0.1% of the maximum range of the load cell.However, when a pile is tested by HSDT the load is calculated from the measured strains, which means that the outcome is dependent on the pile material properties. In this case the applied load (F) on the pile head is calculated by multiplying the measured strain (?) with either the calculated or estimated elastic modulus of concrete (E) and the pile cross section (A).The elastic modulus is generally back calculated from the (average) stress wave velocity (c), which in turn is derived from the reflection time (T) it takes for a stress wave to travel over the pile length (L) from the pile head to the pile toe and back to the pile head."

Jan 1, 2006

By V. T. Ganpule

The effect of Sulphate and Chloride is well understood by the engineers. Most of the codes stipulate permissible limits for sulphate and chloride content in groundwater. Relatively few reference are available about the effect of organic acids on pile concrete. While executing a pile foundation work around Bombay, the authors came across the peculiar phenomenon. The routine testing of water has indicated that water is non-aggressive; however, on exposing the piles, the piles were found to be highly detonated. The testing of water on the guidelines followed by engineers associated with flow through pipes revealed that water is corrosive as per the Ryznar index concept. The present papers discussess the significance of Ryznar index in under water concreting.

Jan 1, 1996

By H. R. Masoumi

This paper presents a numerical model for the prediction of free field vibrations due to vibratory and impact driving. As the focus is on the response in the far field, where deformations are relatively small, a linear elastic constitutive behavior is assumed for the soil. The free field vibrations are calculated by means of a coupled FE-BE model using a subdomain formulation, proposed by Aubry and Clouteau (1992). The model is validated by means of the results of Kaynia and Kausel (1991) for the impedance of a single pile. First, the case of vibratory pile driving is considered, where the contributions of different types of waves are investigated for several penetration depths. The results show that in the near field, the response of the soil is dominated by a vertically polarized shear wave, whereas in the far field, Rayleigh waves dominate the ground vibration and body waves have been importantly attenuated. Second, the case of impact pile driving is considered. A linear wave equation model is used to estimate the impact force during the driving process. Furthermore, it is investigated how the soil stratification influences the ground vibration considering the case of a soft layer on a stiffer half space. The results show that when the penetration depth is smaller than the layer thickness, the layered medium has a small influence. However, when the penetration depth is larger than the layer thickness, these effects become more significant. Finally, the computed ground vibrations are compared with experimental data reported in the literature.

Jan 1, 2006