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By Haijian Fan

Currently, deep foundation designs for the service limit state are deterministic in nature. The settlements and lateral deflections of deep foundations are calculated by means of numerical techniques whereby the foundation-soil interactions are characterized by discrete load transfer curves such as t-z or p-y curves. The noted deficiency of the deterministic approach is that the uncertainties arising from various sources, such as soil properties and model errors are not considered. To address this deficiency, a performance-based reliability design methodology is developed using Monte Carlo statistical methods. The performance based design criteria are defined in terms of the specified allowable displacement. The input to the numerical solution techniques, including the soil strength parameters, unit weight of the soil are relevant to the generation of the load transfer curves are treated as random field. The well established random field generator algorithm, local averaging subdivision, is used to generate random samples of input, where the mean values, variances, the probability distribution, and correlation structures are required statistical parameters for these random variables. The objective of the performance based reliability design is to determine the optimized foundation dimensions so that the probability of failure is less than the target probability of failure. The probability of failure by the Monte Carlo approach is simply the ratio of the number of unsatisfactory performance to the sample size. A numerical example for laterally loaded drilled shaft is given to illustrate the application of the methodology. The incorporation of the correlation length is shown to be critical for properly accounting for the site soil spatial variability.

Jan 1, 2017

By Prakash Annamalai Rangasamy, Muthukkumaran Kasinathan

"Infrastructure development like elevated expressways, metro train and flyover are required proper foundation system to carry heavy traffic loads/significant lateral load, especially in the presence of hard stratum at shallow depth. Pile foundation under bridge pier system is widely adopted in metro projects where the piles are essentially socketed in rock. However, the drilling in hard rock is a time consuming process and needs heavy machineries which lead to delay in construction activities. In the present study, the influence of free standing height on rock socketing under lateral load is investigated. The experiments were conducted on an instrumented model pile with varying depth of socketing and for varying Lf/D ratios. The experimental results shows the load carrying capacity of the pile increases by increase in Lf/D ratio, where in the case pile without socketing (bearing on rock) is compared with 3D depth of socketing. Thus socketing the pile provides significant benefits on carrying capacity of lateral loads. Embedding the pile into hard strata reduces the lateral displacements substantially compared with pile bearing over hard strata. Form the study, it is noticed that the influence of rock socketing has significant effect in the lateral load capacity. And also, the effect of free sanding height play a major role in the lateral load capacity of the rock socketed piles.1. INTRODUCTIONA substructure carrying heavy lateral load at shallow depth, the structure has to be socketed into hard strata to enhance the efficiency of load carrying capacity. The existing field practice is to socket the end bearing piles in hard strata over a minimum depth of four times the diameter of the pile based on rock classification (IS 14593:1998). Reese (1997) developed p-y curves for analysing drilled shafts in rock under lateral loading, based on strong and weak rock criteria. The proposed p-y curve approach has the ability to simulate the nonlinearity and non-homogeneity of the rock mass surrounding the drilled shaft. Gabr et al. (2002) proposed a hyperbolic p-y criterion based on field tests on small diameter drilled socketed shafts. By considering pile as linearly elastic semi-infinite space and soil as homogeneous isotropic material, Poulos (1971) proposed solution to determine the horizontal displacement and pile head rotation. Poulos (1972) extended this elastic continuum approach to give an approximate solution by considering drilled shaft and pile bearing on rock as fixed and pinned end boundary condition. Zhang et al. (2000) developed a non-linear continuum approach for drilled shafts in a soil and rock mass by considering the effect of soil and/or rock mass yielding on the behaviour of shafts. Randolph (1981) conducted a parametric study on the response of laterally loaded piles embedded in an elastic soil continuum. The study was conducted using the finite element method and the results were fitted with closed-form expressions from which the lateral responses of piles were calculated. The solutions given by Randolph (1981) were expanded by Carter and Kulhawy (1992) from the results of finite element studies on the behaviour of laterally loaded flexible and rigid drilled shafts in rock. Desai and Christian (1977) gave a finite difference program to solve rock socketed problems by considering soil and rock mass as elastic-perfectly plastic. Zhang et al. (2000) verified the proposed finite difference method with existing field test results. Gabr et al. (2002) and Liang and Yang (2006) proposed hyperbolic p-y curves based on filed test results and verified with finite element programs. However the need of field and lab scale experimental studies to validate the existing methods of analysis is necessary."

Jan 1, 2015

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

"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 Masaaki Terashi

The machine for the hybrid method called JACSMAN is ordinarily a dual shaft machine. Each shaft has augers at three different levels and nozzles for jetting at two different levels. The distance between two shafts may be changed according to the particular requirements. Figure 4 shows single shaft and a treated soil column created by the method. The diameter of the auger is 1.0 m. As the jetting nozzles locate at the periphery of the auger, jetting can achieve the additional treated soil column beyond the diameter of the auger. The diameter of the jetting improvement is fixed at 2.3 m.

Feb 10, 2003

By Masaki Kitazume

Five papers were presented orally to the topics of Jet Grouting and Deep Mixing. The session was started with a brief introduction by the moderators. Following the oral presentation, floor discussions were directed by the moderators. A brief introduction of each of the oral presentations is provided before each discussion.

Feb 10, 2003

By Trent Dreese

For critical velocities in gravel units we use Bush-Luckner, Sichardt, other empirical equations, and equations derived from laboratory experiments too. On the base of these, we compiled critical velocity - permeability coefficient dependencies. Under the lower border of these dependencies sand particles can't be moved, and thus they are stable. For critical velocities in the fissures of flysh and volcanic rocks we use Ronzhin (1974) criteria derived from laboratory experiments in Russia. Maximal filtration velocities measured by tracer methods in gravel soils and in fissured rocks have smaller values then the critical ones.

Feb 10, 2003

By Stefan Dahlin

The laboratory tests indicated low permeability but as I said, as a rule, the permeability in the field has been found to be higher. A high permeability has also been found when doing back calculations of rates of settlements in different cases. But as I also said, there's a need for further studies in this area.

Feb 10, 2003

By Timothy Flaherty

We observed the boiling in the water very close to the water adjacent to where we were drilling. That only happened at the very beginning before it was switched to water flushing. Yes, it was performed with water flush.

Feb 10, 2003

By DFI DFI

An Online Conference

By Peter Deming

"PART 1 OF 2INTRODUCTIONSlurry trenches are the least cost hydraulic barrier available, if the excavated spoils can be recycled into backfill. As such, slurry trenches are constructed where possible, sometimes at high risk. Slurry trenches are also used to install biopolymer drainage trenches, which have a low safety factor because the biopolymer slurry weight is marginally greater than the weight of water. In marginal ground the construction risk falls to both the Owner who designs and asks for the construction, and the Contractor who manages the work and promises to complete the project successfully. This paper discusses design and construction of slurry trench barriers in marginally stable ground and where groundwater chemistry invokes the need for slurry management details to obtain proper backfill placement.As a designer, Mueser Rutledge Consulting Engineers works for both Owners and Contractors. We are usually able to convince Owners of their responsibility for design detailing in order to obtain a working final product and to obtain reasonable bids from Contractors by disclosing construction needs and designing to reduce the contractor’s exposure. We often work for Contractors to produce designs which result in successful construction in projects where the Owner’s engineer places the responsibility of design and construction on the Contractor.This paper is intended to inform both Owner and Contractor audiences of resources which are available to reduce the risks of trench collapse in difficult ground conditions. We hope it serves this purpose.DESIGNSubsurface InvestigationsSubsurface conditions should be defined by borings focused on definition of the soil profile and soil design parameters. After general subsurface conditions are defined, barrier borings should be drilled along the final alignment.Definition of Soil Strength and CompactnessCompactness of sand and gravel strata should be defined with Standard Penetration Test N-values. The shear strength of cohesive materials should be defined by laboratory testing. Silt and fine sand strata with little cohesion should be investigated using mud rotary techniques to prevent disturbance. General strength characterization by soil layer should be used for analysis of trench wall stability."

Jan 1, 2006

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 Richard Berry

The spacing of grout injections is typically about 2 to 2 V½ meters if the purpose of the grouting is densification of the in-situ soils. Hole spacing will vary with the in-situ soil properties and the grout injection rate; faster rates requiring closer hole spacing.

Feb 10, 2003

By Brian Koch

Michels installed 242 drilled shafts to support the piers for a new basket-handle, true-arch twin bridge across the Mississippi River from Moline, IL to Bettendorf, IA. The installation of the drilled shafts was completed with the simultaneous use of two Liebherr LB36 and one IMT 300 drill rigs. Utilizing barges, 233 drilled shafts were installed in the river. Michels crews also installed 7-ft to 10-ft permanent steel casing into the bedrock, and drilled to depths of 60 feet for each shaft. Despite working in strong currents, freezing temperatures and on rocking barges, Michels crews placed the shafts within 3 inches of plan position. Since the drilled shafts are the key piece in supporting the bridge structure, Michels provided cross-hole sonic logging to verify the integrity and strength of the concrete within the shafts and to add another level of quality control for the owner/customer. Extensive planning took place each day to ensure that tugboats, the linchpin of the project, were being efficiently utilized to shift the barges and materials daily. On any given day, Michels transported five concrete trucks by barge from shore to shaft sites to pour between 40 and 240 cubic yards of concrete. The Michels environmental team was diligent with preparing, discussing and implementing a water treatment plan that was accepted by all state and federal agencies and adhered to strict environmental regulations. Grain hopper barges were rented to control and treat the water that was used in the drilling operations. Another challenge crews ran into was the discovery of caverns when drilling into some parts of the bedrock. Michels worked with the engineer to develop a plan to construct the drilled shafts that encountered the caverns.

Jan 1, 2019

By Jerry A. Steding

How many times have you heard "You can't drive piles because of the vibration."? You hear these words come out of the mouths of owners, engineers, and contractors. When a piling contractor hears this, he can almost always do a psychological profile of the individual uttering these words of wisdom. If the owner makes the statement, we know the odds are about 95% that the owner owns the building next door or he wouldn't care what happens to it; or the guy next door has threatened to sue the owner if he even so much as walks across the site of the proposed new building. If the owner owns the building next door to the new construction you can also be just as certain the old structure has undergone settlement. If the statement comes from the mouth of the contractor, it is usually just a case of him being inexperienced.

Jan 1, 1988

By Christian Hoyme, Jochen Maurer, Hans Regler

Up to today, it has been very difficult to obtain qualitative and quantitative information about the status and production process of a construction site. It is becoming more and more important to be able to analyze this process so as to notice bottlenecks and interruptions on the site early on. The high costs of each shift in special foundation industry mean that making the wrong decision and/or interruptions can put the financial result at risk. Previously, keeping reliable data meant manual process documentation. This was done either by an additional staff member (incurring high additional costs for training, education, etc.) or by the equipment operators. The latter is critical, because they have to initiate every process step change, leaving no time to log data separately. Studies have shown that there are considerable deviations from the actual process steps. In this paper, a seamless, automated method will be introduced to analyze the construction process. This method recognizes each process step from the equipment data. The main purpose of the data recorded by the piling rig is the need of quality reports and now basis for the presented analysis. Here, a method was successfully transferred from theoretical computer science (compiler construction field) to find application for process recognition. Because the execution of works in special foundation construction can always be defined sequentially and therefore also practiced sequentially, recognition can occur step-by-step. Our method always recognizes the next step, so it does not have to monitor as much data at the same time. Individual trigger points are easier to define. Unlike solutions that are based on a global approach and allocate suitable process steps to data patterns, thereby also creating gaps, the presented method is always seamless. Furthermore, this method can be applied regardless of time or location provided that the necessary machine data is available, which is normally the case with production data logging. This means that construction sites even from the past can also be analyzed and the results used for comparisons. The first results from the analysis of a complete continuous flight augering (CFA piles) installation process of a construction site will be presented.

Sep 8, 2021