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By Hyung-Min Kwon

There are a number of methods available that can be used to estimate the bearing capacity of piles that are subject to lateral load, such as the theory of subgrade reaction or the elastic continuum approach. The objective of these approaches is to determine the lateral load corresponding to the allowable lateral displacement of the pile. It is important to select the appropriate soil stiffness when analyzing soil behavior within the allowable displacement of piles because the stiffness of soil is dependent on the displacement of piles. Even though pressuremeter tests can measure the stress-strain behavior within a wide strain range, pressuremeter test results have been utilized to assess only the fragmentary soil modulus based on either semi-empirical correlations or analytical approaches. This study is concerned with a methodology that can estimate the horizontal deformational property, while taking into consideration the nonlinear deformational characteristics of sandy soils. Pressuremeter tests were conducted for 15 cases using a calibration chamber. Reloading curves were employed in the estimation of horizontal deformational property in order to minimize the effect of soil disturbance caused by the installation of the probe. The shear modulus degradation characteristics were estimated from the curve fitting for the reloading curve and from extrapolation using the exponential function. In addition, the difference was taken into account between the stress state around the probe in reloading and that of the in-situ state. A consistent relationship was observed between the maximum shear modulus taken from the suggested method and the bender element tests performed in the calibration chamber, simultaneously with the pressuremeter tests. In addition, the results showed significant concurrence with the well-known empirical correlation.

Jan 1, 2008

By Sepideh Damavandinejad Monfared

In recognition of the practicality of using inclined micropiles as elements for foundation support to resist static and seismic loading conditions, specifically in retrofitting projects, this study presents an investigation into the beh avior of an inclined micropile subjected to simultaneous lateral load and bending moment. Three-dimensional numerical simulations are performed using the finite element method to assess the influence of micropile geometrical parameters such as angle of inclination, length, and diameter on the response of micropile-soil system. The Mohr-Coulomb failure criterion is used to define the behavior of soil and stabilized soil around micropile materials and the micropile, constructed of concrete and steel, is assumed to be elastic. The interaction between soil and micropile is taken into account by defining interaction elements covering both tangential and normal behavior. The study is carried out using nonlinear FEM analyses. The results of these simulations indicate that negative micropiles, in which slip surface deflects downward, have higher lateral load capacity than positive micropiles with slip surface deflecting upward. The conducted research also shows that increasing the diameter and the length of micropile increases the lateral load capacity. Increasing micropile diameter is more effective in increasing lateral load capacity. A relationship is developed from statistical regression analysis of the finite element modeling computations to estimate the lateral displacement of a micropile inclined at an angle of 30o in silty sands.

By Leonhard Weixler, Alexander Blatt, Franz-Werner Gerressen

Diaphragm wall technique is usually used to construct structural elements in the ground, commonly used for retention systems, permanent foundation elements or deep ground-water barriers, named Cut-Off-Walls (COW). It can be anticipated that global urbanization and increasing demands on environmental considerations will need to be accommodated in underground space in the future. These trends show an increasing requirement for diaphragm walling in even more complex conditions, especially in inner-city applications with limited space. Therefore, there is the demand to minimize the size of equipment to accommodate such projects. Following this demand, a new trench cutter system, the so-called CUBE System, was recently developed. The complete trench cutter system has been fit into container size dimensions so that it can work in very limited space conditions. In addition, complex conditions in terms of space limitations require specifically adapted solutions for slurry, spoil, reinforcement and concrete handling and the related logistics to ensure smooth production. Due to the limited space requirements, the impact on the surrounding environment is limited. As the system is electric driven, an additional reduction of carbon footprint can be expected. First tests of the system have been carried out and the results will be shared. The paper will explain the construction process and the specific challenges and experiences made for these extreme conditions.

Oct 1, 2022

By Kanagarajah Ravishankar

Drilled shaft (caisson) foundations are extensively used in the past. In the central part of New Jersey, the soils consist of silt and clayey silt overlying Triassic age shale bedrock. The shale is friable and generally severely weathered and highly fractured. The shale crumbles readily into small fragments. In general, the shale is encountered in shallow depth. Subsurface investigations indicated that the upper part of the shale is very soft, highly weathered, and able to advance through soil exploration methods. The underlain formation is relatively hard and required rock coring techniques for sapling. Individual core recoveries ranged from 10 to 100 percent and Rock Quality Designations (RQD) vary from 0 to 90 percent. Although several methods available to estimate the axial capacity of drilled shafts, it is a difficult task for the designer choose the suitable method due to self disintegrate nature of the shale. In the recent years several bridge foundations have been constructed using drilled shafts founded on shale rock in the vicinity of the central New Jersey. Based on load tests carried out on drilled shafts during construction, subsurface exploration, and laboratory tests, suitable methods for determining axial capacity of drilled shafts is analyzed. This paper presents the findings of the field tests and suitable methods to determine the axial capacity of drilled shaft founded on soft shale. Key words: Drilled shaft, axial capacity, Osterberg load test, shale.

Jan 1, 2006

By Alan J. Lutenegger

A series of tension tests were performed on prototype scale steel pipe piles at two sites to evaluate the influence of scale and pile plugging on the unit skin friction developed in axial tension. The first site consisted of a clean medium dense fine sand above the water table. The second site consisted of a loose silty sand with the water table within about 0.5 m of the ground surface. Pile load tests performed at each of the sites included piles with diameters ranging from 73 mm to 114.3 mm, which may be considered driven "micropiles". At the first site, pile lengths of 6.1 m were used; at the second site, pile lengths of 9.1 m were used. Some of the piles were driven open-ended while others were fitted with a conical tip to form a closed end. During installation, pile plugging measurements were taken on the open-ended piles after each 0.30 m of penetration. The piles were allowed to rest for a period of about 30 days after driving prior to performing the axial uplift load tests to failure. The results indicate that in the medium dense fine sand the unit skin friction developed in tension is dependent on both the amount of plugging that occurs and on the size of the pile, which was not the case for the loose silty sand.

Jan 1, 2000

By Juhyung Lee

Numerical analyses were performed to analyze the behavior of two different type of suction piles (mono type and group type) under various soil layer conditions (uniform silty clay layer, uniform silty sand layer, and two-layer deposit consisting of clay and sand layers) and lateral loading locations (top, middle, and bottom of the suction pile). According to the results, mono suction pile shows maximum resistance when load is applied on its middle, regardless of the soil layer conditions, while group suction piles varies significantly according to the allowance on head rotation. When head rotation is allowed, the behavior of group type piles become similar to the behavior of mono suction pile. Whereas, when rotation is prevented, resistance is maximized when load is applied on the top head. Moreover, group suction piles show higher efficiency regardless of the ground condition and geological stratum. For further advances, concrete block on the top of group suction piles are suggested as an effective alternative method to prevent partial rotation and maximize ground resistance for group suction piles.

By Daniel Ruffing, Jeffrey Evans

Vertical cutoff, or barrier, walls are an integral part of environmental site remediation efforts. Vertical barriers are commonly deployed to limit the influx of clean ground water and/or to control the off-site migration of contaminated groundwater. The level of detailed design consideration devoted to the vertical cutoff wall component varies widely from project to project and generally decreases with decreasing size and complexity. For those projects receiving minimal design effort, conservative design decisions can lead to unnecessary costs or unanticipated conflicts between the various design considerations. In this paper, the authors discuss several important design and construction aspects of vertical cutoff walls requiring particularly careful consideration during the design phase of the project. These design and construction considerations include the need for and extent of excavation for a key, project target hydraulic conductivity, the use of statistical allowances in the specifications, filter press testing, sand content of in-trench slurry, cleaning of the backfill slope, measurement of stress and strain, the additional of slag in cement-bentonite cutoff walls, and longevity of cutoff walls.

By Mai Yuanjian

The stabilization effect in large excavation slope with vacuum wellpoints system during construction of a dry dock located in Guangzhou is introduced in this paper. In-situ observations indicate that the effect of wellpoints for decreasing seepage in slope is remarkable even though the muddy sitty clay in it has poor permeability and the slope can remain its stability well. Meanwhile, a non-linear partial defferential equation has been set up to the whole unsteady seepage process as water level in the foundation pit excavated under water goes down to the bottom and so does the seepage in slope due to dewater by vacuum wellpoints system at the same time. And the finite-defference method has been used to solve the equation mentioned above, which differes from conventional wqy where the equation will be linearized firstly. Since the water heads in slope with wellpoints dewatering are more variable, it is necessary to keep non-linear. The calculation results are in good accordance with observation. Vacuum wellpoinnts for slope stabilization in this work is successful.

Jan 1, 1991

By George Onorato, Giovanni Bonita

Deep soil mixing (DSM) has now become a ubiquitous ground improvement technique across the globe for producing soil-cementous materials for many types of complex civil and environmental applications. In the field, the cementation bonds of the soil-cement materials are formed under a confining stress conditions; however, these conditions are generally not considered as most wet grab specimens are cured and tested under ambient atmospheric conditions. This has led to an underestimation of the engineering and mechanical properties of the soil-cement mixed material. This paper presents the preliminary findings of the effect of confining stresses on the mechanical properties of soil-cement mixed samples. This paper discusses the specialized field techniques used for modeling confining stresses during curing and presents the preliminary findings from different soil types. The findings indicate a strength increase within samples cured under a confining stress relative to nonconsolidated samples. The magnitude of the strength increase also appears to be different for different soil types. Finer-grained soils appear to exhibit a larger relative strength increase with confining stress relative to predominately granular soils.

By Andrew Budek

Reinforced concrete piles are used to carry foundation loads through considerable depths of soil to provide superstructure stability under gravity loads and lateral forces. The creation of cast-in-place (or cast-in-drilled-hole, i.e., CIDH) piles begins with the auger-drilling of a hole of the appropriate depth, into which a cage of reinforcing steel is placed (the cage length is generally equal to the depth of the hole, a construction joint being used to connect the in-ground pile with the superstructure). The pile is then finished by casting with concrete, and the superstructure then appended. The superstructure may either be a column (denoting the structure a pile-column), a column and cap beam, or a footing. Typical pile-column configurations are shown in Fig. 1 (a CIDH pile used in a footing would be similar in overall configuration to Fig. 1(b), with H=0). CIDH piles are well-suited for alluvial soil profiles with a deep water table; such conditions generally allow the auguring of a clean and regular hole.

Jan 1, 2007

By Ameir Altaee

Unconventional means and methods were utilized to install over 650 contractor-designed micro-piles for the replacement of the Bronx approach to the Bronx-Whitestone Bridge in New York City. The method utilized reverse circulation (RC) drill rods and down-hole-hammers (DHH) along with grouting through the DHH bit. The overall construction sequence of drill-down, grout-up, place reinforcing is similar to auger-grout piling. The extremely tough drilling conditions required the use of a percussive DHH. The piling subcontractor refers to this pile as a hammer-grout pile. Project background, constraints and subsurface conditions are given. The proposed means and methods as well as the collaboration between stakeholders are detailed. Results of load testing and production installation are summarized.

Jan 1, 2010

By Meeok Kim, Thornton Tomasetti, Seth Knihtila, Michael Oakland, Shawn Leary

The transformation of Seattle's historic KeyArena into the state-of-the-art Climate Pledge Arena, home to the NHL's Seattle Kraken, was no small feat. The $930-million renovation and expansion required the near-total demolition of the old structure and construction of an 800,000 sqf (74,000 m2), below grade venue while keeping its landmarked façade and roof intact. To do that, the project team had to come up with solutions for excavating 680,000 cu yd (520,000 m3) of soil to make way for the new 17,000-seat arena while working around the massive temporary shoring supporting the 44 million lb (20 million kg) roof all in time for the NHL's 2021-22 season.

Sep 1, 2023

By Lance Rasband, Richard Hanke, John Starcevich

"The 17.4 meter (57 ft) diameter tunnel boring machine (TBM), the world’s largest at the time of her launch in 2012, locally referred to as “Bertha,” is stuck. Incapacitated due to mechanical failure approximately 36 meters (120 ft) beneath downtown Seattle, situated precariously between the deteriorating Alaskan Way Viaduct and the failing Seattle Seawall. Accessing Bertha with a vertical shaft provides the best approach to address all facets needed for repairs and will allow the full removal of Bertha’s cutter head and related inner workings. Limited area above the tunnel alignment and the physical restrictions of existing infrastructure, create significant challenges for the design of an otherwise symmetrical shaft, requiring special attention to design and layout. Consequently, the access/recovery shaft design required a combination of 3m, 2.5m, 2.2m, 1.5m and 1m diameter unreinforced drilled secant piles coupled with various ground improvement techniques and dewatering, to fully satisfy the shoring design requirements. This paper will describe the shaft installation procedures, equipment used and pitfalls encountered while undertaking access shaft construction of this magnitude.INTRODUCTIONTunneling on Seattle’s SR99 tunnel project began in July of 2013. After slowly mining through a 4.5 m (14.76 ft) thick fiber-reinforced concrete headwall and the first of three stabilized “safe havens,” Bertha would proceed along the proposed alignment through 122 meters (400 ft) of jet grout improved soil at a rate of slightly over 1.6 m (5.25 ft) per day. Once past the improved area, it was planned that “Bertha” – would be moving at a rate of about 11 m (36 ft) per day. By the end of October 2013, Bertha had mined roughly 131 m, (430 ft) averaging 1.4 m (4.6 ft) per day and had begun mining within native soils. By December 2013, tunneling had reached the 244 m mark and Bertha was averaging 3.6 m (11.8 ft) per day, achieving as much as 12.8 m (42 ft) of progress on given days. Unfortunately, on December 6th, 2013, Bertha began to stumble and all progress quickly came to a halt.It was initially reported that an obstruction had stopped Bertha in her tracks. The preliminary investigation involved installation of 10 deep dewatering wells to reduce the hydrostatic pressure around the TBM, and allow visual inspection of the cutter head from within the TBM, and also to investigate for the presence of obstructions at the face of the cutter head. During this inspection, fragments of steel pipe were discovered entangled in the cutter head. The fragments were apparently from an abandoned 254 mm (10 in.) diameter monitoring well casing, previously installed by WSDOT to monitor ground water conditions for the design and planning of this tunnel project. After the steel was removed from the cutter head and cleared from Bertha’s path, tunneling resumed. It was then discovered that Bertha was only able to generate a slow crawl."

Jan 1, 2016

By Frank Haehnig, Kurt Kogler

"With a height of 200 m, a crown width of 626 m and a concrete volume of 1.6 million m³, the Kölnbrein Dam in the upper Malta valley in Carinthia / Austria is the largest concrete dam in Austria. Boasting a storage capacity of 200 million m³ with a received water load of 54 MN, this is one of the strongest arch dams in the world.During its construction from 1974 to 1977, the dam was equipped with a comprehensive monitoring system capable of comparing developing deformations and stresses with the design values.With a planned reservoir level of 1,900 m a.s.l. the dam saw the reservoir level of 1,860 m a.s.l. breached in the year 1978. This led to extremely high seepage losses of up to 200 ltr/sec and a rise in the foundation water pressure up to 100% of the dam’s height. These observations were caused by the development of horizontal cracks in the area of the middle dam blocks, between the lowest inspection walkway and the waterside.As a consequence, power plant operations had to significantly be reduced and a number of additional measures were carried out – though these did not lead to the desired sealings.The developer subsequently decided that the dam should undergo a general rehabilitation from 1998 to 1994 in accordance with a concept developed by Professor Lombardi. This concept involved erecting a 50 m high support structure with a concrete volume of 500,000 m³ on the airside of the dam, along with the addition of neoprene bearings to transfer 1.2 million tons of the horizontal load. These measures were able to reduce the deformations in the dam enough so that mostly load-bearing injections into the cracks in the dam’s concrete could successfully be carried out by way of targeted grouting measures using injection resin (RODUR) specifically developed for this purpose.In the years 1998 - 1994, a total of 130,000 m of grouting, monitoring and control drillings were executed, and around 200,000 kg of synthetic resin was injected into the cracks in the dam’s concrete.These measures have ensured the dam‘s uninterrupted operation since 1994. A number of small re- injections were again carried out on the contact surface in the years 2011 and 2012."

Jan 1, 2016

By Peter Deming

"PART 2 OF 2 (CONTINUED FROM SUMMER 2006 EDITION) CONSTRUCTION ISSUES (cont’d) The Influence of Ground Conditions on Collapse Sand and gravel strata provide frictional resistance to support active earth pressure. The angle of internal friction has only slight influence on computed stability. Sand and gravel material design parameters can be defined with SPT N-values. Silt strata should be analyzed using internal friction. Definition of soil parameters should be performed by laboratory testing. Cohesive materials, especially soft clay and peat, require careful definition for design. Shear strength should be determined by laboratory testing. Work platforms constructed over granular strata improve the ground resistance by increasing confining pressure. However, temporarily increasing overburden stress on cohesive ground reduces trench stability. If the ground contains soft cohesive deposits which are not normally consolidated to the construction overburden, these must be stabilized before attempting trench construction. Use of wick drains and surcharge fill to improve the ground is recommended. Ground stabilization work requires time, and should be performed by the Owner prior to trench excavation. The addition of cement, stone columns, or other measures to support trench excavation equipment is typically determined to be more expensive and less dependable than ground improvement. Excavation through peat can be especially problematic. Peat materials rapidly compress when earth pressures exceed preconsolidation stresses. Backfill materials provide a horizontal stress on the trench wall which can exceed the bearing capacity of peat. As the peat compresses, the trench becomes wider, and slurry levels drop and trench stability can rapidly deteriorate. If the peat is the closure layer, a shallow key is recommended. If peat is present on the trench wall, preconsolidation with surcharge is recommended. Bottom preparation and Backfill Placement Trench wall stability is a temporary condition which must be controlled by proper design and construction of work platforms and slurry features which influence ground support. Backfill materials and intimate contact of the backfill with the closure layer are permanent conditions which are the end goal of the work. The most common reason slurry trenches fail to provide working barriers is improper bottom closure. Either the closure layer is not engaged, or the backfill is not in intimate contact with the closure layer. This can result from construction problems associated with sidewall collapse described above, slurry performance and/or degradation, backfill placement methods, and failure to maintain the trench bottom clear of sediment prior to placing backfill."

Jan 1, 2006

"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 Matthew Janes

The installation of piles and casings is becoming increasingly difficult as restrictions on vibration become common in major urban areas. The use of high frequency, resonant excitation of a pile or casing permits ease of installation of sections to great depths with near imperceptible vibrations as close as 1 pile diameter. The new Resonant Driver is able to excite a pile at its resonant frequency (up to 150 Hz or 9000 VPM) to produce elevated levels of acceleration, force and displacement in the pile. The combination of extremely high acceleration and controlled levels of displacement allow the pile to slice through varied soil with almost no vibration translated into the ground. In direct comparisons between conventional vibrators and impact hammers the Resonant Driver produces less than 1/50th the vibration. The Resonant Driver results in ground vibration of between 1/20 and 1/40 of common limit levels (1 cm/s or 0.5 in/sec) as close as 1 pile diameter. At a distance of 5 m (16 ft) from the pile or casing vibration levels approach imperceptible levels. The Resonant Driver uses a proprietary algorithm to tune the drive vibration to the changing natural frequency of the pile as it is driven into the ground. By maintaining resonance the energy in the pile is built up like in a flywheel on an engine or a child on a swing. This build up of energy aids in driving and significantly reduces waste. Recent experience using the Resonant Driver is proving the technology can drive a variety of steel pile and casing sections through varied soils. Continued use of the Resonant Driver will create a data base of various pile and casing sections, soil types and achieved capacities.

Jan 1, 2008

By Mousaab Majar, Nikolaus Schneider

The technical challenges for accurate drilling positions increase with deep underground structures in inner city areas. Designed for jet grouting, specific sensors have been developed to record the alignment of rods during drilling by integrating microchips into the drilling rods. By feeding the rod with constant electric current, microchips, integrated in special couplings, can be read during the drilling process and tracked on monitors installed in the operator’s cockpit. The orientation for the drilling rod is provided by magnetic points and a compass, positioned above ground on the drilling rig. In combination with asymmetric drilling bits, it is now possible to steer the drilling hole to predetermined positions to compensate for deviations in deep bores. This type of drilling rod for jet grouting has been used in Berlin since summer 2019.

May 1, 2022

By R. K. M. Bhandari

Geotechnical investigation for a LPG plant located in Assam state - an area of high seisimicty - revealed a layer of loose to medium silty sand susceptible to liquefaction at some depth below the finished ground surface. Liquefaction analyses were carried out using simplified Seed's approach as well as considering the progressive buildup of pore pressures with cyclic earthquake loading. Seismic settlements were computed for areas where the analysis indicated partial liquefaction. Pile foundations in areas where complete liquefaction was indicated, were treated with gravel drains to prevent buildup of pore pressures. The paper presents and discusses the liquefaction analyses, effect of non-liquefiable overburden soil on the liquefaction potential of the silty sand and the remedial measures that have been taken to ensure safety of the pile foundations in transmitting vertical and lateral loads.

Jan 1, 1996

By Ali Bouafia

Five full-scale horizontal loading tests of piles carried out by the LCPC in France are interpreted in order to analyse P-Y load-transfer curves. The experimental piles are either bored or jacked into quite homogenous sandy soils and instrumented by strain gauges for measuring bending moments along the pile. Successive differentiation and integration of bending moment profiles have led to derive respectively lateral soil reaction and displacements then to construct the load-transfer P-Y curves. The initial horizontal lateral reaction modulus was derived from these curves and shows linear variation with depth in accordance with Gibson soils profiles. P-Y curves are validated by back-computation of the pile on the basis de these curves and the horizontal reaction modulus was compared to the recommendations frequently used in pile design practice.

Jan 1, 2002