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By Tracy Brettmann, Melis Sutman, C. Guney Olgen

"The use of energy piles for geothermal heat exchange has been steadily increasing during the last decade, yet there are still pending questions on their behavior during temperature changes. This paper focuses on the thermo-mechanical response of three full-scale energy piles installed in Richmond, TX. The behavior of test piles subjected to thermo-mechanical loadings was studied in situ with the aim of quantifying the thermal influence on the performance and capacity of energy piles. An extensive field test program, including conventional pile loading tests and application of heating-cooling cycles was conducted on the test piles during a period of six weeks. For thermal load applications, the heat exchanger fluid with maximum temperature of 113°F (45°C) and minimum of 47°F (8°C) was circulated in the geothermal loops placed at the center of the test piles. Optical fiber sensors, vibrating wire strain gages, thermistors and thermal integrity profile wires were installed to monitor the strain and temperature variations along the energy piles throughout the field tests. The strain and temperature profiles during heating-cooling cycles on the test piles under static loads and without a maintained load were monitored to investigate the effect of thermo-mechanical and pure thermal loads on the energy piles, respectively. Conventional pile load tests were applied before and after the application of thermal cycles. The results of the pile load tests are compared to evaluate the effect of temperature cycles on pile capacity.IntroductionEnergy piles are deep foundation elements designed to access and exploit the relatively constant temperature of the ground and its heat storage capacity for efficient heating and cooling of buildings. The deep foundation elements that are already in place for structural support are integrated with adsorber pipes to perform as heat exchangers connected to ground source heat pump (GSHP) systems. With the use of energy piles, the heat energy is fed into and withdrawn from the ground for cooling in the summer and heating in the winter, respectively.Energy piles present an innovative way to harvest near-surface geothermal energy and to provide lower carbon emissions, however, there are still pending question on their performance. During heating-cooling cycles, energy piles experience temperature changes, which result in expansion or contraction of the piles."

Jan 1, 2017

By Bosco Poon, Kim Chan, Luis Raúl Castañeda, Geoff McKay

"Driven steel tubular piles of up to 2 m diameter have been used to support abutments and piers of a bridge over Nambucca River and floodplain. The bridge was designed by Arup-Aurecon Design Joint Venture (Lead Designers) with GHD leading the geotechnical design assessment in conjunction with Acciona Ferrovial Joint Venture (AFJV – Principal Contractor). Piles were to be driven through alluvium and founded on foliated Phyllite bedrock. The large diameter piles posed significant challenges on bearing capacity assessment and pile acceptance criteria, especially for anisotropic rock strength. Prior to pile driving, boreholes were drilled at each pile location, accompanied with a suite of rock index and UCS testing. AFJV and GHD oversaw geotechnical construction verification. All production piles were monitored with a Pile-Driving-Analyser to manage driving stresses and pile termination. Wave matching CAPWAP analyses were performed on 40% of the piles at the end-ofdrive, or restrike, to satisfy specification requirements and limit over-driving. This paper presents discussions on the design and construction of the driven piles with findings from the extensive dynamic pile data obtained. Based on the shaft resistance distribution and toe resistance obtained from CAPWAP analysis, the mobilised pile shaft frictions fs of the soil / rock materials, as well as the end bearing fb of the founding Phyllite bedrock, are examined. The impact of the rock fabric foliation angle on the m obilised fb, and the relationship between rock strength and the mobilised fs are outlined.INTRODUCTIONThe Bridge over Nambucca River consists of a single bridge structure, comprising single substructures and separate superstructures. The 850 m long bridge facilitates the crossing of the Northbound and Southbound carriageways of the Pacific Highway Upgrade over Nambucca River, with central median barriers, separated by a horizontal clearance of 50 mm. The bridge is required to span over the Nambucca River, which is a navigational channel, and over the adjacent floodplains, including two local access roads and the existing Pacific Highway. The bridge superstructure consists of 21 simply supported spans, each comprises four 2.25 m deep precast post-tensioned U-Girders, with two girders across the width of each carriageway. The spans of girders vary from eleven spans of 39.5m and ten spans of 41.5 m. The floodplain section of the bridge was founded on up to 2m diameter steel tubular piles, designed to be driven through alluvial sediments and weak rock to nominal refusal on sound rock. Dynamic load testing using wave matching CAPWAP (CAse Pile Wave Analysis Program) analyses in conjunction with PDA (Pile Driving Analyser) were used to verify the pile integrity and mobilised capacity. This paper discusses geotechnical aspects associated with design and construction of driven piles. The methodology developed for construction to verify pile capacity and to meet acceptance criteria is outlined. Based on the shaft resistance distribution and toe resistance obtained from CAPWAP analysis, the mobilised pile shaft friction, fs of the soil / rock materials, as well as the end bearing, fb of the founding Phyllite bedrock, are examined. The impact of the rock fabric foliation angle on the mobilised fb, and the relationship between rock strength and the mobilised fs are outlined."

Jan 1, 1900

By Matthias Pulsfort, Hanna Nissen, Markus Herten

An insufficient integrity of cast in-situ bored piles can lead to a reduction of the load bearing capacity and may require cost intensive repairs. Reasons for an insufficient pile integrity are linked to the construction process, mainly to poor concrete quality leading to bleeding and segregation of the fresh concrete. Moreover, the entrapment of soil and an insufficient concrete cover can pose a problem. Knowledge about the time-dependent development of the fresh concrete pressure during the construction process of bored piles is needed for a better understanding of the underlying processes causing these defects. Therefore, pressure measurements were carried out on different construction sites with pressure cells being installed at different depths along the reinforcement cage. The measurements revealed the maximum pressure acting on the surrounding soil. The achievement is a better understanding of the effects of the concrete placement specifically and the construction process in general on the surrounding soil to reduce the risk of pile imperfections.

Sep 8, 2021

By George C. Webb

A wide variety and variable depth (up to 40 ft.) of compressible, uncontrolled fill (including construction debris and a perched water condition) was present at a proposed Kroger construction site in Dent, Ohio. An innovative solution using a combination of an ACIP foundation system with a Tensar geogrid reinforced load distribution platform was used to provide a high quality building pad. This system allowed the use of conventional shallow foundations for structure support. This system was used in lieu of more costly solutions, such as complete undercutting of the entire existing fill and replacement with engineered fill or a deep foundation/ structural slab system. The selected ground modification included a system of augercast piles bearing on shale bedrock, which were installed on a grid pattern over the entire building footprint. Then, three layers of Tensar polyproplene biaxial geogrid were used to create a reinforced soil mat, which was supported on the augercast piles. An eight-foot blanket of engineered fill was placed above the geogrid-reinforced mattress fill to establish the building subgrade elevation. Standard shallow footings and slab-on-grade construction methods were then used to support the 26-ft. tall masonry block building. A small-scale instrumentation program included monitoring the geogrid reinforced mat settlement, geogrid strain and earth pressure distribution under the reinforced mat to evaluate design assumptions and theoretical analyses. This case history describes the first application of a pile supported geogrid reinforced mat for structure support which has been documented in the United States.

Jan 1, 2003

By George C. Webb

A wide variety and variable depth (up to 40 ft.) of compressible, uncontrolled fill (including construction debris and a perched water condition) was present at a proposed Kroger construction site in Dent, Ohio. An innovative solution using a combination of an ACIP foundation system with a Tensar geogrid reinforced load distribution platform was used to provide a high quality building pad. This system allowed the use of conventional shallow foundations for structure support. This system was used in lieu of more costly solutions, such as complete undercutting of the entire existing fill and replacement with engineered fill or a deep foundation/ structural slab system. The selected ground modification included a system of augercast piles bearing on shale bedrock, which were installed on a grid pattern over the entire building footprint. Then, three layers of Tensar polypropylene biaxial geogrid were used to create a reinforced soil mat, which was supported on the augercast piles. An eight-foot blanket of engineered fill was placed above the geogrid-reinforced mattress fill to establish the building subgrade elevation. Standard shallow footings and slab-on-grade construction methods were then used to support the 26-ft. tall masonry block building. A small-scale instrumentation program included monitoring the geogrid reinforced mat settlement, geogrid strain and earth pressure distribution under the reinforced mat to evaluate design assumptions and theoretical analyses. This case history describes the first application of a pile supported geogrid reinforced mat for structure support which has been documented in the United States.

Jan 1, 2005

By Vince Luongo

"INTRODUCTIONThe West Side Combined Sewer Overflow (CSO) Tunnel Project is located in Portland, Oregon and is part of the Willamette River CSO Control Project. The purpose of the West Side CSO Project is to reduce the frequency and volume of combined sewage overflows from the drainage areas on the west side of the Willamette River using the West Side CSO tunnel as a combined storage and conveyance facility. The sewage is then directed to the Pump Station on Swan Island, which is located on the east side of the Willamette River. From here the combined sewage is pumped through force mains that discharge into the existing Peninsular and Portsmouth tunnels.The West Side CSO tunnel has an inside diameter of 14-feet (4.27m) and is approximately 18,150-feet (5,532m) long. The tunnel slopes at a constant down gradient of 0.0018 from south to north over the entire length of its alignment.The tunnel passes beneath six existing bridges; Hawthorne Bridge, Morrison Bridge, Burnside Bridge, Steel Bridge, Broadway Bridge and Fremont Bridge. The general tunnel alignment follows beneath the Naito Parkway starting at Clay Street Shaft and connecting three other shafts on the west side of the Willamette River, Ankeny Shaft, Upshur Shaft and Nicolai Shaft. It then passes below the Willamette River and on to Swan Island to connect with the Confluent Shaft, which will combine flows from the West Side CSO and East Side CSO (not part of this contract) and then continues to the Pump Station Shaft.The Nicolai Shaft is the primary mining shaft from which two TBM’s were launched to construct the West Side CSO tunnel. The first TBM started mining south and terminated at the Clay Street Shaft. The second TBM started mining north below the Willamette River and terminated at the Swan Island Pump Station Shaft."

Jan 1, 2006

By Thomas Domanski

Any type of deep excavation whether for Bored Piling, Diaphragm Walls or Contiguous Bored Piling Walls depends on forming a stable borehole with a defined cross-section to receive safely the permanent materials. In modern construction the excavation depth can reach well the range of 100 m and above. The diameters of the Piles reach often sizes of 2.5 m and bigger. Top casings in Bored Piles (Diaphragm Wall none) are rather short and stability below the casing, need to be secured by stabilization slurry. The boreholes need to be formed through a variety of different materials and stand open for an extended period. Without a safe stable borehole, it is impossible to produce quality products and work cost-efficient. The understanding and proper usage of a suitable slurry is a key element essential for the delivery of Foundation Elements with high quality and within a reasonable budget. The setting of mechanical and rheological parameters in specifications is necessary and helpful, but probably insufficient to embrace and control such a key element in the practical implementation of foundation construction. The proper selection, design, implementation and supervision of slurries on site requires both from Contractors and Engineers to understand how different slurries do function. Only with this knowledge the right decisions in slurry operations can be made. This talk is directed to give some help to both, Contractor’s and Engineer’s, in understanding how different type of slurries do work. (Which ones should be preferred in what kind of soils.) The better knowledge will help the Contractor to control cost and enhance production. The Engineer will be able to assist in arriving at the appropriate technical choices and include in the specifications.

Sep 1, 2022

By Bernardo J. Jiménez Vega, Edy L. T. Montalvan

During the last phase of the Circunvalacion Norte project in San Jose, Costa Rica, preliminary designs for an underpass structure of over 16 km (10 miles) considered drilled shafts as an earth retaining system. Since the project’s execution was delayed and close to the deadline, it was necessary to optimize this structure, with the drilled shafts being the most critical aspect. The key element in order to obtain an improved design was characterizing the job site with a specific site study for seismic demand, and the use of advanced numerical modelling, considering soil-structure interaction. The site investigation comprised the CPT, PMT, MASW geophysical tests, deep exploration drilling, and triaxial compression tests. The terrain was modeled using an advanced constitutive model with hardening plasticity calibrated from the triaxial tests. Plaxis software was used to calibrate the seismic model for the terrain and for the dynamic analysis. Two conditions were considered for the retaining structure: free-head and fixed head. A parametric study with drilled shafts of 1.0 m (3.3 ft) and 1.2 m (3.9 ft) in diameter, and center-to-center spacing of 1.3 m (4.3 ft) and 3.0 m (9.8 ft) was conducted in order to obtain an optimized structure. For each condition of the drilled shaft wall, the computed deformations were compared for two spectrum designs: site-specific spectrum and seismic code generic spectrum. Finally, a dynamic analysis was performed to check the performance of the drilled shafts with optimized spacing using a control earthquake. Based upon seismic performance curves, the analysis showed the possibility of greater spacing for the drilled shafts compared to the original design, obtaining a 32% reduction in the total length of the drilled shafts in the project.

Oct 1, 2022

By Nabil F. Ismael, Mohamed El Deeb

"The behavior of laterally loaded step tapered bored piles in calcareous sand was examined by field tests. Lateral load tests were carried out on straight and step tapered bored piles 5.3 m long embedded 5 m below ground level. All piles were installed by augering. The straight piles were 0.2 m, and 0.3 m in diameter. The step tapered piles have a diameter of 0.3 m along the upper 10%, 20%, and 40% segment, respectively, changing to 0.2 m for the lower section. Two piles were instrumented with strain gages to measure the bending strains. All tests were carried out to failure. The purpose being to examine the ultimate lateral capacity and the deflection at working loads. Test results indicate non linear response and substantial increase in lateral capacity and decrease of deflection for the step tapered piles compared with the 0.2 m diameter straight shaft piles. However, beyond a depth of 40% of the pile length, the strengthening of the pile section by enlargement of its diameter had little effect on the lateral capacity and the deflection of step tapered bored piles.IntroductionFor many structures on pile foundations the ultimate capacity under lateral loads is important and may be the controlling factor in foundation design. Examples include transmission tower foundations and fender piles at sea port facilities. Increasing loads on these structures has resulted in piles of large diameter and depth at a significantly higher cost.In this work, the use of step tapered bored piles with a larger diameter along the upper segment of the piles is examined by field testing and analysis on single piles in calcareous desert sands. Lateral load tests were carried out on straight and step tapered piles 5.3 m long embedded 5 m below ground level. The straight piles were 0.2 m, and 0.3 m in diameter. The step tapered piles had a diameter of 0.3 m along the upper 10%, 20%, and 40% segment, respectively, changing to 0.2 m for the lower section. Two piles were instrumented with strain gages to measure the bending strains. All tests were carried out to failure. The purpose being to examine the ultimate lateral capacity and the deflection at working loads for step tapered bored piles."

Jan 1, 2005

By Marco Fellin, Van E. Komurka

Significant cost and construction benefits were obtained from performing a bi-directional static load test prior to construction on the Russell Street Bridge Replacement project in Missoula, Montana. The project utilized 24 drilled shafts to support two three-span bridges across the Clark Fork River. A bi-directional static load test (“BDSLT”) was performed on a large-diameter production shaft to demonstrate construction methods and confirm design assumptions. Subsurface conditions consisted of gravel with sand to a depth of 20 feet (6.1 m), underlain by gravel with sand, silt, cobbles, and occasional boulders. The test shaft had a nominal diameter of 5.9 feet (1.8 m), and an embedded length of 75.5 feet (23.0 m). The geotechnical engineer of record and the BDSLT test engineer collaborated to optimize the BDSLT jack assembly location within the test shaft, determine appropriate instrumentation locations, and plan the test protocol. The maximum applied test load was 10,707 kips (47.6 kN). Significant benefits were obtained from performing the BDSLT test, including 1) reducing each production shaft’s length by using a higher LRFD resistance factor allowed by having performed the testing, 2) using test-determined unit shaft resistances to evaluate and accept two production shafts that may have otherwise required remediation, and 3) providing the Montana Department of Transportation (and other designers) with increased presumptive unit resistance values in the gravel/cobble/boulder deposits. PROJECT DESCRIPTION The project was constructed in Missoula, Montana for the Montana Department of Transportation (“MDT”). The original bridge was approximately 60 years old, and consisted of a two-lane, 420-foot-long (128-m), four-span, riveted steel plate girder design spanning the Clark Fork River. The bridge was due for replacement owing to its deteriorated state, and the need for increased traffic volume capability afforded by a four-lane structure. HDR was the structural engineer. The preferred bridge alternate was a 459-foot- long (140-m), three-span, welded steel plate girder design. The new bridge was designed to meet current standards in accordance with MDT bridge design and AASHTO LRFD criteria. The new bridge was constructed in phases to keep traffic open during construction.

Jan 1, 2019

By Chu E. Ho, Paul Napoli

A new waterfront park was developed on Long Island in close proximity to the East River and Newtown Creek. The existing ground consisted of fill over soft organic clay, medium dense silty sand, glacial till and schist bedrock. The ground was initially raised to preload the underlying soft soils to stabilize the ground in preparation for site development. The ground was subsequently cut down to temporary grades for installation of foundation piles for the overlook structures and construction of reinforced concrete cantilever retaining walls forming pathways located adjacent to the water bodies. The retaining walls were located in two rows at different elevations along the sides of a steep embankment. Where the pathways converge, some of the walls were too close to each other, and were redesigned as a combined U-wall with a common base slab. The individual retaining walls were designed for adequate bearing, sliding and overturning resistance. Ground anchors were installed to enhance global stability of the retaining walls. This paper presents the design considerations for the retaining walls for various loading conditions, and evaluation of the trial and proof tests for the anchors. INTRODUCTION The New York City Master Plan included the transformation of an approximately 30-acre parcel of land in Long Island City, Queens, New York from a former manufacturing zone into a residential, commercial and recreational zone for middle-income community. The site was located at Hunters Point South along the eastern shoreline of the East River and Newtown Creek (Figure 1). The development included low to high- rise residential buildings, a public school, and retail structures. Open spaces were provided along the East River and Newtown Creek waterfronts in the form of a continuous park providing for recreational and community-related activities. Waterfront structures included small park buildings, walkways and viewing platforms. The shoreline was surrounded by revetments as part of the flood mitigation strategy. The project involved extensive site re-grading and several retaining walls were constructed. The earthwork volume amounted to approximately 47,000 cubic yard of imported fill and 93,000 cubic yard of cut. The exposed height of the retaining walls ranged from 3 to 15 feet. This paper focuses on the design and construction of the retaining walls for the project.

Jan 1, 2019

By Takefumi Takuma, Tsunenobu Nozaki, Masashi Nagano

Using sheet piles and pipe piles for permanent earth retaining is one of the most economical methods for constructing basement walls since they can also work as temporary shoring during construction. A major mixed-use redevelopment project in the UK, encompassing two to three large city blocks, utilized both sheet and pipe pile walls for a two-level subterranean parking structure. The 290m (950ft) x 100m (330ft) basement’s steel walls were designed to temporarily support excavation during construction and eventually to become a load carrying permanent structure in order to expedite the construction process and to achieve cost reduction. Two types of press-in piling machines, one for sheet piles and the other for pipe piles, were used for the job because of their abilities to press in sheet and pipe piles within tight tolerances for finished walls, for difficult installation conditions with very hard soil, and for its very low noise and practically zero-vibration operation; an essential factor for the job in close proximity to other businesses and residents. BACKGROUND Steel sheet pile and pipe piles have been used for many purposes including earth retaining. They are produced at steel mills and spirally welded at a fabrication yard to their corresponding specifications under strict quality control measures. Therefore, they can form highly reliable walls to its design capacity with proper installations. Their advantages as underground walls are:  They can form a high level of water cut-off function with their interlocks sealed by welding or with hydrophilic materials. See Figure 1 for a few examples for a sheet pile application.  They can carry vertical loading in addition to horizontal load and bending moment.  They can be a self-standing and temporary/permanent wall with flexible design and construction processes; bottom-up, top-down or hybrid sequences can be chosen per the project’s needs.  They can form a thinner wall than other wall types, creating larger inner space. See Figure 2.

Jan 1, 2019

By A. Daugiala, D. Coleman

In 2014 the New York State Department of Transportation (NYSDOT) awarded a Design-Build contract to the joint venture team consisting of Skanska which is the managing partner; Kiewit Corporation and Ecco III (SKE) and HNTB as the lead design firm. The design build team employed methods to provide schedule savings and commercial benefits to the owner NYSDOT. This paper presents the design approach and construction methods used to accelerate drilled shaft installation supporting the main span foundation for the cable stayed bridge. The drilled foundation contractor Underpinning and Foundation Skanska, a division of Skanska was responsible for assisting with design, budgeting and construction of the drilled shaft foundation construction. As part of the Request for Proposal (RFP) bid process, Alternate Technical Concepts (ATC) was encouraged by the NYSDOT. The JV team proposed an ATC which involved a scaled production shaft testing method to simulate the ultimate load level, commonly referred to as the “Chicago Method” was used in the rock socket employing the Osterberg Cell (O-Cell) testing procedures. To the authors knowledge this was the first NYSDOT project where this approach was utilized on a Demonstration/Production installation to validate construction procedures and load bearing capacities. Construction procedures, challenges and solutions are discussed in detail. Upon completion of successful drilled shaft construction, concrete integrity is verified using two methods – Cross Hole Sonic Logging (CSL) and Thermal Integrity Profiling (TIP). A comparison from the contractor’s perspective is provided. Finally the drilled shaft rock socket is tested to ultimate end bearing values while rock socket side shear stresses are not exceeding the service level loading. Lateral load test was also a RFP requirement; the test arrangement and performance are discussed in detail as well. The Kosciuszko Bridge location poised unique geotechnical challenges on many levels shifting towards an extreme boundary of parameters encountered in New York City Area for drilled shaft construction. The JV team and specialty drilled shaft contractor actively participating in the shaft design and construction practice coordination and working with NYSDOT yielded a successful foundation solution which provided cost and schedule savings to the project.

Jan 1, 2016

By Nikolas Schmitz

For today’s construction industry, large-diameter piles are common practice, as they are more competitive than drilling a larger number of smaller piles. More and more piles are installed by drilling rigs, replacing the installation by hammer, vibrators or caisson. Equipment capabilities and technics with rotary drill rigs are highly developed, but very costly and time-consuming when it comes to rock drilling, large diameters and deep foundations. Pile top drill rigs (PBA), based on reverse circulation drilling (RCD) technology, overcome these challenges and are an efficient solution for large diameter drilling (0.6 m to 8.0 m/19.7 ft to 26.3 ft) and drilling depths of up to 500 m (1,640 ft.)in various geological conditions onshore and offshore. The paper will explain benefits of RCD technology and prove this with figures from the Mumbai Trans Harbour Link project.

Nov 1, 2022

By Justin Lukens, Di Stasim Jeffrey, Frank Di Salvo

Columbia University’s Manhattanville Campus expansion includes the construction of two new business school buildings. The new buildings require development of an entire city block bound by 12th Avenue, W 131st Street, W 130th Street and Broadway in Upper Manhattan. A support of excavation (SOE) package was first released, followed by a foundation package. The SOE package consisted of approximately 100 soldier piles and 280 anchors, up to 215’ long, to support a cut anywhere from 30’- 50’ below street level. The foundation package alone included approximately 1600 drilled micropiles. Given the breadth of the work scope, Hayward Baker Inc and Moretrench joint ventured on these two projects to bring sufficient knowledge and work resources to complete the work in an efficient and timely manner. This included working with the Owner/Engineer to propose different means and methods for construction to significantly reduce the schedule while meeting the design intent, such as large diameter (36” diameter) augercast piles in place of conventionally drilled soldier piles and large hollow-bar micropiles (103/51 bars) in lieu of pressure-grouted micropiles. The anchors, ranging from 3 to 22 strands, were used for earth retention through both soldier pile and lagging walls and existing slurry walls. These anchors were complicated based not only on their size and length, but also the need to drill some of them under the historic Studebaker building. The overall magnitude of the project with considerations to resource management and material lead times will be addressed, highlighting critical strengths provided by the Contractor to ensure project success. The scope of work discussed in this paper was executed under two separate competitive bid contracts. The first contract included the support of excavation work and the second contract included the foundation package. The support of excavation comprised of drilled soldier piles (performed by Case Foundation as a subcontractor to the JV), driven soldier piles, driven sheet piles, hollow bar tiebacks, multi-strand tieback anchors and micropile soldier piles. The foundation package consisted of drilled micropiles. Due to the large scope of work and critical schedule requirements of the project, the JV had to think outside the box and present value engineered alternates to expedite installation durations.

Jan 1, 2019

By Randy R. Williams, Brian W. Wilson, George M. Filz, Marina S. W. Li

"Detailed design of an extensive deep mixing (DM) scheme using the Cutter Soil Mixing (CSM) technique was completed for foundation support of mechanically stabilized earth (MSE) walls for Kitimat Liquefied Natural Gas (LNG) at Bish Cove, British Columbia, Canada. The design was based on the provision of soil-cement structures, constructed in highly variable subsurface conditions that consisted of thick deposits of fine-grained soils overlying granular soils, and required to meet project-specific performance criteria, to support the MSE walls. The design, consisting of rectangular CSM panels constructed to form barrettes connecting to a longitudinal wall of continuous CSM panels, was configured to manage the distribution of stresses and strains that could be developed within the soil-cement structure.The results from 2D finite element analyses were used to determine the necessary arrangement and properties of the CSM panels to accommodate localized areas of relatively high shear, tensile and compressive stresses within the soil-cement structure. The relationships between unconfined compressive strength and elastic modulus for fine-grained and granular soil-cement structures obtained from the Bish Cove data were compared with published references and were found to be significantly different in the higher strength range materials.BACKGROUNDDeep Mixing design was completed for the development of the Kitimat LNG Facility located in Bish Cove, British Columbia, for support of two relatively high MSE walls and associated bulk earthwork operations. Deep mixing was necessary to treat the very weak native deposits in-situ to meet project performance requirements and physical constraints without the need for significant excavation and disposal work. The DM design was undertaken on the basis of adoption of the CSM technique for in-situ ground improvement of the native foundation soils which consisted of very soft to soft fine-grained marine deposits and loose to compact sandy silt to silty sand, overlying dense sand and gravel (Fig. 1). The DM area is located immediately upslope of the Bish Cove beach area, and is “L” shaped in plan, approximately 300 m long by approximately 28.8 m wide (parallel to the beach area) and 165 m long by an average width of 21.0 m (perpendicular to the beach area). The depth of the DM ranged from about 5.0 m to 30.7 m with typically 2.0 m embedment into dense granular soils. Details of the design philosophy, including an overview of the DM design and the project background information are presented by Li et al. (2014a). Details of the construction aspects of the Kitimat LNG deep mixing are presented by Wilson et al. (2014)."

Jan 1, 2015

By Matt Fenwick, Douglas R. Schwarm

Stringent underwater noise limits at the Fairview Ave. N. bridge replacement on Seattle's Lake Union required an innovative approach to supporting the 470-ft long drill trestle. Screw-in foundations would reliably mitigate noise, but the required 500-kip bearing resistance were an order of magnitude higher than typical helical piles. This paper describes the process of designing, installing, monitoring, and testing 22-inch dia. helical piles 80 feet long with 36- and 42-inch dia. helices. A static load test confirmed that the conventional k-factor design method can be extended to capacities of up to 800 kips. A 375 ft-kip drive mechanism had to be fabricated because no North American equipment could supply the necessary installation torque. Real time installation monitoring and later "re-torque" tests confirm that helical piles gain capacity with time, analogous to driven piles under restrike. Underwater and on-land measurements confirmed very low noise, suggesting the possibility of widespread adoption where similar limits are imposed. Overall, this case history illuminates the need for innovative deep foundation types in response to ever-increasing regulatory constraints.

Sep 8, 2021

By Federico Pagliacci

"Many existing dams are subject to underwater seepage due to subsoil conditions, like deep alluvial deposits or pervious rocks or karst. Remedial works are necessary in order to install new cut-off walls to stop the water flow. In some cases the cut-off walls have to be executed at depths never reached so far, and difficult to reach with traditional foundation techniques. In many cases the Hydromill technology proved to be the best system to overpass rocky layers and ensure the required verticality. The maximum depth reached by the industry was in the range of 120-150 meters. This article describes the test performed to excavate and cast in place a 3.2x1.5 m panel to a depth of 250 m. The article will also describe the stratigraphy of the site down to 250 meters, as well as the technique adopted to achieve the said depth with deviations from verticality of 30 cm along the longitudinal axis (0.12%) and 20 cm along the transverse axis (0.10%), measured at the bottom of the excavation. The concreting of the panel, for about 1,100 m³, with plastic concrete in the lower portion and conventional concrete in the upper portion will be illustrated. Finally, the tests performed during the excavation and after concrete casting will be also described, with special attention to the continuous directional core drilling that was performed along the whole length of the panel to verify the results of the deviation from verticality, through the onboard instruments, and to control the quality of concrete at a depth never reached before. IntroductionMany existing dams are subject to underwater seepage due to subsoil conditions, like deep alluvial deposits or caves and cavities or acid solutions in the bedrock formations.Conventional remedial works generally consist in the construction of an additional cut-off wall throughout the dam body and the subsoil, in most cases being deeper than the original one. Today, many examples of successful remedial cut-off walls allow the engineers to design the most suitable solution according to the dam and subsoil characteristics and nature.The real difficulty stems from the depth at which the new cut-off wall has to be socketed in competent rock or soil, so as to eliminate underwater seepage. The maximum depth ever achieved with a cut-off wall is 122.5 m for the remedial work of Mud Mountain Dam, Washington, USA, in 1988-1990. This 0.85-1.0 m thick cut-off wall was realized by means of a Hydromill, by excavating single 2.8 m-wide secant panels."

Jan 1, 2017

By Abhijit Saha

"Two analytical closed-form elastic-rigid-plastic solution methods to predict the rigid foundation behaviour on stone-column reinforced soil are compared, both of which takes into account the stone material yield within the host soil according to stress-dilatancy theory. These are the mechanistic methods developed by the author (2004, 2005) [that presently incorporates the dilatancy angle as per Schanz and Vermeer (1996)] and that developed by Pulko and Majes (2006), that takes into account the column yield as per Rowe dilatancy theory. Since optimal design of stone column necessitates optimum stress concentration on column, which is generally composed of dense gravel with/or without sand, the vertical stress on granular column is often close to its peak strength and the material dilates. To arrive at closed-form analytic solution to this complex soil-stone column interaction problem, some common assumptions like axi-symmetric soilstone column ‘unit-cell’, elastic host soil and rigid-plastic Mohr-Coulomb stone column material are combined with equilibrium and kinematic conditions. The results reflect the beneficial effect of dilatancy within the optimal range or techno-economic domain of area-ratio. The settlement predictions are compared with other analytical methods available in literature as well as with measured settlement reduction of stonecolumn reinforced ground at different subsoil conditions around the globe reported in literature.INTRODUCTIONStone columns or granular piles are frequently used in stabilization of soft clays, silts and loose silty-sands with large amount of fines. The majority of analytical methods assume infinitely wide loaded area with end-bearing columns having constant diameter and spacing that approximate to axi-symmetric conditions, and the approach is known as ‘unit-cell concept’. Several analytical solutions are available, and many of them (Aboshi et al; 1979, Balaam & Booker; 1981) are based on elastic approach considering the stonecolumn and surrounding soil as elastic materials. However, elastic methods give the ratio between the vertical stress in the column to soil (stress concentration factor) approximately equal to the ratio of constrained modulus of both materials. This ratio was found to be considerably higher than measured in the field and it is believed that elastic methods may overestimate the effects of stone columns on settlement reduction (Barksdale & Bachus, 1983). The elastic and elasto-plastic solutions presented by Balaam and Booker (1981, 1985) indicate that the problem can be idealized by assuming that the stone column is in a triaxial state and possibly yielding, such that there is no shear stress at the stone-soil interface and no yielding in the soil. Similar assumptions of stone column to be in a state of limiting equilibrium and under a triaxial stress state are considered in other methods also (Priebe; 1976, Van Impe & De Beer; 1983, Van Impe & Madhav; 1992, Saha & De; 1994, Saha; 2004, 2005, Pulko & Majes; 2006). In majority of the methods it is assumed that under load the stone-column yields at constant volume. However, the last three cases cited consider another parameter; the dilation of stone column. In Van Impe and Madhav’s (1992) and author’s (2004, 2005) method, the dilation is taken into account through the final value of the volumetric strain of column, whereas Pulko & Majes (2006) considered the stone column as Mohr-Coulomb rigid-plastic; dilating at yield in line with Rowe (1962) dilatancy theory."

Jan 1, 2015

By Seth K. Martin, Tony Nichlany, Alan R. Poeppel, Konstantinos Syngros

"This paper presents a case study on bored pile construction in challenging karst conditions below a supertall building in Kuala Lumpur. Innovative design and construction techniques helped keep the project moving through very difficult and unpredictable geological and drilling conditions. The development encompasses about 12,400 square meters and includes a 77-story tower, a 59-story tower, a five-story podium, and four contiguous basement levels. The site is underlain by a residual soil derived from a siltstone/claystone (the Kenny Hill formation), then limestone bedrock. Subsurface conditions are relatively uniform within the Kenny Hill and highly variable at the limestone surface. Extreme cases included 40-meter-tall underground caverns, 40-meter-tall pinnacles, and a 50-meter-tall underground rock ledge. Local piling practice in Kuala Lumpur involves deriving pile capacity entirely in the Kenny Hill formation to avoid the unpredictable limestone surface. However, the massive tower foundation loads and relatively shallow bedrock required the piles to be socketed in the limestone. The 77-story tower will be supported by 2.0- and 2.2-meter-diameter bored piles 50 to 100+ meters long, socketed in limestone, with working loads between 40 and 70 Meganewtons. Two Osterberg-cell load tests were used to develop a site-specific rock socket skin friction correlation with RQD. Exploratory rock probes were drilled at each pile location to design the rock socket length based on the rock quality and sloping rock conditions. The rock mass was pressure-grouted during each rock probe to improve the rock quality and fill voids in the rock.INTRODUCTIONThe Kuala Lumpur City Centre, home of the Petronas Towers and the world’s deepest foundations, will be the future home of a new supertall tower. The 77-story tower will be supported by a piled-raft foundation that relies on piles terminating in the highly erratic, karstic Kuala Lumpur limestone formation. The high building loads coupled with relatively shallow limestone across the majority of the tower footprint forced the piles to extend into the limestone."

Jan 1, 2016