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By Y. M. Ha, T. D. Nguyen, D. T. Nguyen, H. K. Choi

Conventionally, cement deep mixing (CDM) columns are designed to have constant diameters over the improved depth as this facilitates the construction procedures. However, this design pattern may be inefficient in cases of spread footings or shallow foundations. This paper first briefly introduces principles of an improved CDM method that can create head-enlarged CDM (termed PF) columns. A simple analysis approach was introduced to obtain optimal shape of PF columns that results in minimum settlement. The effectiveness of this improved method over the conventional CDM method was then illustrated by settlement analysis for an actual footing in a case study using two recommended analytical methods in the literature. Analysis results from the case indicated that by using the same amount of soil-cement mixed volumes, settlement from a footing on PF columns can reduce up to 10 % compared with that from the same footing on CDM columns. In addition, a material quantity comparison for the case indicated that to have the same settlement values the volume of each PF column can be reduced of around 10% compared with that of the CDM column. INTRODUCTION The cement deep mixing (CDM) method is one of the most popular methods in ground improvement works. Details on the method such as construction procedures, necessary equipment and recommendations are described in many references or manuals (e.g. Bruce et al. 2013, BS EN 2015, Kitazume and Terashi 2013). Conventionally, CDM columns are designed to have constant diameters over the improved depth as this facilitates the construction procedures. However, this design pattern is found inefficient in cases of spread footings or shallow foundations as the upper soil layers are naturally weaker than the deeper ones but are subjected to larger amount of induced stress from the superstructures.

Jan 1, 2019

By Ross T. McGillivray, David S. Graham, Dan A. Brown, Steven D. Dapp

"The Selmon Expressway includes an elevated structure extending across several miles of weathered karstic limestone geology, and represents a challenge for design because of the high variability of the material and the difficulty in characterizing the strength. The nature of the epikarst in this region of Tampa is such that variability can be extreme within distances of only a few feet. The weathered rock includes extremely soft soil infill within solution features on and within the formation. The limestone is so weathered that coring typically does not yield useful samples for strength testing, and in-situ Standard Penetration Testing (SPT) tests often encounter refusal blow counts. Thus the challenge for foundation design includes two components of reliability risks: the uncertainty associated with the ground conditions at a given foundation location plus the uncertainty associated with the foundation performance at a given location even when the stratigraphy is determined.This paper describes the design approach that has been implemented successfully for two projects at the Lee Roy Selmon Crosstown Expressway (LRS) in Tampa, Florida: the assessment and remediation of the reversible elevated lane (REL) foundations constructed in 2004, and the elevated expressways widening project constructed in 2012. Included in this design approach is a method developed for computing axial resistance in this local geology. Design for axial loading relies primarily on the development of side resistance, which was considered less subject to performance risks than base resistance. The calculation method incorporates a statistical analysis of SPT data, tempered by engineering judgment, to characterize stratigraphy at a given location into either soil, intermediate geomaterial (IGM) or rock.IntroductionThe subsurface stratigraphy of sites underlain by weathered limestone formations can be highly variable with respect to material layer thicknesses and strengths, even over short horizontal distances. This is the case for much of Florida, and particularly the Tampa area. These conditions present a challenging environment for the design of drilled foundations because of the need for a reliable determination of subsurface conditions at each foundation location, as they relate to the expected axial performance. Contributing factors include:"

Jan 1, 2015

By Terzis D. PhD, Katterbach M.

While awareness around the environmental impact of existing grout materials and chemical binders is increasing rapidly, biotechnologies are growing traction as sustainable alternatives in groundwork operations. Herein we present the principles and application methods of bio-grouting. The term is used to describe a system which is based on soil, groundwater or marine enzymes which are able to catalyze the production of calcite replicating a natural phenomenon. The system’s end result are mineral crystalline bridges which act as binders to improve the geotechnical properties of soils. This paper presents a comprehensive description of bio-grouts, their underlaying mechanisms contributing to mineralization as well as environmental considerations. With their water-like rheology, bio-grouts have a wide application range and are minimally invasive, requiring only very limited injection pressures. The equipment is the same as that used in conventional cement grouting, and the reactant components are worldwide available or easily suppliable, which explains why bio-grouting has nowadays become a valuable and sustainable alternative towards efficient soil treatment. Recent developments in the last years have allowed to further increase the applicability and efficiency of bio-grouts to ultimately bridge the gap between research and practice. A case study is illustrated in this paper showing the successful implementation of bio-grout for the stabilization of weakly cemented sandstone to safeguard an adjacent road segment in Switzerland

May 1, 2022

By George W. Little, John Councilman

"The selection, evaluation, and modification of contractor mix designs for self-hardening seepage barriers, completed by the slurry trench excavation method, can be one of the most critical and challenging tasks to ensure the cutoff wall meets the design performance criteria. Contractor mix designs should incorporate all available geotechnical data, including subsurface soil characteristics, groundwater information, and potential site contaminates. However, the pre-construction mix design can have limitations if subsurface data is limited or shows variability from initial investigations. Placement of the seepage barrier material needs to be evaluated during construction to identify in-situ performance. In one particular case study, the self-hardening cutoff wall mix design was evaluated over a one year period followed by a year and a half installation period, in which, a number of adjustments were made to the laboratory mix design during construction due to performance in the field. Installation for the selected mix was monitored on a real-time basis, using quality control data, as well as early strength and permeability results to determine if adjustments to the self-hardening mix were necessary. Evaluation of early results and relationships between strength and permeability were used to make adjustments prior to achieving the final test results for 28-day strength and permeability. Test results of the installed mix illustrated a direct correlation between strength and permeability. Achieving a minimum unconfined compressive strength was necessary to meet the minimum permeability of the seepage barrier. Other determinations conclude that the thorough development of a pre-construction mix design can have limitations even when all geotechnical data and site conditions are taken into account. Understanding early indicators and key strength and permeability relationships are necessary to determine seepage barrier performance and limitations.IntroductionThe evaluation of contractor mix designs for self-hardening seepage barriers was reviewed for one particular case study where a mix was developed using available geotechnical background information, including considerations for impacted groundwater. Following development of the laboratory mix design, the seepage barrier wall was installed over a one and a half year period, where the contractor mix design was evaluated and modified to accommodate field conditions affecting performance. The objective of the project was to cutoff and collect impacted groundwater and prevent the migration of contaminants to the creek running adjacent to the project. The self-hardening seepage barrier wall was installed using the slurry trench excavation method along 4700 ft of alignment and extended to depths ranging from 20 to 85 ft below ground surface, where it tied in with a low permeability stratum or competent bedrock."

Jan 1, 2016

By Steven D. Scherer

The highest earthquake risk in the United States east of the Rockies is along the New Madrid Fault System, which extends for 193 km (120 miles) through the Central Mississippi Valley from northeastern Arkansas, through southwestern Missouri, western Tennessee and western Kentucky to southern Illinois. Historically, this fault has generated some of the most powerful earthquakes in U.S. history, notably three Magnitude 8 events in 1811. Apart from the West Coast, this region experiences more earthquakes than anywhere else in the United States, with more than 200 events recorded along the fault annually. These events are typically of much lower magnitude than those experienced in California. Most are too small to be felt. However, should a significant event occur, damage can be expected to be widespread because of the underlying geology. In recent years, earthquake preparedness and seismic upgrade of vulnerable structures has become a focus for a number of State Departments of Transportation, including those in Illinois and Missouri where there is a potential for future damage. This paper presents three case histories illustrating three different techniques used to retrofit interstate highway bridge foundations bearing on potentially liquefiable soils. Friction minipiles were installed at the approach span of the I-57 bridge crossing the Mississippi River near Cairo, Illinois to provide additional support to the pile caps in the event of liquefaction of the underlying sands during a seismic event. In St Louis, Missouri, rock-socketed minipiles were installed to increase the capacity of drilled shaft foundations supporting a section of Interstate 64. In Mounds, Illinois, compaction grouting was used to densify loose sand deposits beneath a pile-supported interstate bridge on I-57.

Jan 1, 2001

By Abid O. Adekunte

The design, construction and monitoring of the deep excavation support for the basement of a large-scale commercial development in Cavan, Ireland is presented. Excavation area was adjacent to existing structures and retained height H varied between 4.0m ? 11.0m. In areas where excavation depth H < 5.0m, wall was designed as cantilevered section. However in sections where 5.0m = H = 11m, additional wall supports were required for serviceability reasons. Traditionally, designers often provide additional wall support through the use of tie-back ground anchors, raking props and braces. On the current project, the main contractor was not in support of the use of temporary props so as to maximise working space, while owners of adjacent properties disapproved the use of tie-backs. The limited set-back between the wall line and site boundary also contributed to the complexity of the project. A rare alternative solution has been adopted. This novel approach involved buttressing the wall with steeply raking bored tension piles at regular intervals along the wall. Comparison of the monitored deflections in the cantilevered sections with those recorded at sections where tension piles were used shows the novel solution to be safe and quite effective. This approach is also considered to be more economical when compared with ground anchorage and propping.

Jan 1, 2008

By Clayton A. Signor

Abstract: Expansive soils cause more damage to structures annually than a combination of other major natural disasters. Because of the cost to our society, all means and methods need to be fully explored to mitigate the problems associated with expansive soils. This study will present a foundation design approach that is underutilized in this application, driven piles. The main objective of the study is to present pile test results and analysis from four driven pile project sites in three types of expansive soils found in central Texas: Del Rio formation, Taylor/Navarro formation, and expansive alluvium. High strain dynamic pile tests were conducted on each of the four studies with rigorous signal matching analysis from the CAse Pile Wave Analysis Program (CAPWAP). Ultimate pile capacities ranged from 73 to 311 kips with an average of 61% of the total capacity coming from the pile shaft and were two to six times the structural capacity needed. Allowable loads calculated from Modified Gates dynamic formula best modeled allowable test results. Average unit skin frictions ranged from 0.50 to 4.71 ksf. Restrike pile tests of 1 to 17 days after initial driving reported 30 to 100% shaft capacity gain. All open-ended pipe piles driven produced soil plugs ranging from 4 to 14 feet thick. Small diameter, thick-walled, open-ended pipe piles reached penetration of twice the depth of designated zone of seasonal moisture change without problem. The observed production rate of the driven piles was on average 8 minutes, which implied daily production of 15 to 40 piles. Predrills or augered holes should be specified for underground obstructions found in soil investigation.

By Sylvia S. Eskander, Sherif S. AbdelSalam, Mona B. Anwar

Expanded Polystyrene (EPS) geofoam has long been used in numerous geotechnical applications due to its lightweight and durability. Among these applications is the use of EPS as an alternative fill material to conventional roadway soil embankments. This study investigates the benefits of using EPS roadway embankments to reduce the induced stresses and strains on the underlying peat and soft clay. Firstly, mechanical and interface properties of the EPS were acquired from a companion study that also considered the cyclic loading and creep effects. In order to determine the actual stress-strain distribution within the EPS blocks, a physical prototype was developed in this study with overall dimensions of 1.2 x 1.0 x 0.5 m, with a density of 35 kg/m3. The prototype EPS blocks were subjected to cyclic loading with intensities ranging from 10 to 50 kN. Then, a numerical model was developed to simulate the behavior of EPS roadway embankments. The numerical model outcomes were verified against the prototype measurements. A parametric design study was also conducted to develop a correlation between EPS embankment height and the stress-strain that occur in the underlying strata. Results showed that EPS embankments could reduce stress and settlement in the underlying soil by about 40% and 54%, respectively. EPS APPLICATIONS AND BACKGROUND Expanded Polystyrene (EPS) geofoam blocks have been effectively used during the past several decades in numerous geotechnical applications. EPS static and dynamic properties as well as interface behavior were extensively characterized in various published studies such as that conducted by Horvath, 1994; Stark et al., 2004; Zarnani and Bathurst, 2008; Trandafir et al., 2010; Athanasopoulos et al., 2012; AbdelSalam and Azzam, 2016; and others. However, to be able to use locally produced EPS blocks, its physical and mechanical properties must be thoroughly determined. The lightweight and compressible material of EPS geofoam makes it suitable both as a backfill and for absorbing pressure in both the vertical and horizontal directions. Kim et al. (2010) adopted EPS as an alternative for soil backfill around buried pipes; their model showed a reduction in the vertical stress acting on the pipes by up to 36%. Oshati et al. (2012) presented a case study of a field-instrumented box culvert with EPS blocks on top, which reduced vertical stress by 58%. Meguid et al. (2017) used an EPS inclusion to surround culverts and achieved up to 72% stress reduction, depending on the EPS density and the culvert depth to width ratio. AbdelSalam et al. (2017) used a relatively thin EPS inclusion behind flexible cantilever retaining walls, verifying that the lateral pressure can be significantly reduced by 25%; they also developed a design chart for this application. Moreover, AbdelSalam et al. (2019) investigated the use of EPS as a lightweight alternative for soil backfill above shallow tunnels. It was found that EPS had created a differential movement between the wedge located above the tunnel and the neighboring soils, which accordingly reduced the vertical stress acting on the tunnel by 85%, due to the use of lightweight EPS material and positive soil arching.

Jan 1, 2019

By Mohamad H. Hussein

A minipile system was employed in underpinning a historical structure in Florida. The existing structure is founded on shallow foundations. Subsurface conditions at the project site consist of deep organic deposits interbedded with loose sand and silty sand. A minipile foundation system was deemed the most appropriate underpinning corrective measure for the already badly cracked structure. A total of 68 minipiles, 3.5 inch OD and 0.25 inch wall thickness closed-ended concrete-filled steel pipes, were installed to depths varying from 55 to 175 feet. Installation was accomplished with a pile driving hammer having a rated energy of 1 kip-ft. Highest required pile design load was 15 kips. Conventional static and wave equation analyses were performed to establish preliminary pile lengths, to assess pile drivability and establish driving resistance criteria. Dynamic pile testing using the Pile Driving Analyzer was conducted on six of the production piles. This paper describes geotechnical design considerations, installation procedures, and dynamic field monitoring. This case represents unique applications of pile dynamic testing and such slender, very long minipiles in compressible soils.

Jan 1, 1993

By Bengt H. Fellenius

It is a truism that in the design of pile foundations one must consider both capacity and settlement. As to capacity, most basic text books contain simple methods of design of capacity of single pile. More sophisticated methods are the subject of many journal papers. However, methods for design considering settlement of pile foundations are scarce. (Most confuse settlement with the movement due to load-transfer?the transfer of load from the pile to the soil). Furthermore, for both capacity and settlement, most methods include several simplifying assumptions regarding soil layering and neglect the effect of the frequently occurring fill and excavations, as well as changes of the groundwater table and pore pressure distribution. Therefore, the methods may provide qualitative results, but not quantitative. Because of this situation, pile design often appears as somewhat of a guessing game and a very subjective?and risky?occupation. This need not be. Pile foundation design is controlled by three factors: capacity, strength, and settlement requirements and these have been combined in a method called "the unified design of piles and pile groups considering capacity, settlement, and negative skin friction" (Fellenius, 1984; 1989), which method is summarized in this guide.

Jan 1, 1991

By Seth H. Hamblin, Leo J. Hart, John E. Regan

The Route 6 /10 10 Interchange Design/Build project, located in Providence, Rhode Island, involves the design and construction of five (5) new elevated bridge structures to replace and reconfigure the existing interchange and to provide a link between Route 10 northbound and Route 6 westbound. Due to site logistics, headroom restrictions, and depth to bedrock, 50 ton drilled micropiles installed in the deep medium dense sand strata were initially proposed as the deep foundation solution. Post project award, Geosciences Testing and Research, Inc. (GTR) performed various analyses and developed an alternate driven pile solution using steel Tapertube. The results of these analyses indicated that driven steel taper tube and steel pipe piles could develop greater capacities than the drilled micropiles in the granular soil layer, thereby reducing the number of foundation elements, decreasing construction schedule and providing a more cost effective foundation alternative. A comprehensive driven pile load test program was subsequently executed by GTR and the Design Build Team led by Barletta Heavy Division of Canton, Massachusetts, to assess the performance of Tapertube and steel pipe piles, including pile drivability, load-deformation characteristics under static and dynamic loading, and to develop site-specific design parameters in two (2) distinct test areas. The test pile program included dynamic, static compression, tension and lateral load tests on each test pile. Load test measurements were automated with embedded Vibrating Wire Strain Gages (VWSG) to measure load transfer with depth. The execution and results of the successful pile load test program are presented and offer unique case study and valuable data for the use of Tapertube piles on deep foundation projects in the New England region INTRODUCTION The Rhode Island Department of Transportation (RIDOT) Route 6 / Route 10 Interchange is located west of downtown Providence. Originally constructed in the 1950’s as a highway bypass around the historic Olneyville neighborhood, the interchange consists of a series of nine (9) bridges and ramps that serve as a vital east-west link between Interstate 295, 95 and 195. Based on recent bridge rating assessments, seven of the nine bridge structures are rated “structurally deficient”. With many bridge structures shored with temporary supports as many as 15 years ago, the interchange is in critical need of replacement. In 2018, RIDOT awarded the Route 6/10 Reconstruction Design-Build Project to 6/10 Constructors, Joint Venture. Led by Barletta Heavy Division of Canton, Massachusetts, the Design Build team includes O&G Industries, DW White Construction, Aetna Bridge Co. and AECOM. The scope of work includes the replacement of the bridges and ramps, and will provide direct access from Route 10 northbound to Route 6 westbound. Valued at over $400M (US), this is currently the largest project awarded in RIDOT history.

Jan 1, 2019

By Racquel Nottingham, Freddy Lopez, Ole Gadermann

The ongoing urban development is a global phenomenon, placing has high demands on urban infrastructure (housing, public services, transportation, telecommunications, etc.). Micropiling is one of the most successfully implemented deep foundation technologies in urban interventions, and in densely populated and built-up areas. The use of micropiles enabled the implementation of several solutions within short time frames, with minimal disturbance to the daily activities of the population. Since urban interventions usually represent a very important investment and have an economic impact, special attention should be paid to the serviceability of the urban infrastructure in the middle and long term. For the foundations, the design loadbearing capacity of the used structural elements needs to be guaranteed during the planned life time of the structures. In the case of micropiles, it must be ensured that the steel load bearing elements are effectively protected against corrosion. This paper presents the structural design of permanent self-drilling micropiles, subject to tension due to uplift loads. For the case study, different micropile systems - available worldwide - will also be evaluated. For the afore mentioned micropile systems, the design considerations regarding the durability of the reinforcement, based on their corrosion protection approaches, will be presented in this paper.

By Aly Mohammad, Dongyi Yue

"The design of rock sockets for drilled shafts and piles proves to be a challenge for the Design Engineer. The magnitude of loads on the shaft and the behavior of the rock are critical in determining the required socket length. Several acceptable methods are available in the literature to analyze a rock socket under a combination of axial loads, lateral loads and moments. This paper will present a state-of-the-art methodology to analyze rock sockets utilizing deformation characteristics of the rock. This design methodology was implemented in the design of a major project in New York City.The project discussed herein is a marine transfer station planned for construction at East 91st Street along the East River in Manhattan. In order to support the piers and platform structures at a site with relatively shallow depth of the bedrock, rock sockets were required for the drilled shaft foundations. Rock sockets were utilized to provide the required fixity to the foundations and the structures. Acting at the top of the rock sockets are large shear forces and moments created by the lateral loads transferred from the structure.Upon review of the available techniques, a simplified method was proposed and used to analyze the rock sockets with a significant magnitude of lateral loading. The method recognizes two mechanisms through which the lateral shear and moment are transferred to the rock; a) load transfer through horizontal resistance of rock and b) the vertical shear resistance of the bond between socket and rock.The first load transfer mechanism was analyzed using the p-y curve method based on a rock model developed by Reese. The second was analyzed using a bond stiffness derived from the formula and curves utilized in the AASHTO Specifications for calculation of rock socket displacement. By comparing the two mechanisms, the main contribution to the large horizontal shear force that developed in the rock socket is identified.The paper will present a summary of the design methodology utilized in determining the length of the rock socket. It is believed that the presented method will provide substantial cost saving in selecting the most economical and efficient design length."

Jan 1, 2005

By James Coull, Brian Wilson, David Siddle

"In 2012, Golder Construction Inc. was awarded a Design-Build contract for the design and construction of an extensive, deep ground improvement scheme to support up to 20 metres (66 ft) high Mechanically Stabilized Earth walls and bulk earthworks required for the development of the proposed Kitimat Liquefied Natural Gas (LNG) facility at Bish Cove, British Columbia (BC). Utilizing Cutter Soil Mixing (CSM) to construct barrettes consisting of overlapping rectangular panels of in-situ cement-treated soils, a deep mixing scheme, covering an area of approximately 12,900 m2 (15,430 yd2) and comprising some 1645 CSM panels to depths of up to 30.7 m (101 ft), was developed to provide the required static and seismic stability for the LNG structures, and meet the project-specific performance criteria.CSM panels were constructed through varying thicknesses and discontinuous layers of fine-grained, very soft to soft marine deposits, and loose to compact sands, with occasional interbeds of dense sands and gravels. Panel completion criteria was based on soil response factors, as measured by the CSM equipment, with the design requiring a typical embedment of about 2 m (7 ft) into dense silty sand to sand and gravel to provide the required bearing. A total volume of approximately 73,900 m3 (96,660 yd3) of soil was treated with cement to consistently yield average unconfined compressive strengths exceeding 2.5 MPa (363 psi).This paper outlines the challenges associated with the construction and quality control of this large deep mixing scheme in highly variable geotechnical conditions at a remote location with barge-only access, and limited communication facilities. Specifically the paper will discuss the logistical challenges faced and solutions adopted for the project; equipment redundancy requirements for a 24/7 operation; the impacts of wear and tear, as well as variability in subsurface conditions on productivity; quality control processes adopted for the project, including the value of provision of an on-site laboratory; and materials handling issues, and their impacts on mix design and quality control."

Jan 1, 2017

By Steve Davidow, Ashely E. Evans, Peter M. Kandaris

"Annually thousands of deep foundations are constructed across North America supporting high voltage transmission line structures. However, a recent state of the practice survey by the Deep Foundation Institutes’ Electric Power Systems Foundation Working Group discovered that the electric power utility industry lacks consistent foundation design guidelines. The survey identified a wide variability in design assumptions, a minimal understanding of risk based analysis, and a need to standardize design methodologies. This paper summarizes the state of practice in electric system foundation design and proposes a framework for risk-based foundation design by accounting for uncertainty from both loads and resistances. Loads derived from electric system codes do not necessarily provide a compatible level of reliability for the design of foundations, as they are a mixture of probabilistic and deterministic values. Load uncertainty is derived from variability in weather conditions, structural models and material properties, typically accounted for by code derived overload factors. Resistance uncertainty arises from variability in natural soil properties, resistance models, subsurface construction techniques, material sampling methods, and limited observations. A consistent methodology is offered relating nominal resistance capacity (strength) to structure loads and service state criteria. Discussion also includes the need for risk-based assessments to account for non-structure load influences (fluvial loads, scour ground loss, liquefaction, etc.).INTRODUCTIONNearly 40 years ago the Electric Power Research Institute (EPRI) embarked on a major research effort to optimize reliability and economics of transmission line foundation design. Strategies focused on improvements in design models, site characterization, exploration strategies and testing to reduce uncertainty and variance in analysis. Transmission line engineers realized that safety and reliability advancements in design based on probabilistic approaches, with a focus on the unique nature of transmission line, could better control risk and cost.Some transmission line professionals took full advantage of these advancements, particularly where research led to improved software and models. Yet, even after two decades of extensive research, by 1995 the industry still had made little progress in changing design habits. The majority of designers were still characterizing sites via deterministic methods, using loads that may or may not relate to a consistent probability of occurrence, and applying a traditional global factor of safety approach (Phoon, et al. 1995). The following two decades have seen even greater developments in software and reliability-based analysis methods, but old habits seem to die hard as recent surveys show less than half of design professional quantitatively assess risk in their design process."

Jan 1, 2017

By Sunil Arora, Lisheng Shao, Chris Conkle

"The East Garden Grove - Wintersburg Channel located in Orange County, California, required upgrades along the levees to mitigate potential liquefaction and lateral spreading hazards. The Orange County Public Works designed soilcrete columns constructed between two rows of steel sheet piles along both sides of the channel between Graham Street and Warner Avenue (approximately 2,500 ft), and along an approximately 2,000-ft-long stretch of the south levee. The earthen embankment, approximately 13- to 15-ft high and damaged significantly by erosion, was then excavated to widen the channel to increase the channel flood conveyance capacity.The site is located within the Los Angeles Basin, underlain by several thousand ft of marine sedimentary strata. Uncontrolled fill materials were encountered to approximately 10 ft below ground surface, underlain by tidal and flood plain deposits. Groundwater was encountered at sea level, which is approximately 10 ft below grade.This paper will discuss site soil conditions, and the construction and quality control of soilcrete columns constructed by wet soil mixing; also, the paper will introduce the Drilling Index (DI) as a measurement tool, similar to the cone penetration test (CPT), to evaluate the soil strength in more detail. Finally, the statistical analysis of soil mixing strength distributions for the project quality control will be presented.INTRODUCTIONWintersburg Channel in Orange County, California, required ground improvements along the existing levees to mitigate potential liquefaction and lateral spreading under the site design earthquake. Orange County Public Works designed and developed a cellular pattern of soilcrete columns sandwiched between two rows of steel sheet piles along both sides of the channel between Graham Street and Warner Avenue, and adjacent an approximately 2,000-ft-long stretch of the south levee (Fig. 1). An earthen embankment approximately 13 to 15 ft high, damaged significantly by erosion, was then excavated to widen the channel and increase the channel flood conveyance capacity.Stiff, soilcrete cellular wall structures can reduce the earthquake-induced cyclic shear stress ratio (CSR) in the soil within the cells, thus preventing excess pore water pressure build up which may trigger soil liquefaction. For this project, approximately 6,700 soilcrete columns were constructed in a cellular pattern to an approximate depth of 40 ft. All of the soilcrete columns are 3 ft in diameter with the design unconfined compressive strength (UCS) of 150 psi."

Jan 1, 2015

By Janaka J. Kumara, Takashi Kurashina, Yoshiaki Kikuchi, Takahiro Yajima

"The inner frictional resistance of open-ended piles depend heavily on the degree of soil plugging. Many factors including pile diameter, relative density and end conditions of the piles influence the degree of soil plugging. In this paper, the effects of inner sleeves attached at the pile base on the inner frictional resistance are discussed. The experiments were conducted on a medium-dense sandy ground using smallscale model piles. The results suggest that the inner frictional resistance is influenced by sleeve height for 50 mm diameter piles although it is independent for 30 mm diameter piles. The results also indicate that soil plug height is influenced by the sleeve height. The results of the incremental filling ratio (IFR) showed that penetration of non-sleeved piles is closer to unplugged state than the sleeved piles. The results of the IFR also reveal that the degree of soil plugging is affected by the sleeve height for 50 mm diameter piles although the variation is very limited in 30 mm diameter piles. The results on the coefficient of lateral earth pressure suggested that it increases from 1.08 – 1.75 when the sleeve height is increased from 10 – 100 mm for 50 mm diameter piles.INTRODUCTIONPrevious studies have shown that the behaviour of open-ended piles is different from closed-ended piles (Szechy, 1961; Randolph et al., 1979; Paikowsky and Whitman, 1990). Open-ended driven piles are widely used for deep foundations, in particular in offshore deep foundations. Generally, it is accepted that a short open-ended pile produces a smaller bearing capacity than a similar closed-ended pile (Nauroy and Tirant, 1983). However, a long open-ended pile can produce a similar bearing capacity as a closed-ended pile due to a large inner frictional resistance mobilised between the inner pile shaft and inner soil (Lehane and Randolph, 2002). The ultimate bearing capacity of an open-ended pile, Qu consists of three components as given in Eq. 1."

Jan 1, 2017

By Armin W. Stuedlein, Steven R. Saye

The differences between calculated axial pile capacity and the capacity realized during and following installation has long presented a significant concern for foundation engineers and contractors. Such differences have increased in prevalence with the increased use of larger diameter steel pipe piles and the significant increase in design-build contracting. The writers present concepts to close the gap between calculated axial pile capacity and the capacity realized during and following installation of driven pile foundations, including: (1) pile set-up in plastic soils, (2) limitation of re-driving of piles after setup which serves to reduce pile capacity, (3) the use of a vibratory hammer to install piles in cohesive soils disturbs the supporting soils and reduces the pile side resistance capacity significantly, and (4) long pile installation times for open-ended piles can damage the pile side resistance. Examples are presented from practice to illustrate these concepts and to guide pile installation planning to recognize the installation impacts and either consider alternate installation approaches or to properly consider the installation impacts during design.

By Roberto A. Lopez, Eric Lindquist, Jon Bussiere, Dean Iwasa

"The new 11-story U.S. Federal Courthouse building in downtown Los Angeles demanded a cost effective foundation system capable of attaining a strict total settlement criterion of 0.5 inches (12 mm) under high applied loads. A design-build ground improvement system consisting of 3 ft (0.9 m) and 7 ft (2.1 m) diameter deep soil mix (DSM) columns embedded into the relatively soft Fernando Formation bedrock was selected for the project. The DSM columns support applied stresses of up to 8,800 psf from four large concrete core elements that transfer concentrated building loads to a 3 to 6 ft (0.9 to 1.8 m) thick reinforced concrete mat. The soil mixing ground improvement solution provided flexibility by allowing installation of the DSM columns around existing belled caissons left in place from prior structures, and by allowing repositioning of some of the DSM columns to avoid other existing obstructions in the fill. DSM spoils were used to construct a 2 ft (0.6 m) thick load transfer platform on top of the DSM columns. Quality control measures included utilizing equipment outfitted with automated data acquisition systems, performing three full scale load tests, performing daily wet-mix sampling and compression testing, performing full-depth coring and unconfined compression testing on core samples, and using a borehole acoustic televiewer to evaluate the uniformity of the DSM columns where core recovery was problematic. The results of subsurface investigation and the load tests were used to develop 3-dimensional finite differences models for evaluating stress distribution and deformation of the foundation system.INTRODUCTIONThe new U.S. Federal Courthouse building is currently under construction in downtown Los Angeles, California. The new courthouse will be 11 stories tall with one partial below-grade B1 basement level. The building will have four structural core elements that extend from the main building foundation at the B1 level to the top of the structure. The majority of the building loads will be transferred through the structural core elements to a new 3 to 6 ft (0.9 to 1.8 m) thick reinforced concrete mat beneath the central portion of the structure. The foundation pressures beneath each of the core element locations will be approximately 6,200 to 8,800 psf (300 to 420 kPa) with lower foundation pressures at locations farther away from the central core area."

Jan 1, 2015

By Paul Pedini

The challenge of Contract C19E1 of Boston&apos;s Central Artery Project called for the construction of two roadways under the commuter rail yard at North Station. Two options were offered for the method of their construction: Slurry Wall Roof-First or Soft Ground Tunneling. The instability of the indigenous soils seemed to rule out the use of tunneling, so the slurry wall method was chosen. However, these soils were incapable of holding up during slurry trench excavation. After many episodes of ground loss on early panel excavations, Modem Continental Construction suggested a method of trench wall stabilization. The Contractor (MCC) both suggested wall stabilization method and requested that the owner participate in the funding for the effort. The Project and the Contractor were able to agree on a solution which resulted in collapse-free excavation...and found an innovative way to fund the solution.

Jan 1, 2002