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By Bengt H. Fetlenius

The "Pile Prediction Event" at the ASCE GeoInstitute's Deep Foundation Conference in February 2002 involved prediction of drivability and capacity of three 14m long, 324mm diameter, closed-toe pipe piles driven into loose to compact fine sand to slightly silty sand. Predictors were provided the results of two soil borings and three cone penetrometer tests, as well as type and model of hammer to be used for the pile driving. A total of 33 persons submitted predictions. As to penetration resistance distribution, many predictions were far below actually observed values. As to capacity in compression, the predicted values ranged from 270KN through 2,340KN with a mean of 1,070KN. As to capacity in tension, the predicted values ranged from 100KN through 1,650KN. The maximum load applied to the compression pile in the static loading test was 1,25OKN, at which no more reaction load was available. The reaction system for the tension test failed early in the test. CAPWAP analysis on End-of-Driving blows showed capacities at the end of the driving for the push and pull piles of 670KN, and 710KN, respectively. No restrike tests were made. Additional CPT soundings indicate that the pile driving had densified the soil. Static analysis and calculations from the CPT indicated that capacities ranged from 1,000KN through 2,000KN. The paper presents the data and discusses the various methods of determining pile capacity and addresses influence of set-up Lessons useful for future similar events are indicated.

Jan 1, 2004

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 Joseph A. Mann

"Soil mixing is a proven solution for the construction of ground improvement adjacent to sensitive structures due to the use of computer controlled and monitored equipment. The precision to which geometry is controlled can often be the deciding factor for selection of soil mixing versus other means of ground improvement. Protection of existing structures and utilities requires careful planning, investigation, and may demand supplemental control measures. During planning, it is imperative that the process be fully developed by the project team to ensure proper control measures are budgeted; otherwise, the success and safety of a project can be jeopardized.This paper discusses case histories of soil mixing performed in close proximity to large, sensitive, and critical utilities, including foundation support for an existing earthen dam impounding a water reservoir in upstate NY, a buffer zone for a tunnel drop shaft at an operating wastewater treatment plant in Washington DC, and a containment system to protect a major water line along an interstate widening project in Baltimore, MD. The function of soil mixing as ground improvement varied; however, the selection and application of the technique versus other means of ground improvement was specific due to the controlled manner of construction with soil mixing. Through the three case studies, small diameter (3- ft [0.9 m]), large diameter (8-ft [2.4 m]), and mass mixing applications will be discussed. Furthermore, the case studies offer insight into how the geotechnical community in the Mid-Atlantic utilizes soil mixing technology for widely varying applications. Additional topics of discussion will be the design and construction of the ground improvement systems, procedures and execution of the work to protect existing structures, and the QA/QC methods, procedures, and results from the projects.INTRODUCTIONWet soil mixing, also known as the Deep Mixing Method, is a ground improvement technique that improves the characteristics of weak soils by mechanically mixing them with cementitious binder slurry. To construct columns, a powerful drill advances a mixing tool with radial mixing paddles located near the bottom of the drill string. The binder slurry is pumped through the drill string to the tool as it advances and additional soil mixing is achieved as the tool is withdrawn.Wet soil mixing is applicable in a wide range of soils. Soil mixing has been performed at depths more than 100 lf (30 m). Soils vary widely in their ability to be mixed, depending on the soil type, strength, water content, plasticity, stratigraphy, and texture. Almost any soil type, including organics, can be treated with certain soil mixing technologies, although they may require high binder contents and/or pretreatment to achieve the required results. In cases when the target soil is very soft, including some very weak clays and peats, 100% of the soil may require treatment. This complete coverage of soil mixing is referred to as mass mixing."

Jan 1, 2015

By Jack Hayes

The design and construction of deep foundations involve many uncertainties. For the designer there are uncertainties regarding soil and ground water variability, regarding sampling and lab testing, regarding analytical techniques and regarding construction technique. The latter being the uncertainty over which the engineer has least control and which may have the greatest impact on capacity. Foundations with a high design factor of uncertainty can be very costly. Foundations designed with a high factor of uncertainty may have a low factor of safety, which can be even more costly.

Jan 1, 2000

By Sven Schröer, Lilma Schimmel, Dimiter Alexiew

"The Geotextile Encased Columns (GEC) deep foundation system for embankments on soft soils was introduced some 20 years ago and is now considered State-of-the-art worldwide.The GECs consist of compacted granular fill, similar to common gravel columns, with one decisive difference: they are confined in a high-strength low-strain flexible geotextile “cylinder” (encasement). This engineered element provides a very efficient tool to control and optimize the behavior of the system. GECs perform very well even in extremely soft soils ensuring bearing capacity (stability) and reducing settlements. Due to the encasement, they a lso provide high lateral ductility. A wide range of fills including sands can be used.The remarkable reduction of vertical stresses in the soft soil surrounding the GECs results in a decrease of lateral pressure as well. Such reduction combined with the lateral ductility allow GECs to be also used for lateral pressure-relief adjacent to sensitive foundations, e.g. rigid piles. The application of GECs as lateral pressure relief was recently used in Brazil and Germany where bridge abutments were built on concrete reinforced-piles. The GECs below the bridge approaches and adjacent to the piles decreased the lateral pressure to acceptable values.This paper presents two case studies for which the most relevant parameters, the geotechnical conditions, specific problems, engineering philosophy, final solution and lessons learned are discussed. Furthermore, instrumentation programs were applied in both projects. The most important results in terms of displacements and stresses are shown, evaluated, summarized and commented upon, focusing on the lateral stress-relief, followed by conclusions and recommendations."

Jan 1, 2016

By Arjan Jovani, Arjan Beqiraj, Përparim Alikaj, Altin Karriqi

"Koman dam is one of most important high dams in Drin River Cascade. Safety of these dam is very important not only in power production but also in social and environmental aspects connected with vital activity of local people living in downstream of Drini River and in economic development of the country. In December 2014, during the rehabilitation works on some protection measures at the downstream dam toe, a considerable amount of water leakage emerged from the dam toe. This was noticed even before, but its amount and physical-chemical properties were not evaluated. In order to study the origin and flow direction of this water leakage, KESH sh.a. (Albanian Power Corporation) realized Geophysical and Hydro chemical surveys, turbidity and flow measurements and respective analyses of them. Geophysical survey consist in Apparent Resistivity surveys and Self Potential survey. The survey was done in 3 lines using Resistivity “Real Section” technique. Results are plotted in Sections and plan maps of resistivity and SP parameter. There are defined possible leakage areas and the main flow directions are defined. Also, there is done a hydro chemical analyse. Nine water samples were taken from the different places as Komani lake, service galleries of dam, dam toe and two karst springs which were analysed for both physical-chemical parameters and isotopic composition of O-18 and D. The attained analytical data found that water from the dam toe leakages shows the same chemical signature and isotopic composition of O-18 and D as the water from the lake, thus confirming the hydraulic connection between them.Also, There is done the analyse of water leakage turbidity and amount of this leakage"

Jan 1, 2016

By Thomas D. Humbert, Christopher J. Ramsey

Construction of a new underground parking structure in State College, Pennsylvania, is situated on a site constrained by limited ROW and required excavations ranging in depth from 25 ft to 40 ft. Additional complications included busy surface streets, an active intersection, and numerous underground utilities that could not be disrupted by construction activities. To combat these challenges, an innovative approach for earth retention was designed that combined multiple types of retention systems. The overall system included alternating sections of soil nail walls and a hybrid system of soldier pile walls (consisting of micropiles) that were partially restrained by a soil nail wall in the lower portions of the excavation. Further, due to the limited space within the property limits that inhibited the length of the permanent nails, the wall design team collaborated with the project designers to develop a solution such that the completed wall became an integral part of the final design/construction of the underground parking structure. INTRODUCTION HERE at State College is a mixed-use, high-rise building in State College, Pennsylvania. The 12-strory building has up to 3 levels of below-grade parking, with the above-grade levels consisting of residential and commercial/retail space. The existing property was a parking lot bound by the streets Calder Way to the north, Garner Street to the east, East Beaver Avenue to the south, and Heister Street to the west. The overall property sloped approximately 20 ft in elevation from southeast to northwest. Excavation for the below-grade levels extended 21 ft to 36 ft (6.4 m to 11 m) below street level. During design-development phases of the project, it became evident that due to subsurface conditions and right-of- way limitations, conventional construction techniques would not be feasible. The full perimeter of the excavation would require earth retention including the weak shale bedrock along the bottom of the excavation. The project developer (CA Ventures) and general contractor (Brinkmann) coordinated with the specialty contractor and wall design engineer to find a solution. At this time, Coastal Drilling East (specialty contractor) and Wood Environment & Infrastructure Solutions (wall design engineer) became involved. The project developer and general contractor were aware they needed an earth retention system, but given the many variables the project faced, a single, straightforward solution would not work in this application.

Jan 1, 2019

By Heman Manchanda, Sandeep Sharma

Several infrastructure projects are in various stages of construction and planning in India and almost all of them involves open ground excavation extending to varying depths. These structures are generally multipurpose and fulfil several needs of the society, their failure can be catastrophic. The design and construction of deep open excavations is generally associated with a high level of risks due to a whole series of uncertainties involved, and the success of such projects depends on various factors including appropriate evaluation of ground behavior and response to excavation stages, correct choice and analysis of construction supports, control of ground water flow during excavation, etc. One of the most critical amongst all these is ground water flow during construction and stability of underground excavation depends to a large extent on ground water control. This paper uses numerical studies for the assessment of the potential impact of ground water and ground water movement for the design of underground deep structures. The studies are being conducted using PLAXIS 2D finite element software and analysis all construction stages to which an open underground excavation shall be subjected. The paper discussed in detail the impact of water table fluctuations and comparative evaluation of different water flow conditions – a) Different Stages of excavation in line with the construction sequence (Phreatic), b) Coupled flow analysis (Transient- 1 year and 2-year duration) and c) Steady state flow conditions. The paper also covers seepage calculation and design of dewatering system.

Sep 1, 2022

By Paul Hewitt, Aaron Rastall

The New South Wales South Coast rail corridor is key infrastructure for both freight and passenger transport. Geomorphological and geological evidence suggests that land instability has been widespread throughout sections of the rail corridor, long before the first documented record of landslide activity in 1879. Major landslides occurred along a 25-km length of the South Coast Railway connecting Sydney and Wollongong because of significant rainfall events of the late 1980s. Since this time, several sites have been identified as subject to instability and treated progressively under a risk priority and safety management system. Two such sites comprise a station footbridge and overhead wiring structure (OHWS), both founded on high embankments overlying colluvial materials resulting in the structures’ potential movement and associated stability concerns. This paper presents these two sites as case studies, and discusses the project geology, geotechnical models developed, interpretation of monitoring data, and successful remediation of the rail structures using sleeved bored piles. The sleeved pile system was used to isolate bored piles, which separated the bridge foundations and OHWS from the moving soil mass to ensure the piles can carry the rail structure loads, unaffected by downslope soil movements.

Nov 1, 2022

By Guo Qian, Du Guangyin, Deng Yongfeng, Liu Songyu, Wang Ningping

"Metakaolin (MK) can efficiently enhance the strength and the impermeability of concretes and mortars. However, it has rarely been attempted in admixtures of cement-stabilized soils until presently. As deep mixing method is wildly used in ground improvement, the strength of cemented soils (soilcrete) and the applicability of the MK should be considered. This paper focuses on the macro-strength development of cement-stabilised silty soil mixed with MK. The result shows that the addition of MK can enhance the unconfined compressive strength of the soilcrete, which attributes to a combination of the rates of OPC hydration and the MK-CH reaction. Note that the strength of soilcrete was influenced by the properties of soil, water-to-binder mass ratio (W/B) in admixtures, which needs to be reconsidered since the binder mass composes that of cement and MK totally.INTRODUCTIONCement was used in ground modification techniques, such as the jet grouting, deep mixing method (DMM) which was put into practices in Japan and Nordic countries in the middle of the 1970s, and then spread to China, South East Asia[1]. For last decades, fly ash, slag or silica fume was mixed with cement to form the new cement base stabilizing agent in the view of economy and performance improvement. The mechanical behavior of these soil-binder admixtures (nominated as “soilcrete”), was investigated. But the soilcrete modified with the metakaolin (MK) was still not investigated much and lots of further work needs to be conducted.Some laboratory experiments of the soilcretes modified with MK have been taken[2~4]. Kolovos et al. (2013) indicates that the unconfined compressive strength has a more significant improvement when W/B equals 0.4 than that when W/B equals 1.20 concerning the water-to-binder mass ratio (W/B). Sonebi et al. (2013) investigates the mechanical behaviors of cement grouting containing MK with W/B equals 0.4, and also found the effectiveness of the addition of MK. Zhang et al. (2014) performed the studies on Lianyungang marine clay improvement showed that MK obviously enhanced the quality of cemented soils.In this paper, the strength of soilcrete modified with MK is further investigated, where the unconfined compressive strength at different curing time, the content of MK and cement (w/w) in lab conditions was discussed."

Jan 1, 2015

By Donald A. Bruce

"The Deep Mixing Methods (DMM), in their current forms, have been employed in the United States since 1986, although an earlier version had seen service from 1954. The earlier developments were strongly influenced by practices in the Nordic countries and Japan, while by the late 1980’s several DMM systems had been developed in the U.S. itself. Since then, DMM has continued its evolution, principally via the challenges of a series of large, landmark projects, but also via distinct, significant technological advances. This paper highlights the key points in the history of DMM in the U.S., and provides an overview of the different methods currently in use.IN THE BEGINNINGIt is a common misconception that the history of applications of the Deep Mixing Methods (DMM) in the United States dates from 1986 when SMW Seiko Inc. — a subsidiary of Japan’s Seiko Kogyo Company — was established in the Bay Area. However, the author believes that Intrusion Prepakt Co.’s patented MIP (Mixed in Place) system had been used, albeit sporadically (about 30 projects are recorded), since 1954 (FHWA 2000, 2001). Ironically, by 1961 this single auger method had been extensively used under license in Japan for excavation support and groundwater control — by the Seiko Kogyo Company. By 1972, the original MIP technique had been succeeded by more advanced Japanese methods, involving multiple augers. Intrusion Prepakt have long since become defunct.The first systematic studies of contemporary Deep Mixing Methods in Japan began in 1967 when the Port and Harbor Research Institute of the Ministry of Transportation began laboratory testing using granular and powdered lime for treating soft marine soils. Fundamental studies continued through the early 1970’s, by which time the development of industrial scale equipment was well advanced, having its first application on a marine trial near Haneda Airport. Coincidentally, laboratory and field research also began in 1967 in Sweden (“Swedish Lime Column Method”) for treating soft clays using unslaked lime. Reportedly the progenitor was a Norwegian, Kjeld Paus, who had made observations on fluid lime columns in the U.S. It would seem that developments in Japan and the Nordic countries proceeded independently until 1975 when the technology leaders from each group (Broms and Boman; and Okumura and Terashi, respectively) presented their — very similar — findings at a conference in Bangalore, India. Limited technical exchanges ensued thereafter.Whereas the Nordic developments continued to focus on the use of dry reagents (cement and lime) and relatively light equipment compatible with operating on and in very soft clays and organics, the Japanese progressed into the use of fluid reagents (cement-based grouts) and heavier equipment for both marine and land-based projects. Thus, by 1986, there were a large number of proprietary (wet and dry) DMM systems in Japan, and a rapidly growing market already by then accounting for over 12,000,000 m3 of ground treatment."

Jan 1, 2015

By Brian Wilson, Franz-Werner Gerressen

"Cutter Soil Mixing, also known as CSM, was developed in Europe as an alternate method of Deep Mixing to the more traditional single and multiple auger techniques, and brought to market by Bauer Maschinen GmbH (Bauer), towards the end of 2003. Initial development of the technique had been completed in a joint venture between Bauer and Bachy Soletanche. In 2004 the concept was introduced to the North American market. Continued development of the method and demonstration of its versatility, both in terms of applications and applicable soil types has seen a steady growth in the number of designs incorporating the approach, and contractors offering the technique. This paper provides a brief overview of the variety and size of projects and applications where the method has been adopted, discusses some lessons learned with respect to equipment operation as well as the improvements that have been introduced to the equipment, and briefly reviews the current state of practice, as well as some of the associated on-going research and development.BACKGROUNDCutter Soil Mixing (CSM) is a technique for deep soil mixing that was initially developed as a collaborative effort between Bauer Maschinen (Bauer) and Bachy Soletanche, but which ultimately resulted in the separate development of two somewhat different brands of CSM tool. The Bauer brand of CSM entered the European market in 2004, and was first promoted in the North American market in late 2004, with the first project starting in 2005. The Bachy Soletanche brand, sometimes referred to as “Geomix” was first marketed in Europe in 2005 and the first model introduced in North America in 2007.The development of the Cutter Soil Mixing technique utilized the experiences gained from Trench Cutter/Hydrofraise equipment, developing a technique that incorporates two cutting wheels rotating about a horizontal axis as opposed to the more conventional deep soil mixing approach which utilizes augers and mixing paddles rotating about vertical axes. Whereas the Trench Cutter/Hydrofraise technique excavates the soil from within a panel, and supports the open hole using a bentonite slurry, the CSM technique cuts and displaces the soil whilst pumping a slurry/grout directly into the soil through a port located between the wheels. The combination of cutting the soil while introducing an appropriate volume of slurry effectively fluidizes the column of soil around and above the cutter head. While this process achieves a high degree of mixing, even on the downward cutting stroke, thorough in-situ mixing typically occurs on the withdrawal stroke, when most of the slurry is added."

Jan 1, 2015

By Ramin Motamed, Farshid Ghazavi, Joseph A. W. Toth

"Post-disaster reconnaissance of areas affected by earthquakes has documented extensive damage to buildings with shallow foundations located in liquefaction-prone areas. Currently, estimation of liquefaction settlement is based on empirical correlations that evaluate settlement in the free-field environment and are based on one-dimensional consolidation. However, observations have shown that liquefaction settlement under buildings can be considerably greater. This research is based on a series of 1- g shake table experiments using a transparent soil box to reproduce liquefaction-induced building settlement. Building settlements were evaluated using a scaled model of a building foundation representing a 1-2 story building. Comprehensive parametric study was carried out to establish the effects of several parameters on free-field and building settlements such as building width and thickness of liquefiable soil layer. The experiments utilized accelerometers and pore-water pressure sensors to monitor ground accelerations and buildup of pore-water pressures in both the free-field and model building footprint. Results of these experiments are compared to available centrifuge tests and field observations and conclusions are drawn with respect to the potential scaling effects. Lastly, this paper discusses the feasibility of installing helical piles as a mitigation strategy to reduce the building settlements by presenting some of the exploratory experimental data obtained from this series of 1-g shake table tests.INTRODUCTIONThe 2010-2011 Canterbury earthquake sequence and the 2011 Great Tohoku earthquake are some of the most recent examples where large numbers of low-story structures sustained damage resulting from liquefaction-induced settlements. This damage has commonly been observed in residential and commercial areas developed over loose, unconsolidated and saturated coarse grained soils resulting from both natural and man-made deposits. Damages incurred from the 2010-2011 Canterbury earthquake sequence occurred in the largely unconsolidated fluvial environment bordering the Avon River in Christchurch (Henderson 2013). Similar damage was also incurred during the 2011 Great Tohoku earthquake where liquefaction of soils occurred in both young alluvial deposits and fill materials (Ashford et al. 2011). Figure 1 presents typical modes of failure to structures resulting from the effects of liquefaction. Current practices in evaluation of liquefaction settlement rely on empirical correlations (Tokimatsu et al. 1987; Ishihara et al. 1992) developed for liquefiable soils in the freefield environment (Dashti et al. 2010a). However, recent observations of the performance of foundations suggest that settlement of rigid shallow foundations in liquefiable soils are commonly greater than those predicted in the free-field. Therefore, new correlations should be developed to better predict the degree of settlement of shallow foundations in liquefiable soils. Current research is beginning to focus on the mechanisms of settlement during liquefaction in regards to confining stress, pore-water pressure and shear stress induced from foundations (Dashti et al. 2010b)."

Jan 1, 2016

Jan 1, 1984

By Peter J. Nicholson

"IntroductionDuring my more than 40 years in the practice of underground construction and engineering, the industry has seen progress from the dig down to rock or hardpan or alternatively drive concrete or steel into the ground and count the blows; then you can be sure of you have a solid foundation; to the modern day, I’m willing to try anything to save money. Of course these are both exaggerations, but not gross ones. After getting bored being supervision on jobs counting blows, I struck out into the new field of “tie-backs” as they were called in the United States, or “ground anchors” as they were then termed in the United Kingdom. After installing some of the first permanent ground anchors for the Corps of Engineers on Lake Michigan as well as the highest loaded rock anchors of the time at two dams on the Ohio River, we were at the top of our game in the 1970’s. Subsequently in the 1980’s when my view of the future of ground anchors saw their installation becoming a commodity item, we branched out into “Pin Piles” now known as Micro Piles, high capacity, steel tube encased, small diameter (5-12” or so), high capacity (100-500 tons) piling. Next came soil nailing, both temporary and permanent retaining walls, as at Cumberland Gap Kentucky. My next morph was into “Cement Deep Soil Mixing” earlier on, known simply as “soil mixing”. For this education I traveled to Japan several times and established a long-term, Joint Venture, relationship with one of the better known Japanese specialty ground modification companies. In Boston at the “Big Dig” we established the then record size soil mixing project, 500,000 or so cubic meters of CDSM concluding in the year 2000. Since then I’ve been involved as a consultant mainly for dams and levees. Below is the story of how I came to be at this place in the road to innovation in Geotechnical processes."

Jan 1, 2017

By Peter J. Nicholson

During my more than 40 years in the practice of underground construction and engineering, the industry has seen progress from the dig down to rock or hardpan or alternatively drive concrete or steel into the ground and count the blows; then you can be sure of you have a solid foundation; to the modern day, I?m willing to try anything to save money. Of course these are both exaggerations, but not gross ones. After getting bored being supervision on jobs counting blows, I struck out into the new field of ?tie-backs? as they were called in the United States, or ?ground anchors? as they were then termed in the United Kingdom. After installing some of the first permanent ground anchors for the Corps of Engineers on Lake Michigan as well as the highest loaded rock anchors of the time at two dams on the Ohio River, we were at the top of our game in the 1970?s. Subsequently in the 1980?s when my view of the future of ground anchors saw their installation becoming a commodity item, we branched out into ?Pin Piles? now known as Micro Piles, high capacity, steel tube encased, small diameter (5-12? or so), high capacity (100-500 tons) piling. Next came soil nailing, both temporary and permanent retaining walls, as at Cumberland Gap Kentucky. My next morph was into ?Cement Deep Soil Mixing? earlier on, known simply as ?soil mixing?. For this education I traveled to Japan several times and established a long-term, Joint Venture, relationship with one of the better known Japanese specialty ground modification companies. In Boston at the ?Big Dig? we established the then record size soil mixing project, 500,000 or so cubic meters of CDSM concluding in the year 2000. Since then I?ve been involved as a consultant mainly for dams and levees. Below is the story of how I came to be at this place in the road to innovation in Geotechnical processes.

By Musbah A. Hasan, Ahmed M. Nasr, Fauzi Jarushi

Many transmission towers, high-rise buildings and bridges are supported by piles. These structures may be subjected to large lateral loads. Therefore, experimental investigations on model piles under lateral loads were conducted in uniform dry sand. Small-scale model tests were carried out considering the influence of pile length, pile diameter, sand density, roughness of pile surface and vertical load on the lateral resistance of a pile. Furthermore, the effect of pile load eccentricity (e/L) on the ultimate lateral resistance was studied. Investigations, of the influence of various parameters on the magnitude of the coefficient of subgrade reaction (nh), were also performed. It was found that the lateral load capacity of piles increases with increase in pile length, pile diameter, pile surface roughness and increase in the sand density. The results also showed that the coefficient of horizontal modulus of subgrade reaction, (nh), decreases with deflection increase. From the results, the coefficient of subgrade reaction for a smooth pile embedded in medium dense sand would decrease by (134%) when the lateral pile head deflection (yg) changes from (2% to 5%) of pile diameter.

Jan 1, 2017

By Shawna Munn, Nadir Ansari, Allison Bennett

"This paper outlines how specification driven design has made Toronto Area transit infrastructure projects more expensive than similar private projects, and provides a case study of the results of an excavation at Launch Shaft 1 (LS1) for the Eglinton Crosstown Light Rail Transit project in Toronto, Ontario. The paper will describe the impact specification driven design parameters can have on design economy, constructability, and schedule and will suggest an alternative approach utilizing the Observational Method. As a result of the initial specification based design, Isherwood was retained by both the General Contractor and the Specialty Excavation Shoring Contractor to provide value engineering leveraging the Observational Method to improve constructability and construction schedule. By using well known, accepted design methods coupled with local experience in lieu of the specified design pressures and parameters, the redesigned bracing scheme reduced construction cost and schedule. This excavation case history can be a lesson learned for future transit projects.The City of Toronto has been developing its transportation network since the mid 1800’s. “Canada’s First Subway” along Yonge Street opened in March 1954 (TTC 1954), with a few additions to the subway network through to the 1980’s. The following two decades marked a long period of slow development due to recessions, budget cuts, and politics along with several cancelled projects. To fill the gap left by years of underfunding, several new transit projects are now under construction in the city as a part of Metrolinx’s $50B, 25 year, “The Big Move” initiative (Metrolinx 2013). The work on these types of infrastructure projects is highlighting a different and developing challenge within the tendering and design specification structure we will call Prescriptive Specification Design (PSD).PSD is a method used within contract specifications to control design risk on a project by applying conservative design methods, factors of safety, or other parameters to make a “fool proof” design. It is akin to requesting a colouring by numbers approach from a painter. There are inherent risks of using this method of tendering a project including increased project costs, longer construction schedules, and decrease of overall project economy. In PSD, the Owner “owns” all of the design risk on a project, including any additional costs due to changed site conditions. However, the Contractor commonly “owns” the risk of any deviations from the design specification they pursue, therefore making any improvements to the design, cost, or schedule less desirable from the Contractor’s point of view. The impact of this type of strict specified approach to design has been seen in transit infrastructure projects in the Toronto area. Figure 1 outlines the range of specified AEPD design pressures as a function of excavation height (H) specified for use in Toronto underground transit projects since the 1970’s to present day. A clear trend can be seen with respect to increased design pressures specified. The ranges shown for each project are intended to account for the potential differences in soil conditions for the highly overconsolidated glaciated soils in the Toronto area. The graph also highlights the typical range, in blue, for the industry practice in Toronto for comparison."

Jan 1, 2017

By Yazn Khasawneh Ph. D. P. E., Will Tjaden, Spencer E. Ness P. E., Mohammed Nasim Ph. D. P. E.

Wind turbine components undergo many loading cycles during their operational life. Additionally, wind turbines may undergo extreme loading conditions from natural hazards, mechanical failures, or emergency stops. Current design practice for the foundations of wind turbines accounts for these complex loading conditions through a simplified pseudo-static approach based structural loading combinations. A rotational stiffness for the foundation is estimated from the pseudo-static analysis and then compared to an acceptable minimum rotational stiffness provided by the turbine manufacturer. These minimum rotational stiffnesses are based on dynamic analysis of the tower and nacelle system with the foundation represented as linear springs. This approach provides a reasonable approach to the foundation design but does not accurately capture the true dynamic performance of the entire soil-foundation-tower-nacelle system. This becomes especially important for pier-type foundations, which are being more commonly used to support modern and future generations of larger turbines. Additionally, the dynamic performance of the foundation will vary as the adjacent soil undergoes a large number of loading cycles of varying strain magnitudes. In this study, the full turbine-tower-foundation-soil system was modeled using finite element methods. An advanced non-linear soil constitutive model and dynamic loading time histories were used to investigate changes in stiffness of the soil, and the possible impact on the dynamic response of the system. Results were compared to conventional design methodologies with the goal of reducing foundation capital costs while avoiding increases in O&M costs and which can lower the LCOE of wind energy.

Oct 1, 2022

By Leykam Chris J., Jacobs Scott. A.

"Construction of the New NY Bridge over the Hudson River 25 miles north of New York City is one of the largest civil infrastructure projects presently underway in the United States (formerly Tappan Zee Hudson River Crossing). The $3.14 billion Design-Build contract is also the largest ever awarded by the state of New York using an Alternative Project Delivery method, and the first major public project to use Design-Build. The new 3.1 mile long bridge will replace the existing Governor Malcolm Wilson Tappan Zee Bridge with a modern twin crossing featuring: Iconic side by side cable stay main spans; significant deck widths accommodating eight lanes of regular traffic, wide shoulders, and a shared use pedestrian and bike path; foundation with excess capacity to fully support a future rail bridge; more than 1,000 large diameter pipe piles driven in deep glacial deposits; drilled shafts installed through steep blast-rock slopes on the east shore landings. Geotechnical challenges included varied bedrock and glacial till surfaces with steep slopes and depths in excess of 750 ft.The purpose of this paper is to highlight major features of the New NY Bridge project with specific focus on the design and construction of the foundations supporting the approach and main span structures from abutment to abutment, provide background on alternative project delivery in NY, as well as provide an overview of the design-build process as it was applied to foundation delivery.The 3.1 mile Governor Malcolm Wilson Tappan Zee Bridge was constructed across the Hudson River connecting Nyack and Tarrytown (Rockland and Westchester Counties). Construction started in March 1952 and was completed in 1955 for a cost of $81 million. The seven lane crossing first opened to traffic on December 15, 1955 and coincided with the opening of a 28 mile segment of highway I-87 / I-287 between Suffern NY and Yonkers NY. The bridge is part of the extensive 574 mile New York State Thruway road system owned and operated by the New York State Thruway Authority (NYSTA)."

Jan 1, 2016