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By John P. Turner, Benjamin J. Turner

"Non-destructive testing and evaluation (NDT/NDE) methods have become standard tools as part of the post-construction quality assurance of drilled shaft foundations. In responding to anomalies, foundation designers, owners, and contractors face a number of choices, including: (i) acceptance of a shaft with known anomalies, (ii) further investigations of integrity (e.g., concrete coring), (iii) repair schemes, and (iv) reject and replace. To assist in selecting the best option, analyses are often performed that involve assessing the structural performance of reinforced concrete shafts that may include defective concrete or voids. Currently, the analytical tools for predicting the flexural strength and stiffness of drilled shafts with defective concrete located in discrete regions of the cross section are limited. This paper presents a robust moment-curvature analysis tool for drilled shafts based on the fiber-element discretization method. The tool allows for consideration of anomalous or defective concrete regions in the shape and location that they are believed to exist in the shaft while considering explicitly the nonlinear material behavior of the intact regions based on expected material properties. A case study is used to illustrate the practical application of the analysis to drilled shaft projects.INTRODUCTIONImperfections such as defective concrete or accidental eccentricity of reinforcing cages are an inherent part of the drilled shaft construction process that will occur occasionally even when construction best-practices are followed. Petek et al. (2002), O’Neill and Sarhan (2004), Poulos (2005), and others have described the effects that construction defects can have on the axial and lateral performance of drilled shafts. Our industry has seen rapid progress in recent years in the development and improvement of tools for detecting drilled shaft anomalies, such as gamma-gamma and crosshole-sonic logging, sonic-echo testing, thermal integrity profiling, and even visual inspection with invasive video cameras. Nonetheless, in most cases the wealth of data from these tests is used by foundation engineers to make a fairly “black or white” decision—should the defects be repaired, or should the shaft be rejected? A third option that is not typically considered is to directly analyze the section, including anomalies, and compare the reduced strength and/or ductility to the actual project demands. This option takes full advantage of the data collected during integrity testing, and may provide a justifiable means for avoiding further construction costs and delays, whether for repair or replacement."

Jan 1, 2016

By Brandon M. Robinson, Osman F. Besler, Dominik Gaechter

The Sandbukta-Moss-Såstad (SMS) project is a part of the Intercity development project, which is part of the largest transport project in Norway, consisting of 270 km of new double-track rail. The SMS project consists of 10km of double-track railway including three open stretches and two tunnels. Soil conditions consist of quick clay underlain by Bedrock. Dry soil mixing (DSM) was considered as the main soil improvement method to allow for excavation of the quick clay and construction of the D-Wall panels. The preliminary design revealed around 25,000 ton of binder installation. Therefore, a test field has been conducted to evaluate binder alternatives in means of improved soil strength by considering CO2 emissions. Multicem and Standard cement (Standard FA) have been compared for that purpose. Multicem is a type of binder which mainly consists of Portland cement and cement kiln dust (CKD). CKD is a fined-grained, solid, highly alkaline material removed from the cement kiln exhaust gases. reverse column penetration test (FOPS) and pre-drilled column penetration test (FKPS), which are common tests to evaluate DSM strength have revealed comparable strength outcome for both binder types. Therefore, Multicem has been selected as the main binder type to be used further which provided a reduction in CO2 footprint of up to 40%.

May 1, 2022

By Andrea Gambi, Giancarlo Olivucci, Maurizio Lenzi

"In the paper a criterion for the evaluation of the sharing of the lateral loads in a piled foundation is presented. It relies on the the compatibility condition between the rotation of the rigid pile cap and the rotations of the pile heads, following in that the criterion suggested by the Eurocode 8 - Part 5. This assumption leads to an analytical solutions which allows to deal with the sharing of the lateral loads and moments by means of two main interaction parameters only. A sharing domain is also derived and it shows the role played by the eccentricity of the lateral load on the values of the axial forces and of the bending moments at the head of the piles.INTRODUCTIONIt is well known that the interaction among soil, piles and foundation is one of the most complex subject to deal with in Geotechnical Engineering. Its rigorous study needs to employ suitable finite element software nowadays available and able to take into account the non linear behavior of the soil as a continuum and the inelastic response of the structure. A deep insight to the topic of the sharing of the loads cannot obviously renounce to this approach.On the other hand it is a daily need of the designers to have at their disposal simple tools that allow to make preliminary evaluations of the basic equilibrium conditions. To this purpose many methods of analysis have been developed in the past to face the sharing of the loads in a simplified version. The present contribution follows this way trying however to introduce some improvements that leads to find a solution that satisfies both the equilibrium of the forces and the compatibility of the movements (Lenzi, Gambi, Olivucci, 2002). The proposed model allows to identify the basic parameters which govern the sharing of the lateral load and it allows to perform also parametric analysis and quick checks that may be useful in the design of the piles."

Jan 1, 2005

By Viswanadham B. V. S., Babu K. V

Wind energy is one of the most economical renewable energy sources. In order to support wind turbines onshore or offshore open-ended monopile foundations are widely used. Unlike conventional structures, wind turbine foundations experience a large magnitude of lateral loads in the order of 20 % to 30% of total vertical loads. The presence of soft clayey layers at shallow depth along the coastal region, offers lesser lateral load resistance to monopile foundations. One option to enhance lateral load capacity is by introducing fins to the outer surface of the monopiles. Studies pertaining to lateral load response of finned piles in clayey soils are very sparse. This paper presents some of the numerical model studies on the lateral load response of monopiles and finned piles in soft and stiff clay. In the present study, three-dimensional finite element analyses were performed on monopiles as well as finned piles. Analyses were performed in clay with different consistency varying from soft to stiff. Pile material is mild steel for all analyses. The pile section modeled as linear elastic material whereas soil was modeled as Mohr – Coulomb constitutive model with non-associated flow rule. Monopiles and finned piles having four and eight fins with different fin sizes and configurations are considered during the analyses. Finned piles advantage over monopiles to resist lateral load is highlighted in the present study. The results have shown that fins are effective to enhance the lateral load carrying capacity of monopiles and also it reduces the bending moment in monopiles for a given design load.

Sep 1, 2022

By John Kvinsland

"The Block 43 Project is the future home of the Paul Allen Institute for Brain Science located just off the southern shore of Lake Union in Seattle, Wash. The South Lake Union (SLU) district experienced considerable development over the last 10 years and Vulcan, Inc., which is headquartered in Seattle, is at the forefront of this transition. Once a light industrial/residential location, SLU has transformed into a hub of medical technology comprising new residential units and mixed-use buildings. Malcolm Drilling Company, Inc. constructed four shoring projects for Vulcan in this vicinity over the last year, beginning with Vulcan Block 44, which consisted of 42,000 sq ft (3,902 sq m) of soldier pile and tieback wall to support a below-grade parking facility. Block 44 construction began in February 2013 and ended in mid-April. The feature project, Vulcan Block 43, was in planning stages at the time and began construction in late fall 2013.Awarded by GLY Construction of Bellevue, Wash., in September 2013, Block 43 was the most complex of the block projects performed by Malcolm. Block 43 featured dewatering and ground improvement components along with a water-tight secant pile wall. Following the commencement of Block 43, Malcolm also began work on Vulcan Block 52 in December 2013. Block 52 consisted of 43,000 sq ft (3,995 sq m) of conventional shoring in conjunction with dewatering of 8 ft (2.4 m) of excavation located below the water table. The final Vulcan project was Block 45, which started in January 2014 for Turner Construction of Seattle and consisted of 41,000 sq ft (3,809 sq m) of conventional shoring and required dewatering to complete the final 15 ft (4.6 m) of excavation.Scope and Subsurface ConditionsBlock 43 involved a wide variety of drilling applications for the building to be constructed and properly founded. The primary scope of work involved shoring support for an underground parking structure requiring excavation of approximately 82,000 cu 3 yds (62,694 m ) of soil. The cuts for the excavation were up to 43 ft (13.1 m) in depth, and the excavation was bounded by city streets as well as the South Lake Union Light Rail on its perimeter. In order to excavate beneath the water table, an extensive, deep dewatering system was required to drain the upper fill and reduce the impact of the pressurized aquifer located beneath the excavation. In addition, drilled rigid inclusions, along with compaction grouting, were required for foundation support of the future structure."

Jan 1, 2014

By Filippo Maria Leoni, Alessandro Bertero, Gianluca Pianezze

"As part of the Southeast Louisiana (SELA) drainage program, designed by the U.S. Army Corps of Engineers (USACE) to reduce flood damages in the City of New Orleans and surrounding parishes through the construction of new pumping stations and better drainage canals, the SELA-22 project entailed the installation of a concrete covered canal along Jefferson Ave. and Prytania Street, in a highly urbanized portion of Uptown New Orleans, LA. The scope of the required soil improvement was to replace the soil between two parallel lines of sheet piles with a soil-cement mass to eliminate underseepage and provide structural support for the concrete culvert. The USACE selected the jet grouting (Jet Grout) technology for the construction of the bottom plug. The bottom plug is between 18 and 21.5 ft thick with a maximum depth of approximately 40 ft, for a total length of approximately one mile. The treated soil comprised soft clays and silts with occasional presence of sands. Project specifications required 100% area coverage, a 28-days unconfined compressive strength of 100 psi and hydraulic conductivity of 1x10-6 cm/s, to be verified by testing specimens from cored samples. The specialty geotechnical contractor proposed to accomplish the task utilizing their proprietary and innovative elliptical bi-fluid Jet Grout technology, and elected to perform a pre-construction bench scale laboratory mixing program to determine the most suitable grout mix features (i.e. binder type and proportions, binder content, etc.) to be applied in the subsequent field test and production stages. This paper will summarize and compare the results obtained from the different pre-construction and construction stages; interpretations of the data will be provided, along with general considerations regarding the effectiveness and significance of bench scale testing for jet grouting applications.INTRODUCTIONIn general, the effectiveness of the construction parameters in any ground improvement work depends largely on the physical and mechanical properties of the soil to be treated. Therefore, well designed laboratory and field test programs, aimed to disclose the interaction between the site-specific soils and the mixing parameters, are essential to achieve the desired end product."

Jan 1, 2016

By Arash Khosravifar, Amalia Giannakou

"Nonlinear foundation springs for bridge caisson foundations show significant coupling between the shear force and bending moment. Implementing foundation stiffness matrix with coupling effects (off-diagonal components) into the global bridge model presents numerical challenges. A simplified approach is developed to model foundation springs including coupling effects using a simple methodology. This simplified model include one translational spring and one rotational spring combined with a rigid link in 2D space. Results show that nonlinear springs (translational, rotational and coupling) can be reasonably captured using this simplified procedure.INTRODUCTIONThe Izmit Bay Bridge is a 3-km long suspension bridge that crosses Izmit Bay in Turkey and is being constructed in a highly seismic region. Figure 1 shows the project location. The South Approach Viaduct (SAV), located along the western margin of Hersek peninsula, is within 5 km from the North Anatolian Fault and within a zone of secondary deformation around the primary trace of the North Anatolian Fault. The proposed SAV consists of 11 Piers and an abutment at the south end of the structure."

Jan 1, 2017

By Frank Rausche

Why testing What tests can be done Dynamic load testing Loading device Measurements Analysis Examples

Jan 1, 2001

By William (Bill) H. Walton

"I arrived in Chicago in 1993 with Dr. Ralph Peck’s University of Illinois bulletin titled Engineering Properties of Chicago Subsoils (Bulletin 429), which he published in 1954 with William Reed. Being an outsider, I wanted to learn from Chicago geotechnical practice leaders that included Clyde Baker, Jr., John Gnaedinger, Charles Pfingsten, Dr. Safdar Gill, Robert Lukas and Dr. Jorj Osterberg, who have influenced foundation designs for the structures that make up the contemporary Chicago skyline. One of my immediate goals was to get the Illinois Structural Engineering license to be on par with the likes of Eli Cohen, Mike Tylk, Stan Korista, Bob Halverson, Joe Burns, Ron Johnson, Bill Baker, Bob Sinn, Chuck Anderson and Dave Eckmann, who have led their structural firms in the design of the skeletal core and frames of many of Chicago’s iconic buildings (and for many other buildings around the world). From my time with GEI Consultants (GEI), then on with STS Consultants (STS, and now AECOM), and now back with GEI, I have had the opportunity to analyze and design foundations and, with the help of many skilled foundations and building constructors, to verify that predicted foundation performance matches actual movement data. The theme of Chicago’s foundation design practice is to assume and verify. In 1948, Peck published the History of Building Foundations in Chicago (Bulletin 373) that was updated in 1998 by Baker, Pfingsten and Gnaedinger, who meticulously documented hundreds of Chicago’s foundations, and have shown the value of advanced analyses and testing to advance the deep foundation design practice that includes a variety of high-capacity driven and drilled deep foundations. Mehmet Uyanik, Peck and Baker have made Chicago’s subsurface into a full-scale foundation test laboratory. They confirmed soil mechanics principles like Terzaghi’s 1-D consolidation theory when early foundations bearing on sand-clay crust over soft to medium silty clays (e.g., Auditorium, Masonic Temple, Monadnock Block and Old Board of Trade buildings) took 40 to 60 years to consolidate clay 1 to 2 ft (0.3 to 0.6 m). They also confirmed proven increases in bearing pressures based on measured performance of deep foundations bearing on the glacially derived hardpan clay till and in solid dolomite that underlies Chicago."

Jan 1, 2017

By Robert S. Thomas, Bernard M. Tarralle, Nasser Massoudi

"The Commonwealth of Virginia is restoring and expanding its Capitol of great historic significance. Designed by Thomas Jefferson in 1785, it is the second oldest Capitol building in the United States. The building expansion required excavations immediately adjacent to its South Portico. The building, which rests on shallow brick footings, is very sensitive to any disturbance caused by construction and excavation. A comprehensive and secure plan of operations was devised by the design team to ensure that this national monument remains unharmed by the new construction. Various construction techniques were implemented to satisfy the strict movement goal of 0.25 inch and distortion of U2000. They consisted of jet grout columns to stabilize the upper soils, compensation grouting for future foundation leveling, a tied-back reinforced concrete diaphragm wall for excavation retention and foundations, and realtime instrumentation for monitoring. This paper describes the design approach for the retention system, providing information on the various construction phases and techn iques, and reports on the movements recorded by the real-time monitoring system during the course of the project. At the time of this manuscript preparation, and the deep excavation complete to final grade, the results indicate that the extremely restrictive building movement criteria have been met. The success can be credited to detailed design, close cooperation among the project team, prudent construction methods, and real-time monitoring. INTRODUCTIONThe Commonwealth of Virginia is undertaking a comprehensive renovation and expansion of the Virginia Capitol building located in Richmond, Virginia. The Capitol building was designed by Thomas Jefferson in 1785, with construction of the original building starting the same year. The Capitol building was designated a National Historic Landmark in 1960 and was listed on the National Register of Historic Places in 1966.A part of the comprehensive renovation and expansion of the Capitol is a 25,000-square foot, two-level subterranean extension on the south side of the Capitol building, which will serve as a new Visitor Center and public entrance for the Capitol. Deep excavations were required for the construction of the new Visitor Center. The excavation required a permanent retention system to accommodate an approximately 40- foot deep excavation."

Jan 1, 2005

By Edmund Cardoza

In the spring of 1993, construction began on an ambitious building project in Boston, Massachusetts. The Shriners organization committed to offer state-of-the-art adolescent burn treatment and rehabilitation in its Boston facility by expanding in a most unusual way. In short, the concept included installation of caisson foundations and perimeter slurry wall panels to enable construction of a completely independent structure around and above the existing, continually functioning, hospital. Two distinct phases of work were detailed in the Contract Documents. At the completion of the first phase, patients will be moved into the new building, above, and demolition of the old structure, beneath, will be performed. In Phase I, sections of the slurry wall and caissons, located outside the footprint of the existing building, were planned. The next phase of the work includes the installation of the remaining caissons and slurry wall. Once excavation is completed, the balance of the new hospital structure will be constructed from the bottom upward, connecting to the under side of the new structure.

Jan 1, 1994

By Nick Hytiris, Mohammed Al Maadheedi, Slobodan B. Mickovski

This paper explores the capacity effects of a square steel plate welded at the ground surface on a driven open-ended steel pile (i.e. the plate would touch the ground surface after the pile achieves the required penetration). A series of strain-controlled, 1-g laboratory tests were undertaken on piles with and without a square steel plate attached. The piles were driven in dry, loosely packed, uniform sand. Two plates were used, one with a breadth equal to two times the diameter of the pile (2D) and the other with a breadth equal to three times the diameter of the piles (3D). A 20% increase in capacity was recorded for the 2D plate, and a 110% increase in capacity was recorded for the 3D plate when compared to the pile without an attached steel plate. The back-analysis of the results allowed the derivation of a new expression to calculate the capacity of bearing plates, which accounted for the effects of sands compaction and dilation. By extrapolating the findings of these tests to a hypothetical scenario, a model design problem was described where the length of a pile can be reduced by 20% to 60% (depending on the load) by using a plate attached to the pile. The results of this study can help designers to minimise penetration depth; thus, achieving a more economical and sustainable design.

By Mohammed Al Maadheedi

This paper explores the capacity effects of a square steel plate welded at the ground surface on a driven open-ended steel pile (i.e. the plate would touch the ground surface after the pile achieves the required penetration). A series of strain-controlled, 1-g laboratory tests were undertaken on piles with and without a square steel plate attached. The piles were driven in dry, loosely packed, uniform sand. Two plates were used, one with a breadth equal to two times the diameter of the pile (2D) and the other with a breadth equal to three times the diameter of the piles (3D). A 20% increase in capacity was recorded for the 2D plate, and a 110% increase in capacity was recorded for the 3D plate when compared to the pile without an attached steel plate. The back-analysis of the results allowed the derivation of a new expression to calculate the capacity of bearing plates, which accounted for the effects of sands compaction and dilation. By extrapolating the findings of these tests to a hypothetical scenario, a model design problem was described where the length of a pile can be reduced by 20% to 60% (depending on the load) by using a plate attached to the pile. The results of this study can help designers to minimise penetration depth; thus, achieving a more economical and sustainable design.

By Terence Ma, Seok hyeon Chai, Jeff Lam, Thamer Yacoub, Brigid Cami, Sina Javankhoshdel

The Limit Equilibrium (LE) analysis of pile-supported geotechnical structures normally assumes a constant shear force for the pile instead of considering the non-linear capacity of the pile which is related to the pile displacement. In this study, a 3D Limit Equilibrium analysis is carried out for a landslide model supported with piles by considering the constant and non-linear capacity of the pile which is computed using a separate Finite Element (FE) algorithm. The depth of the pile, soil layering, and the pile properties are used with an assumed maximum displacement to compute the geotechnical non-linear capacity of the pile. In this study, the results of the initial unreinforced 3D LE model was first compared to the 3D FE analysis results. Then, the pile pattern was applied to the failure region in the 3D LE model, and then the factor of safety was recomputed. The results of the constant shear piles were compared to the model with the non-linear piles.

Sep 8, 2021

By Andrew Middleton, Mark Wyatt

"The Brickworks Marketplace Project is a significant shopping centre development in inner north west Adelaide constructed by Badge Constructions in 2014 and 2015. The site was a former brickworks with a deep pit containing various extents of uncontrolled fill which was to remain on site, and with a remaining void up to 6 m in depth. The existing uncontrolled fill was improved using the High Energy Impact Compaction system, and the pit backfilled using a quarry crusher byproduct selected by trial and a recycled crushed concrete and bricks and compacted in deep lifts. This approach resulted in significant savings in compaction time, cost and building foundations. The settlements of various parts of the completed works have been monitored since February 2015 and this monitoring has demonstrated small settlements which meet the user’s constraints.INTRODUCTIONThe Torrensville Brickwork Markets project involved the transformation of a former brickworks and clay pit site into a regional 17,000m2 shopping centre, opening in June 2015.The site was a former brickworks with adjoining clay borrow pit. The clay pit had been partially backfilled over many years with ‘uncontrolled’ fill comprising ‘clean’ soil, bricks and kiln dust typically of the following thicknesses:??of the order of up to 7 m to 10 m but locally up to 15 m in the western part of the site??2 m to 5 m in the south-eastern part of the site; and??less than 0.5 m in the north-eastern part of the siteAnecdotal reports suggested compaction of some of the fill may have been undertaken, although this not able to be confirmed nor records obtained.Initially it was proposed to take up the existing uncontrolled fill, sort and recompact or remove to landfill, followed by backfilling in conventional means over 500,000 cubic metres of imported filling to a thickness of up to approximately 6m to backfill the former pit. This work represented a significant cost and was not economically viable.During early negotiations, the contractor proposed an alternative to retain and ground improve the existing filling on site, and to backfill the pit with fill placed and compacted in deep lifts, thereby significantly improving the economics, environmental and community impacts of the proposed works.The developer agreed to the proposal with the following performance criteria:??a settlement of =10 mm after 10 passes by the Impact Compactor (on existing subgrade areas);??a bearing capacity of 250 kPa for high level footings;??a maximum long term differential settlement of 40 mm (measured over 16 m), ie. 1 in 400; and??a minimum modulus of 40MPa."

Jan 1, 1900

By Vijaya R, Boominathan A

The design of a rubble mound breakwater resting on a problematic seabed is quite challenging and expensive. In the present study, stage-wise construction of a typical section of the breakwater for a proposed port on the eastern coast of India is carried out. The major challenge envisaged in the design of breakwater is the subsoil strata which consists of soft clayey soil. As it is difficult to improve the soft clayey soil in the marine condition, construction stages are meticulously planned in such a way that consolidation takes place due to the preloading of breakwater, which in turn leads to the strength improvement without any special ground treatment. Thus, the breakwater is designed to be constructed in 7 stages. An initial geostatic analysis is carried out, followed by a plastic stress-strain analysis, consolidation analysis, and safety analysis for each stage, using finite element (FE) code PLAXIS. It is found from the FE analysis that due to the presence of the soft clayey soil, the critical slip circle was formed in the base. It was observed that the staged construction over a period of 2 years provides a sufficient increase in the factor of safety of above 1.5 at the various stages of construction. Hence, it was recommended to construct the breakwater with 7 stages over a period of 2 years.

Sep 1, 2022

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 Nick O’Riordan, Kaitlyn L. Fleming, Michael Riemer, Youssef M. A. Hashash, Stephen McLandrich, Mohamad Jammoul, Pierre Gouvin, Andrew Yeskoo

"To accommodate urbanization, cities are developing more underground space as a means to house public transportation systems and other entities. Underground developments often require construction of deep excavations in an environment dense with infrastructure. The success of such a project is related to the amount of impact imposed on adjacent structures and economic activity; impact should be limited to insignificant amounts in order to mitigate damage and disruption. Thus, large-scale urban construction projects require extensive monitoring of ground movements and installed support performance to facilitate informed decisions for adjustment of construction activities and support design when necessary.In downtown San Francisco, a unique large-scale excavation in saturated soft soils was constructed for the Transbay Transit Center (TTC). Construction of the excavation began in April 2012 and was completed almost two years later in February 2014. To monitor ground and structure response to construction, the project team used an extensive instrumentation network that included automatic inclinometers, piezometers, strain gages and total stations paired with survey markers. Innovative imaging techniques developed a record of construction in order to relate measured deformations to construction activity.Transbay Transit CenterThe Transbay Transit Center (TTC) is being constructed as a modern day transportation hub in downtown San Francisco to replace the former Transbay Terminal. The project is located in the South of Market area, less than half a mile from the San Francisco Bay. The final center will connect eight counties in the Bay Area through 11 different transportation systems, some of which will be housed in the TTC including Caltrain, Golden Gate Transit and California High Speed Rail. The aboveground structure will consist of two levels for retail and a third level with a bus terminal beneath a rooftop garden. There will be two subgrade levels to serve as a lower concourse and the train platforms. This structure required construction of a deep excavation closely surrounded by buildings and roads in an area thriving with economic activity."

Jan 1, 2015

By Murad Y. Abu-Farsakh, Md Habibur Rahman

The properties of all natural soil deposits are highly variable, and they are rarely homogeneous. Cone penetration tests (CPT) were used to assess the site variability, which was then incorporated into the Load and Resistance Factor Design (LRFD) of pile foundations. Data from six project sites with multiple CPT tests conducted at various locations were collected for this research. The semi-variogram was used to assess the spatial variability of CPT data (corrected tip resistance, qt) for each location. For each location, the coefficient of variation due to spatial variability (COVR,spatial) was calculated. From COVR,spatial and COVR,method, the total coefficient of variation (COVR,total) for each site was calculated, which was then used to calibrate the resistance factors (ϕspatial, ϕtotal) for use in LRFD pile foundation design. The findings of this study demonstrated the importance of using site variability in LRFD pile design. For sites with lower site variability than the design method (i.e., COVR, spatial < COVR, method), the value of the COVR, total will be decreased, and hence the resistance factors (ϕspatial or ϕtotal) will be increased (credit), and vice versa.

Sep 8, 2021

By Giulia M. B., Ferruccio Cribari, Alessandro Bertero, Eliano Romani, Roberto Sorge, Francesca Casini

"The use of Artificial Ground Freezing (AGF) to form earth support and seepage control barrier systems has had applications worldwide. These cover a variety of construction problems, including the formation of frozen earth walls to support deep excavations, structural underpinning for foundation improvement, and temporary control of ground water in construction processes. An application of AGF during construction of Line C of Rome underground is described in detail.The new line “C” of San Giovanni metro station was constructed adjacent to the existing line “A” of San Giovanni station; the new metro line “C” is deeper than line “A” and runs below the existing station. The underpass project envisages an Artificial Ground Freezing in order to create a structural and waterproof temporary cut-off suitable to the two new tunnels excavation, while keeping trains running in the safest possible condition. The excavation of tunnels under the water table, with a hydraulic head of over 10 m in not homogeneous soils having different mechanical properties and permeability and below existing sensitive structures, involves special ground freezing sequences and methods, as well as peculiar drilling systems and operations, such as TDDT (Trevi Directional Drilling Technology).Artifical Ground Freezing IntroductionNatural freezing occurs seasonally in many areas of the globe and can affect negatively the engineering performance of geotechnical structures; on the other hand, man-made freezing is a controllable process that can be used by civil engineers to stabilise temporarily the ground in order to support and/or exclude groundwater from an excavation until the final retaining and lining structures are constructed. Freezing and thawing of the pore fluid within soils involve complex thermal, hydraulic and mechanical processes that have significant mutual interactions. For example, phase changes of the pore fluid caused by temperature variations can modify the pore water pressure in the soil, which, in turn, can induce mechanical deformation. At the same time, any changes in the hydraulic and mechanical conditions affect the thermal processes by advection and changes of ice and water contents.An application of AGF which will be presented in the paper, refers to the construction works of Line C of Rome underground. In this case AGF was carried out to provide temporary support during excavation of the two Line C running tunnels directly underneath the existing S. Giovanni station of Line A, in the safest possible condition. In order to keep the trains of Line A operational during excavation, a temporary structure was installed and a real-time monitoring system was conceived in order to control the temperatures of the soil during freezing and the response of the structures of the existing station."

Jan 1, 2016