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By Andrew Lees

Where in-situ ground is too weak to support piling rigs and other mobile plants, a temporary platform of stronger granular material may be constructed to distribute plant loads safely to the underlying ground. A critical step in the construction of a safe working platform is its design. Essentially, the optimal thickness of the platform material needs to be determined such that it is large enough to distribute piling rig track pressures safely to the ground without bearing failure, but not so large that it becomes unnecessarily expensive and time-consuming to construct. Platform failure can take several geotechnical forms including punching shear failure through the platform into the underlying soil and a rotational slip failure. Any, or a combination, of these could lead to platform failure and a catastrophic toppling of a piling rig. Safe design of these temporary struc- tures requires a calculation method that can cover these failure modes in a reliable manner. The T-value calculation method considers multiple failure modes since it is derived from validated finite element analysis (FEA) that has no predetermined failure modes. Since its introduction in 2019, it has been applied to the design of hundreds of working platforms around the world. On its fifth birthday, the method's author provides a quick overview and advice on its use.

Jan 1, 2025

By Dimitrios Konstantakos

When writing this article almost 10 years ago about the future of the deep foundations industry, little did I have in mind that ChatGPT would be created. Nevertheless, the mere act of writing up the article created a spark within me to prep up for what was coming. So, we put together some form of natural language communication with our deep excava- tion software, and although cumber- some, we could voice command it. When ChatGPT came to being, this allowed us to create the first AI assistant for generating deep excavation models. In November, we are releasing the first AI system for predicting pile capacity, which was one of the items described in the original article.

Jan 1, 2015

By Matthew Conte

Overgrown vegetation. Little to no effective drainage. Three or four different construction methods over the years. Live loads from above. Property line to navigate. Buildings on either side. I drove by this site for years wondering when someone was going to have to deal with it. That day came, and it turned out to be us. This particular project had typical attributes: limited space and restrictive conditions. This retaining wall system supported the neighbor's parking lot above, roughly 14 ft (4 m) in elevation change. At a length of 92 ft (28 m), both ends of the wall abut an active building in the lower property. Only a small parking area of roughly 50 ft (15 m) in depth lies before the heavily traveled state route in Westport, Connecticut. Roughly two-thirds of the existing wall was tiered, and the other third was taller, with a concrete masonry unit (CMU) wall that appeared to be part of a former structure. The existing wall was failing and leaning over the parking spaces. The drainage system showed signs of failure, and the vegetation was clearly retaining moisture and frost was heaving the walls a little more each year. During the initial kick-off of the project, it was decided we would immediately shore up this taller portion of the existing wall. That shoring would stay in place through construction. With active tenants and neighbors, the property owner needed a solution that would allow businesses to stay open and limit any disturbance to the above property. Very little documentation existed showing the construction of the walls or the soil conditions. Above, the neighboring property had added a small retaining wall when its parking lot was constructed. Soil borings were found, but nothing showing details on that newer retaining wall. The borings indicated structural fill was compacted in lifts beneath the lot, but nothing indicating any geotechnical measures beneath the wall, at the property line. We were forced to design a new wall considering the 'worst case' conditions. This new wall also required construction methods that would allow all aspects of the surrounding area to remain intact.

May 1, 2025

By Yasir Husain, Deepankar Choudhury, Hamzah M. B. Al-Hashemi, Marwan Alzaylaie

An existing warehouse spanning 12,000 sq m (130,000 sq ft), located in Jazan City on the southwestern coast of the Red Sea in Saudi Arabia, was supported by a reinforced concrete slab- on-grade, while its steel columns stood on bored piles and pile caps. Completed approximately a decade ago, the structure developed severe cracking and floor deformation reaching up to 170 mm (7 in), as per recent site surveys. The deformation evolved without any progressive instrumentation or moni- toring in place, and thus, neither the onset nor the time- dependent behaviour of the issue could be precisely estab- lished. The warehouse remained operational throughout this period, and the owners, faced with ongoing challenges, decided to announce a public bid inviting contractors and con- sultants to propose a feasible rehabilitation solution, given the unique nature of the site and the ongoing operations. To begin with, the city of Jazan is not an easy geotechnical ground to conquer. The region is defined by complex and problematic ground conditions: collapsible loess soil, Sabkha deposits (salt flats), salt domes (which are highly deformable over time), organic expansive clays, flood-prone zones, extreme temperatures, aggressive environmental effects and moderate seismic activity. Salt domes are large underground formations of salt that have pushed upward through overlying layers of rock due to their lower density. Over time, they can deform and shift, causing ground instability at the surface. These structures are particularly problematic for foundations, as the salt can dissolve with water infiltration or move plastically under stress, leading to uneven settlement or sudden subsidence of built structures. Furthermore, the structure in question had to remain in service, limiting the options for rehabilitation due to spatial, operational and construction-related constraints.

Aug 1, 2025

By Bengt Fellenius

I remember the 1983 conference and this "DFI News" note with its summary of my lecture - and how I cringed on seeing the heading of the note, claiming that I had "released the wave equation." The WEAP (wave equation analysis of pile driving) had been "released" about a decade earlier by the founders of GRL Engineers and Pile Dynamics, George Goble and Frank Rausche, marking the beginning of their great contributions to the geotechnical engineering practice "the quantum leap." I appreciate the opportunity, now 40 years later, to correct the heading implication. Several typos in the note, then irritating, are now more amusing, such as, "dull complex" instead of "full" and "restriction" instead of "restrike." My lecture tried to introduce some of the then recently developed dynamic monitoring and analysis state of the practice: the WEAP and PDA/CAPWAP (Pile Driving Analyzer/CAse Pile Wave Analysis Program). The lecture and the notes should be read in the light of how they were operated in early years. The mainframe computer and input was by means of punch cards. The field testing using the PDA was by lugging the analyzer, a bulky tape recorder, an oscilloscope, and power-cable and gage-chord bundles to the site. If travel was by air, the analyzer sat on the seat next to the engineer. For assessing the pile in the field, the measurements were printed out on a paper roll. In the mid-1980s, a screen was added to the analyzer, it became digital, and data were stored and accessible electroni- cally also in the field. No more tape recorder and oscilloscope. At about the same time, the PC arrived and the WEAP became available for running on the office machine. Process was slow; while the PC ran a WEAP, it was time for a cigarette and a cup of coffee. To think through the input to the analysis, there- fore, became an important time-saving effort. Soon thereafter, the CAPWAP also became available for use on a PC. The first International Stress Wave Conference in Stockholm in 1980 (it continued every fourth year, thereafter) started the international acceptance of monitoring. At the third conference, in Ottawa in 1988, the number of indi- viduals outside of GRL performing CAPWAP analysis amounted to 17, with 14 from outside the U.S. Today, the high-strain dynamic monitoring is routine wherever piles are driven, and its use has been extended to testing non-driven piles. The wave equation and high-strain dynamic method, then and now, is for assessing pile-soil response in terms of pile capacity and hammer perfor- mance. Over the years since, it has been extended to low-strain integrity testing and current advancement of tech- nology has been incorporated. For example, the connection between pile gages is now wireless and the analyzer is a tablet. The pile monitoring data can be sent to the "cloud" and enable remote testing. The process is so fast that an automatic signal matching can be made in real time on every blow. At some sites, every pile is tested, thus, the method is used for continuous quality control of the hammer-pile-soil system.

Jan 1, 2025

By Manny a. Fine

Manny Fine, who was once my boss and mentor, provides a sentient account of the perils of the specialist foundation subcontractor in a world of public sector design-build contracting. He opens by relating the comfort foundation specialists have with the private sector design-build model. A model that, he states, enjoys the freedom of innovation with what is believed to be a genuine interest and flexibility in concept, receptivity and contract in the private sector, which has led to public sector interest and dabbling in the design- build delivery method. Fine then describes a public sector arena for design-build fraught with difficulty for the specialist foundation subcontractor, which includes great effort for low return, contract restric- tions, narrow interpretation of alter- natives, and a low flexibility by the owner for alternative methods and risk assumption. His conclusion is that the design-build delivery method in the public sector results in duplication and wasted effort by the foundation specialist(s). He deems the evaluation process to be unsophisticated and lacking the ability to select the best proposal in terms of solution and or cost benefit and that the owner needs "to find ways to be more receptive to alternative or value engineered proposals." Now, 27 years later, we witness a well-established and flexible private sector design-build market driven by specialist foundation contractors and their partner consultants that has welcomed new technologies and driven innovation. Typically, there is more definition to the small- to medium-sized private projects (up to $15 million in value), whereas large design-build projects often see early contractor input and a team selected during the design process. The success of public sector design-build delivery has increased significantly since the time of Fine's commentary with many very suc- cessful applications and new 'models

Jan 1, 1998

By Keshab Sharma, Jibendra Misra

Caissons and piles are mostly used as foundation types in bridges. Caissons are particularly suitable for bridges with expansive spans, locations with deep alluvial deposits, soil prone to lique- faction and when there's a notable risk of vessel collisions. However, they face challenges related to sinking and limited resistance against earthquakes. On the other hand, pile foundations are not well suited for deep-water scenarios due to their excessive length, diminished rigidity, susceptibility to vessel col- lisions and complications associated with construction. A potential solution to the issues mentioned above could be the adoption of CCPF. These foundations can also be applied to enhance existing caisson. foundations through retrofitting techniques in wind turbines, trans- mission lines and bridge foundations, demonstrating their adaptability and potential for improving the perfor- mance of foundation systems. There has been successful implementation in China, as evidenced by projects like the Qiongzhou Straits Bridge and the Longna Highway Yangtze River Bridge. Moreover, this foundation approach has been adopted for numerous cross- sea bridges globally, including ex- amples like the Benicia Martinez Bridge (U.S.) and the Hitsuichi-Jima Bridge (Japan). Research from 2016 has shown CCPF systems can be potentially used for offshore wind turbine foundations and retrofitting existing caisson foundations. The construction sequences of CCPF systems involve the sinking of caissons followed by driving the pile beneath the caisson. There are two possible options for connecting the pile with the caisson. The first option can be provided by ending the pile at the bottom plug level of the caisson, in which the pile is threaded into the caisson bottom to achieve a connection joint between the caisson base and the pile tops. This methodology enhances the flexibility of the foundation. The second method is to continue the pile up to the cap level of the caisson. The pile up to the cap level of the caisson provides better integrity than the first option between caisson

May 1, 2025

By Matthew Meyer, Rosa Castro-krawiec, Charles Bartlett

The PortMiami Tunnel project stands as an engineering milestone in Florida, marking the first large-diameter tunnel designed and constructed in the state. As we celebrate Deep Founda- tions Institute's 50th anniversary, it's apropos to revisit this groundbreaking work, first documented by Matthew Meyer, P.E., Rosa Castro-Krawiec, P.E., and Charles Bartlett, P.E., in the January-February 2012 edition of Deep Foundations magazine. Their account details the project's formidable chal- lenges and the innovative solutions that led to its success. Completed in 2014, the PortMiami Tunnel project was a monumental undertaking to alleviate commercial traffic congestion in Downtown Miami. The tunnel links the interstate high- way network to PortMiami in Biscayne Bay, easing city traffic while boosting cargo and cruise ship capacity. This project was not just a feat of engineer- ing but a catalyst for economic growth and regional development. One of the project's most remark- able aspects was its pioneering use of advanced ground improvement tech- niques, particularly deep soil mixing (DSM) for support of excavation (SOE) and groundwater control. Miami's geotechnical conditions presented a unique set of challenges, including highly permeable subsurface materials and high static groundwater levels. Traditional excavation methods were deemed too risky and costly, necessi- tating creative solutions. To launch and retrieve the 40 ft (12 m) diameter tunnel boring machine that was required to construct the tunnel, the project team opted for cutter-soil-mix walls with embedded.

Jan 1, 2012

By John Morris, Scott Stonecheck

The University of Pittsburgh wanted a new arena constructed for its collegiate wrestling, volleyball, and gymnastics, dance and cheer programs. Due to space constraints for the arena in the university's congested urban setting, the school selected a location atop a previously demolished football stadi- um originally constructed in 1925. The new Victory Heights Arena and Sports Performance Center is nestled between the Peterson Events Center, student residence buildings Panther and Irvis Halls, and other critical campus infrastructure. Due to the site's con- straints, a permanent tied back soldier beam wall system was programmed for the subterranean portion of the arena's perimeter foundation wall, with the soldier beams and tiebacks using a delegated design-build approach and the permanent wall facing being designed by the building's structural engineer of record. Design and construction of the soldier beam wall system required a mix of conventional and unique approaches to address topographical, geological and site challenges. This article will provide an over- view of the approaches to the various challenges, the design concept, effi- ciencies gained through the design assist strategies employed through the early phase of the project, and lessons learned from site and geological dis- coveries uncovered and safely over- come during the physical work.

Mar 1, 2025

By Fatemeh Pariafsai, Ali Doostvandi

To assess the stability of a soil slope considering uncertainty in soil characteristics (C, Φ), it is necessary to conduct repeated calculations to determine both the Factor of Safety (FS) and the Probability of Failure (PF). The absence of analytical solutions leads researchers to use surrogate approaches of probabilistic modeling. This study aims to assess the PF and FS of a saturated soil slope using one of the Machine Learning (ML) method subsets, the regression Least Squares Support Vector Machine (LS-SVM). The results are compared to those obtained from the Limit Equilibrium Method (LEM) to compare the accuracy of LS-SVM. According to the FS-PF plot, it is concluded that LS-SVM is a reliable tool for determining the stability of a multi-layered saturated soil slope, which significantly improves computational efficiency. Furthermore, since predicting FS and PF from field data requires fewer data points, it will result in significant time and cost savings. However, to avoid false predictions, limitations must be removed, for instance, each layer should be included in the analysis within its probabilistic distribution, so using this method is more efficacious in clay soils where there are values for cohesion, unlike sands (c=0). This helps training data to be prepared well and to prevent misprediction in local failures. In addition, training data are debated in terms of the percentage employed. Furthermore, showing the importance of dataset scattering is concluded that adopting data with uniform distributions plays a crucial role in preparing training data sets and consequently, in having a better prediction of the possible slope failures.

Oct 7, 2024