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By Howard A. Perko, Melinda J. Hummel

"Hydraulically jacked piles, herein referred to as jacked piles, are commonly used for underpinning existing structures to arrest settlement or augment an existing foundation for higher loads. They consist of steel pipe segments coupled together and jacked into the ground using a hydraulic ram. Pipe sections can vary in size from 3"" diameter to 18"" diameter or larger. Jacking resistance is typically provided by dead loads of existing structures. This type of piling system has been utilized for foundation underpinning, repair, and augmentation for more than 120 years, yet little has been published on the capacity, installation standards, and reliability of these systems. Pile load tests from a number of projects are presented and analysed. The data show that previous methods of jacked pile capacity and depth prediction are crude at best. Empirical relationships between capacity, depth, soil type, and standard penetration resistance blow count contain a high degree of scatter. Scatter in the data indicate capacity prediction for jacked piles needs further research and refinement.INTRODUCTIONPush pier, resistance pile, steel pier, and jacked pile are some of the names often applied to hydraulically jacked piles used for underpinning. The term ‘jacked pile’ is more common in building codes and will be used herein. Although jacked piles can be installed for new construction, this paper is focused on piles used for support of existing structures.Jacked piles consist of short segments of pipe or structural steel tube that are coupled together and forced into the ground using a hydraulic ram fastened to or beneath a footing, stem wall, or grade beam of an existing structure. In this way, the weight of the structure provides the resistance necessary to force the pile into the ground. A factor of safety can be achieved in design by redundancy, which is consecutively installing more than one jacked pile to support the same portion of foundation. Installing jacked piles consecutively using the same dead load and then releasing the load after each pile installation allows one to continue adding piles to the same general area until a total aggregate capacity is achieved to account for anticipated dead plus live loads and a desired factor of safety for that area.An engineering schematic of an example jacked pile connected to a footing foundation is shown in Figure 1. Modern jacked piles typically incorporate a steel bracket. There are many sizes and styles of brackets available. Some categories include plate brackets that bolt to the outside of an existing foundation wall, wide and narrow angle brackets that extend under existing footings, pin brackets for attachment to structural steel, and reverse angle brackets for attachment to footing and wall. Table 1 lists example brackets and their benefits."

Jan 1, 2017

By Mohsen Elsayed, Amr Sallam, Ahmad Mohamed, Xuebing Zheng, Mohamed Alrowaimi

The foundation is an essential component of the wind turbine that ensures continued operation under stable and safe conditions. Both shallow and deep foundations are utilized to support wind turbines including gravity spread foundation, anchor foundation, pier or drilled shaft foundation and pile and pile cap foundations. Conventional methods were typically utilized to design the wind turbine foundations. With the advances in numerical modeling in the geotechnical field, foundation designers may utilize numerical analysis to design wind turbine foundations. Geotechnical numerical packages allow modeling structural components and soil-structure interaction that is usually neglected in conventional methods. Furthermore, the subsoil conditions, geometries, stress-strain behavior, boundary conditions and load staging can be modeled, minimizing the assumptions and generalization. This results in better understanding of the stress strain behavior of the foundation leading to optimized foundation designs. This paper includes a brief review of current foundations used to support wind turbines with an emphasis on post tensioned single pier foundations. The current conventional foundation design methodologies and state-of-the-art foundation design utilizing numerical modeling of the single pier foundation will be discussed. Two case histories where the single pier foundation, designed using numerical modeling, were utilized to support the wind turbines will be presented. INTRODUCTION The foundation is an essential component of every wind turbine that ensures continued operation under stable and safe conditions. Turbine manufacturers provides load specifications for designers to be utilized for wind turbine foundations design. Loads include bending moments, torsional moments, lateral forces and vertical forces in both operational and extreme wind conditions. Essential specifications under seismic conditions might also be provided in seismic prone areas. Turbine manufacturers also include foundation design criteria including minimum rotational stiffness, minimum horizontal stiffness, maximum allowed inclination and maximum allowed lateral movement under both operational and extreme loads. Geotechnical explorations and evaluations are typically performed at early stages of the wind development projects. The field explorations usually include Standard Penetration Test (SPT) borings, Cone Penetration Test (CPT) Soundings, geophysical surveys, and laboratory tests to define soils stratification system and soil strength and compressibility characteristics. The most critical soil parameters for turbine foundation design are shear strength parameters (cohesion and friction), shear modulus, Poisson’s ratio, and unit weight. The depth to the groundwater table is also a crucial parameter in design. Advanced field explorations techniques such as Dilatometer Tests and Pressuremeter Tests may also be utilized. Laboratory tests for foundation design typically include index parameters, consolidation and triaxial tests.

Jan 1, 2019

By Remco Offenberg, Marcel Bielefeld, Martijn van Delft

The question of the continued suitability of existing foundations arises when the function of the superstructure changes. This can occur when the superstructure is replaced or when the existing structure is expanded, leading to higher loads on the existing foundation. Quite often it is a challenge to define the suitability (with respect to integrity, bearing capacity or both). The lack of information on the existing foundation (such as pile dimensions, installation records, original soil investigation, design calculations, etc.) makes it frequently seemingly impossible to assess whether the foundation or foundation elements can be re-used. The paper outlines the tools available to an engineer to evaluate existing foundation piles for potential re-use. The paper illustrates the application of these tools through a few case studies from The Netherlands, including the evaluation of a 400 years old bridge foundation to address increasing traffic loads.

May 1, 2022

By Jeffrey C. Schuh, Logan Bloemer, Daniel P. Dietzler

Over the past 30 years, the authors have encountered numerous projects where recognizing the geology, soil properties and groundwater conditions, and considering alternative construction techniques have promoted efficient and cost-saving construction. The construction documents for these projects, produced by various engineering firms, provided basic information on geotechnical conditions. The authors became involved in each project either because there was a problem during design or construction or, as a contractor, won the project because they saw a value engineering opportunity to take advantage of the geologic setting of the project to design and build alternatives to what the designer depicted. Understanding the geologic setting is critical before planning and designing begins. Being able to work with the geology and the materials on site is preferred before specifying more costly and complex solutions, which often require the importing of materials and adherence to unnecessary and/or inappropriate specifications. Failing to understand the geology or not knowing all the techniques available for construction can lead designers to develop solutions that could be inappropriate. This paper presents several examples of value engineering and project performance enhancements developed through knowledge of basic soil mechanics and implementing innovative solutions. History and Background Most people attend DFI meetings, present their experiences, listen to others, and read articles and papers with the hope they can learn from others. Geotechnical engineers and contractors often interface with others in the execution of projects who have, at best, a rudimentary knowledge of geology and soil mechanics. Of course, there is a need for architects, bankers, and regulators, etc., but they typically do not have much interest in the nuances of geotechnical engineering, which relies on both art and science. Thus, significant time is spent educating counterparts in the need for comprehensive subsurface investigation programs and the intricacies of construction in the “dirt,” as they typically refer to soil and rock.

Jan 1, 2019

By Stefan Mewes

Europe’s second-largest seaport has installed a new combi wall consisting of pipe piles, sheet piles and inclined shaft grouted piles to support it. The new Liebherr piling rig with swinging leader was used to drive shaft grouted piles into a very dense soil layer of sand with glauconite. The 60 m Liebherr swinging leader was suspended at an inclination of 45° via a suspension frame and suspension ropes from the crawler crane. This inclined installation of shaft grouted piles via freely hanging swinging leader, as used for this project, is unique in Belgium. Moreover, the pile length of 43 m is a novelty for this type of pile. Shaft grouted piles consist of a steel profile with a separate box-like pile shoe with an open top. A thin grout is injected via an injection pipe during driving and emerges just above the pile shoe. As the pile is driven further down, so compressing the ground, the space above the pile foot is immediately filled with grout under pressure. This piling system is ideally suited for the transfer of high tensile loadings. It is a method to increase geotechnical load-bearing capacity and to reduce negative skin friction during pile driving.

Sep 1, 2022

By Ronaldo Luna, Donald Deardorff

"The use of load and resistance factor design (LRFD) is well documented since the 1960s for structural applications when it was first adopted into the American Concrete Institute Building Code in 1963 and was established for geotechnical applications by the Danish Geotechnical Institute about the same time under the name of Limit State Design (LSD).The Federal Highway Administration required all federally funded projects to use the LRFD method by 2007. Due to this funding requirement, recent LRFD research for geotechnical applications has focused on common bridge foundations (i.e., driven or drilled shafts), resulting in good documentation for design using these methods. Unfortunately, the practicing geotechnical engineer does not intuitively know how to create resistance factors for deep foundations systems that have design methodologies and installation techniques significantly different from driven or drilled shaft foundation systems.Helical anchors typically use semiempirical methods for preliminary capacity design and a torque correlation methodology during installation to verify required capacity. Here we provide basic information on the LRFD methodology for helical anchor design. Additionally, the First- Order Second Moment (FOSM) method is applied to a previous helical anchor study (Hoyt and Clemence 1989) to determine resistance factors for an ultimate tension capacity strength limit state.MethodologyThe concept of the LRFD method is to establish factors for both the load and resistance that account for uncertainties using probability theory. The factors increase the nominal load and/or decrease the nominal resistance such that the probability of failure is an acceptable value. LRFD also accounts for the effects of load combinations (dead, live, seismic, wind, etc.) by determining the probability of the combined occurrence. The general form of the LRFD equation used by American Association of State Highway and Transportation Officials (AASHTO) is:"

Jan 1, 2009

By Stefan Swartling, Rudy Lyon, Donald A. Bruce

"Since their first production application in Sweden in 1995, water-powered, down-thehole hammers (WDTH) have been used throughout the world in many different drilling applications, total lines, over 25 million lineal meters of drill hole. This paper reviews the history and principles of down-the-hole drilling (DTH) in general with both air and water, before focusing on the details of WDTH hammers. A summary of the numerous and considerable advantages of WDTH drilling is provided, with particular emphasis on their superior productivity, smaller deviation, applicability in sensitive/urban conditions, environmental protection and much reduced energy requirements.HISTORICAL PERSPECTIVE ON PRODUCTION DRILLING METHODSAir-flushed drilling with top hammers began in the mining industry in Sweden in 1873, while down-the-hole (DTH) drills, again with air flush (and activation) became operational in 1950. During that same time interval, Simon Ingersoll had patented the first steam-powered, top hammer rock drill to provide higher productivity in blast hole drilling. It is well known that water, as an activating, flushing and cooling medium, has many significant advantages over the use of air. However, it was not until 1973 that top hammer systems (either air or hydraulically activated) for larger rigs were adapted to the use of water flush, typically via “under the head” swivels.The concept of a water-powered, down-the-hammer (WDTH) had been explored prior to G. Drill acquiring the original patent from Atlas Copco in 1988. LKAB, a huge underground mining company owned by the Swedish Government and providing about 90% of the European Union’s iron ore, purchased G. Drill in 1991 and encouraged the commercial development of the WDTH. The first full-scale WDTH production works were carried out for LKAB in 1995, since when over 25 million lineal meters of drilling have been recorded in both underground and surface applications.In 2001, G-Drill was renamed Wassara, which today still holds the worldwide patents for WDTH technology. Regarding North American usage, the first significant application was by Advanced Construction Techniques (ACT) Ltd. during the test grouting program conducted for the U.S. Army Corps of Engineers at McCook Reservoir, Chicago, in 2002. Since then, WDTH has become the tool of choice for specialty drilling and grouting contractors on dams and other major structures throughout the U.S."

Jan 1, 2015

By Sanjay Gupta, Sorabh Gupta, Ravi Sundaram, Abraham Varghese

"Geotechnical investigation for the Kochi Metro revealed a critical section of the Viaduct near Ernakulam Junction Railway Station. Four piers, located over a 220 m stretch, were passing through an area with substantial thickness of soft clay. The scope of the geotechnical investigation included two boreholes and a static cone penetration test at each pier location. In the boreholes, field vane shear test was conducted at different depths in addition to the routine SPT. The design of heavily loaded piles in such strata is a challenge due to the liquefaction of the shallow sands and negative skin friction / down-drag in the soft under-consolidated clay. Bored cast-in-situ piles of 1500 mm diameter extending to 50-60 m depth were used to carry 500-600 tonnes load.INTRODUCTIONThe first phase of the rapid transit system at Kochi, Kerala (See Fig. 1) whose elevated route spans from Aluva to Thripunithura covers a total distance of about 25 kilometers. One of the more critical sections of the viaduct exists near the Ernakulam Junction Railway station where the alignment takes a sharp curve to move towards Vyttila, crossing the railway tracks and running partially over the approach of South over-bridge.In this section, four piers located on either side of the railway tracks near the Route Relay Cabin of Ernakulam Junction Railway Station pass through an area with substantial thickness of soft underconsolidated clay.The alignment is geotechincally challenging due to the presence of loose liquefiable sand and soft underconsolidated and sensitive clay.Initial investigations by the owner based on limited boreholes only yielded conservative and inconclusive pile capacities. For a thorough understanding of the soil behaviour, a detailed geotechnical investigation was carried out to assess the engineering behaviour of the soil strata.The scope of the geotechnical investigation included two boreholes and a static cone penetration test at each pier location. In the boreholes, field vane shear tests were conducted at different depths in addition to the routine SPT."

Jan 1, 2015

By K. Madhusudan Reddy

"Pile response under combined uplift and lateral load is very important and it is imperative to evaluate the effect of combined loading and only few studies were reported on pile behavior under combined uplift and lateral loads. Model pile made-up of aluminum having an outer and inner diameter of 25.4 mm and 19.4 mm respectively is used. Dimensions of the model steel tank are fixed as 1.0 m x1.0 m x 1.2 m (depth) to avoid the boundary effects under combined lateral and uplift loads. Experiments were carried out on single piles at isolated uplift, isolated lateral loading and combined lateral and uplift loading, embedded in sandy soil. Results indicate that load–deflection behavior is nonlinear for isolated uplift and lateral load tests as well as in case of combined loadings. It is also observed that the behavior of piles under isolated loadings is substantially different when compared to combined loading.INTRODUCTIONPile foundations are generally used to support compressive loads from superstructures. Some structures, like transmission towers, mooring systems for ocean surface or submerged platforms, tall chimneys, jetty structures, etc. are constructed on pile foundations, which have to resist large lateral and uplift loads and moments. The various loads (compressive, lateral and uplift) and moments act on the piles simultaneously rather than isolated manner. There are well-established theoretical methods present to evaluate the pile behaviour under different isolated loadings namely, verticalcompressive, vertical-uplift and lateral (Poulos and Davis, 1980), but there are very limited studies focused on pile behaviour under combined loadings. Though there is good number of studies reported on pile behaviour under combined compressive-lateral and compressive-uplift loadings (Ramasamy, 1974; Jain et al. 1987; Zhang and Small, 1999; Dash and Pise, 2003; Karthigeyan et al. 2006 & 2007; , there are only very few studies reported on pile behaviour under combined uplift and lateral loads. Darr et al. (1990) described an approach to a rational solution of the interaction of pile to combined uplift and lateral loads based on analytical and experimental studies. Influence of cyclic loading was also considered. Narasimha Rao and Prasad (1993) investigated the uplift behaviour of pile anchors subjected to lateral cyclic loading. There were many onshore and offshore situations where lateral cyclic loading may affect both the pullout and lateral loading capacity of pile anchors. Jetty and wharf structures are usually subjected to lateral forces from wave and wind action. If these cyclic lateral loads are acting on the supporting piles, the resulting movement of the upper part of the embedded length of pile may reduce the skin friction. This progressive deterioration in pullout resistance may not be reflected by a pullout test made soon after the installation. Hence, Tomlinson and Woodward (2008) pointed out that a generous safety factor on the ultimate pullout load should be adopted for piles in such situations. Mroueh and Shahrour (2007, 2008) presented a threedimensional finite element analysis of the response of battered piles to the combined lateral and vertical pullout loads. Nevertheless, the model is not validated well due to lack of good experimental data based on rigorous experiments. Thus there is a scope for investigating the effect of lateral load on pile behaviour under uplift load and vice versa based on carefully designed experiments, which is main focus of the present investigation."

Jan 1, 2017

By Burt G. Look, David W. Lacey

"Certification of foundation capacity during the construction phase is often assessed by strength or weathering state descriptors based on visual observations. This case study used the Point Load Index (PLI) test as a quantitative tool in the construction certification of a pile’s design capacity. Construction phase tests were completed on irregular sized rock samples whilst comparable design phase testing was completed on intact rock core samples. Statistical comparisons were made to assess the repeatability between the PLI tests, with best-fit Probability Distribution Functions (PDFs) determined for both datasets. Pronounced differences were observed based on the PDF adopted to characterize the PLI dataset, the consequence of which would be a significant change to the pile’s design capacity. The adoption of the lower quartile value is shown to satisfy both design conservatism and construction simplicity requirements. The commonly held belief that rock samples produced during socket excavation may be biased towards the higher strength portion of the rock mass, is shown to be invalid for this site. As the central bridge piers were certified using Plate Load Tests (PLTs), the resultant load-settlement relationships were compared with the PLI strength assessments made for similar materials recovered from the adjacent abutment piles.INTRODUCTIONThe upgrade of the Foxwell Road Overpass across the Pacific Motorway in South East Queensland required the duplication of an existing four span bridge structure. The foundations of the new bridge included the installation of 1.2m diameter cast in place (bored) piles at the bridge abutments and 900mm diameter cast in place (bored) piles below a retaining wall to be constructed adjacent to the existing abutment.The site geology was dominated by the Palaeozoic Neranleigh–Fernvale Beds, predominantly comprised of argillite, sandstone and greywacke. Limited soil materials existed at the site, with Extremely Weathered (EW) rock typically encountered within metres of the existing ground surface. The exception to the existence of shallow rock were locations where existing filling of the site had occurred – i.e. approach embankments to existing bridge structure.Capacity of pile sockets is typically assessed onsite by descriptive rock strength or weathering assessment. Such descriptors encompass a wide range of values and lack precision. Due to the subjectivity of such assessment techniques – a factor of 3 is often observed in terms of strength assessment based on one’s interpretation of rock strength descriptors alone – uncertainty on site often occurs regardless of whether a lower bound, average or other characteristic design parameter applies."

Jan 1, 1900

By Takefumi Takuma, Tsunenobu Nozaki, Masashi Nagano

The city of Naruto in the southwestern part of Japan is situated at the mouth of the mighty Yoshino River. An approximately 1,000m-long levee/bulkhead along one of the river’s tributaries in the city was raised with prefabricated steel panel walls on a concrete base bulkhead. Some sections of the walls’ foundations were combi-walls made of sheet pile cut-off walls and interspaced pipe piles; both of which were installed with press-in piling because the new wall alignment was very close to existing homes and businesses. A Clamp Crane, which clamped onto already installed piles and moved forward and backward on them, was utilized for a segment where the access to its piling location was too tight for a conventional crane or a track-mounted pile driver to maneuver.

Sep 8, 2021

By Eleonora Di Mario, Colin B. Turnbull, Matthew G. Mills, Chengbin Miao, Wilhelm S. Degen

"In the past decade, the ‘zero-dredge’ philosophy has become the preferred option for the formation of marine seawalls and reclamations, compared to the partially or fully dredged options, as this solution presents several environmental advantages. Recent relevant project experience is presented herein in order to highlight key design principles and construction issues central to the successful construction and performance of a sloping rubble seawall founded on soft soil improved by stone columns. If designed and installed with proper quality control, correct treatment intensity and sensible construction staging, stone columns are a safe and cost effective method for seawall foundations. This paper provides guidelines with regards to the design, construction and quality control for the correct implementation of stone columns as a foundation element for sloping rubble marine seawalls.INTRODUCTIONBenefits of sloping marine seawalls founded on stone columnsTo suit the current environmental requirements in Hong Kong, recent projects are tending to favour zero-dredge solutions, such as the Hong Kong Boundary Crossing Facility and the forthcoming Three-Runway System. The installation of stone columns allows the underlying deposits, generally consisting of very soft to soft clay and silt (soft soil), to improve in strength to the extent that the seawall can be directly placed on the seabed. This negates the need to dredge the soft soil and, therefore, this ground improvement technique represents an ideal solution for zero-dredge projects.Stone columns can also provide several other beneficial effects, including: accelerated drainage, reduced settlement, increased slope stability and soil reinforcement in the event of an earthquake. Stone columns, in contrast to competing cementitious methods, are a very ductile foundation method. This ductile behaviour is part of the design concept of stone columns in soft soil. Past projects located in Hong Kong and elsewhere, with an improved soft soil layer thickness of over 15m, have shown that stone columns can remain fully functional in terms of both drainage and horizontal reinforcement, even after settlements of over 3m and lateral displacements of up to 1m have occurred."

Jan 1, 2017

By Leonardo Massone

The p-y method is one of the most popular methods in pile design and has been calibrated for various boundary conditions using numerical and experimental studies during recent years. Most studies on reinforced concrete (RC) piles have included the impact of flexural nonlinearity, (e.g. nonlinear moment?curvature relations) but not considered associated pile shear deformations when deriving p-y curves from field data. Common p-y curves may be better applicable for piles with flexure dominated failures (e.g. piles with free- head boundary conditions). For piles with fixed head boundaries (i.e. rotation restrained piles) shear deformations could be of significant influence. To study this problem, a coupled shear flexure interaction model for axial-bending-shear behavior coded in OpenSees is applied to a 0.61 m flagpole and a 0.61m fixed head pile specimen to investigate the possible influence of shear deformations to the overall pile responses. The surrounding soil is represented by p-y curves derived from prior large scale testing on piles with similar boundary conditions. Analysis results show that for flagpole piles, shear forces and shear deformations were insignificant. Considerable contributions of pile shear displacements and forces were observed for the fixed head pile, with shear displacements contributing up to 40% of the total pile displacement. Results suggest that nonlinear shear deformations for reinforced concrete piles should be considered for fixed-head or similar conditions, and that currently used p-y curves may underestimate the actual lateral pile displacement and possibly lead to unsafe design for the particular boundary condition.

Jan 1, 2011

By Joel B. Dellaria, Justin R. Lewis

"No. 9 Walton is a new high-rise condominium building located in the Gold Coast area of Chicago. The adjacent building, Walton on the Park, featured 4 levels of below grade parking and utilized a secant pile wall with integral drilled shafts to support the exterior columns. The earth retention system (ERS) for No. 9 Walton also employed a secant pile wall in combination with drilled shafts. The excavation into the soft Chicago clays varied in depth from 9.75 m to 12.5 m (32 feet to 41 feet) below grade. The temporary excavation support used internal braces from the new secant piles to the existing foundation system of Walton on the Park to provide earth retention. Engineering teams for both projects worked together to design the bracing scheme and connections to ensure that the new excavation and internal bracing would not overstress any elements of the existing structure. Further complicating the project, immediately to the west of the project was a historic church founded on shallow spread footings which required underpinning to minimize movements.The project involved three different building owners, small values for acceptable wall movement, an extensive monitoring program and the challenges of merging two earth retention systems. The subsurface conditions at the site, the adjacent structures, the excavation, and the performance are described. A summary of the design methods and the expected movements of the ERS are discussed, and the performance monitoring system is described. Overall, the ERS performed better than expected with less than 1 inch of measured lateral wall movement during and after the excavation was completed. Measured performance of the ERS is compared to the predicted performance and to the performance requirements for the project.INTRODUCTIONNo. 9 Walton is a new high-rise condominium building in Chicago located in the Gold Coast. The building has 3 levels of below grade parking and 36 levels of living space above grade. Developers originally slated the project to be Phase 2 of the Walton on the Park development built in the mid 2000’s, using portions of the existing foundation system for development of the new structure. However, the housing market crash in 2007 prompted cancellation of Phase 2 of the Walton on the Park development. The property sat undeveloped until 2015 when design and construction for No. 9 Walton began under a new development and design team. The project team completed foundation excavation and below grade structures in 2016 with the first units of the building turned over to new homeowners in 2017.The structural design for No. 9 Walton consisted of reinforced concrete columns and slabs, supported laterally by a heavily reinforced concrete central core. Drilled shafts to rock supported the interior columns and core with the exterior columns and foundations integrally included in the earth retention system. The structure had a below-grade footprint of approximately 1,490 m2 (16,000 ft2). The general excavation extended 9.75 m to 12.5 m (32 feet to 41 feet) below street level with the deepest portions at the central building core mat foundation."

Jan 1, 2017

By Joe Harris

Large structures, such as a multistory office building or a large storage tank, are constructed the most economical way possible, which may involve a shallow foundation system placed on native soil or compacted fill material. Over the life of the structure, the foundation system may not perform as originally anticipated, leading to differential settlement. Minor differ- ential settlement is expected; however, settlement that exceeds allotted tolerance can render the structure inoperable. Compaction grouting is a well-known and accepted ground improvement technique that can be used to not only stabilize but relevel multistory buildings and large dia- meter storage tanks. Two projects, each with differing types of structures, were successfully remediated utilizing com- paction grouting as the primary method to remedy settlement.

Sep 1, 2023

By Shreya Vivek Hokam, Dr. A. I. Dhatrak, S. W. Thakare, Dr. Vivek S. Hokam

Construction in congested urban areas has necessitated tall and massive structures. In urban areas, it is common to construct underground structure nearby existing buildings. Selection of an appropriate support structure system to be implemented in the excavation in an urban area is heavily dependent upon the geotechnical conditions and safety of the surroundings and neighbouring structures. Urban Rail, popularly referred to as Metro Rail, has seen substantial growth in India in the recent years. More cities are experiencing the need for metro rail to meet their day-today mobility requirements. The metro structures involved deep excavation for foundations which induces the stresses and thereby alters the existing equilibrium and thus may affect stability of neighbouring structures considering safety point of view. Hence, design and execution of deep excavations become one of the important challenging tasks of any geotechnical engineer in the modern era. Further, it is important to control the ground movement in order to prevent the failure of excavations. This involves specialized foundation technologies, usage of sophisticated equipment and new methods in underground construction, safety and monitoring systems. In this paper the methodology used for protecting adjoining structures due to deep excavation for Nagpur Metro station is studied.

Sep 1, 2022

By Kirk Ellison, Sherif Elfass, Ramin Motamed, Kevin V. Stanton

"The determination of accurate load transfer curves are essential for estimating deep foundation loadsettlement response using t-z style analyses. While recently developed semi-empirical methods from Ashour et al. (2010) and Ashour & Helal (2012) have shown promise in preliminary studies, they have not yet been thoroughly benchmarked against a more widely accepted approach. To address this issue, these recent procedures are implemented in the computer program CGI-DFSAP to predict the results of four Osterberg-cell (O-Cell) load tests. These predictions are compared to outcomes obtained following the recommendations from Reese & O’Neill (1988) for t-z analyses of drilled shafts in sand and clay which are carried out with the program TZ-PILE. Overall, the results suggest that the new approach offers improved accuracy regarding predictions of drilled shaft response to axial loading.INTRODUCTIONThe behavior of axially loaded deep foundations is often analyzed using a technique known as the t-z method. In this method, deep foundation elements are broken into multiple segments which are supported by discrete nonlinear springs to capture the contribution of both side-friction (t-z springs) and end-bearing (Q-z springs). Hence, the t-z and Q-z relationships dictate the predicted load-settlement response. A number of different approaches have been developed to estimate load-transfer curves with some relying solely on empirical data from laboratory and field experiments (i.e. Coyle & Reese, 1966; Vijayvergiya, 1977) and others based mainly on analytical frameworks (i.e. Kraft et al., 1981; Randolph, 1994). Reese & O’Neill (1988) provide recommendations which are widely used for developing t-z and Q-z curves for analyzing drilled shafts. This method is hereafter referred to as Method 1 (M1). It should be noted that these empirically derived relationships are only applicable for problems associated with drilled shafts and are therefore not appropriate for developing load-transfer curves for other types of deep foundations (i.e. driven piles). This is because of the difference in the frictional resistance which can be developed between a circular concrete-soil interface as opposed to that of other materials (i.e. steel) and/or different cross sectional geometries.The M1 load-transfer curves form the basis for the t-z analysis of drilled shafts implemented in the computer program TZ-PILE (Ensoft, 2014). In light of this, TZ-PILE is employed herein as a reference to compare against the capabilities of another method of implementing t-z style analyses. This method is based on a semi-empirical framework for soil behavior developed by Norris (1986) and is implemented using the program CGI-DFSAP (Computers & GeoEngineering Inc., 2011). More information concerning this approach, hereafter referred to as Method 2 (M2), is given in subsequent sections."

Jan 1, 2017

By Shyam Chengalath, Johan Jeansson, Magnus Hörman

Down-The-Hole (DTH) drilling usually uses compressed air to power the hammer. However, there are now DTH hammers on the market which instead of compressed air use high pressure water to power the hammer. There are several benefits with using water DTH compared to air DTH, which are discussed in more detail in this paper. From a physics point of view many of the benefits arise from the fact that water is an incompressible media and air is not. Energy consumption is roughly a quarter compared to air, resulting in lower carbon emission and a lower energy bill. In the case of water DTH the water leaving the drill bit in the hole is at a low velocity and ambient pressure. However, with air DTH the air leaving the drill bit in the hole is at a high velocity and high pressure. This means that the risk of damaging surrounding structures in sensitive areas such as urban environments and dams, is greatly reduced with water DTH. In this paper two cases where water DTH is used in jet-grouting applications are discussed in detail. As these cases show there is a clear improvement in productivity when using water DTH hammers.

Sep 1, 2022

By Heman Manchanda, Jyoti Agarwal

Several infrastructure projects are under construction in India; many of them involves construction of deep foundations like reinforced concrete and steel piles to support super structures. As most of the piles being constructed in India are reinforced concrete bored piles, there are always uncertainties relating to the quality of construction, and in this case non-destructive methods to ascertain quality of piles becomes very crucial to success of any project. Non-destructive pile testing is becoming more and more popular with growing technologies wherein geophysical techniques and wave propagation theories are being used for pile quality and length analysis. Low-strain pulse echo method and cross-hole sonic logging testing are two pile integrity testing techniques being currently practiced in India which are cost effective and provides reliable near accurate results if analyzed properly. Paper presents current practices being adopted in India for conducting these two tests, highlighting the critical site considerations and analysis techniques. The paper also discusses various execution and interpretation challenges faced by practicing engineers and recommends a way forward.

Sep 1, 2022

By Yazen Khasawneh, Osvaldo P. M. Vitali, Mohammad Nassim

Wind turbines are subjected to complex form of cyclic loadings with variable amplitudes and frequencies. The cyclic loading and the accumulation of plastic strains with the number of cycles will result in degradation of the foundation soil stiffness. The foundation stiffness degradation will result in a shift (reduction) of the fundamental frequency of the wind turbine. Although this issue is recognized in the guidelines for wind turbines foundation design, no specific provisions are provided in the guidelines to consider the long-term stiffness degradation. In this paper, a practical procedure to consider the long-term cyclic loading effects on the stiffness of wind turbine foundations in cohesive soil is proposed. The procedure is based on 3D FEM modeling and reliable empirical methods to estimate the stiffness degradation due to the cyclic loading. Using the proposed procedure, the long-term performance of the P&H tensionless pier foundation with and without a reinforcing collar at the top of the pier is assessed. The numerical results demonstrated that the long-term performance of the P&H tensionless pier foundation with a reinforcing collar at the top of the pier is outstanding with negligible long-term degradation of the foundation stiffness.

Sep 8, 2021