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By John P. Briand III, Douglas J. Aghjayan, Robert E. Fosse

This paper highlights the successful pile load testing program for the redevelopment of Pier One in East Boston, Massachusetts. Pier One is a 5.4-acre parcel on a dormant waterfront site used in the 1950s as a warehouse and distribution facility. The developer plans to re-use the existing 14-inch-diameter concrete-filled steel pipe piles to support four 5- to 7-story apartment buildings above a 2-story parking garage. A pile load testing program was developed to establish if the existing piles could support design loads of 240 kips for project financial feasibility and up to 300 kips for a significant reduction in future foundation costs. The Phase 1 program consisted of statnamic and dynamic load testing on two piles with two loading intervals (200 and 240 kips). Based upon the favorable results of the Phase 1 program, the Phase 2 program involved statnamic load testing on two piles and dynamic load testing on ten piles with three loading intervals (200, 240, and 300 kips). The Phase 2 program confirmed the favorable results which were applied across varying strata thicknesses and pile embedment depths. The average allowable capacity for the piles tested was greater than 300 kips with pile movement up to 0.3 inches.

By Marcelo Chuaqui

We certainly have the data to back calculate it. I must admit that I haven't, at the moment my priority is not on what is the stiffness of the jet grout but is making sure that the jet grout is really there. It's a bit like what Stuart Littlejohn was talking about this morning in terms of grouting on the dams a small window causes a big problem so it's having the jet grouting there at all, at the moment must have been my focus rather than just what is the stiffness once you've got it there.

Feb 10, 2003

By Junho Lee, Leopoldo Bello, Mohammad Khan

Multiline ring anchor (MRA) was developed as a cost-effective solution for securing floating offshore wind turbines (FOWTs) to the seabed. Since FOWTs are placed in arrays compared to conventional oilgas platforms, the availability of multiple mooring lines attached to a single anchor can make FOWTs economically competitive. Additionally, the MRA can provide a small and light-weight anchor with high resistance to mooring line loads due to its deep embedment depth. The combined benefits of fewer and smaller anchors allow substantial reductions in anchor material, transport, and installation costs. Such cost reductions are critical to reducing foundation costs for the wind turbine, which can comprise well over 25% of the capital costs for offshore wind power development. Since it substantially reduces the required number of anchor footprints, the multiline anchor concept also permits significant reductions in seabed site characterization costs. This study evaluates how potential advantages of the MRA can reduce the capital costs and provide a reliable cost analysis of the foundation component for offshore wind farms.

By Frank Albrecht, Brian McCarthy

"The Ararat Terminal Station (ARTS) is located 190km to the north-west of Melbourne, approximately 1.7km to the north of Elmhurst Township in the Pyrenees region of western Victoria, Australia. The site occupies an area of approximately 7.2 hectare of farmland. The electricity generated by the Ararat Wind Farm is directed to the ARTS terminal station before being connected to the grid. The ARTS structural design includes more than 180 steel yard support structures, three 25m-tall gantry ‘A’ frames, three modular control room buildings, a precast transformer bund, precast fire wall structures and related foundation design. Innovative driven engineered glue laminated timber (glulam) piles in a cruciform shape were used to reduce the foundation construction time, cost and the amount of concrete used in the project. It is the first time that engineered timber piles made from farmed Australian pine trees have been used in a large-scale environmentally-friendly project. Durability of the timber was achieved by H5 treatment and the use of reinforced concrete pile caps to protect the cruciform timber piles at the ground line. A pile-driving sequence was developed based on field trials. The lateral load capacities of the piles were estimated using engineering principles and from full-scale tests in the field. This paper provides an overview of details of engineered timber cruciform piles, durability of timber piles, design information, pile construction procedures, pile-driving procedures, the testing protocol, test results and validation. The test results were compared with predictions from several methods. In addition, potential future applications of similar systems in other infrastructure projects, and opportunities for future improvements are discussed. The structural aspects of this project were presented in a previous paper at the World Conference on Timber Engineering in Vienna in August 2016. See http://wcte2016.conf.tuwien.ac.at/home/ for further information."

Jan 1, 1900

By N. V. Nayak

Konkan Railway Project is one of the most ambitious railway construction projects in India, involving construction of a 760.km long, Broad Gauge (1676 mm), single track railway line, connecting Roha in Maharashtra State with Mangalore in Kamataka State. The railway line travels along the Western Coast of Indian subcontinent, through states of Maharashtra (382 km), Goa (105 km) and Karnataka (273 km) (Fig.1). The project alignment traverses through one of the most formidable terrains ever encountered, in the history of railway construction in India. In the State of Goa only, railway alignment is crossing 6 major rivers Terekhol, Chapora, Mandovi, Zuari, Sal and Talpona. Zuari Railway Bridge (1305.6 m), Mandovi Railway Bridges (I and II) (1182.7 m) rank as 2nd and 3rd long bridges, (first longest bridge being Sharavati Bridge (2.2 km} at Honavar) which have been constructed on Konkan Railway. All these three bridges have been constructed by M/s.Asia Foundations and Constructions Ltd. (AFCONS). This paper presents, case history of construction of pile/caisson foundations for Zuari and Mandovi Bridges.

Jan 1, 1996

By Matthew C. Janes, Mark C. Spence

"A former coal gasification site next to Rock Bay in Victoria, BC, Canada required a barrier to permit dewatering and excavation of the bay and surrounding property. The adjacent property owners had stringent requirements at the boundaries of their properties. Isherwood Geostructural Engineers designed a temporary steel sheet pile (SSP) water retention structure and excavation shoring system along the perimeter of the site. The project involved challenging geotechnical conditions in soft clay soils and a multi-faceted construction staging plan involving the diversion of two large storm water outfalls that drained into the bay. Despite a well-conceived design and construction plan, unexpected site conditions and delays led to significant changes in design and construction approach. Employment of the Observational Method and on-the-fly geotechnical investigation were instrumental in maintaining project momentum and schedule. The paper presents the geotechnical and geostructural design details and construction events as they transpired, highlighting the key issues, discussions and lessons learned.INTRODUCTIONFor over 100 years, the Rock Bay Site, in Victoria, British Columbia, Canada, had a legacy of contamination left behind from previous industrial activities. The site was the former location of a coal gasification plant that was in operation from 1862 to 1952. The site was also an infilling location for a nearby tannery and sawmill. The remediation of the Rock Bay Site involved the excavation and replacement of approximately 300,000 tonnes of contaminated soils on Transport Canada’s property. The project commenced in 2004 and has occurred over several phases on multiple properties. In the third and final phase of the project, a temporary steel sheet pile (SSP) excavation shoring system and ocean barrier wall – required to seal off the bay – was employed to enable disposal and replacement of approximately 90,000 tonnes of contaminated soils from the shoreline and base of the bay."

Jan 1, 2016

By Akhila Manne, Prasad P. V S R

Storage tanks are heavily loaded thin-shelled structures that exert large loads on and require large foundations to support them. They are generally very sensitive to foundation settlements as it may hinder the performance of tanks resulting in significant commercial or social impacts. Selection of their foundation is dependent on availability of suitable ground and limitations imposed by design specifications. Design of the tank foundations is generally based on theoretical methods and validation by representative field tests. This paper reviews settlement criteria for storage tanks as per national and international standards, case studies of large to medium diameter tanks supported on deep foundation i.e., bored cast-in-situ piles and shallow foundations on improved ground and their performance during load tests & hydro-tests is discussed. Paper concludes that storage tanks can also be supported on shallow foundations resting on improved ground reducing the settlement, time and cost significantly depending on the sub-soil.

Nov 1, 2022

By Pier Luigi Iovino

As Technical Director of the Naples, Italy based Fondedile, a geotechnical construction firm specializing in static restoration of structures, Fernando Lizzi, Ing., devoted over 30 years to the pursuit and advancement of static restoration and subsoil strengthening. Seismic events, construction of new structures on polluted and/or unstable soils in urban areas, and a need to carefully preserve and restore delicate, war-damaged historical structures, manifested the need for underpinning projects. Traditional construction methods and approaches, such as underpinning with additional foundation masonry, were not suitable and would have further jeopardized the stability of the structures. The introduction of the palo radice (root pile) revolutionized the field of underpinning. At the time of the first application of micropiles, the industry standard was driven piles. The drilled micropile was conceived and first implemented in the early 1950s, as an innovative means to underpin sensitive, historic structures and structures in urban areas. Specifically, the new construction technique was conceived as a less expensive alternative, designed to accept structural loads, be installed in limited access areas, in varied working and sub-surface conditions, which did not involve changing soil characteristics, and had minimal disturbance to the structure being underpinned, or to adjacent structures.

Jan 1, 2003

By Babak Mamaqani, Pirooz Barar

The Moanalua trestle spanned over Moanalua Stream, Honolulu, HI and was designed to accommodate construction of five 10 feet diameter cast in drilled hole (CIDH) piers as a part of Honolulu Authority for Rapid Transportation (HART) project. Due to the proximity of piers to the existing bridge, the trestle was elevated 20 feet above grade. Stratigraphy of the site consisted of shallow depth of fill and 150 feet of loose to very loose recent alluvium (soft clay) underlain with stiff to hard old alluvium (stiff clay). CIDH casings were installed by a rotator or oscillator depending on the diameter of the piers. The challenge was to design the trestle, not only for heavy gravity loads, but also to resist significant lateral loads from rotator and oscillator with minimal deflection. Series of piles, called reaction piles, were integrated into the trestle at each CIDH pier location to provide adequate lateral support for the rotator/oscillator. Due to the lack of information regarding soil Young’s modulus (E), a methodology was developed to calibrate and calculate E with two methods. Extensive analyses using LPILE and finite element analysis program, PLAXIS, were performed to model reaction piles and calculate lateral deflection. PROJECT SPECIFICATIONS The Honolulu Rail Transit includes 20-mile route and 21 stations to be built from East Kapolei to Ala Moana Center, with $1.55 billion construction budget. The project is divided into two phases as shown in Fig. 1: Phase 1 which connects East Kapolei to Aloha Stadium with expected operation in late 2020, and Phase 2 which connects Aloha Stadium to Ala Moana Center with expected operation in 2025.

Jan 1, 2019

By John Dunn, Matt Hawley, Kashif Butt, Nicholas Gura

"This paper presents the results of a static load testing program completed on helical pile foundations for the replacement of high voltage transmission line tower structures. The foundations were part of the Northeast Grid Reliability Project (NGRP) for the Public Service Electric & Gas Company (PSE&G) near Newark, New Jersey. Structure foundations “anchor bolts down” was a design build contract model with the superstructure as bid-build.The soil stratigraphy along the alignment generally consisted of fill over about 10 ft of organic deposits underlain by up to 260 ft of normally consolidated glacial lake clays and silts. Additional project challenges included working under/adjacent the existing live high voltage lines, narrow site access due to environmental permits, foundations in a tidally influenced area, and pile projections in the order of 10 feet to meet the 10 year flood level requirements.The helical piles were constructed of 12.75 inch diameter open ended pipe piles with 36 to 40 inch diameter helices. A total of seven static load tests (compression and tension) were completed on 60 ft and 90 ft long piles, using both welded and mechanical pile splices. To evaluate pile-soil setup in the sensitive fine grained soil and determine representative longer term installation torque factors (Kt) for the production piles, the static load tests were performed 7 to 49 days after pile installation.Helical piles were found to be the most cost effective foundation alternative for this project. The required length of helical piles was less than other alternatives for similar allowable axial capacity. Helical piles with mechanical splices were installed for the varying structure foundations including tangent and heavy deadend, to a deadend monopole. Installation of 448 production piles (34,320 linear ft) was completed in three months. The installation timeline was critical to meeting the semi-annual PSEG outage for switching the old and new structures. Helical piles employing a mechanical splice resulted in an efficient and effective foundation solution for the conditions encountered on the project."

Jan 1, 2017

By Travis Coleman, Elvis Ishimwe

Currently, more than 400 drilled shafts have been constructed by various contractors at the I-90/94 and I-290 Jane Byrne (Circle) Interchange, located near downtown Chicago, Illinois. Cross-Hole Sonic Logging (CSL) and Thermal Integrity Profiling (TIP) tests were performed to evaluate the integrity and concrete quality of the drilled shafts installed at this project. For Phase I of the project the shafts were tested using CSL methods, and the shaft integrity was identified by analyzing the First Arrival Time (FAT) and the signal strength (energy) measurements. For the major portion of Phase II, the Illinois Department of Transportation (IDOT) accepted TIP testing as a substitute for CSL at the request of the contractors. The CSL testing results indicated 54 percent of the tested shafts had anomalies, and 78 percent of these anomalies were located within the lower three diameters of the shafts. To date, TIP testing results indicated the shaft integrity was as expected and acceptable for the all 34 tested shafts. A review of the testing results and a discussion of the detected anomalies are presented. In addition, a comparison of both TIP and CSL measurements is presented in this paper.

By Konstantin G. Ashkinadze

The paper considers performance of piles supporting transient pipe anchors in heavy industrial pipelines. Events such as pump trips or opening and closing of large valves produce short-term dynamic pulses in the pipeline with variable spectral characteristics. Their magnitude is large enough to cause major damage to the pipeline and its anchors, which face horizontal impact loads amounting to hundreds of kN. Design of pile foundations supporting these anchors is often governed by limitation of deflection of the support to prevent overstressing pipeline connections and equipment nozzles. The maximum deflection does not always correspond to the largest load because the stiffness of the soil surrounding the piles heavily depends on the rate of loading. Faster actions encounter stiffer soil response while loads of smaller magnitude applied slowly may be more critical for the deflection time history of the anchor. A typical transient action has both high- and low-frequency harmonics, which makes the response complex. Using load rate-dependent p-y curves published in literature, the paper develops methods of analysis of pile foundations for transient anchors. Pile displacement amplitude – input frequency – natural frequency correlations and time histories of pile response are constructed for typical profiles of transient actions, considering nonlinear soil response to large horizontal loads.

Jan 1, 2016

By Paul Suver

The closed loop standing column well (CLSCW) system uses a closed circuit of water to develop the same thermal heat exchange characteristics that are achieved from traditional open circuit standing column well that uses the ground water directly. Pipe pile and pipe anchor foundations can be used as CLSCW components for ground source heat exchange. New data gathering and analysis techniques and equipment installed in the heat pumps allow any mechanical engineer to design the system without specialty engineering equipment and certifications.

By David R. Sutfin, Joseph Lodde

110 N. Carpenter is new commercial building located in the West Loop neighborhood of Chicago, Illinois. The new home to the McDonalds Corporation work headquarters, accelerated project delivery methods were essential to meet the scheduling demands for this project along with other projects slated to start in the region. As such top-down construction methods were utilized to allow for above and below grade construction to proceed in parallel in lieu of more conventional bottom-up construction methods, thus compressing the project schedule. To achieve this plan, perimeter secant pile walls were constructed in conjunction with interior columns/drilled shafts and a shear wall core constructed from inside a temporary cofferdam. The use of secant pile walls allowed for efficient accommodation of a variety of loading conditions including: exterior curtain walls loads, perimeter column loads, tower crane foundation loads, and in-plane shear loads. Furthermore, this system allowed for efficient and fluid operation of equipment on site in order to accommodate the 90-day window allotted for initial foundation construction. INTRODUCTION 110 N. Carpenter is a recently-constructed 9-story commercial building located on the old Harpo Studios property in the West Loop neighborhood of Chicago, IL. The construction of this 55,750m2 (600,000 ft2) structure is significant to the continued commercial development of Chicago as nearly 46,450m2 (500,000 ft2) of the building houses the new world headquarters for the McDonald’s Corporation, which had moved from Chicago to the suburb of Oak Brook in 1971. McDonald’s recommitment to this urban environment is not only a reinvention of the long-established fast food giant but the anchor for a broader redevelopment of the West Loop neighborhood. Since the opening of this building was seen by the developer, the City of Chicago and others as a key to future local projects, innovative solutions were required to showcase forward-thinking design as well as expedite the construction process. The final result of the design/planning process is a structure consisting of nine levels of above-grade commercial space and two levels of below-grade parking, providing approximately 300 parking spaces. The above-grade structure consists of a reinforced concrete flat plate system, including two-way slabs, columns, and two core/shear wall systems for lateral support. With an average depth of 7m (23ft), the below-grade structure consists of interior components similar to the above-grade structure (structural slabs, columns, shear walls) but includes a perimeter secant pile wall that was designed to support lateral earth pressures; vertical forces from the exterior curtain walls, perimeter columns, and the construction tower cranes; and in-plane lateral forces to reduce the demand on and quantity of interior shear walls. The use of a secant pile wall is a key component to the project because it accommodated the use of top-down construction methods to accelerate the construction schedule.

Jan 1, 2019

By Terzis D. PhD, Katterbach M.

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

May 1, 2022

By Ihab Allam PE, Meeok Kim. PE. Ph. D

The wet weather equalization basin (EB) planned for Pacifica, CA is a 45 feet deep rectangular shaped underground water tank containing over 2.1 million gallons of water, and located only 500 feet away from the Pacific Ocean. The location and size of the water tank, and the geotechnical characteristics of the selected site presented many engineering and construction challenges. The engineering had to consider a structural system which can fit into the limited area of the site and yet need to meet the storage volume requirement. In addition, the system construction should meet the city’s tight budget and schedule.

By Rich A. Lamb, Paul J. Axtell, Michael K. Muchard

"Since 2010, the Minnesota Department of Transportation (MnDOT) has performed eight full-scale compressive load tests on large-diameter pipe piles at four different project locations across the state. All of the piles were 42-in diameter, open-ended pipes driven to practical refusal on sedimentary bedrock with D125-32 diesel hammers from three separate manufacturers. The rapid load test method in general accordance with ASTM D7383-10 (Statnamic method) was used along with high-strain dynamic testing and subsequent signal matching. Results of these tests indicate that the axial nominal resistance of these piles in compression is not controlled by geotechnical considerations when driven with an appropriately sized hammer and installation criterion. Rather, the predominantly elastic load-deflection behavior of the piles under compressive load suggests the axial nominal compressive resistance is controlled by the structural capacity of the pile. In all instances, the rapid load tests indicated a nominal resistance exceeding that produced by high-strain dynamic tests due to insufficient hammer energy to fully mobilize resistance. In all cases, the hammers used were able to easily install the piles through the soil overburden. Mobilizing a larger hammer simply to demonstrate high-strain dynamic resistance is not economical or practical. This paper presents the subsurface conditions at each location, the ensuing test results, and the ramifications for future projects in Minnesota utilizing large-diameter open-ended pipe piles.INTRODUCTIONThe Minnesota Department of Transportation (MnDOT) has recently performed eight full-scale compressive load tests on large-diameter pipe piles at four different project locations across the state. The four project locations described in this paper where pile load testing was performed are shown in Figure 1 and exist in the southeastern portion of Minnesota. The projects are all major bridges crossing the Mississippi River in three instances and the St. Croix River just above the Mississippi River in the other instance. The first project is the TH 61 Mississippi River crossing in Hasting, MN where two load tests were conducted. The second is the TH 36 St. Croix River crossing in Stillwater, MN where two load tests were performed. The third project is the I-90 Mississippi River crossing in Dresbach, MN where three load tests were conducted. The final project is the TH 43 Mississippi River crossing in Winona, MN where one load test was performed."

Jan 1, 2017

By Zhou Haizuo, Diao Yu, Zheng Gang

"The conventional design method for the embankment supported by DM columns usually assumes the simultaneous failure of all the columns. However, the progressive failure may occur in practice, especially considering that many researches have justified the critical load of DM columns is bending moment. In this study, a finite difference method was adopted to simulate the embankment on soft clay improved by DM columns. An increasing surcharge was applied on the embankment surface to investigate the mechanism of the progressive failure of columns beneath embankment. To capture the brittle bending failure of the DM columns, the model employed a cut-off method, in which the column was separated on failed section as long as the ultimate bending failure was reached. Furthermore, high-strength DM columns were used to enhance the global stability of embankment in this study. The numerical results showed that the ultimate bending failure was first reached at the column beneath embankment toe, and then a continuous collapse extended to the column beneath the embankment shoulder. It is found that the reinforcement could be obviously effective when the reinforced area of high-strength DM columns was extended to a certain area.INTRODUCTIONDeep mixed (DM) columns have been commonly used as a soil-improvement technique to increase stability and to reduce settlement of embankment. Research on failure modes of DM columns owing to embankment fill and surcharge has been the subject of interest for a number of investigators (Miyake 1991; Kitazume 2000; Han 2005; 2006).The potential failure modes of DM column include bending, inclination, shearing, rotating, soil flowing and a combination of these modes (Kitazume and Terashi 1991; Broms 1999). Many researchers have found that bending failure of DM columns was more critical than the shear failure. A centrifuge test was performed by Kitazume (2000) and the results showed that the columns failed in bending before shear failure. In addition, several numerical computations illustrated that design method using the shear strength overestimated the stability of embankment over DM columns (Han and Huang 2005; 2006; Navin 2006; Liu 2007; Wang 1996). In practice, an equivalent shear strength method based on bending failure could better reflect the stability of embankment (Zheng 2010; China Code JGJ79-2011)."

Jan 1, 2015

By Michael G. Batten, Brian D. Keaney

]The Virginia Department of Transportation (VDOT) and the harbors on the James River routinely use precast concrete piles founded in the Yorktown formation to support bridges and other coastal structures. However, axial pile resistances for large diameter piles in this area have been historically overestimated on past projects. This may be due to a common assumption that very large unit end bearing resistance will be developed for a large diameter displacement pile that is driven a significant depth. This assumption is integrated in the Nordlund (1963; 1979) method which is commonly used to estimate axial pile resistance for bridge foundations. A static and dynamic pile load testing program was implemented as part of the Hampton Roads Bridge and Tunnel Expansion project in Norfolk, VA in the James River. A primary objective of this program was to calibrate an axial resistance calculation method against the measured load test results. A method developed by Eslami and Fellenius (1997) that uses CPTu data directly was effective at calibrating to the measured load test results, and allowed for clearer interpretation of the unit resistance values than indirect, semi-empirical methods that require interpretation of soil friction angle and undrained shear strength.

Sep 8, 2021

By Jason Herron, Joseph Brown

The common couplings for joining sections of helical piles with an outside diameter of 6.625 inches and 8.625 inches are square on square, flange to flange, external pipe sleeve, internal pipe sleeve, and welded joint. Each coupling type has advantages and disadvantages in efficiency, capacity, installation, and economics of the installed pile. All these coupling types have been used in the helical pile market in North America for various applications and designs. Many of these applications require on-site testing, but test records are not typically shared with the helical pile industry. Due to the lack of information available for square on square and flange to flange couplings, testing was done to compare the efficiency of installation, load to deflection response, and torque to capacity ratios of external pipe sleeve, square on square, and flange to flange couplings. Field installations and tension tests were performed in non-cohesive (sand type) soil near Caseyville, IL and in cohesive (clay type) soil in Centralia, MO. The data collected during these tests included rotations per foot during installation, installation torque, applied pressure, and deflection. The results of this testing are analyzed and discussed within this paper. The results indicate that the square to square coupling is the most efficient of the designs tested, but this conclusion cannot be fully justified without further testing due to the variability in the data gathered and the small number of piles tested. INTRODUCTION A helical pile is typically assumed to be a medium-displacement pile when its outside diameter is between 4.5 inches and 8 inches and a high-displacement pile when its outside diameter is greater than 8 inches. A helical pile designer has multiple options when selecting a coupling type for medium- to high-displacement helical piles. Each type of coupling has advantages and disadvantages and must be analyzed on the bases of efficiency, capacity, installation, and economics of a project. Typical couplings that are chosen by designers include square on square, flange to flange, external pipe sleeve, internal pipe sleeve, and welded joint. A helical pile must transfer axial, lateral, bending moment, and torsional loads, and the coupling must be designed to effectively and efficiently transfer each type of load. During the installation of a helical pile, the rate of penetration and the disturbance of soil layers play a critical role in the efficiency and torque to capacity ratio (Kt) of the pile. It is common for a coupling to protrude beyond the outside diameter of the pipe section being used. This is necessary for the function of certain coupling types and can facilitate the connection of couplings. However, it causes increased soil disturbance and reduce the rate of penetration due to soil bearing against the protruding portion of the coupling. A helical pile designer typically will work to minimize the coupling protrusion and create a pile with optimal installation efficiency but may choose a design with lower installation efficiency if it offers sufficient economic advantage.

Jan 1, 2019