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By Mohammed Faizal, Abdelmalek Bouazza

"The operation of ground source heat pumps combined with foundation piles can have an effect on the thermal behaviour of the pile and the surrounding soil. This paper presents the effects of continuous heating, continuous cooling, and alternate heating and cooling operations on ground and pile temperatures as well as the thermo-mechanical behaviour of a field scale energy pile. The effect of pile operation on the ground temperatures is highest near the pile and reduces with increasing radial distance. The results of the present studies generally showed that the thermal elasticity of the pile is not affected.INTRODUCTIONGeothermal energy piles are foundation piles used as underground heat exchangers to maintain thermal comfort in buildings, via the use of ground source heat pumps (GSHPs). Ground source heat pumps are more economical and environmental friendly compared to conventional heat pumps. Energy piles can be combined with supplemental surface heaters or coolers, known as hybrid systems, for forcefully recharging the ground during non-operational times of the GSHP. Alternative heating and cooling of the GSHP improves geothermal energy usage and alleviates heat build-up in the ground and provides a balance of ground temperatures around the heat exchanger (Jalaluddin and Miyara, 2012).The temperatures induced in the piles during GSHP operation can lead to a complex response of thermal strains and stresses in the pile concrete. An assessment of the thermo-mechanical response of energy piles for various thermal loads may assist engineers in the design process. Furthermore, an assessment of ground temperatures will also highlight any potential thermal interactions with other energy piles in actual building operations.At present, the thermal strain and stress distribution in field scale energy piles has mostly been studied for continuous operation (Laloui et al., 2006; Bourne-Webb et al., 2009; McCartney and Murphy, 2012; Akrouch et al., 2014; Mimouni, 2014; Murphy and McCartney, 2014; Murphy et al., 2014; Wang et al., 2015). These studies have contributed considerably to the understanding of the axial thermal strain and stress distributions in the piles and have shown that pile thermal behaviour is mostly thermo-elastic without inducing major structural concerns.The present paper adds to the current knowledge by assessing the pile thermo-mechanical and ground thermal response for continuous and alternating thermal loads of a field scale energy pile. The operation modes studied are 24 hours continuous cooling (Faizal et al., 2015), 24 hours continuous heating, (Wang et al., 2015) and alternate heating and cooling operation (Faizal and Bouazza, 2016). The forced ground thermal recharging is done during the non-operating times of the cooling unit, simulating a solar hybrid GSHP system for a scheduled intermittent mode of operation."

Jan 1, 1900

By Nick M. Withers, Suthagarann Visvalingam, Cillian Mc Colgan

The level crossings removal project in Victoria is removing 75 level crossings across Melbourne to improve safety by separating trains from traffic, with other benefits such as reduced congestion, an upgraded road network, connected communities and support of urban regeneration. The level crossing at Station Street in Carrum forms part of the scope being delivered by the Southern Program Alliance (SPA), which is delivering level crossing removal works associated with the Frankston Train Line. At Station Street, a rail viaduct consisting of 19 spans and totalling approximately 545 m in length is under construction to remove the former level crossing. The viaduct consists of two parallel reinforced concrete Utrough girders and steel trough girders, one for each rail line. The foundations of the rail viaduct are founded on groups of Continuous Flight Auger (CFA) piles. The characterisation of geological units encountered at Carrum for the foundation design has been based on insitu testing and interpretation of test results from high strain dynamic pile testing (PDA) and Case Pile Wave Analysis Program (CAPWAP) from the Seaford Road Bridge, located approximately three kilometres South of Carrum, in similar ground conditions. By conducting pile load-deformation analyses based on pile testing significant savings were made for the client compared to the original design which was based on more traditional empirical correlations. This paper discusses the pile design methodology adopted using pile test data for this viaduct foundation. The results of this assessment are also compared to existing empirical correlations, and the limitations are discussed. The performance of the adopted pile design methodology using pile test data at Carrum rail viaduct is also discussed.

Nov 1, 2022

By Anthony T. C. Goh

"For deep excavations in soft clay, it is common to use jet grouting piles (JGP) prior to excavation to minimize wall deflections and ground settlement, and to prevent basal heave instability. In this paper, finite element analyses were carried out to assess the basal heave factor of safety for excavations in soft clay supported by JGP. Comparison of the factor of safety from the finite element analyses with limit equilibrium methods was then performed. Subsequently, to account for the uncertainties in the soil and JGP properties, a simplified reliability analysis procedure is proposed to estimate the probability of basal heave failure for deep excavations supported by JGP.INTRODUCTIONJet grout piles (JGP) are often used to prevent basal heave instability and to minimize excessive wall and ground movements associated with deep excavations in soft clay deposits (Shirlaw 2003; Wen 2005; Ou 2006). The jet grouting process which is carried out prior to any excavation works produces a series of short overlapping grout columns resulting in a “continuous” base slab (commonly termed as jet grout pile or JGP) below the final excavation level that spans across the entire excavation (Gaba 1990; Hsieh et al. 2003; Ho and Hu 2006). Typically, the JGP thickness ranges from 2 m to 4 m.The focus of this paper is on the assessment of basal heave instability for deep excavations in clay stabilized with JGP. Finite element analyses were first conducted to determine the basal heave factor of safety for deep excavations in clay with JGP. Comparisons were then carried out with factors of safety based on conventional limit equilibrium methods. Since the conventional factor of safety approach does not explicitly reflect the uncertainties of the soil and JGP properties, it is demonstrated in this paper that a simple reliability based approach (Hasofer and Lind 1974) can be used to assess the probability of basal heave failure.LIMIT EQUILIBRIUM METHODFor excavations is clay, the Terzaghi (1943), Bjerrum and Eide (1956) and Eide et al. (1972) methods which are based on bearing capacity theory, are commonly used to determine the basal heave factor of safety. Another commonly adopted method in Japan and Taiwan is the slip circle method which involves taking moments about the lowest strut level (JSA 1988; Hsieh et al. 2008; Luo et al. 2012). The slip circle method has also been applied for excavations with a JGP at the base by incorporating the undrained shear strength of the JGP. In the slip circle method, the basal heave factor of safety FSslip is assessed by taking moments about the lowest strut level (Fig. 1)"

Jan 1, 1900

By Filippo Maria Leoni, Wesley Schmutzler

"Deep Mixing Method (DMM) for the Rio Puerto Nuevo Project in San Juan was chosen by the Corps of Engineers to improve the soils adjacent to a 90 inch forced sewer main relocation and to improve the soils for the base of a new drainage channel. The project is located just east of San Juan and south of the Horizon Port. The soils to be improved consisted of fill, marine clay, organics (peat) and the foundation clay layer. A preconstruction soil investigation campaign was performed to assess soil properties and to retrieve samples of the different soil layers for the laboratory Bench Scale Testing program (BST). The BST was conducted using various binder contents and water/cement ratios in each of the soil types; the selection of the different combinations and dosages was based on past extensive experiences on similar materials. Following the laboratory program, a full scale Field Test (FT) was done installing several DMM elements to verify the results of the BST and fine tune the construction parameters. Each element consisted of two 5.5 feet diameter overlapping mixing augers installed simultaneously to a depth of approximately 60 feet using a SOILMEC SR-90 dual axis drilling rig. The FT construction and post-construction coring results showed significant differences between the lab study and the actual field conditions. This paper will highlight these differences and the importance of performing both pre-construction laboratory and field tests in order to ascertain the proper mixing parameters in the different soil layers.IntroductionThe Puerto Nuevo project consists of the stabilization of a major drainage channel using Deep Mixing Method (DMM) and the relocation of a 90 inch forced main sanitary sewer outfall. The first portion of this project was a 40 x 16 x 2,000 foot box culvert installed in 2004. In order for the drainage system to be completed and function properly, the 90 inch forced main needed to be lowered about 20 feet to allow for proper drainage.DMM was chosen by the US Army corps of Engineers to stabilize the drainage channel as well as improve the soil under the relocated sewer main. The overall layout of the project is shown in Figure 1. The DMM is arranged in different zones (A through E) with variable top and bottom design elevations as can be seen in the typical cross section for ZONE A and B as an example. (Figure 2) The total amount of soils to be treated by DMM is approximately 84,000 cubic yards up to a maximum depth of 57 feet from ground surface and an Area Replacement Ratio of 100%.The equipment used to perform the DMM is a Soilmec SR90 twin-shaft jet assisted deep mixing rig (Figure 3) coupled with a LODOS 30 grout plant and two Soilmec 7T-500J high pressure pumps."

Jan 1, 2015

By Timothy C. Siegel, Derrick Dasenbrock, Rich Lamb, Paul J. Axtell

"The axial resistance provided by deep foundations may be divided into two components: side resistance and tip resistance. The direction that the side resistance acts depends on the relative movement between the deep foundation and the adjacent soil. That is, when the foundation moves downward relative to the soil, then the side resistance is positive and acts upward. Conversely, when the soil moves downward relative to the foundation the side resistance is negative and acts downward. Research supports that both positive side resistance and negative skin friction develop in essentially all deep foundations. The side resistance distribution is a function of the soil strength and stiffness, the applied top loads, and whether the top load is sustained, transient, or a combination of sustained and transient loads. Consideration of drag load and downdrag has become more convoluted with implementation of geotechnical aspects into the AASHTO LRFD Bridge Design Specifications and its use of load and resistance factors. This paper examines the current AASHTO Specifications and presents an alternative design approach for drag load and downdrag using the LRFD framework. The alternative design approach is illustrated by two examples involving drag load and downdrag.IntroductionThe axial resistance provided by deep foundations may be divided into two components: side resistance and tip resistance. The direction that the side resistance acts depends on the relative movement between the deep foundation and the adjacent soil. That is, when the foundation moves downward relative to the soil, then the side resistance is positive and acts upward. Conversely, when the soil moves downward relative to the foundation the side resistance is negative and acts downward. Research supports that both positive side resistance and negative skin friction develop in essentially all deep foundations. The side resistance distribution is a function of the soil strength and stiffness, the applied top load, and whether the top load is sustained, transient, or a combination of sustained and transient.Consideration of drag load and downdrag has become more convoluted with implementation of geotechnical aspects into the LRFD Bridge Design Specifications and its use of load and resistance factors. This paper examines current LRFD design specifications and presents an alternative design approach for drag load and alternative design approach is applied to several examples where drag load and/or downdrag may control design."

Jan 1, 2015

By Michael J. Marasa

"Geotechnical engineering and construction primarily relies on the subsurface characteristics of the particular site; however, obtaining both accurate and precise information on those features is challenging due to the numerous factors involved in testing procedures used to analyze varying site geology. This includes a detailed and thorough geotechnical investigation to understand the site conditions, allowing the implementation of the most practical and economical solution.This paper presents a case history of the installation of wick drains and construction of aggregate piers on the site of a large facility to be constructed in Memphis, Tennessee. Throughout intensive subsurface investigations, highly variable soils were encountered, requiring settlement control and increased bearing capacity. This paper will discuss the design and installation of the systems constructed, and procedures and execution of the work to ensure design specifications were achieved.BackgroundA 1.4 million square foot expansion directly adjacent to an existing 1.1 million square foot distribution facility in Memphis, Tennessee was planned to serve as a centralized facility for increased production. The first phase of construction included an 858,000 square foot warehouse and parking lot for approximately 400 trucks to the north of the existing structure. The anticipated column load for the warehouse was 125 kips; slab design bearing pressures ranged from 200 to 500 pounds per square foot (psf) and elevations ranged from EL. 264 to 282. Parking lot elevations ranged from EL. 264 to 290, requiring a design life of 10 years with an estimated 100 in- and out-bound trucks daily and maximum weight of 80 kips per truck. The second phase of construction took place east of the existing structure, and included a 794,000 square foot multi-level warehouse, a 100,000 square foot office, and additional employee parking. The anticipated column load for the second warehouse was 225 kips and slab design bearing pressures ranged from 200 to 500 psf. Elevations ranged from EL. 267 to 282. Anticipated column loads from the office were 25 125 kips, with slab design bearing pressures ranging from 100 to 200 psf. Due to the varying elevations within each planned footprint, up to 18 feet of new fill was required to match the existing structure’s finished floor elevation (FFE) at EL. 282."

Jan 1, 2017

By Abolfazl Eslami, Samieh Rezazadeh

"Semi-Deep skirted foundations are considered to be a viable option for a variety of onshore and offshore applications. It is necessary to determine appropriate foundation configurations that allow loads to be transferred safely to the surrounding soil. For this purpose the bearing capacity and stability analyses subjected to combined vertical, horizontal and moment loadings must be found. In this paper the vertical undrained bearing capacity is estimated via finite element analyses. The circular skirted foundations with different geometries considering embedment depth (embedment ratio between 0-2) and size effects (diameter equals to 5, 10, and 20) have been studied. Stress field, kinematic mechanism accompanying failure and bearing capacity factors for total, end and shaft resistance in semi-deep foundations with various embedment ratios are investigated. Furthermore, two probable mechanisms i.e. internal flow and soil plug for estimating foundation capacity for design purpose in practice have been assessed. Comparisons with different research works including conventional methods, upper and lower bound approaches, and finite element analyses have indicated that the conventional methods underestimate the bearing capacity due to ignoring the significant role of shaft resistance. Determining appropriate economic foundation configurations to transfer loads safely to the surrounding soil is a major issue in geotechnical engineering. Shape and dimension of foundations, embedment depth, soil characteristics and applied loading, all affect the foundation performance. Recent studies have shown that for foundations with large breadth and of D/B between 1 to 4, kinematic mechanisms and failure modes are different from the two main types of foundation (i.e. shallow and deep). Therefore, D/B factor must not be considered as the only factor for defining foundation type. ""Semi-Deep foundations"" are another foundation category distinguished based on their performance. This relatively new concept is becoming increasingly an optimum alternative for shallow and deep foundations to support structures especially in accessible depth. As illustrated in ""Fig. 1"", different types of semi-deep foundations consist of:"

Jan 1, 2017

By David White

"When finished (projected completion in 2016) the Hong Kong-Zhuhai-Macau Bridge Project will comprise three cable-stayed span bridges and a 4.15 mile immersed tube tunnel - linking Hong Kong to Macau and the mainland Chinese city of Zhuhai. The design included two artificial Islands to serve as the transition structures for the tunnel to bridges, entailing a massive seaborne land reclamation project, and the use of thousands of sheet piles, and man-hours. The challenges of driving individual steel sheet in 100’ of water are well known, let alone in the open waters of the South China Sea.In 2010 a joint effort between American Piledriving Equipment (APE) and Allnamics Pile Testing Experts convinced the Chinese contractor First Harbor Marine Group China that a massive multi-vibro hammer can be used to drive 130’ long, 72’ diameter steel pipe piles weighing 662 US tons each into the sea bed of the South China Sea for the Hong Kong - Zhuhai - Macau bridge artificial islands. Combining APE’s hammer design, production and operation know-how with the pile driving simulation and installation know-how of Allnamics made it possible to show the feasibility of driving these gigantic piles into bottom of the sea to the required depth.INTRODUCTIONThe challenges of driving individual steel sheets in deep water are well known, let alone in the open waters of the South China Sea. Often the challenges of construction are overcome with engineering or equipment. The challenges of China’s Hong Kong-Zhuhai-Macau Bridge, on the drawing board since 1983, were to overcome both. The challenges of overcoming the skepticism of the Chinese Engineering community would be another story.The finished project will comprise three cablestayed span bridges and a 4.15 mile immersed tube tunnel linking Hong Kong on an eastern span to the China mainland cities of Zhuhai and Macau via two western spans."

Jan 1, 2017

By James G. Ulinski, Sebastian Lobo-Guerrero, Vishal B. Patel

"Recently modified design equations used in the transportation industry to calculate side friction and end bearing capacity for drilled shafts are now providing more realistic estimations of capacities than did previous methods. Using multiple case studies and test results from various projects, a more realistic design approach was formulated by the Federal Highway Administration (FHWA), which resulted in greater values of ultimate capacity for side friction and end bearing and in a more efficient design overall.In 2010, the FHWA published GEC-10 – Drilled Shafts: Construction Procedures and LRFD Design Methods, which illustrates a different method of calculating side friction and end bearing resistance and results in greater values for design. In 2014, the Association of State Highway and Transportation Officials (AASHTO) adopted the method put forth by FHWA, which was included in its LRFD Bridge Design th Specifications, 7 Edition. The Pennsylvania Department of Transportation (PennDOT) recently adopted and incorporated the similar methodology as AASHTO for calculating side friction and end bearing for drilled shafts in rock, and these changes are reflected in the 2015 edition of the PennDOT Design Manual, Part 4 (DM-4). This article discusses the past and current design methodology along with a project case study with results from Osterberg Cell (O-cell) load testing, which presents a comparison between the design resistances of ultimate side friction and end bearing and the measured capacities at failure.The Old and the NewEditions of the AASHTO LRFD Bridge Design Manual from 2012 and earlier estimated ultimate side resistance, qs, in rock using the following equation (modified from Horvath and Kenney, 1979):qs=0.65aEpa(qu/pa)0.5 < 7.8pa(f ’c/pa)0.5 where: qu is the uniaxial compressive strength of the rock in ksf; pa is the atmospheric pressure in ksf; aE is the reduction factor to account for jointing in rock; and f ’c is the compressive strength of the concrete in ksi. For intact rock, previous versions of the AASHTO manual required that the ultimate end bearing resistance, qp, was calculated using the following equation: qp=2.5qu."

Jan 1, 2017

By Spencer Ness, Yazen Khasawneh, William Tjaden, Mohammad Nassim

The evaluation of long-term performance of the wind turbine structures is essential in lowering the Levelized Cost of Electricity (LCOE) from wind sources. The required maintenance of the wind turbine foundation during the design-life time of the wind turbine may result in escalated cost, if not properly evaluated during the planning and designing phases. The degradation of the foundation soils’ stiffness due to the accumulation small plastic strains resulting from normal and/or extreme operating cyclic loading may result in escalating the O&M cost. The foundation’s stiffness degradation will result in a shift of the wind turbine system natural frequency, which may result in amplifying the vibrations generated at the hub. The anticipated shift of the wind turbine system natural frequency during the design-life time should be investigated through numerical simulations of the anticipated dynamic loading utilizing soil constitutive models that are capable of capturing the foundation stiffness degradation due to the accumulation of such small plastic strains. This study presents the validation of an element model that will be used to evaluate the performance of existing and/or proposed constitutive model.

Oct 1, 2022

By Francisco A. Flores, José L. Aguirre, Héctor A. de la Fuente, Erika Bernal, Jorge Arroyo-Esquedla

This paper presents the analysis, design, and construction of soil improvement for storage tanks foundation support at a site in Tabasco, Mexico. A total of 980 Rammed Aggregate Piers of 12.5 m in length and 0.5 m in diameter were designed and constructed to support four storage tanks. The soil conditions at the site generally consist of loose to medium dense silty/clayey sand to about 8m depth, underlain by very loose to medium dense silty/clayey sand with seams of very soft clay. The use of Rammed Aggregate Piers induced densification of the soil to increase its stiffness and reduce the liquefaction potential to control both static and dynamic induced settlements. Standard Penetration Test (SPT) and Cone Penetration Test (CPTu) explorations were performed prior to and post soil improvement to compare the liquefaction potential and the Factors of Safety associated with the two conditions. Finally, the soil improvement installation rate is presented. Soil improvement using Rammed Aggregate Piers represented a suitable alternative to support storage tanks foundation in potentially liquefiable areas.

Oct 1, 2022

By Thomas A. Printz

The wide use of carbon steel in construction and engineering projects makes this engineering material accountable for approximately 85% of the total annual steel production worldwide. Despite the lack of corrosion resistance of carbon steel, it is incorporated into the permanent work for marine applications, power plants, transportation projects, chemical processing, mining, petroleum production and refining, pipelines, mining and construction equipment. Corrosion is an electro-chemical process that occurs in the presence of water and air. When an electric current is introduced to water or soil, the rate of carbon steel corrosion increases rapidly. Gaseous atmospheric constituents that are capable of electrolytic activity can also increase the rate of corrosion. Corrosion tends to be more rapid in environments in which the steel is exposed to water, and then air, rather than being constantly submerged. The exposure to seawater increases steel pitting because the electrical conductivity is improved in salt water.

Jan 1, 2013

By Harry Schnabel

A 6200 m² cement deep soil mixed (CDSM) wall was constructed for an addition to the Museum of Fine Arts in Boston, Massachusetts. The addition was located along the east side of the existing museum within an existing courtyard and in the area of a recently demolished structure. The basement for the new addition extended up to 9.1 m below the floor slabs of the adjacent buildings. The adjacent buildings are supported on a variety of foundations including; shallow spread footings on alluvial sand deposits, low capacity piles bearing in the alluvial sands and Boston blue clay, and caissons bearing on the alluvial sands and clay. Groundwater was less than one meter below the top of the CDSM wall. The new addition was founded on shallow foundations in the desiccated crust of the Boston Blue Clay. The CDSM wall was selected as the most economical means to control deep seated ground movements, limit movements of adjacent structures, and inhibit groundwater flow into the excavation. Braces and a continuous wale were used to support the CDSM wall where it was located adjacent to structures. Tiebacks were used where there were no structures. Other geotechnical construction at the site included: ? Jet grouting (JG) to improve the ground and provide an impervious subgrade layer at the west end of the addition, ? Concrete pier underpinning was used to support an existing structure on the west end of the site, and ? A secant pile wall using alternating drilled shafts and jet grout columns was used for earth support and a barrier to groundwater flow to allow for the installation of a storage tank at the south end of the site. Inclinometers, total station surveying, vibrating wire strain gauges on the braces and wales and load cells on the tiebacks were used to monitor performance of the excavation support system. The excavation support system performed better than required limiting lateral movements of the adjacent structures to less than 13 mm and vertical settlement to less than 8 mm. No settlements or movement were detected during the construction of the wall. Lateral movement of the CDSM wall was typically below 15 mm with the maximum movement occurring near subgrade.

Jan 1, 2011

By Marco D. Boscardin, Benjamin H. MacKinney, Kenneth R. Allard, Kenneth A. Pidgeon, Adriane G. Boscardin

This paper presents a case history for a unique application of a system of vertical micropiles with horizontal soil nail bracing and shotcrete facing for underpinning. The system was used to support and protect an existing 2-story hospital building during demolition and renovation. The goal was to limit building movements and have the building remain in use during construction of an abutting addition. Soils at the site consisted of clean, loose to dense, sand and gravel. The original underpinning design was revised after the initial excavation revealed unsuitable soil conditions for traditional underpinning pits. An alternative system consisting of vertical micropiles (hollow bars) through the footing, combined with shotcrete and soil nails was proposed, accepted by the owner, and successfully constructed. Excavation depths were up to 15 feet (4.6 m) below the existing footings. Wall movements were monitored at regular, horizontal and vertical intervals along the hospital wall, and less than 0.6 inches (15 mm) of settlement and 0.1 inches (3 mm) of horizontal displacement throughout underpinning and construction were reported. The challenges with the original proposed support of excavation design and other alternative approaches considered will also be discussed.

Oct 1, 2022

By Tsuda Wakaki, Naoki Takahashi, Natsuki Okuno, Hidenori Takahashi, Ikuo Towhata, Yoshiyuki Morikawa

"Deep mixing (DM) method has been increasingly employed as a countermeasure against subsoil liquefaction in recent years. Pile-type DM, however, is considered to have little effect as a liquefaction countermeasure, because the shear deformation of unimproved soil around the piles cannot be reduced. However, experimental results, which imply that shear deformation of unimproved soil around DM piles can be reduced, were reported. Furthermore, a new plane-arrangement of DM piles has been proposed to mitigate lateral flow induced by liquefaction. The DM piles in this arrangement confront the lateral flow in any direction, compared with the piles arranged in conventional pattern such as square and triangular arrangements. In this study, a series of dynamic centrifuge model tests was conducted to verify the lateral flow resistance of DM plies in the new arrangement. The results indicate that the DM plies can reduce the lateral flow of liquefied ground when the pile displacement and the pile head rotation are restricted. In addition, lateral load acting on DM pile from liquefied ground, which is required for design strength of the DM pile, was investigated.INTRODUCTIONDeep mixing (DM) method has been increasingly employed as a countermeasure against subsoil liquefaction in recent years. The solidified body formed by the deep mixing method is usually block or lattice shape, composed of solidified columns that overlap each other horizontally. Lattice-type solidification has been shown to be effective as a liquefaction countermeasure despite the presence of unimproved soil inside the lattice wall, because the shear deformation of the interior soil is restrained by the wall (Suzuki et al., 1989). On the other hand, it has been thought that pile-type DM cannot reduce shear deformation of unimproved soil around the piles, because the displacement of the pile is less restricted than that of the lattice wall. DM piles have been reported to have little effect as a liquefaction countermeasure, but to be superior in terms of construction cost and applicability around existing underground structures (Koga et al., 1986). However, there are experimental results implying that DM piles have reduced the shear deformation of unimproved soil and mitigated its liquefaction (Yasuda et al., 2003; Tanaka et al., 2003). Yamamoto et al. (2006) conducted dynamic analyses of ground improved with lattice- and pile-type DM. Their results showed that pile-type DM with an improvement ratio of more than 35% reduces excess pore water pressure generated by earthquakes. Furthermore, the new pile arrangement shown in Fig. 1(a) has been proposed to mitigate lateral flow induced by liquefaction. It was developed and has been verified using dynamic model testing in a 1 g field (Takahashi et al., 2010a; 2010b; 2013; Towhata et al., 2010, Morikawa et al., 2014). The DM piles in this configuration interrupt lateral flow in any direction, unlike those placed in square and triangular arrangements."

Jan 1, 2015

By Teresa M. Bodas Freitas, Arianna Lupattelli, Peter J. Bourne-Webb, Diana Salciarini, Martina Zito, Donatella Sterpi

The thermomechanical response of thermally-activated (TA) piles under monotonic thermal loads is quite well understood and the remaining uncertainties relate to the effect of long-term, cyclic loading of individual TA piles and pile groups. Recent studies undertaken by the authors have provided insights into the behaviour of TA pile foundations undergoing cyclic thermal loading. Despite their simplicity, the analyses show that key aspects of the observed response of piles in sand, under cyclic thermal loading can be reproduced, providing confidence in the outcomes of the analyses. The studies examined isolated piles and pile groups, and concluded that irrecoverable thermally-induced settlement may be mitigated through the choice of an appropriate margin of safety on the pile shaft resistance under service mechanical load conditions, and the maximum thermal stress can also be readily estimated. This paper consolidates these works and provides guidance regarding the safe geotechnical and structural design of the piles, then looks towards the remaining issues around the safe provision of thermally-activated pile foundations.

May 1, 2022

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

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

Jan 1, 2017

By Siavash Mahvelati, Alireza Kordjazi, Joseph Thomas Coe

Deep foundations are often constructed as end bearing members with a significant amount of their capacity derived from bedrock. Sites with highly variable bedrock conditions therefore present a unique challenge when attempting to estimate the design elevation of deep foundations. Typical subsurface characterization techniques such as drilling, standard penetration testing (SPT), and cone-penetration testing (CPT) may fail to adequately establish top-of-rock elevation in geologic settings prone to karst and/or significant amounts of residuum, saprolite, and deformed bedrock. Seismic surface wave geophysical methods have been increasingly used to map bedrock topography in such settings. However, the current standard of practice for these methods introduces resolution limitations in spatially variable subsurface conditions due to averaging effects from the analytical framework used to process the acquired data. This study explores the use of a tomographic approach with full waveform inversion (FWI) to map top-of-rock elevations at a numerically simulated site representative of highly variable bedrock topography. Comparisons are made with seismic refraction (SR) and a dispersion-based multichannel analysis of surface waves (MASW) approach as more commonly used in geophysical subsurface investigations. The results highlight that FWI provides a superior estimate of top-of-rock topography than SR and MASW at a cost of a significant increase in the required computational resources and time.

Sep 8, 2021

By Siavash Mahvelati, Alireza Kordjazi, Joseph Thomas Coe

Deep foundations are often constructed as end bearing members with a significant amount of their capacity derived from bedrock. Sites with highly variable bedrock conditions therefore present a unique challenge when attempting to estimate the design elevation of deep foundations. Typical subsurface characterization techniques such as drilling, standard penetration testing (SPT), and cone-penetration testing (CPT) may fail to adequately establish top-of-rock elevation in geologic settings prone to karst and/or significant amounts of residuum, saprolite, and deformed bedrock. Seismic surface wave geophysical methods have been increasingly used to map bedrock topography in such settings. However, the current standard of practice for these methods introduces resolution limitations in spatially variable subsurface conditions due to averaging effects from the analytical framework used to process the acquired data. This study explores the use of a tomographic approach with full waveform inversion (FWI) to map top-of-rock elevations at a numerically simulated site representative of highly variable bedrock topography. Comparisons are made with seismic refraction (SR) and a dispersion-based multichannel analysis of surface waves (MASW) approach as more commonly used in geophysical subsurface investigations. The results highlight that FWI provides a superior estimate of top-of-rock topography than SR and MASW at a cost of a significant increase in the required computational resources and time.

Oct 1, 2021

By F Debidin

The progressive rise of an H-pile during driving of an adjacent pile is described in this case history in which piles 15 to 18 m long were driven to end-bearing for the foundations for a 230 m long building. The use of a reaction beam-soil anchor system for compression load tests is discussed. The results of static load tests to determine pile capacity are compared with those obtained by the Pile Driving Analyzer and by theory. Unusual high temporary compressions were observed by field control staff. Proof testing was necessary to determine the need for restriking of some piles in which rise had occurred.

Jan 1, 2010