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By Bengt H. Fellenius

The design of pile foundations is much more commonly verified by means of a full-scale test, than is the design of other foundation units. The reason is not that our knowledge of pile behavior is more uncertain than our knowledge of other foundation types making the verification necessary, but more that the loads in a structure are more concentrated to single foundations in a structure founded on piles as opposed to structures on footings or mats. Therefore, should a pile cap fail or move, the adverse consequence of this is often drastic, as the piled structure has little freedom to transfer its need for support to other foundation units. Consequently, it becomes important to assure the design of piled foundations. In many, maybe in most instances, the static pile loading test is routine and geared toward determining an at least capacity, only. However, in these times there is an ever increasing liability of the professional, demands for increased economy of the foundation, and frequent lack of the involvement in the test of the experienced old-timer exercising good judgment. Furthermore, modern pile design is leaving the single, simple concept of capacity and requires more information from the test to assist in determining aspects of long-term behavior and settlement. Therefore, even the straight forward, routine static loading test requires improved planning, execution, and analysis.

Jan 1, 1990

By Harry Schnabel, Mitchell L. Fong, Douglas R. Jenevein, Thomas S. Lee

"The Warm Springs Extension (WSX) is one of a series of projects that will eventually extend the Bay Area Rapid Transit System (BART) from Fremont to San Jose, California. A cut and cover tunnel was used for a portion of the extension that runs through Fremont Central Park to minimize the impacts that an at-grade railway would have on the Park. A cement deep soil mix (CDSM) wall was selected by the engineer as the preferred method of providing structural support and groundwater cut-off for a portion of the tunnel where it passes through an important aquifer and near Lake Elizabeth. In addition to the CDSM wall, a jet grout plug was constructed at the base of the tunnel to provide a complete groundwater cut-off.This paper will discuss the unique quality assurance and quality control measures taken for the soil mix wall and jet grout plug as well as the methods used to repair leaks and mitigate water seepage through the exposed wall and grout plug.PROJECT DESCRIPTIONThe Bay Area Rapid Transit (BART) Warm Springs Extension (WSX) project is located south of the existing Fremont BART station extending 8.9-km (5.4 miles) to Warm Springs District in Fremont, California. The WSX project has been divided into two contracts with different delivery methods. In order to minimize impacts to Fremont Central Park, a subway was selected at this portion of the alignment under a conventional design/bid/build contract.The Fremont Central Park Subway (FCPS) which begins on the south side of Walnut Ave and ends just north of Paseo Padre Parkway and is about 2.3-km (1.4 miles) long. Fig. 1 shows the entire WSX and the FCPS project. The FCPS contract consists of a cut-and-cover subway box, subway transition structures, ventilation structures and a section of which transverses Lake Elizabeth (a man-made lake). The geologic conditions consist of fill (sand, silt, clay and construction debris), Young Alluvium (clay and silt), Basin Deposits (clay, silt, and sand), and Older Alluvium (sand and gravel) as shown in Fig. 2.HYDROGEOLOGY OF THE PROJECT SITEThe FCPS is dominated by two geologic features - the Hayward Fault and the Above Hayward Fault (AHF) aquifer. The AHF aquifer provides a significant source and storage of water for the local water district. The underground subway will penetrate this aquifer and is up to 11m (36 ft) below the groundwater table. No groundwater was allowed to be pumped during construction of the subway box by Alameda County Water District (ACWD). To facilitate excavation for the subway box, temporary cut-off walls and a grout plug were designed to retain and resist high differential hydraulic pressure. The following section describes the selection of a deep soil mixing method for water cutoff. Design of the grout plug has been described in Lee, et al., 2011 and Fong and Lee, 2009, and is not the focus of this paper."

Jan 1, 2015

By D. S. Yang, Y. D. Wang, G. Watanabe, A. P. Notaro

"Deep soil mixing (DSM) walls reinforced with steel soldier piles were installed for excavation support and groundwater control for the construction of a grade separation structure at the intersection of Warren Avenue and the Union Pacific Railroad in Fremont, California to mitigate traffic conditions during the busy commute hours and for the extension of San Francisco Bay Area Rapid Transit (BART) system. Instead of treating the DSM wall as a temporary structure, the reinforced DSM walls were integrated in the design of the permanent structures including retaining walls, and the abutments and pier of the railroad and BART bridges. The integration of steel members inside the DSM wall as part of the permanent structures is an innovation which facilitates the use of top down construction techniques to speed construction and utilizes the steel soldier piles that would have been disregarded after the use as a temporary shoring wall. This paper will review the background of the project and DSM method and present the design and construction of the DSM wall composite structure for this grade separation project.INTRODUCTIONUsing the concept of mixed-in-place piles initiated in the 1950’s in the United States, Japanese contractors in the late 1960’s and early 1970’s installed single mixed-in-place soil-cement piles along a row to create a wall for excavation support and groundwater control. Due to the high groundwater conditions in most of the coastal cities in Japan, wall continuity and uniformity became the requirements of soil-cement walls for reliable groundwater control to minimize ground movement and impacts to adjacent buildings and facilities. In late 1970s, Seiko Kogyo, Co. Ltd. developed the Soil Mix Wall (SMW) method, which uses a triple auger mixing tool to improve the uniformity and continuity of soilcement wall. The SMW method is considered a wall installation method in contrast to the Cement Deep Mixing (CDM) method, also developed in Japan, for ground stabilization in soft soils, especially in the marine environment. In the U.S., generic terms like DMM (Deep Mixing Method), DSM (Deep Soil Mixing) or CDSM (Cement Deep Soil Mixing) are used by various government agencies and private organizations to describe the soil mixing technologies without differentiating the origin, procedure and application. The method used in this project is called DSM method by the project owner, Santa Clara Valley Transportation Authority (VTA), to produce a single continuous soil-cement wall for use as shoring wall and composite structure. The mixing tool for DSM wall installation can vary from 3 to 6 mixing augers. Due to the need to install steel soldier piles into the DSM wall for resisting lateral forces, high water cement ratio slurry with bentonite is used to produce low strength soil-cement, generally in the range of 70 to 100 psi (500 to 690 kPa), with high fluidity to facilitate the installation of steel soldier piles. To maintain the wall continuity for groundwater control, overlapping of one full DSM column is made between neighboring elements using two types of installation procedures as illustrated in Figures 1a and 1b. Steel soldier piles, as shown in Figure 2, are used to reinforce the soil-cement wall to resist the lateral shear force and bending moment induced during the excavation."

Jan 1, 2015

By J. S. Lee, R. K. Massarsch

"A 3.2 km long immersed road tunnel forms part of the Busan-Geoje Fixed Link in South Korea, which connects Korea's second largest city Busan, with the island of Geoje. To ensure the water tightness of the joints of the segmental tunnel structure and to limit the forces in the shear keys, the differential settlements have to be limited. This was achieved by extensive soil improvement of the marine clay below the tunnel with cement deep mixing (CDM) and sand compaction piles (SCP). This paper focuses on the characteristics of the marine clay, the basic design principles, layout and constructional issues of the CDM soil improvement, and numerical and numerical analyses to predict settlement and stability.INTRODUCTIONThe Busan-Geoje Fixed Link consists of two short cut & cover tunnel access ramps, a 3.2 km long immersed tunnel (Figure 1) and two long span cable stayed bridges. The tunnel consists of eighteen concrete elements each of 180 m length having a rectangular cross section of 26.5 m in width and 10 m in height. The tunnel elements are cast in a dry dock on shore and floated out to the sea, immersed in their final positions on a gravel bed in pre-excavated trench and connected to each other by a dual gasket system. The water depth was up to 50 m making the tunnel of the deepest yet constructed. After immersion, the tunnel is protected by backfill material at the sides and rock armour on top. Each tunnel element consists of eight 22.5 m long segments. The joints between the segments and between the tunnel elements are equipped with EDPM water stops, Omega seals and concrete shear keys. The longitudinal displacement behaviour of the segmental tunnel structure in the varying ground conditions represents a complex soil-structure interaction problem which has been modelled with a FEM structural model representing the tunnel, the joints and with springs to represent the soil that are derived from the PLAXIS soil/foundation models. In order to ensure the water tightness of the joints which have limited opening capacity and to limit the forces in the shear keys, differential longitudinal settlements have to be limited. This is achieved by limiting the variations in subgrade modulus along the alignment and it in practice means that differential settlements are limited to a few tens of millimetres. Without soil improvement of the marine clay below the tunnel, long-term tunnel settlements of up to 400 mm were predicted when taking into account the likely variations in the trench profile, backfilling and uncertainties in the soil properties. Such large total settlements led to large variations in the sub-grade reaction along the alignment, which in turn resulted in significant differential settlements, unacceptable joint opening and large shear key loading. It was therefore decided to carry out extensive soil improvement with cement deep mixing (CDM) (CDIT, 1999) and sand compaction piles (SCP) (Kitazume, 2005) after studying a number of foundation alternatives."

Jan 1, 2015

By Sunil S. Basarkar, Dilip M. Dewaikar, Rajesh H. Gajjar

"A load transfer program AXPILE was developed for simulation of the loadmovement characteristics of socketed piles of the Mumbai reg ion. This program used empirical relationships for ultimate shaft resistance at pile-rock interface recommended by Zhang and Einstein (1998). According to their recommendation, ultimate shaft resistance at pile-rock interface is related to the square-root of uniaxial compressive strength of intact socket material by a parameter C, which ranges from 0.4 for smooth sockets to 0.8 for rough sockets. Results of three instrumented pile load tests were compared with the AXPILE generated results. The comparison of analytical and field estimates of the unit shaft resistance confirm the recommendations of Zhang and Einstein (1998) on the unit side shear parameter c,, which was found to be in the range of 0.35 to 0.67.INTRODUCTIONInstrumented pile load tests were carried out on the test piles at the Bandra-Worli sea link project in Mumbai city of western India. High capacity socketed piles were required to take up loads from the superstructure. Hence, in addition to the available toe resistance, an accurate measurement of the shaft resistance in socket portion was desired. The instrumented load tests incorporated Osterbergcell (0-cell) assisted by strain gauge instrumentation to estimate the shaft resistance mobilization in the socket portion.AXPILE load transfer program was developed for load-movement simulation of socketed piles (Basarkar, 2004). The load transfer algorithm based on Coyle and Reese (1966) was incorporated in this program, which used empirical correlations and functions to account for load transfer in piles through shaft and toe resistance.This paper compares the computed unit shaft resistance from the AXPILE program with the measured values recorded from the instrumented pile load test."

Jan 1, 2005

By Wu Jian-tao, LI Guo-wei

"The Cement Mixing Pile (CMP) quality assurance assessment is an important programme in evaluating the efficiency of foundation improvement. Coring is the current specified method of quality assessment in China which has the shortcomings of long cycle, high cost and low efficiency. The field and laboratory test show that the regular cone penetration test can only detect maximum of 4m of effective detection depth in CMP. In contrast, the method of cone penetration test in the reserved hole can detect the quality continuously along the pile at any depth. The tip resistance of reserved hole penetration in the 7th day has good linear relationship with unconfined compressive strength in the 28th day. The slope of linear relationship decreases with the increasing of clay particles content.INTRODUCTIONThe method of Cement Mixing Pile (CMP) is often used to improve soft soil foundation in highway construction, with the major purpose of reducing settlements under embankments (Bruce et al., 2000),which is a form of what is known as the Deep Mixing Method (Bruce et al., 2013). The CMP technology spread quickly in China in the 1980s. CMP quality assurance assessment is an important programme in evaluating the efficiency of foundation improvement. Coring is the current specified method of quality assessment in China (China Academy Of Building Research, 2002). The method of Coring is perceived in some quarters that samples will provide lower strengths given the distress caused to the core during drilling and extraction (Bruce et al., 2002).The cone penetration test CPT can provide continuous measurements of the penetration resistance, sleeve friction at the tip of the probe, which has advantages of simple operation, low cost and high efficiency compared with coring. However, CPT tests have not been established to assess CMP in Sweden because of difficulties in maintaining verticality (Larsson, 2005). In Finland and Norway, however, CPT tests are commonly used (Halkola, 1999). One of the disadvantages of CPT is the tendency of the cone to steer out of the column (Porbaha et al., 2003). Darya Mokrousova (2010) states this tendency to deviate can be overcome by pre-boring and starting the penetration test from the base of the pre-bored hole. Sheng Haiyang (1999) found that probes may be deflected out, sometimes even at small penetration depths, and may not give a complete inspection of the pile. Liu Songyu et al. (2003) suggested that the Standard Penetration Test (SPT) is an effective way to evaluate the strength and quality of stabilized soil-cement columns. In general, Regular CPT can’t test the full length of CMP, and SPT still needed drilling which causes discontinuous detection. From the existing standard of China, core sampling compressive strength test is the main method, evidently, coring displays a longer test cycle, high cost and low efficiency. Therefore, an improvement of CMP quality assessment, by conjuring a fast and reliable detection and evaluation method, is necessary. The aim of this paper is to research the feasibility of using CPT in assessing the quality of CMP and presents an improved CPT method."

Jan 1, 2015

By Karsten Beekhaus, Sander W. Odijk, Rabea Bahlum, Mazin Adnan, Ayman Abdelh Al Nuaimat, Hassan Farhat

The Arab Potash Company, APC, is one of the 10 largest potash producers of the world. The solar ponds at the Dead Sea, used for the enrichment of the salt content in the brine, are of crucial importance for the first step in the exploitation of the potassium salt. Targeting at the expansion of production in the since over 50 years utilized facilities, the increase of the brine exploitation capacity, reducing the substantial brine seepage losses from the ponds, becomes a crucially required measure. In this context, the remediation measures on the over 11 km long Dyke 1, being a main dyke of the solar ponds system, became inevitable to reduce the brine losses, prevent further development of sinkholes and cavities and hence assuring the stability of the dyke. The highly aggressive environment, the acting hydraulic conditions and the sensitive stratification and nature of the existing ground represented remarkable challenges for the design, as well as its implementation by the construction activities. Royal Haskoning developed a solution addressing the challenges above and targeting at a high sustainability of the executed structure, especially in view of the various geological and hydrological hazards repeatedly occurring in this Dead Sea region, including sinkholes of several meters by diameter and depth. The construction works, consisting of a cut-off wall, with depths reaching down to 31 m, were awarded to Bauer International FZE, a subsidiary of Bauer Spezialtiefbau GmbH. Upon the execution of the first section of 4.2 km length, additional sections were subsequently commissioned, also on further dykes, totaling to about 300,000 m² of cut-off wall. The specific project conditions, such as utilization of cutter technique for the excavation in Halite rock, the stability of open trench exposed to hydrostatic pressure of salt-saturated ground water, resulted in unconventional requirements towards the supporting fluid. The extremely aggressive saline conditions –with a Dead Sea water density of 1.25 tons/m3; one of the world's saltiest water–, were further a decisive factor for the definition of the backfill material concept. Despite its clear advantage for construction of cut-off walls with installed sheet piles, the single-phase system with hardening slurries, fulfilling both functions of excavation support and cut-off wall backfill material, had to be abandoned in favor of the two-phase system, to construct a hybrid cut-off wall made of sheet piles and plastic concrete.

May 1, 2022

By Danielle Nhanqulumanga, Pranith Bhatt, Snehal Patel, Khadeeja Priyan

The Bi-Directional Static Load Test (BDSLT) is a test that determines the capacity of piles when loaded under bi-axial static compression. In recent years the BDSLT has seen an increase in demand due to its safety, speed, and affordability. This innovative foundation testing method has been universally used over the last 50 years, however respective codes and standards have only been published within the recent years. Detailed test procedures and methodology are expatiated in the ASTM D8169 M-18 [1], and the IRC 78 2014 Clause 709.2.5. [2] These standards provide the minimum requirements for the execution of the BDSLT. In this paper we did a comparative study of both standards envisaging to bring attention to the similarities and discrepancies found therein, with an aim to highlight the impacts and challenges that differing provisions of each standard could pose on the conduct of the BDSLT. Discrepancies found have been explained on the basis of geotechnical engineering theories and relevant field occurrences observed by superior engineers. Additionally, we emphasize on the relevance of experienced engineer’s judgement when utilizing the standards.

Sep 1, 2022

By Arash Khosravifar Ph. D. P. E., Thomas Torkelson P. E., Milad Souri Ph. D. P. E.

Kinematic demands from lateral ground deformations can be a major cause of damage to maritime and highway transportation structures such as wharves, piers, and bridges. These kinematic demands are different from the ground deformations in the free field in that the resisting forces from piles will reduce the ground deformations to some extent (i.e., pile pinning effect). Current design codes for wharf structures allow the beneficial resisting forces from pile pinning effects to be incorporated in pseudostatic slope stability analysis (e.g., ASCE/COPRI 61-14). While design guidelines that are specifically developed for bridge foundations provide recommendations on how to incorporate the pile pinning effects (e.g., Caltrans 2012), their applicability to wharf structures need to be evaluated. This study uses the results of a large-scale centrifuge test on a pile-supported wharf structure to evaluate the accuracy of available Newmark sliding block analysis in estimating the lateral ground deformations. Pile pinning effects are incorporated based on the approach outlined by Caltrans. The results of this study support the use of existing pile pinning methods that were primarily developed for bridge foundations in maritime structures (e.g., wharves and piers). It was found that median Newmark displacements provide a good estimate of the permanent end-of-shaking displacements and that the median plus 1 standard deviation Newmark displacements provide a good estimate of the peak transient displacements. Design considerations for use in the Newmark sliding block analysis to estimate the kinematic demands on piles are discussed.

Oct 1, 2022

By A. Fisher

The use of thermal integrity testing to verify the quality of deep foundations has increased significantly in the UK and other world markets over the last 5 years. The introduction of distributed fibre optic sensing to this field has broadened the range of applications in which it can be deployed and the types of foundations which can be tested. This paper presents how fibre optic sensing technology can be successfully deployed in the construction environment the range of foundation techniques to which it can be applied. Alongside developments in the practical aspects of thermal testing, progress has been made in establishing assessment criteria which can be used to evaluate the results. This paper presents recent examples of comparative studies on foundations which include both thermal integrity testing, cross hole sonic logging and intrusive coring. The use of distributed strain measurement during pile load testing presents an alternative means to verify the assessment criteria used for integrity testing. This new approach can achieve comparable results to foundation exhumation or intrusive investigation and at a fraction of the cost. This paper presents the findings of several such studies, highlighting the benefits and opportunities for future improvement of the method.

Oct 1, 2022

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 Darren S. Diehm

"Construction for the restoration and expansion of 102-year-old Wrigley Field in Chicago, Illinois began at the conclusion of the 2014 baseball season. This six year project involves structural upgrades to the Stadium, improvements to the facade, infrastructure, restrooms, concourses, suites, press box, and bullpens, as well as the addition of restaurants, patio areas, batting tunnels, video boards, an adjacent Office-retail Tower and a new Hotel. The Bleachers were demolished and replaced, and a new underground Clubhouse was constructed for the Chicago Cubs beneath a new open-air Plaza. The 1060 Project is privately funded, projected at $750 million (US). The work will be completed in phases during consecutive off-seasons, each with a maximum 23-week duration extending through the Chicago winter. Ownership mandated that on-going construction cause no disruption to the Major League Baseball season, have no impact on hosting concerts and other special events, and it should not adversely affect seating capacity, or diminish the fan experience.The 1060 ProjectAfter purchasing the Chicago Cubs baseball team in 2009 from the Tribune Company, the Ricketts family began planning the renovation and improvement of Wrigley Field and its near neighborhood surroundings in Chicago, Illinois. What came to be known as the 1060 Project was officially announced at the annual Cubs Convention in 2013. Construction began on the $750M privately funded project in October 2014 at the conclusion of the Major League Baseball season. In their vision, the Ricketts committed the 1060 Project to three primary goals. First and foremost as a MLB franchise, the work should provide a meaningful contribution toward winning the World Series and ending the championship drought which stretched to the last win in 1908. Second, the project should be focused on preserving and improving Wrigley Field. Finally, the project should be committed to outcomes that enable the team to be a good neighbor and provide economic and social benefit to the local community.Constructed as Weeghman Park in 1914 for an estimated total cost of $250,000, the stadium provided seating for 18,000 fans and a home for the Chi-Feds and Whales of the National Federal League. The Chicago Cubs were enticed to move from the West Side Grounds in 1915. In the next 100 years, the Wrigley Field would be sliced apart and expanded, double its seating capacity with the addition of double deck grandstands, be enclosed by bleachers (and an ivy covered wall), and, in 1988, experience its first nighttime baseball game with the addition of lighting.The 1060 Project has a total budget of $750M, with an expected construction value of $350M. It is projected to add over 2,100 jobs to the economy and be completed before the 2020 baseball season. The work will be completed in phases during consecutive off-seasons, each with a maximum 23-week duration extending through the Chicago winter. Ownership mandated that on-going construction cause no disruption to the Major League Baseball season, have no impact on hosting concerts and other special events, and it should not adversely affect seating capacity, or diminish the fan experience."

Jan 1, 1900

By Franklin M. Grynkewicz

The subject of bearing pile performance installed by vibratory hammers has been a matter of increasing study and continued controversy. A recent case study from a major bridge replacement project is discussed which provides encouraging data on the use of vibratory pile hammers as a primary means of pile installation and also presents the problems associated with its general acceptance. The bridge project case study foundations consisted of HP 14 x 89 pile sections, designed to develop capacity primarily in friction. Preliminary tip elevations were determined by traditional static analyses. Production pile installation was performed using an IHC S-70 Hydro-Hammer. Driving criteria and final production pile tip elevations were determined after preliminary indicator pile drive tests and static load test results at bridge pier cofferdam locations. Based on impact driven production pile performance, the Contractor wished to investigate vibratory driven piles as a means to accelerate construction schedule. Dynamic pile testing procedures were used as the primary measurement tool and test results were compared to the production pile drive records and prior static load tests. Field testing consisted of driving and monitoring with the PDA impact driven piles to the design tip elevation. Three vibratory driven piles were installed to the same tip elevation and immediately subjected to impact driving and dynamic testing to compare dynamic pile resistance. The results indicated that the site soil conditions were favorable for vibratory pile hammer installation. Recommendations and procedures for proceeding with vibratory hammer pile installation were presented to the Owner. These procedures included quality control in conformance with latest AASHTO recommendations. The Owner, in spite of the site specific data base and QA/QC procedures, would not accept vibratory pile hammer installation, due to the absence of precedence. It is concluded that for vibratory methods to become accepted a rational method of analysis, design and field QA/QC procedures requires development. In addition, the engineering community and Owners/Agencies must be more open to alternate methods of foundation construction. The continued development of dynamic methods of monitoring vibratory pile installation is considered to be key to the general acceptance of this installation procedure.

Jan 1, 1991

By Diane Reid, Antonio Marinucci, Robin Mao

Super Cells are an innovative, open-shaped bi-directional static load testing device used to promote concrete flow during placement while utilizing greater cross-sectional area of the pile to achieve large applied axial loads at relatively low hydraulic pressures (≤ 250 bar). This paper describes the results of multi-level load testing performed on a sacrificial drilled shaft that was 3.8 m (12.7 ft) in diameter and 110.6 m (363 ft) in length for the Jiaxing-Shaoxing River Crossing Bridge that spans Hangzhou Bay in Shaoxing, China. The test shaft was instrumented with embedded strain gauges and telltale rods along with displacement transducers at the top of the pile to measure the load-induced displacements along the length of the shaft. Load testing was performed twice using a Super Cell placed near the tip of the shaft, prior and subsequent to tip post-grouting, and then again using a Super Cell placed higher in the shaft. The axial resistance for the tested conventional drilled shaft was more than 5 times greater than the estimated axial resistance. In addition, the axial resistance after tip post-grouting (347,100 kN (39,033 ton)) was about 5.3% greater than the ungrouted axial resistance (329,600 kN (37,050 ton)). INTRODUCTION During the past few decades, the magnitude of axial, lateral, and flexural loading has considerably increased due to updated design codes, larger superstructures, and the manner in which extreme event loading (e.g. seismic and scour) is incorporated into design. The diameter and depths to which bored piles or drilled shafts are constructed have increased considerably during the last three decades due to the advancements in equipment technology and capabilities. In addition, monoshaft foundations have become increasingly used, as one large drilled shaft is able to replace a group of smaller diameter piles connected by a cap. Correspondingly, adequate strata, for both side and end resistance, must be discovered/determined as well as achievable to be able to construct the required foundations to support the greater design demands. As design demands have increased, the need to ensure integrity, quality, and performance of a constructed drilled shaft has become ever more crucial. Load tests are essential to validate design assumptions of side and end resistances, to assess the behavior and load transfer characteristics of the constructed drilled shafts, and to evaluate construction methods. Load tests utilizing a bi-directional static load testing (BDSLT) device can achieve considerably large applied axial loads and can be performed more economically, in less time, and in a much safer manner than conventional top-down static load testing methods.

Jan 1, 2019

By Abolfazl Eslami, Sepide Lotfi, Mohammad M. Eslami

"Via direct CPT methods for pile capacity prediction, correlation coefficients smaller than unity are used to relate cone tip resistance (qc) and sleeve friction (fs) to pile toe capacity (rt) and shaft capacity (rs), respectively. For linking CPT data to pile capacity, factors such as diameter, penetration rate, partial embedment of pile toe into a hard layer, mechanism of plunging, failure zone, data processing, and stress-strain conditions must be considered. The aim of this paper is to investigate the role and significance of scale effects and establish direct relation between CPT data and pile shaft capacity. A database has been compiled including 40 full scale pile load tests and CPT sounding records for calibration and validation of the proposed approach. Analytical studies demonstrate that differences between pile and penetrometer penetration rate, geometry, and stress-strain conditions influence the relation between fs and rs. By considering the determinants, a procedure is proposed from which the pile shaft capacity can be predicted. This approach demonstrates better agreement with measured capacity by static loading test and less scatter than other current CPT methods.IntroductionAmong different approaches for pile capacity prediction, in-situ tests such as SPT and CPT have been used as supplementary of static analysis. Due to similarities between CPT and pile, the measured cone tip resistance and sleeve friction can be employed for prediction of unit toe and shaft capacities, respectively.Determination of pile capacity from CPT data includes two main approaches: direct and indirect methods. Direct CPT methods apply the measured values of cone tip resistance (qc) for pile toe capacity (rt), and sleeve friction (fs) for pile shaft capacity (rs) with some modifications regarding scale effects. Indirect CPT methods employ friction angle and undrained shear strength values that have been estimated from CPT data.When using direct CPT methods to relate qc and fs to rt and rs, correlation coefficients smaller than unity are used. Factors such as diameter, penetration rate, mechanism of plunging, failure zone, data processing, and stress-strain conditions must be considered for correlation between CPT and pile capacity. The work presented in this paper aims toward ameliorating the situation in the area of pile shaft capacity prediction, based on cone sleeve friction.Case histories from full-scale tests are compiled and analyzed by means of six methods including five direct CPT methods for shaft capacity prediction and the proposed method."

Jan 1, 2015

By Lance A. Roberts

Expansive soil formations can be found throughout the United States. When subjected to wetting, these formations have the potential to swell and exert large uplift forces on buildings and foundations. Lightly loaded structures, such as single family residences founded in areas of expansive soils, can be significantly damaged due to uplift movement from swelling actions. Designing an economical deep foundation that can resist uplift forces is critical to prevent damage to these structures. The current solutions to control uplift due to swelling soils, such as over-excavation and replacement of the expansive material or the use of drilled shafts can be costly. Piles made from recycled polymer materials could provide a solution. Due to a lower coefficient of friction along the interface of the soil-pile interface compared to traditional pile materials, solid recycled plastic piles can allow expansive soils to move nearly independently from the pile when wetted. This results in a much smaller magnitude of uplift force being transferred to the structure, which minimizes the risk of significant structural damage from excessive movements. This paper presents the results of research conducted on the use of recycled plastic piles in an expansive shale environment. The preliminary phase of the project involved the installation of six recycled plastic piles at a test site on the South Dakota School of Mines and Technology campus. Two of the piles were subjected to a full-scale compression load test in order to determine ultimate capacity. The remaining four piles were subjected to long-term monitoring of uplift movement during the course of the project. A concrete anchor was also installed at the test site for uplift monitoring. Data gathered during the field and laboratory testing was utilized in a non-linear soil-structure interaction model to predict the displacement behavior and internal stresses within a plastic pile and concrete anchor subjected to uplift forces from the swelling shale. While more research is needed to further understand the application for recycled plastic piles, the results from this research indicate that their use is a viable alternative for support of lightly loaded structures in expansive soil environments.

Jan 1, 2010

By Alex Grenoble, Alex Reeb, George Filz, Farzad Abedzadeh

"This paper summarizes available information on the characteristics and properties of deep-mixed soilcement produced by the wet method. The topics covered in this paper include: unit weight, unconfined compressive strength, strength variability for field mixed materials, influence of curing time, influence of consolidation pressure, Young’s modulus, differences in strength and stiffness between small and large samples, creep deformations, Poisson’s ratio, and tensile strength. In addition, this paper discusses the development of design considerations and recommended property values for a project that uses soilcement to protect an existing dam penstock from loads applied by an overlying stability berm. Some of the key recommendations for the deep-mixed soil-cement to be used in this project are that (1) a curved strength envelope that includes tensile strength can be used in the analysis, (2) the stress-strain and strength properties can be characterized using Duncan and Chang's (1970) hyperbolic model, and (3) a specification based on the median unconfined compressive strength value is appropriate.INTRODUCTIONFor many projects, including foundation and embankment support, deep mixing can be designed based on simplified procedures and following standardized guidelines (e.g., FHWA 2013). However for unusually complex or critical projects, it is often necessary to perform numerical analyses, and in order to perform these numerical analyses well, a thorough understanding of the material properties is needed.This paper summarizes information on the characteristics and properties of deep-mixed soil-cement produced by the wet method, and it discusses the development of design considerations and recommended property values for a specific project, herein referred to as the penstock project, that requires numerical analyses. For the penstock project, a horseshoe-shaped enclosure of soil-cement is being considered beside and above an existing dam penstock to protect it from loads applied by an overlying stability berm that will be constructed for seismic remediation. The concept is to use soilcement created by the deep mixing method along the sides of the penstock and to use compacted soilcement above the deep mixing to create the crown of the protective soil-cement zone around the penstock. For this application, the soil-cement stiffness, rather than its strength, is the controlling design parameter. To achieve the necessary soil-cement stiffness, the strength will be high enough that the factor-of-safety values against instability along potential failure surfaces passing through the soil-cement are high. Following conventional practice, the soil-cement acceptance criteria will be based on the unconfined compressive strength, and the specified strength will be selected to produce the desired modulus value."

Jan 1, 2015

By John D. Nelson

Foundation underpinning is a common component of remediation schemes for distressed foundations on expansive soils. For many applications in expansive soil, micropiles have distinct advantages over other techniques. This paper will concentrate on the design and construction of micropiles in expansive soil. It discusses the nature of building distress and the relationship between foundation movement and soil heave. It presents methods for determining the factors that are required for the design of micropiles. Such factors include calculation of expected free-field heave, depth of soil wetting, and prediction of pier movement. A finite element program developed by the authors and others to determine pier heave and internal forces is presented. The input parameters that are required for pier analysis are discussed, and the nature of the output and the sensitivity of the results to the output are described. A case example illustrates the advantages of micropiles over other methods.

Aug 1, 2013

By Nicolas Denies, Jeroen de Leeuw, Bart Lameire, Jan Maertens, André Vervoort, Flip Hoefsloot, Noël Huybrechts, Flor De Cock

"In recent years, the Deep Mixing Method has increasingly been applied for the construction of earth and water retaining structures. From practice, it has been experienced that there is a real need to develop execution and design rules adapted to the function of the soil mix wall (retaining wall, water barrier, foundation solution or a combination) including the temporary or permanent character of the application. Based on the results of the BBRI Soil Mix project (2009-2013), a design approach has been developed in collaboration with the SBRCURnet. The present paper briefly discusses the principles of this design approach which takes into account the function of the soil mix wall and the characteristics of the soil mix material. The interaction between the soil mix material and the steel reinforcement can be considered in the calculations depending on the function of the soil mix wall. Design and quality control requirements are given in function of the application and take the lifetime of the structure into account. Durability aspects of the soil mix material are therefore considered in the present design approach.INTRODUCTIONSince several decades, the deep mixing method is used for ground improvement works. A more recent application is the use of soil mix as structural elements such as in the case of the earth-water retaining soil mix walls. Since 2000, due to the economic and environmental advantages of the method, this particular application has shown an amazing growth in Belgium and in the Netherlands. A typical excavation (16 m depth), realized with CSM (Cutter Soil Mix) panels, is shown in Fig. 1. For temporary applications, the questions related to the mechanical characteristics of the material, its permeability and its adherence with steel have been investigated with success within the framework of the BBRI Soil Mix project (2009- 2013) (see Denies et al. 2012 for more details). The durability of the soil mix material remains a complex topic while permanent applications are more and more observed in practice. In order to define an obvious design approach, it was necessary to clarify the potential functions of soil mix walls and to establish the requirements related to their design and construction. The BBRI (in Belgium) and SBRCURnet (in the Netherlands) have therefore worked together to publish guidelines in the form of a handbook titled ‘Soil Mix Walls’ (publication foreseen in 2015). In this handbook, a methodology is proposed for the design of the soil mix walls for which the interaction between steel and soil mix can possibly be taken into account dependent upon the application. Each potential function of the soil mix wall is described (e.g. earth retaining wall, cut-off wall, etc.) and the temporary or permanent character of the application is always considered."

Jan 1, 2015

By Greg Canivan, Bernie Hertlein, Les Chernauskas, Joram Amir, Garland Likins, E. Anna Sellountou, Tim Kovacs, Peter Kandaris

Nondestructive testing of drilled shaft foundations via Crosshole Sonic Logging (CSL) is often performed as part of the quality assurance process to assess the soundness of concrete. The intent of CSL testing is to identify irregularities such as soil intrusion, necking, soft bottom, segregation, voids and other defects that could result in poor structural performance of the foundation. Over time, CSL rating criteria based on first arrival time and relative energy have incorrectly evolved to often be the sole means of determining the acceptability of a shaft. Some of these criteria have found their way into regulatory agency specifications, with acceptance values often differing from agency to agency.The purpose of this document is to review the state of the practice (including experience gained over the past 20 years), propose improved CSL rating criteria and make recommendations for additional assessment, as well as educate the industry on the proper interpretation of CSL test. CSL test results alone should not be the sole means of rejecting or accepting a shaft. A task force of industry exerts was formed to review the existing CSL rating criteria and propose improvements where appropriate. The recommendations presented herein are the consensus of the task force, which believes that they should be incorporated into future criteria, codes and specifications. This paper was produced as a joint effort between the Codes and Standards Committee, the Drilled Shafts Committee and Testing and Evaluation Committee. A task force was authorized under Testing and Evaluation Committee. The task force contributed their expertise in web-based discussions often every two weeks over a period of three years. Interested participants were invited to participate at any time. The document had two rounds of broad industry review, two rounds of DFI Technical Advisory Committee reviews, and a Public Comments process. All comments were considered in producing the final document.

Jan 1, 2019