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By Gregory A. Stephan

A case history of design, prediction, instrumented static load tests on probe piles, installation monitoring, and integrity testing of production piles is presented. Based upon project-specific subsoil conditions, as obtained from several 60 to 80 ft (18.3 to 24.4 m) deep test borings, deep foundation system alternatives included driven concrete and steel pipe piles as well as augered cast-in-place (ACIP) piles. High structural loads, site-specific constraints, and the production time frame mandated by the project owner led to the selection of an ACIP pile foundation system that was designed for a pile capacity of 75 tons (667 kN) in compression and 35 tons (309 kN) in tension. Site-specific concerns were raised about the highly porous nature of fragmented and decomposed sandy limestone as well as the high grout intake during construction that could result in increased foundation cost as well as interconnecting of the piles in the rock layer. Consequentially, a multi-phase ACIP pile evaluation program consisting of instrumented compression pile load tests, in conjunction with single-hole ultrasonic pile testing, pile echo testing (sonic testing), as well as full-time production pile monitoring by an experienced geotechnician was specified. As a result of this testing and evaluation program, while grout usage was determined to be within an acceptable range, the instrumented compression load tests yielded data that allowed use of 55 ft (16.8 m) long ACIP piles in lieu of the original plans to use 70 ft (21.3 m) long precast concrete piles. This information was effectively utilized as part of the overall quality control program to install a total of 268, 14 in. (356 mm) diameter ACIP piles within the building footprint to depths of 55 ft (16.8 m) below the pile cut-off elevation as part of the foundation support system. Information recorded during installation included rate of insertion/extraction of the auger, grout pump strokes and pressure, total grout volume, and grout factors, as well as quality and strength of grout. Additionally, many pre-selected installed piles were tested for integrity with a Pile Integrity Sonic Analyzer (PISA) using both sonic and ultrasonic methods. This engineered, monitored, and tested foundation solution provided an effective and quality intensive basis for completion and approval of the foundation work for the building that resulted in cost savings over other foundation alternatives for the owner.

Jan 1, 1999

By Arvindh Gupta

BC Hydro proposed to improve the stability of the existing Seven Mile Dam with 54 corrosion protected, re-stressable anchors comprising 92/0.6? strands each, in phase 2 of the program. Being globally the largest capacity anchors ever build, coupled with extra ordinary specifications, the project was a challenge for the entire post tensioning industry. The paper discusses the challenges associated with the anchor material supply as per specifications, extensive research and development carried out by Con-Tech Systems ltd. to overcome the challenges and contribute in making the project a success. The substance of this article is published in the Aug/Sep issue of ADSC magazine.

Jan 1, 2004

By George J. Tamaro

In 1967 the Port Authority of New York and New Jersey undertook the construction of the World Trade Center (WTC) diaphragm walls, installation of the lateral support system and the excavation of the site, commonly referred to as the "Bathtub". The work took two years to complete. In 2001 the City of New York undertook the re-excavation of the site after the terrorist attacks. The recovery work will take eight months to complete. This paper describes the initial work on the WTC "bathtub" in the late 1960s and the recent work during the recovery.

Jan 1, 2002

By Jeffrey R. Hill

This paper discusses the use of micropiles for the rehabilitation of the following two structures: the Milwaukee Auditorium Theatre, in Milwaukee, Wisconsin, and the Cupples Ballpark Lofts, in St. Louis, Missouri. The paper focuses on the similarities and differences of the remediation techniques used for each structure. The discussion highlights the method of attaching the micropiles to each respective structure. Generally the paper discusses the micropile installation at each project with supporting photos, figures and data. Load testing at each project is also discussed, including the comparison of load test results for each project. The paper will focus on the load testing program at the Milwaukee Auditorium Theatre where high capacity micropiles were designed and tested as friction piles founded in stiff clays and end bearing micropiles in dolomitic limestone. The results of the test were used to determine if the micropiles on the project would be installed as end bearing or friction bearing elements. Strain gauges were used in addition to conventional deflection vs. load data for the Milwaukee Auditorium Theatre project. Other aspects of the paper will include the differences in design methodology for end bearing micropiles in massive dolomitic limestone vs. design in softer, weathered limestone.

Jan 1, 2008

By Frank Rausche

The more widespread use of Augered Cast-in-Place (ACIP) Piles has generated increased demand for improved quality control measures. These deep foundation elements are often relatively long and slender and their structural quality depends on the experience of the installers, the adequacy of their drilling and pumping equipment, and of course, the properties of the soil. Since the concrete of ACIP piles is pumped under pressure into the borehole, the piles may achieve a very high unit shaft resistance if conditions are favorable and the piles are well constructed. Three types of methods can help assure that the piles are properly executed. During construction, monitoring the volume of concrete pumped and the pressure applied helps avoid structural defects. After installation, and once the concrete has hardened, the Pulse Echo Method allows for a check of the structural integrity of the shaft. Finally, a load test, performed some time after installation, yields a check of both bearing capacity and structural integrity of an individual pile. Because of their expense and associated construction delays, static load tests are normally done for only a few piles. However, at large construction sites, it may be necessary to perform many load tests either as a planned construction control activity or as a means of spot checking or verifying suspect piles. For smaller sites, however, static load testing may be prohibitively expensive. In such situations, dynamic load testing, originally developed for driven piles, has frequently been employed for drilled shafts and ACIP piles. In the latter case special consideration must be given to the ACIP pile slenderness and their often relatively low concrete design strength, which may not tolerate high dynamic loading stresses even though their unit resistance along the shaft is relatively high. Lately, the dynamic load test has become more feasible with the availability of loading systems that are custom tailored to this particular pile type. These systems produce a low velocity, low stress and high energy impact. Recent developments have also made the instrumentation process simpler: force measurements are now made on the ram rather than on the pile for increased reliability and simplicity. This presentation describes the requirements for successful dynamic load testing of auger cast piles and summarizes results from several projects where the new loading system and newly developed instrumentation was employed. A few cases are presented correlating static load test results with dynamic predictions, calculated by CAPWAP®.

Jan 1, 2001

By Timothy C. Siegel, Paul J. Axtell

The Missouri Department of Transportation (MoDOT) recently replaced the Hurricane Deck Bridge that carries Highway 5 traffic across the Osage Arm of the Lake of the Ozarks in Camden County, Missouri. The former bridge was constructed in the 1920's and was supported on pneumatic caissons bearing on dolostone bedrock. The replacement structure is founded on drilled shafts socketed into the bedrock. During the design phase of this bid-build project, a baseline design was developed and Alternative Technical Concepts (ATC's) were allowed from approved contractors. Those ATC's were confidential and not shared between teams. Either the baseline design or the approved ATC design could be bid by the respective contractors. The baseline design included re-use of the 90-year old caisson foundations. Accordingly, an extensive evaluation of the caissons and underlying bedrock were conducted by coring, laboratory testing, acoustic tele-viewer (ATV), and cross-hole sonic logging (CSL) methods. The results of the investigation indicated the caissons were in excellent condition and suitable for re-use. However, a more cost-effective ATC was submitted, awarded, and constructed that did not re-use the existing caisson foundations but rather reduced the span lengths, increased the number of piers in the water, and supported those piers on drilled shafts. Interestingly, the difference in low bid price between the awarded ATC and the baseline design was less than one percent of the construction cost. This paper describes the multiple foundation designs that were necessary for this interesting project. The various foundation evaluations include the existing pneumatic caissons, large-diameter open-ended pipe piles to support the baseline design, and the design of rock-socketed drilled shafts that were successfully constructed in 2012.

Jan 1, 2017

By Trent Dreese

For critical velocities in gravel units we use Bush-Luckner, Sichardt, other empirical equations, and equations derived from laboratory experiments too. On the base of these, we compiled critical velocity - permeability coefficient dependencies. Under the lower border of these dependencies sand particles can't be moved, and thus they are stable. For critical velocities in the fissures of flysh and volcanic rocks we use Ronzhin (1974) criteria derived from laboratory experiments in Russia. Maximal filtration velocities measured by tracer methods in gravel soils and in fissured rocks have smaller values then the critical ones.

Feb 10, 2003

By Andrew Baxter

The Crystal Bridges Museum of American Art in Bentonville, Arkansas is a beautiful glass and concrete structure cut into a valley that mingles with water ponds spanned by multiple bridges with suspended roofs. Or, at least it will be when completed in 2009. At Crystal Bridges, most of the proposed buildings involve cuts up to 50 ft high to be retained by the building structures. This requires the construction of retaining walls adequately founded to support lateral loads of up to 70 kip/ft. To add to this difficulty, the site is within a karst region with all the variability and irregularities associated with solutioning and erosion of the parent rock in this environment. The irregular rock profile made it virtually impossible to conceive a predictable arrangement of shallow footings and shear keys for the retaining walls. The existence of layers of soft soils within a hard rock formation made a caisson foundation impractical. The authors developed an innovative solution based on micropiles, which proved to be invaluable from a cost and schedule point of view. In areas where rock was shallow, micropiles were used as ?shear pins? to transfer the horizontal loads to the rock. In areas with significant overburden, a system of vertical and battered micropiles was devised to carry vertical and horizontal loads from the retaining walls. This paper presents a detailed description of the design and installation of the micropiles used as shear pins, and includes the results of lateral load tests performed on full-scale models of the grade beams on shear pins. The work performed shows that micropiles in rock can be effectively utilized for support of significant lateral loads provided that an adequate arrangement of suitably sized micropiles is provided, and that micropiles used as shear pins may develop significant tensile stresses when loaded laterally.

Jan 1, 2008

By James D. Hussin

The Florida limestone is a relatively soft rock which presents many challenges to engineers when designing deep foundations. One alternative is micropiles which have grown significantly from their early days as very small diameter, light capacity elements. Also known as minipiles, pin piles, needle piles or root piles, micropiles offer an attractive deep foundation alternative for sites with tight access, low headroom, and where difficult subsurface conditions or obstructions necessitate a small diameter, high capacity deep foundation. The ability to confirm the competence of the limestone bearing formation by drilling in a rock socket has made micropiles a growing deep foundation selection in Florida.

Jan 1, 2003

By Larry D. Olson

Research, hardware development, and field testing have been conducted on systems to allow easy and accurate determination of both foundation tip depth as well as the properties of the soils at and above the foundation tip. The nondestructive testing method used for tip depth determination is the Parallel Seismic (PS) method, while the soil properties are determined by a Cone Penetrometer Test (CPT). The research and development effort reported herein uses a novel combination of the two methods to allow a single piece of portable field equipment to perform both tests. A system has been developed and tested that includes a triaxial geophone and a hydrophone in the cone probe tip to allow collection of the PS data by a CPT rig without requiring a drill rig with hollow stem augers. Using the instrumented tip along with a standard instrumented CPT cone allows for the simultaneous determination of both the depth of unknown foundations and the measurement of soil properties along the length of the unknown foundation. The combined system allows for a more complete and accurate analysis of foundation capacity and scour susceptibility.

Jan 1, 2007

By Rohrbach

Crosshole Sonic Logging (CSL) testing is commonly used to verify the integrity, quality and ultimately the acceptability of the concrete in structural elements such as drilled shaft foundations, secant pile cutoff walls, and secant/tangent pile earth retention structures. Besides concrete quality, many factors can impact CSL test results (e.g. laitance, air temperature, access tube spacing, access tube debonding, etc.). Effective use of CSL testing requires fully informed qualified practitioners capable of distinguishing between abnormal readings unrelated to deficiencies in the drilled shaft concrete and similar readings indicating the presence or possible presence of drilled shaft defects. Based on data and experience gathered from CSL testing of thousands of drilled shafts across North America, this paper discusses such factors and other information useful when evaluating CSL test results, and provides practical recommendations intended to reduce the potential for incorrect test data interpretation. The CSL testing industry is lacking in a clear, universally accepted guideline for the interpretation of CSL data and acceptance criteria of these concrete elements. This paper proposes terminology and a streamlined process for use when atypical results are obtained. The proposed terminology and method are intended to simplify and expedite the submittal review and approval process. Because construction activities for these elements are often on the project?s critical path, the benefits obtained in terms of project savings and reducing costly delays are undoubtedly valuable.

By Mark A. Rohrbach, Timothy R. Kovacs, PhD Saidin

"Crosshole Sonic Logging (CSL) testing is commonly used to verify the integrity, quality and ultimately the acceptability of the concrete in structural elements such as drilled shaft foundations, secant pile cutoff walls, and secant/tangent pile earth retention structures. Besides concrete quality, many factors can impact CSL test results (e.g. laitance, air temperature, access tube spacing, access tube debonding, etc.). Effective use of CSL testing requires fully informed qualified practitioners capable of distinguishing between abnormal readings unrelated to deficiencies in the drilled shaft concrete and similar readings indicating the presence or possible presence of drilled shaft defects. Based on data and experience gathered from CSL testing of thousands of drilled shafts across North America, this paper discusses such factors and other information useful when evaluating CSL test results, and provides practical recommendations intended to reduce the potential for incorrect test data interpretation. The CSL testing industry is lacking in a clear, universally accepted guideline for the interpretation of CSL data and acceptance criteria of these concrete elements. This paper proposes terminology and a streamlined process for use when atypical results are obtained. The proposed terminology and method are intended to simplify and expedite the submittal review and approval process. Because construction activities for these elements are often on the project’s critical path, the benefits obtained in terms of project savings and reducing costly delays areundoubtedly valuable.1. INTRODUCTIONCSL testing is used extensively throughout the world on many projects to verify the quality of concrete used for drilled shaft foundations, secant pile walls, diaphragm walls, etc. In this paper, these structural elements will be referred to as “drilled shafts,” as they are the most common subject of this test method. In the United States, CSL testing is frequently specified by state and regional transportation agencies, ports, design builders, and others. Although other methods are currently available such as Gamma-Gamma Logging and low-strain Impulse-Echo or Sonic-Echo testing, and new methods are under development such as the Thermal Integrity testing, CSL testing is likely to remain one of the most useful tools for evaluating the acceptability of constructed drilled shafts for quite some time. The popularity of CSL as a testing method can be attributed to two main factors: 1) there is no depth limitation to the method and 2) the apparent ease of interpreting the results. A third advantage of CSL testing is that, when correctly interpreted and with adequate test coverage, it is unlikely to misrepresent a defective profile resulting in acceptance of a defective or inadequate drilled shaft. In other words, CSL testing is very likely to underestimate concrete quality/drilled shaft acceptability within its area of coverage."

Jan 1, 2017

By Ali Bouafia

Five full-scale horizontal loading tests of piles carried out by the LCPC in France are interpreted in order to analyse P-Y load-transfer curves. The experimental piles are either bored or jacked into quite homogenous sandy soils and instrumented by strain gauges for measuring bending moments along the pile. Successive differentiation and integration of bending moment profiles have led to derive respectively lateral soil reaction and displacements then to construct the load-transfer P-Y curves. The initial horizontal lateral reaction modulus was derived from these curves and shows linear variation with depth in accordance with Gibson soils profiles. P-Y curves are validated by back-computation of the pile on the basis de these curves and the horizontal reaction modulus was compared to the recommendations frequently used in pile design practice.

Jan 1, 2002

By Matthew D. Marks

The Sacramento Area Flood Control Agency initiated the Natomas Levee Improvement Program in 2006 which would bring the entire 42 mile Natomas Basin perimeter levee system into compliance with applicable Federal and State standards for levee protecting urban areas. The soil-bentonite slurry cutoff has been utilized as the primary construction method for addressing the under seepage deficiencies. To date, a combined total of over 4,500,000 square feet of slurry cutoff wall have been constructed utilizing excavation methods to a maximum depth of 75 feet and deep soil mixing methods to a depth of 90 feet. The construction of these cutoff walls has required the use of newly designed and custom built long boom and stick attachments for large hydraulic excavators and additional resource will be required to complete future phases. Key components of the NLIP program have included advancements in the development of soil-bentonite backfill mix designs, specified ranges on the soil backfill gradation to address concerns of long term consolidation of the backfill material, evaluation of the trench slurry filtrate loss with regard to cutoff wall acceptance, maintenance high slurry densities to provide greater trench stability, and continued development of backfill mixing procedures.

By Matthew D. Marks

"The Sacramento Area Flood Control Agency initiated the Natomas Levee Improvement Program in 2006 which would bring the entire 42 mile Natomas Basin perimeter levee system into compliance with applicable Federal and State standards for levee protecting urban areas. The soil-bentonite slurry cutoff has been utilized as the primary construction method for addressing the under seepage deficiencies. To date, a combined total of over 4,500,000 square feet of slurry cutoff wall have been constructed utilizing excavation methods to a maximum depth of 75 feet and deep soil mixing methods to a depth of 90 feet. The construction of these cutoff walls has required the use of newly designed and custom built long boom and stick attachments for large hydraulic excavators and additional resource will be required to complete future phases. Key components of the NLIP program have included advancements in the development of soil-bentonite backfill mix designs, specified ranges on the soil backfill gradation to address concerns of long term consolidation of the backfill material, evaluation of the trench slurry filtrate loss with regard to cutoff wall acceptance, maintenance high slurry densities to provide greater trench stability, and continued development of backfill mixing procedures.IntroductionThe Natomas Levee Improvement Program (NLIP) was initiated by the Sacramento Flood Control Agency (SAFCA) in 2006. The long term objective of the NLIP is to provide 200-year level flood protection to the basin. To date, approximately 21 of the 42 mile Natomas Basin perimeter levee system has been completed, totaling over $100,000,000 in construction contracts, of which slurry cutoff walls make up approximately $25,000,000. Other construction elements include excavation and removal of unsuitable levee materials, raising or widening existing levees, construction of landside seepage berms, drainage canals, and miscellaneous structures.Although each construction phase of the NLIP includes various construction elements of levee restoration program, the slurry cutoff wall is the primary construction element for addressing the under seepage deficiencies. To date, approximately 4,500,000 square feet of slurry cutoff walls have been installed using excavation and deep soil mixing (DSM) methods. This includes approximately 2,000,000 square feet of slurry cutoff wall along 5 miles of the NCC South Levee and 2,500,000 square feet of slurry cutoff wall along 16 miles of the Sacramento River East Levee (SREL). The work has been completed under 8 separate contracts, through SAFCA, and performed between September 2007 and December 2012. A summary of the contract phases and associated cutoff wall square footage is provided in Table 1. Most of the work has been performed within the seasonal dry weather period in the Sacramento valley, which occurs between April and October. This has required much of the work to be performed on an aggressive construction schedule, year after year."

Jan 1, 2017

By Frank Haehnig, Harald Krenn, Harm-Christoph Claassen

"The Wadi Dayqah Dam Water Supply Scheme represents one of the most important projects implemented by the Sultanate of Oman to ensure sustainability of water resources. The principal components of the project comprise two dams to impound the Wadi Dayqah, to store and supply drinking water to the local area and to Muscat, the capital city of the Sultanate.The Main Dam with a central spillway is a RCC Gravity Dam with a maximum height above foundations of 75m, crest length 400m; the Saddle Dam is a rockfill dam with central clay core, max height above foundations is 49m and crest length 360m. During construction of the Saddle Dam a key trench was excavated to 10m depth and filled with compacted clay connected to the central core of the embankment. Grouting utilizing cement grout was performed as a single line grout curtain prior to each filling operations. Both Dams are founded on soft Siltstone, Claystone, Sandstone and inter-bedded harder limestone.After construction of the Saddle Dam, once water was in the reservoir it became evident in early 2010 that some seepage was occurring apparently from the right abutment. This seepage became more marked when the reservoir first filled to discharge over the spillway in June 2010. In order to reduce the seepage, additional sealing works by drilling and grouting of a three row curtain up to 80 meter target depth were initiated to supplement the existing single row curtain. Part of this project for the sealing works has also been to drill additional investigation holes to provide more information and confirm extend of the additional sealing works and its limits.Züblin Ground Engineering was awarded the Additional Sealing Works Contract. Whilst Equipment was on Site, the opportunity was taken to carry out drilling and grouting on the Left Abutment of the Main Dam to reduce seepage through that abutment and to install additional standpipe piezometer for future monitoring of seepage patterns.Work on this Contract started on site in January 2013 and was substantially completed in January 2015.At the time of Tender Züblin Ground Engineering propose and Alternative Design in the form of a Secant PileCut-Off Wall, 85m long to a depth of 40m with additional drilling and grouting below the foot of the cut-off which was then included in the contractual scope."

Jan 1, 2016

By Gopal Ranjan

An insitu prtotype study on precast driven spliced piles in soft marine clay deposit has been carried out to study negative drag. The drag is generated by loading the ambient clay. For reduction in negative skin friction, in addition to use of bitumen layer on piles, the ambient clay is transformed into composite mass of low compressibility by utlizing different ground imporvment techniques e.g. plain granular piles, mini grouted piles and self setting soil slurry piles. Adoption of these techniques resulted in significant reduction in settlement of ambient ground and consequently the negative drag on piles. On the basis of the study it has been established that these techniques improve ground condition resulting in lowering of down drag/negative friction.

Jan 1, 1996

By Emad Farouz

This paper presents a case history of a successful construction-phase pile load test program that optimized the pile design in challenging ground conditions at the Great Neck Wastewater Treatment Plant in the Town of North Hempstead in Nassau County, New York. The improvements and expansion of the wastewater treatment plant included the construction of several new structures to comply with new stringent nitrogen discharge requirements and new design flow. The challenging ground conditions included up to 20-ft thick organic deposits with weight of hammer blow counts and up to 14 percent organic content and tidal ground water that was near the ground surface. The foundation design evaluated various deep foundation alternatives and selected driven closed-ended pipe piles then filled with concrete as the most suitable foundation. The selection process included considerations of cost, risk, vibrations, noise, and schedule. The contract documents utilized an innovative approach of performing an optimization load test program that was implemented during construction to optimize pile lengths and reduce potential vibration and construction schedule. This paper discusses the details of the successful load test program including static testing, dynamic testing, and the innovative contracting approach utilized to implement the construction phase load test program. It also discusses the successful development and implementation of driving criteria for production piles and construction challenges. The successful load test program resulted in savings of several hundred thousand dollars, optimized schedule, and lower environmental impacts.

By B. Francis

Literature provides only limited information regarding the behaviour of laterally loaded piles socketed into weak rock masses. A laboratory program, comprising a number of tests of scaled models of the pile/rock mass system has been conducted. A synthetic rock, known as Johnstone was used to simulate a naturally weathered and fractured siltstone. The load-deflection behaviour of the test piles was measured, and strain gauges were fixed to the model piles to assess the bending moments. The laboratory results are compared with the results from several theoretical models, some of which are in the form of commercial software packages. This study highlights the inadequacy of existing methods to adequately model the influence of rock joint orientation in geotechnical design. Additionally, numerical modelling of the pile/rock mass system was carried out using the discrete element program UDEC. The importance in modelling the system using discontinuum mechanics is highlighted, particularly to capture the anisotropy of the rock mass.

Jan 1, 2004

By Michael W. Neill, O&apos

The performance of foundations that combine the high bearing capacity of rafts (mats) with the settlement reduction capability of piles is described through a summary of 24 case histories. Structures included are high-rise commercial office buildings, governmental buildings, industrial facilities and residential buildings, and subsurface conditions range from soft clay to stiff soil overlying rock. Pile types are bored, augered and driven. Since piled rafts are not commonly used in the United States, most of the case histories are from overseas. In all cases the performance of the foundations was monitored during and after construction. Particular emphasis is placed on measured settlements of the piled-raft foundations, distribution of resistance between piles and raft, and general analysis methods that were used by the designers for various geotechnical circumstances. Finally, patterns of behavior are summarized. In most cases, the piles were not designed to mobilize their full capacities under sustained loading of the foundation; therefore, under long-term loading conditions, the piles typically carried more load than the raft. This paper is the result of a study conducted by ITC-18 (Deep Foundations, Willem Van Impe, Chair) of the International Society for Soil Mechanics and Geotechnical Engineering by a subcommittee chaired by the author.

Jan 1, 2003