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By Travis Coleman, Elvis Ishimwe

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

By Gerald Verbeek, Erick Baziw

"Downhole Seismic Testing (DST) is an important geotechnical testing technique for site characterization as it provides low strain (<10-5) in-situ interval compression (Vp) and shear (Vs) wave velocity estimates. These velocities are determined by obtaining relative arrival times of source waves as they travel through the stratigraphy and are recorded by one or more vertically offset seismic sensors. A challenging aspect of this process is to characterize the seismic data sets to determine the analysis method that will result in the most accurate interval velocity values. This paper introduces an assessment technique which utilizes linearity estimates (i.e., hodograms fitting straight lines) from the polarization analysis in conjunction with crosscorrelation coefficient calculations of the full waveforms as well as the deviation of the source wave frequency spectrum from a desirable bell-shaped curve. The paper will provide an overview of the technique and include some examples of actual data sets where the technique was applied to analyze those data sets.1. INTRODUCTIONIn general terms, Downhole Seismic Testing (DST) such as Seismic Cone Penetration Testing (SCPT) is a geotechnical technique for measuring in-situ shear and compression wave velocities (VS and VP respectively). The main goal in DST is to obtain arrival times as the source wave travels through the soil profile of interest, and from these arrival times the velocities are then calculated. Figure 1 shows a schematic of the typical DST configuration: a seismic source is used to generate a seismic wave train at the ground surface. One or more downhole seismic receivers are used to record the seismic wave train at predefined depth increments. The downhole receiver(s) may be positioned at selected test depths in a borehole or advanced as part of an instrumentation package as in the case of SCPT. When triggered by the seismic source a data recording system records the response of the downhole receiver(s)."

Jan 1, 2017

By Liqun Liang

Various nondestructive testing (NDT) inspection methods are available to evaluate the structural integrity of cast-in-place shafts. The widely used methods include Cross Hole Sonic Logging Testing and Low Strain Testing. Due to its advantages such as low cost, easy operation, quickness and flexibility (no need to plan ahead and prepare inspection tubes or other devices), Low Strain Test is frequently specified in quality assurance programs of many countries or when doubts arise as to the integrity of the finished shafts/piles. The method is well suited for small to middle sized shafts. However it is an indirect NDT testing method and has certain limitations. Data interpretation requires proper training, experience and judgment and, therefore, inconsistent conclusions and reporting may be provided by different testers. To avoid or reduce such inconsistencies, it is best to follow a standardized data interpretation and record classification system. In this paper, a new classification method is presented with examples. A step-by-step data evaluation and interpretation procedure is proposed with examples of real cases to help understand the LST data. The paper also makes recommendations for measures to be taken when anomalies are detected in tested production piles.

Jan 1, 2011

By Thomas Passlick

By means of further developed machines and techniques and with growing experiences in jet grouting, the challenge of this building method becomes more and more complex. To keep the concerning risks as low as possible, the requirements on the quality assurance continuously in­crease. The construction of a 37.0m deep seated slab for the Amsterdam metro station Vijzelgracht in marine clay represents such a complex task. This paper summarises the required measures of quality assurance. In particular a new hydraulic measuring device is introduced with which it was possible to detect the column diameter of 2.6m at a depth of 37.0m during the production process and with a very high accuracy.

Jan 1, 2006

By Bill Starke

The acceptance of AugerCast piles in Canada has been limited. Many engineers are apprehensive about the quality of the piles produced by this method. However, advances in the sensing instruments and computer technology can now provide satisfactory levels of quality assurance. Post construction tests such as the sonic echo method can give an indication of pile shaft integrity. Computerized monitoring of the pile installation process is an immediate and more positive method of quality assurance. The computer continuously measures and records the parameters which indicate the quality of the pile. If these parameters do not indicate a satisfactory pile, it is replaced before the concrete hardens. Computerized monitoring of the installation process is another tool available to the engineer. The data from this system analyzed with soil borings, site inspections, and possibly sonic tests can provide the engineer with enough information for pile certification.

Jan 1, 1997

By Mario A. Terceros Herrera, Mario Terceros Arce, Antonio Marinucci

This paper describes the general principles of the expander body with post-grouting (EBI) system, and how it is similar in nature to a large-scale pressuremeter device. The results from the installation of an EBI can be used to provide information about the stress-strain characteristics of the soil adjacent to the device and to compute estimates of nominal axial resistance. As the EBI expands during grouting, pressure is applied to the in-situ soil surrounding the device thereby compacting/densifying the soil. The nominal axial resistance for small diameter piles/ground anchors can be increased due to the greater soil stiffness and shear strength around the device, larger surface and end area, and improved soil-to-EBI interaction in side resistance. The shape of the response curves depends on the geotechnical conditions of the soil (e.g., in-situ stress state, strength, and stiffness) and the installation method of the piling/ground anchor. This technique has been used successfully with different pile types and ground anchors in a wide range of conditions from very loose sands/silts to very dense sands and medium-dense gravels as well as in soft to stiff clays. This paper also describes a mini case history in which 80 piles were installed to support an office building, and the results of the static axial compression load tests performed on a production FDP+EBI pile is also included.

By David Chadwick, Paul Marsden, Chris Hughes, Mathias Delapille

"Following damage caused by the 2011 Christchurch earthquakes, the NZ$127.5million Christchurch Town Hall Restoration project is due for completion in 2018. The building is undergoing extensive repairs and a strengthening regime to meet New Zealand’s New Building Standard. One major aspect of the project is the stabilisation of the soil directly beneath the building using interconnected jetgrouting columns installed a cellular configuration, the purpose of this being to decrease the likelihood and severity of foundation movements caused by earthquake-induced soil liquefaction and lateral spreading. The soils encountered on the site ranged from cobbles and gravels through to sandy silts with a significant quantity of timber and rootlets. This wide variation of soil types presented a number of challenges with regard to effective and consistent treatment by jet grouting. The paper presents an overview of the quality assurance practices and also the testing regime adopted on this project.INTRODUCTIONMost of the deformation experienced by the Christchurch Town Hall structure over the course of the Canterbury earthquakes was caused by movement of the underlying ground. Two primary mechanisms of ground deformation were observed:- Liquefaction of the soils underlying the building foundation- Lateral spread of surface soils towards the free face at the river edge which runs 20 metres from the building. This mechanism also resulted in additional vertical settlement of the building foundations.The overall foundation design philosophy adopted by the project team for the Christchurch Town Hall Conservation Project has been to improve the ground directly beneath the structure to mitigate against these two mechanisms of ground movement. Additionally, a robust raft slab is proposed to distribute the foundation loading more evenly and increase the ability of the structure to resist lateral stretch of the underlying ground.The ground improvement system proposed by the Client’s geotechnical consultants, Tonkin &Taylor, comprised a cellular arrangement of interlocking jet grout columns, this arrangement would effectively encapsulate the soil within the cells preventing lateral spread.In total 1,097 interlocking jet grout columns, extending over the entire floor plan of the structure, were required to satisfy the design requirements."

Jan 1, 1900

By Timothy L. Roberts

For many years practicing geotechnical and structural engineers in Texas and Louisiana were reluctant to include augered cast-in-place (ACIP) piles as a viable deep foundation alternate. Three primary concerns were the lack of a final driving resistance to confirm adequate capacity, the inability to inspect ACIP piles prior to installation, and the fact that pile integrity is highly dependent on the skill of the ACIP pile contractor&apos;s field personnel. The Deep Foundations Institute (DFI) Committee on Augered Cast-In-Place Piles has responded to these quality control concerns by establishing standards of practice for ACIP pile installation and ACIP pile inspection. Regional areas of the country have different subsurface soil and rock conditions and many times this will influence local installation and inspection requirements. The best way structural and geotechnical engineers can address quality control concerns is to be familiar with the DFI standards of practice, to know the special requirements for a particular project site, and to incorporate them into a well-written ACIP pile specification. The purposes of this paper are to: 1) review the main fundamentals of a successful quality control program, 2) describe how these fundamentals can be applied to the installation of ACIP piles, and 3) add personal experiences from ACIP pile projects in Texas and Louisiana. Nondestructive test methods are frequently used as a quality control tool to evaluate questionable piles. An additional brief discussion of two nondestructive test methods is presented to complete the paper.

Jan 1, 1998

By Francis J. Arland

The installation of augered cast-in-place (ACIP) piles requires careful quality control to assure a successful pile installation. Unlike steel, pre-stressed concrete or other types of driven piles, which are shop fabricated, delivered to the site and typically driven to a minimum tip resistance, augered cast-in-place piles are installed to a pre-determined tip elevation or to a refusal criteria. The structural section of the ACIP pile is constructed during pile installation and cannot be inspected prior to installation. Therefore, a carefully administered quality control program is essential to a pile foundation that will meet or exceed design requirements. This requires an experienced team consisting of the Geotechnical Engineer, Contractor and Inspector. The focus of this paper is to discuss the responsibilities and duties of the ACIP piling Inspector. Qualifications of the Inspector The qualifications of the inspector are related to the complexity and difficulty of the proposed project. Ideally, the Inspector should be an individual with a degree in civil engineering with special emphasis in geotechnical engineering. A properly trained technician with geotechnical engineering experience working under the direct supervision of a geotechnical engineer may be able to provide competent inspection on some projects. It is important that the Inspector have a good understanding of subsurface and ground water conditions and how they will affect pile installation. The Inspector must understand ACIP pile installation procedures and be able to communicate with the Contractor, Structural and Geotechnical Engineers; and maintain a detailed pile record for each installed pile.

Jan 1, 1997

By Rudolph P. Frizzi

Quality control is essential for augered cast-in-place (ACIP) piles (also known as continuous flight auger (CFA) piles outside the United States) and drilled displacement (DD) piles since the pile is constructed below the ground surface out of the direct sight of the personnel constructing and inspecting the pile. ACIP piles are being successfully constructed to support high-rise structures, hospitals, arenas and stadiums, mass transit systems, and power and industrial facilities. The use of DD pile technology is also gaining ground in the United States, typically utilizing proprietary systems such as Omega (currently utilized by Richard Goettle Inc., and LG Barcus and Sons, Inc.), Berkel, and DeWal (currently utilized by Morris-Shea). Different types of ACIP/DD pile installation equipment are shown in Figures 1 and 2. ACIP piles are installed into granular and cohesive soils, and soft rock to lengths currently approaching 130 ft (39.5 m), with diameters up to 24 to 36 inches (610 to 915 mm), and sustaining design loads approaching 900 kips (4000 kN). Current DD pile installation equipment in the United States is capable of installing up to 79-ft-long (24 m) piles with diameters ranging from 12 to 18 inches (305 mm to 460 mm).

Jan 1, 2003

By Rudolph P. Frizzi

Quality control is essential for augered cast-in-place (ACIP) piles (also known as continuous flight auger (CFA) piles outside the United States) and augered displacement (AD) piles since the pile is constructed below the ground surface out of the direct sight of the personnel constructing and inspecting the pile. ACIP piles are being successfully constructed to support high-rise structures, arenas and stadiums, mass transit systems, and power and industrial facilities. The use of AD pile technology is also gaining ground in the United States, typically utilizing proprietary systems such as Omega (currently utilzed by Richard Goettle Inc., and LG Barcus and Sons, Inc.), Berkel, and DeWal (currently utilized by Morris-Shea). Different types of ACIP/AD pile installation equipment are shown in Figures 1 and 2. ACIP piles are installed into granular and cohesive soils, and soft rock to lengths currently approaching 130 ft (39.5 m), with diameters up to 24 to 36 inches (610 to 915 mm), and sustaining design loads approaching 900 kips (4000 kN). Current AD pile installation equipment in the United States is capable of installing up to 79-ft-long (24 m) piles with diameters ranging from 12 to 18 inches (305 mm to 460 mm).

Jan 1, 2002

By Hee-suk Yun, Dae-jin Hwang, Jeong-woo Seok, Myoung-mo Kim

"In this paper, the accuracy of the data measured by a newly developed displacement measuring system, DPRMs (Digital Pile Penetration and Rebound Monitoring system) and its applicability as a quality control tool were verified by field measurements of pile penetration and rebound for pile driving performed at 3 construction sites and 1 test site. The DPRMs data were found to be much better than handwork data. A new dynamic formula for pile capacities is proposed uses the results of a pilot dynamic load test and the final pile penetration. The ratios of pile capacities obtained by the new formula to those by the dynamic load test were 94%±7.4% in the contrast with 123±28.3% by the 5S formula and 68±24.0% by Hiley's formula. This result shows the superiority of the new formula. The ratios of the maximum compressive stresses calculated by using DPRMs to those calculated by using PDA (Pile Driving Analyzer) were about 90-110±10%. This result confirms the applicability of DPRMs as an overdriving monitoring tool. Two sets of DPRMs were used to measure the 3-D displacement behavior of a pile head at the test site. The more the pile head moves laterally, the less the final set values were expected because of the loss of driving energy, but this trend was not obvious within the limited data obtained at the test site.INTRODUCTIONPile construction monitoring consists of two parts. In the first part, enough capacity of the pile is secured to stand the design load. In the other part, pile damage during driving is prevented. Although several methods can be applied to achieve the first part, PDA is nearly the only tool for measuring pile stress.Several methods such as a static load test, a dynamic load test, an Osterberg cell, and numerous driving equations can determine the pile capacity. Among them, the static load test and the dynamic load test are most widely used. The static load test is advantageous because it has the highest reliability. The disadvantages are as follows: it is costly and time-consuming. Also, the capacity of the pile under construction cannot be evaluated. The dynamic load test has lower reliability than the static load test, but it is cheaper than the static load test, is reliable enough to determine the pile capacity, can evaluate the capacity of a pile during construction, and can offer information about construction conditions such as the pile integrity and the pi le stress during driving. The dynamic load test takes a relatively short time and is low cost compared with the static load test. However, it is still costly, time-consuming, and unnecessary to apply to all piles in the field as a construction measurement tool. Therefore, driving resistance (blowcounts) is commonly measured to confirm the pile capacity at construction sites."

Jan 1, 2005

By D. Goossens

Quality control is a system which should guarantee that quality is achieved. It is the execution and verification of a project in an organised way, in order to obtain the maximum of certainty that the results meet the requirements. This concerns all stages of the project, from the soil investigation, over the design, to the execution. Quality control can and has been successfully realised for important projects by means of a quality plan. A quality plan is based on a number of general considerations, but should certainly be focussed on the particularities of a specific project. Practical examples of quality plans, which have been realised on sites in Belgium, are developed and the advantage of the system is shown by concrete case studies.

Jan 1, 1996

By Kevin Kuhl

With the destruction of the US-90 Bridge spanning St. Louis Bay by Hurricane Katrina, the State of Mississippi awarded its first major design-build contract in order to have a completed four-lane bridge in a period of less than two years. The structure consists of 76 pre-cast concrete beam spans with a total bridge length from Bent 1 to Bent 77 of 11,124 ft (2.1 miles). All 77 bents are founded on pre-cast, pre-stressed concrete piles and consist of two foundation types: pile bents and water line footings. A total of 53 pile bents were utilized where the deck is less than 52 ft above the water. Further divided, 10 pile bents, supported by 24 in. square, solid piles, are located on land. The remainder of the pile bents are located within St. Louis Bay and supported by 36 in. square, voided piles. All the waterline footings are supported by 30 in. square, voided piles. In total, 138 -24 in., 437 -30 in., and 463 -36 in. piles support the structure. Production pile design was based upon information gathered from the subsurface investigation, design soil profile and 23 out-of-position test piles. Verification of the design was established by monitoring the first production pile driven at each bent using the Pile Driving Analyzer. Particular challenges included highly variable coastal deposits, loads in excess of 1600 kips per pile and a compressed construction schedule. Initial drive capacity of a portion of the production test piles was less than expected resulting in a minimum 14 day setup. Following the setup period, restrikes were necessary to verify capacity. Project production piles ranging from 50 ft in length to in excess of 160 ft in length were used to achieve the required resistance. This paper includes a brief overview of the foundation design and indicator test pile program. The main objective is to provide a summary of the quality control procedures including establishing the driving criteria for each bent and to present issues that arose during production pile driving and the solutions that followed.

May 11, 2007

By Michael Cianchetti, Nadir Ansari, Matthew Janes

"PROJECT DESCRIPTIONThe R C Harris Filtration Plant underwent an expansion to install an underground sludge treatment capability consisting of a series of underground tanks within stepped excavations 12m (39 ft) and 10m (33 ft) deep into compact, wet sands over stiff clays and clayey silts.Concerns regarding the original structure influenced designers to set the lateral deflection limit for the proximal front footing at 4mm (1/6 in), (0.03% excavation depth). The design-build team indicated at the time of tender that the movement criteria was unattainable using the tender design. Through extensive Fast Lagrangian Analysis on Continua (FLAC) and a novel construction geometry the design-build team crafted an alternative that produced significant savings over the original concept and met deflection concerns.GEOTECHNIQUEThe hillside site drops 14.5m (47.6 ft) over a distance of 53m (174 ft) between the existing Filter Building on the north and the Services Building on the south. The soils adjacent to the Filter Building consist of 6m (20 ft) of sandy fills, to the footing elevation, over compact sands and layered dense sands and silts to a depth of 10m (33 ft) below existing footing. Beneath the silts lies a 10m (33 ft) thick stiff clayey silt, 2m (6.6 ft) of sandy silt till (containing cobbles and boulders) and an artesian gravelly sand at a total depth of 30m (98.5 ft).The tender information was deemed inadequate to accurately determine soil parameters for a finite element analysis. As a result, the design-build team performed pre-tender Cone Penetrometer Testing (CPT), including dynamic analysis. The CPT data indicated stratigraphy consistent with the conventional bore hole exploration (SPT results) however, the CPT data provided consistently superior soil strengths. The CPT data indicated the sands and silts were dense to very dense throughout their full thickness. The clayey silts below the sands were found to have shear strengths in the 100 to 200 kPa (14.5 to 29 psi) range with an Over-Consolidation Ratio (OCR) ratio of 1.5 to 2. The dynamic analysis, while low strain, indicated very competent behavior with Young’s Modulus values in the 200 to 350 MPa (29,000 psi to 51,000 psi) range. The CPT derived shear moduli and OCR values were vital in determining the soil engineering parameters used for the FLAC analyses."

Jan 1, 2007

By Wojciech Szczepiński, Dominik Gächter

In early 2020, the construction phase began for the new complex of buildings for Radium Hospital in Oslo – the leading facility for cancer treatment in Norway. Settlements in the surrounding area, caused by pore pressure changes, allowed for the introduction of an alternative solution for the construction of the excavation pit. The presence of solid bedrock and sensitive clay – the same material that causes major landslides in the Scandinavia – in the excavation pit, lead to a combination of techniques, which were never applied in Norway before. For the stabilization of the clay Dry Deep Soil Mixing was applied to allow safe execution of the geotechnical works. Interlocking Bored Piles with footbolts and Jet Grouting columns, in combination with anchors, provided the retaining structure for the excavation pit. Rock injections were performed to avoid any ground water ingress into the pit. Underpinning of fully operational, adjacent buildings was carried out with jet grouting columns. These works were performed from the basement of the hospital and the ‘ACI – Acoustic Column Inspector’ was used to ensure proper installation of 2 m diameter columns to a maximum depth of 25 m. The buildings were later founded on Steel Core Piles, the most common pile type in Scandinavia.

Oct 1, 2021

By Dominik Gächter, Wojciech Szczepiñski

In early 2020, the construction phase began for the new complex of buildings for Radium Hospital in Oslo – the leading facility for cancer treatment in Norway. Settlements in the surrounding area, caused by pore pressure changes, allowed for the introduction of an alternative solution for the construction of the excavation pit. The presence of solid bedrock and sensitive clay – the same material that causes major landslides in the Scandinavia – in the excavation pit, lead to a combination of techniques, which were never applied in Norway before. For the stabilization of the clay Dry Deep Soil Mixing was applied to allow safe execution of the geotechnical works. Interlocking Bored Piles with footbolts and Jet Grouting columns, in combination with anchors, provided the retaining structure for the excavation pit. Rock injections were performed to avoid any ground water ingress into the pit. Underpinning of fully operational, adjacent buildings was carried out with jet grouting columns. These works were performed from the basement of the hospital and the ‘ACI – Acoustic Column Inspector’ was used to ensure proper installation of 2 m diameter columns to a maximum depth of 25 m. The buildings were later founded on Steel Core Piles, the most common pile type in Scandinavia.

Sep 8, 2021

By Moi Arzamendi, Jose Ramirez, Kenneth Kniss, Sunil Arora, James Gingery

Construction of a new approach embankment for a railroad bridge over a river in Southern California required placing up to 12 ft of fill over soft to medium stiff silts and clays along an approximate 1,500-ft long stretch. The embankment, situated within a narrow railroad right-of-way between an existing live track and existing buildings, would have been susceptible to excessive settlement that could damage existing buildings and numerous underground utilities if regular weight soil fill had been placed over the unimproved ground. To limit total and differential static settlements to tolerable levels, a design was developed using a combination of mechanically stabilized earth wall with lightweight cellular concrete fill and rigid inclusions ground improvement. This paper describes the design of the ground improvement system, construction methods used, and challenges of working next to live railroad traffic. Ground improvement quality control and assurance measures, and verification of performance by settlement monitoring are also addressed. INTRODUCTION AND BACKGROUND The 0.9-mile San Diego River Double Track (SDRDT) project is located on the Los Angeles-San Diego- San Luis Obispo (LOSSAN) Corridor in San Diego, California. The project includes the replacement of the existing 900-ft long single track railroad bridge over the San Diego River with twin double track structures. Construction of the project is phased and closely coordinated with the associated Mid-Coast light rail project (San Diego Trolley Blue Line Extension). The new bridge is a 7-span, twin steel, through girder structure supported by six cast-in-place reinforced concrete pier caps and two abutments. The large diameter cast-in-drilled-hole (CIDH) foundations are up to 9 ft in diameter, with upper portions encased in a 1.5-in.-thick permanent steel casing. The north abutment approach embankment includes a mechanically stabilized earth (MSE) retaining wall up to approximately 10 ft high and 1,520 ft long. This paper focuses on the design and construction of the north approach embankment. The project site is characterized by challenging geotechnical and seismic conditions. The site contains liquefiable soils interbedded with soft cohesive soils, underlain by competent layers of sand/gravel/cobble and other sedimentary formations. Static settlement of the new railroad, crossing utilities and adjacent buildings was a primary design concern for the north approach embankment.

Jan 1, 2018

By Gokhan Inci

Stability problems with dam spillways on existing landslides and appropriate mitigation measures to remedy them are ongoing concerns for geotechnical engineers. The first successful application of drilled piers as stabilizing structures under the spillway was at the Trinity Dam in Sicily, Italy. ?Underpinning? was considered as an alternative to spillway relocation during the Alpaslan 2 embankment dam design in eastern Turkey. Based on the available literature the first application of drilled piers to stabilize a spillway chute in the U.S. was at the Ralston Dam in Colorado. Ralston Dam, which is a 175-foot-high zoned fill dam located 15 miles northwest of downtown Denver, was built in the late 1930s. The concrete spillway for the dam was built on the Pierre Shale Formation in the left abutment. Since reservoir operations began, mass movements have occurred downstream of the chute area. These movements have required periodic spillway maintenance. After the occurrence of recent movements and because of high piezometeric levels, URS was contracted by Denver Water to develop a more permanent solution by the installation and monitoring of additional instrumentation, analysis of slope stabilizing measures, design, repair, and reconstruction of the distressed section of the spillway chute. With state of the art modifications that include: 1) a stabilizing berm with a toe trench that improves the global stability; 2) seepage prevention and control measures that prevent the infiltration of water; and 3) the structural support of the replaced chute section with drilled piers and reinforced concrete the probability of future displacements or other problems have been reduced for the Ralston Dam Spillway.

Jan 1, 2007

By Brian Metcalfe, Kord Wissmann, Gianni Martinez

The Middle East consists of vast deserts that reach temperatures up to 50 degrees Celsius, with some areas characterized by endless sand dunes. When the project team selected the location for a large new transportation project, little did they know that the site would be characterized by soft, nearly normally consolidated silt and clay extending below a thin sand crust. Searching for solutions, the design team elected to reinforce the subsurface with Rammed Aggregate Pier® (RAP) ground improvement elements and desired verification that the novel method would stand the test of prolonged static loads. Because the concrete pavements would serve to spread the load, a “zone load test” was performed, consisting of applying a uniform bearing pressure of 150 kPa over a 7.5m square concrete footing. Unlike individual pier load tests, the zone test allowed the project engineers the opportunity to confirm design parameter values under large-loading area conditions, a situation not often available to most designers. This paper presents the results of the zone load test whose results may be interpreted to better understand design parameter values. This paper is of particular significance because it adds a value contribution to the relatively few numbers of “group load tests” available in the literature for ground improvement applications.

May 1, 2022