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Honeycutt J.N.,GRL Engineers Inc. | Kiser S.E.,AMEC Environment and Infrastructure Inc. | Anderson J.B.,Auburn University
Journal of Geotechnical and Geoenvironmental Engineering | Year: 2014

This study examined the energy transfer ratio (ETR) of Central Mine Equipment (CME) automatic standard penetration test (SPT) hammers utilizing a large database of SPT energy measurements. The database consisted of energy measurements from 17,825 SPT hammer blows obtained from 33 CME automatic hammers over a 5-year period, many of which were tested multiple times. The average ETR for all 17,825 CME automatic hammer blows in the database was 82.9% with a COV of ±7:4%. The database also provided an opportunity to determine the impacts of hammer calibration, test depth, and calibration interval on the measured ETR. The impact on average ETR of eliminating hammer blows due to D4633-10 restrictions was also demonstrated. © 2014 American Society of Civil Engineers.

Rausche F.,GRL Engineers Inc. | Robinson B.,North Carolina State University
Proceedings of the Symposium on the Application of Geophyics to Engineering and Environmental Problems, SAGEEP | Year: 2010

For the past half century, great efforts have been made and progress has been achieved in developing a variety of electronic testing methods for the quality control and quality assurance of deep foundations. These developments took advantage of major advances in ever more accurate and sensitive sensor manufacturing and faster and more powerful computers. The dynamic pile testing methods were the primary beneficiaries of these R & amp;D efforts and its application has been expanded from bearing capacity assessment of driven piles to drilled shafts, micro piles and even penetrometers. In addition to soil resistance, results from construction monitoring now provide information about stresses along the pile, pile integrity and occasionally soil vibrations. Dynamic pile testing methods also include nondestructive techniques involving sonic and ultra sonic signals. Much of the recent developments involved not only ruggedizing hardware and preparation of more user friendly software, but also deriving reliable calculation procedures and presenting results in a way which is easy for the report recipient to understand. Additionally, experiences from construction sites showed that an immediate assessment of the foundation characteristics is imperative. This requirement lead to the need for easily used simulation software and workshops. Today such training events are frequently performed over the internet. This presentation summarizes several recent hardware and software developments and shows a few typical results.

Cote B.,GEI Consultants Inc. | Robinson B.,GRL Engineers Inc. | Gabr M.A.,North Carolina State University | Borden R.H.,North Carolina State University
Journal of Construction Engineering and Management | Year: 2013

An approach for comparatively evaluating the performance cost of undercut subgrade stabilization measures is presented. The performance-cost analysis coupled results from laboratory cyclic load testing with material prices and estimated cost factors for stabilization alternatives. The study utilized data from 22 simulated undercut sections with different stabilization configurations over a soft subgrade with a California bearing ratio of approximately 2.0%. The computed cost factors are normalized with respect to the rut-depth magnitude and subgrade strength. Sections with lime-stabilized subgrade were the most economical with respect to initial and postrut repair cycles. Unreinforced aggregate based course (ABC) sections between 356 and 508 mm (14 and 20 in.) in thickness were economical during initial cycles. Sections with geosynthetic reinforcement showed that once enough rut depth is induced to mobilize the strength of the reinforcement, economical performance was comparable with other stabilization measures excluding lime-stabilized subgrade. When the ABC layer was thicker [between 457 and 508 mm (18 and 20 in.)], differences in the reinforcement type were less significant. Tests with 914 mm (36 in.) select fill overlaid by 76 mm (3 in.) ABC stabilization exhibited a high unit cost but were moderately economical. This study shows the advantage of including performance aspects, such as rut depth and subgrade strength, when considering the overall cost of stabilization. © 2013 American Society of Civil Engineers.

Lamiman E.C.,Froehling and Robertson Inc. | Robinson B.,GRL Engineers Inc.
Geotechnical Special Publication | Year: 2014

This paper presents a case history where 91.4-centimeter (36-inch) diameter open-end pipe piles were installed using both impact and vibratory installation techniques. Thirteen dynamically tested piles were installed along a new sheet pile containment wall located in the Southern Branch of the Elizabeth River, bounded by Chesapeake and Portsmouth, Virginia. The soil conditions encountered generally consisted of interbedded layers of silt, sand, and clay forming the Alluvium and the Norfolk Formations. The piles were advanced into the underlying Yorktown Formation bearing stratum consisting of clayey to silty sand with varying amounts of marine shell fragments. At two test pile locations, impact-driven test piles were extracted and relocated by vibratory hammer and subjected to restrike driving with dynamic analysis to assess bearing capacity. Seven to 14 day restrikes were performed on the 13 hammer-driven test piles. Restrikes at one or more months were performed on one impact-driven pile, and both vibratory installed test piles. Signal matching analyses of restrike-driving events indicate an approximate 50% reduction in overall bearing capacity of the vibrated piles compared with the driven piles. Additionally, long-term restrike driving of vibrated piles did not continue to gain capacity akin to driven piles. © 2014 American Society of Civil Engineers.

Park Y.J.,Tunnel Geotechnical Engineer | Gabr M.A.,North Carolina State University | Robinson B.R.,GRL Engineers Inc. | Borden R.H.,North Carolina State University
Journal of Geotechnical and Geoenvironmental Engineering | Year: 2012

The stability of subgrade soils is a major concern during roadway construction with inappropriately soft layers often undercut and replaced by competent or stabilized materials. Systematic undercut criteria are established using numerical modeling with varying the strength and stiffness parameters of the subgrade and representing the mechanistic behavior as an elastic-perfectly plastic medium. Two modes of domain configurations were considered: the plane strain and axisymmetric conditions. The plane strain mode is assumed to simulate proof roller loading with four parallel tires and mainly provides information about excessive pumping response as materials at deeper layers are affected. The axisymmetric mode provides information related to excessive rutting and is used to simulate the effect of single or dual tires representing construction traffic, rather than a series of closely spaced axle loads. Undercut criteria are proposed for meeting a deformation limit state of 25 mm for both pumping and rutting, with the additional requirement of a performance capacity ratio (PCR) of 1.5. The proposed criteria are applied to data from four field cases in which decisions were made regarding the need for undercutting, and the applicability of the criteria is discussed. © 2012 American Society of Civil Engineers.

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