Civil & Environmental Engineering

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Browsing Civil & Environmental Engineering by Author "Afsharikia, Zahra"

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    Modulus Based Compaction Quality Assurance for Unbound Materials Using Lightweight Deflectometer
    (2019) Afsharikia, Zahra; Schwartz, Charles W; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Moving away from traditional density-based methods of compaction quality assurance (QA) towards modulus-based procedures using Light Weight Deflectometer (LWD) require developing practical framework to: (1) determine soil- specific LWD target modulus, and (2) evaluate LWD modulus in the field effectively. This dissertation draws upon work from two research studies, TPF-5(285) pooled fund study and pilot projects conducted by Maryland State Highway Administration to refine the two proposed QA specifications for road base, subgrade, and embankment construction. The practical method of establishing the target modulus based on LWD drops on compacted Proctor molds was proposed and evaluated. Three types of LWDs (Zorn ZFG3000, Olson LWD-01, Dynatest 3031) were utilized and their field to target modulus ratio was compared to the percent compaction as a criterion for goodness of compaction. Results confirmed the validity of procedures for the variety of geomaterials tested and suitability for practical implementation by field inspection personnel. Target modulus values, calibrated acceptance criteria, sampling method, and frequency is presented for future implementation in the state of Maryland and other state DOTs. The LWD manufacturers collaborated to facilitate the implementation by instrument design and improvement or software/application development.
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    PARAMETRIC STUDY OF SOIL DRYING IN THE FIELD FOR COMPACTION QUALITY ASSURANCE
    (2017) Afsharikia, Zahra; Schwartz, charles W.; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Moving towards modulus based methods of soil compaction quality assurance using lightweight deflectometers (LWD) requires evaluation of the LWD measured modulus in the field. The resilient modulus of geomaterials is not only influenced by the moisture content (MC) at the time of compaction, but also by the MC at the time of testing, which may be up to few hours after compaction. A parametric study was performed using SoilVision’s SVFlux analysis package to model the variation of soil moisture profile with depth versus time as a function of environmental factors. Then the drying in a compacted soil layer was modeled and compared to the volumetric water content measurements in an instrumented large-scale test pit. Finally, LWD modulus values in the field were captured immediately and a few hours after compaction to exhibit the variation of modulus with time and to identify if the stiffness gain in geomaterial is significant.