2013 Session: 205

• Characterization of Moisture-Dependent Changes in Stiffness of Unbound Aggregate Base Materials in Florida
  Abstract: The Mechanistic-Empirical Pavement Design Guidelines (MEPDG) recommend use of material modulus in lieu of structural number for pavement base layer thickness design. Modulus is nonlinear with respect to effective confinement stress, loading strain, and moisture (suction), and modulus nonlinearity should be considered for an efficient base layer design and analysis. Fixed-free resonant column tests were conducted on two base materials used in the State of Florida to characterize shear modulus (G) nonlinearity in the strain range of 10-5% to 10-1%, including small-level strains, under different loading confinements and moisture contents. The suction effect on nonlinear modulus due to drying was evaluated, and it was found that unsaturated modulus is linear at strains lower than 10-5% and nonlinear thereafter. Compared to dry materials, the presence of moisture in unsaturated material makes it more nonlinear with respect to strain. The suction effect increases G in the strain range of 10-5% to 10-1%, with very significant increases at strain levels below 10-3%. Empirical equations were developed to calculate very small-strain modulus (Gmax) of dry material. A procedure to calculate an approximate G value at known moisture content, confinement, and strain magnitude was developed.
  Authors: Ayithi, Aditya; Hiltunen, Dennis R.
  Authors: Ayithi, Aditya; Hiltunen, Dennis R.
  Year: 2013
  Document Type: Paper
  Subject: Geotechnology; Pavements
  Session: 205
  Paper Number: 13-0829
• Suction Characteristics of Two Expansive Soils
  Abstract: An investigation was conducted to determine the effects of temperature, compaction water content, and compaction effort on soil suction of two expansive soils. For this purpose, two bentonites were statically compacted at target water contents ranging from 5% to 20%. This made it possible to explore a broad spectrum of compaction conditions. Filter paper method and thermocouple psychrometer were used to measure soil suction at temperatures ranging from 10¢XC to 60¢XC. Experimental results show that compaction water content, compaction effort, and temperature have influences on soil suction. As water content increases, the influences of compaction effort and temperature on suction become less significant. Finally multiple regression formulations for predicting the soil suction of as-compacted clayey soil were established.
  Authors: Yang, Shu-Rong; Huang, Wei-Hsing; Chung, Shao-Hung
  Authors: Yang, Shu-Rong; Huang, Wei-Hsing; Chung, Shao-Hung
  Year: 2013
  Document Type: Paper
  Subject: Geotechnology; Pavements
  Session: 205
  Paper Number: 13-2011
• An Investigation in the Influence of Contact Angle on Soil Water Characteristic Curve with a Modified Capillary Rise Method
  Abstract: Contact angle quantifies the physicochemical interactions at the liquid-solid interface and is therefore critical to many physical processes involving the interaction of soil and water. In geotechnical engineering, such interactions are the basis for the formulation of the Soil Water Characteristic Curve (SWCC). However, the role of contact angle in SWCCs has not been adequately recognized. This paper reports a comprehensive study on applying Capillary Rise Method (CRM) to measure the contact angles of soils. Analytical solutions to two forms of the Lucas-Washburn equation were presented to provide the theoretical basis for applying CRM to soils. The disadvantages of conventional CRM analyses were demonstrated with experiments. A modified CRM was proposed based on an analytical solution to a more complicated form of the Lucas-Washburn equation. This modified CRM exhibited reliable performance on numerous specimens made of a subgrade soil and a silicon dioxide sand. Testing procedures were designed and strictly followed, and innovative apparatuses for the preparation, transport, and accommodation of soil specimens were fabricated to ensure repeatability. For the modified CRM, experiment results for virgin specimens demonstrated good repeatability; while for sieved soils, clear trends were observed in the variations of contact angle with respect to pore size. Contact angles much greater than zero were observed for all of the tested specimens which contradicts the assumption of perfect wettability in previous SWCC studies. In addition, it was demonstrated that neglecting the variations of contact angles with respect to pore radius could result in significant errors in the SWCC construction.
  Authors: Liu, Zhen; Yu, Xiong; Wan, Lin
  Authors: Liu, Zhen; Yu, Xiong; Wan, Lin
  Year: 2013
  Document Type: Paper
  Subject: Geotechnology; Pavements
  Session: 205
  Paper Number: 13-2652
• Integrating National Database of Subgrade Soil-Water Characteristic Curves and Soil Index Properties with Mechanistic-Empirical Pavement Design Guide
  Abstract: The database developed under the NCHRP 9-23A project, entitled "Development of a National Catalog of Subgrade Soil-Water Characteristic Curves (SWCC) Default Inputs to Use in the Mechanistic Empirical Pavement Design Guide (M-EPDG)", included not only measured soil index properties needed in all hierarchical levels of the Enhanced Integrated Climatic Model (EICM) but also soil-water characteristic curve (SWCC) parameters, which are key in the implementation of Level 1 analysis. A set of maps in portable document format (pdf) displaying the location of every soil unit identified within the continental US, Hawaii, Alaska and Puerto Rico; and a simple interface in Excel to aid in the query of data were also developed for the project. Under NCHRP 9-23B project, entitled "Integrating the National Database of Subgrade Soil-Water Characteristic Curves and Soil Index Properties with the M-EPDG", a second research effort was directed to integrate an enhanced version of the GIS-enabled database with the M-EPDG. Specifically, NCHRP 9-23B project aimed at the implementation of an interactive tool that allows the M-EPDG (current DarWin-ME) users to retrieve both appropriate soil unit maps and soil properties relevant to a particular user-specified location by inputting either state milepost information or geographical coordinates. The final product was integrated into a public website that can be accessed by the guide users, agencies, industry and academicians through a simple link. This document presents details of the development of this useful search tool and outlines its main features.
  Authors: Zapata, Claudia E.; Cary, Carlos Ernesto
  Authors: Zapata, Claudia E.; Cary, Carlos Ernesto
  Year: 2013
  Document Type: Paper
  Subject: Geotechnology; Pavements
  Session: 205
  Paper Number: 13-4809
  Practice-Ready: Yes
• Suction Characteristics of Two Expansive Soils
  Authors: Huang, Wei-Hsing
  Authors: Huang, Wei-Hsing
  Year: 2013
  Document Type: Presentation
  Subject: Geotechnology; Pavements
  Session: 205
  Paper Number: 13-2011
• Characterization of Moisture-Dependent Changes in Stiffness of Unbound Aggregate Base Materials in Florida
  Authors: Ayithi, Aditya
  Authors: Ayithi, Aditya
  Year: 2013
  Document Type: Presentation
  Subject: Geotechnology; Pavements
  Session: 205
  Paper Number: 13-0829
• Characterization of Moisture-Dependent Changes in Stiffness of Unbound Aggregate Base Materials in Florida
  Authors: Hiltunen, Dennis
  Authors: Hiltunen, Dennis
  Year: 2013
  Document Type: Presentation
  Subject: Geotechnology; Pavements
  Session: 205
  Paper Number: 13-0829
• An Investigation in the Influence of Contact Angle on Soil Water Characteristic Curve with a Modified Capillary Rise Method
  Authors: Liu, Zhen
  Authors: Liu, Zhen
  Year: 2013
  Document Type: Presentation
  Subject: Geotechnology; Pavements
  Session: 205
  Paper Number: 13-2652
• Integrating National Database of Subgrade Soil-Water Characteristic Curves and Soil Index Properties with Mechanistic-Empirical Pavement Design Guide
  Authors: Zapata, Claudia
  Authors: Zapata, Claudia
  Year: 2013
  Document Type: Presentation
  Subject: Geotechnology; Pavements
  Session: 205
  Paper Number: 13-4809