2013 Session: 259

• Modeling and Prediction of Effects of Moisture on Unconfined Compressive and Tensile Strength of Soils
  Abstract: Unconfined compressive strength (UCS) and tensile strength are two important geomaterial parameters that are used for performance prediction and design criteria. Both UCS and tensile strength are affected by moisture content and thus the characterization of their dependence on moisture content is of paramount importance. The unified effective stress theory proposed by Lu and Likos based on the suction stress enables the characterization of soils under both saturated and unsaturated conditions with one closed-form equation. This theory was verified by triaxial and shear test results for relatively high moisture contents and, therefore, low suction levels (typically more than -700 kPa). Using two types of soils, the current study presented in this paper provides experimental verification of this effective stress theory via indirect tensile (IDT) and UCS tests, both of which are widely used in pavement engineering. The verification is extended in this study to low moisture contents ranging from 2.56% to 18.9% and high matric suction levels ranging from 600 kPa to 16,000 kPa, which are the typical ranges for the base, sub-base, and subgrade layers in pavements. A new method is proposed to predict a soil¡¯s UCS and tensile strength at specified moisture contents by taking simple soil water characteristic curve (SWCC) measurements and conducting UCS and IDT tests at two unsaturated moisture contents, which is experimentally validated in this paper. On the other side, the IDT strength and UCS at a few different moisture contents can be used to obtain the parameters ¦Á and n of SWCCs to avoid time-consuming SWCC measurements.
  Authors: Li, Xiaojun; Wen, Haifang; Muhunthan, Balasingam; Wang, Jingan
  Authors: Li, Xiaojun; Wen, Haifang; Muhunthan, Balasingam; Wang, Jingan
  Year: 2013
  Document Type: Paper
  Subject: Geotechnology
  Session: 259
  Paper Number: 13-4111
• Discrete Element Modeling of Effect of Moisture in Lightweight Deflectometer Test Using Liquid Bridges
  Abstract: Moisture content influences the mechanical response of granular materials used in the subbase of a pavement system, but there is a limited understanding of the manner in which the moisture content affects the mechanical response. In this paper, the effect of moisture content on the mechanical response of a coarsely graded granular material is investigated computationally using the Discrete Element Method (DEM) with an established nonlinear contact model and an additional term to account for moisture. Specifically, the presence of moisture in unsaturated granular material is modeled using liquid bridges dispersed throughout the granular material, and the mechanical response is considered in the context of a model Lightweight Deflectometer (LWD) test. When the volumetric moisture content is increased systematically, there is a decrease in the elastic modulus computed from the simulations. These results are similar, though somewhat less dramatic than the decrease in elastic modulus with increasing moisture content measured from the experiments. The difference may be due to the lack of explicit representation of fine particles in the simulations. As discussed in this paper, some aspects of the fines may be qualitatively represented in the model by varying the surface tension of the modelled liquid, but this fails to quantitatively capture many details associated with the affect of fines on the mechanical response of moist granular materials. Suggestions for improvements to the model will be discussed.
  Authors: Tan, Danielle; Khazanovich, Lev; Siekmeier, John A.; Hill, Kimberly
  Authors: Tan, Danielle; Khazanovich, Lev; Siekmeier, John A.; Hill, Kimberly
  Year: 2013
  Document Type: Paper
  Subject: Geotechnology
  Session: 259
  Paper Number: 13-4664
• Resilient Modulus-Moisture Relationships for Unsaturated Subgrade Soils
  Abstract: In recent years there has been an increased interest in determining the influence of moisture changes on the resilient modulus (MR) of subgrade soils beneath a pavement. Also efforts have been made to develop mathematical models that predict the change in MR values with moisture. These models are expected to account for seasonal variations in subgrade moisture content. The present study evaluates the variation of resilient modulus with post-compaction moisture content of soils in Oklahoma. A series of specimens were compacted at optimum moisture content and then tested for resilient modulus; other series of specimens were prepared at optimum moisture content and then either wetted to higher moisture contents or dried to lower moisture contents prior to MR testing. Results showed that MR-moisture content relationships varied with soil types. MR decreased as moisture content increased and increased with a decrease in moisture content. Finally, an MR-moisture model is proposed that predicts the variation of resilient modulus with moisture contents. This model would be helpful in predicting the changes in bearing capacity of pavements due to seasonal variations of moisture content.
  Authors: Khoury, Naji; Brooks, Robert; Khoury, Charbel
  Authors: Khoury, Naji; Brooks, Robert; Khoury, Charbel
  Year: 2013
  Document Type: Paper
  Subject: Geotechnology
  Session: 259
  Paper Number: 13-4830
• Modeling and Prediction of Effects of Moisture on Unconfined Compressive and Tensile Strength of Soils
  Authors: Li, Xiaojun
  Authors: Li, Xiaojun
  Year: 2013
  Document Type: Presentation
  Subject: Geotechnology
  Session: 259
  Paper Number: 13-4111
• Discrete Element Modeling of Effect of Moisture in Lightweight Deflectometer Test Using Liquid Bridges
  Authors: Siekmeier, John
  Authors: Siekmeier, John
  Year: 2013
  Document Type: Presentation
  Subject: Geotechnology
  Session: 259
  Paper Number: 13-4664
• Resilient Modulus-Moisture Relationships for Unsaturated Subgrade Soils
  Authors: Khoury, Naji
  Authors: Khoury, Naji
  Year: 2013
  Document Type: Presentation
  Subject: Geotechnology
  Session: 259
  Paper Number: 13-4830