Characterization of Permanent Deformation Behavior of Silty Sand Subgrade Soil Under Repeated Load Triaxial Tests

The design and the analysis of flexible pavement systems depend on soil layer characterization, traffic loads, and number of passes. The current AASHTO design method for flexible pavements uses resilient characteristics of subsoils to characterize and determine the structural support of each layer and to design the thickness of the layers. This moduli property, however, does not fully account for the plastic strain or rutting potentials of subsoils, as in the cases in which silt and mixed soils undergo high plastic deformations but possess high resilient properties. A study was initiated to establish a test procedure to use a repeated load triaxial device to measure plastic strain potentials of subgrade soils. Laboratory-compacted soil specimens were subjected to a repeated deviatoric load, determined as a percentage of static deviatoric load at failure under un-consolidated undrained conditions. The plastic strains were monitored during 10,000 repeated load cycles, and the accumulated plastic deformations were determined. The test procedure and test results conducted on two types of soils, a coarse sand and silty sand, are presented. Effects of soil type, compaction moisture content, dry unit weight, confining pressure, and deviatoric stresses on the plastic strains were addressed.

Download Full-text

Resilient Modulus and Permanent Deformation of 40-mm Open-Graded Aggregates based on Repeated-Load Triaxial Tests

Korean Society of Hazard Mitigation ◽

10.9798/kosham.2019.19.7.367 ◽

2019 ◽

Vol 19 (7) ◽

pp. 367-374

Author(s):

Yongjin Choi ◽

Tan Hung Nguyen ◽

Jaehun Ahn

Keyword(s):

Resilient Modulus ◽

Permanent Deformation ◽

Triaxial Tests ◽

Repeated Load ◽

Repeated Load Triaxial

Download Full-text

Field and Laboratory Characterization of Subgrade Resilient Modulus for Pavement Mechanistic-Empirical Pavement Design Guide Application

Transportation Research Record Journal of the Transportation Research Board ◽

10.1177/0361198120926171 ◽

2020 ◽

Vol 2674 (8) ◽

pp. 921-930

Author(s):

Kazi Moinul Islam ◽

Sarah Gassman ◽

Md Mostaqur Rahman

Keyword(s):

South Carolina ◽

Resilient Modulus ◽

Pavement Design ◽

Coarse Grained ◽

Triaxial Tests ◽

Laboratory Characterization ◽

Design Guide ◽

Repeated Load ◽

Repeated Load Triaxial

The resilient modulus (MR) of subgrade material is an important parameter in pavement design using the Mechanistic-Empirical Pavement Design Guide (MEPDG) and has a significant influence on pavement performance. MR can be obtained indirectly from falling weight deflectometer (FWD) data using a back-calculation tool (i.e., AASHTOWare 2017) or from empirical correlations with soil index properties. MR can also be obtained directly using repeated load triaxial tests (AASHTO T 307-99, 2017). In this study, the field test program included FWD tests and soil sampling. These field tests were performed on six asphalt pavement sections in South Carolina, U.S., to estimate the MR of the subgrade soil. This study involved extensive laboratory characterization of subgrade soils collected from underneath the pavement sections. Laboratory characterization included index tests (sieve analysis, Atterberg limits, specific gravity, moisture content, and standard Proctor density tests) on bulk samples and repeated load triaxial tests on thin-walled tube samples to obtain a direct measure of MR. Results show that the MR values found from the FWD data have similar trends to the laboratory-measured MR values. However, results from lab testing were 33%–75% lower than the back-calculated MR. Laboratory-measured MR, and back-calculated MR were used to determine a C-factor of 0.33, 0.25, and 0.29 for coarse-grained, fine-grained, and all types of soils, respectively. This parameter can be used to estimate resilient modulus for MEPDG Level 2 design inputs across South Carolina and similar geologic regions. The research studies will be facilitated by the local calibration and implementation of the MEPDG.

Download Full-text

Repeated Load Triaxial Testing of Recycled Excavation Materials Blended with Recycled Phyllite Materials

Materials ◽

10.3390/ma15020621 ◽

2022 ◽

Vol 15 (2) ◽

pp. 621

Author(s):

Solomon Adomako ◽

Christian John Engelsen ◽

Rein Terje Thorstensen ◽

Diego Maria Barbieri

Keyword(s):

Mechanical Performance ◽

Resilient Modulus ◽

Permanent Deformation ◽

Economic Benefits ◽

Base Layer ◽

Triaxial Tests ◽

Similar Response ◽

Weak Rocks ◽

Repeated Load ◽

Repeated Load Triaxial

Recycled Excavation Materials (REM) are becoming viable alternative construction resources due to their economic benefits. However, REM may be composed of weak rocks, e.g., phyllites, limiting the use in a base layer. The present paper attempts to further the knowledge of the mechanical performance of REM by performing Repeated Load Triaxial Tests (RLTT). REM are mixed with Recycled Phyllite Materials (RPM) in systematic blends of 0%, 25%, 50%, and 100%. The batches’ resilient modulus (MR) and permanent deformation (PD) characteristics were assessed to establish the maximum RPM allowed into REM while maintaining the required performance. Hicks and Monismith’s and Uzan’s models were used to characterize the stiffness behavior. A wide variation in the stiffness between the two materials was observed. Batches comprised of 0% RPM–100% REM and 25% RPM–75% REM showed high stiffness performance. The Coulomb model assessed the PD behavior, and the results showed a similar response for all batches. Unlike the stiffness, blended mixtures did not show sensitivity to increased RPM content in the PD. This study may help end-users to understand the performance of REM given the documented threshold on the allowable quantity of RPM in REM.

Download Full-text