Predicting Resilient Modulus of Unsaturated Subgrade Soils Considering Effects of Water Content, Temperature, and Hydraulic Hysteresis

Author(s):  
Masood Abdollahi ◽  
Farshid Vahedifard
2009 ◽  
Vol 36 (4) ◽  
pp. 639-654 ◽  
Author(s):  
Dieter Stolle ◽  
Peijun Guo ◽  
Ying Liu

An essential component of the new Guide for mechanistic–empirical design of new and rehabilitated pavement structures for the design of flexible pavement structures is the use of resilient modulus for base / subbase materials and subgrade soils. This study reports on resilient modulus (Mr) test results for unbound pavement materials that were obtained according to the American Association of State Highway and Transportation Officials (AASHTO) standard T307–99. Laboratory tests were performed on 36 representative aggregates from across Ontario and empirical relations between Mr and the bulk stress were investigated, as well as the sensitivity of Mr to moulding water content and gradation. This paper proposes to replace the nonlinear relation between resilient modulus and bulk stress with a linear relation between the two, taking into account the uncertainties that include the effect of varying water content through stochastic analysis. The effects of deviatoric stress on resilient modulus were found to be negligible for the granular aggregates that were tested. The use of a linear relation was computationally more efficient than the use of a nonlinear law; however, differences in strain predictions were observed. The findings from the finite element simulations were consistent to other studies that compared solutions using various constitutive models.


Materials ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4146
Author(s):  
Xunli Jiang ◽  
Zhiyi Huang ◽  
Xue Luo

Soft soils are usually treated to mitigate their engineering problems, such as excessive deformation, and stabilization is one of most popular treatments. Although there are many creep models to characterize the deformation behaviors of soil, there still exist demands for a balance between model accuracy and practical application. Therefore, this paper aims at developing a Mechanistic-Empirical creep model (MEC) for unsaturated soft and stabilized soils. The model considers the stress dependence and incorporates moisture sensitivity using matric suction and shear strength parameters. This formulation is intended to predict the soil creep deformation under arbitrary water content and arbitrary stress conditions. The results show that the MEC model is in good agreement with the experimental data with very high R-squared values. In addition, the model is compared with the other classical creep models for unsaturated soils. While the classical creep models require a different set of parameters when the water content is changed, the MEC model only needs one set of parameters for different stress levels and moisture conditions, which provides significant facilitation for implementation. Finally, a finite element simulation analysis of subgrade soil foundation is performed for different loading levels and moisture conditions. The MEC model is utilized to predict the creep behavior of subgrade soils. Under the same load and moisture level, the deformation of soft soil is largest, followed by lime soil and RHA–lime-stabilized soil, respectively.


Author(s):  
Andrew G. Heydinger

One objective of the FHWA’s Long-Term Pavement Performance (LTPP) program is to determine climatic effects on pavement performance. The LTPP instrumentation program includes seasonal monitoring program (SMP) instrumentation to monitor the seasonal variations of moisture, temperature, and frost penetration. Findings from the SMP instrumentation are to be incorporated into future pavement design procedures. Data from SMP instrumentation at the Ohio Strategic Highway Research Program Test Road (US-23, Delaware County, Ohio) and other reported results were analyzed to develop empirical equations. General expressions for the seasonal variations of average daily air temperature and variations of temperature and moisture in the fine-grained subgrade soil at the test site are presented. An expression for the seasonal variation of resilient modulus was derived. Average monthly weighting factors that can be used for pavement design were computed. Other factors such as frost penetration, depth of water table, and drainage conditions are discussed.


2020 ◽  
Vol 32 (9) ◽  
pp. 06020011
Author(s):  
Behnam Ghorbani ◽  
Arul Arulrajah ◽  
Guillermo Narsilio ◽  
Suksun Horpibulsuk ◽  
Myint Win Bo

2013 ◽  
Vol 723 ◽  
pp. 527-534
Author(s):  
Shu Rong Yang ◽  
Wei Hsing Huang ◽  
Shao Hung Chung

An investigation was conducted to determine the effects of temperature, compaction water content, and compaction efforts on soil suction of two expansive subgrade soils. For this purpose, two expansive soils 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°C to 60°C. 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.


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