Matric Suction Measurement in Stress Path Cyclic Triaxial Testing of Unbound Granular Base Materials

Abstract

Unbound granular base (UGB) materials are commonly placed as part of pavement foundations. These materials are generally designed to be in an unsaturated state in order to resist the dominantly cyclic loading. Therefore, the response of UGB materials under cyclic loading needs to be studied using the framework of unsaturated soil mechanics. This requires the measurement of matric suction evolution during cyclic loading, which is a major experimental challenge to be resolved. This paper presents the development of a cyclic triaxial testing system and associated experimental techniques that meet the challenges of testing UGB materials as unsaturated soils. The testing system enables the initializing of matric suction of a specimen and facilitates direct measurement of its evolution during cyclic loading. Two types of cyclic loading could be imposed: with constant cell pressure and with cyclic cell pressure. Selected test results of both types of cyclic loading were presented to demonstrate satisfactory performance of the proposed methodology. Furthermore, a detailed analysis of these selected test results was also undertaken to show the importance of matric suction for understanding the behavior of UGB materials under cyclic loading.

Cyclic Direct Simple Shear Test to Measure Strain-Dependent Dynamic Properties of Unsaturated Sand

“…At medium shear strain levels (0.01 %-0.1 %), modifications were made to triaxial systems to incorporate suction control to study the dynamic properties of unsaturated soils (Cui et al 2007;Chin et al 2010;Craciun and Lo 2010;Biglari et al 2011;Kimoto et al 2011;Ghayoomi et al 2017). These studies indicated an increase in stiffness of unsaturated soils in higher suction following a strain-dependent modulus reduction pattern similar to the ones in dry condition.…”

Extensive overview of soil constitutive relations and applications for geotechnical engineering problems

“…Hysteretic behavior is represented by rock masses under such circumstances, and the deformability and strength are closely associated with the loading history and stress state. Thus, under conventional triaxial and uniaxial loading circumstances, the necessities of engineering practice in more complicated circumstances are not met by current constitutive models [ 102 ]. The deformability and strength of rocks have been investigated from two aspects: one included building frameworks for rock flaws and interfaces under various loading circumstances.…”

Model for predicting resilient modulus of unsaturated subgrade soil using soil-water characteristic curve

“…However, soil suction measurements from these methods are user dependent, sensitive to testing protocols, and neglect the influence of the applied stress on the (Ng and Pang 2000;Power et al 2008;Power and Vanapalli 2010;Ng et al 2012). In recent years, modified cyclic triaxial testing systems equipped with various techniques (e.g., thermal dissipation sensor, psychrometer, suction probe, axis-translation technique) are used to measure or control the soil suction during the RLTTs for obtaining reliable testing results (Gupta et al 2007;Yang et al 2008;Craciun and Lo 2010;Cary and Zapata 2011;Ng et al 2013;Sivakumar et al 2013). Trained professionals are required to conduct these tests.…”

“…Extensive experimental investigations were conducted by several researchers during the past decade using advanced testing techniques to measure the M R -relationships and propose models for predictions (Khoury and Zaman 2004;Yang et al 2005Yang et al , 2008Liang et al 2008;Sawangsuriya et al 2009;Craciun and Lo 2010;Cary and Zapata 2011;Nowamooz et al 2011;Azam et al 2013;Ng et al 2013;Sahin et al 2013;Sivakumar et al 2013;Salour et al 2014). These studies have provided valuable information for better understanding the influence of the on the M R .…”

“…(iv) Several investigators reported that the soil suction decreases during the application of the cyclic loading(Yang et al 2008;Craciun and Lo 2010;Sivakumar et al 2013). Such behavior can…”