Diametric splitting tests on unsaturated expansive soil with different dry densities based on particle image velocimetry technique

Abstract

There is a close relationship between tensile strength of soil and crack development, but the tensile stress-strain in full failure process is rarely studied because challenges exist in accurately measuring shear strain using traditional methods. In this paper, we employed a newly developed diametric splitting testing apparatus and particle image velocimetry (PIV) system to study the tensile strength of compacted unsaturated expansive soil with different water contents and initial dry densities. Soil water characteristic curves of compacted expansive soil with different initial dry densities were determined using the filter paper method. Test results show that the tensile strength increases first and then decreases with increasing water content, and there is a critical water content for the peak load vs. water content curve. The diametric splitting test process can be divided into four stages on the basis of the plotted load-displacement curves: a stress contact adjustment stage (I); stress approximately linear increasing stage (II); tensile failure stage (III); and residual stage (IV). Under the same water content, the angle between the major directions of the displacement vector and the major crack decreases with increasing the dry density, especially when the fissure appears. Using the particle image velocimetry technique, the displacement and strain during the test process recorded is helpful for better understanding the soil failure mechanism.

Splitting tensile strength and microstructure of xanthan gum-treated loess

“…CD : The specimen load was stable with increasing displacement. Cracks developed on the surface and inside the specimen until the specimen was destroyed 45 , 46 .…”

“…The universal testing machine parameters can be set as required, with automatic constant speed loading. Because the linear variable differential transducer (LVDT) deformation sensor and loading device collect information simultaneously, the specimen deformation can be considered to be coordinated with the load imposed by the loading device 45 , 46 .

Figure 2 Schematic diagram of splitting tension device.

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“…However, there are few studies on the influence of XG on the tensile strength of loess. The radial splitting tensile test can measure soil tensile strength indirectly and is selected in this paper because it is a rapid and straightforward technique 45 , 46 .…”

Experimental PIV Radial Splitting Study on Expansive Soil during the Drying Process

“…Methods of measuring the tensile strength of soil primarily include the direct tens test [19][20][21], the radial splitting test [22,23], the bending beam test [24], and the ring specimen method [25]. The use of the radial splitting test to perform tensile strength tests is feasible because of its simplicity and ease of operation [26]. In addition, particle image velocimetry (PIV) technology has become a well-established technique in the field of geotechnical model tests and displacement field calculations.…”

“…White et al [34] investigated the penetration characteristics of piles in sandy soils based on the PIV technique. Zhang et al [35] used a PIV device to divide the radial splitting experiment process into four stages; the feasibility of the test device was demonstrated, but the object of study was remolded expansive soil, which did not involve undisturbed expansive soil.…”