Study on Mechanism of Freeze-Thaw Cycles Induced Changes in Soil Strength Using Electrical Resistivity and X-Ray Computed Tomography

2017 ◽  
Vol 139 (2) ◽  
Author(s):  
Xiaoliang Yao ◽  
Lili Fang ◽  
Jilin Qi ◽  
Fan Yu
Keyword(s):  
Computed Tomography ◽  
Electrical Resistivity ◽  
Triaxial Compression ◽  
Friction Angle ◽  
Soil Samples ◽  
Soil Particles ◽  
X Ray ◽  
Freeze Thaw ◽  
Apparent Cohesion ◽  
X Ray Computed

In this study, freeze-thaw cycles were conducted on samples of a fine grained soil from the Qinghai–Tibetan plateau which had been prepared with different dry unit weights. During freeze-thaw cycles, electrical resistivity was measured. The soil samples were also scanned by X-ray computed tomography (CT) before and after freeze-thaw cycles. Unconsolidated and drained (UD) triaxial compression test was performed to obtain the apparent friction angle and cohesion. Changes in the arrangement and connections between soil particles were analyzed so as to investigate the mechanisms of changes in the strength parameters. The electrical resistivity increased in all samples, regardless of the different original dry unit weights, which implies that in all cases the arrangement of soil particles became more irregular and attached area between soil particles was increased. These changes contributed to the increase of apparent friction angle. On the other hand, the CT scans indicated that, depending upon the original dry unit weight, freeze-thaw cycles induced strengthening or deterioration in particle connections, and thus apparent cohesion was increased or decreased. With three freeze-thaw cycles, changes in microstructure of soil samples led to increases or decrease in both the apparent friction angle and cohesion.

scholarly journals Pore Structure Analysis of Mortar Under Freeze-Thaw Cycles Using X-Ray Computed Tomography

◽  
2016 ◽  
Author(s):  
Katsufumi Hashimoto ◽  
◽  
Hiroshi Yokota ◽  
Takafumi Sugiyama ◽  
◽  
...  
Keyword(s):  
Computed Tomography ◽  
Pore Structure ◽  
Structure Analysis ◽  
X Ray ◽  
Freeze Thaw ◽  
X Ray Computed ◽  
Pore Structure Analysis

Estimating the depth of the restrictive layer of soil in a cranberry field based on CT scan images

2020 ◽  
Author(s):  
Elnaz Shahriarinia ◽  
Silvio Jose Gumiere ◽  
Christian Dupuis
Keyword(s):  
Computed Tomography ◽  
Ct Scan ◽  
Fine Particles ◽  
Pore Network ◽  
Imaging Method ◽  
Pore Characteristics ◽  
Soil Particles ◽  
X Ray ◽  
Soil Media ◽  
X Ray Computed

<p><strong>Estimating the depth of the restrictive layer of soil in a cranberry field based on CT scan images</strong></p><p> </p><p>Cranberry production is a dominant culture in Québec, Canada. In cranberry production, there is a substantial need for water whether for irrigation, harvesting, or frost control. Some farms are implementing subirrigation procedures in order to reduce water use and increase fruit yields. However, this irrigation method may impose hydraulic stresses on soil particles which results in the movement of fine particles. The accumulation of the soil particles in narrow pore throats leads to the formation of restrictive layers in soil.  In this respect, we are going to study the changes in soil media and its porosity based on X-ray computed tomography (CT) which is a non-destructive imaging method. Consequently, X-ray CT has become a great asset to analyze soil physical properties. With the analysis of the images captured by the use of X-ray computed tomography, it is possible to visualize and analyze the pore network structure in the soil media.</p><p> </p><p>This study reports the results of subirrigation experiments for four different sandy soils. These column experiments aimed to reproduce the effects of subirrigation in cranberry fields for 40 years. Seven different time steps were taken with a medical CT scanner SOMATOM Definition AS+ 128 (Siemens, Germany). The 2-D horizontal 16-bit gray-scale images were captured by an X-ray energy level of 140 KeV. For each column, we got 1677 images of 512  512 pixels with a voxel size of 0.1 × 0.1 × 0.6 mm (x, y, z). Studying our images for further analysis, we used several global and local methods to find the most reliable and efficient one to binarize our images. Results show that the methods and the image analysis neighborhood have a great impact on the accuracy of the image segmentation. We were able to reconstruct a 3-D visualization of the soil pore network for each column. We used this reconstruction to demonstrate that the variation of porosity and soil pore characteristics can be studied over time. We find that the transport of soil particles tends to be highest when there are fine sandy soil particles on top of a layer of coarse soil. These finer particles have sufficient energy to be remobilized within the pore network while coarser particles remain in place. Our results show that soil particle transport can be assessed using time-lapse imagery and thus makes it possible to approximate the depth and amount of time that will be required for these restrictive layers to form in different soil profiles. Finally, it would be possible to find the best structure of soil in construction of a cranberry field in the future.</p><p> </p><p> </p><p> </p><p> </p><p> </p><p> </p>

Specimen nonuniformities in water-pluviated and moist-tamped sands under undrained triaxial compression and extension

2008 ◽  
Vol 45 (7) ◽  
pp. 939-956 ◽  
Author(s):  
P. R. Thomson ◽  
R. C.K. Wong
Keyword(s):  
Computed Tomography ◽  
Axial Load ◽  
Void Ratio ◽  
Triaxial Compression ◽  
Stress Path ◽  
Saturated Sand ◽  
Ratio Distribution ◽  
X Ray ◽  
X Ray Computed ◽  
Insight Into

X-ray computed tomography (CT) methods and specialized triaxial equipment were developed to quantify void ratio distribution within saturated sand specimens reconstituted by water pluviation and moist tamping methods during undrained triaxial compression and extension. The CT measurements were obtained at several points along the stress path of each specimen without significant removal of axial load. It was observed that two reconstitution methods yielded very different void ratio distributions within specimens. Significant void ratio redistribution occurred within each specimen during the undrained shearing tests. The influences of void ratio redistribution on globally observed specimen responses are discussed. The findings of this research investigation provide unique insight into fundamental aspects of saturated sand behaviour during undrained triaxial shearing.

Microstructural damage characterization of concrete under freeze-thaw action

2017 ◽  
Vol 27 (10) ◽  
pp. 1551-1568 ◽  
Author(s):  
Q Luo ◽  
DX Liu ◽  
Pizhong Qiao ◽  
QG Feng ◽  
LZ Sun
Keyword(s):  
Computed Tomography ◽  
Transition Zone ◽  
Three Dimensional ◽  
Interfacial Transition Zone ◽  
X Ray ◽  
Freeze Thaw ◽  
Microstructural Damage ◽  
Damage Characterization ◽  
X Ray Computed ◽  
Concrete Materials

This paper conducts a quantitative analysis of microstructural damage evolution of concrete materials under freeze-thaw action using three-dimensional X-ray computed tomography. The study employs two resolution-scales to evaluate concrete samples under various cycles of freeze-thaw action. The three-dimensional microstructural damage characterization, pore network (porosity, pore size, and pore distribution) as well as the defects in the aggregates are specifically investigated. The microstructures of concrete under different freeze-thaw action show that the interfacial transition zone is most likely to be damaged first under frost attack. Furthermore, the freeze-thaw action deteriorates not only the interfacial transition zone but also cement matrix and aggregates. The impact of freeze-thaw cycles is notable on the internal micro-pores and micro-cracks of the concrete. More pores and cracks can be nucleated during the freeze-thaw action, and further accumulate and grow in the paste and aggregates, eventually leading to final failure of concrete materials. As demonstrated in this study, three-dimensional X-ray computed tomography is capable of acquiring microstructures of concrete and revealing existence of internal pores and cracks in different phases of concrete, and more effective to characterize accumulated damage of concrete due to freeze-thaw action.

Sign in / Sign up

Export Citation Format

Share Document