Experimental Study of the Pore Structure Deterioration of Sandstones under Freeze‐Thaw Cycles and Chemical Erosion

Li, Jielin; Kaunda, Rennie B.; Zhu, Longyin; Zhou, Keping; Gao, Feng

doi:10.1155/2019/9687843

Cited by 21 publications

(9 citation statements)

References 30 publications

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“…e pores became larger and more connected; cavities and microcracks were also observed. is result indicates the pores collapsed under high pore pressure caused by the cyclic freezing-thawing cycles [10][11][12]. ere is only one macrocrack appearing on the exterior surface of the sample (Figure 6(c)), indicating that most internal microcracks are still not interconnected and the damage is not severe.…”

Section: Resultsmentioning

confidence: 98%

“…Most of the existing studies [10][11][12]16] focus on the understanding of damage caused by the freezing-thawing cycles and some of them [3,4,13,15] examine the dynamic rock characteristics under triaxial unloading tests but without freezing-thawing treatments. us, our study becomes one of the first attempts to comprehensively understand the damage behaviors of the tunneling sandstones in cold regions, where both freezing-thawing and unloading treatments could occur.…”

Section: Discussionmentioning

confidence: 99%

“…Recently, many infrastructure engineering projects such as tunneling have been carried out in the freezing-thawing zones in China and Asian countries as a result of the implementation of the Belt and Road Initiative. In cold region, the rock is under freeze-thaw cycles, and its internal pores are subject to high pore pressure, causing damage on the microstructure of pores and then on the whole mechanical properties of rocks [10][11][12]. Besides, the mechanical properties of the rocks under unloading state are rather different from those under loading state [2,13,14], and it is thus necessary to study the physical characteristics of the rock under unloading condition [3], particularly those in the cold region.…”

Section: Introductionmentioning

confidence: 99%

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Mechanical and Acoustic Emission Characteristics of Sandstone through Triaxial Unloading Test after Cyclic Freezing‐Thawing Treatment

Shen

Zhu

2020

Advances in Civil Engineering

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The dynamic failure behaviour of tunneling rock in the cold region where freezing-thawing frequently occurs is unclear. This study aimed to test and understand the damage characteristics of tunneling sandstone samples in the cold region via triaxial unloading test and acoustic emission (AE) technique. The sandstone samples were first subject to different cycles of freezing-thawing. Their stress-strain curves, deformation modulus, and the AE characteristics were then measured under triaxial unloading conditions and through the AE test. The results showed that the freezing-thawing treatment with less than 60 freezing-thawing cycles caused rather less damage compared to the triaxial unloading condition. For the samples subject to more severe freezing-thawing treatment, more cracks were produced. These cracks were not closed under small confining pressure during the triaxial test, causing weaker mechanical properties of samples. We also found that the freezing-thawing treatment had a significant deterioration on the mechanical properties of the sandstone samples when the number of freezing-thawing cycles exceeded a certain threshold (between 60 and 80 in this study). As the AE characteristics matched well with the key stages of the measured axial stress-strain curves and the deformation modulus that varied with the decreasing confining pressure, the AE characteristics can be potentially used to quantify the released energy of rock cracking and identify the critical damage phases during the tunneling engineering process.

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Section: Resultsmentioning

confidence: 98%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Mechanical and Acoustic Emission Characteristics of Sandstone through Triaxial Unloading Test after Cyclic Freezing‐Thawing Treatment

Shen

Zhu

2020

Advances in Civil Engineering

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“…According to previous research [39]- [41], changes of the porosity was caused by the change of amount and size of pores, however, porosity represents overall change of the pores rather than specific change of the internal structure of the rock. Therefore, it is necessary to make further quantitative analysis on internal structure of rock through the distribution of T 2 spectrum to determine the specific changes in the number and size of pores.…”

Section: Results and Analysis A Porosity Evolution Of Samplesmentioning

confidence: 99%

Investigation on Microstructure and Damage of Sandstone Under Cyclic Dynamic Impact

Jiang

Deng

et al. 2019

IEEE Access

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In order to study the microscopic damage evolution of rock under the cyclic dynamic impact, red sandstone was selected as samples, and Split Hopkinson Pressure Bar (SHPB) loaded with impact pressure of 0.3 MPa was adopted to exert cyclic dynamic impact on samples. After each dynamic impact, nuclear magnetic resonance (NMR) system was then applied to test the microscopic structure of samples, and then, the parameters of red sandstone, including porosity, transverse relaxation time (T 2 ) spectrum, permeability, and magnetic resonance images (MRI) after each dynamic impact, were obtained. The results show that both porosity and permeability increase with the number of dynamic impacts that red sandstone undertakes, and the increasing range of them also increases gradually. The T 2cutoff value gradually decreases when the number of dynamic impacts increases and their decrease range increases gradually, which is consistent with the trend of microscopic damage represented by porosity and permeability. Also, it is found through analyzing the T 2 spectrum that the dynamic impact produced by the impact pressure of 0.3 Mpa leads to the gradual increase of primary pore size, an increase of macro pores, and enhancement of samples' connectivity, rather than the generation of new microspores. The MRI images reveal that cyclic dynamic impact leads to the generation of microcracks in red sandstone, which coalesces and extends with the number of dynamic impact increase and forms larger micro crack zones finally.INDEX TERMS Cyclic dynamic impact, connectivity of pores, microscopic damage, MRI, NMR.

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“…According to the theory of NMR, the parameter T 2 is linearly related with the pores radii. Their relationship can be expressed as Equation 5 [15,[34][35][36].…”

Section: Pore Size Distributionmentioning

confidence: 99%

Microscopic Characteristic Analysis on Sandstone under Coupling Effect of Freeze–Thaw and Acidic Treatment: From Nuclear Magnetic Resonance Perspective

Deng

Tian

et al. 2020

Applied Sciences

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Microscopic characteristics greatly affect mechanical and physical properties as they exert vital impact on the stability and durability of materials. In this paper, widely distributed sandstone was chosen as the research object. Sandstone was treated with a coupled effect of Freeze–Thaw (F–T) weathering and acid solution, where freeze–thaw cycles were set as 0, 10, 20, 30 and 40 cycles, and the pH of the acid solution were set as 2.8, 4.2, 5.6 and 7.0, respectively. Then, nuclear magnetic resonance was applied to measure the microscopic characteristics of sandstone, then porosity, pore size distribution and permeability before the fractal dimensions were obtained and calculated. Results show that porosity increases when F–T cycles increase, and its increase grows with the pH of acid solution decrease during the first 10 F–T cycles. Macro porosity, meso porosity and micro porosity account for the largest, second largest and smallest ratio of porosity growth. Meso porosity, micro porosity and macro porosity account for the largest, second largest and smallest ratio of total porosity. Permeability increases obviously with F–T cycle increase, while acid erosion exerts little influence on permeability increment overall. Fractal dimensions of meso pores and macro pores increase with F–T cycle increase overall, and they increase with pH decrease overall. Porosity has strong exponentially correlation with permeability. Fractal dimensions of meso pores and macro pores have good linearly correlation with permeability, while correlation between porosity and fractal dimensions are not that obvious.

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Experimental Study of the Pore Structure Deterioration of Sandstones under Freeze‐Thaw Cycles and Chemical Erosion

Cited by 21 publications

References 30 publications

Mechanical and Acoustic Emission Characteristics of Sandstone through Triaxial Unloading Test after Cyclic Freezing‐Thawing Treatment

Mechanical and Acoustic Emission Characteristics of Sandstone through Triaxial Unloading Test after Cyclic Freezing‐Thawing Treatment

Investigation on Microstructure and Damage of Sandstone Under Cyclic Dynamic Impact

Microscopic Characteristic Analysis on Sandstone under Coupling Effect of Freeze–Thaw and Acidic Treatment: From Nuclear Magnetic Resonance Perspective

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