Characterisation and evolution of the full size range of pores and fractures in rocks under freeze-thaw conditions using nuclear magnetic resonance and three-dimensional X-ray microscopy

Sun, Yong; Xu, Jizhao; Cong, Yuzhou; Qin, Lei; Zhao, Chen

doi:10.1016/j.enggeo.2020.105616

Cited by 90 publications

(28 citation statements)

References 24 publications

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“…The 3D-XRM is more accurate to measure the pore with the pore size in the micron meter scale, and therefore the pore diameter range obtained from 3D-XRM is from 15.05 µm to 484.72 µm [17,21]. As we can see from Figure 5, the pore in the high water grouting material is almost spherical and is scattered homogeneously.…”

Section: The Results Of 3d-xrmmentioning

confidence: 95%

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The Relationship between Compressive Strength and Pore Structure of the High Water Grouting Material

Han

Xia

et al. 2021

Crystals

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To elucidate the relationship between compressive strength and pore structure of the high water grouting material with different water-binder ratios and CaO contents, the compressive strength was tested while pore structure including pore characteristic parameters and pore diameter distribution were investigated by BET, MIP, and 3D-XRM. Moreover, the evolution of hydration products was observed by TGA and SEM, illustrating the reactive mechanism of the material. Furthermore, the grey correlation coefficients between compressive strength and pore structure parameters were illustrated according to the grey correlation theory. The results show that CaO content in lime is proportional to the compressive strength with the water-binder ratio of 1.0 or 1.5, while the inverse trend appears with the water-binder ratio of 2.0. The high water grouting material belongs to the macropore material with the pores mainly within 100 nm to 2 μm. Its hydration products contain ettringite crystals, aluminum gels, and C-S-H gels. The productions of the hydration products are positively correlated with its compressive strength. In addition, the compressive strength of the high water grouting material is closely related to the pore characteristic parameters and the pore size distribution, especially the porosity, the most probable pore diameter, and the pore volumes within 100~500 nm and 10~100 nm.

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Section: The Results Of 3d-xrmmentioning

confidence: 95%

“…The rotation angle was 360 degrees and the resolution was 12.13 µm in the test. The high-resolution 3D X-ray microscopic imaging system (Xradia 510 Versa) produced by the Germany Karl Zeiss company was used [17,21].…”

Section: Pore Structure Analysismentioning

confidence: 99%

The Relationship between Compressive Strength and Pore Structure of the High Water Grouting Material

Han

Xia

et al. 2021

Crystals

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“…He suggested that more freeze-thaw cycles are better than a longer freezing time in improving coal seam permeability [24], and it is the difference in the initial porosity that causes the different increments of permeability under liquid nitrogen freeze-thaw conditions [25]. Sun et al found that the impact of freeze-thaw on rocks pores and fractures is sandstone > limestone > granite, which is also related to their initial porosities [26]. Using nitrogen adsorption and mercury injection, Qin et al found that the cumulative seepage pore volume and total pore volume have an exponential relationship with freezing time, and cumulative pore volume has a quadratic relationship with freeze-thaw cycles [27].…”

Section: Introductionmentioning

confidence: 99%

Characteristics Evolution of Multiscale Structures in Deep Coal under Liquid Nitrogen Freeze-Thaw Cycles

Sun

Zhao

et al. 2021

Geofluids

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Liquid nitrogen freeze-thaw fracturing has attracted more and more attention in improving the coal reservoir permeability. In order to reveal the impact of liquid nitrogen freeze-thaw on the multiscale structure of deep coal, the multiscale structure evolution law of deep and shallow coal samples from the same seam in the Qinshui coalfield during the liquid nitrogen freeze-thaw cycling was investigated using NMR T 2 spectrum, NMRI, and SEM. The connectivity between mesopores and macropores in deep and shallow coal is improved after liquid nitrogen freeze-thaw cycles. The influence of liquid nitrogen freeze-thaw cycles on the structure evolution of deep and shallow coal is the formation and expansion of microscopic fractures. The initial NMR porosity of deep coal is lower than that of shallow coal from the same coalfield and coal seam. The NMR porosity of both the deep and shallow coal samples increases with the increase of the number of freeze-thaw cycles, and the NMR porosity growth rate of the deep sample is lower than that of the shallow sample.

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“…Several scholars have discussed the evolution in the pore structure of rocks with F-T cycles using nuclear magnetic resonance (hereinafter NMR) technology. They found that repeated F-T cycles directly destroy the internal pore structure of the rock, causing the increase in porosity [ 28 , 29 , 30 , 31 ]. Moreover, X-ray computed tomography (CT) and scanning electron microscopy (SEM) observations have also confirmed remarkable changes in the microscopic pore structure of rock due to F-T action, clearly showing that micro-cracks inside the rock expand and grow significantly [ 32 , 33 , 34 ].…”

Section: Introductionmentioning

confidence: 99%

Frost Damage in Tight Sandstone: Experimental Evaluation and Interpretation of Damage Mechanisms

Ding

Jia

Zi³

et al. 2020

Materials

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Low-porosity tight rocks are widely used as building and engineering materials. The freeze–thaw cycle is a common weathering effect that damages building materials in cold climates. Tight rocks are generally supposed to be highly frost-resistant; thus, studies on frost damage in tight sandstone are rare. In this study, we investigated the deterioration in mechanical properties and changes in P-wave velocity with freeze–thaw cycles in a tight sandstone. We also studied changes to its pore structure using nuclear magnetic resonance (NMR) technology. The results demonstrate that, with increasing freeze–thaw cycles, (1) the mechanical strength (uniaxial compressive, tensile, shear strengths) exhibits a similar decreasing trend, while (2) the P-wave velocity and total pore volume do not obviously increase or decrease. (3) Nanopores account for >70% of the pores in tight sandstone but do not change greatly with freeze–thaw cycles; however, the micropore volume has a continuously increasing trend that corresponds to the decay in mechanical properties. We calculated the pressure-dependent freezing points in pores of different diameters, finding that water in nanopores (diameter <5.9 nm) remains unfrozen at –20 °C, and micropores >5.9 nm control the evolution of frost damage in tight sandstone. We suggest that pore ice grows from larger pores into smaller ones, generating excess pressure that causes frost damage in micropores and then nanopores, which is manifested in the decrease in mechanical properties.

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Characterisation and evolution of the full size range of pores and fractures in rocks under freeze-thaw conditions using nuclear magnetic resonance and three-dimensional X-ray microscopy

Cited by 90 publications

References 24 publications

The Relationship between Compressive Strength and Pore Structure of the High Water Grouting Material

The Relationship between Compressive Strength and Pore Structure of the High Water Grouting Material

Characteristics Evolution of Multiscale Structures in Deep Coal under Liquid Nitrogen Freeze-Thaw Cycles

Frost Damage in Tight Sandstone: Experimental Evaluation and Interpretation of Damage Mechanisms

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