Microstructure, Deformation Characteristics and Energy Analysis of Mudstone under Water Absorption Process

Abstract

In geological engineering, a series of safety problems caused by expansive mudstone are common, such as slope instability and roadbed up-arch. In this paper, the mineral composition of mudstones in the Xining area was analyzed by X-ray diffraction (XRD), and the microstructural and morphological changes of mudstones after water absorption were observed by scanning electron microscopy (SEM) test to analyze the internal factors and microstructural evolution patterns of water absorption and swelling of mudstones. Based on the microstructural units, the mudstones were defined into two categories, one is N-type mudstone with flat sheet-like stromatolite units, and the other is SN-type mudstone with more clastic particle units. Water absorption experiments were conducted on the rock samples to study the microstructure of these two types of mudstones under different water absorption conditions. The pore characteristics of the mudstones were analyzed by using Image-Pro Plus to reveal the water absorption mechanism. The results show that the pore area of N-type mudstone is smaller, as well as the distribution of pore diameter. The pore area of N-type mudstone develops rapidly, in the early stage of water absorption, lots of pores are produced, and the pore area of SN-type mudstone shows an overall decreasing trend. The pore area and the number of SN-type mudstones are at a low level after full water absorption. Under the condition of full immersion, water enters the pores rapidly and soluble salts are dissolved in large quantities. The change of water absorption rate of mudstone with time can be divided into the stage of sudden increase, decrease and stability of water absorption rate. Then, based on the stress theory, the relationship between the macroscopic expansion process and the microstructure of mudstone was analyzed. Finally, the energy basis of mudstone water absorption is discussed. In the swelling of mudstone, the energy gradually turns into swelling strain energy.

Study on Uniaxial Mechanical Behavior and Damage Evolution Mechanism of Water-Immersed Mudstone

“…Furthermore, the distribution of voids plays a crucial role in influencing the tensile strength and crack mode of the material. Feng et al [23] observed the microstructure and morphological changes of mudstone after water immersion. The results indicated that the nonhomogeneous strain of mudstone led to the expansion between adjacent clay mineral aggregates and particle clusters, resulting in the reduction in or disappearance of pores, which causes a decrease in the number of large-diameter pores and an increase in the number of small-diameter pores in the internal pores of mudstone.…”

Analysis of the deterioration process of the dolomite with the interlayer in different directions during wetting

“…Water rock interaction exists widely in various practical geotechnical engineering. Under the action of water, the rock will often be softened, cracked, expanded, disintegrated and other deterioration phenomena (Zhao et al, 2021;Zhou K. et al, 2022;Feng et al, 2022;, and this deterioration of rock in water has a great impact on the safety of various engineering construction (Bai et al, 2021;Du et al, 2022;Fu et al, 2022). Therefore, the research on the law of rock wetting deterioration has always been the focus of researchers (Jiang et al, 2015;Hua et al, 2019).…”