Pore Structure Of Sandstone Research Articles

Effects of CO2–water–rock cycling cycles on sandstone pore structure

Effects of CO2–water–rock cycling cycles on sandstone pore structure

Strength degradation characteristics and damage constitutive model of sandstone under freeze-thaw cycles.

Thorough investigation into the laws governing frozen rock damage in high-altitude and cold regions can offer valuable insights for advancing infrastructure construction, ecological environment protection, and sustainable development on the Qinghai-Xizang Plateau. This study combined with the seasonal variation patterns of frozen rocks in the Qinghai-Xizang Plateau, and processed the rock samples using a freeze-thaw interval of -20 °C~20 °C. Uniaxial compression test was conducted based on the MTS816 rock mechanics testing system. The porosity changes of rock samples with different freeze-thaw cycles were analyzed using the MesoMR12-060H-I nuclear magnetic response analysis system. A rock freeze-thaw load coupled damage constitutive model was derived using the Lemaitre equivalent strain theory. Research has shown that during the freezing process, the pore water inside the rock sample is affected by the phase change of water-ice, resulting in frost heave force, which further promotes the expansion of the pore walls and the initiation of new cracks. When melted, pore water migrates towards newly formed micropores, thereby affecting the changes in the pores of rock samples. The increase in porosity at the micro level weakens the mechanical parameters of rocks at the macro level. The segmented freeze-thaw damage constitutive model based on Lemaitre equivalent strain theory can well fit the experimental results involved in this study, as well as the experimental results obtained by other researchers. The compaction stage can partially reflect the changes in sandstone pore structure under freeze-thaw cycles.

A 3D convolutional neural network model with multiple outputs for simultaneously estimating the reactive transport parameters of sandstone from its CT images

Porosity, tortuosity, specific surface area (SSA), and permeability are four key parameters of reactive transport modeling in sandstone, which are important for understanding solute transport and geochemical reaction processes in sandstone aquifers. These four parameters reflect the characteristics of pore structure of sandstone from different perspectives, and the traditional empirical formulas cannot make accurate predictions of them due to their complexity and heterogeneity. In this paper, eleven types of sandstone CT images were firstly segmented into numerous subsample images, the porosity, tortuosity, SSA, and permeability of the subsamples were calculated, and the dataset was established. The 3D convolutional neural network (CNN) models were subsequently established and trained to predict the key reactive transport parameters based on subsample CT images of sandstones. The results demonstrated that the 3D CNN model with multiple outputs exhibited excellent prediction ability for the four parameters compared to the traditional empirical formulas. In particular, for the prediction of tortuosity and permeability, the 3D CNN model with multiple outputs even showed slightly better prediction ability than its single-output variant model. Additionally, it demonstrated good generalization performance on sandstone CT images not included in the training dataset. The study showed that the 3D CNN model with multiple outputs has the advantages of simplifying operation and saving computational resources, which has the prospect of popularization and application.

Improved pore structure characterization and classification of strong diagenesis sandstones by data-mining analytics in Tazhong area, Tarim Basin.

The Silurian system in Tazhong area is characterized by extensive, low-abundance lithological reservoirs with strong diagenesis, resulting in significant heterogeneity. The complex pore structure in this area significantly impacts fluid control, making accurate characterization and classification of pore structures crucial for understanding reservoir properties and their influence on oil and gas distribution. Based on 314 Mercury Injection Capillary Pressure (MICP) samples in combination with core slices and thin casting slices observation, a pipeline of characterization and classification scheme by data-mining analytics of strong diagenesis sandstone pore structure types in the study zone is established, and the characteristics of different pore structures are clarified. According to the pore structure parameter abstracted by MICP data compression and variable analysis based on hierarchical clustering and principal component analysis (PCA) analysis, the variables are reasonably evaluated and screened, and the screened variables can be divided into three groups: mean pore throat radius-maximum pore throat radius-median pore throat radius-pore throat diameter mean variable group, microscopic mean coefficient variable group, and median pressure displacement pressure-relative sorting coefficient variable group. The combination of classification schemes analysed by decision tree model and linear discriminant analysis (LDA) model was determined. In the two-dimensional projection diagram of LDA model, a relatively obvious distribution of low displacement pressure, middle displacement pressure and high displacement pressure was obtained, and three distribution lines were nearly parallel. Based on the relevant information, 6 combined classification schemes suitable for final pore structure modelling were determined verified by microscopic observation. The correct characterization and classification of pore structure can be applied to the prediction of pore type, which can be used to improve the prediction of oil and gas distribution and oil and gas recovery in the future.

Characterization of evolution of reactive transport parameters during leaching process of sandstone uranium ore by combining porosity and lacunarity

During the in-situ leaching process of sandstone uranium ore deposits, the dynamic evolution of reactive transport parameters, including permeability, tortuosity, and specific surface area (SSA), plays a crucial role in solution flow and solute transport. Characterizing the evolution of these parameters is essential for understanding the leaching process. However, the heterogeneous pore structure of sandstone renders porosity alone insufficient to capture changes in these parameters. This study combines porosity and lacunarity to comprehensively characterize these parameters. For this purpose, leaching experiments were conducted on sandstone uranium ore samples, and CT imaging was performed at different leaching time points. The evolution of reactive transport parameters was analyzed by studying cubic subsamples from the images. The results indicate that both porosity and lacunarity are significant factors influencing the reactive transport parameters. However, neither parameter alone adequately characterizes their evolution. In contrast, combining them accurately characterizes the evolution of reactive transport parameters. Porosity reflects pore quantity, while lacunarity represents pore heterogeneity. Combining these measures facilitates a comprehensive understanding of the evolution of reactive transport parameters and the influence of pore microstructure on macroscopic reactive transport parameters. This research provides valuable insights for optimizing the leaching process in sandstone uranium ore deposits.

3D imaging and flow analysis of sandstone pore structure

Abstract Micro CT technology can provide three-dimensional high-precision digital images with micrometer (or smaller) resolution, offering robust technical support for the study of the internal structure of rocks. Based on the data obtained from the CT scanning of Leopard sandstone, a series of image processes were carried out using the Avizo software to extract pore distribution. The watershed algorithm was employed to independently segment each pore, and the largest sphere algorithm was used to establish a sphere-tube model. Based on the constructed pore network model, quantitative analyses of the porosity, fractal dimensions, permeability, and other parameters of the sandstone sample were conducted. Moreover, the connectivity of the pores was analyzed using an automatic skeleton model. Results show: ① CT scanning digital core technology can not only visualize the three-dimensional connectivity and isolated pores of sandstone but also quantitatively characterize the pore structure parameters; ② The analyzed Leopard sandstone has a connected porosity of 13.76%, an isolated porosity of 0.53%, and the pore radius is mainly concentrated in the 0-70μm small pore range, occupying 76.1% of the total pore volume; ③ The lower the sample porosity, the higher the fractal dimension, indicating a more complex pore structure.

Investigating the causes of permeability anisotropy in heterogeneous conglomeratic sandstone using multiscale digital rock

Heterogeneous conglomeratic sandstone exhibits anisotropic physical properties, rendering a comprehensive analysis of its physical processes challenging with experimental measurements. Digital rock technology provides a visual and intuitive analysis of the microphysical processes in rocks, thereby aiding in scientific inquiry. Nevertheless, the multiscale characteristics of conglomeratic sandstone cannot be fully captured by a single-scale digital rock, thus limiting its ability to characterize the pore structure. Our work introduces a proposed workflow that uses multiscale digital rock fusion to investigate permeability anisotropy in heterogeneous rock. We use a cycle-consistent generative adversarial network to fuse computed tomography scan data of different resolutions, creating a large-scale and high-precision digital rock that comprehensively represents the conglomeratic sandstone pore structure. Subsequently, the digital rock is partitioned into multiple blocks, and the permeability of each block is simulated using a pore network. Finally, the total permeability of the sample is calculated by conducting an upscaling numerical simulation using the Darcy-Stokes equation. This process facilitates the analysis of the pore structure in conglomeratic sandstone and provides a step-by-step solution for permeability. From a multiscale perspective, this approach reveals that the anisotropy of permeability in conglomeratic sandstone stems from the layered distribution of grain sizes and differences in grain arrangement across different directions.

Estimation of unfrozen water content of saturated sandstones using nuclear magnetic resonance, mercury intrusion porosimetry, and ultrasonic tests

The unfrozen water content (UWC) is a crucial parameter that affects the strength and thermal properties of rocks in relation to engineering construction and geological disasters in cold regions. In this study, three different methods were employed to test and estimate the UWC of saturated sandstones, including nuclear magnetic resonance (NMR), mercury intrusion porosimetry (MIP), and ultrasonic methods. The NMR method enabled the direct measurement of the UWC of sandstones using the free induction decay (FID). The MIP method was used to analyze the pore structures of sandstones, with the UWC subsequently calculated based on pore ice crystallization. Therefore, the MIP test constituted an indirect measurement method. Furthermore, a correlation was established between the P-wave velocity and the UWC of these sandstones based on the mixture theory, which could be employed to estimate the UWC as an empirical method. All methods demonstrated that the UWC initially exhibited a rapid decrease from 0 °C to −5 °C and then generally became constant beyond −20 °C. However, these test methods had different characteristics. The NMR method was used to directly and accurately calculate the UWC in the laboratory. However, the cost and complexity of NMR equipment have precluded its use in the field. The UWC can be effectively estimated by the MIP test, but the estimation accuracy is influenced by the ice crystallization process and the pore size distribution. The P-wave velocity has been demonstrated to be a straightforward and practical empirical parameter and was utilized to estimate the UWC based on the mixture theory. This method may be more suitable in the field. All methods confirmed the existence of a hysteresis phenomenon in the freezing-thawing process. The average hysteresis coefficient was approximately 0.538, thus validating the Gibbs–Thomson equation. This study not only presents alternative methodologies for estimating the UWC of saturated sandstones but also contribute to our understanding of the freezing-thawing process of pore water.

3D Characterization of Pore Structure and Pore Scale Seepage Simulation of Sandstone Based on Computational Tomography

The microscopic pore structure of sandstone determines its macroscopic permeability. Based on computer tomography (CT) technology, CT scans were performed on three different types of sandstone pore structures, namely coarse sandstone, medium sandstone, and fine sandstone. And the three-dimensional microscopic structure of sandstone pores was reconstructed. Furthermore, based on the Navier–Stokes equations, the fluid flow process in the pore structure of sandstone was simulated, and the effective permeability of sandstone was obtained. By extracting the pore structure from sandstone CT images, the average porosity of coarse sandstone, medium sandstone, and fine sandstone was 16.43%, 12.03%, and 11.64%, respectively. And the porosity of unconnected pores is less than 0.5%. The porosity and permeability of coarse sandstone are higher than those of medium sandstone and fine sandstone with an average value of 1.7 D. The porosity of medium sandstone and fine sandstone is relatively similar. However, the average pore radius and pore throat radius of medium sandstone are larger than those of fine sandstone. More importantly, although the permeability and porosity of sandstone are generally linearly related, when the porosity is low, the data show a large dispersion, and auxiliary indicators such as pore structure characteristic parameters such as pore throat radius should be adopted to evaluate the permeability of sandstone. The flow trajectory of fluid in the pore structure of sandstone is revealed through the streamline of fluid in the pore structure, revealing the mechanism of fluid flow.

Evolution of pore structure and reactive transport parameters during acid leaching of sandstone uranium ore

The changes in the micro-scale pore structure during the acid leaching of sandstone uranium ore significantly affect its reactive transport parameters, which, in turn, directly influence the leaching efficiency of uranium. Consequently, understanding and managing the dynamic evolution of the pore structure of sandstone at micro-scale during acid leaching is beneficial for enhancing the leaching efficiency of uranium. This paper employs a dynamic continuous water-rock reaction experiment on sandstone uranium ore to simulate the in-situ acid leaching process. Additionally, X-ray micro-computed tomography (μCT) scanning was utilized to produce three-dimensional (3D) images at various leaching stages. Subsequently, image processing techniques were employed to characterize and parameterize the pore structure within these images. The results revealed that, during the leaching process, mineral dissolution led to an increase in the interconnected pores, while there was a decrease in the isolated pores. Nonetheless, at the leading edge of the sandstone uranium ore, detachment of mineral grains occurred during the leaching process along the direction of fluid flow. The migration of mineral grains resulted in a reduction of interconnected pores and an increase in the isolated pores. The analysis of 3D images indicated that porosity, permeability, the percentage of connected pore area and the reactive surface area exhibited similar variation trends throughout the leaching process. Furthermore, the permeability, the percentage of connected pore area and the reactive surface area displayed a positive correlation with porosity. The study holds valuable insights to develop a deeper understanding of the evolutionary patterns regarding the pore structure during the in-situ acid leaching of sandstone uranium ore.

Experimental Study on the Pore Structure of Sandstone Damaged by Blasting and Changes in Energy Dissipation Under Triaxial Loading

Experimental Study on the Pore Structure of Sandstone Damaged by Blasting and Changes in Energy Dissipation Under Triaxial Loading

Influence of coupled dissolution-precipitation processes on the pore structure, characteristics, and evolution of tight sandstone: A case study in the upper Paleozoic reservoir of Bohai Bay Basin, eastern China

Due to the limitations of pore throat characterization techniques, in-depth studies on the evolution and influencing variables of tight sandstone reservoirs remain lacking, despite the importance of pore structure in evaluating their storage and seepage capacities. In this study, the effect of coupled dissolution–precipitation on the heterogeneity of the pore structure of tight sandstone was investigated using advanced techniques in conjunction with traditional geochemical analyses. The primary reasons for the variability in tight sandstone pore structure were different diagenetic processes and tectonic evolution. In tight sandstones, numerous burial phases led to a significant loss of porosity. However, tight sandstones that have been successively leached by meteoric water and deep burial organic acid have improved secondary pore space due to Yanshan tectonic uplift and Himalayan tectonic burial. The redistribution or blockage of pore space can occur as a result of dissolved material migrating and re-precipitating in tight sandstones that have been deeply buried and altered by organic acidic fluids. Furthermore, nuclear magnetic resonance cryoporometry and nuclear magnetic resonance experiments were used to provide precise and accurate quantitative analysis for discussing the evolution of pore structure by complex dissolution–precipitation process within the pore scale. The formation of good pore structure was mainly dependent on the increase in pore volume generated by dissolution in the submicron and micron range (less than 10 μm). Due to interfacial energy effects, authigenic minerals precipitated preferentially in macropores, resulting in a preponderance of microporosity and small changes in porosity but at least an order of magnitude reduction in permeability. This study provides a reliable reference for genesis analysis and evaluation of tight sandstones as well as a new perspective for understanding the formation and evolution of complex pore structures.

Impact of H2-CH4 mixture on pore structure of sandstone and limestone formations relevant to subsurface hydrogen storage

Subsurface Hydrogen (H2) storage is a promising technology to achieve net-zero carbon emissions. Depleted gas reservoirs can provide safe storage of hydrogen in the long term, and effective recovery during the cycling process. The pre-existing Methane gas (CH4) or its traces in these formations can mix with the injected hydrogen and might cause in-situ geochemical reactions with the storage rock. Despite the recent interest in evaluating H2-rock interactions, the available knowledge on the impact of H2–CH4 mixture on the petrophysical properties of storage rocks is scarce. Motivated by the lack of experimental work that exists on this topic, we provide an experimental investigation on the reactivity of sandstone and limestone formations to H2–CH4 mixture. Samples from Bandera Gray Sandstone and Indiana Limestone samples were aged in H2–CH4 mixture at 75 °C and 1400 psi for 90 days, and Nuclear Magnetic Resonance (NMR) and gas porosity analysis were performed. The results showed limited reactivity of the samples to H2–CH4 mixture, and subsequently, insignificant changes occurred in the petrophysical properties. The average porosity of BG and IL samples decreased by 3.32 % and 1.00 % respectively. NMR analysis indicates no significant changes in T2 distribution times curves, indicating no major alterations occurred in the pore structure or rock geometry. Moreover, the average NMR porosity of BG was reduced by 3 %, while the reduction of IL porosity did not exceed 6 %. We conclude that the potential geochemical reactions (dissolution/precipitation) between the H2–CH4 mixture and rock minerals are very weak within 90 days of H2–CH4 mixture treatment, thus the suitability of sandstone and limestone rocks for hydrogen storage is promising.

Study on the evolution of microscopic pore structure of sandstone under freeze-thaw cycles

In cold regions, rocks undergo freeze-thaw (FT) cycles, leading to damage caused by the evolution of pores. This phenomenon significantly influences the rock mass stability. A comprehensive and accurate study of FT damage evolution in rock pores was conducted in this research. The microscopic morphology and pore size distribution (PSD) of sandstone samples subjected to FT cycles were measured utilizing scanning electron microscopy (SEM), nitrogen adsorption/desorption (NAD) method, and mercury intrusion porosimetry (MIP). Multifractal analysis was applied to explore the evolution of PSD. A gradual weakening of the cementation degree of mineral particles under FT cycles was observed based on SEM results, resulting in the formation of larger connected pores. A decrease of 37.3% in the number of pores was recorded after 40 cycles. According to NAD and MIP results, a greater effect on mesopores and large pores were found, with a minimal impact on micropores and transition pores. Multifractal characteristics were identified in the PSD of sandstone samples with different FT cycles. Initially, the connectivity of sandstone pores was found to decrease and then increase gradually after 10 cycles. Uneven PSD was observed to concentrate stress among pores, exacerbate frost heave damage, and drive the PSD towards a more uniform direction. It was concluded that the non-uniform degree of PSD does not consistently increase with FT cycles. The findings of this study can serve as a reference for further research on rock FT damage mechanisms.

Pore Structure Characteristics and Main Control Factors of Sandstone in the Jurassic Zhiluo Formation in the Northern Ordos Basin

The Jurassic Yan’an Formation in the Ordos Basin is one of the main coal seams mined in the basin, and the enrichment of water bodies in the upper part of this coal seam is closely related to the sand bodies in the Zhiluo Formation. This study is based on the use of core observations in the northern part of the Ordos Basin for studying the pore characteristics of the permeable sand layer of the Zhiluo Formation in the study area through testing methods such as ordinary thin sections, cast thin sections, scanning electron microscopy (SEM), mercury intrusions, and physical property analysis. The results indicate that the primary pores of the Zhiluo Formation sandstone in the study area include primary intergranular pores, residual intergranular pores, and interstitial micropores. The secondary pores are mainly intergranular pores, feldspar dissolution pores, and rock debris dissolution pores. The throat-type pores are mainly variable fault contractions, sheets, curved sheets, and bundle-shaped throats. The pore structures of the Zhiluo Formation sandstone in the research area are complex, and the permeability is influenced by the throat characteristics. The main controlling factors of the pore structure characteristics of the Zhiluo Formation sandstone in the study area are sedimentation and diagenesis. Compaction and cementation are the main factors that destroy the sandstone pore structure, while later dissolution plays a certain role in the improvement of the pores. Section 1 of the Zhiluo Formation is greatly affected by diagenesis, and section 2 is greatly affected by sedimentation.

A comprehensive study of damage characteristics and acoustic emission response mechanism of sandstone with different water contents

The mechanical characteristics and fracture mechanisms of rocks are usually affected by water–rock interaction. This study conducted uniaxial compression tests on sandstone to analyse the variation law of its mechanical properties and macroscopic failure morphology for various water contents. Furthermore, the relationships between the roughness of the crystal fracture surface and mechanical properties were discussed based on the scanning electron microscope (SEM) fracture morphology. The development of an internal fracture in sandstone was described using acoustic emission (AE) and low-field nuclear magnetic resonance (NMR) techniques, and the response mechanism and controlled factors of an AE dominant frequency–amplitude signal were revealed. Results reveal that the uniaxial compressive strength and elastic modulus of sandstone exhibit a nonlinear decreasing trend with an increase in water content. The deterioration to the sandstone structure by water is divided into three periods: intense, stable growth, and calm. The macroscopic fracture shape of sandstone gradually changes from single-shear failure to axial-split failure, whereas the roughness of the crystal fracture surface positively correlated with the water content, with the mechanical strength negatively correlating. Four response mechanisms of the AE spectrum exist in sandstone fracture process: sliding friction between the mineral particles or crystal fracture (transgranular or intergranular crack) corresponds to the LF–LA signal, friction of microcracks corresponds to the IF–LA signal, fracture of microcracks corresponds to the HF–LA signal, and large-scale macroscopic cracks correspond to the LF–HA signal. Moreover, the characteristics of the AE dominant frequency–amplitude signal are affected by the mineral composition and pore structure of sandstone. This study can enrich the existing research literature on sandstone damage characteristics in water-bearing state and provide new perspectives and approaches for quantitatively describing the fracture mechanism of rock.

Influence of Strain Rate on the Physical–Mechanical Characteristics and Pore Structure of Sandstone in the Shanxi-Tong Chuan Reservoir Region Subjected to Sulfate Attack

The fracture toughness (KIC) of Mode I cracked sandstone exposed to sodium sulfate was investigated in this study. The uniaxial behavior of sandstone specimens soaked in different sodium sulfate solutions was determined for different strain rates. The results revealed that the strain rate has a significant and positive influence on the deformation and strength characteristics of sandstone. Compression strength gradually increased with strain rate at an increased slope, but peak strain decreased gradually with an increase in strain rate. The physical–mechanical characteristics and brittleness of sandstone gradually declined with increasing immersion time under sodium sulfate attack, but its plasticity increased significantly. There were holes and pitting corrosions in specimen surfaces exposed to sodium sulfate attack, and the edges and corners were somewhat weakened. Chemical damage variables were proposed to analyze the damage degree of sandstone, based on the change in porosity. Based on the testing results, regression analysis was conducted to determine the relations between ion concentrations (Ca2+ and Mg2+) in corresponding sodium sulfate solutions and for corresponding degrees of damage, and indirectly realize correlations between physical–mechanical characteristics, damage degree, and ion concentration.

A Comprehensive Classification Method for the Pore Permeability of Deep-Mine Sandstone Used to Guide Grouting

One type of seepage water that is difficult to plug by grouting is the water exuding through the pores of sandstone in deep underground engineering. Aiming at this problem, this paper collected deep-mine sandstone samples from the Southwest Shandong coalfield, studied the sandstone pore structure and its influential factors by casting thin slices, scanning electron microscopy, mercury intrusion and physical property tests, and selected five representative permeability classification indicators: permeability, porosity, average pore throat radius, comprehensive diagenetic coefficient and sorting coefficient. According to these five indicators, the pore permeability of all the sandstone samples was divided into four subcategories (I1, I2, II1, and II2) from the perspective of grouting. I1 has medium pores and medium pore throats that can be filled with ultrafine cement-based slurries; I2 has medium-small pores and fine pore throats; II1 has medium-small pores and fine pore throats or small pores and microthroats; both I2 and II1 can be filled with chemical slurries; and II2 has micropores and microthroats that cannot be grouted. This case study provides a reference for the classification and evaluation of the pore permeability of sandstone for grouting and lays a foundation for classified permeation grouting and subsequent pore-expanding permeation grouting.

The Permeability Evolution of Sandstones with Different Pore Structures under High Confining Pressures, High Pore Water Pressures and High Temperatures

Seepage from the pores of sandstone exposed in deep mines is difficult to block by grouting. In this paper, the permeability evolution of four subcategories of sandstone with different pore structures under different confining pressures, pore water pressures and temperatures is analyzed by experiments. (1) With increasing confining pressure, the permeabilities of the four tested subcategories of sandstone all decrease, but at different rates and to different extents. (2) With increasing pore water pressure, the permeability of subcategory I1, I2 and II1 sandstones increases linearly, while that of subcategory II2 sandstone decreases following a power function under low confining pressures and tends to be stable under high confining pressures. (3) With increasing temperature, the permeabilities of the four sandstone subcategories decrease at different rates. (4) The orthogonal experimental results show that the confining pressure has the greatest influence on the permeability, followed by the water pressure and temperature. (5) The confining pressure, pore water pressure and temperature produce stress-strain in sandstone and thus change the sandstone pore structure and permeability. The permeability evolution of sandstones varies with pore structure. The findings of this study can inform the classified grouting of deep sandstone and optimize grouting parameters.

Study of mechanical characteristics and damage mechanism of sandstone under long-term immersion

The microscopic pore structure of sandstone gradually changes under long-term immersion, resulting in dynamic changes in the mechanical and damage properties of sandstone, which brings challenges to maintain the long-term stability of underground engineering. In this paper, the evolution of pore structure and mechanical behavior of sandstones at different immersion times (0d, 3d, 30d, 90d, 180d and 360d) is studied. A series of physico-chemical experiments and uniaxial compression tests (with simultaneous acquisition of acoustic emission (AE) signals) are conducted to explore the weakening mechanism and failure mode of sandstones during long-term immersion. The results show that long-term immersion has a significant effect on the pore structure and mechanical behavior of sandstones. Various physical parameters indicate that the change in the pore structure of a sandstone with increasing immersion time can be divided into two stages, namely the swelling stage of clay minerals (saturation process) and the corrosion stage of potassium feldspar (long-term immersion process). The variation of pH value and K+ concentration in soaking solution can provide a basis for the division of pore structure stages. From the perspective of mechanical behavior, the uniaxial compressive strength (UCS) and cumulative AE counts of a sandstone decrease by 83% and 96.8% respectively after 360 d of immersion, with enhanced plastic characteristics. The macroscopic failure mode of a sandstone changes from combination of shear and tensile crack surfaces to a single shear crack surface. Based on the results of physico-chemical experiments and mechanical tests, it can be assumed that microcracks in long-term immersion sandstones are more prone to develop along weakened cementation surfaces. Under the effect of stress, corrosion pores formed by potassium feldspar provide space for the rotation and movement of quartz grains, making it more prone to shear slip. The study results enhance our understanding of weakening mechanisms at long-term immersion and provide a basis for assessing the long-term stability of underground engineering.