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The presence of internal fissures holds immense sway over the gas permeability of sustainable cement mortar, which in turn dictates the longevity and steadfastness of associated edifices. Nevertheless, predicting the gas permeability of sustainable cement mortar that contains internal cracks poses a significant challenge due to the presence of numerous influential variables and intricate interdependent mechanisms. To solve the deficiency, this research establishes an innovative machine learning algorithm via the integration of the Mind Evolutionary Algorithm (MEA) with the Adaptive Boosting Algorithm-Back Propagation Artificial Neural Network (ABA-BPANN) ensemble algorithm to predict the gas permeability of sustainable cement mortar that contains internal cracks, based on the results of 1452 gas permeability tests. Firstly, the present study employs the MEA-tuned ABA-BPANN model as the primary tool for gas permeability prediction in cement mortar, a comparative analysis is conducted with conventional machine learning models such as Particle Swarm Optimisation Algorithm (PSO) and Genetic Algorithm (GA) optimised ABA-BPANN, MEA optimised Extreme Learning Machine (ELM), and BPANN. The efficacy of the MEA-tuned ABA-BPANN model is verified, thereby demonstrating its proficiency. In addition, the sensitivity analysis conducted with the aid of the innovative model has revealed that the gas permeability of durable cement mortar incorporating internal cracks is more profoundly affected by the dimensions and quantities of such cracks than by the stress conditions to which the mortar is subjected. Thirdly, puts forth a novel machine-learning model, which enables the establishment of an analytical formula for the precise prediction of gas permeability. This formula can be employed by individuals who lack familiarity with machine learning skills. The proposed model, namely the MEA-optimised ABA-BPANN algorithm, exhibits significant potential in accurately estimating the gas permeability of sustainable cement mortar that contains internal cracks in varying stress environments. The study highlights the algorithm's ability to offer essential insights for designing related structures. [ABSTRACT FROM AUTHOR]

The plastic waste has huge potential being used as the aggregate of concrete but the premise requires to have a sound understanding about the seepage mechanical properties of the light-weight concrete. In this study, initially, the physical experiment was conducted to measure the permeability and porosity of light-weight concrete with various amount of plastic waste aggregate (PWA) in different confining pressure and pore pressure. Based on the test results, a database was established. On this basis, a unique machine learning method was developed via combining the Logic Development Algorithm (LDA) with the ensemble technique of Adaptive Boosting Algorithm (BA) and Artificial Neural Network (ANN), which is the first attempt to utilize this model for estimating the permeability of PWA cement mortar. The research outcomes indicate, the corrected permeability and porosity of PWA cement mortar rises with the increase of PWA content, and the changing magnitude is more significant in high confining pressure; The corrected permeability and porosity of cement mortar with a higher content of PWA is more sensitive to the variation of confining pressure; The BA-ANN model optimised by LDA outperforms than the conventional machine learning models in terms of predictive accuracy and efficiency when assessing the permeability of PWA cement mortar; The sensitivity analysis by using the novel model reveals that confining pressure, PWA content and porosity have a relatively high impact on the permeability of PWA cement mortar, while the impact of pore pressure is relatively small. The study findings can provide guidance for the permeability and porosity design of relevant PWA concrete engineering facilities. • Permeability and porosity tests on plastic waste aggregate concrete were conducted. • A unique machine learning method was developed based on the experimental results. • Permeability of the concrete was preciously estimated by using the developed model. [ABSTRACT FROM AUTHOR]

In this paper, the permeability and porosity of self-prepared artificial columnar jointed rock masses (CJRM) with different columnar dip angles under different pore pressures during cyclic loading-unloading of confining pressure were measured. The experimental results indicate that the gas permeability of the artificial CJRM gradually decreases with the rise of pore pressure due to the existence of Klinkenberg effect, and Klinkenberg effect gradually decreases with the rise of columnar dip angle. The existence of it improves significantly the intrinsic permeability. Besides, the intrinsic permeability and porosity of artificial CJRM are more sensitive to the first loading than that of the intact cement mortar specimen. The permanent deformation of pores in the specimens mainly appears in the first cycle, and the subsequent cycles have smaller effects on the intrinsic permeability and porosity. The permanent deformation results in the intrinsic permeability, and porosity in the loading process is always higher than those in the unloading process. The intrinsic permeability gradually increases with the growth of columnar dip angle, exhibiting obvious permeability anisotropy. Under high confining pressure, the permeability anisotropy of artificial CJRM is less than that under low confining pressure. Meanwhile, under the same confining pressure, during the repeated loading-unloading cycles, the permeability anisotropy decreases gradually. The existence of a representative element volume (REV) for CJRM is verified; thus, the equivalent continuum media model can be utilized to analyse the seepage characteristics of CJRM. [ABSTRACT FROM AUTHOR]

In this paper, a method is proposed to prepare rock-like materials with different thicknesses of hidden joints. Then, permeability and porosity of the self-prepared jointed specimens under different pore pressures during confining pressure loading and unloading are measured. The experimental results indicate that the gas permeability of the jointed specimens gradually decreases with the rise of pore pressure due to the existence of Klinkenberg effect, and Klinkenberg effect gradually decreases with the rise of hidden joint thickness. As the main seepage channels, hidden joints govern the seepage characteristics, and due to the existence of hidden joints, the intrinsic permeability is improved significantly. Besides, due to the existence of hidden joints, the intrinsic permeability and porosity are more sensitive to confining pressure loading than that of the intact specimen, and the sensitivity increases with the rise of hidden joint thickness. During confining pressure loading, there is a permanent deformation of the hidden joints and pores in the specimens, which results in both the intrinsic permeability and porosity being always lower than those in the loading process. Meanwhile, the permanent deformation rises with the increases of hidden joint thickness, which leads to the increases of gap of intrinsic permeability and porosity under loading and unloading processes. Additionally, after comparison of the fitting results, the sub-cubic law can reflect the relationship between flow rate and the thickness of non-persistent joints better than the cubic law. [ABSTRACT FROM AUTHOR]

• A method for preparing cement mortar with diverse numbers of internal cracks was proposed. • Permeability and porosity for the samples under diverse stress states were measured. • The stress-dependent permeability and porosity for the prepared samples was analysed. In this paper, gas permeability and porosity for the prepared cement mortar samples with diverse numbers of internal cracks under diverse pore pressure during confining pressure loading and unloading was measured. According to the outcomes of experiments, the following findings were obtained: Klinkenberg correction is appliable to the modification on gas permeability of cement mortar samples containing different number of internal cracks to obtain the intrinsic permeability, with the quadratic equation (Coefficient of Determination R2 is above than 0.92) having a better performance than that of Klinkenberg equation; Owing to the increase in the equivalent pore radius of seepage passages, Klinkenberg Effect of the cement mortar samples reduces when the number of internal cracks rises. When the number of internal cracks rises from 0 to 12, the slippage factor decreases over 90 %; When the number of internal cracks is high, the same changing extent in the number of internal cracks can lead to higher influence on the intrinsic permeability than that when the number of internal cracks is low. The variation magnitude of intrinsic permeability when the number of internal cracks increases from 6 to 12 is around 3–10 times higher than that when the number goes up from 0 to 6; When confining pressure increases, the sensitivity of intrinsic permeability to the changes in confining pressure reduces. The variation magnitude of intrinsic permeability when confining pressure is loaded from 0 MPa to 25 MPa is 5–10 times higher than that when confining pressure is loaded from 25 MPa to 45 MPa; Owing to the permanent deformation of pores and cracks, under the same confining pressure, the intrinsic permeability and porosity during the unloading stage are less than those during the loading stage, respectively; The sub-cubic law (R2 is above than0.90) is able to describe gas seepage in cement mortar specimens with different number of internal cracks more precisely compared to the cubic law. [ABSTRACT FROM AUTHOR]

Monzonitic granite is a low-permeability rock. Monzonitic granite formations are ideal for underground storage of oil due to their low permeability and high mechanical strength. In this study, a series of coupled hydromechanical triaxial tests are carried out using monzonitic granite specimens. The influence of confining and fluid pressures on stress, strain, and permeability is investigated. Failure characteristics under different confining and fluid pressures are discussed based on the analysis of macro fracture planes and micro scanning electron microscopy (SEM). The test results show that the change of permeability with stress and strain reflects the deformation stages of compaction, compression, crack propagation, coalesce, and failure of cracks. Due to the low porosity, the change of permeability is small in the initial phases of compaction and compression, whereas there is a significant increase in permeability when new cracks start to develop and coalesce. Confining pressures have a significant impact on the strength and permeability, particularly the crack damage stress of the rock. Compared with confining pressure, the effect of fluid pressure on rock strength and crack damage stress is small. For the monzonitic granite specimens tested, changing the confining pressure results in different failure modes, whereas the fluid pressure has a relatively small effect on the failure modes. [ABSTRACT FROM AUTHOR]

In this paper, compact sandstone with different moisture saturation from 0% to 73.60% was prepared. Subsequently, gas permeability and porosity of the prepared rock specimens under different pore pressure during confining pressure loading and unloading was measured. The experimental results indicate that, for rock specimen with moisture saturation 0%, 9.63%, 22.10%, 33.60%, and 42.30%, gas permeability rises with the increase of pore pressure due to Klinkenberg Effect, while for rock specimens with moisture saturation 54.36% and 73.60%, the opposite phenomenon was observed because the flow rate of gas has the dominant influences on the gas permeability than that of Klinkenberg Effect. The quadratic equation has better performance in describing the Klinkenberg Effect than that of Klinkenberg equation. Klinkenberg Effect enhances with the increase of moisture saturation and confining pressure, respectively, due to the decrease of equivalent pore radius for gas flow. With the rise of moisture saturation, the decreasing rate of intrinsic permeability under low moisture saturation is low than that under high moisture saturation. The intrinsic permeability of rock specimens with high moisture saturation is more sensitive to loading and unloading than that with low moisture saturation. The relationship between intrinsic permeability/porosity of rock specimens and confining pressure can be described correctly by adopting the exponential function model and power function model, respectively. Additionally, the gradual increase in moisture content in rock specimens revealed significant decrease on intrinsic permeability. This was attributed to clay swelling which contributed to blockage of seepage paths. • The quadratic equation can describe the Klinkenberg Effect of compact sandstone. • Klinkenberg Effect enhances with the increase of moisture saturation and confining pressure, respectively. [ABSTRACT FROM AUTHOR]

• A novel approach is used to obtain the relationships of the porosity and the permeability of low-permeability rock. • The logarithmic bulk modulus was obtained from the gas permeability experiments. • The tested parameters make the fluid-solid coupling simulation of low permeability sandstone a reality. • Numerical simulations of low-permeability sandstone are conducted based on the triaxial compression experiments. This paper proposed a novel approach, which combines an analytical model and a formula fitting function, to determine the hydromechanical relationships between the porosity and the permeability of low-permeability sandstone (LPS) that is further applied for the hydromechanical modelling. Then, several gas permeability experiments are conducted to measure the permeability and porosity of LPS under different confinement pressure. In conjunction with the Finite Element Method, the fracture propagation processes of LPS, which take physical triaxial experiments as reference experiments, are simulated by the considering hydromechanics. The results demonstrate that the absolute permeability is exponentially related to the porosity of LPS. Additionally, the porous media nonlinear elastic model and the modified Drucker–Prager cap plasticity model can accurately describe the deformation process of LPS. The simulation results correlate well with the experimental counterparts while being less scattered than the experimental data. This demonstrates the effectiveness of the proposed method in characterizing fracture properties of LPS considering hydromechanics. [ABSTRACT FROM AUTHOR]