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  • Article
    Abstract: Ore production is usually affected by multiple influencing inputs at open-pit mines. Nevertheless, the complex nonlinear relationships between these inputs and ore production remain unclear. This becomes even more challenging when training data (e.g. truck haulage information and weather conditions) are massive. In machine learning (ML) algorithms, deep neural network (DNN) is a superior method for processing nonline

    Ore production is usually affected by multiple influencing inputs at open-pit mines. Nevertheless, the complex nonlinear relationships between these inputs and ore production remain unclear. This becomes even more challenging when training data (e.g. truck haulage information and weather conditions) are massive. In machine learning (ML) algorithms, deep neural network (DNN) is a superior method for processing nonlinear and massive data by adjusting the amount of neurons and hidden layers. This study adopted DNN to forecast ore production using truck haulage information and weather conditions at open-pit mines as training data. Before the prediction models were built, principal component analysis (PCA) was employed to reduce the data dimensionality and eliminate the multicollinearity among highly correlated input variables. To verify the superiority of DNN, three ANNs containing only one hidden layer and six traditional ML models were established as benchmark models. The DNN model with multiple hidden layers performed better than the ANN models with a single hidden layer. The DNN model outperformed the extensively applied benchmark models in predicting ore production. This can provide engineers and researchers with an accurate method to forecast ore production, which helps make sound budgetary decisions and mine planning at open-pit mines.

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  • Article

    Sliding behaviors of the trapezoidal roof rock block under a lateral dynamic disturbance

    Feng Dai, Wancheng Zhu, Min Ren, Shunchuan Wu, Leilei Niu

    2024, 16(3): 741-760. doi:10.1016/j.jrmge.2023.10.008

    Abstract: The surrounding rock of underground space is always affected by external dynamic disturbance from the side position, such as blasting vibration from a stope at the same level or seismic waves from adjacent strata. A series of laboratory tests, numerical simulations and theoretical analyses were carried out in this study to disclose the sliding mechanism of roof rock blocks under lateral disturbance. Firstly, the expe

    The surrounding rock of underground space is always affected by external dynamic disturbance from the side position, such as blasting vibration from a stope at the same level or seismic waves from adjacent strata. A series of laboratory tests, numerical simulations and theoretical analyses were carried out in this study to disclose the sliding mechanism of roof rock blocks under lateral disturbance. Firstly, the experiments on trapezoidal key block under various clamping loads and disturbance were conducted, followed by numerical simulations using the fast Lagrangian analysis of continua (FLAC3D). Then, based on the conventional wave propagation model and the classical shear-slip constitutive model, a theoretical model was proposed to capture the relative displacement between blocks and the sliding displacement of the key block. The results indicate that the sliding displacement of the key block increased linearly with the disturbance energy and decreased exponentially with the clamping load when the key block was disturbed to slide (without instability). Meanwhile, when the key block was disturbed to fall, two types of instability process may appear as immediate type or delayed type. In addition, the propagation of stress waves in the block system exhibited obvious low-velocity and low-frequency characteristics, resulting in the friction reduction effect appearing at the contact interface, which is the essential reason for the sliding of rock blocks. The results can be applied to practical underground engineering and provide valuable guidance for the early detection and prevention of rock-falling disasters.

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  • Article
    Abstract: Accurately picking P- and S-wave arrivals of microseismic (MS) signals in real-time directly influences the early warning of rock mass failure. A common contradiction between accuracy and computation exists in the current arrival picking methods. Thus, a real-time arrival picking method of MS signals is constructed based on a convolutional-recurrent neural network (CRNN). This method fully utilizes the advantages of

    Accurately picking P- and S-wave arrivals of microseismic (MS) signals in real-time directly influences the early warning of rock mass failure. A common contradiction between accuracy and computation exists in the current arrival picking methods. Thus, a real-time arrival picking method of MS signals is constructed based on a convolutional-recurrent neural network (CRNN). This method fully utilizes the advantages of convolutional layers and gated recurrent units (GRU) in extracting short- and long-term features, in order to create a precise and lightweight arrival picking structure. Then, the synthetic signals with field noises are used to evaluate the hyperparameters of the CRNN model and obtain an optimal CRNN model. The actual operation on various devices indicates that compared with the U-Net method, the CRNN method achieves faster arrival picking with less performance consumption. An application of large underground caverns in the Yebatan hydropower station (YBT) project shows that compared with the short-term average/long-term average (STA/LTA), Akaike information criterion (AIC) and U-Net methods, the CRNN method has the highest accuracy within four sampling points, which is 87.44% for P-wave and 91.29% for S-wave, respectively. The sum of mean absolute errors (MAESUM) of the CRNN method is 4.22 sampling points, which is lower than that of the other methods. Among the four methods, the MS sources location calculated based on the CRNN method shows the best consistency with the actual failure, which occurs at the junction of the shaft and the second gallery. Thus, the proposed method can pick up P- and S-arrival accurately and rapidly, providing a reference for rock failure analysis and evaluation in engineering applications.

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  • Article

    Failure characterization of fully grouted rock bolts under triaxial testing

    Hadi Nourizadeh, Ali Mirzaghorbanali, Mehdi Serati, Elamin Mutaz, Kevin McDougall, Naj Aziz

    2024, 16(3): 778-789. doi:10.1016/j.jrmge.2023.08.013

    Abstract: Confining stresses serve as a pivotal determinant in shaping the behavior of grouted rock bolts. Nonetheless, prior investigations have oversimplified the three-dimensional stress state, primarily assuming hydrostatic stress conditions. Under these conditions, it is assumed that the intermediate principal stress (σ2) equals the minimum principal stress (σ3). This assumption overlooks the potential variati

    Confining stresses serve as a pivotal determinant in shaping the behavior of grouted rock bolts. Nonetheless, prior investigations have oversimplified the three-dimensional stress state, primarily assuming hydrostatic stress conditions. Under these conditions, it is assumed that the intermediate principal stress (σ2) equals the minimum principal stress (σ3). This assumption overlooks the potential variations in magnitudes of in situ stress conditions along all three directions near an underground opening where a rock bolt is installed. In this study, a series of push tests was meticulously conducted under triaxial conditions. These tests involved applying non-uniform confining stresses (σ2 ≠ σ3) to cubic specimens, aiming to unveil the previously overlooked influence of intermediate principal stresses on the strength properties of rock bolts. The results show that as the confining stresses increase from zero to higher levels, the pre-failure behavior changes from linear to nonlinear forms, resulting in an increase in initial stiffness from 2.08 kN/mm to 32.51 kN/mm. The load-displacement curves further illuminate distinct post-failure behavior at elevated levels of confining stresses, characterized by enhanced stiffness. Notably, the peak load capacity ranged from 27.9 kN to 46.5 kN as confining stresses advanced from σ2 = σ3 = 0 to σ2 = 20 MPa and σ3 = 10 MPa. Additionally, the outcomes highlight an influence of confining stress on the lateral deformation of samples. Lower levels of confinement prompt overall dilation in lateral deformation, while higher confinements maintain a state of shrinkage. Furthermore, diverse failure modes have been identified, intricately tied to the arrangement of confining stresses. Lower confinements tend to induce a splitting mode of failure, whereas higher loads bring about a shift towards a pure interfacial shear-off and shear-crushed failure mechanism.

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  • Article

    Nonlinear constitutive models of rock structural plane and their applications

    Wenlin Feng, Shuangjian Niu, Chunsheng Qiao, Dujian Zou

    2024, 16(3): 790-806. doi:10.1016/j.jrmge.2023.11.021

    Abstract: Structural planes play an important role in controlling the stability of rock engineering, and the influence of structural planes should be considered in the design and construction process of rock engineering. In this paper, mechanical properties, constitutive theory, and numerical application of structural plane are studied by a combination method of laboratory tests, theoretical derivation, and program development

    Structural planes play an important role in controlling the stability of rock engineering, and the influence of structural planes should be considered in the design and construction process of rock engineering. In this paper, mechanical properties, constitutive theory, and numerical application of structural plane are studied by a combination method of laboratory tests, theoretical derivation, and program development. The test results reveal the change laws of various mechanical parameters under different roughness and normal stress. At the pre-peak stage, a non-stationary model of shear stiffness is established, and three-dimensional empirical prediction models for initial shear stiffness and residual stage roughness are proposed. The nonlinear constitutive models are established based on elasto-plastic mechanics, and the algorithms of the models are developed based on the return mapping algorithm. According to a large number of statistical analysis results, empirical prediction models are proposed for model parameters expressed by structural plane characteristic parameters. Finally, the discrete element method (DEM) is chosen to embed the constitutive models for practical application. The running programs of the constitutive models have been compiled into the discrete element model library. The comparison results between the proposed model and the Mohr-Coulomb slip model show that the proposed model can better describe nonlinear changes at different stages, and the predicted shear strength, peak strain and shear stiffness are closer to the test results. The research results of the paper are conducive to the accurate evaluation of structural plane in rock engineering.

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  • Article

    Mechanical behaviors of backfill-rock composites: Physical shear test and back-analysis

    Jie Xin, Quan Jiang, Fengqiang Gong, Lang Liu, Chang Liu, Qiang Liu, Yao Yang, Pengfei Chen

    2024, 16(3): 807-827. doi:10.1016/j.jrmge.2023.08.012

    Abstract: The shear behavior of backfill-rock composites is crucial for mine safety and the management of surface subsidence. For exposing the shear failure mechanism of backfill-rock composites, we conducted shear tests on backfill-rock composites under three constant normal loads, compared with the unfilled rock. To investigate the macro- and meso-failure characteristics of the samples in the shear tests, the cracking behavi

    The shear behavior of backfill-rock composites is crucial for mine safety and the management of surface subsidence. For exposing the shear failure mechanism of backfill-rock composites, we conducted shear tests on backfill-rock composites under three constant normal loads, compared with the unfilled rock. To investigate the macro- and meso-failure characteristics of the samples in the shear tests, the cracking behavior of samples was recorded by a high-speed camera and acoustic emission monitoring. In parallel with the experimental test, the numerical models of backfill-rock composites and unfilled rock were established using the discrete element method to analyze the continuous-discontinuous shearing process. Based on the damage mechanics and statistics, a novel shear constitutive model was proposed to describe mechanical behavior. The results show that backfill-rock composites had a special bimodal phenomenon of shearing load-deformation curve, i.e. the first shearing peak corresponded to rock break and the second shearing peak induced by the broken of aeolian sand-cement/fly ash paste backfill. Moreover, the shearing characteristic curves of the backfill-rock composites could be roughly divided into four stages, i.e. the shear failure of the specimens experienced: stage I: stress concentration; stage II: crack propagation; stage III: crack coalescence; stage IV: shearing friction. The numerical simulation shows that the existence of aeolian sand-cement/fly ash paste backfill inevitably altered the coalescence type and failure mode of the specimens and had a strengthening effect on the shear strength of backfill-rock composites. Based on damage mechanics and statistics, a shear constitutive model was proposed to describe the shear fracture characteristics of specimens, especially the bimodal phenomenon. Finally, the micro- and meso-mechanisms of shear failure were discussed by combining the micro-test and numerical results. The research can advance the better understanding of the shear behavior of backfill-rock composites and contribute to the safety of mining engineering.

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  • Article

    Slope stability of reclaimed coal mines through a new water filling index

    Antonios Mikroutsikos, Alexandros I. Theocharis, Nikolaos C. Koukouzas, Ioannis E. Zevgolis

    2024, 16(3): 828-839. doi:10.1016/j.jrmge.2023.08.022

    Abstract: A common reclamation practice for closed coal surface mines is filling them with water to form pit lakes. The creation and sustainability of these lakes are significantly affected by the stability of the corresponding slopes. The present study provides a general framework for analyzing the water filling's effect on slope stability based on a new water filling index, which can indirectly consider the factors affecting

    A common reclamation practice for closed coal surface mines is filling them with water to form pit lakes. The creation and sustainability of these lakes are significantly affected by the stability of the corresponding slopes. The present study provides a general framework for analyzing the water filling's effect on slope stability based on a new water filling index, which can indirectly consider the factors affecting the process and efficiently quantify the filling speed's influence. The assumptions of the proposed approach are thoroughly discussed, and the range of the water filling index is identified. Furthermore, the safety factor is calculated using the finite element method with the shear strength reduction technique during the filling process for various conditions (soil properties, slope geometry, hydraulic conditions, and water filling speed). Results are presented as normalized stability charts for practical use. During the water filling, the stability gradually decreases until the reservoir reaches a critical level of 10%–40% of the total height; it then increases to even more stable conditions than the initial one. Overall, the present analysis allows for the preliminary stability evaluation of a coal mine during the formation of a pit lake and the appropriate quantification of the water filling's effect.

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  • Article
    Abstract: Traditional global sensitivity analysis (GSA) neglects the epistemic uncertainties associated with the probabilistic characteristics (i.e. type of distribution type and its parameters) of input rock properties emanating due to the small size of datasets while mapping the relative importance of properties to the model response. This paper proposes an augmented Bayesian multi-model inference (BMMI) coupled with GSA met

    Traditional global sensitivity analysis (GSA) neglects the epistemic uncertainties associated with the probabilistic characteristics (i.e. type of distribution type and its parameters) of input rock properties emanating due to the small size of datasets while mapping the relative importance of properties to the model response. This paper proposes an augmented Bayesian multi-model inference (BMMI) coupled with GSA methodology (BMMI-GSA) to address this issue by estimating the imprecision in the moment-independent sensitivity indices of rock structures arising from the small size of input data. The methodology employs BMMI to quantify the epistemic uncertainties associated with model type and parameters of input properties. The estimated uncertainties are propagated in estimating imprecision in moment-independent Borgonovo's indices by employing a reweighting approach on candidate probabilistic models. The proposed methodology is showcased for a rock slope prone to stress-controlled failure in the Himalayan region of India. The proposed methodology was superior to the conventional GSA (neglects all epistemic uncertainties) and Bayesian coupled GSA (B-GSA) (neglects model uncertainty) due to its capability to incorporate the uncertainties in both model type and parameters of properties. Imprecise Borgonovo's indices estimated via proposed methodology provide the confidence intervals of the sensitivity indices instead of their fixed-point estimates, which makes the user more informed in the data collection efforts. Analyses performed with the varying sample sizes suggested that the uncertainties in sensitivity indices reduce significantly with the increasing sample sizes. The accurate importance ranking of properties was only possible via samples of large sizes. Further, the impact of the prior knowledge in terms of prior ranges and distributions was significant; hence, any related assumption should be made carefully.

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  • Article
    Abstract: The anisotropic mechanical behavior of rocks under high-stress and high-temperature coupled conditions is crucial for analyzing the stability of surrounding rocks in deep underground engineering. This paper is devoted to studying the anisotropic strength, deformation and failure behavior of gneiss granite from the deep boreholes of a railway tunnel that suffers from high tectonic stress and ground temperature in the

    The anisotropic mechanical behavior of rocks under high-stress and high-temperature coupled conditions is crucial for analyzing the stability of surrounding rocks in deep underground engineering. This paper is devoted to studying the anisotropic strength, deformation and failure behavior of gneiss granite from the deep boreholes of a railway tunnel that suffers from high tectonic stress and ground temperature in the eastern tectonic knot in the Tibet Plateau. High-temperature true triaxial compression tests are performed on the samples using a self-developed testing device with five different loading directions and three temperature values that are representative of the geological conditions of the deep underground tunnels in the region. Effect of temperature and loading direction on the strength, elastic modulus, Poisson's ratio, and failure mode are analyzed. The method for quantitative identification of anisotropic failure is also proposed. The anisotropic mechanical behaviors of the gneiss granite are very sensitive to the changes in loading direction and temperature under true triaxial compression, and the high temperature seems to weaken the inherent anisotropy and stress-induced deformation anisotropy. The strength and deformation show obvious thermal degradation at 200 °C due to the weakening of friction between failure surfaces and the transition of the failure pattern in rock grains. In the range of 25 °C–200 °C, the failure is mainly governed by the loading direction due to the inherent anisotropy. This study is helpful to the in-depth understanding of the thermal-mechanical behavior of anisotropic rocks in deep underground projects.

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  • Abstract: The aim of this study is to investigate the impacts of the sampling strategy of landslide and non-landslide on the performance of landslide susceptibility assessment (LSA). The study area is the Feiyun catchment in Wenzhou City, Southeast China. Two types of landslides samples, combined with seven non-landslide sampling strategies, resulted in a total of 14 scenarios. The corresponding landslide susceptibility map (L

    The aim of this study is to investigate the impacts of the sampling strategy of landslide and non-landslide on the performance of landslide susceptibility assessment (LSA). The study area is the Feiyun catchment in Wenzhou City, Southeast China. Two types of landslides samples, combined with seven non-landslide sampling strategies, resulted in a total of 14 scenarios. The corresponding landslide susceptibility map (LSM) for each scenario was generated using the random forest model. The receiver operating characteristic (ROC) curve and statistical indicators were calculated and used to assess the impact of the dataset sampling strategy. The results showed that higher accuracies were achieved when using the landslide core as positive samples, combined with non-landslide sampling from the very low zone or buffer zone. The results reveal the influence of landslide and non-landslide sampling strategies on the accuracy of LSA, which provides a reference for subsequent researchers aiming to obtain a more reasonable LSM.

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  • Article

    Uncertainty quantification of inverse analysis for geomaterials using probabilistic programming

    Hongbo Zhao, Shaojun Li, Xiaoyu Zang, Xinyi Liu, Lin Zhang, Jiaolong Ren

    2024, 16(3): 895-908. doi:10.1016/j.jrmge.2023.07.014

    Abstract: Uncertainty is an essentially challenging for safe construction and long-term stability of geotechnical engineering. The inverse analysis is commonly utilized to determine the physico-mechanical parameters. However, conventional inverse analysis cannot deal with uncertainty in geotechnical and geological systems. In this study, a framework was developed to evaluate and quantify uncertainty in inverse analysis based o

    Uncertainty is an essentially challenging for safe construction and long-term stability of geotechnical engineering. The inverse analysis is commonly utilized to determine the physico-mechanical parameters. However, conventional inverse analysis cannot deal with uncertainty in geotechnical and geological systems. In this study, a framework was developed to evaluate and quantify uncertainty in inverse analysis based on the reduced-order model (ROM) and probabilistic programming. The ROM was utilized to capture the mechanical and deformation properties of surrounding rock mass in geomechanical problems. Probabilistic programming was employed to evaluate uncertainty during construction in geotechnical engineering. A circular tunnel was then used to illustrate the proposed framework using analytical and numerical solution. The results show that the geomechanical parameters and associated uncertainty can be properly obtained and the proposed framework can capture the mechanical behaviors under uncertainty. Then, a slope case was employed to demonstrate the performance of the developed framework. The results prove that the proposed framework provides a scientific, feasible, and effective tool to characterize the properties and physical mechanism of geomaterials under uncertainty in geotechnical engineering problems.

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  • Article

    A method to predict rockburst using temporal trend test and its application

    Yarong Xue, Zhenlei Li, Dazhao Song, Xueqiu He, Honglei Wang, Chao Zhou, Jianqiang Chen, Aleksei Sobolev

    2024, 16(3): 909-923. doi:10.1016/j.jrmge.2023.07.017

    Abstract: Rockbursts have become a significant hazard in underground mining, underscoring the need for a robust early warning model to ensure safety management. This study presents a novel approach for rockburst prediction, integrating the Mann-Kendall trend test (MKT) and multi-indices fusion to enable real-time and quantitative assessment of rockburst hazards. The methodology employed in this study involves the development o

    Rockbursts have become a significant hazard in underground mining, underscoring the need for a robust early warning model to ensure safety management. This study presents a novel approach for rockburst prediction, integrating the Mann-Kendall trend test (MKT) and multi-indices fusion to enable real-time and quantitative assessment of rockburst hazards. The methodology employed in this study involves the development of a comprehensive precursory index library for rockbursts. The MKT is then applied to analyze the real-time trend of each index, with adherence to rockburst characterization laws serving as the warning criterion. By employing a confusion matrix, the warning effectiveness of each index is assessed, enabling index preference determination. Ultimately, the integrated rockburst hazard index Q is derived through data fusion. The results demonstrate that the proposed model achieves a warning effectiveness of 0.563 for Q, surpassing the performance of any individual index. Moreover, the model's adaptability and scalability are enhanced through periodic updates driven by actual field monitoring data, making it suitable for complex underground working environments. By providing an efficient and accurate basis for decision-making, the proposed model holds great potential for the prevention and control of rockbursts. It offers a valuable tool for enhancing safety measures in underground mining operations.

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  • Article
    Abstract: The aperture of natural rock fractures significantly affects the deformation and strength properties of rock masses, as well as the hydrodynamic properties of fractured rock masses. The conventional measurement methods are inadequate for collecting data on high-steep rock slopes in complex mountainous regions. This study establishes a high-resolution three-dimensional model of a rock slope using unmanned aerial vehic

    The aperture of natural rock fractures significantly affects the deformation and strength properties of rock masses, as well as the hydrodynamic properties of fractured rock masses. The conventional measurement methods are inadequate for collecting data on high-steep rock slopes in complex mountainous regions. This study establishes a high-resolution three-dimensional model of a rock slope using unmanned aerial vehicle (UAV) multi-angle nap-of-the-object photogrammetry to obtain edge feature points of fractures. Fracture opening morphology is characterized using coordinate projection and transformation. Fracture central axis is determined using vertical measuring lines, allowing for the interpretation of aperture of adaptive fracture shape. The feasibility and reliability of the new method are verified at a construction site of a railway in southeast Tibet, China. The study shows that the fracture aperture has a significant interval effect and size effect. The optimal sampling length for fractures is approximately 0.5–1 m, and the optimal aperture interpretation results can be achieved when the measuring line spacing is 1% of the sampling length. Tensile fractures in the study area generally have larger apertures than shear fractures, and their tendency to increase with slope height is also greater than that of shear fractures. The aperture of tensile fractures is generally positively correlated with their trace length, while the correlation between the aperture of shear fractures and their trace length appears to be weak. Fractures of different orientations exhibit certain differences in their distribution of aperture, but generally follow the forms of normal, log-normal, and gamma distributions. This study provides essential data support for rock and slope stability evaluation, which is of significant practical importance.

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  • Article

    Impact of effective stress on permeability for carbonate fractured-vuggy rocks

    Ke Sun, Huiqing Liu, Juliana Y. Leung, Jing Wang, Yabin Feng, Renjie Liu, Zhijiang Kang, Yun Zhang

    2024, 16(3): 942-960. doi:10.1016/j.jrmge.2023.04.007

    Abstract: To gain insight into the flow mechanisms and stress sensitivity for fractured-vuggy reservoirs, several core models with different structural characteristics were designed and fabricated to investigate the impact of effective stress on permeability for carbonate fractured-vuggy rocks (CFVR). It shows that the permeability performance curves under different pore and confining pressures (i.e. altered stress conditions)

    To gain insight into the flow mechanisms and stress sensitivity for fractured-vuggy reservoirs, several core models with different structural characteristics were designed and fabricated to investigate the impact of effective stress on permeability for carbonate fractured-vuggy rocks (CFVR). It shows that the permeability performance curves under different pore and confining pressures (i.e. altered stress conditions) for the fractured core models and the vuggy core models have similar change patterns. The ranges of permeability variation are significantly wider at high pore pressures, indicating that permeability reduction is the most significant during the early stage of development for fractured-vuggy reservoirs. Since each obtained effective stress coefficient for permeability (ESCP) varies with the changes in confining pressure and pore pressure, the effective stresses for permeability of four representative CFVR show obvious nonlinear characteristics, and the variation ranges of ESCP are all between 0 and 1. Meanwhile, a comprehensive ESCP mathematical model considering triple media, including matrix pores, fractures, and dissolved vugs, was proposed. It is proved theoretically that the ESCP of CFVR generally varies between 0 and 1. Additionally, the regression results showed that the power model ranked highest among the four empirical models mainly applied in stress sensitivity characterization, followed by the logarithmic model, exponential model, and binomial model. The concept of “permeability decline rate” was introduced to better evaluate the stress sensitivity performance for CFVR, in which the one-fracture rock is the strongest, followed by the fracture-vug rock and two-horizontal-fracture rock; the through-hole rock is the weakest. In general, this study provides a theoretical basis to guide the design of development and adjustment programs for carbonate fractured-vuggy reservoirs.

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  • Article

    A process-oriented approach for identifying potential landslides considering time-dependent behaviors beyond geomorphological features

    Xiang Sun, Guoqing Chen, Xing Yang, Zhengxuan Xu, Jingxi Yang, Zhiheng Lin, Yunpeng Liu

    2024, 16(3): 961-978. doi:10.1016/j.jrmge.2023.05.014

    Abstract: Geomorphological features are commonly used to identify potential landslides. Nevertheless, overemphasis on these features could lead to misjudgment. This research proposes a process-oriented approach for potential landslide identification that considers time-dependent behaviors. The method integrates comprehensive remote sensing and geological analysis to qualitatively assess slope stability, and employs numerical a

    Geomorphological features are commonly used to identify potential landslides. Nevertheless, overemphasis on these features could lead to misjudgment. This research proposes a process-oriented approach for potential landslide identification that considers time-dependent behaviors. The method integrates comprehensive remote sensing and geological analysis to qualitatively assess slope stability, and employs numerical analysis to quantitatively calculate aging stability. Specifically, a time-dependent stability calculation method for anticlinal slopes is developed and implemented in discrete element software, incorporating time-dependent mechanical and strength reduction calculations. By considering the time-dependent evolution of slopes, this method highlights the importance of both geomorphological features and time-dependent behaviors in landslide identification. This method has been applied to the Jiarishan slope (JRS) on the Qinghai-Tibet Plateau as a case study. The results show that the JRS, despite having landslide geomorphology, is a stable slope, highlighting the risk of misjudgment when relying solely on geomorphological features. This work provides insights into the geomorphological characterization and evolution history of the JRS and offers valuable guidance for studying slopes with similar landslide geomorphology. Furthermore, the process-oriented method incorporating time-dependent evolution provides a means to evaluate potential landslides, reducing misjudgment due to excessive reliance on geomorphological features.

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  • Article

    Effects of thawing-induced softening on fracture behaviors of frozen rock

    Ting Wang, Hailiang Jia, Qiang Sun, Xianjun Tan, Liyun Tang

    2024, 16(3): 979-989. doi:10.1016/j.jrmge.2023.07.016

    Abstract: Due to the presence of ice and unfrozen water in pores of frozen rock, the rock fracture behaviors are susceptible to temperature. In this study, the potential thawing-induced softening effects on the fracture behaviors of frozen rock is evaluated by testing the tension fracture toughness (KIC) of frozen rock at different temperatures (i.e. −20 °C, −15 °C, −12 °C, −10 °C, &minu

    Due to the presence of ice and unfrozen water in pores of frozen rock, the rock fracture behaviors are susceptible to temperature. In this study, the potential thawing-induced softening effects on the fracture behaviors of frozen rock is evaluated by testing the tension fracture toughness (KIC) of frozen rock at different temperatures (i.e. −20 °C, −15 °C, −12 °C, −10 °C, −8 °C, −6 °C, −4 °C, −2 °C, and 0 °C). Acoustic emission (AE) and digital image correlation (DIC) methods are utilized to analyze the microcrack propagation during fracturing. The melting of pore ice is measured using nuclear magnetic resonance (NMR) method. The results indicate that: (1) The KIC of frozen rock decreases moderately between −20 °C and −4 °C, and rapidly between −4 °C and 0 °C. (2) At −20 °C to −4 °C, the fracturing process, deduced from the DIC results at the notch tip, exhibits three stages: elastic deformation, microcrack propagation and microcrack coalescence. However, at −4 °C–0 °C, only the latter two stages are observed. (3) At −4 °C–0 °C, the AE activities during fracturing are less than that at −20 °C to −4 °C, while more small events are reported. (4) The NMR results demonstrate a reverse variation trend in pore ice content with increasing temperature, that is, a moderate decrease is followed by a sharp decrease and −4 °C is exactly the critical temperature. Next, we interpret the thawing-induced softening effect by linking the evolution in microscopic structure of frozen rock with its macroscopic fracture behaviors as follow: from −20 °C to −4 °C, the thickening of the unfrozen water film diminishes the cementation strength between ice and rock skeleton, leading to the decrease in fracture parameters. From −4 °C to 0 °C, the cementation effect of ice almost vanishes, and the filling effect of pore ice is reduced significantly, which facilitates microcrack propagation and thus the easier fracture of frozen rocks.

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  • Article

    Soil disturbance evaluation of soft clay based on stress-normalized small-strain stiffness

    Yanguo Zhou, Yu Tian, Junneng Ye, Xuecheng Bian, Yunmin Chen

    2024, 16(3): 990-999. doi:10.1016/j.jrmge.2023.08.019

    Abstract: Soil disturbance includes the change of stress state and the damage of soil structure. The field testing indices reflect the combined effect of both changes and it is difficult to identify the soil structure disturbance directly from these indices. In the present study, the small-strain shear modulus is used to characterize soil structure disturbance by normalizing the effective stress and void ratio based on Hardin

    Soil disturbance includes the change of stress state and the damage of soil structure. The field testing indices reflect the combined effect of both changes and it is difficult to identify the soil structure disturbance directly from these indices. In the present study, the small-strain shear modulus is used to characterize soil structure disturbance by normalizing the effective stress and void ratio based on Hardin equation. The procedure for evaluating soil sampling disturbance in the field and the further disturbance during the subsequent consolidation process in laboratory test is proposed, and then validated by a case study of soft clay ground. Downhole seismic testing in the field, portable piezoelectric bender elements for the drilled sample and bender elements in triaxial apparatus for the consolidated sample were used to monitor the shear wave velocity of the soil from intact to disturbed and even remolded states. It is found that soil sampling disturbance degree by conventional thin-wall sampler is about 30% according to the proposed procedure, which is slightly higher than that from the modified volume compression method proposed by Hong and Onitsuka (1998). And the additional soil disturbance induced by consolidation in laboratory could reach about 50% when the consolidation pressure is far beyond the structural yield stress, and it follows the plastic volumetric strain quite well.

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  • Article

    Dredged marine soil stabilization using magnesia cement augmented with biochar/slag

    Chikezie Chimere Onyekwena, Qi Li, Yong Wang, Ishrat Hameed Alvi, Wentao Li, Yunlu Hou, Xianwei Zhang, Min Zhang

    2024, 16(3): 1000-1017. doi:10.1016/j.jrmge.2023.05.005

    Abstract: Dredged marine soils (DMS) have poor engineering properties, which limit their usage in construction projects. This research examines the application of reactive magnesia (rMgO) containing supplementary cementitious materials (SCMs) to stabilize DMS under ambient and carbon dioxide (CO2) curing conditions. Several proprietary experimental tests were conducted to investigate the stabilized DMS. Furthermore, the carbon

    Dredged marine soils (DMS) have poor engineering properties, which limit their usage in construction projects. This research examines the application of reactive magnesia (rMgO) containing supplementary cementitious materials (SCMs) to stabilize DMS under ambient and carbon dioxide (CO2) curing conditions. Several proprietary experimental tests were conducted to investigate the stabilized DMS. Furthermore, the carbonation-induced mineralogical, thermal, and microstructural properties change of the samples were explored. The findings show that the compressive strength of the stabilized DMS fulfilled the 7-d requirement (0.7–2.1 MPa) for pavement and building foundations. Replacing rMgO with SCMs such as biochar or ground granulated blast-furnace slag (GGBS) altered the engineering properties and particle packing of the stabilized soils, thus influencing their performances. Biochar increased the porosity of the samples, facilitating higher CO2 uptake and improved ductility, while GGBS decreased porosity and increased the dry density of the samples, resulting in higher strength. The addition of SCMs also enhanced the water retention capacity and modified the pH of the samples. Microstructural analysis revealed that the hydrated magnesium carbonates precipitated in the carbonated samples provided better cementation effects than brucite formed during rMgO hydration. Moreover, incorporating SCMs reduced the overall global warming potential and energy demand of the rMgO-based systems. The biochar mixes demonstrated lower toxicity and energy consumption. Ultimately, the rMgO and biochar blend can serve as an environmentally friendly additive for soft soil stabilization and permanent fixation of significant amounts of CO2 in soils through mineral carbonation, potentially reducing environmental pollution while meeting urbanization needs.

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  • Article

    Thermo-hydro-poro-mechanical responses of a reservoir-induced landslide tracked by high-resolution fiber optic sensing nerves

    Xiao Ye, Hong-Hu Zhu, Gang Cheng, Hua-Fu Pei, Bin Shi, Luca Schenato, Alessandro Pasuto

    2024, 16(3): 1018-1032. doi:10.1016/j.jrmge.2023.04.004

    Abstract: Thermo-poro-mechanical responses along sliding zone/surface have been extensively studied. However, it has not been recognized that the potential contribution of other crucial engineering geological interfaces beyond the slip surface to progressive failure. Here, we aim to investigate the subsurface multi-physics of reservoir landslides under two extreme hydrologic conditions (i.e. wet and dry), particularly within s

    Thermo-poro-mechanical responses along sliding zone/surface have been extensively studied. However, it has not been recognized that the potential contribution of other crucial engineering geological interfaces beyond the slip surface to progressive failure. Here, we aim to investigate the subsurface multi-physics of reservoir landslides under two extreme hydrologic conditions (i.e. wet and dry), particularly within sliding masses. Based on ultra-weak fiber Bragg grating (UWFBG) technology, we employ special-purpose fiber optic sensing cables that can be implanted into boreholes as “nerves of the Earth” to collect data on soil temperature, water content, pore water pressure, and strain. The Xinpu landslide in the middle reach of the Three Gorges Reservoir Area in China was selected as a case study to establish a paradigm for in situ thermo-hydro-poro-mechanical monitoring. These UWFBG-based sensing cables were vertically buried in a 31 m-deep borehole at the foot of the landslide, with a resolution of 1 m except for the pressure sensor. We reported field measurements covering the period 2021 and 2022 and produced the spatiotemporal profiles throughout the borehole. Results show that wet years are more likely to motivate landslide motions than dry years. The annual thermally active layer of the landslide has a critical depth of roughly 9 m and might move downward in warmer years. The dynamic groundwater table is located at depths of 9–15 m, where the peaked strain undergoes a periodical response of leap and withdrawal to annual hydrometeorological cycles. These interface behaviors may support the interpretation of the contribution of reservoir regulation to slope stability, allowing us to correlate them to local damage events and potential global destabilization. This paper also offers a natural framework for interpreting thermo-hydro-poro-mechanical signatures from creeping reservoir bank slopes, which may form the basis for a landslide monitoring and early warning system.

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  • Article
    Abstract: Elastic moduli, e.g. shear modulus G and bulk modulus K, are important parameters of geotechnical materials, which are not only the indices for the evaluation of the deformation ability of soils but also the important basic parameters for the development of the constitutive models of geotechnical materials. In this study, a series of triaxial loading-unloading-reloading shear tests and isotropic loading-unloading-rel

    Elastic moduli, e.g. shear modulus G and bulk modulus K, are important parameters of geotechnical materials, which are not only the indices for the evaluation of the deformation ability of soils but also the important basic parameters for the development of the constitutive models of geotechnical materials. In this study, a series of triaxial loading-unloading-reloading shear tests and isotropic loading-unloading-reloading tests are conducted to study several typical mechanical properties of coral calcareous sand (CCS), and the void ratio evolution during loading, unloading and reloading. The test results show that the stress-strain curves during multiple unloading processes are almost parallel, and their slopes are much greater than the deformation modulus at the initial stage of loading. The relationship between the confining pressure and the volumetric strain can be defined approximately by a hyperbolic equation under the condition of monotonic loading of confining pressure. Under the condition of confining pressure unloading, the evolution of void ratio is linear in the e-lnp′ plane, and these lines are a series of almost parallel lines if there are multiple processes of unloading. Based on the experimental results, it is found that the modified Hardin formulae for the elastic modulus estimation have a significant deviation from the tested values for CCS. Based on the experimental results, it is proposed that the elastic modulus of soils should be determined by the intersection line of two spatial surfaces in the G/K-e-p'/pa space (pa: atmosphere pressure). “Ye formulation” is further proposed for the estimation of the elastic modulus of CCS. This new estimation formulation for soil elastic modulus would provide a new method to accurately describe the mechanical behavior of granular soils.

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  • Article
    Abstract: Phosphogypsum has often been used as an effective and environmentally friendly binder for partial replacement of cement, improving the engineering properties of slurries with high water content. However, the influence of phosphogypsum on the physicomechnical properties of stabilized soil subjected to wetting–drying cycles is not well understood to date. In this study, the effect of phosphogypsum on the durabili

    Phosphogypsum has often been used as an effective and environmentally friendly binder for partial replacement of cement, improving the engineering properties of slurries with high water content. However, the influence of phosphogypsum on the physicomechnical properties of stabilized soil subjected to wetting–drying cycles is not well understood to date. In this study, the effect of phosphogypsum on the durability of stabilized soil was studied by conducting a series of laboratory experiments, illustrating the changes in mass loss, pH value and unconfined compressive strength (qu) with wetting-drying cycles. The test results showed that the presence of phosphogypsum significantly restrained the mass loss in the early stage (lower than the 4th cycle), which in turn led to a higher qu of stabilized soil than that without phosphogypsum. After the 4th cycle, a sudden increase in mass loss was observed for stabilized soil with phosphogypsum, resulting in a significant drop in qu to a value lower than those without phosphogypsum at the 6th cycle. In addition, the qu of stabilized soils correlated well with the measured soil pH irrespective of phosphogypsum content for all wetting–drying tests. According to the microstructure observation via scanning electron microscope (SEM) and X-ray diffraction (XRD) tests, the mechanisms relating the sudden loss of qu for the stabilized soils with phosphogypsum after the 4th wetting-drying cycle are summarized as follows: (i) the disappearance of ettringite weakening the cementation bonding effect, (ii) the generation of a larger extent of microcrack, and (iii) a lower pH value, in comparison with the stabilized soil without phosphogypsum.

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  • Article
    Abstract: Lunar base construction is a crucial component of the lunar exploration program, and considering the dynamic characteristics of lunar soil is important for moon construction. Therefore, investigating the dynamic properties of lunar soil by establishing a constitutive relationship is critical for providing a theoretical basis for its damage evolution. In this paper, a split Hopkinson pressure bar (SHPB) device was use

    Lunar base construction is a crucial component of the lunar exploration program, and considering the dynamic characteristics of lunar soil is important for moon construction. Therefore, investigating the dynamic properties of lunar soil by establishing a constitutive relationship is critical for providing a theoretical basis for its damage evolution. In this paper, a split Hopkinson pressure bar (SHPB) device was used to perform three sets of impact tests under different pressures on a lunar soil simulant geopolymer (LSSG) with sodium silicate (Na2SiO3) contents of 1%, 3%, 5% and 7%. The dynamic stress–strain curves, failure modes, and energy variation rules of LSSG under different pressures were obtained. The equation was modified based on the ZWT viscoelastic constitutive model and was combined with the damage variable. The damage element obeys the Weibull distribution and the constitutive equation that can describe the mechanical properties of LSSG under dynamic loading was obtained. The results demonstrate that the dynamic compressive strength of LSSG has a marked strain-rate strengthening effect. Na2SiO3 has both strengthening and deterioration effects on the dynamic compressive strength of LSSG. As Na2SiO3 grows, the dynamic compressive strength of LSSG first increases and then decreases. At a fixed air pressure, 5% Na2SiO3 had the largest dynamic compressive strength, the largest incident energy, the smallest absorbed energy, and the lightest damage. The ZWT equation was modified according to the stress response properties of LSSG and the range of the SHPB strain rate to obtain the constitutive equation of the LSSG, and the model's correctness was confirmed.

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  • Article
    Abstract: The boundary condition is a crucial factor affecting the permeability variation due to suffusion. An experimental investigation on the permeability of gap-graded soil due to horizontal suffusion considering the boundary effect is conducted, where the hydraulic head difference (ΔH) varies, and the boundary includes non-loss and soil-loss conditions. Soil samples are filled into seven soil storerooms connected in

    The boundary condition is a crucial factor affecting the permeability variation due to suffusion. An experimental investigation on the permeability of gap-graded soil due to horizontal suffusion considering the boundary effect is conducted, where the hydraulic head difference (ΔH) varies, and the boundary includes non-loss and soil-loss conditions. Soil samples are filled into seven soil storerooms connected in turn. After evaluation, the variation in content of fine sand (ΔRf) and the hydraulic conductivity of soils in each storeroom (Ci) are analyzed. In the non-loss test, the soil sample filling area is divided into runoff, transited, and accumulated areas according to the negative or positive ΔRf values. ΔRf increases from negative to positive along the seepage path, and Ci decreases from runoff area to transited area and then rebounds in accumulated area. In the soil-loss test, all soil sample filling areas belong to the runoff area, where the gentle-loss, strengthened-loss, and alleviated-loss parts are further divided. ΔRf decreases from the gentle-loss part to the strengthened-loss part and then rebounds in the alleviated-loss part, and Ci increases and then decreases along the seepage path. The relationship between ΔRf and Ci is different with the boundary condition. Ci exponentially decreases with ΔRf in the non-loss test and increases with ΔRf generally in the soil-loss test.

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  • Article
    Abstract: The presence of waste tires poses an environmental challenge as they occupy a significant amount of land and are expensive to dispose in landfills. However, reusing waste tires can address this issue when waste tires are used in geotechnical applications. To determine the viability of this approach, laboratory-scale tests were conducted to investigate load-bearing capacity of circular footings on sand-tire shred (STS

    The presence of waste tires poses an environmental challenge as they occupy a significant amount of land and are expensive to dispose in landfills. However, reusing waste tires can address this issue when waste tires are used in geotechnical applications. To determine the viability of this approach, laboratory-scale tests were conducted to investigate load-bearing capacity of circular footings on sand-tire shred (STS) mixtures with shredded waste tire contents of 5%–15% by weight and three different widths of shreds. The investigation focused on analyzing the thickness of layers composed of STS mixtures, the soil cap, and the impact of geogrids on bearing capacity. The results indicate that a specific mixture of sand and tire shreds provides the highest footing-bearing capacity. In addition, the optimal shred content and size were found to be 10% by weight and 2 cm × 10 cm, respectively. Furthermore, for a given tire shred width, a particular length provides the largest bearing capacity. The results agree well with that of previous research conducted by the first author and his colleagues in direct shear and California bearing ratio (CBR) tests. The primary finding of this research is that the use of two-layered STS mixtures reinforced by geogrids significantly enhances the bearing capacity.

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  • Technical Note
    Abstract: Soils are not necessarily uniform and may present linearly varied or layered characteristics, for example the backfilled soils behind rigid retaining walls. In the presence of large lateral thrust imposed by arch bridge, passive soil failure is possible. A reliable prediction of passive earth pressure for the design of such wall is challenging in complicated soil strata, when adopting the conventional limit analysis

    Soils are not necessarily uniform and may present linearly varied or layered characteristics, for example the backfilled soils behind rigid retaining walls. In the presence of large lateral thrust imposed by arch bridge, passive soil failure is possible. A reliable prediction of passive earth pressure for the design of such wall is challenging in complicated soil strata, when adopting the conventional limit analysis method. In order to overcome the challenge for generating a kinematically admissible velocity field and a statically allowable stress field, finite element method is incorporated into limit analysis, forming finite-element upper-bound (FEUB) and finite-element lower-bound (FELB) methods. Pseudo-static, original and modified pseudo-dynamic approaches are adopted to represent seismic acceleration inputs. After generating feasible velocity and stress fields within discretized elements based on specific criteria, FEUB and FELB formulations of seismic passive earth pressure (coefficient KP) can be derived from work rate balance equation and stress equilibrium. Resorting to an interior point algorithm, optimal upper and lower bound solutions are obtained. The proposed FEUB and FELB procedures are well validated by limit equilibrium as well as lower-bound and kinematic analyses. Parametric studies are carried out to investigate the effects of influential factors on seismic KP. Notably, true solution of KP is well estimated based on less than 5% difference between FEUB and FELB solutions under such complex scenarios.

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  • Technical Note

    Limit load and failure mechanisms of a vertical Hoek-Brown rock slope

    Jim Shiau, Warayut Dokduea, Suraparb Keawsawasvong, Pitthaya Jamsawang

    2024, 16(3): 1106-1111. doi:10.1016/j.jrmge.2023.05.018

    Abstract: The problem considered in this short note is the limit load determination of a vertical rock slope. The classical limit theorem is employed with the use of adaptive finite elements and nonlinear programming to determine upper and lower bound limit loads of a Hoek-Brown vertical rock slope. The objective function of the mathematical programming problem is such as to optimize a boundary load, which is known as the limi

    The problem considered in this short note is the limit load determination of a vertical rock slope. The classical limit theorem is employed with the use of adaptive finite elements and nonlinear programming to determine upper and lower bound limit loads of a Hoek-Brown vertical rock slope. The objective function of the mathematical programming problem is such as to optimize a boundary load, which is known as the limit load, resembling the ultimate bearing capacity of a strip footing. While focusing on the vertical slope, parametric studies are carried out for several dimensionless ratios such as the dimensionless footing distance ratio, the dimensionless height ratio, and the dimensionless rock strength ratio. A comprehensive set of design charts is presented, and failure envelopes shown with the results explained in terms of three identified failure mechanisms, i.e. the face, the toe, and the Prandtl-type failures. These novel results can be used with great confidence in design practice, in particularly noting that the current industry-based design procedures for the presented problem are rarely found.

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