Hasil untuk "Engineering geology. Rock mechanics. Soil mechanics. Underground construction"

XU Peng 1, MENG Yuhan 2, LI Ting 2, YANG Guangqing 2

The Material Point Method (MPM) is a mesh-free simulation technique that integrates the advantages of Lagrangian and Eulerian methods, providing a novel approach for simulating large deformations of slopes subjected to rainfalls. A two-dimensional two-phase single-point MPM is employed to analyze slope responses under short-duration heavy rainfall with varying soil saturated permeability coefficients and rainfall intensities. The research findings indicate that: (1) The onset of slope instability is delayed as the intensity of short-duration heavy rainfall decreases. Concurrently, the displacement curve at the slope toe transitions from rapid steep increases to gradual increments during instability progression. (2) Primary failure modes under short-duration heavy rainfall manifest as deep and shallow overall sliding or retrogressive sliding, with the latter exhibiting greater destructive potential. Under identical rainfall intensities, slopes with lower and higher saturated permeability coefficients tend to result in shallow and deep sliding failures, respectively. (3) Decreasing soil saturated permeability coefficients progressively weakens the influence of rainfall intensity on both the magnitude and distribution patterns of pore water pressure within slopes.

Mahdieh Azimi, Amin Soltani, Mehdi Mirzababaei et al.

Chao Liu, Guanhua Zhao, Yijie Liu et al.

With the expansion of international terrorism and the potential threat of attacks against civil infrastructure, the dynamic response and failure modes of underground tunnels under explosive loads have become a prominent research topic. The high cost and inherent danger associated with explosion experiments have limited current research on tunnel internal explosions, particularly in the context of scaled model tests of shield tunnels. This study presents a series of scaled model tests under 1g-condition simulating internal blast events within a shield tunnel based on the prototype of the Shantou Bay Tunnel, considering the influences of surrounding stratum and equivalent explosive yield. Three different TNT explosive yields are considered in the model tests, namely 0.2, 0.4, and 1.0 kg. The model tests focus on the damage behavior and collapse modes of the shield tunnel lining under internal explosive loads. The model tests reveal that the shield tunnel is prone to damage at the joints of the tunnel crown and shoulder when subjected to internal explosive loads, with the upper half of the tunnel lining experiencing segment collapse, while the lower half remains largely undamaged. As the TNT equivalent increases, the damage area at the tunnel joints expands, and the number of segment failures in the upper half of the tunnel rises, transitioning from a damaged state to a collapsed state. The influence of “stratum-structure” interaction is investigated by comparing two models, one with overburden soil and the other positioned at the ground surface. The model tests reveal that the presence of soil pressure and confinement can significantly enhance the tunnel resistance to internal blast loads. Based on the observation of the model tests, five different damage modes of segment joints under internal explosion are proposed in this study.

WANG Jun 1, 2, 3, 4 , ZHANG Kaiyu 1, NI Junfeng 1, 2, 3, 4 , FU Hongtao 1, 2, 3, 4, PENG Yi1

To address the issues of poor permeability and long consolidation time of dredged sludge, the flocculation-vacuum preloading method has been widely employed to treat such soil. For the existing soft soil foundation, a combined method that integrated grouting flocculation and vacuum preloading was proposed. The indoor model tests were conducted on the dredged sludge with varying initial water contents where different lime contents were controlled. The changes of the pore water pressure, displacement and settlement were monitored. The pH, salinity, water content and vane shear strength of soil were measured after the tests. The optimal lime content, considering the influence of strength growth and soil salinization, was determined for the grouting flocculation-vacuum preloading. Then the efficacy of the combined method was further verified through its application in Longwan Phase Ⅱ coastal wetland restoration project. The results of this study can be used as a design reference for the applications of the combined method in other similar projects.

Govindarajan Kannan, Brendan C. O'Kelly, Evangelin Ramani Sujatha

WANG Jingzhou 1, MA Gang 1, 2, 3, ZHAO Tingting 4, ZHANG Wenyu 1, HU Jinfang 2, ZHOU Wei 1, 2, 3

The particle materials are characterized by discontinuity and dispersion, so they face great computational pressure in numerical simulation. The exact scaling criterion and coarse-grained method are introduced into the combined finite-discrete element method (FDEM) to provide a solution for accelerating the numerical simulation of granular materials based on the FDEM. Based on the theories of exact scaling and coarse granulation, the exact scaling criteria for the FDEM are derived. On this basis, the numerical triaxial shear tests for equal diameter particle system and binary particle system are carried out respectively. The test results show that without the introduction of the exact scaling criteria, the mechanical response characteristics of the coarse-grained model will change, resulting in distortion, and the parameters of the coarse-grained model need to be corrected. After the introduction of the exact scaling criteria, the mechanical response characteristics of the coarse-grained model are corrected. The test results demonstrate the effectiveness of introducing the exact scaling criteria and coarse granulation method into the FDEM. It can greatly improve the computational efficiency of numerical simulation of granular materials using the FDEM under the similar conditions to the original particle system. Based on the numerical test results, the macroscopic stress deformation and mesoscopic contact force are correlated, and the micromechanical mechanism of the exact scaling and coarse-grained methods is revealed.

Liangjie Gu, Xia-Ting Feng, Rui Kong et al.

Surrounding rocks at different locations are generally subjected to different stress paths during the process of deep hard rock excavation. In this study, to reveal the mechanical parameters of deep surrounding rock under different stress paths, a new cyclic loading and unloading test method for controlled true triaxial loading and unloading and principal stress direction interchange was proposed, and the evolution of mechanical parameters of Shuangjiangkou granite under different stress paths was studied, including the deformation modulus, elastic deformation increment ratios, fracture degree, cohesion and internal friction angle. Additionally, stress path coefficient was defined to characterize different stress paths, and the functional relationships among the stress path coefficient, rock fracture degree difference coefficient, cohesion and internal friction angle were obtained. The results show that during the true triaxial cyclic loading and unloading process, the deformation modulus and cohesion gradually decrease, while the internal friction angle gradually increases with increasing equivalent crack strain. The stress path coefficient is exponentially related to the rock fracture degree difference coefficient. As the stress path coefficient increases, the degrees of cohesion weakening and internal friction angle strengthening decrease linearly. During cyclic loading and unloading under true triaxial principal stress direction interchange, the direction of crack development changes, and the deformation modulus increases, while the cohesion and internal friction angle decrease slightly, indicating that the principal stress direction interchange has a strengthening effect on the surrounding rocks. Finally, the influences of the principal stress interchange direction on the stabilities of deep engineering excavation projects are discussed.

Mojtaba Mohammadi, Hossein Jahantigh, Farahad Zolfaghari

Introduction Evaporation, the process by which water molecules escape a surface after absorbing sufficient energy to overcome vapor pressure, is a major contributor to water scarcity, especially in arid and semi-arid regions where heat readily facilitates this escape. Accurately estimating evaporation losses is crucial for effective water resource management, crop water demand prediction, and irrigation scheduling. Machine learning (ML) has emerged as a powerful tool for tackling the complex and stochastic nature of environmental problems. ML models excel at identifying relationships between predictor variables and outcomes (predictands), often surpassing traditional methods. However, their performance can vary depending on input factors and climatic conditions. Recently, hybrid techniques that combine multiple models have gained traction in climate and hydrology studies. These techniques leverage the strengths of different approaches within a single algorithm, potentially capturing more complex patterns in data series. This research will explore the potential of various individual ML models and propose a novel hybrid approach for estimating pan evaporation in Sistan and Baluchistan Province.   Materials and Methods This study investigates pan evaporation simulation and prediction in Sistan and Baluchistan Province, Iran. Synoptic station data (1980-2019) served as model inputs, while pan evaporation measurements from these stations provided the observed values. In this research, in the approach of individual performance of data mining models, eight data mining models were used to simulate and predict evaporation from the pan. In addition to the individual performance approach, the combined VEDL approach was used to provide a hybrid model (a combination of the mentioned eight individual models of deep learning). In this hybrid approach to regression issues, the estimators of all models are averaged to obtain an estimate for a set called vote regressors (VRs). There are two approaches to awarding votes: average voting (AV) and weighted voting (WV). In the case of AV, the weights are equivalent and equal1. A disadvantage of AV is that all of the models in the ensemble are accepted as equally effective; however, this situation is very unlikely, especially if different machine learning algorithms are used. WV specifies a weight coefficient for each ensemble member. The weight can be a floating-point number between Zero and one, in which case the sum is equal to one, or an integer starting at one denoting the number of votes given to the corresponding ensemble member. the weight of each model was selected based on the accuracy of the model's performance using the evaluation criteria obtained from the training implementation section of individual models. the model’s performance was assessed using statistical measures, including R2, RMSE, MAE, and Taylor diagram.   Results and Discussion The results showed that all the models had very good results in both the training and testing stages. All models exhibited excellent performance during training and testing. The Artificial Neural Network (ANN) achieved the highest accuracy in both phases at the Zahedan station (R² = 0.89, RMSE = 45.95 in training; R² = 0.96, RMSE = 44.18 in validation). It emerged as the best model for monthly pan evaporation prediction at this station. Other models also performed well, with the Support Vector Machine (SVM) and Random Forest (RF) models achieving R² values of 0.89 and 0.88 in training, respectively. Notably, the BART model ranked second in validation (R² = 0.96). The Tree Model (TM) had the lowest accuracy (R² = 0.84 and 0.93 in training and validation, respectively). Across all stations, ANN, SVM, and RF consistently delivered the best results in both training and testing. In the test phase, the SVM model outperformed others in Khash, Iranshahr, and Chabahar stations (R² = 0.94, 0.96, and 0.94, respectively). At the Saravan station, the RF model achieved the highest R² (0.94) during testing. To develop a hybrid data mining model, the Voting Ensemble for Deep Learning (VEDL) technique was employed with weighted voting in the training stage. The combined model significantly improved upon the best individual model. RMSE decreased from 45.95 to 33.1, R² increased from 0.89 to 0.94, and MAE improved from 32.92 to 23.9. Evaluation using the Taylor diagram further confirmed the superior performance of the VEDL model compared to the individual ANN model.   Conclusion The results showed that among all the models, ANN, SVM, and RF models had the best performance in the two stages of training and verification. In the validation stage, the SVM model with R2 values equal to 0.94, 0.96, and 0.94 performed best in the Khash, Iranshahr, and Chabahar stations. At the Saravan station, in the Sensji validity stage, the RF model with an R2 value of 0.94 had the best performance among the models. The excellent performance of the models in the two stages of training and validation is another finding of the research, These results are consistent with the results of researchers who have expressed the appropriate efficiency of machine learning models in estimating evaporation/evaporation and transpiration in different climatic regions of Iran. The results of the combined model showed that the combined model improved the results compared to the best individual model so that the RMSE values increased from 45.95 to 33.1, the R2 values increased from 0.89 to 0.94, and the MAE value improved from 32.92 to 23.9. The use of the VEDL approach to estimate evaporation from the pan was a new approach that has not been used in past studies. Therefore, according to the results of this research, the proposed deep sensing model is proposed to estimate the evaporation of arid and semi-arid areas for water resources management and agricultural planning.

Tomohiro Kato, Atsushi Takai, Yusuke Iwata et al.

The leaching behavior of arsenic and boron is evaluated in this work through two types of excavated rocks with geogenic contaminants under different temperatures. Excavated rocks with geogenic contaminants are expected to be used in embankments with appropriate countermeasures being taken against the risks brought about by geogenic contamination. The leaching behavior might change because of changes in the ground temperature. However, the effects of temperature on the leaching behavior of such rocks have not been well examined. Herein, batch leaching tests at temperatures between 5 and 60 °C were performed under shaking and nonshaking conditions. Mudstone and shale rock were crushed into particles smaller than 2 mm, which were required for the tests. The tests were carried out for durations ranging from 6 h to 15 days because changes in leaching kinetics also require careful evaluation. After conducting the nonshaking tests for 15 days at 40 °C, the mudstone sample leached arsenic and boron at concentrations of approximately 0.7 and 1.0 mg/L, respectively. The arsenic and boron concentrations were about 20 and 40% higher than those of the sample leached at a temperature of 20 °C. Elevated temperatures were seen to increase the leaching kinetics of the toxic elements. For the shale rock sample, the leaching rate for arsenic was 7.7 × 10-2/h at 40 °C, which was about 2.5 times greater than the value at 30 °C. The nonshaking tests showed higher leaching amounts of arsenic and boron than the shaking tests, especially at elevated temperatures. As unrealistic estimations should be avoided, nonshaking tests are suggested. Moreover, nonshaking tests lasting longer than 6 h are necessary due to the relatively slow dissolution of minerals.

Akiyoshi Kamura, Tomomi Kaneko, Noboru Sato et al.

Check dams constructed in steep mountainous areas require the rationalization of the dam body and foundation system. In general, soil cement replacement or caissons are often adopted for foundations. In such cases, reducing the construction effort is a critical issue. To address this, the authors studied the viability of a new type of check dam foundation consisting of a group of micropiles whose heads are structurally disconnected from the dam body. The system, coined a head-separated micropile group (HMG) foundation, enables the saving of labor and a reduction in the cross-sectional forces applied to the micropiles. Firstly, a full-scale loading test of the HMG was conducted. Then, a finite element model was formulated and its parameters fitted to make it suitable for reproducing the experimental results. Finally, using the FE model, the performance of a typical rigidly connected micropile foundation and that of the HMG system were compared in terms of the bearing capacity and displacement of the check dam body. The results confirmed that, although its displacement was 1.25 times larger than that of the rigidly connected foundation, the HMG system led to a factor of safety of 3.5 against micropile buckling.

Xie Weiwei, Zhou Lingmei, Zheng Hao

During the processing and utilization of coal resources, some heavy metal elements will be enriched in the environment, which is harmful to the environment and the human body.In this study, low-ash, high-sulfur coal samples and high-ash, low-sulfur coal samples from Inner Mongolia were selected for float-and-sink test and flotation, and were analyzed by inductively coupled plasma mass spectrometer (ICP-MS), X-ray diffraction analysis, X-ray fluorescence analysis, and scanning electron microscopy energy spectrum analysis.Infrared spectroscopy and other test methods were used to study the occurrence form of heavy metal arsenic in coal and its migration and enrichment law during the processing.The experimental results show that the two coal samples demonstrates the highest proportion of arsenic present in the aluminosilicate bound state, reaching more than 50 %, but the types of aluminosilicate minerals are not the same, and the occurrence of arsenic has obvious differences.Flotation results show that arsenic in low-ash and high-sulfur coal sample is mainly associated with minerals and concentrated in the denser part, while high-ash and low-sulfur coal is mainly concentrated in the part with lower density and higher organic content; there are also differences in the migration law of arsenic in flotation.During the flotation, the arsenic in low-ash and high-sulfur coal migrates to the tailings, while the arsenic in the high-ash and low-sulfur coal migrates to the clean coal.The above findings show that it is feasible to remove arsenic from low-ash and high-sulfur coal sample by flotation but the effect is not so good for high-ash and low-sulfur coal sample, indicating that the removal of arsenic must consider the impact of coal type.

Xubo Gao, Hongyu Li, Peili Gong et al.

The karst area is widely distributed in China, and the ecological environment is fragile. Acid mine drainage (AMD) produced by mining activities in karst areas seriously threatens the safety of regional ecological environment. In this paper, carbonate rocks and corn cobs (biochar) widely distributed in karst areas were used as raw materials, and an alkaline sustained release material (ASRM) that could be used for in-situ injection and repair was prepared by means of modification, granulation and film coating. In addition, in-situ injection and repair experiments under alternating effects of wet and dry conditions were carried out in the laboratory, to verify and determine the ability and removal mechanism of ASRM in the in-situ remediation of heavy metals in acid mine wastewater. The results showed that ASRM can effectively improve the pH of water, and the pH of AMD can be increased from 2.8 to approximately 5-7, and it had a good removal effect on many harmful heavy metals, such as Fe2+, Mn2+, Zn2+, Cu2+, Cd2+, Pb2+ and Cr3+. XRD and SEM analyses showed that the reaction precipitates mainly existed in the form of FeOOH. The removal mechanism of heavy metals mainly includes: ①some metal ions were removed in the form of precipitation, such as hydroxides produced by the reaction; ②a large amount of FeOOH produced by the reaction system can adsorb and remove heavy metals. This experimental study provides a reliable theoretical and technical basis for the in-situ treatment of AMD in karst mountain mines with high efficiency by using slow-release materials.

Jijo James

Fengshun Zhao, Shan Hua, Hao Wu et al.

Sumatra Island, located on the western edge of Indonesia, is an important part of the Pacific Rim metallogenic belt, and has abundant mineral resources such as copper, gold(silver) lead and, zinc.The quantitative prediction for these mineral resources can provide basic data for the "Belt and Road" strategic decisions of China.Based on the geologic investigations and the 1:1 000 000 low-density geochemical survey, this paper analyzed the mineralized characteristics, key ore-controlling factors, and prospecting indicators for the epithermal gold(silver) deposits, and established a prediction model for this type of gold(silver) deposit.This model suggested that the NW-trending Sumatra fault and its secondary faults have a close spatial-temporal coupling relationship with Cenozoic arc magmatic rocks, and they jointly control the gold(silver) mineralization in this area.The NW-trending faults, the Cenozoic magma rocks, the distribution of gold(silver) deposits, and the 1:1 000 000 low-density Au-Ag-Cu geochemical anomalies can be used to rapidly delineate the prospecting areas of the epithermal gold(silver) mineralization.Five prospecting areas were delineated according to the prediction model.Furthermore, a general density model was used to predict the number of undiscovered mineral deposits in various prospecting areas under different probabilities, and the probabilistic number of the gold(silver) resources were estimated for the epithermal gold(silver) deposits by the "three-part" quantitative assessment method.

Zhixiang Chen, Xiaoxia Guo, Longtan Shao et al.

In the construction of artificial freezing methods and cold region engineering, the determination of the accurate temperature field is the demand of both ensuring the stability of frozen soil and reducing the project investment. Affected by the external environment, phase change latent heat, non-linear thermal parameters, etc., the temperature evolution of the soil freezing process is a non-linear form, and the temperature field evolution will be more complex with the change of different influencing factors. Scientific control and utilization of the influencing factors of the frozen soil temperature field play a vital role in improving the freezing efficiency and accuracy of the soil temperature field. This study aims to analyze the sensitivity of thermal factors on the nonlinear formation process of frozen soil temperature field, and to provide the results for the control of various factors in frozen soil engineering. A freezing model test was designed and implemented, the boundary conditions and temperature evolution in the model were monitored. Meanwhile, the thermal parameters and unfrozen water content of the model soil were tested indoor. Then the theoretical relationship between unfrozen water content and parameters was deduced to determine the variation range of unfrozen water content. The boundary condition values (including the maximum, minimum and average values) and thermal parameters were used in the orthogonal simulation of the freezing model, respectively. The temperature simulation values were compared with the model test values, and the factors affecting the nonlinear heat transfer of frozen soils were analyzed quantitatively by both the range method and variance analysis method. Several suggestions of the vital factors in the soil freezing construction were offered based on this research.

ZHANG Chuang, REN Song, ZHANG Ping et al.

Phylite is widely distributed in southwest of China. Factors such as groundwater, bedding, micro-pores and micro-cracks will weaken its mechanical properties to some extent, thus posing severe challenges to the stability of the related projects. Therefore, in this paper, based on Brazilian splitting test, the evolutions of the tensile strength, energy and failure forms of phyllite under the coupling effects of water, bedding and pore are studied. The results show that the tensile strength decreases gradually with the increase of moisture content, pore diameter and bedding angle. However, the tensile strength has different sensitivities to the changes of them, which is mainly reflected in that bedding angle is the most significant, pore diameter is the second, and moisture content is the least. The tensile strength shows obvious anisotropy under different beddings. The anisotropy of tensile strength increases with the increase of water content and pore diameter, and the rate of increase with water content is more significant. Moreover, the energy increases gradually with the increase of moisture content, pore diameter and bedding angle, which is consistent with the changes of tensile strength. Although the energy under different beddings also presents obvious anisotropy, its anisotropy degree is generally higher than that of the tensile strength under the same condition. The failure form of specimens is affected by pore size, bedding angle and moisture content, among which, the existence of hole mainly affects the crack initiation position, the size of pore mainly affects the crack initiation strength, the bedding angle mainly affects the crack propagation path, and the moisture content mainly affects the number of cracks. This research results are valuable for further understanding the tensile properties of rocks and improving the stability of geotechnical engineering.

Cristhian Mendoza, Márcio Muniz de Farias

Массивы медно-порфировых месторождений, преимущественно кварцдиоритового состава, приурочены к бортовым частям субмеридиональных вулканогенных мегазон. Наблюдается длительная эволюция рудоносного магматизма - от S2 до C1-2, проявленная в основном по латерали. U-Pb возраста цирконов и Rb-Sr датировки кварцевых диоритов изменяются с запада на восток от S2-D1-2 в Магнитогорской мегазоне (412-390 млн. лет - Вознесенское и Гумешевское месторождения) и в западной части Восточно-Уральской мегазоны (430-420 млн. лет - Томинско-Березняковский рудный узел в Увельской зоне) до D32-C11 в восточной части Восточно-Уральской мегазоны (350-366 млн. лет - Михеевское и Тарутинское месторождения) и до C1-2 в самой восточной части Урала - Валерьяновской мегазоне (Бенкалинское месторождение). Михеевское и Гумешевское месторождения по запасам меди относятся к крупным промышленным объектам. В целом, значения (87Sr/86Sr)t = 0.7040-0.7051 и (εNd)t = 3-7 в диоритоидах всех зон близки, и отвечают близмантийным значениям. Изотопные и петрогеохимические данные позволяют отнести рудоносные диоритоиды к островодужному геохимическому типу с базитовым (метабазитовым) источником в нижней коре-верхней мантии или в верхней мантии. Метабазитовый "слой" имеет стабильный состав по латерали и инициирует рудоносный кварцдиоритовый магматизм с омоложением на восток. Гидротермалиты наследуют изотопно-геохимические особенности магматизма. На всех стадиях минералообразования в рудные поля поступает магматический флюид - в аподиоритовых кислотных метасоматитах и минералах послерудных жил величины (87Sr/86Sr)t составляют 0.7043-0.7055, во флюиде - δ18О = 6…11‰ и δD = -49…-61‰ (SMOW). Однако, если в рудном поле присутствуют мрамора (и другие вмещающие породы), то происходит смешение различных изотопных резервуаров. В результате безрубидиевые силикаты и карбонаты из эндоскарнов, эпидозитов, ретроградных и рудных метасоматитов характеризуются промежуточным значением87Sr/86Sr (0.7052-0.7065) между диоритом и мрамором. Изотопное смешение подчеркивается прямой корреляцией на диаграммах δ13С-87Sr/86Sr и δ13С-δ18О для части послерудных жильных карбонатов в условиях бинарной системы магматический флюид-мрамор при отсутствии существенного изотопного фракционирования C и O. При возрастании в рудных полях роли мраморов и кислотного выщелачивания87Sr/86Sr отношение в послерудных карбонатах возрастает от 0.7039-0.7051 (мрамора отсутствуют) до 0.7053-0.7058 и более. Величина δ34S в сульфидах составляет 0 ± (1-3)‰. Послерудные кварцевые жилы образуются из магматического флюида (соленость 3-12 мас. % в экв. NaCl), иногда содержащего примесь метеорной или метаморфической воды (δ18О = 4-10‰ для 300°C).