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

Gang Liu, Yao Zeng, Dongwei Wang et al.

When underground tunnels in coal mines traverse geological structurally abnormal zones (faults, collapse columns, fractured zones, etc.), excavation-induced unloading leads to instability and failure of the engineering rock mass. Rock masses in fractured zones are in elastic, plastic, and post-peak stress states, and the process of excavation through these zones essentially involves unloading under full stress paths. To explore the mechanical response of sandstone under different stress levels, based on the investigation of possible stress paths, a systematic study is conducted on various unloading paths, including elastic-axial compression with unloading of confining pressure, elastic-constant principal stress with unloading of confining pressure, plastic-axial compression with unloading of confining pressure, plastic-constant principal stress with unloading of confining pressure, plastic-constant axial D1 displacement with unloading of confining pressure, plastic-equal proportional unloading of axial and confining pressures, and post-peak-synchronous unloading of axial and confining pressures. Characteristics of full stress-strain curves under seven unloading paths are obtained. The deformation patterns caused by unloading are analyzed, and the relationship between unloading paths and strain increments is investigated. Results show that, as the degree of unloading increases, the unloading deformation modulus ( E ) in the elastic stress state exhibits a trend of initial increase, then stabilization, followed by decrease, while in the plastic stress state, E gradually decreases. Both elastic and plastic states show an increasing trend in Poisson’s ratio (µ). The normalized plastic shear strain γp/γpmax and dilation angle (ψ) conform to a single exponential function, and there is a negative correlation between initial confining pressure and dilation angle. These findings support the enrichment and development of unloading rock mechanics.

B. Jia, Yi Yang, Xuyang Wang et al.

Accurate prediction of shield tunneling attitude is crucial for preventing engineering risks such as tunnel misalignment, structural collisions, and ground subsidence in underground construction projects. This study develops a real-time prediction method for shield tunneling parameters using the Qingdao Jiaozhou Bay Second Subsea Tunnel as a case study. We systematically compare three machine learning approaches (XGBoost, Transformer, and LSTM) enhanced with discrete wavelet transform (DWT) for noise reduction and Bayesian optimization (BOA) for hyperparameter tuning. Results show that BOA-XGBoost achieved the R2 is 0.98 with the Mean Absolute Percentage Error (MAPE) errors below 2% for all five output parameters (horizontal/vertical deviations at shield head/tail and roll angle). While BOA-XGBoost outperformed other models in accuracy, BOA-LSTM demonstrated superior computational efficiency—33.44% faster than XGBoost and 96.79% faster than Transformer. Under complex geological conditions, deep learning models (BOA-LSTM and BOA-Transformer) showed better adaptability than BOA-XGBoost, particularly in mixed soil-rock strata. This study provides practical guidance for selecting appropriate prediction models based on geological conditions and computational constraints in tunnel engineering projects.

Mengzhe Huo, Weizhong Chen, Jingqiang Yuan et al.

Shield tunneling in urban underground space necessitates tight control over support pressure at the tunnel face and a thorough insight into ground collapse mechanisms. This study conducts a model test and a theoretical validation to clarify the mechanisms of face failure and subsequent ground collapse in sand during earth pressure balanced shield (EPBS) tunneling operations. The experiment investigates the changes in soil pressure and surface subsidence patterns during shield tunneling and collapse stages, to elucidate the entire process of ground collapse triggered by shield tunneling disturbances. A novel methodology was proposed to ensure effective verification of the rotational failure mechanism, focusing on the collapse pit morphology and the critical collapse pressure. The results indicate that: (1) precise control over the shield tunneling and screw conveyor rotation speeds is essential for tunnel face stability; (2) the sand with low moisture content is prone to stepwise ground collapse under shield tunneling disturbances; (3) soil pressure measurements at the cutterhead are more indicative of face failure and imminent ground collapse than those from the soil chamber; (4) there is a consistent alignment between the rotational failure mechanism and observed collapse pit morphology, albeit with slight variations due to tunneling disturbances; (5) the experimentally determined critical collapse pressure is higher than the theoretical prediction, indicating an underestimation of risks in the current model. The study advances the understanding of the face failure mechanisms in shield tunnels, thereby providing insights into the design and safety of shield tunneling within engineering practices.

SUN Junyuan 1, ZHOU Shilong 2, LUO Jiugang 3, CUI Min 3, CHENG Xuesong 2, LI Qinghan 2

Long-term operation of recharge wells leads to progressive decline in recharge efficiency, that is, the phenomenon of well clogging. As the most critical factor constraining recharge technology application, the mechanisms underlying recharge well clogging remain inadequately understood, with insufficient research on clogging causes and influencing factors during recharge operations. This study investigates the influence mechanisms of soil particle size distribution on recharge well clogging through laboratory model tests. Results indicate that fine particle migration during recharge induces hydraulic conductivity variations in different zones. When the proportion of the coarse particles is high, fine soil particles fail to completely fill soil voids. While no significant clogging occurs, this process alters local permeability characteristics, and particle size distribution will still change.

Parlindungan Hasibuan, M. Chaerul, Sri Gusty

The research location is within the IUP area of PT. IFISHDECO Tbk (122.168°–122.204° E and 4.371°–4.404° S), Tinanggea, South Konawe Regency, Southeast Sulawesi Province. This study aims to analyze the Safety Factor (SF) values of the slopes and the probability of landslide potential at the green pit mining slopes, as well as the landslide hazard mitigation map. The data used include engineering geological characteristics, topographic measurements obtained via total station, aerial photographs (drone), and rock mechanics sample test results. The SF analysis applied is the Simplified Bishop method with Mohr-Coulomb analysis, processed using Slide ver.6 software, along with landslide hazard potential maps and landslide hazard mitigation maps based on the Ministry of Energy and Mineral Resources of the Republic of Indonesia Decree (KEPMEN ESDM RI) No. 1827 K/30/MEM/2018.The research results are derived from slope stability analysis at the green pit mining site based on the static Safety Factor (SF) according to the rules of KEPMEN ESDM RI No. 1827 K/30/MEM/2018, which are as follows:  - Single Slope Type: SF 0.91 - 1.26 (Unstable – Balanced)  - Inter-ramp Slope Type: SF 1.15 - 1.25 (Balanced)  - Overall Slope Type: SF 1.31 – 1.37 (Stable). The probability of soil movement (landslide) potential is 10 – 25%, with a medium severity landslide category. The medium severity landslide category applies when there are consequences such as serious human injuries, damage to facilities and infrastructure from 25% to 50%, production stoppages of more than 12 hours but less than 24 hours, buried reserves that can still be recovered, and environmental damage within the scope of the IUP area.The landslide hazard potential map is divided into three severity categories: low landslide severity, medium landslide severity, and high landslide severity. The landslide hazard mitigation map for the green pit open-pit mining site provides information on potential hazard zones covering an area of 0.33 hectares at the pit slope, safe zones covering 2 hectares outside mining activities, evacuation routes with distances ranging from 68 m to 267 m to the safe zone, and worker assembly points (muster points) equipped with emergency response facilities such as first-aid supplies, transportation means, mobilization facilities, and communication equipment, all of which are part of the mining safety management system.

Yue ZHU, Ronghua PENG, Xiangyun HU et al.

Objective In geothermal exploration, a clay cap is a typical hydrothermal geothermal system, and its depth and distribution range can provide crucial information for delineating the scope of geothermal resources and determining the location of geothermal drilling. Clay caps are usually composed of a clay layer formed through hydrothermal reactions and are characterized by low resistance. The low-resistivity cap can be effectively imaged using the audio-frequency magnetotelluric method. To obtain uncertainty information about the distribution of clay cap layers and imaging results, this paper employs the 1D trans-dimensional Bayesian inversion method to investigate the detection capabilities of low-resistance cap layers in geothermal areas through audio electromagnetic data. Methods In this paper, a model test is first carried out to establish a geoelectric model of a typical geothermal system.Subsequently, a 1D trans-dimensional Bayesian algorithm is used to invert the synthetic data to obtain the uncertainty information of the subsurface electrical structure and interface position. Then, the method was applied to the processing of measured audio frequency magnetotelluric data in the Yanggao geothermal area of Shanxi Province. Results This method has relatively accurate identification ability for low-resistivity clay caps, and the obtained uncertainty analysis results of the upper and lower interfaces of low-resistivity caps are also relatively reliable according to numerical tests. It was found that this method has a good ability to identify shallow low-resistivity caps and can provide an uncertainty evaluation of the clay cap interface position via field data tests. The 2D inversion results of this survey line verify the reliability of the 1D inversion. Conclusion This method has relatively accurate imaging capabilities and uncertainty analysis capabilities for shallow geothermal clay caprocks and has strong application prospects in geothermal detection.

Lua Thi Hoang, Xi Xiong, Tatsunori Matsumoto

When designing a piled raft foundation (PRF) on clay, it is essential to understand the time-dependent behaviors of the foundation. However, little attention has been paid to this issue. On the basis of physical model tests, this study presents the long-term behaviors of piled raft foundations with different pile arrangement schemes. In the experiments, three foundation models with the same square raft but different numbers of piles were tested to observe long-term foundation behavior under different vertical load levels. During the observation time, the applied load, the PRF settlement, the axial forces along the piles, and the pore water pressure (PWP) beneath the raft base were carefully measured. The results show that the piles were effective at supporting the applied load and suppressing the settlement of the foundation when the applied loads were smaller than the bearing capacities of the corresponding pile groups. At the larger loads, the raft shared significant proportions of the increment parts of the applied load. The level of the applied load affected the load sharing not only between the raft and the piles, but also between the piles. The corner piles carried larger load at small applied loads but smaller load at larger applied loads, in comparison with the center piles. In addition, due to the variations in load sharing between the raft and the piles, the pile arrangement and the level of applied load affected the distributions of ground strength in both the magnitude and the depth of the affected zone in long-term load tests.

ZHANG Cun, FANG Shangxin, JIA Sheng et al.

Coal is a porous material containing pore structures and mineral components, exhibiting pronounced anisotropy and size effects.In order to investigate the influence of coal anisotropy and size effects on its failure characteristics, this paper proposes a simulation method for characterizing and reconstructing three-dimensionally the internal pores and mineral components of coal samples based on CT scanning, nuclear magnetic resonance, and X-ray diffraction.Specifically, we obtained simulation parameters of three-dimensional reconstruction models of coal matrix and mineral components through inverse laboratory uniaxial compression experiments, while simulated and analyzed the strength damage characteristics of coal bodies with different aspect ratios.The simulation results show that: ① During the loading process, the plastic zone first gradually expands and connects outward around the pores and mineral components.In terms of spatial distribution, the plastic zone expands vertically from the loading end to the interior in the early stage, and in the later stage, it expands horizontally from the surroundings to the interior.After the model is damaged, a "double truncated cone structure" is formed in the non-plastic zone.② The increase of aspect ratio leads to an increase in the compressive strength(p) of coal samples, the strain(ζ) at yielding strength, and the elastic modulus(K), among which ζ and K increase linearly, while the margin of increase in p gradually decreases.③ The total energy and elastic energy of coal sample loading increase exponentially, while the dissipated energy increases linearly.The increase of aspect ratio leads to an increase both in the accumulated elastic energy in the coal body and in the released energy during failure, which easily induce dynamic impact-related disasters.This study provide references for the reasonable selection of coal pillar size in impact mine pressure area.

WANG Liye 1, ZHOU Fengxi 1, 2, ZHOU Lizeng 3, LIANG Yuwang 1

To reveal the impact of physicochemical effects on the compressive behaviors of unsaturated clay containing salt solution and its dependence properties on stress level, one-dimensional compression tests are performed on the specimens with pores containing distilled water, sodium chloride solution, sodium sulfate solution and controlled matric suction conditions. Then, the compression index, secondary compression coefficient and yield stress of clay under different conditions are measured according to the test results, and their variation laws with the matric suction and osmotic suction are calibrated. Furthermore, the stress-dependent characteristics of physicochemical action are clarified through an in-depth analysis of the primary and secondary consolidation behaviors of unsaturated saline clay under different matric suctions and osmotic suctions, and the LC yielding behaviors of unsaturated saline clay are explored. The results show that the ratio of the secondary compression coefficient to the compression index Ca/Cc and the yield stress of unsaturated saline clay at different physicochemical forces can be described uniformly using the osmotic suction and matric suction. From the slope of compression curve in the plastic loading zone and the correlation between characteristic parameter, Ca/Cc and the vertical stress, it is noted that the physicochemical action of unsaturated saline clay is closely related to the stress level. Moreover, the LC yield curve of unsaturated saline clay is a smooth curve composed of MLC yield curve and OLC yield curve under chemo- hydro-mechanical coupling.

Qing Li, Tong-de Zhao, Chen Huang et al.

Lianfu Hai, Rui Tao, Xiaojun Zhang et al.

The Weiningbeishan area in the eastern section of the North Qilian orogenic belt is one of the areas with the best metallogenic conditions and the most metallogenic signs of gold polymetallic deposits in Ningxia. In recent years, the Jinchangzi gold deposit is one of the breakthroughs in exploration work in this area. Based on the previous data, this paper summarizes the ore-controlling factors and prospecting indicators of the Jinchangzi gold deposit. A multielement comprehensive prospecting model based on geological-geophysical-geochemical prospecting was constructed, and the mining area and surrounding prospecting target areas were delineated. The research shows that the ore-controlling factors of the Jinchangzi gold deposit are mainly stratigraphic and structural. Stratigraphic factor is mainly manifested in specific strata and lithological combinations, and structural factor is mainly controlled by east-west regional faults and their secondary fissures. Hematitization-limonitization, silicification, sericitization, pyritization, jarosite alteration and other surrounding rock alterations, Au-Ag-As-Sb geochemical anomalies, and medium resistivity and medium-high polarizability anomalies are the main prospecting indicators in this area. Based on ore-controlling factors and prospecting indicators, a comprehensive gold prospecting model suitable is proposed for this area. 6 prospecting target areas and 3 deep prospecting target areas are delineated based on this model. Through the geochemical profile and the deep drilling of the target area, the rationality of target area has been confirmed, providing a well tool for future prospecting work in this area.

Alula Kassa, Shovon Raihan, Kimitoshi Hayano et al.

In this study, a novel testing method was developed to evaluate the water absorption and retention of waste-based stabilizers using suction filtration. Suction filtration was seen to remove most of the unabsorbed and unretained water from the waste-based stabilizer without losing any waste-based stabilizer particles. Therefore, oven-drying of the wet stabilizer, which can deteriorate the stabilizer, was not necessary. In addition, a formula was introduced to estimate the residual free water in the stabilizer after suction filtration based on the particle size. This estimate was used as a correction to determine the water absorption and retention rate (Wab) of the stabilizer. Subsequently, newly developed tests were conducted on fly ash (FA), a paper sludge ash-based stabilizer (PSAS), biomass ash (BMA), and the PSAS–BMA hybrid to evaluate Wab. The results show that the PSAS exhibited the highest Wab, followed by the BMA and FA. This is attributed to the CaO content of each stabilizer, which may have initiated hydration reactions. The Wab of the PSAS–BMA hybrid was similar to that of the PSAS, which is attributed to the synergistic effects of the components of each type of waste. Finally, the strength development of the FA, PSAS, BMA, and PSAS–BMA hybrid-treated clays was investigated via cone index tests. In addition to the stabilizer addition ratio (A), the Wab of the stabilizers is suggested to be an essential indicator for predicting the strength development of clays treated with waste-based stabilizers. Parameter β, which is the product of Wab and A, governs the cone index qc of the treated clays instead of A and Wab. Thus, the modified water content, w*, which considers the absorbed and retained water as a solid instead of a liquid, was applied to the cone index test results. The results show that the qc of the treated clays is more correlated to w* than to the measured water content. An empirical relationship for predicting cone index qc using w* was also proposed.

Fengzhou Liu, Hui-wen Xing, Bo Wu et al.

ZHANG Qian, YE Wei-min, LIU Zhang-rong et al.

Soil cementation technology based on microbially or enzymatically induced calcium carbonate precipitation (MICP/EICP) is one of the hot topics in the field of geotechnical and geological engineering in recent years. In this study, a systematic review was performed on this technology, focusing on advances in the cementation mechanisms of MICP/EICP and the influence of soil pore structures, properties of bacterium, urease and cementation solution, and cementation methods on characteristics of calcium carbonate (CaCO3). The results indicate that the smaller the soil pores are, the more difficult the infiltration of microorganisms or urease is and the worse the cementation uniformity is. More contact points among soil particles will produce more deposition points for CaCO3, resulting in stronger bonding and bridging effects and better cementation effects. The generation rate and total amount of CaCO3 increase as the concentration of bacterium or urease and the activity of urease increase in a certain range. However, too high concentration or activity will induce a too high generation rate of CaCO3, resulting in clogging near the injection end. The calcium carbonate crystals obtained from low concentration cementation solution are relatively small and evenly distributed in the soil. The use of appropriate grouting saturation can increase the proportion of CaCO3 with bonding effect. Multilayer alternating injection or one-phase low pH injection can improve the distribution uniformity of CaCO3 in the sample. Based on influencing factors of CaCO3 precipitation characteristics, the improvement of cemented soil uniformity, durability verification, and the adaptability and improvement scheme of applying the laboratory test results to the field scale should be the focus points of the future research.

Qiang Sun, Weiqiang Zhang, Yanmin Zhu et al.

Hong‐Xiang Zheng, Sheng Yan, Tao Chen et al.

The inversion of three-dimensional in situ stress fields in complex river valleys is of great significance for evaluating the excavation stability of deep underground caverns. Based on known in situ stress measurements, it is a major method for obtaining the geostress of the engineering area through the inversion geostress of the whole area with the application of geo-mathematical mechanics. However, the inversion results are often limited by the geological structure and heterogeneous alterated rock, as well as the measurement data reliability. A three-dimensional nonlinear neural network inversion was combined with a simulation of stratigraphic denudation by stages, tectonic compression, and alteration degree in the fault structure. The model was then applied to an underground cavern group of the Yingliangbao Hydropower Station. Comparative analysis showed that the inversion results were in reasonable accordance with the measured in situ stress values. Moreover, the reliability of the three-dimensional in situ stress field obtained using this method was further verified from the stress-induced failure during the cavern excavation. This technique is helpful for optimizing the design of subsequent excavation and reduces the potential instability of surrounding rock during a layered excavation.

Habtamu Semunigus Demisse, Abebe Temesgen Ayalew, Melkamu Teshome Ayana et al.

Characteristics of ungauged catchments can be studied from the hydrological model parameters of gauged catchments. In this research, discharge prediction was carried out in ungauged catchments using HEC-HMS in the central Omo-Gibe basin. Linear regression, spatial proximity, area ratio, and sub-basin mean were amalgamated for regionalization. The regional model parameters of the gauged catchment and physical characteristics of ungauged catchments were collated together to develop the equations to predict discharge from ungauged catchments. From the sensitivity analysis, crop coefficient (CC), storage coefficient (R), constant rate (CR), and time of concentration (TC) are found to be more sensitive than others. The model efficiency was evaluated using Nash–Sutcliffe Efficiency (NSE) which was greater than 0.75, varying between −10% and +10% and the coefficient of determination (R2) was approximated to be 0.8 during the calibration and validation period. The model parameters in ungauged catchments were determined using the regional model (linear regression), sub-basin mean, area ratio, and spatial proximity methods, and the discharge was simulated using the HEC-HMS model. Linear regression was used in the prediction where p-value ≤ 0.1, determination coefficient (R2) = 0.91 for crop coefficient (CC) and 0.99 for maximum deficit (MD). Constant rate (CR), maximum storage (MS), initial storage (IS), storage coefficient (R), and time of concentration (TC) were obtained. The result is that an average of 30 m3/s and 15 m3/s as the maximum monthly simulated flow for ungauged sub-catchments, i.e. Denchiya and Mansa of the main river basin.

Emad Jahangir, Laura Blanco-Martín, Faouzi Hadj-Hassen et al.

This paper proposes a new interface constitutive model for fully grouted rock-bolts and cable-bolts based on pull-out test results. A database was created combining published experimental data with in-house tests. By means of a comprehensive framework, a Coulomb-type failure criterion accounting for friction mobilization was defined. During the elastic phase, in which the interface joint is not yet created, the proposed model provides zero radial displacement, and once the interface joint is created, interface dilatancy is modeled using a non-associated plastic potential inspired from the behavior of rock joints. The results predicted by the proposed model are in good agreement with experimental results. The model has been implemented in a finite element method (FEM) code and numerical simulations have been performed at the elementary and the structural scales. The results obtained provide confidence in the ability of the new model to assist in the design and optimization of bolting patterns.

Artem V. Degterev, Marina V. Chibisova

The Ebeko volcano located in the northern part of Paramushir Island (Northern Kuril Islands) is currently the most active volcano of the Kuril Island arc: since 2016, next explosive eruption has continued, proceeding in the form of regular ash-gas explosions of moderate force. In the period from January 2018 to October of 2020 a total of at least 1834 emissions were recorded (during daylight hours and under good weather conditions). In May–July 2020, the intensification of the eruptive activity of the volcano was observed, that manifested in a sharp increase of the emissions frequency and height. During this period, 296 emissions were recorded, 90 of which were at an altitude of 3 km or more.