Bulletin of Engineering Geology and the Environment最新文献

Slope failure triggered by collaboration of coal-mining activities, structural plane, karstification and rainfall is very frequently occurred in Guizhou, China. Subsequent four rock topples occurred in Daxian village, Bijie City since October 2022 continuously threatening the safety of the residents and exhibited a high possibility of reoccurring geohazards in the Yiziyan unstable rock belt. Temporal and spatial multi-source data from GNSS, sensors, video footage, aerial image and remote sensing are integrated to reveal the unstable rock belt deformation behavior. Detailed macro- and microscopic data reveal that slope experienced a three-stage deformation process with different displacement rate since devices started to monitor. Based on the comprehensive monitoring data, inverse-velocity method (IVM) was improved with two quantitative indexes: displaced angle and crack width, and it indicated a slope failure event approximately on 23rd June 2023. According to the prediction result, government emergently evacuated all the residents and took effective disaster management. Therefore, fatalities were avoided in the major rock topple event occurred on 20th June 2023 in Yiziyan which served as a highly valuable case of successfully forecast approaching slope failure. The modified IVM provides specific precursor of future potential geohazards in the similar geological condition in Guizhou.

This paper presents a case study in which wet and top feed vibro replacement stone columns are used to support a 20-m-high fuel tank built on loose to medium sand deposits. The design considerations, installations, applications, field tests, correlations, and subsequent three-dimensional finite element analyses are presented. The soil profile of the case study comprised approximately 8 to 12 m thick loose to medium-dense silty sand layers with a high groundwater table. The 1-m-diameter stone columns were installed in a triangular pattern with a spacing of 2.1 m. The improvement depths were 8, 11, and 12 m. After construction was completed, quality assurance of the stone column installation was performed via various field tests. Based on the hydro test results, the improved ground could carry an allowable bearing capacity of 200 kPa transferred from the 20-m-high fuel tank and exhibited a maximum settlement of less than 50 mm, which met the design criteria of this project. Owing to reasonable quality control during stone column installation, the tilt of the tank caused by the nonuniformity of the improved sands was less than 10 mm. The enhanced strength ratio of the surrounding sands was 2 the densification effect. Furthermore, three-dimensional finite element simulations were performed. The results were consistent with the field measurements, verifying the effectiveness of the ground improvement technique. This case study demonstrates the practical application and benefits of vibro-replacement stone columns in enhancing bearing capacity, minimizing settlement, and improving overall foundation stability in challenging geotechnical environments, contributing to future engineering practices for similar projects.

Debris flows represent significant threats in the Northern Andes of Patagonia (NAP). On May 1, 2019, during the winter season, an extreme hydrometeorological event of 122 mm accumulated in 24 h triggered debris flows in the Chaiguaco sector (42.1°S/72.4°W), cutting off different sections of the interregional highway with their deposits, leading southern Patagonia with no connection to the rest of Chile. The Chaiguaco debris flow represents the largest event generated at 1,240 m a.s.l. in an area heavily affected by faults. In this study, we conducted a comprehensive assessment of the factors influencing the generation of debris flows in the area, integrating field and laboratory analyses based on this representative event. The study explores three main aspects. The study explores a comprehensive interconnection of geomorphological, hydrometeorological, geotechnical, lithological, structural and mineralogical analysis, emphasizing the initiation of mass movements that can evolve into debris flows. We conclude that the Chaiguaco event represents a typical case of the NAP where an extreme hydrometeorological event in an environment where multiple factors interact triggers debris flows. We suggest addressing future studies from an interdisciplinary perspective, which can serve as baseline inputs for decision-making entities within the framework of the civil protection system of the NAP.

The frequent occurrence of geological disasters in the Loess Plateau is related to the low tensile strength of the loess. Previous studies on fiber-reinforced loess mainly focused on compressive properties, and there have been fewer studies on tensile behaviors, especially when subjected to dry-wet cycles. In this paper, the tensile strength and deformation behaviors of basalt fiber-reinforced loess in the range of 0 to 10 dry-wet cycles were studied by uniaxial tensile test combining digital image correlation (DIC) technology. The results reveal that the unreinforced loess has no visible post-peak curve and brittle fracture occurs, while the reinforced loess has a residual strength and shows distinct ductile failure. The uniaxial tensile strength (UTS) of reinforced loess decreases with dry-wet cycles, but the decay rate decreases. The resistance of reinforced loess to dry-wet action is better than loess, with an optimal fiber content of 0.6%. The variation of failure strain of reinforced loess is consistent with UTS with a linear correlation between the two, indicating that the strength is directly related to its deformation resistance. The maximum axial strain in the surface strain field of reinforced loess shows an increasing trend with dry-wet cycles and a decreasing and then increasing trend with fiber content, which is opposite to UTS and failure strain. Fiber reinforcement improves the plastic properties of loess, and the deformation of reinforced loess is more uniform. This study reveals the deterioration law of reinforced loess under dry-wet cycles, providing theoretical support for engineering construction in loess areas.

In order to improve and optimize the advance classification and prediction method of tunnel surrounding rock, a prediction method based on Tunnel Seismic Prediction (TSP) and Probabilistic Neural Network (PNN) is proposed. Based on the characteristics of science, maneuverability and representativeness, several factors that greatly affect rock mass classification are selected as evaluation indices based on analysis of numerous TSP data, establishing an advance classification index system for surrounding rock, and designing the “Advance classification and prediction system for surrounding rock” to predict the classification. Engineering application of Jinpingyan Tunnel of Chenglan Railway in high altitude and high intensity area of China is taken as a case study, and proved that the evaluation indices are easy to obtain and the evaluation results are accurate and reliable, and compared with Back Propagation (BP) neural network prediction results, the results show that PNN has some advantages in predicting the calculation speed of surrounding rock classification, the ability to add samples and the classification accuracy in practical engineering applications. The PNN-TSP method can be further used for other tunnel engineering.

Accurately estimating the blastability of rock mass is crucial for precise blasting design, enhancing blasting efficiency, and minimizing unnecessary damage to the rock mass. Despite the development of various methods for blastability evaluation, none has gained wide acceptance due to the complexity of rock masses. This paper aims to systematically review the development of blastability evaluation research to enhance understanding in this area. Firstly, factors affecting the blastability of rock mass were summarized and classified. Based on this, blastability evaluation indexes were categorized into four classes: characteristic parameters of rock, structural parameters of rock mass, blasting parameters, and external factors. The selection principles of blastability evaluation indexes were discussed. Secondly, the methods of blastability evaluation including single index empirical criterion method, multiple indexes aggregation method, comprehensive evaluation method, and machine learning method, were summarized. The applicability and advantages of each evaluation method were introduced. Finally, trends in blastability evaluation of rock mass were proposed, including the intelligent acquisition of rock mass parameters, three-dimensional blastability evaluation, broadening the scope of evaluation, and widespread application.

Ultrasonic sounding, petrographic image analysis, and mercury intrusion porosimetry was performed on 52 Westerly granite (Rhode Island, USA) specimens exposed to controlled heating from 100 °C to 800 °C. Elastic wave velocities, dynamic elastic moduli, and amplitudes decreased quasilinearly by more than 65% (P-wave), 75% (S-wave), and over 90% (elastic moduli). Damage evaluation by using two crack density parameters proved similar behavior. Direct and indirect evaluation of thermal treatment related microcracks by means of petrographic image analysis and mercury intrusion porosimetry revealed exponential character of porosity evolution, being accelerated above the (alpha -beta) quartz phase transition. Discrepancy between thermal treatment and profoundly non-linear increase in porosity and microcrack density can be satisfactorily explained from direct microscopic observation which revealed formation of crushed/powdered minerals within newly formed microcracks in 650‒800 °C range being related to tension-shearing along grain boundaries of phases with contrasting linear thermal expansion coefficients. This damage phenomenon, resulting in the so-called “clogged” porosity evidently overvalued measured elastic wave velocities. Current results thus underline importance of application of various methods / techniques during examination of changes in rock microfabric from decay processes because none of the methods is capable to cover all important factors alone.

An important parameter of the Hoek-Brown failure criterion for intact rock materials is m_i, a dimensionless material constant that depends on the frictional characteristics of the component minerals. In this study a laboratory testing program was carried out in order to experimentally study the correlations between m_i and two frictional parameters: (a) the sliding friction angle which is determined from direct shear tests on pre-fractured rock specimens and (b) the Mohr-Coulomb internal friction angle which is determined from triaxial compression strength tests conducted at low confining stresses. We carried out direct shear tests on rough tension joints of ten fresh, low porosity (< 5%) natural rocks, including two igneous, three sedimentary and five metamorphic under normal stresses ranged from 0 to 2 MPa and determined the sliding friction angle φ_nd using peak shear stress and dilation measurements. An independent series of triaxial compression tests was conducted on intact cylindrical specimens of the same rocks at various confining pressures up to 70 MPa and the values of the internal friction angle φ_i0 at low confining stresses were determined as well as the values of m_i, σ_ci and the principal stresses at the brittle-ductile transition. Our experimental results show that, within the used range of values of the parameters m_i, φ_nd and φ_i0, m_i increases linearly with decreasing sliding friction angle and increasing internal friction angle. Both correlations were found to be statistically significant at a significance level of 0.001.

This study analyzes static and dynamic ruptures in deep coal mining and their impacts on working faces. Using a 2-D numerical model with PyLith, we evaluate the energy, stress disturbances, and seismic wave effects induced by a nearby reverse fault. By pioneering PyLith in induced seismicity research, we provide critical insights into the interactions between mining operations and geological structures. The model simulates fault slip processes and their effects on the working face, focusing on stress changes, energy concentration, peak particle velocity (PPV), and peak particle acceleration (PPA) under varying conditions of mining-induced seismicity. Static deformation due to fault slip caused significant stress changes on both the ceiling and floor of the working face, with stress values ranging from 0.9 MPa to 39 MPa in σ_xx, 0.6 MPa to 14.7 MPa in σ_xy, and 1.1 MPa to 22 MPa in σ_yy. Energy concentration was observed at the corners of the working face near the fault. Dynamic analysis revealed rupture durations ranging from 250 ms to 670 ms, with rupture velocities decreasing from 1.25 km/s to 0.62 km/s as the characteristic slip distance (D_c) increased. Seismic waves showed that both PPV and PPA decreased with increasing D_c. Our findings highlight the necessity of advanced numerical modeling to predict and manage hazards associated with mining-induced seismic events. Additionally, the study emphasizes the importance of designing robust support systems and implementing safety measures to ensure the stability and safety of mining operations under seismic conditions.

This paper aims to investigate the influence of particle breakage on the dynamics and deposition of rockslides. A rigid-body finite element formulation incorporating bond beam element is proposed to model rock breakage behaviors. This approach enables simulations of particle fragment rolling, collisions between adjacent pieces, and impacts of pieces with the bedrock. Numerical analyses were conducted considering the variations in volumes, breakage modes, breakage efficiency, and the friction coefficient of bedrock surfaces. Simulation results demonstrate a negative linear correlation between the runout distance and the volume of rock blocks. Incorporating fragmentation effects, this study reveals that the breakage efficiency of maternal rock blocks significantly influences the energy dissipation process and the downslope movement of rockslides. Despite variations in breakage modes leading to distinct deposit configurations, run-out distances remain basically consistent. Analysis of block contributions from various source locations indicates that the longitudinal spreading of the deposit primarily depends on blocks distributed on the periphery of the rock mass.