Bulletin of Engineering Geology and the Environment最新文献

The maximum impact force (F_max) and maximum penetration depth (δ_max) are critical parameters in the design of rockfall protection structures. Current methods for calculating rockfall impact force often simplify the rockfall as a sphere, thereby neglecting the significant effects of rockfall shape and impact angle, which can lead to estimation inaccuracies. Through experimental and numerical analyses, we demonstrate that the F_max occurs at a 90° impact angle, with the F_max of an ellipsoidal rockfall (sphericity = 0.6) being 1.42 times greater than that of a spherical rockfall. Conversely, at a 0° impact angle, the δ_max of ellipsoidal rockfall is 1.72 times greater than its spherical rockfall. This phenomenon indicates that calculating impact force by assuming a spherical rockfall shape may underestimate the actual impact force, resulting in inadequate safety of the protective structure. Based on these findings, we propose two innovative calculation methods for evaluating the F_max and δ_max exerted by an ellipsoidal rockfall impacting a sand cushion. The first method proposes the shape magnification coefficient, and establishes the quantitative conversion relationship for F_max and δ_max between ellipsoidal and spherical rockfalls through experiments and simulations. The second method, based on Hertz contact theory, the analytical solution including shape parameters is derived. The suggested values of F_max and δ_max for ellipsoidal rockfalls are given. Verification indicates that new models enable more accurate prediction of F_max and δ_max for ellipsoidal rockfalls. The results can be applied to the design of protective structures such as shed tunnels, effectively enhancing the accuracy and economy of rockfall disaster prevention and control.

Thermal shock from high temperatures and prolonged heat exposure can cause irreversible damage to natural stones, underscoring the need for thorough characterisation. This study examines the effects of thermal exposure at 300 °C and 600 °C, temperatures simulating moderate and high thermal shock, on thirteen carbonate lithologies, including limestones, marbles, travertine, and breccia. Key surface properties, colour, gloss, and roughness, are evaluated to quantify aesthetic impacts and understand the underlying chemical and mineralogical processes. FeO-richer stones show significant increases in the a* coordinate (up to Δa* = +34.37) at 300 °C, driven by the transformation of goethite into hematite. In contrast, stones richer in organic matter exhibit marked decreases in lightness (up to ΔL* = −18.78) at 600 °C, due to the transformation of amorphous organic matter into crystalline phases. Porosity plays a critical role at higher temperatures, correlating with higher ΔL* values, since more porous stones enhance heat transfer and promote the combustion of organic matter. Lightness is influenced by both gloss and surface roughness, with gloss having a more pronounced effect on L*. Statistical analyses, including Tukey’s HSD test, reveal significant differences in stone responses to thermal shock, highlighting their varying degrees of thermal susceptibility. Principal Component Analysis (PCA) identifies colour as the main driver of variability, followed by gloss and roughness. These findings provide a predictive framework for assessing the thermal vulnerability of carbonate stones in relation to their residual composition and texture. Such insights support informed decisions in material selection, conservation strategies, and architectural design, thereby enhancing the long-term durability of natural stones in both heritage and contemporary contexts.

Küfeki stone, a fossiliferous limestone, is one of the essential stone types in many monumental structures and historical buildings constructed throughout the history of İstanbul. For this reason, selecting a suitable stone instead of the Küfeki stone is a critical issue in restoration. In this study, the petrographic, mineralogical, physical, and mechanical properties of travertine and different types of limestone obtained from quarries close to the region, which have been used instead of Küfeki stone in restorations so far, were compared with the properties of Küfeki stone. After all analyses and experiments, microscopic and petrographic analyses were found to be determinative studies in interpreting the physical and mechanical properties of the stones and the effects of durability tests on them. In addition, it is important to perform color and ultrasonic velocity measurements as they are easily applicable, non-destructive methods in the field and provide interpretable and meaningful results. Care should be taken to ensure that the durability tests planned to be carried out represent the environmental conditions of the structure where the stone will be used. The stones most similar to Küfeki in matrix and allochem type generally gave the most compatible results.

Volcanic ash (VA) has the potential to serve as a filling material in volcanic regions. Despite the available research on various soil materials, there remains a noticeable gap in the literature concerning the dynamic engineering properties of volcanic ash fill materials. Therefore, 104 dynamic triaxial tests were conducted to investigate the influence of initial water content, confining pressure, and dynamic stress on the dynamic properties of VA. The results revealed that the accumulated plastic strain positively correlates with water content and dynamic stress, while an increase in confining pressure improves deformation resistance. At high dynamic stress levels, the strength of specimens becomes insufficient, leading to shear instability. In an unsaturated state, the dynamic modulus exhibits a triphasic behavior characterized by a sequence of “reduction - increase - reduction”, which can be attributed to the three stages of “structural damage - compression densification - particle breakage”. The damping ratio decreases with vibrations. When specimens are saturated, they display liquefied damage with an increase in dynamic stress. The dynamic modulus decreases with dynamic strain, while the damping ratio initially decreases before increasing. This study enhances the understanding of dynamic properties of volcanic ash soils and provides a reference for the application of volcanic ash in geotechnical engineering.

Longyou Grotto argillaceous siltstone is highly sensitive to water infiltration, and its strength degradation poses a serious threat to the stability of grotto chambers and underground engineering. In this study, in situ uniaxial compression tests combined with high-energy CT real-time scanning and PFC2D numerical simulations were conducted to investigate crack evolution under different moisture distributions. Stress–strain curves and fracture morphologies obtained from CT experiments were used to calibrate the numerical model. Experimental results show that the strength–moisture relationship is nonlinear. When the moisture content is below 50%, strength decreases with increasing water content, whereas when the moisture content exceeds 50% and approaches saturation, the strength reduction becomes less significant. The numerical simulations reproduced the entire loading process, capturing strength characteristics and fracture patterns consistent with CT observations, and revealed that crack evolution and acoustic emission (AE) features also vary systematically with moisture content. Higher moisture levels promote shear rather than tensile cracking, with vertical fractures predominating, and AE activity shifting toward more numerous, smaller, and more dispersed events. Both experimental and numerical results further demonstrate a distinct transition in fracture patterns: from single inclined shear failure under low moisture, to X-shaped conjugate shear failure under moderate moisture, and finally to splitting-induced surface spalling and internal shear damage near saturation. These findings clarify how moisture content governs the strength and fracture mechanisms of argillaceous siltstone, providing new insights for the preservation and long-term stability assessment of water-affected underground grottoes.

Dispersive soil has attracted extensive attention from the academic community due to their rapid dispersion and disintegration upon contact with water, thus affecting the stability of engineering construction. In this study, a range of tests including the pinhole test, crumb test, unconfined compressive strength test, direct shear test, moisture content test, particle size analysis, infiltration test, resistivity test, disintegration test, and scanning electron microscope examination were conducted. The purpose was to investigate the effects of varying salt content, clay content, and reservoir environmental conditions on the dispersibility, physical, and mechanical properties of dispersive soil. The test results indicated that the rise of salt content led to enhanced soil dispersion and a corresponding decrease in the soil mechanical strength. Consequently, the unconfined compressive strength of the soil samples decreased from 126.0 kPa to 94.0 kPa, and the cohesive force was reduced from 50.9 kPa to 44.3 kPa. The increase in clay content reduced soil dispersion and enhanced the mechanical strength of the soil. As a result, the unconfined compressive strength of the soil samples increased from 125.0 kPa to 298.0 kPa, and the cohesive force increased from 53.6 kPa to 122.5 kPa. In both processes, the soil liquid limit and plastic limit increase, while the coefficient of permeability and electrical resistivity decrease. This occurs because NaHCO₃ enhances the thickness of the bound water film on the soil particles surfaces, which reduces the inter-particle connecting force. Clay contributes to the soil connectivity and fill the pore spaces, thereby altering the soil physical and mechanical properties. In acidic and alkaline reservoir water environments, the disintegration rate of soil samples accelerated with the increase in both acidity and alkalinity. In salt solution environments, the disintegration rate of soil samples initially increased and then decreased as the mass fraction of the salt increased. These findings offer an empirical foundation for the design of geotechnical and water conservancy projects, enhancing the comprehension of the engineering geological characteristics of dispersed soil, holding significance in both practical and theoretical realms.

The failure characteristics, crack propagation of gas-containing coal seam and variation of effective stress and energy of coal seam before and after working face excavation were revealed in this paper. The results demonstrated that: (1) The damage along any direction with more cracks, formation of an X-shaped failure surface, and formation of a monoclinic failure surface were observed after loading in gas-containing coal samples with confining pressures of 0 MPa, 1.5 MPa and 2 MPa, respectively. (2) As the confining pressure increased, the peak strength, peak volume strain, difference between volume strain and crack volume strain, crack axial strain rate and time required to reach peak stress of gas-containing coal samples successively increased. After the gas-containing coal sample reached the peak stress, crack radial strain rate was greater than crack volume strain rate, while the average crack volume strain rate and the average crack radial strain rate successively increased. (3) The numerical simulation results reveled that energy and effective stress in coal seam decreased, when roof of transportation roadway was cut. The energy and effective stress significantly reduced when the inclined length of advanced working face was in the range of 50–110 m. (4) The field monitoring showed that there was no gas overrun in roadway after the implementation of the roof-cutting and pressure-relief technology without coal pillar. The average gas extraction concentration in the gas extraction pipeline increased by 23.3% in advance working face of transportation roadway during the period of roadway retention, which improved gas extraction concentration.

The Los Angeles abrasion (LAA) value is one of the basic properties of rock aggregates reflecting their resistance to mechanical abrasive factors such as repeated impact loading. Brittleness represents a key mechanical attribute of rocks, exerting a strong influence on their behavior during excavation, drilling, blasting, and aggregate production. This study investigates the relationship between LAA values and five strength-based brittleness indices (B₁-B₅) derived from uniaxial compressive strength (UCS) and Brazilian tensile strength (BTS) values of different rock types. A dataset of 138 rocks (76 sedimentary, 42 igneous, and 20 metamorphic) compiled from 11 literature sources was analyzed using regression methods. Results show that while brittleness indices B₁ and B₂ do not exhibit any significant correlation with LAA, brittleness indices B₃, B₄, and B₅ show moderate inverse-logarithmic relationships across all investigated rock types. After normalization with UCS, brittleness indices B₃, B₄, and B₅ exhibit very strong inverse relationships with LAA values (R² up to 0.96). Normalized LAA significantly improved correlations, particularly for B₃, which provided the most reliable predictor across all rock types according to ANOVA. An empirical model based on B₃ was developed and validated with 16 different rock samples, demonstrating close agreement between measured and predicted LAA values. These findings confirm that strength-based brittleness indices, especially B₃, can serve as robust predictors of aggregate abrasion resistance.

Tensile failure in jointed rock masses governs the safety of underground excavations and hydraulic structures, yet the combined roles of joint inclination, joint roughness coefficient (JRC) and matrix strength under splitting conditions remain insufficiently quantified. Here we fabricate disc specimens with 3D-printed rough joint molds and cement-mortar matrices calibrated against field sandstone properties, and conduct Brazilian tests across seven inclinations (0°–90°), four JRC levels (4–16), and three matrix strengths. We further perform PFC2D simulations with geometrically prescribed roughness and a contact-weakening scheme on the joint plane to reveal microcrack evolution. Results show a hierarchy of sensitivity inclination > matrix strength > JRC; two critical inclinations (α_J, α_L) control transitions among Type I: matrix, Type II: combined, and Type III: joint plane damage. The observed intensity dips in normalized strength coincide with α_J and α_L, reflecting shifts in the tensile–shear microcrack ratio localized on the joint plane. Theory rationalizes how decreasing matrix strength lowers α_L, promoting earlier joint-plane dominance, whereas JRC mainly modulates crack kinematics at small–moderate inclinations and becomes marginal at 90°. The study provides a micro-to-macro framework for interpreting tensile behavior of jointed rocks under splitting.

The mechanical properties of metal rock mass are important factors affecting the wide application of microwave-assisted stress wave blasting in geological exploration and mining, as well as blasting efficiency and safety. In this paper, the genetic algorithm optimization of long short-term memory (GA-LSTM) model is applied to predict the dynamic compressive strength (DCS) of magnetite. With heating time and heating power as the test variables, the simulated blasting test of microwave-treated magnetite is carried out by using separated Hopkinson pressure bar. The fracture characteristics of magnetite under microwave-assisted stress wave blasting under laboratory conditions are revealed. Results show that under different microwave heating conditions, the decrease rate of DCS of the specimen is 19.95% to 56.67% and the P-wave velocity is reduced by 2.21% to 13.22%. The black crystallized spots near the fracture zone dominated by iron minerals are caused by microwave heating, which becomes the main reason to enhance the fracture dissociation of magnetite. Under the synergistic action of microwave and dynamic load, irregular section and rough zone are produced inside the magnetite, which intensifies the impact and extrusion between particles and promotes the deep breaking of the magnetite.