Bulletin of Engineering Geology and the Environment最新文献

Cemented sandy gravel is often used to enhance the foundation soil of engineering projects. This paper presents results of triaxial tests on cemented sandy gravel specimens. We compared 8 cemented specimens and 4 uncemented specimens. The strength, dilatancy, and stiffness behavior of both cemented and uncemented specimens are compared. The strength of cemented specimens is significantly greater than that of uncemented specimens, and the cemented specimens demonstrate pronounced expansion characteristics. The peak friction angle of the cemented specimen shows a linear relationship with the confining pressure: ψ = 68.1–18.2·lg(σ₃/pa). To quantify the structural strength of the cemented specimens, a structural damage parameter is introduced based on the differences in mechanical properties between the two materials. The structural damage parameter first increases and then decreases as shearing progresses, and a hump curve function is used to describe this behavior. In the frame of the generalized plasticity, a novel elastoplastic model is established, considering the structural parameter as a factor of the plastic modulus, loading vectors and plastic flow direction vectors. The calculated values fit well with the experimental results. The model can reflect the characteristics of cemented sandy gravel, in terms of stress softening, residual strength, and volumetric dilation. Finally, the model is used to evaluate the deformation of a sluice dam foundation after being enhanced with cemented sandy gravel. The results show that after treatment, both the settlement of the gate floor and the shear deformation of the waterstops can be reduced by more than 10%.

Focusing on the complex challenges faced in the field of earthquake emergency response, this paper innovatively introduces a semi-supervised incremental learning (SSIL) strategy, which skillfully integrates the fast response characteristics of the physics-based analytical method with the data mining capabilities of the data-driven method. The framework relies on the Newmark method to build the semi-supervised learning foundation, and iteratively optimizes the machine learning (ML) model by continuously absorbing new data through the incremental algorithm, which demonstrates excellent information extraction performance and data fusion capability under resource-limited conditions. The study applies Bayesian optimization (BO) algorithms to tune the parameters of various machine learning models, such as Convolutional Neural Network (CNN) and Support Vector Machine (SVM). which significantly enhances the flexibility and prediction accuracy of the models, thus advocating the inclusion of BO in the process of standardizing machine learning models. In addition, this paper innovatively proposes a new evaluation criterion for Landslide Sensitivity Interval Frequency Ratios Index (LSIFRs), which directly maps the regional landslide risk sensitivity and can be used as a scale for landslide sensitivity prediction (LSP) accuracy. The results show that the SSIL strategy proposed in this paper is an ideal solution to meet the needs of post-earthquake emergency response. After a comprehensive assessment of the model performance, it was found that the SSIL-BOSVM model, which underwent BO enhancement, demonstrated significant utility and efficiency in practical applications, with a high area under the ROC curve (AUC) of 0.884 and an LSIFRs value of 0.416. The model can serve in future earthquake emergency management and post-disaster reconstruction work with technical support and data support.

To investigate the impact of fault fracture zones on the seepage field distribution and groundwater discharge of tunnels, three-dimensional numerical models with different distribution patterns of fault permeability coefficient are established. These models reveal the varying characteristics of groundwater head, water pressure and water inflow as the tunnel traversed faults or their adjacent areas. By combining on-site measurement and synthetic conceptualizations of three cases, the distribution of seepage field and water inrush control measures of the Paoma Tunnel passing through multiple faults are studied. In the case of tunnel crossing a single fault, the water head values of the overlying and underlying strata significantly decrease once the fault is revealed during tunnel excavation. Transitioning from a C-shaped to L-shaped or U-shaped distribution pattern of fault permeability coefficient enhances the fault's impact on groundwater head distribution. In the case of tunnel near fault, increasing tunnel-fault distance results in lower permeability around the tunnel and steeper hydraulic gradient. The existence of fault causes asymmetrical distribution of hydraulic head, water pressure, and water inflow in the tunnel site. The case of tunnel crossing multiple faults mirrors the real conditions encountered in the Paoma Tunnel. Simulation results show the maximum water pressure and groundwater discharge within fault zones are 10 ~ 30 times higher than those in the non-fault section. After grouting reinforcement of the fault fracture zone, the groundwater head and water pressure significantly increases, and the maximum water inflow decreases by nearly 90% compared to the non-grouted state.

Vehicle-induced disturbances pose significant risks to forest soil integrity. This study investigates the effects of gravel content and freeze–thaw (F-T) cycles on the shear strength of layered forest soils obtained from northeastern China. By analyzing the relationship between the shear strength variations and pore structure evolution of layered forest soils, this study provides critical insights into mitigating environmental challenges and maintaining the stability of such soils. Specifically, 216 remolded forest soil samples obtained from two soil layers were collected and tested and the corresponding findings revealed that changes in gravel content and F-T cycles alter the soil pore structure, consequently influencing soil shear strength. The results also indicated that an increase in the gravel content results in a reduction of soil volume in small pore spaces within the investigated forest soils, while the volume of medium and large pore spaces increases. This leads to gravel particles that gradually dominate the soil framework, causing the soil structure to become loose with an increased porosity. The impact of F-T cycles on the forest soil pore structure was found to be particularly pronounced. Notably, the observed trends found in the current study differ from previous studies on other soil types such as farmland and paddy fields. The results of this study help in refining soil engineering design in forested areas and mitigating the compaction impact resulting from forestry machinery interactions with the soil. Furthermore, the results offer vital data that support assessing geological hazard risks and analyzing soil stability in forested regions.

Rock slope failure is commonly regarded as the most significant phase in the evolution of an unstable rock slope. However, many rock slopes do not fail in a single event but rather in several individual ones. Such polyphase rock slope failures impose a challenge, as their post-failure evolution is hard to predict, and the time interval between the failure events, their magnitude, and running-out distance can differ significantly for each respective event. In this study, we present a unique data-set of high-resolution remote sensing data acquired from a 170 m high, steep to overhanging post-failure rock slope over a 3.5-year survey. By applying ground-based interferometric synthetic aperture radar, unmanned aerial vehicle photogrammetry, and a 3D distance approach on terrestrial laser-scan data, we unravel the post-failure rock slope evolution on the example of the Hüttschlag study site (Salzburg, Austria). Accompanied by meteorological data and supported by a discrete element modelling approach, i.e. the asymmetric Voronoi logic, we (i) prove that the post-failure rock slope remains an active system, even 3.5 years after the latest major rock slope failure event, (ii) outline advantages and limitations of the respective remote sensing techniques, (iii) emphasise the challenge of identifying unambiguous triggers, and link this challenge to progressive failure within a fractured, anisotropic rock mass. Our findings highlight the importance of considering the time-dependency of rock mass strength and improve our understanding of post-failure rock slope evolution and rock mechanical processes in complex geological media.

The development of cracks and deterioration of mechanical properties in aeolian deposits are common phenomena during dry-wet cycles. The redistribution of soil particles and the change of clay mineral aggregates are some of the reasons for the change in soil properties in this process. In this paper, the physical and mechanical properties, apparent digital images, and scanning electron microscopy (SEM) were used jointly to analyze the properties of silty clays (Xiashu loess) during the dry-wet cycle. The amplitude design of the dry-wet cycle is 2.52%-28.39%, and the number of cycles was designed to be 2,4,6,8and 10 times. The results show that the shrinkage and breakage of clay minerals and the release of pore water stress are caused by the change in water content leading to the redistribution of aggregate particles. The permeability and swelling ability of soil tend to be stable, indicating the stable trend of particle redistribution. The soil cohesion and internal friction angle have an exponential relationship with the number of dry-wet cycles, and the exponential relationship parameters are related to the soil type. Based on the analysis of particle migration, it can better explain the reasons for the deterioration of soil mechanical properties.

The changes in landslide material and human engineering activities have often posed important impacts on debris flow risk. In this study, multi-period remote sensing images and unmanned aerial vehicle aerial images are used to monitor the prolonged variation in landslide materials transfer for debris flow initiation. Simultaneously the FLO- 2D model and vulnerable curve were used to detect the risk of debris flow in the later period (after 2023). After 15 years of the Wenchuan earthquake, the hillslope landslide materials delivery for debris flow initiation is limited. Impacted by the changes in solid materials, topography and human engineering activities, the risk of debris flow with a recurrence period of 10, and 20 years has been effectively reduced, but for the 50 and 100 years of recurrence period situation, the impact of human engineering activities and channel topography on debris flow risk is limited. For the 10, 20, 50 and 100 years of recurrence period situation, the buildings are at"extreme"and"high"risk was 0, 21, 38, and 115, respectively. Therefore, the monitoring and early warning is still an important measure to reduce economic losses and casualties in the later period.

Assessing the Geological Strength Index (GSI) of subsurface rock masses often presents challenges to inexperienced engineers, primarily due to the limited exposure of discontinuities in the rock masses. This study combines data from 12 drilled cores from Maerdang and Shanyang hydropower stations, including their Lugeon test results. The statistical results show the GSI of the rock mass rises with depth and falls with an increase in Lugeon values, both these relationships are weak correlations. The correlation between the GSI and Lugeon values is significant only when the Lugeon values surpass a specific threshold. There exists difference in the Lugeon value threshold and the correlation between GSI and Lugeon values in monzonite and metamorphic sandstone. For monzonite, a power-law relationship is observed when the Lugeon value exceeds 2, a linear relationship arises for metamorphic sandstone when the Lugeon value surpasses 0.5. On the basis of above, the research develops GSI prediction equations for monzonite and metamorphic sandstone using multiple regression methods. Given the limited data from only two projects, more research is needed to validate the wider application of the GSI prediction equation.

The properties of soils are highly complex, and therefore, the classification system should be based on multiple perspectives of soil properties to ensure effective classification in geotechnical engineering. The current study of research demonstrates a lack of correlation between classification systems based on soil plasticity and those based on in-situ mechanical properties of soils. A CPTu-based plasticity classification system is proposed using the soil behaviour type index (I_c), with its reliability and limitations discussed. The results indicate that (1) I_c has the capacity to predict the stratigraphic distribution from the in-situ mechanical properties of soils. It showed a significant linear correlation with w_L, which soil classification zone was similar to that of clay factor (C_F); (2) A CPTu-plasticity classification system is proposed to characterize both plasticity and in-situ mechanical properties of soils. This system allows for the initial classification of soils solely based on CPTu data. Furthermore, it has been established that I_c = 2.95 can delineate the boundary between high- and low-compressibility soils. (3) The error is only 25.2% relative to the Moreno-Maroto classification chart, and the system tends to classify soils of intermediate nature as clay or silt. The distance between the data points and both the C-line and the new C-line (ΔI_p, ΔI_pIc) showed a significant positive correlation. Only one data point was misclassified, considering human error in measuring I_p. (4) The new classification chart has been found to be more applicable to offshore and marine soils.

Weathering can have significant impacts on the geoengineering properties of limestone and dolomite, leading to notable changes in their characteristics and behavior. In this study, two aggregate quarries located in Gebze, Türkiye were investigated to understand the weathering characteristics of limestone and dolomite. In the context of this study, a simple chemical index to identify weathering grades of limestone and dolomite was proposed. To propose this abovementioned weathering grade index, not only various analyses, including mineralogical, petrographic, chemical, physical and mechanical investigations, but also field studies and in situ observations were considered. In terms of field observations, the studied rocks are primarily gray in color, but a brownish red color dominates weathered rocks. Along the rock mass, it was also clear that the spacing of discontinuities decreased while the apertures increased due to weathering. The number and geometry of karstic cavities that formed as a result of chemical changes are also highly distinctive properties for determining weathering, particularly for certain weathering grades. In terms of laboratory tests, on the other hand, as weathering increased, the specific gravity decreased, whereas the unit weight and water absorption values increased for the studied rock samples. Significant correlation coefficients (R² > 0.80) were obtained from the relationships between the Weathering Index for Carbonate Rocks (WICR) values and the corresponding laboratory tests, i.e., loss on ignition, dry unit weight, specific gravity, and uniaxial compressive strength. The mechanical properties also considerably decreased with increasing weathering. This paper also discusses the typical and dominant weathering profiles observed for limestone and dolomite weathering.