Bulletin of Engineering Geology and the Environment最新文献

Rock discontinuities are crucial to the stability of rock mass. Under complex high-steep slope conditions, such as the interference of vegetation, a large number of discontinuity sets, and a high degree of weathering, the characterization of rock discontinuities is usually challenging. To this end, this paper proposed an approach for rock discontinuity identification and characterization based on UAV photogrammetry and artificial neural network (ANN) algorithm. UAV photogrammetry was used to obtain 3D point clouds of the study area. The vectors of multi-dimensional features including point cloud orientation features (Normal vectors), geometric features (Anisotropy, Planarity, Roughness, etc.), and optical features (RGBVI), were obtained by calculation. Then, by constructing an ANN model and using the multi-dimensional feature vectors as the network input, the multivariate classification task of rock discontinuities was realized. The ANN algorithm can simultaneously identify and classify all discontinuities of the rock mass and non-discontinuities, as well as each rock discontinuity set. On this basis, the extraction of the individual discontinuities was achieved by the Fast-marching approach. Two case studies were utilized to illustrate the methodology. The results show that this approach has high accuracy and high computational efficiency. The main advantage of the proposed approach is that the ANN can handle complex discontinuity extraction tasks without a complicated pre-processing process, making it highly applicable.

The salinization of sulfate saline soil in frozen regions can lead to severe potential environmental hazards, such as increased salt heaving and collapsibility. Corn stalk ash (CSA), a typical agricultural waste that is non-polluting to soil, groundwater, and the environment, possesses high pozzolanic activity and is a potential amendment for sulfate saline soil. To verify the feasibility of using CSA to improve sulfate saline soil, a series of experiments were conducted to study the effects of CSA content, salt content, and freeze–thaw cycles on the mechanical properties of the improved soils. A statistical damage constitutive model was established that comprehensively considers the coupled effects of freeze–thaw, salinity, moisture, and loading to more accurately describe the improvement effects of CSA. The study shows that CSA is highly effective in improving sulfate saline soil. The application of this method can significantly increase the unconfined compressive strength (UCS) of sulfate saline soil and greatly enhance their freeze–thaw resistance. The best improvement effect was observed with a CSA content of 15%. Furthermore, the coupled statistical damage constitutive model more accurately and intuitively analyzed the entire deformation and failure process of the improved soil under coupled effects, showing that the addition of CSA enhances the brittle characteristics of the improved soil while reducing its plastic deformation and ductile failure characteristics. In summary, the method of using CSA to improve sulfate saline soil is highly effective and environmentally friendly, providing a theoretical basis for improving sulfate saline soil in seasonally frozen regions.

Several machine learning-based Newmark sliding displacement prediction models have been developed by researchers to assess the seismic performance of numerous slopes in a region. Sliding displacements induced by pulse-like ground motions (PGMs) are larger and cause more severe damage. However, existing machine learning-based models cannot accurately predict PGMs-induced sliding displacements. In this research, a Newmark sliding displacement prediction model considering PGMs is developed by improving in two aspects: sliding displacement generation and intensity measurements (IMs) selection. The improvement in sliding displacement generation can avoid unfavorable underestimation of sliding displacements. While the improvement in IMs selection can increase the efficiency of models in previous studies, the R² is improved by up to 83.71% and the RMSE is reduced by up to 45.49%. In addition, the proposed prediction models can satisfy the sufficiency requirement.

Toppling in layered anti-inclined rock slopes generally trends towards self-stabilization over long periods of time. This progressive process poses a distinct challenge in the accurate evaluation of the stability condition of an anti-inclined rock slope. The universal distinct element code (UDEC) was used in this study to reproduce the mechanics of a toppling failure. We developed two FISH functions to capture detailed joint damage and track the evolution of the interlayer normal forces. The initiating and resisting mechanisms of toppling were investigated based on the results of the numerical simulation. An improved limit equilibrium method, which considers the effects of the interlayer forces, was established to quantitatively evaluate the stability of anti-inclined rock slopes subjected to initial rotation. We proposed a ratio between the actual slope deformation and the deformation in the layer symmetry condition to determine the self-stabilization of toppling deformations. The results demonstrate that initial rotation of rock columns is prone to occur on steep slopes with larger layer dip angles and lower internal friction angles of the rock layers. Significant differentials between principal stresses create larger interlayer shear stresses, thereby facilitating the initial rotation of rock columns. The toppling deformation is considered to have reached a stable state when the sum of the orientations between the initial and deflected layers in the middle of the slope equals 180°. The case study indicates that the formation of gaps between layers and the downward movement of interlayer normal forces significantly reduce the slope stability, with (:{F}_{mathrm{s}}) decreasing from 1.99 to 1.01. As toppling deformations reach self-stabilization, the deformation factor of safety in the middle of the slope remains approximately 1.

The southwestern region of country is characterized by its complex topography and high average elevation, with numerous jointed rock slopes. Additionally, the intricate terrain of high-altitude areas frequently results in seismic activity. This paper is based on the #1 tunnel slope project in the region, employing both shake table experiments and numerical simulations to analyze the failure modes of the jointed rock slope under seismic conditions and the stability of the jointed rock slope under different parameters. The integrated evaluation method was used in this paper to evaluate the dynamic stability of the slope, which considered both the seismic permanent displacement method and the Dynamic Strength Reduction Method. The specific conclusions are as follows: (1) The failure process of the jointed rock slopes was categorized into three distinct stages: local shear slip, slip surface formation and complete failure. The failure mode was summarized as shear slip failure occurring along the joint surfaces, accompanied by the collapse of locally fragmented rock masses. (2) the slope angle emerged as a significant factor influencing the failure mode of jointed rock slopes. Larger slope angles, greater joint dip angles and smaller joint spacings correlated with increased failure severity and diminished stability. (3) the maximum permanent displacement is positively correlated with both the slope angle and joint dip angle.

This paper presents a case study of soft-sediment deformation structures (SSDSs) in mining tailings from Central Mexico’s Guanajuato Mining District (GMD). We analyse SSDSs formed in anthropogenic historical environments (tailings) and under static (non-seismic) conditions in three inactive tailings deposits. Physical characterisation tests and sedimentological analyses were conducted at each site for SSDSs and their associations. We found that rapid sedimentation resulted in excess pore pressure, which caused overloading. This overloading was enough to trigger liquefaction and the formation of various SSDS types like flame structures, convolutes, folds, load casts, detached pseudo-nodules, and clastic dykes. The SSDSs and mechanisms described show that the tailings were momentarily liquefied and locally fluidised. However, no flow failure has been reported in the tailing deposits studied. SSDS studies based on known contexts are needed to improve and document the diagnostic features of liquefaction and fluidisation studies of non-seismic origin. Also, it is important to exercise caution when undertaking mining activities near tailing storage areas to prevent catastrophic consequences.

A fluid flowing through fractured rock masses has complex characteristics, and the fracture permeability of these rock masses is an essential parameter to evaluate the capacity of the fluid. In this work, five groups of fractured limestone samples with different joint roughness coefficient (JRC) were prepared using an innovative method. The effects of the JRC, filling fracture width (B_e), permeating solution, and confining and seepage pressures on the fracture permeability characteristics of limestone were investigated. The variation pattern of the fracture surface morphology was revealed, and the evolution of the fracture permeability of limestone was discussed. At constant confining and seepage pressures, the fracture permeability exhibited three distinct evolution stages with time: rapid decline, gradual decline, and stabilization. The stable value of the fracture permeability showed logarithmic and linear relationships with the JRC and B_e, respectively. Further, the results of permeability tests conducted on fractured limestone samples immersed in a sodium sulfate solution showed an increase in JRC from 2.50% to 36.61% for different fracture surfaces and a decrease in the sample permeability. The fracture permeability of the samples with different JRCs decreased with increasing pressure. There was a significant hysteresis effect during the unloading of the confining pressure. The loading and unloading of the seepage pressure reduced the fracture surface permeability at a confining pressure of 3.0 MPa and in the seepage pressure range of 0.2–1.5 MPa. This study provides a theoretical basis for estimating the fracture permeability of limestone and similar rocks.

As national energy demand increases, mining activities are extending deeper, raising concerns over the instability of anti-dip slopes. NPR anchor cables, known for high strength and ductility, address the limitations of traditional cables and are more suitable for deep slope support. Using the slope failure at the Changshanhao Gold Mine as a reference, based on the similarity ratio theory, we conducted model tests using the “Engineering Disaster Model Testing System” to compare disaster prevention effect between 2G-NPR and traditional anchor cables. The experimental results indicate that 2G-NPR cable can effectively redistribute external loads, achieving a stable constant resistance of approximately 35.2 N and demonstrating excellent adaptability under complex conditions. A thorough analysis was conducted on the stress-strain, temperature, and displacement fields throughout the slope failure process. The evolution of the monitoring data was summarized, and the failure patterns under 2G-NPR and traditional anchor cable support were compared. The study revealed the failure mechanism of anti-dip slopes and the working principles of the 2G-NPR cable in landslide control. A comprehensive evaluation of the application effectiveness of 2G-NPR anchor cables in landslide hazard mitigation was conducted, providing insights and guidance for the use of NPR anchor cables in anti-dip slope control projects.

The theoretical scheme of the Hoek–Brown criterion and Geological Strength Index (GSI) has been critical during analyzing engineering problems in karst geological environments. However, it is very difficult to explore the mechanical features of karstified rock mass. In this paper, a new corresponding way was put forward based on the Discrete Element Method (PFC^2D). Firs,a dissolution algorithm inspired by Cellular Automata was proposed to simulate discontinuity of karstified rock mass; then, according to the Hoek–Brown criterion, the relations between the GSI value of the karstified rock mass and GSI value of the jointed rock mass were deduced based on the results of a series of compression tests; finally, the karstified characteristics were incorporated into the GSI scheme. The following conclusions can be drawn: 1) in addition to the karstified rate (k), the karstified uniformity-coefficient (u) proposed in this paper is also an important influencing factor of GSI value, and the influencing degree of k is greater than u by about 3 times; 2) tensile-microcrack expansions reflect the low strength of the karstified rock mass due to the stress concentration at the rock-bridge between the karst cavity-gaps; 3) the GSI value of the karstified rock mass is expressed as a reduction to the GSI value of the jointed rock mass, so the karst features play the role of a karst correction-coefficient λ (0 < λ < 1) to update the GSI from the discontinuity features, and λ decreases linearly with k, and the decreasing degree is also negatively linearly correlated with u.

Expansive soils, characterized by significant volume changes in response to moisture fluctuations, present substantial engineering challenges globally. This study explores the efficacy of lignosulfonate (LS), an industrial by-product, as a sustainable stabilizer for expansive soils. Three soil samples with varying degrees of expansiveness (weak, mid, and strong) were treated with LS, and their geotechnical properties were evaluated. For weak, mid, and strong expansive soil, the optimum lignosulphonate content (OLS) determined based on the free swelling rate and plasticity index was 0.75%, 2%, and 6%, respectively. The addition of LS resulted in a reduction of the liquid limit, plasticity index, and free swell index across all soil types. Furthermore, LS-treated soils exhibited enhanced resistance to volume changes and improved shear strength under cyclic wet-dry conditions. Moreover, crack development is inhibited in LS-modified soil. LS decreases the soil’s affinity for water by creating a hydrophobic barrier around soil particles. Furthermore, the interaction between LS and the layered clay minerals results in stronger binding, which contributes to the stabilization process. The findings indicate that LS not only reduces the swelling nature of expansive soils and improves their shear strength and stability under wet and dry cycling conditions, but also provides an environmentally friendly solution for soil stabilization and sustainable construction practices.