Bulletin of Engineering Geology and the Environment最新文献

In the study of the stability of shield tunnel excavation face in urban environment, most of the construction stratum is assumed to be homogeneous soils, and the coupled effects of layered characteristics and earthquake action are seldom considered. Therefore, this paper provides a 3D logarithmic spiral mathematical model to evaluate the excavation face stability considering earthquake action in layered soils. Firstly, the pseudo-static approach simplifies the dynamic reaction brought by the earthquake to the inertial forces operating in horizontal and vertical directions. Secondly, a 3D logarithmic spiral mathematical model that may be applied to layered soils is developed based on the 3D logarithmic spiral mathematical model in homogeneous soils. Then, according to the upper limit theorem, the upper limit solution of the support force on the excavation surface of the shield tunnel can be obtained by introducing the power generated by the earthquake inertia force into the imaginary work equation under the layered soils and earthquake action conditions. Lastly, the upper limit analytical solution is compared with the 3D numerical simulation results and existing model experimental results, and good consistency is obtained. Additionally, the key physical characteristics are analyzed for earthquake, geotechnical, and tunneling parameters.

Landslides in reservoir areas pose substantial risks to hydropower facilities, surrounding infrastructure, and the safety of local populations. Landslide Susceptibility Mapping (LSM) evaluates the likelihood of landslide occurrences, aiding in the mitigation and prevention of these risks. Data-driven LSM faces reliability constraints due to its inherent uncertainty and limited interpretability. This study constructs a physics-enhanced data-driven model to innovatively map landslide susceptibility in wide reservoir areas, considering the physical effects of impoundment-stage reservoir water-level rise. Surface deformation data acquired through InSAR technology are merged with geomorphological features to create a comprehensive inventory of active landslides in the Lianghekou Reservoir area. Subsequently, results from physics-based models are incorporated as factors into the data-driven model, merging the predictive strengths of data-driven models with insights from physics-based analyses. This integration not only enhances the accuracy of the LSM model but also improves its interpretability. Additionally, SHAP (SHapley Additive exPlanations) clarifies how various conditioning factors and enhancement strategies shape the model’s performance. It also reveals the key drivers of landslide susceptibility during reservoir impoundment. The results indicate that the physics-based model makes a notable contribution, playing a crucial role in model classification decisions. This study provides new insights into integrating data-driven and physics-based approaches within LSM, aiding in the accurate localization and prevention of landslide hazards.

The seismic behavior and post-seismic strength of soils are crucial to the seismic safety of surrounding structures. Compared with uniaxial dynamic triaxial tests, bidirectional cyclic loading better simulates the shear conditions induced by earthquakes. In this study, a series of bidirectional dynamic triaxial tests were performed on soft clay samples to investigate the dynamic behavior under equivalent seismic loading, considering the effects of both confining pressure and consolidation stress ratio. The monotonic shear behavior before and after equivalent seismic loading was also compared. The results show that the hysteretic behavior of soft clay under equivalent seismic loading exhibits both confining pressure dependency and anisotropic effects. Isotropically consolidated soft clay samples showed more pronounced stiffness degradation, whereas anisotropically consolidated samples accumulated larger deformations. The post-cyclic peak shear strength decreased under various confining pressures. However, under different consolidation stress ratios, the post-cyclic shear strength showed an increase of up to 17.6%. Following seismic loading, the excess pore water pressure decreased significantly by an average of approximately 65%. In addition, a model to predict the post-cyclic shear strength of soft clay samples was established. These findings shed light on the dynamic response and post-cyclic monotonic behavior of soft clay under equivalent seismic loading.

The tunnel face as an intrinsic end restraint significantly impacts the excavation stability. However, the previous studies scarcely address the end restraint effect (ERE) especially under high stress conditions. To address this gap, true-triaxial experiments equipped with the integrated acoustic-optic-mechanical (AOM) multi-physics field monitoring techniques are conducted on a laboratory simulated excavation model. Results show that the excavation instability processes under high stress can be divided into four stages: calm, crack initiation and directional growth, spalling damage and slab buckling, and post-peak collapse and failure. Due to the ERE, the hypothetical supporting force around the tunnel face is present, which renders the first macro-failure initiating far away from the tunnel face. As the continuous stress transfer, the occurrence of V-shaped notch and the collapse of the tunnel face gradually dominate the damage progression. Besides, with the aid of ultrasonic testing, the 3D field data of the P-wave velocities reliably quantify the crack damage zone, the distributions of which show good consistency with the 3D numerical simulations. The end friction effect induced by the rigid loading is also discussed. This study provides a realistic simulation of in-situ excavation instability with the ERE and helps interpret the field observations.

Toppling failure in interbedded anti-inclined slopes represents a critical geological hazard, threatening infrastructure and resident safety. This study proposes a base friction test method for analyzing interbedded anti-inclined slope models with varying cross joint angles. Using a non-contact measurement method combining Digital Image Correlation and Particle Image Velocimetry, nine physical model tests revealed the influence of different cross joint angles on the deformation and failure mechanisms. The results demonstrate that the cross joint angle has a greater impact on deformation depth than the slope angle and exhibits a distinct threshold effect on overall stability. As the cross joint angle shifts from inward to outward inclination, the failure plane transitions from a large-scale, deep-seated failure with a rough, stepped morphology to a small-scale, shallow feature with a smooth, linear geometry. Deformation is predominantly horizontal, increasing with slope height and maximizing at the crest, where the − 0.02 strain contour effectively delineates the boundary between stable and deformed rock masses. Furthermore, increasing the slope and cross joint angles shifts the temporal evolution of deformation from a creep-accelerated to a sudden-acceleration mode. The formation of multiple failure planes is attributed to the obstruction of deep-seated failure surfaces, prompting internal crack development and coalescence in the overlying rock mass. These findings provide valuable insights for determining the failure plane morphology and assessing the stability of interbedded anti-inclined slopes under similar conditions.

Commonly used soil stabilization methods often overlook the degree of decomposition in peat soil. Highly decomposed peat exhibits lower strength and higher acidity than slightly decomposed peat due to the breakdown of cellulose and hemicellulose into humic acids. This study employed corrosion-resistant aluminate cement, phosphogypsum (PG), and manufactured sand to stabilize highly decomposed peat soil. Unconfined compressive strength (UCS) and shear tests were conducted to evaluate the effectiveness of the stabilization, while microstructural analyses were performed to investigate the underlying mechanisms. An optimal dosage of 15% PG, 30% aluminate cement, and 30% manufactured sand increased the UCS of highly decomposed peat soil by 22 times, from 10.2 kPa to 221.0 kPa, and increased cohesion by 4.2 times, from 16.3 kPa to 67.9 kPa. Furthermore, the stabilized peat soil exhibited early strength development under the optimal dosage: after just 3 days of curing, the strength reached 61% of the strength achieved after 90 days. Adding PG and aluminate cement raised the pH from 5.48 to above 9.0, meeting the minimum requirement for hydration reactions. PG promoted ettringite formation, which filled pores and densified the microstructure, while calcium carbonate formed through the carbonation of hydration products further enhanced compactness through both filling and bonding effects. These findings highlight the proposed method as a practical and effective solution for stabilizing highly decomposed peat soil.

Accurate determination of the equivalent mechanical parameters of jointed rock masses is essential for tunneling and underground excavation. However, the random distribution of joints hinders a comprehensive understanding of the mechanical behavior of such complex systems. This study proposes a methodology based on the discrete fracture network–discrete element method (DFN–DEM) to determine the equivalent mechanical parameters of rock masses with different joint densities. First, an enhanced Mask R-CNN algorithm was employed to extract joint geometries from tunnel surrounding rocks, and statistical features were used to construct discrete fracture networks. Synthetic rock mass technology was used to generate jointed rock specimens with varying densities and sizes, enabling analysis of anisotropy, size effects, and representative elementary volumes (REV). Numerical simulations were complemented by tests on 3D-printed rock-like specimens, from which elastic modulus, cohesion, and internal friction angle were obtained through triaxial compression experiments. Results for limestone with low, medium, and high joint densities (P₃₂ = 3.1, 5.8, and 8.2 m⁻¹) indicated REV sizes of 8 m, 8 m, and 10 m, respectively. Equivalent parameters under different loading directions varied by less than 70%, and results deviated by under 16% from Hoek–Brown criterion estimates, confirming method reliability. The integration of intelligent joint identification, DFN–DEM modeling, and 3D printing provides a precise parameter determination method. The method assumes statistical representativeness of extracted joint features, while laboratory validation remains limited in scale. The findings of this study provide a theoretical basis for underground tunnel design and construction.

A model of a steep bedding rock slope is designed and produced, and large-scale shaking table tests are conducted to analyze the dynamic response and deformation failure mode of the steep bedding rock slope under earthquake action. The results show that the natural vibration frequency of the steep bedding rock slope model decreases gradually with increasing vibration number and that the damping ratio increases gradually with increasing vibration frequency. The horizontal acceleration amplification coefficient of the model slope shows an obvious elevation amplification effect and surface trend effect. There are obvious differences in the slope acceleration response under the action of different types of input seismic waves. The acoustic emission parameters increase nonlinearly with increasing input seismic wave amplitude, and the acoustic emission characteristics during the failure process of the steep bedding rock slope can be divided into two stages: a slow rise period and a sharp rise period. The deformation evolution process of the steep bedding rock slope under the action of seismic dynamics can be divided into three stages: the formation of a tensile crack; the downward expansion of the tensile crack; and the sudden shear of the locked segment and the sudden instability of the slope. According to the abrupt cusp catastrophe theory, a correlation instability criterion is established based on the test results; the critical acceleration amplitude of the slope dynamic instability is quantitatively determined to be 0.4 g.

Electrochemical grouting with nanosilica sol offers a promising low-disturbance solution for reinforcement of coastal soft soils. This study systematically evaluate the feasibility of electrochemical grouting using nanosilica sol via its gelling regulation, migration behavior, and reinforcement efficacy through a three-stage approach. Single-variable experiments demonstrate that the gelation time and strength are controllable via Na⁺ concentration gradients, particle size and SiO₂ concentration. U-tube electrophoretic tests reveal migration rates of 0.078, 0.0125, and 0.00981 cm²/(min·V) in coarse sand, fine sand, and clay, governed by pore structure and interfacial charge interactions. Electrochemical grouting model experiments show that the nanosilica sol forms a continuous reinforcement zone in the cathode region, increasing the effective reinforcement area increases from 21% to 63%, and reducing the coefficient of variation (CV) in bearing capacity by 50% (to 43.8%) compared to conventioanl CaCl₂-Na₂SiO₃ grouting. The synergistic mechanism of directed migration, gradient-induced gelation, and pore-scale filling effectively overcomes the limitations of conventional grouting techniques, which offten result in the formation of isolated reinforcement zones.

Liquefaction of saturated soils is typically characterized by macroscopic variables such as pore pressure ratio and double-amplitude strain, which often fail to capture the underlying microscopic mechanisms and may lead to inconsistent judgments under certain conditions. To overcome these limitations, this study utilizes the inertial number — a concept originally proposed for granular materials — to characterize the soil liquefaction process. Through integrated experimental tests on multiple soil types (Nanjing fine sand, silt, calcareous sand) and discrete element method (DEM) simulations, the micro-macro physical significance of the inertial number is revealed as the ratio of the microscopic particle rearrangement time scale to the macroscopic shear deformation time scale. The evolution of the inertial number follows a Boltzmann distribution curve, effectively capturing the three-stage characteristics of liquefaction: initial stability, rapid transition, and post-liquefaction stabilization. Results demonstrate that the inertial number synchronously integrates the evolution of pore pressure and strain, providing a unified criterion for liquefaction identification. Moreover, it shows great potential for predicting post-liquefaction behavior and serving as a governing parameter in liquefaction analysis. Future work will focus on validating its applicability through centrifuge tests and integrating field data (e.g., CPT/SPT) for engineering-scale applications.