Bulletin of Engineering Geology and the Environment最新文献

Due to their unique aesthetic and functional properties, serpentinites are considered valuable natural materials in construction and architecture. Although present in some parts of Croatia, serpentinites did not attract significant attention of researchers in the aspect of application. Our work presents first compilation of the results dealing with petrographic, physical and mechanical properties of serpentinites from the Ljeskovac locality (Croatia). Two varieties are identified: serpentinites and serpentinite breccia. The main petrographic difference is carbonate content, which is much higher in the serpentinite breccia (up to 73.47%), where it acts as cement holding serpentinite fragments. Textural elements such as open and filled cracks, carbonate cement and serpentinite fragments contributed to much higher textural heterogeneity in serpentinite breccias. Serpentinites have higher real and apparent density (2739 and 2579 kg/m³) then serpentinite breccias (2659 and 2469 kg/m³). Open porosity reaches up to 7.76% and 8.54%; water absorption 3.20% and 3.54%; water desorption 2.29% and 2.46%; point load strength index (PLSI) 3.12 and 1.99 MPa; Leeb rebound hardness (LRH) 749.20 and 685.80; Schmidt rebound hardness max values are 39.70 and 32.46 in serpentinites and serpentinite breccias respectively. The interdependence of aesthetic and physical properties is best observed in the ratio between serpentinite fragments and carbonate cement in the serpentinite breccia. Carbonate cement is shown to have a positive effect on the PLSI. The overall properties of the Ljeskovac serpentinites suggest that this material is not suitable for utilisation, directing further research towards the direction of refinement of these varieties.

To investigate the uniaxial compression characteristics of carbonaceous mudstone soil-rock mixture (CMSRM) subjected to dry-wet cycles, uniaxial compression tests were performed on CMSRM with varying dry-wet cycles and rock block proportions (RBP). The results indicate that both the number of dry-wet cycles and RBP significantly affect the stress-strain relationship, uniaxial compressive strength (UCS), failure strain, and elastic modulus of CMSRM. The stress-strain curves for CMSRM consistently display strain softening, with failure occurring in a brittle manner. Notably, UCS, failure strain, and elastic modulus decrease as RBP and the number of dry-wet cycles increase. This trend is primarily attributed to the evolution of the internal structure of the sample from a “dense-suspended” configuration to a “skeleton-void” structure as RBP increases. Furthermore, the strength of the rock blocks within the CMSRM is lower than that of the fine-grained soil. Dry-wet cycles induce irreversible damage in the CMSRM and reduce the bonding capacity between the soil and rock components. A binary medium model of dry-wet cycles CMSRM was developed based on the concept of a binary medium from a microscopic perspective. Comparisons of the model’s predictions with experimental values demonstrate that the proposed model effectively predicts the uniaxial compressive stress-strain curve of CMSRM under dry-wet cycles.

Landslide dams are widely occurring geological disasters. When a river is obstructed by the collapse of slopes, a landslide, debris flow, or other forms of mass movement, landslide dams are formed. Damage to these dams may cause a severe flood disaster downstream. Most landslide dams are formed in remote mountains, leading to the difficulty of performing on-site surveys and stability assessments. Hence, data can only be collected on landslide dams through satellite images or drone photography. This increases the difficulty of assessing the dam failure type and dam stability, posing a challenge to the prevention and mitigation of landslide dam disasters. To overcome these challenges, this study proposes a method for the remote survey and stability assessment of inaccessible landslide dams that involves the use of multi-period satellite images, helicopter surveys, drone photography, and downstream water level monitoring. The remote stability assessment and evaluation of downstream water levels enable the long-term monitoring of landslide dams formed from two or more collapses of river slopes at the same location within a short duration as well as a rolling review of dam stability. The proposed method was applied for conducting a case study of the Danan River landslide dam located in the eastern mountains of Taiwan in 2021. The dam was damaged three times; this process was recorded in its entirety to provide a reference for formulating innovative disaster prevention and mitigation measures for landslide dams.

Expansive soil commonly exhibits over-consolidation, yet its influence on damage-induced softening remains insufficiently understood. In this study, ring shear tests were conducted on expansive soils with varying over-consolidation ratios to quantify the damage softening behavior under large deformation. Three representative damage evolution equations were introduced to model the observed softening responses. The results show that the peak-to-residual strength reduction ratio ranges from 17.1% to 44.2% and increases systematically with over-consolidation ratio, indicating progressively stronger post-peak softening. Damage softening is governed by deformation-driven micro-crack propagation and shear zone formation, leading to cohesion degradation and shear localization. The Weibull model and Logistic model exhibit superior predictive performance, with RMSE values of 0.80–4.28 and MAE values of 0.53–2.93, whereas the Harris model fails to capture the pronounced softening of over-consolidated expansive soil. A novel generalized hybrid damage model was further proposed, resulting in improved modeling accuracy. Based on the maximum post-peak strength attenuation rate, a brittleness index was proposed, with values ranging from 1.03 to 6.62 kPa/mm and exhibiting an increasing trend with over-consolidation ratio, indicating enhanced brittleness under higher over-consolidation. These findings provide quantitative insight into the damage softening mechanism of over-consolidated expansive soil and offer a practical basis for the assessment of expansive soil slopes.

Evaluating the stability of slopes under rainfall conditions is essential for preventing geohazards caused by slope failures. A key factor affecting the slope stability is the water-induced weakening of soft rocks during rainfall infiltration. The varying porosities of rocks result in different water content under saturated conditions, leading to varying degrees of weakening in their physical and mechanical properties. The heterogeneity of rocks is also essential in determining slope stability during rainfall. In this study, FISH functions in FLAC^3D were utilized to investigate the impact of different porosities and heterogeneity levels on the peak strength of sandstone during uniaxial compression tests. This methodology was subsequently extended to model stability changes in a two-dimensional rock slope subjected to heavy rainfall. A comparative analysis was conducted between two approaches: one that simplifies the physical and mechanical parameters of the slope model into only dry and saturated states during rainfall infiltration, and another that dynamically adjusts these parameters in real-time based on varying saturation levels. The results demonstrated that the latter approach is more reliable for analyzing slope stability under heavy rainfall conditions. Further, a three-dimensional slope model was employed to validate this approach. The factor of safety (FoS) of the slope was determined to be 1.09 after two days of rainfall, which closely aligns with the observed slope failure in reality. The outcome highlights the importance of accounting for the heterogeneity of weathered layers in rock slopes and dynamically adjusting physical and mechanical parameters according to rock porosity and saturation levels.

Landslides triggered by rainfall are major catastrophes from climate-driven wetting and drying soil cycles. The soil-water characteristic curve (SWCC) is of great significance in the evaluation of slope stability. It is also noted that SWCC behaves differently in the drying and wetting process, which is commonly referred to as the hysteresis of SWCC. The current equipment for the measurement of SWCC in the field are limited to a particular suction range, time-consuming, and tedious in operation. On the other hand, the estimation of the soil suction from SWCC in the field are mainly limited to the drying process. In this paper, a framework is proposed for the estimation of soil suction from field-measured water content by calibration with the laboratory-measured drying and wetting SWCC. The framework employs Newton-Raphson’s numerical technique to derive soil suction from the established fitting parameters and water content. Residual soils obtained from a slope at Sembawang in Singapore were used for calibration, with field instrumentation including moisture sensors, rain gauges, and piezometers installed to enable real-time monitoring. The results of the proposed framework were compared with experimental data from published literature. Strong correlations were observed between the measured and estimated drying and wetting SWCC. The in-situ soil suction responses were depth-dependent, with rapid variations near the surface and delayed changes at greater depths. Moisture accumulation was more obvious at the toe than at the crest, possibly increasing the risk of landslides. Therefore, the proposed framework for the estimation of soil suction from water content is recommended.

Offshore wind turbine foundations must withstand cyclic loads generated by wind and waves. In current practice, irregular site-specific load histories are typically idealized as uniform-amplitude cycles arranged in ascending order (IAL) with constant average shear stress. This study investigates the influence of loading sequence on the undrained cyclic behavior of normally consolidated marine soft clay using triaxial cyclic tests. Nine tests with ascending (IAL), descending (IDL), and mix-sorted (MSL) sequences were conducted to assess strain accumulation, pore-pressure development, stiffness degradation, and post-cyclic undrained shear behavior. A critical cyclic stress ratio of q_cyc/q^max_cyc ≈ 0.5 was identified, separating stable cyclic response from degradation-dominated behavior. Loading sequence exerts strong control on cyclic response: IDL results in the greatest stiffness degradation and strain/pore-pressure accumulation, followed by MSL and IAL, primarily due to the early application of high cyclic stresses. Increasing average shear stress qₐᵥₑ from 0 to 70 kPa magnifies sequence effects, approximately doubling accumulated strain and tripling pore-pressure buildup between IDL and IAL. These findings demonstrate that Miner’s rule, which neglects loading order, is not applicable to soft clay. When a relatively high q_cyc ​ occurs early in the loading history, special caution and a higher safety factor are warranted. Undrained cyclic loading also generates excess pore pressure and reduces effective stress, leading to more dilative post-cyclic monotonic behavior and an apparent overconsolidation effect. Overall, both loading sequence and the combined effects of q_cyc and qₐᵥₑ must be incorporated into offshore wind-turbine foundation design. IDL loading with elevated qₐᵥₑ provides a more reliable representation of soil response, whereas conventional IAL may underestimate deformation and pore-pressure development.

The soil-structure interface typically represents the weakest point in a structure. Elucidating the shear mechanism at this interface is crucial for resolving issues such as bearing capacity deficiencies and shear strength limitations in precast structures. To investigate the effects of interface roughness and structural inclination angle on interface shear strength, this study implemented Triaxial Contact Surface Shear Tests to characterize interfacial shear behavior of saturated soft clay-structure contact interfaces. Distinct interface roughness levels and structural inclination angles were configured to systematically analyze the mechanical properties of the soft clay-structure contact interface. The results show that the interfacial shear strength demonstrates a positive correlation with interface roughness. In addition, the structural inclination angle significantly modulates the shear strength response, with interfacial shear stress progressively increasing as the inclination angle increases. Under both parametric conditions, the stress–strain curves exhibit strain-hardening behavior. Moreover, increased interface roughness induces pronounced variations in the internal friction angle, demonstrating linear relationship with shear stress. In contrast, the structural inclination angle follows an exponential relationship with the internal friction angle and shear stress. Subsequently, predictive formulations for the internal friction angle and interfacial shear stress of saturated soft clay-structure interfaces across different inclination angles are proposed, while accounting for the influence of roughness. These findings provide a reference for selecting interface parameters in soft clay-structure systems, and the proposed predictive equations offer guidance for designing and constructing precast structures at varying inclination angles.

In the Chinese Loess Plateau with crisscrossing gullies and ravines, the under-compacted and weakly cemented loess strata are prone to collapse and landslide disasters. It is crucial to understand the mechanical properties of loess. The past climate change has affected the microstructure of loess, resulting in different mechanical properties. However, few studies have linked past sedimentation and pedogenesis processes with current mechanical properties. Exploring the relationship between the mechanical properties of loess and climate change is beneficial for providing a reference for engineering construction in the loess region, thereby helping to regulate human activities reasonably. This study takes a primary loess-paleosol sequence with a thickness of 21.9 m as the research object. Through field sampling, laboratory experiments and data analysis, the abundant precipitation promotes the enhancement of soil mechanical stability, and the formation mechanism of the mechanical properties of loess-paleosol sequences under pedogenesis is supplemented and verified. This research indicates that Quaternary cold-dry/warm-wet climate change is the driving force that shapes the loess mechanical structures, and the weathering pedogenesis plays a dominant role in the mechanical properties of loess. The effect of pedogenesis on mechanical properties is primarily reflected in two aspects, with the contents of clay, calcium carbonate, and iron oxide being the primary factors: (1) the effect of decarbonatization on the collapsibility and compressibility; (2) the particle cementation caused by the adhesion effect enhances the shear strength. This study helps realize the practical application of Quaternary paleoclimate research and provides a data foundation for loess engineering and tillage research.

Seepage is one of the primary causes of instability in earth-rock dams. As the weak link in seepage control systems, the soil-structure interface exhibits particularly prominent seepage erosion issues, which often directly trigger catastrophic failures. However, research on the characteristics and mechanisms of seepage erosion at this interface remains relatively scarce. In this study, a visual seepage apparatus and nuclear magnetic resonance (NMR) technology were employed to systematically investigate the effects of three critical factors—clay content, compaction degree, and hydraulic gradient duration—on the evolution process, microscopic mechanisms, and critical hydraulic gradient of seepage erosion at the soil-structure interface between an earth-rock dam and a culvert. Results show that the interface seepage erosion process can be divided into three distinct stages: seepage stabilization, seepage transition, and particle erosion. Notably, hydraulic gradient duration significantly alters the phased characteristics of this process. Microscopic analysis indicates that clay content, compaction degree, and hydraulic gradient duration collectively influence the impermeability of the interface by differentially regulating pore-filling effects, initial structural compactness, and pore evolution processes. Analysis of variance (ANOVA) demonstrates that clay content is the most significant factor influencing the critical hydraulic gradient, with an optimal clay content maximizing the interface’s resistance to seepage failure. Predictive models for critical hydraulic gradients of the interface were established based on nonlinear regression analysis, providing valuable reference for quantifying the stability of interfacial seepage. These findings hold significant theoretical value for the impermeability design and safety assessment of earth-rock dams.

Graphical Abstract