Bulletin of Engineering Geology and the Environment最新文献

This study used green low-carbon biopolymer composite (Xanthan Gum (XG), Guar Gum (GUG) and Gellan Gum (GG)) as solidified agents for red clay. To elucidate the effects of compound solidified agents (mixtures of XG, GUG, and GG in varying proportions) with single solidified agents (XG, GUG, and GG added individually) on mechanical properties, microstructural changes, and solidification mechanism. The results show that the stress-strain of XG-4 and GUG-4 is a trend of hardening then softening. The stress-strain curves of the compound solidified agents show strain hardening except for A-8 and A-9. When the strain reaches 15%, the unconfined compressive strength (UCS) of A-1 is 219.78 kPa, while the GUG-4 exhibits a strength of 236.02 kPa. The A-1 shows excellent healing properties in the crack resistance test. No new mineral phase is formed in the X-ray diffraction (XRD). Fourier-transform infrared spectroscopy (FTIR) indicates that the addition of biopolymers enhances the interaction between Si-O groups and hydrogen bonds. Scanning electron microscopy (SEM) observes that biopolymers formed a dense network structure. The biopolymer composite solidified agents not only reinforce red clay but also serves as a substitute for traditional cement-based solidified agents, contributing to the reduction of carbon emissions. Its biodegradability further benefits environmental protection.

To facilitate the development of a performance-based framework for liquefaction hazard assessment in a regional scale, this paper proposed probabilistic predictive models for estimating the permanent settlement of low-rise buildings with shallow foundations on liquefiable sites based on numerical simulation results and available case history database. The primary predictors of foundation settlement were identified as foundation bearing pressure, foundation embedment depth, depth from the bottom of the foundation to the middle of the first susceptible sand layer, foundation length-to-width ratio, as well as empirically computed liquefaction-induced free-field ground settlement. The cumulative absolute velocity was identified as the optimal intensity measure (IM), utilized to develop a single IM model. A second set of models using PGA and earthquake magnitude, which were easily assessed as the intensity measure, was developed. However, this model showed greater variability compared to the CAV-based model. The proposed models captured the key trends in permanent foundation settlement observed in available field case histories with simple functional form and easily assessable IMs. These results highlight the potential tradeoffs associated with model uncertainty and efficiency in the model application that should be considered in liquefaction hazard assessment. Moreover, the models provided a link between the liquefaction triggering analysis framework and the estimation of engineering demand parameters, enabling regional estimation of liquefaction consequences.

Since 2020, heavy rainfall has triggered two intensely deforming landslide bodies on a slope in Chaotian District, China, showing a "upper-lower superimposed" spatial distribution. Currently, research on the instability mechanisms and dynamic evolution of such landslides remains relatively limited. This study comprehensively employs high-precision UAV mapping and FLAC3D-Massflow coupled simulation technology, and combines them with field investigation, trench profile analysis, and borehole stratum exploration to construct a 3D geomechanical model of the study area. On this basis, the instability mechanisms and dynamic evolution of potential landslides with spatial superimposition characteristics were analyzed. The results show that under heavy rainfall conditions, the stability coefficient of the upper landslide decreased from 1.043 to 0.961. It became unstable along the contact interface between crushed stone soil and phyllite and moved toward the lower landslide. Under the dual effects of impact load and colluvial load, the stability coefficient of the lower landslide dropped from 1.121 to 0.954, triggering shear failure at the soil-rock interface and forming a landslide disaster chain. Eventually, the landslide volume reached 75.5 × 10⁴ m³, direct impact area 0.29 km², and residential buildings on the opposite bank of the slope also faced direct threats. This study reveals for the first time the dynamic evolution mechanism of "impact-colluvial load coupling" in spatially superimposed landslides, and simultaneously proposes a 3D quantification and stability analysis method for impact loads of such superimposed landslides. The research results contribute to deepening the understanding of similar superimposed landslides and their disaster impacts.

Dynamic load increases the complexity of mechanical properties of frozen soil-filled joints in rock masses. Cylindrical sandstone specimens containing an inclined joint filled with frozen soil under different freezing temperature (–7 ~ − 25 ℃) were prepared and dynamic compression–shear tests were conducted on them using a split Hopkinson pressure bar (SHPB) system to explore the characteristics of failure, deformation, strength, and energy dissipation. The fracture modes of the frozen soil primarily exhibit shear fracture and tensile fracture, which are mainly controlled by the joint inclination angle. When the inclination angle exceeds 45°, it becomes easier to form a tensile fracture. The deformation and failure process can be divided into compaction stage, elastic stage, yielding stage, and failure stage. The dynamic elastic modulus and peak stress increase with decreasing freezing temperature, but the increase rate decreases gradually. During the dynamic impact process, the growth of incident energy, reflected energy, and dissipated energy starts slowly, then rapidly increases, and eventually stabilizes, while the change in transmitted energy is minimal. Overall, the energy dissipation decreases with decreasing freezing temperature. The dynamic compression–shear strength data can be fitted using the Drucker–Prager criterion, with the internal friction angle and cohesion significantly increasing with decreasing freezing temperature. The Drucker–Prager strength criterion for frozen soil-filled joints under dynamic compression–shear loading was established considering the effect of freezing temperature.

Sand storms are catastrophic geological challenges worldwide in arid and semiarid areas with growing intensity. Engineering geologists and geotechnical engineers are always trying to monitor the desertification phenomenon and stabilize weak soils with dust storms origin through environmentally friendly procedures. It is assumed that erosion resistance can be improved by improving the strength of soils. In the past few years, microbial-induced calcite precipitation (MICP) has been utilized as a sustainable ground improvement technique. In this method, urea is fractured by bacterial urease enzymes, and the biochemical reaction network is then completed by adding cementation solution and instigating calcite precipitation which improves the mechanical and physical properties of the soil. In the presented research, a single culture of Sporosarcina urea (S. urea) and a mixed culture of Sporosarcina urea and Bacillus subtilis (S. urea + B. subtilis) mediums were used for the bio-cementation of typical dune sand. Firstly, the medium culture was gravitationally injected into the soil specimens in one cycle. Secondly, the cementation reagent (urea + calcium chloride) was injected into the specimens in two cycles. After a specific curing period, the specimens were evaluated using unconfined compression strength (UCS), permeability, direct shear, and California bearing ratio (CBR) tests. The tests outcomes revealed a considerable enhancement in strength and stiffness and a significant reduction in permeability for all treated soil specimens. Finally, the improvement of stabilized specimens was verified by quantifying calcite content, scanning electron microscopy (SEM) images, and X-ray diffraction (XRD) analyses on selected treated specimens.

Hydraulic fracturing operations frequently induce seismic activity, posing unprecedented challenges to underground infrastructure integrity and regional safety. The induced seismicity waveform is more complex than the Ricker wavelet, restricting the application of the Continuous Fourier Transform (CFT) in the theoretical analysis of transient stress. In this study, the Discrete Fourier Transform (DFT) was introduced into the theoretical solution process of transient response, and a minimum-phase seismic wavelet was proposed to represent the induced seismicity load, exhibiting multiple oscillations, gradual attenuation and energy concentrated primarily in the initial phase. The dynamic stress concentration distribution of the lined tunnel under induced seismicity disturbances was analyzed by combining the DFT and wave function expansion method. The theoretical results were further validated through comparison with numerical results. The effects of the lined tunnel parameters and disturbance characteristics on transient response were evaluated in detail, and practical insights for seismic-resistant management were provided. The theoretical and numerical results revealed that the seismic-resistance mechanisms of flexible and rigid linings differed. Dynamic stress concentrations primarily occur at the rock interface for the flexible lined tunnel. The flexible lining absorbs the seismic energy, thereby reducing the peaks of dynamic stresses. For the rigid lined tunnel, dynamic stress concentrations mainly appeared at the tunnel interface. The high strength and stiffness of rigid linings enable them to directly withstand the high dynamic stresses. Selecting lining materials with shear modulus values similar to the rock and increasing the lining thickness can effectively reduce dynamic stress concentrations around both types of tunnels.

Disc cutters installed on conical cutterheads play a critical role in rock-cutting during the downward excavation process for shaft boring machines (SBMs). The rock-cutting characteristics of inclined cutters constitute an essential basis for cutter layout and optimization of operational parameters. This study investigates the rock-cutting characteristics of disc cutters at different installation angles under various cutting parameters through full-scale cutting tests. Compared with traditional TBM normal cutters, the penetration direction of the SBM inclined cutter does not coincide with its symmetry axis. As the cutter installation angle increases, the cutter-rock contact area decreases, and the dense core and crushed zone deviate toward the lower side of the symmetry axis. The normal force and the rolling force of rock-cutting decrease, while the side force of the inclined cutter is significantly larger than that of the normal cutter, and the degree of rock fragmentation on the lower side of the cutter blade is higher than that on the upper side. The cutting specific energy tends to decrease with the increase of cutter installation angle. When the cutter spacing to penetration depth ratio is 30, the SE of disc cutters with installation angles of 0°, 15°, and 25° are 66.2, 85.9, and 147.8 MJ/m³, respectively. Furthermore, large-sized rock debris is more prone to appearing under the rock-cutting by the cutter with a lower installation angle. The findings of this study provide valuable guidance for the design of the installation angle for the SBM inclined cutters.

The paper outlines the physical parameters and textural differences of clay marl, marl, and calcareous marl, focusing on the physical changes that are caused by water. The characterization of marls is often very difficult since their properties are variable, covering a broad range from low-strength friable rock to highly cemented durable lithologies. Consequently, the prediction of their physical parameters requires further consideration. The paper addresses this issue by physically and texturally characterizing Eocene marly lithologies and comparing their properties to various limestones. Density, water absorption, ultrasonic pulse velocity, uniaxial compressive strength (UCS), Brazilian tensile strength, Young’s modulus, and their interdependencies are explained. The link between physical properties and various micro-fabrics is also outlined, with the help of new equations. Our tests show that UCS of calcareous marl can be as high as 100 MPa, but it decreases when the sample is water saturated. Relationships were calculated between the physical parameters of air-dry and water-saturated samples. Correlations between Young’s moduli and uniaxial compressive strength are also explained. The results of our analyses were compared to published physical parameters of marls and limestone, and relationships were outlined between the parameters of these carbonates.

The Helankou petroglyphs are carved on feldspathic metagreywacke weathering crusts on both sides of the Helankou gorge. These petroglyphs are undergoing severe deterioration primarily attributed to deformation of weathering crusts induced by thermal cycling under solar radiation. However, the response patterns and mechanisms of feldspathic metagreywacke weathering crusts under solar radiation remain poorly understood. Monitoring of TBQ total radiation (total solar radiation), atmospheric temperature, and the temperature and strain of feldspathic metagreywacke weathering crusts with different orientations and dip angles is conducted at the study site. Extreme event analyses and finite element numerical simulations are performed, systematically revealing the response patterns and mechanisms of feldspathic metagreywacke weathering crusts under solar radiation. The results indicate that feldspathic metagreywacke weathering crusts with varying orientations and dip angles exhibit differential responses under solar radiation. There is a strong linear correlation between the temperature and the strain of the feldspathic metagreywacke weathering crusts. The highest temperature was found in feldspathic metagreywacke weathering crusts with a south orientation and dip angles of 15 ° on July 6, 2023, while it was identified in those with a south orientation and dip angles of 60 ° on December 21, 2023. The heterogeneous thermal stresses caused by the differences in spatial geometric attributes induce differential thermal expansion–contraction cycles, which ultimately result in spatially heterogeneous exfoliation in the feldspathic metagreywacke weathering crusts. These findings enhance our understanding of thermal degradation in metamorphic rocks under solar radiation and contribute to long-term durability prediction and conservation of such sites.

Soft rocks are prevalent in construction environments and are frequently subjected to cyclic loading conditions, making them susceptible to fatigue failure. In practical applications, cyclic stresses often coexist with pre-existing static (mean) stresses, necessitating the explicit consideration of mean stress effects in fatigue life evaluation. Additionally, mean stress variations are inherently introduced when irregular cyclic loadings are idealized into regular waveform patterns in both experimental and analytical frameworks. This study investigates the influence of cyclic mean stress on the fatigue behavior of artificially prepared, weakly cemented sandstone specimens under uniaxial cyclic compression. Force-controlled fatigue tests with a constant amplitude were conducted at stress ratios (R = σ_min/σ_max) of 0.0, 0.1, and 0.2 with a loading frequency of 0.5 Hz. The maximum cyclic stress level ranged from 68 to 98% of the monotonic compressive strength. Stress-life (S–N) curves were established, accompanied by detailed analyses of dissipated and elastic energies accumulation per cycle. Results showed that, for a given maximum cyclic stress level, the fatigue life increases as the stress ratio increases, while the dissipated energy per cycle decreases. An empirical fatigue life prediction model was developed based on the cumulative dissipated energy at failure, explicitly incorporating mean stress effects. Model parameters were determined solely from the stress-life data at a stress ratio of R = 0.0. Validation indicates that the proposed model accurately captures the sensitivity of fatigue life to mean stress variations across different regimes, providing a robust tool for designing fatigue-resistant rock materials in cyclic loading conditions.