[Objective]This study investigates the evolution characteristics of deformation and damage in the cavern-type dam abutment slope of a hydropower station under multi-field coupling conditions in an alpine region. [Methods]The key governing equations for the thermohydromechanical (THM)multi-field coupling theory in alpine rocks and a freeze-thaw damage deterioration model are established. Based on a raster digital elevation model (DEM)imported into COMSOL Multiphysics, a numerical simulation of the slope stability under multifield coupling is conducted. Based on the geological investigation report of the dam site area and relevant meteorological data, such as annual temperature variations, the evolution laws of stress, deformation, and damage of the left abutment slope of Zhongyu Hydropower Station under multifield coupling are studied. [Results]The results indicate that under freeze-thaw cycling, progressive damage accumulation in the rock mass of the dam abutment slope leads to increased pore sizes, a decreased elastic modulus, and a corresponding rise in frost-heaving tensile stress. Due to excavation unloading and freeze-thaw damage, the surrounding rock of the abutment trench undergoes a certain degree of rebound deformation. [Conclusion]The degree of overhang on the upstream and downstream excavation sides of the dam abutment significantly affects the overall stability of the abutment slope. [Significance]The research findings can provide a theoretical basis for promoting the application of cavern-type excavation technology for dam abutments in alpine regions.
[Objective]To investigate the interaction mechanisms within the “nutrient-microorganism-antibiotic” ternary system, this study aimed to clarify the effects of the coexistence of phosphate and phosphate-accumulating organisms (PAOs)on the transformation of typical antibiotics in aquatic environments. [Methods]A microcosm model was constructed to analyze the influence of the phosphate-PAO coexistence system on the transformation of three antibiotics:sulfamethoxazole (SMX), ciprofloxacin (CIP), and norfloxacin (NOR). Drug susceptibility tests were conducted using the Kirby-Bauer disk diffusion method and the broth microdilution method to determine the antibiotic sensitivity of PAOs. Changes in environmental parameters, growth curves, phosphate concentrations, and antibiotic concentrations were monitored, and the Monod model was applied to fit the phosphate degradation kinetics. [Results]The results showed that PAOs were highly sensitive to CIP and NOR (minimum inhibitory concentrations (MICs)of 1 μg·mL - 1 and 2 μg·mL - 1, respectively)but exhibited low sensitivity to SMX (MIC of 50 μg·mL - 1). The addition of antibiotics inhibited the utilization of carbon sources by PAOs, with NOR showing the most pronounced inhibition (total organic carbon utilization rate of 88.9%). Growth curve analysis revealed that the blank group achieved the highest OD600 peak, while the CIP group exhibited the most restricted growth, and the NOR group displayed competitive advantages of resistant subpopulations in the later stage. Photodegradation was the primary degradation pathway for SMX and CIP under light conditions, whereas microbial degradation contributed 39.2% and 46.4%, respectively, under dark conditions. [Conclusion]The metabolism and phosphorus removal efficiency of PAOs exhibited differential responses to various antibiotics:NOR exerted the weakest inhibitory effect, while CIP and SMX significantly inhibited phosphorus removal efficiency. [Significance]This study elucidates the effects of the coexistence of phosphorus and PAOs on antibiotic transformation, providing a scientific basis for the risk assessment and remediation of combined pollution.
[Objective]The Jinshan gold orefield is an important gold-concentration area in northeastern Jiangxi, China. Recent deep and peripheral exploration has revealed significant differences in ore-bearing capacity among different ductile shear zones. The major orebodies show stable spatial coupling relationships with specific lithologic sequence and structural rock assemblages, indicating that the traditional interpretation of ductile-shear-zonecontrolled mineralization is insufficient to explain the formation and localization of large orebodies. [Methods] Based on the exploration results and available geological data, this study systematically analyzes the lithologic compositions of the composite lithologic sequences, the types of ductile shear zones, and the structural-alteration zoning characteristics, and comparatively examines the occurrence, geometry, ore-controlling interfaces, and ore mineral composition of the V1 and V2 orebodies in the orefield. [Results]The composite lithologic sequence, composed of meta-basaltic andesite, gold-bearing cryptocrystalline intermediate-acid rocks and flysch formations, constitutes the key geological host for the formation of large orebodies in the Jinshan orefield. Later-stage ductile shearing was preferentially superimposed on this lithologic sequence, forming structural rock assemblages characterized by mylonite and ultramylonite interlayered with meta-basaltic andesite, together with an ore-controlling system defined by the main shear plane. Both the V1 and V2 orebodies are strictly controlled by the main shear plane and the adjacent mylonite-ultramylonite zone. [Conclusion]The formation of large orebodies in the Jinshan orefield results from the coupling between the early-developed composite lithologic sequence and later-stage superimposed ductile-shear modification. Areas where the composite lithologic sequence is well developed and strongly modified by ductile shearing are favorable sites for gold enrichment. The deep steeply dipping extension of the Xijiang-Shibei shear zone and the predicted structural turning sites are the key targets for further exploration. [Significance]This study provides new insights into the metallogenic mechanism of the Jinshan gold orefield from the perspective of coupling between composite lithologic sequence development and superimposed ductile-shear modification, and provides geological constraints for deep and peripheral prospecting in the orefield.
[Objective]As the primary spatial setting for uranium occurrence in sandstone-type uranium deposits, fracture structures have attracted significant attention in the field of exploration. However, fracture structures can introduce interference into uranium content assessments. [Methods]Therefore, this paper analyzes the epithermal neutron logging responses under different uranium content (mass fraction)and fracture angle conditions to identify the patterns of interference and improve the accuracy of uranium deposit assessments. [Results]The results indicate that there is a distinct correlation between the distribution patterns of epithermal neutrons and fracture angles. In environments with nearly horizontal fracture angles (0° ～ 30°), the average statistical value of epithermal neutron counts is 1.37 × 10 - 4, whereas in environments with high-angle (60° ～ 90°)fractures, this value rises to 2.83 × 10 - 4, representing an increase of 106.57% . These phenomena indicate that, in high-angle environments, epithermal neutrons produce a more sensitive logging response to high-grade uranium deposits, with higher counts and a wider diffusion range. Furthermore, the slope of the epithermal -to-thermal neutron ratio used to assist in the quantitative assessment of uranium deposits, is significantly greater in high-angle environments than in medium- to low-angle environments (an average increase of nearly 7-fold). [Conclusion]Based on the differences in logging responses resulting from varying fracture angles, this paper introduces the concept of effective fracture length, defined as the amount of fracture-type uranium ore capable of participating in reactions within the same radiation range of the neutron source. [Significance]Analyzing the logging response results derived from the effective fracture length can provide a reference for assessing the content of fracture-type uranium ore.
[Objective]Geopolymers can effectively improve the poor engineering properties of coastal silty soft soils, but their strength evolution characteristics and solidification mechanism need to be further studied. [Methods]Taking metakaolin-slag powder geopolymers, coastal silty soft soil, etc. as the research objects, specimens of coastal silty soft soil solidified by metakaolin-slag powder geopolymers with different proportions and ages were prepared. Unconfined compressive strength (UCS), X-ray diffraction (XRD)tests and scanning electron microscopy (SEM)tests were conducted. Based on the response surface method, the influence of the interaction of various factors on the strength of the solidified soil specimens was analyzed, and the microscopic action mechanism of geopolymers in solidifying silty soft soil was revealed. [Results]The research shows that the optimal proportion of the metakaolin-slag powder geopolymer is a mass ratio of metakaolin to slag powder of 1.69, a modulus of the alkali activator of 1.34, and a silica fume content of 3.23% . Under the optimal proportion, the 7-day and 28-day compressive strengths of the soil solidified by the metakaolin-slag powder geopolymer are increased by 137% and 47% respectively compared with those of the soil solidified by cement with the same content. Hydration products such as calcium silicoaluminate hydrate and calcium silicate hydrate generated by the metakaolin-slag powder geopolymer will adhere to the surface of the particles of the silty soft soil, and fill the pores between the soil particles in a cross-lapping manner, increasing the adhesive force between the particles, thus improving the soil strength. [Conclusion]Relatively speaking, the mass ratio of metakaolin to slag powder has a more significant impact on the uniaxial compressive strength of the solidified silty soft soil at both 7-day and 28- day curing ages. [Significance]This study provides a reference for the collaborative improvement of soft soil in coastal areas using multiple geopolymers.
