Investigating the bearing performance of the foundation under the combined effects of flood scouring and soaking

Abstract Bearing capacity degradation of foundations under the impact of the flood is one of the major reasons responsible for the collapse and damage to the rural buildings, posing a serious threat to the local village societies. Based on a case study of a rural building foundation had been destroyed by flooding. This paper investigated the deterioration process of rural building foundations under the combined effect of dynamic scouring and static soaking caused by flooding. Using the two-dimensional shallow water equation, erosion depth was calculated for different flood velocities. Then, the bearing capacity degradation under the combined scouring-soaking effect was analyzed using the finite element method. Finally, investigating the influence of inflow direction and building group masking on the foundation's bearing capacity. The results indicate that under the combined effect, the bearing capacity of village building foundations decreases by 47.88%, with scouring slightly more impactful than soaking. Inflow angle has minimal effect on bearing performance, while the masking effect of the building group provides better protection for the foundation of rear buildings

An Integrated Approach for Simulating Debris-Flow Dynamic Process Embedded with Physically Based Initiation and Entrainment Models

Recent studies have indicated that the accurate simulation of debris flows depends not only on the selection of numerical models but also on the availability of precise data on the initial source location and depth. Unfortunately, it is currently difficult to obtain quantitative data on source locations and depths during field investigations or model experiments of debris flow disasters. Therefore, in this study, we propose an integrated approach for simulating the debris-flow dynamic process that includes the physically based slope initiation source estimation and the entrainment-incorporated process simulation. We treat the potential slip surfaces’ locations and depths as random variables to search for the critical surface corresponding to the minimum stability factor by Monte Carlo simulation. Using the spatial variation interval of the soil parameters, we estimate the range of possible critical slip surfaces and the interval of the initiation source volume. Moreover, we propose a wet/dry front treatment method applied to the finite difference scheme and integrate it into our entrainment-incorporated model to improve the stability and accuracy of the numerical solution over complex topography. The effectiveness of the method is demonstrated through a case study of the 2010 Hongchun debris flow event in Yingxiu town. The result indicates that our method is effective in simulating debris flow dynamics, including slope initiation source estimation and dynamic process simulation

Ultrafast Photoinduced Interfacial Proton Coupled Electron Transfer from CdSe Quantum Dots to 4,4′-Bipyridine

Pyridine and derivatives have been reported as efficient and selective catalysts for the electrochemical and photoelectrochemical reduction of CO₂ to methanol. Although the catalytic mechanism remains a subject of considerable recent debate, most proposed models involve interfacial proton coupled electron transfer (PCET) to electrode-bound catalysts. We report a combined experimental and theoretical study of the photoreduction of 4,4′-bipyridium (bPYD) using CdSe quantum dots (QDs) as a model system for interfacial PCET. We observed ultrafast photoinduced PCET from CdSe QDs to form doubly protonated [bPYDH₂]^+• radical cations at low pH (4–6). Through studies of the dependence of PCET rate on isotopic substitution, pH and bPYD concentration, the radical formation mechanism was identified to be a sequential interfacial electron and proton transfer (ET/PT) process with a rate-limiting pH independent electron transfer rate constant, <i>k</i>_int, of 1.05 ± 0.13 × 10¹⁰ s^–1 between a QD and an adsorbed singly protonated [bPYDH]⁺. Theoretical studies of the adsorption of [bPYDH]⁺ and methylviologen on QD surfaces revealed important effects of hydrogen bonding with the capping ligand (3-mercaptopropionic acid) on binding geometry and interfacial PCET. In the presence of sacrificial electron donors, this system was shown to be capable of generating [bPYDH₂]^+• radical cations under continuous illumination at 405 nm with a steady-state photoreduction quantum yield of 1.1 ± 0.1% at pH 4. The mechanism of bPYD photoreduction reported in this work may provide useful insights into the catalytic roles of pyridine and pyridine derivatives in the electrochemical and photoelectrochemical reduction of CO₂