•Baffles system can reduce the deposit area of rock avalanches by more than 13.5%.•Shape changing (cylindrical to arc-shaped) will up-regulate the fragment blockage degree; the following avalanches ...will take place close to the avalanche deposition, leading to a huge dissipation of kinetic energy.•Arc-shaped baffle system showed competitive blocking ability when Sc=3.5 and Sr=4.5.•The number of rows mainly affects the avalanches deposit area and the baffles blocking capacity.•Baffles’ spacing Sc mainly affects its blocking efficiency.
To reduce the flow energy of rockfall in rmountain area, a baffle array is set up in the protection zone. The optimized design can enhance the efficiency of hazard source energy dissipation project. In the present study, the arc-shaped baffles were studied as compared with the conventional baffles (square baffles and cylindrical baffles) based on practical engineering. The comparison of three types of baffles was discussed in detail by experimental studies, which primarily focused on the blocking ability and effectivity. In particular, by determining the optimal case using those different types of baffles, the effects of the optimization of baffle system column spacing, row spacing and Ld (distance between first baffle row and chute terminal) were investigated. According to the results, the arc-shaped baffle is the best case among those three types of baffle, i.e. the deposit area and runout are all shorter than those of any other cases with the same value of Sr. Shape changing (cylindrical to arc-shaped) will up-regulate the fragment blockage degree; the following avalanches will take place close to the avalanche deposition, leading to a huge dissipation of kinetic energy. Moreover, by comparing deposition, dimensionless velocity (U*) and velocity reduction ratio (VRR), arc-shaped baffle system showed competitive blocking ability when Sc=3.5 and Sr=4.5. With the rise in the Ld, the energy dissipation efficiency can be enhanced through the particle collision and particle friction during the geo-disaster movement. Furthermore, it can effectively narrow the deposit area and reduce deposit depth and deposit width. The results obtained from this study are useful for facilitating design of baffles against rock avalanches.
Taking the disaster prevention and mitigation project for Ermanshan landslide as the research object, this study conducts the physical model test of rock avalanches and uses three parameters of
Sc
...(column spacing),
Sr
(row spacing), and
Ld
(the distance between the first row of the array of baffles and the chute port) to determine the optimal layout of three different types of array of baffles (square baffles, circular baffles, and arc-shaped baffles). Then, PFC3D is used to build a numerical simulation model of rock avalanches–array of baffles–retaining wall. Finally, this paper compares the impact force on each baffle type under the optimal layouts as well as the displacement and impact force on the retaining wall of the array of baffles. The results show that the impact force of rock avalanches on the array of baffles and retaining wall decreases with the increase of
S
c
. As
S
c
increases from 2.5 to 4.5, the average impact force on the circular baffles, square baffles, and arc-shaped baffles is reduced by 26.4%, 17.1%, and 23.4%, respectively. Besides, under the different layouts, the arc-shaped baffles show the best effect of blocking and energy dissipating among the three. Under the same working conditions, the average impact force on the first row of arc-shaped baffles is lower than that of the circular baffles and square baffles by 12.5–22.5% and 2.1–10.1%, respectively. Moreover, the arc-shaped baffles have an advantage in dissipating the impact force. Under the S2 working condition (S2: the optimal configuration for square baffles system), the maximum impact force on the first row of the circular baffles and the square baffles is increased by 21.3% and 14.9% compared with the S1 working condition (S1: the optimal configuration for circular baffles system). The chute shape of the arc-shaped baffles can form a cushion under the condition of particle accumulation, resulting in that the maximum impact force on the first row of the arc-shaped baffle under S2 condition is reduced by 17.3% compared with that under S1 condition.
Limestone calcined clay cement (LC3) is an environment-friendly and sustainable cementitious material. It has recently gained considerable attention for the stabilization/solidification (S/S) of ...soils contaminated by heavy metals. However, the existing studies on S/S of Zn-contaminated soils using LC3 in terms of hydraulic conductivity and microstructural properties as compared to ordinary Portland cement (OPC) are limited. This study focuses on the evaluation of the mechanical, leaching, and microstructural characteristics of Zn-contaminated soils treated with different contents (0%, 4%, 6%, 8%, and 10%) of low-carbon LC3. The engineering performance of the treated Zn-contaminated soils is assessed over time using unconfined compressive strength (UCS), hydraulic conductivity (
k
), toxicity characteristic leaching procedure (TCLP), and synthetic precipitation leaching procedure (SPLP) tests. Experimental results show that the UCS of Zn-contaminated soils treated with LC3 ranged from 1.47 to 2.49 MPa, which is higher than 1.63%–13.07% for those treated with OPC. The
k
of Zn-contaminated soils treated with LC3 ranged from 1.16×10
−8
to 5.18×10
−8
cm/s as compared to the OPC treated samples. For the leaching properties, the leached Zn from TCLP and SPLP is 1.58–321.10 mg/L and 0.52–284.65 mg/L as the LC3 contents ranged from 4% to 10%. Further, the corresponding pH modeling results indicate that LC3 promotes a relatively suitable dynamic equilibrium condition to immobilize the higher-level Zn contamination. In addition, microscopic analyses demonstrate that the formations of hydration products, i.e., Zn(OH)
2
, Zn
2
SiO
4
, calcium silicate hydrate (C–S–H), calcium silicate aluminate hydrate (C–A–S–H) gel, ettringite, and CaZn(SiO
4
)(H
2
O), are the primary mechanisms for the immobilization of Zn. This study also provides an empirical formula between the UCS and
k
to support the application of LC3-solidified Zn-contaminated soils in practical engineering in the field.
In mountainous areas, channelized rock avalanches swarm downslope leading to large impact forces on building structures in residential areas. Arrays of rock avalanche baffles are usually installed in ...front of rigid barriers to attenuate the flow energy of rock avalanches. However, previous studies have not sufficiently addressed the mechanisms of interaction between the rock avalanches and baffles. In addition, empirical design approaches such as debris flow (Tang et al., Quat Int 250:63–73,
2012
), rockfall (Spang and Rautenstrauch, 1237–1243,
1988
), snow avalanches (Favier et al., 14:3–15,
2012
), and rock avalanches (Manzella and Labiouse, Landslides 10:23–36,
2013
), which are applied in natural geo-disasters mitigation cannot met construction requirements. This study presents details of numerical modeling using the discrete element method (DEM) to investigate the effect of the configuration of baffles (number and spacing of baffle columns and rows) on the impact force that rock avalanches exert on baffles. The numerical modeling is firstly conducted to provide insights into the flow interaction between rock avalanches and an array of baffles. Then, a modeling analysis is made to investigate the change pattern of the impact force with respect to baffle configurations. The results demonstrate that three crucial influencing factors (baffle row numbers, baffle column spacing, and baffle row spacing) have close relationship with energy dissipation of baffles. Interestingly, it is found that capacity of energy dissipation of baffles increases with increasing baffle row numbers and baffle row spacing, while it decreases with increasing baffle column spacing. The results obtained from this study are useful for facilitating design of baffles against rock avalanches.
This study investigates the segregation processes and impact response of binary granular mixtures with identical densities but different sizes particles subjected to gravity. Deposition was compared ...using discrete element method (DEM) numerical experiment and laboratory experiment to determine the material parameters in the particle flow code in three dimensions (PFC3D). With proper material parameters, many numerical experiments were performed on an idealized binary granular mixture avalanche to reveal its kinetic properties, with a particular focus on the results of the final run-out distance, fluid velocity, and impact force exerted on defending structures. The simulation results show that the energy dissipation in granular avalanches is higher with uniform particle sizes than with mixed particle sizes, indicating lesser energy dissipation in segregation processes. Coarse particles also play an important role in determining the kinetic properties of binary granular mixture avalanches; specifically, they obviously affect the maximum impact force when the storage area length is small. On the other hand, fine particles play an important role when the storage area length is large. These results suggest that the effects of coarse particles in granular avalanches containing more than one particle size may be at least as important.
Accurate prediction of the scour hole depth and dimensions downstream of ski-jump spillways has been an important issue among hydraulic researchers for decades. In recent years, computing methods ...such as Artificial Neural Networks (ANNs), Adaptive Neuro-Fuzzy Inference Systems (ANFISs) and Support Vector Regression (SVR) have shown a powerful performance in the prediction of scour characteristics owing to their flexibility and learning nature. In the present paper, a new hybrid approach has been proposed for the first time in order to improve the estimation power of the SVR tool for scour hole geometry prediction below ski-jump spillways. The principal characteristics of the scour hole pattern in the equilibrium phase have been predicted using SVR optimized with Fruitfly Optimization Algorithms (FOAs). The hybrid model is compared with the corresponding simple SVR model. To evaluate the proposed hybrid model further, it is also compared with other machine learning and empirical methods, such as ANNs, ANFISs and regression equations. The results show that the proposed SVR-FOA method performs well, improves remarkably on Support Vector Machines (SVMs) results, estimates scour hole geometrical parameters more accurately than the simple SVR model, and can be applied as an alternative reliable scheme for estimations on which simple SVR and other methods demonstrate shortcomings. The proposed hybrid method improves the precision level for scour depth prediction by about 8% compared with simple SVM in terms of the correlation coefficient.
In this paper, a discussion is presented about the impact-induced damage suffered by bridge pier columns during rockfall events through model tests and impact force, column top displacement, ...stress-strain response, and other parameters in relation to the process of impact. On this basis, the following conclusions are drawn. Firstly, the impact force, as well as the displacement and strain of the column top, increases rapidly after taking a hit, while the displacement is reduced after reaching its maximum. Secondly, at the same falling height, the higher the impact position, the smaller the peak of impact force and the longer the attenuation period. Thirdly, at the same impact height, the impact energy, the displacement of the column top, and the peak of the impact force increase as the falling height of the pendulum ball is on the rise, but the attenuation period remains unchanged. Fourthly, the failure mode of column impacted by the swing ball conforms to shear-flexural failure. Fifthly, it is recommended to strengthen the preventative measures for those weak positions like 1/2 height and 1/4 height of bridge pier, so as to minimize the potential damage caused by rockfalls. Besides, a theoretical formula used to estimate the maximum impact force is proposed. Lastly, under the axial load of bridge deck, the performance of the pier in impact resistance under rockfall is better and the damage is less severe than in the experimental impact test. The axial load applied by the deck imposes some constraints on the pier, thus reducing concrete damage. The research results can contribute to the research on addressing the rockfall-bridge pier collision problem. The experimental research demonstrates its theoretical significance to engineering for the prevention of rockfall.
•Innovative combined process for a biomass-fed solid oxide fuel cell-gas turbine plant.•Use of heat recovery and compressed air energy storage for peak shaving.•Conducting a thorough parametric study ...and defining five distinct optimization scenarios.•The most suitable ERTE and LTE equal 51.06 % and 0.64 kg/MWh, respectively.•The most suitable NPV and payback period equal 7.44 M$ and 1.54 years, respectively.
This paper explores the potential of a combined solid oxide fuel cell and gas turbine technology for medium- to large-scale power generation, emphasizing its applicability and sustainability, particularly with biomass feedstock. An innovative heat integration process is developed for a modified solid oxide fuel cell and gas turbine power plant, incorporating a steam power cycle, compressed air energy storage, a Kalina cycle, and a domestic hot water production subsystem. The system utilizes biomass through a downdraft gasifier, enabling a comprehensive evaluation of thermodynamic, economic, and environmental performance during both charging and discharging phases. A detailed parametric sensitivity analysis is performed to investigate two operational modes. Subsequently, five multi-objective optimization scenarios are formulated and optimized using the cuckoo search algorithm and two decision-making approaches. The results indicate that the optimization scenario focusing on exergetic round-trip efficiency and the unit cost of products during the discharging phase achieves superior thermodynamic and environmental performance. Specifically, the system exhibits energetic and exergetic round-trip efficiencies of 59.20 % and 51.06 %, respectively, with a levelized total emission of 0.64 kg/MWh. Furthermore, when considering the objectives of exergetic round-trip efficiency and net present value, the optimal economic performance is achieved with a payback period of 1.54 years and a net present value of $7.44 million.
•Novel ELM and GTB models are used for estimating brine/CO2/mineral contact angles.•Accuracy of models are proved for simulation of CO2/brine wettability on minerals.•Outlier detection and ...sensitivity analyses are used for further investigation.
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•A modified plastic concrete for cut-off walls was synthesized using the silica fume.•Permeability of the optimal sample can meet the anti-seepage and mechanical requirement.•Internal ...structural parameters were analyzed through the pore-scale modeling.•Permeability and velocity fields were simulated using the Lattice Boltzmann Method.
A modified plastic concrete cut-off wall was synthesized using different mass ratios of silica fume (0–21.3%) and constant cement content (8%) based on the conventional soil-bentonite cut-off wall. The slump test, hydraulic conductivity and mechanical performance were analysed to determine the optimal material ratio. The hydraulic conductivity of the optimal sample could meet theanti-seepagerequirement (~10-9 m/s). The amended plastic concrete cut-off wall could obtain the appropriate compressive strength (0.896 MPa) and a low elastic modulus (1244.5 MPa). The characterization of the clayey soil materials and modified plastic concrete cut-off walls were analysed by X-ray diffraction (XRD) methods, which demonstrated that the clayey soil mainly contained quartz and feldspar (anorthite). The pozzolanic reaction between the silica fume and calcium hydroxide and the refinementofthe porestructure could increase the compressive strength and reduce the hydraulic conductivity. Microscale three-dimensional real geometry images of the modified plastic concrete for cut-off walls were obtained from X-ray microcomputed tomography. The internal structural parameters were analysed through pore-scale modelling. The hydraulic conductivity and velocity fields were simulated using the lattice Boltzmann method. The results showed that most of the pores and throats in the modified plastic concrete for cut-off walls were micropores and microflow paths (diameter ≤ 5 μm), and the connected porosity was approximately 25.89%. The simulated hydraulic conductivity was in good agreement with the measured value, and the velocity fields indicated that the microflow paths were tortuous and complex. The silica fume-modified plastic concrete for cut-off walls enabled the realization of the requirements for good controlof the waterseepage in hydraulic engineering construction applications at a low cost.
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