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To mitigate accidents in submarine cable construction within the rapidly expanding offshore wind power sector, this study employed the analytic hierarchy process (AHP) and risk matrix method (LS) to assess the risks associated with identified factors. Based on project research and expert consultations, five primary and twenty-two secondary risk factors were identified. AHP was utilized to rank the primary risk factors by severity, probability, and detection difficulty, with the highest risk being the environmental impact, followed by third-party destruction and worker error. LS was applied to rank the secondary risk factors by likelihood and severity, with the highest risks being complex submarine topography, low underwater visibility, and fishing operations. The study proposes risk reduction measures based on these evaluations and offers methodological guidance for improving construction safety in similar enterprises. [ABSTRACT FROM AUTHOR]

To improve the safety level of pile foundation construction for offshore wind power, in this study, the risk indicators of pile foundation construction were evaluated using the analytic hierarchy process (AHP) and comprehensive evaluation methods. The pile foundation construction operation process for offshore wind power mainly includes four phases: preparation for construction, pile sinking, end of construction, and foundation scour protection construction. Pile foundation construction risk indicators are systematically identified as human factors, material factors, management factors, and environmental factors. The most important indicators for pile foundation construction for offshore wind power were evaluated using AHP and comprehensive evaluation methods, which included five indicators: piling equipment, protective equipment, special skills, safety awareness, and emergency management. The four more important indicators are workplace environment, lifting equipment, fire protection systems, and operations. According to the results of our evaluation of the pile foundation construction safety indicators presented herein, corresponding recommendations are made that consider four aspects—human factors, material factors, management factors, and environmental factors. The construction industry should focus on improving the safety measures related to aspects with greater risk indicators. Pile foundation construction for offshore wind power can be evaluated using the method discussed in this paper, allowing industry stakeholders to prioritize and focus on improving safety measures related to aspects with greater risk indicators. [ABSTRACT FROM AUTHOR]

In view of the current situation that there are many but no uniform coal molecular modeling methods, this paper explores the structuve of lignite macromolecules and optimizes them from a microscopic perspective by selecting physical methods that have less impact on molecular structure.A relatively simple coal macromolecule modeling method was put forward.Based on the experimental methods of elemental analysis, 13C-NMR and XPS, molecular dynamics simulation software method was used to analyze and study lignite and build molecular structure models.The results show that the aromatic structure of lignite macromolecules is mostly pentaphenyl.The fat carbon structure is mostly methylene and methine, and the alkane chain is mostly cycloalkanes.Oxygen atoms are mostly ether bond oxygen, followed by carboxyl oxygen and carbonyl oxygen.Nitrogen atom exist in the form of Pyridinic nitrogen N-6.After the optimization, the structure of the coal molecular model is more compact and the energy is obviously reduced.As the main component of the non-bonding potential energy and the main factor to maintain the stability of the coal molecular structure, the van der Waals potential energy has the most obvious change.In order to construct coal molecular cell, periodic boundary conditions were added.According to the energy variation, the cell density was 1.2 g/cm3 and the total energy was 1 140.624 kJ/mol, which was basically consistent with the actual situation and verified the effectiveness of the modeling method.This study provides a method for the direct understanding of the macromolecular structure of coal, and is of great significance for the mechanism research and prevention of coal and gas outburst, coal spontaneous combustion and other disasters.

The numerical simulation of HJC constitutive model is carried out to analyze the dynamic changes of the stress field, strain field and energy field of coal and rock mass under dynamic loading process. The results show that the change of load change rate has the greatest influence on the failure mode of coal and rock mass, followed by the maximum pressure value of the load, and finally the action time. Under the five kinds of load pressures, the kinetic energy, internal energy and total energy of coal and rock mass are consistent with time. When coal and rock mass is not destroyed, these three kinds of energy increase with time. When coal and rock mass is destroyed, the kinetic energy is finally reduced to zero, and the internal energy is reduced. The more severe coal and rock mass damage, the greater the reduction of the three types of energy. When coal and rock mass reaches the critical stress, only minor damage occurs, and then the maximum damage is reached when the maximum total energy is reached. When the pressure and the action time reach a certain value, coal and rock mass will be destroyed, and the change of the load change rate will increase the damage capacity of coal and rock mass.

With the increasing complication of production and geology conditions, and the increase of mining intensity and depth in coal mine, the coal structure presents varying degrees of deformation. In order to study the influence of uniaxial tension–compression effect on mechanical properties of coal matrix and CH4/CO2 adsorption characteristics, a macromolecular model reflecting the realistic bituminous coal structure was established. Results demonstrate that the influence of tension strain on the microporous structural parameters is greater than that of compression strain, and the tension strain weakens the mechanical properties but enhances the adsorbates adsorption amount. For the pure gases adsorption, there is a negative linear correlation between the total energy and adsorption amount. Additionally, the strain ranging from −0.20 to 0.20, the distribution of punctated adsorbates density develops to that of banded adsorbates density, and the mean adsorption density and saturated adsorption amount increase linearly. For the binary components adsorption (1:1), the CH4 adsorption strength increases while the CO2 adsorption strength slightly decreases. The minimum of total energy decreases in a quadratic polynomial relationship with the strain, and the proportion of van der Waals energy is 75.8–85.5%. Nevertheless, the competitive adsorption and strain have little effect on the potential energy range of the adsorbates. Furthermore, the diffusibility of CO2 molecular layers is relatively good, and the strain enhances the stability of CH4 molecular layers for the saturated binary adsorption. The findings provide essential guidance for the improvement of carbon capture and storage and CO2-enhanced coalbed methane technologies in the deformation area of coal seam. [ABSTRACT FROM AUTHOR]

The effects of H 2 O on the low-temperature oxidation characteristics of coal have always been one of the keys in the research of coal spontaneous combustion, but most studies rely on experiments for macroscopic derivation, and theoretical researches at the microlevel are rarely mentioned. In this paper, phenylacetaldehyde, phenylethyl alcohol, phenylacetic acid, and ethylbenzene hydroperoxide were used as modeling compounds of coal molecules containing aldehyde (-CHO), alcohol hydroxyl (-OH), carboxyl (-COOH), and peroxide (-C-O-OH). The surface electrostatic potential (ESP), electron density of atoms in molecules (AIM), and reduced density gradient (RDG) of coal molecules were calculated by density functional theory (DFT), and the thermokinetic parameters of low-temperature oxidation of coal molecules with or without H 2 O were analyzed. The results show that the extreme positive and negative ESPs are located at the H and O atoms of oxygen functional groups (OFGs), respectively, which are the active sites for H 2 O adsorption. The AIM and RDG show that the phenylacetaldehyde···H 2 O complexes have two kinds of adsorption configurations with two and three hydrogen bonds, and that the phenylethyl alcohol···H 2 O complexes also have two kinds of adsorption configurations with one and three hydrogen bonds, and that both phenylacetic acid···H 2 O and ethylbenzene hydroperoxide···H 2 O only have one adsorption configuration, forming two and three hydrogen bonds, respectively. According to electron density ρ( r ) and potential energy density V ( r ), the adsorption strength of H 2 O by four kinds of oxygen functional groups is ranked as -C-O-OH > -COOH > -OH > -CHO. The thermokinetic parameters show that H 2 O can increase the activation energy (Δ E ) of the oxidation reactions of phenylacetaldehyde and phenylethyl alcohol, which can inhibit the reaction and decrease the activation energy (Δ E ) of the oxidation reaction of phenylacetic acid and ethylbenzene hydroperoxide, which can promote the reactions., Competing Interests: The authors declare no competing financial interest., (© 2021 The Authors. Published by American Chemical Society.)