Failure Mechanism and Stability Control of Surrounding Rock of Docking Roadway under Multiple Dynamic Pressures in Extrathick Coal Seam

In view of multiseam mining under goaf, the surrounding rock control problem of lower coal roadway will be affected by concentrated coal pillar left in upper coal seam goaf and dynamic pressure superposition of working face in this coal seam. Under the geological environment of No. 16 extrathick coal seam in the Laoshidan coal mine and taking the working face 031604 as the research background, the reasonable docking position selection of the withdrawal roadway and the docking roadway in the middle mining period and the surrounding rock stability control problems of the withdrawal roadway and the docking roadway during the final mining period were studied by using the methods of field theoretical analysis, numerical simulation, and field measurement. The mechanical mechanism of the nonuniform failure of the retreating roadway and the docking roadway during the final mining period is shown, and the control method of the surrounding rock stability of the roadway is put forward and applied. The results show that (1) through the analysis of the superimposed stress under the concentrated coal pillar and the coal seam in advance, the specific butt joint position is arranged at 860 m away from the open-off cut, which is 10 m away from the goaf of No. 12 coal seam. (2) With the working face 031604 advancing through the process, the deviatoric stress value of the withdrawal roadway gradually increases, the maximum principal stress of the two sides of the roadway deflects clockwise from the vertical direction to the horizontal direction, its angle also gradually increases, and the shape of the plastic zone gradually expands from symmetry to asymmetry. (3) It is revealed that the peak value of deviatoric stress on both sides of the docking position of docking roadway increases gradually under the influence of mining and deflects anticlockwise to the vertical direction with the principal stress angle. The joint action of both is the mechanical mechanism that causes the plastic zone to expand in an asymmetric shape. (4) The coordinated control scheme of support (anchor bolt and anchor cable)—modified (grouting)—is adopted for the withdrawal roadway, and the coordinated control scheme of support (anchor bolt and anchor cable)—changing the cross-section shape of the roadway—is adopted for the docking roadway. The purpose of the smooth connection of working face and rapid and safe withdrawal of equipment is achieved on site

Assessing the decarbonization potential of China’s light-duty truck fleet by electrification

Light-duty trucks (LDTs) play an important role in last-mile delivery. To assess the CO2 mitigation potential of the electrification pathway of the LDT fleet in China, a dynamic fleet-based life cycle assessment model is developed. Four scenarios with different electrification progress are designed to evaluate the LDT stock growth, energy demand and the life cycle CO2 emissions quantitatively. The results show that LDT stock will increase to about 38 million in 2050. Energy demand and life cycle CO2 emissions of the LDT fleet can be greatly reduced with the increase in the proportion of battery electric vehicles (BEVs) in the LDT stock. The electrification mitigation benefit obtained from the fuel cycle will eventually outweigh the additional CO2 emissions generated by the vehicle cycle, especially in the long term with a cleaner power grid and a higher proportion of BEV in the LDT stock

Potential Dermal Exposure and Risk Assessment for Applicators of Chlorothalonil and Chlorpyrifos in Cucumber Greenhouses in China

<div><p>ABSTRACT</p><p>Occupational exposure to pesticides has not been conducted in depth so far in China. The potential dermal exposure and risk assessment were conducted for applicators through application with a knapsack power sprayer in cucumber greenhouses. The spray suspension was prepared with 75% chlorothalonil WP and 48% chlorpyrifos EC. The dermal patch method was applied to assess the potential dermal exposure (PDE) of applicators during application. The average total PDE on the whole body of applicators during application of chlorothalonil and chlorpyrifos was 83.2 mL h⁻¹ and 85.1 mL h⁻¹, respectively. The most exposed part of the body was arms, especially the right arm. For risk assessment, the margin of safety (MOS) was calculated from the PDE. The MOS values were 0.1 and 0.2 for application of chlorothalonil and chlorpyrifos, respectively, both less than 1, which indicated low possibility of health risk.</p></div