Analysis on control technology for collapsing vibration generated by building demolition blasting

The mechanism of ground vibration in building demolition blasting was investigated,taking into account the prevailing influential factors, including the building's heightof mass center, the quantity size, the structural feature, the component material quantity,the demolition method, the geological structure of the region, earthquake resistance rank,as well as the earthquake wave dissemination.The proposed method was applied efficientlyto reduce the blasting effects on the environment, which enriches the control theoriesof vibration caused by collapse in the blasting process and may provide a good referencefor the related engineering practices.

Characterization of the fracture compressibility and its permeability for shale under the effects of proppant embedment and compaction:A preliminary study

Hydraulic fracturing technology plays a key role in improving the recovery rate of shale gas.The improvement of permeability in relation to hydraulic fracturing depends on changes brought about by the proppant on the fracture structure in reservoirs.Then it is of great significance to describe the microscopic changes during this process by means of an accurate theoretical model.In this study,based on the heterogeneity of shale fracture and the compaction and embedment of a proppant,we proposed a permeability model to examine the combined effects of a proppant and stress to describe the change mechanism in permeability.Further,changes in fracture width and porosity were considered,and a calculation model of fracture compressibility under proppant compaction and embedment was proposed.The difference from previous studies is that the compressibility and permeability of supported fractures can be further quantified and analyzed by this model.Moreover,its rationality was verified by publicly released test data.The results show that,the compressive effect of stress and the embedding of proppant both have a negative impact on shale permeability.

Adsorption of rare earth elements on organic matter in coal

The occurrence modes of rare earth elements(lanthanide and yttrium,abbreviated as REY) in coal are impo rtant both for coal geochemistry studies and the application potential of REY as a by-product of coalbased resources.In this study,the adsorption behaviors of REY on organic matter in coal were investigated by leaching tests using REY solution and ultra-low ash coal samples.On this basis,the adsorption mechanism of REY on organic matter in coal was also studied by molecular simulation calculations.The leaching tests show that the organic matter in coal has a relatively strong adsorption capacity for REY,and that the average adsorption rate or the net adsorption amount of heavy rare earth elements(HREY:Gd,Tb,Y,Dy,Ho,Er,Tm,Yb and Lu) is always higher than that of the light rare earth elements(LREY:La,Ce,Pr,Nd,Sm and Eu).A molecular model of humic acid(HA) was constructed and the adsorption amount between REY and HA was calculated.The results show that the theoretical adsorption rate of HREY(84.88%) is higher than that of the LREY(84.00%).The analysis of the adsorption distances between REY atoms and various functional groups on HA molecules shows that the minimum adsorption distance of LREY is 0.372 nm on average,which is larger than that of HREY(0.368 nm),indicating that the adsorption capacity of the latter is stronger.In addition,a coal molecule(C_(18)H_(22)O) was also constructed to investigate the adsorption characteristics of various REY atoms on the molecule.As a result,it is found that the average binding ene rgy and bond length between the hydroxyl functional group and LREY atoms are 0.12469 Ha(Hartree,the unit of energy in the atomic unit system) and 0.1407 nm,respectively,while for HREY,0.12883 Ha and 0.1121 nm,respectively.This confirms that HREY is more stable than LREY in binding on organic matter in coal.To conclude,both leaching tests and molecular simulation calculations reveal that REY has a strong adsorption affinity for organic matter in coal,and in particular,HREY shows a stronger organic adsorption preference in coal than LREY,which is probably due to stronger chemical bonding between the former and the functional groups on the coal molecule.

Modes of occurrence and pre-concentration of rare earth elements in No.17 coal in Liupanshui coalfield,China

Rare earth elements(lanthanide and yttrium,abbreviated as REY) provide important support for national security,energy production,environmental protection and economic growth.In recent years,many studies have shown that the content of REY in some coal or coal by-products is close to or even higher than that in traditional REY ore,which makes coal a potential source of REY.This study took the No.17 coal of Panzhou mining area in Liupanshui coal field as the research object,and the content and occurrence modes of REY in raw coal and 7 density fraction samples were studied.The results show that the content of REY in the raw coal reaches 220.67 μg/g,which is significantly higher than the average REY content in the world coal and Chinese coal as reported in the literature.Gravity separation has a certain pre-enrichment effect on REY and the fraction sample> 1.8 g/cm~3 has the highest REY of 426.27 μg/g(equal to rare earth oxide 0.1%).Study on correlation between REY and ash yields reveals that the organic affinity of the light rare earth is higher than that of the medium rare earth and the heavy rare earth.As shown by X-ray diffraction(XRD) and X-ray flouresence spectroscopy(XRF),the major minerals in coal are kaolinite,quartz and calcite,and the content of REY in coal is significantly related to Al,Si and kaolinite,which implies that REY occur mainly in kaolinite.Laser ablation inductively coupled plasma mass spectroscopy(LA-ICP-MS) was adopted to determine chemical composition of micro-zone in kaolinite in coal and the results show that there is no obvious correlation between REY and the contents of Al and Si.This indicates that the REY occur probably in the form of adsorption.The research results provide a scientific reference for the potential extraction of the associated REY in the coal.