Instability energy mechanism of super-large section crossing chambers in deep coal mines

The stress concentration and failure at chamber intersections in coal mine are intense,especially in deepburied,super-large section conditions.In this paper,the plastic radius of super-large section chamber under unequal pressure was corrected on the basis of the size effect.Then,stress and failure evolution of intersections under different crossing angles and equivalent angular bisectors were revealed.Furthermore,2 trajectory curves of failure and stress were analytically expressed,which divided the intersection into 5 influencing zones in the light of stress superposition degree.After determining instability trigger point and instability path,instability energy criterion of intersection can be obtained as K>1,which means that the external energy is greater than the sum of energy consumed by surrounding rock instability and supporting structure failure.Taking coal-gangue separation system of Longgu Coal Mine as example,it was found that there was instability risk under original parameters.For long-term stability,an optimization design method was proposed by considering safety factor,and optimal support scheme was obtained.Field monitoring showed intersections deformations were relatively small with the maximum of 125 mm,which verified the rationality of theoretical analysis.This study provides guidance for the stability control of the intersections under the same or similar conditions.

Effects of the <i>Camellia oleifera </i>Shell Substrate on the Yield and Nutritional Composition of <i>Pleurotus geesteranus</i>

Pleurotus geesteranus was cultivated on the substrates blended with different ratios of treated and untreated Camellia oleifera shells using cottonseed hull as the control substrate. The mycelial growth rate, yield, nutritional composition, ash and heavy metals of the Pleurotus geesteranus cultivated on these substrates were compared. The results suggest that the Camellia oleifera shell in substrate can accelerate the mycelial growth and increase the yield, nutrients and the contents of protein, ash, crude fiber and amino acid of Pleurotus geesteranus. It was found that the contents of tannin and saponin in Camellia oleifera shell affected the mycelial growth rate. The optimal C/N of the substrate for the growth of Pleurotus geesteranus was determined to be 27 ± 0.7. The C/N ratios higher than 30 reduced the protein, fat and soluble sugar contents of the cultivated Pleurotus geesteranus. The contents of heavy metals including Hg, As, Cd and Pb were found in Pleurotus geesteranus cultivated on the substrates containing Camellia oleifera shell complex.

Effects of the <i>Castanea mollissima Blume</i>Shell Cultivation Substrate on the Yield and Nutritional Composition of <i>Pleurotus geesteranus</i>

Cottonseed hull substrates blended with different ratios of Castanea mollissima Blume shell were prepared and used for the cultivation of Pleurotus geesteranus. The effects of the chestnut shell content on the mycelial growth rate, yield, nutritional composition and contents of heavy metals of the cultivated Pleurotus geesteranus were investigated. The results suggest that the Castanea mollissima Blume shell in substrate can increase the mycelial growth rate, yield, biological efficiency and the contents of protein, crude fiber, amino acids and essential amino acids of Pleurotus geesteranus. Further investigation suggests that the tannin and saponin in Castanea mollissima Blume shell and the C/N ratio of substrate significantly influence the mycelial growth rate. The crude fat content of Pleurotus geesteranus decreased, while the contents of heavy metals including mercury (Hg), arsenic (As), cadmium (Cd) and lead (Pb) increased with the increase of the Castanea mollissima Blume shell content in substrate. Based on these results, the content of Castanea mollissima Blume shell was optimized to be less than 30% for the cultivation of Pleurotus geesteranus.

Infrared-Spectral Characteristics of <i>Camellia oleifera</i>Shell/Meal during Composting

The compost products of Camellia oleifera shell/meal mixed at different mass ratios were characterized by Fourier-transform infrared spectroscopy (FTIR) at different composting stages to monitor the structural changes of their components. The results showed that the amount of Camellia oleifera meal significantly affected the composting rate of the shell, but did not change the degradation order and decomposition of the related compounds. During the composting process, microorganisms used the highly decomposable carbon source materials, such as proteins and sugars, first to grow and multiply, and then decomposed hemicellulose, cellulose and lignin by oxidative cleavage after these nutrients were consumed to a certain extent. The decomposition products were then condensed into more stable humic acids. The degradation rates of the compounds were directly proportional to the amount of Camellia oleifera?meal. The compounds in Camellia oleifera shell were composted faster with higher amounts of Camellia oleifera meals, resulting in less lignocellulose in the final products.

Rheological mechanical properties and its constitutive relation of soft rock considering influence of clay mineral composition and content

Rheological mechanical properties of the soft rock are afected signifcantly by its main physical characteristics-clay mineral.In this study,taking the mudstone on the roof and foor in four typical mining regions as the research object,frstly,the clay mineral characteristic was analyzed by the X-ray difraction test.Subsequently,rheological mechanical properties of mudstone samples under diferent confning pressures are studied through triaxial compression and creep tests.The results show that the clay mineral content of mudstone in diferent regions is diferent,which leads to signifcant diferences in its rheological properties,and these diferences have a good correlation with the content of montmorillonite and illite-montmorillonite mixed layer.Taking the montmorillonite content as an example,compared with the sample with 3.56%under the lower stress level,the initial creep deformation of the sample with 11.19%increased by 3.25 times,the viscosity coefcient and longterm strength decreased by 80.59%and 53.94%,respectively.Furthermore,based on the test results,the damage variation is constructed considering the montmorillonite content and stress level,and the M–S creep damage constitutive model of soft rock is established.Finally,the test results can be ftted with determination coefcients ranging from 0.9020 to 0.9741,which proves that the constitutive relation can refect the infuence of the clay mineral content in the samples preferably.This study has an important reference for revealing the long-term stability control mechanism of soft rock roadway rich in clay minerals.

Similar simulation study on the deformation and failure of surrounding rock of a large section chamber group under dynamic loading

Large and super-large section chamber groups in coal mines are frequently affected by dynamic loads resulting from production activities such as roadway driving and blasting.The stability of the surrounding rock is poor,and it is difficult to control.In this paper,a similar simulation test was used to study the deformation and evolution laws of the surrounding rock of a triangle-shaped chamber group under different dynamic loads.The results showed that under dynamic loading,the vertical stress of the surrounding rock of the chamber group increased in an oscillatory form.The maximum stress concentration coefficient reached 4.09.The damage degree of the roof was greater than that of the two sides.The deformation of the roof was approximately 1.2 times that of the two sides.For the chamber closer to the power source,the stress oscillation amplitude of the surrounding rock was larger,and the failure was more serious.The force of the anchorage structure showed a phased increasing characteristic;additionally,the force of the anchorage structure on the adjacent side of the chambers was greater than that on the other side.This study reveals the deformation and failure evolution laws of the surrounding rock of large section chamber groups under dynamic loading.

Effect of <i>Carya cathayensis Sarg</i>Shell Substrate on Yield and Nutrient Amount of <i>Pleurotus geesteranus</i>

Using cottonseed hull as the control substrate, different proportions of the untreated and treated Carya cathayensis Sarg shells were added to cultivation of Pleurotus geesteranus. The mycelial growth rate, yield, nutritional composition and contents of heavy metals of the Pleurotus geesteranus cultivated on these substrates were determined. The results suggest that added to treated Carya cathayensis Sarg shell promoted the mycelial growth and increased the yield, biological efficiency and the contents of crude fiber, ash, amino acids and essential amino acids of Pleurotus geesteranus. In addition, the fat content and soluble sugar contents of Pleurotus geesteranus were decreased with the increase of the Carya cathayensis Sarg shell content in substrate, but their contents of heavy metals including mercury (Hg), arsenic (As), cadmium (Cd) and lead (Pb) were higher than that obtained on control substrate.

Research and Practice of the Construction Mode of the Practical Training Base for Agriculture and Forestry

In response to bottlenecks and dilemmas faced by institutions for agricultural and forestry practical training base construction, and based on Agriculture practical training base of Langfang Polytechnic Institute, this article illustrates the effective exploration and practice of the mode and ways for the construction of the practical training base,which provides some useful experience for the construction of the training base in agricultural and forestry institutions.

FTIR and Thermogravimetric Analysis of Three Kinds of Nutshells

The main components and pyrolysis characteristics of Camellia oleifera Abel hells, Castanea mollissima Blume shells, and Castanea mollissima Blume shells were analyzed by using FTIR and thermogravimetric methods. The experimental results indicated that the main components of the three kinds of raw materials consisted of cellulose, hemicellulose, and lignin. The highest contents of hemicellulose, cellulose, and lignin were in Camellia oleiferaAbel shells (49.34% ± 0.07%), Castanea mollissima Blume shells (27.34% ± 0.01%), and Carya cathayensis Sarg shells (49.78% ± 0.01%), respectively. The pyrolysis processes of three kinds of shells generally included three stages, namely dehydration, pyrolysis, and carbonization. The peak values and the appearance times of their pyrolysis rates were closely related to their compositions.

A Method for Measuring the Degree of Fermentation of the Edible Mushroom Cultivation Substrate

In the study, eight treated substrates were designed to explore the possibility to determine the degree of fermentation of the substrate by the mycelial growth rate, whose main raw material includes?composted pine sawdust, oil tea shell and hickory shell respectively, and auxiliary materials contain rice bran, soybean powder, etc. The result showed that the shiitake mushroom grew well in 7 treatments whose mycelial growth rate could be measured on 3rd?days when the mycelial growth rates of P1, C1 and H1 were 5.0 mm/d, 9.66 m/s, 13.33?m/s.?Auricularia cornea?var.?Li exhibited the fastest growth on P1 substrate. And mycelial growth rates of P1, P0 and CK1 were 5.8 mm/d,?3.66?mm/d,?and?4.66 mm/d on 3rd?day, respectively. The growth rates?of?Pleurotusgeesteranus?of C1, CK2 and P0 were 9.0 mm/d,?11.66 mm/d,?and?4.00 mm/d on 3rd?day, respectively. So the degree of fermentation of the substrate could be determined within 3 days according to the mycelial growth rate. As the growth of edible fungi?is?affected by degree of fermentation of the substrate and there is little literature on degree of fermentation of edible fungi substrate, the study will provide theoretical and technical basis for determination of substrate fermentation.

Electrophysiological characteristics of atrial tachycardia originating from the coronary sinus

A 22-year-old girl was admitted to our cardiology institute with Permanent tachycardia in last 6 years for diagnostic assessment and therapy. Doppler echocardiography show structural of heart is normal, ECG revealed a varied resting rate from 120 to 140 bpm, 1:1 AV ratio and long RP interval. P wave morphology was negative on leads I, II, III, aVF, and V4 to V6, positive on lead V1, and diphasic 1 /2 on lead aVL. Electrophysiology (EP) study was performed, Although the exactly mapping was performed in left inferior pulmonary vein and mitral annulus, however, no target point was found ahead of CS1-2, the tried discharge was invalid. The ablation catheter was entered the coronary sinus to guide electrical isolation, curing the tachycardia. The ECG returned to normal sinus rhythm. Through three years follow up, no AT recurrence.

Energy mechanism of bolt supporting effect to fissured rock under static and dynamic loads in deep coal mines

The stability control of fissured rock is difficult,especially under static and dynamic loads in deep coal mines.In this paper,the dynamic mechanical properties,strain rate evolution and energy dissipation of fissured and anchored rocks were respectively obtained by SHPB tests.It was found that bolt can provide supporting efficiency-improving effect for fissured rock against dynamic disturbance,and this effect increased quadratically with decrease in anchoring angles.Then,the energy dissipation mechanism of anchored rock was obtained by slipping model.Furthermore,bolt energy-absorbing mechanism by instantaneous tensile-shear deformation was expressed based on material mechanics,which was the larger the anchoring angle,the smaller the energy absorption,and the less the contribution to supporting efficiency improvement.On this basis,the functional relationship between energy dissipation of anchored rock and energy absorption of bolt was established.Taking the coal-gangue separation system of Longgu coal mine as an example,the optimal anchoring angle can be determined as 57.5°–67.5°.Field monitoring showed fissured rock with the optimal anchoring angle,can not only effectively control the deformation,but also fully exert the energy-absorbing and efficiency-improving effect of bolt itself.This study provides guidance to the stability control and supporting design for deep engineering under the same or similar conditions.

Characteristics of the vertical structure of the atmospheric turbulence in the Tibetan Plateau

The Tibetan Plateau(TP)has unique atmospheric dynamics and thermal structures that originate from its giant terrain and complex climate.High vertical-resolution thermal radiosondes were launched near the central(Lhasa,91°06′E,29°36′N,3670 m above sea level(ASL))and marginal(Da Qaidam,95°21′E,37°51′N,3180 m ASL)areas of the TP during the summers of 2018 and 2020,respectively.Atmospheric turbulence parameters were calculated,and the characteristics of the atmospheric turbulent vertical structure at sunset in these two areas were analyzed and compared.Affected by TP thermal forcing and stably controlled by the summer monsoon anticyclone,the atmospheric refractive index structure constant(C_(n)^(2))tended to increase and then decrease with increasing height,reaching a maximum at the tropopause(~18 km ASL)at the Lhasa site.Although C_(n)^(2) at the Da Qaidam site also tended to increase at the tropopause,the position of the strong turbulent band(STB)(5–7 km ASL)was below the tropopause height corresponding to the potential temperature lapse rate minimum.The vertical distribution of C_(n)^(2) at the two sites,particularly regarding the position of the STB,was highly correlated with the atmospheric stability(Ri)and the thermal mixing scale(L_(T)).The significant correlations among the three parameters(STB,Ri,and L_(T))indicated that the strong fluctuations in temperature caused by thermal mixing were the dominant factor causing the Ri to be less than its critical value of 0.25.Moreover,the suppression strength involving the upward transport of the heat sources was the main reason for the different turbulent vertical structures and STB positions at the two sites.The zonal mean thermodynamic and dynamical fields derived from the reanalysis data also showed a height difference in the heat sources transported to the troposphere at the two sites.In the marginal TP,the material and energy in the lower troposphere were transported by the turbulent atmosphere upward along the slope of the mountain and converged at the central TP(28°N–35°N)with strong thermal forcing up to the tropopause.In the STB of the Lhasa site,the turbulent dissipation rate and eddy diffusion coefficient increased sharply,indicating that the turbulent atmosphere in this central site was highly diffused,and the small-scale turbulence transported the material and energy upward.