Macroscopic and microscopic mechanical behavior and seepage characteristics of coal under hydro-mechanical coupling

Understanding the physical,mechanical behavior,and seepage characteristics of coal under hydro-mechanical coupling holds significant importance for ensuring the stability of surrounding rock formations and preventing gas outbursts.Scanning electron microscopy,uniaxial tests,and triaxial tests were conducted to comprehensively analyze the macroscopic and microscopic physical and mechanical characteristics of coal under different soaking times.Moreover,by restoring the stress path and water injection conditions of the protective layer indoors,we explored the coal mining dynamic behavior and the evolution of permeability.The results show that water causes the micro-surface of coal to peel off and cracks to expand and develop.With the increase of soaking time,the uniaxial and triaxial strengths were gradually decreased with nonlinear trend,and decreased by 63.31%and 30.95%after soaking for 240 h,respectively.Under different water injection pressure conditions,coal permeability undergoes three stages during the mining loading process and ultimately increases to higher values.The peak stress of coal,the deviatoric stress and strain at the permeability surge point all decrease with increasing water injection pressure.The results of this research can help improve the understanding of the coal mechanical properties and seepage evolution law under hydro-mechanical coupling.

Effect of dry-wet cycles on dynamic properties and microstructures of sandstone:Experiments and modelling

Underground pumped storage power plant(UPSP)is an innovative concept for space recycling of abandoned mines.Its realization requires better understanding of the dynamic performance and durability of reservoir rock.This paper conducted ultrasonic detection,split Hopkinson pressure bar(SHPB)impact,mercury intrusion porosimetry(MIP),and backscatter electron observation(BSE)tests to investigate the dynamical behaviour and microstructure of sandstone with cyclical dry-wet damage.A coupling FEM-DEM model was constructed for reappearing mesoscopic structure damage.The results show that dry-wet cycles decrease the dynamic compressive strength(DCS)with a maximum reduction of 39.40%,the elastic limit strength is reduced from 41.75 to 25.62 MPa.The sieved fragments obtain the highest crack growth rate during the 23rd dry-wet cycle with a predictable life of 25 cycles for each rock particle.The pore fractal features of the macropores and micro-meso pores show great differences between the early and late cycles,which verifies the computational statistics analysis of particle deterioration.The numerical results show that the failure patterns are governed by the strain in pre-peak stage and the shear cracks are dominant.The dry-wet cycles reduce the energy transfer efficiency and lead to the discretization of force chain and crack fields.

A STUDY OF CLOUD-SYSTEM MODEL:MACRO AND MICRO STRUCTURE SIMULATION OF CLOUD FIELD

The macro and micro cloud physics structures and their evolution with time are the core of describing cloud fields in essence.They are necessary atmospheric environment not only in aviation and spaceflight activities but also for atmos- pheric radiation transfer and acid rain formation research.Unfortunately it is difficult to obtain an entire environmental cloud field by using observation methods directly.Thus,by use of computation physics method to build a cloud-system model may be an indispensable way for this topic.This paper presented a cloud-system model for this goal,and simu- lated a real case.The results of computation showed that the macro structure of the cloud field was better consistent with real observation,and the micro structure was fairly reasonable.The output of model could provide all the information about the cloud field:(1)size-distribution spectrum of hydrometeor particles (point),(2)vertical profile (line),(3)hori- zontal or vertical section of macro and micro parameters (surface),and (4)cloud cover,pattern of cloud and configura- tion of cloud,etc.(body).

Diagnosis and Recommendation Integrated System Assessment of the Nutrients Limiting and Nutritional Status of Tomato

Tomato is an important field crop,and nutritional imbalances frequently reduce its yield.Diagnosis and Recommendation Integrated System(DRIS),uses ratios for nutrient deficiency diagnosis instead of absolute concentration in plant tests.In this study,local DRIS norms for the field tomatoes were established and the nutrient(s)limiting tomatoes yield were determined.Tomato leaves were analyzed for nutrients,to identify nutritional status using the DRIS approach.One hundred tomatoes fields were selected from Chatter Plain Khyber Pakhtunkhwa and the Sheikupura Punjab Pakistan.The first fully matured leaf was sampled,rinsed,dried and ground for analyzing P,K,Ca,Mg,Cu,Fe,Mn and Zn using an Inductively Coupled Plasma Atomic Emission Spectrophotometer(ICP AES).Plant tissue N and S were measured by the combustion method.The tomatoes yields were recorded at each location.The data were divided into high-yielding(≥3.79 kg/10 plant)and low-yielding(<3.79 kg/10 plant)populations and norms were computed using standard DRIS procedures.High-yielding plant population had a statistically greater mean S and Fe than the low-yielding population.The average balance index,the sum of functions,for S and Fe were−11.04 and−5.17 which reflected deficiency of S and Fe.Plant nutrients norms established may optimize plant nutrition in field tomatoes for high yield.

Effect of Exogenous Organic Matter Application on Soil and Plant Elemental Composition in Pot Experiments

Content of macro- and microelements in plant and soil was studied after biochar, compost, digestate, lignite, and lignohumate application. Pot experiments were carried out in Phytotron CLF Plant Master （Wertingen, Germany）. As tested plant lettuce （Lactucasativa） was used. Elemental composition was determined by AAS and XRF spectroscopy. Macronutrients content （Ca, Mg, K, and P） was determined by Mehlich III. Total content of carbon and nitrogen were determined by LECO TruSpec CN analyser. Results showed that different exogenous organic amendments statistically significantly influenced macro and micronutrients content in soil and plant. Satisfactory C/N ratio for soil microorganisms was measured only after compost and digestate application. As concerns hazardous elements, no legislation limits were overstepped after application of the tested organic amendments. Bioavailability and their uptake by plants followed the order： Cd 〉 Mn 〉 Zn 〉 Fe.

Paleo and New Earthquakes and Evaluation of North Tabriz Fault Displacement in Relation to Recurrence Interval of Destructive Earthquakes

Azerbaijan is one of the most active segments of the Alpine-Himalayan seismic belt and marks the junction between the African-Arabian and Indian plate to the south and Eurasian plate to the north. Several regional earthquakes have been strongly felt and caused damages in and around Tabriz during history. For example, the magnitude 7 to 7.7 Tabriz earthquake in 1780, which is the most strongest experienced one in Lesser Caucasus and east of Turkey and caused severe damage in Azerbaijan territory including Tabriz City. The urban area of Tabriz City lies on Miocene to Quaternary soft sediments （clays, sands, silts, and gravels.） resting on an old Tertiary basement. Previous studies have shown that the thickness of such soft sediments could largely influence the site response in case of an important regional earthquake. The accurate information about historical earthquakes and new faulting is an important tool for viewing the active tectonic and analyzing the earthquake risk and seismic migration. Historical records of earthquakes in Tabriz based on macro and micro seismic observations cover period of 1,000 to 1,400 years. Our study aims at mapping the seismic response of a pilot zone of Tabriz for different earthquake scenarios, a simple but robust.

Research on failure criterion of composite based on unified macro- and micro-mechanical model

A new unified macro- and micro-mechanics failure analysis method for composite structures was developed in order to take the effects of composite micro structure into consideration. In this method, the macro stress distribution of composite structure was calculated by commercial finite element analysis software. According to the macro stress distribution, the damage point was searched and the micro-stress distribution was calculated by reformulated finite-volume direct averaging micromechanics （FVDAM）, which was a multi-scale finite element method for composite. The micro structure failure modes were estimated with the failure strength of constituents. A unidirectional composite plate with a circular hole in the center under two kinds of loads was analyzed with the traditional macro-mechanical failure analysis method and the unified macro- and micro-mechanics failure analysis method. The results obtained by the two methods are consistent, which show this new method＇s accuracy and efficiency.

Macro-/micro-coupling regulation of nanoporous metals via vapor phase alloying-dealloying

Nanoporous metals with bicontinuous ligament-channel structure are of great importance in catalysis,electro-catalysis,actuation and energy storage and conversion.However,the intrinsic brittleness of nanoporous metals has always been the“Achilles heel”that impedes their practical applications.Utilizing the vapor pressure difference of metals,herein we propose a flexible and general vapor phase alloying(VPA)-dealloying strategy to fabricate nanoporous layers supported on the substrates with the same element.By adjusting the VPA time and temperature,the thickness and microstructure control over nanoporous layers can be realized by combining with diverse dealloying methods.Besides,various metals including Ag,Au,Cu,Co and Ni with different macro sizes and shapes can be fabricated into nanoporous structures through this method.More importantly,the greatly improved tensile ductility owing to the nanoporous layersubstrate structure and well enhanced catalytic performance for hydrogen evolution reaction of the as-fabricated nanoporous metals signify great potentials of the VPA-dealloying strategy for practical applications.