| 1 | Determination of time-dependent strengths of salt pillars based on strain energy principle显示文摘The objective of this study is to determine the time-dependent strengths of salt mine pillars in the Maha Sarakham formation, northeast of Thailand. Strain rate-controlled triaxial compression tests have been performed on salt specimens under confining pressures from 0 MPa to 12 MPa. The strain rates are from 10^(-7) s^(-1) to 10^(-4) s^(-1). The axial stresses and lateral strains are monitored through the strain-softening region. The results indicate that the strengths and elastic moduli increase exponentially with the strain rates. The power creep law parameters are calibrated with the test results, and hence allows constructing series of strain-time curves for the salt pillars under different depths and extraction ratios. The strain energy density principle is applied to develop a strength criterion for the salt pillars. Combining this criterion with the series of the strain-time curves the time-dependent strengths of the salt pillars for different extraction ratios can be predicted. | Prapasiri Junthong Supattra Khamrat Suratwadee Sartkaew Kittitep Fuenkajorn | 2019 | International Journal of Mining Science and Technology2019，29，2： | 1 |
| 3 | Revealing the Effects of Pore Size and Geometry on the Mechanical Properties of Graphene Nanopore Using the Atomistic Finite Element Method显示文摘Graphene nanopore has been extensively employed in nanoscale sensing devices due to its outstanding properties.The understanding of its mechanical properties at nanoscale is crucial for sensing improvement.In this work,the mechanical proper ties of graphene nanopore are t hus investigated using the atomistic finite element met hod.Four graphene models with different pore shapes(circle(CR),horizontal rec tangle(RH),vertical rec tangle(RV)and square(SQ))in sub-5nm size,which could be successfully fabricated experimentally,have been studied here.The force normal to a pore rim is applied to mimic the impact force due to a fluid flow.As expected,the strength of nanoholed graphene is pore size dependent.Increasing pore size results in the reduction in its str ength.Comparing bet ween different pore shapes with comparable sizes,the order of pore st rength is CR>RH>RV>SQ.In addition,two different corner st rue tu res(V-like or zigzag and C-like or armchair corners)are observed,where the V-like st rue ture causes higher tensile stress.Besides,we find that the highest tensile stress is produced at the corner in all cases.This finding suggests the corners as an origin of pore fracture.The results of RH and RV highlight the impact of a direction of pore orientation on mechanical properties.Aligning a long side of a pore along the zigzag direction gains more tensile stress,while aligning on an armchair side causes a deflection.Not only the pore geometry and size,but also the pore orientation is crucial for defining the mechanical properties of nanopores. | Prapasiri Pongprayoon Attaphon Chaimanatsakun | 2019 | Acta Mechanica Solida Sinica2019，32，1： | 0 |
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