Based on strength reduction theory,the stability numbers of shallow tunnels were investigated within the framework of upper and lower bound theorems of limit analysis. Stability solutions taking into account of water ...Based on strength reduction theory,the stability numbers of shallow tunnels were investigated within the framework of upper and lower bound theorems of limit analysis. Stability solutions taking into account of water seepage were presented and compared with those without considering seepage. The comparisons indicate that the maximum difference does not exceed 3.7%,which proves the present method credible. The results show that stability numbers of shallow tunnels considering seepage are much less than those without considering seepage,and that the difference of stability numbers between considering seepage and without considering seepage increase with increasing the depth ratio. The stability numbers decrease with increasing permeability coefficient and groundwater depth. Seepage has significant effects on the stability numbers of shallow tunnels.展开更多
Here we present six key parameters that have been applied to evaluate the Silurian Longmaxi shale gas accumulations of southern Sichuan Province.These parameters include richness of organic matter,single layer shale t...Here we present six key parameters that have been applied to evaluate the Silurian Longmaxi shale gas accumulations of southern Sichuan Province.These parameters include richness of organic matter,single layer shale thickness,burial depth of the shale,maturity,shale properties,and brittle mineral content.In combination with drilling data,the lower limits of these six parameters for marine shale gas have been evaluated and the following conclusions are drawn:(1)Organic carbon recovery, gas content inversion,and production tests have been applied for the first time to measure the lower limit of TOC,which is determined to be 1.0%.(2)Based on the hydrocarbon generation and expulsion theory for source rocks and the characteristics of Longmaxi shale,the lower limit of the single-layer thickness is estimated to be 30 m,of which a thickness of at least 15 m should contain high-quality shale.(3)Based on the correlation of TOC and porosity,the lower limit of gas-filled porosity is 1.2%.(4)Other parameters,such as maturity,burial depth,and brittle mineral content have also been studied with regard to the geologic conditions of southern Sichuan.Based on the study results,an evaluation index system has been established for highly evolved marine shale gas,and the system has been applied successfully to geologically screened shale gas occurrences in southern Sichuan Province.展开更多
基金Project(200550) supported by the Foundation for the Author of National Excellent Doctoral Dissertation of ChinaProject(09JJ1008) supported by Hunan Provincial Natural Science Foundation of ChinaProject(200631878557) supported by West Traffic of Science and Technology of China
文摘Based on strength reduction theory,the stability numbers of shallow tunnels were investigated within the framework of upper and lower bound theorems of limit analysis. Stability solutions taking into account of water seepage were presented and compared with those without considering seepage. The comparisons indicate that the maximum difference does not exceed 3.7%,which proves the present method credible. The results show that stability numbers of shallow tunnels considering seepage are much less than those without considering seepage,and that the difference of stability numbers between considering seepage and without considering seepage increase with increasing the depth ratio. The stability numbers decrease with increasing permeability coefficient and groundwater depth. Seepage has significant effects on the stability numbers of shallow tunnels.
基金supported by National Science Foundation for Distinguished Young Scholars of China(Grant No.51125019)
文摘Here we present six key parameters that have been applied to evaluate the Silurian Longmaxi shale gas accumulations of southern Sichuan Province.These parameters include richness of organic matter,single layer shale thickness,burial depth of the shale,maturity,shale properties,and brittle mineral content.In combination with drilling data,the lower limits of these six parameters for marine shale gas have been evaluated and the following conclusions are drawn:(1)Organic carbon recovery, gas content inversion,and production tests have been applied for the first time to measure the lower limit of TOC,which is determined to be 1.0%.(2)Based on the hydrocarbon generation and expulsion theory for source rocks and the characteristics of Longmaxi shale,the lower limit of the single-layer thickness is estimated to be 30 m,of which a thickness of at least 15 m should contain high-quality shale.(3)Based on the correlation of TOC and porosity,the lower limit of gas-filled porosity is 1.2%.(4)Other parameters,such as maturity,burial depth,and brittle mineral content have also been studied with regard to the geologic conditions of southern Sichuan.Based on the study results,an evaluation index system has been established for highly evolved marine shale gas,and the system has been applied successfully to geologically screened shale gas occurrences in southern Sichuan Province.
