Considering the delay effect of initial lining and revising the Winkler elastic foundation model,an analytical approach based on Pasternak elastic foundation beam theory for pipe roof reinforcement was put forward. Wi...Considering the delay effect of initial lining and revising the Winkler elastic foundation model,an analytical approach based on Pasternak elastic foundation beam theory for pipe roof reinforcement was put forward. With the example of a certain tunnel excavation,the comparison of the values of longitudinal strain of reinforcing pipe between field monitoring and analytical approach was made. The results indicate that Pasternak model,which considers a more realistic hypothesis in the elastic soil than Winkler model,gives more accurate calculation and agrees better with the result of field monitoring. The difference of calculation results between these two models is about 7%,and Pasternak model is proved to be a better way to study the reinforcement mechanism and improve design practice. The calculation results also reveal that the reinforcing pipes act as levers,which increases longitudinal load transfer to an unexcavated area,and consequently decreases deformation and increases face stability.展开更多
The scheduling utility plays a fundamental role in addressing the commuting travel behaviours. A new scheduling utility,termed as DMRD-SU, was suggested based on some recent research findings in behavioural economics....The scheduling utility plays a fundamental role in addressing the commuting travel behaviours. A new scheduling utility,termed as DMRD-SU, was suggested based on some recent research findings in behavioural economics. DMRD-SU admitted the existence of positive arrival-caused utility. In addition, besides the travel-time-caused utility and arrival-caused utility, DMRD-SU firstly took the departure utility into account. The necessity of the departure utility in trip scheduling was analyzed comprehensively,and the corresponding individual trip scheduling model was presented. Based on a simple network, an analytical example was executed to characterize DMRD-SU. It can be found from the analytical example that: 1) DMRD-SU can predict the accumulation departure behaviors at NDT, which explains the formation of daily serious short-peak-hours in reality, while MRD-SU cannot; 2)Compared with MRD-SU, DMRD-SU predicts that people tend to depart later and its gross utility also decreases faster. Therefore,the departure utility should be considered to describe the traveler's scheduling behaviors better.展开更多
A unified constitutive model is proposed to describe the mechanical behavior of weak sandstone at different time scales.The instantaneous behavior of this material is characterized by the Drucker-Prager elastoplastic ...A unified constitutive model is proposed to describe the mechanical behavior of weak sandstone at different time scales.The instantaneous behavior of this material is characterized by the Drucker-Prager elastoplastic model,while the time-dependent deformation is described in terms of the microstructure evolution.This evolution is numerically simulated by progressive degradation of the elastic modulus and failure strength of the material.The proposed model is used to simulate the instantaneous triaxial compression and the multi-loading creep tests.Generally,good concordance is obtained between numerical simulations and experimental data.The proposed model is capable of describing the main features of these rocks,particularly irreversible deformations,pressure dependency,volumetric transition between compaction and dilatancy,and creep behavior.展开更多
The original descriptive model of shear stress and shear displacement only reflects the stress deformation characteristics of plastic structural plane.The index model was revised and piecewise index model was built to...The original descriptive model of shear stress and shear displacement only reflects the stress deformation characteristics of plastic structural plane.The index model was revised and piecewise index model was built to describe the stress deformation characteristics of plastic structural plane and brittle structural plane.The relation of stress and strain to the failure mode of structural plane considering the effect of its shape was investigated,and a model which could reflect the relation between undulate angle and shear strength was built.The result indicates that structural plane presents nonlinear characteristics,specifically,the value of undulate angle,as well as corresponding shear strength,becomes larger as the normal stress decreases.展开更多
基金Project(IRT0518) supported by the Program of Innovative Research Team of Ministry of Education of China
文摘Considering the delay effect of initial lining and revising the Winkler elastic foundation model,an analytical approach based on Pasternak elastic foundation beam theory for pipe roof reinforcement was put forward. With the example of a certain tunnel excavation,the comparison of the values of longitudinal strain of reinforcing pipe between field monitoring and analytical approach was made. The results indicate that Pasternak model,which considers a more realistic hypothesis in the elastic soil than Winkler model,gives more accurate calculation and agrees better with the result of field monitoring. The difference of calculation results between these two models is about 7%,and Pasternak model is proved to be a better way to study the reinforcement mechanism and improve design practice. The calculation results also reveal that the reinforcing pipes act as levers,which increases longitudinal load transfer to an unexcavated area,and consequently decreases deformation and increases face stability.
基金Projects(71131001,71271023,71471014)supported by National Natural Science Foundation of ChinaProject(2012CB725403)supported by National Basic Research Program of ChinaProject(2011AA110303)supported by National High Technology Research and Development Program of China
文摘The scheduling utility plays a fundamental role in addressing the commuting travel behaviours. A new scheduling utility,termed as DMRD-SU, was suggested based on some recent research findings in behavioural economics. DMRD-SU admitted the existence of positive arrival-caused utility. In addition, besides the travel-time-caused utility and arrival-caused utility, DMRD-SU firstly took the departure utility into account. The necessity of the departure utility in trip scheduling was analyzed comprehensively,and the corresponding individual trip scheduling model was presented. Based on a simple network, an analytical example was executed to characterize DMRD-SU. It can be found from the analytical example that: 1) DMRD-SU can predict the accumulation departure behaviors at NDT, which explains the formation of daily serious short-peak-hours in reality, while MRD-SU cannot; 2)Compared with MRD-SU, DMRD-SU predicts that people tend to depart later and its gross utility also decreases faster. Therefore,the departure utility should be considered to describe the traveler's scheduling behaviors better.
基金Project(51409261)supported by the National Natural Science Foundation of ChinaProjects(ZR2014EEQ014)supported by the Natural Science Foundation of Shandong Province,ChinaProjects(16CX05002A,15CX05039A)supported by the Fundamental Research Funds for the Central Universities of China
文摘A unified constitutive model is proposed to describe the mechanical behavior of weak sandstone at different time scales.The instantaneous behavior of this material is characterized by the Drucker-Prager elastoplastic model,while the time-dependent deformation is described in terms of the microstructure evolution.This evolution is numerically simulated by progressive degradation of the elastic modulus and failure strength of the material.The proposed model is used to simulate the instantaneous triaxial compression and the multi-loading creep tests.Generally,good concordance is obtained between numerical simulations and experimental data.The proposed model is capable of describing the main features of these rocks,particularly irreversible deformations,pressure dependency,volumetric transition between compaction and dilatancy,and creep behavior.
基金Project(50878212) supported by National Natural Science Foundation of ChinaProject(1298011-2) supported by the Funding of Scientific Research and Technology Development Projects of Guangxi Province,China+2 种基金Project(12JJ6052) supported by Natural Science Foundation of Hunan Province,ChinaProject(kfj120402) supported Open Fund of Key Laboratory of Special Environment Road Engineering of Hunan Province(Changsha University of Science&Technology),ChinaProject(13C1010) supported by the Research Foundation of Education Bureau of Hunan Province,China
文摘The original descriptive model of shear stress and shear displacement only reflects the stress deformation characteristics of plastic structural plane.The index model was revised and piecewise index model was built to describe the stress deformation characteristics of plastic structural plane and brittle structural plane.The relation of stress and strain to the failure mode of structural plane considering the effect of its shape was investigated,and a model which could reflect the relation between undulate angle and shear strength was built.The result indicates that structural plane presents nonlinear characteristics,specifically,the value of undulate angle,as well as corresponding shear strength,becomes larger as the normal stress decreases.
