Surrounding rocks at different locations are generally subjected to different stress paths during the process of deep hard rock excavation.In this study,to reveal the mechanical parameters of deep surrounding rock und...Surrounding rocks at different locations are generally subjected to different stress paths during the process of deep hard rock excavation.In this study,to reveal the mechanical parameters of deep surrounding rock under different stress paths,a new cyclic loading and unloading test method for controlled true triaxial loading and unloading and principal stress direction interchange was proposed,and the evolution of mechanical parameters of Shuangjiangkou granite under different stress paths was studied,including the deformation modulus,elastic deformation increment ratios,fracture degree,cohesion and internal friction angle.Additionally,stress path coefficient was defined to characterize different stress paths,and the functional relationships among the stress path coefficient,rock fracture degree difference coefficient,cohesion and internal friction angle were obtained.The results show that during the true triaxial cyclic loading and unloading process,the deformation modulus and cohesion gradually decrease,while the internal friction angle gradually increases with increasing equivalent crack strain.The stress path coefficient is exponentially related to the rock fracture degree difference coefficient.As the stress path coefficient increases,the degrees of cohesion weakening and internal friction angle strengthening decrease linearly.During cyclic loading and unloading under true triaxial principal stress direction interchange,the direction of crack development changes,and the deformation modulus increases,while the cohesion and internal friction angle decrease slightly,indicating that the principal stress direction interchange has a strengthening effect on the surrounding rocks.Finally,the influences of the principal stress interchange direction on the stabilities of deep engineering excavation projects are discussed.展开更多
The lack of understanding of plastic hardening(softening)laws,especially under anisotropic stress conditions,results in inappropriate geotechnical management.Most of the yielding envelopes do not consider the effect o...The lack of understanding of plastic hardening(softening)laws,especially under anisotropic stress conditions,results in inappropriate geotechnical management.Most of the yielding envelopes do not consider the effect of intermediate principal stress and the influence of Lode's angle.In addition,the application of plastic flow rules regarding yielding surfaces compromises the softening of rock internal friction as well as the influence of Lode's angle on the plastic potential.Moreover,the ductility to brittleness transition in the intermediate principal stress direction still requires a theoretical foundation.In this study,based on poly-axial testing results of Yunnan sandstone,we adopted a failure criterion with the intermediate principal stress proposed by Menétrey and Willam.The proposed new failure envelope was applied to capture the plastic evolution of rock samples.A plastic hardening-softening model is constructed,based on the framework of the plastic theory.The softening envelope is modified to better present the stress drop and considers the deterioration of rock internal friction in the post-peak stage of poly-axial loading.The differential of plastic potential according to the principal stresses is also modified,considering the rotation of Lode's angle in the poly-axial loading tests.The model results were compared with laboratory testing results,which showed great consistency across 9 different loading tests(5 under triaxial stress and 4 under poly-axial stress with 22 stress-strain curves in total).The induced brittleness by the intermediate principal stress is also well captured by the proposed model.展开更多
To analyze and predict the mechanical behaviors of deep hard rocks,some key issues concerning rock fracturing mechanics for deep hard rock excavations are discussed.First,a series of apparatuses and methods have been ...To analyze and predict the mechanical behaviors of deep hard rocks,some key issues concerning rock fracturing mechanics for deep hard rock excavations are discussed.First,a series of apparatuses and methods have been developed to test the mechanical properties and fracturing behaviors of hard rocks under high true triaxial stress paths.Evolution mechanisms of stress-induced disasters in deep hard rock excavations,such as spalling,deep cracking,massive roof collapse,large deformation and rockbursts,have been recognized.The analytical theory for the fracturing process of hard rock masses,including the three-dimensional failure criterion,stress-induced mechanical model,fracturing degree index,energy release index and numerical method,has been established.The cracking-restraint method is developed for mitigating or controlling rock spalling,deep cracking and massive collapse of deep hard rocks.An energy-controlled method is also proposed for the prevention of rockbursts.Finally,two typical cases are used to illustrate the application of the proposed methodology in the Baihetan caverns and Bayu tunnels of China.展开更多
With the rapid social and economic development of the Tibet Autonomous Region,the situation in regard to energy supply and demand is increasingly tense.Meanwhile,the development of renewable energy in Tibet has been g...With the rapid social and economic development of the Tibet Autonomous Region,the situation in regard to energy supply and demand is increasingly tense.Meanwhile,the development of renewable energy in Tibet has been given considerable practical significance by its peculiar ecological environment.Given the complementarity of renewable energies in Tibet,using the method of factor analysis,we derived four major factors:level of economic development,social development,industrial development,and energy endowment,which help to evaluate development conditions in different regions of Tibet.Treating these four factors equally,we used the hierarchical clustering method to determine the order of regional development.Thus we acquire a three-stage planning project for renewable energy.In the first stage,Lhasa plays a leading role in promoting the development of renewable energy,particularly that based on solar and wind energy.There are two phases in the second stage,the first being to simultaneously develop solar and wind energy in Xigaze and Nyingchi.The second is to develop solar and wind energy in accordance with the time of year in Qamdo,Nagqu,and Ali,with 1.145billion kWh electricity to be generated.The third stage is to develop energy production in Lhoka Prefecture,with 1.369billion kWh electricity to be generated.At the end of the three-stage project,consumption of available electricity will have reached 4.045 billion kwh,with major social and economic benefits.展开更多
Solar interface water evaporation has been demonstrated to be an advanced method for freshwater production with high solar energy utilization.The development of evaporators with lower cost and higher efficiency is a k...Solar interface water evaporation has been demonstrated to be an advanced method for freshwater production with high solar energy utilization.The development of evaporators with lower cost and higher efficiency is a key challenge in the manufacture of practical solar interface water evaporation devices.Herein,a bamboo leaf-derived carbon-based evaporator is designed based on the light trace simulation.And then,it is manufactured by vertical arrangement and carbonization of bamboo leaves and subsequent polyacrylamide modification.The vertically arranged carbon structure can extend the light path and increase the light-absorbing area,thus achieving excellent light absorption.Furthermore,the continuous distribution of polyacrylamide hydrogel between these vertical carbons can support high-speed water delivery and shorten the evaporation path.Therefore,this evaporator exhibits an ultrahigh average light absorption rate of~96.1%,a good water evaporation rate of 1.75 kg m^(-2) h^(-1),and an excellent solar-to-vapor efficiency of 91.9%under one sun irradiation.Furthermore,the device based on this evaporator can effectively achieve seawater desalination,heavy metal ion removal,and dye separation while completing water evaporation.And this device is highly available for actual outdoor applications and repeated recycling.展开更多
Zinc phenylphosphonate(PPZn), a benign and biocompatible nucleating agent, was prepared and incorporated into the biodegradable poly(ethylene adipate)(PEA) to investigate its effect on the crystallization behavior, cr...Zinc phenylphosphonate(PPZn), a benign and biocompatible nucleating agent, was prepared and incorporated into the biodegradable poly(ethylene adipate)(PEA) to investigate its effect on the crystallization behavior, crystallization kinetics and spherulite morphology of PEA.Upon addition of PPZn, the crystallization temperature and crystallinity of PEA in the non-isothermal crystallization process increased significantly.Analysis of crystallization kinetics by Avrami equation suggests that the crystallization time shortened greatly and crystallization rate increased markedly after addition of PPZn.In the presence of PPZn, the spherulite size decreased and spherulite density increased significantly.It suggests that PPZn is an efficient nucleating agent for the crystallization of PEA.The accelerated crystallization in the presence of PPZn is mainly attributed to the epitaxial nucleation of PEA crystals on the surface of PPZn crystals, that is, a perfect lattice matching between PEA crystal and PPZn crystal occurs.展开更多
Acute pancreatitis(AP)is a complicated disease with rising incidence over the years.Twenty percent of AP will develop into acute necrotizing pancreatitis(ANP).Interventions for ANP have evolved from traditional open s...Acute pancreatitis(AP)is a complicated disease with rising incidence over the years.Twenty percent of AP will develop into acute necrotizing pancreatitis(ANP).Interventions for ANP have evolved from traditional open surgery to minimally invasive step-up approaches.Infected pancreatic necrosis(IPN)is the most serious event of ANP and associated with extremely poor prognosis.The contrast-enhanced computed tomography(CECT)-based classification of IPN describes various types of IPN and will help to carry out surgical interventions for each subtype.Nevertheless,many challenges are still remaining during the treatment of ANP.Including the balance between endoscopic and surgical approaches,and the selection of optimal timing of surgical intervention for infected necrosis.In nowadays treatment scenario of ANP,the necessity for open surgery remains to be debated.Despite of the development of advanced interventional techniques,postoperative residual infection(PRI)remains thorny,and effective prevention and treatment of PRI is of significance.展开更多
Acute pancreatitis(AP)is a complicated disease with rising incidence over the years.20%of AP will develop into acute necrotizing pancreatitis(ANP).Interventions for ANP have evolved from traditional open surgery to mi...Acute pancreatitis(AP)is a complicated disease with rising incidence over the years.20%of AP will develop into acute necrotizing pancreatitis(ANP).Interventions for ANP have evolved from traditional open surgery to minimally invasive step-up approaches.Infected pancreatic necrosis(IPN)is the most serious event of ANP and associated with extremely poor prognosis.The CT-based classification of IPN describes various types of IPN and will help to carry out surgical interventions for each subtype.Nevertheless,many challenges are still remaining during the treatment of ANP.Including the balance between endoscopic and surgical approaches,and the selection of optimal timing of surgical intervention for infected necrosis.In nowadays treatment scenario of ANP,the necessity for open surgery remains to be debated.Despite of the development of advanced interventional techniques,postoperative residual infection(PRI)remains thorny,and effective prevention and treatment of PRI is of significance.展开更多
基金the financial support from the National Natural Science Foundation of China(Grant Nos.51839003 and 42207221).
文摘Surrounding rocks at different locations are generally subjected to different stress paths during the process of deep hard rock excavation.In this study,to reveal the mechanical parameters of deep surrounding rock under different stress paths,a new cyclic loading and unloading test method for controlled true triaxial loading and unloading and principal stress direction interchange was proposed,and the evolution of mechanical parameters of Shuangjiangkou granite under different stress paths was studied,including the deformation modulus,elastic deformation increment ratios,fracture degree,cohesion and internal friction angle.Additionally,stress path coefficient was defined to characterize different stress paths,and the functional relationships among the stress path coefficient,rock fracture degree difference coefficient,cohesion and internal friction angle were obtained.The results show that during the true triaxial cyclic loading and unloading process,the deformation modulus and cohesion gradually decrease,while the internal friction angle gradually increases with increasing equivalent crack strain.The stress path coefficient is exponentially related to the rock fracture degree difference coefficient.As the stress path coefficient increases,the degrees of cohesion weakening and internal friction angle strengthening decrease linearly.During cyclic loading and unloading under true triaxial principal stress direction interchange,the direction of crack development changes,and the deformation modulus increases,while the cohesion and internal friction angle decrease slightly,indicating that the principal stress direction interchange has a strengthening effect on the surrounding rocks.Finally,the influences of the principal stress interchange direction on the stabilities of deep engineering excavation projects are discussed.
基金the research grant supported by the State Key Laboratory Cultivation Base for Gas Geology and Gas Control(Henan Polytechnic University,China)(No.WS2020A01)。
文摘The lack of understanding of plastic hardening(softening)laws,especially under anisotropic stress conditions,results in inappropriate geotechnical management.Most of the yielding envelopes do not consider the effect of intermediate principal stress and the influence of Lode's angle.In addition,the application of plastic flow rules regarding yielding surfaces compromises the softening of rock internal friction as well as the influence of Lode's angle on the plastic potential.Moreover,the ductility to brittleness transition in the intermediate principal stress direction still requires a theoretical foundation.In this study,based on poly-axial testing results of Yunnan sandstone,we adopted a failure criterion with the intermediate principal stress proposed by Menétrey and Willam.The proposed new failure envelope was applied to capture the plastic evolution of rock samples.A plastic hardening-softening model is constructed,based on the framework of the plastic theory.The softening envelope is modified to better present the stress drop and considers the deterioration of rock internal friction in the post-peak stage of poly-axial loading.The differential of plastic potential according to the principal stresses is also modified,considering the rotation of Lode's angle in the poly-axial loading tests.The model results were compared with laboratory testing results,which showed great consistency across 9 different loading tests(5 under triaxial stress and 4 under poly-axial stress with 22 stress-strain curves in total).The induced brittleness by the intermediate principal stress is also well captured by the proposed model.
基金financial support from the National Natural Science Foundation of China(Grant Nos.51839003 and 41827806)Liaoning Revitalization Talents Program of China(Grant No.XLYCYSZX1902)。
文摘To analyze and predict the mechanical behaviors of deep hard rocks,some key issues concerning rock fracturing mechanics for deep hard rock excavations are discussed.First,a series of apparatuses and methods have been developed to test the mechanical properties and fracturing behaviors of hard rocks under high true triaxial stress paths.Evolution mechanisms of stress-induced disasters in deep hard rock excavations,such as spalling,deep cracking,massive roof collapse,large deformation and rockbursts,have been recognized.The analytical theory for the fracturing process of hard rock masses,including the three-dimensional failure criterion,stress-induced mechanical model,fracturing degree index,energy release index and numerical method,has been established.The cracking-restraint method is developed for mitigating or controlling rock spalling,deep cracking and massive collapse of deep hard rocks.An energy-controlled method is also proposed for the prevention of rockbursts.Finally,two typical cases are used to illustrate the application of the proposed methodology in the Baihetan caverns and Bayu tunnels of China.
基金supported by geological survey project Foundation item:"A strategic research on important mineralresources in Tibet",from the China Geological Survey Bureau[grant number[2011]03-02-55]
文摘With the rapid social and economic development of the Tibet Autonomous Region,the situation in regard to energy supply and demand is increasingly tense.Meanwhile,the development of renewable energy in Tibet has been given considerable practical significance by its peculiar ecological environment.Given the complementarity of renewable energies in Tibet,using the method of factor analysis,we derived four major factors:level of economic development,social development,industrial development,and energy endowment,which help to evaluate development conditions in different regions of Tibet.Treating these four factors equally,we used the hierarchical clustering method to determine the order of regional development.Thus we acquire a three-stage planning project for renewable energy.In the first stage,Lhasa plays a leading role in promoting the development of renewable energy,particularly that based on solar and wind energy.There are two phases in the second stage,the first being to simultaneously develop solar and wind energy in Xigaze and Nyingchi.The second is to develop solar and wind energy in accordance with the time of year in Qamdo,Nagqu,and Ali,with 1.145billion kWh electricity to be generated.The third stage is to develop energy production in Lhoka Prefecture,with 1.369billion kWh electricity to be generated.At the end of the three-stage project,consumption of available electricity will have reached 4.045 billion kwh,with major social and economic benefits.
基金supports from Zhejiang Provincial Key Research and Development Project(2019C02037)the Fundamental Research Funds for the Provincial Universities of Zhejiang(2020YQ005)+3 种基金Zhejiang Provincial Natural Science Foundation of China(LY20E020004)National Natural Science Foundation of China(31870548)Research Foundation of Talented Scholars of Zhejiang A&F University(2020FR069)151 Talent Project of Zhejiang Province.
文摘Solar interface water evaporation has been demonstrated to be an advanced method for freshwater production with high solar energy utilization.The development of evaporators with lower cost and higher efficiency is a key challenge in the manufacture of practical solar interface water evaporation devices.Herein,a bamboo leaf-derived carbon-based evaporator is designed based on the light trace simulation.And then,it is manufactured by vertical arrangement and carbonization of bamboo leaves and subsequent polyacrylamide modification.The vertically arranged carbon structure can extend the light path and increase the light-absorbing area,thus achieving excellent light absorption.Furthermore,the continuous distribution of polyacrylamide hydrogel between these vertical carbons can support high-speed water delivery and shorten the evaporation path.Therefore,this evaporator exhibits an ultrahigh average light absorption rate of~96.1%,a good water evaporation rate of 1.75 kg m^(-2) h^(-1),and an excellent solar-to-vapor efficiency of 91.9%under one sun irradiation.Furthermore,the device based on this evaporator can effectively achieve seawater desalination,heavy metal ion removal,and dye separation while completing water evaporation.And this device is highly available for actual outdoor applications and repeated recycling.
基金financially supported by the National Natural Science Foundation of China(No.21304070)Natural Science Foundation of Tianjin City(No.15JCYBJC47300)+1 种基金Major Program of National Natural Science Foundation of China(No.11432016)the Municipal Key Program of Natural Science Foundation of Tianjin(No.14JCZDJC40700)
文摘Zinc phenylphosphonate(PPZn), a benign and biocompatible nucleating agent, was prepared and incorporated into the biodegradable poly(ethylene adipate)(PEA) to investigate its effect on the crystallization behavior, crystallization kinetics and spherulite morphology of PEA.Upon addition of PPZn, the crystallization temperature and crystallinity of PEA in the non-isothermal crystallization process increased significantly.Analysis of crystallization kinetics by Avrami equation suggests that the crystallization time shortened greatly and crystallization rate increased markedly after addition of PPZn.In the presence of PPZn, the spherulite size decreased and spherulite density increased significantly.It suggests that PPZn is an efficient nucleating agent for the crystallization of PEA.The accelerated crystallization in the presence of PPZn is mainly attributed to the epitaxial nucleation of PEA crystals on the surface of PPZn crystals, that is, a perfect lattice matching between PEA crystal and PPZn crystal occurs.
基金National Natural Science Foundation of China(82270665,81871974,82070658)Natural Science Foundation of Heilongjiang Province(TD2021H001)
文摘Acute pancreatitis(AP)is a complicated disease with rising incidence over the years.Twenty percent of AP will develop into acute necrotizing pancreatitis(ANP).Interventions for ANP have evolved from traditional open surgery to minimally invasive step-up approaches.Infected pancreatic necrosis(IPN)is the most serious event of ANP and associated with extremely poor prognosis.The contrast-enhanced computed tomography(CECT)-based classification of IPN describes various types of IPN and will help to carry out surgical interventions for each subtype.Nevertheless,many challenges are still remaining during the treatment of ANP.Including the balance between endoscopic and surgical approaches,and the selection of optimal timing of surgical intervention for infected necrosis.In nowadays treatment scenario of ANP,the necessity for open surgery remains to be debated.Despite of the development of advanced interventional techniques,postoperative residual infection(PRI)remains thorny,and effective prevention and treatment of PRI is of significance.
基金This work was supported by the National Natural Science Foundation of China(82270665,81871974,82070658)the Natural Science Foundation of Heilongjiang Province(TD2021H001).
文摘Acute pancreatitis(AP)is a complicated disease with rising incidence over the years.20%of AP will develop into acute necrotizing pancreatitis(ANP).Interventions for ANP have evolved from traditional open surgery to minimally invasive step-up approaches.Infected pancreatic necrosis(IPN)is the most serious event of ANP and associated with extremely poor prognosis.The CT-based classification of IPN describes various types of IPN and will help to carry out surgical interventions for each subtype.Nevertheless,many challenges are still remaining during the treatment of ANP.Including the balance between endoscopic and surgical approaches,and the selection of optimal timing of surgical intervention for infected necrosis.In nowadays treatment scenario of ANP,the necessity for open surgery remains to be debated.Despite of the development of advanced interventional techniques,postoperative residual infection(PRI)remains thorny,and effective prevention and treatment of PRI is of significance.
