Many tunnels all over the world have been in service for several decades,which require effective inspection methods to assess their health conditions.Microtremor,as a type of ambient vibration originating from natural...Many tunnels all over the world have been in service for several decades,which require effective inspection methods to assess their health conditions.Microtremor,as a type of ambient vibration originating from natural or artificial oscillations without specific sources,has attracted more and more attentions in the recent study of the microtremor dynamic properties of concrete structures.In this study,the microtremors of the tunnel lining were simulated numerically based on the Distinct Element Method(DEM).The Power Spectra Density(PSD)of signals obtained from numerical simulations were calculated and the nature frequencies were identified using the peak-picking method.The influences of the rock-concrete joint,the rock type and the concrete type on the nature frequencies were also evaluated.The results of a comprehensive numerical analysis show that the nature frequencies lower than 100 Hz can be identified.As the bonding condition becomes worse,the nature frequencies decrease.The nature frequencies change proportionally with the normal stiffness of the rock-concrete joint.As the concrete grade decreases,the third mode of frequency also decreases gradually while the variation of the first two modes of frequencies can hardly be identified.Additionally,the field microtremor measurements of tunnel lining were also carried out to verify the numerical results.展开更多
The construction of modern livable cities faces challenges in karst areas,including ground collapse and engineering problems.Wuhan,with a population of 13.74×10^(6) and approximately 1161 km^(2)of soluble rocks i...The construction of modern livable cities faces challenges in karst areas,including ground collapse and engineering problems.Wuhan,with a population of 13.74×10^(6) and approximately 1161 km^(2)of soluble rocks in the urban area of 8569.15 km^(2),predominantly consists of concealed karst areas where occasional ground collapse events occur,posing significant threats to underground engineering projects.To address these challenges,a comprehensive geological survey was conducted in Wuhan,focusing on major karstrelated issues.Geophysical methods offer advantages over drilling in detecting concealed karst areas due to their efficiency,non-destructiveness,and flexibility.This paper reviewed the karst geological characteristics in Wuhan and the geophysical exploration methods for karst,selected eight effective geophysical methods for field experimentation,evaluated their suitability,and proposed method combinations for different karst scenarios.The results show that different geophysical methods have varying applicability for karst detection in Wuhan,and combining multiple methods enhances detection effectiveness.The specific recommendations for method combinations provided in this study serve as a valuable reference for karst detection in Wuhan.展开更多
基金Development of this study is supported by the Civil Engineering Division,Nagasaki Prefectural Government.
文摘Many tunnels all over the world have been in service for several decades,which require effective inspection methods to assess their health conditions.Microtremor,as a type of ambient vibration originating from natural or artificial oscillations without specific sources,has attracted more and more attentions in the recent study of the microtremor dynamic properties of concrete structures.In this study,the microtremors of the tunnel lining were simulated numerically based on the Distinct Element Method(DEM).The Power Spectra Density(PSD)of signals obtained from numerical simulations were calculated and the nature frequencies were identified using the peak-picking method.The influences of the rock-concrete joint,the rock type and the concrete type on the nature frequencies were also evaluated.The results of a comprehensive numerical analysis show that the nature frequencies lower than 100 Hz can be identified.As the bonding condition becomes worse,the nature frequencies decrease.The nature frequencies change proportionally with the normal stiffness of the rock-concrete joint.As the concrete grade decreases,the third mode of frequency also decreases gradually while the variation of the first two modes of frequencies can hardly be identified.Additionally,the field microtremor measurements of tunnel lining were also carried out to verify the numerical results.
基金jointly supported by the project of Chinese National Natural Science Foundation(42107485)National Key R&D Program(2020YFC1512400,2018YFC800804)China Geological Survey(DD20190282,DD20221734,and DD20230323)。
文摘The construction of modern livable cities faces challenges in karst areas,including ground collapse and engineering problems.Wuhan,with a population of 13.74×10^(6) and approximately 1161 km^(2)of soluble rocks in the urban area of 8569.15 km^(2),predominantly consists of concealed karst areas where occasional ground collapse events occur,posing significant threats to underground engineering projects.To address these challenges,a comprehensive geological survey was conducted in Wuhan,focusing on major karstrelated issues.Geophysical methods offer advantages over drilling in detecting concealed karst areas due to their efficiency,non-destructiveness,and flexibility.This paper reviewed the karst geological characteristics in Wuhan and the geophysical exploration methods for karst,selected eight effective geophysical methods for field experimentation,evaluated their suitability,and proposed method combinations for different karst scenarios.The results show that different geophysical methods have varying applicability for karst detection in Wuhan,and combining multiple methods enhances detection effectiveness.The specific recommendations for method combinations provided in this study serve as a valuable reference for karst detection in Wuhan.
