A new reflection approach for field distribution measurement of ultrasonic transducers was investigated. Instead of a point-like reflection target （rigid sphere） or thin wires （line-like targets）, a line response ...A new reflection approach for field distribution measurement of ultrasonic transducers was investigated. Instead of a point-like reflection target （rigid sphere） or thin wires （line-like targets）, a line response function of experimental knife-edge distribution combined with the inverse Abel transforms was used to estimate the lateral beam distributions of ultrasonic transducers. The measurement steps were as follows：① A knife-edge was scanned perpendicularly to acoustic beam axis of the transducer using an ultrasonic C-scan system to obtain its ultrasonic image line response function, ② the transverse beam distribution was solved by the inverse Abel transforms, and ③ experiments were performed to obtain the lateral beam profiles of two transducers, with and without focus, and the results were compared with those from a hydrophone. The results showed that this method was effective for ultrasonic field measurement and could be as a substitute for hydrophone in most cases.展开更多
Surface settlements caused by twin tunneling are a major interest in underground space engineering.Most prevailing studies have investigated the surface settlements observed over twin tunnels constructed in clay.Yet,l...Surface settlements caused by twin tunneling are a major interest in underground space engineering.Most prevailing studies have investigated the surface settlements observed over twin tunnels constructed in clay.Yet,less attention is given to the twin tunnels exca-vated in silty sand,which is the focus of this study.A comprehensive field monitoring scheme was designed in the Hangzhou metro line six project to measure the surface settlements during twin tunneling by adopting earth pressure balance shields.The influence of four shield operational parameters,namely,face pressure,tail grouting pressure,penetration rate,and pitching angle on the surface settle-ments due to twin tunneling are explored.In general,the total settlement profiles observed over twin tunnels follow an inverted bimodal shape.The post-settlement observed over the 1^(st)tunnel due to the 2^(nd)tunnel excavation is non-trivial when the twin tunnels are spaced closely.Low face pressure and tail grouting pressure can induce excessive peak surface settlements during twin tunneling in silty sand.展开更多
文摘A new reflection approach for field distribution measurement of ultrasonic transducers was investigated. Instead of a point-like reflection target （rigid sphere） or thin wires （line-like targets）, a line response function of experimental knife-edge distribution combined with the inverse Abel transforms was used to estimate the lateral beam distributions of ultrasonic transducers. The measurement steps were as follows：① A knife-edge was scanned perpendicularly to acoustic beam axis of the transducer using an ultrasonic C-scan system to obtain its ultrasonic image line response function, ② the transverse beam distribution was solved by the inverse Abel transforms, and ③ experiments were performed to obtain the lateral beam profiles of two transducers, with and without focus, and the results were compared with those from a hydrophone. The results showed that this method was effective for ultrasonic field measurement and could be as a substitute for hydrophone in most cases.
基金the financial support funded by The Science and Technology Development Fund,Macao SAR(File Nos.0057/2020/AGJ,SKLIOTSC-2021-2023)National Natural Science Foundation of China(Grant No.52022001)+2 种基金the University of Macao Research Fund(MYRG2018-00173-FST)Zhejiang Natural Science Foundation(LHZ20E080001)Zhejiang Province Key R&D Program Project(2020C01102).
文摘Surface settlements caused by twin tunneling are a major interest in underground space engineering.Most prevailing studies have investigated the surface settlements observed over twin tunnels constructed in clay.Yet,less attention is given to the twin tunnels exca-vated in silty sand,which is the focus of this study.A comprehensive field monitoring scheme was designed in the Hangzhou metro line six project to measure the surface settlements during twin tunneling by adopting earth pressure balance shields.The influence of four shield operational parameters,namely,face pressure,tail grouting pressure,penetration rate,and pitching angle on the surface settle-ments due to twin tunneling are explored.In general,the total settlement profiles observed over twin tunnels follow an inverted bimodal shape.The post-settlement observed over the 1^(st)tunnel due to the 2^(nd)tunnel excavation is non-trivial when the twin tunnels are spaced closely.Low face pressure and tail grouting pressure can induce excessive peak surface settlements during twin tunneling in silty sand.
