Correctly locating the tunnel lining cavity is extremely important tunnel quality inspection.High-accuracy imaging results are hard to obtain because conventional one-way wave migration is greatly aff ected by lateral...Correctly locating the tunnel lining cavity is extremely important tunnel quality inspection.High-accuracy imaging results are hard to obtain because conventional one-way wave migration is greatly aff ected by lateral velocity change and inclination limitation and because the diff racted wave cannot be accurately returned to the real spatial position of the lining cavity.This paper presents a tunnel lining cavity imaging method based on the groundpenetrating radar(GPR)reverse-time migration(RTM)algorithm.The principle of GPR RTM is described in detail using the electromagnetic wave equation.The finite-difference timedomain method is employed to calculate the backward extrapolation electromagnetic fi elds,and the zero-time imaging condition based on the exploding-reflector concept is used to obtain the RTM results.On this basis,the GPR RTM program is compiled and applied to the simulated and observed GPR data of a typical tunnel lining cavity GPR model and a physical lining cavity model.Comparison of RTM and Kirchhoff migration results reveals that the RTM can better converge the diff racted waves of steel bar and cavity to their true position and have higher resolution and better suppress the eff ect of multiple interference and clutter scattering waves.In addition,comparison of RTM results of diff erent degrees of noise shows that RTM has strong anti-interference ability and can be used for the accurate interpretation of radar profi le in a strong interference environment.展开更多
Leakage at tunnel structural joints represents a critical vulnerability in tunnel waterproofing systems.The interaction between secondary lining cavity development and waterproofing system failure creates a vicious cy...Leakage at tunnel structural joints represents a critical vulnerability in tunnel waterproofing systems.The interaction between secondary lining cavity development and waterproofing system failure creates a vicious cycle that accelerates tunnel structural joint leakage instability risks.Forty physical model tests were conducted to investigate and quantify the impacts of cavity depth,dimension,and spatial distribution on joint leakage under varying hydraulic heads.The study employed a self-developed tunnel lining leakage defect simulation apparatus.Experimental investigation elucidates the coupled hydro-mechanical mechanisms governing seepage evolution and stress redistribution in defective lining structures.Key findings indicate that water pressure progressively accumulates at the lining with increasing hydraulic head height,while cavity zones maintain consistently lower pressure due to pressure relief effects.This pressure distribution causes the water pressure sharing ratioηto increase with higher head height,while gradually decreasing as cavity breakage becomes more severe.Cavity extent expansion demonstrates the most significant influence,decreasing vault earth pressure by 23.8%compared to 15.8%and 19.5%reductions from depth extension and spatial redistribution.Cavity depth expansion resulted in a 25.4%increase in the axial force at the vault,along with a 3-fold increase in the bending moment.Expansion of the cavity extent mainly led to a 40.3%increase in axial force and a 1.8-fold increase in bending moment.These findings provide quantitative insights for optimizing waterproofing design and developing targeted maintenance strategies for cavity-affected tunnel structures.展开更多
This is an expand of the complex function method in solving the problem of interaction of plane.SH-waves and non-circular cavity surfaced with linig in anisotropic media.the use the method similar to that incorporated...This is an expand of the complex function method in solving the problem of interaction of plane.SH-waves and non-circular cavity surfaced with linig in anisotropic media.the use the method similar to that incorporated in [2] added with Savin's method for solving stress concentration of non-circular cavity surfaced with lining in elasticity.Anisotropic media can be used ic simulate the conditions of thegeology.The solving proceeding for this problem can be processed conveniently in the manner similar to that introduced in [2].In this paper.as illustrated in example numerical studies have been done for a square cavity surfaced with lining in anisotropic media.展开更多
Er3+-Yb3+ co-doped fiber of 2 m long is used as the laser gain medium. Two fiber lasers with different structures have been set up, one is the line cavity fiber laser with the dielectric mirror being replaced by an al...Er3+-Yb3+ co-doped fiber of 2 m long is used as the laser gain medium. Two fiber lasers with different structures have been set up, one is the line cavity fiber laser with the dielectric mirror being replaced by an all-fiber reflecting mirror,the other is the ring cavity all-fiber laser. Both set-ups have achieved lasing operation at the wavelength of 1.53 μm. Pumped by the 1 064 nm light from all-solid-state Nd ∶YAG laser, the two fiber lasers at 1 530 nm are operational. Their output powers are 7.8 mW and 2 mW with 130 mW and 160 mW pump powers.展开更多
基金supported by the National Natural Science Foundation of China (Nos. 41764005, 41604039, 41604102, and 41574078)Guangxi Natural Science Foundation of China (Nos. 2016GXNSFBA380082 and 2016GXNSFBA380215)+2 种基金Guangxi Young and Middle-aged Teacher Basic Ability Improvement Project (No. KY2016YB199)Guangxi Collaborative Innovation Center for Exploration of Hidden Nonferrous Metal Deposits and Development of New Materials Project (No. GXYSXTZX2017-II-5)Guangxi Scholarship Fund of Guangxi Education Department。
文摘Correctly locating the tunnel lining cavity is extremely important tunnel quality inspection.High-accuracy imaging results are hard to obtain because conventional one-way wave migration is greatly aff ected by lateral velocity change and inclination limitation and because the diff racted wave cannot be accurately returned to the real spatial position of the lining cavity.This paper presents a tunnel lining cavity imaging method based on the groundpenetrating radar(GPR)reverse-time migration(RTM)algorithm.The principle of GPR RTM is described in detail using the electromagnetic wave equation.The finite-difference timedomain method is employed to calculate the backward extrapolation electromagnetic fi elds,and the zero-time imaging condition based on the exploding-reflector concept is used to obtain the RTM results.On this basis,the GPR RTM program is compiled and applied to the simulated and observed GPR data of a typical tunnel lining cavity GPR model and a physical lining cavity model.Comparison of RTM and Kirchhoff migration results reveals that the RTM can better converge the diff racted waves of steel bar and cavity to their true position and have higher resolution and better suppress the eff ect of multiple interference and clutter scattering waves.In addition,comparison of RTM results of diff erent degrees of noise shows that RTM has strong anti-interference ability and can be used for the accurate interpretation of radar profi le in a strong interference environment.
基金support provided by the National Natural Science Foundation of China(Grant Nos.52578454 and 52278383).
文摘Leakage at tunnel structural joints represents a critical vulnerability in tunnel waterproofing systems.The interaction between secondary lining cavity development and waterproofing system failure creates a vicious cycle that accelerates tunnel structural joint leakage instability risks.Forty physical model tests were conducted to investigate and quantify the impacts of cavity depth,dimension,and spatial distribution on joint leakage under varying hydraulic heads.The study employed a self-developed tunnel lining leakage defect simulation apparatus.Experimental investigation elucidates the coupled hydro-mechanical mechanisms governing seepage evolution and stress redistribution in defective lining structures.Key findings indicate that water pressure progressively accumulates at the lining with increasing hydraulic head height,while cavity zones maintain consistently lower pressure due to pressure relief effects.This pressure distribution causes the water pressure sharing ratioηto increase with higher head height,while gradually decreasing as cavity breakage becomes more severe.Cavity extent expansion demonstrates the most significant influence,decreasing vault earth pressure by 23.8%compared to 15.8%and 19.5%reductions from depth extension and spatial redistribution.Cavity depth expansion resulted in a 25.4%increase in the axial force at the vault,along with a 3-fold increase in the bending moment.Expansion of the cavity extent mainly led to a 40.3%increase in axial force and a 1.8-fold increase in bending moment.These findings provide quantitative insights for optimizing waterproofing design and developing targeted maintenance strategies for cavity-affected tunnel structures.
文摘This is an expand of the complex function method in solving the problem of interaction of plane.SH-waves and non-circular cavity surfaced with linig in anisotropic media.the use the method similar to that incorporated in [2] added with Savin's method for solving stress concentration of non-circular cavity surfaced with lining in elasticity.Anisotropic media can be used ic simulate the conditions of thegeology.The solving proceeding for this problem can be processed conveniently in the manner similar to that introduced in [2].In this paper.as illustrated in example numerical studies have been done for a square cavity surfaced with lining in anisotropic media.
文摘Er3+-Yb3+ co-doped fiber of 2 m long is used as the laser gain medium. Two fiber lasers with different structures have been set up, one is the line cavity fiber laser with the dielectric mirror being replaced by an all-fiber reflecting mirror,the other is the ring cavity all-fiber laser. Both set-ups have achieved lasing operation at the wavelength of 1.53 μm. Pumped by the 1 064 nm light from all-solid-state Nd ∶YAG laser, the two fiber lasers at 1 530 nm are operational. Their output powers are 7.8 mW and 2 mW with 130 mW and 160 mW pump powers.
