Study On The Mechanism Of Parallel Helical Sensing Cable Used For Deformation Distributed Measurement

Monitoring and timely warning of geological disasters has been an important part of the national geological disaster prevention.Surface and underground displacement are important physical quantities for geological hazard monitoring.The parallel helical sensing cable is a sensor cable used to measure the displacement of tensile deformation.It can be used to realize distributed measurement of soil deformation displacement.In order to improve the mechanism of the parallel helical sensing cable deformation measurement,this subject carried out analysis from two aspects of theory and simulation,designed a distributed measurement system of deformation,verified the theoretical content,and laid a good foundation for practical application,and the specific research contents are as follows:(1)The main technical methods of ground deformation monitoring at home and abroad were discussed,and the characteristics of various technical methods were compared and analyzed.The parallel helical sensing cable has great advantages in the field of distributed deformation measurement because of its large capacity of stretching.(2)The mechanism of deformation measurement based on parallel helical sensing cable was described comprehensively.The characteristic impedance of parallel helical sensing cable will change after stretching.By combining with the time domain reflection technology,the location and size of the parallel helical sensing cable characteristic impedance change can be measured,and the distributed deformation displacement measurement can be realized.(3)The distributed capacitance,the distributed inductance and the characteristic impedance formula of the parallel helical sensing cable was derived.According to the Gauss theorem,it was found that the capacitance gradually decreases with the expansion of the parallel helical sensing cable.According to Biot Savart law analysis,it was found that the inductance increases with the expansion of the transmission line,and the characteristic impedance increases with the expansion of the parallel helical sensing cable.(4)The change of inductance and capacitance during the stretching process of the parallel helical sensing cable was simulated.The parallel helical sensing cable was simulated by Maxwell software,and the simulation results and the electromagnetic field distribution map were analyzed in detail.It was found that the simulation results was basically consistent with the theoretical results.(5)The whole measurement platform was optimized and supplemented.The semi automatic production of the parallel helical sensing cable was realized,the motor drive control of the stretching platform was added,and the host computer software of the whole system was developed.(6)The experimental analysis and analysis of variance were carried out for the distributed measurement of the transmission line.The accuracy of multiple point positioning measurement can reach 0.2 level,and the measurement error of multiple point tensile deformation is less than 3mm.Temperature has a significant effect on measurement,so temperature calibration was added,and humidity has no significant effect on measurement.The research of the theoretical analysis and the experimental results were closely connected,further clarified the mechanism of deformation of parallel helical sensing cable,deduced the characteristic impedance formula of parallel helical sensing cable,analyzed the process of the change of impedance,and provided a powerful theoretical basis for the application of parallel helical sensing cable in distributed tensile deformation measurement.But the accuracy of parallel helical sensing cable can be further improved,the prediction model can be further optimized.