Study Of Tunneling Internal Damage Rapid Detection Methods Based On PLC System Control Of TEM Instrument

It is well known that the construction of high speed railways in our country has made great progress for the past few years.The travelling train has increased its speed for six times,and up to 250 kilometers per hour.And considering the increasing numbers of high speed railway tunnels has been officially put into operation,there will be inevitable internal damages in the operating tunnels.Within those internal damages,the karst caves and cavities behind lining is especially prominent,which not only affects the stability of the tunnel structure,and even still dramatically put the running train in danger.However,the traditional low efficiency detecting way for the cavities is mostly depending on percussion method manually operated by maintainers,which is mainly conditioned by the experience level of the personnel and short of systematic and scientific detecting way to tunnel damages,and endanger the physical safety for those maintainers even worse.Aiming at this issue,the thesis designs to utilize Time Domain Electromagnetic Method(TEM)to detect the exist of cavities behind the lining by sensing the changes in secondary field strength and validate its feasibility.Furthermore,in purpose of realizing rapid detecting for accomplishing the detection of tunneling internal damage within the finite maintaining sky-light time more efficiently,the thesis predesigns an automatic TEM instrument detecting system based on Programmable Logic Controller(PLC)system,aiming to replace the traditional working mode in keyboard-type instruments.And this thesis achieves PLC system automatically operates TEM instrument by programming ladder diagram to start/stop the transmitter and receiver.The main research accomplishments of thesis as following:1.Simulates exciting field source activates Smoke Ring effect under the half-space environment and Water Wave effect under the full-space environment on electromagne-tism and compared with theory resolution to verify and ensure the reasonableness and effectiveness of this modeling.2.Makes use of finite element software ANSYS to build up three-dimension solid model,simulates the spread and attenuation law of transient electromagnetic field near the anomalous bodies in different time delay moments in the real tunnel-space environment when exciting field source activates step current pulse.3.Predesigns an automatic TEM instrument detecting system based on PLC system from both hardware and software aspect.In terms of hardware,the thesis selects meet-functionally TEM instrument transmitter and receiver and appropriate PLC model serving as the control center of this automatic detecting system.And as the software,chooses the suited programming software,system programming language and instruction set along with analyzing and comparing their relative merits.4.Predesigns the basic ladder diagram code and download into lower computer(PLC control system)to control the operation of transmitter and receiver of TEM instrument by receiving input signals and analyzing and processing the output control signals to implement the basic control functions.5.Designs the system communication protocol to achieve the message passing between PLC and upper computer.Then download the main program into PLC system to operate for debugging.Accomplishing the detecting progress in one period shows the automation of the whole system was initial implemented.