Development Of Shallow Seismic Acquisition System In Urban Underground Space

With the rapid economic development of cities and the influx of population,the lack of experience in urban underground space detection and the inadequacy of urban management have become prominent.Some cities have successively experienced subway pavement collapse,engineering pipeline leakage and explosion,underground water accumulation and waterlogging.Such incidents sounded the alarm for the development of the city and the safety of the people.In order to effectively,fully and safely develop urban underground space,efficient and accurate detection is a prerequisite for the safe development of urban underground space.Shallow seismic exploration technology determines the boundaries and specific thicknesses of different strata by analyzing the collected data.Information such as the specific shape of the underground space in the detection area and the structure type of the stratum helps the system to safely and accurately determine the specific depth and location area suitable for the development of urban underground buildings.In this paper,the research is carried out from the aspect of shallow seismic exploration technology in urban underground space,and the seismic wave reflection method is used as the theoretical basis,aiming at the large noise,high power consumption,unstable real-time transmission,and small dynamic range of the existing urban underground space shallow seismic acquisition system And the complicated construction and other issues,a practical and effective design plan was proposed.First of all,to address the problem of excessive noise,through the design of front-end conditioning circuits,anti-surge diodes,small ripple power chips and high-precision and low-noise analog-to-digital acquisition chips;in order to meet long-term field work and avoid frequent battery replacement,this article passed The hardware level,drive level and system level are optimized to improve unnecessary losses.The hardware level is mainly to select low quiescent current and high efficiency power supply chips,optimize the schematic circuit and circuit board layout,etc.,and the drive level is to select and collect according to actual needs.The specific working mode of the chip AD7768,test chip AD9837 and other devices,the system level is to apply the Tickless low-power mechanism in the Free RTOS(Free Real Time Operating System)embedded operating system;in view of the existing slow real-time transmission rate,this system Relay data transmission through dual-port Ethernet transceiver;in response to the insufficient dynamic range of traditional urban underground space shallow seismic exploration,a hardware system with broadband,large dynamic range,and high signalto-noise ratio is designed;for the current strict In the urban construction environment,this paper designs a metal instrument case that is small,portable,easy to carry,dustproof and waterproof.Taking into account the above requirements,the research content of this article mainly includes the design of the overall hardware circuit,the transplantation of the lower computer system and the development of the program,the logic design of the FPGA(Field Programmable Gate Array)and the design of the data interaction program,which have achieved the system acquisition function test,data acquisition,Goals such as storage and transmission.Finally,the prototype of the urban underground space shallow seismic data acquisition system was completed and the performance index test and the hammering seismic source experiment were carried out on the prototype.The result of the test has reached the expected design goal,the instrument works normally,and the communication between the various modules and between the upper and lower computers is stable and reliable.