| Deep foundation pit is the basic part of high-rise building and underground space construction.In order to ensure the safety of building construction,it is necessary to monitor the horizontal displacement,inclination and supporting axial force of the supporting structure during the construction of the deep foundation pit.This is one of the important ways to ensure the safety of deep foundation pit construction.Using advanced detection methods and information transmission technology to develop deep foundation pit supporting structure state detection instruments with real-time monitoring has important social and economic benefits for safe construction.Firstly,the paper introduces the development status and trend of the state monitoring of deep foundation pit supporting structure.Then,based on the analysis of existing monitoring methods,network communication technology and software technology,it proposes the overall scheme of remote real-time monitoring system for wireless sensor network of deep foundation pit supporting structure.The entire monitoring system includes sensor perception layer,data transmission layer,server database layer and user layer.We obtain the horizontal displacement,inclination,support axial force and groundwater level information of the supporting structure in the sensor perception layer,and then collect and process the acquired data information through the data transmission layer and upload it to the server.After the server parses the data,it stores the data in the database.The user layer interacts with the server to obtain the data in the database and displays it through dynamic oscillogram and tables.Aiming at the problem of measuring the reference point in the horizontal displacement measurement of the traditional deep foundation pit supporting structure,this paper proposes a method of relative displacement detection.And based on the principle of phase laser triangulation,it realizes the horizontal displacement measurement of deep foundation pits,establishes a mathematical model of relative displacement measurement,verifies the correctness of the mathematical model through computer simulation of 3D model,and solves the problem that the reference point must be established in the traditional measurement method.The simulation results show that the method can meet the accuracy requirements of the horizontal displacement measurement of the supporting structure.In the deep foundation pit water level monitoring,we adopt the laser phase ranging method to realize the monitoring of the groundwater level in deep foundation pits.Using the advantages of laser ranging and LoRa technology,we develop a wireless groundwater level measurement instrument with a measurement accuracy of 1mm.In order to monitor the supporting axial force,we have developed a wireless vibrating wire sensor signal acquisition terminal with an acquisition accuracy of 1 Hz.In order to meet the construction site and wireless monitoring requirements,the monitoring instruments in the deep foundation pit supporting structure condition monitoring system have adopted the power supply mode combining solar panel and lithium battery.Based on the analysis and research of the communication mode between structures of each layer,we have completed the development of data transmission unit(DTU)based on the combination of LoRa and 4G technology,and developed the server-based remote monitoring management platform and client softwareFinally,we deployed the developed monitoring instruments and DTUs to the pit construction site for testing.The results show that the monitoring system runs stably,the communication delay is less than 1.5s,and the packet loss probability is less than 0.8%,which can meet the condition monitoring of the supporting structure during deep foundation pit construction. |
