Full-automatic foundation pit monitoring system and method based on wireless displacement sensor

Abstract

The invention relates to a full-automatic foundation pit monitoring system and method based on a wireless displacement sensor, the system comprises a sensing layer, an acquisition and transmission layer, a cloud platform and an application layer, the sensing layer comprises a wireless laser displacement sensing system and a fixed sensor, and the wireless laser displacement sensing system carries out surface displacement monitoring; the horizontal displacement of the deep layer is monitored by a wireless inclinometry sensor; the acquisition and transmission layer is composed of a transmission gateway and a transmission node, the transmission node is used for transmitting near-field transmission data acquired by the sensing layer to the gateway, and the gateway uploads the data to the cloud platform; and the laser displacement sensor system comprises a laser ranging module, a laser receiving device and a laser spot image processing terminal, the laser ranging module transmits laser to the laser receiving device, and the processing terminal calculates the displacement of a monitoring point by identifying the change of the position of a light spot on a receiving screen. Whole-process wireless automatic intelligent monitoring of the civil engineering foundation pit is achieved, and monitoring of surface displacement and deep horizontal displacement of the foundation pit is achieved.

Description

Technical Field

[0001] The invention belongs to the field of civil engineering monitoring, and in particular relates to a full-automatic foundation pit monitoring system and method based on a wireless displacement sensor. Background Art

[0002] With the continuous advancement of infrastructure construction in my country, the utilization rate of underground space has also been continuously improved. In the construction of buildings, bridges and tunnels, excavation of foundation pits is inevitable. The excavation of deep foundation pits is a dynamic process. Affected by various complex factors, it is difficult to predict possible problems based on existing theories. Once the support structure is unevenly stressed, the soil will tilt at best, and the foundation pit will collapse at worst. The excavation of foundation pits also poses hidden dangers to the safety of surrounding buildings. If the surrounding soil becomes unstable, it is likely to cause the destruction of the upper structure and bring adverse social impacts. Therefore, monitoring the foundation pit is an indispensable part of foundation pit construction.

[0003] Foundation pit monitoring requires monitoring of supporting structures, foundation pits and surrounding rock and soil, groundwater, protected objects in the surrounding environment, and other objects to be monitored. The current mainstream monitoring method is still to use manual traditional foundation pit monitoring, that is, to manually monitor the monitored objects regularly by using equipment such as theodolites, total stations, inclinometers, water level gauges, and axial force gauges. However, due to the large workload of monitoring, these data are often affected by factors such as weather, personnel, and site conditions, and there are often human errors. In addition, since each monitoring information is measured and collected separately by a dedicated person, it is difficult to organize and analyze it in a timely manner. Therefore, it is impossible to combine the construction conditions, geological conditions, environmental conditions, and changes in the monitoring data of related monitoring projects in real time to analyze the data of the monitoring project and predict the development trend. At the same time, due to the dispersion and discontinuity of each monitoring data, the processing of monitoring data and information feedback are also difficult to be updated and presented in real time, and timely viewing and warning are impossible.

[0004] In order to meet the requirements of dynamic monitoring and safety warning of the project in terms of continuity, real-time performance and automation, some automatic monitoring solutions for foundation pits have emerged. For groundwater level, a wireless water level meter can be used for real-time measurement; for stress data that need to be monitored, such as support axial force, anchor stress, and steel bar stress, the corresponding stress strain sensors can be used to measure, and real-time measurement can be achieved through wireless transmission modules. However, there is still no good solution for the automatic monitoring of foundation pit displacement.

[0005] Foundation pit displacement monitoring includes foundation pit surface displacement monitoring and deep soil displacement monitoring.

[0006] For surface displacement monitoring, traditional manual measurement is performed using the sight line method through theodolite, but it requires specialist operation and the monitoring data is not continuous. At present, some automated surface displacement monitoring technologies have emerged, such as automated static level, GNSS, total station robot, three-dimensional laser scanning, machine vision and other methods. However, the automated static level requires liquid level tube measurement, has high requirements for ambient temperature, equipment air tightness, and equipment durability, poor stability, and low applicability; GNSS uses satellite positioning, has poor accuracy, and low anti-interference ability, which makes it difficult to monitor the actual foundation pit; although the total station robot meets the accuracy requirements, it is expensive and requires specialist operation; the cost of three-dimensional laser scanning is relatively high; the machine vision method is easily affected by weather and obstacles, and has high requirements for camera lenses and photosensitive elements when the monitoring distance is far. Therefore, there is still no better solution for automated monitoring of foundation pit surface displacement.

[0007] For deep soil displacement monitoring, the traditional method is to manually read the inclination angle and depth of the inclinometer tube to obtain the horizontal displacement of the soil layer at different depths of the monitoring point. At present, there are two types of automatic inclinometer equipment: the pull-type inclinometer robot and the fixed inclinometer. The former simulates the manual inclinometer method and uses a motor to replace the manual pull-up of the inclinometer sensor. Since the sensor is always in motion during the measurement process, the data stability is poor. At the same time, because the pull-up measurement takes a long time (a depth of 10 meters often takes dozens of minutes), it is impossible to obtain real-time data; although the latter solves the problem of manual lifting and release, the data can be obtained in real time. However, if the array inclinometer method is used, each section of the inclinometer rod needs to pull a cable to the wellhead separately, and the limited inclinometer tube cannot put more cables; if the series method is used, if one of the inclinometer rods is damaged, the subsequent inclinometer rods cannot report the measurement data, and the stability is poor. In addition, the length of the inclinometer rod cannot be changed at will, and if you want to change the inclinometer spacing, you must return to the factory for modification. Therefore, the existing solutions for the automated monitoring of deep displacement of foundation pit soil have not yet achieved the ideal effect.

[0008] In summary, foundation pit monitoring is mainly manual, with a large workload, affected by factors such as weather, personnel and site conditions, and there are human errors. In addition, the monitoring data is not continuous, making it difficult to grasp the problems and risks in the project in a timely manner. Especially for the surface displacement and deep soil displacement monitoring of foundation pits, the existing automated displacement monitoring technology cannot meet the project's needs for data, cost and use. Therefore, in order to achieve efficient and real-time automated monitoring of foundation pits and ensure a certain degree of economy, solve the problem of automated monitoring of foundation pit displacement, and develop a new type of automatic monitoring method for foundation pits in combination with electronic information technology and computer science and technology, it is a very valuable task. Summary of the invention

[0009] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a fully automatic foundation pit monitoring system and method based on wireless displacement sensors, which can realize the monitoring of surface displacement and deep horizontal displacement of foundation pits, reduce the difficulty of monitoring, have a high degree of automation, and at the same time, the measurement data has continuity, which can meet the automatic real-time monitoring needs of deep foundation pits and other projects.

[0010] To this end, the present invention adopts the following technical scheme: a fully automatic foundation pit monitoring system based on wireless laser displacement sensors, including a perception layer, an acquisition and transmission layer, a cloud platform and an application layer, characterized in that the perception layer includes a wireless laser displacement sensing system and a fixed sensor, and the wireless laser displacement sensing system performs layer displacement monitoring; the deep horizontal displacement is monitored by a wireless inclination sensor; the acquisition and transmission layer is composed of a transmission gateway and a transmission node, and the transmission node is used to transmit the near-field transmission data collected by the perception layer to the gateway, and the gateway uploads the data to the cloud platform; the laser displacement sensor system includes a laser ranging module, a laser receiving device and a laser spot image processing terminal, the laser ranging module emits laser to the laser receiving device, and the laser spot image processing terminal calculates the displacement of the monitoring point by identifying the change of the spot position on the receiving screen.

[0011] Preferably, a plurality of laser displacement sensors are evenly arranged in a loop at the monitoring points of the foundation pit, a reference point is set far away from the foundation pit and laser displacement sensors are also arranged therein, and a loop is formed by the sensors transmitting and receiving lasers.

[0012] Preferably, the wireless tilt sensor is a wireless inclinometer, which is a single inclinometer with a fixed cable length, and multiple inclinometers can be spliced ​​together for data transmission to adapt to different inclinometer hole depths.

[0013] Preferably, the fixed sensor also includes a strain sensor, a water level sensor and an earth pressure gauge.

[0014] Preferably, the cloud platform performs data processing and analysis, forms weekly and monthly reports, and generates analysis and evaluation reports, and data collection is completed at a fixed time, frequency and number of times.

[0015] Preferably, when the cloud platform monitoring data exceeds system indicators or other abnormal conditions occur, the system will issue an early warning and provide information on abnormal sensors.

[0016] Preferably, the transmission node adopts a serial cascade structure, can be connected to multiple sensor terminals of different types at the same time, and adopts a unified connection interface.

[0017] Preferably, the acquisition and transmission layer adopts a terminal address allocation algorithm, which can automatically allocate and clear nodes by location, realize near-field wireless Mesh networking, and integrate node control services and networking functions.

[0018] The present invention also provides a foundation pit displacement monitoring method based on laser displacement sensors, which is characterized in that laser displacement sensors are arranged at the positions of the points to be measured in the foundation pit and the reference points far away from the foundation pit; the laser of the laser displacement sensor at each point is emitted to the laser receiver of the adjacent sensor, so that all sensors form a loop to obtain multiple laser lines from the points to be measured to the reference points; the relative displacement between the points is measured by using the laser displacement sensor, and the relative displacement with the reference point is calculated by using the laser spot image processing terminal to obtain the foundation pit displacement data, and the foundation pit displacement data is corrected by using multiple displacement data measured by multiple lines; the measured data is uploaded to the cloud platform for data processing and analysis to form weekly and monthly reports, and generate professional analysis and evaluation reports; when the cloud platform monitoring data exceeds the system indicators or other abnormal conditions, the system will issue an early warning and provide information on the abnormal sensor.

[0019] Preferably, the inclinometer is buried by the drilling installation method, and holes are drilled at the points where inclinometer measurement is required; stress and strain sensors are arranged on the foundation pit support to obtain the axial force exerted on the support; water level sensors are buried in the soil layer to obtain groundwater level information, and soil pressure gauges are buried in the soil near the foundation pit; other sensors are installed and buried according to monitoring needs, and transmission nodes are installed to establish a connection with the transmission gateway, so that the sensor enters the test state and monitors other required monitoring information in real time.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] 1. It can realize fast and efficient foundation pit monitoring, saving manpower and time costs. It solves the problem that traditional foundation pit monitoring requires personnel to manually operate measuring instruments, and the measurement process is cumbersome, time-consuming and labor-intensive.

[0022] 2. Through the coordinated monitoring of wireless laser displacement sensing system, various fixed sensors and wireless inclinometers, the problem that the existing automatic displacement monitoring technology cannot meet the actual engineering requirements for data, cost and use is solved. It can automatically realize the monitoring of surface displacement and deep horizontal displacement of foundation pit.

[0023] 3. The monitoring data of the present invention is continuous and can meet the requirements of real-time monitoring and timely early warning of foundation pits.

[0024] 4. The present invention adopts automated networking to reduce the difficulty of automated monitoring networking for foundation pits and improve the stability of the automated monitoring network.

[0025] 5. The wireless inclinometer solves the problem that the existing fixed inclinometer needs to be customized according to the depth. The inclinometer modules can be spliced ​​independently to adapt to different hole depths.

[0026] 6. The present invention completes the automatic processing of measurement data through the cloud platform, realizing the automatic operation of foundation pit monitoring. It can not only improve the efficiency of measurement, but also reduce human errors and the complexity of data processing. When abnormal conditions occur in the monitoring data, the system will issue an early warning and provide information about the abnormal sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a schematic diagram of the appearance of the transmission gateway in the present invention;

[0028] Figure 2 This is a schematic diagram of the internal functions of the transmission gateway in the present invention;

[0029] Figure 3 This is a schematic diagram of the appearance of a transmission node in the present invention;

[0030] Figure 4 It is a schematic diagram of the internal functions of the transmission node in the present invention;

[0031] Figure 5 It is a schematic diagram of the installation position of the sensor in the foundation pit in the present invention;

[0032] Figure 6 It is a schematic diagram of burying the inclinometer in the present invention;

[0033] Figure 7 It is a schematic diagram of the world coordinate system, laser coordinate system, receiving screen coordinate system, camera coordinate system, normalized camera plane and pixel coordinate system of the wireless laser displacement sensor in the present invention;

[0034] Figure 8 The arrangement diagram of the laser displacement sensor in the present invention (illustration numbers: 1, 2, 3, 4, 5, 6, 7, 8 are points to be measured, 11, 12, 13, 14 are reference points, 9 is the foundation pit edge, and 10 is the construction range);

[0035] Fig. 9 This is a flow chart of the automated monitoring technology in the present invention. DETAILED DESCRIPTION

[0036] The present invention is further described below in conjunction with specific embodiments.

[0037] The invention discloses a fully automatic foundation pit monitoring system based on a wireless laser displacement sensor, comprising a perception layer, an acquisition and transmission layer, a cloud platform and an application layer. The perception layer comprises a wireless laser displacement sensing system and a fixed sensor. The wireless laser displacement sensing system monitors the displacement of the installed layer. The deep horizontal displacement is monitored by a wireless inclination sensor. The acquisition and transmission layer is composed of a transmission gateway and a transmission node. The transmission node is used to transmit the near-field transmission data collected by the perception layer to the gateway, and the gateway uploads the data to the cloud platform. The laser displacement sensor system comprises a laser ranging module, a laser receiving device and a laser spot image processing terminal. The laser ranging module emits laser to the laser receiving device, and the laser spot image processing terminal calculates the displacement of the monitoring point by identifying the change of the spot position on the receiving screen.

[0038] like Figure 1-Figure 2 The figure shows a wireless intelligent gateway of the present invention, which includes a 433MHz transmitting antenna 1, a 4G transmitting antenna 2, a 4G module 3, an aluminum alloy shell 4, a power supply and charging circuit 5, a 4G SIM card slot 6, a DC power supply interface 7, a backup power supply interface 8, a working indicator light 9, an RJ45 network interface 10, an Ethernet communication line 11, a Lora transceiver module 12 and a single-chip microcomputer main control module 13.

[0039] like Figure 3-Figure 4 The figure shows a wireless transmission node, which includes an antenna 14, a working indicator light 15, an aviation socket 16, an outdoor waterproof housing 17, a 485 communication module 18, a single-chip microcomputer 19, a wireless transceiver part 20, a lithium battery 21 and a solar charging module 22.

[0040] like Figure 5 and Figure 6 As shown, the schematic diagram of the installation position of the sensor in the foundation pit in the present invention, the retaining wall 23 and the steel support 24 are arranged in the pit body 31, and the axial force meter 25, the earth pressure box 26, the inclinometer 27, the water level meter 28, the thermometer and hygrometer 29 and the displacement sensor 30 are arranged at various positions in the pit body. The setting position and installation method of each sensor are described in detail in the specific implementation method part below.

[0041] The following is a specific implementation of the present invention:

[0042] (1) Select a suitable location to install the transmission gateway.

[0043] (2) Arrange the wireless laser displacement sensor system.

[0044] a) Foundation pit monitoring method based on wireless laser displacement sensor:

[0045] i. According to the requirements of foundation pit monitoring, a wireless laser displacement sensor system is arranged at the monitoring point, and a wireless laser emission and ranging module is arranged at the reference point (such as Figure 8).

[0046] ii. Each laser ranging module projects laser light onto the receiving board of the adjacent monitoring point. Figure 8 The lasers of sensor systems 1, 2, 3, 4, 5, 6, 7, and 8 can be projected onto the receiving plates of adjacent sensor systems in sequence to form a loop. At the same time, the laser ranging modules on reference points 11, 12, 13, and 14 can be projected onto the receiving plates of the nearest monitoring points 1, 7, 5, and 3 in sequence.

[0047] Each laser displacement sensor system is calibrated by applying a known displacement to the receiving device.

[0048] The wireless transmission module establishes a connection with the wireless gateway, so that the displacement sensor system enters a state to be tested.

[0049] iii. The vertical displacement monitored by the sensor coincides with the gravity direction, which is used to monitor the settlement of the monitoring point; the horizontal direction of the sensor is adjusted according to the horizontal displacement direction of the monitoring point, which is used to monitor the horizontal displacement of the monitoring point. Using adjacent laser displacement sensors, the relative displacement between each point is preliminarily calculated through the processing terminal, and then the relative displacement with the reference point is calculated to obtain the foundation pit displacement data. Figure 8 According to the arrangement situation, the receiving plates of monitoring points 1, 3, 5, 7 directly receive the lasers projected by reference points 11, 14, 13, 12, and the displacement of the reference points is 0. The settlement data z'1, z'3, z'5, z'7 and horizontal displacement data x'1, x'3, x'5, x'7 obtained by collection and processing are the settlement z1, z3, z5, z7 and horizontal displacement x1, x3, x5, x7 of the monitoring points. Monitoring points 2, 4, 6, and 8 only receive the lasers from adjacent monitoring points 1, 3, 5, and 7. The settlement data obtained through collection and processing are z'2, z'4, z'6, and z'8, and the horizontal displacement data are x'2, x'4, x'6, and x'8. Then the settlement of the monitoring point is z2 = z1 + z'2, z4 = z3 + z'4, z6 = z5 + z'6, and z8 = z7 + z'8, and the horizontal displacement is x2 = x1 + x'2, x4 = x3 + x'4, x6 = x5 + x'6, and x8 = x7 + x'8. Similarly, the settlement and horizontal displacement of other monitoring points that are not directly connected to the benchmark can be calculated through the monitoring displacement and monitoring data of the adjacent points. In addition, cross-validation can be performed through the data of different adjacent monitoring points. In particular, if the horizontal displacement direction of the monitoring point forms a certain angle α with the horizontal direction of the sensor, the horizontal displacement x=x′cosα+y′sinα can be measured, where y′ is the monitoring value of the laser direction change.

[0050] b) Arrangement and measurement method of wireless laser displacement sensor (such as Figure 7 ):

[0051] i. Arrange the front end of the wireless laser transmitter at the monitoring point, which includes a ranging module that can emit laser, a three-axis slide module, a three-axis tilt module and a wireless transmission module; arrange the wireless laser receiver relay at the reference point, which includes a laser spot receiving board, a camera module, a wireless transmission module and a shell; arrange the laser spot image processing terminal at the monitoring end, which includes a PC and a wireless transmission module. Define the monitoring coordinate system at the monitoring point m X m Y m Z m As follows, X l Axis, Y l Axis and Z l The axes coincide with the three axes of the front three-axis slide module respectively, and the origin method has no effect on the calculation of displacement; define the receiving plate coordinate system O at the reference point b X b Y b A plane coordinate system defined for visual landmarks.

[0052] ii. The terminal sends a command, and the relay takes a photo of the receiving board and transmits it to the terminal. The terminal applies image recognition algorithms to extract the pixel coordinates of the black dot array. Combined with the known actual spacing of the dot array, the Zhang Zhengyou calibration algorithm is used to solve the internal and external parameters and distortion coefficients of the camera.

[0053] iii. The terminal issues a command, the front end projects the laser and transmits the ranging information and the three-axis tilt angle, and the relay captures the laser spot image on the receiving board and transmits it. The terminal first uses the distortion coefficient obtained in step ii to dedistort the laser spot image, and then applies the laser spot image recognition algorithm to extract the pixel coordinates of the spot centroid. Finally, based on the monocular camera pinhole imaging distortion-free model, the internal and external parameters of the camera obtained in step ii are used to solve the coordinates of the spot centroid in the receiving board coordinate system.

[0054] iv. According to the derivation, the displacement of the laser ranging module in the monitoring coordinate system is related to the change in the coordinates of the light spot receiving plate and the change in the ranging:

[0055]

[0056] in, is the displacement of the laser ranging module in the monitoring coordinate system at time t, is the transformation matrix from the receiving plate coordinate system to the monitoring coordinate system, is the change in the coordinates of the laser spot receiving plate relative to the initial value at time t, Δl t is the change of the laser ranging result relative to the initial value at time t, is the direction vector of the laser beam in the monitoring coordinate system. Note that The z-direction component of is always 0, and the above formula can be specifically written as:

[0057]

[0058] Among them, r ij (i=1,2,3;j=1,2) is the transformation matrix Elements of In order to solve the 9 unknown parameters in the above formula, it is necessary to apply at least 3 known displacements to the laser ranging module, and the point set formed by all new emission points and the initial emission points must not be coplanar. v. The terminal issues a command to drive the front-end three-axis slide module to apply a known displacement to the laser ranging module. After the displacement is completed, the front end performs laser ranging and the relay performs spot shooting. The terminal operates according to step iii to obtain the receiving plate coordinates of the laser spot corresponding to the new laser emission point, calculate its change relative to the initial coordinates, and calculate the change of the ranging result relative to the initial value.

[0059] vi. Repeat step v at least twice to obtain at least 3 sets of sample information on the displacement of the laser ranging module, the change in the coordinates of the light spot receiving plate, and the change in the ranging:

[0060]

[0061] The terminal solves the unknown parameters through numerical optimization algorithms.

[0062] vii. The terminal issues a command, and the front-end three-axis slide module restores the laser ranging module to the initial position and fixes it. The front end starts to project the laser continuously or at a certain time interval, and transmits the ranging information and the three-axis inclination angle. According to the light spot image taken by the relay, the terminal can obtain the coordinates of the laser spot receiving plate according to the process in step iii, and then calculate the displacement of the front-end laser ranging module, that is, the three-dimensional displacement of the monitoring point, based on the system parameters obtained in step vi. In addition, the terminal compares the three-axis inclination angle with the initial value obtained in step iii. If the change is higher than the set threshold, it is considered that a large angle has occurred at the monitoring point, and an alarm message is issued to remind manual inspection.

[0063] viii. Complete three-dimensional displacement monitoring.

[0064] (3) The inclinometer is buried by drilling installation. Drill holes at the points where inclination measurement is required (the relative positions of the sensors in the foundation pit are as follows: Figure 5 ), the borehole opening diameter should be ≥110mm, the effective aperture should be ≥100mm; the hole wall should be smooth; the hole should be cleaned after drilling, and the residual rock powder and debris in the hole should be removed. The number of inclinometers per hole is determined according to the depth (1 / m). Connect the transmission node of the inclinometer to the gateway, debug the data, and enter the test state.

[0065] (4) Lay stress and strain sensors on the foundation pit support to obtain the axial force on the support. Connect the transmission node of the stress and strain sensor to the gateway, and after debugging the data, enter the test state.

[0066] (5) Bury a water level sensor in the soil layer to obtain groundwater level information. Connect the transmission node of the water level sensor to the gateway, and after debugging the data, enter the test state.

[0067] (6) An earth pressure gauge is buried in the soil near the foundation pit, and a transmission node is installed to establish a connection with the transmission gateway, so that the earth pressure gauge enters the test state and obtains real-time foundation pit earth pressure.

[0068] (7) Install other buried sensors according to monitoring needs, install transmission nodes, establish connections with transmission gateways, put sensors into the test state, and monitor other required information in real time.

[0069] (8) The displacement data and other monitoring data (such as supporting axial force, groundwater level, soil pressure, etc.) are uploaded to the cloud platform. The cloud platform processes and analyzes the data to form weekly and monthly reports. The professional data analysis team regularly prepares professional analysis and evaluation reports and uploads them to the cloud platform.

[0070] (9) Use computer technology to automate the data collection process. Use programming languages ​​to collect and process data. Use fixed collection time, frequency or number of collections in accordance with regulations and specifications.

[0071] like Fig. 9 The figure shows the automatic monitoring technology flow chart of the present invention. When the monitoring data exceeds the system indicators or other abnormal situations occur, the system will issue an early warning and provide information of the abnormal sensor. Professionals will go to the site for analysis and processing to realize daily data monitoring, early warning and maintenance.

[0072] It should be understood that these embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope limited by the appended claims of the application.

Claims

1. A fully automatic foundation pit monitoring system based on wireless laser displacement sensor, including a perception layer, a collection and transmission layer, a cloud platform and an application layer, characterized in that The perception layer includes a wireless laser displacement sensing system and a fixed sensor. The wireless laser displacement sensing system monitors the displacement of the installed layer. The deep horizontal displacement is monitored by a wireless inclination sensor. The acquisition transmission layer consists of a transmission gateway and a transmission node. The transmission node is used to transmit the near-field data collected by the perception layer to the gateway, and the gateway uploads the data to the cloud platform. The laser displacement sensor system includes a laser ranging module, a laser receiving device and a laser spot image processing terminal. The laser ranging module emits laser to the laser receiving device, and the laser spot image processing terminal calculates the displacement of the monitoring point by identifying the change in the spot position on the receiving screen.

2. According to claim 1, a fully automatic foundation pit monitoring system based on wireless sensor Internet of Things is characterized in that Multiple laser displacement sensors are evenly arranged in a loop at the monitoring points of the foundation pit. A reference point is set far away from the foundation pit and laser displacement sensors are also arranged there. The sensors transmit and receive lasers to form a loop.

3. A fully automatic foundation pit monitoring system based on wireless sensor Internet of Things according to claim 1 or 2, characterized in that The wireless inclination sensor is a wireless inclinometer, which is a single inclinometer with a fixed cable length. Multiple inclinometers can be spliced ​​for data transmission and are adapted to different inclinometer hole depths.

4. The fully automatic foundation pit monitoring system based on wireless sensor Internet of Things according to claim 1 is characterized in that The fixed sensor comprises a strain sensor, a water level sensor and an earth pressure gauge.

5. The fully automatic foundation pit monitoring system based on wireless sensor Internet of Things according to claim 1 is characterized in that The cloud platform performs data processing and analysis, forms weekly and monthly reports, and generates analysis and evaluation reports. Data collection is completed at a fixed time, frequency and number of times.

6. The fully automatic foundation pit monitoring system based on wireless sensor Internet of Things according to claim 5 is characterized in that When the cloud platform monitoring data exceeds the system indicators or other abnormal conditions, the system will issue an early warning and provide information on the abnormal sensors.

7. The fully automatic foundation pit monitoring system based on wireless sensor Internet of Things according to claim 1 is characterized in that The transmission node adopts a serial cascade structure, can be connected to multiple sensor terminals of different types at the same time, and adopts a unified connection interface.

8. The fully automatic foundation pit monitoring system based on wireless sensor Internet of Things according to claim 1 is characterized in that The acquisition transmission layer adopts a terminal address allocation algorithm, which can automatically allocate and clear nodes by location, realize near-field wireless Mesh networking, and integrate node control services and networking functions.

9. A method for monitoring foundation pit displacement based on a laser displacement sensor, characterized in that Laser displacement sensors are arranged at the positions of the points to be measured in the foundation pit and the positions of the reference points far away from the foundation pit; the laser of the laser displacement sensor at each point is emitted to the laser receiver of the adjacent sensor, so that all sensors form a loop to obtain multiple laser lines from the points to be measured to the reference points; the relative displacement between the points is measured by using the laser displacement sensor, and the relative displacement with the reference point is calculated by using the laser spot image processing terminal to obtain the foundation pit displacement data, and the foundation pit displacement data is corrected by using multiple displacement data measured by multiple lines; the measured data is uploaded to the cloud platform for data processing and analysis, forming weekly and monthly reports, and generating professional analysis and evaluation reports; when the cloud platform monitoring data exceeds the system indicators or other abnormal conditions, the system will issue an early warning and provide information on the abnormal sensor.

10. A method for monitoring foundation pit displacement based on a laser displacement sensor according to claim 9, characterized in that The inclinometer is buried by the drilling installation method. Holes are drilled at the points where inclinometer measurement is required. Stress and strain sensors are arranged on the foundation pit support to obtain the axial force on the support. Water level sensors are buried in the soil layer to obtain groundwater level information, and soil pressure gauges are buried in the soil beside the foundation pit. Other sensors are installed and buried according to monitoring needs, and transmission nodes are installed to establish a connection with the transmission gateway, so that the sensor enters the test state and monitors other required monitoring information in real time.

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