CN108168510B - Subgrade settlement deformation monitoring system based on fiber grating and its installation method - Google Patents

Abstract

The invention discloses a fiber grating-based subgrade settlement deformation monitoring system, comprising a fiber grating demodulator, a power supply device and a receiving device connected with the demodulator, and a fiber grating settlement gauge connected with the demodulator, and a settlement The support device connected to the top of the meter, and the settling device connected to the bottom of the settler; the settling device is fixed on the bedding layer through the support device, the settler and the settler synchronously settle down and deform, and the demodulator causes the settling to settle due to the sinking of the settling device. After analyzing the wavelength deformation of the fiber grating in the meter, the wavelength signal is transmitted to the receiving device. When the system is installed, the support device is fixed to the top of the subsidence gauge; the subsidence base is fixed to the bottom of the subsidence gauge, and the subsidence of the base drives the bottom of the subsidence gauge to stretch, so as to realize the monitoring of the deformation of the fiber grating. Compared with the prior art, the invention cooperates with the soft foundation soil to deform together and accurately monitors the displacement change, and has the advantages of anti-electromagnetic interference and high sensitivity.

Description

Subgrade settlement deformation monitoring system based on fiber grating and its installation method

technical field

The invention relates to a monitoring system for roadbed settlement and deformation, in particular to a fiber grating-based roadbed settlement deformation monitoring system and an installation method thereof.

Background technique

In recent years, with the rapid development of expressway construction, the requirements for the comfort, safety and durability of expressways have been increasing day by day. Therefore, more stringent requirements have been put forward for the treatment of the lower soft foundation. The settlement monitoring is to evaluate the soft foundation. The key part of whether the treatment method is reliable; the monitoring of soft foundation settlement is very important to prevent the common problems in highway construction and operation such as slope instability, differential settlement, and bridge jumping of high-fill roadbed.

The traditional settlement monitoring system mostly adopts the method of burying the settlement plate, which has the disadvantages of large workload, need for personnel cooperation, easy to be affected by weather factors, and low monitoring accuracy, and cannot fully obtain the deformation characteristics of highway subgrade settlement. As a new type of material, fiber grating has the characteristics of corrosion resistance and high precision, and has been widely used in various engineering fields such as civil engineering, water conservancy and transportation, geological engineering and aerospace; however, fiber grating is more suitable for small strain displacement detection. , and the highway settlement is a large deformation, and the fiber grating material is easily damaged by the construction equipment during the highway subgrade filling period. Therefore, how to reasonably apply the fiber grating technology to the settlement monitoring of the highway soft foundation, so that it can be combined with the soft foundation of the highway. Co-deformation of the base soil and accurate monitoring of displacement changes have become a technical problem that needs to be solved urgently.

SUMMARY OF THE INVENTION

Purpose of the invention: The purpose of the present invention is to provide a fiber grating-based subgrade settlement and deformation monitoring system and an installation method thereof, so that the fiber grating technology and the soft foundation soil can be deformed together and the displacement change can be accurately monitored.

Technical solution: a monitoring system, including a fiber grating demodulator, a power supply unit and a receiving device connected to the fiber grating demodulator, and a fiber grating sedimentation meter connected to the fiber grating demodulator, fixed to the top of the fiber grating sedimentation meter The connected support device, and the settlement device fixedly connected to the bottom of the fiber grating settlement meter; the settlement device is fixed on the ground bedding layer through the support device, the fiber grating settlement meter and the settlement device are synchronously settled down and deformed, and the fiber grating demodulator can adjust the settlement. The subsidence of the device causes the wavelength deformation of the fiber grating in the sedimentometer to be analyzed, and then the wavelength signal is transmitted to the receiving device.

The fiber grating sedimentation meter also includes a top fixed section, a bottom tensile section and a fiber grating lead; the top fixed section and the supporting device are connected and fixed by a fixing fixture, the lower end of the bottom tensile section is fixedly connected with the sedimentation device, and the fiber grating lead is connected to the temperature compensation device. Sensor connection.

The bottom stretching section includes a bottom stretching rod and a stretching rod protection tube fixed on the base by a disc. The bottom stretching rod contains metal wires, and flexible fillers are contained around the metal wires. The metal wires sink with the sinking device. And stretch, and then drive the deformation of the fiber grating in the top stationary section.

The support device includes steel bars, and a support base plate for reducing the subsidence of the steel bars at the soft base, and the steel bars are vertically fixed on the support base plate.

The settlement device includes a base, a connecting pipe and a pipe hoop. The base is fixed on the bedding layer by steel bars. After several connecting pipes pass through the steel bars in sequence, the connecting pipes and connecting pipes are connected by pipe hoop.

The fixing fixture includes two fasteners, which connect and fix the top of the steel bar and the top of the fiber grating sedimentation meter.

The installation method of the roadbed settlement deformation monitoring system based on fiber grating technology includes the following steps:

(1) Drill holes at the left, middle and right positions of the highway subgrade respectively, the drilling depth is to reach the bedrock at the bottom of the subgrade, insert the steel bar (11) into the bottom of the hole and perform shotcrete anchoring around it as a fixed point;

(2) Excavate the leveled original ground downward, level the excavated pit bottom, spread fine sand as a bedding layer (5), and pass the settlement plate base (21) through the steel bars (11) , placed on the bedding layer (5) at the bottom of the pit;

(3) fixing the bottom tension rod disc (31) of the settlement meter (3) with the settlement base (21), and the top of the settlement meter (3) and the steel bar (11) are connected by the fixing fixture (4);

(4) After the settlement nozzle (22) is put on the upper part of the steel bar (11), the nozzles are connected end-to-end and tightened until the nozzle is higher than the set distance from the original ground. 22) Internal lead;

(5) tie the outgoing optical fiber lead coil on the take-over (22), and cover the optical fiber jumper connector;

(6) Backfill is carried out around the settlement device (2) until the original ground, and compacted;

(7) Connect the optical fiber lead to the fiber grating demodulator (6), connect the demodulator (6) to the power supply and the computer, record the wavelength data of the sensing fiber, and record and capture the peak value.

Working principle: The present invention applies the Fiber Bragg Grating FBG (Fiber Bragg Grating) technology, which combines transmission and sensing media into one, in monitoring the settlement and deformation of highway subgrades. Specifically, the FBG with a certain grating pitch is arranged on the optical fiber, and the wavelength division multiplexing technology is used to measure the stress and temperature. When the measured strain, temperature, etc. change, the grating pitch of the grating itself will change, causing the reflection wavelength. The settlement displacement of the roadbed can be calculated from the wavelength drift of the reflected wavelength. The settlement meter comes with a temperature self-compensation function, which can eliminate the influence of temperature changes on the wavelength drift.

In the monitoring system, the support device fixed at the fixed point of the soft foundation is fixed to the top of the fiber grating settler to ensure that the top of the fiber grating settler does not move; the settlement base is fixed to the bottom of the fiber grating settler, and the sinking of the base drives the settler. The bottom is stretched to realize the monitoring of the deformation of the fiber grating; in addition, the traditional monitoring of the deformation of the roadbed can also be realized by using the settlement device, and the results of monitoring the deformation of the roadbed by the fiber grating technology can be verified. This system combines the fiber grating sedimentation meter with the traditional sedimentation device to realize the dual monitoring method of fiber monitoring and traditional monitoring, which makes the monitoring method diverse and selective.

Beneficial effects: Compared with the prior art, the present invention cooperates with the soft foundation soil to deform together and accurately monitors the displacement change, and has the advantages of anti-electromagnetic interference and high sensitivity.

Description of drawings

Figure 1 is a schematic diagram of the monitoring system;

Figure 2 is a front view of the installation of the fiber grating sedimentation meter;

Fig. 3 is the top view of Fig. 2;

Figure 4 is a front view of the on-site installation of the fiber grating sedimentation meter;

Figure 5 is a top view of the layout of the fiber grating settlement meter;

FIG. 6 is a cross-sectional view of FIG. 5 .

Detailed ways

As shown in Figure 1, the monitoring system includes a support device 1, a settlement device 2, a fiber grating settlement meter 3, a fixing fixture 4, a bedding layer 5, a fiber grating demodulator 6, a computer 7, a battery 8 and a voltage converter 9; Corresponding processing software is installed in the computer 7; the fiber grating demodulator 6 is used to analyze the wavelength transmitted by the fiber grating sensor 39, and transmit the wavelength signal obtained by the analysis to the computer 7; the voltage of the battery 8 is 12V, and the voltage converter The conversion voltage of 9 is 12V-220V; the fiber grating demodulator 6 is respectively connected with the lead wire 38 of the grating fiber settler, the computer 7 and the voltage converter 9.

As shown in FIG. 2 and FIG. 3 , the support device 1 includes a circular long straight steel bar 11 and a square iron support base plate 12 , wherein the steel bar 11 is vertically welded on the support base plate 12 .

The settlement device 2 includes a base 21 with a central hole, a connecting pipe 22 and a pipe hoop 23, wherein the long straight steel bars 11 in the supporting device 1 penetrate downward from the center hole of the base 21, and the connecting pipe 22 contains a set of wires on the upper and lower parts. The first one is connected to the base 21, the inner side of the pipe hoop 23 has a ferrule, and the adjacent pipes are connected by a pipe hoop.

The fiber grating sedimentation meter 3 includes a top stationary section 37 and a bottom stretching section. The top stationary section 37 contains a fiber grating lead wire protection tube 36 up and down, and the bottom stretching section includes a bottom stretching rod 32 and a stretching rod protection tube. 35. The stretching rod protection tube 35 contains metal wire 33, and the surrounding metal wire 33 contains flexible fillers. The metal wire 33 is stretched as the settling device sinks, and the tensile deformation of the metal wire 33 drives the top stationary section 37. For the deformation of the inner fiber grating, a disc 31 is fixed at the bottom of the stretching rod 32 and is welded with the bottom of the settlement base 21 . One end of the fiber grating lead 38, as a transmission channel of the wave, is connected with a temperature compensation sensor 39 to compensate the wavelength change caused by the temperature change.

The fixing fixture 4 includes two stainless steel fasteners 41, one stainless steel fastener 41 is connected with the long straight steel bar 11, the other is connected with the fiber grating settlement meter 3, and the two stainless steel fasteners 41 are fastened by bolts 42, It plays the role of connecting and fixing the long straight steel bar 11 and the top 37 of the fiber grating settlement meter.

As shown in Figure 4, the installation method of the monitoring system includes the following steps:

(1) Drill holes at the left, middle and right monitoring positions of the highway subgrade respectively. After the drilling depth reaches the bedrock at the bottom of the soft foundation, insert the long straight steel bars 11 welded with the supporting bottom plate 12 into the bottom of the hole, and carry out The shotcrete anchoring is used as a fixed point; the support bottom plate 12 can prevent the steel bar 11 from penetrating into the soil, and the shotcrete anchoring ensures the stability of the support structure and the reliability of the monitoring device.

(2) After the original ground 10 is leveled, use the excavator to cooperate with manual excavation for 1 m downwards, level the pit bottom after excavation, spread fine sand with a thickness of 4 to 6 cm as the bedding layer 5, After the settlement plate base 21 passes through the long straight steel bar 11, it is placed on the bedding layer 5 at the bottom of the pit.

(3) Weld the stretch rod 32 at the bottom of the subsidence gauge with the base 21 of the settlement plate, so that the stretch rod and the base of the settlement plate are displaced downward synchronously, which increases the coordination and sensitivity of the monitoring system; The straight steel bars 11 are connected by the fixing fixture 4 .

(4) Put a plurality of nozzles 22 on the long straight steel bar 11 and the upper part of the settlement meter 3, connect and tighten them end to end, stop when the nozzles are 50 cm higher than the original ground, and lead out the fiber grating lead 38 from the nozzle 22; the settlement meter It is placed in the settlement tube to avoid the damage to the fiber grating settlement meter caused by the construction equipment during the filling.

(5) Tie the outgoing optical fiber lead coil on the connecting tube 22, and cover the upper part with an isolation bag to reduce the influence of rain and wind and dust.

(6) Backfilling is carried out around the settlement device 2, backfilling to the original ground 10, and compacting with a compactor.

(7) Use an iron fence on the outside of the connecting pipe 22, and insert a warning sign to prevent the impact of construction machinery during the filling period.

(8) one of the leads 38 of the grating fiber is connected with the fiber grating demodulator 6, the fiber grating demodulator 6 is connected to the computer 7, the accumulator 8 and the voltage converter 9, and the wavelength data and the peak value of the sensing fiber are recorded;

(9) With the increase of the roadbed fill, continuously take over, place the measuring ruler on the top of the take-over, read through the optical level or electronic level, and combine the fiber grating settlement meter with the traditional settlement plate for monitoring.

As shown in Figure 5 and Figure 6, three fiber grating subsidence gauges are arranged in sequence at the left shoulder, road center line, and right shoulder, and the three points are located on the same vertical line.

Claims (2)

1. a subsidence deformation monitoring system based on fiber grating, is characterized in that: comprise fiber grating demodulator (6), the power supply device and the receiving equipment that are connected with demodulator (6); Also comprise and fiber grating demodulator (6); The adjustment instrument (6) is a fiber grating subsidence meter (3) connected through the fiber grating lead wire (38), a support device (1) fixedly connected to the top of the fiber grating subsidence meter (3), and a bottom part of the fiber grating subsidence meter (3) A fixedly connected settling device (2); the settling device (2) is fixed on the ground bedding layer (5) through the supporting device (1), and the fiber grating settling meter (3) and the settling device (2) move downward synchronously Settling deformation, the fiber grating demodulator (6) transmits the wavelength signal to the receiving device after analyzing the deformation of the wavelength of the fiber grating in the fiber grating settling meter (3) caused by the sinking of the settlement device (2); The fiber grating sedimentation meter (3) includes a top stationary section (37), a bottom stretching section and two fiber grating lead wires (38); the top stationary section (37) and the supporting device (1) pass through a fixing fixture (4) The connection is fixed, the lower end of the bottom stretching section is fixedly connected with the settling device (2), and the fiber grating lead (38) is connected with the temperature compensation sensor (39); The bottom stretch section includes a bottom stretch rod (32) and a stretch rod protection tube (35) fixed on the base (21) by a disc (31), and the bottom stretch rod (32) contains metal The wire (33) contains flexible fillers (34) around the wire (33), and the wire (33) stretches with the sinking of the settling device (2), thereby driving the interior of the stationary section (37) at the top Deformation of fiber grating; The supporting device (1) comprises a steel bar (11) and a support bottom plate (12), and the steel bar (11) is vertically fixed on the support bottom plate (12); The settling device (2) includes a base (21), a connecting pipe (22) and a pipe hoop (23). 22) After passing through the steel bars (11) in sequence, the connecting pipe and the connecting pipe are connected by a pipe hoop (23). 2. an installation method of a fiber grating-based roadbed settlement deformation monitoring system as claimed in claim 1, is characterized in that: comprise the following steps: (1) Drill holes at the left, middle and right positions of the highway subgrade respectively, the drilling depth reaches the bedrock at the bottom of the subgrade, insert the steel bars (11) with the supporting bottom plate (12) fixed at the bottom into the bottom of the hole and spray the surrounding Anchoring as a fixed point; (2) Excavate the leveled original ground downwards, level the excavated pit bottom, spread fine sand as a bedding layer (5), and vertically pass the base (21) through the steel bars (11). ), placed on the bedding layer (5) at the bottom of the pit; (3) fixing the bottom tension rod disc (31) of the fiber grating sedimentation meter (3) with the base (21), and the top of the sedimentation meter (3) and the steel bar (11) are connected by the fixing fixture (4); (4) After putting several nozzles (22) on the upper part of the steel bars (11), the nozzles are connected end to end and tightened until the nozzles are higher than the set distance from the original ground, and the two fiber grating leads (38) Lead out from the receiver (22); (5) tie the outgoing optical fiber lead coil on the take-over (22), and cover the optical fiber jumper connector; (6) Backfill is carried out around the settlement device (2) until the original ground, and compacted; (7) Connect the optical fiber lead to the fiber grating demodulator (6), connect the demodulator (6) to the power supply and the computer, record the wavelength data of the sensing fiber, and record and capture the peak value.

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