CN108168510B - Roadbed settlement deformation monitoring system based on fiber bragg grating and installation method thereof - Google Patents

Abstract

The invention discloses a roadbed settlement deformation monitoring system based on fiber bragg gratings, which comprises a fiber bragg grating demodulator, a power supply device and a receiving device, wherein the power supply device and the receiving device are connected with the demodulator; the settlement device is fixed on the bedding layer through the supporting device, the settlement meter and the settlement device synchronously settle and deform downwards, and the demodulator analyzes the deformation of the fiber bragg grating wavelength in the settlement meter caused by the settlement of the settlement device and transmits the wavelength signal to the receiving equipment. When the system is installed, the supporting device is fixed with the top of the settlement gauge; the sedimentation base is fixed with the bottom of the sedimentation meter, and the sedimentation of the base drives the bottom of the sedimentation meter to stretch, so that the fiber bragg grating monitors deformation. Compared with the prior art, the invention has the advantages of cooperative deformation with soft foundation soil, accurate displacement monitoring, electromagnetic interference resistance, high sensitivity and the like.

Description

Roadbed settlement deformation monitoring system based on fiber bragg grating and installation method thereof

Technical Field

The invention relates to a highway subgrade settlement deformation monitoring system, in particular to a subgrade settlement deformation monitoring system based on fiber bragg gratings and an installation method thereof.

Background

In recent years, with the rapid development of highway construction, the requirements on the comfort, safety and durability of the highway are increasingly improved, so that more strict requirements on the soft foundation treatment of the lower part of the highway are provided, and settlement monitoring is a key ring for evaluating whether the soft foundation treatment mode is reliable or not; the soft foundation settlement monitoring is of great importance to prevent the common problems in the construction and operation of high-speed roads such as slope instability, differential settlement, bridge head bumping and the like of the high-fill subgrade.

The traditional settlement monitoring system is mainly carried out by adopting a mode of embedding settlement plates, has the defects of large workload, personnel cooperation, easy influence of weather factors, low monitoring precision and the like, and cannot comprehensively acquire the deformation characteristics of highway subgrade settlement. The fiber bragg grating as a novel material has the characteristics of corrosion resistance, high precision and the like, and is widely applied to the fields of civil engineering, water conservancy and traffic, geological engineering, aerospace and other engineering; however, the fiber bragg grating is more suitable for displacement detection with small strain, the settlement of the expressway is large in deformation, and the fiber bragg grating material is easily damaged by construction machines and tools in the filling period of the roadbed of the expressway, so that how to reasonably apply the fiber bragg grating technology to soft foundation settlement monitoring of the expressway makes the fiber bragg grating technology and a soft foundation soil body cooperatively deform and accurately monitor displacement change become a technical problem which needs to be solved urgently.

Disclosure of Invention

The purpose of the invention is as follows: the invention aims to provide a roadbed settlement deformation monitoring system based on fiber bragg gratings and an installation method thereof, so that the fiber bragg gratings and soft foundation soil body cooperatively deform and accurately monitor displacement change.

The technical scheme is as follows: the monitoring system comprises a fiber grating demodulator, a power supply device and a receiving device, wherein the power supply device and the receiving device are connected with the fiber grating demodulator; the settlement device is fixed on the ground bedding layer through the supporting device, the fiber grating settlement meter and the settlement device synchronously settle and deform downwards, and the fiber grating demodulator analyzes the deformation of the fiber grating wavelength in the settlement meter caused by the settlement of the settlement device and transmits the wavelength signal to the receiving equipment.

The fiber bragg grating settlement gauge also comprises a top immovable section, a bottom stretching section and a fiber bragg grating lead; the top fixed section is fixedly connected with the supporting device through a fixing clamp, the lower end of the bottom stretching section is fixedly connected with the sedimentation device, and the fiber grating lead is connected with the temperature compensation sensor.

The bottom stretching section comprises a bottom stretching rod and a stretching rod protection tube which are fixed on the base through a disc, the bottom stretching rod contains a metal wire, flexible fillers are contained around the metal wire, and the metal wire is stretched along with the sinking of the settling device so as to drive the deformation of the fiber bragg grating in the top immobile section.

The supporting device comprises a steel bar and a supporting bottom plate for reducing the sinking amount of the steel bar at the bottom of the soft foundation, and the steel bar is vertically fixed on the supporting bottom plate.

The sedimentation device comprises a base, connecting pipes and pipe hoops, wherein the base is fixed on the bedding layer through reinforcing steel bars, and the connecting pipes are connected with the connecting pipes through the pipe hoops after sequentially penetrating through the reinforcing steel bars.

The fixing clamp comprises two fasteners, and the fasteners connect and fix the top of the steel bar and the top of the fiber bragg grating settlement meter.

The method for installing the roadbed settlement deformation monitoring system based on the fiber grating technology comprises the following steps:

(1) respectively punching holes at the left, middle and right positions of the highway subgrade, inserting reinforcing steel bars (11) into the bottoms of the holes and carrying out guniting anchoring around the reinforcing steel bars as fixed points, wherein the punching depth is that the holes reach a bedrock at the bottom of the subgrade;

(2) downwards excavating the leveled original ground, leveling the excavated pit bottom, spreading fine sand as a bedding layer (5), and putting a settlement plate base (21) on the pit bottom bedding layer (5) after penetrating through a reinforcing steel bar (11);

(3) fixing a stretching rod disc (31) at the bottom of the settlement gauge (3) with a settlement base (21), and connecting the top of the settlement gauge (3) with a steel bar (11) through a fixing clamp (4);

(4) after the settlement connecting pipes (22) are sleeved on the upper parts of the reinforcing steel bars (11), the connecting pipes are connected end to end and screwed until the connecting pipes are higher than the original ground by a set distance, and the fiber bragg grating lead wires (38) are led out from the connecting pipes (22);

(5) tying the led-out optical fiber lead wire coil on the connecting pipe (22) to shield and cover the optical fiber jumper wire joint;

(6) backfilling the periphery of the sedimentation device (2) until the original ground is reached, and compacting;

(7) and connecting the fiber lead with a fiber grating demodulator (6), connecting the demodulator (6) with a power supply and a computer, recording wavelength data of the sensing fiber, and recording and capturing a peak value.

The working principle is as follows: the invention applies the fiber Bragg grating FBG (fiber Bragg Grating) technology which combines transmission and sensing media into a whole to the monitoring of the settlement and deformation of the roadbed of the highway. The method is characterized in that FBGs with a certain grating pitch are arranged on an optical fiber, the wavelength division multiplexing technology is adopted for measuring stress and temperature, when measured strain, temperature and the like are changed, the grating pitch of the grating per se is changed to cause the change of reflection wavelength, the settlement displacement of a roadbed can be obtained by calculating the wavelength drift of the reflection wavelength, and the settlement gauge has a temperature self-compensation function and can eliminate the influence of temperature change on the wavelength drift.

In the monitoring system, a supporting device fixed at a fixed point of a soft foundation is fixed with the top of the fiber grating settlement meter so as to ensure that the top of the fiber grating settlement meter does not generate displacement; the sedimentation base is fixed with the bottom of the fiber grating settlement gauge, and the base sinks to drive the bottom of the settlement gauge to stretch, so that the fiber grating monitors deformation; in addition, the settlement device can also be used for realizing the traditional monitoring of the roadbed deformation, and simultaneously, the roadbed deformation monitoring result of the fiber bragg grating technology can be verified. This system combines together fiber grating settlement gauge and traditional settlement device, realizes the dual monitoring mode that fiber monitoring and traditional monitoring were lifted simultaneously for the monitoring mode has pluralism and selectivity.

Has the advantages that: compared with the prior art, the invention has the advantages of cooperative deformation with soft foundation soil, accurate displacement monitoring, electromagnetic interference resistance, high sensitivity and the like.

Drawings

FIG. 1 is a schematic view of a monitoring system;

FIG. 2 is a front view of the fiber grating settlement gauge;

FIG. 3 is a top view of FIG. 2;

FIG. 4 is a front view of a fiber grating settlement gauge installed in the field;

FIG. 5 is a top view of the layout of the fiber grating settlement gauge;

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

Detailed Description

As shown in fig. 1, the monitoring system comprises a supporting device 1, a sedimentation device 2, a fiber bragg grating settlement meter 3, a fixing clamp 4, a bedding layer 5, a fiber bragg grating demodulator 6, a computer 7, a storage battery 8 and a voltage converter 9; wherein, the computer 7 is internally provided with corresponding processing software; the fiber grating demodulator 6 is used for analyzing the wavelength transmitted by the fiber grating sensor 39 and transmitting the wavelength signal obtained by analysis to the computer 7; the voltage of the storage battery 8 is 12V, and the conversion voltage of the voltage converter 9 is 12V-220V; the fiber grating demodulator 6 is respectively connected with a lead 38 of the grating fiber settlement meter, the computer 7 and the voltage converter 9.

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

The settling device 2 comprises a base 21 with a central hole, connecting pipes 22 and pipe hoops 23, wherein long straight steel bars 11 in the supporting device 1 penetrate downwards from the central hole of the base 21, the connecting pipes 22 are cylindrical connecting pipes with upper parts and lower parts both provided with mantle wires, the first connecting pipe is connected with the base 21, mantle wires are arranged on the inner sides of the pipe hoops 23, and adjacent connecting pipes are connected through the pipe hoops.

The fiber grating settlement gauge 3 comprises a top fixed section 37 and a bottom stretching section, wherein the top fixed section 37 respectively comprises a fiber grating lead protective tube 36 from top to bottom, the bottom stretching section comprises a bottom stretching rod 32 and a stretching rod protective tube 35, the stretching rod protective tube 35 contains a metal wire 33, flexible fillers are contained around the metal wire 33, the metal wire 33 stretches along with the settlement of the settlement device, the stretching deformation of the metal wire 33 drives the deformation of the fiber grating in the top fixed section 37, and a disc 31 is fixed at the bottom of the stretching rod 32 and welded with the bottom of the settlement base 21. The fiber grating lead 38, which serves as a transmission channel of the wave, has one end connected to a temperature compensation sensor 39 to compensate for a wavelength change due to a temperature change.

The fixing clamp 4 comprises two stainless steel fasteners 41, one stainless steel fastener 41 is connected with the long straight steel bar 11, the other stainless steel fastener is connected with the fiber grating settlement meter 3, the two stainless steel fasteners 41 are fastened through bolts 42, and the effect of connecting and fixing the long straight steel bar 11 and the top 37 of the fiber grating settlement meter is achieved.

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

(1) respectively punching holes at the left, middle and right monitoring positions of the highway subgrade, inserting the long straight steel bar 11 welded with the supporting bottom plate 12 at the bottom into the bottom of the hole after the punching depth reaches the bed rock at the bottom of the soft foundation, and performing guniting anchoring around the hole to serve as a fixed point; wherein, the supporting bottom plate 12 can prevent the reinforcing steel bar 11 from penetrating into the soil body, and the guniting and anchoring ensure the stability of the supporting structure and the reliability of the monitoring device.

(2) After the original ground 10 is leveled, an excavator is used for being matched with manpower to excavate downwards for 1m, the excavated pit bottom is leveled, fine sand with the thickness ranging from 4 cm to 6cm is spread to serve as a bedding layer 5, and a settlement plate base 21 is placed on the pit bottom bedding layer 5 after penetrating through a long straight steel bar 11.

(3) The bottom stretching rod 32 of the settlement gauge is welded with the settlement plate base 21, so that the stretching rod and the settlement plate base synchronously move downwards, and the coordination and the sensitivity of a monitoring system are improved; the sinker top 37 is connected to the long straight reinforcing bar 11 by the fixing jig 4.

(4) Sleeving a plurality of connecting pipes 22 from the upper parts of the long straight steel bars 11 and the settlement gauge 3, continuously connecting the connecting pipes end to end, screwing the connecting pipes, stopping the connecting pipes when the connecting pipes are 50cm higher than the original ground, and leading out fiber bragg grating leads 38 from the connecting pipes 22; the settlement gauge is placed in the settlement pipe, so that the damage of construction machines to the fiber bragg grating settlement gauge during filling is avoided.

(5) The led-out optical fiber lead wire coil is tied on the connecting pipe 22, and the upper part of the optical fiber lead wire coil is covered by a shielding bag so as to reduce the influence of rain and wind dust.

(6) Backfilling around the sedimentation device 2 to the original ground 10, and compacting with a compacting machine.

(7) And an iron fence is used for blocking the outer side of the connecting pipe 22, and a warning board is inserted to prevent the influence of construction machinery in the filling period.

(8) One lead 38 of the grating optical fiber is connected with the fiber grating demodulator 6, the fiber grating demodulator 6 is connected with the computer 7, the storage battery 8 and the voltage converter 9, and the wavelength data and the peak value of the sensing optical fiber are recorded;

(9) along with the increase of road bed soil filling, constantly take over, place the measuring tape in and take over the top, carry out the reading through optical leveling instrument or electronic level, combine fiber grating settlement gauge and traditional settlement plate and monitor.

As shown in fig. 5 and 6, three fiber grating settlement meters are sequentially arranged at the left shoulder, the center line and the right shoulder, the three points are positioned on the same vertical line, and the burying depth of the settlement meter support structure reaches the bottom bedrock.

Claims (2)

1. The utility model provides a road bed settlement deformation monitoring system based on fiber grating which characterized in that: the device comprises a fiber bragg grating demodulator (6), a power supply device and receiving equipment, wherein the power supply device is connected with the demodulator (6); the fiber grating settlement meter further comprises a fiber grating settlement meter (3) connected with the fiber grating demodulator (6) through a fiber grating lead (38), a supporting device (1) fixedly connected with the top of the fiber grating settlement meter (3), and a settlement device (2) fixedly connected with the bottom of the fiber grating settlement meter (3); the sedimentation device (2) is fixed on a ground bedding layer (5) through a supporting device (1), the fiber grating settlement meter (3) and the sedimentation device (2) synchronously settle and deform downwards, and the fiber grating demodulator (6) analyzes the deformation of the fiber grating wavelength in the fiber grating settlement meter (3) caused by the settlement of the sedimentation device (2) and transmits the wavelength signal to a receiving device;

the fiber bragg grating settlement gauge (3) comprises a top fixed section (37), a bottom stretching section and two fiber bragg grating leads (38); the top fixed section (37) is fixedly connected with the supporting device (1) through a fixing clamp (4), the lower end of the bottom stretching section is fixedly connected with the sedimentation device (2), and the fiber bragg grating lead (38) is connected with a temperature compensation sensor (39);

the bottom stretching section comprises a bottom stretching rod (32) and a stretching rod protection tube (35), wherein the bottom stretching rod (32) is fixed on the base (21) through a disc (31), a metal wire (33) is contained in the bottom stretching rod (32), flexible fillers (34) are contained around the metal wire (33), and the metal wire (33) stretches along with the sinking of the settling device (2) so as to drive the deformation of the fiber bragg grating in the top stationary section (37);

the supporting device (1) comprises a steel bar (11) and a supporting bottom plate (12), wherein the steel bar (11) is vertically fixed on the supporting bottom plate (12);

subside device (2) including base (21), takeover (22) and ferrule (23), base (21) are fixed on bedding course (5) through reinforcing bar (11), a plurality of takeover (22) pass reinforcing bar (11) back in proper order, take over and adopt ferrule (23) to be connected.

2. A method for installing a fiber grating-based roadbed settlement deformation monitoring system according to claim 1, wherein the method comprises the following steps: the method comprises the following steps:

(1) respectively punching holes at the left, middle and right positions of the highway subgrade, inserting a reinforcing steel bar (11) with a supporting bottom plate (12) fixed at the bottom into the bottom of the hole, and performing guniting and anchoring around the reinforcing steel bar as a fixed point, wherein the punching depth is up to the bedrock at the bottom of the subgrade;

(2) downwards excavating the leveled original ground, leveling the excavated pit bottom, spreading fine sand as a bedding layer (5), vertically penetrating a base (21) through a steel bar (11), and placing the base on the pit bottom bedding layer (5);

(3) fixing a stretching rod disc (31) at the bottom of the fiber grating settlement gauge (3) with a base (21), and connecting the top of the settlement gauge (3) with a steel bar (11) through a fixing clamp (4);

(4) after a plurality of connecting pipes (22) are sleeved on the upper part of the steel bar (11), the connecting pipes are connected end to end and screwed until the connecting pipes are higher than the original ground by a set distance, and two fiber bragg grating leads (38) are led out from the connecting pipes (22);

(5) tying the led-out optical fiber lead wire coil on the connecting pipe (22) to shield and cover the optical fiber jumper wire joint;

(6) backfilling the periphery of the sedimentation device (2) until the original ground is reached, and compacting;

(7) and connecting the optical fiber lead to an optical fiber grating demodulator (6), connecting the demodulator (6) to a power supply and a computer, recording wavelength data of the sensing optical fiber, and recording and capturing a peak value.

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