CN205785182U - A kind of soft soil base sedimentation sensor based on fiber grating sensing technology - Google Patents

Abstract

A soft soil foundation settlement sensor based on fiber Bragg grating sensing technology, including a settlement tube, an inclinometer tube, a stainless steel plate, an optical fiber grating sensitive element, an optical cable, and a fiber grating demodulator, wherein the settlement tube and the inclinometer tube interact with each other The vertical connection is buried in the soft soil foundation, and there are cross slots for fixing multiple stainless steel plates on the inner walls of the settlement tube and the inclinometer tube respectively. The thickness of the stainless steel plates is consistent with the width of the cross slots; A fiber grating sensitive element, the fiber grating sensitive element is connected with the fiber grating demodulator through an optical cable; at the same time, a steel plate is installed on the upper part of the settlement tube. The utility model adopts the optical fiber grating as the sensing element, makes full use of the superiority of the optical fiber grating sensing material, facilitates the formation of a monitoring network, and realizes real-time on-line monitoring of the settlement of the entire cross-section of the soft foundation and the deformation in the soft soil body, and has high sensitivity, Strong anti-interference, can automatically obtain data, good water resistance, long service life.

Description

A Soft Soil Foundation Subsidence Sensor Based on Fiber Bragg Grating Sensing Technology

technical field

The utility model relates to the technical field of foundation monitoring devices, in particular to a soft soil foundation settlement sensor based on fiber grating sensing technology.

Background technique

Due to the complexity and particularity of geological formation, there is usually a thick soft soil layer under the subgrade along the road, and the soft soil layer has disadvantages such as high water content, strong compressibility, and large void ratio, which directly affect the stability and safety of the road. ; When building a road on this foundation, if the treatment method adopted for the roadbed does not meet the requirements, the use function of the road will be jeopardized due to excessive settlement of the road foundation or differential settlement. Therefore, foundation settlement monitoring is an important content in engineering applications.

At present, the method for monitoring the settlement of soft soil roadbeds in road construction mainly adopts the settlement plate method, and the settlement plate method uses traditional measuring instruments, which not only has low precision, but also has a large volume of the settlement plate, which is inconvenient to install, and the measuring points are fragile, requiring manual inspection. Point measurement, data cannot be automatically obtained, the measurement error is large, and it is impossible to measure in rainy weather. At the same time, the cost of long-term manual measurement is high; in addition, the settlement plate method can only be measured during construction. Once the road is opened to traffic, it cannot continue to monitor the subgrade The condition of subsidence lacks long-term nature. Although, in recent years, the use of vibrating wire settlement sensors has been used for monitoring, but such sensors have problems such as poor anti-electromagnetic interference, poor anti-water interference, short service life, and low degree of automation, and vibrating wire settlement sensors can only be monitored Fixed-point measurement cannot monitor the deformation of the entire cross-section, which has certain limitations.

Utility model content

The technical problem solved by the utility model is to provide a soft ground subsidence sensor based on fiber grating sensing technology to solve the above-mentioned shortcomings in the background technology.

The technical problem solved by the utility model adopts the following technical solutions to realize:

A soft soil foundation settlement sensor based on fiber Bragg grating sensing technology, including a settlement tube, an inclinometer tube, a stainless steel plate, an optical fiber grating sensitive element, an optical cable, and a fiber grating demodulator, wherein the settlement tube and the inclinometer tube interact with each other The vertical connection is buried in the soft soil foundation, and there are cross slots for fixing multiple stainless steel plates on the inner walls of the settlement tube and the inclinometer tube respectively. The thickness of the stainless steel plates is consistent with the width of the cross slots; A fiber grating sensitive element is connected to the fiber grating demodulator through an optical cable; at the same time, a steel plate is installed on the upper part of the settlement tube to facilitate the coordinated deformation of the settlement tube and the soft soil foundation.

In the utility model, a hinge is arranged at the vertical connection between the settlement tube and the inclinometer tube.

In the utility model, the settling tube and the inclinometer tube are made of PVC material, and the outer diameter of the settling tube and the inclinometer tube is 65mm, the inner diameter is 60mm, and the depth of the cross groove on the inner wall is 2mm and the width is 2mm.

In the utility model, the two ends of the settling tube are respectively provided with protective covers, the upper part of the inclinometer tube is provided with a protective cover, and the lower part is provided with a sleeve, and the sleeve is a tapered sleeve.

In the utility model, a plurality of stainless steel plates are connected and fixed by connecting steel plates on both sides, so as to ensure that the rigidity of joints after the stainless steel plates are connected reaches the rigidity of the original steel plates.

In the present utility model, the thickness of the stainless steel plate is 2mm, the width is 61mm, and the length is 1000mm.

In the present utility model, the thickness of the connecting steel plate is 2mm, the width is 10mm, and the length is 40mm.

In the utility model, a fiber grating sensitive element is welded every 500mm at the centerline position of the same side on the stainless steel plate.

In the utility model, the optical fiber grating sensitive element is connected with the optical cable through the connecting flange.

In the utility model, the inclinometer tube is installed first, and the bottom of the inclinometer tube is required to be buried in the hard soil layer of the soft soil foundation for more than 1m, so as to ensure that the lower side of the inclinometer tube does not shift; and the fiber grating sensing element is welded on the stainless steel On the board, each stainless steel plate is connected and fixed by a connecting steel plate, and the fiber grating sensing elements on the stainless steel plate are connected in series through an optical cable, and then the stainless steel plate is inserted into the cross notch of the inclinometer tube; When the hole reaches the design elevation, put the inclinometer tube covered with the sleeve into the drilled hole, and at the same time make the cross notch in the inclinometer tube vertical or parallel to the trend direction of rock and soil; install the settlement tube again, and measure the settlement tube Buried in the surface layer of soft soil foundation, the stainless steel plate used to be placed in the settlement tube is connected and fixed through the connecting steel plate, the fiber grating sensing element is welded on the stainless steel plate, and the fiber grating sensing element on the stainless steel plate is passed through the optical cable Then put the stainless steel plate into the settling tube, align it with the cross notch of the settling tube when placing it, and the stainless steel plate in the settling tube is on the same horizontal line, and then cover the upper part of the inclinometer tube and the measuring cover respectively. Both ends of the settling tube are used to prevent impurities from entering and affecting the accuracy of the measurement; a hinge is installed at the connection between the inclinometer tube and the settling tube, and the optical cable passes through the hinge to connect with the fiber grating demodulator, and finally the upper part of the settling tube is tested A steel plate is placed at a certain distance so that the settlement tube and the soft soil foundation will sink together; when the soft soil foundation settles and deforms, the soil will squeeze the settlement tube downward and the inclinometer tube to the left, and this When the settlement tube, the inclinometer tube and the soil are deformed together, the stainless steel plate installed in the settlement tube and the inclinometer tube is also deformed, so it is determined that the deformation in the soft soil foundation and the deformation of the stainless steel plate Consistency, through the bending theory of the beam, using the differential calculation method, deduce the relationship between the strain value and the deflection value of each fiber grating sensitive element measurement point, and then use the fiber grating demodulator to measure the value of each measurement point The surface strain value can be used to calculate the deflection value of each fiber grating sensitive element measuring point, and the settlement of the soft soil foundation can be known.

Beneficial effect:

1) The strain monitoring of the stainless steel plate in the settlement tube and the inclinometer tube of the utility model adopts the optical fiber grating as the sensing element, makes full use of the superiority of the optical fiber grating sensing material, and connects the optical fiber grating sensitive element in the inclinometer tube to the sensor through the optical cable. The optical fiber grating sensitive elements in the settlement tube are connected in series for signal transmission, which facilitates the formation of a monitoring network and data collection, so as to realize real-time on-line monitoring of the settlement of the entire cross-section of the soft foundation and the deformation of the soft soil body. It is of great practical significance to carry out long-term stability monitoring and safety early warning and forecasting of internal deformation to ensure the safe operation of the highway;

2) The sensor in this utility model is composed of a settlement tube and an inclinometer tube, which can not only measure the vertical settlement of the entire cross-section of the soft soil foundation, but also measure the horizontal deformation of the soft soil at different depths;

3) The stainless steel plate in the utility model is simple in design, easy to carry, easy to install, and greatly saves engineering costs;

4) The fiber grating sensing technology is adopted in this utility model, which has the advantages of high sensitivity, strong anti-interference, automatic data acquisition, good water resistance, long service life, and real-time online monitoring of soft foundation settlement.

Description of drawings

Fig. 1 is a schematic structural view of a preferred embodiment of the present invention.

Fig. 2 is a cross-sectional view of the PVC settlement pipe in a preferred embodiment of the present invention.

Fig. 3 is a schematic diagram of the connection between the PVC settlement pipe and the PVC inclinometer pipe in a preferred embodiment of the present invention.

Fig. 4 is a left side view of the connection between the PVC measuring settlement pipe and the PVC inclinometer pipe in a preferred embodiment of the present invention.

Fig. 5 is a schematic diagram of connection of stainless steel plates in a preferred embodiment of the present invention.

Fig. 6 is a top view of the pre-embedded PVC measuring settlement pipe in a preferred embodiment of the present invention.

Fig. 7 is a schematic diagram of embedding of a preferred embodiment of the present invention.

detailed description

In order to make the technical means, creative features, goals and effects achieved by the utility model easy to understand, the utility model will be further elaborated below in conjunction with specific illustrations.

Referring to Figures 1 to 7, a soft soil foundation settlement sensor based on fiber grating sensing technology includes a PVC settlement pipe 1, a PVC inclinometer pipe 2, a sleeve 3, a protective cover 4, a stainless steel plate 5, a connecting steel plate 6, Bolt 7, fiber grating sensitive element 8, connecting flange 9, hinge 10, optical cable 11, fiber grating demodulator 12, cross notch 13 and steel plate 14.

In this embodiment, the PVC settlement pipe 1 and the PVC inclinometer pipe 2 are perpendicular to each other, and protective covers 4 are provided at both ends of the PVC settlement pipe 1, and a protective cover 4 is provided on the upper part of the PVC inclinometer pipe 2. The lower part of the inclinometer pipe 2 is provided with a sleeve 3, and a hinge 10 is provided at the junction of the PVC inclinometer pipe 1 and the PVC inclinometer pipe 2, and the protective cover 4 on the upper part of the PVC inclinometer pipe 2 is connected by the hinge 10 and the bolt 7. It is connected and fixed with the protective cover 4 at the left end of the PVC settling pipe 1; the inner walls of the PVC settling pipe 1 and the PVC inclinometer pipe 2 are respectively provided with a cross notch 13, and the width of the cross notch 13 is consistent with the thickness of the stainless steel plate 5. The stainless steel plate 5 is double-sidedly connected and fixed by connecting the steel plate 6 and the bolt 7, and the connected and fixed stainless steel plate 5 is inserted into the PVC settlement tube 1 and the PVC inclinometer tube 2 one by one, and the stainless steel plate is fixed through the cross groove 13 5; A plurality of fiber grating sensitive elements 8 are welded on the stainless steel plate 5, and the fiber grating sensitive elements 8 are connected in series with the optical cable 11 through the connecting flange 9, and then the optical cable 11 passes through the protective cover 4, the hinge 10 and the fiber grating demodulator 12 Connection; when the PVC survey settlement pipe 1 is pre-embedded, a steel plate 14 is installed on the PVC survey settlement pipe 1 top.

In this embodiment, the joints between the stainless steel plates 5 are connected and fixed at two sides of the connecting steel plates 6 to ensure that the stiffness of the joints after the stainless steel plates 5 are connected reaches the rigidity of the original steel plates.

In this embodiment, the outer diameter of the PVC settling pipe 1 and the PVC inclinometer pipe 2 are both 65 mm and the inner diameter is 60 mm, and the depth of the cross groove 13 on the inner wall is 2 mm and the width is 2 mm. The length of the inclinometer pipe 2 is 2000 mm, and it is fixed with screws after being extended through a PVC sleeve connection.

In this embodiment, the stainless steel plate 5 has a thickness of 2 mm, a width of 61 mm, and a length of 1000 mm.

In this embodiment, the connecting steel plate 6 has a thickness of 2 mm, a width of 10 mm, and a length of 40 mm.

In this embodiment, a fiber grating sensitive element 8 is welded at intervals of 500mm on the center line of the same side of the stainless steel plate 5 .

In this embodiment, the sleeve 3 is a tapered sleeve.

In this embodiment, a steel plate 14 is installed at a certain distance on the upper part of the PVC settlement pipe 1 to facilitate coordinated deformation of the PVC settlement pipe 1 and the soft ground.

In this embodiment, during on-site installation, the PVC inclinometer pipe 2 is first installed, and the bottom of the PVC inclinometer pipe 2 is required to be buried in the hard soil layer of the soft soil foundation for more than 1m, so as to ensure that the lower side of the PVC inclinometer pipe 2 does not shift. Drilling equipment is used for positioning drilling, and the drilled hole is kept vertical as much as possible. After the drilling reaches the design elevation, the PVC inclinometer pipe 2 covered with the sleeve 3 is put into the drilled hole, and the PVC inclinometer is placed at the same time. The cross notch 13 in the pipe 2 is perpendicular or parallel to the trend direction of the rock and soil mass; and the fiber grating sensing element 8 is welded on the stainless steel plate 5, and each stainless steel plate 5 is connected and fixed by connecting the steel plate 6 and the bolt 7, and the stainless steel plate 5 The fiber grating sensing element 8 on the plate 5 is connected in series through the optical cable 11, and then the stainless steel plate 5 is inserted into the cross groove 13 of the PVC inclinometer pipe 2; the PVC settlement pipe 1 is installed again, and the PVC settlement pipe 1 is buried in the soft ground In the surface layer, the stainless steel plate 5 used to be placed in the PVC settlement tube 1 is connected and fixed by connecting the steel plate 6 and the bolt 7, the fiber grating sensing element 8 is welded on the stainless steel plate 5, and the optical fiber on the stainless steel plate 5 The grating sensing element 8 is connected in series through the optical cable 11, and then the stainless steel plate 5 is put into the PVC measuring settling pipe 1, and is aligned with the cross groove 13 of the PVC measuring settling pipe 1 when placed, and then each section of PVC measuring settling pipe is placed with a PVC sleeve. The settling tube 1 is connected and fixed by screws, and the stainless steel plate 5 in the PVC measuring settling tube 1 is on the same horizontal line, and finally the protective cover 4 is respectively covered on the upper part of the PVC inclined measuring tube 2 and the two ends of the PVC measuring settling tube 1 to prevent The entry of impurities will affect the accuracy of the measurement; in addition, a hinge 10 is installed at the connection between the PVC inclinometer pipe 2 and the PVC settlement pipe 1, and the optical cable 11 passes through the hinge 10 to connect with the fiber grating demodulator 12, and then the PVC A steel plate 14 is placed on the top of the settling pipe 1 every certain distance, and when the soft ground subsides, the steel plate 14 is driven to settle, and the PVC settling pipe 1 is deformed thereupon.

Before installing the PVC settlement pipe 1 on site, dig out a detection ditch with a width of 70 mm and a height of 70 mm and the same length as the PVC settlement pipe 1 on the surface of the soft soil foundation, and then place the installed PVC settlement pipe 1 on the test site. ditch.

The fiber grating demodulator 12 is used to detect the wavelength change of each fiber grating sensitive element 8, and after considering the temperature compensation, the strain at the measuring point of each stainless steel plate 5 is given, and then the formula relationship between strain and deflection is used to calculate each The deflection value at one point, because the PVC inclinometer pipe 2 and the PVC inclinometer pipe 1 are connected to each other, so that the PVC inclinometer pipe 1 and the PVC inclinometer pipe 2 have a rotation angle and a horizontal displacement, so each of the PVC inclinometer pipe 1 must be The measured point value is corrected.

The working principle of the soft soil foundation settlement sensor is:

When the soft soil foundation settles and deforms, the soil will squeeze the PVC settlement pipe 1 downward and the PVC inclinometer pipe 2 to the left, and the PVC settlement pipe 1 and the PVC inclinometer pipe 2 will deform together with the soil. The stainless steel plate 5 installed in the PVC settlement tube 1 and the PVC inclinometer tube 2 is also deformed accordingly, so it is determined that the deformation in the soft soil foundation is consistent with the deformation in the stainless steel plate 5, and through the bending theory of the beam , use the differential calculation method to deduce the relationship between the strain value and the deflection value of each fiber grating sensitive element 8 measuring point, and then use the fiber grating demodulator 12 to measure the surface strain value of each measuring point, and calculate each The deflection value of the fiber grating sensitive element 8 measuring point can know the settlement of the soft soil foundation.

The basic principles and main features of the present utility model and the advantages of the present utility model have been shown and described above. Those skilled in the art should understand that the utility model is not limited by the above-mentioned embodiments. The above-mentioned embodiments and descriptions only illustrate the principle of the utility model. Without departing from the spirit and scope of the utility model, the utility model The new model also has various changes and improvements, and these changes and improvements all fall within the scope of the claimed utility model. The scope of protection required by the utility model is defined by the appended claims and their equivalents.

Claims (9)

1. a soft soil base sedimentation sensor based on fiber grating sensing technology, including surveying sedimentation pipe, inclinometer pipe, rustless steel Plate, fiber grating sensing element, optical cable and fiber Bragg grating (FBG) demodulator, it is characterised in that survey sedimentation pipe and be mutually perpendicular to inclinometer pipe Connect and be embedded in soft soil foundation, and survey sedimentation pipe and inclinometer pipe inwall have for fix polylith corrosion resistant plate ten Word notch, corrosion resistant plate thickness is consistent with cross width of rebate；And on corrosion resistant plate, it is welded with multiple fiber grating sensing element, Fiber grating sensing element is connected with fiber Bragg grating (FBG) demodulator by optical cable；On survey sedimentation pipe top, steel plate is installed simultaneously.

A kind of soft soil base sedimentation sensor based on fiber grating sensing technology the most according to claim 1, its feature It is, surveys sedimentation pipe and the inclinometer pipe place of being mutually connected vertically is provided with hinge.

A kind of soft soil base sedimentation sensor based on fiber grating sensing technology the most according to claim 1, its feature Being, surveying sedimentation pipe is that PVC material is made with inclinometer pipe, and survey sedimentation pipe and inclinometer pipe external diameter are 65mm, and internal diameter is 60mm.

A kind of soft soil base sedimentation sensor based on fiber grating sensing technology the most according to claim 1, its feature Being, cross depth of rebate is 2mm, wide 2mm.

A kind of soft soil base sedimentation sensor based on fiber grating sensing technology the most according to claim 1, its feature Being, surveying sedimentation pipe two ends and be respectively arranged with protective cover, inclinometer pipe top is provided with protective cover, and bottom is provided with sleeve.

A kind of soft soil base sedimentation sensor based on fiber grating sensing technology the most according to claim 5, its feature Being, sleeve is tapered sleeve.

A kind of soft soil base sedimentation sensor based on fiber grating sensing technology the most according to claim 1, its feature Being, polylith corrosion resistant plate is fixed by the two-sided connection of junction steel plate.

A kind of soft soil base sedimentation sensor based on fiber grating sensing technology the most according to claim 1, its feature Being, on corrosion resistant plate, the same side position of center line welds a fiber grating sensing element every 500mm.

A kind of soft soil base sedimentation sensor based on fiber grating sensing technology the most according to claim 1, its feature Being, fiber grating sensing element is connected with optical cable by adpting flange.