CN111576498B

CN111576498B - Gravel pile model test device based on transparent soil and FBG (fiber Bragg Grating) optical fiber sensor

Info

Publication number: CN111576498B
Application number: CN202010297848.0A
Authority: CN
Inventors: 高俊丽; 王琴月
Original assignee: University of Shanghai for Science and Technology
Current assignee: University of Shanghai for Science and Technology
Priority date: 2020-04-16
Filing date: 2020-04-16
Publication date: 2021-08-27
Anticipated expiration: 2040-04-16
Also published as: CN111576498A

Abstract

The invention provides a gravel pile model test device based on transparent soil and FBG (fiber Bragg Grating) optical fiber sensors, and relates to the technical field of geotechnical engineering. This gravel pile model test device based on transparent soil and FBG optical fiber sensor, including the workstation, be provided with a transport section of thick bamboo in the transparent soil, gravel pile surface bonding has FBG optical fiber sensor's front end and FBG optical fiber sensor's rear end and SM125 fiber demodulation appearance interconnect, workstation outer front end one side is provided with the CCD camera corresponding with transparent mold box position. Can gather pile shaft through FBG fiber sensor and meet an emergency and distribute, can obtain the motion form of soil around the gravel pile through the PIV software, bury gravel pile and FBG fiber sensor in transparent soil through a transport section of thick bamboo, labour saving and time saving, and FBG fiber sensor is not fragile, and make the bottom plate keep the atress balanced through door type steelframe and removal steelframe moreover, can be steady when loading the weight apply static loading to transparent soil, be worth wideling popularize.

Description

Gravel pile model test device based on transparent soil and FBG (fiber Bragg Grating) optical fiber sensor

Technical Field

The invention relates to the technical field of geotechnical engineering, in particular to a gravel pile model test device based on transparent soil and FBG optical fiber sensors.

Background

The gravel pile is a composite foundation reinforcing pile made of gravel as a main material, and the gravel pile, the sand pile and the like are collectively called as a discrete pile or a coarse-grained soil pile abroad, the discrete pile refers to a pile without bonding strength, a composite foundation consisting of the discrete pile such as the gravel pile or the sand pile and soil among the piles can also be called as a discrete pile composite foundation, and the composite foundations of the gravel pile, the sand pile, the slag soil pile and the like which are widely applied at home and abroad at present are all discrete pile composite foundations.

FBGs are known as Fiber Bragg gratings, i.e., gratings with periodic spatial phase distribution formed in the core, and essentially function to form a narrow-band (transmissive or reflective) filter or mirror in the core, which can be used to fabricate many unique optical Fiber devices.

At present, the optical fiber sensing technology is widely applied to monitoring engineering of various structures and rock-soil bodies, but a test model which can carry out simulation analysis on strain distribution of a pile body and motion forms of soil around a gravel pile in the compression process of the gravel pile does not exist, the optical fiber sensor is a very fragile precise electronic element, the optical fiber sensor is usually buried after the soil body model is dug out by hands when the optical fiber sensor is placed in the soil body model, time and labor are wasted, the optical fiber sensor is also easily damaged, monitoring data is lost, and the optical fiber sensor is difficult to keep stable by directly loading weights by hands when static loading is applied to the soil body model, and collected monitoring data can be influenced.

Disclosure of Invention

Technical problem to be solved

Aiming at the defects of the prior art, the invention provides a gravel pile model test device based on transparent soil and FBG optical fiber sensors, which solves the problems of a test device for simulating a gravel pile model, safe placement of the optical fiber sensors into a soil body model and stable force application on the soil body model.

(II) technical scheme

In order to achieve the purpose, the invention is realized by the following technical scheme: the gravel pile model test device based on the transparent soil and the FBG optical fiber sensor comprises a workbench, the two sides of the top of the workbench are fixedly connected with the two ends of the bottom of the door-shaped steel frame, the interior of the door-shaped steel frame is hollow, the two sides of the inner side of the door-shaped steel frame are fixedly connected with slide rails which are connected with the two ends of the movable steel frame in a sliding way, the middle position of the bottom of the movable steel frame is connected with the top end of the rigid rod through a bolt, the bottom end of the rigid rod is fixedly connected with a bottom plate, a transparent model box is arranged in the middle of the top of the workbench, transparent soil is arranged in the transparent model box, a conveying cylinder is arranged in the transparent soil, a gravel pile is arranged in the conveying cylinder, the surface of the gravel pile is adhered with the front end of the FBG optical fiber sensor, the rear end of the FBG optical fiber sensor is mutually connected with the SM125 optical fiber demodulator, and a CCD camera corresponding to the transparent model box is arranged on one side of the outer front end of the workbench.

Preferably, bottom both ends all are provided with pneumatic cylinder and the equal fixed connection in pneumatic cylinder bottom at the workstation top in the door type steelframe, all be provided with hydraulic stem and hydraulic stem top in the pneumatic cylinder and all upwards extend and fixed connection in top ejector pad bottom, the top of ejector pad all is provided with the equal sliding connection in spacing groove and the spacing groove and has the balancing weight.

Preferably, two fixing supports are fixedly connected to two sides of the top of the door-shaped steel frame, first fixed pulleys corresponding to the second lifting lugs are rotatably connected to the bottoms of the fixing supports at two outer side positions of the door-shaped steel frame through rotating shafts, second fixed pulleys corresponding to the first lifting lugs are rotatably connected to the bottoms of the fixing supports at two inner side positions of the door-shaped steel frame through rotating shafts, through holes corresponding to the second fixed pulleys are formed in two sides of the bottom of the top of the door-shaped steel frame, first lifting lugs corresponding to the through holes are fixedly connected to two sides of the top of the movable steel frame, the second lifting lugs are fixedly connected to the tops of the counterweight blocks, the top of the counterweight blocks is fixedly connected to one ends of the steel wires, and the other ends of the steel wires are fixedly connected to the tops of the first lifting lugs after passing through the through holes and bypassing the tops of the first fixed pulleys and the second fixed pulleys.

Preferably, the four corners of the bottom of the transparent model box are fixedly connected with universal wheels.

Preferably, the equal fixedly connected with first in command in transport section of thick bamboo top both sides, equal sliding connection has the slide bar in the equal fixedly connected with fixed sleeve in both sides top and the fixed sleeve in the transport section of thick bamboo, the equal fixedly connected with second in slide bar top handle, transport section of thick bamboo bottom both sides all are connected with the drill bit through the hinge rotation, the equal fixedly connected with in the inboard top of drill bit rotates the connector and rotates the connector top and all rotate and connect in the slide bar bottom.

Preferably, the bottom of the CCD camera is fixedly connected with a triangular support.

Preferably, the transparent soil is a mixture of transparent pore fluid and transparent fused silica sand, the refractive index of the pore fluid is equal to that of the fused silica sand, and the sum of the masses of the movable steel frame, the bolt, the rigid rod, the bottom plate and the two first lifting lugs is equal to the sum of the masses of the two balancing weights and the two second lifting lugs.

The working principle is as follows: before a gravel pile model test is carried out, a transparent model box is moved to a position, opposite to a bottom plate, of a workbench, the position, opposite to the transparent model box, of a CDD camera is adjusted through a triangular support, then the front end of an FBG optical fiber sensor is adhered to the gravel pile through an adhesive tape and the gravel pile is placed in a conveying cylinder, then a first handle is held to vertically insert the conveying cylinder into transparent soil in the transparent model box, the gravel pile is embedded in the transparent soil to a certain depth, then a second handle is pressed and a sliding rod is pushed to slide downwards in the fixing sleeve, further the inner side of a drill bit is pushed through a rotating connector, the drill bits on two sides rotate around a hinge and are opened, then the conveying cylinder is slowly pulled upwards to embed the gravel pile and the FBG optical fiber sensor in the transparent soil, finally the rear end of the FBG optical fiber sensor is connected with an SM25 optical fiber demodulation instrument, and when the gravel pile model test is carried out, two first hydraulic cylinders are started to enable a first hydraulic rod to move upwards and push two counter weights to push the two counter weights through a pushing block And then the movable steel frame moves upwards along with the movable steel frame, so that the two steel wires slide on the first fixed pulley and the second fixed pulley, the movable steel frame moves downwards through the sliding steel wires, and the bottom plate at the bottom of the rigid rod is driven to move onto the transparent soil in the transparent model box along with the sliding steel wires, because the sum of the mass of the movable steel frame, the bolts, the rigid rod, the bottom plate and the two first lifting lugs is equal to the sum of the mass of the two balancing weights and the mass of the two second lifting lugs, the bottom plate does not apply force on the transparent soil, when a gravel pile model test is carried out, weights are placed on the bottom plate according to the static loading requirement, the mass of the weights can be completely applied on the transparent soil through the bottom plate, so that the static loading is stably applied on the transparent soil, and therefore pile body strain distribution data in the gravel pile can be acquired through the FBG optical fiber sensor and transmitted to the SM125 optical fiber sensor for data analysis, and meanwhile, the CCD camera can also acquire photos when the static loading is applied, and analyzing the picture through PIV software to obtain the motion form of the soil around the gravel pile.

(III) advantageous effects

The invention provides a gravel pile model test device based on transparent soil and an FBG optical fiber sensor. The method has the following beneficial effects:

1. according to the invention, the FBG optical fiber sensor and the CCD camera are arranged in the gravel pile test model, the strain distribution of the pile body in the compression process of the gravel pile can be acquired through the FBG optical fiber sensor, and the motion form of the soil around the gravel pile in the compression process can be obtained by analyzing the picture shot by the CCD camera through PIV software.

2. According to the invention, the gravel pile and the FBG optical fiber sensor are embedded in the transparent soil through the conveying cylinder, so that time and labor are saved, and the FBG optical fiber sensor is not extruded by the transparent soil in the embedding process, is not easy to damage and is safer.

3. According to the invention, the door-shaped steel frame and the movable steel frame are arranged on the workbench, and the balancing weight is arranged in the door-shaped steel frame, so that the sum of the mass of the movable steel frame, the bolt, the rigid rod, the bottom plate and the two first lifting lugs is equal to the sum of the mass of the two balancing weights and the mass of the two second lifting lugs, thus the bottom plate can be kept stressed uniformly through the door-shaped steel frame and the movable steel frame, the bottom plate is more stable when placed on the transparent soil and can not exert force on the transparent soil, then the mass of the weights placed on the bottom plate can be completely exerted on the transparent soil during a test, and thus static force loading is stably exerted on the transparent soil, the monitoring data error caused by the instability of the loaded weights during the test is prevented, and the door-shaped steel frame is worth being widely popularized.

Drawings

FIG. 1 is a schematic front view of the present invention;

FIG. 2 is a side schematic view of the present invention;

FIG. 3 is a schematic view of the internal structure of the portal steel frame of the present invention;

FIG. 4 is an enlarged view taken at A of FIG. 3 in accordance with the present invention;

FIG. 5 is an enlarged view taken at B of FIG. 3 in accordance with the present invention;

FIG. 6 is a schematic view of the interior of the mold box of the present invention;

FIG. 7 is an enlarged view of the invention at C of FIG. 6;

fig. 8 is an enlarged view of the invention at D in fig. 6.

Wherein, 1, a workbench; 2. a portal steel frame; 3. a slide rail; 4. moving the steel frame; 5. a bolt; 6. a rigid rod; 7. a base plate; 8. a transparent mold box; 9. transparent soil; 10. a universal wheel; 11. an FBG optical fiber sensor; 12. SM125 fiber optic demodulator; 13. a CCD camera; 14. a triangular bracket; 15. a hydraulic cylinder; 16. a hydraulic lever; 17. a balancing weight; 18. a steel wire; 19. fixing a bracket; 20. a rotating shaft; 21. a first fixed pulley; 22. a second fixed pulley; 23. a through hole; 24. a first lifting lug; 25. a second lifting lug; 26. pushing the pushing block; 27. a limiting groove; 28. a delivery cartridge; 29. a first handle; 30. a second handle; 31. fixing the sleeve; 32. a slide bar; 33. gravel piles; 34. rotating the connector; 35. a hinge; 36. a drill bit.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Example (b):

as shown in fig. 1-8, an embodiment of the present invention provides a gravel pile model testing apparatus based on transparent soil and FBG fiber sensors, which includes a workbench 1, two sides of the top of the workbench 1 are fixedly connected to two ends of the bottom of a door-shaped steel frame 2, the door-shaped steel frame 2 is hollow, two sides of the inner side of the door-shaped steel frame 2 are fixedly connected with slide rails 3, the slide rails 3 are slidably connected to two ends of a movable steel frame 4, the movable steel frame 4 can slide up and down in the slide rails 3, the middle position of the bottom of the movable steel frame 4 is connected to the top of a rigid rod 6 through a bolt 5, the bottom of the rigid rod 6 is fixedly connected with a bottom plate 7, the bottom plate 7 is used for loading weights, the middle position of the top of the workbench 1 is provided with a transparent model box 8, the transparent model box 8 is provided with transparent soil 9, the transparent soil 9 is used for simulating soil around a gravel pile 33, the transparent soil 9 is provided with a conveying cylinder 28, the gravel pile 33 is provided in the conveying cylinder 28, the front end of the FBG optical fiber sensor 11 is adhered to the surface of the gravel pile 33, the rear end of the FBG optical fiber sensor 11 is connected with the SM125 optical fiber demodulator 12, one side of the front end outside the workbench 1 is provided with a CCD camera 13 corresponding to the position of the transparent model box 8, the front end of the FBG optical fiber sensor 11 is adhered to the gravel pile 33 by an adhesive tape before the test, the gravel pile 33 and FBG optical fiber sensor 11 are then safely buried in the transparent soil 9 with the delivery cylinder 28, the rear end of the FBG optical fiber sensor 11 is connected with the SM125 optical fiber demodulator 12 after the delivery cylinder 28 is taken out, wherein, the FBG optical fiber sensor 11 can collect the strain distribution data of the pile body in the compression process of the gravel pile 33 and transmit the data to the SM125 optical fiber demodulator 12 for data analysis, and the CCD camera 13 can collect the photos in the compression process, the picture is then analyzed by the PIV software to obtain the movement state of the transparent soil 9 around the gravel pile 33.

Bottom both ends all are provided with pneumatic cylinder 15 and the equal fixed connection in the 1 top of workstation in door type steelframe 2, all be provided with hydraulic stem 16 and hydraulic stem 16 top in the pneumatic cylinder 15 and all upwards extend and fixed connection in ejector pad 26 bottom, ejector pad 26 top all is provided with equal sliding connection in spacing groove 27 and the spacing groove 27 and has balancing weight 17, start-up pneumatic cylinder 15 and can make 16 rebound of hydraulic stem, and promote also along with it the rebound through ejector pad 26.

Two fixed bolster 19 of equal fixedly connected with in top both sides in door type steelframe 2, the fixed bolster 19 bottom of two outside positions all rotates through pivot 20 in door type steelframe 2 and is connected with the first fixed pulley 21 corresponding with second lug 25, the fixed bolster 19 bottom of two inboard positions all rotates through pivot 20 in door type steelframe 2 and is connected with the second fixed pulley 22 corresponding with first lug 24, the bottom both sides at door type steelframe 2 top all are provided with the through-hole 23 corresponding with second fixed pulley 22, the equal fixedly connected with in 4 top both sides of removal steelframe and the first lug 24 corresponding with through-hole 23, the equal fixed connection in one end at steel wire 18 in the top of the equal fixedly connected with second lug 25 in balancing weight 17 top and second lug 25, the steel wire 18 other end is around the top of first fixed pulley 21 and second fixed pulley 22 and runs through-hole 23 after fixed connection is on the top of first lug 24.

The universal wheels 10 are fixedly connected to four corners of the bottom of the transparent model box 8, and the universal wheels 10 are used for conveniently moving the transparent model box 8 and adjusting the position of the transparent model box 8.

The two sides of the top of the conveying cylinder 28 are fixedly connected with a first handle 29, the tops of the two sides in the conveying cylinder 28 are fixedly connected with a fixed sleeve 31, the inside of the fixed sleeve 31 is slidably connected with a sliding rod 32, the top ends of the sliding rods 32 are fixedly connected with a second handle 30, the two sides of the bottom end of the conveying cylinder 28 are rotatably connected with drill bits 36 through hinges 35, the tops of the inner sides of the drill bits 36 are fixedly connected with a rotating connector 34, the top ends of the rotating connector 34 are rotatably connected with the bottom ends of the sliding rods 32, when the gravel pile 33 is buried in the transparent soil 9, the gravel pile 33 and the FBG optical fiber sensor 11 are firstly placed in the conveying cylinder 28, then the first handle 29 is held to vertically insert the conveying cylinder 28 into the transparent soil 9, the second handle 30 is pressed and the sliding rods 32 are pushed to slide in the fixed sleeve 31, the rotating connector 34 is pushed through the bottom ends of the sliding rods 32 to enable the drill bits 36 on the two sides of the bottom of the conveying cylinder 28 to rotate around the hinges 35 and to be opened, the gravel pile 33 and the FBG fiber sensor 11 can then be embedded in the transparent soil 9 by slowly pulling the delivery cylinder 28 upwards.

The bottom of the CCD camera 13 is fixedly connected with a triangular support 14, and the triangular support 14 is used for enabling the CCD camera 13 to be aligned to the transparent model box 8 and facilitating image information acquisition.

The transparent soil 9 is a mixture of transparent pore fluid and transparent fused silica sand, the refractive index of the pore fluid is equal to that of the fused silica sand, the transparent soil 9 made of the transparent fused silica sand and the pore fluid with the same refractive index is convenient for observing and collecting image information, and can also prevent the FBG optical fiber sensor 11 from collecting data information due to different refractive indexes, the sum of the masses of the movable steel frame 4, the bolt 5, the rigid rod 6, the bottom plate 7 and the two first lifting lugs 24 is equal to the sum of the masses of the two balancing weights 17 and the two second lifting lugs 25, so that the bottom plate 7 can keep a state of being balanced in vertical stress, and therefore, the bottom plate 7 does not exert force on the transparent soil 9 during testing, and can exert the mass of the loaded weights on the transparent soil 9 completely and stably.

Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.

Claims

1. Gravel pile model test device based on transparent soil and FBG optical fiber sensor, including workstation (1), its characterized in that: the workbench (1) is fixedly connected with the two ends of the bottom of a portal steel frame (2) at the two sides of the top of the workbench and is internally hollow in the portal steel frame (2), the two sides of the inner side of the portal steel frame (2) are fixedly connected with sliding rails (3), the sliding rails (3) are slidably connected with the two ends of a movable steel frame (4), the middle position of the bottom of the movable steel frame (4) is connected with the top end of a rigid rod (6) through bolts (5), the bottom end of the rigid rod (6) is fixedly connected with a bottom plate (7), the middle position of the top of the workbench (1) is provided with a transparent model box (8), transparent soil (9) is arranged in the transparent model box (8), a conveying cylinder (28) is arranged in the transparent soil (9), a gravel pile (33) is arranged in the conveying cylinder (28), the surface of the gravel pile (33) is adhered with the front end of an FBG optical fiber sensor (11) and the rear end of the FBG optical sensor (11) is connected with an SM125 optical fiber demodulation instrument (12), and a CCD camera (13) corresponding to the transparent model box (8) is arranged on one side of the outer front end of the workbench (1).

2. The gravel pile model test device based on transparent soil and FBG optical fiber sensors as claimed in claim 1, wherein: bottom both ends all are provided with pneumatic cylinder (15) and the equal fixed connection in workstation (1) top in door type steelframe (2) bottom, all be provided with hydraulic stem (16) and hydraulic stem (16) top in pneumatic cylinder (15) and all upwards extend and fixed connection in top ejector pad (26) bottom, equal sliding connection has balancing weight (17) in top ejector pad (26) top all is provided with spacing groove (27) and spacing groove (27).

3. The gravel pile model test device based on transparent soil and FBG optical fiber sensors as claimed in claim 2, wherein: two sides of the inner top of the door-shaped steel frame (2) are fixedly connected with two fixed supports (19), the bottoms of the fixed supports (19) at two outer side positions in the door-shaped steel frame (2) are rotatably connected with first fixed pulleys (21) corresponding to the second lifting lugs (25) through rotating shafts (20), the bottoms of the fixed supports (19) at two inner side positions in the door-shaped steel frame (2) are rotatably connected with second fixed pulleys (22) corresponding to the first lifting lugs (24) through rotating shafts (20), two sides of the bottom of the top of the door-shaped steel frame (2) are respectively provided with through holes (23) corresponding to the second fixed pulleys (22), two sides of the top of the movable steel frame (4) are fixedly connected with first lifting lugs (24) corresponding to the through holes (23), the top of the balancing weight (17) is fixedly connected with second lifting lugs (25), and the top of the second lifting lugs (25) are fixedly connected to one end of the steel wire (18), the other end of the steel wire (18) winds the tops of the first fixed pulley (21) and the second fixed pulley (22), penetrates through the through hole (23), and is fixedly connected to the top end of the first lifting lug (24).

4. The gravel pile model test device based on transparent soil and FBG optical fiber sensors as claimed in claim 1, wherein: the four corners of the bottom of the transparent model box (8) are fixedly connected with universal wheels (10).

5. The gravel pile model test device based on transparent soil and FBG optical fiber sensors as claimed in claim 1, wherein: carry a section of thick bamboo (28) the equal fixedly connected with first in command (29) in both sides top, equal sliding connection has slide bar (32) in the equal fixedly connected with fixed sleeve (31) in both sides top and fixed sleeve (31) in a section of thick bamboo (28), equal fixedly connected with second in slide bar (32) top (30), carry a section of thick bamboo (28) bottom both sides all to rotate through hinge (35) and be connected with drill bit (36), the equal fixedly connected with in drill bit (36) inboard top rotates connector (34) and rotates connector (34) top and all rotates and connect in slide bar (32) bottom.

6. The gravel pile model test device based on transparent soil and FBG optical fiber sensors as claimed in claim 1, wherein: the bottom of the CCD camera (13) is fixedly connected with a triangular support (14).

7. The gravel pile model test device based on transparent soil and FBG optical fiber sensors as claimed in claim 3, wherein: the transparent soil (9) is a mixture of transparent pore fluid and transparent fused silica sand, the refractive index of the pore fluid is equal to that of the fused silica sand, and the sum of the masses of the movable steel frame (4), the bolt (5), the rigid rod (6), the bottom plate (7) and the two first lifting lugs (24) is equal to the sum of the masses of the two balancing weights (17) and the two second lifting lugs (25).