CN107560776B - A joint test method for multi-interface shear stress of non-metallic anti-floating anchor - Google Patents

Abstract

The invention belongs to the technical field of civil engineering in-situ tests, and relates to a multi-interface shear stress joint test method for a non-metal anti-floating anchor rod, which is used for synchronously measuring the axial force and the shear stress of a rod body, an anchoring body and an interface of the rock body and the anchoring body of the non-metal anti-floating anchor rod in real time, and simultaneously obtaining the pull-up amount of the rod body and the anchoring body by using a novel test device so as to research the mechanical transmission mechanism and the deformation characteristic of the anti-floating anchor rod; the method has the advantages of simple and convenient process, simple structure, high testing precision, strong operability, direct and accurate numerical value result, capability of obtaining multi-interface shear stress of the non-metal anti-floating anchor rod, and strong applicability and feasibility.

Description

A joint test method for multi-interface shear stress of non-metallic anti-floating anchor

Technical field:

The invention belongs to the technical field of in-situ testing of civil engineering, and relates to a multi-interface shear stress joint test method of a non-metallic anti-floating anchor, which is simple in operation and accurate in testing, and can simultaneously obtain the body of the non-metallic anti-floating anchor, the anchor body and the second The axial force and shear stress of the two interfaces (rock mass and anchor body interface) provide a basis for the research and application of non-metallic anchor rods.

Background technique:

Glass fiber reinforced polymer (Glass Fiber Reinforced Polymer, GFRP) bolts have the advantages of high tensile strength, good corrosion resistance, low relaxation and strong anti-electromagnetic interference ability, and their application in the field of anti-floating engineering can not only solve the traditional The problem of serious corrosion and aging of metal anchors in offshore engineering and adverse geological environments can also break the restriction that traditional metal anchors cannot be used for anti-floating in the construction of underground rail transit. It can be seen that the application of non-metallic anti-floating anchors The research has strong applicability and advanced nature.

In the anti-floating anchor structure, the rod body, the anchor body and the surrounding rock and soil jointly play a structural anti-floating role. Their respective bearing capacity, mutual mechanical transmission mechanism and bonding performance determine the failure mode and bearing capacity of the structure. size. In the existing research on the stress of GFRP anti-floating anchors, the stress test device is generally used to obtain the distribution form and size of the axial stress and shear stress of the anchor during the pulling process of the anchor, and to understand the loading mechanism of the anchor. Mechanical properties of bonded interfaces. Therefore, a joint test method for multi-interface shear stress of non-metallic anti-floating anchor rods is sought, using more advanced self-compensating miniature Fiber Bragg Gating (FBG) strain sensors to simultaneously arrange self- Compensate the miniature FBG strain sensor string, and obtain the strain change during the bolt pulling process, so as to obtain the corresponding axial force and shear stress value, so as to comprehensively study the mechanical transmission mechanism and anchoring performance of the GFRP anti-floating bolt.

Invention content:

The purpose of the present invention is to overcome the shortcoming that prior art exists, seek to design a kind of non-metallic anti-floating bolt multi-interface shear stress joint test method, realize synchronous real-time measurement nonmetallic anti-floating bolt body, anchor body and the second interface ( The axial force and shear stress of the interface between the rock mass and the anchoring body), and the uplift of the rod body and the anchoring body are obtained by using a new test device, and then the mechanical transmission mechanism and deformation characteristics of the anti-floating anchor are studied.

In order to achieve the above object, the present invention adopts the multi-interface shear stress joint testing device of non-metallic anti-floating anchor rod to realize, and its specific process is:

(1) Put the anchor rod body implanted with the self-compensating miniature FBG strain sensor string into the anchor rod bracket every 0.5m, and tighten the fixing nuts to ensure that the anchor rod bracket is firm and stable in the anchoring section of the rod body and does not move up and down The survival rate of the self-compensating miniature FBG strain sensor string in the rod body is tested before and after being implanted in the anchor rod body, and the survival rate shall not be lower than 90%;

(2) Fix the hard steel wire on the bolt bracket according to the requirements, and ensure that the hard steel wire is respectively located in the middle position of the mortar anchor in the radial direction and at the second interface. The second interface is the outer surface of the anchor and the surrounding rock. On the contact surface of the soil layer, the self-compensating miniature FBG strain sensor string in the anchor body prefabricated in advance and the second interface self-compensating miniature FBG strain sensor string are firmly tied to the hard steel wire with binding wires, and the fiber grating demodulation is turned on at this time Instrument to test the survival rate of the self-compensating miniature FBG strain sensor string in the anchor body and the second interface self-compensating miniature FBG strain sensor string, the survival rate shall not be lower than 90%;

(3) Lower the above-mentioned prefabricated anchor rods into the drilled anchor rod holes, and pour commercial mortar into them. After curing for 28 days and reaching 75% of the required strength, the self-made displacement testing device is symmetrically bonded with structural glue On the anchor rod 0.5cm above the surface of the anchor, make sure it is stable and vertical;

(4) Place the two I-shaped steel support beams symmetrically on both sides of the anchor rod body, so that they are located on the fine stone concrete cushion, and ensure that the distance between them is 25-30cm, so that the anchor rod body is located on the two I-shaped steel beams. The center of the anchor rod is guaranteed to be tensioned; the through-center reaction beam passes through the anchor rod body and is placed on the I-beam support beam to ensure that the centroid of the through-center reaction beam coincides with the anchor body, and the Install the third core-through steel backing plate, the through-core jack, the second through-core steel backing plate, the load sensor, and the first through-core steel backing plate from bottom to top on the central reaction beam to ensure that each component is perpendicular to the anchor rod body , the centroid is coaxial with the anchor rod, so that the anchor rod axis is under tension during the loading process;

(5) Fix the stress diffusion tray on the anchor rod body through threads, and then insert the locking anchor. In order to provide greater reaction force, several locking anchors can be connected in series according to actual needs and locked in the anchor. AB glue with good fluidity is dripped between the thread gap between the tool and the anchor rod body, so as to ensure that the anchor has sufficient locking force and prevent shear damage caused by locking the anchor tool and the stress diffusion tray when the load is applied;

(6) Install the fiber grating displacement gauge vertically on the self-made displacement test device and the exposed surface of the anchor, and install the magnetic base of the fiber grating displacement gauge on the reference beam to ensure that it does not shake; then install the self-compensating miniature FBG strain sensor in the rod body The series, self-compensating miniature FBG strain sensor series in the anchor body, the second interface self-compensating miniature FBG strain sensor series and the external connector of the fiber grating displacement meter are connected to the fiber grating demodulator, and the relevant parameters are adjusted and set to ensure accurate and stable acquisition Relevant data, so far the non-metallic anti-floating anchor multi-interface shear stress test device has been installed, and the through-hole jack and load sensor have been calibrated to ensure the accuracy of the load applied at each level during the test;

(7) Use a through-hole jack to load, and control the rise of the through-jack to less than 10cm. The reaction force of the through-jack causes the uplift of the anchor rod body and the anchor body, and automatically records it with a fiber grating displacement meter. The measured uplift of the anchor rod body and anchor body under various loads S _rod and S _anchor are substituted into the formula (1), that is, the relative slippage of the anchor rod and anchor body is obtained,

S＝(S _Rod -S _{Rod Bomb} )－(S _Anchor -S _{Anchor Bomb} ) (1)

In the formula: S _rod is the displacement of the rod body measured in the test (mm); S _{rod elastic} is the elastic elongation of the rod anchorage section (mm); S _anchor is the displacement of the anchor body measured in the test (mm); S _anchor is the anchorage Body elastic elongation (mm), because the calculation value of S- _{rod bomb} and S _{-anchor bomb} is relatively small, it can be ignored;

Substituting the strain change values at each position of the rod body, the anchor body and the second interface measured by the fiber grating demodulator into the formula (2), the axial force at any position of the rod body, the anchor body and the second interface can be obtained,

N _i =πD ² EΔε/4 (2)

In the formula: N _i is the axial force (kN) at any section i of the measured structure (rod body, anchor body and the second interface); E is the elastic modulus of the measured structure (GPa); Δε is the measured structure (rod body, anchor body and the second interface) strain variation, obtained by formula (3); D is the diameter (mm) of the structure to be measured, about the value of D: for the anchor rod body, take the diameter of the rod body, For the diameter of the anchor at the second interface, for the inside of the anchor, take twice the horizontal distance from the centroid of the rod body to the self-compensating miniature FBG strain sensor string in the anchor,

Δε=Δλ/K (3)

In the formula: Δλ is the central wavelength change (nm); K is the strain sensitivity coefficient of the self-compensating miniature FBG strain sensor.

Put the axial force values at each position of the rod body, the anchor body and the second interface calculated by the formula (2) into the formula (4), that is, the shear stress at each position of the rod body, the anchor body and the second interface can be obtained,

τ _i =(N _i -N _i-1 )/πDΔL (4)

In the formula: N _i is the axial force (kN) at a certain section i of the tested structure; N _i-1 is the axial force (kN) at the next section i-1 of the tested structure; The distance between sections _i -1 (mm); τi is the shear stress at the midpoint between the two sections, which is approximately considered as the average shear stress (MPa).

The main structure of the non-metallic anti-floating anchor multi-interface shear stress joint test device of the present invention includes an anchor rod body, a locking anchor, a stress diffusion tray, a first through-hole steel backing plate, a load sensor, and a second through-hole steel Backing plate, through-hole jack, third through-hole steel backing plate, through-hole reaction beam, self-made displacement test device, fiber grating displacement meter, magnetic table base, reference beam, I-beam support beam, anchor bracket, Self-compensating miniature FBG strain sensor strings in the rod, self-compensating miniature FBG strain sensor strings in the anchor body, self-compensating miniature FBG strain sensor strings in the second interface, commercial mortar, fiber grating demodulator, binding wire, hard steel wire and fine stone concrete The cushion layer; the anchor rod body is a solid glass fiber reinforced polymer anchor rod; the locking anchor and the stress diffusion tray match the size of the anchor rod body, the locking anchor is embedded and installed on the stress diffusion tray, the locking anchor and The stress diffusion trays are tightly connected with the anchor rod body through threaded coupling to provide reaction force; the first through-core steel backing plate, the load sensor, and the second through-core steel backing plate are installed sequentially below the stress diffusion tray from top to bottom 1. The through-core jack and the third through-core steel backing plate. The load sensor is externally connected to a pressure display to display the pulling force provided by the jack in real time; the third through-core steel backing plate is installed on the through-center reaction beam, and the displacement test device is self-made. It is welded by semi-circular steel pipe and angle iron, and is symmetrically bonded on the anchor body slightly higher than the surface of the anchor body with structural glue. The self-made displacement test device is perpendicular to the surface of the anchor body; two I-shaped symmetrically placed on both sides of the anchor body Steel support beam, the I-steel support beam is located on the fine stone concrete cushion, the distance between the two I-steel support beams is 25-30cm; On the seat beam, the self-made displacement test device and the exposed surface of the anchor body are installed vertically with the fiber grating displacement meter, and the magnetic base of the fiber grating displacement meter is installed on the reference beam. It is spliced with iron nuts, and the aperture size is controlled according to the size of the anchor rod body and evenly installed in the lower part of the anchor rod body to be implanted in the soil body; the self-compensating miniature FBG strain sensor string in the rod body, and the self-compensating miniature FBG strain sensor string in the anchor body and the second interface self-compensating miniature FBG strain sensor strings are produced according to the test requirements, wherein the self-compensating miniature FBG strain sensor strings in the rod body are implanted in the bolt body to be tested, the self-compensating miniature FBG strain sensor strings in the rod body, and the self-compensating miniature FBG strain sensor strings in the anchor body. The compensating miniature FBG strain sensor string and the second interface self-compensating miniature FBG strain sensor string are arranged according to the principle of dense top and sparse bottom, and three self-compensating miniature FBG strain sensors in each cross-section are at the same depth; In the drilled anchor hole, its strength is determined according to the strength level required by the test; the hard steel wire is fixed on the anchor bracket by wire binding, the self-compensating miniature FBG strain sensor string in the anchor body, and the second interface self-compensating miniature FBG strain sensor The string is firmly bound on the hard steel wire with binding wire; the fiber grating demodulator is connected with the fiber grating displacement meter, the self-compensating miniature FBG strain sensor string in the rod, and the self-compensating miniature FBG strain sensor in the anchor body. The sensor string is connected in series with the second interface self-compensating miniature FBG strain sensor.

The outer diameter of the self-compensating miniature FBG strain sensor adopted in the present invention is 1.5 mm, and the length is 10 mm. The quasi-distributed series connection is realized by using the optical fiber fusion technology, which can eliminate the influence of the temperature on the test data during the test drawing process; The force is not evenly distributed, and it is the largest near the bolt hole, and decreases significantly at a certain depth below the hole, and finally reduces to 0 (related to the physical and mechanical parameters of rock and soil). Therefore, three self-compensating miniature FBG strain sensor strings Take the layout form of dense top and sparse bottom, that is, within 1.5m from the orifice, the self-compensating miniature FBG strain sensors are arranged more densely, with a spacing of 0.1-0.3m, and at the lower end of 1.5m from the orifice, the self-compensating miniature FBG The arrangement of strain sensors is relatively sparse, and the spacing is controlled at 0.4-0.8m. The number of self-compensating miniature FBG strain sensors is determined by the anchorage length of the bolt; The risk of strain sensor damage is high, so when making self-compensating miniature FBG strain sensor strings, each self-compensating miniature FBG strain sensor is packaged with a miniature steel sleeve for protection, and the series optical fiber is armored for protection, and these forms of protection will not damage The nature of the self-compensating miniature FBG strain sensor itself affects; in order to accurately test the stress value at the GFRP anti-floating anchor body, the anchor body and the second interface, the self-compensating miniature FBG strain sensor used in the present invention needs to be connected in series and calibrated in the factory in advance In the bolt production workshop, a series of self-compensating miniature FBG strain sensors are implanted in the center of the rod body, and the two series of self-compensating miniature FBG strain sensors are accurately connected at the test site with matching centering brackets, hard steel wires and cable ties. Fixed at the center of the anchor and at the second interface.

The present invention uses a new type of non-metallic anchor supporting the stress diffusion tray and locking anchorage, and directly connects the non-metallic anchor tightly through the thread coupling method to provide the reaction force required for the test. The method is convenient and reliable, and overcomes the Non-metallic anti-floating anchors have poor shear resistance. In the previous anchor pulling device, a metal sleeve needs to be bonded to the loading end of the anchor, and the pull-out test is carried out by welding the iron plate anchor. Test method and device more complex disadvantages.

The present invention pastes a displacement test device near the anchor body to record the uplift of the rod, and at the same time pastes a self-made displacement test device (iron sheet) on the exposed surface of the anchor, and sets up a fiber grating displacement meter on the iron sheet to record the uplift of the anchor. Then the uplift of the anchor rod body relative to the anchor body can be obtained, and the interface bonding characteristics of the non-metallic anti-floating anchor rod can be better studied; in the structural anti-floating system, the bonding force between the anchor rod body and the anchor body The bearing capacity of the structure has a great influence. In the previous bolt displacement test, the displacement of the anchor head was generally recorded to reflect the deformation characteristics of the bolt, and the accuracy of the measurement data was low.

Compared with the prior art, the present invention adds the anti-floating anchor body and the second interface stress test to the existing test device, and cancels the non-metallic anchor bonded steel casing and welded through-core iron plate anchorage The method of pulling out is improved; the anti-floating bolt displacement test device is improved, and the test method for the uplift of the rod body and the anchor is proposed; the process is simple, the device structure is simple, the test accuracy is high, and the operability is strong. The results are direct and accurate, and the multi-interface shear stress of non-metal anti-floating anchors can be obtained, with strong applicability and feasibility.

Description of drawings:

Figure 1 is a schematic diagram of the main structure of the non-metallic anti-floating anchor multi-interface shear stress combined testing device of the present invention.

Fig. 2 is a structural diagram of the test device for the uplift measurement of the anchor rod body and the anchor body according to the present invention.

Fig. 3 is a structural diagram of a reaction force device composed of a locking anchor and a stress diffusion tray according to the present invention.

Fig. 4 is a schematic diagram of the installation structure of the self-compensating miniature FBG strain sensor string of the present invention.

Fig. 5 is a cross-sectional schematic diagram of the self-compensating miniature FBG strain sensor string of the present invention.

Fig. 6 is a schematic diagram of the structural principle of the anchor bracket according to the present invention.

Fig. 7 is a graph showing the relationship between the relative slippage between the anti-floating anchor body and the anchor body according to the embodiment of the present invention.

Fig. 8 is the variation curve of the axial force of the G8-28-1 anchor rod body with depth according to the embodiment of the present invention.

Fig. 9 is the variation curve of the shear stress of the G8-28-1 anchor body (first interface) with depth according to the embodiment of the present invention.

Fig. 10 is the variation curve of the internal axial stress with depth of the G8-28-1 anchor of the embodiment of the present invention.

Fig. 11 is the variation curve of the internal shear stress with depth of the G8-28-1 anchor of the embodiment of the present invention.

Fig. 12 is the variation curve of the axial stress of the second interface with the depth of the embodiment G8-28-1 of the present invention.

Fig. 13 is the variation curve of the second interface shear stress with depth in the embodiment of G8-28-1 of the present invention.

Detailed ways:

The present invention will be further described below through the embodiments and in conjunction with the accompanying drawings.

Example:

This embodiment is realized by using a multi-interface shear stress joint test device for non-metallic anti-floating anchor rods, and the specific process is as follows:

(1) Put the anchor rod body 1 implanted in the self-compensating miniature FBG strain sensor string 16 into the anchor rod bracket 15 every 0.5m, and tighten the fixing nuts to ensure that the anchor rod bracket 15 is firm and stable in the anchoring section of the rod body, Ensure not to move up and down (the self-compensating miniature FBG strain sensor string 16 in the rod body checks its survival rate (survival rate must not be lower than 90%) respectively before and after being implanted in the anchor rod body 1);

(2) Fix the hard steel wire 22 on the anchor bracket 15 with the binding wire 21 as required, and ensure that the hard steel wire 22 is respectively located in the middle position of the radial direction of the mortar anchor and the second interface (the outer surface of the anchor and the surrounding rock and soil). Layer contact surface) position, then the self-compensating miniature FBG strain sensor string 17 in the anchor body prefabricated in advance, and the second interface self-compensating miniature FBG strain sensor string 18 are firmly bound on the hard steel wire 22 with the binding wire 21. Through the fiber Bragg grating demodulator 20, check the survival rate of the self-compensating miniature FBG strain sensor string 17 in the anchor body and the second interface self-compensating miniature FBG strain sensor string 18 (survival rate must not be lower than 90%);

(3) Lower the above-mentioned prefabricated anchor rod into the drilled anchor rod hole, and pour commercial mortar 19 into it. After curing for 28 days and reaching 75% of the required strength, make the self-made displacement test device 10 symmetrical with structural glue Bonded to the anchor rod 0.5cm above the surface of the anchor to ensure its stability and verticality;

(4) Place the two I-beam support beams 14 symmetrically on both sides of the anchor rod body 1, so that they are located on the fine stone concrete cushion 23, and ensure that the distance between them is 25-30 cm, so that the anchor rod body 1 is located on the two sides. The center of the root I-beam ensures that the axis of the anchor rod is under tension; the through-center reaction beam 9 passes through the anchor rod body 1 and is placed on the I-beam support beam 14 to ensure that the centroid of the through-center reaction beam 9 is in line with the The bolt bodies 1 overlap, and the third through-hole steel backing plate 8, the through-hole jack 7, the second through-hole steel backing plate 6, the load sensor 5, the first Through the steel backing plate 4, ensure that each component is perpendicular to the anchor rod body 1, and the centroid is coaxial with the anchor rod, so that the anchor rod axis is under tension during the loading process;

(5) Fix the stress diffusion tray 3 on the anchor rod body 1 through threads, and then insert the locking anchor 2. In order to provide greater reaction force, several locking anchors 2 can be connected in series according to actual needs. AB glue with good fluidity is dripped between the thread gap between the locking anchor 2 and the anchor rod body 1, so as to ensure that the anchor has sufficient locking force and prevent the locking anchor 2 and the stress diffusion tray 3 from being generated when the load is applied. shear failure;

(6) Install the fiber grating displacement meter 11 vertically on the self-made displacement test device 10 and the exposed surface of the anchor body, and install the magnetic table base 12 of the fiber grating displacement meter 11 on the reference beam 13 to ensure that it does not shake; Compensation miniature FBG strain sensor string 16, self-compensation miniature FBG strain sensor string 17 in the anchor body, second interface self-compensation miniature FBG strain sensor string 18 and the external joint of fiber Bragg grating displacement meter 11 are connected to fiber grating demodulator 20, and Debug and set relevant parameters to ensure accurate and stable collection of relevant data. So far, the non-metallic anti-floating anchor multi-interface shear stress test device has been installed, and the through-hole jack 7 and load sensor 5 have been calibrated to ensure that the load applied at each level during the test Quantitative accuracy;

(7) Use the core-through jack 7 to load, and control the rise of the core-through jack 7 to be less than 10cm. The reaction force of the core-through jack 7 causes the uplift of the anchor rod body 1 and the anchoring body, and use the fiber grating displacement meter 11 Automatically record, substituting the measured anchor rod body 1 and anchor uplift S _rod and S _anchor under each load into the formula (1), the relative slippage of the anchor rod and the anchor body can be obtained,

S＝(S _Rod -S _{Rod Bomb} )－(S _Anchor -S _{Anchor Bomb} ) (1)

In the formula: S _rod is the displacement of the rod body measured in the test (mm); S _{rod elastic} is the elastic elongation of the rod anchorage section (mm); S _anchor is the displacement of the anchor body measured in the test (mm); S _anchor is the anchorage Body elastic elongation (mm), because the calculation value of S- _{rod bomb} and S _{-anchor bomb} is relatively small, it can be ignored;

Substituting the strain change values at each position of the rod body, the anchor body, and the second interface measured by the fiber grating demodulator 20 into the formula (2), the axial force at any position of the rod body, the anchor body, and the second interface is obtained,

N _i =πD ² EΔε/4 (2)

In the formula: N _i is the axial force (kN) at any section i of the measured structure (rod body, anchor body and the second interface); E is the elastic modulus of the measured structure (GPa); Δε is the measured structure (rod body, anchor body and the second interface) strain variation, obtained by formula (3); D is the diameter (mm) of the structure to be measured, about the value of D: for the anchor rod body, take the diameter of the rod body, Take the diameter of the anchor body at the second interface, and take twice the horizontal distance from the rod body centroid to the self-compensating miniature FBG strain sensor string 17 in the anchor body in the anchor body,

Δε=Δλ/K (3)

In the formula: Δλ is the central wavelength change (nm); K is the strain sensitivity coefficient of the self-compensating miniature FBG strain sensor.

Put the axial force values at each position of the rod body, the anchor body and the second interface calculated by the formula (2) into the formula (4), that is, the shear stress at each position of the rod body, the anchor body and the second interface can be obtained,

τ _i =(N _i -N _i-1 )/πDΔL (4)

In the formula: N _i is the axial force (kN) at a certain section i of the tested structure; N _i-1 is the axial force (kN) at the next section i-1 of the tested structure; The distance between sections _i -1 (mm); τi is the shear stress at the midpoint between the two sections, which is approximately considered as the average shear stress (MPa).

The main structure of the non-metallic anti-floating anchor multi-interface shear stress joint test device described in this embodiment includes an anchor rod body 1, a locking anchor 2, a stress diffusion tray 3, a first through-hole steel backing plate 4, and a load sensor 5 , second through-core steel backing plate 6, through-core jack 7, third through-core steel backing plate 8, through-core reaction beam 9, self-made displacement test device 10, optical fiber grating displacement meter 11, magnetic table base 12, reference beam 13. I-beam support beam 14, anchor rod bracket 15, self-compensating miniature FBG strain sensor string 16 in the rod body, self-compensating miniature FBG strain sensor string 17 in the anchor body, second interface self-compensating miniature FBG strain sensor string 18, Commodity mortar 19, fiber grating demodulator 20, binding wire 21, hard steel wire 22 and fine stone concrete cushion 23; anchor rod body 1 is a solid glass fiber reinforced polymer anchor rod; locking anchor 2, stress diffusion tray 3 Matching the size of the anchor rod body 1, the locking anchor 2 is embedded and installed on the stress diffusion tray 3, and both the locking anchor 2 and the stress diffusion tray 3 are tightly connected with the anchor rod body 1 through threaded coupling for Provide reaction force; the first through-hole steel backing plate 4, the load sensor 5, the second through-hole steel backing plate 6, the through-hole jack 7 and the third through-hole steel backing plate are sequentially installed under the stress diffusion tray 3 from top to bottom 8. The load sensor 5 is externally connected to a pressure indicator to display the pulling force provided by the jack in real time; the third through-hole steel backing plate 8 is installed on the through-hole reaction beam 9, and the self-made displacement test device 10 is welded by a semicircular steel pipe and an angle iron It is formed by using structural glue to symmetrically bond on the anchor rod body 1 slightly higher than the surface of the anchor body, and the self-made displacement test device 10 is perpendicular to the surface of the anchor body; two I-shaped steel support beams are symmetrically placed on both sides of the anchor rod body 1 14. The I-shaped steel support beam 14 is located on the fine stone concrete cushion 23, and the distance between the two I-shaped steel support beams 14 is 25 to 30 cm; On the steel support beam 14, the self-made displacement test device 10 and the exposed surface of the anchor body are vertically installed with a fiber grating displacement meter 11, the magnetic table 12 of the fiber grating displacement meter 11 is installed on the reference beam 13, and the anchor rod bracket 15 is composed of four A quarter of a circular ring with feet is spliced with nuts, and its aperture size is controlled according to the size of the anchor rod body 1 and evenly installed in the lower part of the anchor rod body 1 and implanted in the soil part; the self-compensating miniature FBG strain sensor in the rod body The string 16, the self-compensating miniature FBG strain sensor string 17 in the anchor body and the second interface self-compensating miniature FBG strain sensor string 18 are manufactured according to the test requirements, wherein the self-compensating miniature FBG strain sensor string 16 in the rod body is implanted into the anchor rod body to be tested 1, the self-compensating miniature FBG strain sensor string 16 in the rod, the self-compensating miniature FBG strain sensor string 17 in the anchor body and the second interface self-compensating miniature FBG strain sensor string 18 are all arranged according to the principle of dense top and sparse bottom. The three self-compensating miniature FBG strain sensors are at the same depth; the commercial mortar 19 is poured into the pre-drilled bolt hole, and its strength is determined according to the strength level required by the test; the hard steel wire 22 adopts the binding wire 21 Fixed on the anchor rod bracket 15, the self-compensating miniature FBG strain sensor string 17 in the anchor body, and the second interface self-compensating miniature FBG strain sensor string 18 are firmly bound on the hard steel wire 22 with the binding wire 21; the fiber grating demodulator 20 respectively It is connected with the fiber grating displacement meter 11, the self-compensating miniature FBG strain sensor series 16 in the rod body, the self-compensating miniature FBG strain sensor series 17 in the anchor body and the second interface self-compensating miniature FBG strain sensor series 18.

In this embodiment, different anchor rods are tested, and the specific test results are as shown in Table 1:

Table 1:

Anchor No. Anchorage length failure load Anchor bolt limit uplift Anchorage limit uplift form of destruction G8-28-1 6.5m 395kN 14.02mm 12.63mm Pull out damage G8-28-2 6.5m 378kN 16.47mm 12.64mm shear slip failure G8-28-3 6.5m 412kN 14.89mm 12.25mm Pull out damage G8-28-4 6.5m 387kN 18.26mm 13.27mm shear slip failure G8-28-5 6.5m 398kN 15.16mm 12.445mm Pull out damage G6-28-1 4.5m 407kN 15.86mm 12.035mm Pull out damage G6-28-2 4.5m 381kN 17.03mm 12.67mm shear slip failure G6-28-3 4.5m 394kN 15.21mm 11.47mm Pull out damage G6-28-4 4.5m 375kN 16.74mm 11.35mm shear slip failure G6-32-1 4.5m 467kN 15.87mm 12.31mm shear slip failure G6-32-2 4.5m 453kN 17.69mm 12.64mm pull out damage

Among them, G in G8-28-1 indicates GFRP anti-floating anchor; 8 indicates that the total length of the anchor is 8m; 28 indicates that the diameter of the anchor is 28mm; G8-28-1...G8-28-5 indicates 5 parallel tests; By analogy; the test results of the relative slip between the anti-floating anchor rod body and the anchor body are shown in Figure 7, where G8-28 represents the average of the five parallel tests of G8-28-1...G8-28-5 in Table 1 The value G6-28 represents the average value of the four parallel tests of G6-28-1...G6-28-4 in Table 1, and G6-32 represents the two parallel tests of G6-32-1 and G6-32-2 in Table 1 The average value is taken; the multi-interface shear stress results of the bolt described in G8-28-1 are shown in Figure 8-13.

Claims (1)

1. A non-metallic anti-floating bolt multi-interface shear stress combined testing method is characterized in that it adopts a non-metallic anti-floating anchor multi-interface shear stress combined testing device to realize, and its specific process is: (1) Put the anchor rod body implanted with the self-compensating miniature FBG strain sensor string into the anchor rod bracket every 0.5m, and tighten the fixing nuts to ensure that the anchor rod bracket is firm and stable in the anchoring section of the rod body and does not move up and down The survival rate of the self-compensating miniature FBG strain sensor string in the rod body is tested before and after being implanted in the anchor rod body, and the survival rate shall not be lower than 90%; (2) Fix the hard steel wire on the bolt bracket according to the requirements, and ensure that the hard steel wire is respectively located in the middle position of the mortar anchor in the radial direction and at the second interface. The second interface is the outer surface of the anchor and the surrounding rock. On the contact surface of the soil layer, the self-compensating miniature FBG strain sensor string in the anchor body prefabricated in advance and the second interface self-compensating miniature FBG strain sensor string are firmly tied to the hard steel wire with binding wires, and the fiber grating demodulation is turned on at this time Instrument to test the survival rate of the self-compensating miniature FBG strain sensor string in the anchor body and the second interface self-compensating miniature FBG strain sensor string, the survival rate shall not be lower than 90%; (3) Lower the above-mentioned prefabricated anchor rods into the drilled anchor rod holes, and pour commercial mortar into them. After curing for 28 days and reaching 75% of the required strength, the self-made displacement testing device is symmetrically bonded with structural glue On the anchor rod 0.5cm above the surface of the anchor, make sure it is stable and vertical; (4) Place the two I-shaped steel support beams symmetrically on both sides of the anchor rod body, so that they are located on the fine stone concrete cushion, and ensure that the distance between them is 25-30cm, so that the anchor rod body is located on the two I-shaped steel beams. The center of the anchor rod is guaranteed to be tensioned; the through-center reaction beam passes through the anchor rod body and is placed on the I-beam support beam to ensure that the centroid of the through-center reaction beam coincides with the anchor body, and the Install the third core-through steel backing plate, the through-core jack, the second through-core steel backing plate, the load sensor, and the first through-core steel backing plate from bottom to top on the central reaction beam to ensure that each component is perpendicular to the anchor rod body , the centroid is coaxial with the anchor rod, so that the anchor rod axis is under tension during the loading process; (5) Fix the stress diffusion tray on the anchor rod body through threads, and then insert the locking anchor. In order to provide greater reaction force, several locking anchors can be connected in series according to actual needs and locked in the anchor. AB glue with good fluidity is dripped between the thread gap between the tool and the anchor rod body, so as to ensure that the anchor has sufficient locking force and prevent shear damage caused by locking the anchor tool and the stress diffusion tray when the load is applied; (6) Install the fiber grating displacement gauge vertically on the self-made displacement test device and the exposed surface of the anchor, and install the magnetic base of the fiber grating displacement gauge on the reference beam to ensure that it does not shake; then install the self-compensating miniature FBG strain sensor in the rod body The series, self-compensating miniature FBG strain sensor series in the anchor body, the second interface self-compensating miniature FBG strain sensor series and the external connector of the fiber grating displacement meter are connected to the fiber grating demodulator, and the relevant parameters are adjusted and set to ensure accurate and stable acquisition Relevant data, so far the non-metallic anti-floating anchor multi-interface shear stress test device has been installed, and the through-hole jack and load sensor have been calibrated to ensure the accuracy of the load applied at each level during the test; (7) Use a through-hole jack to load, and control the rise of the through-jack to less than 10cm. The reaction force of the through-jack causes the uplift of the anchor rod body and the anchor body, and automatically records it with a fiber grating displacement meter. The measured uplift of the anchor rod body and anchor body under various loads S _rod and S _anchor are substituted into the formula (1), that is, the relative slippage of the anchor rod and anchor body is obtained, S＝(S _Rod -S _{Rod Bomb} )－(S _Anchor -S _{Anchor Bomb} ) (1) In the formula: S _rod is the displacement of the rod body measured in the test, in mm; S _{rod elastic} is the elastic elongation of the anchorage section of the rod body, in mm; S _anchor is the displacement of the anchor body measured in the test, in mm; S _{anchor The bullet} is the elastic elongation of the anchor body, and the unit is mm. Since the calculation values of the S- _{rod bullet} and the S _{-anchor bullet} are relatively small, they are negligible; Substituting the strain change values at each position of the rod body, the anchor body and the second interface measured by the fiber grating demodulator into the formula (2), the axial force at any position of the rod body, the anchor body and the second interface can be obtained, N _i =πD ² EΔε/4 (2) In the formula: N _i is the axial force at any section i of the measured structure in the rod body, the anchor body and the second interface, the unit is kN; E is the elastic modulus of the measured structure, the unit is GPa; Δε is the rod body, The change in strain of the measured structure in the anchor body and at the second interface is obtained by formula (3); D is the diameter of the measured structure in mm, and the value of D is: for the anchor rod body, the diameter of the rod body is taken, For the diameter of the anchor at the second interface, for the inside of the anchor, take twice the horizontal distance from the centroid of the rod body to the self-compensating miniature FBG strain sensor string in the anchor, Δε=Δλ/K (3) In the formula: Δλ is the central wavelength change, the unit is nm; K is the strain sensitivity coefficient of the self-compensating miniature FBG strain sensor; Put the axial force values at each position of the rod body, the anchor body and the second interface calculated by the formula (2) into the formula (4), that is, the shear stress at each position of the rod body, the anchor body and the second interface can be obtained, τ _i =(N _i -N _i-1 )/πDΔL (4) In the formula: N _i is the axial force at a section i of the tested structure, in kN; N _i-1 is the axial force at the next section i-1 of the tested structure, in kN; ΔL is the axial force at the section i to The distance between the next section _i -1, the unit is mm; τi is the shear stress at the midpoint between the two sections, which is approximately considered as the average shear stress, and the unit is MPa; The main structure of the multi-interface shear stress joint test device for non-metallic anti-floating anchors includes an anchor rod body, a locking anchor, a stress diffusion tray, a first piercing steel backing plate, a load sensor, and a second piercing steel backing plate , through-hole jack, third through-hole steel backing plate, through-hole reaction beam, self-made displacement test device, optical fiber grating displacement meter, magnetic table base, reference beam, I-beam support beam, anchor bracket, rod body Self-compensating miniature FBG strain sensor strings, self-compensating miniature FBG strain sensor strings in the anchor body, self-compensating miniature FBG strain sensor strings on the second interface, commercial mortar, fiber Bragg grating demodulator, binding wire, hard steel wire and fine stone concrete cushion The anchor rod body is a solid glass fiber reinforced polymer anchor rod; the size of the locking anchor and the stress diffusion tray are matched with the size of the anchor rod body, and the locking anchor is embedded and installed on the stress diffusion tray, and the locking anchor and stress diffusion The trays are tightly connected with the anchor rod body through threaded coupling to provide reaction force; the first through-hole steel backing plate, load sensor, second through-hole steel backing plate, through-hole steel backing plate, and The core jack and the third through-core steel backing plate, the load sensor is externally connected to a pressure display, which can display the pulling force provided by the jack in real time; the third through-core steel backing plate is installed on the through-center reaction beam, and the self-made displacement test device consists of a semicircular The steel pipe and angle iron are welded, and the structural adhesive is used to symmetrically bond the anchor body above the surface of the anchor body. The self-made displacement test device is perpendicular to the surface of the anchor body; two I-steel supports are symmetrically placed on both sides of the anchor body Beam, the I-beam bearing beam is located on the fine stone concrete cushion, the distance between the two I-beam bearing beams is 25-30cm; , the self-made displacement test device and the fiber grating displacement meter are installed vertically on the exposed surface of the anchor body, the magnetic base of the fiber grating displacement meter is installed on the reference beam, and the anchor rod bracket is spliced by four quarter-legged ring iron nuts According to the size of the anchor rod body, the aperture size is controlled and evenly installed in the lower part of the anchor rod body and implanted in the soil part; the self-compensating miniature FBG strain sensor string in the rod body, the self-compensating miniature FBG strain sensor string in the anchor body and the second interface The self-compensating miniature FBG strain sensor string is made according to the test requirements, wherein the self-compensating miniature FBG strain sensor string in the rod is implanted in the anchor rod body to be tested, the self-compensating miniature FBG strain sensor string in the rod body, and the self-compensating miniature FBG strain sensor string in the anchor body The sensor string and the second interface self-compensating miniature FBG strain sensor string are arranged according to the principle of dense top and sparse bottom, and three self-compensating miniature FBG strain sensors in each cross-section are at the same depth; commercial mortar is poured into the pre-drilled anchor In the rod hole, its strength is determined according to the strength grade required by the test; the hard steel wire is fixed on the anchor bracket by tie wire, and the self-compensating miniature FBG strain sensor string in the anchor body and the second interface self-compensation miniature FBG strain sensor string are used by tie wire It is firmly bound on the hard steel wire; the fiber grating demodulator is connected with the fiber grating displacement meter, the self-compensating miniature FBG strain sensor string in the rod body, the self-compensating miniature FBG strain sensor string in the anchor body and the The second interface is connected in series with self-compensating miniature FBG strain sensors.