A fiber grating intelligent prestressed steel anchor pipe structure and its construction method

Abstract

The present invention discloses a fiber grating intelligent prestressed steel anchor pipe structure, including a grouting prestressed steel anchor pipe, a fiber grating stress monitoring device, and an external anchoring end, wherein the grouting prestressed steel anchor pipe is engraved with a full-length embedded groove, and a sheathing tube is provided on the outer wall of the free section of the grouting prestressed steel anchor pipe; the fiber grating stress monitoring device includes an optical fiber and a grating stress sensor, the fiber grating sensor is embedded in the embedded groove of the grouting prestressed steel anchor pipe, and the top of the embedded groove of the anchoring section is filled with sealant, and the optical fiber of the free section is wrapped with armor. The present invention also discloses a construction method of the fiber grating intelligent prestressed steel anchor pipe, including the production of the fiber grating stress monitoring device, the processing of the grouting prestressed steel anchor pipe, drilling, pipe placement, primary grouting, secondary grouting, tension locking and anchor sealing of the grouting prestressed steel anchor pipe. The fiber grating intelligent prestressed steel anchor pipe provided by the present invention has the advantages of saving space, high survival rate, long service life, and high measurement accuracy.

Description

Technical Field

[0001] The present invention relates to the technical field of slope anchoring engineering, and in particular to a fiber grating intelligent prestressed steel anchor pipe structure and a construction method thereof. Background Art

[0002] Slope anchoring is a concealed project, and its main materials, steel and concrete, are buried in various types of rock and soil. The anchoring section is in strata with relatively developed groundwater and is in contact with groundwater and site soil for a long time, which can easily lead to loss of anchoring force or even failure.

[0003] In the past, stress monitoring of steel anchor pipes usually used equipment such as resistance strain gauges and concrete strain gauges. In view of the fact that resistance strain gauges attached to the outer wall of the steel pipe are prone to disconnection and short circuit, and have a low survival rate in complex external environments, the strain gauges are large in size, the number of installations is limited, and they are easily damaged by friction on the hole wall during the lowering of the steel anchor pipe, there is an urgent need to study a new type of steel anchor pipe stress monitoring technology. By monitoring the stress changes of the steel anchor pipe during the tensioning process and during service, it can provide reference and support for the later design, construction, and operation stages. Summary of the invention

[0004] The purpose of the present invention is to solve the problems of low accuracy, low survival rate, limited monitoring quantity and the like of existing prestressed steel anchor pipe stress monitoring equipment, and to provide a fiber grating intelligent prestressed steel anchor pipe structure.

[0005] A fiber grating intelligent prestressed steel anchor pipe structure, comprising a grouting prestressed steel anchor pipe arranged in a borehole, a fiber grating stress monitoring device arranged on the outer wall of the grouting prestressed steel anchor pipe, and an outer anchoring end arranged outside the borehole and connected to the grouting prestressed steel anchor pipe, wherein the grouting prestressed steel anchor pipe is engraved with a full-length embedding groove, the grouting prestressed steel anchor pipe comprises an anchoring section and a free section, a conical guide head is fixed to the front end of the anchoring section, and a sheath tube is provided on the outer wall of the free section; the fiber grating stress monitoring device comprises an optical fiber and a grating stress sensor, the grating stress sensor is connected in series to the optical fiber, the fiber grating sensor is embedded in the embedding groove of the grouting prestressed steel anchor pipe, the top of the embedding groove of the anchoring section is filled with sealant, and the optical fiber of the free section is wrapped with armor.

[0006] Furthermore, the external anchoring end includes a concrete beam arranged outside the drilled hole, a wedge-shaped anchor pier fixed to the outside of the concrete beam, a support plate fixed on the wedge-shaped anchor pier, a locking nut and an anchoring concrete. The end of the grouting prestressed steel anchor pipe passes through the concrete beam, the wedge-shaped anchor pier and the support plate in sequence and is locked to the support plate by the locking nut. Finally, the anchoring concrete is poured to form the external anchoring end.

[0007] Furthermore, the grouting prestressed steel anchor pipe is provided with a plurality of secondary grouting holes, the outer sides of the secondary grouting holes are wrapped with strong adhesive tape, and an embedding groove is respectively provided on the upper and lower sides of the grouting prestressed steel anchor pipe.

[0008] In addition, the present invention also provides a construction method of a fiber Bragg grating intelligent prestressed steel anchor pipe structure, comprising the following steps:

[0009] S1. Fabrication of a fiber Bragg grating stress monitoring device: Connect the grating stress sensor in series to the optical fiber, wrap the armor on the free section of the optical fiber, connect the fiber Bragg grating stress monitoring device to the fiber Bragg grating modulator to preliminarily collect data from the optical fiber stress sensor, and confirm that the fiber Bragg grating stress monitoring device works normally;

[0010] S2. Processing of grouting prestressed steel anchor pipe: including

[0011] Threading: The end of the free section is threaded so that it is threadedly connected with the locking nut;

[0012] Drilling: Drill secondary grouting holes in the anchoring section;

[0013] Sealing hole: inject glass glue into the secondary grouting hole and wrap the secondary grouting hole with strong tape;

[0014] Grooving: A full-length groove is opened on the upper and lower sides of the grouting prestressed steel anchor pipe;

[0015] Embedding: The fiber Bragg grating stress monitoring device is embedded in the embedding groove;

[0016] Sealing: Squeeze sealant into the top of the embedding groove of the anchoring section to seal and fix the FBG stress monitoring device, and put a steel hoop on the grouting prestressed steel anchor pipe of the free section to fix the FBG;

[0017] Test: The grouting pipe is fixed three times on the free section of the grouting prestressed steel anchor pipe and then covered with a sheath pipe. The bottom of the pipe is sealed, and the first grouting pipe is fixed to the outer wall of the sheath pipe and the anchor section. The data of the fiber Bragg grating stress monitoring device is collected for the second time to confirm that the fiber Bragg grating stress monitoring device is fully alive;

[0018] S3. Drilling: The process of drilling is to determine the hole position → set up the drilling platform → composite hole position → precise positioning of the drilling rig → drilling → inspection;

[0019] S4, pipe placement: insert the processed grouting prestressed steel anchor pipe into the required position in the borehole, collect the fiber grating sensor data again, and confirm the number of surviving sensors;

[0020] S5. Primary grouting: The primary grouting body is pressed in reverse from the bottom to the top through the primary grouting pipe from the bottom of the borehole, and it continues until the clean cement slurry overflows from the borehole mouth. After the primary grouting is completed, if the slurry at the hole mouth is found to shrink, the primary grouting body should be replenished in time on site;

[0021] S6. Secondary grouting: inject high-pressure secondary grouting into the steel anchor pipe through the grouting prestressed steel anchor pipe port, split the secondary grouting holes and the primary grouting on the anchoring section, spread them around, fill the gaps in the developed cracks, weak rock formations and soil layers, and improve the anchoring force;

[0022] S7. Tensioning and locking of grouting prestressed steel anchor pipe: When the strength of the primary grouting body and the secondary splitting grouting body reaches the design requirements, the grouting prestressed steel anchor pipe is tensioned to the designed anchoring force, and the locking nut is screwed in to lock the end of the free section on the support plate. During the tensioning process, the data of the fiber grating stress monitoring device is continuously collected;

[0023] S8. Anchor sealing: Continuously monitor the stress changes of the grouting prestressed steel anchor pipe. After the anchoring force is stable, inject the tertiary grouting body into the gap between the free section and the casing pipe at normal pressure through the tertiary grouting pipe until the gap between the free section and the casing pipe is filled. Seal the anchor head with anchor sealing concrete, collect data regularly, and monitor the stress changes of the grouting prestressed steel anchor pipe.

[0024] The beneficial effects of the present invention are:

[0025] 1. Save space

[0026] Traditional steel anchor pipe stress monitoring equipment, such as strain gauges, especially strain gauges, are large in size and require more space in the hole. The above equipment is all single-point lead-out and cannot be connected in series. When performing multi-point monitoring, it is often difficult to lower the steel anchor pipe due to the lead-in. The fiber grating embedded section used in the present invention is directly embedded in the outer wall of the steel pipe, and the non-embedded section is extremely small and can be basically ignored. In particular, the fiber grating sensor can realize multi-point series connection, so it basically does not occupy the space in the hole.

[0027] 2. High survival rate

[0028] Traditional steel anchor pipe stress monitoring equipment is attached to the outer wall of the steel pipe to monitor the stress of the steel pipe. It is very easy to rub against the hole wall during the lowering of the steel pipe, causing damage to the equipment. The present invention is embedded in the steel pipe, and the friction is still borne by the steel pipe during the lowering process, so the equipment will not be damaged. In addition, the underground environment in the cave is unpredictable, which may also cause damage to the monitoring equipment. The embedded section of the present invention is sealed with special glue, and the free section is protected by optical fiber armor, which can basically isolate the impact of the external environment on the equipment.

[0029] 3. Improved measurement accuracy and equipment service life

[0030] Since the outer periphery of the optical fiber is sealed with sealant, the impact of the external environment is reduced, the external signal influence is eliminated through physical isolation, and the acid-base effect of concrete on the equipment is reduced, which can not only increase the service life of the equipment, but also improve the accuracy of stress monitoring.

[0031] In summary, the fiber Bragg grating intelligent prestressed steel anchor pipe structure of the present invention fully utilizes the advantages of fiber Bragg grating such as small size, easy installation, high measurement accuracy, etc., and is a new type of slope reinforcement monitoring technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for describing the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0033] Figure 1 It is a schematic diagram of the cross-sectional structure of the fiber Bragg grating intelligent prestressed steel anchor pipe structure;

[0034] Figure 2 It is a schematic diagram of the cross-sectional structure of the anchoring section of the grouting prestressed steel anchor pipe;

[0035] Figure 3 It is a schematic diagram of the cross-sectional structure of the free section of the grouting prestressed steel anchor pipe;

[0036] In the accompanying drawings, the components represented by the reference numerals are listed as follows:

[0037] 1-anchor cable, 2-grouting prestressed steel anchor pipe, 3-grating stress sensor, 4-optical fiber, 5-secondary grouting body, 6-sealant, 7-primary grouting body, 8-drilling hole, 9-armor, 10-anchor section, 11-free section, 12-sheath pipe, 13-secondary grouting hole, 14-primary grouting pipe, 15-surrounding rock. DETAILED DESCRIPTION

[0038] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0039] like Figure 1-3As shown, a fiber grating intelligent prestressed steel anchor pipe structure includes a grouting prestressed steel anchor pipe 2 arranged in a borehole, a fiber grating stress monitoring device arranged on the outer wall of the grouting prestressed steel anchor pipe, and an outer anchoring end arranged outside the borehole and connected to the grouting prestressed steel anchor pipe, the grouting prestressed steel anchor pipe is engraved with a full-length embedded groove, the grouting prestressed steel anchor pipe includes an anchoring section 10 and a free section 11, a conical guide head is fixed to the front end of the anchoring section 10, and a sheath tube 12 is provided on the outer wall of the free section 11; the fiber grating stress monitoring device includes an optical fiber 4 and a grating stress sensor 3, the grating stress sensor 3 is connected in series to the optical fiber 4, the fiber grating sensor is embedded in the embedded groove of the grouting prestressed steel anchor pipe, the top of the embedded groove of the anchor section 10 is filled with sealant, and the optical fiber of the free section 11 is wrapped with armor 9.

[0040] The external anchoring end includes a concrete beam arranged outside the drilled hole, a wedge-shaped anchor pier fixed to the outside of the concrete beam, a support plate fixed on the wedge-shaped anchor pier, a locking nut and an anchoring concrete. The end of the grouting prestressed steel anchor pipe passes through the concrete beam, the wedge-shaped anchor pier and the support plate in turn and is locked to the support plate by the locking nut. Finally, the anchoring concrete is poured to form the external anchoring end.

[0041] The grouting prestressed steel anchor pipe 2 is provided with a plurality of secondary grouting holes 13 , the outer sides of the secondary grouting holes 13 are wrapped with strong adhesive tapes, and the upper and lower sides of the grouting prestressed steel anchor pipe 2 are each provided with an embedding groove.

[0042] The present invention provides a construction method of a fiber grating intelligent prestressed steel anchor pipe structure, comprising the following steps:

[0043] Step 1: Fabrication of a fiber Bragg grating stress monitoring device: connect the grating stress sensor 3 in series to the optical fiber 4, wrap the armor 9 on the optical fiber of the free section 11, connect the fiber Bragg grating stress monitoring device to the fiber Bragg grating modulator to preliminarily collect data from the grating stress sensor 3, and confirm that the fiber Bragg grating stress monitoring device works normally;

[0044] The second step is the processing of grouting prestressed steel anchor pipe 2: including

[0045] Threading: threading the end of the free section 11 so that it is threadedly connected with the locking nut;

[0046] Drilling: Drill secondary grouting holes 13 in the anchoring section 10;

[0047] Sealing: inject glass glue into the secondary grouting hole 13 and wrap the secondary grouting hole 13 with strong tape;

[0048] Grooving: A through-length groove is opened on the upper and lower sides of the grouting prestressed steel anchor pipe 2;

[0049] Embedding: The fiber Bragg grating stress monitoring device is embedded in the embedding groove;

[0050] Sealing: a sealant is squeezed into the top of the embedding groove of the anchoring section 10 to seal and fix the FBG stress monitoring device, and a steel hoop is clamped on the grouting prestressed steel anchor pipe 2 of the free section 11 to fix the FBG;

[0051] Test: The free section 11 of the grouting prestressed steel anchor pipe 2 is fixed with a grouting pipe three times and then covered with a sheath pipe 12, the bottom of the pipe is sealed, the first grouting pipe is fixed to the outer wall of the sheath pipe 12 and the anchor section 10, and the data of the fiber Bragg grating stress monitoring device is collected for the second time to confirm that the fiber Bragg grating stress monitoring device is fully alive;

[0052] The third step is drilling: the process of drilling is to determine the hole position → set up the drilling platform → compound hole position → precise positioning of the drilling rig → drilling → inspection;

[0053] Step 4: Pipe placement: insert the processed grouting prestressed steel anchor pipe 2 into the required position in the borehole, collect the fiber optic Bragg grating sensor data again, and confirm the number of surviving grating stress sensors 3;

[0054] Step 5, primary grouting: the primary grouting body 7 is reversely pressed from bottom to top from the bottom of the borehole through the primary grouting pipe 14, and it continues until the borehole 8 overflows with clean cement slurry. After the primary grouting is completed, if it is found that the slurry at the hole mouth shrinks, the primary grouting body should be replenished in time on site;

[0055] Step 6, secondary grouting: inject high-pressure secondary grouting body 5 into the steel anchor pipe through the grouting prestressed steel anchor pipe 2, split the secondary grouting hole 13 and the primary grouting body 7 on the anchoring section, spread them around, fill the gaps in the developed cracks, weak rock formations and soil layers, and improve the anchoring force;

[0056] Step 7: tensioning and locking of the grouting prestressed steel anchor pipe 2: when the strength of the primary grouting body 7 and the secondary grouting body 5 reaches the design requirements, tension the grouting prestressed steel anchor pipe 2 to the designed anchoring force, screw in the locking nut to lock the end of the free section 11 on the support plate, and continuously collect data from the fiber grating stress monitoring device during the tensioning process;

[0057] Step 8. Anchor sealing: Continuously monitor the stress changes of the grouting prestressed steel anchor pipe 2. After the anchoring force is stable, inject the tertiary grouting body into the gap between the free section and the casing pipe at normal pressure through the tertiary grouting pipe until the gap between the free section and the casing pipe is filled. Seal the anchor head with anchor sealing concrete, collect data regularly, and monitor the stress changes of the grouting prestressed steel anchor pipe.

[0058] In the description of this specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example.

[0059] The preferred embodiments of the present invention disclosed above are only used to help illustrate the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific implementation methods described. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A construction method of a fiber grating intelligent prestressed steel anchor pipe structure, the fiber grating intelligent prestressed steel anchor pipe structure comprising a grouting prestressed steel anchor pipe arranged in a borehole, a fiber grating stress monitoring device arranged on the outer wall of the grouting prestressed steel anchor pipe, and an outer anchoring end arranged outside the borehole and connected to the grouting prestressed steel anchor pipe, the grouting prestressed steel anchor pipe is engraved with a full-length embedded groove, the grouting prestressed steel anchor pipe comprises an anchoring section and a free section, a conical guide head is fixed to the front end of the anchoring section, and a sheath tube is arranged on the outer wall of the free section; the fiber grating stress monitoring device comprises an optical fiber and a grating stress sensor, the grating stress sensor is connected in series to the optical fiber, and the fiber grating The sensor is embedded in the embedding groove of the grouting prestressed steel anchor pipe and the top of the embedding groove of the anchoring section is filled with sealant, the optical fiber of the free section is wrapped with armor, the outer anchoring end includes a concrete beam arranged outside the drilled hole, a wedge-shaped anchor pier fixed to the outer side of the concrete beam, a support plate fixed to the wedge-shaped anchor pier, a locking nut and a sealing anchor concrete, the end of the grouting prestressed steel anchor pipe passes through the concrete beam, the wedge-shaped anchor pier and the support plate in turn and is locked on the support plate by the locking nut, and finally the sealing anchor concrete is poured to form the outer anchoring end, the grouting prestressed steel anchor pipe is provided with a plurality of secondary grouting holes, the outer side of the secondary grouting holes is wrapped with a strong adhesive tape, and the upper and lower sides of the grouting prestressed steel anchor pipe are each provided with an embedding groove; It is characterized in that The following steps are involved: S1. Fabrication of a fiber Bragg grating stress monitoring device: Connect the grating stress sensor in series to the optical fiber, wrap the armor on the free section of the optical fiber, connect the fiber Bragg grating stress monitoring device to the fiber Bragg grating modulator to preliminarily collect data from the optical fiber stress sensor, and confirm that the fiber Bragg grating stress monitoring device works normally; S2. Processing of grouting prestressed steel anchor pipe: including Threading: The end of the free section is threaded so that it is threadedly connected with the locking nut; Drilling: Drill secondary grouting holes in the anchoring section; Sealing hole: inject glass glue into the secondary grouting hole and wrap the secondary grouting hole with strong tape; Grooving: A full-length groove is opened on the upper and lower sides of the grouting prestressed steel anchor pipe; Embedding: The fiber Bragg grating stress monitoring device is embedded in the embedding groove; Sealing: Squeeze sealant into the top of the embedding groove of the anchoring section to seal and fix the FBG stress monitoring device, and put a steel hoop on the grouting prestressed steel anchor pipe of the free section to fix the FBG; Test: The grouting pipe is fixed three times on the free section of the grouting prestressed steel anchor pipe and then covered with a sheath pipe. The bottom of the pipe is sealed, and the first grouting pipe is fixed to the outer wall of the sheath pipe and the anchor section. The data of the fiber Bragg grating stress monitoring device is collected for the second time to confirm that the fiber Bragg grating stress monitoring device is fully alive; S3. Drilling: The process of drilling is to determine the hole position → set up the drilling platform → composite hole position → precise positioning of the drilling rig → drilling → inspection; S4, pipe placement: insert the processed grouting prestressed steel anchor pipe into the required position in the borehole, collect the fiber grating sensor data again, and confirm the number of surviving sensors; S5. Primary grouting: The primary grouting body is pressed in reverse from the bottom to the top through the primary grouting pipe from the bottom of the borehole, and it continues until the clean cement slurry overflows from the borehole mouth. After the primary grouting is completed, if the slurry at the hole mouth is found to shrink, the primary grouting body should be replenished in time on site; S6. Secondary grouting: inject high-pressure secondary grouting into the steel anchor pipe through the grouting prestressed steel anchor pipe port, split the secondary grouting holes and the primary grouting on the anchoring section, spread them around, fill the gaps in the developed cracks, weak rock formations and soil layers, and improve the anchoring force; S7. Tensioning and locking of grouting prestressed steel anchor pipe: When the strength of the primary grouting body and the secondary splitting grouting body reaches the design requirements, the grouting prestressed steel anchor pipe is tensioned to the designed anchoring force, and the locking nut is screwed in to lock the end of the free section on the support plate. During the tensioning process, the data of the fiber grating stress monitoring device is continuously collected; S8. Anchor sealing: Continuously monitor the stress changes of the grouting prestressed steel anchor pipe. After the anchoring force is stable, inject the tertiary grouting body into the gap between the free section and the casing pipe at normal pressure through the tertiary grouting pipe until the gap between the free section and the casing pipe is filled. Seal the anchor head with anchor sealing concrete, collect data regularly, and monitor the stress changes of the grouting prestressed steel anchor pipe.

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