CN112726597B - Method for designing prestressed anchor rod anchor head anchor sealing concrete block - Google Patents
Method for designing prestressed anchor rod anchor head anchor sealing concrete block Download PDFInfo
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- CN112726597B CN112726597B CN202011618720.6A CN202011618720A CN112726597B CN 112726597 B CN112726597 B CN 112726597B CN 202011618720 A CN202011618720 A CN 202011618720A CN 112726597 B CN112726597 B CN 112726597B
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D5/00—Bulkheads, piles, or other structural elements specially adapted to foundation engineering
- E02D5/74—Means for anchoring structural elements or bulkheads
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F30/00—Computer-aided design [CAD]
- G06F30/20—Design optimisation, verification or simulation
- G06F30/23—Design optimisation, verification or simulation using finite element methods [FEM] or finite difference methods [FDM]
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F2111/00—Details relating to CAD techniques
- G06F2111/10—Numerical modelling
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F2119/00—Details relating to the type or aim of the analysis or the optimisation
- G06F2119/14—Force analysis or force optimisation, e.g. static or dynamic forces
Abstract
The method for designing the prestressed anchor rod anchor head anchor sealing concrete block effectively improves the impact resistance and the safety coefficient of the anchor sealing concrete block and solves the problem that no theoretical basis exists in the design of the prestressed anchor rod anchor head anchor sealing concrete block. The method comprises the following steps: s01, collecting prestressed anchor rod design parameters including the cross section area, the weight per unit length, the elastic modulus, the tensile strength and the length of a free section before tensioning of the anchor rod; s02, calculating the speed v of the free end of the free section at the side of the anchor head when the free section of the prestressed anchor rod is broken and the stored strain energy is completely released according to the following formula2:S03, modeling and dynamic analysis, preliminarily drawing up the size and the strength grade of the anchor-sealing concrete block at the anchor head, and establishing a finite element or finite difference numerical model for dynamic analysis so as to detect and calculate the impact stress of the anchor-sealing concrete block under different working conditions of the fracture of the free section of the prestressed anchor rod; s04, determining an anchoring scheme between the anchor sealing concrete block and the existing structure; and S05, completing design.
Description
Technical Field
The invention belongs to the technical field of anchoring between tunnel and underground engineering and slope engineering structures and surrounding rocks, and relates to a design method of a prestressed anchor rod anchor head anchor-sealing concrete block.
Background
The prestressed anchor rod (cable) is generally composed of anchor rod (cable) anchoring section, anchor rod (cable) free section and anchor head, in which the anchor head can transfer the tension of anchor rod (cable) to the supporting structure surface or wall rock surface, and includes backing plate and nut (anchor). A prestressed anchor rod (or anchor cable, hereinafter referred to as anchor rod) is an active supporting structure that can transmit tensile force to a stable or suitable rock (soil) body, thereby anchoring the structure and the rock (soil) body together or reinforcing the rock (soil) body.
The prestressed anchor is widely applied to projects such as tunnels, underground projects, side slopes, foundation pits and the like, and the prestressed anchor support has two situations, one is anchor-spraying support, the prestressed anchor is combined with structures such as sprayed concrete, reinforcing mesh, steel frames and the like for use, and the anchor head of the prestressed anchor is completely sealed by a general sprayed concrete layer; and secondly, the prestressed anchor rods anchor the structure and the rock (soil) body together, such as the prestressed anchor rods anchor an upper arch section roadbed of a railway tunnel, an existing grotto structure, a foundation pit maintenance structure, a side slope frame beam and the like.
When the prestressed anchor rod is used in combination with structures such as sprayed concrete, reinforcing mesh, steel frame and the like, the anchor rod is generally filled and grouted into the free section anchor hole after tensioning is finished, and grouting materials are used for cementing the free section rod body and the hole wall on one hand and performing anticorrosion protection on the anchor rod body on the other hand. When the prestressed anchor rod anchors the structure and the rock (soil) body together, some designs fill and slip-casting the anchor hole of the free section, but some designs do not fill and slip-casting the anchor hole of the free section, and at the moment, the anchor head of the prestressed anchor rod generally adopts a concrete block or a steel cover for protection. When the anchor hole of the free section of the prestressed anchor rod is not filled, the anchor head of the anchor rod is broken to seal the anchor concrete block or the steel cover, the free section of the anchor rod can be tensioned again, and the working state of the anchor rod is readjusted.
The service life of an anchoring structure embedded in a rock body depends on the durability of the anchor rod, and the greatest threat to life comes from corrosion. To date, the corrosion destruction phenomenon of the prestressed anchor rods occurs at home and abroad. Before 1986, the international association for prestressing force earth anchor working group had received 35 examples of corrosion destruction of anchor rods all over the world, and the fracture site was mostly located near the anchor head and at the free section length. After the prestressed anchor rod of the Meishan reservoir in Anhui China is used for 8 years, the rupture of a part of steel wires in 3 holes due to stress corrosion (hydrogen embrittlement) is discovered. In recent years, the upper arch section of the bottom structure of a certain domestic high-speed railway tunnel is anchored by using a prestressed anchor rod, and the rod body of the prestressed anchor rod is broken or the rod body at the joint of the prestressed anchor rod and a connecting sleeve slides to cause the cracking and the damage of an anchor head concrete block. From typical cases collected at present, the failure modes of the free section of the prestressed anchor rod mainly include three modes, namely corrosion failure, stress failure, and slippage failure of the rod body and the connecting sleeve. The stress failure of the free section of the prestressed anchor rod is mainly caused by the prestress of prestressed tendons caused by the deformation or displacement of strata so as to cause the fracture of a rod body.
Because a large amount of strain energy is stored before the free section rod body of the prestressed anchor rod is fractured, the strain energy stored when the free section rod body of the anchor rod is fractured is converted into the kinetic energy of the free section rod body, and the free section rod body which obtains the kinetic energy can impact the anchor head anchor sealing concrete block. The prestressed anchor rod is adopted for anchoring between the structure and the rock (soil) body, if the free section anchor hole is not filled, the design of the anchor head sealing concrete block is an important content of the prestressed anchor rod design, and how to ensure that the anchor sealing concrete is not damaged under the condition of the damage of the free section rod body or secondary loss is not caused after the damage (the reinforcing failure of the prestressed anchor rod of the upper arch section track bed of the railway tunnel causes the damage of the anchor head sealing concrete block to influence the running safety of the train and the like) is an important target of the design of the anchor sealing concrete block.
Disclosure of Invention
The invention aims to solve the technical problem of providing a method for designing a prestressed anchor rod anchor head anchor sealing concrete block, so as to effectively improve the impact resistance and the safety coefficient of the anchor sealing concrete block and solve the problem that no theoretical basis exists in the design of the prestressed anchor rod anchor head anchor sealing concrete block.
The technical scheme adopted by the invention for solving the technical problems is as follows:
the invention relates to a method for designing a prestressed anchor rod anchor head anchor sealing concrete block, which comprises the following steps:
s01, collecting design parameters of the prestressed anchor rod, including the cross section area of the anchor rod bodyA 0Weight per unit lengthm 0Modulus of elasticityE sTensile strength of the steel sheetR mLength of free section before tensioningl 0;
S02, calculating the speed of the free end of the free section at the side of the anchor head when the free section of the prestressed anchor rod is broken and the stored strain energy is completely released according to the following formulav 2:
In the formula (I), the compound is shown in the specification,v 2the speed of the free end of the free section at the side of the anchor head when the strain energy is completely released is in the unit of m/s;A 0is the cross-sectional area of the anchor rod body in m2;m 0Weight per unit length in kg/m;E sis the modulus of elasticity, in Pa;R mfor tensile strength, the unit N/m2;l 0Length of free segment before tensioningl 0,l 10The original length of the free section at the inner side of the anchor hole before deformation, l 20is the original length of the free section at the side of the anchor head before deformation, unit m, andl 0=l 10+l 20;
s03, modeling and dynamic analysis, preliminarily drawing up the size and the strength grade of the anchor-sealing concrete block at the anchor head, and establishing a finite element or finite difference numerical model for dynamic analysis to detect and calculate the impact stress of the anchor-sealing concrete block under different working conditions of the fracture of the free section of the prestressed anchor rod;
when the analysis results of various working conditions show that the tensile stress of the anchor-sealing concrete blockσAre both less than or equal to the allowable tensile stress [ solution ]σ t]Then, the size of the anchor sealing concrete block and the strength grade of the concrete meet the design requirements; otherwise, repeating the step and continuing the modeling dynamic analysis until the size of the anchor sealing concrete block and the strength grade of the concrete meet the design requirements;
s04, determining an anchoring scheme between the anchor sealing concrete block and the existing structure;
and S05, completing design.
In the above technical solution, the anchoring scheme in step S04 includes embedding anchoring steel bars in the sealed and anchored concrete block at longitudinal and lateral intervals, and anchoring the overhanging sections of each anchoring steel bar and the existing structure by using a chemical anchoring agent;
the anchoring scheme in the step S04 further comprises the steps of arranging spring ribs with two ends respectively acting on the backing plate and the anchor sealing concrete block in the anchor sealing concrete block;
the anchoring scheme in step S04 further includes filling anchor cement in the existing structure at a localized section of the anchor hole.
The beneficial effects of the invention are embodied in the following aspects:
according to the energy conservation law and the momentum conservation law, assuming that the free section of the prestressed anchor rod is broken and the stored strain energy is completely converted into system kinetic energy, the rod body speed of the free section is linearly distributed, deducing a calculation formula of the speed of the free end of the free section on the side of the anchor head, then drawing the size of the concrete block and the strength grade of the concrete, modeling and carrying out dynamic analysis, and thus detecting whether the size of the concrete block meets the design requirement or not, so that the anchor-sealing concrete block is designed with scientific theoretical basis;
secondly, an anchoring scheme between the anchor sealing concrete block and the existing structure is provided, anchoring reinforcing steel bars are implanted into the existing structure at the anchor head, spring bars are installed, and then the concrete block is poured in situ, so that the anchoring effect between the anchor sealing concrete block and the existing structure is enhanced, the impact resistance of the anchor sealing concrete block is improved, and secondary loss or accidents cannot be caused even if the anchor sealing concrete block is impacted and damaged; the anchor head is filled with anchoring materials at the local section of the anchor hole in the existing structure, so that the impact stress of the anchor sealing concrete block can be effectively reduced, and the size of the anchor sealing concrete block is optimized.
Drawings
The specification includes the following seven drawings:
FIG. 1 is a flow chart of a design method in the method for designing a prestressed anchor head anchor-sealing concrete block according to the present invention;
FIG. 2 is a schematic diagram illustrating a fracture position of a free section of a prestressed anchor in the method for designing a prestressed anchor head-sealed concrete block according to the present invention;
FIG. 3 is a schematic diagram illustrating the velocity distribution of the free section rod body on the anchor head side when the free section of the prestressed anchor is broken and the stored strain energy is completely converted into the kinetic energy of the system in the method for designing the prestressed anchor head-sealed concrete block according to the present invention;
FIG. 4 is a schematic view of a dynamic analysis model in the method for designing a prestressed anchor head anchor-sealing concrete block according to the present invention;
FIG. 5 is a schematic view of a design scheme of an anchor-sealing concrete block in the method for designing the anchor head anchor-sealing concrete block of the prestressed anchor rod;
FIG. 6 is a schematic view of an anchoring scheme of the anchoring steel bars of the sealed anchor concrete block in the method for designing the prestressed anchor head sealed anchor concrete block of the present invention;
FIG. 7 is a schematic diagram of the optimization measure of the size of the anchor-sealing concrete block in the method for designing the anchor head anchor-sealing concrete block of the prestressed anchor rod.
The symbols in the figures and the corresponding meanings: 11-free section at the inner side of an anchor hole, 12-free section at the side of an anchor head, 13-anchoring section of a prestressed anchor rod, 20-backing plate, 30-nut, 40-anchor sealing concrete block, 50-existing structure, 60-rock (soil) body, 70-anchor hole, 80-spring rib, 90-anchoring reinforcing steel bar, 100-chemical anchoring agent and 200-anchoring cementing material.
Detailed Description
The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.
Referring to fig. 1, 2, 3 and 4, the method for designing the prestressed anchor head-sealed concrete block of the present invention comprises the following steps:
s01, collecting design parameters of the prestressed anchor rod, including the cross section area of the anchor rod bodyA 0Unit length ofWeight (D)m 0Modulus of elasticityE sTensile strength of the steel sheetR mLength of free section before tensioningl 0。
And S02, according to the law of conservation of energy and the law of conservation of momentum, the strain energy stored in the free section when the free section of the prestressed anchor rod is broken is converted into system kinetic energy along the axial direction of the anchor rod body, and the sum of the momentums of the free section 11 on the inner side of the anchor hole and the free section 12 on the side of the anchor head after the free section is broken is zero. Assuming that the free section of the prestressed anchor rod is broken and the speed of the free section rod body is linearly distributed when the stored strain energy is completely converted into the system kinetic energy, namely the constraint end is 0 and the free end is the maximum, the speed of the free end of the free section on the side of the anchor head can be deduced to be:
according to the formula, the speed of the free end of the free section at the anchor head side when the free section of the prestressed anchor rod is broken and the stored strain energy is completely released is calculatedv 2。
In the formula (I), the compound is shown in the specification,v 2the speed of the free end of the free section at the side of the anchor head when the strain energy is completely released is in the unit of m/s;A 0is the cross-sectional area of the anchor rod body in m2;m 0Weight per unit length in kg/m;E sis the modulus of elasticity, in Pa;R mfor tensile strength, the unit N/m2;l 0Length of free segment before tensioningl 0,l 10The original length of the free section at the inner side of the anchor hole before deformation, l 20is the original length of the free section at the side of the anchor head before deformation, unit m, andl 0=l 10+l 20。
s03, modeling and dynamic analysis, preliminarily drawing up the size of the concrete block 40 for sealing the anchor and the strength grade of the concrete, establishing a finite element or finite difference numerical model for dynamic analysis, and detecting and calculating different working conditions of the free section fracture of the prestressed anchor rod (l 20、l 10/l 20) Lower seal anchor concrete block 40Impact stress of (2).
Under various working conditions (l 20、l 10/l 20) The analysis result shows the tensile stress of the anchor-sealing concrete block 40σAre both less than or equal to the allowable tensile stress [ solution ]σ t]In time, the size of the anchor sealing concrete block 40 and the strength grade of the concrete meet the design requirements; otherwise, repeating the steps and continuing the modeling dynamic analysis until the size of the anchor-sealing concrete block 40 and the strength grade of the concrete meet the design requirements.
S04, determining an anchoring scheme between the anchor sealing concrete block 40 and the existing structure;
the anchoring scheme comprises one or any combination of the following technical measures:
1. embedding anchoring steel bars 90 in the anchor sealing concrete block 40 at intervals in the longitudinal and transverse directions, and anchoring the overhanging sections of the anchoring steel bars 90 and the existing structure 50 by adopting a chemical anchoring agent 100 so as to enhance the anchoring effect between the anchor sealing concrete block 40 and the existing structure 50;
2. the anchor sealing concrete block 40 is internally provided with a spring rib 80 of which two ends respectively act on the backing plate 20 and the anchor sealing concrete block 40 so as to consume the impact energy of the anchor head side free section 12 and enhance the anti-cracking performance of the anchor sealing concrete block 40;
3. the local section of the anchor hole in the existing structure 50 is filled with the anchoring cementing material 200, so that the bearing capacity of the existing structure 50 can be adjusted, the impact stress of the anchor sealing concrete block 40 is reduced, and the size of the anchor sealing concrete block 40 is optimized.
And S05, completing design.
According to the energy conservation law and the momentum conservation law, the invention supposes that the speed of the free section rod body is linearly distributed when the free section of the prestressed anchor rod is broken and the stored strain energy is completely converted into the system kinetic energy, deduces a calculation formula of the speed of the free end of the free section on the side of the anchor head, then draws up the size of the concrete block and the strength grade of the concrete and carries out dynamic analysis by modeling, thereby detecting whether the size of the concrete block meets the design requirement or not, and enabling the anchor-sealing concrete block to be designed with scientific theoretical basis. Meanwhile, an anchoring scheme between the anchor sealing concrete block and the existing structure is provided, so that the anchoring effect between the anchor sealing concrete block and the existing structure is enhanced, the impact resistance of the anchor sealing concrete block is improved, the impact stress of the anchor sealing concrete block is effectively reduced, and the size of the anchor sealing concrete block is optimized.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (4)
1. The design method of the prestressed anchor rod anchor head anchor sealing concrete block comprises the following steps:
s01, collecting design parameters of the prestressed anchor rod, including the cross section area of the anchor rod bodyA 0Weight per unit lengthm 0Modulus of elasticityE sTensile strength of the steel sheetR mLength of free section before tensioningl 0;
S02, calculating the speed of the free end of the free section at the side of the anchor head when the free section of the prestressed anchor rod is broken and the stored strain energy is completely released according to the following formulav 2:
In the formula (I), the compound is shown in the specification,v 2the speed of the free end of the free section at the side of the anchor head when the strain energy is completely released is in the unit of m/s;A 0is the cross-sectional area of the anchor rod body in m2;m 0Weight per unit length in kg/m;E sis the modulus of elasticity, in Pa;R mfor tensile strength, the unit N/m2;l 0Length of free segment before tensioningl 0,l 10The original length of the free section at the inner side of the anchor hole before deformation, l 20is the original length of the free section at the side of the anchor head before deformation, unit m, andl 0=l 10+l 20;
s03, modeling and dynamic analysis, preliminarily drawing up the size and the concrete strength grade of the anchor-sealing concrete block (40), and establishing a finite element or finite difference numerical model for dynamic analysis to detect and calculate the impact stress of the anchor-sealing concrete block (40) under different working conditions of the fracture of the free section of the prestressed anchor rod;
when the analysis results of various working conditions show that the anchor-sealing concrete block (40) has tensile stressσAre both less than or equal to the allowable tensile stress [ solution ]σ t]When the size and the strength grade of the anchored concrete block (40) meet the design requirements; otherwise, repeating the steps and continuing the modeling dynamic analysis until the size of the anchor sealing concrete block (40) and the strength grade of the concrete meet the design requirements;
s04, determining an anchoring scheme between the anchor sealing concrete block (40) and the existing structure;
and S05, completing design.
2. The method for designing the prestressed anchor head-sealed concrete block as claimed in claim 1, wherein: the anchoring scheme in the step S04 comprises the steps that anchoring steel bars (90) are embedded in the anchor sealing concrete block (40) at intervals in the longitudinal direction and the transverse direction, and the outward extending sections of the anchoring steel bars (90) and the existing structure (50) are anchored by chemical anchoring agents (100).
3. The method for designing the prestressed anchor head-sealed concrete block as claimed in claim 2, wherein: the anchoring scheme in the step S04 further comprises the step of arranging spring ribs (80) with two ends respectively acting on the backing plate (20) and the anchor sealing concrete block (40) in the anchor sealing concrete block (40).
4. The method for designing the prestressed anchor head-sealed concrete block as claimed in claim 2 or 3, characterized in that: the anchoring scheme further includes filling a partial section of the anchor hole in the existing structure (50) with an anchoring cement (200) at step S04.
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AU2487601A (en) * | 2000-03-06 | 2001-09-13 | Screw In Technologies Pty Ltd | Anchor elements and methods and apparatus for fabricating anchor elements |
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CN108756943A (en) * | 2018-05-28 | 2018-11-06 | 湖南科技大学 | A kind of tunnel tunnel face support reinforcement Parameters design |
CN111576408A (en) * | 2020-06-09 | 2020-08-25 | 江苏景源万河环境科技有限公司 | Construction method of expanded head prestressed concrete anchor rod |
CN112095633A (en) * | 2020-08-26 | 2020-12-18 | 浙江佳途勘测设计有限公司 | Construction process of die-free concrete beam |
Family Cites Families (1)
Publication number | Priority date | Publication date | Assignee | Title |
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AUPQ479699A0 (en) * | 1999-12-21 | 2000-02-03 | Tristanagh Pty Ltd | Earth retention and piling systems |
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Patent Citations (5)
Publication number | Priority date | Publication date | Assignee | Title |
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AU2487601A (en) * | 2000-03-06 | 2001-09-13 | Screw In Technologies Pty Ltd | Anchor elements and methods and apparatus for fabricating anchor elements |
CN107587506A (en) * | 2017-09-08 | 2018-01-16 | 江苏景源万河环境科技有限公司 | A kind of precast prestressed anchor pole rod member and construction |
CN108756943A (en) * | 2018-05-28 | 2018-11-06 | 湖南科技大学 | A kind of tunnel tunnel face support reinforcement Parameters design |
CN111576408A (en) * | 2020-06-09 | 2020-08-25 | 江苏景源万河环境科技有限公司 | Construction method of expanded head prestressed concrete anchor rod |
CN112095633A (en) * | 2020-08-26 | 2020-12-18 | 浙江佳途勘测设计有限公司 | Construction process of die-free concrete beam |
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