Anchor rod based on stress wave transmission and reflection theory and preparation method and system thereof

Abstract

The invention relates to the technical field of rock-soil anchoring, in particular to an anchor rod based on a stress wave transmission and reflection theory and a preparation method and system thereof. Comprising the following steps: acquiring the acoustic longitudinal wave velocity and density of an anchored surrounding rock body, and calculating the wave impedance of the anchored surrounding rock body according to the acoustic longitudinal wave velocity and density; determining the wave impedance of the concrete mortar material according to the wave impedance of the anchoring surrounding rock body; the wave impedance required by the anchor rod is obtained based on the wave impedance of the concrete mortar material, and the anchor rod is prepared based on the wave impedance condition of the anchor rod. According to the method, the stress wave intensity transmitted by the stress waves is reduced, and then the stress wave incident intensity of the rear anchor rod body is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of rock and soil anchoring, and in particular to an anchor rod based on stress wave transmission and reflection theory and a preparation method and system thereof. Background Art

[0002] Anchor support is an indispensable support form in underground engineering. It relies on bonding to reinforce the surrounding rock with stable rock mass to improve the stability of the surrounding rock. It is widely used in excavation support of water conservancy, hydropower, transportation, mining and other projects. When excavating underground caverns by drilling and blasting, the anchor body behind the face is constantly subjected to stress wave transmission and reflection under frequent blasting disturbances, which reduces or fails the bonding force between the mortar, the anchor and the surrounding rock, thereby weakening the anchoring force of the anchor and even causing the anchor to fall off from the borehole. The main reason for the reduction or failure of the bonding force between the mortar, the anchor and the surrounding rock under the action of blasting disturbance is that the interface stress wave intensity exceeds the bonding strength between the mortar, the anchor and the surrounding rock. Therefore, how to reduce the stress wave effect at the surrounding rock-mortar interface and the mortar-anchor interface is the main way to solve the problem of anchor failure.

[0003] At present, ordinary mortar anchors, hollow grouting anchors, etc. are commonly used in underground engineering support. The stress wave is incident from the rock mass from one side of the anchor hole to the other side of the anchor hole. The dielectric wave impedance experienced is high (rock mass) → low (mortar) → anchor body (high) (→ low (mortar) → high (anchor body, hollow grouting anchor) → low (mortar) → high (rock mass). In this case, the dielectric wave impedance matching - the difference between the two adjacent dielectric wave impedances is large, which makes the stress wave intensity at the mortar-anchor interface and the surrounding rock-mortar interface too large, which easily causes the bonding strength between the mortar and the anchor and the surrounding rock to decrease or fail. Summary of the invention

[0004] The present invention provides an anchor rod and a preparation method and system thereof based on stress wave transmission and reflection theory, aiming to solve the problem of reduced or failed bonding strength between the surrounding rock-mortar interface and the mortar-anchor rod interface of the anchor rod body under frequent blasting disturbances.

[0005] The objective of the present invention is achieved by the following technical solutions:

[0006] A method for preparing an anchor rod based on stress wave transflection theory, comprising:

[0007] Acquiring the acoustic longitudinal wave velocity and density of the anchored surrounding rock mass, and calculating the wave impedance of the anchored surrounding rock mass according to the acoustic longitudinal wave velocity and density;

[0008] Determine the wave impedance of concrete mortar material based on the wave impedance of the anchored surrounding rock mass;

[0009] The wave impedance required by the anchor rod is obtained based on the wave impedance of the concrete mortar material, and the anchor rod is prepared based on the wave impedance condition of the anchor rod. The interior of the anchor rod body is a hollow structure.

[0010] As a further improvement of the present invention, the wave impedance matching relationship between the anchor rod, the concrete mortar material and the anchored surrounding rock mass satisfies:

[0011] ρ r V r >ρ c V c >ρ1V1

[0012] In the formula, ρ r is the density of the anchored surrounding rock mass; V r is the acoustic longitudinal wave velocity of the anchored surrounding rock mass; c is the density of concrete mortar material; V c is the acoustic longitudinal wave velocity of the concrete mortar material; ρ1 is the density of the anchor rod; V1 is the acoustic longitudinal wave velocity of the anchor rod.

[0013] As a further improvement of the present invention, the anchor rod is made of glass fiber reinforced plastic.

[0014] As a further improvement of the present invention, the structure of the anchor rod comprises at least two layers, and the wave impedance from the outermost layer to the inner layer of the anchor rod meets the requirement of decreasing successively.

[0015] As a further improvement of the present invention, the central portion of the anchor rod is a hollow structure, and during the grouting process of the anchor rod, the hollow portion is not grouted.

[0016] As a further improvement of the present invention, the concrete mortar is prepared by adding iron sand to cement mortar, and adjusting the mixing ratio of cement, water and iron sand to obtain concrete mortar with a wave impedance smaller than the wave impedance of the anchored surrounding rock body.

[0017] The present invention also provides an anchor rod based on the stress wave transflection theory, comprising an anchor rod body, wherein the anchor rod body is prepared based on the above-mentioned anchor rod preparation method based on the stress wave transflection theory.

[0018] The present invention also provides an anchor preparation system based on stress wave transflection theory, comprising:

[0019] Anchored surrounding rock mass design module, used to obtain the acoustic longitudinal wave velocity and density of the anchored surrounding rock mass, and calculate the wave impedance of the anchored surrounding rock mass according to the acoustic longitudinal wave velocity and density;

[0020] Concrete mortar design module, used to determine the wave impedance of concrete mortar materials based on the wave impedance of the anchored surrounding rock mass;

[0021] The anchor rod design module is used to obtain the wave impedance required by the anchor rod based on the wave impedance of the concrete mortar material, and prepare the anchor rod based on the wave impedance condition of the anchor rod.

[0022] The beneficial effects of the present invention are as follows: the present invention can ensure that the stress wave incident from the rock mass propagates from the high wave impedance medium to the low wave impedance medium in sequence, has a reflection unloading effect, can reduce the intensity of the reflection tensile effect in front of the interface, reduce the stress wave intensity effect of the surrounding rock-mortar interface and the mortar-anchor interface, and at the same time utilize the air layer energy consumption in the hollow part of the anchor to reduce the stress wave intensity of the stress wave transmitted out, thereby reducing the stress wave incident intensity of the rear anchor body. The anchor and design method have significant anchoring energy consumption and crack prevention effects, reliable support capacity, and a lightweight rod body that is easy to install and construct. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0024] Figure 1 It is a schematic diagram of transmission and reflection of one-dimensional compressive stress wave under vertical incidence condition;

[0025] Figure 2 It is a schematic diagram of the transmission and reflection of multiple interfaces of a double-layer hollow FRP anchor under the condition of vertical incidence of one-dimensional compressive stress wave;

[0026] In the figure, 1-rock mass; 2-high wave impedance concrete mortar; 3-double-layer hollow glass anchor rod; 4-interface between mortar and rock mass; 5-interface between mortar and anchor rod. DETAILED DESCRIPTION

[0027] In order to make the purpose and technical solution of the present invention clearer and easier to understand, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. The specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0028] The concept of the present invention is to provide an anchor rod and a preparation method and system thereof based on the stress wave transmission and reflection theory, the method mainly comprising: obtaining the acoustic longitudinal wave velocity and density of the anchored surrounding rock mass, and calculating the wave impedance of the anchored surrounding rock mass according to the acoustic longitudinal wave velocity and density;

[0029] Determine the wave impedance of concrete mortar material based on the wave impedance of the anchored surrounding rock mass;

[0030] The wave impedance required by the anchor rod is obtained based on the wave impedance of the concrete mortar material, and the anchor rod is prepared based on the wave impedance condition of the anchor rod, and the interior of the anchor rod body is a hollow structure.

[0031] The technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and specific embodiments, wherein the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments.

[0032] Example 1

[0033] like Figure 1 , Figure 2 The method for preparing an anchor rod based on the stress wave transmission and reflection theory shown mainly includes the following steps.

[0034] Firstly, the acoustic longitudinal wave velocity and density of the anchored surrounding rock mass are obtained, and the wave impedance of the anchored surrounding rock mass is calculated according to the acoustic longitudinal wave velocity and density.

[0035] The wave impedance of the concrete mortar material is then determined based on the wave impedance of the anchored surrounding rock mass.

[0036] The wave impedance required for the anchor rod is obtained based on the wave impedance of the concrete mortar material, and the anchor rod is prepared based on the wave impedance condition of the anchor rod.

[0037] Specifically, the acoustic longitudinal wave velocity of the concrete mortar material and the anchor rod is measured by a wave velocity tester. The wave impedance matching relationship between the anchor rod, the concrete mortar material and the anchored surrounding rock mass satisfies:

[0038] ρ r V r >ρ c V c >ρ1V1

[0039] In the formula, ρ r is the density of the anchored surrounding rock mass; V r is the acoustic longitudinal wave velocity of the anchored surrounding rock mass; c is the density of concrete mortar material; V c is the acoustic longitudinal wave velocity of the concrete mortar material; ρ1 is the density of the anchor rod; V1 is the acoustic longitudinal wave velocity of the anchor rod.

[0040] The anchor rod in this embodiment is a multi-layer hollow glass fiber reinforced plastic anchor rod structure, and the number of layers from the outside to the inside is 1, 2, ..., n-1, n. Among them, the wave impedance matching relationship between the multi-layer hollow glass fiber reinforced plastic anchor rod, concrete mortar and anchored surrounding rock mass is:

[0041] ρ r V r >ρ c V c >ρ1V1>ρ2V2>…>ρn-1 V n-1 >ρ n V n

[0042] In the formula, ρ1-ρ n are the density of the first layer of anchor rods to the density of the nth layer of anchor rods; correspondingly, V1-V n are the acoustic longitudinal wave velocities from the first layer of anchor to the nth layer of anchor, respectively.

[0043] A beam of one-dimensional compressive stress wave is incident from the rock mass into the anchoring system composed of a multi-layer hollow fiberglass anchor structure and concrete mortar. Multiple transflections will occur at the interface of the medium. To simplify the calculation, after the stress wave is transflected for the first time at the interface between each different medium, only the full transmission of the reflected wave after transflection at the next interface is considered, and the attenuation of the wave during propagation in the same medium is not considered. For example, Figure 2 The superposition values ​​of stress wave intensities and transmitted stress wave intensities of common mortar anchors, common hollow grouting anchors and hollow FRP anchors with different layers at the surrounding rock-mortar interface and mortar-anchor interface under unit incident wave intensity are statistically calculated, as shown in Table 1. Among them, the surrounding rock is granite with a wave impedance of 1.38×107kg·m-3·m·s-1; the wave impedance of ordinary mortar anchors and ordinary hollow grouting anchors is 4.08×107kg·m-3·m·s-1; the wave impedance of ordinary mortar is 0.88×107kg·m-3·m·s-1; the wave impedance of high-impedance mortar prepared for multi-layer hollow FRP anchor grouting is 1.24×107kg·m-3·m·s-1, and the wave impedance of each layer of the multi-layer hollow FRP anchor decreases from the outside to the inside, the nth layer is 0.9 times that of the n-1th layer, and the wave impedance of the outermost layer is 0.9 times that of the mortar, that is, 1.116×107kg·m-3·m·s-1; the wave impedance of air is 0.044×107kg·m-3·m·s-1; the intensity of the incident wave is 1.

[0044] It can be seen that in the surrounding rock support mode of multi-layer hollow FRP anchor rods combined with high wave impedance concrete mortar, the superposition value of the surrounding rock-mortar interface, mortar-anchor interface and the transmitted stress wave intensity is much lower than that of ordinary mortar anchor rods and ordinary hollow grouting anchor rods. For multi-layer hollow FRP anchor rods, the stress wave intensity of the surrounding rock-mortar interface and mortar-anchor interface on the wavefront side gradually decreases with the increase of the number of layers, while the surrounding rock-mortar interface, mortar-anchor interface and the transmitted stress wave intensity on the back wavefront side first decrease and then gradually increase with the increase of the number of layers, and are the lowest at 2 layers. Under this wave impedance matching relationship, the more layers there are, the surrounding rock-mortar interface, mortar-anchor interface and the transmitted stress wave intensity on the back wavefront side will increase significantly, and the stress wave incident intensity of the rear anchor body will also increase accordingly, which is unfavorable. Therefore, a double-layer hollow FRP anchor structure is designed and a high-impedance concrete mortar is prepared so that the wave impedance matching relationship between the double-layer hollow anchor, high-impedance concrete mortar and rock mass is ρ r V r >ρ c V c >ρ1V1>ρ2V2, and using the air layer to dissipate energy, the stress wave intensity at the surrounding rock-mortar interface and the mortar-anchor interface can be reduced, and the stress wave intensity of the stress wave transmitted out can be reduced, thereby reducing the stress wave incident intensity of the rear anchor body and reducing the damage to the anchor. This embodiment also uses ordinary mortar anchors and ordinary hollow grouting anchors for comparison, and the comparison results are shown in Table 1.

[0045] Table 1 Superposition values ​​of stress wave intensities at surrounding rock-mortar interface, mortar-anchor interface and transmitted stress wave at unit incident wave intensity for different anchor types

[0046]

[0047] Among them, interface A represents the surrounding rock-mortar interface, and interface B represents the mortar-anchor interface.

[0048] As shown in Table 1, the double-layer hollow anchor is made of fiberglass. While ensuring the anchoring force of the surrounding rock, the rod body is light and easy to install and construct. The wave impedance matching relationship between the anchor, concrete mortar material and the anchored surrounding rock can reduce the stress wave intensity at the surrounding rock-mortar interface and the mortar-anchor interface, thereby improving the surrounding rock anchoring effect.

[0049] Furthermore, the hollow part of the anchor is not grouted, and the air energy is used to reduce the stress wave reflection loading intensity on the back wave surface side of the anchor body. At the same time, the transmitted stress wave intensity is weakened, and the stress wave incident intensity of the rear anchor body is reduced, thereby improving the surrounding rock anchoring effect and ensuring the stability of the cavern surrounding rock.

[0050] Example 2

[0051] In this embodiment, an anchor rod based on the stress wave transmission and reflection theory includes an anchor rod body, wherein the central part of the anchor rod body structure is a hollow structure, and the rod body is double-layered. The corresponding structure of the anchor rod is specifically as follows:

[0052] The outermost part of the anchor rod body in contact with the rock mass 1 is the mortar-rock interface 4, the first layer is made of high-wave impedance concrete mortar 2, the second layer is made of double-layer hollow glass anchor rod 3, and the interface between the first and second layers is the mortar-anchor rod interface 5.

[0053] The anchor rod body is prepared by using an anchor rod preparation method based on stress wave transflection theory as described in Example 1, and the preparation method mainly comprises:

[0054] Acquiring the acoustic longitudinal wave velocity and density of the anchored surrounding rock mass, and calculating the wave impedance of the anchored surrounding rock mass according to the acoustic longitudinal wave velocity and density;

[0055] Determine the wave impedance of concrete mortar material based on the wave impedance of the anchored surrounding rock mass;

[0056] The wave impedance required for the anchor rod is obtained based on the wave impedance of the concrete mortar material, and the anchor rod is prepared based on the wave impedance condition of the anchor rod.

[0057] The acoustic longitudinal wave velocity of the concrete mortar material and the anchor rod is measured by a wave velocity tester. The wave impedance matching relationship between the anchor rod, concrete mortar material and the anchored surrounding rock mass satisfies:

[0058] ρ r V r >ρ c V c >ρ1V1

[0059] In the formula, ρ r is the density of the anchored surrounding rock mass; V r is the acoustic longitudinal wave velocity of the anchored surrounding rock mass; c is the density of concrete mortar material; V c is the acoustic longitudinal wave velocity of the concrete mortar material; ρ1 is the density of the anchor rod; V1 is the acoustic longitudinal wave velocity of the anchor rod.

[0060] The anchor rod in this embodiment is a multi-layer hollow glass fiber reinforced plastic anchor rod structure, and the number of layers from the outside to the inside is 1, 2, ..., n-1, n. Among them, the wave impedance matching relationship between the multi-layer hollow glass fiber reinforced plastic anchor rod, concrete mortar and anchored surrounding rock mass is:

[0061] ρ r V r >ρ c V c >ρ1V1>ρ2V2>…>ρ n-1 Vn-1 >ρ n V n

[0062] In the formula, ρ1-ρ n are the density of the first layer of anchor rods to the density of the nth layer of anchor rods; correspondingly, V1-V n are the acoustic longitudinal wave velocities from the first layer of anchor to the nth layer of anchor, respectively.

[0063] A beam of one-dimensional compressive stress wave is incident from the rock mass into the anchoring system composed of a multi-layer hollow fiberglass anchor structure and concrete mortar. Multiple transflections will occur at the interface of the medium. To simplify the calculation, after the stress wave is transflected for the first time at the interface between each different medium, only the full transmission of the reflected wave after transflection at the next interface is considered, and the attenuation of the wave during propagation in the same medium is not considered. For example, Figure 2 The superposition values ​​of stress wave intensities and transmitted stress wave intensities of common mortar anchors, common hollow grouting anchors and hollow FRP anchors with different layers at the surrounding rock-mortar interface and mortar-anchor interface under unit incident wave intensity are statistically calculated, as shown in Table 1. Among them, the surrounding rock is granite with a wave impedance of 1.38×107kg·m-3·m·s-1; the wave impedance of ordinary mortar anchors and ordinary hollow grouting anchors is 4.08×107kg·m-3·m·s-1; the wave impedance of ordinary mortar is 0.88×107kg·m-3·m·s-1; the wave impedance of high-impedance mortar prepared for multi-layer hollow FRP anchor grouting is 1.24×107kg·m-3·m·s-1, and the wave impedance of each layer of the multi-layer hollow FRP anchor decreases from the outside to the inside, the nth layer is 0.9 times that of the n-1th layer, and the wave impedance of the outermost layer is 0.9 times that of the mortar, that is, 1.116×107kg·m-3·m·s-1; the wave impedance of air is 0.044×107kg·m-3·m·s-1; the intensity of the incident wave is 1.

[0064] Example 3

[0065] In this embodiment, an anchor preparation system based on stress wave transflection theory includes:

[0066] Anchored surrounding rock mass design module, used to obtain the acoustic longitudinal wave velocity and density of the anchored surrounding rock mass, and calculate the wave impedance of the anchored surrounding rock mass according to the acoustic longitudinal wave velocity and density;

[0067] Concrete mortar design module, used to determine the wave impedance of concrete mortar materials based on the wave impedance of the anchored surrounding rock mass;

[0068] The anchor rod design module is used to obtain the wave impedance required by the anchor rod based on the wave impedance of the concrete mortar material, and prepare the anchor rod based on the wave impedance condition of the anchor rod.

[0069] The acoustic longitudinal wave velocity of the concrete mortar material and the anchor rod is measured by a wave velocity tester. The wave impedance matching relationship between the anchor rod, the concrete mortar material and the anchored surrounding rock mass satisfies:

[0070] ρ r V r >ρ c V c >ρ1V1

[0071] In the formula, ρ r is the density of the anchored surrounding rock mass; V r is the acoustic longitudinal wave velocity of the anchored surrounding rock mass; c is the density of concrete mortar material; V c is the acoustic longitudinal wave velocity of the concrete mortar material; ρ1 is the density of the anchor rod; V1 is the acoustic longitudinal wave velocity of the anchor rod.

[0072] The anchor rod in this embodiment is a multi-layer hollow glass fiber reinforced plastic anchor rod structure, and the number of layers from the outside to the inside is 1, 2, ..., n-1, n. Among them, the wave impedance matching relationship between the multi-layer hollow glass fiber reinforced plastic anchor rod, concrete mortar and anchored surrounding rock mass is:

[0073] ρ r V r >ρ c V c >ρ1V1>ρ2V2>…>ρ n-1 V n-1 >ρ n V n

[0074] In the formula, ρ1-ρ n are the density of the first layer of anchor rods to the density of the nth layer of anchor rods; correspondingly, V1-V n are the acoustic longitudinal wave velocities from the first layer of anchor to the nth layer of anchor, respectively.

[0075] The operation steps of each module have been specifically described in the anchor preparation method based on stress wave transflection theory in Example 1, and will not be repeated here.

Claims

1. A method for preparing an anchor rod based on the stress wave transflection theory, characterized in that: include: Acquiring the acoustic longitudinal wave velocity and density of the anchored surrounding rock mass, and calculating the wave impedance of the anchored surrounding rock mass according to the acoustic longitudinal wave velocity and density; Determine the wave impedance of concrete mortar material based on the wave impedance of the anchored surrounding rock mass; The wave impedance required by the anchor rod is obtained based on the wave impedance of the concrete mortar material, and the anchor rod is prepared based on the wave impedance condition of the anchor rod. The interior of the anchor rod body is a hollow structure.

2. The anchor rod preparation method based on stress wave transflection theory according to claim 1 is characterized in that: The wave impedance matching relationship between the anchor rod, concrete mortar material and the anchored surrounding rock mass satisfies: r r V r >r c V c >p1V1 In the formula, ρ r is the density of the anchored surrounding rock mass; V r is the acoustic longitudinal wave velocity of the anchored surrounding rock mass; c is the density of concrete mortar material; V c is the acoustic longitudinal wave velocity of the concrete mortar material; ρ1 is the density of the anchor rod; V1 is the acoustic longitudinal wave velocity of the anchor rod.

3. The anchor rod preparation method based on stress wave transflection theory according to claim 2 is characterized in that: The anchor rod is made of glass fiber reinforced plastic.

4. The anchor rod preparation method based on stress wave transflection theory according to claim 3 is characterized in that: The structure of the anchor rod at least includes two layers, and the wave impedance from the outermost layer to the inner layer of the anchor rod meets the requirement of decreasing successively.

5. The anchor rod preparation method based on stress wave transflection theory according to claim 4 is characterized in that: The central part of the anchor rod is a hollow structure, and during the grouting process of the anchor rod, the hollow part is not grouted.

6. The anchor rod preparation method based on stress wave transflection theory according to claim 4 is characterized in that: The concrete mortar is prepared by adding iron sand to cement mortar, and adjusting the mixing ratio of cement, water and iron sand to obtain the concrete mortar with a wave impedance smaller than the wave impedance of the anchored surrounding rock mass.

7. An anchor rod based on stress wave transflection theory, comprising an anchor rod body, characterized in that: The anchor rod body is prepared based on the anchor rod preparation method based on the stress wave transmission and reflection theory as described in any one of claims 1 to 6.

8. An anchor preparation system based on stress wave transflection theory, characterized in that: include: Anchored surrounding rock mass design module, used to obtain the acoustic longitudinal wave velocity and density of the anchored surrounding rock mass, and calculate the wave impedance of the anchored surrounding rock mass according to the acoustic longitudinal wave velocity and density; Concrete mortar design module, used to determine the wave impedance of concrete mortar materials based on the wave impedance of the anchored surrounding rock mass; The anchor rod design module is used to obtain the wave impedance required by the anchor rod based on the wave impedance of the concrete mortar material, and prepare the anchor rod based on the wave impedance condition of the anchor rod.

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