Multi-stage anchoring tunnel type anchorage

Abstract

The invention provides a multi-stage anchoring tunnel type anchorage which is buried in a stratum below the earth surface and comprises a cavern system, a main cable and strand system and an anchoring system. The anchoring system comprises at least two anchor bodies which are distributed in series along the axis of the main cable; the cavern system comprises an auxiliary cavern arranged corresponding to the anchor body; the anchor body is located in an anchor hole of the auxiliary cavern, a gallery is arranged in the middle of the anchor hole, and the gallery is a channel communicating the front anchor chamber with the rear anchor chamber after the anchor body is built. The main cable and cable strand system comprises a first main cable forming a bridge main cable, and the first main cable is dispersed into cable strands through all levels of auxiliary caverns. And the cable strands in each stage of auxiliary cavern are anchored with the anchor body through the prestressed steel beams to form a multi-stage load transmission path. The bearing capacity is effectively improved by increasing the number of the anchor bodies, so that the large-tonnage main cable load can be borne, and the anchor is particularly suitable for anchoring of a large-span suspension bridge main cable.

Description

Technical Field

[0001] The invention relates to the technical field of bridge engineering, in particular to a multi-stage anchor tunnel type anchor. Background Art

[0002] Tunnel anchor is a main anchor structure for suspension bridges. The anchor is buried underground by excavating an anchor hole. The anchor and the surrounding rock bear the bridge load together. After nearly 30 years of development, the design and construction technology of tunnel anchor has made great progress. It has been successfully applied to rock formations of different rock mass qualities, and the bridge load it bears has gradually increased. In order to meet the needs of anchoring large-tonnage bridge loads, the method of increasing the size of the anchor is usually adopted to improve the bearing capacity of the tunnel anchor.

[0003] Existing studies have shown that simply increasing the size of the anchor, such as changing the length and cross-sectional dimensions of the anchor, has a good effect on improving the bearing capacity of the anchor within an appropriate range, but the effect is not ideal beyond this range. In addition, when the anchor is larger, the stability of the anchor hole becomes worse, and excavation support is also more difficult. Summary of the invention

[0004] In view of the defects of the prior art, the present invention provides a multi-stage anchor tunnel type anchor. The tunnel type anchor of the present invention effectively improves the bearing capacity by increasing the number of anchor bodies, so it can bear large-tonnage main cable loads and is particularly suitable for anchoring main cables of large-span suspension bridges.

[0005] A multi-stage anchor tunnel type anchorage, comprising a cavern system, a main cable and strand system and an anchor system;

[0006] The anchoring system comprises at least two anchor bodies distributed in series along the main cable axis;

[0007] The cavern system includes an auxiliary cavern arranged corresponding to the anchor body, and the auxiliary cavern includes a traffic cavern, a front anchor chamber, an anchor cavern, and a rear anchor chamber which are connected in sequence; the anchor body is located in the anchor cavern of the auxiliary cavern, and a corridor is arranged in the middle of the anchor cavern, which is a passage connecting the front anchor chamber to the rear anchor chamber after the anchor body is built;

[0008] The main cable and strand system includes a first main cable constituting the main cable of the bridge. The first main cable enters the front anchor chamber through the traffic tunnel of the first-level auxiliary cavern and is dispersed into multiple strands and the second main cable. The second main cable passes through the corridor and the rear anchor chamber in the first-level auxiliary cavern and then enters the second-level auxiliary cavern for similar dispersion until the last-level auxiliary cavern, in which only the main cable is dispersed into strands. The strands in the auxiliary caverns of each level are anchored to the anchor body through prestressed steel strands to form a multi-level load transfer path.

[0009] Furthermore, the anchor body is a wedge-shaped body with a variable cross-section.

[0010] Furthermore, the front anchor chamber is a passage connecting the traffic tunnel to the anchor tunnel, providing space for the cable strands to be dispersed and space for the anchor body to be constructed.

[0011] Furthermore, the anchor hole is a passage connecting the front anchor chamber to the rear anchor chamber, and the outer surface is a variable-section wedge-shaped, providing space for the anchor body.

[0012] Furthermore, the rear anchor chamber is a passage connecting the anchor hole to the traffic hole in the next-level auxiliary cavern, providing space for anchor body construction and space for maintenance during operation.

[0013] Furthermore, the traffic tunnel, front anchor room, anchor tunnel, rear anchor room and corridor all adopt straight wall semicircular arch sections, and the width-to-height ratio of the sections is close to or equal.

[0014] Furthermore, a cable saddle is provided at the intersection of the traffic tunnel and the front anchor chamber, and the main cable is dispersed into multiple cable strands at the cable saddle.

[0015] Furthermore, the anchoring system also includes a front anchor and a rear anchor for locking the prestressed steel bundle. The front anchor is evenly distributed in a ring shape on the front surface of the anchor body, and the rear anchor is evenly distributed in a ring shape on the rear surface of the anchor body.

[0016] Furthermore, the steps for determining the number of anchor bodies are as follows:

[0017] (1) Obtain the design parameters of the anchor body:

[0018] Front anchor width and height: d1, h1;

[0019] Width and height of rear anchor surface: d2, h2;

[0020] Corridor width and height: d3, h3;

[0021] Anchor body length L;

[0022] Anchor elevation angle α;

[0023] Anchor expansion angle β;

[0024] Main cable design load P;

[0025] Anchor body bulk density γ;

[0026] Shear strength of surrounding rock: cohesion C', internal friction angle f';

[0027] (2) According to the obtained design parameters of the anchor body, calculate the side area A and volume V of the anchor body:

[0028] The calculation formula of anchor body side area A is as follows:

[0029] A=L×(C1+C2) / 2

[0030] in:

[0031] C1=d1+(h1-d1 / 2)×2+π×d1 / 2

[0032] C2=d2+(h2-d2 / 2)×2+π×d2 / 2

[0033] The calculation formula of anchor body volume V is as follows:

[0034] in:

[0035] V=L×(S1+S2) / 2-L×S3

[0036] S1=d1×(h1-d1 / 2)+π×(d1 / 2) 2 / 2

[0037] S2=d2×(h2-d2 / 2)+π×(d2 / 2) 2 / 2

[0038] S3=d3×(h3-d3 / 2)+π×(d3 / 2) 2 / 2

[0039] (3) Calculate the allowable pullout resistance P1 of the anchor body based on the calculated side area A and volume V of the anchor body;

[0040] The calculation formula of P1 is as follows:

[0041] P1=f'×W F +C'×A+W L

[0042] in:

[0043] W F =V×γ×cos(α+β)

[0044] W L =V×γ×sinα

[0045] (4) The number of anchors n is calculated based on the calculated allowable pull-out resistance P1 of the anchor. The calculation formula for the number of anchors is as follows:

[0046] n=KP / P1

[0047] n is rounded up to the nearest integer and is the number of anchors.

[0048] Where: K is the pull-out safety factor of the anchor body.

[0049] Furthermore, the value of K is 2.

[0050] Compared with the prior art, the present invention has the following beneficial effects:

[0051] 1. The tunnel type anchor provided by the present invention can improve the bearing capacity by increasing the number of anchor bodies. Compared with the existing method of increasing the size of the anchor body, the improvement of the bearing capacity of the anchor is effective and clear, which provides a better new method for anchoring large-tonnage bridge loads.

[0052] 2. The main cable of the bridge of the present invention is anchored on multiple anchor bodies of the tunnel-type anchorage. The load of the main cable is borne in stages, and the load value borne by each anchor body is relatively low, so the anchoring system has good reliability.

[0053] 3. The steel bundles of the anchoring system of the present invention are distributed in an annular manner in the concrete between the inner gallery surface of the anchor body and the outer surface of the anchor body. The anchor body concrete is stressed evenly, thereby improving the stability of the anchoring system.

[0054] 4. The anchor body of the present invention is provided with a corridor inside, which can provide a passage for the main cable to pass through, and can also be used as a passage for personnel, pipelines and equipment to enter and exit during the operation period. There is no need to dig other pedestrian holes and drainage holes, which can effectively reduce the cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 A vertical cross-sectional structural layout diagram of the multi-stage anchor tunnel type anchorage of the present invention;

[0056] Figure 2 The oblique cross-section anchor hole arrangement diagram of the multi-stage anchor tunnel type anchorage of the present invention;

[0057] Figure 3 A schematic diagram of the cross-sectional shape of a traffic tunnel according to the present invention;

[0058] Figure 4 A schematic diagram of the cross-sectional shape of the first-stage anchor body rear anchor chamber and the second-stage gallery of the present invention;

[0059] Figure 5 Schematic diagram of steel bundle embedding of the anchoring system in the first and second level anchor bodies of the present invention;

[0060] Figure 6 Schematic diagram of the front shape of the first and second level anchor bodies and the front anchor arrangement of the present invention;

[0061] Figure 7 Schematic diagram of the tail shape of the first and second stage anchor bodies and the arrangement of the rear anchors of the present invention. DETAILED DESCRIPTION

[0062] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are 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.

[0063] See also Figure 1 and Figure 2 An embodiment of the present invention provides a multi-stage anchor tunnel type anchor, which is buried in a stratum 2 below the surface 1, and includes a cavern system 3, a main cable and strand system 4 and an anchor system 5.

[0064] The cave system 3 includes a first traffic tunnel 31a, a first front anchor room 32a, a first anchor hole 33a, a first rear anchor room 34a, a first corridor 35a, a second traffic tunnel 31b, a second front anchor room 32b, a second anchor hole 33b, a second rear anchor room 34b and a second corridor 35b.

[0065] The first traffic tunnel 31a is a passage connecting the ground surface 1 to the first front anchor chamber 32a.

[0066] The first front anchor chamber 32a is a passage connecting the first traffic hole 31a to the first anchor hole 33a, and provides a space for the first cable strands 43a to be dispersed and a space for the first anchor body 53a to be constructed.

[0067] The first anchor hole 33a is a passage connecting the first front anchor chamber 32a to the first rear anchor chamber 34a, and its outer surface is a variable cross-section wedge-shaped, providing a space for the first anchor body 53a. A first corridor 35a is provided in the middle of the first anchor hole 33a, which is a passage connecting the first front anchor chamber 32a to the first rear anchor chamber 34a after the first anchor body 53a is built.

[0068] The first rear anchor chamber 34a is a passage connecting the first anchor hole 33a to the second traffic hole 31b, providing a space for the construction of the first anchor body 53a and a space for maintenance during the operation period.

[0069] The second communication tunnel 31b is a passage connecting the first rear anchor chamber 34a to the second front anchor chamber 32b.

[0070] The second front anchor chamber 32b is a passage connecting the second traffic hole 31b to the second anchor hole 33b, and provides a space for the second cable strands 43b to be dispersed and a space for the second anchor body 53b to be constructed.

[0071] The second anchor hole 33b is a passage connecting the second front anchor chamber 32b to the second rear anchor chamber 34b, and its outer surface is a variable cross-section wedge, providing a space for the second anchor body 53b. A second corridor 35b is provided in the middle of the second anchor hole 33b, which is a passage connecting the second front anchor chamber 32b to the second rear anchor chamber 34b after the second anchor body 53b is built. The second rear anchor chamber 34b provides a space for the construction of the second anchor body 53b and a space for maintenance during the operation period.

[0072] Preferably, the traffic tunnels (31a, 31b), front anchor chambers (32a, 32b), anchor holes (33a, 33b), rear anchor chambers (34a, 34b) and corridors (35a, 35b) of the embodiment of the present invention all adopt straight wall semicircular arch sections, and the width-to-height ratios of the sections are close to or equal, such as Figure 3 , Figure 4 , Figure 6 and Figure 7 shown.

[0073] The main cable and strand system 4 comprises a first main cable 41a, a first loose cable saddle 42a, a first strand 43a, a second main cable 41b, a second loose cable saddle 42b and a second strand 43b.

[0074] The first main cable 41a is a main component for transmitting bridge loads. After passing through the first cable saddle 42a, the first main cable 41a is dispersed into a plurality of first cable strands 43a and second main cables 41b. The first main cable 41a is made of steel strands.

[0075] The first strand 43a is an auxiliary component for transferring bridge loads, and is connected to the first steel strand 52a, and transfers loads to the first anchor body 53a through the first steel strand 52a. The material of the first strand 43a is the same steel strand as that of the first main cable 41a.

[0076] The second main cable 41b is a main component for transmitting bridge loads. After passing through the second cable saddle 42b, the second main cable 41b is dispersed into a plurality of second cable strands 43b. The second main cable 41b is made of the same steel strand as the first main cable 41a.

[0077] The second strand 43b is an auxiliary component for transferring bridge loads, and is connected to the second steel strand 52b, and transfers loads to the second anchor body 53b through the second steel strand 52b. The second strand 43b is made of the same steel strand as the second main cable 41b.

[0078] The anchoring system 5 includes a first front anchor 51a, a first steel strand 52a, a first anchor body 53a, a first rear anchor 54a, a second front anchor 51b, a second steel strand 52b, a second anchor body 53b and a second rear anchor 54b.

[0079] The first front anchors 51a are evenly distributed in an annular manner on the front surface of the first anchor body 53a. Figure 6 As shown, it is a component for locking the first steel bundle 52a, and the first front anchor 51a is composed of an anchor plate, an anchor ring and a clip. The anchor plate is buried in the first anchor body 53a and is used to install the anchor ring and the clip.

[0080] The first steel bundle 52a is buried in the steel protective tube of the first anchor body 53a. Figure 5 As shown, the number of the first steel bundles 52a is equal to the number of the first cable strands 43a. After the first steel bundles 52a are connected to the first cable strands 43a, they bear the bridge load and transfer it to the first anchor body 53a.

[0081] The first anchor body 53a is cast by concrete in the first anchor hole 33a, is a wedge-shaped body with a variable cross-section, and is the main load-bearing component.

[0082] The first rear anchors 54a are evenly distributed in an annular shape on the rear surface of the first anchor body 53a. Figure 7 As shown, it is a component for locking the first steel bundle 52a and transmitting the tension of the first steel bundle 52a to the anchor body. The first rear anchor 54a is composed of an anchor plate, an anchor ring and a clip. The anchor plate is buried in concrete and is used to install the anchor ring and the clip.

[0083] The second front anchors 51b are evenly distributed on the front surface of the second anchor body 53b in an annular shape. Figure 6 As shown, it is a component for locking the second steel bundle 52b, and the second front anchor 51b is composed of an anchor plate, an anchor ring and a clip. The anchor plate is buried in the second anchor body 53b and is used to install the anchor ring and the clip.

[0084] The second steel bundle 52b is buried in the steel protective tube of the second anchor body 53b. Figure 5 The number of the second steel bundles 52b is equal to the number of the second cable strands 43b. After the second steel bundles 52b are connected to the second cable strands 43b, they bear the bridge load and transfer it to the second anchor body 53b.

[0085] The second anchor body 53b is cast by concrete in the second anchor hole 33b, is a wedge-shaped body with a variable cross-section, and is the main load-bearing component.

[0086] The second rear anchor 54b is located on the rear surface of the second anchor body 53b. Figure 7 As shown, it is a component for locking the second steel bundle 52b and transmitting the tension of the second steel bundle 52b to the anchor body. The second rear anchor 54b is composed of an anchor plate, an anchor ring and a clip. The anchor plate is buried in concrete and is used to install the anchor ring and the clip.

[0087] The embodiment of the present invention further provides a method for constructing the above-mentioned multi-stage anchor tunnel type anchor, comprising the following steps:

[0088] Step S1, excavation and support of the cave system 3 to form a through space. Step S1 specifically includes:

[0089] Step S11, excavating and supporting the first traffic tunnel 31a, the first front anchor chamber 32a, the first anchor hole 33a and the first rear anchor chamber 34a in sequence from the ground surface.

[0090] Step S12: excavating the second traffic tunnel 31b, the second front anchor chamber 32b, the second anchor hole 33b and the second rear anchor chamber 34b in sequence from the first rear anchor chamber 34a.

[0091] Step S2: Construction of anchoring system 5 and installation of equipment. Step S2 specifically includes:

[0092] Step S21, use steel brackets to fix the anchor plate of the second front anchor 51b, the steel protective pipe of the second steel bundle 52b and the anchor plate of the second rear anchor 54b, make the outer contour template of the second corridor 35a and the partition template for the second anchor body 53b to be cast in compartments, and cast and maintain the concrete of the second anchor body 53b multiple times until the casting is completed.

[0093] Step S22, installing and assembling all the second steel bundles 52b. Taking one second steel bundle 52b as an example, the second steel bundle 52b passes through the second front anchor 51b and the steel protective tube in sequence, reaches the second rear anchor 54b and is locked with a clip; the second steel bundle 52b is tensioned at the second front anchor 51b by a tensioning device, and is locked with a clip after reaching a predetermined tension.

[0094] Step S23, use steel brackets to fix the anchor plate of the first front anchor 51a, the steel protective pipe of the first steel bundle 52a and the anchor plate of the first rear anchor 54a, make the outer contour template of the first corridor 35a and the partition template for the compartment casting of the first anchor body 53a, and cast and maintain the concrete of the first anchor body 53a multiple times until the casting is completed.

[0095] Step S24, install and assemble all the first steel bundles 52a. Taking one first steel bundle 52a as an example, the first steel bundle 52a passes through the first front anchor 51a and the steel protective tube in sequence, reaches the first rear anchor 54a and is locked with a clip; the first steel bundle 52a is tensioned at the first front anchor 51a using a tensioning device, and is locked with a clip after reaching a predetermined tension.

[0096] Step S3: installing the main cable and the cable strand system 4. Step S3 specifically includes:

[0097] Step S31, transport and assemble the cable saddle. Transport the second cable saddle 42b to the intersection of the second traffic tunnel 31b and the second front anchor chamber 32b, assemble and fix it on the bedrock at the bottom of the tunnel. Transport the first cable saddle 42a to the intersection of the first traffic tunnel 31a and the first front anchor chamber 32a, assemble and fix it on the bedrock at the bottom of the tunnel.

[0098] Step S32: The main cable 41 passes through the ground surface 1 from the first traffic tunnel 31a into the ground layer 2, and is dispersed into a plurality of first cable strands 43a and second main cables 41b at the first cable saddle 42a.

[0099] Step S33: The second main cable 41b passes through the first corridor 35a and the first rear anchor chamber 34a to reach the second traffic tunnel 31b, and is dispersed into a plurality of second cable strands 43b at the second cable saddle 42b.

[0100] Step S34: All the second strands 43b are connected to the second steel strands 52b, and all the first strands 43a are connected to the first steel strands 52a.

[0101] Step S4: anchor anti-corrosion and operation period maintenance. Step S4 specifically includes:

[0102] Step S41, anchor anti-corrosion treatment: The exposed concrete surface of the cavern system 3 is coated with an anti-corrosion agent, and the exposed steel strands and steel products of the main cable and strand system 4 and the anchor system 5 are coated with anti-corrosion grease.

[0103] Step S42, anchorage operation period maintenance. The first traffic tunnel 31a, the first corridor 35a, the second traffic tunnel 31b and the second corridor 35b are used as passages for personnel, pipelines and equipment to enter and exit the cavern system 3, and ventilation and drainage equipment are installed in the first front anchor chamber 32a, the first rear anchor chamber 34a, the second front anchor chamber 32b and the second rear anchor chamber 34b to carry out long-term maintenance management during the operation period.

[0104] The number of anchor bodies of the tunnel anchor of the present invention can be increased. The above implementation is described by taking two anchor bodies as an example. If the number of anchor bodies increases, the number of first anchor bodies and auxiliary caverns and anchoring equipment can be increased proportionally.

[0105] The embodiment of the present invention also provides a method for calculating the number of anchor bodies:

[0106] (1) Obtaining the design parameters of the anchor body

[0107] According to the design documents of the anchor body, the parameters of the anchor body are obtained as follows:

[0108] Front anchor width and height: d1, h1;

[0109] Width and height of rear anchor surface: d2, h2;

[0110] Corridor width and height: d3, h3;

[0111] Anchor body length L;

[0112] Anchor elevation angle α;

[0113] Anchor expansion angle β;

[0114] Main cable design load P;

[0115] Anchor body bulk density γ;

[0116] Shear strength of surrounding rock: cohesion C', internal friction angle f';

[0117] (2) Based on the obtained design parameters of the anchor body, calculate the side area A and volume V of the anchor body.

[0118] The calculation formula of anchor body side area A is as follows:

[0119] A=L×(C1+C2) / 2

[0120] in:

[0121] C1=d1+(h1-d1 / 2)×2+π×d1 / 2

[0122] C2=d2+(h2-d2 / 2)×2+π×d2 / 2

[0123] The calculation formula of anchor body volume V is as follows:

[0124] in:

[0125] V=L×(S1+S2) / 2-L×S3

[0126] S1=d1×(h1-d1 / 2)+π×(d1 / 2) 2 / 2

[0127] S2=d2×(h2-d2 / 2)+π×(d2 / 2) 2 / 2

[0128] S3=d3×(h3-d3 / 2)+π×(d3 / 2) 2 / 2

[0129] (3) Based on the calculated side area A and volume V of the anchor body, calculate the allowable pull-out resistance P1 of the anchor body.

[0130] The calculation formula of P1 is as follows:

[0131] P1=f'×W F +C'×A+W L

[0132] in:

[0133] W F =V×γ×cos(α+β)

[0134] W L =V×γ×sinα

[0135] (4) Calculate the number of anchors n based on the calculated allowable pull-out resistance P1 of the anchor

[0136] The calculation formula for the number of anchor bodies is as follows:

[0137] n=KP / P1

[0138] n is rounded up to the nearest integer and is the number of anchors.

[0139] Where: K is the pull-out safety factor of the anchor body. The "Design Code for Highway Suspension Bridges" stipulates that this value should not be less than 2, so K is taken as 2.

[0140] The following is a specific implementation example for calculating the number of anchor bodies:

[0141] (1) Obtaining the design parameters of the anchor body

[0142] According to the design documents of the anchor body, the parameters of the anchor body are as follows:

[0143] Front anchor width and height: d1 = 6m, h1 = 6m

[0144] Width and height of rear anchor surface: d2 = 10m, h2 = 10m

[0145] Corridor width and height: d3 = 2m, h3 = 2m

[0146] Anchor length L = 30m

[0147] Anchor elevation angle α=40°

[0148] Anchor expansion angle β = 3.81°

[0149] Main cable design load P = 400000 kN

[0150] Anchor body density γ=24kN / m 3

[0151] Surrounding rock shear strength: C'=700kPa, f'=0.81

[0152] (2) Calculation of the lateral area A and volume V of the anchor body The lateral area A of the anchor body is calculated as follows: A = L × (C1 + C2) / 2 = 856.8 m 2

[0153] in:

[0154] C1=d1+(h1-d1 / 2)×2+π×d1 / 2=21.4m

[0155] C2=d2+(h2-d2 / 2)×2+π×d2 / 2=35.7m

[0156] The calculation formula of anchor body volume V is as follows:

[0157] in:

[0158] V=L×(S1+S2) / 2-L×S3=1713.6m 3

[0159] S1=d1×(h1-d1 / 2)+π×(d1 / 2) 2 / 2=32.1m 2

[0160] S2=d2×(h2-d2 / 2)+π×(d2 / 2) 2 / 2=89.3m 2

[0161] S3=d3×(h3-d3 / 2)+π×(d3 / 2) 2 / 2=3.6m 2

[0162] (3) The calculation formula for the allowable pullout resistance P1P1 of the anchor body is as follows:

[0163] P1=f'×W F +C'×A+W L =650233.4kN

[0164] in:

[0165] W F =V×γ×cos(α+β)=29676.4kN

[0166] W L =V×γ×sinα=26435.5kN

[0167] (4) Calculate the number of anchors

[0168] The calculation formula for the number of anchor bodies is as follows:

[0169] n=KP / P1=1.2

[0170] n is rounded up to 2, which is the number of anchors.

[0171] Where: K is the pull-out safety factor of the anchor body. The "Design Code for Highway Suspension Bridges" stipulates that this value should not be less than 2, so K is taken as 2.

[0172] The present invention arranges multiple series-connected anchor bodies and auxiliary caverns on the main cable axis of the bridge, and a corridor is arranged in the middle of the anchor body so that all the caverns are connected. The main cable enters the stratum from the surface, passes through the traffic tunnel and the corridor, reaches the front anchor chamber of each anchor body, and is dispersed into multiple cable strands after passing through the cable saddle. The cable strands are connected to the steel bundles of the anchoring system, and the load is transferred to multiple anchor bodies to achieve the anchoring effect. The tunnel anchor of the present invention has a deterministic large-tonnage load-bearing capacity and is particularly suitable for the anchoring of the main cable of a large-span suspension bridge.

[0173] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A multi-stage anchor tunnel type anchor, characterized in that: Buried in the ground below the surface, it includes the cavern system, main cable and strand system and anchoring system; The anchoring system comprises at least two anchor bodies distributed in series along the main cable axis; The cavern system includes an auxiliary cavern arranged corresponding to the anchor body, and the auxiliary cavern includes a traffic cavern, a front anchor chamber, an anchor cavern, and a rear anchor chamber which are connected in sequence; the anchor body is located in the anchor cavern of the auxiliary cavern, and a corridor is arranged in the middle of the anchor cavern, which is a passage connecting the front anchor chamber to the rear anchor chamber after the anchor body is built; The main cable and strand system includes a first main cable constituting the main cable of the bridge. The first main cable enters the front anchor chamber through the traffic tunnel of the first-level auxiliary cavern and is dispersed into multiple strands and the second main cable. The second main cable passes through the corridor and the rear anchor chamber in the first-level auxiliary cavern and then enters the second-level auxiliary cavern for similar dispersion until the last-level auxiliary cavern, in which only the main cable is dispersed into strands. The strands in the auxiliary caverns of each level are anchored to the anchor body through prestressed steel strands to form a multi-level load transfer path.

2. The multi-stage anchor tunnel type anchorage according to claim 1, characterized in that: The anchor body is a wedge-shaped body with a variable cross-section.

3. The multi-stage anchor tunnel type anchorage according to claim 1, characterized in that: The front anchor chamber is a passage connecting the traffic tunnel to the anchor tunnel, providing space for the cable strands to be dispersed and space for the anchor body to be constructed.

4. The multi-stage anchor tunnel type anchorage according to claim 1, characterized in that: The anchor hole is a passage connecting the front anchor chamber to the rear anchor chamber, and its outer surface is a variable-section wedge-shaped hole, providing a space for the anchor body to be stored.

5. The multi-stage anchor tunnel type anchorage according to claim 1, characterized in that: The rear anchor chamber is a passage connecting the anchor hole to the traffic hole in the next-level auxiliary cavern, providing space for anchor body construction and space for maintenance during operation.

6. The multi-stage anchor tunnel type anchorage according to claim 1, characterized in that: The traffic tunnel, front anchor room, anchor tunnel, rear anchor room and corridor all adopt straight wall semicircular arch section, and the width-to-height ratio of the section is close or equal.

7. The multi-stage anchor tunnel type anchorage according to claim 1, characterized in that: A cable saddle is provided at the intersection of the traffic tunnel and the front anchor chamber, and the main cable is dispersed into multiple cable strands at the cable saddle.

8. The multi-stage anchor tunnel type anchorage according to claim 1, characterized in that: The anchoring system also includes a front anchor and a rear anchor for locking the prestressed steel bundle. The front anchor is evenly distributed in a ring shape on the front surface of the anchor body, and the rear anchor is evenly distributed in a ring shape on the rear surface of the anchor body.

9. The multi-stage anchor tunnel type anchorage according to claim 1, characterized in that: The steps for determining the number of anchor bodies are as follows: (1) Obtain the design parameters of the anchor body: Front anchor width and height: d1, h1; Width and height of rear anchor surface: d2, h2; Corridor width and height: d3, h3; Anchor body length L; Anchor elevation angle α; Anchor expansion angle β; Main cable design load P; Anchor body bulk density γ; Shear strength of surrounding rock: cohesion C', internal friction angle f'; (2) According to the obtained design parameters of the anchor body, calculate the side area A and volume V of the anchor body: The calculation formula of anchor body side area A is as follows: A=L×(C1+C2) / 2 in: C1=d1+(h1-d1 / 2)×2+π×d1 / 2 C2=d2+(h2-d2 / 2)×2+π×d2 / 2 The calculation formula of anchor body volume V is as follows: in: V=L×(S1+S2) / 2-L×S3 S1=d1×(h1-d1 / 2)+π×(d1 / 2) 2 / 2 <h2 style=";text-align:left;direction:ltr">S2 = d2 × (h2 - d2 / 2) + π × (d2 / 2)<h2 style=";text-align:left;direction:ltr"> 2 <h2 style=";text-align:left;direction:ltr"> / 2 S3=d3×(h3−d3 / 2)+π×(d3 / 2) 2 / 2 (3) Calculate the allowable pullout resistance P1 of the anchor body based on the calculated side area A and volume V of the anchor body; The calculation formula of P1 is as follows: P1=f'×W F +C'×A+W L in: W F =V×γ×cos(α+β) IN L =V×γ×sinα (4) The number of anchors n is calculated based on the calculated allowable pull-out resistance P1 of the anchor. The calculation formula for the number of anchors is as follows: n=KP / P1 n is rounded up to the nearest integer and is the number of anchors. Where: K is the pull-out safety factor of the anchor body.

10. The multi-stage anchor tunnel type anchorage according to claim 9, characterized in that: The value of K is 2.

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