Anchor tray and method of using the same

Abstract

The present invention provides an anchor tray and a method for using the same, and belongs to the technical field of laneway and tunnel support. The anchor tray includes a sleeve, a lower pressure plate and an upper pressure plate, wherein the sleeve is composed of a steel pipe and four steel claws welded at one end thereof, the lower pressure plate is composed of a rectangular steel plate and a center hole, the upper pressure plate is composed of a rectangular steel plate, a center hole and a reinforcing bar, and the center holes of the lower pressure plate and the upper pressure plate are both internal threads, which match the external threads of the anchor head and are connected by threads. The present invention changes the shortcomings of the traditional sprayed anchor net support process of first installing the anchor net and then spraying, or first spraying concrete and then installing the anchor, or first spraying and then installing the anchor net and then spraying, and improves the support effect of the sprayed anchor net process. In addition, this type of anchor tray improves the problem of insufficient bearing capacity of the anchor nuts, and also greatly improves the bearing capacity of the anchor tray.

Description

Technical Field

[0001] The invention relates to the technical field of lane and tunnel support, in particular to an anchor tray and a use method thereof. Background Art

[0002] Shotcrete and anchor net support has become one of the most commonly used support methods for underground mine tunnels, highway and railway tunnels at home and abroad. The mechanism of action of shotcrete and anchor net is to connect the unstable surface rock mass with the stable rock mass deep in the tunnel through the anchor rod body, so as to achieve a joint support system of shotcrete and anchor net and surrounding rock. The shotcrete and steel net form a hard shell on the surface of the surrounding rock. The shell is constrained by one end of the anchor rod and connected to the stable surrounding rock at the other end, forming a high pressure circle within the range of 1-2m inside the tunnel surface. The bearing capacity of the high pressure circle is used to achieve the purpose of maintaining the stability of the tunnel (see Figure 1 ). It can be seen that the effective restraint of the shotcrete and steel mesh by the anchor rod and its tray plays a vital role in maintaining the stability of the roadway. On the contrary, if the anchor rod and tray cannot be used to effectively restrain and pressurize the shotcrete layer and the steel mesh, the shotcrete layer will be squeezed and cracked without restraint, because the shotcrete can withstand large compressive stress but cannot withstand large tensile stress or shear stress, which will eventually lead to the instability of the roadway ( Figure 2 ).

[0003] However, from the current construction technology of shotcrete mesh, there are the following problems:

[0004] (1) When single-layer shotcrete mesh support is used in mines with relatively low ground stress, after the excavation of the tunnel, anchor rod + steel mesh support is implemented first, and then concrete is sprayed (if concrete is sprayed first and then the anchor mesh is constructed, it is necessary to spray again to cover the steel mesh, which increases the construction cycle). In this case, the anchor rod tray cannot effectively restrain the shotcrete and steel mesh layer. Although the steel mesh and shotcrete can form a hard shell, the anchor rod and its anchor rod tray cannot tightly connect the shell with the deep surrounding rock, and the role of the shotcrete mesh combined support body cannot be fully exerted;

[0005] (2) Some mines with relatively high ground stress adopt a double-layer sprayed anchor mesh support method, that is, first hang the mesh and install the anchor rod, then spray grout to cover the anchor rod and steel mesh, then hang the mesh and install the anchor rod for the second time, and then carry out the excavation process of spraying grout. The problem with this construction sequence is that the surface of the secondary support anchor tray (generally a 150mm×150mm×10mm tray, or a 200mm×200mm×12mm tray) blocks the contact between the primary and secondary support shotcrete, and the secondary support shotcrete at the tray cannot firmly adhere to the primary support shotcrete surface, forming a support weak zone. When the ground stress gradually appears, the shotcrete of the secondary support construction on the surface of the primary support anchor tray is not constrained, so it first deforms and breaks, and gradually causes the surrounding shotcrete to crack and become unstable and the anchor rod to fail, eventually leading to the overall deformation, damage and instability of the tunnel;

[0006] (3) For high-stress mines using the above-mentioned double-layer shotcrete mesh, the same principle as mentioned above, the first anchor tray cannot hold down the first shotcrete, and the second shotcrete cannot be constrained by the anchor tray. Therefore, the hard shell formed by the shotcrete mesh cannot be constrained to the maximum extent by the anchor rods and their trays supported twice, which greatly reduces the support effect of the double-layer shotcrete mesh. However, if the construction process is not carried out according to the above process, the third shotcrete must be implemented (because the steel mesh must be covered with shotcrete to work);

[0007] (4) Traditional anchor trays use nuts to fix them on the anchors. Due to the limited bearing capacity of the nuts, it is often seen that the nuts fall off the anchor rod body under the action of high ground stress. Without the constraints of the nuts, the anchor tray's constraint load on the shotcrete becomes zero, and the support effect is greatly reduced.

[0008] (5) If no special measures are taken during the construction of underground shotcrete mesh, it is easy to cause uneven thickness of shotcrete. From the actual mining production point of view, this problem has not been well solved. Therefore, how to make full use of the anchor tray to constrain the shotcrete and steel mesh layer, and achieve convenient and efficient construction, has become a support technology problem. Summary of the invention

[0009] The present invention provides an anchor tray and a method for using the same, aiming at the problem of tunnel instability caused by cracking of the concrete layer and inconsistent thickness of the concrete spray layer during the construction of the shotcrete mesh in underground mine tunnels, highway and railway traffic tunnels, water conservancy and hydropower tunnels, etc. due to the above-mentioned reasons.

[0010] The novel anchor tray comprises a sleeve, a lower pressure plate and an upper pressure plate, wherein the sleeve is composed of a steel pipe and four steel claws welded at one end thereof, the sleeve is sleeved on the anchor, and the lower pressure plate, the upper pressure plate and the anchor head are connected by threads.

[0011] The steel pipe is made of Q235 steel or other non-metallic materials with strength that can meet the requirements. The inner diameter of the steel pipe is 1.2-1.4 times the diameter of the anchor rod, the wall thickness is 2-3mm, and the height of the steel pipe is consistent with the thickness of the shotcrete.

[0012] The steel claws are steel bars made of Q235 steel bars or other non-metallic materials with strength that can meet the requirements. The diameter of the steel bars is φ2-4mm, and the length of each steel claw is 0.6-0.8 times the mesh size of the steel mesh. One end of the four steel claws is welded to one end of the steel pipe. The plane formed by the four steel claws is perpendicular to the axis of the steel pipe, and adjacent steel claws are evenly distributed at 90°.

[0013] The lower pressure plate is a rectangular steel plate with a center hole, 150-200mm long, 40-60mm wide, and 10-12mm thick. The center hole is an internal thread, and the diameter of the center hole is the same as the diameter of the anchor rod.

[0014] The upper pressure plate consists of a rectangular steel plate with a central hole and two triangular steel plates containing reinforcing strips. The triangular steel plates are welded to both sides of the central hole of the rectangular steel plate. The rectangular steel plate is 150-200mm long, 40-60mm wide, and 10-12mm thick. The central hole is internally threaded, and the diameter of the central hole is the same as the diameter of the anchor rod.

[0015] The method for using the anchor tray comprises the following steps:

[0016] S1: After the anchor is inserted into the anchor hole and fixed, hang the steel mesh, and then insert the casing into the end of the anchor rod body exposed outside the hole, with the steel claw end of the casing facing the rock surface;

[0017] S2: Install the lower pressure plate to one end of the exposed anchor rod and tighten it so that the steel claws of the lower sleeve press the steel mesh tightly against the rock surface;

[0018] S3: Screw the upper pressure plate onto the anchor rod, use the triangular stiffened plate as the attachment point of the clamping wrench, tighten the upper pressure plate, and make the long axis of the upper and lower pressure plates perpendicular to each other.

[0019] The present invention effectively improves the problem that in the traditional sprayed anchor mesh support process, the anchor mesh is installed first, and the tray cannot compact the sprayed concrete, which greatly reduces the support effect of the sprayed anchor mesh. If the concrete is sprayed first, the steel mesh is outside the sprayed concrete and cannot play a role in reinforcing the reinforced concrete. The construction sequence of first spraying and then installing the anchor mesh and then spraying again, although it takes into account the advantages of the anchor tray outside the sprayed concrete and the steel mesh inside the sprayed concrete, it makes the construction process too complicated.

[0020] The beneficial effects of the above technical solution of the present invention are as follows:

[0021] 1. The new anchor tray is a double-strip tray structure with a lower pressure plate and an upper pressure plate. The center holes of the lower pressure plate and the upper pressure plate are both internally threaded, which can be regarded as a double-nut structure, eliminating the need for the traditional method of fixing the anchor tray with nuts;

[0022] 2. The use of the new anchor tray solves the problem that the traditional single-layer shotcrete mesh support cannot place the anchor tray outside the shotcrete without implementing the two-step shotcrete support process, while taking into account the construction process of placing the steel mesh inside the shotcrete; it also solves the problem that the first and second installations of the traditional double-layer shotcrete mesh support are both in the inner layer of the shotcrete, greatly improving the restraint effect of the two-layer anchor and anchor tray on each layer of shotcrete and steel mesh, and greatly improving the support effect of the shotcrete mesh;

[0023] 3. The new anchor tray adopts a long strip shape. The local isolation effect of the long strip structure tray on the concrete will not be too concentrated. The upper and lower layers of shotcrete can be well contacted and bonded, which greatly reduces the problem of local strength weakening of shotcrete caused by traditional square trays, and ultimately causes domino-like point-to-surface instability of the support body;

[0024] 4. The reinforced anchor tray greatly improves the tray's compressive and deformation resistance. The hard shell formed by the steel mesh and shotcrete can be more and better constrained, so that the combined support body formed by the anchor, steel mesh and shotcrete can provide maximum support for the surrounding rock, effectively improving the stability of the tunnel;

[0025] 5. The use of casing with steel claws can not only effectively press the steel mesh to make it close to the rock surface, but also serve as an indicator of the thickness of the shotcrete. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is the force diagram of the sprayed concrete support mechanism in the "shell" theory in the background technology of the present invention;

[0027] Figure 2 This is a diagram showing the phenomenon that the anchor rod does not move with the shotcrete in the background technology of the present invention;

[0028] Figure 3 It is a front view of the sleeve of the present invention;

[0029] Figure 4 For the present invention Figure 3 Sectional view of the middle casing at section AA;

[0030] Figure 5 It is a front view of the lower pressing plate of the present invention;

[0031] Figure 6 For the present invention Figure 5Cross-sectional view of the middle and lower pressure plates, where (a) is the BB cross-section and (b) is the CC cross-section;

[0032] Figure 7 It is a front view of the upper pressing plate of the present invention;

[0033] Figure 8 For the present invention Figure 7 Cross-sectional view of the middle and upper pressure plate, where (a) is the DD cross-section and (b) is the EE cross-section;

[0034] Fig. 9 It is a front view of the tray of the present invention;

[0035] Fig.10 For the present invention Fig. 9 Cross-sectional view of the middle tray, where (a) is the FF cross-section and (b) is the GG cross-section. DETAILED DESCRIPTION

[0036] In order to make the technical problems, technical solutions and advantages to be solved by the present invention more clear, a detailed description will be given below with reference to the accompanying drawings and specific embodiments.

[0037] The invention provides an anchor rod tray and a use method thereof.

[0038] The anchor tray comprises a sleeve, a lower pressure plate and an upper pressure plate, wherein the sleeve is composed of a steel pipe and four steel claws welded at one end thereof, the sleeve is sleeved on the anchor, and the lower pressure plate, the upper pressure plate and the anchor head are connected by threads.

[0039] The steel pipe is made of Q235 steel, the inner diameter of the steel pipe is 1.2-1.4 times that of the anchor rod, the wall thickness is 2-3mm, and the height is consistent with the thickness of the shotcrete.

[0040] like Figure 3 and Figure 4 As shown in the figure, the steel claw is a steel bar made of Q235 steel bar, the diameter of the steel bar is φ2-4mm, and the length of the steel claw is 0.6-0.8 times the mesh size of the steel mesh; one end of the four steel claws is welded to one end of the steel pipe, the plane where the steel claws are located is perpendicular to the axis of the steel pipe, and the adjacent steel claws are evenly distributed at 90°. The diameter of the steel pipe is slightly larger than the diameter of the anchor rod, and the four steel claws are welded to one end of the steel pipe. Each steel claw is perpendicular to each other and maintained in a plane that is perpendicular to the axis of the steel pipe. The steel claw is used to press the steel mesh to make it close to the rock surface; the height of the steel pipe is equal to the thickness of the shotcrete. One of its functions is to indicate the thickness of the shotcrete. The second function is that due to the spacing effect of the sleeve between the anchor tray and the steel mesh, even if the construction sequence of hanging the mesh first and then spraying is adopted, the anchor tray can be pressed on the outer surface of the shotcrete, and the bearing capacity of the shotcrete layer is maximized through the anchor rod and the anchor tray, and the joint support resistance formed by the spray anchor mesh is used to improve the stability of the roadway.

[0041] like Figure 5 and Figure 6 As shown, the lower pressure plate is a rectangular steel plate with a central hole, 150-200mm long, 40-60mm wide, and 10-12mm thick. The central hole is an inner thread that matches the outer thread of the anchor head. The lower pressure plate can be screwed to the end of the anchor through the hole. The diameter of the central hole is the same as the diameter of the anchor. The lower pressure plate can not only assume the function of the anchor tray, but also replace the function of the traditional anchor nut, improving the problem of insufficient bearing capacity of the traditional anchor nut; the lower pressure plate transmits its preload force to the steel mesh through the casing and the four steel claws arranged on the casing, which can make the steel mesh close to the rock surface to the maximum extent; the indication function of the casing height can also facilitate the shotcrete personnel to control the thickness of the shotcrete, and facilitate the quality inspectors to check the thickness of the shotcrete; due to the isolation effect of the casing, even in the construction process of hanging the net first and then spraying, the anchor tray can be placed on the outer surface of the shotcrete layer, greatly improving the support effect of the shotcrete mesh; in addition, since the lower pressure plate is a long strip structure, the shotcrete can easily enter the lower part of the anchor tray during the shotcrete process. During the secondary shotcrete, the secondary shotcrete concrete can also be bonded to the primary shotcrete concrete to the maximum extent. Due to the long strip tray structure, there will be no weak support area caused by the large isolation area between the upper and lower concrete layers in the local area.

[0042] like Figure 7 With Figure 8 As shown, the upper pressure plate consists of a rectangular steel plate with a central hole and two triangular steel plates containing reinforcing strips. The triangular steel plates are welded to both sides of the central hole of the rectangular steel plate. The rectangular steel plate is 150-200mm long, 40-60mm wide and 10-12mm thick, and mainly serves as an anchor tray. The central hole is an internal thread, and the diameter of the central hole is the same as the diameter of the anchor.

[0043] The upper platen mainly plays the role of an anchor tray. At the same time, because it is a long strip structure, it is easier to spray the concrete densely at its lower part when spraying concrete. Compared with the square tray, the local isolation effect of the long strip structure tray on the concrete will not appear too concentrated, and it is not easy to have the low bonding force between the primary and secondary supports due to the spacing effect of the traditional square tray on the concrete, which makes it easy for the concrete on the square tray to fall off, and finally cause domino-like concrete cracking and instability of the support body; the center hole of the upper platen is arranged at the center of the upper platen plane, and the hole is processed into an inner thread, which matches the outer thread of the anchor rod. The upper platen can be tightened to the end of the anchor rod through the hole; the reinforcement strip is two triangular steel plates, the plane of the triangular steel plate is perpendicular to the plane of the upper platen steel plate, and one right-angled side of each triangle is welded to the center line of the long axis direction of the upper plane of the upper platen steel plate, and the other two right-angled sides of the two triangles stand opposite to each other. The gap left in the middle is larger than the diameter of the anchor rod, and the central axis of the gap is consistent with the axis of the central hole of the upper platen steel plate. The upper pressure plate can not only play the role of anchor tray, constrain the wet sprayed concrete steel mesh below, but also play the role of pressing the lower pressure plate, and also play the role of anchor nut. The lower pressure plate and the upper pressure plate also play a similar double nut anchor and tray connection structure, greatly improving the problem of insufficient nut bearing capacity of traditional anchors; the upper pressure plate makes up for the problem of insufficient bending resistance of the long strip structure by welding triangular steel plates. The reinforcement of the triangular structure is consistent with the bending moment image of the strip anchor tray under uniform load conditions, which can greatly improve the bearing capacity of the anchor tray; the gap formed between the two triangles is used as a reserved space for the anchor end to meet the actual needs of the site under different conditions when the anchor end is exposed to different depths.

[0044] This will be described below with reference to specific embodiments.

[0045] Example 1

[0046] Since the new anchor tray needs to be designed differently according to different sprayed anchor net support parameters, for the convenience and accuracy of the description, the new anchor tray described below is suitable for support parameters with an anchor diameter of φ20mm, a steel mesh size of 150mm×150mm, and a single shotcrete thickness of 60mm. The processing requirements of the new anchor tray are as follows:

[0047] (1) The new anchor tray consists of three parts: casing, upper pressure plate and lower pressure plate;

[0048] (2) The casing consists of a steel pipe and four steel claws welded at the lower end. The inner diameter of the steel pipe is φ=24mm, the wall thickness is 2mm, and the height is 60mm (consistent with the thickness of shotcrete). It is made of Q235 or similar steel materials. A single steel claw is a steel bar made of a steel bar with a length of 66mm and a diameter of φ3mm. It can also be made of Q235 steel bars. One end of each of the four steel claws is welded to one end of the steel pipe. The plane where the steel claws are located is perpendicular to the axis of the steel pipe. Adjacent steel claws are evenly distributed at 90 degrees. Figure 3 , Figure 4 As shown;

[0049] (3) The lower pressure plate is a rectangular steel plate with a central hole, which can be made of Q235 steel plate. Its length × width × thickness = 200mm × 50mm × 12mm. The inner thread of the center hole is φ20mm, which matches the outer thread of the anchor rod. Figure 5 , Figure 6 As shown;

[0050] (4) The upper pressure plate consists of a rectangular steel plate with a hole in the center and two right-angled triangular steel plates welded on both sides of the center hole. It can be made of Q235 steel plate. The length × width × height of the rectangular steel plate = 200mm × 50mm × 12mm, the diameter of the center hole φ = 20mm, and it is an internal thread; the right-angled triangular steel plate is made of Q235 material, and the lengths of the two right-angled sides are 88mm and 40mm respectively. The long right-angled sides of each triangle are welded to the two ends of the center line of the long axis direction of the upper plane of the upper pressure plate steel plate (the plane of the triangular steel plate is perpendicular to the plane of the upper pressure plate steel plate), and the short right-angled sides of the two triangles stand opposite each other, such as Figure 7 , Figure 8 As shown, the gap between the two right-angled sides is 24mm, slightly larger than the diameter of the anchor rod, and the center axis of the gap is consistent with the center axis of the upper plate steel plate. The center hole of the upper plate steel plate is arranged at the center of the upper plate plane. The hole is processed with an inner thread, which matches the outer thread of the anchor rod. The upper plate installed on the anchor rod can not only press the lower plate, limit the movement of the lower plate, and strengthen the preload between the anchor rod tray and the anchor rod, but also the lower plate and the upper plate act as a double nut structure, which greatly improves the problem of insufficient bearing capacity of traditional anchor rod nuts; the upper plate can also play the role of an anchor rod tray, and together with the lower plate, it constrains the wet sprayed concrete steel mesh below it; the upper plate compensates for the problem of insufficient bending resistance of the long strip structure by welding triangular steel plates, greatly improving the bearing capacity of the anchor rod tray.

[0051] When single-layer sprayed anchor net support is used, the construction process of the new anchor tray for implementing the sprayed anchor net support is as follows (for the convenience of description, the following uses the manual installation of resin anchor support as a representative):

[0052] (1) When the excavation working face is slag-free, first drill anchor holes in the tunnel roof and both sides according to the designed spacing and row spacing;

[0053] (2) The resin anchoring agent is sent into the hole, and then the resin anchor rod is inserted and stirred to ensure that the resin anchor rod is firmly anchored in the designed tunnel position, and a length of 120 mm is reserved at the hole mouth; the rest of the resin anchor rods in the proposed support area are installed in place using the same method;

[0054] (3) The steel mesh is hung on the surface of the tunnel where the resin anchor has been installed. The spacing, row spacing and overlap between the steel meshes are strictly constructed in accordance with the relevant design requirements. The sleeve of the new tray is inserted into the end of the resin anchor body exposed outside the hole. One end of the steel claw on the sleeve faces the rock surface to press the steel mesh. Then the lower pressure plate is installed on the exposed end of the anchor and tightened so that the sleeve and its steel claws under it press the steel mesh tightly against the rock surface. Then the upper pressure plate is screwed onto the anchor. The triangular reinforced plate can also be used as the attachment point of the clamping wrench to tighten the upper pressure plate to the maximum extent and make the long axis axes of the upper and lower pressure plates perpendicular to each other. Fig. 9 and Fig.10 ;

[0055] (4) Carry out shotcrete operations and achieve the expected design thickness.

[0056] When double-layer sprayed anchor mesh support is adopted, the construction sequence of installing the anchor mesh with the new anchor tray to implement the sprayed anchor mesh support is basically the same as above, except that the above construction process is repeated again.

[0057] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. An anchor tray, characterized in that: It includes a sleeve, a lower pressure plate and an upper pressure plate, wherein the sleeve is composed of a steel pipe and four steel claws welded at one end thereof, the sleeve is sleeved on the anchor rod, and the lower pressure plate, the upper pressure plate and the anchor rod head are connected by threads; The inner diameter of the steel pipe is 1.2-1.4 times that of the anchor rod, the wall thickness is 2-3 mm, and the height of the steel pipe is consistent with the thickness of the shotcrete; The lower pressure plate is a rectangular steel plate with a central hole, and the upper pressure plate is composed of a rectangular steel plate with a central hole and two triangular steel plates containing reinforcing strips. The lower pressure plate can not only serve as an anchor tray, but also replace the traditional anchor nut function, thereby improving the problem of insufficient bearing capacity of traditional anchor nuts; the lower pressure plate transmits its pre-tightening force to the steel mesh through the casing and four steel claws arranged on the casing, thereby maximizing the adhesion of the steel mesh to the rock surface.

2. The anchor tray according to claim 1, characterized in that: The steel claws are steel bars processed from steel bars with a diameter of φ2-4mm. The length of each steel claw is 0.6-0.8 times the mesh size of the steel mesh. One end of the four steel claws is welded to one end of the steel pipe. The plane formed by the four steel claws is perpendicular to the axis of the steel pipe, and adjacent steel claws are evenly distributed at 90°.

3. The anchor tray according to claim 1, characterized in that: The lower pressing plate is 150-200 mm long, 40-60 mm wide, 10-12 mm thick, has an inner thread in the center hole, and the diameter of the center hole is the same as the diameter of the anchor rod.

4. The anchor tray according to claim 1, characterized in that: The triangular steel plate of the upper pressure plate is welded to both sides of the central hole of the rectangular steel plate. The rectangular steel plate is 150-200mm long, 40-60mm wide, and 10-12mm thick. The central hole is an internal thread, and the diameter of the central hole is the same as the diameter of the anchor rod.

5. The method for using the anchor tray according to claim 1, characterized in that: The steps include: S1: After the anchor is inserted into the anchor hole and fixed, install the steel mesh first, then insert the sleeve into the end of the anchor rod body exposed outside the hole, with the steel claw end of the sleeve facing the rock surface; S2: Install the lower pressure plate to one end of the exposed anchor rod and tighten it so that the steel claws of the lower casing can press the steel mesh tightly against the rock surface; S3: Screw the upper pressure plate onto the anchor rod on which the lower pressure plate is installed in S2, use the triangular stiffened plate as the attachment point of the clamping wrench, tighten the upper pressure plate, and make the long axis axes of the upper and lower pressure plates perpendicular to each other.

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