CN111779518A - Anchor rod tray and using method thereof - Google Patents

Abstract

The invention provides an anchor rod tray and a using method thereof, and belongs to the technical field of roadway and tunnel supporting. The anchor rod tray comprises a sleeve, a lower pressing plate and an upper pressing plate, wherein the sleeve is composed of a steel pipe and four steel claws welded at one end of the steel pipe, the lower pressing plate is composed of a cuboid steel plate and a central hole, the upper pressing plate is composed of a cuboid steel plate, a central hole and reinforcing ribs, the central holes of the lower pressing plate and the upper pressing plate are both internal screw threads, and the lower pressing plate and the upper pressing plate are mutually matched with the external screw threads of the anchor rod head and are connected through the screw threads. The invention overcomes the defects of the traditional shotcrete net supporting process that the anchor net is firstly installed and then shotcrete is carried out, or concrete is firstly sprayed and then the anchor rod is installed, or shotcrete is firstly carried out and then the anchor net is installed and then the shotcrete is carried out, and the like, and improves the supporting effect of the shotcrete net supporting process. In addition, the anchor rod tray solves the problem that the bearing capacity of the anchor rod nut is insufficient, and the bearing capacity of the anchor rod tray is greatly improved.

Description

Anchor rod tray and using method thereof

Technical Field

The invention relates to the technical field of roadway and tunnel support, in particular to an anchor rod tray and a using method thereof.

Background

The shotcrete net support is one of the most common support modes of underground mine tunnels and highway railway tunnels at home and abroad, and the action mechanism of the shotcrete net is to connect unstable surface rock masses and stable rock masses at the deep part of the tunnel together through anchor rod bodies so as to achieve a combined support whole under the combined action of the shotcrete net and surrounding rocks. Wherein the sprayed concrete and the steel mesh form a hard shell on the surface of the surrounding rock, one end of the anchor rod is used for restraining the shell, the other end of the anchor rod is connected with the stable surrounding rock, a high pressure bearing ring within the range of 1-2m inside the surface of the roadway is formed, and the purpose of maintaining the stability of the roadway is realized by utilizing the bearing capacity of the high pressure bearing ring (see figure 1). Therefore, the anchor rods and the trays thereof can effectively restrict the sprayed concrete and the steel mesh, and play a vital role in maintaining the stability of the roadway. On the contrary, if the anchor rods and the trays cannot be adopted to effectively restrain and apply pressure to the sprayed concrete layer and the steel mesh, the sprayed concrete can bear larger compressive stress but cannot bear larger tensile stress or shear stress, and the sprayed concrete layer can be internally extruded and cracked under the condition of no restraint, so that the roadway is unstable (figure 2).

However, the current construction process of the spray anchor net has the following problems:

(1) when a mine with relatively low ground stress is supported by a single-layer shotcrete net, after a driving tunnel is subjected to slag tapping, firstly performing anchor rod and steel net supporting, and then spraying concrete (firstly spraying concrete and then constructing an anchor net, then spraying grout again to cover the steel net is needed, and construction cycle is increased), so that the anchor rod tray cannot effectively restrain the sprayed concrete and a steel net layer, although the steel net and the sprayed concrete can form a hard shell, the shell cannot be tightly connected with deep surrounding rock by the anchor rod and the anchor rod tray, and the effect of the shotcrete net combined supporting body cannot be fully exerted;

(2) and a part of mines with higher local stress adopt a double-layer shotcrete net support mode, namely, firstly hanging a net and installing an anchor rod, then spraying slurry to cover the anchor rod and a steel mesh, then hanging the net and installing the anchor rod for the second time, and then performing a tunneling process of spraying the slurry. The problem with this construction sequence is that the contact between the shotcrete of the primary and secondary supports is obstructed by the surface of the anchor tray of the secondary support (typically 150mm x 10mm or 200mm x 12 mm), and the shotcrete of the secondary support at the tray does not adhere firmly to the shotcrete surface of the primary support, forming a weak area of support. When the ground stress gradually appears, the sprayed concrete of the secondary supporting construction on the surface of the primary supporting anchor rod tray is deformed and damaged because the sprayed concrete is not restrained, and the cracking instability of the sprayed concrete around and the failure of the anchor rod are gradually caused, so that the overall deformation damage and the instability of the roadway are finally caused;

(3) for the high-stress mine adopting the double-layer shotcrete net, as for the same principle, the first anchor rod tray cannot press the first shotcrete, and the second shotcrete cannot be restrained by the anchor rod tray, so that the hard shell formed by the shotcrete net cannot be restrained to the maximum extent by using the anchor rods and the anchor rods supported twice, and the supporting effect of the double-layer shotcrete net is greatly reduced. However, if the construction is not carried out according to the procedures, the third time of guniting is required (because the steel mesh is covered by sprayed concrete to play a role);

(4) the traditional anchor rod tray is fixed on an anchor rod by adopting a nut, because the bearing capacity of the nut is limited, the nut is usually seen to fall off from the anchor rod body under the action of high ground stress, the anchor rod tray is not restrained by the nut, the restraining load applied to sprayed concrete by the tray is changed into zero, and the supporting effect is greatly reduced;

(5) in the underground anchor net spraying construction, if special measures are not taken, the problem of uneven thickness of sprayed concrete is easily caused. From the practical point of view of mine production, this problem is not well solved either. Therefore, how to exert the restriction of the anchor rod tray on sprayed concrete and a steel mesh layer can be achieved, construction is convenient and efficient, and the anchor rod tray becomes a supporting technical problem.

Disclosure of Invention

The invention provides an anchor rod tray and a using method thereof, aiming at the problem of instability of a tunnel caused by cracking of a concrete layer, inconsistent thickness of a concrete spraying layer and the like due to the above reasons in the construction of an anchor spraying net in projects such as underground mine tunnels, highway and railway traffic tunnels, water conservancy and hydroelectric tunnels and the like.

The novel anchor rod tray comprises a sleeve, a lower pressing plate and an upper pressing plate, wherein the sleeve is composed of a steel pipe and four steel claws welded to one end of the steel pipe, the sleeve is sleeved on an anchor rod, and the lower pressing plate, the upper pressing plate and an anchor rod head are connected through screw threads.

The steel pipe is made of Q235 steel or other non-metal materials with strength meeting the requirements, the inner diameter of the steel pipe is 1.2-1.4 times of 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 sprayed concrete.

The steel claws are steel bars processed by Q235 steel bars or other non-metallic materials with the strength meeting the requirements, the diameter of the steel bars is phi 2-4mm, and the length of each steel claw is 0.6-0.8 times of the mesh size of the steel bar mesh; one end of each of the four steel claws is welded at one end of the steel pipe, the plane formed by the four steel claws is perpendicular to the axis of the steel pipe, and the adjacent steel claws are uniformly distributed at 90 degrees.

The lower pressing plate is a rectangular steel plate with a central hole, the length is 150-200mm, the width is 40-60mm, the thickness is 10-12mm, the central hole is an internal screw thread, and the diameter of the central hole is the same as that of the anchor rod.

The upper pressure plate consists of a rectangular steel plate with a hole at the center and two triangular steel plates with ribs inside, the triangular steel plates are welded at two sides of the central hole of the rectangular steel plate, the length of the rectangular steel plate is 150-200mm, the width is 40-60mm, the thickness is 10-12mm, the central hole is an inner screw thread, and the diameter of the central hole is the same as that of the anchor rod.

The use method of the anchor rod tray comprises the following steps:

s1: after the anchor rod is inserted into the anchor rod hole and fixed, hanging a steel mesh, inserting a sleeve into one end of the anchor rod body, which is exposed out of the hole, and enabling one end of a steel claw on the sleeve to face a rock surface;

s2: mounting a lower pressing plate at one end of the exposed anchor rod and screwing the lower pressing plate so that the steel claw of the lower sleeve tightly presses the reinforcing mesh on the rock surface;

s3: the upper pressing plate is screwed on the anchor rod, the triangular stiffened plate is used as an attachment point of the clamping wrench, the upper pressing plate is screwed, and the long axis of the upper pressing plate and the long axis of the lower pressing plate are perpendicular to each other.

The invention effectively solves the problem that the construction process is too complicated although the anchor rod tray is outside the sprayed concrete and the steel mesh is inside the sprayed concrete in the construction sequence of firstly spraying the concrete, then installing the anchor net and then spraying the concrete again.

The technical scheme of the invention has the following beneficial effects:

1. the novel anchor rod tray is of a double-strip tray structure with a lower pressing plate and an upper pressing plate, the central holes of the lower pressing plate and the upper pressing plate are both provided with internal screw threads, the novel anchor rod tray can be regarded as a double-nut structure, and the traditional mode of fixing the anchor rod tray by nuts is not needed;

2. the use of the novel anchor rod tray solves the problems that the anchor rod tray cannot be arranged outside the sprayed concrete on the premise that the traditional single-layer sprayed anchor net support is not implemented by the two-time sprayed concrete support process, and simultaneously, the construction process of arranging the steel mesh inside the sprayed concrete is considered; the problem that anchor rod trays installed for the first time and the second time in the traditional double-layer shotcrete net support are both in the sprayed concrete inner layer is also solved, the constraint effect of the two layers of anchor rods and the anchor rod trays on sprayed concrete and steel meshes of each layer is greatly improved, and the support effect of the shotcrete net is greatly improved;

3. the novel anchor rod tray is in a long strip shape, the local isolation effect of the tray in the long strip structure on concrete cannot be too concentrated, the upper layer sprayed concrete and the lower layer sprayed concrete can be well contacted and bonded, and the problem that the traditional square tray causes local strength weakening areas of the sprayed concrete and finally causes a support body to generate domino type break-and-break instability through points and surfaces is greatly reduced;

4. the anchor rod tray with the reinforced ribs greatly improves the pressure resistance and the deformation resistance of the tray, and a hard shell formed by the steel mesh and the sprayed concrete can be restrained more greatly and better, so that the anchor rod, the combined support body formed by the steel mesh and the sprayed concrete can play a role in supporting the surrounding rock to the maximum extent, and the stability of a roadway is effectively improved;

5. the sleeve with the steel claw is adopted, so that the steel mesh can be effectively compressed to be tightly attached to the rock surface, and the effect of indicating the thickness of the sprayed concrete is also achieved.

Drawings

FIG. 1 is a diagram illustrating the support mechanism of shotcrete in the "shell" theory in the background of the present invention;

FIG. 2 is a diagram illustrating the prior art anchor rod not moving with shotcrete;

FIG. 3 is a front view of the bushing of the present invention;

FIG. 4 is a cross-sectional view of the bushing A-A of FIG. 3 according to the present invention;

FIG. 5 is a front view of the lower platen of the present invention;

FIG. 6 is a cross-sectional view of the lower platen of FIG. 5, wherein (a) is a cross-section taken along line B-B and (B) is a cross-section taken along line C-C, in accordance with the present invention;

FIG. 7 is a front view of the upper platen of the present invention;

FIG. 8 is a cross-sectional view of the upper platen of FIG. 7, wherein (a) is a section taken at D-D and (b) is a section taken at E-E, in accordance with the present invention;

FIG. 9 is a front view of the tray of the present invention;

FIG. 10 is a cross-sectional view of the tray of FIG. 9, wherein (a) is a section F-F and (b) is a section G-G.

Detailed Description

In order to make the technical problems, technical solutions and advantages of the present invention more apparent, the following detailed description is given with reference to the accompanying drawings and specific embodiments.

The invention provides an anchor rod tray and a using method thereof.

The anchor rod tray comprises a sleeve, a lower pressing plate and an upper pressing plate, wherein the sleeve is composed of a steel pipe and four steel claws welded to one end of the steel pipe, the sleeve is sleeved on an anchor rod, and the lower pressing plate, the upper pressing plate and an anchor rod head are connected through screw threads.

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

As shown in fig. 3 and 4, the steel claws are steel bars processed by Q235 steel bars, the diameter of the steel bar is phi 2-4mm, and the length of the steel claw is 0.6-0.8 times of the mesh size of the steel bar mesh; one end of each of the four steel claws is welded at one end of the steel pipe, the planes where the steel claws are located are perpendicular to the axis of the steel pipe, and the adjacent steel claws are uniformly distributed at 90 degrees. The diameter of the steel pipe is slightly larger than that of the anchor rod, four steel claws are welded at one end of the steel pipe, the steel claws are mutually vertical and are kept on a plane, and the plane is mutually vertical to the axis of the steel pipe. Wherein the steel claw is used for pressing the steel mesh to enable the steel mesh to be tightly attached to the rock surface; the height of the steel pipe is equal to the thickness of the sprayed concrete, one of the functions is to indicate the thickness of the sprayed concrete, the second function is to press the outer surface of the sprayed concrete due to the interval function of the sleeve between the anchor rod tray and the steel mesh, even if the construction sequence of firstly hanging the mesh and then spraying the concrete is adopted, the bearing capacity of the sprayed concrete layer is improved to the maximum extent through the anchor rod and the anchor rod tray, and the stability of the roadway is improved through the combined supporting resistance formed by the sprayed anchor mesh.

As shown in fig. 5 and 6, the lower pressing plate is a rectangular steel plate with a central hole, the length is 150-200mm, the width is 40-60mm, the thickness is 10-12mm, the central hole is an inner screw thread which is matched with an outer screw thread of the anchor rod head, and the lower pressing plate can be screwed to the end of the anchor rod through the hole. The diameter of the central hole is the same as that of the anchor rod. The lower pressure plate can not only take the function of the anchor rod tray, but also replace the function of the traditional anchor rod nut, thereby improving the problem of insufficient bearing capacity of the traditional anchor rod nut; the lower pressing plate transmits the pretightening force to the steel mesh through the sleeve and the four steel claws arranged on the sleeve, so that the steel mesh can be attached to the surface of a rock body to the maximum extent; the indication function of the height of the sleeve pipe can also facilitate guniting personnel to control the thickness of guniting and facilitate quality inspection personnel to inspect the thickness of guniting; due to the isolation effect of the sleeve, even under the construction process of firstly hanging the net and then spraying the slurry, the anchor rod tray can be arranged on the outer surface of the sprayed concrete layer, so that the supporting effect of the sprayed anchor net is greatly improved; in addition, because the holding-down plate is rectangular form structure, the shotcrete very easily gets into stock tray lower part among the whitewashing process, and during the secondary whitewashing, the concrete of secondary whitewashing also can be in the same place with the concrete of primary whitewashing can furthest's bonding, owing to be rectangular form tray structure, can not appear the weak area of strutting that local area upper and lower layer concrete isolation area is great to lead to.

As shown in fig. 7 and 8, the upper pressing plate is composed of a rectangular steel plate with a central hole and two triangular steel plates with ribs inside, the triangular steel plates are welded at two sides of the central hole of the rectangular steel plate, the rectangular steel plate has a length of 150-200mm, a width of 40-60mm and a thickness of 10-12mm, and mainly plays a role of an anchor rod tray; the central hole is an internal thread, and the diameter of the central hole is the same as that of the anchor rod.

The upper pressing plate mainly plays a role of the anchor rod tray, and meanwhile, due to the long-strip structure, when concrete is sprayed, the lower part of the upper pressing plate can spray the concrete more easily and compactly, compared with a square tray, the local isolation effect of the long-strip structure tray on the concrete cannot be too concentrated, so that the problems that the bonding force between primary and secondary supporting concrete is low due to the spacing effect of the traditional square tray on the concrete, the concrete on the square tray is easy to drop, and finally the domino type concrete cracks and the support body is unstable are caused; the center hole of the upper pressure plate is arranged at the center of the plane of the upper pressure plate, the hole is processed into an inner screw thread which is matched with an outer screw thread of the anchor rod, and the upper pressure plate can be screwed to the end head of the anchor rod through the hole; the reinforcing ribs are two triangular steel plates, the plane of each triangular steel plate is perpendicular to the plane of the upper pressing plate steel plate, one right-angle side of each triangle is welded on the central line of the long axis direction of the upper plane of the upper pressing plate steel plate, the other two right-angle sides of the two triangles are opposite and vertical, 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 central axis of the central hole of the upper pressing plate steel plate. The upper press plate can play the role of the anchor rod tray, restrain the wet-sprayed concrete steel mesh below the upper press plate, play a role in compressing the lower press plate, and also serve as the function of the anchor rod nut. The lower pressing plate and the upper pressing plate also have a connecting structure of the anchor rod and the tray similar to double nuts, so that the problem of insufficient bearing capacity of the nut of the traditional anchor rod is greatly improved; the upper pressure plate overcomes the problem of insufficient bending resistance of a long strip-shaped structure by welding a triangular steel plate, the reinforcing ribs of the triangular structure are consistent with bending moment images of the strip-shaped anchor rod tray under the condition of uniformly distributed loads, and the bearing capacity of the anchor rod tray can be greatly improved; a gap formed between the two triangles is used as a reserved space of the end head of the anchor rod so as to adapt to the actual field requirements of the end head of the anchor rod under different conditions of different exposure depths.

The following description is given with reference to specific examples.

Example 1

Because the novel anchor rod tray needs carry out different designs according to the anchor spraying net support parameter of difference, for the convenience and the accuracy of exposition, the novel anchor rod tray that the following describes is applicable to stock diameter phi 20mm, steel mesh size 150mm x 150mm, and single shotcrete thickness is 60 mm's support parameter. The processing requirements of the novel anchor rod tray are as follows:

(1) the novel anchor rod tray consists of a sleeve, an upper pressing plate and a lower pressing plate;

(2) the sleeve consists of a steel pipe and four steel claws welded at the lower end, the inner diameter phi of the steel pipe is 24mm, the wall thickness is 2mm, the height is 60mm (the thickness is consistent with that of sprayed concrete), and the sleeve is processed by adopting similar steel materials such as Q235 and the like; a single steel claw is a section of steel bar processed by a steel bar with the length of 66mm and the diameter of 3mm, and can also be made of a Q235 steel bar. Welding one ends of the four steel claws to one end of the steel pipe, wherein the planes of the four steel claws are perpendicular to the axis of the steel pipe, and the adjacent steel claws are uniformly distributed at 90 degrees, as shown in fig. 3 and 4;

(3) the lower pressing plate is a rectangular steel plate with a hole in the center, and can be made of a Q235 steel plate, the length, the width and the thickness of the lower pressing plate are 200mm, 50mm and 12mm, the inner screw thread of the center hole is phi 20mm, and the lower pressing plate is matched with the outer screw thread of the anchor rod, as shown in fig. 5 and 6;

(4) the top board comprises the cuboid steel sheet of central trompil to and two right angled triangle steel sheets of welding in centre bore both sides, can adopt the Q235 steel sheet to make. The length multiplied by the width multiplied by the height of the rectangular steel plate is 200mm multiplied by 50mm multiplied by 12mm, the diameter phi of a central hole is 20mm, and the rectangular steel plate is an inner screw thread; the right-angle triangular steel plate is made of Q235 materials, and the side lengths of the two right-angle sides are 88mm and 40mm respectively. The long right-angle side of each triangle is respectively welded at two ends of the central line of the upper plane of the upper pressing plate steel plate in the long axis direction (the plane of the triangle steel plate is vertical to the plane of the upper pressing plate steel plate), the short right-angle sides of the two triangles are opposite and vertical, as shown in figures 7 and 8, the gap left between the two right-angle sides is 24mm and is slightly larger than the diameter of the anchor rod, and the central axis of the gap is consistent with the central axis of the upper pressing plate steel plate. The center hole of the steel plate of the upper pressure plate is arranged at the center of the plane of the upper pressure plate, and an inner screw thread is processed in the hole and is matched with an outer screw thread of the anchor rod. The upper pressing plate is arranged on the anchor rod, so that the lower pressing plate can be pressed to limit the movement of the lower pressing plate, the pre-tightening force between the anchor rod tray and the anchor rod is strengthened, the lower pressing plate and the upper pressing plate also serve as a double-nut structural form, and the problem that the traditional anchor rod nut is insufficient in bearing capacity is greatly solved; the upper pressing plate can also play the role of the anchor rod tray and restrain the wet-sprayed concrete steel mesh below the upper pressing plate together with the lower pressing plate; the upper pressure plate makes up the problem that the bending resistance of a long strip-shaped structure is not enough by welding the triangular steel plate, and the bearing capacity of the anchor rod tray is greatly improved.

When single-layer spray anchor net support is adopted, the construction process of the novel anchor rod tray for implementing spray anchor net support is as follows (for convenience of description, the manual installation of resin anchor rod support is taken as a representative in the following description):

(1) when the slag on the driving face is removed, firstly, drilling anchor bolt holes on a top plate and two sides of the roadway according to the designed space and row spacing;

(2) feeding the resin anchoring agent into the hole, then inserting and stirring the resin anchor rod to ensure that the resin anchor rod is firmly anchored at the designed roadway position, and reserving the length of 120mm in the hole opening; installing the rest resin anchor rods in the area to be supported in place by the same method;

(3) hanging steel meshes on the surface of the roadway with the resin anchor rod installed, constructing the spacing, the row spacing, the lap joint and the like among the steel meshes strictly according to related design requirements, inserting a sleeve of a novel tray into one end of the rod body of the resin anchor rod exposed out of the hole, enabling one end of a steel claw on the sleeve to face a rock surface for compressing the steel meshes, installing a lower pressing plate at one end of the exposed anchor rod and screwing the lower pressing plate, and enabling a sleeve and the steel claw below the lower pressing plate to tightly press the steel meshes on the rock surface; then, the upper pressure plate is screwed on the anchor rod, the triangular stiffened plate can also be used as an attachment point of a clamping wrench, the upper pressure plate is screwed to the maximum extent, and the long axis axes of the upper pressure plate and the lower pressure plate are mutually vertical, as shown in fig. 9 and fig. 10;

(4) the shotcrete operation is performed and the desired design thickness is achieved.

When the double-layer spray anchor net is adopted for supporting, the construction sequence of the novel anchor rod tray for installing the anchor net and implementing the spray anchor net supporting is basically the same as that of the construction process, and the construction process is repeated again.

While the foregoing is directed to the preferred embodiment of the present invention, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the appended claims.

Claims (6)

1. An anchor rod tray which characterized in that: the anchor rod sleeve comprises a sleeve, a lower pressing plate and an upper pressing plate, wherein the sleeve is composed of a steel pipe and four steel claws welded to one end of the steel pipe, the sleeve is sleeved on an anchor rod, and the lower pressing plate and the upper pressing plate are connected with an anchor rod head through screw threads.

2. The anchor tray of claim 1, wherein: the inner diameter of the steel pipe is 1.2-1.4 times of that of the anchor rod, the wall thickness is 2-3mm, and the height of the steel pipe is consistent with the thickness of the sprayed concrete.

3. The anchor tray of claim 1, wherein: the steel claws are steel bars processed by steel bars, the diameter of the steel bars is phi 2-4mm, and the length of each steel claw is 0.6-0.8 times of the mesh size of the steel bar mesh; one end of each of the four steel claws is welded at one end of the steel pipe, the plane formed by the four steel claws is perpendicular to the axis of the steel pipe, and the adjacent steel claws are uniformly distributed at 90 degrees.

4. The anchor tray of claim 1, wherein: the lower pressing plate is a rectangular steel plate with a hole in the center, the length is 150-200mm, the width is 40-60mm, the thickness is 10-12mm, the center hole is an inner screw thread, and the diameter of the center hole is the same as that of the anchor rod.

5. The anchor tray of claim 1, wherein: the upper pressure plate is composed of a rectangular steel plate with a hole in the center and two triangular steel plates with ribs inside, the triangular steel plates are welded on two sides of a 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 inner screw thread, and the diameter of the central hole is the same as that of the anchor rod.

6. The method of using the anchor tray of claim 1, wherein: the method comprises the following steps:

s1: after the anchor rod is inserted into the anchor rod hole and fixed, firstly, a reinforcing mesh is installed, then, a sleeve is inserted into one end of the anchor rod body, which is exposed out of the hole, and one end of a steel claw on the sleeve faces to the rock surface;

s2: mounting a lower pressing plate at one end of the exposed anchor rod and screwing the lower pressing plate so that the steel claw of the lower sleeve pipe tightly presses the reinforcing mesh on the rock surface;

s3: and screwing the upper pressure plate on the anchor rod provided with the lower pressure plate in the S2, taking the triangular stiffened plate as an attachment point of the clamping wrench, screwing the upper pressure plate, and enabling the long axis axes of the upper pressure plate and the lower pressure plate to be vertical to each other.

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