CN115711707A - Shield segment joint waterproof system performance test device and method considering bolt holes - Google Patents

Abstract

The invention discloses a shield segment joint waterproof system performance test device and method considering bolt holes, and the device comprises the following steps: a chassis; two sets of sealed pad pasting boards of section of jurisdiction that set up relatively, wherein a set of sealed pad pasting board of section of jurisdiction is fixed in on the chassis, the sealed pad pasting board of another group of section of jurisdiction slide set up in on the chassis, the sealed pad pasting board two double-phase right inner faces of section of jurisdiction are provided with three rings from inside to outside and paste the groove, paste inslot detachable and be provided with rubber seal pad, paste the groove in the outside and paste and seted up curved bolt hole and straight bolt hole on the sealed pad pasting board of section of jurisdiction that the groove corresponds in middle part, the sealed pad pasting board of section of jurisdiction is provided with the thickening board outwards, be provided with a plurality of bolt sleeve pipes on the thickening board, the coaxial intercommunication of bolt sleeve pipe corresponds curved bolt hole/straight bolt hole, the sealed inner face of pasting the board of section of jurisdiction is provided with round scarf joint groove all around. The method is used for testing the sealing performance of the bolt hole and provides reference for shield waterproof design.

Description

Performance test device and method for waterproofing system of shield segment joints considering bolt holes

technical field

The invention relates to the technical field of shield tunneling construction. More specifically, the present invention relates to a performance test device and method of a shield segment joint waterproof system considering bolt holes.

Background technique

At present, the domestic shield segments are mainly connected by bolts. In order to prevent the leaking water from seeping out of the bolt holes due to the seal failure of the segment, generally, water-expandable sealing rings are installed at both ends of the connecting bolts, and the water will expand and stop the water after contacting the leaking water. However, due to the The water expansion and shear resistance is poor. During the tightening process of the bolts, the eccentricity is easily damaged by the shearing action of the oblique edges and corners outside the bolt holes, resulting in the failure of the bolt holes for waterproofing. At present, in order to improve the stability of the sealing ring, some projects have begun to use ternary Ethylene-propylene seal ring, but the thickness of EPDM seal ring is relatively large, which is easy to affect the fastening force of bolts, and it is difficult to detect the waterproof performance and damage after compression. Due to the high failure of bolt hole sealing, bolt hole leakage has become an important disease of shield tunnel leakage during the operation period. The internal and external double-channel waterproofing is adopted, but due to the failure of the bolt holes, when the outer waterproofing fails, the seepage water will flow out from the bolt holes, causing the entire segment waterproofing to fail, and the current specification only gives the compression of the segment joint gasket And the waterproof performance test method, there is no relevant regulation on the performance of the bolt hole waterproof system. At the same time, the industry mainly improves the bolt hole waterproof type, and the bolt hole waterproof system is rarely tested.

Contents of the invention

The purpose of the present invention is to provide a shield segment joint waterproof system performance test device and method considering bolt holes, which are used to test the sealing performance of bolt holes and provide reference for shield waterproof design.

The technical solution adopted by the present invention to solve this technical problem is: a performance test device for shield segment joint waterproof system considering bolt holes, including:

Chassis;

Two sets of segment sealing pad sticking plates are arranged oppositely, one set of segment sealing pad sticking plates is fixed on the bottom frame, and the other set of segment sealing pad sticking plates is slidably arranged on the bottom frame, and the segment sealing pad There are three ring-shaped pasting grooves on the inner surfaces of the pasting plates opposite to each other. The rubber sealing gaskets are detachably arranged in the pasting grooves, and the segment sealing pads corresponding to the outer pasting grooves and the middle pasting grooves are provided with curved joints on the pasting plates. Bolt holes and straight bolt holes, a thickened plate is provided on the outward side of the adhesive plate of the segment gasket, and a plurality of bolt sleeves are arranged on the thickened plate, and the bolt sleeves are coaxially connected to the corresponding bends. Bolt holes/straight bolt holes, 1 to 2 sets of fastening bolt holes are provided at the four corners of the bonding plate of the segment gasket, and a ring of caulking grooves is provided around the inner surface of the bonding plate of the segment sealing gasket;

A pair of sliding grooves are symmetrically arranged on the bottom frame, and the segment sealing gasket sticking plate is slidably connected in the sliding grooves through a slider. The section of the sliding grooves is a convex groove, and the slider includes A connection block and a longitudinal adjustment bolt, the connection block is slidably connected in the chute, the size of the chute is slightly larger than the size of the connection block, the upper end of the connection block is connected with the longitudinal adjustment bolt, the Adjusting nuts are arranged on the longitudinal adjusting bolts, and the longitudinal adjusting bolts penetrate the bottom of the thickened plate, and horizontal adjusting bolt holes are symmetrically opened on the side of the bottom frame close to the fixed segment gasket pasting plate and equipped with Horizontal adjustment bolts, the horizontal adjustment bolt holes pass through the chute on the same side vertically, a reaction force frame is arranged on the frame body, and an oil cylinder is fixed on the reaction force frame, and the oil cylinder is used to push the thickened plate along the slide slot move;

The central part of the fixed segment gasket bonding plate is provided with an exhaust hole and a water injection hole and runs through the thickened plate. The fixed segment sealing gasket bonding plate is also equipped with four sets of pressure gauges to detect three annular bonding grooves respectively. The pressure of the four zones separated by the segment gasket adhesive plate.

Preferably, chamfers are provided on the curved bolt holes and the straight bolt holes, and sealing rings are provided at the chamfers.

Preferably, it also includes a high and low temperature integrated machine and a circulation pipeline, the thickened plate is provided with a card slot, and the circulation pipeline is fixed on the card slot and arranged on the segment gasket sticking plate and the thickened plate Between them, the circulation pipeline is bent and arranged in a snake shape, the water inlet end of the circulation pipeline is connected to the water outlet joint of the high and low temperature integrated machine through the pipeline, and the water outlet end of the circulation pipeline is connected through the pipeline Connect with the water inlet joint of the high and low temperature integrated machine.

The present invention also provides a method for testing the waterproofing of bolt holes by using the shield segment joint waterproof system performance test device considering the bolt holes, comprising the following steps:

S1. Number the three ring-shaped pasting grooves set on the pasting plate of the segment gasket 1, 2 and 3 from the outside to the inside;

S2. According to the actual situation of the rubber gasket of the shield segment, paste the corresponding two rubber gaskets in the paste groove, and simulate the inner and outer double seals and the outer double seal by adjusting the position of the rubber gasket and the curved bolt hole/straight bolt hole two situations;

When simulating the double sealing inside and outside of the shield segment, stick the rubber gasket 1, 2 or 1, 3 first;

When simulating the outer double-channel gasket, paste the gasket 2 and 3;

S3. Sliding the segment gasket pasting plate, according to the actual displacement of the shield segment, adjust the position of the segment gasket pasting plate to the misalignment between the two segment gasket pasting plates through the horizontal adjustment bolt and the longitudinal adjustment bolt. The amount of units corresponds to the actual amount of staggered units of the shield segment;

S4. The oil cylinder is pressurized to push the segment gasket pasting plate to move toward the fixed segment gasket pasting plate, compressing the rubber gasket;

S5. Fix the two sets of segment sealing pad sticking plates by fastening the bolts, adjust the tightness of the fastening bolts, and control the angle between the two sets of segment sealing pad sticking plates to be consistent with the angle between the two sets of shield segments;

S6. According to the shape of the bolt hole of the shield segment, insert a sealing ring into the curved bolt hole/straight bolt hole of the segment gasket sticking plate, insert the bolt into the bolt hole, tighten the bolt with an air wrench, and the remaining one The bolt hole of the shape is blocked at the bolt sleeve by the plugging piece;

S7. According to the design requirements, a circle of caulking around the periphery is blocked;

S8. Inject clean water through the water injection hole in the central area. When the vent hole is stably discharged, plug the vent hole with a plug, and then continue to inject water and pressurize. The pressurization method is the waterproof test in the rubber gasket for the tunnel segment of the shield tunneling method. Pressurization step by step;

Observe the pressure changes of pressure gauges in different areas during the pressurization process, observe the leakage of rubber gaskets or bent bolt holes/straight bolt holes, analyze the weak links of segment leakage, and the water pressure resistance of bolt hole seals.

Preferably, it also includes:

S9. Check the deformation and damage of the sealing ring after compression, and analyze the durability of the bolt hole seal.

The present invention at least includes the following beneficial effects:

(1) The structure of the device is simple. By adjusting the size of the sealing gasket paste plate and the size of the bolt hole, the performance test of straight bolts and inclined bolts of different sizes and specifications can be carried out through simple tooling, and the applicability is strong.

(2) The device can truly simulate the working environment of the segment joint waterproof system, and can carry out tests such as single and double seal waterproof performance analysis, bolt hole waterproof, and bolt hole seal ring damage.

(3) The device can alternately change the working temperature of the sealing ring and the surrounding water body through the constant temperature circulating water device, and carry out research on the influence of seasonal changes on the waterproof performance of the segment joints.

(4) The device can study the synergistic waterproof ability of gaskets, bolt holes, and caulking, analyze the waterproof weak links of the entire segment joint, and improve the design quality of tunnel waterproof construction.

Other advantages, objectives and features of the present invention will partly be embodied through the following descriptions, and partly will be understood by those skilled in the art through the study and practice of the present invention.

Description of drawings

Fig. 1 is the schematic diagram of the performance test device of the shield segment joint waterproofing system of the present invention considering bolt holes;

Fig. 2 is a schematic diagram of double-channel segment waterproofing of the present invention;

Fig. 3 is a schematic diagram of bolt waterproofing of the present invention;

Fig. 4 is a schematic diagram of the location of the chute of the present invention;

Fig. 5 is a rear view of the shield segment joint waterproof system performance test device considering the bolt holes of the present invention.

Explanation of reference signs: 1 segment body; 2 segment outer waterproof gasket; 3 segment inner waterproof gasket; 4 segment oblique bolt nut hole; 5 oblique bolt; 6 sealing ring; 7 segment gasket paste plate ;8 waterproof gasket; 9 thickened plate; 10 straight bolt hole; 11 bent bolt hole; 12 oil cylinder; 13 reaction frame; 14 chute; 15 slider; Frame; 19 horizontal adjustment bolt; 20 exhaust hole; 21 water injection hole; 22 pressure gauge; 23 longitudinal adjustment bolt, 24 chamfer, 25 clearance, 26 circulation pipeline, 27 water inlet end of circulation pipeline, 28 circulation pipeline of the water outlet.

Detailed ways

The present invention will be described in detail and completely below in conjunction with the accompanying drawings. Those skilled in the art will be able to implement the present invention based on these descriptions. Before describing the present invention in conjunction with the accompanying drawings, it needs to be particularly pointed out that: the technical solutions and technical features provided in each part of the present invention, including the following description, in the case of no conflict, these technical solutions and Technical features can be combined with each other.

In addition, the embodiments of the present invention referred to in the following description are generally only some embodiments of the present invention, not all of them. Therefore, based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

The current specification only provides relevant provisions on the performance and test methods of segment joint waterproof gaskets, but does not provide relevant provisions on the performance of the bolt hole waterproof system, and now the industry mainly studies the structural optimization of the bolt hole waterproof system, and seldom applies to waterproofing. System performance is tested with a suite of tests.

Below in conjunction with accompanying drawing and implementation the present invention is described in further detail, and its specific implementation process is as follows:

As shown in Figures 1 to 5, the present invention provides a shield segment joint waterproof system performance test device considering bolt holes, including:

chassis 18;

Two groups of segment sealing pad sticking plates 7 are arranged oppositely, one set of segment sealing pad sticking plates 7 is fixed on the bottom frame 18, and the other set of segment sealing pad sticking plates 7 is slidably arranged on the bottom frame 18. There are three ring-shaped adhesive grooves arranged on the opposite inner surfaces of the segment seal pads 7 from the inside to the outside. The rubber seal pads are detachably arranged in the adhesive grooves, and the segment seal pads corresponding to the outer adhesive grooves and the middle adhesive grooves There are bent bolt holes 11 and straight bolt holes 10 on the pasting plate 7, and a thickened plate 9 is provided on the outward side of the segment gasket pasting plate 7, and a plurality of bolt sleeves are arranged on the thickened plate 9 The bolt sleeve is coaxially connected to the corresponding curved bolt hole 11/straight bolt hole 10, and the four corners of the segment sealing pad bonding plate 7 are provided with 1 to 2 sets of fastening bolt holes 16, and the segment A circle of caulking grooves 17 is arranged around the inner surface of the gasket pasting plate 7;

A pair of slide grooves 14 are arranged symmetrically on the bottom frame 18, respectively located on both sides of the bottom of another group of segment gasket sticking plates 7, and the segment seal gasket sticking plates 7 are slidably connected to the sliding block 15. In the groove 14, the section of the chute 14 is a convex groove, and the slider 15 includes a convex connection block and a longitudinal adjustment bolt 23, and the connection block is slidably connected in the chute 14, and the chute 14 is slightly larger than the size of the connecting block, the upper end of the connecting block is connected with the longitudinal adjustment bolt 23, and the longitudinal adjustment bolt 23 is provided with an adjustment nut, and the longitudinal adjustment bolt 23 penetrates into the At the bottom of the thick plate 9, the height of the thickened plate 9 is adjusted by rotating the adjusting nut. The side of the bottom frame 18 close to the fixed segment sealing pad paste plate 7 is symmetrically provided with 19 holes for horizontal adjustment bolts and is equipped with horizontal adjustment bolts 19 , the horizontal adjustment bolt 19 holes vertically pass through the chute 14 on the same side, and the reaction force frame 13 is arranged on the frame body, and the reaction force frame 13 is fixed with the oil cylinder 12, and the oil cylinder 12 is used for pushing and thickening The plate 9 moves along the chute 14;

The central part of the fixed segment gasket sticking plate 7 is provided with an air vent 20 and a water injection hole 21 and runs through the thickened plate 9, and the fixed segment gasket sticking plate 7 is also provided with four sets of pressure gauges 22, respectively Detect the pressure of the four areas separated by the three annular pasting grooves separating the pasting plate 7 of the segment gasket.

The technical solution may also include the following technical details to better achieve the technical effect: Preferably, the total thickness of the thickened plate 9 and the segment sealing gasket sticking plate 7 is not more than 20 cm.

The technical solution may also include the following technical details to better achieve technical effects: chamfers 24 are provided on the curved bolt holes 11 and straight bolt holes 10 , and sealing rings 6 are provided at the chamfers 24 .

This technical solution may also include the following technical details to better achieve technical effects: It also includes a high and low temperature integrated machine and a circulation pipeline 26, the thickened plate 9 is provided with a card slot, and the circulation pipeline 26 is fixed on the The clamping groove is arranged between the segment gasket sticking plate 7 and the thickened plate 9, the circulation pipeline 26 is bent and arranged in a snake shape, and the water inlet end 27 of the circulation pipeline passes through the pipeline and the The water outlet joint of the high and low temperature integrated machine is connected, and the water outlet 28 of the circulation pipeline is connected with the water inlet joint of the high and low temperature integrated machine through the pipeline, and valves are arranged on the pipeline to control the entry and exit of cold and hot water.

(1) By changing the temperature of the circulating water and indirectly controlling the temperature of the sealing water in the adhesive plate 7 of the segment gasket and the rubber gasket, the influence of seasonal changes on the waterproofing of the tunnel can be simulated.

(2) An insulating layer is provided at the rear of the segment sealing gasket bonding plate 7, which can reduce the temperature loss of the cold and hot pipes and ensure that the sealing gasket as a whole is in a constant temperature environment.

The present invention also provides a method for testing the waterproofing of bolt holes by using the shield segment joint waterproof system performance test device considering the bolt holes, which is characterized in that it includes the following steps:

S1. As shown in Figure 2, according to the configuration of the inner and outer gaskets of the segment body 1, the segment body 1 has a waterproof gasket 82 outside the segment, a waterproof gasket 83 inside the segment, and slanted bolts 5 and nut holes 4 of the segment. There is a gap 25 between the bolt hole and the segment, and the corresponding segment gasket bonding plate 7 is processed, and the three annular bonding grooves set on the segment sealing gasket bonding plate 7 are numbered 1, 2, and 3 from the outside to the inside;

S2. According to the actual situation of the shield segment rubber gasket, paste the corresponding two rubber gaskets in the paste groove, and simulate the inner and outer double seals and the outer double seal by adjusting the position of the rubber gasket and the curved bolt hole 11/straight bolt hole 10. There are two cases of road sealing;

When simulating the double sealing inside and outside of the shield segment, stick the rubber gasket 1, 2 or 1, 3 first;

When simulating the outer double-channel gasket, paste the gasket 2 and 3;

S3. Slide the segment gasket sticking plate 7. According to the actual displacement of the shield segment, adjust the position of the segment gasket sticking plate 7 through the horizontal adjustment bolt 19 and the longitudinal adjustment bolt 23 until the two segment gaskets are pasted. The amount of misalignment between plates 7 corresponds to the actual amount of misalignment of the shield segment;

S4. The oil cylinder is pressurized to push the segment sealing pad pasting plate 7 to move toward the fixed segment sealing pad pasting plate 7, compressing the rubber sealing pad;

S5. Fix the two groups of segment sealing pad pasting plates 7 by fastening the bolts, adjust the tightness of the fastening bolts, and control the angle between the two groups of segment sealing pad pasting plates 7 and the angle between the two groups of shield segments consistent;

S6. According to the shape of the bolt hole of the shield segment, insert the sealing ring 6 on the curved bolt hole 11/straight bolt hole 10 of the segment gasket sticking plate 7, insert the bolt into the bolt hole, and tighten the bolt with a pneumatic wrench. The remaining bolt holes of another form are blocked at the bolt casing by the plugging piece;

S7. According to the design requirements, a circle of caulking around the periphery is blocked;

S8. Inject clean water through the water injection hole 21 in the central area. When the vent hole 20 is stably discharged, plug the vent hole 20 with a plug, and then continue to inject water and pressurize. The pressurization method of medium waterproof test is pressurized step by step;

During the pressurization process, observe the pressure changes of the pressure gauge 22 in different areas, observe the leakage of the rubber gasket or the curved bolt hole 11/straight bolt hole 10, and analyze the weak links of segment leakage and the water pressure resistance of the bolt hole seal.

S9. Change the positional relationship of the pasting plates 7 of the two segment gaskets, repeat steps S1-8, analyze the leakage laws of rubber gaskets and bolt holes under different conditions, and optimize the entire sealing system according to the test conditions.

This technical solution can also include the following technical details, so as to better realize the technical effect: it also includes:

S9. Check the deformation and damage of the sealing ring 6 after compression, and analyze the durability of the bolt hole seal.

In S6, the seal ring 6 can also be placed obliquely at the edge chamfer 24 of the groove, and then the bolts are tightened to analyze the shear failure of the bolt hole chamfer 24 to the seal ring 6 when the bolt holes are skewed.

Although the embodiment of the present invention has been disclosed as above, it is not limited to the use listed in the specification and implementation, it can be applied to various fields suitable for the present invention, and it can be easily understood by those skilled in the art Therefore, the invention is not limited to the specific details and embodiments shown and described herein without departing from the general concept defined by the claims and their equivalents.

Claims (5)

1. A shield segment joint waterproofing system performance test device considering bolt holes, characterized in that it comprises: Chassis; Two sets of segment sealing pad sticking plates are arranged oppositely, one set of segment sealing pad sticking plates is fixed on the bottom frame, and the other set of segment sealing pad sticking plates is slidably arranged on the bottom frame, and the segment sealing pad There are three ring-shaped pasting grooves on the inner surfaces of the pasting plates opposite to each other. The rubber sealing gaskets are detachably arranged in the pasting grooves, and the segment sealing pads corresponding to the outer pasting grooves and the middle pasting grooves are provided with curved joints on the pasting plates. Bolt holes and straight bolt holes, a thickened plate is provided on the outward side of the adhesive plate of the segment gasket, and a plurality of bolt sleeves are arranged on the thickened plate, and the bolt sleeves are coaxially connected to the corresponding bends. Bolt holes/straight bolt holes, 1 to 2 sets of fastening bolt holes are provided at the four corners of the bonding plate of the segment gasket, and a ring of caulking grooves is provided around the inner surface of the bonding plate of the segment sealing gasket; A pair of sliding grooves are symmetrically arranged on the bottom frame, and the segment sealing gasket sticking plate is slidably connected in the sliding grooves through a slider. The section of the sliding grooves is a convex groove, and the slider includes A connection block and a longitudinal adjustment bolt, the connection block is slidably connected in the chute, the size of the chute is slightly larger than the size of the connection block, the upper end of the connection block is connected with the longitudinal adjustment bolt, the Adjusting nuts are arranged on the longitudinal adjusting bolts, and the longitudinal adjusting bolts penetrate the bottom of the thickened plate, and horizontal adjusting bolt holes are symmetrically opened on the side of the bottom frame close to the fixed segment gasket pasting plate and equipped with Horizontal adjustment bolts, the horizontal adjustment bolt holes pass through the chute on the same side vertically, a reaction force frame is arranged on the frame body, and an oil cylinder is fixed on the reaction force frame, and the oil cylinder is used to push the thickened plate along the slide slot move; The central part of the fixed segment gasket bonding plate is provided with an exhaust hole and a water injection hole and runs through the thickened plate. The fixed segment sealing gasket bonding plate is also equipped with four sets of pressure gauges to detect three annular bonding grooves respectively. The pressure of the four zones separated by the segment gasket adhesive plate. 2. The shield segment joint waterproof system performance test device considering bolt holes as claimed in claim 1, characterized in that, the curved bolt holes and the straight bolt holes are provided with chamfers, and the chamfers are provided with sealing rings. 3. The shield segment joint waterproof system performance test device considering bolt holes as claimed in claim 1, further comprising a high and low temperature integrated machine and a circulation pipeline, the thickened plate is provided with a slot, The circulation pipeline is fixed on the card slot and arranged between the segment sealing gasket bonding plate and the thickened plate, the circulation pipeline is bent in a snake shape, and the water inlet end of the circulation pipeline passes through the pipe The pipeline is connected to the water outlet joint of the high and low temperature integrated machine, and the water outlet end of the circulation pipeline is connected to the water inlet joint of the high and low temperature integrated machine through the pipeline. 4. A method for testing the waterproofing of bolt holes by utilizing the shield segment joint waterproofing system performance test device considering bolt holes as described in any one of claims 1 to 3, characterized in that it comprises the following steps: S1. Number the three ring-shaped pasting grooves set on the pasting plate of the segment gasket 1, 2 and 3 from the outside to the inside; S2. According to the actual situation of the rubber gasket of the shield segment, paste the corresponding two rubber gaskets in the paste groove, and simulate the inner and outer double seals and the outer double seal by adjusting the position of the rubber gasket and the curved bolt hole/straight bolt hole two situations; When simulating the double sealing inside and outside of the shield segment, stick the rubber gasket 1, 2 or 1, 3 first; When simulating the outer double-channel gasket, paste the gasket 2 and 3; S3. Sliding the segment gasket pasting plate, according to the actual displacement of the shield segment, adjust the position of the segment gasket pasting plate to the misalignment between the two segment gasket pasting plates through the horizontal adjustment bolt and the longitudinal adjustment bolt. The amount of units corresponds to the actual amount of staggered units of the shield segment; S4. The oil cylinder is pressurized to push the segment gasket pasting plate to move toward the fixed segment gasket pasting plate, compressing the rubber gasket; S5. Fix the two sets of segment sealing pad sticking plates by fastening the bolts, adjust the tightness of the fastening bolts, and control the angle between the two sets of segment sealing pad sticking plates to be consistent with the angle between the two sets of shield segments; S6. According to the shape of the bolt hole of the shield segment, insert a sealing ring into the curved bolt hole/straight bolt hole of the segment gasket sticking plate, insert the bolt into the bolt hole, and tighten the bolt with a pneumatic wrench. The bolt hole of the shape is blocked at the bolt sleeve by the plugging piece; S7. According to the design requirements, a circle of caulking around the periphery is blocked; S8. Inject clean water through the water injection hole in the central area. When the vent hole is stable, plug the vent hole with a plug, and then continue to inject water and pressurize. The pressurization method is the waterproof test in the rubber gasket for the tunnel segment of the shield tunneling method. Pressurization step by step; Observe the pressure changes of pressure gauges in different areas during the pressurization process, observe the leakage of rubber gaskets or bent bolt holes/straight bolt holes, analyze the weak links of segment leakage, and the water pressure resistance of bolt hole seals. 5. utilize as claimed in claim 4 the test method that the shield segment joint waterproofing system performance test device that considers bolt hole carries out bolt hole waterproof, it is characterized in that, also comprises: S9. Check the deformation and damage of the sealing ring after compression, and analyze the durability of the bolt hole seal.

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