Assembled tunnel reinforcement combined lining and its prefabricated components and construction method

Abstract

The present invention relates to an assembled tunnel reinforcement combined sleeve and its prefabricated components and construction method, wherein the prefabricated components are rectangular arc plate-shaped prefabricated blocks, which are circumferentially bent; the outer convex surface of the prefabricated block is provided with annular main ribs and longitudinal auxiliary ribs, the main ribs are located at the longitudinal edges of the prefabricated block, and the longitudinal outer sides of the main ribs are provided with longitudinal convex supporting auxiliary ribs; the circumferential end faces of the prefabricated blocks are provided with convex strips or grooves for circumferential assembly and longitudinal assembly. The present invention adopts standardized prefabricated components for on-site assembly of tunnel reinforcement sleeves, shortens the construction period of on-site construction, and quickly locates and fixes prefabricated components through hanging hooks, so that the construction is fast and efficient; in addition, annular main ribs and longitudinal auxiliary ribs are designed on the outer convex surface of the prefabricated block, and an embedded structure is formed after pouring concrete to achieve longitudinal and circumferential limiting, which solves the problem of poor construction quality of the current assembled sleeves and effectively avoids the slippage of the sleeve structure.

Description

Technical Field

[0001] The invention relates to the technical field of tunnel construction, and in particular to an assembled tunnel reinforcement combined lining, a prefabricated component thereof and a construction method. Background Art

[0002] After long-term service, tunnels are at risk of disease, and the lining may crack, have voids, or fall off, which seriously endangers the operational safety of the tunnel. Therefore, when the tunnel lining quality is no longer up to standard, the secondary lining load-bearing structure can be reinforced as necessary to continuously ensure structural stability and driving safety.

[0003] At present, the commonly used method of secondary lining reinforcement is to construct a sleeve lining, that is, to construct a new lining structure within the original secondary lining load-bearing structure surface, and to fill the gap behind it with grouting to achieve the purpose of reinforcing the secondary lining load-bearing structure. The existing sleeve lining reinforcement construction method is mainly to construct a concrete sleeve lining in a mold, which generally has problems such as long construction period, great impact on traffic, and high construction cost. During the construction of concrete sleeve lining, the construction space requirement is large and the efficiency is low, and the existing line needs to be closed for daily traffic for a long time. The use of prefabricated components for assembly construction can speed up the construction of the sleeve lining, but after the sleeve lining components are assembled, the degree of integration with the existing structure is limited, and relative displacement is prone to occur, especially longitudinal relative displacement, which affects the construction quality of the sleeve lining.

[0004] Therefore, it is necessary to propose new measures to overcome the above-mentioned defects. Summary of the invention

[0005] The purpose of the present invention is to provide an assembled tunnel reinforcement combined lining and its prefabricated components and construction method, so as to solve the problems of poor construction quality and easy slippage of the installed structure in the existing assembled lining construction structure.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is: Prefabricated components of assembled tunnel reinforcement combined lining, wherein the prefabricated components are rectangular arc plate-shaped prefabricated blocks, which are circumferentially bent; The outer convex surface of the prefabricated block is provided with an annular main rib and a longitudinal auxiliary rib, the main rib is located at the longitudinal edge of the prefabricated block, and the longitudinal outer side of the main rib is provided with a longitudinal convex supporting auxiliary rib; The circumferential end surface of the prefabricated block is provided with convex strips or grooves for circumferential assembly and longitudinal assembly.

[0007] Furthermore, the outer convex surface of the prefabricated block is provided with two circumferential main ribs, which is a double-main-rib type prefabricated block; the main ribs are located on both sides of the longitudinal edge of the double-main-rib type prefabricated block, and form a starting ring after circumferential assembly; Alternatively, the outer convex surface of the prefabricated block is provided with a circumferential main rib, which is a single main rib type prefabricated block; the main rib is located on one side of the longitudinal edge of the single main rib type prefabricated block, and forms a continuous ring after circumferential assembly.

[0008] Furthermore, the cross section of the main rib is T-shaped, including an outer wing plate and an inner web plate, and a longitudinal tie rod hole is opened on the web plate.

[0009] Furthermore, the annular end of the main rib is provided with a protruding horseshoe and an annular connecting bent hole.

[0010] On the other hand, an assembled tunnel reinforcement composite sleeve is provided, wherein the reinforcement composite sleeve is an assembly obtained by circumferentially and longitudinally assembling the prefabricated components, and longitudinally comprises a starting ring and multiple continuous rings in sequence.

[0011] Furthermore, a steel bar flower stand is arranged behind the longitudinal joint of two circumferentially adjacent prefabricated blocks.

[0012] Furthermore, at the longitudinal joints of two circumferentially adjacent prefabricated blocks, the circumferential connecting bent holes of the two blocks are interconnected, and arc-shaped bolts are inserted to perform circumferential connection and fixation.

[0013] Furthermore, the plurality of prefabricated blocks in the longitudinal direction are longitudinally tightened and fixed by inserting tie rods into the tie rod holes.

[0014] On the other hand, a construction method of the assembled tunnel reinforcement combined lining as described is provided, the method comprising: Prefabricated double main rib type precast blocks and single main rib type precast blocks are transported to the construction site; Double main rib prefabricated blocks are installed circumferentially on the inner side of the existing secondary lining to form a starting ring; Starting from one side of the starting ring, single main rib type prefabricated blocks are installed ring by ring to form a multi-ring continuous ring; the auxiliary ribs of the first ring of single main rib type prefabricated blocks are supported on the supporting auxiliary ribs of the double main rib type prefabricated blocks; starting from the second ring of single main rib type prefabricated blocks, the auxiliary ribs of the single main rib type prefabricated blocks are supported on the supporting auxiliary ribs of the previous ring of single main rib type prefabricated blocks; Pour concrete behind the precast blocks through the grouting holes reserved on the precast blocks.

[0015] Furthermore, the method further comprises: Longitudinal mounting holes are preset on the main rib web of the prefabricated block; Before installing the prefabricated blocks, install a hanging hook with a bent end on the existing secondary lining surface; Align the mounting hole of the prefabricated block with the mounting hook, then insert the mounting hook into the mounting hole and hang it vertically on the mounting hook.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides an assembled tunnel reinforcement combined sleeve and its prefabricated components and construction method, which adopt standardized prefabricated components for on-site assembly of tunnel reinforcement sleeve, shorten the construction period of on-site construction, and quickly locate and fix the prefabricated components through hanging hooks, so that the construction is fast and efficient. In addition, annular main ribs and longitudinal auxiliary ribs are designed on the outer convex surface of the prefabricated block, and an embedded structure is formed after pouring concrete to achieve longitudinal and annular limiting, which solves the problem of poor construction quality of the current assembled sleeve and effectively avoids the slippage of the sleeve structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, drawings of other embodiments can be obtained based on these drawings without paying creative work.

[0018] Figure 1 It is a structural diagram of the assembled tunnel reinforcement combined lining of the present invention.

[0019] Figure 2 This is the structural diagram of the double main rib type prefabricated block.

[0020] Figure 3 This is the structural diagram of a single main rib type prefabricated block.

[0021] Figure 4 It is a schematic diagram of the assembly of double main rib type prefabricated blocks and single main rib type prefabricated blocks.

[0022] Figure 5 This is a schematic diagram of the location of the mounting hook.

[0023] Figure 6 It is a schematic diagram of the internal structure of the main rib.

[0024] Figure 7 This is a diagram of the horseshoe position.

[0025] Figure 8 This is a schematic diagram of the grouting hole location.

[0026] Fig. 9 This is the structural diagram of the steel flower rack at the horizontal joints of the prefabricated blocks.

[0027] Fig.10 This is a schematic diagram of the location of the injection holes for a single main rib precast block.

[0028] Fig.11 It is a structural diagram of a multi-stage pad.

[0029] Fig.12 It is a schematic diagram of the position of multi-level pads.

[0030] The symbols in the figure are: 1-existing secondary lining, 2-reinforced combined sleeve lining, 3-prefabricated block, 4-tie rod, 5-starting ring, 6-continuous ring, 7-hanging hook, 8-horseshoe, 9-arc bolt, 10-steel flower rack, 11-grouting hole, 12-multi-stage pad; 31-single main rib precast block, 32-double main rib precast block, 33-panel, 34-main rib, 35-auxiliary rib, 36-supporting auxiliary rib, 37-tie rod hole, 38-structural reinforcement, 39-grouting hole. DETAILED DESCRIPTION

[0031] In order to facilitate the understanding of the present invention, the present invention will be described more fully below with reference to the relevant drawings. The preferred embodiments of the present invention are given in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present invention more thoroughly understood.

[0032] In the description of the present invention, it is necessary to understand that the terms "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "longitudinal", "lateral", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0033] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installation", "connection", "setting" and the like should be understood in a broad sense, for example, it can be fixedly connected or set, or detachably connected or set, or integrally connected or set. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0034] It should also be noted that although the order of steps is mentioned in the method description, in some cases, they may be performed in an order different from that shown here, and this should not be construed as a limitation on the order of the steps.

[0035] In a specific implementation manner, the tunnel line direction is defined as the longitudinal direction, the direction perpendicular thereto is defined as the transverse direction, and the contour line direction of the secondary lining of the tunnel is defined as the circumferential direction.

[0036] After a tunnel has been in service for many years, it is prone to various lining diseases. Applying a sleeve lining inside the tunnel secondary lining can effectively reinforce the existing secondary lining and ensure the safety of the structure and driving. In existing construction practices, there have been many prefabricated construction methods that use prefabricated components to assemble the sleeve lining on site. The construction speed is fast and the impact period on existing traffic is significantly shortened. However, the sleeve lining is not set throughout the entire length. It is generally applied within the key length range where the disease occurs, so it only has a limited length. After the prefabricated sleeve lining is applied, under the influence of internal vehicle driving vibration and surrounding rock deformation, because its prefabricated components are all simple unit plate structures with a flat surface, the bonding with the existing secondary lining is easily weakened, causing slippage, affecting the structural stiffness and stability. In response to this problem, the present invention provides an assembled tunnel reinforcement combined sleeve lining, which constructs a limit assembly on its surface to strengthen the bonding between the sleeve lining and the secondary lining, avoid relative displacement between the existing structure and the added structure, and improve the construction quality of the sleeve lining.

[0037] The assembled tunnel reinforcement combined lining is composed of prefabricated components, which are rectangular arc plate-shaped prefabricated blocks 3, which are circumferentially bent and are reinforced concrete prefabricated structures. The prefabricated block 3 has a panel 33, and the outer convex surface of the panel 33 is provided with circumferential main ribs 34 and longitudinal auxiliary ribs 35. The main ribs 34 and the auxiliary ribs 35 are perpendicular to each other, and the main ribs 34 are located at the longitudinal edge of the prefabricated block 3. The main ribs 34 and the auxiliary ribs 35 are reinforcements for the panel 33. At the same time, after pouring concrete behind them, they can form mutually embedded, longitudinal and circumferential limiting structures with the concrete structure.

[0038] In addition, the panels 33 of the prefabricated blocks 3 are of equal thickness, and the circumferential end faces are provided with convex strips or grooves for circumferential assembly and longitudinal assembly. When they are assembled together, the corresponding convex strips are inserted into the grooves to facilitate positioning and connection. In some embodiments, waterproof strips are also provided in the grooves to enhance the waterproof performance at the joints.

[0039] like Figure 4 , longitudinally outwardly protruding supporting auxiliary ribs 36 are also provided on the longitudinal outer side of the main ribs 34. When longitudinally spliced, the front prefabricated block 3 can be supported on the auxiliary ribs 35 of the rear prefabricated block 3 through the supporting auxiliary ribs 36. The supporting auxiliary ribs 36 extend beyond the panel 33 by a certain length. When installed, adjacent prefabricated blocks 3 are interlaced with each other through the protruding supporting auxiliary ribs 36 to form a shear-resistant connection.

[0040] According to the number of main ribs 34 on the prefabricated block 3 and the deployment position of the prefabricated block 3, the prefabricated block 3 of the present invention has two structural forms, namely, a double main rib type prefabricated block 32 and a single main rib type prefabricated block 31. Specifically: 1. Double main rib prefabricated block 32: like Figure 2The prefabricated block 3 includes a panel 33, and the outer convex surface of the panel 33 is provided with two circumferential main ribs 34, which is a double main rib type prefabricated block 32. The main ribs 34 are located on both sides of the longitudinal edge of the double main rib type prefabricated block 32, and the auxiliary ribs 35 are located between the two main ribs 34 and are perpendicular to the main ribs 34, that is, they are arranged longitudinally. In addition, a supporting auxiliary rib 36 is arranged on the outer side of one of the main ribs 34, which is longitudinally opposite to the auxiliary rib 35 and is used to support the next ring of prefabricated blocks 3.

[0041] Based on this structural form, the prefabricated blocks 3 are assembled in a circular direction to form a starting ring 5 , which is the first ring lining structure of the reinforced combined sleeve lining 2 and is located at the end of the reinforced combined sleeve lining 2 .

[0042] 2. Single main rib prefabricated block 31: like Figure 3 The prefabricated block 3 includes a panel 33, and a circumferential main rib 34 is arranged on the outer convex surface of the panel 33, which is a single main rib type prefabricated block 31. The main rib 34 is located on one side of the longitudinal edge of the single main rib type prefabricated block 31, and the auxiliary rib 35 is located on the inner side of the main rib 34 and is perpendicular to the main rib 34, that is, it is arranged longitudinally. In addition, a supporting auxiliary rib 36 is also arranged on the outer side of the main rib 34, which is longitudinally opposite to the auxiliary rib 35 and is used to support the next ring of prefabricated blocks 3.

[0043] Based on this structural form, the prefabricated blocks 3 are assembled in a circular direction to form a continuous ring 6, which is a multi-ring structure that is continuously constructed on one side of the starting ring 5 after the starting ring 5 is completed. The main rib 34 is not provided on the inner side thereof, and the continuous ring 6 can be overlapped with the previous ring sleeve through the supporting auxiliary rib 36. Finally, as Figure 1 The reinforced combined sleeve 2 includes a starting ring 5 and a plurality of continuous rings 6 in sequence in the longitudinal direction.

[0044] The above two prefabricated block 3 structures also have the same other structural features: 1. If Figure 2 The main rib 34 has a T-shaped cross section, including an outer wing plate and an inner web plate, and a longitudinal tie rod hole 37 is provided on the web plate for longitudinal connection through the tie rod 4. The longitudinal prefabricated blocks 3 are longitudinally tightened and fixed by inserting the tie rod 4 into the tie rod hole 37, which has strong integrity and improves waterproof ability.

[0045] 2. If Figure 6 , a structural rib 38 is preset in the main rib 34 to strengthen the structural rigidity of the main rib 34. Figure 2 The cross section of the auxiliary rib 35 is rectangular, and the structural rib 38 may not be preset inside.

[0046] 3. If Figure 6 and Figure 7The annular end of the main rib 34 is provided with a protruding horseshoe 8 and an annular connecting bent hole for annular connection by an arc bolt 9. At the longitudinal joint of two annularly adjacent prefabricated blocks 3, the annular connecting bent holes of the two blocks are interconnected and annularly connected and fixed by inserting an arc bolt 9. The number can be selected as one or two as needed.

[0047] The prefabricated block 3 has other reinforcement measures during the splicing process. Fig. 9 A steel flower stand 10 is arranged behind the longitudinal joint of two circumferentially adjacent prefabricated blocks 3. After pouring concrete, a force-bearing whole is formed, which is an effective reinforcement of the joint. To install the steel flower stand 10, the corresponding position of the prefabricated block 3 can be pre-buried with connecting steel bars and exposed. After assembly, the steel flower stand 10 is tied or welded to the connecting steel bars of the prefabricated block 3.

[0048] The construction method of the assembled tunnel reinforcement combined lining specifically comprises the following steps: S1: Prefabricate double main rib type prefabricated blocks 32 and single main rib type prefabricated blocks 31 and transport them to the construction site.

[0049] The two types of prefabricated blocks 33 have similar structures except for the number of main ribs 34 , and structural ribs 38 need to be embedded in advance, and various through holes need to be reserved.

[0050] In addition, the prefabricated blocks 33 can also be divided into ordinary type and arch-closed type, mainly because the inclination of the annular end face is different. The annular end face of the ordinary type is perpendicular to the contour line of the second lining, while the annular end face of the arch-closed type is not perpendicular to the contour line of the second lining and can be more inclined to form a wedge shape for easy assembly.

[0051] S2: Double main rib type prefabricated blocks 32 are installed circumferentially on the inner side of the existing secondary lining 1 to form a starting ring 5.

[0052] S3: Starting from one side of the starting ring 5, single main rib type prefabricated blocks 31 are installed ring by ring to form a multi-ring continuous ring 6; the auxiliary ribs 35 of the first ring of single main rib type prefabricated blocks 31 are supported on the supporting auxiliary ribs 36 of the double main rib type prefabricated blocks 32; starting from the second ring of single main rib type prefabricated blocks 31, the auxiliary ribs 35 of the single main rib type prefabricated blocks 31 are supported on the supporting auxiliary ribs 36 of the previous ring of single main rib type prefabricated blocks 31.

[0053] The prefabricated blocks 3 are connected by the convex strips and the grooves on the outer periphery, and waterproof strips can be sandwiched between them.

[0054] like Figure 5 , longitudinal mounting holes are preset on the webs of the main ribs 34 of the prefabricated block 3. Before installing the prefabricated block 3, a hanging hook 7 with a bent end is installed on the surface of the existing secondary lining 1, such as Figure 5 Align the mounting hole of the prefabricated block 3 with the hanging hook 7, then insert the mounting hook into the mounting hole and hang it vertically on the hanging hook 7. While positioning, it can also achieve effective connection with the existing secondary lining 2, avoiding the use of anchor rods.

[0055] S4: Figure 8 , pour concrete into the back of the prefabricated block 3 through the grouting holes 39 reserved on the prefabricated block 3.

[0056] In addition, if Fig.10 A grouting hole 11 is provided on the prefabricated block 3 at the top, and the top is filled with concrete by pressurized grouting to ensure that the top grouting is dense.

[0057] like Fig.11 and 12 The construction of the present invention can be leveled with the help of multi-stage pads 12. The multi-stage pads 12 are double-sided wedge-shaped structures with multiple steps of different thicknesses. According to the actual gap between the prefabricated block 3 and the existing secondary lining 2, appropriate gears can be used for leveling.

[0058] In summary, the present invention provides an assembled tunnel reinforcement combined sleeve lining, which effectively improves the construction speed and the controllability of the component quality by combining the factory prefabricated standard parts delivered to the site for assembly and the on-site pouring of concrete. In addition, a rib structure that can be limited is constructed in the prefabricated block, which can effectively prevent the relative slip of the structure while reinforcing the panel strength, thereby improving the structural quality. More importantly, since the rigidity of the prefabricated block has been significantly improved, the overall structure is more stable, and the deformation generated when pouring the cast-in-place layer is small, therefore, the area of ​​the prefabricated block can be greatly increased, that is, it is prefabricated into a large block component, and the installation speed of the ring will be significantly accelerated. When constructing in a running tunnel, the cycle will be shorter and the interference to traffic will be small. In addition, there are no leaking bolts after the entire construction process, and the nuts will not fall off when the vibration of the high-speed railway tunnel is relatively large. After the construction is completed, there is no leakage of steel, and the structure will not rust. The life cycle is long and the scope of use is wide.

[0059] The above specific examples are used to illustrate the present invention, which is only used to help understand the present invention and is not intended to limit the present invention. For those skilled in the art, according to the concept of the present invention, some simple deductions, modifications or substitutions can be made.

Claims

1. Prefabricated components of assembled tunnel reinforcement combined lining, characterized by: The prefabricated component is a rectangular arc plate-shaped prefabricated block (3) that is annularly bent; The outer convex surface of the prefabricated block (3) is provided with an annular main rib (34) and a longitudinal auxiliary rib (35), the main rib (34) is located at the longitudinal edge of the prefabricated block (3), and the longitudinal outer side of the main rib (34) is provided with a longitudinal convex supporting auxiliary rib (36); The circumferential end surface of the prefabricated block (3) is provided with convex strips or grooves for circumferential assembly and longitudinal assembly.

2. The prefabricated component of the assembled tunnel reinforcement combined lining according to claim 1 is characterized in that: The outer convex surface of the prefabricated block (3) is provided with two circumferential main ribs (34), forming a double-main-rib type prefabricated block (32); the main ribs (34) are located on both sides of the longitudinal edge of the double-main-rib type prefabricated block (32), and after being assembled in a circumferential direction, they form a starting ring (5); Alternatively, the outer convex surface of the prefabricated block (3) is provided with a circumferential main rib (34), which is a single main rib type prefabricated block (31); the main rib (34) is located on one side of the longitudinal edge of the single main rib type prefabricated block (31), and after circumferential assembly, a continuous ring (6) is formed.

3. The prefabricated component of the assembled tunnel reinforcement combined lining according to claim 2 is characterized in that: The main rib (34) has a T-shaped cross section, comprising an outer wing plate and an inner web plate, and a longitudinal tie rod hole (37) is provided on the web plate.

4. The prefabricated component of the assembled tunnel reinforcement combined lining according to claim 3 is characterized in that: The annular end of the main rib (34) is provided with a protruding horseshoe (8) and an annular connecting bent hole.

5. Assembled tunnel reinforcement combined lining, characterized by: The reinforced combined lining (2) is an assembly obtained by circumferentially and longitudinally assembling the prefabricated components described in claim 4, and longitudinally comprises a starting ring (5) and a plurality of continuous rings (6).

6. The assembled tunnel reinforcement combined lining according to claim 5 is characterized in that: A steel bar flower stand (10) is arranged behind the longitudinal joints of two circumferentially adjacent prefabricated blocks (3).

7. The assembled tunnel reinforcement combined lining according to claim 6 is characterized in that: At the longitudinal joints of two circumferentially adjacent prefabricated blocks (3), the circumferential connecting bent holes of the two blocks are interconnected and are circumferentially connected and fixed by inserting arc-shaped bolts (9).

8. The assembled tunnel reinforcement combined lining according to claim 7 is characterized in that: The plurality of prefabricated blocks (3) are longitudinally tightened and fixed by inserting tie rods (4) into the tie rod holes (37).

9. The construction method of the assembled tunnel reinforcement combined lining according to claim 8, characterized in that: The method comprises: Prefabricate double main rib type prefabricated blocks (32) and single main rib type prefabricated blocks (31), and transport them to the construction site; Installing double main rib type prefabricated blocks (32) in an annular direction on the inner side of the existing secondary lining (1) to form a starting ring (5); Starting from one side of the starting ring (5), single main rib type prefabricated blocks (31) are installed ring by ring to form a multi-ring continuous ring (6); the auxiliary ribs (35) of the first ring of single main rib type prefabricated blocks (31) are supported on the supporting auxiliary ribs (36) of the double main rib type prefabricated blocks (32); starting from the second ring of single main rib type prefabricated blocks (31), the auxiliary ribs (35) of the single main rib type prefabricated blocks (31) are supported on the supporting auxiliary ribs (36) of the previous ring of single main rib type prefabricated blocks (31); Concrete is poured into the back of the prefabricated block (3) through the grouting holes (39) reserved on the prefabricated block (3).

10. The construction method of the assembled tunnel reinforcement combined lining according to claim 9 is characterized in that: The method further comprises: Pre-set longitudinal mounting holes on the web of the main rib (34) of the prefabricated block (3); Before installing the prefabricated block (3), a hanging hook (7) with a bent end is installed on the surface of the existing secondary lining (1); Align the mounting hole of the prefabricated block (3) with the mounting hook (7), then insert the mounting hook into the mounting hole and hang it vertically on the mounting hook (7).

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