Symmetrical Y-shaped branch pipe capable of reducing deformation of joint with concrete

Abstract

The invention provides a symmetrical Y-shaped branch pipe capable of reducing deformation of a concrete joint, and the branch pipe comprises a pipe body which comprises a main pipe and a plurality of branch pipes connected with the main pipe; the reinforcing plate set comprises a plurality of reinforcing plates, the reinforcing plates are arranged on the peripheries of the main pipe and the branch pipes at intervals in the circumferential direction of the pipe body, and each reinforcing plate is provided with a reinforcing hole. Through the technical scheme provided by the invention, the problem that the safety is influenced by the deformation of the branch pipe in the related technology can be solved.

Description

Technical Field

[0001] The invention relates to the technical field of bifurcated pipes, and in particular to a symmetrical Y-shaped bifurcated pipe capable of reducing deformation of a joint with concrete. Background Art

[0002] The bifurcated pipe is an important part of a hydropower station, responsible for guiding water flow into two or more turbine generator sets to save project investment. In recent years, with the development of conventional hydropower and pumped storage, bifurcated pipes have been increasingly used in engineering. Bifurcated pipes are usually buried in tunnels, and their shapes are usually divided into three types: asymmetric Y-shaped, symmetric Y-shaped and three-branched. Among them, the safety of bifurcated pipes is crucial to the safety of hydropower projects.

[0003] In engineering, the structural design of the bifurcated pipe pays more attention to its hydraulic characteristics, such as water flow pattern, head loss, erosion characteristics, etc., but pays less attention to its structural deformation. The deformation of the bifurcated pipe will affect the deformation of the joint with the concrete, which will cause the vibration of the pipeline system and affect the safety of the unit. For high-head units, the deformation of the bifurcated pipe is more obvious, and it is extremely important to strictly control it. Summary of the invention

[0004] The invention provides a symmetrical Y-shaped fork pipe which can reduce the deformation of the joint with concrete, so as to solve the problem that the deformation of the fork pipe affects the safety in the related art.

[0005] The invention provides a symmetrical Y-shaped fork pipe for reducing deformation of a joint with concrete. The fork pipe comprises: a pipe body, comprising a main pipe and a plurality of branch pipes connected to the main pipe; a reinforcing plate group, comprising a plurality of reinforcing plates, wherein the plurality of reinforcing plates are arranged at intervals along the circumference of the pipe body on the outer periphery of the main pipe and the plurality of branch pipes, and each reinforcing plate is provided with a reinforcing hole.

[0006] Further, the multiple reinforcement plates include multiple main plate segments and multiple sub-plate segments, the multiple main plate segments are arranged at intervals along the circumference of the main pipe on the outer periphery of the main pipe, the multiple sub-plate segments are arranged at intervals along the circumference of the branch pipe on the outer periphery of the branch pipe, and the reinforcement holes include a first hole segment arranged on the main plate segment and a second hole segment arranged on the sub-plate segment.

[0007] Furthermore, the plurality of reinforcing plates further include a connecting plate segment, the connecting plate segment is connected to the outer periphery of two adjacent branch pipes, and the reinforcing hole includes a third hole segment arranged on the connecting plate segment.

[0008] Furthermore, the branch pipe includes an inclined pipe section and a straight pipe section, two ends of the inclined pipe section are respectively connected to the main pipe and the straight pipe section, the auxiliary plate section includes an inclined plate section and a straight plate section, two ends of the inclined plate section are respectively connected to the main pipe section and the straight plate section, the inclined plate section is connected to the outer periphery of the inclined pipe section, the straight plate section is connected to the outer periphery of the straight pipe section, the second hole section includes a fourth hole section arranged on the inclined plate section and a fifth hole section arranged on the straight plate section, and the connecting plate section is connected to the outer wall of the inclined pipe section and the outer wall of the straight pipe section.

[0009] Furthermore, the ratio between the length of the first hole segment and the length of the main plate segment is greater than or equal to 0.6 and less than or equal to 0.7; the ratio between the length of the fourth hole segment and the length of the inclined plate segment is greater than or equal to 0.5 and less than or equal to 0.6; the ratio between the length of the fifth hole segment and the length of the straight plate segment is greater than or equal to 0.55 and less than or equal to 0.65.

[0010] Furthermore, there are two inclined pipe sections and two straight pipe sections, the ends of the two inclined pipe sections are connected to the main pipe, and there are four inclined plate sections and four straight plate sections, which are respectively connected to the corresponding main plate sections.

[0011] Furthermore, the connecting plate section includes a connecting straight plate, a connecting inclined plate and a connecting transverse plate. The outer wall of each inclined pipe section is connected to a connecting inclined plate, and the outer wall of each straight pipe section is connected to a connecting straight plate. The two ends of the connecting straight plate are respectively connected to the connecting inclined plate and the connecting transverse plate. The connecting straight plate, the connecting inclined plate and the connecting transverse plate together form a third hole section.

[0012] Further, the main plate segment, the inclined plate segment and the straight plate segment are all rectangular structures; and / or, the first hole segment, the fourth hole segment and the fifth hole segment are all rectangular holes.

[0013] Furthermore, the angle between two adjacent main plate segments is 90°; and / or the angle between two adjacent auxiliary plate segments is 90°.

[0014] Furthermore, the diameter of the main pipe is equal to the diameter of the branch pipe, and the ratio between the width of the reinforcing plate and the diameter of the main pipe is greater than or equal to 0.4 and less than or equal to 0.6.

[0015] By applying the technical solution of the present invention, the branch pipe includes a pipe body and a reinforcement plate group. When pouring concrete, the branch pipe is buried in the concrete, and a plurality of reinforcement plates can be used to increase the contact area between the branch pipe and the concrete to increase the restriction effect on the branch pipe. At the same time, the reinforcement holes arranged on the reinforcement plates can allow concrete to flow through to avoid the generation of interaction force between the reinforcement plates and the pipe body due to the squeezing effect of the concrete, thereby reducing the deformation of the branch pipe during the operation of the unit through the reinforcement plates, and reducing the deformation of the joint between the branch pipe and the concrete. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The drawings constituting a part of the present application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0017] Figure 1 A schematic diagram of the structure of a bifurcated pipe according to an embodiment of the present invention is shown;

[0018] Figure 2Another structural schematic diagram of a bifurcated pipe provided according to an embodiment of the present invention is shown.

[0019] The above drawings include the following reference numerals:

[0020] 10. pipe body; 11. main pipe; 12. branch pipe; 121. inclined pipe section; 122. straight pipe section;

[0021] 20. Reinforcement plate group; 21. Main plate section; 211. First hole section; 22. Auxiliary plate section; 221. Inclined plate section; 2211. Fourth hole section; 222. Straight plate section; 2221. Fifth hole section; 23. Connecting plate section; 231. Connecting straight plate; 232. Connecting inclined plate; 233. Connecting transverse plate; 234. Third hole section. DETAILED DESCRIPTION

[0022] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] like Figure 1 and Figure 2 As shown, an embodiment of the present invention provides a symmetrical Y-shaped fork pipe for reducing deformation of the joint with concrete, the fork pipe includes a pipe body 10 and a reinforcing plate group 20, the pipe body 10 includes a main pipe 11 and a plurality of branch pipes 12 connected to the main pipe 11; the reinforcing plate group 20 includes a plurality of reinforcing plates, the plurality of reinforcing plates are arranged at intervals along the circumference of the pipe body 10 on the outer periphery of the main pipe 11 and the plurality of branch pipes 12, and each reinforcing plate is provided with a reinforcing hole.

[0024] By applying the technical solution of the present invention, a symmetrical Y-shaped branch pipe for reducing deformation of the joint with concrete includes a pipe body 10 and a reinforcing plate group 20. When pouring concrete, the branch pipe is buried in the concrete, and a plurality of reinforcing plates can be used to increase the contact area between the branch pipe and the concrete to increase the limiting effect on the branch pipe. At the same time, the reinforced holes arranged on the reinforcing plates can be used to allow concrete to flow through to avoid the generation of interaction force between the reinforcing plates and the pipe body 10 due to the squeezing effect of the concrete, thereby reducing the deformation of the branch pipe during the operation of the unit through the reinforcing plates, and reducing the deformation of the joint between the branch pipe and the concrete.

[0025] In this embodiment, since reinforcing plates are provided on both the main pipe 11 and the branch pipe 12, when pouring concrete, the reinforcing plates can simultaneously increase the contact area between the main pipe 11 and the concrete, and the contact area between the branch pipe 12 and the concrete, so that the contact area between the entire pipe body 10 and the concrete is larger.

[0026] The forked pipe may also be any one of an asymmetric Y-shape, a symmetric Y-shape and a three-forked shape.

[0027] It should be noted that in order to further reduce the interaction force between the tube body 10 and the reinforcing plate, the multiple reinforcing plates cannot interfere with each other.

[0028] In addition, the reinforcing plate can increase the contact area with the concrete, ensure full and tight filling of concrete during the concrete pouring process, strengthen the restriction of concrete on the branch pipe, and reduce the deformation of the branch pipe during the operation of the unit.

[0029] like Figure 1 As shown, the plurality of reinforcing plates include a plurality of main plate segments 21 and a plurality of auxiliary plate segments 22. The plurality of main plate segments 21 are arranged at intervals along the circumference of the main pipe 11 on the outer periphery of the main pipe 11, and the plurality of auxiliary plate segments 22 are arranged at intervals along the circumference of the branch pipe 12 on the outer periphery of the branch pipe 12. The reinforcing holes include a first hole segment 211 arranged on the main plate segment 21 and a second hole segment arranged on the auxiliary plate segment 22. The reinforcing plate with the above structure increases the contact area between the main pipe 11 and the concrete by using the main plate segment 21, and increases the contact area between the branch pipe 12 and the concrete by using the auxiliary plate segment 22, thereby making the contact area between the entire pipe body 10 and the concrete larger.

[0030] Among them, the number of main board segments 21 and the number of auxiliary board segments 22 can be the same, or the number of main board segments 21 can be greater than the number of auxiliary board segments 22, or the number of main board segments 21 can be less than the number of auxiliary board segments 22. The specific setting is determined according to actual conditions.

[0031] Furthermore, the main plate segment 21 can be connected to the auxiliary plate segment 22 or can be separately arranged.

[0032] like Figure 1 As shown, the plurality of reinforcing plates further include a connecting plate segment 23, the connecting plate segment 23 is connected to the outer periphery of two adjacent branch pipes 12, and the reinforcing hole includes a third hole segment 234 provided on the connecting plate segment 23. The connecting plate segment 23 can not only increase the connection strength between the branch pipes 12, but also increase the contact area with the concrete, thereby reducing the deformation of the branch pipe during the operation of the unit.

[0033] When the number of branch pipes is three, a connecting plate section 23 may be provided between two adjacent branch pipes 12 .

[0034] like Figure 1As shown, the branch pipe 12 includes an inclined pipe section 121 and a straight pipe section 122, the two ends of the inclined pipe section 121 are connected to the main pipe 11 and the straight pipe section 122 respectively, the auxiliary plate section 22 includes an inclined plate section 221 and a straight plate section 222, the two ends of the inclined plate section 221 are connected to the main plate section 21 and the straight plate section 222 respectively, the inclined plate section 221 is connected to the outer periphery of the inclined pipe section 121, and the straight plate section 222 is connected to the outer periphery of the straight pipe section 122, the second hole section includes a fourth hole section 2211 arranged on the inclined plate section 221 and a fifth hole section 2221 arranged on the straight plate section 222, and the connecting plate section 23 is connected to the outer wall of the inclined pipe section 121 and the outer wall of the straight pipe section 122. With the above structure, the contact area between the inclined pipe section 121 and the concrete can be increased by using the inclined plate section 221, and the contact area between the straight pipe section 122 and the concrete can be increased by using the straight plate section 222, thereby making the contact area between the branch pipe 12 as a whole and the concrete larger.

[0035] The ratio between the length of the first hole section 211 and the length of the main board section 21 is greater than or equal to 0.6 and less than or equal to 0.7. With the above ratio range, a suitable first hole section 211 can be provided in the main board section 21 under the condition of ensuring the structural strength of the main board section 21, so that concrete can flow through, thereby increasing the contact area between the main board section 21 and the concrete and reducing the force of the concrete on the main board section 21.

[0036] Specifically, the ratio between the length of the fourth hole segment 2211 and the length of the inclined plate segment 221 is greater than or equal to 0.5 and less than or equal to 0.6. With the above ratio range, it is possible to provide a suitable fourth hole segment 2211 in the inclined plate segment 221 while ensuring the structural strength of the inclined plate segment 221, so that concrete can flow through, thereby increasing the contact area between the inclined plate segment 221 and the concrete and reducing the force of the concrete on the inclined plate segment 221.

[0037] The ratio between the length of the fifth hole section 2221 and the length of the straight plate section 222 is greater than or equal to 0.55 and less than or equal to 0.65. By adopting the above ratio range, a suitable fifth hole section 2221 can be provided in the straight plate section 222 while ensuring the structural strength of the straight plate section 222, so that concrete can flow through, thereby increasing the contact area between the straight plate section 222 and the concrete and reducing the force of the concrete on the straight plate section 222.

[0038] like Figure 1 As shown, there are two inclined pipe sections 121 and two straight pipe sections 122, and the ends of the two inclined pipe sections 121 are connected to the main pipe 11. There are four inclined plate sections 221 and four straight plate sections 222, and the four inclined plate sections 221 are respectively connected to the corresponding main plate sections 21. With the above structure, the shape of the inclined plate section 221 and the straight plate section 222 can be adapted to the shape of the branch pipe 12, thereby facilitating the setting of the reinforcing plate.

[0039] In this embodiment, there are four main plate segments 21, which are evenly distributed on the periphery of the main pipe 11. There are six auxiliary plate segments 22, and three auxiliary plate segments 22 are arranged on the periphery of each branch pipe 12. Among them, the two auxiliary plate segments 22 located on the upper side of the pipe body 10 and the two auxiliary plate segments 22 located on the lower side of the pipe body 10 are connected to the corresponding main plate segments 21 respectively.

[0040] like Figure 1 As shown, the connecting plate segment 23 includes a connecting straight plate 231, a connecting inclined plate 232 and a connecting transverse plate 233. The outer wall of each inclined pipe segment 121 is connected to a connecting inclined plate 232, and the outer wall of each straight pipe segment 122 is connected to a connecting straight plate 231. The two ends of the connecting straight plate 231 are respectively connected to the connecting inclined plate 232 and the connecting transverse plate 233. The connecting straight plate 231, the connecting inclined plate 232 and the connecting transverse plate 233 together form a third hole segment. The connecting plate segment 23 with the above structure can be adapted to the shape of the branch pipe 12, and the space arrangement between the two branch pipes 12 is fully utilized.

[0041] In this embodiment, there are two connecting straight plates 231 and two connecting inclined plates 232 . The connecting transverse plate 233 is connected between the two connecting straight plates 231 .

[0042] like Figure 1 As shown, the main plate segment 21, the inclined plate segment 221 and the straight plate segment 222 are all rectangular structures, and the first hole segment 211, the fourth hole segment 2211 and the fifth hole segment 2221 are all rectangular holes. The above structure has the advantages of simple structure and easy processing.

[0043] The angle between two adjacent main plate segments 21 is 90°, and the angle between two adjacent auxiliary plate segments 22 is 90°. The above angle range has the advantages of simple structure and easy installation.

[0044] like Figure 1 As shown, the diameter of the main pipe 11 is equal to the diameter of the branch pipe 12, and the ratio between the width of the reinforcing plate and the diameter of the main pipe 11 is greater than or equal to 0.4 and less than or equal to 0.6. By adopting the above ratio range, the reinforcing plate can increase the contact area with the concrete without causing deformation to the outer side of the pipe body 10.

[0045] The ratio of the width of the reinforcing plate to the diameter of the main pipe 11 may be 0.4, 0.5, 0.6, or any value greater than or equal to 0.4 and less than or equal to 0.6.

[0046] It should be noted that the bifurcated pipe provided in this embodiment is a symmetrical structure with the horizontal mid-plane of the pipe body 10. Among them, the reinforcing plates located above and below the pipe body 10 can increase the strength of the bifurcated pipe in the vertical direction, reduce the deformation of the bifurcated pipe in the vertical direction caused by the impact of unstable water flow in the pipeline, and further reduce the deformation of the joint between the bifurcated pipe and the concrete in the vertical direction through the restraining effect of concrete on the bifurcated pipe. The reinforcing plates located on both sides of the pipe body 10 can increase the strength of the bifurcated pipe in the horizontal direction, reduce the deformation of the bifurcated pipe in the horizontal direction caused by the impact of unstable water flow in the pipeline, and further reduce the deformation of the joint between the bifurcated pipe and the concrete in the horizontal direction through the restraining effect of concrete on the bifurcated pipe. The connecting plate section 23 can further increase the strength of the bifurcated pipe, reduce the inward deformation of the bifurcated pipe caused by the impact of unstable water flow in the pipeline, and further reduce the deformation of the joint between the bifurcated pipe and the concrete through the restraining effect of concrete on the bifurcated pipe.

[0047] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0048] Unless otherwise specifically stated, the relative arrangement, numerical expressions and numerical values ​​of the parts and steps set forth in these embodiments do not limit the scope of the present invention. Meanwhile, it should be understood that, for ease of description, the sizes of the various parts shown in the accompanying drawings are not drawn according to the actual proportional relationship. The technology, method and equipment known to those of ordinary skill in the relevant art may not be discussed in detail, but in appropriate cases, the technology, method and equipment should be considered as a part of the specification. In all examples shown and discussed here, any specific value should be interpreted as being merely exemplary, rather than as a limitation. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters represent similar items in the following drawings, and therefore, once a certain item is defined in an accompanying drawing, it does not need to be further discussed in subsequent drawings.

[0049] In the description of the present invention, it is necessary to understand that the directions or positional relationships indicated by directional words such as "front, back, up, down, left, right", "lateral, vertical, perpendicular, horizontal" and "top, bottom" are usually based on the directions or positional relationships shown in the drawings. They are only for the convenience of describing the present invention and simplifying the description. Unless otherwise specified, these directional words do not indicate or imply that the devices or elements referred to must have a specific direction or be constructed and operated in a specific direction. Therefore, they cannot be understood as limiting the scope of protection of the present invention. The directional words "inside and outside" refer to the inside and outside relative to the contours of each component itself.

[0050] For ease of description, spatially relative terms such as "above", "above", "on the upper surface of", "above", etc. may be used here to describe the spatial positional relationship between a device or feature and other devices or features as shown in the figure. It should be understood that spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation described in the figure. For example, if the device in the accompanying drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below other devices or structures". Thus, the exemplary term "above" can include both "above" and "below". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatially relative descriptions used here are interpreted accordingly.

[0051] In addition, it should be noted that the use of terms such as "first" and "second" to limit components is only for the convenience of distinguishing the corresponding components. If not otherwise stated, the above terms have no special meaning and therefore cannot be understood as limiting the scope of protection of the present invention.

[0052] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A symmetrical Y-shaped branch pipe for reducing deformation of the joint with concrete, characterized in that: The bifurcated pipe comprises: A pipe body (10) comprising a main pipe (11) and a plurality of branch pipes (12) connected to the main pipe (11); The reinforcing plate group (20) comprises a plurality of reinforcing plates, wherein the plurality of reinforcing plates are arranged at intervals along the circumference of the tube body (10) on the outer circumference of the main tube (11) and the plurality of branch tubes (12), and each of the reinforcing plates is provided with a reinforcing hole.

2. The bifurcated pipe according to claim 1, characterized in that: The plurality of reinforcing plates include a plurality of main plate segments (21) and a plurality of auxiliary plate segments (22); the plurality of main plate segments (21) are arranged at intervals along the circumference of the main pipe (11) on the outer periphery of the main pipe (11); the plurality of auxiliary plate segments (22) are arranged at intervals along the circumference of the branch pipe (12) on the outer periphery of the branch pipe (12); and the reinforcing holes include a first hole segment (211) arranged on the main plate segment (21) and a second hole segment arranged on the auxiliary plate segment (22).

3. The bifurcated pipe according to claim 2, characterized in that: The plurality of reinforcing plates further include a connecting plate segment (23), wherein the connecting plate segment (23) is connected to the outer periphery of two adjacent branch pipes (12), and the reinforcing hole includes a third hole segment (234) arranged on the connecting plate segment (23).

4. The bifurcated pipe according to claim 3, characterized in that: The branch pipe (12) comprises an inclined pipe section (121) and a straight pipe section (122), the two ends of the inclined pipe section (121) are respectively connected to the main pipe (11) and the straight pipe section (122), the auxiliary plate section (22) comprises an inclined plate section (221) and a straight plate section (222), the two ends of the inclined plate section (221) are respectively connected to the main pipe section (21) and the straight plate section (222), the inclined plate section (221) is connected to the outer periphery of the inclined pipe section (121), and the straight plate section (222) is connected to the outer periphery of the straight pipe section (122), the second hole section comprises a fourth hole section (2211) arranged on the inclined plate section (221) and a fifth hole section (2221) arranged on the straight plate section (222), and the connecting plate section (23) is connected to both the outer wall of the inclined pipe section (121) and the outer wall of the straight pipe section (122).

5. The bifurcated pipe according to claim 4, characterized in that: The ratio between the length of the first hole section (211) and the length of the main plate section (21) is greater than or equal to 0.6 and less than or equal to 0.7; The ratio between the length of the fourth hole section (2211) and the length of the inclined plate section (221) is greater than or equal to 0.5 and less than or equal to 0.6; The ratio between the length of the fifth hole section (2221) and the length of the straight plate section (222) is greater than or equal to 0.55 and less than or equal to 0.

65.

6. The bifurcated pipe according to claim 4, characterized in that: There are two inclined pipe sections (121) and two straight pipe sections (122), and the ends of the two inclined pipe sections (121) are connected to the main pipe (11). There are four inclined plate sections (221) and four straight plate sections (222), and the four inclined plate sections (221) are respectively connected to the corresponding main plate sections (21).

7. The bifurcated pipe according to claim 4, characterized in that: The connecting plate section (23) comprises a connecting straight plate (231), a connecting inclined plate (232) and a connecting transverse plate (233); the outer wall of each of the inclined pipe sections (121) is connected to the connecting inclined plate (232); the outer wall of each of the straight pipe sections (122) is connected to the connecting straight plate (231); two ends of the connecting straight plate (231) are respectively connected to the connecting inclined plate (232) and the connecting transverse plate (233); the connecting straight plate (231), the connecting inclined plate (232) and the connecting transverse plate (233) together form the third hole section.

8. The bifurcated pipe according to claim 4, characterized in that: The main plate segment (21), the inclined plate segment (221) and the straight plate segment (222) are all rectangular structures; and / or the first hole segment (211), the fourth hole segment (2211) and the fifth hole segment (2221) are all rectangular holes.

9. The bifurcated pipe according to claim 2, characterized in that: The angle between two adjacent main plate segments (21) is 90°; and / or the angle between two adjacent auxiliary plate segments (22) is 90°.

10. The bifurcated pipe according to claim 1, characterized in that: The diameter of the main pipe (11) is equal to the diameter of the branch pipe (12), and the ratio between the width of the reinforcing plate and the diameter of the main pipe (11) is greater than or equal to 0.4 and less than or equal to 0.6.

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