AU639114B2 - A manhole - Google Patents

Description

"A MANHOLE"

This invention relates to a base lining for a manhole, a manhole and a method of constructing a manhole.

The invention will he described by way of example with reference to a sewer manhole. It should be appreciated that the manhole may be a stormwater manhole and the invention is not limited just to sewer manholes.

A sewer manhole typically consists of a base, an upstanding cylindrical wall, a converter slab or tapered cone section positioned adjacent the upper periphery of the wall and a cast concrete ring for receiving a manhole cover. At least one inlet opening extends through the wall and an outlet opening is provided at the base of the wall. The inlet openings extend through the wall either slightly higher than the outlet opening or spaced above that opening. Sewer pipes may be positioned relative to the openings.

Where only one inlet opening exists, that opening and the outlet opening may provide for straight through flow and be diametrically opposed in the wall. Alternatively the outlet opening and the inlet opening may be angularly spaced from one another by an angle up to 90º for example. Where two inlet openings are present the branching angle may be less than 30°, between 30° to 60° or between 60° to 90°. Three inlet openings may sometimes be present and one of these openings may be in line with the outlet opening and the other two inlet openings may be at a desired branch angle.

The base of the manhole needs to be contoured to promote the free flow of sewage. Thus, channels exist between each inlet opening and the outlet opening. The area between openings is generally required to be flat and slopes both towards the centre of the base and towards the outlet opening to form benches. The shape of the benches and channels are governed by standards set down for sewer design requirements and need to be particularly smooth to promote free flow. If this is not the case the manhole needs regular maintenance and cleaning and this is undesirable. It is also of paramount importance that the manhole is totally and permanently waterproof to eliminate ground water infiltration.

Manholes at present are sometimes formed in the following manner. Inlet and outlet pipes are positioned and a base of concrete is poured either with or without the presence of formwork. The base needs to be shaped and rendered to achieve the desired channel and bench shape and smoothness. This shaping and rendering is currently carried out by hand and is difficult to achieve. The work is carried out in a confined space and the worker needs to rest his feet on the actual work surface. The work can only be satisfactorily achieved with the concrete at a desired consistency. That is, the concrete must not be too wet or too dry.

Once the base has been poured and shaped the wall is poured. If desired an internal cylindrical liner may be employed to line the wall or instead of this internal formwork is employed.

A concrete converter slab or tapered cone section is positioned adjacent the upper periphery of the wall and a concrete ring positioned above it for receiving a manhole cover.

As indicated above, the formation of the base of the manhole is time consuming and difficult to construct and prone to ground water infiltration.

Australian patent specification 515883 discloses an arrangement for forming a manhole for connection with a plurality of pipes. The floor of the manhole is flat and does not promote smooth flow of fluids between the pipes. In addition the construction and provision of openings in the lower ring require the use of tapered sleeves and sealing rings for positioning the pipes relative to the lower ring.

Australian patent specification 554583 discloses an inspection chamber having a plastics base portion with preformed tubular inlets/outlets provided with socketed ends. This construction requires the use of sealing rings to secure pipes to the socketed ends and therefore it is not possible with this construction to cater for more than just slight deflections of the pipes from their ideal positions for securing them to the socketed ends.

Australian patent specification 572539 discloses a manhole assembly where the base is formed integrally with the side wall. Socketed inlets are present. This manhole assembly is not versatile and is only suitable for one particular inlet/outlet configuration. It is unable to cater for deflection variations in inlet/outlet pipes.

It is an object of the present invention to provide a base lining for a manhole, a manhole and a method of building a manhole which eliminates the disadvantages referred to above.

According to one aspect the invention provides a base lining for a manhole having at least one inlet portion, a major channel extending between the inlet portion of the lining to an outlet side of the lining and a plurality of surfaces above the channel and sloping towards the channel and the outlet side an aperture may be formed at the inlet portion and at the outlet side to enable pipes to be coupled to the lining and said lining is made of plastics material.

The base lining may have an upstanding or outwardly directed peripheral flange extending around it and, where the lining is circular, the flange may comprise a short cylindrical extension to the lining.

Where the base lining is intended to line the base of a manhole having one inlet and one outlet the inlet portion may be diametrically opposite the outlet side and the channel may provide for diametric flow of sewage across the base lining, that is, straight through flow. The flow need not be diametric and thus the inlet portion may be at an angle to the outlet side of the lining. The angle may be between 180º to 90º either sid of the outlet side. Where the base lining is intended to line the base of a manhole having branched inlets at less tha 30º, 30º to 60º or 60º to 90º to one another and on outlet, the inlet portions need not be diametrically spaced from the outlet side of the lining and may have minor channels merging with a major channelleading to the outlet side.

Where the base lining is intended to line the base of a manhole having three inlets, one inlet portion may be diametrically opposed to the outlet side while the other inlet portions may be adjacent the one inlet portion and at an angle to the outlet side to form a desired branching angle of between 30º to 60º or 60° to 90º. Benches extend between adjacent inlet portion and between the outlet side and the nearest inlet portion. Channels may lead from the inlet portions and merge with a major channel leading to the outlet side.

The base lining is made from plastics material. Preferably glass reinforced plastic or fibre reinforced Plastic is employed. vinyl esther or polyester thermosetting plastics material is preferred. Although the lining may have any suitable thickness a lining of about 5mm thick material is preferred. The lining may have inlet and outlet pipe couplings fixed in position at the required gradient prior to being positioned in situ.

An alternative to this is to use short split sleeves and position them extending through apertures formed in the inlet portion and the outlet side of the lining. The free end of the sleeve may project into sewer pipes and a wedge employed to expand the sleeve to form a tight fit in the aperture and in the sewer pipe. Subsequent to this concrete may be poured over the pipe and sleeve to couple and seal the pipe relative to the lining.

According to another aspect of the invention there is provided a method of constructing a manhole including forming an excavation, positioning a base lining on a floor of the excavation and supporting the base lining spaced from the floor by a predetermined distance, pouring concrete into the space between the floor and the lining and biasing the base lining against the concrete. Preferably biasing involves using a force substantially equal to the pressure created by upward hydraulic force of the poured concrete under the base lining.

The method preferably includes vibrating the concrete with a mechanical vibrator to ensure uniform consistency and minimise or prevent air entrapment.

The biasing step may involve the use of ballast. The ballast may be placed directly on the base lining or onto internal formwork employed for casting the upstanding walls of the manhole. Where the walls are not case in situ and prefabricated wall sections are used the ballast may be applied to the wall sections after they have been positioned on the base lining. The upward hydraulic pressure of wet concrete is typically about 330 kg. Sand bags may be used as ballast.

The method may include providing formwork in the excavation for the base and the upstanding wall of the manhole. Where a cylindrical wall is being cast the formwork may include outer and inner formwork.

The method of constructing the manhole may include positioning a wall lining within the upstanding wall although such a wall lining need not be present if desired.

The method of constructing the manhole may include providing a finish to the upper periphery of the manhole. This may include providing either as a preformed slab or a slab case in situ a concrete converter slab adjacent the upper periphery of the wall.

The converter slab is preferably circular in plan view with an opening for access into the manhole. The finish may also include positioning a ring over the slab. The ring being adapted for receiving a manhole cover.

According to another aspect of the invention there is provided a manhole having a base formed of concrete and having a base lining of plastics at least one inlet opening and one outlet opening and an upstanding wall.

The manhole may have a finish including a concrete slab and a cover receiving ring. Preferably the manhole includes a sleeve or wall lining extending upwardly of the base. The wall lining may have a joining lip for sealing against the base lining. The wall lining may be present as one or more lining sections.

The invention will now be described by way of example with reference to the drawings in which:

Figures 1 to 5 illustrate various stages of the method of constructing a manhole according to an embodiment of the invention;

Figure 6 is a sectional view of part of a manhole;

Figure 7 is a plan view of a manhole;

Figure 8 is a sectional view of a base lining according to one embodiment of the invention;

Figure 9 is a sectional view through part of a base lining;

Figure 10 is a table showing minimum falls across the base lining

Figure 11 is a partial cutaway perspective view of a manhole utilizing the base lining of Figure 7;

Figure 12 is a diagrammatic view of a base lining having a straight through flow path and the inset view further illustrates that configuration;

Figure 13 illustrates another base lining configuration with the inset views showing possible variations for branching between 90° to 112°;

Figure 14 illustrates another base lining configuration with the views showing possible variations for branching between 112° to 125°;

Figure 15 illustrates another base lining configuration with the inset views showing possible variations for branching between 125° to 140°;

Figure 16 illustrates another base lining configuration with the inset views showing possible variations for branching between 140° to 150°; and

Figure 17 illustrates another base lining configuration with the inset views showing possible variations for branching between 150° to 170°.

With reference to figures 1 to 5 the way in which a manhole is constructed is shown. An excavation

10 is formed. Base lining 12 is positioned spaced from the floor of the excavation by about 150 mm and connected to the outlet by a short length of pipe, loaded at 13 and concrete poured to form base 14. The lining 13 may be supported and concrete poured or alternatively some of the concrete may be poured first (see figure 1) and then the lining is positioned, supported and the remainder of the concrete poured. It is not necessary for the lining to have inlet and outlet short pipes in position prior to placing the lining in the excavation although this can be done if desired. An rnative method involves the use of a split sleeve a edge as shown in figure 5 to temporarily secure the pipeline to the lining while concrete is being poured. This eliminates fixing of the short pipes prior to placing the liner. The concrete may be vibrated to achieve an even consistency. The lining 12 in this instance has an upstanding peripheral wall 15, an inlet portion 16 including split sleeves 22, and an outlet side 17 including coupling 21. Channel 18 extends across the lining and benches 19, 20 slope towards the channel and towards outlet side 17.

Pipes 23, 24 are positioned relative to sleeve

22 and wedge 22a driven in to expand the sleeve into pipe

23 and into the aperture in the lining 12. The wall 25 (see figure 6) is then poured with the aid of internal formwork (not shown), or lining 27 (with temporary internal bracing) and an external formwork (not shown) or against wall 26 of excavation. An internal lining 27 may complete the interior of the wall 25 in the event that wall 25 is constructed of pre-cast concrete sections.

Figure 6 shows a similar sectional view to that of figure 4 except that the lining 27 is not present and pipe couplings 23a, 24a are used instead of sleeves 22.

Figure 7 shows a plan view of an alternative base lining configuration 40. In this instance there are three inlets 41, 42, 43 with minor channels 44, 45, 46 leading into major channel 47 and outlet 48. Benches of the slope indicated exist between the inlets and outlet.

Figure 8 shows a typical base lining 12 in situ in a manhole. In this embodiment there is one inlet and one outlet with the channel 18 having a 5:1 wall slope and benches 19, 20 having a 1:8 slope. The manhole has a slab 30 with an opening 31. A ring 32 rests on slab 30 and has an opening 33 for a manhole cover.

Figure 9 shows a transverse section through the channel 18 of figure 6.

Figure 10 shows a table of manhole base configurations with a variety of possible inlet and outlet branch configurations.

Figure 11 shows a lining 40 like that of Figure 7. The lining 40 has a flange 50 on which upstanding cylindrical wall 27 may rest and be secured.

Figure 12 shows in diagrammatic form a base lining 51 having a straight through flow channel 52 with an inlet 53 and an outlet. The inset view forming part of this figure gives is schematic for this diagrammatic view.

Figure 13 shows a diagrammatic representation of the lining 40 of figure 11. Inset views give schematic representations of other lining configurations with branching between 90° to 112°.

Figure 14 illustrated another lining 60 with the inset views showing variations for branching between 112° to 125°.

Figure 15 illustrated another lining 61 with the inset views showing variations for branching between 125° to 140°.

Figure 16 shows a lining 62 with the inset views showing branchings between 140° to 150°.

Figure 17 shows a lining 63 with the inset views showing branchings between 150° to 170°. The base lining of the invention eliminates the need for manual and time consuming rendering of the base of a manhole and provides a consistent smooth finish to the manhole base. This smooth lining promotes smooth flow across the lining and ensures minimum maintenance requirements for the manhole and totally eliminates any infiltration of ground water into the manhole.

Claims (20)

CLAIMS :

1. A base lining for a manhole having at least one inlet portion, a major channel extending between the inlet portion of the lining to an outlet side of the lining and a plurality of surfaces above the channel and sloping towards the channel and out outlet side, an 2aperture may be formed at the inlet portion and at the outlet side to enable pipes to be coupled to the lining, and said lining being formed of plastics material.

2. The lining of Claim 1 including an outwardly directed peripheral flange extending around a free periphery thereof.

3. The lining of Claim 1 wherein said lining is substantially circular when viewed in plan.

4. The lining of Claims 1, 2 or 3 having a plurality of said inlet portions and said inlet portions form an angle of less than 30º, 30° to 60° or 60° to 90º2 to one another and a respective minor channel is associated with each inlet portion, said minor channels merge into said major channel.

5. The lining of Claim 4 including sloping surfaces between adjacent said inlet portions.

6. The lining of any one of Claims 1 to 5 wherein said plastics material is glass or fibre reinforced.

7. The lining of Claim 1 wherein the inlet portion is diametrically opposed to said outlet side.

8. The lining of any one of Claims 1 to 3 wherein said lining has one said inlet portion and said outlet side is either diametrically opposed to the outlet side or spaced from the diameter.

9. The lining of Claim 8 wherein the spacing is at angle of between 180° to 90° either side of the outlet side of the lining.

10. The lining of any one of Claims 1 to 3 wherein said inlet portions is spaced from the outlet side by between 90° to 112°, 112° to 125°, 125° to 140° or 140° to 150°.

11. The lining of any one of Claims 1 to 6 wherein said plastics material is either vinyl ester or a polyester thermosetting plastics material.

12. The lining of Claim 11 having a thickness of about 5 mm.

13. A method of constructing a manhole including forming an excavation, positioning a base lining on a floor of the excavation and supporting the base lining spaced from the floor by a predetermined distance, pouring concrete into the space between the base lining and the floor and biasing the base lining against the concrete.

14. The method of Claim 13 wherein said biasing involves using a force substantially equal to the pressure created by upward hydraulic force of the poured concrete under the base lining.

15. The method of Claims 13 or 14 including vibrating the concrete with a mechanical vibrator to ensure uniform consistency of the concrete and minimise or prevent air entrapment.

16. The method of Claim 14 wherein the biasing involves the use of ballast.

17. The method of any one of Claims 13 to 16 including casting an upstanding wall and the base lining.

18. The method of any one of Claims 13 to 16 including positioning one or more preformed wall sections onto the base lining.

19. The method of Claim 17 or 18 including finishing the upper periphery of the manhole by providing a converter slab adjacent an upper periphery of the wall and positioning a ring onto the slab.

20. A manhole including a base lining according to any one of Claims 1 to 12.