WO1986006133A1

WO1986006133A1 - Improvements relating to construction of submerged roadways and other structures

Info

Publication number: WO1986006133A1
Application number: PCT/GB1986/000200
Authority: WO
Inventors: Martin James Tomlinson; Andrew David Tomlinson; Murray Lloyd Chapman; Timothy John Woods Ballard
Original assignee: Martin James Tomlinson; Andrew David Tomlinson; Murray Lloyd Chapman; Timothy John Woods Ballard
Priority date: 1985-04-11
Filing date: 1986-04-11
Publication date: 1986-10-23
Also published as: GB2175944A; AU5690186A; EP0218702A1; GB8608695D0

Abstract

A submerged roadway is constructed from individual sections which may be floated into position above prepared sites such as in a river bed (26). The sections are floated in without ballast so that they will be of relatively shallow draught and will then be flooded through valve controlled openings (29) so that they can be installed in place and interconnected together. A number of ballast blocks (10) or loose ballast largely comprising a high specific gravity material, such as dense iron ore is loaded into the base of each section which is then dewatered and commissioned. The walls (1, 2, 3) of the roadway sections are of sandwich construction comprising steel plates filled with concrete (14) which is keyed to the plates (7) by shear transfer formations (15, 15A, 16, 17, 18, 19) projecting inwardly of the plates.

Description

"Improvements relating to construction of submerged roadways and other structures"

This invention is mainly concerned with the construction of roadways which are to be partially or totally submerged such as in estuaries or river crossings. If a submerged roadway is to be installed in relatively shallow water or if a roadway channel is to be built on the bed of the river or estuary but with the tops of the side walls projecting above thewater level, then difficulties can arise in installing sections of the roadway in place. A conventional procedure is to construct^'fully preformed- enclosed roadway sections, which will normally require deep draughts, and float them into place and sink them onto the river or estuary bed. However, in shallow water conditions there may be insufficient depth to allow such deep draught sections to be floated in and this may require special large-scale dredgingoperations to be carried out or alternatively the submerged roadway has to be constructed by another method. It is an object of this invention to provide roadway structures which may be installed relatively rapidly in a prepared site to construct a submerged roadway without-major disruption to the surrounding environs. Accordingly, from one aspect, the invention provides a roadway section comprising an open-topped or closed box-section having walls of composite form, being constructed from spaced-apart rigid metal plates provided with shear transfer formations defined on the surfaces of the plates which face one another, the space between^' the plates being filled with concrete to define a sandwich construction. The sandwich construction of the metal plates either side of the layer of concrete, which is keyed by the shear transfer formations, provides very robust walls for the box-section, thus enabling the sections to be transported readily, particularly as shallow draught vessels by water. The shear transfer formations will ideally comprise or include shear studs or connectors, indentations or bosses. In order to achieve enhanced overall shear capacity, the shear transfer formations will ideally comprise elongated shea-r studs or the like projecting, from the facing plates so as to overlap one another in order to carry the shear force in tension alone. Some of the shear studs may extend to the opposite metal plate to act as spacers. Additionally or alternatively the walls of the plates which face one another may be interconnected by bent bar trusses or other load transfer plates or devices. This is especially useful at weld junctions. The roadway surface of the section may be defined or supported by an internal floor of the box-section and/or by an outer upper wall (when provided) of the box-section. The roadway section may be for use in constructing wholly or partially submerged roadways, in the form of a shallow draught vessel, wherein the base of the hollow interior of the box-section defines a region for receipt of sufficient high specific gravity ballast to create a significant negative buoyancy for the box- section, and the box-section also incorporating means for flooding the section to create negative buoyancy

*» for the section prior to the incorporation of ballast.. Because the roadway section is constructed without the ballasting necessary to hold it in place on the bed of the river or estuary it has a high buoyancy and hence can be floated into position in conditions where shallow draught vessels only can pass. Hence this increases the scope for installing submerged roadways. Furthermore because the sections have a shallow draught they can be floated into prepared positions near to the shore and installed as open-topped tunnel approach sections which reduces the extent of civil engineering required.

The side walls at least, and preferably the bottom wall also of the box-section will be lined with concrete. However, if the box-section is closed (for use in totally submerged roadways) the top wall may be defined by spaced steel plates creating a space which is either filled with concrete or left as a void to be filled with concrete. The top wall of a closed box- section might incorporate openings for the insertion of the ballast.

The top of the region for receipt of the ballast may advantageously be defined by a preformed roadway platform or supports for such a platform. The walls of the box-section will ideally incorporate valve controlled openings through which water may flow to flood the section..

The invention further extends to a method of constructing a wholly or partially submerged roadway which comprises floating a requisite number of roadway sections of this invention as hereinbefore defined to positions above prepared underwater sites, flooding the sections to sink them into position on the prepared sites, loading the high specific gravity ballast into the base of the hollow interiors of the box-sections, interconnecting the sections by permanent joints, and dewatering each of the sections, and removing bulkheads to create continuous tunnels.

The high specific gravity ballast installed will be as dense as possible, subject to cost, and a dense iron ore is particularly suitable. Local conditions or other considerations may make it substantially more economical to use other types of ballast and although a heavy metallic ore is preferred it would be possible either to pour concrete into the sections as the ballast, or place it as precast blocks, even though this is of a much lower specific gravity than, for example, dense iron ore.

If desired the ballast could be grouted over with concrete after installation in the sections. The invention may be performed in various ways and preferred embodiments thereof will now be described with reference to. the accompanying drawings, in which:-

Figure 1 comprises a .diagrammatic vertical cross- section through^' a roadway section constructed in accordance with this invention;

Figure 2 illustrates a method of positioning a roadway section of Figure 1 on a river bed;

Figures 3 and 4 are detail sections through a wall of the roadway section of Figure 1 showing a number of different types of shear transfer formations and trusses which may be utilised; and

Figure 5 is an end view onto one of the trusses illustrated in Figure 4.

The roadway section A shown in Figure 1 of the drawings is constructed from a number of closed box- sections, each having side walls 1, a base 2, a top wall 3, and end walls, pre-constructed from welded steel sheets. A double skin is formed at each side by further steel walls 4, and a central double walled section is defined by steel sheets 5. The base 2 of the section is also formed as a double walled section by steel sheets 6. The spaces between the double walls are pre-filled with concrete 14 whilst the section is in the fabrication dock. Further steel plates 7 define a void space 8 with the top wall 3 at the top of the section which may be pre-filled with concrete or filled at a later stage of construction.

The roadway section shown in Figure 1 can be floated from the fabrication dock to the site where ^■ it is to be -installed and because this roadway section will have a substantial buoyancy it can be manoeuvred into place in shallow water and of course can be shipped from any suitable construction site by sea or river. The installation site on the river or estuary bed will have been prepared in advance by dredging and the sections can be positioned on the bed by controlled flooding through valve controlled openings in the end walls (for example) . A position for one such valve controlled opening is illustrated at 29 in an end wall 30. It is envisaged that each section will incorporate bulkheads to form individual watertight compartments in each of the two tubular portions 9 so that the balancing and the extent of flooding of the section can be controlled in a precise manner. As a sectionbecomes sufficiently filled with water it will sink into position and will be controlled during the final lowering phase from pontoons moored above the prepared site.

An alternative method of positioning the roadway section A in the prepared site is illustrated in Figure 2. Winch units 23 mounted temporarily on top of the roadway section A will be connected by cables 24 to bolts 25 fixed into the bed 26 of the river so as to draw the roadway section down into a prepared trench 27. Detachable external buoyancy tanks 28 provide a..small degree of positive buoyancy for the roadway section A after it has been filled with water so that the roadway section can be manoeuvred readily into the prepared site. The buoyancy tanks 28 are fitted by releasable connections and can, for example, be filled with water when no longer needed so as to fall. away and be removed. As an alternative cables 24 could be fixed to the roadway section, pass through pulleys at 25 and then to winches positioned elsewhere.

Once the roadway sections are in place they can receive the permanent ballasting. As shown the ballasting comprises preformed blocks 10 constructed from a dense iron ore bonded with concrete. The compartments of the roadway sections will be dewatered progressively, followed by removal of the relevant bulkheads. The blocks 10 then can be run into each compartment progressively of the fully positioned roadway sections, using simple transporters. Alternatively the ballast could comprise the dense iron ore in loose form which can be poured in.

The particular iron ore material envisaged has a specific gravity in air of about 3.9 (as compared to 2.4 for concrete alone). The relative submerged densities for the iron ore ballast and concrete are about 2.8 and 1.34 respectively so it will be seen that the iron ore ballast is approximately twice*, as effective as concrete as ballasting material. This means that the ballast occupies much less volume than the same weight of concrete so that the overall size of the roadway section and the amount of dredging required on the prepared site is significantly lower than for a roadway section relying on concrete as the ballasting material..

The iron ore could, for example, be poured in through temporary funnels passing through the roof 3 of the section. Once the ballast is in place the openings in the roof can be sealed off and the void area 8 will then be filled with concrete if this has not already been done on the preparation site. Permanent joints will be installed between adjacent sections and once the iron ore has been levelled and grouted up if necessary the sections can be dewatered. Once the process of emplacing the ballast, dewatering the compartments and removing the bulkheads has been completed two continuous tunnels 9 will be defined. Additional ballasting blocks 11 can be secured to the top of the roadway sections as shown, at any convenient stage of construction, ideally prior to dewatering so as to assist in holding down the roadway section until all the internal ballast has been emplaced. Roadway platforms 12 can be installed (either as part of the original manufacture or later once the sections are in place). Concrete facing panels 13 on the walls 4 and 5 provide additional ballast, fire protection and an impact resistance surface.

Open-topped sections (omitting top wall plates 3 and 7) may be utilised beyond the tunnel portals which could result in significant cost savings compared with a conventional cut and fill method of construction by normal civil engineering techniques. The open-topped roadway sections can be floated in and positioned in prepared channels formed in the shallows at the banks of the river or estuary by the dredger which will already be on the site. Temporary sheet piling and/or bunds are avoided. As well as saving on material costs the overall construction time in constructing these approaches to the tunnel portals could be reduced considerably and this would be added to the savings in construction time in completing the submerged tunnel sections themselves. The facing surfaces of the plates,which define the walls of the double tube, have shear studs welded to them and provide a key between the concrete 14 and the plates. These shear studs are not illustrated in Figure 1 , but can be seen more clearly from Figure 3. A preferred form of shear stud is of the form shown at 15 and these will be provided throughout the sandwich construction of the plates_^ with concrete 14 between them. Also illustrated in Figure 3 are other forms of shear transfer formations such as preformed bosses 16 on the walls of the steel plates and indentations 17 formed into the walls of the steel plates. One advantageous construction is to employ elongated rods or plates 18, 19 which will overlap, as shown. They may have T-shaped ends such as for the shear studs 15. Also bosses 20 or indentations could be formed as shown, for example, on the member 19. Some or all of the shear transfer formations can be of a length equal to the spacing between the plates, such as the elongated studs 15A, so as to"act as spacers. This facilitates fabrication of the walls, keeps the plates apart and minimises plate deformation.

Bent bar trusses 21 (Figure 4) may be welded between the plates to hold the plates apart. These trusses 21 will be welded to the plates and will provide a shear key which may be in addition to, or as an alternative to the shear transfer formations formed on the walls of the plates. The alternative form of bent bar truss 22 illustrated in Figure 4 is preferred. It is envisaged that the bent bar trusses will particularly be employed at weld junctions for the plates as illustrated in

Figure 5 to create added strength and rigidity at this point and to serve as a backing strip for welding. If a shear stud should fail, for example, the bent bar trusses 25 or 26 will resist a possible unzipping effect which might otherwise occur.

Other forms of load transfer plates or devices may be welded between the plates instead of the bent bar trusses 21 or 22 as illustrated. One possibility is to provide diaphragms welded between the two metal plates. if desired these diaphragms could incorporate holes which might have their edges reinforced if this is felt desirable. Another possibility is to join the two plates by rods which will act as load transfer members as well as performing a shear transfer function. Again the rods may be welded onto the plates. It should also be understood that the load transfer members and certain types of shear transfer formations may be bolted or otherwise fixed to the plates instead of being welded on.

Referring again to Figure 1 , it should be noted that roadways could be formed additionally on the upper surface either of walls 3 or the ballast blocks 11. The sections may be laid end to end to construct a continuous roadway in the form of a bridge structure or underground or underwater tunnels. Whilst the sections shown in the drawings are of double tube form of essentially square cross-section it will be appreciated that single tubes or multi-tube sections and open-topped ^'sections may be constructed to any desired shape such as circular, polygonal, U or C-shaped.

Should damage occur to an external wall of the roadway section water could seep in to the region between the inner and outer plates and could ultimately create high hydrostatic pressures capable of blowing off the inner skin. This can be prevented by providing small drainage holes at strategic points in the inner skin so that small quantities of water will then just seep into one of the tunnels 9 or 20 and can be pumped out as required. It should be noted that the term "roadway" used here is meant to define any passageway (whether for vehicles, materials or other purposes) which is to be formed in a wholly or partially submerged manner.

It will be appreciated that the sections as manufactured are structurally sound and can therefore be towed into the estuary and sunk into position immediately without further on-site fabrication. Thus the only on-site work is the attachment of the necessary winching equipment, the provision of detachable buoyancy tanks and the provision of ballast when the section is in position.

Claims

1. A roadway section comprising an open-topped or closed box-section having walls of composite form being constructed from spaced apart rigid metal plates provided with shear transfer formations defined on the

5 surfaces of the plates which face one another, the space between the plates being filled with concrete to define a sanwich construction.

2. A roadway section according to claim 1 , wherein the shear transfer formations comprise or

10 include shear studs, shear connectors, indentations or bosses, or elongated shear studs projecting from .^" facing plates- so as to overlap one another and optionally at least some of the shear studs extend to the opposite metal plate to act as spacers.

^~ 2. A roadway section according to claim 1 , wherein walls of the plates which face one another are interconnected by bent bar trusses, rods, plates or other load ^'transfer members or devices, which may be secured to the plates at junctions between plates 0 forming the walls.

3. A roadway section according to claim 1 or claim 2, wherein the roadway surface of the section is defined or supported by an internal floor of the box-section and/or by an outer upper wall (when 5 provided) of the box-section.

4. A roadway section according to any one of claims 1 to 3, for use in constructing wholly or partially submerged roadways, in the form of a shallow draught vessel, wherein the base of the hollow interior of the box-section defines a region for receipt of sufficient high specific gravity ballast to create a significant negative buoyancy for the box-section, and the box-section also incorporating means for flooding the section to create negative buoyancy for the section prior to the incorporation of the ballast.

5. A roadway section according to claim 4, wherein the box-section is closed and the top wall is defined by spaced steel plates^" creating a space which is either filled with concrete or left as a void to be filled with concrete, and/or the box-section is closed and the top wall incorporates openings for the insertion of the ballast.

6. A roadway section according to claim 5 or claim 6, wherein the top of the region for receipt of ballast defines a preformed roadway platform or supports for such a platform, and/or walls of the box-section incorporate valve controlled openings through which water may flow to flood the section.

7. method of constructing a wholly or partially submerged roadway comprising floating a requisite number of roadway sections as defined in any oneof claims 4 to 6 to positions above prepared underwater sites, flooding the sections to sink them into position on the preapred sites, loading the high specific gravity ballast into the base of the hollow interiors of the box-section, interconnecting the sections by permanent joints, dewatering each of the sections and removing bulkheads to create continuous tunnels.

8. A method according to claim 1 , wherein the ballast comprises dense iron ore, which may be in loose form or bonded with concrete to create discrete ballast blocks, and optionally the ballast is grouted over with- concrete after installation.

9. A submerged or partially submerged roadway constructed in accordance with a method as defined in claim 7 or claim 9.

10. A roadway section or a method of constructing a wholly or partially submerged roadway substantially as herein described with reference to the accompanying drawings.