GB2175944A - Construction of submerged roadways - Google Patents

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

SPECIFICATION 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 roadwayisto be installed in relatively shallow water or if a roadway channel is to be built on the bed ofthe river or estuary but with the tops ofthe side walls projecting above the water level, then difficulties can arise in installing sections ofthe 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 sinkthem 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 dredging operations to be carried out or alternatively the submerged roadway hasto be constructed by another method.

It is an object ofthis invention to provide roadway structures which may be installed relatively rapidly in a prepared siteto 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 sheartransferformations defined on the surfaces ofthe plates which face one another, the space between the plates being filled with concreteto define a sandwich construction.

The sandwich construction ofthe metal plates either side of the layer of concrete, wh ich is keyed by the sheartransferformations, provides very robust walls forthe box-section, thus enabling the sections to be transported readily, particularly as shallow draught vessels by water.

The sheartransferformations will ideally comprise or include shear studs or connectors, indentations or bosses. In order to achieve enhanced overall shear capacity, the sheartransferformations will ideally comprise elongated shear studs orthe like projecting from the facing plates so asto overlap one another in order to carry the shearforce in tension alone. Some ofthe shear studs may extend to the opposite metal plateto act as spacers. Additionally oralternativelythe walls ofthe 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 ofthe section may be defined or supported by an internal floor ofthe box-section and/or by an outer upperwall (when provided) ofthe box-section.

The roadway section may 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 two create a significant negative buoyancyforthe boxsection, and the box-section also incorporating means forflooding the section to create negative buoyancy forthe section prior to the incorporation of ballast.

Because the roadway section is constructed without the ballasting necessaryto hold it in place on the bed of the river or estuary it has a high buoyancy and hence can befloated into position in conditions where shallow draught vessels only can pass. Hence this increases scope for installing submerged roadways.

Furthermore because the sections have a shallow draught they can be floated into prepared positions nearto 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 ofthe 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 avoid to be filled with concrete. The top wall of a closed box-section might incorporate openings for the insertion ofthe ballast.

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

The invention further extends to a method of constructing a whooly or partially submerged roadway which comprises floating a requisite number of roadway sections of this invention as hereinbefore defined to positions above prepared underwatersites.

Flooding the sections to sinkthem into position on the prepared sites, loading the highspecific gravity ballast into the base of the hollow interiors of the boxsections, interconnecting the sections by permanent joints, and dewatering each ofthe sections, and removing bulkheads to create continuous tunnels.

The high specific gravity ballast installed will be as dense as possible, subjectto cost, and a dense iron ore is particularly suitable. Local conditions or other considerations may make it substantially more economical to use othertypes 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 routed over with concrete after installation in the sections.

The invention may be performed in various ways and preferred embodimentsthereofwill now be described with reference to the accompanying draw- ings, in which: Figure 1 comprises a diagrammatic vertical crosssection 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 ofsheartransferformations and trusses which may be utilised; and Figure5 is an end view onto one of the trusses illustrated in Figure 4.

The roadway section A shown in Figure1 ofthe drawings is constructed from a number of closed box-sections, each having side walls 1, a base 2, a top wall 3, and endwalls, pre-constructed from welded steel sheets. A double skin is formed at each side by furthersteel walls 4, and a central doublewalled section is defined by steel sheets 5. The base 2 ofthe section is also formed as a doublewalled 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 plates7 define a void space 8 with the top wail 3 atthetop ofthe section which may be pre-filledwith concrete orfilled at a later stage of construction.

The roadwaysection shown in Figure 1 can be floated from thefabrication dockto the site where it is to be installed and because this roadway section will have a substantial buoyancy it can be manoeuvred into place inshallowwaterandofcoursecan be shipped from any suitable construction site by sea or river. Theinstallation site on the riverorestuarybed 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 endwalls (for example). A position for one such valve controlled opening is illustrated at29 in an end wall 30.It is envisaged that each section will incorporate bulkheads to form individual watertight compartments in each ofthetwotubular portions 9so thatthe balancing and the extentofflooding ofthe section can be controlled in a precise manner. Asa section becomes sufficentlyfilled with water itwill sink into position and will be controlled during the final lowering phase from pontoons mbored above the prepared site.

An alternative method of positioning the roadway section Ain the prepared site is illustrated in Figure 2.

Winch units 23 mounted temporarily on top ofthe roadway section Awill be connected by cables 24to 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 forthe roadway section A after it has been filled with water so thatthe 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 waterwhen 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 eisewhere.

Once the roadway sections are in place they can receive the permanent ballasting. As shown the ballastingcomprises preformed blocks 10 constructed from a dense iron ore bonded with concrete. The compartments ofthe roadway sections will be dewatered progressively, followed by removal of the relevantbulkheads.The blocks 10then can be run into each compartment progressively ofthe fully positioned roadwaysections, 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 about3.9 (as compared to 2.4 for concrete alone). The relative submerged densities forthe iron ore ballast and concrete are about 2.8 and 1.34 respectively soit 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 sameweightof concrete so that the overall size ofthe roadway section and the amountofdredging 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 temporaryfunnels passing through the roof3 ofthe section. Oncethe ballast is in place the openings in the roof can be sealed off and the void area 8 will then be filled with concrete ifthis has not aleady-been done on the preparation site. Permanentjoints will be installed between adjacent sections and once the iron ore has been levelled and grouted up if necessary the sections can bedewatered.

Once the process ofemplacing the ballast, dewatering the compartments and removing the bulkheads has beencompleted two continuoustunnels 9 will be defined. Additional ballasting blocks 11 can be secured to the top ofthe roadway sections as shown, at anyconvenientstageof construction, ideally priorto dewatering so as toassist 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 com-pared with a conventionai cut and fill method of construction by normal civil engineering techniques.

The open-topped roadway sections can befloated in and positioned in prepared channels formed in the shallows atthe banks ofthe 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-considerablyand this would be added to the savings in construction time in complet ingthesubmergedtunnel sections themselves.

Thefacing surfaces ofthe plates, which definethe walls ofthe doubletube, have shear studs welded to them and providea key between theconcrete 14and the plates. These shear studs are not illustrated in Figure 1, but can be seen more clearly from Figure 3. A preferred form of shearstud is is oftheform shown at 15 and these will be provided throughoutthe sandwich construction ofthe plates with concrete 14 between them. Also illustrated in Figure 3 are otherforms of sheartransferformations such as preformed bosses 16 on the walls ofthe steel plates and indentations 17 formedintothewallsofthesteel plates. One advantageous construction is to employ elongated rods or plates 18, 19 which will overlap, as shown.

They ma.y haveT-shaped ends such asfortheshear studs 15. Also bosses 20 or indentations could be formed as shown, for example, on the member 19.

Some or all ofthesheartransferformations can be of a iength equal to the spacing between the plates, such as the elongated studs 1 5A,so as ss to act as spacers.

This facilitates fabrication of the walls, keeps the plates apart and minimises plate deformation.

Bent bartrusses 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 shearkeywhich may be in addition to, orasan alternative to the sheartransferformationsformed on the walls ofthe plates. The alternative form of bent bar truss 22 illustrated in Figure 4 is preferred. It is envisaged thatthe bent bar trusses will particularly be employed atweld junctions for the plates as illustrated in Figure 5to create added strength and rigidity at this point and to serve as a backing strip for welding.

If a shear stud should fail, for exampie, 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 ofthe 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 sheartransferfunction. Again the rods may be welded onto the plates. It should also be understood that the load transfer members and certain types of sheartransferformations 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 eitherofwalls 3 orthe ballast blocks 1 1.The sections may be laid end to end to construct a continuous roadway in the form of a bridge structure or underground orunderwatertunnels.

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 occurto an external wall ofthe roadway section water could seep into the region between the inner and outer plates and could ultimately create high hydrostatic pressures capable of blowing offthe inner skin. This can be prevented by providing small drainage holes at strategic points in theinnerskinsothatsmallquantitiesofwaterwill then just seep into one ofthetunnels 9 or20 and can be pumped out as required.

ltshould be noted thattheterm "roadway" used here is meant to define any passageway (whetherfor 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 structu rally sound and can therefore be towed into the estuary and sunk into position im mediately withoutfurther on-site fabrication. Thus the only on-site work is the attachment ofthe necessary winching equipment,the provision of detachable buoyancy tanks and the provision of ballast when the section is in position.

Claims (20)

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 transferformations 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.

2. A roadway section according to claim 1, wherein the sheartransferformations comprise or include shear studs, shear connectors, indentations or bosses.

3. A roadway section according to claim 1 or claim 2, wherein the sheartransferformations comprise elongated shear studs projecting from facing plates so asto overlap one another.

4. A roadway section according to any one of claims 1 to 3, wherein at least some of the shearstuds extend to the opposite metal plate to act as spacers.

5. A roadway section according to any one of claims 1 to 4,wherein walls of the plates which face one another are interconnected by bent bar trusses, rods, plates or other load transfer members or devices.

6. A roadway section according to claim 5, wherein the load transfer members are secured to the plates atjunctions between plates forming the walls.

7. A roadway section according to any one of claims 1 to 6, wherein the sheartransferformations and/orthe load transfer members are secured to the wall plates by welding or bolting.

8. A roadway section according to any one of claims 1 to 7, wherein the roadway surface ofthe section is defined or supported by an internal floor of the box-section and/or by an outer upper wall (when provided) ofthe box-section.

9. A roadway section according to any one of claims 1 to 8, for use in constructing wholly our partially submerged roadways, intheform of a shallow draught vessel, wherein the base of the hollow interior ofthe box section defines a region for receipt of sufficient high specific gravity ballast to create a significant negative buoyancyforthe box-section, and the box-section also incorporating meansforflooding the section to create negative buoyancyforthe section prior to the incorporation ofthe ballast.

10. A roadway section according to claim 9, 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.

11. A roadway section according to claim 9 or claim 10, wherein the box-section is closed and the top wall incorporates openings for the insertion ofthe ballast.

12. A roadway section according to any one of claims 9 to 11, wherein the top of the region for receipt of ballast defines a preformed roadway platform or supportsforsuch a platform.

13. A roadway section according to any one of claims 9 to 12, wherein walls ofthe box-section incorporate valve controlled openings through which water mayflow to flood the section.

14. Amethod ofconstructing awholly or partially submerged roadway comprising floating a requisite number of roadway sections as defined in any one of claims 9 to 13 to positions above prepared underwater sites, flooding the sections to sinkthem into position on the prepared sites, loading the high specific gravity ballast into the base ofthe hollow interiors ofthe box-sections, interconnecting the sections by perma nenticints, dewatering each ofthe sections and removing bulkheads to create continuous tunnels.

15. A method according to claim 14,wherein the ballast comprises dense iron ore.

16. A method accordingto claim 1 5,wherein the dense iron ore is bonded with concrete to create discrete ballast blocks.

17. A method according to any one of claims 14to 16, wherein the ballast is grouted over with concrete after installation.

18. A submerged or partially submerged roadway constructed in accordance with a method as defined in anyoneofclaims 14to 14 to 17.

19. A roadway section substantially as herein described with reference to the accompanying drawings.

20. A method of constructing awholly or partially submerged roadway substantially as herein described with reference to the accompanying drawings.