Road structure – process – or apparatus – Pavement – Modules or blocks
Reexamination Certificate
1997-07-03
2001-01-09
Lillis, Eileen D. (Department: 3673)
Road structure, process, or apparatus
Pavement
Modules or blocks
C404S037000, C404S043000
Reexamination Certificate
active
06171015
ABSTRACT:
An anchoring of outdoor traffic areas provided with cobblestones or paving stones made of a plastic or natural stone material is cited, in which the stones are laid in a bed of sand and/or grit. The anchoring method provides for the stones to be further supported by an extensive supporting structure provided with openings and laid on top of the bed.
The invention relates to anchoring of outdoor traffic areas provided with cobblestones or paving stones made of a plastic or natural stone material, in which the stones are laid in a bed of sand and/or grit referred to herein as “sand bedding”.
In such anchoring, the sand bedding forms the foundation for the paving stones and consists of the leveled and compacted soil with a sub-base or non-freezing layer provided on top.
The foundation thus constructed constitutes a firm support for the stones which, particularly with specially-shaped stones or appropriate dimensioning of the gaps between the stones, is also capable of diverting accumulated surface water.
However, there is a problem with regard to the durability of such a stone surface in conditions of recurring high localized loads, as they are unavoidable even in pedestrian areas, particularly through particularly in areas used by heavy motor vehicles these areas. The relatively small contact surfaces of vehicle wheels, when driving over the stones, exert tilting forces on the latter and these forces can assume a high value particularly during vehicle acceleration. Furthermore, the stones are also subject to torsional forces about an axis perpendicular to their laying plane for example by the vehicle's steering mechanism being actuated at slow speed or even when stationary.
The load profile thus outlined can lead to the stones gradually losing their solid position and no longer having a level supporting surface in their sand bedding, this phenomenon capable of being significantly intensified by surface water continuously penetrating the surface particularly in conjunction with frost. In the end, the stones no longer lie level with each other and can tilt on their foundation. This leads to the development of uneven edges and breaking up of individual stones, such a risk of fracture existing in particular for paving stones because of their unfavorable depth-to-length ratio.
In fact numerous forms of stones are known which, due to their peripheral profile, are capable of distributing such forces to adjacent stones. Such “coupled stones” are frequently employed with good results for example in the field of industrial spaces; however these often do not meet the enhanced requirements for a pleasing design of surfaces in the urban and private sector. In that case, cobbles and paving stones are frequently preferred in rectangular or square format for visual reasons.
In the case of the loads described above, measures to lay such stones in a mortar bed cannot be regarded as a lasting solution, since frost and the use of thawing salt gradually destroy this bedding. Also it has been shown that thermal influences as well as translatory and slewing movements of vehicles cause instability in the road surface.
On the basis of this, the purpose of the invention is to design an anchoring method of the type mentioned at the start, so that increased durability and permissible loading of the road surface is achieved with use of stones with rectangular or square format in particular.
This task is achieved according to the invention in that the stones are further supported by an extensive supporting structure provided with openings and laid on top of the bed.
Compared with the sand bedding, this measure according to the invention has the effect that the stones have a practically rigid support against localized loads and the tilting movements caused by them, at the same time good dissipation of the locally occurring forces being combined with support.
By providing the supporting structure with openings, it can work its way well into the sand bedding with vibratory motion so that the stones remain supported by the sand bedding in the usual way in the region of the openings. On the other hand, the desired drainage of surface water is not impaired, thanks to the openings.
With all that, it will be appreciated that the design size of the supporting structure is selected so that the supporting structure locally has a cross-section of satisfactory load-bearing capacity, and therefore sufficient supporting surface for the stones, and is inherently very stable, though on the other hand contains no accumulation of material exceeding the necessary size.
According to the invention, there is provided an additional structural member which provides a supporting surface easily spread out on the prepared sand bedding before the stones are laid. On the other hand, the stones at this point can be formed in principle as simple plain cuboids so that aesthetic requirements are permanently met in the field of highly-loaded surfaces. The stability obtained in the road surface and the saving thus achieved in repair costs compensate by far for the additional expenditure attributed to the supporting structure.
With certain designs of the supporting structure according to the invention, the other common boundary reinforcement by curbstones and the like can be dispensed with, which leads to a further increase in economy.
Even if in principle no special requirements, with the exception of the above-mentioned design criteria, have to be made for the design of the supporting structure according to the invention, then it has proved to be advantageous to design the supporting structure as a support grating, since it is produced in this form particularly conveniently for example as continuous material and also with regard to the design of its grating structure, the size can be matched to the stones to be laid. In that connection, care is to be taken that the mesh of the grating formed by adjacent openings corresponds at best to the smallest size of the cobbles to be laid.
It is advantageous if the supporting structure is formed by intersecting rod-shaped or strip-shaped profiles which are usefully joined together at their points of intersection to form one piece, therefore the intersections do not extend beyond the surface plane. At the same time, depending on the circumstances in individual cases, provision can of course be made for each of the profiles to be arranged at least in pairs parallel with one another.
In the form described, the supporting structure can consist of steel, reinforced concrete, recycled plastic or other corrosion-resistant material, a recycled plastic being preferred. Then such supporting structures can subsequently be spread out together in the form of matting, it even being possible to wind supporting structures manufactured from plastic as a continuous product onto a drum, so that they can be drawn off in continuous lengths when laying the supporting members.
If one starts from a supporting structure with a grating design, then the relative position between the supporting structure and stones can be chosen so that either the stones are located in position with their bottom surface on the supporting structure, at least in the area of the periphery, or the stones are located in position with their bottom surface at least on one point of intersection of the profiles and the profile section following it. Of course, combinations of the two types can also be considered here.
As an improvement in the object of the invention and in order to give the stones additional positional security and to facilitate the orderly laying of the stones, provision can be made for the stones to be at least indirectly in positive engagement with the supporting structure. There are various possibilities for this.
Firstly, provision can be made for the bottom of the stones to be equipped with recesses for partial engagement with the supporting structure. These recesses can be for example grooves on the bottom of the stones, the said grooves matching the grating design of the supporting structure. However, the supporting structure
Barth Gunter
Schmitz Michael
Addie Raymond W.
F. von Langsdorff Licensing Limited
Lillis Eileen D.
Orrick Herrington & Sutcliffe LLP
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