This invention is in the field of temporary or portable roadways, and in particular such roadways that are suitable for use in sensitive environments and soft ground.
It is often required for construction, exploration, and like purposes to construct roadways through rough territory including soft ground. These roadways are often temporary and in the interests of preserving the environment, it is desired to have a roadway wherein heavy equipment can enter an area to do a job as required and leave the area with as little damage to the ground surface as possible.
The military, emergency measures organizations and the like also have occasion to move equipment quickly into areas where no roads are available. Temporary air strips must sometimes be made under adverse conditions as well as roadways.
Also in soft ground vehicles get stuck and are unable to proceed until pulled by a tractor or the like, and even then they may not be able to proceed. The tractor further damages the ground, making ruts and so forth.
Corduroy roads, wherein logs and so forth are laid lengthwise across the path of the road have been used in the past to cross soft areas of ground. Improvements to the well known corduroy road have also been known, for example as disclosed in U.S. Pat. No. 5,282,692 to McLeod. The McLeod patent discloses a series of parallel members joined together and extending substantial perpendicular to the path of the roadway.
A problem with such prior art apparatuses for roadways is that the members are substantially perpendicular to the path of vehicles travelling on the roadway with the result that the wheels of the vehicles pass suddenly and directly from one lateral member to the next, causing significant impact loading. The weight of a vehicle on each member, combined with the impact loading, also causes the same to sink somewhat relative to the next adjacent member where no weight is present, and as the wheel rolls, it must climb up onto the next adjacent member to progress down the roadway, decreasing the efficiency of the vehicle. This effect also causes the wheels of the vehicle to push against the members of the roadway, putting added stress on the links holding one member to the next.
It is an object of the present invention to provide an apparatus that can be laid on the ground, including soft ground, as a roadway to facilitate travel by vehicles over the apparatus.
It is a further object of the present invention to provide such an apparatus that reduces damage caused to the ground surface by the vehicles.
It is a further object of the present invention to provide such an apparatus that enables a temporary roadway to be hauled to a site and quickly assembled for use.
The present invention addresses these objectives by providing a flexible roadway with advantages over apparatuses currently employed in the art. The apparatus comprises a number of sections held adjacent to each other by a retainer. Each of these sections comprises a top surface, a bottom surface, a front face and a back face. The front face of a section mates with the back face on an adjacent section to form an interface. The interface of the mating faces is at a non-perpendicular angle to the direction of travel substantially along its length.
This invention addresses the problem created by prior art roadways, which consist of members substantially perpendicular to the path of the vehicle, where the weight of the wheel passing over the sections causes an impact load on each section in turn. In the present design, the interface between adjacent sections is not perpendicular to the path of the vehicle so that the weight of the vehicle is applied gradually to each adjacent section rather than suddenly loading it. While even a minor deviance from the perpendicular will effect some reduction in impact loading, the greater the angle the more gradual the weight transfer. For practical design purposes, it is anticipated that an angle between 40 and 50 degrees will be most suitable for most applications.
The reduction in impact loading will reduce the amount each member sinks in relation to the adjacent members.
The present invention may further include a system to interlock a section to adjacent sections. The back face of one section may contain a groove that interlocks with a corresponding tongue contained in the front face of the adjacent section. Thus downward force on one section will exert a downward force on the adjacent sections, thereby increasing the area of the ground surface the force is being applied to, and further reducing the amount each section sinks.
The apparatus may also include hollow vertical tubes passing through the sections. These tubes brace the top surface of each section, reduce damage to the ground beneath the roadway by releasing pressure built up under the sections, and provide somewhat improved traction for the vehicle wheels on the surface of the apparatus.
Where the apparatus is made from a hollow formed plastic, the apparatus could be made light enough to be easily moved and quickly placed in position.