As rural and urban infrastructure continues to age and develop, there is a continual demand for cost-effective technologies relating to the construction and maintenance of highways, railways and the like. Often unappreciated but vitally important to the construction of such infrastructure is the underpass system. Underpass systems are typically designed to carry not only dead loads, but also live loads. While some of the most impressive underpass systems are used in mining or forestry applications where spans can exceed 20 m, they are also very common in regular highway construction to allow passage of railway, watercourses or other vehicular/pedestrian traffic. While concrete structures have been regularly employed for these purposes, they are very expensive to install, are cost prohibitive in remote areas and are subject to strength weakening due to corrosion of the reinforcing metal and hence, repair.
In the field of arch-type structures, there have been significant advances in respect of the use of corrugated metal culverts, arch culverts and box culverts. For example, U.S. Pat. No. 5,118,218 discloses the use of sheets of metal having exceptionally deep corrugations where by, using significant material on the crown portions of the culvert and perhaps as well in the haunch portions of the culvert, significant loads can be carried by the culvert design. Ovoid and circular structures are described in U.K. Patent Application No. 2,140,848 where wing members are used to increase the load carrying capabilities, and in particular avoid bending of the crown or roof structure as live loads pass thereover.
U.S. Pat. No. 5,326,191 discloses a reinforced metal box culvert which is provided with a special form of continuous reinforcement along at least the crown or top portion of the culvert. Significant advantages are provided in load carrying characteristics, reduced overburden requirements and the ability to provide large span structures that reduce the cost. These systems greatly facilitate the installation of large span structures with the ability to carry live loads under a variety of conditions. Improvements to the box culvert and arch culvert designs are also described in U.S. Pat. No. 5,375,943 and International PCT Application No. PCT/CA97/00407.
The use of mechanically-stabilized earth in archway construction is described in U.S. Pat. No. 4,618,283. This construction technique avoids arching of the structure because the sidewalls of the archway are built as successive layers of mechanically-stabilized earth which are deposited along side and over top of the structure. The technique involves building on each side of the archway mechanically-stabilized earth which constitutes vertical support sections, and then building across the top of the arch again using mechanically-stabilized earth to define the roof of the archway. As the archway is built step-by-step, facings are applied to contain the mechanically-stabilized earth and prevent such compacted unbound fill of the mechanically-stabilized earth structure from coming loose and falling into the archway. Such facing may be simply attached to the vertical portions of the wire mesh which terminate at the edge of the archway envelope. Alternatives to the facing material include spraying of concrete to provide a liner within the archway or the use of a corrugated metal liner. Optionally, the facing of the mechanically-stabilized earth vertical structures may be attached to the corrugated metal liner. The liner is not designed to carry any structural load either live or dead, instead the live and dead loads are carried by the mechanically-stabilized earth vertical support sections as well as the mechanically-stabilized earth roof section.
A further method for controlling deformation of an erected structure, principally during the backfilling process is described in U.S. Pat. No. 6,050,746.