Reinforced arch with floating footer and method of constructing same

A reinforced soil arch having a floating footer is provided. The reinforced soil arch has an archway form, a plurality of layers of reinforcement material and compacted fill associated with the archway form, and a floating footer supporting the archway form. The archway form floats on a compressible squeeze block in the floating footer. Methods of constructing a reinforced soil arch are provided.

TECHNICAL FIELD

Some embodiments of the present invention pertain to reinforced soil arch structures. Some embodiments of the present invention pertain to reinforced soil arch structures having a yielding footer. Some embodiments of the present invention pertain to methods of making such structures.

BACKGROUND

Geosynthetic reinforced soil arch structures provide an environmentally preferable and/or less expensive alternative to more traditional construction materials used for bridges, culverts, overpasses and the like, e.g. steel structures, reinforced concrete structures, plastic structures and the like. Geosynthetic reinforced soil arches for use in the design of structures such as bridges, overpasses, snowsheds, landslide or rock fall protection structures, or the like are described, for example, in U.S. Pat. Nos. 6,874,974 and 8,215,869 to VanBuskirk, which are incorporated by reference herein in their entirety. Some such arches have a supporting form (typically but not necessarily an arch form) made from a rigid material such as metal, concrete, reinforced concrete, plastic or reinforced plastic. A plurality of alternating layers of compacted soil and reinforcement made from geosynthetics, plastic, metal, wood and/or the like are associated with the supporting form. Some such arches have an archway form, a combination of alternating and interacting layers of compacted mineral soil and reinforcement material associated with the archway form, and a plurality of shear resisting devices extending from the exterior surface of the archway into the reinforced soil mass. Mineral soil can include clay, silt, sand, gravel, cobbles, boulders, broken rock, or mixtures of any of the foregoing.

U.S. Pat. No. 4,010,617 to Fisher, which is incorporated by reference herein, discloses a composite arch structure comprising an arched liner with compacted fill material or dense soil thereagainst to form a soil arch thereabout. The liner has a foundation comprising yielding footer means.

There remains a need for improved footers for geosynthetic reinforced soil arch structures.

SUMMARY

One embodiment provides a reinforced soil arch having an archway form, a plurality of alternating layers of compacted fill and reinforcement material associated with the archway form, and a floating footer independent of the archway form. The archway form is supported by the floating footer. The floating footer can comprise a solid base and a squeeze block, with the squeeze block interposing the solid base and the archway form. A load distributing member can interpose the squeeze block and a longitudinal edge of the archway form. The archway form is not coupled to the load distributing member, the squeeze block or the solid base.

One embodiment provides a method of providing a reinforced soil arch having a floating footer. A floating footer is provided along a first edge of the reinforced soil arch. A floating footer is provided along a second edge of the reinforced soil arch. An archway form is positioned on the floating footers on the first and second edges. The archway form is independent of the floating footers. A plurality of alternating layers of compacted fill and reinforcement material associated with the archway form are provided and the archway form is allowed to compress the floating footer.

DESCRIPTION

With reference toFIG. 1, a first example embodiment of a reinforced soil arch with a floating footer20is illustrated. Reinforced soil arch20has an archway form22, a reinforced soil arch structure24and a floating footer, indicated generally at26.

In the illustrated embodiment ofFIG. 1, reinforced soil arch structure24is formed from a plurality of layers of reinforcement material28and compacted fill30overlying and associated with archway form22. Reinforced soil arch structure24has a plurality of shear resisting devices32secured to the exterior surface of archway form22. Shear resisting devices32cooperate with proximate portions of the alternating layers of compacted fill30and reinforcement material28to keep archway form22in contact with reinforced soil arch structure24by preventing shear and separation between archway form22and reinforced soil arch structure24(i.e. shear resisting devices32ensure that the alternating layers of compacted fill30and reinforcement material28remain associated with archway form22). In some embodiments, reinforcement material28restrains archway form22from moving inwardly (i.e. towards the centre of the opening defined by archway form22) relative to floating footer26. In some embodiments, the earth pressures associated with the construction of the reinforced soil arch24restrain archway form22from moving outwardly (i.e. away from the centre of the opening defined by archway form22) relative to floating footer26. In some embodiments, shear resisting devices32help reinforced soil arch24support archway form22.

Archway form22can be formed of any suitable material, such as metal, plastic, concrete, wood, or a composite of two or more of the foregoing. In one example embodiment, archway form22is formed from structural metal plate. Archway form22can have any suitable shape, for example a semicircle or shallow semicircle, a reentrant arch, a vertical or horizontal ellipse, a pear shape, a box shape, or a curved overpass or underpass.

Reinforcement material28can be constructed from any suitable material including geosynthetics, plastic, metal, wood, or the like. In some embodiments, reinforcement material28is woven geotextile.

The layers of compacted fill30can be formed from any suitable material. In some embodiments, the layers of compacted fill30are formed from mineral soil, for example, clay, silt, sand, gravel, cobbles, boulders, broken rocks, or the like, or mixtures of any of the foregoing. In some embodiments, the layers of compacted fill30are made from manufactured materials such as: rubber; plastics; glass; expanded shale, clay or slate; aggregate; or shredded or chipped wood.

Shear resisting devices32can be any suitable material. In some embodiments including the illustrated embodiment, shear resisting devices32are angle plates attached to the exterior surface of the archway form. The angle plates can be affixed to the archway form in any suitable manner, for example by welding, bolting or the like. In some embodiments, shear resisting devices32are affixed to archway form22so that shear resisting devices32extend generally orthogonally outwardly from archway form22.

A floating footer26is provided at the base of each edge of archway form22, and extends longitudinally for the length or for substantially the length of archway form22. With reference toFIG. 2, the illustrated example embodiment of a floating footer26has a solid base34and a compressible squeeze block36. Each longitudinal edge38of archway form22floats on a squeeze block36, and squeeze block36is supported on solid base34. Archway form22is supported on but independent of squeeze block36, i.e. archway form22is not coupled or otherwise secured to squeeze block36or solid base34.

In some embodiments, including the illustrated embodiment, a bearing plate39interposes all or a portion of longitudinal edge38of archway form22and squeeze block36, so that the downward force applied as archway form22settles is applied evenly across all or a portion of the upper surface of squeeze block36. In some embodiments, bearing plate39is omitted or replaced by channel41, described below. In some embodiments, for example as illustrated inFIG. 6, the archway form is in direct contact with the floating footer. The dimensions of bearing plate39can be selected by one skilled in the art based on the characteristics of the soil supporting floating footer26, solid base34, and/or squeeze block36to provide a desired rate and extent of compression of squeeze block36. Archway form22is not secured to bearing plate39or to squeeze block36, i.e. archway form22floats on floating footer26.

Squeeze block36can be formed from any suitable material. In some embodiments, squeeze block36is formed from a material having a known compressibility. In some embodiments, squeeze block36is formed from expanded polystyrene foam. In some embodiments, squeeze block36is formed of wood (including solid wood, logs, wood chips or chunks, shredded wood or the like), soil, sand, plastic, rubber, paper, weakly cemented sand and gravel (engineered concrete), corrugated metal, or liquid- or air-filled bladders. In some embodiments, two or more of the foregoing materials may be used to provide squeeze block36.

In some embodiments in which the material used to provide squeeze block36is loose material (e.g. soil), a trench or other structure may be provided to hold squeeze block36in place. For example, in some embodiments, the soil on either side of the location where squeeze block36is to be provided is compacted, leaving uncompacted soil disposed within the trench to provide squeeze block36. In other embodiments, the soil at and adjacent to the location where squeeze block36is to be provided is compacted, and then a trench is excavated within the compacted soil and filled with loose soil or other material to provide squeeze block36. In some other embodiments in which the material used to provide squeeze block36is loose, no structure is used to hold squeeze block36in place, and the material is dispersed across a sufficiently large area to ensure that the bearing plate39or other load distributing member is supported on the material providing squeeze block36. For example, in embodiments in which bearing plate39is approximately 0.5 m wide, a zone of loose soil approximately 10-12 cm deep and 50 cm wide or wider can be spread to provide squeeze block36.

Without being bound by theory, the squeeze block36undergoes deformation, allowing archway form22to settle downward at a similar rate to the reinforced soil arch structure24, thus relieving a significant portion of the load from archway form22. Bearing plate39and/or channel41described below (where used) cooperate with squeeze block36, solid base34, and the underlying soil37to produce sufficient settlement of archway form22so that the majority of the dead load of the structure and live loads imposed on the structure are transferred onto the reinforced soil arch24. By selecting the material used for squeeze block36to have desired characteristics of compressibility and dimensions, squeeze block36can be designed to undergo a controlled deformation as the load on archway form22is increased as layers of reinforcement material28and compacted fill30are built up over archway form22. The dimensions of squeeze block36are selected based on the engineering properties of the material used for squeeze block36.

The dimensions of bearing plate39can also be selected to control the rate of deformation of squeeze block36. Selecting a larger bearing plate39will cause the downward force on archway form22to be distributed across a greater surface area of squeeze block36, thereby producing a smaller deformation.

Solid base34can be formed from any suitable material. In some embodiments, solid base34comprises a concrete footing. In some embodiments, solid base34comprises a steel reinforced concrete footing. In some embodiments, solid base34comprises compacted fill. In some embodiments, solid base34comprises native mineral soils. In some embodiments, solid base34comprises wood, including solid wood, logs, pressure-treated wood, or the like. In some embodiments in which solid base34comprises wood, reinforced soil arch20is temporary in nature, since wood may eventually rot, causing additional settlement.

The dimensions of solid base34are selected based on factors including the engineering properties of the material selected for solid base34, the expected load, and the allowable bearing capacity of the underlying soil. In some embodiments, the dimensions of solid base34, and particularly the width of solid base34, are selected to be sufficiently large to minimize settlement of solid base34relative to the underlying soil. Although solid based34has been illustrated as being wider than squeeze block36, this is not necessary in all embodiments. In some embodiments, solid base34has the same width as squeeze block36.

In some embodiments, a channel41interposes squeeze block36and the base of each edge of archway form22instead of or in addition to bearing plate39. Channel41and bearing plate39are examples of load distributing members and act to distribute the force applied by the longitudinal edges38of archway form22more evenly on the surface of squeeze block36. The bearing plate39or channel41cooperate with squeeze block36, solid base34, and the underlying soil to provide sufficient settlement of archway form22to transfer the majority of the dead load of the structure and the live loads imposed on the structure onto reinforced soil arch structure24. In some embodiments, channel41is a uniform channel. In some embodiments, channel41is an unbalanced channel. Archway form22is supported by but independent of, i.e. is not coupled directly to, the load distributing member.

Any suitable material can be used to provide the load distributing member, for example metal, concrete, wood or other relatively rigid material.

With reference to the example embodiment illustrated inFIG. 3in which like reference numerals have been used to indicate like parts, in some embodiments, the solid base is provided by native mineral soils. In such embodiments, squeeze block36is supported directly on the soil or sub-soil surface underlying archway form22, indicated by reference numeral40. In some embodiments, the surface40is a rigid surface, for example bedrock. In some embodiments, the surface40is compacted mineral soils.

The selection of materials to be used to provide solid base34(or which can be used to provide surface40) and squeeze block36can be made by one skilled in the art based on the particular considerations at any given site. Solid base34or surface40should be selected to be relatively more rigid than squeeze block36to allow compression of squeeze block36between solid base34/surface40and bearing plate39/channel41. In some embodiments, the material used to provide solid base34or surface40is between 2 times and 1000 times stiffer than the material used to provide squeeze block36, or any value therebetween, e.g. 10 times stiffer, 100 times stiffer, or the like. The material used to construct squeeze block36can be selected and made of an appropriate height to provide the desired level of compression of squeeze block36based on the anticipated load to be experienced by archway form22and the compressibility of the material used to provide squeeze block36.

Changing the surface area of channel41and/or bearing plate39that contacts squeeze block36can affect deformation because a smaller deformation will occur if a larger surface area contacts squeeze block36(the load will be more evenly distributed across the surface of squeeze block36, and squeeze block36will undergo a correspondingly smaller deformation in the vertical direction). Changing the material used to provide squeeze block36will affect deformation because a stiffer material will undergo a smaller level of deformation than a less stiff material.

In some embodiments, the material used to provide squeeze block36and the size of channel41and/or bearing plate39are selected to provide an expected deformation of between about 1% and about 2% of the overall height of reinforced soil arch20. For example, if reinforced soil arch20is 2 meters in height, the material used to provide squeeze block36and the size of channel41and/or bearing plate39are selected to provide an expected deformation of between about 2 to 4 centimeters. For a reinforced soil height of 10 meters, the target deformation range in some embodiments is in the range of 10 to 20 centimeters. Different levels of deformation may be desirable depending on the type of soil present at the site where reinforced soil arch20is being erected. It has been found that for typical soil, deformation of approximately 1% of the overall height of the structure is common.

In one example embodiment of a reinforced soil arch having a 12 meter arch with 12 meters of fill, the rigid base is concrete overlying bedrock, the squeeze block is made from expanded polystyrene foam (EPS) and the bearing plate is made from steel. The deformation of the squeeze block is approximately 12 centimeters.

In another example embodiment, the squeeze block is compacted sand having a height of approximately 10 centimeters and the load distributing member is an unbalanced channel. The rigid base is compacted cobbles and boulders and the deformation of the squeeze block is approximately 5 centimeters.

In some embodiments, squeeze block36is restrained on solid base34so that squeeze block36is not displaced when archway form22is initially placed during construction on squeeze block36. In the example embodiment ofFIG. 2, squeeze block36is restrained against lateral movement by a wire mesh form42. In other embodiments, geotextile fabric and compacted fill such as compacted mineral soils or manufactured materials are used to secure squeeze block36. Any other suitable mechanism for restraining squeeze block36on solid base34during construction could be used in place of wire mesh form42, for example plastic dowels extending between solid base34and squeeze block36, a trench formed in the top of solid base34that is dimensioned to partially receive squeeze block36therein, adhesive securing squeeze block36to solid base34, soil piled on either side of squeeze block36to secure squeeze block36, or the like. In some embodiments, the securing of squeeze block36is only used as a construction aid and does not influence the as-constructed performance of the structure.

Generally it will be convenient to provide floating footer26extending along the full length or substantially the full length of archway form22. However, floating footer26could be provided discontinuously along the length of archway form22(e.g. a floating footer26extending less than half the length of archway form22could be provided at each longitudinal end of archway form22, so that a middle portion of archway form22is not supported on a floating footer, or a further floating footer26could be provided to support a middle portion of archway form22, or the like), so long as floating footer26allows archway form22to settle a desired amount.

Typically, floating footer26will be provided along both edges of archway form22. However, in some embodiments, floating footer26could be provided only along one edge of archway form22.

FIG. 4illustrates an alternative embodiment of a reinforced arch70having a floating footer. Reinforced arch70has an archway form72, a reinforced soil arch structure74, and a floating footer generally indicated by reference numeral76.

Reinforced soil arch structure74has a plurality of layers of reinforcement material78between a plurality of layers of compacted fill80. In the illustrated embodiment, the plurality of layers of reinforcement material78and compacted fill80are associated with archway form72via the interconnection of reinforcement material78with an outside surface73of archway form72. In some embodiments, reinforcement material78is interconnected with archway form72via securement to welded wire mesh82, bars, or other means secured to the outside surface of archway form72. Reinforcement material78may be connected to archway form72in any suitable manner. In some embodiments, the interconnection of reinforcement material78with outside surface73of archway form72restrains archway form72against inward movement relative to floating footer76. In some embodiments, the earth pressures associated with the construction of reinforced soil arch74restrains archway form72against outward movement relative to floating footer76.

Reinforcement material78and compacted fill80can be made from the same materials as reinforcement material28and compacted fill30. Archway form72can be made from the same materials and comprise the same variety of shapes as archway form22.

Floating footer76is generally similar in construction to floating footer26and can be constructed from the same type of materials used to construct floating footer26. In the illustrated embodiment, floating footer76has a solid base84, a compressible squeeze block86, and a bearing plate90. Compressible squeeze block86is supported on solid base84and can be supported thereon in any suitable manner as described with reference to compressible squeeze block36. Bearing plate90sits on compressible squeeze block86, and each longitudinal edge88of archway form72floats on one of the bearing plates90. The longitudinal edges88are supported on but independent of the bearing plate90, i.e. the longitudinal edges88are not coupled to the bearing plates90.

In the example embodiment of a floating footer26A illustrated inFIG. 5, the squeeze block is provided discontinuously. A plurality of portions of squeeze block36A are supported on a solid base34to provide a floating footer to support archway form22. Each portion of squeeze block36A is separated from adjacent portions by a gap44. Squeeze block86or other portions of floating footer26or73could similarly be provided in discontinuous fashion. Although gaps44have been illustrated inFIG. 5as being of relatively uniform size, the discontinuous portions of the floating footer and/or the gaps therebetween could be of different sizes.

While a number of exemplary aspects and embodiments have been discussed above, those of skill in the art will recognize certain modifications, permutations, additions and sub-combinations thereof. For example:compressible squeeze block86could have cross-sectional shapes other than square or rectangular;while the bearing plate/channel, squeeze block and solid base have been described as being unconnected, in some embodiments these elements could be coupled together for convenience of construction.
It is therefore intended that the following appended claims and claims hereafter introduced are interpreted to include all such modifications, permutations, additions and sub-combinations as are consistent with the broadest interpretation of the disclosure as a whole.