The invention relates to a modular retaining wall system of the type utilizing blocks having channels that receive connectors for aligning and fixing blocks in successive courses in a number of orientations, and further provide means for attaching a soil reinforcing material such as a geogrid.
Walls made of cut stone that is dry stacked, i.e. built without the use of mortar, have been known since ancient times; the Great Wall of China was built in the first millennium BC. Stone walls may be arranged in vertically aligned courses of stones placed end-to-end in rows, or arranged in successive courses that are set back to form a sloped wall for retaining soil or other filling behind the wall.
In recent years, segmental concrete retaining wall units which are dry stacked have become a widely accepted product for the construction of retaining walls. Kiltie Corporation markets its pre-fabricated concrete blocks under the trade name Versa-Lok® and has numerous design patents, e.g. U.S. D319,885, D321,060, and D341,215. Each block is cast with channels or slots and holes that receive pins therethrough to position it with respect to blocks in another course. Keystone Retaining Wall Systems also manufactures modular concrete blocks having holes that receive pins to align adjacent blocks. See, e.g., U.S. Pat. No. 7,971,407 and U.S. D685,502.
The above blocks have a substantially trapezoidal shape. This shape is popular because blocks can be arranged to form vertical and setback retaining walls, as well as freestanding walls, which are either straight or curved. For purposes of the present application, a trapezoidal block will be understood as one having parallel first and second oppositely facing trapezoidal surfaces (top and bottom surfaces), parallel oppositely facing front and rear faces of unequal length extending between the trapezoidal surfaces, and first and second oppositely facing end faces of equal length extending between the trapezoidal surfaces and converging from the front face toward the rear face.
Dueck U.S. Pat. No. 8,240,105 discloses a trapezoidal concrete block having a central cavity to reduce weight, anchor holes extending between the top and bottom surfaces, and a channel in the bottom surface parallel to front face. Connectors each have a bottom portion received in a respective anchor hole so that the connector can rotate, and a top portion received in a channel so that so that blocks in adjacent courses can be placed flushly against each other. The connectors also serve to anchor a geosynthetic grid extending into the soil being retained behind the wall.
Segmental concrete retaining wall units can have other shapes. Forsberg U.S. Pat. No. 4,914,876 (Keystone) discloses a block having a body forming a convex front face, a neck, and a head forming the rear face; blocks are connected by pins received through holes in the body. This patent also describes the use of geogrids anchored to the pins to stabilize the wall. Sievert U.S. Pat. No. 5,294,216 discloses an irregular trapezoid where the side faces have parallel front portions; this patent also details manufacture using a block molding machine. Kliethermes U.S. Pat. No. 4,996,813 discloses a concrete block having parallel front and rear faces, a concave end face formed by three planar surfaces, and an opposing convex end face formed by three planar surfaces. Each convex end face can be received in an adjacent concave end face in three different orientations. Blocks are connected by pins or cables therethrough; channels in the top surfaces serve to anchor a geogrid.
Miller U.S. Pat. No. 5,595,460 (Tensar Corporation) discloses a concrete block having channels provided in opposing top and bottom surfaces parallel to the front face. An elongated asymmetric connector has a row of toothed fingers that are forced into the top channel in an interference fit in one of two orientations, and tabs that are received in the bottom channel of the next course loosely. Since the central axes of the tabs are offset from the central axes of the fingers, the walls may be either setback or vertical, depending on the orientation of the connector. Bailey U.S. Pat. No. 5,619,835 (Tensar) discloses a similar concrete block wherein the top and bottom channels are connected by a tapered opening that facilitates manufacture using a tapered core during the molding process. Bailey also discloses molding a double block which is split along a groove to form front faces that simulate natural stone.
Concrete wall blocks have gained popularity because they are mass produced, and thus relatively inexpensive. Most are structurally sound and easy to install. However the durability of concrete, especially products produced on masonry block machines, has been an ongoing problem. Low compressive strength and high moisture absorption can lead to deterioration caused by freeze-thaw cycles, particularly when exposed to deicing agents. Improper cement hydration and poor aggregate selection can cause efflorescence, which significantly degrades the aesthetic appeal of the wall. UV rays and weathering can degrade iron oxide pigments added for color.
The overwhelming trend in the masonry block and wetcast/precast industries has been simulated stone finishes for their retaining wall products. However the concrete products industry employs a considerably different manufacturing process than quarrying and cutting stone. Instead, quarried stone is crushed and mixed with significant amounts of cement, which uses considerable energy in production and freight, and also contributes to greenhouse gases and a host of other chemicals. All of this to simulate stone in its original form at the quarry.
From the standpoint of durability, aesthetics, and environmental friendliness, natural stone is preferable for retaining walls, but the cost of labor and limited design options often make this choice too costly. Adapting natural stone to a modular block system using automated fabrication would provide an existing and trained labor pool, saving enough to make this an affordable and environmentally sound choice for retaining wall construction. The stone could be quarried, cut into slabs, and shipped to shops for fabrication into usable products that are shipped to the ultimate customer.
A principal object of the invention is to provide a wall block system having modular blocks that can be configured in natural stone and assembled to form both vertical and setback retaining walls, as well as freestanding walls, in a number of different configurations.
This object is achieved with a block having opposed first (top) and second (bottom) surfaces with respective first and second channels, and a plurality of connectors for aligning the blocks, each connector having a first portion profiled for reception in a respective first channel and a second portion profiled for reception in a respective second channel so that two blocks can be placed against each other with a connector in between. The connectors can slide along the channels to achieve different degrees of bonding (overlap) between blocks in successive courses. The second portion is offset from the first portion so that different orientations of blocks with first and second surfaces placed against each other are possible.
Since the channels arc discrete grooves that do not extend through the blocks, they can be formed by a router, preserving the integrity of the stone. Since the channels are offset and the connectors are asymmetric, they may be used to form both freestanding and setback walls utilizing the same channels, simplifying block design. Since it is easy to change the line of the router, blocks can be custom-made to provide different degrees of setback.
According to a preferred embodiment, the first and second channels are formed parallel to each other and to the front and rear faces in a trapezoidal block of cut stone. This facilitates building a freestanding wall wherein the end faces are placed flushly against each other and the front and rear faces alternate in a given course. Vertical and setback retaining walls with the front faces all on the same side of the wall can also be constructed. In this case the connectors not only align the blocks, but can anchor a geogrid extending into the soil being retained. The geogrid stabilizes the blocks in the upper courses, where frictional force between mating surfaces may not be sufficient to stabilize the courses against soil loading.
Trapezoidal blocks are preferred because this shape can be achieved by cutting stone with a saw, with subsequent routing to form channels. However the inventive system is not limited to cut stone, but may be implemented by casting concrete. This opens the possibility of making blocks with shapes that cannot be achieved with straight cuts. For example, blocks with semicircular concave and convex end faces may be cast in concrete with channels according to the invention. Here too the assymmetric connectors would be used between courses.
The invention also relates to a method of a constructing a vertical or setback retaining wall using the wall blocks and connectors described above.
First, a leveling pad of dense base material or unreinforced concrete is placed, compacted and leveled. Second, the initial course of blocks is placed and leveled. Two alignment/connector devices are placed in the first or top channel of each block. Third, succeeding courses of the blocks are placed in a “half bond” pattern such that each block is centered over the two blocks below it. This is done by placing the blocks so that the second or bottom channels fit over connectors placed in the blocks in the course below. As each course is placed, connectors are placed in the blocks, the blocks are backfilled with drainage rock, and the area behind the course is backfilled and compacted until the wall reaches the desired height.
If wall height or loading conditions require, the wall may be constructed using reinforced earth techniques such as geogrid reinforcement. This is often desirable in upper courses where the friction force between mating surfaces is not sufficient to reinforce the wall against the loading of soil being retained. After placement of a course of blocks to the desired height, the geogrid material is placed so that the connectors in the blocks penetrate the apertures of the geogrid. The geogrid is then laid back into the area behind the wall and put under tension by pulling back and staking the geogrid. Backfill is placed and compacted over the geogrid, and the construction sequence continues as described above until another layer of geogrid is called for in the planned design.
The construction of a freestanding wall procedes in similar fashion, without backfilling and placement of a geogrid.
The invention further relates to a method of fabricating wall blocks in natural stone such as limestone, sandstone, metamorphic rock, or granite. It is generally provided in the form of quarry blocks with dimensions 8′×4′×4′. The quarry blocks are then cut into quarry slabs, approximately 8′×4′×6″ thick. This is done at the quarry with either a large gantry saw or wire/belt saw.
The slabs are put through a conventional hydraulic stone splitter which produces rectangular blocks of stone 4′ long×9″ wide×6″ thick, however the width can be adjusted to provide different levels of internal stability for walls. An example of a stone splitter that can split a variety of stones is a Chris Cutter 3 manufactured by Cee-Jay Tool Company, Inc. of Windsor, Colo. A typical stone splitter exerts up to 140 tons of pressure on the slab to split it into uniform stone blocks. The machine's cutting edge consists of multiple chisels that adjust individually to the natural contours of the stone slabs. The individual chisels provide equal pressure so the stone is split in straight lines.
The 4′ long blocks are then moved through a grinder, if necessary, to remove high and low areas on the top surface that create differential settlement and installation issues. The grinder is a conventional grinder and uses a plurality of matching diamond blades mounted on the same shaft traveling on a bridge, or fixed above the conveyed blocks.
The blocks are now processed through the second stage, wherein receiving channels are routed into the bottom of the rectangular block, the block is flipped, and setting channels are routed into the top of the block. This is accomplished using CNC capacity coupled with a standard motor and tooling capable of removal of the material for the channels. The equipment is produced with off-the-shelf components by companies such as Diamond Stone Technologies of Bedford, Ind. This can also be accomplished with a manual multitask machine for stone fabrication. One such model is a Fab King by Rye Corp of Knoxville, Tenn.
The long block is then conveyed to a meter saw to be cut into shorter blocks having the required trapezoidal shape. One such saw, the Model KM24, is available from Kalamazoo Industries, Inc.
The finished blocks are then conveyed to the palletizing robot that will pick and place three nested blocks at a time on a standard 4′×4′ pallet. One such example of a palletizing robot is the R-2000 from Fanuc robotics. The robot is tooled with an off-the-shelf 4′ long vacuum lifting tool.
The foregoing method does not require cement or any other hazardous chemicals; just water, which is preferably recycled.
From the foregoing it will be apparent that many permutations of the illustrated arrangements are possible. For example, a retaining wall may be constructed vertically for two courses, then setback for two courses, forming steeper “steps” in the wall.
As will be apparent to one skilled in the art, many variations and substitutions in the manufacturing method are possible. For example the slabs 41 may be split at the quarry to form blocks 42, eliminating the need for a splitter at the local fabricator. A multi-function fully automated tool, for example a Sasso K600 5-axis CNC bridge saw, may be substituted for the router and miter saw on a bridge. The equipment chosen may ultimately depend on cost considerations dictated by the scale of production.
While the invention is focused on modular blocks that can be fabricated in stone, the inventive shape(s) can also be realized in concrete that is molded or cast. This opens the possibility of achieving shapes that cannot be realized with straight cuts. For example, as shown in
The foregoing is exemplary and not intended to limit the scope of the claims which follow.
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Number | Date | Country | |
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Number | Date | Country | |
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62496311 | Oct 2016 | US |