Patent application title: Segmental retaining wall blocks designed for curved or straight alignment
Tyler Matys (Aurora, CA)
Angelo Risi (Richmond Hill, CA)
IPC8 Class: AE04C100FI
Class name: Earth treatment or control shoring, bracing, or cave-in prevention retaining wall
Publication date: 2009-10-08
Patent application number: 20090252560
A segmented retaining wall block has one side wall that is rearwardly
tapered so as to allow the block to turn a radius when placed in adjacent
position with respect to another similar block. The block also has a rear
wall provided with a protruding wing that projects laterally away from
the tapered side wall. The rear wall is also provided with a bay that
extends inwardly in the side wall that is opposite to the tapered side
wall. The wing and bay have front edges designed as congruent arcs. The
wing may be sized and shaped so as to protrude into the bay of an
adjacent similar block to create a barrier when the adjacent blocks are
in straight, convex or concave alignment for preventing infiltration of
backfill material such as soil, into voids that exist between the backs
of the blocks when installed.
1. A segmented retaining wall (SRW) block having a front wall, a rear wall
and two opposite side walls, wherein:one of said side walls is rearwardly
tapered so as to allow said block to turn a radius when placed in
adjacent position with respect to another similar SRW block,said rear
wall is provided with a protruding wing that projects laterally away from
the tapered side wall;said rear wall is also provided with a bay that
extends inwardly in the side wall that is opposite to the tapered side
wall;said wing and bay have front edges designed as congruent arcs;
andsaid wing is sized and shaped so as to protrude into the bay of an
adjacent similar SRW block to create a barrier when said adjacent SRW
blocks are in straight, convex or concave alignment.
2. The SRW block of claim 1, wherein:the front edge of the wing has a wing radius; andthe front edge of the bay has a bay radius which is equal to the wing radius less the manufacturing and construction tolerances.
3. The SRW block of claim 2, wherein the side wall of the bay is designed to align with the corresponding side wall of the wing of an adjacent block when said blocks are placed at a minimum convex rotation and the wing of said adjacent block completely fills the bay of the one block.
The present invention relates to segmental retaining wall blocks of tapered shape that are configured in such a manner as to prevent infiltration of backfill materials such as soil into voids that exist between the backs of the blocks when installed.
BACKGROUND OF THE INVENTION
It is of common practice for a landscape architect, contractor or homeowner, to design the layout of a proposed segmental retaining wall (SRW) in curved or snaking alignments. Curving alignments with tight or large radii, give a natural organic flow to the retaining wall that may better blend in with the natural environment when compared to straight lines and hard corners.
Currently, the segmental retaining wall blocks used to achieve curved alignments have one or both of their sides that are tapered when the blocks are viewed in top plan view (i.e., the width of the rear of each block is less than the width of the face of the block).
In practise, some manufacturers offer standard blocks with front and rear of the same width for the manufacture of straight walls (see FIGS. 1a and 1b identified as "prior art"). They also offer tapered blocks for used to give curved sections to the walls (see FIGS. 2a and 2b also identified as "prior art").
Alternatively, other manufacturers offer tapered blocks with rear wings that can be knocked off. Where the rear wings are kept, the blocks be used as such to build a straight wall (see FIGS. 3a and 3b identified as prior art). When the rear wings are knocked off, the constructor may then create a tapered version of the block and used such blocks for curved walls (see FIGS. 4a and 4b identified as "prior art").
As may be appreciated, the taper or angle set into the sidewall(s) of the blocks dictate the minimum allowable convex radius the wall will be able to achieve. For a block that is tapered on both sides (dual tapered) or tapered on one side only, the same equation applies to resolve the minimum allowable radius the blocks can achieve when abutted immediately against one another in a curve or a circle. The equation is as follows (see FIG. 5).
D=Depth of Block (front to back depth)
Wf=Width of Face of Block
Wr=Width of Rear of Block
R=Minimum allowable radius of blocks
θt=Total Angle from vertical axis of block sidewalls
θt=(Tan-1((Wf-Wr)/D) (Equation 1)
R = ( 180 Wf ) ( PI ( θ t ) ) ( Equation 2 ) ##EQU00001##
One major flaw exists with the current design of the tapered SRW block. Because the block is a "precast" unit, the taper is permanently set to the "minimum" or smallest possible radius. This allows the user to create curves that have radii ranging from almost straight to the tightest possible radius. Although this does give the user flexibility in creating both large and small radius curves, it also creates a problem. When the tapered blocks are set at the highest possible radius, no gap exists at the rear of the wall (see FIG. 5a identified as "prior art"). In other words, the rear wall formed at the back of the wall is solid, just like the face. However, when a radius is constructed that is larger than the minimum, which occurs most often, the total rotation or taper of the block is not fully utilized. That is, a gap is left at the back of the blocks between each unit. If the radius is significantly larger than the minimum, this gap can be considerable (see FIG. 5b identified as "prior art"). By experience, such a gapping in the back of the wall leads to the three following problems.
Problem 1--Backfill Material Migrate into "Voids" Creating Loss of Compaction and Strength.
First, placement and compaction of backfill materials into these gaps is difficult if not impossible and time consuming for the contractor. In many cases, this leads to backfill being placed loosely or not at all in this "wedge" between the back of the blocks. Through the forces of gravity and/or water flow, the backfill material adjacent to (behind) the back of the blocks may migrate into these voids over time, creating a loss of compaction and soil density immediately behind the wall. The compaction of the backfill materials and subsequent soil density is critical to the strength of the backfill materials and the performance of the wall. As such, this mechanism may cause a loss of strength in the backfill materials, which results in an increase in lateral earth pressure behind the wall, which is not generally accounted for in standard design practices. An increase in the lateral earth pressure, or force, being applied to the wall reduces the overall factors of safety assumed in design and may impact the structural performance of the wall.
Problem 2--Settlement of Backfill Materials Immediately Behind Wall.
Along with an increase in earth pressure, the movement of the backfill materials immediately adjacent to the back of the blocks results in settlement of the material in this zone. Settlement in the area (immediately behind the blocks) results in the following potential problems. First, settlement of backfill behind the wall may cause the grade behind the wall to move downward, perhaps to an unacceptable level. Elements such as swales or asphalt paving constructed immediately behind the top of the wall may deform differentially, or totally, beyond what is allowable if settlement is excessive. Second, settlement by nature produces additional lateral earth pressures as the backfill materials are compressed both vertically and displace laterally. Third, when a geogrid reinforcement material is used to reinforce the backfill zone, settlement immediately behind the blocks may result in a failure. of the connection of the geogrid reinforcement to the block. As the backfill material settles, the geogrid reinforcement, which is installed horizontally, is subjected to a downward dragging force as it extends out from between the blocks and into the backfill zone. This downward force created by the settling backfill materials, acts to drag the geogrid down, over the back edge of the block. In some cases, the square edge at the back of the block, combined with the presence of small concrete burs created at this seam during the manufacturing of the block, are enough to damage or completely sever the geogrid, when it is being pulled down against it by the settling backfill materials immediately behind the block. This results in a lower or non-existent connection to the block, at which point the structural integrity of the wall has been compromised.
Problem 3--Migration of Fine Materials Through the Face of the Wall.
Natural forces of gravity and water flow acting on the backfill materials may carry soil fines into these voids created by the gaps at the back face of the wall. If these forces are sufficient, the soil fines may be carried through the voids and out to the face of the wall. The staining caused by the soil fines being deposited on the face of the wall is often unacceptable to the consumer from an aesthetic point of view.
The problems listed above are the result of a tapered block being used in applications where the radius being constructed is not the minimum radius. As such, gaps are created at the rear of the wall immediately adjacent to the backfill material. The backfill material is then not contained and may migrate into these voids or gaps between the blocks, leading to the above issues.
SUMMARY OF THE INVENTION
The present invention relates to a segmental retaining wall (SRW) block that is unique in that it allows the user to construct inside and outside (concave and convex) radii with the blocks, while maintaining a full barrier at the rear of the block to the infiltration of backfill soils into the facing or through the facing.
Thanks to its particular configuration, the SRW block according to the invention allows straight or curved alignments while directly addressing the issue of the creation of large voids in the back of the wall that occurs with existing tapered SRW blocks that exist when the blocks are not placed in the minimum convex alignment. The plan configuration of the SRW block according to the invention can be applied to any size of block, face shape or orientation. It provides lateral shear between the units such as an integral tongue and groove, mechanical connectors or pins, adhesive, etc. Despite the method of vertically interlocking the units (lateral shear between units), these elements would have to take into account the ability of the block to curve within certain limits.
More specifically, the SRW block according to the invention solves the above mentioned problems encountered with prior art in that, thanks to its configuration, it blocks the migration of backfill materials at the rear of the wall, regardless of the size of the radius or curvature being constructed.
This SRW block is tapered to allow the block to turn a radius. It comprises a protruding wing or tab on one side, and the congruent receiving "bay" area on the other.
When several of these blocks are placed adjacent to each other in a straight alignment, the wing protrudes or overlaps into the bay area a certain distance required to create a barrier against the migration of fines when the block is placed in a concave alignment. The front edge of the wing and the front edge of the receptacle bay are designed as congruent arcs, the front edge of the wing being set to a radius just slightly larger than the radius of the front edge of the bay area to allow for construction and manufacturing tolerance. As the blocks are rotated to achieve a curve, the wing moves further into the bay area, thereby creating an even greater overlap and barrier to the migration of fines. When the blocks are fully rotated to the minimum allowable radius, the wing fills the bay area.
So, the invention as claimed hereinafter is essentially directed to a segmented retaining wall (SRW) block having a front wall, a rear wall and two opposite side walls, wherein: one of said side walls is rearwardly tapered so as to allow said block to turn a radius when placed in adjacent position with respect to another similar SRW block, said rear wall is provided with a protruding wing that projects laterally away from the tapered side wall; said rear wall is also provided with a bay that extends inwardly in the side wall that is opposite to the tapered side wall; said wing and bay have front edges designed as congruent arcs; and said wing is sized and shaped so as to protrude into the bay of an adjacent similar SRW block to create a barrier wherein said adjacent SRW blocks are in straight, convex or concave alignment.
The invention and its advantages will be better understood upon reading the following non-restrictive description of a preferred embodiment thereof, made with reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1a is a top plan view of a standard SRW block;
FIG. 1b is a top plan view of a wall made of several SRW blocks as shown in FIG. 1a;
FIG. 2a is a top plan view of existing tapered SRW block;
FIG. 2b is a top plan view of a wall made of several tapered SRW blocks as shown in FIG. 1b;
FIG. 3a is a top plan view of an existing SRW block with rear wings that can be knocked off;
FIG. 3b is a top plan view of a wall made of SRW blocks as shown in FIG. 3a, with their rear wings still present;
FIG. 4b is a top plan view of a wall made of SRW blocks as shown in FIG. 3b, with their rear wings knocked off;
FIG. 5a is a top plan view similar to FIG. 2b, with no gaps between the rear sides of the blocks where the backfill material may migrate;
FIG. 5b is a top plan view similar to FIG. 5a but with the blocks placed in radius larger than the minimum and backfill material in between;
FIG. 6 is a top plan view of a SRW block according to a preferred embodiment of the invention;
FIG. 7 is a top plan view of two SRW blocks as shown in FIG. 5 adjacent to each other, in a straight alignment;
FIG. 8 is a top plan view of two SRW blocks as shown in FIG. 5 in a convex alignment;
FIG. 9 is a top plan view of two SRW blocks as shown in FIG. 5 in a concave alignment; and
FIG. 10 is a view similar to the one of FIG. 7, but showing an enlarged view of the manufacturing and constructions tolerated.
In these drawings and the following description, the following abbreviations or symbols correspond to the following:
Wface=Width of face of block
Point A=Rotation point of block on Side A
Side A=Left side of the block
Side B=Right side of the block
θ=Taper Angle on Side A of block
δ=Taper Angle on Side of bay B
Arc A=Arc length of protruding wing on Side A
Arc B=Arc length at bottom of bay area on Side B
Xs=Overlap length of arc A over arc B when blocks set in straight alignment
Xconvex=Overlap length of arc A over arc B when blocks set in minimum convex curve (maximum overlap possible)
Xconcave=Overlap length of arc A over arc B when blocks set in minimum concave curve (minimum overlap possible)
D=Front to back depth of block
t=Manufacturing and construction tolerances
Omin=Minimum overlap of wing into bay area in minimum concave alignment (worst case) to prevent infiltration of fines.
DETAILED DESCRIPTION OF THE INVENTION
The SRW block according to the preferred embodiment of the invention as shown in FIG. 6 is rectangular or square block having a left side (Side A) which differ from its right side (side B). The left side (Side A) of the block has an angle or tapered sidewall (angle=θ from the vertical). This angle represents the desired minimum convex radius the user would want to achieve based on Equations 1 and 2 shown above.
In the illustrated preferred embodiment, Side A is tapered and Side B is straight. However, Side A and Side B could also split, provided that the total taper angle (θ) remains between them.
In the illustrated preferred embodiment, the Side B has a straight sidewall for greater ease of explanation. From a manufacturing point of view, it is also desirable to have a flat or straight sidewall on at least one side of the block to move and package the material. The tapered Side A allows the block to turn a convex radius in the traditional way previously described. However, rather than continuing the tapered sidewall right to the rear of the block, a wing protrudes out from the side of the block at the rear. The depth of the wing (Wd) is set to ensure that the wing piece be adequately strong to prevent breaking off during construction and shipping. The lower edge of the wing identified as arc A in FIG. 5, is formed as an arc. When two blocks are placed side by side, point A of one block is adjacent to point B of the other. As the block rotates its point A, the radius of the arc A identified in FIG. 5 as the wing radius (Rw) is as follow:
Rw=D-Wd (Equation 3)
Indeed, when the center of rotation is point A, the radius is the block depth (D), minus the depth of the wing (Wd).
The wing (arc A) extends out past the imaginary vertical edge of Side A (viz. the side which is not tapered) at a distance noted as Xs. This distance Xs is a function of the required minimum overlap in the worst case scenario, which is, when the blocks are rotated outwards to form a concave curve and the overlap is the minimum. This will be described in more details hereinafter.
The straight sidewall (Side B) is designed on a congruent bay area in the top right corner of the block that accepts the wing of side A. The depth of the bay area (Bd) is slightly larger than the depth of the wing (Wd) to allow construction and manufacturing tolerances.
Therefore, the value Bd-Wd is illustrative of the construction and manufacturing tolerances.
The lower edge of the bay area on Side B (arc B) is designed as a congruent arc with arc A. The radius of the arc B is just slightly less than of arc A to allow movement of the wing into the bay area, given to manufacturing and construction tolerances. Therefore, the radius of arc B, hereinafter called bay radius Rb, is equal to the wing radius (Rw) less the Manufacturing and Construction Tolerances (t).
Rb=Rw-t (Equation 4)
The left sidewall of the bay area is designed to align (δ) with the left side wall of the wing when the blocks are placed at the minimum convex rotation and the wing completely fills the bay area. The left sidewall of the wing is vertical when the block is placed in a straight alignment, so as it rotates into a convex curve, the vertical sidewall rotates about point A and is now angled. The left sidewall of the bay area therefore must be set to the maximum angle the block is able to rotate, which is θ.
θ=δ (Equation 5)
The invention is designed to ensure that when the blocks are placed in a straight alignment, convex curve, or concave curve, an overlap of the wing and the bay area exists that is sufficient to prevent the migration of backfill materials into the back of the blocks. FIG. 7 shows two blocks placed adjacent to each other in a straight alignment. As can be seen, overlap is Xs. FIG. 8 shows two blocks placed adjacent to each other in a convex alignment. This minimum convex radius is the best case scenario for providing a barrier to the infiltration of backfill materials. FIG. 9 shows two blocks placed adjacent to each other in a concave alignment. This minimum concave radius is the worst case scenario for providing a barrier to the infiltration of the backfill materials.
The distance Xs which is the one of overlap in a straight alignment (see FIG. 7) is determined by what the minimum offset can be in the worst case scenario which is the distance Xconcave shown in FIG. 9.
Therefore, the protrusion of the wing beyond the imaginary vertical sidewall for Side A is determined as a function of the minimum radius that is required to be achieved by the block and the minimum overlap in the concave alignment.
The total arc length of the arc A is therefore a function of the overlap in a minimum convex position plus the overlap in the minimum concave position plus the minimum overlap in the concave position. The equation for the length of an arc is as follows (all angles being expressed in degrees):
Arc length (arc A)=(θ(PI)Rw)/90+Omin. (Equation 6) and
Arc length (arc B)=arc A+t (Equation 7)
Xs which is the portion of arc A that extends beyond the imaginary vertical line along the sidewall A can then be expressed by the following equation
Xs=(θ(PI)Rw)/180+Omin. (Equation 8)
As may now be better understood, the arcs A and B formed at the bottom of the wing and bay area serve two purposes. First, they allow these elements to rotate about point A while maintaining an exact distance apart (depending on the manufacturing and construction tolerance) as they follow an arc of consistent radius Rw (see FIG. 10). Secondly, the nature of the arc shape automatically creates an "uphill" configuration between the wing and the bay. In other words, if soil materials are being conveyed, either through gravity, water or compaction forces into the bay area, they will encounter the bottom of the bay area and will not be able to continue through the small space between the wing and the bay (left for construction and manufacturing tolerances) due to the fact that the direction of soil materials would have to be forced upward, against the direction of the applied conveyor forces. This "S" shape creates a natural dam to the movement of material by its geometric configuration.
So, the configuration of segmental retaining wall blocks according to the invention allows them to be set in a straight, concave, or convex alignment, while maintaining a mechanical barrier at the rear to the infiltration of backfill soils.
Patent applications by Angelo Risi, Richmond Hill CA
Patent applications by Tyler Matys, Aurora CA
Patent applications in class Retaining wall
Patent applications in all subclasses Retaining wall