BACKGROUND OF THE INVENTION
Field of the Invention
The present invention is in the technical field of civil engineering and is directed generally toward methods and devices for supporting excavations.
Description of the Related Art
The boundary of an excavated space may include one or more substantially vertical sidewalls cut into the soil. One or more temporary support structures, such as contiguous temporary support-of-excavation (“SOE”) walls, are typically installed to support the sidewalls cut into the soil and prevent these sidewalls from collapsing into the excavated space. Examples of contiguous temporary SOE walls include but are not limited to diaphragm walls, cutter-soil-mix slurry walls, and secant pile walls.
A contiguous temporary SOE wall is typically anchored to the soil behind the wall by tieback anchors. Tieback anchors, which are considered active restraint devices, typically include steel cable strands that extend from the wall into the soil, and are grouted into the soil behind the wall. After being grouted into the soil, the tieback anchors are tensioned to a high load using a hydraulic jack. Tieback anchors tensioned in this manner are referred to as being “active.”
Unfortunately, conventional methods of attaching tieback anchors to a contiguous temporary SOE wall suffer from several shortcomings. For example, conventional methods of attaching tieback anchors to a contiguous temporary SOE wall are labor-intensive. Further, tieback anchors installed using conventional methods typically intrude into the excavated space.
A contiguous temporary SOE wall is needed only until a permanent structure (e.g., permanent concrete walls) designed to support the sidewalls of the excavated space is placed or constructed in front of the contiguous temporary SOE wall. After the permanent structure is in place, active tieback anchors are generally considered a liability. Accidentally cutting an active tieback anchor has the potential to cause bodily harm to workers, damage to the permanent structure, or damage to excavation equipment. As a result, most government authorities having jurisdiction over an excavation require that the tension in the tieback anchors be released (referred to as “de-tensioning”) before project completion such that future construction activities will not accidently cut through and inadvertently de-tension one or more of the active tieback anchors.
Unfortunately, no simple means exists for de-tensioning conventional tieback anchors after the permanent structure has been placed or constructed in front of the contiguous temporary SOE wall. In order to facilitate de-tensioning of the tieback anchors, windows or voids are typically incorporated into the permanent structure at locations adjacent to the tieback anchors. These voids provide temporary access to permit removal or de-tensioning of the tieback anchors. Before commissioning the permanent structure, these voids must be filled with concrete. Filling these voids and repairing any associated waterproofing penetrations is time-consuming and expensive, and may compromise the integrity of the permanent structure.
Therefore, a need exists for new methods and devices for attaching tieback anchors to a contiguous temporary SOE wall. Methods and devices that allow active tieback anchors to be more easily de-tensioned are particularly desirable. The present application provides these and other advantages as will be apparent from the following detailed description and accompanying figures.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of an embodiment of a tieback anchor alignment and access device.
FIG. 2 is an exploded perspective view of the tieback anchor alignment and access device of FIG. 1.
FIG. 3A is a top (plan) view of the tieback anchor alignment and access device of FIG. 1 installed in a contiguous temporary SOE wall omitting rebar for clarity.
FIG. 3B is a top (plan) view of a contiguous temporary SOE wall including a plurality of the devices of FIG. 1 and omitting rebar for clarity.
FIG. 4A is a side partial cross-sectional view of the tieback anchor alignment and access device of FIG. 1 installed in a SOE wall omitting rebar for clarity.
FIG. 4B is a side partial cross-sectional view of the tieback anchor alignment and access device of FIG. 1 with a cutting tool inserted into the device to de-tension a tieback anchor coupled to the device.
FIG. 5A is a front (elevation) view of the tieback anchor alignment and access device of FIG. 1.
FIG. 5B is a front (elevation) view of the contiguous temporary SOE wall of FIG. 3B.
DETAILED DESCRIPTION OF THE INVENTION
FIG. 4A illustrates a tieback anchor alignment and access device 10 embedded in a contiguous temporary SOE wall 12 that is supporting soil 14. The device 10 is anchored to the soil by at least one tieback anchor 20. Rebar (not shown), which would typically be included in the SOE wall 12, has been omitted from FIGS. 3A-4B.
As is apparent to those of ordinary skill in the art, any number of laterally spaced apart devices each like the device 10 may be embedded in the SOE wall 12. For example, referring to FIGS. 3B and 5B, a plurality of devices 10A-10C each substantially identical to the device 10 (see FIG. 1) may be embedded within the SOE wall 12. Further, each of the devices 10A-10C is attached to one or more tieback anchors 20 that anchor the devices 10A-10C (and the SOE wall 12 in which the devices 10A-10C are embedded) to the soil 14 (see FIG. 3B). As is apparent to those of ordinary skill in the art, any number of tieback anchors may be attached to each of the device 10A-10C and used to anchor the SOE wall 12 to the soil 14 (see FIG. 3B).
Referring to FIG. 4A, the device 10 includes a different anchor subassembly 30 attached to an upright support assembly 32 for each tieback anchor 20 attached the device 10. Referring to FIGS. 1-3A and 4A-5A, for ease of illustration, the device 10 has been illustrated as including only the single anchor subassembly 30 for attachment to the single tieback anchor 20 (see FIGS. 3A and 4A-5A). However, any number of subassemblies each like the subassembly 30 may be attached to the upright support assembly 32 and coupled to a different tieback anchor 20. For example, referring to FIG. 5B, the device 10A, which is attached to three different tieback anchors 20, includes three subassemblies 30A-30C. Similarly, the device 10B, which is attached to three different tieback anchors 20, includes three subassemblies 30D-30F, and the device 10C, which is also attached to three different tieback anchors 20, includes three subassemblies 30G-30I. The subassemblies 30A-30I are substantially identical to one another and, as shown in FIG. 5B, are each coupled to a different tieback anchor 20.
Referring to FIG. 1, the upright support assembly 32 extends along a longitudinal axis “A1.” As illustrated in FIG. 5B, when the device (e.g., the device 10A) includes multiple subassemblies (e.g., the subassemblies 30A-30C), the subassemblies are attached to the upright support assembly 32 at different locations along the longitudinal axis “A1” (see FIG. 1). Further, the subassemblies 30A-30C may be aligned vertically along the longitudinal axis “A1” (see FIG. 1). If desired, the devices 10A-10C may be aligned such that the subassemblies 30A-30I are arranged in rows horizontally. For example, the subassemblies 30A, 30D, and 30G of the devices 10A-10C, respectively, may be aligned with one another horizontally to define a first horizontal row “R1.” Similarly, the subassemblies 30B, 30E, and 30H of the devices 10A-10C, respectively, may be aligned with one another horizontally to define a second horizontal row “R2,” and the subassemblies 30C, 30F, and 30I of the devices 10A-10C, respectively, may be aligned with one another horizontally to define a third horizontal row “R3.”
Referring to FIG. 5B, together, the lateral or horizontal locations of the devices 10A-10C within the SOE wall 12, and the vertical locations of the subassemblies 30A-30I in the devices 10A-10C provide a template that specifies where (both vertically and horizontally) each of the tieback anchors 20 will be attached to the SOE wall 12. In other words, the locations of the subassemblies 30A-30I within the SOE wall 12 provide predetermined locations for the attachment of the tieback anchors 20 to the SOE wall 12. This differs significantly from prior art methods of attaching tieback anchors, which result in a high degree of variability in their positioning along a contiguous temporary SOE wall.
Referring to FIG. 1, the upright support assembly 32 has a front surface 34 opposite a back surface 36. An open-ended upright through-conduit or hollow core 40 extends through the upright support assembly 32 along the longitudinal axis “A1.” Referring to FIG. 4A, the front surface 34 includes a different front through-hole 42 in communication with the hollow core 40 for each anchor subassembly 30. Similarly, the back surface 36 includes a different back through-hole 44 in communication with the hollow core 40 for each anchor subassembly 30. As shown in FIG. 4A, the front and back through-holes 42 and 44 are offset from one another along the longitudinal axis “A1” (see FIG. 1).
Referring to FIG. 2, in the embodiment illustrated, the upright support assembly 32 includes first and second I-shaped members 50 and 52 positioned side-by-side. The first and second members 50 and 52 are substantially identical to one another and may each be implemented as a steel I-beam. Each of the first and second members 50 and 52 has a front flange or plate “FP” connected to a back flange or plate “BP” by a connecting web or plate “CP.” In the upright support assembly 32, the front plate “FP” of the first member 50 is positioned alongside and aligned with the front plate “FP” of the second member 52. Adjacent edges 51 and 53 of the front plates “FP” of the first and second members 50 and 52, respectively, are welded together. Similarly, the back plate “BP” of the first member 50 is positioned alongside and aligned with the back plate “BP” of the second member 52. Adjacent edges 55 and 57 of the back plates “BP” of the first and second members 50 and 52, respectively, are welded together. Thus, referring to FIG. 1, together, frontwardly facing surfaces of the front plates “FP” form the front surface 34. Similarly, together, backwardly facing surfaces of the back plates “BP” form the back surface 36. The hollow core 40 (see FIGS. 1, 3A, 4A, and 4B) is defined between the connecting plates “CP” of the first and second members 50 and 52.
Referring to FIG. 2, edge cutouts 54 and 56 are formed in the adjacent edges 55 and 57, respectively, of the back plates “BP” for each anchor subassembly 30. The edge cutouts 54 and 56 are aligned with one another and, when the upright support assembly 32 is fully assembled, define the back through-hole 44 (see FIG. 4A). Similarly, edge cutouts (not shown) substantially identical to the edge cutouts 54 and 56 are formed in the adjacent edges 51 and 53 of the front plates “FP” for each anchor subassembly 30. The edge cutouts (not shown) formed in the adjacent edges 51 and 53 are aligned with one another and, when the upright support assembly 32 is fully assembled, define the front through-hole 42 (see FIG. 4A).
While the upright support assembly 32 is illustrated as including the first and second I-shaped members 50 and 52, this is not a requirement. In alternate embodiments, the upright support assembly 32 may be constructed from steel plates, or other shapes joined together to define the hollow core 40 (see FIGS. 1, 3A, 4A, and 4B) and provide the front and back surfaces 34 and 36 (see FIGS. 1, 4A, and 4B) having the front and back through-holes 42 and 44 (see FIG. 4A), respectively, formed therein.
Referring to FIG. 2, the subassembly 30 includes a standoff member 60 and a bearing plate 62. In the embodiment illustrated, the standoff member 60 has a generally square or rectangular cross-sectional shape. The standoff member 60 has a first end 64 opposite a second end 66 and an open-ended conduit 68 that extends from the first end 64 to the second end 66. Referring to FIG. 4A, the first end 64 of the standoff member 60 is mounted to the front surface 34 of the upright support assembly 32 with the conduit 68 aligned with the front through-hole 42. The standoff member 60 may be constructed from hollow structural steel or plates.
Referring to FIG. 1, the bearing plate 62 may be substantially planar. A through-hole 70 is formed in the bearing plate 62. Referring to FIG. 4A, the bearing plate 62 is mounted to the second end 66 of the standoff member 60 with the through-hole 70 aligned with and opening into the conduit 68. Referring to FIG. 1, the bearing plate 62 has a surface 72 that faces outwardly when the bearing plate 62 is mounted to the standoff member 60. The through-hole 70 may be at or near the center of the surface 72 of the bearing plate 62.
Referring to FIG. 4A, the tieback anchor 20 includes an anchor head 80 coupled to anchor strands 82. The through-hole 70 is configured to allow the tieback strands 82 to pass therethrough. The through-hole 70 is aligned with both the front and back through-holes 42 and 44 of the upright support assembly 32. In other words, the through-holes 42, 44, and 70 are collinear along an anchor axis “A2.” The anchor strands 82 extend rearwardly from the anchor head 80 (which is positioned against the outwardly facing surface 72) and pass through the through-hole 70 into the conduit 68 of the standoff member 60. The anchor strands 82 pass through the conduit 68, exit therefrom through the front through-hole 42, and enter the hollow core 40. The anchor strands 82 extend through the hollow core 40 laterally, exit from the hollow core 40 through the back through-hole 44, and extend through a portion of the SOE wall 12 and into the soil 14. A portion of the anchor strands 82 extending into the soil 14 may be grouted into the soil 14. As shown in FIG. 4A, the anchor strands 82 extend through the device 10 along the anchor axis “A2,” which is at an angle (typically between 70 and 90 degrees) with respect to the longitudinal axis “A1” (see FIG. 1).
The anchor head 80 is too large to pass through the through-hole 70 and bears against the bearing plate 62 around the through-hole 70 when the tieback anchor 20 is active. The bearing plate 62 in turn bears against the standoff member 60, which bears against the upright support assembly 32. The standoff member 60 and the bearing plate 62 are configured to resist the load applied thereto by the anchor head 80.
Referring to FIG. 4B, the hollow core 40 provides a conduit through which a cutting device 90 (e.g., a diamond rotary coring bit powered by a drill rig) may be inserted along the longitudinal axis “A1” (see FIG. 1) from above (e.g., from the ground surface) and used to sever the anchor strands 82. The conduit provided by the hollow core 40 is not so large as to allow the cutting device 90 to bypass and accidently miss the anchor strands 82. The sidewalls of the hollow core 40 may help guide the cutting device 90 through the hollow core 40. Thus, the device 10 provides access to the anchor strands 82 from the ground surface that may be used to de-tension the tieback anchor 20 thereby eliminating the need for the inclusion of passageways and voids in the permanent structure of the type used in the prior art to de-tension tieback anchors.
After the anchor strands 82 have been severed (thereby de-tension the tieback anchor 20), the hollow core 40 may remain empty or be backfilled (e.g., with soil). As shown in FIG. 4B, the device 10 may be spaced inwardly from a final outwardly facing SOE wall face 92. Optionally, the subassembly 30 may be positioned behind a front curtain of reinforcing bars (not shown). In the embodiment illustrated, each subassembly 30 is spaced inwardly from the wall face 92 and positioned within a recess 94 formed in the SOE wall 12. Thus, neither the device 10 nor the tieback anchor 20 extends beyond the wall face 92 and into the excavated space. Further, except for the recess 94, the wall face 92 is continuous and smooth. If desired, the recess 94 may be filled and finished such that the wall face 92 is continuous and smooth before or after the tieback anchor 20 has been de-tensioned. After being finished, the wall face 92 may be waterproofed, if desired.
The device 10 may provide several advantages over prior art methods of attaching tieback anchors to a contiguous temporary SOE wall. For example, the device 10 provides means for both installing and de-tensioning tieback anchors when used with contiguous SOE walls. The device 10 provides a template for organizing tieback anchor locations, where current practice results in a high degree of variability in positioning. The device 10 allows tieback anchors to be de-tensioned at any point in time after the permanent structure is in place. Further, the device 10 eliminates the need to leave voids in the permanent structure and patch the subgrade waterproofing system at the locations of those voids. Additionally, if desired, the wall face 92 may be finished smooth and flush.
The device 10 may be implemented using a vertical hollow steel assembly combined with at least one hollow steel standoff and bearing plate having the capacity to accommodate at least one tieback anchor.
While the foregoing written description of the invention enables one of ordinary skill to make and use what is considered presently to be the best mode thereof, those of ordinary skill will understand and appreciate the existence of variations, combinations, and equivalents of the specific embodiment, method, and examples herein. The invention should therefore not be limited by the above described embodiment, method, and examples, but by all embodiments and methods within the scope and spirit of the invention.
Accordingly, the invention is not limited except as by the appended claims.
Patent Application
20170218592
