BACKGROUND There are currently numerous methods available to increase the stability of earthen embankments or to construct retaining walls. Retaining walls are generally constructed by excavating soil or rock at the desired location. Once the soil mass is excavated, the remaining soil mass is typically stabilized to prevent movement of that mass. Slope stability can be increased using soil nails. For example, a slope can be stabilized by drilling holes into an existing embankment, placing steel rods in those holes and then filling the holes with cement. By concurrently placing the steel rods and cement into an existing embankment, the slope stability can be improved so that excavation can be completed in front of that stabilized embankment (i. e. in the plane perpendicular to the orientation of rods placed into the embankment), without risk of the embankment collapsing on the construction site. In another example, rods can also be placed into generally horizontally-oriented shafts drilled into existing embankments. Following insertion of the rods into the shafts, concrete or high strength grout is injected into the shafts. The concrete or grout bonds the rods to the shaft, which results in a reinforced structural column within the soil mass of the embankment. There are currently many products that can be used to construct such"soil nailed structures." Anchored structures can also be used to increase soil stability in site. Anchored structures are tensioned or loaded so that the load is placed on the face of the in situ soil mass. This face load, which is induced by anchor tensioning, holds the face of the anchors and the in situ material at a predetermined position. In contrast, soil nails are typically not loaded or tensioned when they are installed, but become loaded as the earth in front of the soil nailed structure is removed. A minor amount of movement of a soil nailed in situ embankment is typically assumed in the design. Movement of the

embankment is a manifestation of the stabilizing effect of the soil nails replacing the buttressing effect of the existing in situ material in front of the soil nailed structure.

Soil nails and anchors are prone to corrosion failures. For example, if the steel rods or steel strands used as nails or anchors, they can corrode through contact with moisture and the soil. To minimize the effects of corrosion, products have been developed to protect metal rods or strands from corrosion. For example, the"Double Corrosion System"offered by the Dywidag-Systems International uses PVC pre-grouted sheathing over metal rods to provide a water tight barrier. Florida Wire and Cable, Inc., offers plastic sheaths over a flexible steel strand for use a long soil anchors. Dywidag- Systems International also offers a"Dywidur"bar, which is a non-deformed fiberglass bar bolt. Such a bolt is suitable for use in highly corrosive soil because it is resistant to corrosion. This bolt does not have significant surface deformation, so its use is limited in standard grout injection to providing a better bond to the drilled shaft. These products can be effective if installed properly and can offer extended life for the anchored structure.

For anchored structures, corrosion protection is a major consideration. Because metal bars used in such structures are anchored, they are more prone to break under that tension. Therefore, metal bars used in such applications typically have double or triple corrosion requirements to ensure against failure of the anchored slope. Additional corrosion protection adds to the cost of currently available soil reinforcement for anchored slope stability projects.

These and other corrosion-resistant products require proper installation to prevent damage to the corrosion-resistant coating material. The site for such installations are generally uneven (e. g., mountainous or hilly), which requires heavy equipment. Such installation conditions increase the likelihood that damage might occur to the corrosion- resistant coating material. Because corrosion reduces the service length and load capacity of metal rods or cables, corrosion is significant problem which limits the useful life of soil nailed or anchored structures. In view of these shortcomings of currently available devices for soil nailed or anchored structures, there is a need for soil nails and anchors that provide strength comparable to existing materials while providing improved resistance to corrosion.

SUMMARY OF THE INVENTION

The present invention provides a corrosion-resistant, synthetic deformed bar ("SDB") for use in soil stabilization structures, such as soil nailed or anchored structures.

As used herein, the term"bar"refers to a generally elongate synthetic structure which as a generally circular, ellipsoid, square, rectangular, polygonal or other regular or irregular cross section. A typical bar is composed of a synthetic, non-corrosive material, such as a resin. A bar can also be formed of wound strands of synthetic, non-corrosive material.

Suitable non-corrosive synthetic resins will include polyester, vinyl ester, epoxy and epoxy derivatives, urethane-modified vinyl ester, polyethylene terephthalate, recycled polyethylene terephthalate, and the like. Suitable resins can also include combination of any of these resins. The synthetic resin can be a composite fiber material, such as a combination of a synthetic resin and a fiber reinforcement. Suitable fiber reinforcements will include E-glass, S-glass, aramide fiber (e. g., KevlarTM), carbon fiber, ceramic reinforcement, and the like and combinations of any of these. Suitable fiber composite materials are, for example, PSI Fiberbar (Polystructures, Inc., Arkansas) or C-Bar (Marshall Industries). In some applications, the bar can be coated with a corrosion or moisture resistant material.

The invented bars typically have adequate deformations for bonding to grout. As used herein, deformations can be corrugations, dimples, protrusions, and the like, on the circumference of the bar. Such deformations provide a larger surface for bonding of the bar surface to cement, concrete, grout or the like (hereafter generally referred to as "grout"). Such increased bonding area allows a stronger bond to be formed between the bar and the grout, thereby taking advantage of the load capacity of the bar. The deformations on the surface of the bar can optionally form a continuous repeating pattern on the surface of the bar. In such an embodiment, the deformation can have a generally relatively consistent spacing and depth (or height) from the bar's surface to provide a predictable field bonding characteristic. The deformations in the SDB also facilitate the connection of attachment devices, such as couplers, as may be required for in situ soil reinforcement. The SDB can also have a flared end or a threaded end.

Attachment devices are provided to attach the bars to other structural components, which allows the load capacity of the bar to be transmitted to those other components.

Attachment devices can be connected to a bar in a variety of ways. For example, for bars having corrugations or threads as deformations, an attachment device can be threaded onto a bar. Alternatively, an attachment device can be slid or squeezed or otherwise

sufficiently connected to the bar to provide a secure mechanical linkage. An attachment device can be connected to the bar during manufacture or at the construction site. An attachment device can also be molded over an end of a bar. A bonding agent can optionally be used to bond an attachment device to the SDB.

An attachment device can be used to provide a means to transmit in situ earth loads at the face ("face load") of the retained earthen structure to the in situ soil mass.

The tensile strength of the bars is then utilized to transfer the face load to the stable portion of the in situ soil mass. The length of the SDB is determined according to the soil anchor design to insure that soil stability is enhanced. The length is also determined to ensure that the face load can be adequately carried by the SDB and the grout to the in situ soil mass. For some applications, anchor plates, rods or similar devices can be attached to the end of the SDB within the in situ soil mass to increase the loading capacity of the SDB. Attachment devices can also be attached to the portion of the SDB protruding from the face of the soil mass.

Attachment devices on the face end of the bar are typically composed of a corrosion-resistant material that has adequate tensile strength to transmit any face loading to the in situ portion of the SDB. Such an attachment device can be a corrosion resistant metal, such as, for example, stainless steel, a similarly alloyed steel, a high strength aluminum, or the like. The attachment device can also be formed of a synthetic material, such as those disclosed above for the bar. A preferred synthetic material will have a comparable tensile strength to the material of the SDB. Synthetic attachment devices can be molded directly onto the SDBs. Synthetic and metallic attachment devices can be molded onto the SDB or bonded to the SDB. If a threaded type connection is used that roughly mates with the bar deformations, a reduction in the required bond length may result compared to the non-threaded bond length.

For soil nail applications utilizing SDBs, a nailed wall can be constructed by excavating to form a face on the soil mass. Such a face can be substantially vertical or can be at a lesser angle. Following initial face excavation, an exposed cut will exist. The SDBs are typically inserted into shafts placed into the in situ material per the site design.

Grout is the injected into the shafts to secure the SDBs. The grout can be inserted according to conventional methods. Attachment devices, such as those having exposed threaded ends or voided ends, are then attached to the exposed SDB ends. Alternatively, SDBs having previously bonded or otherwise connected attachment devices can be placed in the shafts so that the attachment devices protrude from face of the soil mass. A face

reinforcement is then placed onto the exposed in situ soil face and attached to the exposed SDB bar ends or to the attachment devices on the bar ends. An encapsulation, such as field concrete, is then optionally applied over the face reinforcement. Specific designs may require face drainage materials and"shot crete"layers at various phases of construction.

Soil anchor applications have similar construction phases as those of nailed structures except that the nail or anchor soil reinforcements are required to be tensioned after installation. Anchored applications typically require the use of threaded attachment devices to facilitate face tensioning with conventional jacking equipment. These attachment devices are connected as previously described. Tension can be applied to the bars at various phases of the excavation, according to the specific design criteria.

These and other objects, features, and advantages of the invention will be apparent from the following description of the invention as illustrated in the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Figures la-d depict a schematic construction sequence for an in sitlx soil stabilization application utilizing SDBs.

Figures 2a-c depict isometric views of an assembly of a void coupler and an SDB.

Figure 3a-g depicts details of a void coupler, an SDB and a side view of the assembly.

Figure 4 depicts is a side view of an SDB threaded coupler extension assembly.

Figure 5 depicts a view of another embodiment of a void coupler and an SDB.

Figure 6 depicts another embodiment of an SDB bar.

Figures 7a and 7b depict a pre-bent SDB and an example of the installation of such a bar.

Figure 8 depicts examples of a multi-connector assembly.

Figure 9 depicts additional embodiments of multiple nail assemblies.

Figure 10 depicts an assembled multiple void end nail assembly 37 and installed in situ multiple void end nail assembly.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to Figures la-d, a schematic of a typical soil nail application is depicted. Figure la depicts a partial cross section of an existing soil mass with slope angle 20 and a slope face 23. The in situ soil volume 21 is shown removed in Figure lb.

After removal of the in situ soil volume 21, shafts 24 are prepared in the in situ soil mass.

The shafts 24 can be prepared according to any suitable method, such as drilling. SDBs 26 are then placed in the shafts 24. Referring to Figure Ic, grout 28 is placed around the SDBs 26 in the shafts 24. Attachment devices, such as void couplers 30, are then secured on the exposed ends of SDBs 26.

The length of the SDBs 26 generally conforms to the depth of the shaft 24. The length of the SDB and the shaft 24 can be determined according to standard engineering design, as will be appreciated by those skilled in the art. For field installation, the SDB 26 can typically be hand installed. In other embodiments, a crane can be used to install the SDB 26. In some applications, the SDB 26 can be cut to the desired length in the field with conventional equipment.

Referring to Figures lb, 5 and 6, the SDB 26 can have any suitable end for connection to an attachment device. For example, an SDB can have a generally straight, threaded or flared end. Referring to Figure I c, the void couplers 30 are shown attached to the SDB 26. The void couplers 30 can be attached either prior to insertion of the SDB 26 into the shaft 24 or after the SDB 26 has been installed into the shaft 24. Depending on the type of material used for the void coupler 30, acceptable methods of connection of the void coupler 30 include direct molding, bonding with acceptable bonding agents, such as for example, epoxy adhesives, or by forming a mechanical connection between the coupler and the SDB 26.

Following connection of the void cap 30 to the SDBs 26, face reinforcements 32 are installed. The face reinforcements 32 interconnect the void couplers 30. Typically the face reinforcement 32 will be normal mild steel concrete reinforcing steel or other acceptable bars, cables or the like. The face reinforcement can also be a synthetic material, such as the synthetic materials used to form the SDB. The face reinforcements 32 can be arranged in any suitable pattern, such as for example an orthogonal pattern. In operation, the void cap 30 transfers the in situ face load to the face reinforcement 32. The face reinforcement is optionally encapsulated in either field applied"shot crete", cast-in- place concrete, or a similar material.

Referring to Figures 2a-c, an assembly 34 of a void cap 30 to the SDB 26 is shown. The void cap 30 can either be formed of a high strength synthetic material and

molded directly on the SDB 26, as shown Figure 2a, or the void cap 30 can be prefabricated and separately attached to SDB 26, as shown in Figures 2b and 2c. For example, a circular void 31 can either be formed as the void cap 30 or is fabricated or formed in the following assembly. Acceptable materials for the void cap 30 will include those having adequate strength and comparable corrosion resistance to that of the material of the SDB 26. Alternatively, the void cap 30 can either be formed of a metallic material or a synthetic material, such as the synthetic material used to form the SDB. Suitable metallic materials will include stainless steel, aluminum and the like. In addition, the void cap 30 can be fabricated from circular tube stock or machined from solid bars, depending on the application and cost of fabrication.

Referring to Figure 2c, the longitudinal void 33 is shown as being slightly larger than the diameter of the SDB 26. The pre-assembly isometric portions of Figure 2 show a generic void cap 30 prior to attachment of SDB 26. The bonding of the void cap 30 to the SDB 26, using high strength epoxy or a comparable bonding agent adhesive, will provide adequate strength and corrosion resistance for the connection of the void cap 30 to the SDB 26. In other application, the void cap can be swedged onto the SDB so that the grip of the void cap 30 is increased as the load is increased. The double taper type connection is convenient for use in other applications where the bar and couplers may be disconnected following load application. A void cap 30 can also be threaded onto, or otherwise mechanically attached to, the SDB Referring to Figures 3a-g, another embodiment of a typical SDB 26 and a deformed void end cap 35 is depicted. Figures 3a and b show an end view 41 and a side view of an SDB 26, respectively. In this example, the SDB 26 is generally circular in shape, although other cross-sectional shapes are within the scope of the invention. A deformed void end cap 35 and the end view 15 of the deformed void end cap 47 are shown in Figures 3c and d, respectively. A vertical longitudinal section view (Figure 3e) of the deformed void end cap 35 shows the internal deformations of the deformed void end cap 35. The ridge deformation 45 and the depressed displacement distance 43 are also shown. The dimensions of the ridge deformation 45 and the depressed displacement distance 43 roughly correspond to the comparable deformation pattern on the SDB 26 so that the deformed void cap 35 can be twisted or loosely threaded onto a typical SDB 26.

Due to the interface mating of the male/female deformation patterns on the SDB 26 outer surface 17 and the inner surface 19 of the deformed void cap 35, the deformed void cap 35 has increased shear capacity. The use of the deformed void cap 35 allows for a shorter

cap for an equivalent bond than the use of the non-deformed void cap 30 and may be cost effect for some applications.

Figure 3g shows an SDB 26 deformed void end cap 35 assembly at the exposed end of SDB 26. A plate 39 bearing on the deformed void end cap 35 is inserted over the SDB 26. For field applications where the deformed void end cap 35 length is less than the cast-in-place wall face, the use of the plate 39 can eliminate the need for the void 31 since the face reinforcement 32 can be placed behind the plate 29.

Referring to Figure 4, an attachment device comprising a threaded rod extension 54 at the exposed end of a SDB 26 is shown. The threaded rod extension 54 is typically stainless steel or another high strength, corrosion-resistant material that can be machined or formed to accept threaded nuts. The coupler 52 is shown molded around the threaded rod extension 54 and the SDB 26. In other embodiments, the coupler can be a metallic material. The material for the molded coupler 52 can be a synthetic material with a high strength that is cost effective to mold. Alternatively, the molded coupler 52 can be a modified deformed end cap 35 with internal deformations that correspond to both the threaded rod extension 54 and the exterior deformation of the SDB 26. The molded coupler assembly 50 (coupler 50 and extension 54) facilitates the attachment of conventional tension jacking equipment to the molded coupler assembly 50 so that the SDB 26 can be field tested for pullout capacity to verify compliance with the design specifications. The molded coupler assembly 50 can also be used for soil anchor applications where the SDBs are required to be tensioned to increase the stability of the in situ soil mass. Following tensioning of the SDB 26, nuts and washers or plates can be inserted on the threaded rod extension 54 to facilitate attachment of the face reinforcement 32 in a similar fashion to what is done for currently available soil nailed or soil anchor walls utilizing steel rods.

Referring now to Figure 7a, a side view of a pre-bent SDB 25 is shown. The bend 80 is shown at an approximate 90 degree orientation relative to the length of the bar, although other angles are possible and within the scope of the invention. Figure 7b depicts an example of typical vertical cross-section of a partially constructed soil nail or ground anchored stabilized in situ embankment. A face reinforcing bar 32 is inserted into the void coupler and placed in close proximity to the bend 80 on the pre-bent SDB 25.

The combination of the coupler end 30 or the pre-bent SDB 25 is another method to structurally combine the concrete wall face to the SDB in situ reinforced soil mass.

Referring to Figure 8, additional examples of a multi-connector assembly 100 are shown. Such multi-connector assemblies can be pre-assembled or field assembled. A fixation place 82 and positioning plate 92 are shown in Figure 8a. The left side of Figure 8a shows front and side views of fixation plate 82. The right side of Figure 8a shows front and side views of positioning plate 92. Figure 8b shows an example of the initial assembly of fixation plate 82 and multiple SDB's 26 with void connectors 30. As can be seen, the fixation plate 82 is fitted over the SDB's 26 and then the void couplers 30 are attached. Referring to Figure 8c, a partially completed assembly is shown of fixation plate 82 and SDB's 26 with void connectors 30 and the load application bolt 94 installed.

Figure 8d shows a completely assembled multi-connector assembly 100 with the addition of the positioning plate 92, the positioning nut 96 and positioning nut 96.

Referring again to Figure 8a, the front and side view of the fixation plate 82 is shown on the left side of Figure 8d. The fixation plate 82 is typically made of a high strength metal, such as steel, aluminum or alloys thereof, or of a composite material. The fixation plate connects and equally distributes preloads or test loads into the SDBs 26. In some embodiments, two or more SDBs 26 are joined with the fixation plate 82. An advantage of this assembly method (fixation plate assembly method) is that pre- assembled SDBs 26 with void connectors 30 can be combined in the field. Although void connectors 30 are shown, the fixation plate 82 can also be used with SDBs and connectors according to the present invention.

A fixation plate 82 typically has a circular void 89 that is slightly larger than the diameter of the SDB 26 to be inserted therein. By slightly oversizing the circular void, installation of the SDB 26 through the fixation plate 82 is facilitated. The counterbore circular void 90 is typically slightly larger than the diameter of the load application bolt 94. The width 84 of the fixation plate 82 is typically sufficient to transmit the pre-load or face load to the SDBs 26 via the rear flange 37 of the void connector 30 without bending.

The correctly sized fixation plate 82 can transmit face or pre-loads equally to the embedded SDBs 26.

For utilization of the fixation plate 82, a positioning plate 92 is typically required.

Front and side view of an exemplary positioning plate 92 are shown in Figures 8a and 8d.

The positioning plate 92 typically has a similar shape to that of the fixation plate 82. The circular void 88 of the positioning plate 92 typically has a diameter slightly larger than that of the void connector 30 to facilitate installation of the positioning plate 92 over the void connectors 30. The width 94 of the positioning plate 92 is typically substantially

less than the width 84 of the fixation plate 82 because positioning plate 92 ensures alignment of the void connectors 30 and SDBs 26 during and after any load application.

Axial alignment of the SDBs 26 is preferable because the bending capacity of the SDBs 26 is typically much lower than the tensile strength capacity of the SDBs 26.

Referring again to Figure 8b, a typical assembly sequence of SDBs 26 to a fixation plate 82 is shown. The front view on the left side shows the exposed ends of the void connectors 30. The side view on the right side shows the lower SDB 26 fully inserted into the fixation plate 82 with the rear flange 37 of the void connector 30 against the face of the counter bore 39. The upper SDB 26 is shown partially inserted into the fixation plate 82. Figure 8c shows the SDBs 26 fully inserted into the fixation plate 82.

The load application bolt 94 is also shown inserted into the fixation plate 82. The positioning nut 96 is shown threaded onto the load application bolt 94 to the desired location of the fixation plate 92.

Figure 8d shows a completed fixation plate assembly 100 in front and side views.

The fixation plate 92 is shown inserted over the void connectors 30 and resting against the positioning nut 96. The load application nut 98 is shown threaded onto the end of the load application bolt 94. The completed fixation plate assembly 100 facilitates the use of numerous SDBs 26 because the face or pre-load applied to the load application bolt 94 is uniformly distributed to all SDBs 26. The material of which these components are made is typically of sufficient strength to transmit loads, and it can optionally be corrosion- resistant, depending on the individual project requirements.

Referring now to Figures 9a and b, alternative embodiments of multiple soil nail assemblies are shown. A welded multiple nail assembly 89 is shown in both an end and side views. The end view on the left side of Figure 9a shows a solid void cap 39 (a void cap without an end void) welded or otherwise structurally connected to a tube bar connector 102. The material for the solid void cap 39 and the tube connector 102 will typically be steel, aluminum or other structurally competent material. The shape of the tube connector 102 can be circular as shown or have any convenient cross sectional shape that will facilitate the attachment of the solid void caps 39 to the tube connector 102. In this example, three SDBs 26 are shown grouped in a welded multiple bar assembly 89. In other embodiments, a number of SDBs 26 greater than two can be grouped, as required for the most efficient structural nail assembly.

Referring to Figure 9b, a section of threaded shaft 106 is shown inserted into the tube connector 102. On the left side of the threaded shaft a tensioning nut 108 is shown

partially threaded onto the threaded shaft 106. On the interior of the tube connector 102 another tensioning nut 108 is shown threaded onto the threaded shaft 106. The combination of the tensioning nuts 108 and the threaded shaft 106 perform a similar function as the load application bolt 94 shown in Figure 8. The load application bolt 94 or the threaded shaft 106 with the tensioning nuts 108 can be used for either the welded multiple nail assembly 89 or with the multi-connector assembly 100.

Referring to Figure 10, an assembled multiple void end nail assembly 37 and installed in situ multiple void end nail assembly is shown. In Figure 10a, two SDBs with void end caps 30 are shown pre-assembled with centralizers 29 shown placed between the SDBs 26. The use of either commercially available centralizers 29 or any other spacer device is acceptable for use to secure the relative position of the SDBs 26.

Referring to Figure lOb, a typical installation for the multiple void end assembly 37 is shown. The exposed excavated wall face 23 is shown on the vertical cross section taken through a typical soil nail installation. A grout 17 (e. g., cementitious grout fill) is shown encapsulating the multiple void end nail assembly 37 above the lower assembled multiple void end nail assembly 37 placed in the shaft 24. Face reinforcing bars 32 are shown inserted in the void caps 30. Additional intersecting reinforcing bars 16 are shown placed behind the face reinforcing bars 32 for the assembled multiple void end nail assembly 37 shown in the grout 17. The effect of the intersecting face reinforcement with the face reinforcing bars 32 is to equally distribute the wall loads at the face into the assembled void end nail assembly 37. The in place multiple void end nail assembly 37 is an alternative to the multi-connector assembly 100.

The previous examples are provided to illustrate but not to limit the scope of the claimed inventions. Other variants and equivalents of the invention will be readily apparent to those of ordinary skill in the art and encompassed by the appended claims.