Abstract:
A subsurface support includes a protective outer member that encases an interior support member. The inner support member may typically be a steel or iron rod which is held within the outer tube as by grout or cement. The outer tube is preferably emplaced by forcing the outer tube into the ground by use of a launching device. The distal end of the outer tube is pointed thus allowing easier penetration of the outer tube into the ground. The subsurface support may be used in numerous functional ways to provide support for an overlying man made structure, or to stabilize surrounding rock and soil. The support can be used in compression, tension, bending, and/or shear.

Description:
TECHNICAL FIELD  
       [0001]     The present invention relates generally to subsurface supports placed in the ground, and more particularly, to a method and apparatus for creating a soil or rock subsurface support that can be used in multiple ways to include support for excavations as a passive soil nail in tension, bending and/or shear, support to stabilize sloping terrain as a tieback in tension, support for an above ground structure as a micropile in compression and/or shear, or support for an above ground structure as an anchor in tension.  
       BACKGROUND OF THE INVENTION  
       [0002]     In the construction of buildings, bridges, and other man-made structures, it is well known to place passive supports such as footers, piles, and other subsurface supports for supporting such man-made structures. These types of supports are passive because the earth around the subsurface support must first shift or move to mobilize the available tensile, bending, or shear capacities.  
         [0003]     One particular problem associated with subsurface supports which may be made of iron, steel, or other metals is that over time, corrosion takes place which ultimately degrades the ability of the support to provide designed support for an overlying structure.  
         [0004]     In addition to providing the above mentioned subsurface supports, it is also known to provide ground strengthening by driving elongate reinforcing members, referred to as soil nails, into the ground in an array thus improving the bulk properties of the ground. The soil nails themselves are not used for direct support of an overlying structure; rather, the soil nails are simply used to prevent shifting or other undesirable properties or characteristics of a particular geological formation which is built upon.  
         [0005]     In some cases, the earth surrounding or near a man made structure becomes unstable and requires active support, such as by a tieback. Tiebacks are pre-tensioned subsurface supports that are used to restrain any movement of surrounding soil and rock. Tiebacks are similar to passive soil nails in construction, and can be emplaced in a similar fashion as a soil nail. More recently, soil nails and tiebacks have also been used to provide temporary and permanent excavation support and slope stabilization.  
         [0006]     The U.S. Pat. No. 5,044,831 discloses a method of soil nailing wherein a soil nail is placed in the ground by being fired from a barrel of a launcher. The soil nail is loaded into the barrel, and pressurized gas emitted from the barrel forces the soil nail into the ground to a desired depth. One advantage of using a soil nail launcher, is that the soil nails can be emplaced with a minimum amount of labor and equipment thereby minimizing environmental impacts as well as providing a simple and economical means of strengthening the ground. Drilling is the traditional way to install soil nails, tiebacks, and anchors.  
         [0007]     Although there are a multitude of subsurface supports and methods by which subsurface supports can be emplaced, there is still a need for simple and effective subsurface supports and an environmentally friendly manner in which subsurface supports are emplaced.  
       SUMMARY OF THE INVENTION  
       [0008]     In accordance with the present invention, a method and apparatus are provided to create a subsurface support device that is placed in the ground. The support device of the present invention has many potential uses. In one use, the support device of the present invention can be used as a passive soil nail. In another use, the support device of the present invention can be used as an active tieback in tension. More generally, for use as a tieback, the support device of the present invention can also be referred to as a soil or rock inclusion. The term inclusion refers to the ability of the support device to increase the tensile capacity of the rock and soil. In yet another use, the support device of the present invention can be used as a micropile in compression, bending and shear. The support device when acting as a micropile can be physically connected to an overlying structure. In yet another use, the support device of the present invention can be used as an anchor in tension. For example, the support may be tensioned as by a cable that interconnects the support to a man made structure.  
         [0009]     Once emplaced, the support device of the present invention includes a protective outer member or tube, an inner support member, and a stabilizing mixture, preferably in the form of grout, cement, resin, or combinations thereof which fixes the inner support member within the outer protective member. The stabilizing mixture may also be referred to as a cementious mixture. The outer protective member supports the opening into the native rock and soil, and acts as a housing for the cementious mixture. As discussed further below, the outer member may be perforated thereby allowing the cementious material to exit the perforations and increase the overall tensile and compressive contribution of the support device. The outer protective member also provides a barrier to prevent water or other corrosive materials from contacting the inner support member. The inner support member provides the design tensile and compressive strength of the support. The inner support member may protrude a desired distance above the outer member to connect to an overlying structure to provide support in any desired manner to include bearing/compression, tension, and/or shear. The diameter and length of the outer member and inner member can be selected to provide the necessary support. The outer member and stabilizing mixture provide strengthening support to the inner member. For example, in compression, the forces are transmitted from the inner support member directly to the stabilizing mixture and the outer member. In tension, forces are also transmitted to the stabilizing mixture and the outer member thereby greatly increasing the force necessary to dislodge or pull out the inner member. The method by which the outer member of the subsurface support is emplaced in the ground is preferably by a launching mechanism, such as that disclosed in the U.S. Pat. No. 5,044,831.  
         [0010]     Other features and advantages of the present invention will become apparent by a review of the following figures, taken in conjunction with the detailed description. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]      FIG. 1  is a cross-section of the subsurface support of the present invention in a first embodiment, the support device being emplaced in the ground and providing tensioning support to an overlying above ground structure;  
         [0012]      FIG. 2  is a cross-section illustrating an example launcher which may be used to emplace the outer member of the support device;  
         [0013]      FIG. 3  is a partial cross-section illustrating a second embodiment of the support device emplaced in the ground and providing compression or bearing support to an overlying structure;  
         [0014]      FIG. 3A  is an enlarged section of  FIG. 3  illustrating one way in which to provide holes or perforations in the subsurface support; and  
         [0015]      FIG. 4  is a simplified elevation of a plurality of support devices that may be used as passive soil nails or as tiebacks to stabilize a sloping surface, the supports being emplaced in a horizontal orientation. 
     
    
     DETAILED DESCRIPTION  
       [0016]     Referring to  FIG. 1 , the subsurface support  10  in a first embodiment of the present invention is shown installed in the ground G. The support device includes an outer member, preferably in the form of a steel or iron tube  12  of a selected length and diameter, and having an integral pointed tip  14 . The tip  14  can be conical in shape which facilitates emplacement of the outer tube as by a launcher, as discussed below. After the outer tube is emplaced, the stabilizing mixture is placed in the interior chamber of the outer tube. Then, an inner support member which can be in the form of an epoxy coated steel rod or bar is then placed within the stabilizing mixture prior to hardening of the mixture. When the stabilizing mixture cures, the inner support member  16  can provide support to an overlying structure in compression, tension, and/or shear. Depending upon the design requirements of the particular structure to be built, a plurality of subsurface supports may be emplaced at desired locations at the construction site, and each of the support devices can be sized to provide the necessary support.  
         [0017]      FIG. 1  also illustrates one example of the manner in which the support device  10  provides support. This one example illustrates use of the subsurface support as an anchor in tension. The subsurface support  10  includes a head or cap  20  which is connected to the exposed upper end of the inner support member  16 . This head or cap can be attached by an integral threaded member  21  which is placed into a threaded well formed in the upper end of the inner support member  16 . The cap or head  20  then can be used for attachment to the overlying structure. In the example of  FIG. 1 , a ring  22  attaches to the cap  20 , and a cable  24  connects to the above ground structure (not shown). Thus, in  FIG. 1 , the support device is used for providing tensioning support to the manmade structure. If the device  10  was needed to provide support in compression, the inner support member  16  could be directly connected to the foundation or other base support of the overlying manmade structure, as further discussed below with respect to  FIG. 3 .  
         [0018]     Referring now to  FIG. 2 , a launching device  40  is shown as a preferred method in which to emplace the outer member of the device  10 . The launcher  40  illustrated in  FIG. 2  corresponds to the launcher illustrated in the U.S. Pat. No. 5,044,831, this reference being incorporated herein in its entirety. The launcher  40  is shown in its loaded condition with an outer member/tube  12  loaded in the launcher and ready for firing. The outer tube  12  with the pointed end  14  is capable of penetrating the ground upon sufficient impact force. The launcher  40  comprises a barrel  42  communicating with a breach  44 . The breach  44  defines an upper chamber  45 . The distal or forward end of the outer tube  12  is received within an annular shaped sabo, preferably made of a plastics material, which is slidably received within the barrel  42  adjacent the chamber  45 . The trailing or proximal end of the outer tube  12  extends through the chamber  44  and projects rearwardly of the launcher  40  through an aperture formed in the cap or upper surface  50  of the breach  44 . An annual shaped breach seal  52  seals the outer tube  12  with respect to the upper surface  50 . A gas inlet tube  54  communicates with the chamber  45  for the admission of compressed gas. A baffle  56  of a larger diameter than the barrel  40  forms an axial projection of the barrel extending into contact with the surface of the ground G. On firing the launcher, compressed gas is forced into the chamber  45  which causes outer tube  12  to be fired into the ground. The baffle  56  includes a locating ring  58  which forms a snug fit around the sabo  46  such that the launcher remains in alignment with the outer tube which is emplaced in the ground. Accordingly, the outer tube when emplaced, remains in coaxial alignment with the barrel  42 . As also shown in  FIG. 2 , the breach seal  52  and sabo  46  may be held in position prior to firing by a plurality of resilient members  60  which exert a separating force between the seal and the sabo.  
         [0019]     Although a launcher of a particular construction is illustrated in  FIG. 2 , it shall be understood that other launcher types and methods can be used to emplace the outer tube within the ground. For example, a launcher which makes use of an explosive charge may be used. Alternatively, a vibratory means may also be used along with some force which helps to ease the outer tube into the ground. As stated above, it is preferable to avoid excavation for emplacement of the outer tube as such excavation is equipment and manpower intensive, and environmentally unfriendly.  
         [0020]      FIG. 3  illustrates a second embodiment  10 ′ of the present invention. The support device  10 ′ is the same as shown with respect to the subsurface support of the first embodiment, with the exception of a plurality of perforations/openings  30  which may be formed in the outer tube  12 .  FIG. 3  also illustrates the device  10 ′ used to support an overlying structure S in compression. More specifically, the device  10 ′ has its upper end  28  embedded within a concrete foundation F of a structure S. The foundation is shown as extending a distance below ground level G. As also shown in  FIG. 3 , the plurality of perforations/openings  30  which may be formed in the outer tube allow the stabilizing material  18  to flow out from the openings  30 , thus forming external stabilizing structures  32 . In compression or tension, these external stabilizing features  32  help to strengthen the connection of the device  10 ′ to the surrounding soil. When filling the interior chamber of the outer tube with the stabilizing mixture  18 , such filling may take place under pressure so that a desired quantity of the stabilizing mixture  18  exits the perforation/openings  30 , thereby forming the external stabilizing features  32 . In order to completely fill the interior chamber of the outer tube, it may be preferable to commence filling of the chamber from the lower most portion of the chamber. A line (not shown) carrying the stabilizing mixture under pressure can be inserted in the chamber and extend to the lower most end of the support device, and then as the stabilizing mixture fills the chamber, the line may be raised as necessary. Those skilled in the art can envision other ways in which the stabilizing mixture can fill the chamber of the outer tube.  
         [0021]     Now referring to  FIG. 3A , an enlarged section of the support device  10 ′ is shown specifically illustrating one manner in which holes or perforations may be made in the outer tube  12 . In  FIG. 3A , the openings  30  are formed by creating moon shaped cutouts thereby leaving a chad or tab  34 . The chad or tab  34  would be pushed away from the exterior surface of the outer tube  12  as the pressurized stabilizing mixture exited the interior chamber of the outer tube. Alternatively, holes could be drilled or punched in the outer tube  12  in order to create an opening by which the stabilizing mixture could flow through. Those skilled in the art can envision other ways in which openings may be formed through the outer tube  12  in order to facilitate flow of stabilizing mixture therethrough to create the external stabilizing features  32 .  
         [0022]      FIG. 4  illustrates use of the subsurface support of the invention to stabilize a sloping surface. In the figure, three support devices  10  are illustrated and are spaced from one another in a desired arrangement to best support the sloping surface. The support devices are disposed in a horizontal orientation, but it shall be understood that the support devices may be placed at any angle or orientation depending upon the surrounding terrain. The support devices in  FIG. 4  would be representative of use of the supports as either passive soil nails or tiebacks.  
         [0023]     Additionally, the subsurface support of the present invention can be used in combination at a particular jobsite to support an overlying structure and to stabilize surrounding soil. In this case, one or more support devices can be structurally connected to an overlying structure such as shown in the figures, and one or more additional support devices can be used as soil nails to stabilize the surrounding soil or rock formation. Even in tunnel construction, the support device of the present invention can be used to stabilize the soil or rock formation surrounding the tunnel. In a tunnel, a support device can be emplaced in any orientation to include stabilizing the ceiling/upper surface of the tunnel.  
         [0024]     With the method and apparatus of the present invention, a subsurface support is provided which can be emplaced with a minimum of effort. The subsurface support provides an alternative to other anchoring means because the outer tube provides protection to the inner support member from corrosion or other undesirable environmental factors. Depending upon the geological conditions, the outer tube can be emplaced with a launching device which is adapted to account for varying geological formations. For example, ground formations with little rock allows emplacement of the outer tube with a minimum of force while placement of the outer tube into an actual rock formation would require a greater force provided by the launching mechanism. In any case, the particular launching device chosen may have the capability of emplacing the outer tube to the appropriate depth and through various rock and soil conditions.  
         [0025]     While the method and the apparatus of the present invention have been provided in preferred embodiments, it shall be understood that various other changes and modifications may be made within the spirit and scope of the present invention.