Patent Publication Number: US-7914237-B2

Title: Method and apparatus for inserting sheet piles within highly resistant earth formations

Description:
FIELD OF THE INVENTION 
     This invention relates to a method and apparatus for inserting sheet piles within an earth formation using a separate protective housing or shield, and more particularly to such a method and apparatus especially suited for driving non-metallic or thin metal sheet piles into especially resistant or compacted soils or earth formations. 
     BACKGROUND OF THE INVENTION 
     Sheet piles or piling for certain uses such as seawalls, for example, may be formed of interlocking sheet piling extruded from special vinyl formulations. Vinyl sheet piles are inert to a marine environment, will not deteriorate in fresh, brackish, or salt water applications, and will not leak harmful chemicals into the water or soil. Vinyl sheet piles are also resistant to marine borers, rot, rust, galvanic corrosion, and highly acidic or alkaline soil conditions. However, vinyl sheet piles or piling, like plastic piling and other piling formed of non-metallic material or relatively thin metal material such as aluminum, is particularly vulnerable to becoming damaged when driven into an earth formation. 
     Sheet piling is usually driven or inserted within the soil or earth formation by drop hammers or vibratory hammers. However, certain conditions, for example low temperatures at which vinyl sheet piling tends to be brittle, contribute to the vulnerability of the piling to possible damage during the process of driving the piling into the soil. Also some soils or earth formations are particularly resistant to sheet piling and effectively refuse penetration of the piling. Continued efforts to force the piling in such highly resistant soils can result in damage to the piling. Also, certain known apparatuses and methods believed generally effective for use in installing vinyl sheet piling can be less effective in certain soils due to sticking of the soil on the apparatuses. 
     U.S. Pat. No. 5,503,503, issued Apr. 2, 1996, teaches a protective housing or shield that protects sheet piling during driving or insertion of the sheet piling into soil or an earth formation. The protective housing or shield is preferably formed of metal having a cross section generally similar to the cross section of the sheet pile and adapted to be releasably connected to the sheet pile for simultaneous movement with the sheet pile. The protective housing is of a length greater than the length of the sheet piling and extends beyond the upper and lower ends of the sheet piling. The protective housing and connected sheet pile are driven downward into the formation together to a desired or predetermined depth. Then, the protective housing is lifted upwardly for removal or withdrawal leaving the sheet pile in place. 
     That is, after insertion of the sheet pile at the desired depth in the formation, the protective housing or shield is removed by lifting of the protective housing vertically relative to the sheet pile. While generally quite effective, the protective housing and sheet pile may sometimes adhere or stick to each other, and the protective housing may be difficult to break loose or separate initially from the sheet pile. Such sticking is typically most problematic in certain clay soils. 
     The natural resistance of soils to penetration of piles provides desirably tight holding of piles in an earth formation. However, when soils are so resistant or so compacted as to make driving piles extremely or even prohibitively difficult, the piles, although protected by the housing provided in U.S. Pat. No. 5,503,503, may still not be driven into the earth formation to the desired depth. 
     Conventional methods for reducing soil resistance at the time of driving steel pipe pile into the ground have included spraying water onto the pile surface before attempting insertion of the pile or jetting water into the ground from a jet pipe attached to the central tip of the pile during pile driving. 
     These conventional methods, however, are not always effective, especially with non-metal and thin metal piles. An especial problem with water jetting is weakening the ground with the large quantity of uncontrolled water injected, resulting in failure of the soil to tightly hold the pile as needed. For this reason, water jetting for piling has been disapproved by the United States Army Corps of Engineers and such jetting for piling is now prohibited in many if not all areas of the United States. A need in the pile driving industry continues to exist for improved methods and apparatuses for inserting non-metal and thin metal sheet piling into highly resistant earth formations. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a method and apparatus for facilitating the driving or insertion of sheet piling in earth formations containing sticky clay or soils highly resistant to penetration, while simultaneously protecting the sheet piling from damage from the driving or insertion. 
     A protective housing or shield preferably formed of metal having a shape or cross section generally similar to the shape or cross section of the sheet piling is adapted to be releasably connected to the sheet piling for simultaneous movement with the sheet piling. Although the example embodiments shown in the drawings are directed to Z-shaped pilings, the invention is not limited to use with Z-shaped pilings, and may be used with any shape piling, including u-shaped piling currently gaining in popularity. This advantage of the invention is obtained by designing the protective housing to have a cross-sectional area or shape mimicking that of the sheet piling. 
     The housing has retaining members adjacent its lower end for releasably connecting the sheet piling to the housing for movement therewith. At least some of the retaining members are mounted for movement between engaged and disengaged positions relative to the sheet piling. The housing is of a length greater than the length of the sheet piling and a generally horizontal force exerting member on the housing extends over the upper end of the sheet piling when the sheet piling and housing are connected for exerting a driving force against the upper end of the piling from a vibratory hammer or drop hammer on the housing. 
     A fluid container or gallery extends at least partially across the protective housing and connects or joins to fluid conduits or legs running down the side(s) of the housing and extending lengthwise to (or near) the bottom of the housing. The fluid gallery is positioned at or near the top of the protective housing but below and out of the way of the generally horizontal force exerting member on the housing. The fluid gallery should be large enough to contain sufficient fluid to form a fluid head in the gallery before the fluid proceeds down the fluid conduits. 
     The number of conduits extending down the side(s) of the of the protective housing generally depends on the size of the sheet piling—the bigger the sheet piling, and consequently the bigger the protective housing for the sheet piling, the more conduits needed. Preferably, at least a pair of conduits is used. For example, for a typical sheet piling of two connected Z-shaped sheets (each about 12 to 18 inches in width), a pair of conduits, one on a side of the housing approximately midway the position of each Z-shaped sheet behind the housing, or effectively one on each side of the housing overall, is generally or typically sufficient. For another example, for a sheet piling of three or four connected Z-shaped sheets, about three or four conduits would generally or typically be sufficient. Similarly, two or three conduits would typically be sufficient for a U-shaped sheet, about 30 inches in width. At least three, and more preferably four to six, conduits might be desirable for a modified Z-U-shaped sheet about 50 inches in width. 
     At least one orifice or hole in each of the fluid conduits, preferably located near the bottom of the conduits and the protective housing, allows fluids in the conduits to exit or be discharged from the conduits to the inside of the protective housing, adjacent to the bottom of the sheet piling, and onto the sheet piling. If at least a portion of the protective housing is between the conduit and the sheet piling as may typically occur when the conduit is connected to the protective housing rather than formed into or built within the housing, the orifice extends from the side of the conduit adjacent the housing, through the protective housing, so that the fluid flows out of the conduit onto the sheet piling. The orifices should be located such that the fluid discharges from the conduits and onto the sheet piling preferably in a horizontal plane, and preferably fully wetting or covering the bottom of the sheet piling. The fluid does not jet into the soil, and each conduit and orifice is positioned so that jetting of the fluid into the soil does not occur, even when the fluid is at high pressure. 
     The fluid does not have to be under pressure in flowing through the fluid gallery and down the conduits onto the sheet piling, although pressures as great as at least about 100 psi may effectively be used. The fluid gallery has a pipe fitting or other connection or connector to a fluid source, such as, for example, a pipe or high pressure hose leading into a fluid supply, such as a pump and/or a fluid reservoir. Such connector, preferably adjustable or openable and closeable, allows fluid to flow from the fluid source into a fluid gallery from whence the fluid flows into the conduits (or conduit legs) and ultimately out the orifices at the base of the conduits. The fluid may be water or a synthetic fluid particularly suited for aiding penetration of the pile into the earth formation. Alternatively, the fluid may be air. Embodiments employing air rather than a liquid fluid may be suitably used in soils or earth formations containing water positioned such that the air will contact the water during the driving of the sheet piling. 
     The housing and sheet piling protected by the housing are driven downwardly into the soil together to a desired depth. Preferably fluid is caused to flow through the fluid conduits during this pile driving, and the fluid flow may be begun at the beginning of the pile driving or at some point when undue soil resistance is met (or expected to be met) during the pile driving. The fluid flow may be continued throughout the driving and stopped at the desired depth or stopped at some point earlier. Once the desired depth is reached, the housing is lifted upwardly for removal leaving the sheet piling in place. 
     The protective housing or shield for the sheet piling, particularly sheet piling formed of a rigid vinyl or plastic material, minimizes damage to the sheet piling during installation, and when combined with the fluid permits the sheet piling to be easily driven to a desired depth even with large drop hammers or vibratory hammers and even in highly resistant or sticky clay earth formations. The flow of fluid through the conduit is typically manually activated although such activation may optionally be associated with the activation of the movement of the housing, turning on or allowing fluid flow when the housing is engaged and turning off or ceasing flow when the housing is disengaged, for one non-limiting example. 
     Other features and advantages of this invention will become more apparent after referring to the following specification and drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of one embodiment of the invention showing sheet piling retained by an outer protective housing for movement with the protective housing, and showing a fluid gallery across the top and fluid conduits down sides of the housing; 
         FIG. 2  is a sectional view taken generally along line  2 - 2  of  FIG. 1  showing a perspective of the upper end portion of the connected sheet piling and the protective housing, showing the top of the fluid gallery and connection of the fluid gallery to a connector (to a fluid source not shown), and showing a force exerting member on the housing extending over the upper end of the sheet piling for transferring a driving force to the upper edge of the sheet piling; 
         FIG. 3  is a sectional view taken generally along line  3 - 3  of  FIG. 1  showing a perspective of a portion of the connected sheet piling and the protective housing and showing fluid conduits on said housing; 
         FIG. 4  is an enlarged back perspective view of the lower portion of the protective housing of  FIG. 1  showing the orifices in the fluid conduit through which fluid is discharged onto the sheet piling when it is behind the protective housing; 
         FIG. 5  is a schematic showing the direction of fluid flow from the fluid source through the fluid connector to the fluid gallery and fluid conduits on the protective housing of the embodiment of the invention of  FIG. 1 ; and 
         FIG. 6  is a sectional view showing a perspective of a portion of the protective housing with fluid conduits on the housing of another embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In a preferred embodiment, the present invention is an adaptation or modification of the apparatus shown and described in U.S. Pat. No. 5,503,503. That is, the apparatus of that patent is adapted to include the fluid gallery and fluid conduits and orifices described herein. Thus, the description set forth in U.S. Pat. No. 5,503,503 is background to the present invention and that patent is incorporated in its entirety herein by reference. 
     Referring now to the embodiment of the invention shown in  FIGS. 1-5 , a sheet pile or piling is generally at  10 . Sheet pile  10  is illustrated as a pair of Z-shaped pile sections which have been previously secured to each other at an interfitting tongue and groove joint  10 A. Sheet pile  10  includes side flanges  10 B, central body portion  10 C, integral connecting portions  10 D, tipper end  10 E, and a lower end  10 F. Sheet pile  10  is formed of a rigid plastic or synthetic material such as a rigid vinyl material. A protective housing or shield, generally indicated at  12 , and preferably comprised of metal, is provided for protecting the sheet pile  10  during pile driving. The protective housing  12  is thus releasably connected to pile  10  for being driven with pile  10  into the soil or an earth formation. 
     Protective housing  12  has a shape or cross section generally similar to the shape or cross section of pile  10 , including side flanges  12 B, central body portion  12 C, integral connecting portions  12 D, and lower end  12 F. Protective housing  12  is of a length greater than the length of sheet piling  10  and extends substantially beyond ends  10 E and  10 F and sheet piling  10 . 
     Fluid gallery  11 —an expanded fluid container/conduit—extends at least partially across the upper or top end of housing  12  and joins or connects to fluid conduits or legs  11 A and  11 B, which are preferably attached to the housing  12 . The size of the fluid gallery  11  should be sufficient to contain enough fluid to form a head prior to flow of the fluid down the conduits  11 A and  11 B and yet not so large as to become cumbersome or to interfere with the pile driving. 
     The fluid conduits  11 A and  11 B extend down the side(s) of housing  12 , for example running along or down the integral connecting portions  12 D of the housing  12 , preferably the length of the housing  12  or at least the length of the sheet piling  10 . That is, most preferably, the fluid conduits  11 A and  11 B extend to or even beyond end  10 F of sheet piling  10 . At least one orifice  13 A in fluid conduit  11 A and at least one orifice  13 B in fluid conduit  11 B are positioned so that fluid will be discharged from the conduits  11 A and  11 B only to the interior or back side of housing  12  adjacent to sheet piling  10  and not to the exterior or front side of the housing  12 . The positioning of conduits  11 A and  11 B with respect to each other and the positioning of orifices  13 A and  13 B with respect to each other and with respect to the conduits  11 A and  11 B should preferably be such that fluid exiting from the conduits  11 A and  11 B is discharged onto the sheet piling  10 , most preferably in a horizontal plane, at the bottom or lower end  10 F of the sheet piling  10 . Most preferably, the discharged fluid will entirely cover the lower end  10 F of the sheet piling  10 . If the conduits  11 A and  11 B are separate from the housing  12  rather than built into housing  12  or an integral part of housing  12 , such that a portion of housing  12  lies between the conduits  11 A and  11 B and the sheet piling  10 , then the orifices  13 A and  13 B must extend through that portion of the housing  12  to open into the interior side of the housing  12  adjacent the sheet  10 , as particularly shown in  FIG. 4 . Further, the conducts  11 A and  11 B and orifices  13 A and  13 B must be positioned so that fluid does not jet into the soil during pile driving or when the fluid is discharging onto the sheet piling  10 . 
     Preferably, the fluid gallery  11  and the conduits  11 A and  11 B are comprised of the same material or metal or a compatible material or metal as the material or metal comprising the housing  12  and preferably are welded to the housing  12 . Similarly, and preferably, each conduit  11 A and  11 B is welded to the gallery  11  so that leakage of fluid flowing from the gallery into the conduits can be easily avoided. Alternatively to welding, fittings with “0” rings could be used. 
     Although a pair of conduits  11 A and  11 B with a pair of orifices  13 A and  13 B respectively are shown for example in  FIGS. 1-5 , an alternative example embodiment could include three conduits,  11 C,  11 D,  11 E, on housing  122  and three orifices,  13 C,  13 D,  13 E, in the conduit and through the housing as shown in  FIG. 6 . In still another embodiment, four or more conduits and four or more orifices might be used. The number of conduits extending down the side(s) of the of the protective housing  12  generally depends on the size of the sheet piling—the bigger the sheet piling  10 , and consequently the bigger the protective housing  12  for the sheet piling  10 , the more conduits needed. Preferably, at least a pair of conduits is used. For example, for a typical sheet piling of two connected Z-shaped sheets (each about 12 to about 18 inches in width), a pair of conduits, one on a side of the housing approximately midway the position of each Z-shaped sheet behind the housing, or effectively one on each side of the housing overall, may be generally or typically sufficient. For another example, for a sheet piling of three or four connected Z-shaped sheets, about three or four conduits may be generally or typically sufficient. Similarly, two or three conduits may be sufficient for a U-shaped sheet, about 30 inches in width. At least three, and more preferably four to six, conduits might be desirable for a modified Z-U-shaped sheet about 50 inches in width. 
     Referring to  FIGS. 1 ,  2  and  5 , a connector  15  connects fluid gallery  11  directly or indirectly to a fluid source (not shown) which may be a fluid reservoir or a fluid or high pressure pump which itself may be connected to or associated with a fluid reservoir. The fluid may be water or other fluid suited for facilitating or aiding penetration of the sheet piling  10  into the earth formation. Alternatively, the fluid may be air. Air is effective as a fluid for use in the present invention when the earth formation contains water, and the pile will be driven through such water while air is flowing onto the pile. 
     Secured to the upper end  12 E of housing  12  is an upper support bracket generally indicated at  14  including a lower horizontal base  16  and a vertical support plate  18 . End reinforcing braces  20  are secured between base  16  and vertical support plate  18 . Secured to housing  12  below upper support bracket  14  is a horizontal force exerting plate  22  adapted to extend over and contact upper end  10 E of piling  10  when piling  10  and protective housing  12  are connected together. A downwardly extending retaining lip or extension  24  on force exerting plate  22  extends outwardly of and adjacent sheet piling  10  when releasably connected to protective housing  12  to block outward lateral movement of sheet piling  10  away from housing  12 . Lip  23  is of a shape generally similar to the cross sectional shape of sheet piling  10 . A hanger plate  23  secured to force exerting plate  22  is bolted at  25  to housing  12 . Fluid gallery  11  is generally positioned below base plate  16  and is preferably below the force exerting plate  22 , but on the other side of the housing  12 . 
     Mounted on housing  12  adjacent lower end  12 F are a plurality of retaining members or flaps including generally similar retaining flaps  28  mounted on flanges  12 B and generally similar retaining flaps  29  mounted on central body portion  12 C and connecting portions  12 D as shown in  FIG. 1 . 
     In operation, housing  12  is first positioned adjacent sheet pile  10  with the upper end  10 E contacting force exerting plate  22  adjacent retaining lip  24 , and the lower end  10 F of sheet pile  10  above flaps  28 . A crane or the like positions housing  12  adjacent sheet pile  10  and pivot retainer flaps  28  are caused to move inwardly about the lower end portion of sheet pile  10  to hold pile  10  in releasably connected position with protective housing  12 . 
     Upon connection of housing  12  and sheet piling  10  with flaps  28  engaging piling  10 , the connected piling  10  and protective housing  12  are transported in vertical relation by a suitable crane or the like to the desired location where sheet piling  10  is to be embedded within the soil or earth formation. The connected sheet piling  10  and protective housing  12  are then lowered to the point or position at which it is desired to drive sheet piling  10  into the formation. A vibrator hammer generally indicated at  58  is secured by suitable clamps or jaws  60  to support plate  18  and is connected to a suitable source of power. Fluid connector  15  is connected to a fluid source. Vibrator hammer  58  is then energized and fluid is caused to flow through connector  15  into fluid gallery  11 . Connected sheet piling  10  and protective housing  12  move downwardly within the formation as a result of a driving force exerted by vibrator hammer  58  and force exerting plate  22  against the upper end  10 E of piling  10 , as fluid flows into the fluid gallery and from the fluid gallery  11  down the fluid conduits  11 A and  11 B, out the orifices  13 A and  13 B, and onto the base  10 F of the piling  10 . The fluid preferably covers the entire base of piling  10 . Contact with the adjacent soil will maintain retaining flaps  28  in retaining relation with sheet piling  10  as piling  10  and housing  12  are driven downwardly. Flaps  29  upon engagement with the formation are pivoted inwardly of housing  12  as piling  10  moves downwardly for engaging sheet piling  10  in the same manner as retaining flaps  28 . Thus, retaining lip  24  and retaining flaps  28  and  29  releasably connect sheet piling  10  to housing  12  for being driven downwardly together. When the connected sheet piling  10  and protective housing  12  reach the desired depth for sheet piling  10 , flow of fluid into fluid gallery  11  is stopped (preferably by stopping the flow of fluid into and through connector  15  from the fluid source) and housing  12  is lifted upwardly by a suitable crane or the like and flaps  28 ,  29  are pivoted downwardly upon engagement with the formation to a vertical relation as shown in  FIG. 1  to permit removal of protective housing  12  from sheet piling  10  leaving piling  10  in place. 
     Alternatively, if penetration of sheet piling  10  into the earth formation is proceeding easily or at a satisfactory rate, the flow of fluid into conduit  11  may be stopped before the desired depth of the sheet piling  10  is reached. In still another embodiment, the fluid connector  15  may not be connected to a fluid source until significant or undue soil resistance is encountered during the pile driving and at that time fluid may be caused to flow through the connector  15  into the fluid gallery  11  and then down the conduits  11 A and  11 B, through the orifices  13 A and  13 B, and onto the base  10 F of piling  10 . 
     Another embodiment is especially adapted for use with a drop hammer. In that embodiment, the drop hammer exerts a force against the force exerting plate in the same manner as the embodiment of  FIG. 1  for driving sheet pile  10  downwardly. The fluid gallery  11  is positioned below the force exerting plate and is connected to fluid conduits in a similar manner as in the embodiment of  FIG. 1 . Fluid is caused to flow through the fluid gallery preferably from the time the sheet installation begins until the desired depth is reached or until soil penetration is sufficiently easy without the fluid, as in other embodiments. 
     From the above, it is apparent that an improved method and apparatus has been provided for facilitating the insertion of plastic or vinyl sheet piling or relatively thin metal sheet piling into especially resistant soils or earth formations while maintaining protection of the sheet piling as it is driven into the soils or earth formations. The protective housing is first initially connected to the sheet piling and then the connected sheet piling and protective housing are driven downwardly together in the formation to the desired depth. During this driving, fluid flows into a fluid gallery on the protective housing where it typically builds head and flows through one or more fluid conduits on or of the protective housing, and is released or discharged onto the base of the sheet piling, preferably in a horizontal plane. The fluid may be but is not necessarily released at high pressure. When the sheet piling reaches the desired depth in the formation, the protective housing is lifted upwardly without any further actuation and the fluid flow into and through the fluid gallery and conduit(s) is stopped. Alternatively, the fluid flow into the conduit may be stopped after entry of the sheet piling into the earth formation but before the sheet piling has reached the desired depth. 
     Generally, the advantages of the invention are particularly appreciated when the earth formation has stiff soils that would refuse the piling without the invention. That is, the advantages of the invention are particularly appreciated when, without the invention, a vibratory hammer would have to strike about 35 to 40 blows per foot to effect insertion of the piling or when the piling could not penetrate the soils at all. Under such conditions, the invention will reduce the “resistance” or blow count ranging from about 35 to 40 blows to a blow count of about 25 blows or less. 
     While preferred embodiments of the present invention have been illustrated in detail, it is apparent that modifications and adaptations of the preferred embodiments will occur to those skilled in the art. However, it is to be expressly understood that such modifications and adaptations are within the spirit and scope of the present invention as set forth in the following claims.