Abstract:
A passive annular grout seal assembly is disclosed for sealing an annular opening between a driven pile and a skirt pile sleeve for an offshore platform. The annular seals are located at the bottom of the pile sleeves near sea floor and automatically activated when piles are inserted and driven through the pile sleeves without any active operational procedure during offshore piling. The seal configuration fully utilizes the seal height, the grout column height and the density difference between grout and sea water to produce enhanced sealing capacity against the column of grout above.

Description:
FIELD OF THE INVENTION 
       [0001]    The disclosure relates generally to an offshore platform employing multiple legs of piling and piling guide sleeve annulus subject to being filled with grout after piles have been driven. 
       BACKGROUND OF THE INVENTION 
       [0002]    In an offshore platform installation, a grout seal is typically utilized to seal the annulus between a pile sleeve inner surface and a pile outer surface and against a high column of concrete during the grout hardening period.  FIG. 1  illustrates a deepwater offshore platform with extended legs from water surface to sea floor and a plurality of skirt pile sleeves for housing piles. As shown in  FIG. 1 , an offshore platform deck  1  is supported by a jacket  2  extended from water surface  6  to sea floor  5 . A plurality of pile sleeves  4  are attached to the bottom of the extended legs to house a plurality of piles  3 , which are driven into sea floor  5  to provide the anchoring to the platform. 
         [0003]    A grout seal is usually located at the bottom of a skirt pile sleeve  4  near sea floor. The seal has to be rugged and highly reliable because any seal failure such as grout leaking could cause the connection failure between a pile sleeve and a pile. Consequently, it could result in the foundation failure of the platform. 
         [0004]    Existing Grout Seals for Offshore Structures 
         [0005]    In general, there two types of grout seals for pilings in offshore jacket installation: 1) an active grout seal type such as an inflatable packer, and 2) a passive grout seal type such as a CRUX grout seal or a mechanical grout seal. 
         [0006]    Inflatable Packer 
         [0007]    Inflatable packer was introduced to offshore industry in 1970&#39;s and it has been widely utilized in offshore platform fields. Today, inflatable packers still occupy a very large percentage of grout seal market, especially in deepwater platform applications. Inflatable packer is an active assembly which requires a control system above water surface to activate the seal by injecting air or water to form a sealing function.  FIG. 2  is an ISO cross section view of a typical inflatable packer used as a grout seal. As an active seal, the seal element is in a retracted position without making contact between the seal outer surface and a pile prior to pile lowering and inserting. As shown in  FIG. 2 , an inflatable packer element  8  is fixed to the inner wall of a sleeve  4  in a non-inflated condition; an injection tubing  7  is attached at the outer wall of the sleeve  4 . To prevent mud at sea floor to pollute grout during pile driving, a mud wiper  9  is usually installed below the packer element  8 . 
         [0008]    In installing an offshore jacket, common practice utilizing an inflatable packer is to fabricate the jacket on land with jacket leg members and with inflatable packers installed at the bottom of skirt sleeves as grout seals. The jacket is then towed to an installation site for installation. U.S. Pat. No. 3,468,132 to Harris, issued on Sep. 23, 1969, describes a traditional inflatable packer assembly. Until today, this type of active grout seal is still widely used in offshore jacket installation applications. 
         [0009]    An inflatable packer is composed of three subsystems in addition to the packer assembly located at the bottom of a pile sleeve: a power subsystem and a high pressure air/water injection subsystem and a piping subsystem. There are two major disadvantages for using an inflatable packer assembly as a grout seal: 1) the assembly is very expensive in terms of yard installation, yard testing and field operation; 2) the assembly is very complicated which could have potential damages in each of the three subsystems during jacket site installation. U.S. Pat. No. 4,279,546 to Harris, issued on Jul. 21, 1981, describes some of these potential damages for an inflatable packer during field operations. 
         [0010]    Passive Seals 
         [0011]    A typical passive seal is CRUX annular seal, as described in British Pat. No. GB2194006 to Philip et al., issued on Feb. 24, 1988. The seal assembly has an outer head portion attached at the sleeve inner wall and a bulbous ring functioning as a seal element.  FIG. 4  illustrates a CRUX annular seal element  19  prior to piling activities. As shown, a guide shim  16  is attached to the inner wall of sleeve  4 . An outer head portion  18  is fixed to the sleeve  4  inner wall with an inside cavity  17 . A bulbous ring  20  with a fiber core forms the sealing function. The inner diameter of the bulbous ring  20  is less than the outer diameter of a pile so that the deformed ring produces compression force against the pile outer surface to form a sealing function when a pile is driven through the ring.  FIG. 5  is a partial cross-section view of a CRUX annular seal when a pile  3  is driven through and a column of grout  13  is poured between the pile  3  and pile sleeve  4 . As shown in  FIG. 5 , the bulbous ring  20  is deformed and the annular seal element  19  is bended against the pile  3  outer surface, which has several levels of shear keys  21 , to form a seal for a poured column of grout  13 . 
         [0012]    A passive seal is significantly less expensive than an inflatable packer. However, the common concerns for this type of seals are the protection and the reliability of the seals during offshore pile installation activities such as pile inserting and pile driving. The pile bottom outer edge could function as a knife to damage the resilient section between the bulbous ring  20  and the outer head portion  18  due to dynamic heave motions of a pile during pile lowering and inserting. 
         [0013]    A traditional mechanical grout seal is also a passive seal. A traditional mechanical grout seal is usually only used for shallow water applications because it could not take potential dynamic loading from shear keys which are commonly welded both on the pile top outer surface and on the sleeve inner wall of a deepwater platform for increasing the concrete bonding strength between the sleeve and the pile. A mechanical seal is composed of an annular rubber tubular wall with multiple equally spaced steel bars passing through the rubber tubular wall. These steel bars are bounded and fixed with the rubber tubular wall through a vulcanization process. The bottom of the tubular wall is fixed at the sleeve inner wall and each steel bar top passes through a steel ring which is fixed at the sleeve inner wall. As a result, each steel bar top should be able to slide up and down inside the corresponding steel ring. 
         [0014]      FIG. 3  is an ISO cut-off section view of a typical mechanical seal with a driven pile and a column of grout poured in the annulus between a pile and pile sleeve above the seal. As shown in  FIG. 3 , a mechanical seal element  15 , which has an annular inner diameter less than the outer diameter of the pile  3 , is attached to the inner wall of the sleeve  4 . A plurality of steel bars  11  are through and bonded with the resilient seal element  15  and slides upward through the rings  12  which are fixed at the sleeve  4  inner wall. The seal element  15  forms a seal for the poured column of grout  13  between the pile  3  outer surface and the inner surface of the sleeve  4  during pile  3  grouting. A plurality of tapered guide shims  16  are placed above the seal element  15 . The seal element  15  also prevents the mud  14  pollution during pile  3  driving. 
       OBJECTIVES AND SUMMARY OF THE INVENTION 
       [0015]    The principal objective of the disclosure is to provide a passive grout seal that is rugged and resilient, more specifically, to provide a rugged means for anchoring the seal to the sleeve inner wall, to provide a sufficient compression force against the pile outer surface in order to provide a sealing function against a high column of grout above the seal, and to provide a passive grout seal that is resilient during the sealing action for accepting a limited pile offset from the sleeve axial center induced during pile driving. 
         [0016]    Another important objective of the disclosure is to provide a protection means for the resilient part of the assembly from physical damages especially during the pile lowering and driving activities. 
         [0017]    A still further important objective of the disclosure is to utilize the seal height and the density difference between grout and seawater to produce an increased compression force at pile outer surface along with the seal height and water depth, to further increase the grout sealing capacity. 
         [0018]    Another objective of the disclosure is that the introduced grout seal is a passive one without any expensive power system and any associated piping/control subsystems. The seal should be automatically activated when a pile passes through the seal. 
         [0019]    A further objective of the disclosure is that the introduced grout seal is able to allow the sleeve to have an upward relative sliding against the pile after a pile is driven, due to the requirement of a potential leveling operation. 
         [0020]    A grout seal assembly for sealing an annulus between a pile outer surface and a sleeve inner surface is disclosed. The grout seal assembly is made up with three portions: an upper portion of the assembly is composed of a plurality of spaced hanging strips fixed at the sleeve inner wall surface, the upper portion allows fluid passing into the annulus below; a middle portion of the assembly is composed of a annular tube, made of resilient materials and bonded together with the hanging strips from the upper portion, the middle portion has a cone section on the top of a tubular section; and a bottom portion of the assembly is composed of a tube section extended from the middle section and is fixed to the sleeve inner wall to form a sealed annulus between the sleeve inner surface and the tube outer surface. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]    The drawings described herein are for illustrating purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure. For further understanding of the nature and objects of this disclosure reference should be made to the following description, taken in conjunction with the accompanying drawings in which like parts are given like reference materials, and wherein: 
           [0022]      FIG. 1  is an elevation view of a deepwater offshore platform with extended legs from water surface to sea floor and with a plurality of skirt pile sleeves for housing piles; 
           [0023]      FIG. 2  is an ISO cross section view of a typical inflatable packer used as a grout seal with a mud wiper below; 
           [0024]      FIG. 3  is an ISO cut-off section view of a typical mechanical seal with a driven pile and a column of grout poured in the annulus between the pile and the pile sleeve above the seal; 
           [0025]      FIG. 4  is an enlarged partial cross-section view of a CRUX annular seal without a driven pile; 
           [0026]      FIG. 5  is an enlarged partial cross-section view of a CRUX annular seal with a driven pile and a column of grout poured between the pile and pile sleeve; 
           [0027]      FIG. 6A  is an enlarged partial cross-section view of a grout seal disclosed herein with non-welded connections at the top and a flange connection at the sleeve bottom in accordance with one embodiment; 
           [0028]      FIG. 6B  is an enlarged partial A-A cross-section view of the grout seal shown in  FIG. 6A  with pre-installed fixings to anchor each strip top to the sleeve inner wall in accordance with one embodiment; 
           [0029]      FIG. 7  is an enlarged partial cross-section view of the grout seal shown in  FIG. 6A  with a driven pile, without pile offsetting to one side, and a column of grout poured in the annulus between the pile and the pile sleeve in accordance with one embodiment; 
           [0030]      FIG. 8  is an enlarged cross-section view of a grout seal disclosed herein with a driven pile offsetting to one side and a column of grout poured in the annulus between the pile and the pile sleeve in accordance with one embodiment; 
           [0031]      FIG. 9  is an enlarged partial cross-section view of a grout seal disclosed herein with welded connections at the top and an annular welded connection near the sleeve bottom to form a sealing function accordance with one embodiment; 
           [0032]      FIG. 10  is an enlarged cross-section view of the grout seal shown in  FIG. 9  without a driven pile offsetting to one side and with a column of grout poured in the annulus between the pile and the pile sleeve. 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0033]    Before explaining the disclosed apparatus in detail, it is to be understood that the system and method is not limited to the particular embodiments and that it can be practiced or carried out in various ways. 
         [0034]    In accordance with one embodiment of the present disclosure, the main body of the annular grout seal is composed of three different sections: an upper section, a middle section and a bottom section. 
         [0035]    The upper section of the seal is composed of 8 to 16 equally spaced resilient strips around the sleeve inner wall. The tops of the strips are fixed to the sleeve inner wall. The bottoms of the strips are bounded with the middle section through a vulcanization process. Each resilient strip is made of several layers of steel nets bounded with elastomer materials through the same vulcanization process. In a preferred embodiment, the strips are strong enough to take the potential vertical dynamic loading induced by pile lowering and inserting actions and to take other potential dynamic forces inside the sleeves such as vortex induced force during a jacket launch and vibration forces during pile driving. These strips are also made to be strong enough against the potential cutting and scraping forces induced by the sharpness of the pile bottom outer edge and pile rough outer surface. Under this configuration, there are many designed holes between each pair of strips to let the grout pass through the top section and fill the vacant room below during grouting operation. One advantage of these hanging rubber strip configuration is easy to accept a pile offset inside the sleeve during pile inserting and pile driving operations. 
         [0036]    The middle section of the seal is a resilient tube, with a cone section on top of a tubular section. The top end of the cone section has an inner diameter greater than the corresponding pile outer diameter. The resilient tube is made of several layers of fiber nets bounded with elastomer materials together through the same vulcanization process described above. The inner diameter of the tubular section is less than the diameter of the corresponding pile. In a preferred embodiment, the tubular section has a constant inner diameter and a smooth inner surface, with a height of at least one foot (305 mm) This height requirement is designed to suit the typical one foot vertical spacing of shear keys at pile top outer surface; this will allow the tubular section encounter at least one level of shear keys at the pile top outer surface to further enhance the sealing capacity of the seal assembly. The inner smooth surface of the tubular section helps to reduce the friction force during pile driving operation, while the pile outer surface is sliding through the seal, or while a leveling operation is needed. 
         [0037]    The bottom section of the seal is also a resilient tube made of the same material as the middle section. Diameter of the bottom section varies through the height of the section. The top of the bottom section is an extension of the bottom of the middle section. The bottom of the bottom section is fixed at the sleeve inner wall or at the sleeve bottom by a flange, to form a sealed room for a grout column. As the height of the grout column increases inside the annulus, the grout induced horizontal compression force increases accordingly against the pile outer surface through the middle and the bottom tubes. 
         [0038]      FIG. 6A  illustrates one embodiment of the grout seal. As shown in  FIG. 6A , the grout seal has a plurality of bulbous ring section  22  placed below a tapered guide shim  16  which is fixed to the inner wall of the sleeve  4 . Each bulbous ring section  22  is connected to the top of a hanging strip  24 . In some embodiments, there may be as many as sixteen strips  24  for a grout seal. A tubular section plate  23  is placed just below each bulbous ring section  22 . The tubular section plate  23  pushes the strip  24  firmly against the inner wall of the sleeve  4  so that the bulbous ring section  22  may not move downwardly. Both sides of each tubular section plate  23  are extended and fixed at the sleeve  4  inner wall with a pair of pre-installed fixings  27  at the wall surface, as shown in  FIG. 6B . One exemplary pre-installed fixing is angles plus bottom plates at these angle bottoms. These fixings  27  provide an anchoring means to sleeve  4  wall for the tubular section plate  23  and for the strip  24 . These strips  24  are extended downwardly and placed in front of an annular resilient tube  25 . The annular resilient tube  25  has a tubular section with a constant inner diameter and a smooth inner surface. The bottom of the annular resilient tube  25  has a flange connection  26  at the bottom of sleeve  4  to form a seal for a grout column. The strip  24  and the annular resilient tube  25  are bounded together through a vulcanization process. In a preferred embodiment, the connections of seal top strips  24  to the sleeve inner wall, and the connections at the seal bottom to sleeve inner wall, are designed to be strong enough to allow the grout seal to take relative sliding motion (both upward and downward) between the pile  3  and the pile sleeve  4  during a potential leveling operation. 
         [0039]    Referring now to  FIG. 7 , the grout seal in  FIG. 6A  is activated with a pile  3  driven and without any pile offset. Grout  13  passes through the holes between strips  24  to fill the annulus room below to form a grout column. Shear keys  21  at the pile  3  outer surface make contact with strips  24  and/or annular resilient tube  25  to enhance the sealing capacity. Shear keys are wrapped by these strips and/or resilient tube. Because the density of grout  13  is greater than that of seawater, the fluid pressure of grout  13  at the column bottom near the flange  26  is much greater than the surrounding seawater pressure at the same water depth. The weight of the grout column forces the resilient tube  25  to be extended downwardly and bended. As a result, the fluid pressure induced by the grout  13  column should provide an increasing horizontal compression force against pile  3  outer surface through the annular resilient tube  25 . 
         [0040]    The total sealing capacity from the grout seal disclosed herein comes from three areas: 
         [0041]    1) The constant diameter of the annular resilient tube  25  should have a tubular section with its diameter smaller than the pile  3  outer diameter. As the pile  3  passing through the seal assembly, the annular resilient tube  25  inner diameter should be enlarged to produce a compression force against the pile  3  outer surface; 
         [0042]    2) The wrapped shear keys  21  by these strips  24  and/or the tubular of the annular resilient tube  25  should further enlarge the tubular diameter of the annular resilient tube  25  to produce an increased compression force against the pile  3  outer surface; 
         [0043]    3) The high column of grout  13  at the seal bottom should provide an increasing horizontal fluid pressure against pile  3  outer surface through the bottom portion of the annular resilient tube  25  to create an additional sealing force of the invented seal. 
         [0044]    Referring to  FIG. 8 , when a driven pile  3  has a large offset inside a sleeve  4 , the basic sealing capacity of the grout seal should have little change. As shown in  FIG. 8 , the hanging strips  24  should be easy to compensate the pile  3  offsets at the top of the seal. At the bottom of the seal, the side with a narrower annulus should have a more downwardly extended annular resilient tube  25 , more than the other side. However, the sealing capacity should maintain the same for the whole seal. 
         [0045]    The sealing capacity of the grout seal disclosed herein is independent of the pile  3  offset because of the following three facts: 1) The compression force caused by the annular resilient tube  25  inner diameter is independent of the pile  3  offset; 2) The increased compression force against the outer pile  3  surface due to the wrapping up the shear keys  21  is independent of the pile  3  offset; and 3) The increasing horizontal fluid pressure force against pile  3  outer surface is independent of the narrowness of the annulus and it only depends on the height of the grout  13  column. 
         [0046]    In accordance with another embodiment, the grout seal assembly may be installed inside an independent steel-can. The steel-can may then be welded to the bottom of the sleeve  4 , or it may be directly installed inside the sleeve inner wall near the bottom. 
         [0047]    The connection at the top of each strip  24  to the inner wall of sleeve  4  may be a welded connection or a non-welded connection. In the case of non-welded connections, a part of a bulbous ring section  22  may be added to the top of the strip  24  and a section of a tubular section plate may be utilized combined with some pre-welded fixings to keep the bulbous ring section  22  to the wall. 
         [0048]    Welded connections may be also applied to both the top connections and the bottom connections of the seal. In accordance to one embodiment, at the top of each strip  24 , a section of the strip may be pre-connected to the outer surface of a doubler plate  28  through a vulcanization process. Welding is then applied at the both sides of the doubler plate  34  to fix the top of each strip  24  to the sleeve inner wall. The same method may be also applied to the bottom section. A part of the seal bottom resilient tube  25  may be pre-connected with an annular doubler  34  surface through a vulcanization process and then the annular doubler  34  may be welded around the sleeve inner wall at the top and the bottom to form a sealed annulus. One advantage of this configuration is to reduce the annulus dimension and the size of the tapered guide shims  16 . Another advantage is to place the grout seal directly inside most sleeve  4  designs without attaching an extra can as a traditional inflatable packer does. 
         [0049]      FIG. 9  illustrates an embodiment of the grout seal with welded connections at both the top and the bottom of the seal. A doubler plate  28  for each strip  24  is welded to the inner wall of sleeve  4  at both horizontal sides. A section of each strip  24  top surface is then anchored to a corresponding doubler plate  28  with a bonding surface  30  through a vulcanization process. One section of the bottom annular resilient tube  25  may also be anchored to an annular doubler  34  with a bounding surface  30  through a vulcanization process. The annular doubler  34  is welded at the top and at the bottom to the sleeve  4  inner wall. 
         [0050]    Referring now to  FIG. 10 , the grout seal illustrated in  FIG. 9  is activated with a pile  3  driven and without any pile offset. Grout  13  passes through the holes between strips  24  to fill the annulus room below to form a grout  13  column. Some shear keys  21  at the pile  3  outer surface make contacts and wrapped with strips  24  and/or annular resilient tube  25  to enhance the sealing capacity of the seal. Because the density of grout  13  is greater than that of seawater, the fluid pressure of grout  13  at the column bottom is much greater than the surrounding seawater pressure. As a result, the fluid pressure induced by the grout  13  column should provide a horizontal compression force against pile  3  outer surface through the annular resilient tube  25 . 
         [0051]    Although a preferred embodiment of a grout seal assembly in accordance with the present invention have been described herein, respectively, those skilled in the art will recognized that various substitutions and modifications may be made to the specific features described without departing from the scope and spirit of the invention as recited in the appended claims.