Abstract:
A sealing member having an elongate body formed of an elastomeric material has a generally planar sealing surface adapted to provide an outward sealing force in a direction generally perpendicular to the sealing surface. The seal further includes a plurality of longitudinally extending hollow regions formed within the sealing member which are bounded at least in part by longitudinally extending and transversely spaced apart structural partitions. A layer of elastomeric material on a side opposite the sealing surface spans the structural partitions thus enclosing the hollow regions. The seals are useful in constructing segmented tunnels, ducts, and the like, and are particularly adapted to withstand high pressures.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The invention relates generally to the art of compression-type seals or gaskets. If finds particular application in conjunction with sealing the spaces between constructional pieces of segmented tunnels, ducts, shafts, pipes, and the like, and will be described with particular reference thereto. Exemplary such structures include subway tunnels, segmented ducts for carrying water or other media, sewer pipes, and so on. However, it is to be appreciated that the invention is equally applicable for use in other like sealed environments.  
           [0002]    A number of seals have been developed and used for preventing the entry of water and other environmental contamination into tunnel constructions and shaft installations using segments or tube elements made of concrete, steel, steel reinforced concrete, and so forth. Conversely, such seals are also used for preventing leakage of water or other transported media out of similarly constructed segmented ducts.  
           [0003]    Commonly, prior art seals comprise a generally planar sealing surface which contacts a like sealing surface on an adjacent facing seal to provide a sealing interference therebetween. Such seals also typically include an engaging portion disposed opposite the sealing portion which engages a mating recess formed in the lateral edge of the construction segment. While the prior art seals vary widely in configuration, the normal practice heretofore has been to form one or more grooves or channels in the recess engaging surface. While in no way intended to be an exhaustive listing, cross-sectional views of representative prior art gaskets are illustrated in FIGS.  20 A- 20 L herein. The externally extending channels, in combination with one or more ducts formed therein, form structural partitions which are collapsible/deformable to allow the gasket to compress when adjoining segments of the construction are fastened, e.g., bolted, together. The resiliency of the gasket material results in a contact pressure between the compressed gasket pair.  
           [0004]    It is expected that leakage between two gaskets will occur when the applied pressure approaches the gasket contact pressure. Thus, a gasket pair should theoretically be able to hold a desired water pressure if compressed sufficiently. However, it has been discovered in accordance with the subject invention that the gaskets having grooves in the recessed portion are subject to leakage at water pressures well below the gasket contact pressure. There thus exists a need in the art for an improved gasket construction which is capable of bearing higher pressures and which overcomes the above stated problems and others.  
         SUMMARY OF THE INVENTION  
         [0005]    In a first aspect of the invention, a sealing member having an elongate body formed of an elastomeric material comprises a generally planar sealing surface adapted to provide an outward sealing force in a direction generally perpendicular to the sealing surface. The sealing member further includes a plurality of longitudinally extending hollow regions formed within the sealing member which are bounded at least in part by longitudinally extending and transversely spaced apart structural partitions. A layer of elastomeric material, on a side opposite the sealing surface, spans the structural partitions thus enclosing the hollow regions.  
           [0006]    In a second aspect of the present invention, a seal arrangement includes first and second abutting structural parts. The structural parts are segments of a type that are assembled to form a tubular tunnel with a formation of transverse joints and longitudinal joints. Each segment has a mating side and is provided on the mating side with at least one peripheral recess covering all mating sides of the segment. An elastomeric sealing member, extending in the form of an elongate body located in each recess, comprises integral first and second portions. The irst portion comprises a first sealing surface engaging a second sealing surface belonging to another sealing member located on the second structural part to provide a sealing interference therebetween. The first and second sealing surfaces are in facing relation and substantial alignment when the first structural part is secured to the second. The second portion comprises a plurality of longitudinally extending hollow regions formed within the sealing member. The hollow regions are bounded at least in part by longitudinally extending and transversely spaced apart structural partitions and a layer of elastomeric material on a side opposite the sealing surface. The layer of elastomeric material spans the structural partitions and encloses the hollow regions.  
           [0007]    In a third aspect of the present invention, an improved method for producing a seal of a type for sealing a gap between first and second structural parts carrying a seal includes producing a elongate gasket made of an elastically compressible material comprising a generally planar sealing surface adapted to provide an outward sealing force in a direction generally perpendicular to the sealing surface, and a plurality of longitudinally extending hollow regions formed in the sealing member, the hollow regions bounded at least in part by longitudinally extending and transversely spaced apart structural partitions. A process selected from molding and extrusion is used for producing the elongate gasket. The improvement comprises producing, at the same time the elongate gasket is being produced, a layer of elastomeric material on a side opposite the sealing surface spanning the structural partitions and enclosing the hollow regions.  
           [0008]    In a fourth aspect of the present invention, a method for increasing the sealing pressure of a seal sealing a gap between first and second structural parts is provided. The structural parts are segments of a type that are assembled to form a tubular tunnel with a formation of transverse joints and longitudinal joints. Each segment has a mating side and is provided on the mating side with at least one peripheral recess covering all mating sides of the segment. First and second sealing members are provided, each comprising first and second generally planar sealing surfaces, respectively. A plurality of longitudinally extending hollow regions are formed within the first and second sealing members. The hollow regions are bounded at least in part by longitudinally extending and transversely spaced apart structural partitions. A layer of elastomeric material is provided on the first and second sealing members, on a side opposite the sealing surface. The layer of elastomeric material spans the structural partitions and encloses the hollow regions. The first sealing member is installed on the first segment so that it is positioned within the peripheral recess thereof. The second sealing member is installed relative to the second segment in like manner. The first segment and second segments are aligned such that the first and second sealing surfaces are substantially aligned in facing relation and secured to compress the first and second sealing members and thus provide a sealing pressure between the sealing surfaces.  
           [0009]    In a fifth aspect of the present invention, a construction article comprises a support component having a recess defined about a peripheral edge and a sealing member having an elongate body formed of an elastomeric material. The sealing member comprises a generally planar sealing surface adapted to provide an outward sealing force in a direction generally perpendicular to the sealing surface, and a plurality of longitudinally extending hollow regions formed within the sealing member, the hollow regions bounded at least in part by longitudinally extending and transversely spaced apart structural partitions. A layer of elastomeric material is disposed opposite the sealing surface and engages the recess, the layer spanning the structural partitions and enclosing the hollow regions.  
           [0010]    One advantage of the present invention is the provision of a sealing member having superior sealing behavior as compared to open-legged seals, particularly at high pressures.  
           [0011]    Another advantage of the present invention is found in the stability of the seals or gaskets. The seals are not as prone to failure at a contact surface between the seal and the seal engaging recess due to laterally applied pressure as are open-legged seals.  
           [0012]    Still further benefits and advantages of the present invention will become apparent to those of ordinary skill in the art upon reading and understanding the following detailed description of the preferred embodiments.  
           [0013]    It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention as claimed. The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention and together with the general description, serve to explain the principles of the invention. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]    The following detailed description may be best understood when read in reference to the accompanying drawings wherein similar reference characters denote similar elements throughout the several views:  
         [0015]    [0015]FIG. 1 is a front perspective view of a pipe section formed by a plurality of tunnel pipe segments;  
         [0016]    [0016]FIG. 2 is an enlarged fragmentary front perspective view of two annularly adjacent tunnel pipe segments with the sealing members of the invention mounted therein;  
         [0017]    [0017]FIG. 3 is a greatly enlarged sectional view of a sealing member in accordance with a first embodiment of the invention;  
         [0018]    [0018]FIG. 4 is an enlarged sectional view of adjacent construction segments employing the sealing member shown in FIG. 3, and wherein the sealing surfaces are in alignment;  
         [0019]    [0019]FIG. 5 is a reduced sectional view similar to the view shown in FIG. 4, and additionally showing the placement of optional packing material in the gap between the adjacent structural segments;  
         [0020]    [0020]FIG. 6 is a sectional view similar to the view shown in FIG. 4, but wherein the sealing surfaces are laterally offset;  
         [0021]    [0021]FIG. 7 is a reduced sectional view of a sealing member according to a second embodiment of the invention;  
         [0022]    [0022]FIG. 8 is a sectional view of adjacent construction segments employing the sealing member shown in FIG. 7, and wherein the sealing surfaces are in alignment;  
         [0023]    [0023]FIG. 9 is a reduced sectional view similar to the view shown in FIG. 8, but wherein the sealing surfaces are laterally offset;  
         [0024]    [0024]FIG. 10 is a sectional view of a sealing member according to a third embodiment of the invention;  
         [0025]    [0025]FIG. 11 is a reduced sectional view of adjacent construction segments employing the sealing member shown in FIG. 10, and wherein the sealing surfaces are in alignment;  
         [0026]    [0026]FIG. 12 is a sectional view similar to the view shown in FIG. 11, but wherein the sealing surfaces are laterally offset;  
         [0027]    [0027]FIG. 13 is a sectional view of a sealing member according to a fourth embodiment of the invention;  
         [0028]    [0028]FIG. 14 is a reduced sectional view of adjacent construction segments employing the sealing member shown in FIG. 13, and wherein the sealing surfaces are in alignment;  
         [0029]    [0029]FIG. 15 is a sectional view similar to the view shown in FIG. 14, but wherein the sealing surfaces are laterally offset;  
         [0030]    [0030]FIG. 16 is a sectional view of a sealing member according to a fifth embodiment of the present invention;  
         [0031]    [0031]FIG. 17 is a sectional view of a prior art open-legged sealing member comparatively tested against the embodiment shown in FIG. 16, and which differs therefrom in that it lacks the closed base;  
         [0032]    [0032]FIG. 18 is a graph showing load deformation curves for the gaskets shown in FIGS. 16 and 17;  
         [0033]    [0033]FIG. 19 is a graph of water pressure, gasket contact pressure before applying water pressure, and gasket contact pressure after applying water pressure versus joint gap for water leakage tests conducted using the closed-base and open-legged gaskets of FIGS. 16 and 17, respectively; and  
         [0034]    FIGS.  20 A- 20 L are cross-sectional views of some representative prior art seals. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0035]    Referring to FIG. 1, a tunnel construction  10  comprises a plurality of tunnel segments, e.g.,  12 ,  14 ,  16 , and so forth, sealed against each other via abutting sealing members thereby forming a sealed tunnel or pipe section. FIG. 2 further illustrates a first sealing member  22  of the invention mounted onto a tunnel segment  12  and a second sealing member  24  mounted onto an adjacent tunnel segment  14 . The sealing members  22  and  24  are brought into facing relation and engage each other when the tunnel segments  12  and  14  are assembled. Typically, the tunnel segments are conjoined or secured to each other using bolts or other fasteners, resulting in compression of the sealing members and thus producing a compression seal therebetween.  
         [0036]    Referring now to FIG. 3, there is shown a cross-sectional view of a sealing member  22  in accordance with a first embodiment of the present invention. Seal  22  includes integral first and second portions  30  and  32 , respectively. Although the seals of the present invention are described herein as comprising first and second portions, this distinction is made only for ease of exposition. It will be recognized that the subject sealing members are integrally formed and the terms “first portion” and “second portion” as used herein are not intended to preclude overlap between the two regions, particularly where hollow regions in one portion are staggered or laterally offset with respect to hollow regions in the other portion.  
         [0037]    First portion  30  includes a sealing layer  36  having a generally planar sealing surface  34 . In operation, the sealing surface  34  engages a facing sealing surface, such as surface  64  of adjacent sealing member  24  (see FIG. 4) to provide a sealing interference therebetween.  
         [0038]    The first portion  30  further comprises a plurality of axially extending hollow regions  48  within the elongate body forming the sealing member  22 . Hollow regions having circular cross-sections are shown in the depicted embodiment, although other geometrical configurations are also contemplated. The hollow regions are bounded by the lateral sides  45 , sealing layer  34 , and internal structural partitions  50 , which are defined therearound.  
         [0039]    Second portion  32  comprises a base layer  38  having a generally planar surface  40  which is disposed on an opposite wall of the sealing member  22  from the sealing surface  34  and aligned in a plane generally parallel therewith. The second portion  32  further comprises a plurality of laterally spaced apart and axially extending hollow regions  42 . The hollow regions  42  define and are bounded by lateral side walls  44  and structural partitions  46 , which are defined therearound, and are closed off by the base layer  38 . The embodiment fo FIG. 3 depicts a preferred cross-sectional shape of the hollow regions  42 . As shown, it is generally arch-shaped wherein the curved portion is on the side closest to the sealing surface. That is to say, hollow regions  42  have a closed U-shaped cross-section, which is inverted in the orientation depicted. Other geometrical cross-sectional configurations are contemplated as well.  
         [0040]    The sealing members of the invention are formed by extruding or molding a resilient, compressible, elastic, or flexible material, with the hollow regions  42  and  48  and the base layer  38  being formed directly during the manufacturing process. The material forming the sealing members may be, for example, a synthetic or natural elastomeric or rubber material. Exemplary elastomeric materials which may be used in making the sealing members of the invention include, but are not limited to, polyisoprene, neoprene, butadiene-acrylonitrile copolymers, ethylene-butadiene block copolymers, ethylene-propylene based copolymers, natural rubber, polychloroprene rubber, polyisoprene-isobutylene copolymers, silicone rubber, styrene-acrylonitrile copolymers, styrene-butadiene copolymers, styrene-maleic anhydride copolymers, and so forth. The preferred materials are polyisoprene and neoprene.  
         [0041]    Referring now to FIG. 4, there is shown a pair of adjacent support components  12  and  14 , having grooves or recesses  52  and  54 , respectively, formed about peripheral or lateral edges  56  and  58 , respectively. The lower portion  32  of seal  22  is affixed within recess  52 , preferably using glue or other adhesive. A corresponding portion  62  of seal  24  engages recess  54  in like manner. Although the groove dimensions may vary somewhat, some or all of the second region  32  is contained within the recess, and some or all of the first region  30  protrudes from the recess, when the sealing member is affixed within the recess and is in its uncompressed state.  
         [0042]    In the construction of a tunnel or pipe structure, the segments  12  and  14  are mechanically joined together, e.g., with bolts, and the sealing members  22  and  24  are pressed together. The elasticity or compressibility of the seal material and the space provided by the hollow regions  42  and  48  render the sealing members deformable under the loading or compression force. The energy of deformation provides a high pressure seal between the sealing faces  34  and  36 . The adjacent segments are drawn together until a gap  70  between the surfaces  56  and  58  is closed or nearly closed. optionally, sheets or bands  72  and  74  of a conventional packing material are provided on surfaces  56  and  58 , respectively, as illustrated in FIG. 5.  
         [0043]    [0043]FIGS. 4 and 5 are depicted with opposing seals  22  and  24  in optimal alignment, however, it will be recognized that concrete casting or other part fabrication tolerances sometimes produce a degree of lateral offset or displacement  80  between the sealing pairs, as shown in FIG. 6. The sealing members in accordance with the invention are also advantageously employed when such an offset is present.  
         [0044]    Referring now to FIG. 7, there is shown a cross-sectional view of a sealing member  82  in accordance with a second embodiment of the present invention. Seal  82  includes integral first and second portions  86  and  88 , respectively. First portion  86  includes a sealing layer  98  having a generally planar sealing surface  90  which sealingly engages the facing sealing surface of an adjacent sealing member  84  (see FIG. 8) in the above-described manner. The first portion  86  further comprises a plurality of axially extending hollow regions  92  formed within the elongate body forming the sealing member  82 , e.g., of circular cross-section. The hollow regions  92  are bounded by lateral sides  95 , sealing layer  98 , and structural partitions  96  which are defined therearound.  
         [0045]    The second portion  88  comprises a base layer  108  having a generally planar surface  100  which is disposed opposite and arranged in a plane parallel to the sealing surface  90 . The second portion  88  further comprises a plurality of laterally spaced apart and axially extending hollow regions  102 . The hollow regions  102  define and are bounded by lateral side walls  94 , structural partitions  104 , and are closed off by the layer  108 .  
         [0046]    Referring now to FIGS. 8 and 9, there are shown pairs of adjacent support components  12  and  14 , having the seals  82  and  84  affixed within recesses  52  and  54 , respectively, in the manner described above by way of reference to FIG. 4. FIG. 8 depicts a well-aligned arrangement. FIG. 9 illustrates the sealing members  82  and  84  laterally offset by a distance  110 . Optionally, a conventional packing material may be placed in the gap between the segments  12  and  14  prior to conjoining the segments as described above.  
         [0047]    Referring now to FIG. 10, there is shown a cross-sectional view of a sealing member  112  in accordance with a third embodiment of the present invention. Seal  112  includes integral first and second portions  116  and  118 , respectively. First portion  116  includes a sealing layer  128  having a generally planar sealing surface  120  which sealingly engages the facing sealing surface of an adjacent sealing member  114  (see FIG. 11) in the above-described manner. The first portion  116  further comprises a plurality of axially extending hollow regions  122 . The embodiment of FIG. 10 illustrates some exemplary noncircular cross-sectional geometric configurations. The hollow regions  122  are bounded by lateral sides  125 , sealing face  120 , and structural partitions  126 , defined therearound.  
         [0048]    The second portion  118  comprises a base layer  138  having a generally planar surface  130  which is disposed opposite and arranged in a plane parallel to the sealing surface  120 . The second portion  118  further comprises a plurality of laterally spaced apart and axially extending hollow regions  132 . The hollow regions  132  define and are bounded by lateral side walls  124 , structural partitions  134 , and are closed off by the base layer  138 .  
         [0049]    Referring now to FIGS. 11 and 12, there are shown pairs of adjacent support components  12  and  14 , having the seals  112  and  114  affixed within recesses  52  and  54 , respectively, in the manner described above. FIG. 11 depicts a well-aligned arrangement. FIG. 12 illustrates the sealing members  112  and  114  laterally offset by a distance  140 . Again, the optional use of a conventional packing material in the gap between the segments  12  and  14  is contemplated.  
         [0050]    Referring now to FIG. 13, there is shown a cross-sectional view of a sealing member  142  in accordance with a fourth embodiment of the present invention. Seal  142  includes integral first and second portions  146  and  148 , respectively. First portion  146  includes a sealing layer  158  having a generally planar sealing surface  150  which sealingly engages the facing sealing surface of an adjacent sealing member  144  (see FIG. 14) in the above-described manner. The first portion  146  further comprises a plurality of axially extending hollow regions  152  which are bounded by lateral sides  155 , sealing face  150 , and structural partitions  156  defined therearound.  
         [0051]    The second portion  148  comprises a base layer  168  having a generally planar surface  160  which is disposed opposite and arranged in a plane parallel to the sealing surface  150 . The second portion  148  further comprises a plurality of laterally spaced apart and axially extending hollow regions  162 . The hollow regions  162  define and are bounded by lateral side walls  154  and structural partitions  164 , with the spaced apart hollow regions  162  closed off by the base layer  168 .  
         [0052]    Referring now to FIGS. 14 and 15, there are shown pairs of adjacent support components  12  and  14 , having the seals  142  and  144  affixed within recesses  52  and  54 , respectively, in the manner described above. FIG. 14 depicts a well-aligned arrangement. FIG. 15 illustrates the sealing members  142  and  144  laterally offset by a distance  170 . Again, the optional use of a conventional packing material in the gap between the segments  12  and  14  is contemplated.  
       EMPIRICAL TESTS  
       [0053]    The following comparative tests have been made to demonstrate the high pressure capability of the subject invention. Water pressure tests were performed by applying pressure to the interior volume of two gaskets in a picture frame configuration placed in gasket grooves or recesses in steel plates. The dimensions of the grooves were 1.4 cm deep and 3.5 cm wide at the base, with side slopes of 1 horizontal to 4 vertical. The picture frame dimensions of the gasket grooves were 10.2 cm×45.7 cm, measured inside to inside at the bottom of the groove. The grooves were made by bolting machined plates to larger plates that were 5.1 cm×27.9 cm×63.5 cm. Two holes were tapped in the top plate for applying water pressure and for allowing air to escape in order to fill the cavity with water.  
         [0054]    The gaskets were compressed by placing the steel plates with the gasket grooves between steel plates that were pulled together with 8 threaded 2.5 cm diameter rods. In one set of tests, the plates with the threaded rods that compressed the gaskets consisted of two plates at the top and two at the bottom, each with dimensions 3.8 cm×22.9 cm ×48.3 cm. In subsequent tests, the loading system was modified to increase stiffness by placing four.8 cm×22.9 cm×48.3 cm steel plates at the bottom and a steel plate with dimensions 5.7 cm×58.4 cm×61.0 cm at the top.  
         [0055]    Pressure was applied from a nitrogen tank that was compressed to 170 kg/cm 2  with the gas applied to the top of another nitrogen bottle that was filled with water. A line was connected to the bottom of the water bottle through a fitting that was installed by drilling and tapping a hole.  
         [0056]    The line was connected to the gasket cavity. All the lines and fittings were designed for 700 kg/cm 2  hydraulic pressure. A gas regulator was placed at the outlet of the nitrogen bottle to reduce the pressure and regulate it to the desired the desired values in the water. The water pressure was measured with a digital gas pressure gage with an accuracy of +/−0.25%.  
         [0057]    The gasket cross-section geometry used in these tests is shown in FIGS. 16 and 17. Referring to FIG. 16, there is shown a gasket  172  according to a fifth embodiment of the present invention which includes integral first and second portions  176  and  178 , respectively. First portion  176  includes a sealing layer  188  having a generally planar sealing surface  180  which sealingly engages the facing sealing surface of an adjacent sealing member in the manner described above. The first portion  176  further comprises a plurality of axially extending hollow regions  182  which are bounded by lateral sides  185 , sealing face  180 , and structural partitions  186  defined therearound.  
         [0058]    The second portion  178  comprises a base layer  198  having a generally planar surface  190  which is disposed opposite and arranged in a plane parallel to the sealing surface  180 . The second portion  148  further comprises a plurality of laterally spaced apart and axially extending hollow regions  192 . The hollow regions  192  define and are bounded by lateral side walls  184  and structural partitions is  194  and are closed off by the base layer  198 . For the tested gaskets, the transverse width  200  of the sealing surface  180  was 30 mm, the transverse width  202  of the base surface  190  was 34 mm, and the height  204  of the gasket was 26 mm.  
         [0059]    [0059]FIG. 17 shows the cross-sectional geometry of a gasket  173  used in the comparative tests. The comparative gasket  173 , which is exemplary of the prior art, includes a first portion  176  as described above by way of reference to FIG. 16, and a second portion  179  which differs from the gasket  172  of the subject invention in that it lacks the base layer  198  (see FIG. 16). That is to say, second portion  179  of the gasket  173  includes a plurality of axial grooves  193  which are bounded by lateral sides  184  and partitions  195 , forming channels that open to the exterior of the gasket.  
         [0060]    The tested gaskets  172  and  173  were formed from polyisoprene. The total load on the gaskets was measured with two load cells placed between the top steel plate with the gasket groove and the top plate with the threaded rods. Extrusion of the gasket into the gap was measured with a 0.001 mm dial gage with the plunger inserted horizontally into the gap at the middle of the long side of the gasket. Change in the gap was measured with two 0.01 mm dial gages placed between the top and bottom steel plates, one at each end. These gap measurements were augmented with measurements using a digital micrometer with 0.001 mm accuracy at each corner and at the middle of each side.  
         [0061]    To determine the relationship between the water pressure and the gasket contact pressure, it was necessary to subtract the water pressure load from the total load given by the load cells. To determine the water pressure load, it is necessary to estimate the area over which the water acts. The area over which the water acts was taken as the dimensions inside the top of the gasket groove, or 425.9 square centimeters. Once the load on the gasket was calculated, the area of the gasket was needed to determine the gasket contact pressure. It was assumed that the gasket was compressed so that it had the width corresponding to the top of the gasket groove, which provided a gasket area of 528.8 square centimeters.  
         [0062]    The load-deformation tests of the gaskets were performed in the same device that consisted of two steel bars that were 5.1 cm×12.7 cm×454.7 cm with longitudinal plates bolted on each side of one face to form the gasket grooves. All the plates were machined to provide accurate dimensions of the groove that were 1.4 cm deep and 3.5 cm inches wide at the base, with side slopes of 1 horizontal to 4 vertical. Plates were bolted to the ends of one of the steel bars to prevent longitudinal extrusion of the gaskets. On each of the steel bars opposite to the grooves, a 3.8 cm ×12.7 cm×10.2 cm steel bar was welded perpendicular to the side that could be placed in the grips of a testing machine.  
         [0063]    The tests were performed by clamping the protruding 3.8 cm×12.7 cm×10.2 cm bars into the heads of a 50-KIP (10 5  kg) MTS hydraulic testing machine with the gaskets bonded in place. The swivel heads of the machine were then adjusted so that the faces of the bars containing the gasket grooves were parallel and the heads were locked to prevent rotation. The gaskets were then brought into contact and the gap was measured. The load-deformation curve was continuously recorded with a computer. The rate of loading was programmed on an Instron controller that controlled the testing machine head movement linearly with time at a specified rate and to a specified gap.  
       RESULTS  
       [0064]    Differences in sealant behavior and capacity between the open-legged gasket illustrated in FIG. 17 and the closed-base gasket in accordance with the invention and illustrated in FIG. 16 were observed, even though they have similar load deformation characteristics. FIG. 18 shows load-deformation curves  210  and  212  for the closed- and open-base gaskets, respectively. FIG. 19 is a graph showing the relation between gasket contact pressure before and after applying water pressure, and water pressure at leakage as a function of joint gap for both gaskets. As shown in FIG. 19, leakage occurred at the initial gasket contact pressure for the open-leg gasket, while leakage occurred near the final gasket contact pressure for the closed-base gasket. The final contact pressure for the closed-base gasket was much higher than the initial contact pressure, leading to higher a leakage pressure.  
         [0065]    The differences in sealant behavior between the open-legged gasket and the subject gasket appear to be a result of the difference in the base condition of the two gaskets. Leakage occurred between the contact faces of the adjoining gaskets of the present invention. In contrast, leakage occurred between the gasket groove and the gasket for the conventional open leg gasket. It is expected that the differences in sealant behavior between the two types of gasket lie in the behavior of the legs as the lateral water pressure is applied. The lateral water pressure on the first leg of the open-leg gasket causes the bond to fail at the bottom of the leg and pushes the leg laterally causing it to buckle. This reduces the stiffness of the gasket above the leg and allows water to pass into the cavity between the legs, reaching the second leg which is then forced to buckle in the same way. This type of progressive deformation of the legs reduces the stiffness of the gasket and allows leakage to occur between the gasket and bottom of the gasket groove, as observed in the tests. Such behavior caused the conventional gasket to leak at water pressure less than the gasket-to-gasket contact pressure. When the open-leg gasket tests were disassembled, the openings between the legs were full of water.  
         [0066]    For the closed-leg gasket of the present invention, water was not allowed to pass the first leg of the closed-base gasket, thus preventing the progressive leg failures found with the open-legged design. With the larger bonding surface of the closed bottom, water did not pass under the gasket. In the tests, all the leakage occurred at the gasket-to-gasket interface. When the closed-base gasket tests were disassembled, the gasket bond to the groove was intact and the contact between the groove and gasket base was dry.  
         [0067]    The description above should not be construed as limiting the scope of the invention, but as merely providing illustrations to some of the presently preferred embodiments of this invention. In light of the above description and examples, various other modifications and variations will now become apparent to those skilled in the art without departing from the spirit and scope of the present invention as defined by the appended claims. Accordingly, the scope of the invention should be determined solely by the appended claims and their legal equivalents.