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FIELD 
     This disclosure relates to a method of raising an existing slab which has settled. 
     BACKGROUND 
     Over time, portions of roadways, driveways, garage floors, sidewalks, patios, etc., often have a tendency to settle or sink. One area that is prone to settlement is a roadway slab adjacent to a bridge. This creates step-like structures or cracks to occur between sections of slabs or at joints. 
     There are several conventional ways to repair sunken slabs. One of these ways is to remove the damaged slab and then re-form the slab. Another method that is often used is mud jacking. In this repair method a hole is drilled through the sunken slab and wet mud is pumped under the slab until the slab is returned to its original position. 
     SUMMARY 
     A method of raising a slab is described that raises slabs needing to be raised. The described method is more efficient than conventional repairing methods such as slab re-forming and mud jacking. 
     In one specific application, the described method can be used to raise a sunken slab of a roadway to align to an adjacent slab without closing the roadway and breaking ongoing traffic. In contrast, slab re-reforming and mud jacking need to close at least portions of the roadway and interrupt ongoing traffic while implementing the repair. 
     In one disclosed example, a method of raising a slab resting on the ground includes introducing an inflatable hose underneath at least a portion of the slab needing to be raised. The inflatable hose is disposed between a bottom surface of the slab and the ground. The slab is lifted by inflating the hose with pressurized media so that the hose increases in volume to impose an upward force on the slab. 
     In another disclosed example, a method of slab jacking includes positioning an inflatable hose underneath at least a portion of a slab needing to be raised. The inflatable hose is positioned underneath the slab so as to be able to impose an upward lifting force on the slab when the hose is inflated. The hose is inflated with pressurized media so that the hose increases in volume to impose an upward force on the slab to lift the slab. Fill material is introduced into a space that is created underneath the slab when the slab is lifted. The inflated hose is then deflated and fill material is introduced into a void left by deflating the inflated hose. 
    
    
     
       DRAWINGS 
         FIG. 1  ( a ) is a schematic top view of two sections of sunken roadway approaches to a bridge that illustrates the inventive concepts described herein. 
         FIG. 1(   b ) is a side elevation cross sectional view of  FIG. 1(   a ) taken along line A-A′. 
         FIG. 1(   c ) is a side elevation cross sectional view of the roadway section of  FIG. 1(   b ) that has been raised by lifting the sunken slab and introducing fill material. 
         FIG. 1(   d ) is a side elevation cross sectional view of the roadway section of  FIG. 1(   c ) with the hose deflated and a void left by the deflated hose filled with fill material. 
         FIG. 2(   a ) is a side elevation cross sectional view of two adjacent sunken slabs needing to be raised. 
         FIG. 2(   b ) is a side elevation cross sectional view of the two adjacent slabs of  FIG. 2(   a ) that have been raised by inflating the hoses and introducing fill material into a space that is created underneath the slabs. 
         FIG. 3(   a ) is a side elevation cross sectional view of a sunken slab illustrating the use of a plurality of inflatable hoses to raise the slab. 
         FIG. 3(   b ) is a side elevation cross sectional view of the slab of  FIG. 3(   a ) that has been raised by inflating the hoses and introducing fill material into a space that is created underneath the slab. 
     
    
    
     DETAILED DESCRIPTION 
     A method of raising a slab is described that raises slabs needing to be raised. For purposes of explaining the inventive concepts, the method will be described with respect to raising sunken slabs of roadways to align to their adjacent slabs without closing the roadway and breaking an ongoing traffic. However, the concepts described herein can be used to raise any slab needing to be raised, for example, slabs on driveways, garage floors, sidewalks, patios, etc. The slabs will generally be described as being formed from concrete. However, in appropriate circumstances, the concepts described herein may be used to raise slabs formed from asphalt. 
     With reference to  FIGS. 1(   a ), ( b ), ( c ) and ( d ), a first embodiment of raising a sunken slab is illustrated. In the illustrated embodiment, two concrete approach slabs  120  and  125  to a bridge  130  have settled and need to be raised. The slabs  120 ,  125  are disposed on ground  160  which forms a roadbed underneath the slabs. The slabs  120 ,  125  are lifted using two inflatable holes  140  and  145 , respectively, disposed underneath the slabs, and a space  170  that is created underneath each slab between the bottom of the slab and ground  160  when it is lifted is backfilled after the slabs are lifted. 
     The sunken slabs  120  and  125  need to be raised to align to the remaining roadway  110  and/or to the bridge  130 . Although  FIGS. 1(   a )-( d ) illustrate bridge approach slabs that have settled, the slabs can be any slabs needing to be raised, for example, slabs of sidewalks, driveways, patios, garage floors, etc. 
     The slab  120  has a bottom surface  122  and a top surface  124 . The top surface  124  was at an original level  116  before the slab  120  subsided. In the illustrated mode of slab settlement, a step-like structure  190  is formed between one end of the slab  120  and the bridge  130 , and a crack  195  is formed between the opposite end of the slab and the roadway  110 . Other settlement modes can occur including, but not limited to, settlement where the left end of the slab adjacent the roadway  110  drops down relative to the right end adjacent the bridge, or where the slab settles such that both the right and left ends drop down. The slab  125  is similar to the slab  120  and is not separately described in detail. 
     The inflatable hoses  140  and  145  are introduced underneath the approach slabs  120  and  125 . The hoses are positioned underneath the slabs so as to be able to impose an upward lifting force on the slabs when the hoses are inflated. In the illustrated embodiment, the hoses  140  and  145  are disposed between the bottom surface of the slabs and the ground  160  in direct contact with the bottom surface of the respective slabs and the ground. However, a thin layer of dirt may exist between the hoses and the bottom surfaces of the slabs. In addition, as illustrated in  FIGS. 2(   a ) and  2 ( b ), plates  252 ,  254  may also be introduced between the bottom surface of the slab and the hose and/or between the hose and the ground to help to stabilize the hose relative to the slab and the ground. 
     Returning to  FIG. 1(   a ), the slabs  120  and  125  may be pre-existing slabs and the inflatable hoses  140  and  145  are introduced underneath the slabs in an appropriate way. For example, the inflatable hoses can be introduced by using directional drilling to drill holes underneath the slabs, with the hoses then being directed through the holes. Alternatively, the hoses can be introduced while the slabs are being formed, whereby the hoses are laid on the roadbed and thereafter the slabs are formed. 
     The roadway  110  has a first side edge  112  and a second side edge  114 . In the embodiment illustrated in  FIG. 1(   a ), the hose  140  is introduced so that the hose  140  extends across the entire roadway from the first side edge  112  to the second side edge  114  generally perpendicular to the first and second edges  112  and  114 . The hose  145  is illustrated as extending at an oblique angle from the second side edge  114  partially across the roadway to approximately the center of the roadway  110 . The hose(s) can extend any distance across the roadway, can be located at any position along the slab relative to the ends thereof, and can be disposed at any angle relative to the side edges, that one finds suitable as long as the hose(s) is able to lift the slab needing to be raised. 
     Turning to  FIG. 1  ( c ), the sunken portion of the slab  120  is raised by inflating the hose  140 . The hose  140  is inflated with pressurized media so that the hose  140  increases in volume to impose an upward force on the slab  120 . Suitable pressurized media for inflating the hose includes, but is not limited to, pressurized gases such as air and pressurized liquids such as water. The pressurized media can be generated from a pressurized media source  180  and is injected through one end of the hose  140  into the hose  140 . The opposite end of the hose  140  can be closed to prevent escape of the pressurized media. Alternatively, the opposite end can be connected back to the media source  180  to form a closed loop circulation system. 
     The increase in size of the hose resulting from inflation creates an upward lifting force on the slab  120  that is sufficient to lift the slab. The size of the hose that is used should be sufficient to lift the slab upward a sufficient distance to raise the slab to the desired level. Further, the hose need not be fully inflated. The hose only need be inflated enough to raise the slab to the desired level. In addition, the size of the hose and pressure of the pressurized media should be sufficient to create enough upward lifting force to lift the weight of the slab. When it is desired to implement the method without closing the roadway and while there are objects such as cars or pedestrians on the slab  120  during lifting, the upward force should be sufficient to support both the slab  120  and the objects on the top surface of the slab  120 . In this manner, the slab  120  can be raised without breaking ongoing traffic on the roadway  110 . 
     Although the hose  140  is illustrated as having a cylindrical cross-sectional shape when fully inflated, hoses having other cross sectional shapes can be used, such as rectangle, polygon, oval or irregular shapes. For example, a hose  250  with an oval cross sectional shape when fully inflated is illustrated in  FIG. 2  ( b ). The hose  140  can be made from any suitable material, such as rubber, canvas or nylon, so long as the hose  140  is inflatable to increase the volume from a collapsed or non-pressurized condition, and can hold the pressurized media when inflated. 
     Once the slab  120  is lifted by the inflated hose  140 , the open space  170  is created underneath the raised slab. Fill material is then introduced into the space  170  to fill the space and restore support to the slab. The fill material can be any material suitable for filling the space  170 . Examples of suitable fill material include, but are not limited to, dried fill material such as dried sand or wet fill material such as conventional mud used in mud-jacking. Dried fill materials are useful because they do not need time to dry. If wet fill material is used, drying time must be provided. An explanation of using dried sand to till voids underneath slabs is found in U.S. patent application Ser. No. 09/687,445 filed on Oct. 13, 2000, which is incorporated by reference in its entirety. 
     To introduce the fill material under the slab to fill the space  170 , one or more through-holes  150  (see  FIG. 1(   a )) can be drilled through the slab  120  so that the fill material can be injected into the space  170  via the through-hole  150 . Although one through-hole  150  is illustrated, any suitable number of through-holes can be drilled through the slab to achieve appropriate filling. The through-holes  150  can be disposed at any location on the slab  120  one finds suitable for backfilling the space  170 . In the illustrated embodiment the through-hole  150  is disposed close to the edges  114  of the roadway  110  so that a central region of the roadway  110  can remain open for traffic, e.g., vehicles and pedestrians. After filling, the through-holes  150  are filled in an appropriate way, such as by using concrete fill material. 
     Alternatively, the fill material can be injected into the space  170  from the side of the road. For example, as shown in  FIG. 1(   a ), an injection device  155  can be introduced into the space  170  from the side of the road to inject the fill material into the space  170 . 
     Turning to  FIG. 1(   d ), after the slab  120  is lifted and the space is filled with fill material, the hose  140  is deflated. Deflation of the hose  140  leaves a void resulting from the space occupied by the inflated hose. Additional fill material is then introduced again to fill the void. As shown in  FIG. 1  ( d ), the sunken slab is thus returned to its original level  116 . 
       FIGS. 2(   a ) and ( b ) illustrate another embodiment where two adjacent slabs  220  and  230  have settled and are raised using two inflatable hoses  240  and  250  and a space  270  underneath each slab is backfilled after the slabs  220  and  230  are lifted. Referring to  FIG. 2(   a ), the two sunken slabs  220  and  230  form part of a roadway supported on the ground  260 . The two slabs  220  and  230  have adjacent ends that have settled creating a step-like structure  285  and two cracks  290  and  295 . Each slab  220  and  230  has a bottom surface  222  and  232  and a top surface  224  and  234 , respectively. The top surfaces  224  and  234  were at an original level  216  before the slabs settled. 
     The two inflatable hoses  240  and  250  are positioned underneath the adjacent portions of the two slabs  220  and  230  needing to be raised. The hose  240  has a round cross section shape when fully inflated and the hose  250  has an oval cross section shape when fully inflated. The slabs  220  and  230  may be pre-existing slabs and the inflatable hoses  240  and  250  are introduced underneath them in an appropriate way. Alternatively, the inflatable hoses can be introduced while the slabs are being formed. 
     As discussed above, the two plates  252  and  254  can be used, if considered appropriate, between the slab  230  and the hose  250  and between the hose  250  and the ground  260 , respectively. The plates may be introduced at the same time as the hoses or they can be introduced after the hoses have been installed. The use of plates may be appropriate if there is concern about the stability of the ground or the slab as the hose reacts against it, if one wishes to spread the lifting force more evenly, or if there are concerns about creating punctures in the hose when pressurized media is introduced into the hose. 
     The lifting the slabs  220 ,  230  can be performed while an automobile  205  is traveling on the slabs as shown in  FIGS. 2(   a ) and  2 ( b ). 
     Although one hose is illustrated in  FIGS. 2(   a ) and  2 ( b ) to raise each slab, two or more hoses can be used underneath each slab. In addition, the two slabs could also be raised using only one of the hoses by introducing the hose underneath both of the slabs at a position to provide a lifting force to each slab when inflated. 
     The hoses  240  and  250  are inflated with pressurized media so that each hose increases in volume to impose an upward lifting force on the respective slabs. The pressurized media can be introduced into the hoses and can be same type of media as discussed above for  FIGS. 1(   a ) to  1 ( d ). The upward force on the slab  220  is sufficient to support both the slab  2200  and the car  205  on the slab  220 . In this manner, ongoing traffic on the slabs need not be interrupted during raising the sunken slabs. 
     As shown in  FIG. 2(   b ) once the slabs are raised by inflating the hoses  240 ,  250 , fill material is introduced into the created space  270  underneath the slabs  240 ,  250 . The fill material can be any material suitable for filling the space  270 . Examples of suitable fill material include, but are not limited to, dried fill material such as dried sand or wet fill material such as conventional mud used in mud-jacking. 
     After the slabs  220  and  230  are lifted and the space backfilled to raise the slabs to the original level  216 , the hoses  240  and  250  would be deflated which leaves voids resulting from the space occupied by the inflated hose. Fill material is again introduced to fill the voids. 
       FIGS. 3(   a ) and ( b ) illustrate a sunken slab  320  that forms part of a sidewalk  310 . The slab  320  is lifted using two hoses  340  and  350 , and a space  370  created under the lifted slab is back filled with fill material. The two hoses  340 ,  350  are positioned underneath two portions of the slab  320  near opposite ends thereof. The slab  320  is raised by inflating the hoses  340  and  350  and then by introducing fill material into the space  370  underneath the slab  320 . 
     Both hoses  340  and  350  have a cylindrical structure when being fully inflated. However,  FIG. 3(   b ) shows the hose  340  as being partially inflated while the hose  350  is fully inflated. How much each hose is inflated depends on how high the slab needs to be lifted. 
     The examples disclosed in this application are to be considered in all respects as illustrative and not limitative. The scope of the invention is indicated by the appended claims rather than by the foregoing description; and all changes which come within the meaning and range of equivalency of the claims are intended to be embraced therein.

Summary:
A method of raising a slab is described here that uses inflatable hoses to raise slabs needing to be raised, for example, to raise sunken slabs of a roadway to align to their adjacent slabs without closing the roadway and breaking ongoing traffic. The described method of raising a slab makes it more efficient to repair slabs needing to be raised while conventional repairing methods, for example, re-pouring, or mud jacking, which need to close the roadway and interrupt ongoing traffic, are more expensive, time consuming and less effective.