Hydraulic Pile Cap Removal

Abstract

A pile cage ( 2 ) has a reinforcement structure ( 4 ) having a first part ( 8 ) adapted to remain in a pile, the first part terminating at a predefined cut-off level ( 20 ), and a second part ( 10 ) that is protected in order to debond it from concrete cast around it. A split-wailed annular tube ( 30 ) is located at the cut-off level ( 20 ) and is connected to a supply of pressurised fluid after the concrete has been poured and set. The tube ( 30 ) expands under pressure initiating a crack that is propagated by the escape of fluid from the slit ( 32 ) towards a centre of the pile at the cut-off level ( 20 ). The entire cracked central surface of the cast pile acts as a hydraulic jack separating the pile cap ( 104 ) from the remainder of the pile ( 102 ).

1 . A pile cage ( 2 ) comprising a reinforcement structure ( 4 ) having a first part ( 8 ) adapted to remain in a pile, the first part terminating at a predefined cut-off level ( 20 ), and a second part ( 10 ) that is protected in order to debond it from concrete cast around it; a crack-inducing ring ( 30 ,  96 ) aligned at the cut-off level ( 20 ); and means ( 42 ,  44 ,  50 ,  58 ,  62 ,  64 ,  90 ) for supplying pressurised fluid to the crack-inducing ring ( 30 ); characterised in that the crack-inducing ring is not made of metal, and in that the cage further comprises a crack-directing feature ( 34 ,  88 ,  92 ) on or adjacent the crack-inducing ring and a crack-attracting feature ( 70 ,  116 ) located at the cut-off level ( 20 ) outside the crack-inducing ring ( 30 ,  96 ).  
   
   
       2 . A pile cage ( 2 ) as claimed in  claim 1 , wherein the crack-inducing ring ( 30 ) has a slit or frangible region ( 32 ) in a portion of its wall facing towards a centre of the pile.  
   
   
       3 . A pile cage ( 2 ) as claimed in  claim 2 , wherein the crack-directing feature comprises fins ( 34 ) defining the slit.  
   
   
       4 . A pile cage ( 2 ) as claimed in  claim 1 , wherein the crack-inducing ring ( 30 ) comprises an annular tube ( 30 ) arranged inwardly of the reinforcement structure, the tube having a plurality of apertures in a portion of its wall facing toward the centre of the pile.  
   
   
       5 . A pile cage ( 2 ) as claimed in any one of the preceding claims, wherein the crack-attracting feature ( 70 ,  116 ) has a dimension of at least a quarter of the depth of cover between the pile exterior and a closest part of the reinforcement structure ( 4 ).  
   
   
       6 . A pile cage ( 2 ) as claimed in any one of the preceding claims, wherein the crack-attracting feature ( 70 ,  116 ) has a dimension of at least half of the depth of cover between the pile exterior and a closest part of the reinforcement structure ( 4 ).  
   
   
       7 . A pile cage ( 2 ) as claimed in any one of the preceding claims, wherein the means ( 42 ,  44 ,  50 ,  58 ,  62 ,  64 ,  90 ) for supplying pressurised fluid to the crack-inducing ring ( 96 ) comprises a plurality of crack-inducing plates ( 90 ) each provided with means for connection to a pressurised fluid supply and the crack-inducing ring comprises a radial flow control shield ( 96 ) surrounding the plates ( 90 ) to restrict the flow of escaping fluid.  
   
   
       8 . An assembly ( 110 ) for use in creating a pile cage ( 2 ) as claimed in any one of the preceding claims, comprising a planar support frame ( 112 ) and a crack-inducing ring ( 30 ,  96 ) not made of metal, the frame ( 112 ) having an inner annular member ( 114 ) supporting the crack-inducing ring ( 30 ,  96 ), a concentric outer annular member ( 116 ) that is or supports the crack-attracting feature, and a plurality of spaced spokes ( 118 ) holding the members ( 114 ,  116 ) together.  
   
   
       9 . An assembly as claimed in  claim 8 , wherein the spokes ( 118 ) are positioned to fall between reinforcing bars of pile cages having a variable number of equally spaced reinforcing bars.  
   
   
       10 . A method of breaking a reinforced concrete pile ( 100 ) comprising the steps of placing a fluid-receiving means ( 30 ,  90 ,  96 ) into a pile cage ( 2 ) at a cut-off level ( 20 ), protecting an upper part ( 10 ) of the pile cage ( 2 ) with debonding material ( 22 ), casting the pile, and supplying pressurised fluid to the fluid-receiving means ( 30 ,  90 ,  96 ), characterised in that the fluid-receiving means ( 30 ,  90 ,  96 ) is adapted to permit fluid to flow substantially inwardly towards a centre of the pile at the cut-off level.  
   
   
       11 . A method as claimed in  10 , wherein the step of supplying pressurised fluid to the fluid-receiving means comprises use of a pump that enables the application of pressure to be controlled.