Method and Apparatus for Making an Expanded Base Pier

Abstract

A system for constructing a support column includes a mandrel with an upper portion and a tamper head. A feed tube extends through the mandrel for feeding flowable material to the head. The tamper head includes a lower enlarged chamber with a reducing surface at an upper portion for compacting material and restricting upward flow of aggregate. The tamper head is of a size providing an enclosed region for allowing cementitious materials to be placed therein. The system allows a support column including a cementitious inclusion on top of an expanded base to be built.

1 . A system for constructing a support column, comprising:
 (a) a mandrel having an upper portion and a tamper head, and a feed tube extending therethrough for feeding aggregate, concrete, grout, or other flowable materials through the mandrel to the tamper head; and   (b) the tamper head defining a lower enlarged chamber having a reducing surface at an upper portion thereof for compacting aggregate or concrete and for restricting upward flow of aggregate or concrete into the mandrel during compacting and the temper head being of sufficient size for providing an enclosed region for allowing cementitious material to be placed therein.   
     
     
         2 . The system of  claim 1 , further comprising a valve mechanism movable between an open position and a closed position for closing off the feed tube from communication with the tamper head during tamping operations. 
     
     
         3 . The system of  claim 1 , further comprising stiffening members secured between the reducing surface and the mandrel for providing load support during tamping operations. 
     
     
         4 . The system of  claim 1 , further comprising chains attached within the interior of the tamper head for restricting upward flow of material into the feed tube during downward movement of the mandrel. 
     
     
         5 . The system of  claim 1  further comprising notches within the interior of the tamper head for restricting upward flow of material into the feed tube during downward movement of the mandrel. 
     
     
         6 . The system of  claim 1 , further comprising a second tube extending through the mandrel on the side of the feed tube for allowing cementitious material to flow upward through the second tube for inspection of the cementitious material during pumping. 
     
     
         7 . The system of  claim 1 , further comprising a hopper located at the top of the mandrel for feeding aggregate into the feed tube of the mandrel. 
     
     
         8 . The system of  claim 1 , further comprising a closure cap on an end of the feed tube opposite the tamper head and a concrete supply tube connected to the feed tube. 
     
     
         9 . The system of  claim 8  further comprising an air pressure source connected to the feed tube for evacuating concrete from the feed tube through air pressure supplied thereto. 
     
     
         10 . A method of constructing a support column comprising use of a mandrel assembly having a feed tube connected to a tamper head at an opening thereof for allowing aggregate, concrete, grout, or other flowable material to flow into the tamper head, the method comprising:
 (a) providing the tamper head of a shape with a defined lower enlarged chamber having a reducing surface at an upper portion thereof for compaction and for restricting upward flow of material into the feed tube during tamping, the tamper head further sized to provide an enclosed region for allowing cementitious material to be placed therein;   (b) driving the mandrel assembly into a ground surface to a given depth thereby forming a cavity;   (c) lifting the mandrel assembly to release an initial charge of aggregate or concrete from the tamper head into a bottom of the cavity;   (d) re-driving the mandrel assembly to compact the aggregate or concrete at a bottom of the cavity and to form an expanded base, the expanded base having a width greater than the tamper head; and   (e) withdrawing the mandrel assembly while continuously feeding cementitious material or aggregate to be subsequently fully or partially treated with grout through the feed tube, thereby forming a cementitious inclusion at least partially within the cavity, the cementitious inclusion having a width of the cavity and being formed on top of the expanded base.   
     
     
         11 . The method of  claim 10  wherein the tamper head is filled with the initial charge of aggregate or concrete before driving. 
     
     
         12 . The method of  claim 10  wherein the cementitious material is one selected from the group consisting of concrete, grout, or aggregate that is subsequently fully or partially treated with grout. 
     
     
         13 . The method of  claim 10 , further comprising providing a valve mechanism movable between an open position and a closed position at the opening between the feed tube and the tamper head, for restricting the passage from flow connection into the tamper head, and moving the closure member to an open position for introducing cementitious material into the tamper head, and into a closed position during downward compaction. 
     
     
         14 . The method of  claim 10 , further comprising introducing cementitious material into the enclosed region. 
     
     
         15 . The method of  claim 10 , further comprising introducing a pipe through the feed tube and tamper head after formation of the expanded base, placing aggregate during the withdrawing step to partially surround the pipe, and introducing cementitious material into the pipe following aggregate placement to treat the aggregate. 
     
     
         16 . The method of  claim 10 , further comprising chains attached within the interior of the tamper head for restricting upward flow of material into the feed tube during downward movement of the mandrel. 
     
     
         17 . The method of  claim 10 , further comprising notches within the interior of the tamper head for restricting upward flow of material into the feed tube during downward movement of the mandrel. 
     
     
         18 . The method of  claim 10 , further comprising providing the mandrel with a second tube adjacent the feed tube to allow for the inspection of cementitious material during pumping. 
     
     
         19 . The method of  claim 10 , further comprising a hopper located at the top of the mandrel for feeding aggregate into the feed tube of the mandrel. 
     
     
         20 . The method of  claim 10 , further comprising a closure cap on an end of the feed tube opposite the tamper head and a concrete supply tube connected to the feed tube. 
     
     
         21 . The method of  claim 20  further comprising an air pressure source connected to the feed tube for evacuating concrete from the feed tube through air pressure supplied thereto.