DYNAMIC REPLACEMENT (DR)

TECHNIQUE:

Dynamic replacement is an extension of the Dynamic Compaction process that is applicable for use on highly compressible and weak soils. In this application (DR), the tamping energy drives imported, or site won, granular material down into the compressible soils to form large diameter soil reinforcement columns. Additional improvement can be obtained in the underlying layers through the transmission of the DC energy to depth. This method thus combines advantages of both Dynamic Compaction and stone columns by creating large-sized Dynamic replacement inclusions with high internal shear resistance to promote compaction, and consolidation and reinforcement of the soils.

Dynamic replacement columns are formed by dropping a 10 to 35tons pounders from height ranging 10m to 30m as determined by the soils and settlement and bearing capacity required. With this technique, replacement ratios of us to 10 to 35 % can be achieved. Where the site use is not fully known or designed, DR can be used to treat an entire area on a grid pattern to give a uniform improvement in conjunction with a suitable capping or transition layer (normally part of the subbase make up) or indeed if the foundation layouts are known then a DR pillar (or pillars) can be used to support foundation bases directly.

ADVANTAGES:

  • Increases soil bearing capacity.
  • Reduces total and differential settlement.
  • Reduces the potential of liquefaction.
  • Dynamic replacement is well adapted to substantial loading conditions (up to 150 tons per column) as well as under embankments to improve the factor of safety against slope failure.
  • Dynamic replacement columns can increase the time rate of consolidation due to their draining potential.
  • High production rate can be achieved in comparison to other techniques