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Geopier Impact - Displacement Rammed Aggregate Pier

The Geopier® Impact® system is an efficient and cost-effective intermediate foundadtion solution for the support of settlement-sensitive structures. The Impact® system, like Geopier® GP3, creates stiff Rammed Aggregate Pier® (RAP) elements using a patented vertical ramming process.  The Geopier® Impact® system is extremely cost effective for installations in soils subject to caving because construction is facilitated using a patented displacement mandrel.  It can replace massive overexcavation and replacement, deep foundations, including driven piles, drilled shafts or augered cast-in-place piles.  This high-performing system provides unsurpassed strength, stiffness and superior levels of performance.

Construction Process
 
  1. ​Push/Vibrate a chained mandrel head into the ground to the desired pier depth.
  2. Fill mandrel and hopper with stone sufficient to build the pier.
  3. Raise the mandrel up to preset distance while discharging stone.
  4. Push/vibrate mandrel down a preset distance minus the planned list thickness to create a compacted lift.
  5. Repeat steps 3 and 4 until pier is complete. 
 
Options
  1. Grout can be added at the start and during the process to creat a stiffer and less permeable Impact element.
  2. Concrete can be substituted for stone to create a GeoConcrete Column.
How Impact RAP Works
 
The installation process displaces soil during installation and utilizes vertical impact ramming energy to construct vertical displacement rammed aggregate pier elements.  The cavity is created to full depth by pushing a specially designed chained mandrel head using a relatively large static force augmented by dynamic vibratory impact energy.  The chains allow stone to flow through the mandrel when it is raised up and form a plug to compact the stone when the mandrel is pushed down.  Pier diameters range from 16 o 24 inches in diameter and can be driven to depths of 10 to 60 feet or more depending on the soil conditions and project requirements.
Advantages of Impact Pier Technology
 
  1. Easy construction in caving soils and high groundwater conditions - The Impact mandrel provides continuous casing of the hole.
  2. No Spoils - The Impact pier method is a displacement mehtod so in most cases it eliminates/minimizes spoils for sites with contaminated soils.
  3. Deep Liquefaction Mitigation - Since it can provide deep treatment to densify soils, it is excellent for liquefaction mitigation.
  4. Grouted Impact and GeoConcrete Columns - To acheive higher capacity and stiffness or for environmentally sensitive sites.