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Engineered Aggregate Pier Installation

GeoRam® Engineered Aggregate Pier elements are constructed by densely compacting successive “lifts” of aggregate in pre-drilled shafts. These shafts typically have 18” - 36” diameters, and typically 1’ to 2' of aggregate is compacted in each lift, depending on tamper energy used. Different than a vibrated pier, installation of the Engineered Aggregate Pier uses a specialized beveled tamper. This forces the stone laterally in addition to vertically down. The result is a significant increase in lateral stress and pre-stressing of foundation supporting soils around the pier.

The construction process for Engineered Aggregate Piers is project friendly in terms of simplicity, speed, cost, and reliability. The following illustrates the construction process:

The Vertical Ramming Process:

  1. Predrilling allows you to see the soil between borings ensuring that the piers are stabilizing the right soils.
  2. Each layer of aggregate is placed in thin lifts and rammed with vertical impact energy, creating a high degree of compaction, resulting in high strength and stiffness.
  3. The specialized beveled tamper forces the thin lifts of aggregate into cavity sidewalls resulting in excellent coupling and superior settlement control.
  • The three-step process continues until the Engineered Aggregate Pier is constructed. The high-energy compaction process produces significant lateral prestraining and prestressing of the adjacent matrix soils that increases the lateral stress in the adjacent soils. The improved soils essentially "grab and hold" the very stiff Engineered Aggregate Pier element and, thus, improve the strength and stiffness of the combined pier-soil system.
  • Pier cavities are typically excavated by conventional drilling techniques, using either truck-mounted auguring equipment or "dangle drill" equipment mounted on an excavator or crane.
  • Since Engineered Aggregate Piers are constructed in pre-excavated cavities, there is essentially no remolding of the surrounding soils, as occurs with other stone column techniques. Hence, with the GeoRam technique the surrounding soils cannot experience strength loss due to the construction methods, but rather gain a significant increase in stiffness as each lift of aggregate is rammed. Other aggregate pier systems simply cannot achieve this result.
  • By constructing Engineered Aggregate Piers in clusters spaced from about 1½ to 3 diameters apart, the GeoRam-reinforced soil mass experiences significant permanent prestressing, which greatly improves its strength and consolidation characteristics (extending several feet beyond the outside piers). Hence, the so-called "group effect" is very desirable for the GeoRam engineered system because it improves performance.
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