Dynamic Replacement DR

Description

The Dynamic Replacement (DR) Technology involves constructing large diameter aggregate columns in cohesive soil. The columns are formed by a heavy pounder with a weight ranging from 15 to 30 tons drops from a height ranging from 10 to 30 m. A single column is formed by a few series of pounding. The churning process begins in a shallow trench filled with mineral aggregates. The first series of impacts forms a crater in the substrate, which is refilled with the charging material. Another series of aggregate refills into the excavation and compactions are repeated until the formation of a DR column according to the project objectives. Often the end of the column forming is indicated by a thud combined with a sudden reduction of the pounder penetration value. Large diameter (1.6 to 3.0 m) columns are driven to a depth ranging from 4 to 7 m. The 0,5-1,0 m of stratum surface is compacted with heavy vibratory rollers.

Application

DR columns can act as piles with an extended head for stabilisation of road or rail embankments where the columns improve the stability and increase the safety factor of the embankment. These columns are also successfully applied to reduce the foundation settlement of commercial and industrial buildings and to stabilise landfills.

DR columns can be constructed both in loose non-cohesive and firm soils, soft cohesive soils as well as in organic deposits. Natural aggregates, post–production material (slag, sinters), concrete rubble, crushed asphalt and construction rubble (without wood or metal parts) can be used to form the DR columns. It is necessary to use multigrain materials with the clay fraction below 5%. Typical penetration depth range from 4.0 to 7.0 m and reach a dimeter of 1.6 to 3.0 m. Spacing of columns depends on the transmitted loads and soil conditions. Usage of this technology is associated with generating a shock wave, which can adversely affect the adjacent building structures, therefore it is advisable to conduct work using DR method at a distance of at least 50m away.

Advantages

  • Solidly formed: the column forming technology gives them a stocky shape which guarantees that no washouts nor bulging of the DR columns occur.
  • Global strengthening – carried out as the formation of a column and improvement of the mechanical properties of the soil between the columns;
  • Environmentally friendly: the DR columns can be formed using recycled material (concrete rubble, coarse grain rubble, gravel, etc.).
  • High performance – DR technology is characterized by very high efficiency, reaching up to several hundred square meters of reinforced substrates for the day (using a single kit for making DR columns).