Ground Improvement Specialists.

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Dynamic Compaction

Dynamic Compaction is used to achieve deep ground densification for building foundations, or road and rail embankment foundations, on loose materials. This technique uses the dynamic effect of high energy impacts, caused by dropping large steel weight weighing 15 to 40 tonnes from a height of 10-30 metres.

Dynamic Compaction was invented by Louis Menard in the late 1960’s and has been developed on numerous sites and applications since this time.

The basic principle behind the technique consists in the transmission of high energy waves through a compressible soil layer in order to improve at depth its geotechnical properties. Dynamic Compaction is normally associated with an intensive programme of insitu-testing in order to verify the that the specified improvement has been achieved.

Dynamic Compaction is applicable to all types of granular soils. This technique is particularly well adapted to non-organic, non-homogeneous fill, made ground, and reclamation areas with variable characteristics, even where underground obstructions are present.

Dynamic Compaction is effective in both saturated and un-saturated soils. Typically this technique should not be carried out within 15m of existing services and 30m from existing buildings.

Method
10-40 tonne weights are propped in free or quasi-free fall, from a height of 10-30m. The spacing of the impact points and the unit energy, phasing & rest periods, depend on the soil types and level of improvement required. Specially designed 80-120t. Cranes are normally used. Designs are normally confirmed by on site pilot test areas or calibration zones.

Dynamic Compaction Stages

  1. The immediate effect is normally predominant and results in the immediate reduction in the void ratio, measured by the settlement after impact.
  2. A slower phenomenon occurs in some saturated soils caused by the increase in pore pressure and localised liquefaction. This dissipates during the rest period and results in an improved soil due to the reorganised soil structure.

High Energy Dynamic Compaction
For compaction of soils to more than 10-12m, High Energy Dynamic Compaction can be performed. This technique employs High Energy of more than 600 t.m using drop weights of more than 30t, drop heights of more than 30m and cranes
weighing more than 120t.

High Energy Compaction uses specialist equipment including free fall drop weights requiring a specially designed weight release system using hydraulic clamps to avoid cable damping and friction, plus repeat cycle lifting hooks, shown above.

Due to the greater treatment depths of High Energy Dynamic Compaction the design of the work phases is particularly important, in order to obtain an homogeneous compaction over the thickness of the soil mass.

  • Advantages

    • Compacts large areas of loose granular fills
    • Reduces the volume of landfill waste
    • Increases insitu density and collapses voids
    • Increased bearing capacity
    • Reduces post-construction settlements
  • Applications

    • Port and Airport Platforms
    • Heavy Storage Facilities
    • Landfill sites
Download the Dynamic Compaction pdf