How do you know if ground is compacted enough? HENGDA RIC

Rapid Impact Compaction provides a technically sound and economic method of improving the capacity of a wide variety of loose soils and fills. The Rapid Impact Compactor can work alone on some types of strata (effective treatment in the top layers of typically up to 6 m depth) or in conjunction with other ground improvement techniques, e.g., Deep Dynamic Compaction, where the strata´s depth or grain sizes dictates. Due to the numerous benefits, e.g., compaction control through an on-board computer, operation at safety, quality assurance, versatility and speed, the Rapid Impact Compaction system will become well-established in the dynamic compaction field. Further research, including theoretical, numerical and practical studies, is nevertheless essential to enhance the innovative compaction system. 

The RIC is an innovative dynamic compaction device based on the piling hammer technology and is used to increase the load-bearing capacity of soils through controlled impacts. The general idea of this method is to drop a falling weight from a relatively low height onto a special foot assembly at a fast rate while the foot remains permanently in contact with the ground.

The technique can usually be employed within 10-15m of sound structures with the vibrations significantly less than traditional dynamic compaction. RIC can also be used in shallow granular fills containing contaminants where penetrative ground improvement techniques such as Vibro Stone Columns would risk exposing contaminants to the atmosphere.  

Use of RIC will result in an increase in soil density, stiffness, and angle of internal friction as measured by an increase in SPT N-value, CPT tip resistance or other means of insitu test. The recommended approach is to determine what level of improvement is desired and discuss that required improvement with your technical representative for feasibility. For example, a 2-story commercial light industrial structure is to be constructed on a site underlain by up to 10 ft of existing sandy fill soils. SPT N-values range between 4 and 8 blows per foot (bpf) in the fill. The geotechnical engineer’s correlation between SPT N-Value and soil stiffness for footing settlement analyses indicates that an average N-value in the fill needs be 10 bpf. The geotechnical engineer would perform settlement analyses using the foundation sizes and loading provided by the structural engineer to confirm that the footings will perform acceptably if the fills are improved to 10 bpf. A review of the borings logs indicates that this level of improvement is achievable with RIC. The geotechnical engineer would then complete his or her report with a recommendation that RIC be used to compact the fills in place and that an N-value of 10 bpf will be required.

Rapid Impact Compaction consists of an excavator-mounted, hydraulic pile-driving hammer repeatedly striking a circular plate that rests on the ground.  Energy is then transferred to the ground safely and efficiently, as the RIC’s foot remains in contact with the ground, which avoids concern over flying debris being ejected. Rapid Impact Compaction densifies loose-fill soils of up to 6 m deep or more. Additional benefits of rapid compaction include: an increase of the bearing capacity of the soils, minimization of settlement, and the creation of uniform support for foundation footing. Rapid Impact Compaction is an innovative solution when compared to the time and cost of over-excavation and re-compaction.