1) What is the (DDI) Dynamic Deflection Instrument?
The DDI is a patented accelerometer that provides documentation of movements resulting from cyclic forces. Consistency of signal and durability of the equipment (calibration maintenance) have been proven through millions of cycles of use.
2) Does the DDI work in all soil types?
Yes, the DDI is applicable in all soil conditions.
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Research has been done in silts, sandy silts, silty sands, clayey silts, silty clays, sandy clays, clayey sand and random fills. The consistency and layering of these matrix materials has been seen in the instrumentation output. Soft layers produce larger signals during compaction operations and stiffer layers produce smaller signals.
3) Does the DDI work in groundwater?
Yes, the DDI is effective in groundwater.
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It is known that the degree of saturation of a matrix material influences compaction progress. This is also seen in the blow count and CPT data
In the matrix materials we have worked in, softer layers are evident as larger signals, stiffer layers produce smaller signals.
The following papers have been recommended as sources for additional information on the influences of groundwater within matrix materials:
4) How does the DDI change the aggregate pier construction process?
The DDI significantly enhances the construction process.
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The DDI enhances the construction process by tailoring the compaction effort based upon the variation in the matrix materials. Matrix materials are subject to variability in makeup, stiffness, moisture content, overburden pressure, layering, etc.
The Pier Compaction Performance Indicator (PCPI) provides the operator with continuous real time feedback of the compaction process allowing the operator to tailor ramming efforts.
The DDI enhances benefits the aggregate pier process provides (removing matrix soils, observing them for consistency with the widely spaced geotechnical borings and then replacing those matrix materials with materials having better engineering properties).
The instrumentation allows the contractor to construct a consistently stiff soil reinforced system specific to the soil matrix profile in plane and cross section, across an entire project site.
Every area and depth receives only the compactive effort necessary to achieve consistent reinforcement stiffness. Softer layers and areas, receive greater compactive effort, stiffer layers and areas, receive less.
5) HoW does it change the design process?
It does not change the design process. The DDI validates the design.
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Real time electronic documentation of construction provides the design team with verifiable documentation that the soil reinforcement construction was completed as designed.
Unlike random sampling or visual observation, the DDI provides calibrated, continuous data documentation of soil and rock compaction.
Differential settlement is typically the greatest concern for design performance.
Consistent construction of foundation support across the entire building structure limits differential settlement. Real time electronic documentation of construction results provides the design team with confidence that variation in matrix soils have been properly identified and properly controlled during the aggregate pier soil reinforcement construction process.
6) What research has been done to validate the DDI?
4 years of extensive research was completed in both laboratory and on-site settings prior to introducing the DDI to the market place.
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The use of shake tables and drop test stands have been used to validate millions of cycles of output from the DDI using consistent applications of force and deflection.
Impact force equipment, including drop and hydraulic hammers, have been used to conduct research on crushed aggregates, recycled materials, soils of varying types and conditions, concrete and asphalt. Research has been conducted on aggregate piers constructed in matrix soils of various types, layering and conditions.
7) What are the benefits?
- Consistent subgrade support of foundation, slabs and structures;
- Differential settlement control;
- As Built documentation of sub grade reinforcement construction;
- Millions of dollars saved through reduced liability of construction defects from foundation settlement;
- LEED certification enhancement through efficient use of manpower and natural resources based on the earth conditions across a site and at depth;
8) How much does the DDI cost?
Fees associated with DDI instrumentation are bid based on several factors including number of piers to be monitored, job duration, and site location.
A DFS trained technician will be provided with the DDI instrument to insure proper installation and monitoring.
Typically, the cost is less than ½% of total project cost.
Through the Contact page of the web site, please e-mail or call us with specifics on one of your projects.
9) HOW DO I GET STARTED?
Through the Contact page of the web site, please e-mail or call us, we will be happy to talk with you.
