Engineers Australia

Invalidity of Relative Density for Quality Control of Cohesionless Soils

Babak Hamidi

The concept of relative density (density index) compares the in situ or as placed density of a coarse soil with its index loosest and densest states. This concept was first considered almost 90 years ago and is still a popular tool among geotechnical professionals to assess the state of packing of granular soils and to provide a relative measure for construction quality control purposes.

In the last 40 years the relative density concept has been widely researched and reviewed by academics and engineers around the world, with many published references suggesting that calculated and correlated relative density values may not always be reliable. The speaker will introduce the origin and summarise the evolution of the concept, providing insights that highlight some of the potential sources of measurement error and limitations on the applicability of this concept and its correlations for soils. The speaker will consider the relationship between relative density and soil performance, the influence of mineralogy and geological history on soil properties and will explain why placing reliance on relative density values to assess construction quality could pose a significant technical risk to projects.

Speaker biography

Babak has been involved in civil engineering projects since graduating from university in 1988 and he has spent the majority of his career involved in the design and construction of specialist geotechnical contracting works. Babak’s experience includes involvement in projects totalling more than 10,000,000 m2 of ground improvement and thousands of driven piles. He also has extensive practical experience in the construction of diaphragm walls and permeable and impermeable in-ground barriers.

Babak joined the Soletanche Freyssinet Group in 2002 and his current role is Marketing Manager for GFWA. Working across this group of companies, including Menard Bachy in Australia and Menard in the Middle East, Babak has gained project experience in Australia, UAE, Oman, Bahrain, Iran, Qatar and Saudi Arabia.

Babak is an active member of AGS WA Chapter Committee and represents Australia on the ISSMGE Ground Improvement Technical Committee (TC211). He has been awarded Bachelor’s and Master’s degrees in civil engineering and geotechnical engineering and is currently working towards PhD at Curtin University on the subject of dynamic compaction. Babak has authored and co-authored about 40 papers on ground improvement.

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