First Application of HSS Small Model for Weak Rock Characterisation in Dubai

We are proud to announce the successful application of the Hardening Soil Small-Strain (HSS) Model for the geotechnical characterisation of weak rock in Dubai,  the first of its kind in the region.

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Until now, the mechanical behaviour of Dubai’s soft to weak rock formations has typically been assessed using conventional models such as the Mohr–Coulomb model, calibrated with routine laboratory tests. While widely adopted, this simplified approach presents limitations for design engineers, predicting dilatancy and stiffness at small strain levels. The resulting uncertainty often leads to conservative foundation design, with overstated settlement predictions, inflated safety factors, and unnecessarily high construction costs. Additionally, the lack of detailed material behaviour characterisation could introduce geotechnical risks that may not be identified during design.

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In this project, for the first time, Dubai’s rock was characterised using the HSS Small-Strain model framework. The scope of work included:

•    Chanracterisation of the non-linear stress–strain behaviour of the weak rock with explicitly expressed using mathematic functions with curve fitting coefficient obtained from factual test data.
•    Definition of the shear modulus reduction curve, specifically the reference shear strain γ₀.₇, at which the secant shear modulus reduces to 70% of its initial small-strain value
•    Evaluation of small-strain stiffness (G₀) as a function of effective stress
•    Determination of stress-dependent stiffness parameters, including:
o    E₅₀: secant modulus for primary loading
o    Eᵤʳ: modulus for unloading/reloading
o    Eₒed: one-dimensional modulus from triaxial K₀ consolidation
•    Measurement of shear strength parameters, including friction 
angle and cohesion and dilatacny friction angle of Dubai rock 
•    Determination of K₀ value and Poisson’s ratio
This advanced characterisation now enables more accurate and reliable predictions of pile foundation beahviours, including settlement and pile capacities, etc. The adoption of this framework is expected to contribute significantly to cost optimisation, saving millions of dirhams in foundation construction, while enhancing the technical robustness of the design.

 

We are honoured to have supported the JANU Project, with econstruct and AECOM as the appointed consultants. The work has been officially approved by the Dubai Authority, marking a significant milestone in the application of advanced geotechnical modeling for urban development in the UAE.

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For further technical details, please contact our engineering team.