Journal de géologie et géophysique
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Geomechanical Aspects and Suitability of the Limestone (Sulaiy Limestone Formation) for Foundation Bedrock, Sulaiy Region, Saudi Arabia

Abd El-Aal AK

The present study is a geomechanical study on the Sulaiy Limestone Formation Riyadh region, KSA which the limestone is the main rocks of the subsurface strata in this area. Due to high strength of rock formation, most of the buildings are designed on shallow foundations. Limestone strata may have cavities through its formation in some places which reduces the rock strength and increases its settlement. In our study, the geomechanical and physical analyses included point load strength (Is), uniaxial compressive strength (UCS), Schmidt hummer, dry density, porosity, permeability tests, (TCR), (SCR) and (RQD). The point load strength values are between 2.40 and 6.90 (Mpa). UCS of the different samples shows difference in values (55 to 143 MPa). Dry density shows slight differences in value (1.7 to 2.3 gm/cm3) with an average of 2.32 gm/cm3. Percentage of porosity is noticed by about (12%) and the lowest is (2%). The permeability is 22 milli Darcy (mD) (fair) and 202 milli Darcy (mD) (good). Schmidt hammer tests values are between 33 to 54. TCR is between 15-90%, SCR and RQD are between 20-90%. Then the allowable bearing stress is 18.90 kg/cm2. We can consider only 3.00 kg/cm2. The expected settlement is (Se=1.12 cm). Foundation level for building at 1.50 m below the lowest point on the ground surface. Finally, grouting should be added to fill the open cavities of limestone rock formation (if any) to the significant depth below footings before placing the foundations to gain more strength with reducing the limestone settlement.