Some mechanical properties of the Siwalik sandstones and their relation to petrographic properties

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Some physical and mechanical indices of sandstone samples which were systematically collected from the Siwalik Group，in Mid Western Nepal，have been measured in a laboratory．The measurements show that the dry density of the Siwalik sandstones ranges 2.35 to 2.59 gr/cm^3，and porosity is between 2.88 and 7.68 %．The　former is higher and the latter is lower in calcareous sandstone．Elastic wave velocity ranges from 1.59 to 4.36×10^3 m/sec，and the uniaxial compressive strength is of the order of 0.5 to 1.0×10^2 MPa．Both indices are higher in calcareous sandstone．These　indicates that cement materials such as calcium carbonate fill voids among grains in calcareous sandstone．
Uniaxial compressive strength，elastic wave velocity and elastic modulus are closely correlated to each other，and they have negative curvilinear correlation with porosity．These physical and mechanical properties of sandstones closely depend on lithofacies and the contents of calcium carbonate，and are rather independent of stratigraphical horizon or deposition age．These results indicate that such properties reflect the sedimentary environments that were prevelant during the formation of the sandstones．