The relationship between Schmidt hardness values, uniaxial compressive strength and index properties of weak rocks

Most of the natural stone around the city of Denizli are weak rocks that composed of different travertine types. Operated travertine types in the area can be classified as shrub, reed, noche and crystalline crust type’s travertine. Uniaxial compressive strength of the travertine in the study area ranges from 30 to 80 MPa. Besides that, Black colored dolomite rocks occupies in Bozkurt that is one of the county of Denizli. Strength of the dolomite varies from 80-100 MPa. Clay limestone (Limra) that strength ranges from 30-45 MPa is operated around Elmali County in Antalya and Beige Limestone (80-100MPa) operated in Korkuteli Antalya. Both beige and limestone are wanted type of rocks from the scope of natural stone industry. The county of Bekilli in Denizli has schist also named as kayrak that has strength rages from 90-110MPa and it can be used as cladding side wall of buildings and gardens. Types of travertine in Denizli demonstrate different physical and chemical properties due to included organic materials, amount of clay, void ratio, and texture. According to physical and textural feature, investigated travertine types in field are as follows;
Shrub type travertine can have a color from light cream to light brown; and show irregular lamination that can be ranges from a couple mm to cm.
Reed type travertine was deposited in mash environment. The carbonate precipitation was happened around the grass rood and it causes high porosity and different texture.
Noche type travertine can be dark brown to light brown color. It is dense and the strength of the rock is higher than reed type travertine but depositional condition are slightly different that reed type travertine.
Crystalline crust type travertine that is dense, light color, demonstrates calcite crystal as perpendicular to depositional surface. Strength of this type travertine is higher than reed and noche types but lower than shrub type travertine.
Besides travertine types, dolomite, beige limestone, clayey limestone and schist were gathered from different field to conduct related testing programs.
Dolomite can be classified as medium strength rock. It is operated in the county of Bozkurt in Denizli. It is dense and compact; however it does not show homogeneity.
Beige Limestone that is one of the quarry materials was operated in Korkuteli, Antalya. It demonstrates heterogenic texture, micro-fractures and also classifying as medium strong rock.
Limra limestone that is operated in Elmalı county of Antalya has low strength and high clay content; thus water absorption rate of the rock is relatively high.
Kayrak stone (schist) are commonly occupies in County of Bekilli in Denizli. This type of rock composed of mica, quarsite; thus it can be stronger than expected. They are classified as medium to high strong rock; however, along the cleavage lines, its strength is low and can be easily pull apart.

In this study, 8 different rock types that are operated around the city of Denizli were investigated according to their physical and mechanical properties. The properties including natural unit weight (, density (), water absorption (w), porosity (n), fullness ratio, uniaxial compressive strength (c) and Schmidt hardness (Hs) were investigated using ISRM (International Standard for Rock Mechanics) and TSE (Turkish Standard) standards. For each type of test, 10 samples were prepared and the tests were conducted; after that the average values of these tests were recorded in order to establish dataset. Using established dataset, the relationship between Schmidt hardness, uniaxial compressive strength and basic physical properties including unit weight, density, porosity, and water absorption rate were investigated. As a result, in this study Schimdt hardness values were related with measured basic rock properites and uniaxial compressive strength of rocks. Obtained equations can be used for weak strong rocks with some limitstions during the early stage of the investigation. Further, generated dataset can be expanded and so developed equations can be updated to obtain better accuracy.