Field characterisation of weathered Ankara andesites

This paper presents field and some index properties of weathered Ankara andesites, carried out over a period of 4 years. Ankara andesites are distributed widely around the city of Ankara, on which numerous important structures have been founded. Thus, the weathering characteristics of Ankara andesites, both from the engineering geological and the rock mechanics points of view are important. The field work involved assessment of the rock mass weathering grades, conduction of simple field tests, Schmidt hammer and point load tests on the rock materials, characterisation of discontinuities, and collection of representative samples from each weathering grade for laboratory testing. The relationship between the experimentally determined parameters and quantitative engineering geological descriptions provided a simple geological method for the assessment of the design parameters and mapping the distribution of mass weathering grades. As a result of the evaluation, an idealized weathering profile and the scale of rock mass weathering grades together with their range of thicknesses were proposed. Some index tests such as effective porosity, Schmidt hammer value (SHV), point load strength and seismic velocity, provided good relations with the degree of weathering.