Relationship between micromorphological characteristics and engineering parameters of caliche (calcrete)

Caliches are described as secondary carbonate formations and calcareous, semiconsolidated aragonite or early diagenetic calcite forming in loose materials such as pebble, sand, silt, and soil under semi-arid and arid climatic regimes. The aim of this study is to identify and discuss effects of micro-morphological-mineralogical properties on engineering properties of caliche. Furthermore, correlations derived from mechanical, physical-index properties and micromorphological characteristics are evaluated and establish statistically predictable model for UCS. For this aim, samples were taken from different locations in caliche outcrops occurring in the southern part of Turkey. Based on the statistical analyses, linear relationships were fitted between the Micromorphological index (MI) and each mechanical and physical-index properties. Based on these linear relationships among the engineering properties, uniaxial compressive strength, Pwave velocity, average Young's modulus and point load index there are significant correlations with the micromorphological index (MI). Results suggested that strength of the caliche is controlled by micromorphological properties. Four micromorphological parameters which are effective on engineering properties of caliche were identified: Microstructure, voids, coarse materials and matrix. Microstructure is the most important parameter to assess engineering behaviour of caliche followed by voids, coarse materials and matrix. Statistically most reliable models, which allow the estimating of UCS, are discussed in this study. The empirical equation, UCS = - 7.137 + 3.06x10-3 Vp + 0.38UW + 0.13MI where Vp = P-wave velocity; and UW = Unit weight is assumed to be the best and practical for engineering purposes