Comparison of Aggregate Stability Measurement Methods for Clay-rich Soils in Asartepe Catchment of Turkey

There are many methods and approaches of determining the structural status of soils as a quality indicator. But there is no common method for aggregate stability measurement that can be used for all soil types and circumstances affecting aggregate disruption. This study aimed to compare different aggregate stability methods for clay-rich soil systems of semi-arid lands, where desertification is a significant threat to land resources. The study area is located in the Asartepe catchment of Ankara, Turkey, mainly including land use types of secondary forest, grassland and rainfed arable land. Four research methods were tested: (1) fast wetting (FW); (2) slow wetting (SW); (3) mechanical breakdown (MB) and (4) multiple sieve separation process (MSSP). For clay rich soils (C%38) with different land use types in the semiarid region, it was found that MSSP has a greater potential for soil aggregate stability differences to statistically reflect slight variations in SOC than FW, SW and MB. Although the research specifically includes the results from certain land uses and soil types, it is not limited to those but should provide useful findings to help interpret the impairment of soil structural stability differences under various management systems and the processes that each methodology tries to reproduce in a close linkage to given soil properties. Copyright (c) 2015 John Wiley & Sons, Ltd

Effect of mineralogical properties of expansive soil on its mechanical behavior

Expansive soil contains montmorillonite clay mineral; which has tendency to swell by imbibing water in monsoon season and shrink or become harder by leaving cracks in drier seasons. Excessive drying and wetting of soil progressively deteriorates structures over the years and cause severe damage. Some research has been performed on identification of expansive soil and determination of its expansiveness and shrinkage–swelling potential based on its index properties at various wetting–drying conditions. Few researchers worked on the chemical stabilization of expansive soil to improve its mechanical behavior. However, the relationship of mineralogical properties of expansive soil with its shear strength and compressibility parameters is still unexplored; and these parameters are required in bearing capacity and settlement calculations for soil strata. The current research is focused on relationship of mineralogical properties (CEC, SSA, montmorillonite content) of expansive soil with its mechanical behavior including compressibility, shear strength, swelling potential and index parameters. This experimental research has been performed on expansive soil (black cotton soil) covering major part of Bhavnagar, located along the coast line of Gulf of Khambhat in Gujarat (India), which has serious construction issues due to its severe shrinkage–swelling behavior.by Bhavini Mehta and Ajanta Sacha