Proposal of a New Parameter for the Weathering Characterization of Carbonate Flysch-Like Rock Masses: The Potential Degradation Index (PDI)

Abstract

The susceptibility of clay bearing rocks to weathering (erosion and/or differential degradation) is known to influence the stability of heterogeneous slopes. However, not all of these rocks show the same behaviour, as there are considerable differences in the speed and type of weathering observed. As such, it is very important to establish relationships between behaviour quantified in a laboratory environment with that observed in the field. The slake durability test is the laboratory test most commonly used to evaluate the relationship between slaking behaviour and rock durability. However, it has a number of disadvantages; it does not account for changes in shape and size in fragments retained in the 2 mm sieve, nor does its most commonly used index (Id 2) accurately reflect weathering behaviour observed in the field. The main aim of this paper is to propose a simple methodology for characterizing the weathering behaviour of carbonate lithologies that outcrop in heterogeneous rock masses (such as Flysch slopes), for use by practitioners. To this end, the Potential Degradation Index (PDI) is proposed. This is calculated using the fragment size distribution curves taken from material retained in the drum after each cycle of the slake durability test. The number of slaking cycles has also been increased to five. Through laboratory testing of 117 samples of carbonate rocks, extracted from strata in selected slopes, 6 different rock types were established based on their slaking behaviour, and corresponding to the different weathering behaviours observed in the field.

Influence of Water Content on the Mechanical Properties of an Argillaceous Swelling Rock

“…Adicionalmente, dentro de los factores que depende de la meteorización diferencial se encuentran el desleimiento el cual es un fenómeno que consiste en la desintegración en partículas de las rocas que contienen minerales arcillosos debido a su interacción con el agua, lo cual es común cuando se exponen a la atmosfera; esto es normal en áreas cuyo clima se caracteriza por la ausencia de heladas y hay gradientes de alta temperatura y ciclos de humedecimiento y secado por lluvia y humedad atmosférica (Cano & Tomás, 2016).…”

Weathering Influence on Properties of Siltstones from Istria, Croatia

“…is equal to 0 for nondurable rocks and to 1 for completely durable rocks. The modified disintegration ratio is a similar parameter and it is equal to the ratio of the area under the fragment size distribution curve of the passed fragments to the total area that encompasses the range of fragment size distributions [18]. Different graphs are used to determine these parameters, so is equal to 1 for the maximum degree of degradation.…”

“…This method quantifies 2 Advances in Materials Science and Engineering the fragment size distribution of the slaked material by calculating the disintegration ratio for five slaking cycles. A new weathering characterization based on a newly proposed potential degradation index was introduced by Cano and Tomás [18]. This method analyzes changes in the fragment size distribution curves that are obtained from the material that is retained in the testing drum after each slake cycle.…”

Effect of different buried depth on the disintegration characteristic of red-bed soft rock and the evolution model of disintegration breakage under cyclic drying-wetting

“…According to recent studies, the cyclic drying and wetting process has emerged as a prominent determinant in the disintegration mechanism of red-bed soft rock 24 – 26 . Moreover, a number of scholars have introduced valuable disintegration indices 27 – 30 aimed at characterizing the slaking behavior of rocks under cyclic wetting and drying (WD) conditions. Sadisun et al 31 and Zhou et al 32 underscored the diminishing trend observed in the durability index with escalating numbers of drying-wetting cycles.…”