Preliminary relationship between weathering behaviour profiles and laboratory slake behaviour of carbonatic flysch rocks M.Cano & R. Tom´ as & A. Riquelme Departamento de Ingeniera Civil. Escuela Politcnica Superior, Universidad de Alicante, Spain ABSTRACT: Various studies indicate that most of the slope instabilities affecting heterogeneous rock masses are related to differential weathering and erosion of the lithologies that outcrop in the slope. However, not all these rocks behave similarly, exhibiting considerable differences in the rates and ways of degradation. Thus, it is very useful to link the laboratory tests and the behaviour of the same rocks observed in the field. The slake durability test (SDT) is a worldwide used test to assess the relationship between the slake and durability of rocks. However, it presents some well-known drawbacks, as it does not consider the changes in the shape and the size of the rock fragments retained in the 2 mm sieve mesh of the drum. Furthermore, it is also necessary to perform more than 2 cycles, as in the original test, to better characterize the evolution of the specimens. The main aim of this work is to describe the weathering behaviour of carbonate lithologies that outcrop in heterogeneous flysch- like rock masses slopes by means of the study of the evolution of the fragments retained in the drum along the SDT cycles. For this purpose, the evolution of the fragments along the cycles is standardized based on three factors: rounding, variation in the number of pieces and the size of the fragments. Finally, different slaking behaviour patterns are defined and related to the weathering behaviour patterns and profiles, and weathering rates observed in the field. 1 INTRODUCTION The instability mechanisms of heterogeneous slopes are closely linked to the weathering behaviour of the different lithologies which outcrop in the slope. In these slopes, instabilities resulting from differen- tial erosion/degradation are very habitual (Cano and Tom´ as, 2013a,b). Throughout the service life any work, whose construction results in the creation of slopes, is permanently exposed to the atmosphere. Thus, weathering can induce slope instabilities, re- sulting in significant maintenance and repair costs that may pose a significant safety hazard. Some- times, these processes trigger the failure of the en- tire slope, either suddenly or gradually. Additionally, these degradation processes can often be considered as failure mechanisms by themselves, rather than just triggering factors. Thus, the problem of slope stability along time should also be considered, in case they are not protected against weathering processes (Miscevic and Vlastelica, 2014). The slaking consists of the disintegration of clay- bearing rocks due to their interaction with water, mainly when they are exposed to the atmosphere. In areas whose weather is characterized by the ab- sence of frosts and high temperature gradients, such as the study area (AEMET, 2012), the weathering of the different lithologies is mainly caused by drying- wetting cycles due to rainfall and atmospheric mois- ture. Therefore, in these areas the study of slaking is intrinsically linked to weathering behaviour. The slaking resistance depends on different parameters commonly cited in literature as permeability, poros- ity, adsorption, mineralogy, microscopic texture, mi- crofabric, presence of microfractures, etc. (Gamble, 1971, Franklin and Chandra, 1972, Richardson and Long, 1987, Taylor, 1988, Dick et al., 1994, Dick and Shakoor, 1995, Erguler and Shakoor, 2009, Kaufhold et al., 2013, Gautam and Shakoor, 2016, Cano and Tom´ as, 2016). This makes the characterization of slaking behaviour in rocks using a single parameter extremely complex (Erguler and Ulusay, 2009, Gau- tam and Shakoor, 2016). The weathering susceptibility of clay-bearing rocks is known to influence the stability of heteroge- neous slopes, as it may result in differential ero- sion/degradation. However, not all of these rocks ex- hibit the same behaviour. Considerable differences in the manner of degradation and time taken to degrade may be observed. Moreover, in carbonate lithologies, the more marly lithotypes are responsible for this differential degradation (Cano and Tom´ as, 2013a,b, 2016, 2015). For this reason, it is extremely impor- tant to link slaking behaviour quantified in the labora-