Structure and Mechanical Properties of the Dueñas Clay Formation (Tertiary Duero Basin, Spain): An Overconsolidated Clay of Lacustrine Origin

José Nespereira,Mercedes Suárez,José Antonio Blanco,Mariano Yenes,Serafín Monterrubio,Emilia García-Romero

doi:10.3390/app112412021

José Nespereira, Mercedes Suárez + Show 4 more

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https://doi.org/10.3390/app112412021

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Abstract

The Dueñas Clay Formation is considered an example of a deposit of lacustrine continental origin. It is formed mainly by overconsolidated clays and includes feldspathic arenites, and clayey and silty levels; however, in geotechnical projects it is considered a clay unit and treated as a whole. The structure of each level was assessed in the field, in thin sections, and by SEM in the case of the clayey level. In addition, identification, strength, deformation, and durability tests were undertaken according to the nature of the samples (grain size analysis, Atterberg Limits, point load test, direct shear tests, uniaxial compression tests, swelling pressure, and unidimensional consolidation tests). The durability test was used as a criterion for dividing the levels within the formation according to their behavior as soil or rock. It was observed that the proportion and type of carbonate cementation controls the way in which the material behaves, with sparithic cement increasing the strength. The clay levels are expansive due to the presence of smectite, which also influences their behavior under shear stress. In addition, the massive and laminar structure of the layers caused by the continental conditions, in addition to the processes of post-sedimentation, explain their low compressibility.

Highlights

Overconsolidated clays (OCs) do not have poor mechanical properties but their discontinuities and cementations, in addition to the difficulties in defining realistic behavior models [1,2], justify their study
Marine and continental overconsolidated clays (MOCs and COCs, respectively) share common geological episodes, such as sedimentation, consolidation, bioturbation, erosion, diagenesis, and tectonic activity, all of which are included in the Geotechnical Cycle [15]
When the properties that differentiate them are taken into account, such as water composition, sedimentation rates, air exposure time, crusting processes, or cracking desiccation, is the geomechanical behavior the same? In addition, are their structures similar and what is the effect of the geological history?

Summary

Introduction

Overconsolidated clays (OCs) do not have poor mechanical properties but their discontinuities and cementations, in addition to the difficulties in defining realistic behavior models [1,2], justify their study. Many OCs have been studied in soil mechanics, but most of these were sedimented within geological contexts defined by marine basins [3,4,5,6,7,8,9,10,11]. A common feature of all these clays is that their geomechanical behaviors depend on their structural configurations, and these are the results of their geological histories. Marine and continental overconsolidated clays (MOCs and COCs, respectively) share common geological episodes, such as sedimentation, consolidation, bioturbation, erosion, diagenesis, and tectonic activity, all of which are included in the Geotechnical Cycle [15]. When the properties that differentiate them are taken into account, such as water composition, sedimentation rates, air exposure time, crusting processes, or cracking desiccation, is the geomechanical behavior the same? In addition, are their structures similar and what is the effect of the geological history?

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