Abstract
This paper deals with the study of the physical and hydro-mechanical characteristics of a porous limestone rock. It concerns a historic rock located at El-Haouaria artificial caves on the seacoast in the Northeast of Tunisia. The rock, object of study in this work, has undergone serious alterations, thus compromising the safety of the monuments. This paper focuses on the mechanical behavior of a sedimentary rock with a variable porosity; covering a wide range varying from 25% to 55%. This study is interested in identifying the mineralogical composition and the microscopic structure of the main rocks constituting the historic monument. Several tests were carried out and they showed that the rock’s mineralogical composition was calcite and quartz. The grain dimensions constituting the rock are variable. Its porosity is inter-granular and connected. This porosity changes over time due to weather conditions. Unconfined compressive tests and tensile tests were carried out on several samples with various porosities and in some cases in various saturation states. The performed tests showed the effect of both porosity and water content (suction) on strength characteristics. However, despite the rock’s dependency on the water content, the role of porosity remains more emphasized. Then, porosity seems to be the main factor affecting resistance properties due to the increase of the porosity and due to its variation as a source of humidity. A ‘’Li and Aubertin’s Model’’ was applied to predict the compression and tensile strength dependency on porosity. It highlighted a strong concordance between experimental and analytical model results. All strength characteristics evolutions with porosity and suction make up essential results obtained in this study. This will provide us with the required input data for modeling in order to predict cave structure degradation and eventually to monitor crack propagation.
Highlights
Many geotechnical and geological studies require a deeper understanding of the behavior of porous rocks
It is interesting to note that even with only 0.1 MPa suction, the rock of the caves cannot fully saturate, which shows the importance of macro-porosity of the stone in El-Haouaria caves
The grains are of marine origin with a variable shape inducing a variable porosity
Summary
Many geotechnical and geological studies require a deeper understanding of the behavior of porous rocks. Our work is summarized in the identification of rock microscopic characteristics and the analysis of hydro-mechanical tests at different stages of porosity and humidity (compression and tensile tests), and this in order to scrutinize: The microstructure of complex sedimentary rocks of “El-Haouaria caves”, to determine the mineralogy, the intrinsic properties such as total porosity, pore connectivity, pore size distribution and particle size distribution, The water retention curve (WRC), which relates the water content to suction. Microscopic tests show that the shape and size of the constituent rock grass is variable from one sample to another, which causes variable porosity, cementation presence and its dissolution, creating some void between plants In this sense, several wetting and drying cycles were carried out on the samples in order to understand their effect on rock porosity. The link between mechanical and retention properties is used to explain water content-mechanical resistance dependency
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