Comportamiento hidro-mecánico de agregados gruesos
- Autores: Clara Alvarado de Menendez
- Directores de la Tesis: Eduardo Alonso Pérez de Agreda (dir. tes.), Enrique Edgar Romero Morales (codir. tes.)
- Lectura: En la Universitat Politècnica de Catalunya (UPC) ( España ) en 2017
- Idioma: español
- Tribunal Calificador de la Tesis: Antonio Lloret Morancho (presid.), Francesca Casini (secret.), Marisa Pinheiro (voc.)
- Programa de doctorado: Programa de Doctorado en Ingeniería del Terreno por la Universidad Politécnica de Catalunya
- Materias:
- Enlaces
- Tesis en acceso abierto en: TDX
- Resumen
Rockfill is a coarse material widely used in geotechnical works such as earth-fill dams (shoulders and toe drains), as well as in embankments and well-graded quarry materials for railway infrastructures. These structures are usually submitted to significant changes in water content and to the permanent action of water during the different stages of construction and along the long-term behaviour after construction. Despite being coarse materials they are very sensitive to the action of water, undergoing collapse deformations on wetting, as well as time-dependent deformations associated with particle breakage (sub-critical crack propagation) and their subsequent rearrangement.
This experimental study evaluates some important aspects of these coarse aggregates (slate gravels from Lechago dam, Teruel) in relation to their interaction with water. Particularly, it addresses the long-term volumetric deformations of the material with emphasis placed on particle size, the effect of stress history, and on the current state of stresses and suctions (overconsolidation ratio), as well as on the effect of void ratio (cumulative volumetric deformation). Different phenomenological constitutive expressions have been proposed, which take into account all the aspects mentioned above and allow properly reproducing the long-term experimental results.
As an alternative to the control of total suction through the relative humidity of vapour, this research has explored the effect of controlling the activity of the liquid (water molecules available to induce environmental action on crack propagation) on the hydraulic and mechanical response of the coarse slate aggregates. Experimental protocols have been developed that have allowed the gravel skeleton to be flooded with different saline solutions, as well as performing particle splitting tests (indirect tensile tests). These tests have allowed comparing the kinetics and steady-state conditions of the response at both particle and material scales, when controlling the relative humidity by vapour or alternatively the activity by liquid. This part of the research has focused on the compressibility of the material under oedometer conditions on loading at different suctions, as well as on the volume change behaviour induced by suction changes at constant vertical stress. The results have shown larger compressibility values and lower tensile strengths of the particles when the total suction has been controlled by the activity of the liquid. To help in the interpretation of the results, a phenomenological constitutive expression has been proposed. This expression corrects the total suction associated with the activity of the liquid by a reduction coefficient that depends on the liquid activity (equivalent to an osmotic efficiency).
The kinetics of the processes (vapour diffusion for relative humidity control and diffusion of solutes for the liquid activity) has been simulated on a cylindrical particle with the program CODE_BRIGHT. These simulations have included a specific law for tensile strength as a function of total suction, as well as mass transport parameters that have been measured in the laboratory.
In addition, a new triaxial cell has been developed to study the shear strength properties and the dilatancy induced on shearing by the coarse aggregates at different total suctions. This equipment allows testing samples up to 200 x 400 mm with total suction control and with a novel system of local radial measurements placed on two orthogonal planes of the sample and at different heights. The equipment has been calibrated and some preliminary results have been presented, which can be used as database for future research on this topic.
