Tunnelling in sulphate-bearing rocks-expansive phenomena-
- Autores: Iván Rafael Berdugo De Moya
- Directores de la Tesis: Eduardo Alonso Pérez de Agreda (dir. tes.), Enrique Romero Morales (codir. tes.)
- Lectura: En la Universitat Politècnica de Catalunya (UPC) ( España ) en 2007
- Idioma: inglés
- Tribunal Calificador de la Tesis: Antonio Gens Sole (presid.), Sebastià Olivella Pastallé (secret.), César Sagaseta Millán (voc.), Carlos Oteo Mazo (voc.), Fernando Pardo de Santayana Carrillo (voc.)
- Materias:
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- Resumen
The deleterious effects of rock expansions on tunnels have been demonstrated -maybe better than in any another case-, in those cases in which sulphate-bearing rocks (namely anhydritic-gypsiferous claystones) are involved. Expansive phenomena only affect the foundation material and evolve at rates that, far from slowing down, usually remained steady or increased with time. The classic criterion to explain this behaviour is the existence of a "physical swelling" -due to the expansion of clayey minerals-, followed by a long-term "chemical swelling" -due to the transformation of anhydrite into gypsum-, with a volumetric increase of approximately 60%. If the volumetric increase is partial or totally inhibited in either of these mechanisms, then a corresponding swelling pressure is generated.
This thesis is a contribution to the study of mechanisms underlying both the triggering and the eventual exhaustion of long-term expansive phenomena affecting tunnels excavated through anhydritic-gypsiferous claystones. Theoretical considerations and experimental evidences presented in the thesis suggests that the "physical swelling" is possible even in the absence of active clay minerals and is characterized by relatively low limiting values for both swelling strains and swelling pressures. However, it is demonstrated in this thesis that the transformation of anhydrite into gypsum is an isovolumetric process partially controlled by the epitaxial growth of gypsum on anhydrite, which generates a film protecting the anhydrite from further water actions. So, the classic criterion on long-term "chemical swelling" of anhydritic-gypsiferous claystones is difficult to accept and more realistic mechanism must be considered.
