Hydration swelling effects on time‐dependent deformation of zeolitized tuff

Abstract

Long‐duration creep deformation experiments were performed on zeolitized tuffs from Yucca Mountain, Nevada, at temperatures of 35°–75°C, confining pressure of 5 MPa, and water pore pressure of 0.1 MPa. The test samples were initially loaded to a relatively small fraction of the uniaxial compressive failure stress, and allowed to creep; then the stress was increased periodically until creep failure occurred. The strain versus time creep curves exhibit the classical phenomenological phases of primary, secondary, and tertiary creep analogous to those for ductile metals, although the tuffs deform by dilational microcracking and fail by brittle fracture. Mechanical “steady state” or secondary creep strain rates as low as 1 × 10−10 s−1 were observed in the tests. Tertiary creep axial failure strains averaged about 6 × 10−3. The early, water saturation phases of the tests are characterized by large hydration swelling strains associated with water absorption by the zeolite minerals in the tuffs. The hydration was often incomplete after one month of immersion, and slow, continued hydration affected the creep curves so that the samples appeared to lengthen against axial differential stresses as high as 55 MPa. This strong chemical‐mechanical coupling suggests that in situ hydration state changes could generate stresses of similar magnitude.

Evaluation of three Italian tuffs (Neapolitan Yellow Tuff, Tufo Romano and Tufo Etrusco) as compatible replacement stone for Römer tuff in Dutch built cultural heritage

“…Coupled chemical-mechanicalhydraulic processes (cf. Blacic 1993), controlled in part by the relative stability of zeolites, may influence the durability of the stone by time-dependent change of properties of tuffs. The properties include increasing water absorption with time (as observed for Rhenish tuffs; Brendle 2003) and changes in linear strain and shrinkage with time (as observed for Grey Campanian Tuff; Cioffi et al 1991).…”

Application of Micromechanics to Modeling Compressive Failure of Rock

“…Another important aspect of time-dependent behavior is the effect of environmental conditions such as temperature, existence of water [22]. Lajitai et al [23] conducted creep tests under three different environmental conditions.…”