Mechanical properties of microcrystalline branching selenite gypsum samples and influence of constituting factors  

作　　者：C.Caselle S.Bonetto C.Colombero C.Comina 

机构地区：[1]Department of Earth Sciences (DST),Università degli Studi di Torino [2]Department of Environment,Land and Infrastructure Engineering (DIATI),Politecnico di Torino

出　　处：《Journal of Rock Mechanics and Geotechnical Engineering》2019年第2期228-241,共14页岩石力学与岩土工程学报（英文版）

摘　　要：The high sedimentological variability of gypsum rocks has the effect that a univocal characterization of this material is not easy to establish. This is particularly true from the geomechanical point of view: when the mechanical properties of gypsum rocks are requested, it is therefore necessary to undertake detailed characterization analyses. Common facies of gypsum was observed in the Upper Miocene evaporitic succession(Messinian Salinity Crisis) within the whole Mediterranean Basin. In this work, mechanical tests were conducted on a site-specific facies, represented by the microcrystalline branching selenite. The tested samples came from the Monferrato area(northwestern Italy). Uniaxial compressive strength(UCS)tests were performed in order to obtain reference mechanical parameters. More rapid and economic point load test(PLT) and ultrasonic pulse velocity(UPV) measurements were additionally performed to verify their applicability as complementary/alternative methods for site characterization. Rock-type specific PLT-UCS and UPV-UCS relationships were established. A wide dispersion of the mechanical parameters was observed due to the heterogeneities of the studied material. Consequently, compositional, textural and microstructural observations on selected samples were performed. Two main material classes were recognized based on average grain size and total gypsum content, underlining the significant influence of the grain sorting on the measured mechanical properties.The high sedimentological variability of gypsum rocks has the effect that a univocal characterization of this material is not easy to establish. This is particularly true from the geomechanical point of view: when the mechanical properties of gypsum rocks are requested, it is therefore necessary to undertake detailed characterization analyses. Common facies of gypsum was observed in the Upper Miocene evaporitic succession(Messinian Salinity Crisis) within the whole Mediterranean Basin. In this work, mechanical tests were conducted on a site-specific facies, represented by the microcrystalline branching selenite. The tested samples came from the Monferrato area(northwestern Italy). Uniaxial compressive strength(UCS)tests were performed in order to obtain reference mechanical parameters. More rapid and economic point load test(PLT) and ultrasonic pulse velocity(UPV) measurements were additionally performed to verify their applicability as complementary/alternative methods for site characterization. Rock-type specific PLT-UCS and UPV-UCS relationships were established. A wide dispersion of the mechanical parameters was observed due to the heterogeneities of the studied material. Consequently, compositional, textural and microstructural observations on selected samples were performed. Two main material classes were recognized based on average grain size and total gypsum content, underlining the significant influence of the grain sorting on the measured mechanical properties.

关 键 词：GYPSUM UNIAXIAL compressive strength(UCS) Point load test(PLT) MECHANICAL properties Geological heterogeneity 

分 类 号：O3[理学—力学]