Triaxial compression testing of multicomponent geomaterials from quartz-poor (syenitic) systems

This paper focuses on mafic microgranular enclaves enclosed in quartz-poor igneous rocks and their effect on strength properties of the rock massif. The study examines host rock–enclave multicomponent geomaterials from enclave-bearing syenitic rocks from the Třebíč Massif exposed in the Královec quarry near Jaroměřice nad Rokytnou in the Czech Republic. A series of laboratory tests were performed to describe strength properties of individual constituents of the multicomponent geomaterials. We mainly focused on triaxial compression tests, however, rebound hardness, uniaxial compressive strength and indirect tensile strength were determined as well. The obtained results indicate that enclaves and even the contact zones between the enclaves and host rocks do not have any negative influence on the rock strength. In contrast, enclaves represent “stress concentrators” within such multicomponent systems. Strength properties of various multicomponent geomaterials are practically an unexplored topic in the field of rocks mechanics and future studies are needed to establish a robust database describing the behaviour of such geocomposites

Anisotropy of mechanical properties of greywacke

The paper brings description of the mechanical properties of greywacke sampled in Kobeřice quarry (Lower Carboniferous Culm Basin, Drahany Uplands, Bohemian Massif). Anisotropy of mechanical properties was identified from series of laboratory tests of oriented samples using following procedures: (1) indirect tensile testing, (2) uniaxial compressive testing and (3) triaxial compressive testing. Parameters of Mohr-Coulomb and Hoek-Brown failure criteria were determined by evaluation of the obtained laboratory data. The tested greywacke performed relatively high uniaxial compressive strength, roughly 200 MPa. Better fitting by Mohr-Coulomb criterion was identified than by Hoek-Brown one within the investigated interval of confining stresses (0-15 MPa). In addition, Schmidt hammer test was carried out with comparison of several correlation relationships to uniaxial compressive strength which were compared with directly obtained value from laboratory tests

Mechanical properties of granulite from Horní Bory in Bohemian massif

Granulite represents one of the favourite rock types for the construction of an underground nuclear waste repository in the Czech Republic. Granulite from the Bohemian Massif (locality Horní Bory) was investigated in this study, with a special focus on the evaluation of the rock anisotropy. Investigated rock represents typical fine-grained foliated felsic granulite with principal mineral association: quartz + feldspar (K-feldspar > plag ioclase) + garnet + biotite + kyanite and/or sillimanite. Anisotropy was identified in the rock fabric both at macroscopic and microscopic scale. During the laboratory testing, granulite reached considerable high uniaxial compressive strength (UCS) - up to 240 MPa; and brittle type (Class II) of failure occurred. We found that variability of the UCS and Young's modulus were relatively low. On the other hand, variability of the Poisson's ratio and the constants in Hoek-Brown failure criterion in triaxial loading were significantly hig

A COMPARISON OF TESTING METHODS FOR DETERMINATION OF SPRAYED CONCRETE TENSILE STRENGTH

Sprayed concrete is important construction material in tunnelling. Primary lining is essential in NATM where the sprayed concrete can be loaded by tension due to bending moments. The tension is common reason of failure because concrete has a relatively low tensile strength. The tensile strength is usually determined by splitting tensile test in laboratory. However, the results can be distorted because the specimen is not loaded by pure tension in this case. The paper compares results of concrete tensile strength determined by two methods: indirect by the splitting tensile test and direct by the modified tensile test

A COMPARISON OF TESTING METHODS FOR DETERMINATION OF SPRAYED CONCRETE TENSILE STRENGTH

Sprayed concrete is important construction material in tunnelling. Primary lining is essential in NATM where the sprayed concrete can be loaded by tension due to bending moments. The tension is common reason of failure because concrete has a relatively low tensile strength. The tensile strength is usually determined by splitting tensile test in laboratory. However, the results can be distorted because the specimen is not loaded by pure tension in this case. The paper compares results of concrete tensile strength determined by two methods: indirect by the splitting tensile test and direct by the modified tensile test

The tunnel on the fast railway

Témou práce je vytvorenie koncepčnej štúdie tunela na plánovanej vysokorýchlostnej trati s výberom vhodného priečneho usporiadania a metódy razenia s ohľadom na miestne geologické pomery, taktiež návrh primárneho zabezpečenia a technologický postup výstavby.The theme of this thesis is to create a conceptual study of the tunnel on high speed railway. Selection of suitable cross section and tunnelling method with considering of geological conditions of the site. Design of primary support and technological process of construction.

Effect of active ingredients to the activity of cementing compound with non-alkaline accelerator additive for sprayed concrete.

Bakalárska práca sa zoberá problematikou striekaných betónov zo zameraním na použitie aktívnych prímesí s nealkalickou urýchľovacou prísadou. Teoretická časť je pojatá formou rešerše o dosadávaných poznatkoch používania aktívnych prímesí v striekanom betóne a ich vplyvom na proces hydratácie. V rámci experimentálnej časti bola laboratórne porovnávaná a overovaná reaktivita cementového tmelu s nealkalickými urýchľovačmi na báze síranu hlinitého pri použití aktívnych prímesí (troska, popolček, mikromletý vápenec). Overované boli cementy CEM I 42,5 R od rôznych výrobcov na základe doby tuhnutia a tvrdnutia pomocou Vicatovho prístroja a stanovenia pevnosti v ťahu za ohybu a pevnosti v tlaku po 6 a 24 hodinách.The bachelor thesis deals with the problems of the sprayed concrete with the focus on usage of the active ingredients with non-alkaline accelerator additive. The theoretical part covers the current level of knowledge of how the active ingredients are used in the sprayed concrete and their influence on the process of hydration. In the experimental part the reactivity of cementing compound with non-alkaline accelerator on the basis of aluminium sulphate were compared in a laboratory when the active ingredients (such as slag, fly-ash and very fine limestone) were used. The cements CEM I 42,5 R, made by different producers were verified on the basis of the setting time and early strength gain using the Vicat needle to examine the mechanical properties after 6 and 24 hours.

Permanent Security of Slope Cut

Témou práce je vytvoriť prehľad spôsobov paženia hlbokých výkopov. Ďalej je cieľom prakticky uplatniť tieto poznatky a navrhnúť vhodné riešenie zabezpečenia pre konkrétne stavenisko na základe jeho špecifík. Navrhnuté riešenie potom staticky posúdiť.The theme of this work is to create an overview of casing deep trenches. Furthermore, in order to practically apply the knowledge and propose appropriate security solution for a particular site based on its specifics. The proposed solution then statically assessed.

CALIBRATION OF INPUT PARAMETER VALUES FOR AN ADVANCED MATERIAL MODEL OF SPRAYED CONCRETE

The paper briefly presents an advanced material model for shotcrete involving many aspects of the actual behavior of concrete. However, the contribution is focused on determination and calibration of selected input parameter values for practical use of the model in structural analysis. Two cross sections of different geological conditions were chosen from a utility tunnel in Brno in order to obtain sprayed concrete samples. The laboratory tests conducted are described and then compared with results from numerical approximations

CALIBRATION OF INPUT PARAMETER VALUES FOR AN ADVANCED MATERIAL MODEL OF SPRAYED CONCRETE

The paper briefly presents an advanced material model for shotcrete involving many aspects of the actual behavior of concrete. However, the contribution is focused on determination and calibration of selected input parameter values for practical use of the model in structural analysis. Two cross sections of different geological conditions were chosen from a utility tunnel in Brno in order to obtain sprayed concrete samples. The laboratory tests conducted are described and then compared with results from numerical approximations