Failure triaxial data

Creep tests are run by subjecting a grouted soil sample to a sustained load less than the short-term Unconfined Compression strength, until failure occurs. As the sustained load decreases in value, the time to failure increases. Data from such tests plot as shown in Fig. 11.22, and indicate an asymptote at what may be called a creep endurance limit. For acrylamides these values will range from as low as 20% Unconfined Compression for triaxial tests at low lateral pressure to as high as 40% for triaxial tests at at rest lateral pressures. (For silicates, values may be taken from Fig. 11.11.)... 

The degree of rock anisotropy has a significant effect on the failure envelope. Thus the initiative was to include a parameter in the modified criterion, the range of which relates directly to the degree of anisotropy of the intact rock. The value of this parameter is determined by fitting triaxial data in different loading directions. 

The Hoek-Brown failure criterion parameters of the composite rock (with siltstone percentage equal to 17%) were derived by fitting the criterion to the triaxial data. The uniaxial compressive strength was found equal to = 71 MPa and mj = 12. 

In a recent attempt to bring an engineering approach to multiaxial failure in solid propellants, Siron and Duerr (92) tested two composite double-base formulations under nine distinct states of stress. The tests included triaxial poker chip, biaxial strip, uniaxial extension, shear, diametral compression, uniaxial compression, and pressurized uniaxial extension at several temperatures and strain rates. The data were reduced in terms of an empirically defined constraint parameter which ranged from —1.0 (hydrostatic compression) to +1.0 (hydrostatic tension). The parameter () is defined in terms of principal stresses and indicates the tensile or compressive nature of the stress field at any point in a structure —i.e.,... 

Figure 10.7 (a) Failure lines for grouted and ungrouted granular soils, (b) Drained triaxial test results for silicate grouted coarse and medium sands. (From Ref. 11.15.) (c) Typical stress-strain curve from unconfined compression test on chemically grouted sand, (d) Compression versus time data for creep test on chemically grouted sand, under constant load, (e) Failure time versus percent of unconfined compression failure load. (+) indicates unconfined compression tests, and ( ) indicates triaxial tests with S3 = 25% of Si. 

Abstract The well-known features of the Earth s crust are interpreted as the result of rock fracturing under deep thermodynamic conditions. For this aim, triaxial failure data are scaled up to the crust taking into account temperatures and rock types. The critical depth of hydraulically permeable cracks coincides with the Mohorovicic boundary and that relates to the crust genesis. The annihilation of a crack system at this depth is in accordance with seismic velocity jump known from geophysical exploration. The features of crust floors as well as total thickness, fault inclination, etc, are explained by the suggested mechanical approach. 

Failure of rocks depends on pressure and temperature conditions. The process includes microfracturing, dilatant opening of cracks, rupture localization into shear bands, etc. Triaxial standard test data permit one to find typical features, corresponding to definite PT-intervals. The adequate classification, initiated by Z. Bieniawski, J. Bemaux, H. Einstein et al., can be done by differences in the finite states of ruptured samples. The accounting for temperature effect is essential as is shown in Figure 1, published earlier, Nikolaevskiy (1996), and added here with the amphibole data. 

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