Stress path

In this study, the appearance and evolution sequence of planar slip bands, in addition to a dislocation cell structure with increasing e,, is identical to that observed in quasi-static studies of the effects of stress path changes on dislocation substructure development [27]. The substructure evolution in copper deformed quasi-statically is known to be influenced by changes in stress path [27]. Deforming a sample in tension at 90° orthogonal to the... 

At large W/b9 the stress path, i.e.9 the ratio of 01/02 as 02 increases, is calculable (21), provided that the Poisson s ratio along the path is known. Since Poisson s ratio (if indeed it can be defined for finite strain) varies from about 0.4 typically to about 0.5 at yield, the stress path is not radial, i.e.9 01/02 is not constant. This situation is illustrated schematically in Figure 2. Since accurate values for Poisson s ratio of the polymers tested are not available, the path dependence of our results will have to await further investigation. 

Fig. 21. Schematic diagram of process flow stress paths for elements of material undergoing extrusion through a conical die of small semi-angle, and a uniaxial tensile test...

Five types of tests have been performed in oedometric conditions at various temperatures following different stress paths and suction changes. 

Three tests on bentonite compacted at an initial dry density of 1.7 g/cm with its hygroscopic water content have been performed at different temperatures (20, 40 and 60 °C), following the suction and stress paths indicated in Figure 4. In the first step, under a vertical load of 0.1 MPa, the suction of the sample was equalised to 14 MPa (due to mechanical limitations of the cell, this is the maximum suction that can be controlled). Afterwards, keeping this suction constant, the vertical load was increased up to 5 MPa. Under this vertical load, suction was decreased by steps until... 

Figure 4. Stress path followed in wetting and loading tests under controlled suction at different temperatures.

As the microstructural suction decreases to low values the stress path crosses the yield surface, SD, (Figure 7.b) and some plastic re-arrangements take place. In the model this phenomenon is described by the interaction function fp- A net volumetric compression was observed (and computed) at this stage. 

Rhett D. W. and Teufel L. W. (1992). Stress path dependence of matrix permeability of north sea sandstone reservoir rock. 33rd U.S. symp. Rock Mech. 

Figure 6 presents stress paths (p-s plane) followed in finite elements located near the production well, the injection well and between them. During production phase, stress path in the three points is nearly horizontal this means that suction does not vary a lot during production phase. When injection phase begins, one observes a brutal decrease of suction at the injection well. This leads to the additional compaction when the stress path reaches the LC curve. However, at the production well and at the midpoint, suction does not vary so much during the time scale considered in this simulation because the water front does not yet reach them. 

The stress path generated during loading will depend upon whether the test is run allowing volume to change (drained) or not (undrained). The resulting plot of deviatoric... 

Undrained stress path Rebound compression line... 

Drained stress path Critical state line... 

Stress-strain and stress path for an isotropically consolidated clay material leading to faUttre, e = 0.65, a sc = 392 kN/m, cyclic stress ratio = 0.87. (After Sangrey, D.A. et al., Canadian Geotech. /., 6,241-252,1969. With permission of the Canadian Geotechnical Journal.)... 

Behavior of clay subjected to cyclic loading may be explained in terms of effective stresses. For solution of practical problems, however, the stress-path method based on representative cyclic tests interpreted on total stress basis may be convenient. 

Measurement of these small strains requires use of special apparatus and procedures. These include use of local strain gauges attached to the sample and application of stress paths closely resembling the field stress paths... 

During the finite element analysis, the parameters of slopes be taken as h (height) = 10 m, E (elastic modulus of the soil) = 20 MPa, v(Poisson s ratio) = 0.32, (unit weight) = 18 kN/m or (dip angle) = 30°-80°. In order to obtain the shear stress distributions under the slope s top face and under the slope s incline face respectively, seven stress paths have been defined in slope, their position shown in Figure 2. 

Figure 2. The position of seven stress paths during FEM analysis. 

Martin, C D. 1997. Seventeenth Canadian Geotechnical Colloquium the effect of cohesion loss and stress path on brittle rock strength. Canadian Geotechnical Journal 34 698-725. 

Li Xinping., Xiao Taoli. Wang Bin, et al. 2012. Experimental study of Jin Ping II hydropower station marble underloading and unloading stress paths (in Chinese). 

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