Fracture cross flow

Fracture flow and fracture cross flow experiments... 

The effect of shear displacement under different normal stress conditions on fracture cross-flow for RWS, YBS and LC is illustrated by the TCSFT results in Figs. 12-14. The (current) bulk permeability Kf) at any given shear displacement has been normalized with the initial bulk permeability prior to... 

Fig. 12. Fracture cross flow Yellow Brumunddal sandstone. Normalized bulk permeability versus shear displacement.

The experiments have also demonstrated the flow reducing effect of fracture normal stress and fracture shear displacement on the fracture cross flow. Both fracture normal stress and fracture shear displacement seem to be of equal importance for the weakest rock tested. When the rock strength increases, the stress to strength ratio becomes the dominating factor, and fracture shear displacement seems to be of reduced importance. 

The general observation for all three rock types is decreasing bulk flow with increasing Oj lo ratio, and some effect of the fracture shear displacement on the bulk flow. For the clay containing YBS, bulk flow is actually reduced by 90% for o la = 1.3. The strongest rock (YBS) shows the most pronounced cross-flow reduction, whereas the weakest rock (LC) shows the least reduction. The explanation for the limited cross-flow reduction for the LC sample lies in the low matrix permeability in combination with its special mineralogical composition (>90% carbonate), which reduces the effect of a low permeability gouge layer on the bulk flow. 

In Fig. 18 all cross-flow results from YBS, RWS and LC have been combined in one plot. This is done under the simplifying assumption that the combined effect of factors such as porosity, grain geometry, mineralogy and cementation on the rock strength can represented by the uniaxial compressive strength a, and therefore the normalization procedures applied (o /a and KJK ) allow comparison of results from different rock types. Because of the limited data set available, the only conclusion drawn from Fig. 18 so far, is that the KJK ratio seems to reach minimum values when the effective fracture normal stress approaches two times the uniaxial strength of the intact rock.. 

We consider a synthetic example that mimics the release of radionuclides from a deep underground repository built in low permeability, fractured rock. The example is two-dimensional and its geometry is shown in Figure I. It represents a vertical cross-section, and displays two horizontal formations with a major vertical fracture. Groundwater flow is driven by topography and It occurs from the recharge area to the left of the model to the sea. 

Fig. 5.37 SEI of a molded polyacetal surface shows a smooth texture (A) with little surface detail. Etching for short times results in elongated pits, oriented in the direction of polymer flow (B). Longer etching times result in surface pits deeper below the surface, due to etching larger spherulites in the core (C). Fractured cross sections of plated and etched surfaces do not show the structure near the surface (arrows) (D) except in EDS maps of the plating material (E) or at higher magnification (F).

In the numerical calculations, an elastic-perfectly-plastic ductile rod stretching at a uniform strain rate of e = lO s was treated. A flow stress of 100 MPa and a density of 2700 kg/m were assumed. A one-millimeter square cross section and a fracture energy of = 0.02 J were used. These properties are consistent with the measured behavior of soft aluminim in experimental expanding ring studies of Grady and Benson (1983). Incipient fractures were introduced into the rod randomly in both position and time. Fractures grow... 

Example 2.1. A storage tank of cross-sectional area At = 1 m2 (Figure 2.1) is fed at the top at a flow rate Fq = 0.22147 m3/s with a liquid of density p= 1000 kg/rn. The liquid drains under gravity via a pipe of cross-section Ai = 0.05 m2 located at the bottom of the tank. We will compute the evolution of the tank level h, starting from an empty tank (h = 0 m) under the above conditions, comparing the results with a case in which the bottom of the tank leaks via a small fracture of cross-sectional area A2 =0.0005 m2. 

Melt fracture is the occurrence of distorted extrudate coming from the extruder. It is caused by flow disturbance at the point where flow cross-sectional area is rapidly reduced from the large diameter of the melt feed to the much smaller cross-sectional area of the die orifice. Here again it is aggravated by melt elasticity. 

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