Permeability stress relationship

It is obvious from Equation 14.14 that the most important parameter determining the volumetric air flow rate <2W is the intrinsic permeability K of soil. At this point it is important to stress the difference between water permeability (or hydraulic conductivity) k , air permeability ka, and intrinsic permeability K. In most cases, when permeability data are provided for a type of soil or geological formation, these data are based on hydraulic conductivity measurements and describe how easily the water can flow through this formation. However, the flow characteristic of a fluid depends greatly on its properties, e.g., density p and viscosity p. Equation 14.16 describes the relationship between permeability coefficient k and fluid properties p and p ... 

The stability and permeability of a mix are not sufficient criteria to reflect how a material will perform under the repeated loads generated by traffic. Therefore, any mix design selection process should include an examination of the material s fatigue resistance. Figure 5 shows the relationship between sulfur content and fatigue life for some SAS mixtures at two strain levels [15]. These tests were run at constant stress in third point flexure. Both curves go through a maximum at a sulfur content of 14 percent. 

Figure 2. TOUGH-FLAC simulation of the DST (a) schematics of two-dimensional model geometry (b) conceptual model for stress-permeability coupling (c) normal stress versus aperture relationship for fractures...

Abstract Modeling of the drift-scale heater test at the Exploratory Studies Facility at Yucca Mountain, Nevada, U.S.A. was performed. The objectives of the analysis were to investigate the (i) temperature effects on mechanical deformation surrounding the heated drift and (ii) thermal-mechanical effects on rock-mass permeability. The continuum representation of a deformation-permeability relationship based on fracture normal stress was developed to assess rock-mass permeability variations because of temperature changes. The estimated rock-mass displacements and permeability variations as a function of heating time were compared with field measurements. The estimated trend of permeability responses using a normal stress-based deformation-permeability relationship compared reasonably to that measured. 

To assess the thermal-mechanical effects on rock-mass permeability, a deformation-permeability relationship based on fracture normal stress was developed. 

A normal stress-based deformation-permeability relationship was proposed to investigate the thermal-mechanical effects on rock-mass permeability. The estimated trend of permeability responses to heating compared reasonably to that measured. The modeling results, however, were not able to predict the permeability recovery observed at certain locations. 

UPSCALING OF NORMAL STRESS-PERMEABILITY RELATIONSHIPS FOR FRACTURE NETWORKS OBEYING FRACTIONAL LEVY MOTION... 

A key parameter for modeling T-H-M-C processes is the relationship between in situ stress and permeability. Since this relationship is generally measured at small scales, upscaling is needed for large-scale models. Few studies on upscaling of this relationship have appeared in the literature. In this study, we develop closed-form upscaled normal stress-permeability relationships... 

Stress-induced changes in fracture aperture can give rise to significant changes in the rock mass permeability, through a sensitive cubic relationship between fracture aperture and fracture flow. This section discusses how to determine this relationship for large-scale heterogeneous fractured media (characterized by fLm) from small-scale laboratory measurements. The determination is based on the assumptions that an equivalent... 

A smali-scale stress-permeability (or aperture) relationship is generally obtained from laboratory tests on single fractures. As an example, Figure 3 shows measured normal stress-aperture relations for a rock sample collected from the Shellafield site. The observed function can be fitted by ... 

An important step for upscaling the stress-permeability relationship is to relate local permeability (at a 1.56 m scale) to parameters b, bmax. and fracture frequency f. We assume that at the 1.56 m scale, local permeabilities can be considered to result from horizontal and vertical fractures. Different assumptions regarding relations among local permeability and the relevant parameters (f, b and b ,x) will give rise to different upscaling relationships. In this paper, we present two useful relationships. 

Two methods are developed for calculating gridblock-scale stress-permeability relationships. Although the first method is developed by assuming identical properties for individual hactures and spatially variable fracture densities, it can be mathematically shown that the model is also valid for individual fractures with different aperture parameters (e.g., b, and bmu) as long as Rb is the same for individual fractures. 

A BLOCK-SCALE STRESS-PERMEABILITY RELATIONSHIP OF A FRACTURED ROCK DETERMINED BY NUMERICAL EXPERIMENTS... 

Field observations indicate that the stress condition affects the flow characteristics of fractured rock mass (Barton et al., 1995 Ito and Hayashi, 2003 Pusch, 1989). Many laboratory investigations on single fractures also prove that the normal closure and shear dilation can significantly change the transmissivity of fractures (Makurat et al., 1990 Olsson et al., 2001). When it comes to the block scale stress-permeability relationship, the analytical models based on the orthogonal and/or persistent fracture model are available (Bai and Elsworth, 1994). However, analytical solutions do not generally exist for more realistic fracture systems. Furthermore, to the authors knowledge, block-scale study about the effect of shear dilations of fractures on the... 

INVESTIGATING THE RELATIONSHIP BETWEEN FAULT PERMEABILITY AND EFFECTIVE STRESS USING CONSTRAINTS FROM RESERVOIR INDUCED... 

This research uses observations of reservoir induced seismicity (RIS) at A u reservoir. NE Brazil, to investigate the spatial and temporal evolution of effective stress in the region and its relationship to fault permeability. A u reservoir was constructed in 1983 and has a capacity of 2.4 x lO m maintained by a 34 m high earth-filled dam constructed on Precambrian shield. Annual reservoir variation is 3-6 m which results in annual seismic activity due to a proposed mechanism of pore pressure diffusion (Ferreira et al. (1995), do Nascimento et al. (2003a)). Digital data at A u... 

According to studies abroad and at home, with mechanical stress the permeability decreases rapidly. But when stress is stronger, the decrease can be very limited and remains basically stable (Sheng 2007). The relationship between the permeability and stress is available to be presented by the following formula in the stress range from 0-4 MPa to 15-40 MPa ... 

Blood and lymphatic vessels are soft tissues with densities which exhibit nonlinear stress-strain relationships [1]. The walls of blood and lymphatic vessels show not only elastic [2, 3] or pseudoelastic [4] behavior, but also possess distinctive inelastic character [5, 6] as well, including viscosity, creep, stress relaxation and pressure-diameter hysteresis. The mechanical properties of these vessels depend largely on the constituents of their walls, especially the collagen, elastin, and vascular smooth muscle content. In general, the walls of blood and lymphatic vessels are anisotropic. Moreover, their properties are affected by age and disease state. This section presents the data concerning the characteristic dimensions of arterial tree and venous system the constituents and mechanical properties of the vessel walls. Water permeability or hydraulic conductivity of blood vessel walls have been also included, because this transport property of blood vessel wall is believed to be important both in nourishing the vessel walls and in affecting development of atherosclerosis [7-9]. 

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