Unsaturation conditions

Thus, if we consider unit mass of saturated steam, in equilibrium with liquid (Fig. 36), to be isolated without change of temperature and pressure, and then to be heated, this vapour would become unsaturated, i.e., would take up more liquid at its own temperature if this were offered to it. To prevent the assumption of this unsaturated condition we must compress the vapour during the addition of heat so that the pressure is, at every stage of the process, equal to the vapour-pressure at the corresponding temperature. The heating and compression of the vapour may then be performed in contact with the liquid, so that ... 

Capillary barrier cover systems consist of a finer-grained soil layer (like that of a monolithic cover system) overlying a coarser-grained material layer, usually sand or gravel, as shown conceptually in Figure 25.3. The differences in the unsaturated hydraulic properties between the two layers minimize percolation into the coarser-grained (lower) layer under unsaturated conditions. 

Enzyme assay should be performed under unsaturated conditions. ... 

Porous cups can be used as probes in the monolith and suction can be applied to them to move water out of the soil and into a sample container under unsaturated conditions. Passive samplers that do not involve pressure or vacuum are also available [11]. 

NAPL will migrate from the liquid phase into the vapor phase until the vapor pressure is reached for that liquid. NAPL will move from the liquid phase into the water phase until the solubility is reached. Also, NAPL will move from the gas phase into any water that is not saturated with respect to that NAPL. Because hydraulic conductivities can be so low under highly unsaturated conditions, the gas phase may move much more rapidly than either of the liquid phases, and NAPLs can be transported to wetter zones where the NAPL can then move from the gas phase to a previously uncontaminated water phase. To understand and model these multiphase systems, the characteristic behavior and the diffusion coefficients for each phase must be known for each sediment or type of porous media, leading to an incredible amount of information, much of which is at present lacking. 

If the solute is initially in a liquid form and the solvent is completely miscible with it, the whole of the triangle will represent unsaturated conditions. If the solvent and solute are not completely miscible, the area can be divided into three distinct regions, as shown in Figure 10.17. In region 1, the solvent is present as an unsaturated solution in the solute. In region 2, the liquid consists of two phases — a saturated solution of A in S and a saturated solution of S in A, in various proportions. In region 3, the liquid consists of an unsaturated solution of solute in solvent. 

Wong, T. P., Byappanahalli, M., Yoneyama, B., and Ray, C. (2008). An evaluation of the mobility of pathogen indicators, Escherichia coli and bacteriophage MS-2, in a highly weathered tropical soil under unsaturated conditions. ]. Water ELealth 6,131-140. 

Farrell, J., and M. Reinhard, Desorption of Halogenated Organics from Model Solids, Sediments, and Soil Under Unsaturated Conditions 1. Isotherms. Environ. Sci. Technol., 1994 28, 53-62. 

Farrell, J., and Reinhard, M. (1994). Desorption of halogenated organics from model solids, sediments, and soil under unsaturated conditions. 2. Kinetics. Environ. Sci. Technoi, 28, 63-72. 

Experimental constraints were such that the assumptions of saturated and steady flow were not completely met, especially when the pulse was first introduced to each column. Our experimental conditions did not maintain water-saturated conditions initially and the applied pulse was introduced to moist but not fully water-saturated columns. As a result, effluent adjustments in the concentration of sulfate versus pore volume (V/y,) for the various layers were made in order to reflect the late arrival of a wetting front (outflow) due to the unsaturated condition of the columns. Here VG is the pore volume associated with individual soil layers. Our adjustments, which were based primarily on the initial moisture conditions for individual columns, were V/V(1... 

It is under unsaturated conditions that the structure of the AM fungal mycelium becomes of particular interest. The hydraulic conductivity of the entire hypha (Lp) of fungal hyphae of Phycomyces blakesleeanus was measured at 4.6 x 10 cm (s MPa) (Cosgrove et al., 1987) but that... 

I3) Presbure of the unsaturated solution. The theorems and results developed so far refer to the state of so-called saturation, at least so far as they have been followed out thermo-dynamically only in the graphical representation finally adopted was a place found for the unsaturated condition. This place may be exactly defined by a series of measurements with successively greater concentrations. Each pressure curve so found must correspond with an equation... 

The aims of reclamation are to make Ca2+ the major exchangeable ion and to reduce the salt concentration in the soil solution. The main requirement to reclaim salt-affected soils is that sufficient water must pass through the plant root zone to lower the salt concentration to acceptable values. Passing 1 m of leaching water per meter of soil depth under ponded conditions normally removes approximately 80% of the soluble salt from soils (Fig. 11.6). If leaching is under unsaturated conditions, such as with the use of intermittent pending or sprinkler irrigation, this quantity of water may be reduced to as little as 350 to 200 mm of water. Boron removal can require up to three times more water than removal of Na and Cl salts, because B is retained to some extent by soils. 

Processes being studied in the modeling of the Kamaishi Test included groundwater and heat flow in the rock matrix, fractures, buffer, and their interfaces under varying unsaturated conditions. Before emplacement of buffer and heater, the inflow of water into the test pit was affected, not only by the presence of fractures, but also by the unsaturated condition of the rock near the test pit. Strong variation in the areal distribution of inflow was observed on the walls of the test pit. After the heater and bentonite were emplaced, diffusion of water into the bentonite from the rock occurred simultaneously with drying of the bentonite near the... 

The coupled fluid-solid effects was also studied under non-isotheimal conditions for reservoir engineering, such as reported in Liu and Liu (2001c) for mathematical models of coupled multiphase fluid flow, heat transfer and solid deformation considering capillary pressure and both saturated and unsaturated conditions. Similar works was also reported in Wang and Du (2001). 

During the re-saturation process of buffer, swelling pressure under unsaturated conditions is important, though the above equation is limited to saturated conditions. 

In relation to radioactive waste disposal, during last years a number of laboratory results referring to thermal effects on saturated soils have been presented (Baldi et al. 1988, Towhata et al. 1993, Tanaka et al. 1997, Sultan et al. 2002, Burghignoli et al. 2000). However, results focused on the thermal influence on volume change behaviour of unsaturated soils are still limited (Wiebe et al. 1998, Romero et al. 2003). In particular, information concerning the temperature effects on the mechanical behaviour of highly expansive clays in unsaturated conditions is still scarce (Lingnau et al. 1996, Romero et al. 2001). 

Under unsaturated conditions the compressibility of the bentonite increases with the temperature of the test. This result is coherent with the thermally induced reduction of the size of the yield surface proposed by several authors. 

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