Piezometric pressure

If a reference datum plane (h = 0) is set at the bottom of each of the capillaries shown in the previous Fig. 5.5, the expression for the total driving force, that is the piezometric pressure difference along the penetration length h for a capillary with an upward (I pgh cos a) or a downward (—pgh cos a) orientation, can be represented by following equation (Bouchon and Pyle, 2005b),... 

The pressure intensity is related to the piezometric pressure p, through the definition of the latter quantity ... 

Very often, the water in a confined aquifer is under piezometric pressure, that is, there is an excess of pressure sufficient to raise the groundwater above the base of the overlying bed when the aquifer is penetrated by a well. Piezometric pressures are developed when the... 

Hydraulic uplift phenomena are associated with artesian conditions, that is, when water flowing under pressure through the ground is confined between two impermeable horizons (see the previous text). This can cause serious trouble in excavations, and both the position of the water table and the piezometric pressures should be determined before work commences. Otherwise, excavations that extend close to strata under artesian pressure may heave or, worse, may be severely damaged due to blow-outs taking place in the floors. Slopes also may fail. Indeed, such sites may have to be abandoned. 

Disposal of liquid hazardous waste has been undertaken by injection into deep weiis iocated in rock below freshwater aquifers, thereby ensuring that poiiution of groundwater suppiies does not occur. In such instances, the waste is generally injected into a permeable bed of rock several hundreds or even thousands of metres below the surface, which is confined by relatively impervious formations. However, even where geological conditions are favourable for deep well disposal, the space for waste disposal frequently is restricted and the potential injection zones are usually occupied by connate water. Accordingly, any potential formation into which waste can be injected must possess sufficient porosity, permeability, volume and confinement to guarantee safe injection. Also, the piezometric pressure in the injection zone influences the rate at which the reservoir can accept liquid waste. A further point to consider is that induced seismic activity has been associated with the disposal of fluids in deep wells (see the following text). 

Both the groundwater divide and piezometric level are at a lower elevation than the top water level but higher than that of the reservoir floor. In this case, the increase in groundwater head is low, and the flow from the reservoir may be initiated under conditions of low piezometric pressure in the reservoir flanks. 

The actinide metals up to californium were studied under pressure at room temperature (Fig. lb). For the lighter actinides up to plutonium, the (densest) room temperature allotrope remained in general stable under compression to the highest pressure attained (68 GPa for Th, 53 GPa for Pa, 21 GPa for Pu). a-U was stable up to about 50 GPa preliminary results indicate that at 71 GPa a different structure of uranium may exist. Np was only studied to 3.5 GPa by a piezometric technique. 

Piezometric efficiency Piezometric efficiency is defined as the ratio of the mean pressure and the maximum breech pressure. The mean pressure is taken as that pressure which, if uniformly exerted upon the projectile over the entire length of the bore, will produce the observed muzzle velocity. Thus (Equation 4.2) ... 

In general, the pressure-travel curve becomes flatter with higher piezometric efficiency. 

Conventionally, molecular uptake is recorded gravi-metrically [18-20]. Alternatively, for a limited supply of adsorbate, molecular uptake may also be calculated from a knowledge of the time dependence of the pressure (piezometric method [21, 22]) or composition of the gas phase. Changing the sorbate pressure by a step change of the gas volume has proved to be a very efficient method for following fast sorption processes (single step method [23, 24]). The sorption uptake may also be measured volumctrically by mans of a gas burette arrangement [25]. 

The level water reaches in an artesian well reflects its pressure, called the piezometric, or confined, water head (Fig 2.6). In boreholes drilled at altitudes that are lower than the piezometric head, water will reach the surface in a jet (or wellhead pressure) with a pressure that is proportional to the difference between the altitude of the wellhead and the piezometric head. The piezometric head is slightly lower than the water level in the relevant phreatic section of the system due to the flow resistance of the aquifer. Confined aquifers often underlay a phreatic aquifer, as shown in Fig. 2.7. The nature of such groundwater systems may be revealed by data measured in boreholes and wells. The water levels in wells 1 and 2 of Fig. 2.7 did not rise after the water was encountered, and both wells reached a phreatic aquifer. Well 3 is artesian, and the drillers account should include the depth in which the water was struck and the depth and nature of the aquiclude. The hydraulic interconnection between well 1 and well 3 may be established by... 

Measurement of the transient adsorption or desorption curve for a sample of zeolite crystals exposed to a step change in ambient sorbate concentration (pressure) provides, in principle, a simple and direct method of measuring the intracrystalline diffusivity (D). Such measurements are conveniently carried out by gravimetric, volumetric or piezometric methods. The... 

Piezometric ring— Pressure sensing holes that form a concentric circle around the center of the pipe. 

Saturated zones are common in porous material, and provide significant pathways for the subsurface transport of water and solutes. The term "ground water" commonly refers to continuously saturated zones of appreciable thickness. Saturated conditions also occur on a small scale or short term basis in association with the infiltration and drainage of precipitation or surface runoff. As indicated previously, the pressure and elevation components are the primary contributors to the total moisture potential in the saturated zone. These two are commonly combined into a "piezometric head", representing the addition of the water pressure head to the elevation at which the pressure head is measured. The hydraulic conductivity does not change significantly with... 

The intracrystalline diffusivities of the hydrocarbons were measured under the conditions of the temperature range of 373-773 K and the pressure range of 0-1.33 kPa by the constant volume method [9]. The apparatus and the procedure are the same as employed by Hashimoto et al. [4,5]. Change in the total pressure caused by adsorption was recorded by use of a piezometric sensor with a transducer, the response of which is first enough to measure accurately the pressure change. To eliminate the influence of several factors (such as mass conductivity between the sorbate and the pressure sensor) on the pressure change, the blank tests were conducted without zeolites. Comparing these data obtained with those with zeolites, an uptake curve of the amount adsorbed was obtained. 

Numerous hydraulic tests were carried out, during the various project phases, either in an isolated borehole or between boreholes. Hydraulic experiments consisted of pulse tests, constant head injection and/or extraction and constant rate injection/extraction using borehole intervals delimited in FBX 95001, FBX 95002, BOUS 85.001 and BOUS 85.002 (Figure 1). Both water flow and piezometric level measurements for borehole intervals are available. Continuous pressure monitoring has allowed detecting crosshole responses during pulse testing these have then been used to calibrate the hydraulic conductivities of fractures. 

Piezometric TZLC Packed/wall- Pressure/temp. Multicrystal... 

The piezometric method involves following the pressure response in a dosing cell connected to an uptake cell containing a sample of the adsorbent. According to the results reported in the hterature, the piezometric method can be used to accurately measure intracrystalline diffusivities for fast diffusing and strongly adsorbed species such as benzene on NaX [15,16]. Furthermore, it is also claimed to provide the required accuracy needed to study combined intracrystalline processes such as diffusion and first-order reaction [17]. 

We conclude that the piezometric technique is capable of yielding reliable diffusivity data provided that the pressures are monitored in the uptake cell and the limitations imposed by the time constant of the valve and finite heat dissipation rates are respected. For strongly adsorbed species theses restrictions limit the applicability to relatively slow processes (half times of at least several seconds). For weakly adsorbed species somewhat faster diffusion processes can be measured. A detailed assessment of the range of validity of this method, as a function of the system variables, has been presented by Schumacher and Karge [19]. In reviewing earlier reported piezometric diffusivity data, the values derived from measuring only the pressure in the dosing cell should not be accepted without further detailed analysis. 

The gas pressure in coal seam refers to the pressure of the gas contained in the coal seam. The determination method is to drill holes in the coal seam, bury piezometric tube, grout and seal holes, install pressure gage. The determination of the gas pressure under steady situation is the coal seam gas pressure. 

An elevation head is the height of a fluid column relative to some vertical reference point. The sum of the elevation head and the pressure head is called the piezometric head h. 

Detailed test section is shown in Figure 6. The test section was provided with pressure taps (piezometric ring) at various points in the upstream section and downstream section, sometimes on the pipe fitting like bend, elbow, etc. The static pressure at the different points was measured by means of simple manometer or piezoresistive pressure transducers. The main idea of putting long upstream and... 

For the experimental investigation of compressibility of superheated and saturated vapors, the method of the constant-volume nonballasted piezometer was employed. The fundamental variables (pressure, temperature, and mass of the substance) were measured with instruments of the same class as those used in the work of MEI. The distinguishing feature of the piezometric rig was the use of a membrane zero indicator of pressure of the electrocontact type. The sensitivity of this instrument reached 1 mm water column, but the zero point drifted by 10 mm water column. The authors in Refs. [2.19, 2.21] evaluated the scatter of experimental points on the saturation curve as 0.4% for pressure, and the repeatability of presssure during the forward and reverse tracing along the constant-volume lines was 0.15%. 

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