Dynamic plate test

The dynamic plate test is carried out in situ and determines the stiffness of the subgrade or unbound subbase/base course in terms of a stiffness modulus by using dynamic plate loading. The particular modulus is usually called surface modulus ( ). 

The apparatus consists of a steel handle with a steel circular plate of 300 mm (standard size) or 150 mm in diameter in its end. 

During the test, a certain load (typically 10 kg) drops from a certain height to the steel plate, to produce a certain peak stress ranging from 30 to 150 kPa (typical value used, 100 kPa) with a load pulse time ranging from 8 to 20 ms. The applied load on each impact is measured with a load cell. The vertical displacement, deflection, is measured by a geophone (velocity transducer) positioned at the centre of the loaded area. 

The surface stiffness modulus is calculated using the following general equation (Highways Agency 2009b)  

All data are stored and can be transferred to a portable data processing unit or to a portable computer. 

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General instructions for executing the dynamic plate test with an LWD can be found in ASTM E 2583 (2011). More information about LWD and field measurements can be found in Nazzal et al. (2007), Hossain and Apeagyei (2010) and Marradi et al. (2011). 

The in situ determination of the stiffness of compacted unbound layer is carried out by the dynamic plate test using the light weight deflectometer or, in some countries, using the German dynamic plate equipment (see Section 1.9.3). 

The pulse mode experiments were conducted by placing the sample between the quartz plates and exposing it to 30 second bursts of UV radiation. Dynamic rheological tests were then applied to the sample and this process was repeated until the sample had passed its gel point and became highly cross-linked. 

A sphere vibrating at a specific frequency can be used to obtain magnitudes of G and G" at a specific frequency. Such an instrument was used to follow sol-gel transition of 5,7, and 10% starch dispersions (Hansen et ah, 1990). However, such instruments seem to have a limited range of oscillation frequencies (e.g., 676-680 Hz). In addition, the reliability of the data obtained in comparison to data from dynamic rheological tests in which cone-plate, parallel plate, and concentric cylinder geometries have been used needs to be established. 

This empirical rule seems to hold up quite well for most polymers. Using this rule, it is possible to determine viscosity data up to 500 s with a cone and plate rheometer by applying an oscillatory motion to the cone. This would be impossible if a steady rotational motion was applied to the cone. In steady shear measurements on a cone and plate rheometer, the maximum shear rate that can be measured is around 1 s, which is much too low for applications to extrusion problems. The same is true for measurements in the parallel plate test geometry. Thus, the dynamic measurement extends the shear rate measurement range considerably, while still being able to take advantage of the cone and plate geometry. 

Workers at the Institute for Dynamic Materials Testing in Ulm [58] have developed a new method for determining viscoelastic characteristics of thin coatings. Elasticity and damping components of the dynamic shear modulus as a function of temperature or time can be determined from the resonance frequency and damping of the natural vibration of a coated aluminium carrier plate. 

Demand absorbency plate test method can be converted into a 2D radial dynamic wicking measurement method when the liquid is introduced from a point source into the nonwoven fabric (also known as the point source demand wettability test). One example of this method is the Gravimetric Absorbency Testing System (GATS) system mentioned in Section 6.3.4.4, when a point source liquid introduction cell was used. 

The sessile drop method has several drawbacks. Several days elapse between each displacement, and total test times exceeding one month are not uncommon. It can be difficult to determine that the interface has actually advanced across the face of the crystal. Displacement frequency and distance are variable and dependent upon the operator. Tests are conducted on pure mineral surfaces, usually quartz, which does not adequately model the heterogeneous rock surfaces in reservoirs. There is a need for a simple technique that gives reproducible data and can be used to characterize various mineral surfaces. The dynamic Wilhelmy plate technique has such a potential. This paper discusses the dynamic Wilhelmy plate apparatus used to study wetting properties of liquid/liquid/solid systems important to the oil industry. 

The Wilhelmy hanging plate method (13) has been used for many years to measure interfacial and surface tensions, but with the advent of computer data collection and computer control of dynamic test conditions, its utility has been greatly increased. The dynamic version of the Wilhelmy plate device, in which the liquid phases are in motion relative to a solid phase, has been used in several surface chemistry studies not directly related to the oil industry (14- 16). Fleureau and Dupeyrat (17) have used this technique to study the effects of an electric field on the formation of surfactants at oil/water/rock interfaces. The work presented here is concerned with reservoir wettability. 

Einally, as profiling assays run repeatedly in cycles, unlike HTS campaigns, it is wise to create a reference plate with well characterized, diverse compounds to be tested at a frequency of 3-4 months. This test set ensures that any shift in dynamic range, technical fault associated with plate outlay, alteration of reagent quality or liquid handling is detected. 

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