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Computerised measuring system for analysis of chosen characteristics and processes in porous environment by eis method

Development and realisation of a set of monitoring systems using the electrical impedance spectrometry method for application under real conditions.

The subject of the project solution is the implementation of a set of instruments of a multi-channel automated system of monitoring of electrical impedance of the porous environment and its changes caused by loading a monitored site or a monitored point with water. The project follows the experience obtained by solving Project E!3838, when we developed a 128-channel, fully digitised device Z-meter with remote data transmission. The given system works with an indirect method of electrical impedance spectrometry and its implementation allows for measuring both the real (electric resistance or conductivity) and the imaginary parts (reactance) of electrical impedance. The system was primarily applied in monitoring soil moisture changes (electric conductivity) caused by its suction capability (bank, induced, from precipitation) and by water infiltration. The aim of the submitted project is to modify the given system for manual measurement, to extend the offer of the existing system with an option of choice of the number of measuring points in a set each having 16 measuring channels and to enable recharging a battery source with a solar panel in case of its permanent mounting at a monitored site. To achieve the given aim, we will again apply the principle of monitoring changes of non-electric quantity through electric quantities, when the indirect non-invasive method is electrical impedance spectrometry (or tomography). The method of electrical impedance spectrometry (EIS) allows for indicating changes in electrical impedance in space and time. Its principle is to monitor the given changes in electrical impedance of soils in complex form, whereby it is possible to monitor both changes caused particularly by loading soils with water (measuring the real frequency-independent part of electrical impedance) and changes, if any, in their material composition (measuring the imaginary frequency-dependent component of electrical impedance). The complexity of the problem consists especially in the non-stationary water flow through the unsaturated soil environment. It is experimentally proven that the coefficient of hydraulic conductivity of unsaturated soil is 3 - 4 orders lower than in saturated soil and it is generally known that the content of water in soils (moisture) significantly participates in their shear strength. On the one hand, this is caused by the intergranular bonds of clay minerals, which are reduced under the action of water; in grains of larger dimensions forming especially the skeleton of sands, they are increased under the action of the surface tension of water, which is manifested as untrue (false) cohesion. Added to this are viscose effects of water and water pressure in pores under the action of an external load, which changes in relation to permeability by the effect of load action. For this reason, the monitoring of the content of water in earth bodies is of great significance in geotechnical practice. Due to the great variability of soils (granulometry, material composition, consistency, etc.), it is necessary to pay increased attention also to the interpretation of findings detected by monitoring during the application of indirect, but often also direct, methods. The study of the problems of water flow through soil has led to a design and verification of a highly sensitive laboratory electric measuring device, the laboratory verification of which was conducted by solving GACR Projects No. 103/01/0057 of implementations of a laboratory system for application to protective earthen dams. In the course of the solution of Grant Project No. 103/04/0741, a device was developed, allowing for monitoring changes in moisture on dam bodies in situ. When carrying out International Project E!3838, this system was innovative and was verified in other application conditions at different sites. It will be possible to further apply the monitoring of changes taking place in the porous environment being loaded with water, and the measurement of the movement of the free surface water table for the calibration and verification of mathematical models, the location of failures of soil cohesion, the monitoring of soil moisture in terms of irrigation needs, or other changes. Keywords: electrical impedance, monitoring system, environment.
Acronym: 
EIS METHOD - PEM
Project ID: 
4 981
Start date: 
01-01-2010
Project Duration: 
36months
Project costs: 
1 220 000.00€
Technological Area: 
Sensor Technology related to measurements
Market Area: 
Environment

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