Alternative measurement methods

Alternative measurement methods


The purpose of the geophysical surveys is to determine the geophysical anomalies – studies show effects such as rainfall and groundwater, mechanical influences both lateral and vertical pressure (static power) and real dynamical effects.

Effects of precipitation and underground water leak is a process in which a layer of loosely releases in the country up to the stage where there are gaps in the material of the arteries.

Surface geophysics allows both to locate the area of ​​infiltration, or not so loose in the underground sections, making it possible to estimate the direction of further spread of these processes.

For the rapid detection of geophysical anomalies is often sometimes inappropriate georadar main advantage in the use of GPR for quick finding anomalies, but in some cases the study presents an ambiguous interpretation. Therefore, it is necessary to combine study with combination of other geophysical methods.

To detect leaks, are used appropriate additional methods – to measure the DC resistance (UP, VES), measurement of spontaneous polarization (SP) and shallow seismic reflection (GEOSONAR). To monitor the stability of slopes is used shallow seismic refraction (MRS), VES, SP. These methods are used primarily on paved edges (to the electrodes stuck into the ground or geophone). For methods and VES UP there contactless modifications that can be applied directly to the surface. These are electromagnetic profiling (DEMP) and vertical electromagnetic sounding (VEMS).



Resistance profiling method examines the apparent electrical resistance in the geophysical profiles at the selected depth. For measurements using four electrodes at a constant distance. The two outer electrodes (A, B) are in a natural environment are used for DC or low-frequency electric current. Current flows in the natural environment, and then hits the inner measuring electrodes (M, N) indicating the voltage, which is proportional to the electrical resistance of the studied area in the half-space to a depth of about AB / 4.

The arrangement of electrodes is constant along the profile, followed by step-by-step, and resolution of the method is improved by shortening the steps.

For the purposes of this study, it is advisable to choose a step approximately 0.5 m, while it is desirable that at least one, preferably two sections along each side of the road.



Procedure for vertical electrical sounding (VES) allows the detection of apparent electrical resistance at various depths below the selected point on the surface. Measurements are used four electrodes, two electrodes (M, N) remain in the measured point, the other two electrodes (A, B) remain at the same distance from the measuring point. With each expansion (excitation electrode distance from the measuring electrode) in a natural environment using existing electrodes connected to a DC or low frequency AC electric current.

The current flow in the natural environment, causing the voltage monitor, the electrode is proportional to the electrical resistance in the study area to a depth of about half-space AB / 4.
The distance between the points is determined by the requirements of the VES studies and is intended to be 2-5 meters, and it is desirable to ensure that at least one, preferably two sections along each side.



This method is based on studies of the natural electric field of a local nature, and for this purpose a filter array origin. Filtration of electrical potentials generated by capillary movement of water (porous) environment. Some leaks appear in the filtering area, which can be sized for the direction of filtration. The measurement is performed using special and nepolarizovaných electrodes, one electrode is placed in the ground, the second electrode is placed gradually in the country along the route profile. Profiles realized linearly on the way (moving the electrodes from the standard), or even circular (constant distance between the electrodes). In the measurement, it is appropriate to use the distance between the measured amount of 2 to 5 meters.



Principle GEOSONARU unit is very similar to a GPR. To obtain information about the environment are used seismo-acoustic waves instead of using electromagnetic waves. Seismoacoustic wave causes stress media, analyzing mechanical impulses and spreads, and at the interface between two media with different mechanical properties of that broken parts, and partly broken complete. Reflected part of the mechanical pulse is measured seismoacoustic receiver. Depth depends on the frequency seismo-acoustic waves and mechanical properties of the investigated area. The higher the excitation frequency is used, the less mechanically fixed environment is examined using a shallower depth. Resolution capacity increases with increasing frequency seismo-acoustic waves. Measurements can be carried out continuously with GEOSONAREM, because in each measured point is needed mechanical contact between the sensor and the current environment, which is investigated. Depth range can be increased on the principle of the sum signal and excitation, and several times in the same place. For the purpose of this study is GEOSONAR used only in short sections, usually in increments of 0.2 m, in places such as geophysical anomalies localized GPR with ambiguous interpretations.



Refracted wave method is mainly used to monitor the condition of the rock mass and its overburden. Checks seismic signals generated on the surface of the hammer, recorded in remote areas where the geophone (sensor) transformed the mechanical excitation and recorded by seismographs. Seismic waves passing through geological environment are reflected in the user interface, and their seismic disruption ultimately submitted information on a shallow structure, namely stronger relief the earth on which use higher speed of seismic waves through the m / p. The sediments at the bottom surface to the moving speed of hundreds m / s

This method is very suitable for the investigation of slope stability, since it can be used in conjunction with other geophysical methods, of course, especially for the detection of the release surface of the release.



Meotda Density radiometry is used to detect density of the superstructure, which contains a source of ionizing radiation and a detector. Ionizing radiation passes through the environment between the source and detector, shows that the density of the material in this interval corresponds to the light intensity on the detector. Area device depth is determined by the distance between source and detector and can be adjusted from about 0.1 m to 1 mA continuous measurement is performed in the surface profile and in this case, particularly in areas with potential voids in GPR.