Invited by Philippine DDCP Company, Geomative arranged GD-10 High-density electrical equipment operation training. Also by the training, Geomative assistted DDCP to complete the investigation of the water content and surrounding geological stability of the dam foundation in Mankayan mining area. Meanwhile the investigation provided location reference for the later construction of roads near the abutment.
The geographical location and surrounding conditions of the dam are as follows.
The dam body has no concrete structure and it is a simple earth-rock dam. Both sides of the east and west are high-lying slopes. The two measuring lines are laid out as follows: ERT1, ERT2
The resistivity method is a geophysical method based on the difference in dielectric resistivity. The detection principle of the DC resistance method is to establish an artificial electric field by using a direct current to pass a pair of current poles A and B into the ground. By the difference in conductivity between the interlayer media, another potential pair M, N can be used to measure the potential difference between the electric field between M and N, thereby obtaining the apparent resistivity of the formation and estimating the underground formation. Conductivity distribution
It is often presented as a cross-sectional equivalent image. Physical units often use resistivity (ohm-m) to represent different levels of color with different tones.
Through the electrical resistivity survey, the water content of the base of the dam can be made out, thus, the stability of dam body can be understood indirectly.
Detection was performed using geophysical exploration with Electrical Resistivity tomography. The ERT1 line was laid along the dam top,with a length of 370m and an electrode spacing of 10m. According to the change of the topography of the line, GPS positioning of the corresponding electrode position is required to perform terrain correction. The array types :wen-sch, sch, and dipole-dipole.
Through geophysical investigation, the geological stability of the eastern slope of the dam abutment was studied, and the exploration of the depression zone and the fault zone were simulated.
Investigation plan With Electrical Resistivity tomography, the ERT2 line with the total length 150m was laid from west to east; the electrode spacing was 5m and the total electrodes number was 31. Along the variation of the topography of the line, GPS positioning of the corresponding electrode position is required to perform terrain correction of the inversion process.
1.It can carry out two-dimensional geoelectric section measurement, and has the functions of section method and sounding method. It is an effective means for stratigraphic division, detection of hidden fault structures, karst cavities and geological landslides.
2. It can effectively determine the size, shape, distribution range and projection position of the underground goaf and roadway, and provide suggestions and guidance for the construction of the owner.
3. Compared with other traditional methods, this method has the advantages of low cost, high efficiency, rich geoelectric information and high detection accuracy, and is worthy of popular use in engineering geological exploration.
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