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Comparison Test on AGI and GD-10

1.Objective
(1) Comparison performance of GD-10 multi-channel system and AGI system.
(2) Investigate the distribution of landslide as well as landslide stratification, study the distribution and depth of landslide areas.
 
2. Layout
Studying place named loess plateau, located in the heifangtai Gansu, which is famous for the loess landslide. Geophysical Electrical Resistivity Tomography (ERT)imaging method is applied to this study, we distributed 2 multi-electrode cable along the slip zone, both length 180m long with 36 electrodes and each spacing is a = 5m.
 
3. Instruments
(1)This survey were conducted with GD-10 multi-channel system which is produced by ST.Geomative Shenzhen
(2)AGI SuperSting R8 instruments.
 
4. Array type used
1. Wenner α
2. Schlumberger
3. Dipole-dipole
All above array type was used to collect the 2D electrical resistivity imaging data using GD-10 and AGI instruments.
 
5. Obtained Results
Data processing using AGI Earth Imager 2D inversion software and the inversion diagram is as follows:
Figure 1  Wenner α imaging of first survey line (a) GD-10 system (b)AGI system
Figure 2  Schlumberger imaging of first survey line (a) GD-10 system (b)AGI system
 
Figure 3  Dipole-dipole imaging of first survey line (a) GD-10 system (b)AGI system
 
Figure 4  Wenner α imaging of second survey line (a) GD-10 system (b)AGI system
 
Figure 5  Schlumberger imaging of second survey line (a) GD-10 system (b)AGI system
 
Figure 6  Dipole-dipole imaging of second survey line (a) GD-10 system (b)AGI system
 
6. Result interpretation
According to the inversion result image of GD-10 and AGI, it clearly depicts the layered structure of the stratum, distinguish the interface between high and low resistivity part. The shallow soil keeps in a dry state due to the drought weather, and nature water content normally less than 10%, which corresponding to the inversion image in red region.
It matches the feature of this geological environment that the upper soil structure is homogeneous, loose and porous and deeper is discontinuous zone of distinguished resistivity less than 20 ohm.m, found as poor permeable sand and shale, it characterized by a relatively regular shape and decreased resistivity. It is found that the maximum shear strength and steady state strength of the soil will change with the changed of the salt concentration, in heifangtai area, due to the periodic irrigation and occasional rainfall, may cause groundwater changes. Therefore, it is necessary to monitor the data of soil, salt and water, which highly related to the inside resistivity of soil. To achieve the purpose of monitoring by Electrical Resistivity Tomography (ERT) imaging method, it is easy to detect the change of water and salt in the soil during a period of time.
Compared with AGI, the script dipole-dipole array conducted by GD-10 clearly show that GD-10 output the data measurement at deep layer and good resolution after optimize the small signal
 
7. Working photo