Which Geophysical Method?
There are a few geophysical methods that can assist in slope stability investigation. Seismic refraction, Multi-channel Analysis of Surface Wave (MASW) , Electrical Resistivity Imaging (ERI), Ground Penetrating Radar (GPR) and gravity methods are the favourable geophysical methods in providing key engineering properties for management and monitoring of existing and potential landslide.
Primary targets for geophysics include compressional and shear strength of the rock and overlying sediments together with their relative clay and water composition. Geophysics methods also helpful in obtaining the material properties and boundaries of subsurface materials.
How These Geophysical Techniques Could Help?
In seismic technique,the measurement of mechanical properties of soil and rock masses can be made. If P and S waves are measured, ‘seismic E modulus’ and ‘seismic Poisson’s ratio’ can be determined:
where λ, μ are Lame’s Constant, ρ the density of material.
These mechanical properties of soil and rock masses are very useful in slope stability analysis.
Meanwhile, in electrical resistivity imaging or resistivity technique, measurement is based on the difference in resistivity between different subsurface material. This survey technique can establishes soil and rock mass movement due to present of clay materials or water.
Therefore, all of the information obtained from geophysical techniques are very useful in landslide and/or slope stability investigation.