2D CROSS BOREHOLE

Background

The objective of the investigation was to assist in the evaluation of the integrity of a chimney soil-crete grouting foundation. Drilling to verify the integrity of the foundation suggested the possibility of the soil-crete columns being smaller than the design specifications with potential zones of ineffective grouting. There was also a possibility of voids created during grouting due to possible sand collapse. More grout was also injected than anticipated—raising questions regarding the integrity of the soil-crete foundation in general.

Process

Resistivity data was acquired between each two boreholes using an AGI SuperSting™ 8 channel automatic resistivity system using two 28 electrode cables with 0.5 m separation between electrodes. The Bipole-Bipole and Dipole-Dipole array configurations were used to acquire the data

Results

SuperSting™ R8 resistivity data processed with EarthImager™ 2D software was successfully used to control grout injection. It mapped high resistive gravel levels where no grout penetration and poor grout penetration zones. It also mapped the low resistive grout penetration areas. 

Tools Used

• SuperSting™ R8
• SwitchBox 56 
• EarthImager™ 2D