9 - Geotechnical investigation

Abstract

As discussed in the previous chapters, the success rate of any ground-improvement technique depends upon how much we have understood the subsurface conditions at the project site. Understanding the index and engineering properties of soils is essential before using the soil-stabilization techniques. The proportioning of materials and fixing the dose of stabilizers depends upon the properties of the soils to be stabilized. The effectiveness of many of the deep compaction methods (e.g. blasting, freezing, dynamic compaction, etc.) largely depends upon the presence of groundwater flow and/or site drainage conditions. The dynamic compaction method is not very effective if the fine content exceeds a certain limit. Selection of a dewatering method will largely depend upon the soil permeability. Similarly, the size and distribution of voids/fissures/cracks, presence of joints in rocks, filling materials present in joints, extent of weathering, and groundwater flow conditions comprise the details that must be assessed before doing grouting at a site. As already discussed, some of the techniques are applicable for cohesive soils, whereas some are for the noncohesive soils.