THE PHYSIO-MECHANICAL PROPERTIES OF SOME SELECTED SOIL SAMPLES AS STEMMING MATERIALS FOR EFFICIENT ROCK FRAGMENTATION

Abstract

This research determines the physio-mechanical properties of selected rock types with the view to select the most suitable rock type as stemming materials. The physio-mechanical properties tested include particle sizes distribution, unconfined compressive strength, moisture content, maximum dry density and triaxial compressive strength. Study samples which include stone dust S1; mixture of stone dust and clay S2; loamy soil S3; clay soil S4; laterite S5; mixture of clay and loamy soil S6; and mixture of loamy and laterite S7 were used as stemming material at the same drill depth on boulder of almost equal size. The rocks were gotten from primary blasting operation while stone dust and soils samples (stemming materials) were prepared in laboratory and the geotechnical properties were determined by conducting some physical tests on the samples. The results of the compaction test carried out revealed that S1 (stone dust) has the highest compaction characteristics, highest maximum dry density (MDD) and the least optimum moisture content (OMC); hence it can be concluded that the most efficient stemming material based on these criteria is S1. However, S4 (Clay) has the highest unconfined compressive and shear strength making it a good stemming material. The efficiency of blasting operation (fragmentation) was computed from the test blasting operation carried out using each of the study samples as stemming materials and the result shows that stone dust (S1) has an efficiency of fragmentation of 75% while Clay (S4) has a relatively low efficiency of fragmentation of 56%. This result indicate that stone dust gives a better fragmentation than other studied stemming materials. The efficiency of blasting was plotted against the moisture content, grain size, maximum dry density and the shear strength of each of the study samples. It was therefore concluded from the investigation of the physio-chemical properties of the selected stemming material in contrast with the fragmentation produced from the blasting of the boulders, that stone dust will give the most efficient rock fragmentation when used as a stemming material