Impact of soft loading conditions on the performance of elongate support elements.

Abstract

This project investigates the mechanisms of the rotation and oblique movement of blocks, and analyses the capabilities of elongates to support such unstable blocks. To this end, theoretical, laboratory and underground studies are conducted to ensure meaningful and practically relevant insights and solutions. It was found that the most significant factor contributing to failure of support units by rotation of keyblocks is the support spacing. The reason for this is that the centroid of the potentially rotating block and the resultant reaction force from the support units are brought closer together by increasing the support density (i.e. reducing the support spacing). The probability of blocks failing by rotating out of the hangingwall of a stope depends on the shape of the block. Blocks with shallow dipping sides rotate more readily than blocks with steeply dipping sides. An important output of the project is a computer program to quantify optimum support spacing in geotechnical areas where keyblock rotation is likely.