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‘Blastability’ and blast design
Published in B. Mohanty, Rock Fragmentation by Blasting, 2020
Conventional geotechnical mapping and logging of rock mass fractures is generally conducted for the purpose of assessing the stability of a slope or bench. Many of the rock mass discontinuities of importance to blasting are of smaller scale and not considered relevant to stability. It is thus possible to find that a rock mass described as massive or sparsely jointed may in fact contain close spaced bedding or foliation that has an important influence on fragmentation. Specialised mapping and structural analysis procedures have therefore been developed to record and model the rock mass structures important to blasting (Villaescusa 1991, Hudson and Priest 1979).
Water Erosion Control
Published in R.P.C. Morgan, R.J. Rickson, Slope Stabilization and Erosion Control, 2003
Vegetation can be organized in a layout that will reduce erosion risk on slopes. A vegetation layout aligned across slope, ideally on or close to the contour, will reduce effective slope length and impede or obstruct overland flow due to increased surface roughness. These effects will reduce the accumulation of runoff volume downslope and reduce the flow velocity which in turn will reduce the kinetic energy and, therefore, the capacity of the flow to detach and transport soil particles. Indeed, the reduction in velocity may be sufficient to prevent potentially erosive velocities from being attained. Any small reduction in the erosive power of the flow will have a dramatic impact on reducing the transporting capacity of that flow, as this varies with the fifth power of the velocity (see Chapter 2). Reduced flow velocity results in localized deposition of transported eroded sediments. In some cases this will reduce local slope steepness, in turn reducing hydraulic gradients. Flow velocities are then further decreased and further deposition occurs. Over time, these processes can result in the formation of a series of benches on the hillside, sometimes referred to as ‘erosion-induced’ or ‘erosion-controlled’ terraces.
Open pit slope design
Published in Xia-Ting Feng, Rock Mechanics and Engineering, 2017
Systematic documentation and evaluation of the performance of benches is a basic component of any slope assessment program. Benches are the fundamental building blocks of the pit slope, and their geometry and behavior usually control the inter-ramp angles and hence the overall slope design. Additional factors to be taken into account in the inter-ramp slope design include the inter-ramp or bench stack height that can be sustained by the rock mass between the haul roads and/or any intermediate geotechnical safety berms. Systematic monitoring of the piezometric pressures in the inter-ramp and overall slopes is also required to ensure that depressurization targets are being met (cf. Section 8.3).
A systematic approach for the analyses and design of jointed rock mass slopes against wedge and toppling failures: a case study of the stability of the abutments of the bridge across the Chenab River
Published in International Journal of Geotechnical Engineering, 2021
Srinivas Mantrala, A. K. Verma, T. G. Sitharam
The steps in the ‘Design as You Go’ are indicated in Figure 1. They are similar to the actual design process. For slope stabilization works, the slopes shall be excavated from top to down in the form of benches following the contours. The height of the bench depends on the equipment deployed at the site for various operations. After a bench is excavated, the geological logging of the slope is prepared. The stability against wedge failures depends on the orientation of the joints. Thus the dip and dip directions of the joints shall be recorded. The wedge failure analyses indicate the extent of anchor force required. The design of the slope stabilization measures depend upon the pull-out resistance of the rock bolts/anchors. Thus during the execution, the rock bolts shall be tested to validate the pull-out resistance of the same. Based on the measured dip and dip direction of joints, fresh analyses shall be carried out and the original slope stabilization measures shall be checked for their adequacy. If the measures are not adequate, the data shall be furnished to the designer for the revised design of the slope stabilization measures.