The rockmass parameters that affect the productivity of tractor-mounted ripping are briefly reviewed. The results of a number of field ripping trials in a variety of sedimentary rocks on the Western Lignite open cast mines in the Tuncbilek district in Turkey are presented. Various ripping rates are shown to correlate well with a rippability index based on the discontinuity frequency and strength of the rock. The correlative relationships are fully developed. The costeffectiveness of mechanical ripping and drilling and blasting are compared, from which it is concluded that ripping of relatively hard rock can be considered only in conjunction with scraping of the loosened material.
In the assessment of the reliability of a large water supply system made up of many reservoirs and links, it is important to be able to simulate the performance of the system to assess its characteristics and ask 'what if' questions, without waiting for history to unfold. An essential ingredient in the assessment of system reliability by simulation is a sound generator of artificial hydrological records. This paper descriptionbes the analysis, fitting, verification and validation of a model designed to produce correctly cross-correlated flow sequences at a large number of sites simultaneously in the Vaal River System Study. To check the performance of the model in producing generated streamflow sequences that mimic the historical flows, a set of verification and validation testa were used. This strategy shows that fitting probability models to highly skewed flow data needs to be done by robust methods that must be carefully assessed and demonstrates the absolute necessity of such checking. The variety of flow regimes encountered in the Vaal study, from semi-humid to arid, is large enough to suggest that the model is potentially reliable in a wider context within the subcontinent.