Prediction of in situ rock strength using sonic velocity

Uniaxial Compressive Strength (UCS) and sonic velocity correlations are used widely in the Australian coal mining industry to predict in situ rock strength. These models are cheap, fast and easy to produce, as well as easy to understand and have a number of practical applications in mine planning and design. The major downfall of these models is that there is a large variation in UCS values at high sonic velocities limiting their predictive ability. The aim of this research project is to improve the reliability of UCS/Sonic velocity correlations by reducing the variability in the underlying data. This is performed by identifying and eliminating sources of error affecting the data and looking at the impact of certain factors on the quality of the correlations. Results show that improved models can be obtained by filtering the datasets to remove samples with high length-to-height ratios, conglomerate or pebbly lithologies, and large sonic velocity ranges

Effects of different planting dates on improving yield of Fritillaria imperialis L. and Fritillaria persica L. bulbs damaged by small narcissus fly (Eumerus strigatus Fallen)

Fritillaria imperialis and F. persica were planted during April 2003 and May 2004 growing seasons on the basis of split block design with three replications to investigate the effects of planting dates on various plant parameters and extent of recovery by planting 25% damaged bulbs. The results showed significant effects of planting dates on plant height, number of bulbs per plant and infected bulb ratio. A comparison of the two species showed that F. persica gave more bulblets than F. imperialis. A generalcomparison of the two species also showed that damaged bulbs of F. imperialis produced lesser yield compared to F. persica. Furthermore, both species gave more number of bulblets from early and mid September plantings compared to early and mid October plantings. The most suitable date of planting was determined as September 1st and 15th

A study on wear rates of 100Cr6 steel running against sintered steel surfaces under dry and starved lubrication

This paper investigates the tribological behavior of 100Cr6 steel pin running against sintered steel bearing material used in hermetic compressors. Tests were conducted under dry and starved lubrication sliding conditions in air at room temperature. Although porous structure acts as crack initiation sites thus limiting the wear resistance of sintered iron in dry sliding conditions under high contact stresses, it is believed to be beneficial in lubricated sliding conditions as it absorbs a large amount of lubricant. Wear tests without lubrication show that these pores are completely filled by abrasive particles in the initial stages of the test and no longer maintain their oil absorption capability. Initial results show that oxidation of frictional surfaces by flash temperature in dry conditions reduces weight loss volume by decreasing the coefficient of friction

Modelling of the Occurrence of Hydrogen Sulphide in Coal Seams

Hydrogen Sulphide (H2S) has been encountered within a number of Bowen Basin collieries, Central Queensland, Australia. High concentration occurrence during mining of a longwall panel raises a number of potential problems, which demand greater understanding to allow efficient mining while maintaining safe and healthy environmental conditions. Longwall panels at Mine A and Mine B have recently mined through H2S zones. The high H2S zone mined through at Mine A was wide and covering the whole length of the face comparing to the narrow H2S zone which was cutting the panel at 45° at Mine B. Longwall panels had been sampled for H2S in pre-mining phases with vertical and inseam exploration boreholes and rib sampling of gateroad development headings. During mining face coal samples were collected in an intensive program and tested in a drum tumbler to determine an indicated seam concentration level through contouring that could be used to calculate the concentrations of H2S liberated to the atmosphere. Data was analysed to determine a geostatistical method, which would best represent the indicated seam concentration level from the given data and the block dimension of the data set. This study discusses the different sampling methods used, selection of the most suitable geostatistical method and the impact of grid size on results of data analysis. Some general observations are made correlating indicated seam H2S concentrations from production face sampling with both predictions made from exploration and liberation rates during mining of the longwall panel

Improving the performance of the hardy cross algorithm for large ventilation models

The Hardy Cross algorithm offers a reliable method of solving network systems of fluid flow and has become widely used for solving water and ventilation flow networks. A limitation is that computational iterations and time to solve a network rises rapidly with the size of the model and modern detailed ventilation networks have typically grown to thousands of airways. Non-linear matrix solving methods can offer improved performance, however these are more complex and may be unstable if initial estimates are poor. This paper presents improvements that can be applied to the traditional Hardy Cross algorithm to greatly reduce iterations and solving time for large ventilation models