A reliable estimate of the drilling rate is essential in a successful drill and blast planning and mine production. Owing to this importance, numerous empirical equations of the drilling rate using the rock mass properties and the machine parameters have been proposed. However, these existing equations cannot be used in all site conditions. Hence, this paper aims to develop an empirical model for drilling rate estimation in hard rock mining. The data used for this study were collected from an underground mine located in Selibi-Phikwe, Botswana and included in-situ drilling rate, drilling machine specification and rock mass properties. Nonlinear regression model was used to derive the drill rate model. The result indicates high correlation between the estimated and the actual drill rates. In addition, it was found that the uniaxial compressive strength of the rock, the angle between the rock mass discontinuity planes and the drilling direction are the parameters impacting the drill rate the most. Also, the presence of quartz in the rock indicated good predictability of the drill rates.

In this paper, a probabilistic design chart for coal pillar based on South African coal mine experience is proposed as a tool capable of estimating the pillar strength. A methodology based on the logistic regression is employed to identify failed and intact pillars with their corresponding probabilities of occurrence. The input parameters used for pillar design include the mine depth, pillar width, bord width, height of mining excavation and panel width. The results showed that 84.6% of the pillars, including stable and failed categories, were correctly classified. In addition, the probability associated with the pillar conditions was determined and plotted in form of a pillar strength graph. The results were in good agreement with the field data and existing studies. One of the merits of the current study is that the probability of having a coal pillar intact or failed can be easily determined. This is particularly useful for design purposes since a series of uncertainties are usually involved in collecting the rock mass parameters. It is concluded that the results of this study could improve the empirical design of coal pillars.

The importance of research on sustainable and energy-efficient building design is increasing, considering thathumanity may face a shortage of natural resources as a result of irrational energy use. This article focuses on optimising the window characteristics of the buildings to be constructed in Nur-Sultan, Kazakhstan, in order to improve their energy efficiency and daylight performance. Specifically, simulations were performed with the DesignBuilder software to study the effects of the window-to-wall ratio (WWR), glazing type, shading, and building orientation on the energy performance of the building and the comfort level of the occupants. As a result, triple-pane windows with 10 to 15% WWR oriented mainly to the south were found to have better performance compared to other configurations. However, a life-cycle analysis can be performed to verify its benefits in terms of cost and environmental burden. On the other hand, limitations of the glazed area on each facade may affect the comfort level of the occupants in terms of temperature increases, lack of daylight, and poor ventilation. Thus, a discussion of the simulation results is provided, along with issues that might arise. Suggestions for future studies were also included.