Backfilling of mine voids is mandatory to avoid subsequent ground stability problems in the form of subsidence. River sand and mill tailings have been widely used since a long time as backfilling materials. However, with a strict regulation banning river sand mining in India, research for developing alternative engineering materials substituting sand has gained importance. In the present study four fly ash composite materials (FCMs) was developed from the fly ash obtained from a captive thermal unit of Rourkela Steel Plant (RSP). The main constituent of the composite were fly ash, lime and gypsum. Detailed physical, and engineering properties were determined for the FCMs. Significant increases in the compressive strength were obtained after 56 days of curing time. A detailed SEM studies was undertaken to account for the increase in strength with time. The fly ash composite developed from RSP has potential to be used as substitute to sand for backfilling the mine voids.

No abstract

No abstract

A B S T R A C TFly ash transportation and disposal is a major problem in India. Presently fly ash is being transported as lean slurry in pipe lines requiring about 80 to 85% of water which, in turn, consumes more energy input. The objective of the present study is to evaluate the rheological characteristics of fly ash slurry at varying temperatures with and without an additive to facilitate smooth flow in the pipelines. Six fly ash slurry samples were prepared from the fly ash obtained from a thermal power plant situated in the southern part of India. The main constituents of the slurry were fly ash, water, a cationic surfactant and a counter-ion. Detailed rheological properties were determined for the six slurries at shear rates varying from 25 to 500s 21 .Temperature was varied from 20uC to 40uC for all the shear rates investigated. The slurry exhibited Newtonian flow behaviour with zero yield stress. The slurry prepared in the above manner has a potential to be transported through pipelines with minimal energy consumption. The distinctive reduction of surface tension on colloidal disperse characteristics of the resulting slurry was observed in the presence of the surfactants. Zeta potential measurements also confirmed that the additive has the capability to keep the fly ash particles water borne during its transportation in pipelines.

A two dimensional non-linear finite element simulation model has been developed using a mathematical model for progressive rock failure for understanding the mode and sequence of rock failure under a drag pick cutter. Rock cutting simulation has also been done using linear elastic modeling using local stability factor contouring. It has been observed from the simulation results that during negative rake angle cutting the chipping occurs by shear failure of the elements. Whereas, in positive rake angle cutting, some elements were observed to fail in shear and some under tension. The predicted peak cutting force using the developed models was found to be up to 25% higher than the experimental values. The effect of input parameters such as rake angle, flank wear, depth of cut and rock properties on the predicted peak cutting force has been studied, verified from earlier experimental studies and compared with some earlier proposed theories on rock cutting. The elastic stress analysis model based on the stability factor contouring method has also been found to be an effective tool to bracket the expected peak cutting force for a given operational and rock parameters but failed to simulate the effect of pick geometry (rake angle) correctly. The non-linear simulation model using progressive rock element failure is superior to elastic linear stress analysis model by simulating the correct trends for all the rock and machining parameters.