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Development and use of coal washery refuse for strata control in coal mines

This work involves the development and analysis of a new pump packing material, which utilizes coal washery refuse ( C W R ) as a raw material, for strata control in underground coal mining operations. A review on the state of the art of pump packing systems is presented, together with an analysis of the cost effectiveness of the new pump packing material as compared to other commercial pump packing materials. A method is proposed for use in the design of cement and coal washery refuse ( C C W R ) material mixes to give a required early strength and degree of workability when incorporating C W R . The usefulness of the method is shown by comparison of the results from a large number of tests on C C W R specimens with previously published results. It is shown that the relationship between the strength and curing time of a mix can be accurately described by a simple equation. The effects of the compositions on the strength within the experimental regions are discussed. As expected an increase in the strength of C C W R materials can be obtained either by decreasing the water content or increasing the quantity of O P C used in the mixtures. This study also investigated the influence of moisture content on the mechanical properties of C C W R material. The unconfined compressive strength, Young's modulus, indirect tensile strength, triaxial strength and drying shrinkage were the primary properties investigated. Results indicate that the moisture content has a significant effect on both the strength and elasticity of C C W R material at all curing times. It is evident from the tests that the drying shrinkage of wet mixes is larger than that of dry mixes. In general, moisture content affects the shrinkage of C C W R material as it reduces the volume of the restraining C W R .