Consolidation Characteristics of Stowed Pond Ash and Pond Ash-lime Mixture

摘要

In this paper, the consolidation characteristics of the stowed class F pond ash and pond ash-lime mixture are studied to evaluate the effect of incremental load, time and addition of lime on the consolidation behaviour of the stowed mass. The stowed samples are collected from the goaf of a fabricated mine model used for stowing. After stowing with pond ash slurry having 65 percent solid and 35 percent water (by weight), the samples are collected from the model and tested at intervals of 7 days, 14 days, 21 days, 28 days and 35 days. Lime of 7 percent (by weight) of the total solid is added with the pond ash which makes a slurry mixture of proportion lime: pond ash: water = 4.55 : 60.45:35. From the study it is found that the void ratio of both the stowed pond ash and pond ash-lime mixture decreases with the applied load. Comparatively, the stowed pond ash-lime mixture samples showed a higher void ratio irrespective of their time of collection. The pond ash sample collected after 21 days of stowing showed a maximum void ratio of 1.033 at an applied load of 0.1 kg/cm~2, whereas, the pond ash sample collected after 35 days of stowing showed a minimum void ratio of 0.842 at a load of 3.2 kg/cm~2. In case of stowed pond ash-lime mixture samples, the sample collected after 14 days of stowing showed a maximum void ratio of 1.14 at an applied load of 0.1 kg/cm~2 and the samples collected after 35 days of stowing showed a minimum void ratio of 0.944 at a load of 3.2 kg/cm~2. From the consolidation test it is evaluated that the load bearing capacity of the stowed pond ash reduces with increment of load and time which is marked by the decrease in coefficient of consolidation (C_v) values. Comparatively, the stowed pond ash-lime mixtures showed higher C_v values than the stowed pond ash. By overall analysis, it may be stated that at higher applied load and with the increase of time span the C_v values of stowed pond ash-lime mixture are marginally higher as compared to that of stowed pond ash. In other words addition of lime with pond ash does not offer significant advantage in stowing in underground mines.