Mundhe S.M.S.,Maharashtra Engineering Research Institute |
Narkhede S.C.L.,Maharashtra Engineering Research Institute
Water and Energy International | Year: 2011
Mass works are generally constructed in UCR masonry. It was observed that in this masonry, the voids in the rubbles are not filled up properly with cement mortar which led to heavy seepages through the body of dam after commissioning. This was mainly due to the fact that placement of mortar was not done properly by unskilled inexperienced masons. Colgrout masonry is found to be a best replacement to conventional masonry. Colgrout mortar is a flowy mortar and gets filled in each and every void in rubbles providing dense, strong and impermeable masonry at w/c ratio as high as 0.85. This technique has built in quality control. Fly ash is a wasteful material available in abundant quantity. Generation of fly ash is increasing day by day for want of more & more electricity from thermal power stations. Fly ash is posing stacking, disposal and serious environmental problems. Use of fly ash in mortar/concrete slow down the process of heat of hydration, thereby, strength gain is at later days, generally up to 90 days. Thus, use of fly ash is the need o the day in mass works. Mass works are of the nature of not fully loaded even after 90 days. As they utilize large amount of cement, there is scope of large scale utilization of fly ash as part cement replacement without impairing the properties of masonry. This can economise the cost of project considerably. It improves the impermeability of the structure which is the main requirement for water retaining structures. Thus, use of fly ash is the need of the day in mass works. Therefore, Studies conducted to evolve the suitable % of cement replacement by fly ash in colgrout masonry indicated that fly ash to extent of 20% can be conveniently utilized in colgrout masonry. These results were also compared well with the test results of cores drilled from the blocks of fly ash colgrout masonry, specially constructed at Wan Project, Dist. Akola for the study.
Mundhe M.S.,Maharashtra Engineering Research Institute |
Pandhare V.B.,Maharashtra Engineering Research Institute |
Nakil M.B.,Maharashtra Engineering Research Institute |
Pande S.S.,Maharashtra Engineering Research Institute
Water and Energy International | Year: 2010
All our developmental plans envisage high priority to water resources projects specially construction of reservoirs. Accordingly large numbers of reservoirs have been constructed in Maharashtra. These reservoirs on completion face the problem of sedimentation. The soil erosion is a natural process occurring in the river basin system. To account the soil erosion process, the sediment load is estimated while designing the dead storage of the reservoir. However, it has been found that the sediment also gets deposited in live storage, reducing the utilizable capacity. Evaluation of reduced live storage capacity is essential for assessing useful life of reservoir as well as for Irrigation scheduling. There are many methods of sediment load estimation. The remote sensing technique is effectively used mainly for live storage of the reservoir while Differential GPS based bathymetrie technique can be used for entire storage. The remote sensing based sediment assessment in live storage of reservoir has proved to be most economical method. In Maharashtra this technique has been used since long. In present paper an attempt is made to analyze the sedimentation surveys and rates in live storage capacity of reservoirs. The analysis is based on the available data of 28 reservoirs from different basins in Maharashtra. The live storages of these 28 reservoirs range from 27.476 Mm3 to 2677 Mm3. The sedimentation rate assumed for projects varies from 3.57 to 7.15 ha m/100 km2/year whereas the observed sedimentation rate in live storage of reservoir varies from 0.90 to 38.33 ha m/100 km2/year. This shows that actual sedimentation rate is much higher than the designed rate. It is observed from the data that rate of sedimentation depends on 4 major factors namely rainfall quantity, size of catchment area, sedimentation period, reach of reservoir. The sedimentation rates from small catchments are found to be on higher side as compared to large catchments. Similarly the upper reach reservoirs are having less sedimentation in live storage than downstream region reservoirs. The sedimentation rate is more in early life of reservoir but go on reducing after 15-20 years. The rate is influenced by rainfall pattern. It increases rapidly for area having rainfall more than 2000mm .It is to sum up that the sedimentation rate is combined function of size of catchment area, rainfall, impoundment years, reach etc.