History of Tehri Rockfill Dam Design

A 260.5 m high rockfill dam is one of the main components of Tehri Dam Project which is under construction for the last over seventeen years. During this period detailed site investigations have been carried out and design of the dam is kept under constant review. A number of studies are conducted to provide feasible solutions to anticipated problems. The paper describes main design features of the dam mentioning the changes necessitated time to time with regard to these

Behaviour of Ramganga Dams

Two earth and boulder fill dams of height 127.6 m and 72.2 m are major structures of Ramganga River Project. Their foundation rocks are alternations of clayshale and sandrock of Middle Siwaliks. Both have thick core consisting of central zone of crushed clayshale encased by crushed sandrock zones. The clayshale and sandrock available from spillway excavations, just adjacent to these dams, were utilized as dam fill. No major problem except that of seepage control in cut off trench excavation and compaction near abutments, was encountered during construction. Both the dams are well instrumented. Their construction was completed in 1974-75 and the reservoir has nine fillings since then. Observations reveal that phreatic line has not yet been fully established. The stressmeters installed in clay zone of the core of main dam show effective stresses less than half of the overburden effective stresses, thereby indicating arching due to interaction between clay and sand zones of core

Treatment of Left Bank Slopes of Ichari Dam

The left bank of Ichari Diversion Dam was anticipated unstable because of toe submergence and drawdown effects after the construction of the dam, on the weak geological formations. Extensive laboratory and field investigations were carried out to determine the extent of stabilising measures needed. The proposals of providing pretensioned steel anchors or alternatively, reinforced concrete shaft anchors were considered in details to obviate the possibility of deep seated slides. The choice fell in favour of R.C. anchors mainly because there is no uncertainty about their in situ strength. These anchors were provided in two rows (one having vertical and other inclined anchors) at 9.0m spacing. The design of these anchors was done as continuous space frame with ultimate load theory. The two rows are connected at the top with a 6.0m thick concrete slab (monolith). A massive concrete retaining wall of 9.0m height rests on this slab with provision of shear keys. Above this elevation, concrete bocks and boulder pitching, with back filters, have been used to stabilise the slope at a gradient of 1.5:1 (H:V) in the hill wash material zone

Soil Liquefaction in Nepal-Bihar Earthquake of August 21, 1988

Liquefaction of the soil occurred at many places in the Nepal-Bihar earthquake. In the great earthquake of 1934 in this region, there had also been wide spread liquefaction of soil. Analysis for determining the influence of acceleration level, relative density, particle size and depth of soil on liquefiability of soil has been carried out, using the three most commonly used approaches and the difference in the results brought out

Kinetics and mechanistic study of cetyltrimethylammonium bromide catalyzed oxidation of tetraethylene glycol by N-chlorosaccharin in acidic medium

The kinetics and mechanism of cetyltrimethylammonium bromide catalyzed oxidation of tetraethylene glycol [2,2'-(oxibis(ethylenoxy)diethanol)] by N-chlorosaccharin in aqueous acetic acid medium in presence of perchloric acid have been investigated at 323K. The reaction is first order dependence on Nchlorosaccharin. The reaction rate follows first order kinetics with respect to [tetraethylene glycol] with excess concentration of other reactants. The miceller effect due to cetyltrimethylammonium bromide, a cationic surfactant has been studied. The change in ionic strength shows negligible salt effect. The dielectric effect is found to be positive. Addition of one of the products (saccharin) retards the reaction rate. Activation parameters are calculated from the Arrhenious plot. A possible mechanism consistent with the experimental results has been proposed

Evaluation of Liquefaction Potential for an Earth Dam Site

The foundation of the proposed Polavaram Earth and Rockfill Dam (India) has a sand deposit about 15 to 30 meters deep. The medium size sand is poorly to uniformly graded having relati.ve density in the range of 40-45% and angle of internal friction 30°. Standard Penetration Tests have been conducted in 22 bore holes at site and the N-counts have been observed to range between 4 to 111. The liquefaction potential of deposit under maximum credible earthquake (MCE) for the site has been evaluated by analyzing the data on the basis of prevailing empirical approaches and by the results of the experiments conducted on the sand in laboratory. The results of the analyses indicate that for the design earthquake the liquefaction would occur at some spots where N-counts are very low. The experiments have been conducted by depositing the sand, with the relative density close to that at site, in a box placed on a shaking table. The table was subjected to equivalent number of sinusoidal cycles corresponding to 75, 65 and 50% level of maximum acceleration of the time history of the design earthquake. As the dam provides an overburden pressure to the foundation, experiments have been conducted with loading on sand deposit in the shake table. The effect of frequency of motion has also been observed. The results of these experiments show that for the design acceleration levels of 0.1 g (65% of maximum acceleration) the maximum pore water pressure would be 31% of the effective overburden. The frequency of 3 cps seems the optimum frequency for generation of pore water pressure and at 8 cps this is less by about 20 percent. Thus the experiments indicate only partial loss of shear strength and not the total liquefaction of the foundation sand

An Efficient Photocatalytic Degradation of Methyl Blue Dye by using Synthesised PbO Nanoparticles

We report here the synthesis of visible light sensitive PbO and Ni doped PbO nanoparticles by hydrothermal method and characterized by UV-DRS, photoluminescence spectroscopy (PL), FTIR, X-ray diffraction (XRD), SEM, EDAX and TGA. Further an efficient approach has been developed for degradation of methyl blue (MB) in aqueous medium. The photodegradation of dye was monitored as a function of dye concentration, pH and catalyst amount has been determined. The reduction in the chemical oxygen demand (COD) revealed the mineralization of dye along with colour removal

Magnetization curves of hard superconductor samples with non-zero demagnetization factor

We present exact solutions of Bean's critical state model for some sample shapes having non-zero demagnetization factor N. Virgin and hysteresis magnetization curves are obtained for samples in the shape of (i) a sphere (ii) a spheroid (iii) a cylinder of circular cross-section with its axis perpendicular to the field and (iv) a cylinder of elliptical cross section with its axis perpendicular to the field. Some interesting features seen in these first solutions for N ≠ 0 are discussed