Descriptive Epidemiological Study of Abortion with Special Reference to Brucellosis in Mares

Abstract

The embankment dams require a massive quantity of fill materials. Embankment dams have different zones, and the soils are generally obtained from different borrow areas having different strength and stiffness properties, which may have effect on stability and settlement. If the upper limit of the strength and stiffness properties of various soils is used, there will be an overestimation of stability and underestimation of settlement. The stability and settlement response of a 59 m high embankment dam called Nai Gaj dam situated in District Dadu, Sindh, Pakistan is presented in this study. The parametric analysis was conducted for three main zones of the dam: upstream shell, core and downstream shell, which consisted of sandy gravel, clay and random fill, respectively. The friction angle values of these materials were gradually decreased to represent the soil conditions of different sources. It was observed that the stability requirements for the end of construction and after filling of the reservoir could be satisfied if friction angle values of the sandy gravel and random fill be respectively utilized as 340 and 320 instead of 370 and 340 . However, the value of the friction angle of the core can be used as 300 without any reduction so that the dam could be safe after filling the reservoir. The settlement behaviour of the dam was analyzed by using the MCM and Hardening Soil Model (HSM) models. The MCM model was applied to all material zones and the HSM was used for four major material zones that occupied significant volume. The settlement response of the dam was almost similar when computed with the MCM and HSM for the three material zones (clay core, sandy gravel and random fill), each having a modulus of elasticity (MOE) in the range of 25000 to 50000 kPa. However, it was found that after the end of construction the MCM showed about 57% and 50% more settlement as compared to the HSM when MOE of sandy siltstone was respectively varied from 70000 to 125000 kPa. The rate of increase of settlement at the crest and at a depth of 120 m computed by MCM compared to HSM was 53% and 82% respectively for after filling of the reservoir condition. The settlement computed with MCM and HSM were 2.9% and 1.35% of the dam height. It can be interpreted that the settlement predicted with MCM is unrealistically high xix due to the single constant value of modulus of elasticity (MOE). On the contrary, the predictions of HSM are in agreement with the literature. besides, the long term settlement computed using MCM is about 59% higher than that of HSM for after filling of reservoir condition. The settlement of an embankment dam could be predicted reliably by using HSM even when a limited number of stiffness data is available. The reservoir of the dam was lowered to a depth of 10 m up to 55 m in gradual increments. It was found that the reservoir could be lowered up to a depth of 55 m at a rate of 0.1 m/day when the undrained strength of clay core was 25 kN/m2 . The dam was also subjected to average daily rainfall intensity of 0.086 m/day continuously for five days. The safety factor was reduced to 1.44 when the dam was subjected to the rainfall duration for five days. This indicates that with the increase of duration of rainfall, there is a reduction in the safety factor, because water enters through the embankment and saturates the slopes. However, the stability of the dam is satisfactory for the above-mentioned intensity and duration of the rainfall. Keywords: embankment dam, slope stability, settlement, pore pressure, consolidation, end of construction, filling of the reservoir, rapid drawdown, rainfall induced stability, parametric analysis, modulus of elasticity, Mohr Coulomb model, Hardening Soil model.