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Chemicals are used to increase the settling velocity for suspended deposition colloids which are not settled in sedimentation tanks in water purification plants . For this purpose, the alum is used in wide spread across the water purification projects in Iraq. This research contains studying the factors that effect on alum amount added by conducting laboratory tests of water samples from Euphrates river at the purification plant in AL-Musayyab city over ten years (with monthly rate). It was noted that the amount added depends heavily on the turbidity of water entering the purification plant, in addition to water temperature and its pH. The results of laboratory tests have been approved, which included the measurement of the turbidity, pH, temperature, and the value of alum added. Since this method is applicable in all water purification plants. The results during the period of ten years are accredited, and subjected to multi -regression analysis. A mathematical model was conducted to calculate the alum dose, which must be added depending on the raw water turbidity, temperature, and pH. This model also has been examined by using data of another years and gave satisfactory results to be up to 91% each. This model compensates the use of the Jar-test of raw water to determine the amount of alum that must be added and sufficient by measuring the turbidity, temperature, and pH of the raw water only, and then calculating the value of the required dose of alum.

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The problems caused by suspended sediment overloading in open channels are of great importance to the hydraulic engineers. One of the important problems caused by the sediment overloading during flood seasons is the change in bed level and corresponding water level of rivers due to its deposition on the river bed. At the upstream reaches, the bed slope is high, velocity is high and hence the rivers carry large amount of sediment during flood seasons.In this paper, eighty one experiments on the laboratory open-channel of cross-section dimensions (20*50) cm and (10) m long. The experiments include using sharp crested weir in the last third part of the channel. Three heights of weir are used; namely half width of channel (B), equal the width, and 1.5 times the width of channel . Also three bed slopes of the channel are used; namely 0.015, 0.0225, and 0.03). In all experiments, the values of discharge are limited between 100 and 300 l/min. The concentration of suspended sediment is measured upstream and downstream the weir through each experiment to calculate the sediment reduction ratio (SRR%) The results of the laboratory experiments showed that the sediment reduction ratio increases with the increase of weir height and reaches about (63%) at channel bed slope of (0.015) and weir height 1.5B (where B is the width of channel). When the discharge is more than (100 l/min), the highest values of sediment reduction ratio are obtained for the three slopes used and at weir height (1.5B).

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In this research, the sediment load in Shat AlGharaf River lies in the south of Iraq, has been studied.Two empirical formulas those have been presented by ;Bagnold and Van Rijn were adopted as a deterministicequations for computing the sediment discharge in selectedreaches of the river . The application of these equations requiresto do different hydraulic, sediment, and geometricmeasurements for the selected reaches. Accordingly ,thirteen sections along the river within a study area havebeen adopted. After analyzing the available data, a newthe formula for estimating the suspended sediment load in ShatAl-Gharaf was developed, depending on the data for tensections of this river and by using SPSS program, thedetermination coefficient of the new formula was (R2=0.94).The validity of the established formula has been verifiedusing some well related (i.e., nearly the same hydraulics andgeometrical circumstances) of field data over the world wasselected from published literatures [8] these are: Coloradoriver data of the U.S.B.R.(1958), River data from Leopold(1969) , and India canal data of Chaudry et.al.(1970). As wellAs those observed in the remaining three sections of presentRiver, the verification shows a good agreement.The results of the adopted two formulas and the new formulawere compared with field measurements using DiscrepancyRatio (bais) method. The suggested new formula gave thebest results where 50% of data located within a discrepancya ratio close to one and 30% of data located within an error±20%, that is referred to suitability adoption this formula as athe deterministic equation to estimate the sediment load in ShatAl-Garaf river within a study reach

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The earth-fill dams are simple structures which are able to prevent the sliding and overturning because of their self-weight. Due to lack of suitable clay materials, the dams may be designed as zoned core which is composed of three vertical zones contains central impermeable core and two permeable shells on their two sides of the core. Impervious core is used in zoned earth dam to reduce the quantity of seepage through the body of the dam and to relief part of risk of piping and erosion in the downstream side. This study aims to study the soil properties that is used as a core of earth dam through a series of laboratory experiments that were carried out a several soil samples mixed with both lime and silica fume, in order to stabilize the soil. The process of stabilization aims to increase the soil strength and reducing its permeability and compressibility. Test results show that adding lime and silica fume to the soil decreases the permeability of soil with different cases of study, the percentage of decreases in case of standard compaction about (21%-90%) while in modified compaction test the permeability decreases in range (41.7%-91.3%). Also the unconfined compressive strength of the soil increasing significantly in both cases of compaction which were standard and modified. When add the materials, these values were increased in range (76%-90%) for samples from standard compaction test, while it being (0.21%-42%) in modified compaction test.

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In this research, a study was conducted experimentally to investigate the scour hole dimensions downstream the combined structures which consist of weir and gate. Twelve models have been designed and every model is formed from composite weir consists of two geometric shapes and three types of gates which are rectangular, semi-circular and triangular in shape, where multi factors were studied to find out the effect of changing geometry for both weir and gate, discharge flowing in the flume and particle size of bed material on the dimensions of scour hole. The experiments was conducted in a laboratory channel was constructed from blocks and concrete with length of 18 m, 1 m width and 1 m depth. The laboratory models were installed after 7 m from the main gate which is controlling the passage of water from the main reservoir into the flume. At the beginning, the calibration process was conducted to identify the actual discharge values that pass in the flume, then experiments were conducted to calculate the discharge coefficient for each model, which represents one of the studied factors within the dimensional analysis of the variables to derive the empirical formulas to calculate the dimensions of scour hole. Then the experiments were conducted in order to derive formulas to investigate the depth and length of the scour hole which formed in the sand floor spreading as a layer of 30 cm in thickness for a distance 4 m downstream combined structure. Two samples of sand were used in the experiments with different median size of particles ( d50), the first of 0.7 mm and the second of 1 mm. Using the dimensional analysis by π theorem and IBM SPSS 21 program, Four nonlinear relationships were derived to calculate the dimensionless scour depth (SD / d50) and another four nonlinear relationships calculates the dimensionless length of scour (SL / d50) depending on the laboratory results for each of the relative discharge (Qr), Froude number in terms of mean size of particle of bed material (Frd), non-dimensional difference head between upstream and downstream of combined structure (HD / d50), dimensionless distance between the lower edge of the weir and the upper edge of the gate (y3 / d50), dimensionless head over the crest of compound weir (h/d50) and the discharge coefficient (Cd), where the resulted determination coefficients (R2) from these relationships were good.

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