Deformation in open collector drainage systems

. The article evaluates the hydraulic processes in the collectors which constructed in irrigated fields. Illuminated the washing processes under the influence of the flow velocity in the collector bed. In order to study the washing processes in the collector basin, are covered the results of research conducted in the self-washing collector in natural field conditions. Collector 2-K-4 in Khavas district of Syrdarya region was selected as the object of research. Given cases of changes in the project parameters as a result of washing processes in the core of the collector. Were selected 5 sections in the collector and hydraulic parameters were studied. was evaluated the effect of hydraulic processes on the collector core. The studied sections show cases of change of design parameters under the influence of hydraulic processes. Soil samples were taken from the reservoir and the mechanical composition was determined under laboratory conditions. Based on the laboratory and natural field conditions results, a special graph was developed for the design of collectors on the basis of non-washable speed.


Introduction
It is known that the role of collectors in improving the reclamation of arable land is of particular importance. This is because the collectors serve to transfer excess water generated in the control and collection ditches to subsequent collectors or to a water intake source. Sedimenting drainage of reservoirs, deterioration of water permeability have a negative impact on the entire massif. In some cases, it is common in practice that turbid particles formed as a result of leaching processes in the collector bed can accumulate in the next collector bed, in water intake sources [1,2].
Analysis of the literature showed that the issues of ensuring the static and dynamic stability of irrigation canals during operation have been extensively studied by research scientists, and have been achieved certain positive results. Based on the laws of flow movement in irrigation canals and the formation of the canal, a number of recommendations have been developed to substantiate the hydraulic parameters that provide dynamic stability in the projection process, taking into account the washing and sedimentation processes [3,4,5].
It is known that the movement of water flow in open streams has an effect on the formation of the stream over time. Have been studied to some extent and recommendations have been developed the laws of formation under the influence of the flow movement of irrigation canals [4,5]. However, the laws of bed formation under the influence of water flow movement in collectors have not been sufficiently studied. It should be noted that leaching processes are observed in the reservoirs, which are built on arable lands with a slope of the soil i = 0.002. Have been proposed and are being used a number of methods for construction collectors on the basis of non-washable velocity in the project process. Taken into account soil type, flow rate and depth are when substantiating the unwashed rate on the basis of normative documents [3,4,5,7]. The minimum value of the depth justifying the unwashed speed given in the normative documents is h = 0.5 m, which cannot be used in the design of collectors. This is because most collectors are designed with a flow depth of less than 0.5 m. One of the urgent tasks of our time is to conduct research on the study of washing processes in reservoirs, to evaluate hydraulic processes in the valley, to develop science-based design methods for the prevention of washing processes [6,7,8].

Solution method
Research was conducted in natural field conditions in Khavas district of Syrdarya region, in order to study the washing processes in the collector bed. The 2-K-4 collector in Khavas district was selected as the object of research. The total length of the collector is 8.63 km, and washing processes took place in 70% of the collector bed. The collector serves to transport excess groundwater flowing from 12,000 ha of irrigated crop fields away to collector 8-K-2. The slope varies along its length, with an average slope of i = 0.0035 and an average depth of 5.57 m above ground level.
Commonly accepted methods of hydraulics and hydrology were used in the research. The cross-sections of the collector were determined using the method of measuring relative heights, and the flow velocity was determined using hydrometric vertices [9,10,11]. Identified results were mathematically statistically processed and the leaching processes in the collector bed were evaluated.

Results
As Collector core was washed and the bottom was deepened to a distance of ∆h = 0.75 m, the cross-sectional surface changed from a trapezoidal shape to a parabola (Fig. 4).
-project, -existing As a result of the research, it was found that the side walls of the collector collapsed and fell into its core, and as a result of the high flow rate, it was washed and averaged 0.9 m below the projected bottom.

Analysis
In order to determine the cause of washing processes in the collector, soil samples were taken and the mechanical composition was analyzed in the laboratory [12,13,14,15]. According to the results of the analysis, it was determined that the mechanical composition of the soil of the collector valley consists of different fractions. The results of the analysis are presented in the following tables and figures.  It is known that in the projection of canals, first of all, it is necessary to determine the unwashed speed on the basis of normative documents and not to exceed the specified speed of flow in the channel. When designing collectors, special attention should be paid to the design work based on the above requirements. However, in the given normative documents, for the values of the flow depth from 0.5 m to 5 m for the determination of the velocity of the self-washing, there are problems in the design of collectors on the basis of the unwashed speed [16,17,18]. Because in most cases in the design of collectors, the flow depth is designed at values less than 0.5 m. Based on the results of field studies and analysis of samples taken in the laboratory, non-flushing velocity values were determined in accordance with the flow depth in the design of the collectors (Figure 7).

Conclusion
When reconstructing self-flushing collectors, it is necessary to substantiate the depth and velocity of the non-flushing flow before justifying the width of the flush bottom. If the width of the bottom of the collector core is not based, re-washing processes will occur. This leads to excessive costs. If the slope of the collectors is higher than i> 0.002, leaching processes will occur. Given this situation, it is necessary to substantiate the unwashed speed in the design of collectors. In the design of the collectors, a special graph was developed to justify the unwashed speed. Using this graph, it was possible to design collectors with an average diameter of the ditch soil d = 0.5 mm, d = 0.75 mm, d = 1.00 mm on the basis of non-washing speed.