Method for determining the onset of the erosion process of earth dam models
A small-scale experimental setup with a hydraulic seal and sensors accurately determines the onset of erosion in earthen dams, addressing the challenge of predicting and preventing catastrophic dam failures.
Patent Information
- Authority / Receiving Office
- RU · RU
- Patent Type
- Patents
- Current Assignee / Owner
- FEDERALNOE GOSUDARSTVENNOE BJUDZHETNOE UCHREZHDENIE 3 TSENTRALNYJ NAUCHNO ISSLEDOVATELSKIJ INST MINISTSTVA OBORONY ROSSIJSKOJ FEDERATSII
- Filing Date
- 2025-02-03
- Publication Date
- 2026-07-01
AI Technical Summary
Existing methods fail to accurately determine the onset of erosion in earthen dam models when water overflows the crest, leading to difficulties in predicting and preventing catastrophic dam failures and subsequent flooding.
A small-scale experimental setup with a height-adjustable composite hydraulic seal and erosion sensors is used to measure the onset of erosion in dam models, employing video cameras and calibrated sand to simulate dam overflow conditions, confirming theoretical conditions for erosion onset.
Accurately records the moment of erosion onset, enabling effective prevention strategies for earthen dams, applicable to various erodible materials.
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Abstract
Description
[0001] The invention relates to the field of hydraulic testing and concerns laboratory studies of the process of erosion of dams made of local materials.
[0002] A method for determining the onset of erosion of earthen dam models is implemented using a small-scale experimental setup, which is a technical device that allows for the determination of the onset of erosion of earthen dam models when water overflows the dam crest. The setup includes a small-sized hydraulic flume with a height-adjustable composite hydraulic seal installed close to the dam model, dam models of various sizes made from water-erodible materials, video cameras, and erosion sensors [1] installed along the dam crest along its entire length.
[0003] A dam that retains a large amount of water is a potentially hazardous structure. Its failure leads to severe economic and environmental consequences. The most severe consequences can result from the failure of a cascade of dams within a hydroelectric power plant. If an upstream dam in a cascade of hydroelectric power plants is damaged, the potential energy of the water in the reservoir is released as a break wave, which can lead to water overflowing the crests of the downstream dams, eroding them, and causing catastrophic flooding of the underlying areas. The failure processes of dams made of local materials or of mixed types are described in detail in [2-4]. The practical importance of determining the onset of erosion for earth dam models is explained by the fact that studying the conditions for the onset of dam erosion will allow for the development of recommendations for preventing dam erosion and, thereby, avoiding the catastrophic consequences associated with dam failure and subsequent flooding of the area.
[0004] These circumstances determine the importance and relevance of research to determine the onset of the erosion process of earth dam models when water spills over its crest.
[0005] Laboratory research methods and hydraulic modeling are widely used in hydraulic engineering practice during the design, construction and operation of hydraulic structures.
[0006] A "Method for laboratory studies of river flows in the area of building structures" is known, described in the patent RU No. 2765260, IPC G01M 10 / 00, B02B 1 / 02, published. 01 / 27 / 2022 [5]. The authors conducted research on a laboratory setup for the impact of water flow on a model of building structures, consisting of an open hydraulic flume, a water level control device, a catchment tank and measuring computing equipment. During the experiments, measurements of the kinematic characteristics of the flow were carried out, and the measurement results were fed into the computing device in digital form. A feature of this invention is that the bottom of the hydraulic flume in the simulated area was uniformly filled with calibrated sand with a particle diameter of 0.1 ÷ 0.4 mm, and, subsequently, measurements of the resulting bottom relief were taken after a given flow regime of the water flow after draining the hydraulic flume.
[0007] The hydraulic flume included in this method does not contain a hydraulic seal between two reservoirs with water, the lifting of which from the bottom of the hydraulic flume would simulate the creation of a breakthrough wave after the destruction of the dam in the upper pool, which leads to a change in the water level in the lower pool (reservoir) and subsequent overflow over the crest of the model of the underlying dam.
[0008] The method closest to the invention in terms of its features and selected as a prototype is the one described in the article "Erosion Regimes of a Dam Made of Local Materials During Flow Overflow over its Crest" [4]. This method for simulating the erosion of dam models utilized an open hydraulic flume consisting of two reservoirs and a hydraulic seal between them. The water level in one reservoir was selected to be higher than the other. A dam model made of local materials was installed in the reservoir with the lower water level. While the hydraulic flume was filling with water, the dam model was protected from filtration by polyethylene film. Measuring equipment was used to determine the height of the breakthrough wave and the average velocity of water movement over the crest of the dam model.
[0009] The experiments in the hydraulic flume were conducted as follows. With the hydraulic seal raised, the hydraulic flume was filled with water to a level 2 cm below the model dam crest. After this, the hydraulic seal was lowered, and the water level in front of it rose to a certain value, H. г Then the water seal suddenly rose to a height exceeding H г .
[0010] During the experiments, the water level H was changed г in front of the hydraulic seal and the dam erosion time t was estimated п The erosion was monitored using video cameras and erosion sensors installed in the central part of the crest. Fluctuations in the wave formed after the hydraulic seal was lifted, as well as the agitation of the water in front of the dam after the protective film was removed, created noticeable unevenness in the wave heights overflowing the dam crest, making it difficult to estimate the average depth of the overflowing water along the pressure front and the onset time of dam erosion.
[0011] The technical and design features of the installation, the conditions for conducting experiments on it, and the measurement capabilities made it possible to measure the total time of dam erosion, which was a significant advance in the study of dam erosion processes, but did not make it possible to accurately record the moment of the onset of the erosion process of earth dam models.
[0012] Before the experimental studies began, preliminary conditions for the onset of the dam erosion process by an overflowing water flow were obtained using mathematical modeling.
[0013] Let us write the equations of continuity and conservation of energy for the flow over the crest of the dam in the following form [3]:
[0014] vhL п =Q (1)
[0015]
[0016] where v and h are the average cross-sectional velocity and depth of the flow at the crest of the dam, respectively; L п- the length of the pressure front of the dam; Q - water flow through the dam; α1 and α2 - coefficients; g - acceleration due to gravity; H - excess of the water flow level over the dam crest.
[0017] Since the flow changes in a relatively small space are considered, the flow energy losses are comparatively small and may not be taken into account. However, if necessary, they can be taken into account by the coefficient [4]. Analysis of the system of equations (1) - (2), assuming the values of Q, H, L п constant, after a series of transformations leads to the following dependencies of the depth and velocity of the flow at the crest of the dam on the excess of the water flow level over the crest of the dam:
[0018]
[0019] The stream, overflowing the dam crest, affects the dam soil. Soil erosion begins under condition (5):
[0020] v>v кр , (5)
[0021] where v кр- critical (non-eroding) flow velocity, which is understood as the highest value of the average flow velocity v over the cross-section, at which the flow cannot cause erosion of the bottom soil.
[0022] Substituting equation (4) into (5), we obtain, after some transformations, the requirement for the excess of the water flow level over the dam crest H for the erosion of the dam crest soil by the overflowing flow:
[0023] H>k⋅v 2 кр , (6)
[0024] where k is the coefficient, s 2 / m, 0.149 <k<0,051.
[0025] Condition (6) ensures that condition (5) is met. Both condition (5) and condition (6) ensure the onset of erosion of the dam crest soil.
[0026] To confirm the theoretical results, an experimental setup was created, the diagram of which is shown in Fig. 1. The setup is an open transparent hydraulic channel 5, made of 0.01 m thick organic glass. The length of the channel is 6.05 m, the width is 0.5 m and the depth is 0.4 m. The rigidity of the structure was ensured by fastening the organic glass to 0.4 m high wooden posts made of 0.04 × 0.04 m beams. The bottom of the hydraulic channel was connected to its side walls using a 20 × 20 mm aluminum corner. The joints of the sheets and the joints of the organic glass were insulated with waterproof glue.
[0027] A water seal made of 0.01 m thick plexiglass is installed in front of the dam. It is divided into two equal parts: an upper, lowering part (2) and a lower, stationary part (7). The joints between the lower part of the water seal and the hydraulic flume body are sealed with waterproof adhesive. The upper, lowering part of the water seal is inserted into special grooves cut into the walls of the hydraulic flume, allowing free movement while still ensuring a watertight seal. The upper and lower parts are joined by an overlap to prevent water leakage (seepage) through the joints. The upper part of the water seal (2) is lowered using handle (3), the design of which prevents contact with water.
[0028] The water seal is installed close to the dam crest, which allows for accurate measurement of the excess of the overflowing water level 4 over the dam crest and the creation of a smooth overflow mode.
[0029] The size of the water seal is selected based on the following conditions:
[0030] When folded, the water seal should not cover more than 2 / 3 of the dam height;
[0031] The total height of the water seal should exceed the water level in the trough in front of the dam;
[0032] The width of the water seal is equal to the width of the tray plus twice the depth of the groove.
[0033] During the research work, the processes of water overflowing the dam crest are recorded using two digital video cameras 1. Subsequently, when processing the information from the video camera, the height of the water rise above the dam crest along the entire length of the pressure front is determined.
[0034] Dam models made from local materials 6 were constructed from quartz sand of two compositions: homogeneous fine-grained sand with an average size of 0.15 mm and heterogeneous medium-grained sand with an average size of 0.22 mm. The cross-sections of the dam models are trapezoidal in shape and 0.1 m, 0.2 m, and 0.3 m high. The upstream slope is vertical, while the downstream slope is constructed with a ratio of 1:3 (Fig. 1). The crest width of the dam models was 0.1 m.
[0035] The diagram of the measurements carried out is shown in Fig. 2.
[0036] On the crest of the dam model, at a depth of 1 cm, scour sensors 8 were installed along the entire pressure front to record the onset of scour of the dam model. The time it took for water to pass through the scour sensors was recorded by an analog-to-digital converter 9 and transmitted to a personal computer 10 for further processing.
[0037] As a result of the studies conducted using the proposed setup, the theoretically derived preliminary conditions for the onset of erosion of earthen dams, contained in relations (5)-(6), were confirmed. These results were obtained for fine- and medium-grained cohesionless soils. The proposed method for experimentally determining the onset of erosion of earthen dams using a small-scale experimental setup and the methods for calculating it can be applied to dams constructed from other erodible materials (coarse sand, loam, gravel).
[0038] List of sources used
[0039] 1. Device for determining the moment of dam model erosion. Author's certificate No. 720481, published March 5, 1980.
[0040] 2. K.D. Salamova, M.A. Akhmedov. Statistical analysis of damage and destruction of earth dams / / Innovative ways of solving current problems of nature management and environmental protection: collection of reports. Int. sci. - tech. conf. / Alushta, (June 4-8, 2018). / Belgorod State Technological University; ed. - responsible I.V. Starostin. - Belgorod, 2018, pp. 104-113.
[0041] 3. A.L. Rozov. Physics of a Nuclear Explosion: In 2 volumes. Volume 2. Action of the Explosion / Ministry of Defense of the Russian Federation. Central Institute of Physics and Technology. - M .: Science. Fizmatlit, 1997. - 256 p.
[0042] 4. D.A. Kolpakov, S.I. Kosyakov, A.L. Rozov, N.Yu. Rusina. Erosion modes of a dam made of local materials during a flow over its crest / / NIC BTS 12 Central Research Institute of the Ministry of Defense of the Russian Federation. Issues of defense equipment, series 16, "Technical means of countering terrorism", 2022, issues. 03-04 (165-166), p. 160.
[0043] 5. Method for laboratory studies of river flows in the area of construction structures, patent for invention RU No. 2765260, IPC G01M 10 / 00, B02B 1 / 02, published 01 / 27 / 2022.
Claims
A method for determining the onset of the erosion process of earth dam models, which consists of using a small-scale experimental setup, which is a hydraulic flume consisting of two reservoirs and a hydraulic seal between them, the rise of which makes it possible to achieve the required intensity of the overflow of the water flow over the crest of the dam, ensuring the erosion of the dam model, and monitoring the height of the rise of water above the crest of the dam model along the entire length of the pressure front using two digital video cameras, characterized in that a hydraulic seal is used, divided into two parts of equal height, installed close to the dam, wherein the upper part of the hydraulic seal is designed with the possibility of quickly lowering to ensure a smooth overflow of the water flow with specified parameters, for which purpose it is equipped with a handle that does not come into contact with the water, and erosion sensors, installed on the crest of the dam along the entire length of the pressure front, record the section of the initial erosion of the dam crest.