A method for mitigating the effects of flood rain on slope creep

Abstract

This invention relates to a method for mitigating the impact of rain and fog on slope uplift during flood discharge. By installing anti-fog walls at appropriate locations on the bank slope, the wind speed and direction along the slope during flood discharge are altered, preventing the continuous uplift of large amounts of rainwater. This reduces the protection height and standards of the upper bank slope, protecting sensitive areas and saving significant engineering investment. The changes in wind field and slope rainfall before and after the installation of the anti-fog walls are analyzed using flood discharge wind field calculation models and flood discharge atomized rainfall models, allowing for optimization and adjustment of the layout to improve the blocking effect. An overhanging eaves on the upper part of the anti-fog walls prevents airflow from climbing over them. The method of using a lower concrete base and an upper lightweight steel structure, with segmented installation, adapts to complex terrain and facilitates maintenance. An interpolation method based on a regular grid space is used to quickly calculate the nearby wind speed and bottom height of each raindrop, simulating the movement and settling process of raindrops in the slope wind field.

Description

Technical Field

[0001] This invention relates to a method for mitigating the effects of flood discharge, rain, fog, and slope climb, belonging to the field of water conservancy and hydropower technology. Background Technology

[0002] Figure 1 and Figure 2 This describes the actual flood discharge and atomization situation at the dam body and riverbanks of a hydropower station. Flood discharge atomization is a non-natural rainfall and water mist phenomenon generated during the flood discharge process of a large hydropower station. According to existing prototype observation data, the maximum recorded rainfall intensity has exceeded 1000 mm / h, with a central wind speed reaching 50 m / s. Although most of the floodwater falls in the center of the river channel, the generated atomized rainfall, under the influence of the wind field, rises along the riverbanks, forming localized areas of heavy rainfall. The soil or overburden in these areas is highly susceptible to landslides, adversely affecting the safe operation of the hydropower station and the surrounding environment. Therefore, in the design and normal operation of the power station's flood discharge and energy dissipation, it is necessary to implement high slope management measures on both banks based on the distribution range of the atomized rainfall area during flood discharge. This involves first removing the surface overburden of slopes reaching hundreds of meters high, and then using concrete panels with stress anchors for protection. This adds unnecessary waste and safety hazards in terms of engineering technology, economy, safety protection, and environmental protection investment.

[0003] During the construction and operation of power plants, the problem of flood discharge mist will persist for a long time and be widespread, resulting in a huge investment in the safety protection of high slopes. Therefore, this invention proposes a slope fog-proof wall design method that can effectively reduce the rise of flood discharge rain and mist along the slope and has a relatively reasonable technical and economic investment, thereby reducing the protection range and protection standards of the upper high slope, especially in slope protection areas with sensitive buildings. Summary of the Invention

[0004] To mitigate the impact of rain and fog rising from the slope during flood discharge, this invention proposes a design method for setting up an anti-fog wall within the bank slope protection zone. During flood discharge, the anti-fog wall can act on the rising wind field of both banks, changing the wind speed and direction and preventing it from carrying a large amount of fog and rain upwards. This reduces the protection height and standards of the upper bank slope, thereby saving a significant amount of engineering investment and ensuring the safe operation of the project.

[0005] The objective of this invention is achieved as follows:

[0006] First, by using mathematical modeling, the flood discharge wind field and rainfall distribution range under natural bank slope conditions are calculated, and the fog-proof wall should be arranged in this area;

[0007] Second, based on the distribution of the flood discharge wind field and the orientation of the bank slope topography, determine a suitable fog barrier layout scheme, including the orientation and length of the fog barrier and the cross-sectional shape of the wall. Fog barriers are usually placed in places with smaller vertical heights in the high wind speed zone of the slope to improve the blocking effect.

[0008] Third, by using mathematical modeling methods, the distribution of wind speed and rainfall intensity on the slope after the fog barrier is installed is calculated, the blocking effect is analyzed, and it is determined whether the design requirements are met.

[0009] Fourth, if the fog-proof wall layout does not meet the design requirements, adjust the planar orientation and vertical structure of the fog-proof wall, and repeat steps one through three until the design protection requirements are met.

[0010] The fog-proof wall is a geometric body with a base and a certain material strength. The material is concrete or steel structure, and the base is a concrete structure that can support the upper material and is fixed to the bedrock of the bank slope.

[0011] The fog-proof wall can be installed on the slopes on both banks near the flood discharge area of ​​the dam, or on the slope opposite the outlet of the flood discharge tunnel on the downstream bank. Structurally, it can be implemented in conjunction with existing slope excavation and protection projects.

[0012] Specifically, the location of the anti-fog wall is selected within the range of flood discharge wind speed of 15-30 m / s and rainfall intensity of 50-200 mm / h.

[0013] Specifically, the dimensions of the anti-fog wall are generally selected as follows: bottom width 5-10m, top width 2-5m, and height 10-20m.

[0014] Specifically, the anti-fog wall can be arranged in sections to prevent continuous collapse. The section length is 50-100m. Drainage holes are set on the wall surface to drain excess water in the soil behind the wall into the river.

[0015] Specifically, an eave can be installed on the upper part of the anti-fog wall, with the eave suspended about 2m above the ground. This causes the rising airflow to move in the opposite direction, forming an airflow barrier that prevents the airflow at the higher part of the slope from passing over the anti-fog wall.

[0016] Specifically, the anti-fog wall can also adopt an upper lightweight steel structure and a lower concrete base. The base can be a whole or a combination of multiple smaller bases to adapt to complex terrain, save on engineering investment and facilitate maintenance.

[0017] The mathematical model consists of two parts: a flood discharge wind field calculation model for calculating the slope wind field during flood discharge, and a flood discharge atomized rainfall model for calculating the slope rainfall intensity distribution. The two are coupled and share a common calculation grid.

[0018] The flood discharge wind field calculation model is an Eulerian model, which calculates the three-dimensional wind field data of the slope. The flood discharge atomized rainfall model is a Lagrange model, which calculates the rainfall intensity distribution data of the slope.

[0019] Specifically, the principle of the flood discharge wind field calculation model is to use the flow velocity of the flood discharge as the driving condition of the wind field, and the topography of the river valley in the flood discharge area as the solid boundary of the wind field movement. The three-dimensional wind field caused by the flood discharge flow in the river valley can be calculated, and then the wind field conditions of the bank slope protection area can be obtained.

[0020] Specifically, the principle of the flood discharge atomized rainfall model is to simulate the movement and settling process of a large number of sprayed raindrops formed when the flood discharge flows into the water. In the calculation of raindrop movement and settling, the influence of the surrounding wind field needs to be considered, which is obtained by solving the aforementioned flood discharge wind field calculation model.

[0021] Specifically, the principle of the flood discharge atomized rainfall model is as follows: in order to calculate the movement and settling of each raindrop in the wind field, an interpolation method based on a regular grid space is adopted, which can calculate in real time the nearby wind speed and altitude of each raindrop during its flight.

[0022] By using a flood discharge wind field calculation model, we can analyze the changes in wind field before and after the implementation of the anti-fog wall on the bank slope. By using a flood discharge atomization rainfall model, we can analyze the changes in slope rainfall distribution before and after the implementation of the anti-fog wall. This allows us to optimize and adjust the anti-fog wall layout scheme to improve the blocking effect.

[0023] The beneficial effects of this invention are as follows: This invention employs a geometric shape with a certain material strength as a deceleration measure. During the flood discharge process of a hydropower station, it adjusts the wind field on the bank slope, reducing the rise of flood discharge fog and rain along the bank slope, and decreasing the range and intensity of rainfall on both banks. This geometric shape, set at a certain height on the bank slope, can prevent landslides in the upper soil while simultaneously reducing the rainfall intensity in the upper area, significantly reducing the engineering protection area and protection standards, thereby saving substantial engineering investment. This invention has significant application value for both completed and under-construction projects. In the future, my country plans to construct numerous high-head hydropower stations in the high-altitude, high-slope, and arid regions of Southwest China, and this invention has broad application prospects. Attached Figure Description

[0024] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0025] Figure 1 This is one of the actual situations involving flood discharge from the dam body and flood discharge atomization on the bank in a construction project.

[0026] Figure 2 This is the second example of the actual flood discharge and atomization of the dam body and the bankside flood discharge in the project.

[0027] Figure 3This is the basic design process for the bank slope anti-fog wall layout scheme described in this invention;

[0028] Figure 4 The wind speed distribution on the slope without a fog-proof wall, as described in Embodiment 1 of the present invention;

[0029] Figure 5 This refers to the rainfall distribution on the slope where no fog-proof wall was installed, as described in Embodiment 1 of the present invention.

[0030] Figure 6 The calculation grid is for the layout scheme of the anti-fog wall 1 on the bank slope described in Embodiment 1 of the present invention;

[0031] Figure 7 The slope wind speed distribution after the anti-fog wall 1 is installed on the bank slope according to Embodiment 1 of the present invention;

[0032] Figure 8 The slope rainfall distribution after the anti-fog wall 1 is installed on the bank slope as described in Embodiment 1 of the present invention;

[0033] Figure 9 The wind speed field in the arbitrary grid space is obtained from the flood discharge wind field calculation model described in Embodiment 1 of the present invention.

[0034] Figure 10 The regular grid spatial wind speed field obtained by interpolation transformation as described in Embodiment 1 of the present invention;

[0035] Figure 11 This is a method for rapidly determining the wind speed experienced by moving raindrops in the flood discharge atomized rainfall model described in Embodiment 1 of the present invention;

[0036] Figure 12 The arrangement and shape of the anti-fog wall 2 on the bank slope as described in Embodiment 2 of the present invention;

[0037] Figure 13 The calculation grid is for the arrangement scheme of the anti-fog wall 2 on the bank slope described in Embodiment 2 of the present invention;

[0038] Figure 14 The slope wind speed distribution after installing the anti-fog wall 2 on the bank slope as described in Embodiment 2 of the present invention;

[0039] Figure 15 The slope rainfall distribution after setting up the anti-fog wall 2 on the bank slope as described in Embodiment 2 of the present invention;

[0040] Figure 16 This is the lightweight steel structure form of the slope fog-proof wall described in Embodiment 3 of the present invention. Detailed Implementation

[0041] The basic process of this invention is as follows: Figure 3 As shown.

[0042] The specific technical solutions of the present invention will be described with reference to the embodiments.

[0043] Example 1:

[0044] This embodiment describes a method for reducing rainfall intensity on riverbank slopes by constructing anti-fog walls on the riverbank, protecting the upper bank slope, and lowering the scope and standards of protective engineering construction. First, a flood discharge wind field calculation model is used to calculate the wind field formed on the natural bank slope during flood discharge, such as... Figure 4 As shown, the rainfall distribution on the natural bank slope during the flood discharge process is calculated using a flood discharge atomization rainfall model. Figure 5 As shown. Second, the location and height of the anti-fog wall 1 are determined according to the wind field distribution. Generally, it is located within the wind speed range of 15-30 m / s on the bank slope, with a height of 10-20 m. In this embodiment, the height of the anti-fog wall 1 is 20 m, the maximum wind speed nearby is 30 m / s, and the maximum rainfall intensity is 200 mm / h. The arrangement of the anti-fog wall is as follows. Figure 6 As shown. Third, using the flood discharge wind field calculation model, the change in wind speed field after the installation of anti-fog wall 1 on the bank slope is calculated, as shown. Figure 7 As shown; using the flood discharge atomized rainfall model, the changes in the distribution of flood discharge atomized rainfall after the installation of anti-fog wall 1 on the bank slope are calculated, as follows. Figure 8 As shown. Fourth, analyze whether the layout scheme of the anti-fog wall on the bank slope is reasonable. If it does not meet the requirements, further adjustments can be made and a verification analysis can be conducted until the design requirements are met.

[0045] The slope geology described in this embodiment is generally bedrock + fractured material, with a 0-10m overburden layer on top. The fog-proof wall should be installed on the bedrock and can be fixed by reinforced concrete stress anchors to prevent damage from landslides of the overburden layer, strong winds downstream, etc.

[0046] The fog-proof wall described in this embodiment adopts a straight-line arrangement. In actual engineering, the bank slope terrain is generally a curved path with varying elevations. When the lateral width of the flood discharge wind field is narrow and the high-wind-speed area is relatively concentrated, a straight-line arrangement can be adopted. In this case, the fog-proof wall has a uniform height, and its elevation changes with the undulation of the bank slope terrain. In addition to blocking the rise of fog and rain winds from the front, it also guides fog and rain away from the protected area along both sides. When the lateral width of the flood discharge wind field and the rain area is large, the fog-proof wall should be arranged in sections along a certain elevation. The length of each section is about 50-100m. This is to prevent continuous collapse caused by a section being unable to withstand the flood discharge and heavy rain. At the same time, drainage holes are set on the wall surface to drain excess water in the upper soil into the river channel, thereby reducing the lateral pressure of the soil on the fog-proof wall. The total design flow rate Q of the drainage ditch should be obtained by integrating the rainfall intensity distribution and range within the fog protection area. Q represents the total design flow rate of the drainage ditch, in cubic meters. 3 / s; P represents the intensity distribution of fogged rainfall, mm / h; A represents the distribution range of the rain area on the bank slope, m. 2 .

[0047] The fog-proof wall described in this embodiment, if positioned too low and close to the river channel, offers a large protection area for the upper bank slope. However, with wind speeds exceeding 30 m / s and rainfall intensities exceeding 200 mm / h, the required material and structural strength would be excessive, making it prone to damage. Conversely, if positioned too high and far from the river channel, it might miss some bank slope protection areas. Although ground wind speeds are lower in these areas, the vertical distance of the wind speed band is significant, often requiring a fog-proof wall height exceeding 20 m, increasing the technical difficulty. Therefore, it is necessary to determine its economically reasonable location and height based on the flood discharge wind field and the distribution of rainfall intensity on the bank slope.

[0048] The flood discharge wind field calculation model described in this embodiment is an Eulerian model that treats air as a continuous medium. It uses the water jet entering the water as the driving condition for airflow motion, calculating the three-dimensional wind field data within the valley. The flood discharge atomized rainfall model is a Lagrange model that treats raindrops as a discrete medium. It uses the water jet entering the water as the condition for random raindrop ejection, simulating the movement and settling of a large number of ejected raindrops in the air, and finally obtaining the rainfall intensity distribution on the riverbank. The movement and settling of raindrops in the air need to consider the mechanical effect of the nearby wind speed on the raindrop's flight, as well as the ground elevation at the final landing point of the raindrops.

[0049] The wind speed near the raindrop is derived from wind field data obtained from the flood discharge wind field calculation model. This wind speed dynamically changes with the spatial position of the raindrop and needs to be calculated in real time during flight. Therefore, this invention employs a fast interpolation method based on a regular grid space:

[0050] First, through spatial interpolation calculation, the flood discharge wind field data [x, y, w] in any grid space (such as...) is calculated. Figure 9 Convert the wind field data [i, j, w] to a regular grid space (e.g.) Figure 10 This allows it to be directly stored in the array [W] i，j ];

[0051] Second, for a raindrop with arbitrary coordinates [x, y] flying in space, first find its regular space matrix. like Figure 11 From the storage array [W i，j From the given information, we obtain the wind speed values ​​for the four nodes in the regular space: W i，j W i+1，j W i，j+1 W i+1，j+1 ;

[0052] Third, transform any [x, y] coordinate into a local coordinate [X, Y] within the regular space to obtain the weighted area A of the wind speeds at the four nodes. 00 A 01 A 10 A 11Then, using an area-weighted formula, the nearby wind speed W at the location [x, y] of the raindrop is calculated. x，y .

[0053] The calculation formula for the above method is as follows:

[0054] i = Int(x / L)

[0055] j = Int(y / L)

[0056] X = x / Li

[0057] Y = y / Lj

[0058] A 00 = (1-X)(1-Y)

[0059] A 11 =XY

[0060] A 10 =X(1-Y)

[0061] A 01 =(1-X)Y

[0062] W x，y =A 00 W i，j +A 01 W i，j+1 +A 10 W i+1，j +A 11 W i+1，j+1

[0063] Fourth, the nearby wind speed W x，y Substituting the equations of motion for the raindrop, we can solve for the next position of the raindrop at the end of the time step (which is typically 1-2 seconds). By repeating the above calculations, we can obtain the trajectory of each raindrop in the air until it falls to the ground.

[0064] The interpolation method based on regular grid space can be extended to three-dimensional cases. In addition to determining the wind speed experienced by raindrops, it is also used to calculate the ground elevation below the raindrops to determine whether they have fallen to the ground, and then the rainfall is accumulated into the corresponding ground grid.

[0065] The interpolation method based on regular grid space for distinguishing the wind speed near raindrops and ground elevation has been included in the flood discharge atomized rainfall model.

[0066] Therefore, this invention combines the flood discharge wind field calculation model with the flood discharge atomized rainfall model, which can analyze the rising and falling process of flood discharge raindrops along the slope and obtain the rainfall intensity distribution on the slope, so as to evaluate the implementation effect of the anti-fog wall.

[0067] Example 2:

[0068] This embodiment is an improvement on Embodiment 1. In Embodiment 1, the anti-fog wall 1 is located in an area with a slope wind speed of 30 m / s and a rainfall intensity of 200 mm / h. It is a vertical, windward structure. During flood discharge, the slope airflow near the anti-fog wall has a wind speed of 30 m / s, and the upper airflow can still pass over the top of the wall, forming a 12 m / s wind speed band behind it. Some rain and fog cross the anti-fog wall with the airflow, forming rainfall on the slope behind it. In Embodiment 2, based on the vertical distribution of the slope wind speed band, an area with a lower slope wind speed band is selected to deploy anti-fog wall 2, with a wall height of 10 m. A 2 m overhang is used at the top of the anti-fog wall, causing the rising airflow to move in the opposite direction, forming a barrier to block the upper low-speed airflow, further improving the effectiveness of the anti-fog wall. This embodiment appropriately reduces the height and strength of the anti-fog wall without reducing the fog and rain blocking effect. The deployment principle is as follows: Figure 12 The layout of the anti-fog wall is shown in the figure. Figure 13 After the anti-fog wall 2 is installed, the wind field on the slope changes as follows: Figure 14 As shown, the variation in rainfall distribution on the slope is as follows: Figure 15 As shown, the wind speed on the slope decreases to 20 m / s in front of the anti-fog wall and to below 10 m / s behind the wall. While the rain and fog still move with the airflow, they are blocked by the anti-fog wall, and the rainfall area is primarily located in front of it. In comparison, the anti-fog wall scheme in Example 2 is technically and economically superior to Example 1, demonstrating that the design method described in this invention has good practical value.

[0069] Example 3:

[0070] This embodiment is a supplement to Embodiment 1. The fog-proof wall described in Embodiment 1 is entirely constructed of concrete, cast as a whole or assembled. It can be placed in areas with high wind speeds and heavy rainfall to block raindrops from rising with the airflow. However, some fog droplets located at higher elevations can still pass over the fog-proof wall and continue to rise. At this point, the wind speed decreases and the rainfall intensity weakens. If necessary, a second protective barrier can be deployed. In this case, the wall and base of the fog-proof wall can use different structures. The wall itself is made of lightweight steel, while the lower base is anchored to bedrock with reinforced concrete. If the upper wall structure is damaged due to slope collapse, it can be restored on the base later. When the slope terrain is complex, the base of the fog-proof wall can be cast separately, and the upper structure can be built according to the terrain, such as... Figure 16 As shown.

[0071] Finally, it should be noted that the above is only used to illustrate the technical methods of the present invention and not to limit it. Although the present invention has been described in detail with reference to several arrangement schemes, those skilled in the art should understand that the technical solutions of the present invention (such as the types and functions of mathematical models, the position, shape, height, material, base spacing, etc. of the anti-fog wall) can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for mitigating the effects of slope climb caused by flood discharge rain and fog, characterized in that: By installing anti-fog walls on the bank slope, with the anti-fog walls positioned within the flood discharge wind speed range of 15-30 m / s and the rainfall intensity range of 50-200 mm / h, the wind speed and direction along the bank slope during flood discharge are altered, preventing the rain zone from continuously rising. A flood discharge wind field calculation model is used to analyze the wind field changes before and after the implementation of the anti-fog walls, and a flood discharge atomization rainfall model is used to analyze the changes in slope rainfall distribution before and after the implementation of the anti-fog walls. The anti-fog wall layout scheme is then optimized and adjusted to improve the blocking effect. By setting an eaves on the upper part of the anti-fog wall, the rising airflow moves in the opposite direction, forming an airflow barrier that prevents the airflow on the high slope from passing over the anti-fog wall; The base of the anti-fog wall is made of reinforced concrete and anchored to the bedrock of the bank slope. The upper wall is made of concrete or steel structure. Drainage holes are provided on the wall to drain excess water from the upper soil into the river channel. The anti-fog wall is arranged in sections, with each section being 50-100m long and 10-20m high. The anti-fog wall has a base width of 5-10m and a top width of 2-5m; the eaves are suspended for 2m. The foundation of the anti-fog wall is a combination of multiple small bases to adapt to complex bank slope terrain.

2. The method for mitigating the impact of flood discharge, rain, and fog on slope climb, as described in claim 1, is characterized in that... The flood discharge wind field calculation model is the Eulerian model, which calculates the slope wind field data. The flood discharge atomized rainfall model is the Lagrange model, which calculates the slope rainfall intensity distribution data.

3. A method for mitigating the impact of flood discharge, rain, and fog on slope climb, as described in claim 2, characterized in that... The aforementioned flood discharge atomized rainfall model employs an interpolation method based on a regular grid space to calculate the motion and settling of each raindrop in the wind field, thereby calculating in real time the nearby wind speed and altitude of each raindrop during its flight.

4. A method for mitigating the effects of flood discharge, rain, and fog on slope uplift, as described in claim 1, characterized in that... The fog-proof walls are arranged on the hillsides on both sides of the flood discharge area near the dam body, or on the hillside opposite the outlet of the flood discharge tunnel on the downstream bank.

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