A beach profile scouring and silting method considering the actual tide level and wave variation process

Abstract

The present invention discloses a beach profile scouring and silting method that takes into account the actual tide level and wave change process, and belongs to the intersection of coastal dynamics and fluid mechanics. Obtain relevant data of the actual beach area; extract the water level and wave history curves during the storm landing process; select a scale, and use the gravity similarity criterion to obtain the hydrodynamic parameters of the test; select test sand with appropriate particle size and bulk density according to the beach scouring and silting judgment similarity criterion; classify the water level to determine the wave height and wave period during each water level; before laying the test beach profile, calibrate the input parameters of the wave maker at different water levels; when there is actual beach profile data, scale the measured profile according to the scale relationship and lay it directly in the water tank; carry out the test according to the water level and wave parameters determined above, and record the profile evolution process; compare the measured beach profile elevation with the initial profile to obtain the scouring and silting changes of the beach profile.

Description

Technical Field

[0001] The invention belongs to the cross field of coastal dynamics and fluid mechanics, and more specifically relates to a beach profile scouring and silting method taking into account the actual tide level and wave variation process. Background Art

[0002] At present, the assessment of beach storm response mainly considers the effect of waves, and the change of water level is simulated by only considering a few fixed design water levels. There is a large difference between the actual tidal water level changes and it is difficult to reflect the actual storm dynamic process, thus affecting the reliability of the assessment of beach scouring and siltation changes.

[0003] The wave and water level elements usually considered in the current physical model tests of beach profile storm response are all fixed values. Generally, for storm conditions, the incident wave height is the design wave height of 50-10 years, and the water level is the extreme high water level or the design high water level, which is quite different from the water level changes caused by tides and storm surges during storms, and the process of the nearshore wave height gradually increasing to equilibrium and then gradually decreasing. In fact, the effect of high water levels during storms is often short, especially on strong tide beaches. When low tides are superimposed on storm surges, the effect of high water levels will be further weakened. Therefore, the fixed water level test method is often too conservative for the assessment of beach scouring and siltation, and will overestimate the degree of beach scouring. Summary of the invention

[0004] In view of this, the present invention provides a beach profile scouring and silting method that takes into account the actual tide level and wave change process, accurately reproducing the dynamic process during the actual storm in the laboratory to achieve a reasonable estimation of the beach scouring and silting changes.

[0005] In order to achieve the above object, the present invention adopts the following technical solution:

[0006] A beach profile scouring and silting method considering the actual tide level and wave variation process comprises the following steps:

[0007] Step 1: Obtain relevant data of the actual beach area;

[0008] Step 2: Select the historical typhoon process to be studied and extract the water level and wave history curves within 12-24 hours during the storm landing process;

[0009] Step 3: Combine the laboratory wave machine capacity and the working water depth range of the water tank, select a scale, and use the gravity similarity criterion to obtain the hydrodynamic parameters of the test;

[0010] Step 4: Based on the actual beach sand particle size and beach slope, and according to the similarity criterion of beach erosion and siltation, select test sand with appropriate particle size and bulk density;

[0011] Step 5: Classify the water level into 0.01m levels and determine the wave height and wave period during each water level.

[0012] Step 6: Before laying the test beach profile, calibrate the wave machine input parameters at different water levels;

[0013] Step 7: When there is actual beach profile data, the measured profile is scaled down according to the scale relationship and laid directly in the water tank;

[0014] Step 8: Carry out the test according to the water level and wave parameters determined in steps 5-6, and record the profile evolution process;

[0015] Step 9: Compare the measured beach profile elevation with the initial profile to obtain the scouring and silting changes of the beach profile.

[0016] Alternatively, when measured data are missing, the hydrodynamic parameters are calculated by a wide range of current-wave numerical models, including the TELEMAC-MASCARET model, the DELFT3D model, and the MIKE model.

[0017] Optional beach area data include: water level process during storms, wave height process, wave period process, sediment median particle size and beach profile slope

[0018] Optionally, the hydrodynamic parameters include a wave height change process, a period change process and a water level change process.

[0019] Optionally, in the absence of a measured profile, a uniform slope is laid as the initial profile with reference to the actual beach profile slope.

[0020] Optionally, in step 8, a camera is installed on the side of the water tank to measure the real-time changes of the profile.

[0021] It can be seen from the above technical solution that, compared with the prior art, the present invention discloses a beach profile scouring and silting method that takes into account the actual tide wave change process, accurately reproducing the dynamic process during the actual storm in the laboratory to achieve a reasonable estimate of the beach scouring and silting changes. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0023] Figure 1 It is a diagram of actual typhoon tide level and wave process according to an embodiment of the present invention;

[0024] Figure 2a A test tide map of an embodiment of the present invention;

[0025] Figure 2b A wave process diagram of an embodiment of the present invention;

[0026] Figure 3 is an initial cross-sectional schematic diagram of an embodiment of the present invention;

[0027] Figure 4 The beach profile scouring and silting changes over time obtained in the embodiment of the present invention. DETAILED DESCRIPTION

[0028] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] The embodiment of the present invention discloses a beach profile scouring and silting method taking into account the actual tide level and wave change process, and the steps are as follows:

[0030] Step 1: Obtain hydrodynamic and sediment-related data of the actual beach area, which usually includes: water level process during storms, wave height process, wave period process, median sediment particle size, and beach profile slope.

[0031] When measured data are missing, the hydrodynamic parameters can be calculated by a large range of current-wave numerical models, including but not limited to the TELEMAC-MASCARET model, the DELFT3D model and the MIKE model.

[0032] Step 2: Select the historical typhoon process that needs to be studied, and extract the water level and wave history curves within 12-24 hours (usually determined according to the local main tidal cycle) during the storm landing process.

[0033] Step 3: Based on the laboratory wave maker capacity and the working water depth range of the flume, select a suitable scale and use the gravity similarity criterion to obtain the hydrodynamic parameters of the experiment, including the wave height change process, period change process and water level change process.

[0034] Step 4: Based on the actual beach sediment particle size and beach slope conditions, and according to the similarity criterion of beach erosion and deposition, select test sand of appropriate particle size and bulk density to ensure that under the hydrodynamic conditions after scaling, a sandbar profile can also be formed in the flume to ensure that the evolution trend of the laboratory beach is consistent with that on site.

[0035] Step 5: Classify the water level into 0.01m levels and determine the wave height and wave period during each water level accordingly.

[0036] Step 6: Before laying the test beach profile, calibrate the wave machine input parameters at different water levels.

[0037] Step 7: If there is actual beach profile data, the measured profile can be scaled down according to the scale relationship and laid directly in the water tank. If there is no measured profile, a uniform slope can be laid as the initial profile based on the actual beach profile slope.

[0038] Step 8: Carry out the test according to the water level and wave parameters determined in steps 5-6, and use appropriate methods to record the profile evolution process. Generally, a camera can be set up on the side of the water tank to measure the real-time changes of the profile.

[0039] Step 9: Compare the measured beach profile elevation with the initial profile to obtain the scouring and silting changes of the beach profile.

[0040] The technical solution of the present invention is further explained below in conjunction with the accompanying drawings and embodiments.

[0041] This embodiment uses the Half Moon Bay and Xisha Bay beaches in Chongwu, Quanzhou as prototypes, with a slope of about 1 / 20 and a sediment particle size of about 0.7-0.8 mm. The actual wave and tide level process is calculated by the TELEMAC-MASCARET model.

[0042] The historical typhoons refer to the actual situation during the second landfall of Super Typhoon Fanapi in Fujian Province in 2010. The M2 tidal component in Fujian waters is absolutely dominant, and its period is about 12.4 hours. Therefore, the wave height and tidal level process from 0:00 to 12:00 on the day when Typhoon Fanapi landed was selected for analysis, and the datum of the tidal level is the mean sea level. Figure 1 Shown are the actual typhoon tide levels and wave processes.

[0043] The gravity similarity criterion was adopted, with a length scale of 1:50 and a time scale of 1:7.07.

[0044] The slope of the beaches of Half Moon Bay and Xisha Bay in Chongwu, Quanzhou is about 1 / 20, and the particle size of the supplementary sand is about 0.7-0.8mm. According to the beach scouring and silting judgment number, combined with the actual dynamic process, the beach scouring and silting judgment number at the peak stage is 0.2. By selecting quartz sand with a median particle size of 0.15mm, the beach scouring and silting judgment number in the test can be obtained as 0.19, which can ensure that the beach equilibrium profiles in the test and the actual situation are both sandbar profiles, and the beach evolution trend is consistent.

[0045] The tidal range simulated in the experiment was 0.10m, and the water level was divided into 11 levels with a level of 0.01m. Each level of water level was a group, and the duration was 300s. During the experiment, one high and low tide was considered, with a total of 20 groups. Figure 2a-2b The tide level and wave process are scaled and grouped.

[0046] According to the combination of tide level and waves, the input parameters of the wave maker are calibrated.

[0047] The test sand was laid in the flume to form a beach profile. Figure 3 It is a schematic diagram of an initial cross-section of an embodiment of the present invention.

[0048] An experiment was carried out to measure the real-time changes of the profile by setting up a camera on the side of the water tank.

[0049] Compare the measured beach profile elevation with the initial profile. Figure 4 This is the change process of beach profile erosion and deposition over time.

[0050] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A beach profile scouring and silting method taking into account the actual tide level and wave change process, characterized in that: The following steps are involved: Step 1: Obtain relevant data of the actual beach area; Step 2: Select the historical typhoon process to be studied and extract the water level and wave history curves within 12-24 hours during the storm landing process; Step 3: Combine the laboratory wave machine capacity and the working water depth range of the water tank, select a scale, and use the gravity similarity criterion to obtain the hydrodynamic parameters of the test; Step 4: Based on the actual beach sand particle size and beach slope, and according to the similarity criterion of beach erosion and siltation, select test sand with appropriate particle size and bulk density; Step 5: Classify the water level into 0.01m levels and determine the wave height and wave period during each water level; Step 6: Before laying the test beach profile, calibrate the wave machine input parameters at different water levels; Step 7: When there is actual beach profile data, the measured profile is scaled down according to the scale relationship and laid directly in the water tank; Step 8: Carry out the test according to the water level and wave parameters determined in steps 5-6, and record the profile evolution process; Step 9: Compare the measured beach profile elevation during the test process with the initial profile to obtain the scouring and silting changes of the beach profile.

2. A beach profile scouring and silting method taking into account the actual tide level and wave change process according to claim 1, characterized in that: When measured data are missing, the hydrodynamic parameters are calculated by a large range of current-wave numerical models, including the TELEMAC-MASCARET model, the DELFT3D model, and the MIKE model.

3. A beach profile scouring and silting method considering the actual tide level and wave change process according to claim 1, characterized in that: The relevant data of the beach area include: water level process, wave height process, wave period process, median particle size of sediment and beach profile slope during the storm.

4. A beach profile scouring and silting method considering the actual tide level and wave change process according to claim 1, characterized in that: Hydrodynamic parameters include wave height change process, period change process and water level change process.

5. The beach profile scouring and silting method considering the actual tide level and wave change process according to claim 1 is characterized in that: In the absence of measured profiles, a uniform slope is laid as the initial profile with reference to the actual beach profile slope.

6. A beach profile scouring and silting method considering the actual tide level and wave change process according to claim 1, characterized in that: In step 8, a camera is installed on the side of the water tank to measure the real-time changes of the profile.

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