A method for judging stability of prefabricated revetment blocks of a ramp breakwater

Abstract

The application discloses a kind of slope type breakwater prefabricated facing block stability discrimination methods, this method is based on model test similarity theory, wave section test is carried out to prefabricated facing block, and the critical instability condition of prefabricated facing block under wave action condition is determined.The influence of wave height and wave period on the stability of prefabricated facing block is comprehensively considered, the problem that the wave resistance performance and critical instability condition of the prefabricated facing block of the previous slope type breakwater cannot be determined is solved, and the theoretical defects of the design method of the prefabricated facing block of the slope type breakwater are made up.

Description

Technical Field

[0001] This invention relates to the field of water conservancy engineering technology, and in particular to a method for judging the stability of prefabricated revetment blocks for sloping breakwaters. Background Technology

[0002] Sloping breakwaters are an important type of breakwater, generally composed of core stones and facing riprap or block materials. They are porous media structures that allow both flow and waves to pass through, exhibiting weak wave reflection, insensitivity to uneven foundation settlement, and relatively simple construction, making them widely used in port areas and urban revetments. In sloping breakwater design, the core stones are typically constructed from crushed stone or other loose materials, with the outer side protected by a facing structure. Therefore, the stability of the facing structure directly determines the overall stability of the breakwater. Breakwater facing structures are divided into two categories: riprap facing and block facing. Currently, given China's strict ecological protection requirements and restrictions on quarrying, riprap facing is often limited by raw material availability, leading to the widespread use of easily prefabricated concrete block facing structures.

[0003] Currently, there are various types and interlocking patterns of precast concrete revetment blocks, such as open cubes, twisted U-shaped blocks, etc. These blocks vary greatly in shape and size, and the interlocking patterns are numerous, making stability research very difficult. To date, the stability quality of precast revetment blocks can only be roughly estimated using relevant empirical formulas, leading to potential instability and revetment structure failure in practical applications. Current research on the critical instability conditions of breakwater revetment blocks, both domestically and internationally, mainly considers the critical wave height, with limited research on the effect of wave period on the stability of the revetment blocks.

[0004] The Hudson formula is currently the most widely used formula for calculating the stable weight of revetment blocks in engineering. Due to its simple structure and ease of calculation, it has also become the recommended formula in my country's "Design Code for Breakwaters and Revetments (JTS 154–2018)". The expression is as follows:

[0005]

[0006] In the above formula, W is the stable weight (t) of a single stone block or block; γ b The unit weight (kN / m³) of boulders and block materials 3 ); H F Design wave height (m); K D α is the block stability coefficient, which is related to the revetment type and the allowable instability rate of the revetment blocks, and can be determined according to the "Design Code for Breakwaters and Revetments (JTS 154-2018)"; α is the angle between the slope and the horizontal plane (°); γ is the unit weight of water (kN / m³). 3 ).

[0007] From the above formula, it can be seen that, given the design wave height H F , protective material heavy gamma b Block stability coefficient K D After determining the slope α of the revetment, the stable weight W of the revetment block can be determined. However, this formula does not consider the influence of the wave period T on the block's stability. In reality, the stable weight of the block is also related to the wave period; when a certain wave period occurs, even a small wave height may cause the block to become unstable. Therefore, the Hudson formula for calculating the stable weight of the block has a certain degree of subjectivity. Summary of the Invention

[0008] The purpose of this invention is to solve the above-mentioned problems and to design a stability discrimination method for prefabricated revetment blocks of sloping breakwaters. This method is used in engineering applications of prefabricated revetment blocks to quantify the critical instability conditions of the prefabricated revetment blocks by measuring the wave power at the critical instability point. The method includes:

[0009] S1. Determine the design high water level h1, design low water level h2, design wave height cumulative frequency F, and design wave height H of the engineering area. F Design wave period T F ;

[0010] S2. Calculate the stable weight W of the precast facing block;

[0011] S3. Determine the geometric scale λ of the physical model test based on the site conditions and engineering plan dimensions.

[0012] S4. Construct a physical model and deploy wave height meters. The model construction includes sloping embankments and prefabricated revetment blocks.

[0013] S5. Conduct model design of wave element H′ F and T′ F The rate is fixed;

[0014] S6. Conduct a low-water-level test using the model design. The test water level is taken as the model design low water level h′2. First, run wavelets for 1 hour to compact the blocks, then run wavelets at the model design wave height H′. F With the model design wave period T′ F To simulate wave action, the simulated prototype wave action time must be greater than 2 hours. After wave generation, determine whether any blocks become unstable within a range of one wave height from the still water level. Repeat this process three times, and the blocks are rearranged after each test.

[0015] If one group of the three tests shows no block instability, then the group of blocks is determined to be instable under the low water level h′2 designed in the model, and proceeds to S7;

[0016] If the block becomes unstable in every test, it is determined that the block is unstable under the low water level h′2 designed by the model, and enters S9;

[0017] S7. Conduct a high-water-level test of the model design. Adjust the test water level to the high water level h′1 designed for the model, repeat the test three times, and rearrange the blocks after each test;

[0018] If one group of the three tests shows no block instability, then the group of blocks is determined to be instable under the high water level h′1 designed in the model, and proceeds to S8;

[0019] If the block becomes unstable in every test, it is determined that the block group is unstable at the high water level h′1 designed by the model, and enters S9;

[0020] S8, Model Design Wave Height H′ F Keeping constant, the model design wave period T′ F Increase by 0.1s, then return to S5;

[0021] S9. Design wave height H′ of the block at critical instability. F And the model design wave period T′ F According to wave height ratio λ H Sum of wave period ratio λ T Reverse calculation to the prototype wave height H0 and prototype wave period T0;

[0022] S10. Calculate the critical instability power P0, where P0 is the wave resistance performance of the prefabricated revetment block.

[0023] S11. Determine the critical instability state function of the precast revetment block, as shown in the following expression:

[0024] TH 2 =2P0 (1)

[0025] S12, The stability judgment condition for precast facing blocks is TH 2 <2P0.

[0026] Furthermore, in S1, when H F Greater than or equal to the shallow water limiting wave height H b Take H F =H b ;

[0027] Design wave period T F Take as the average wave period

[0028] Furthermore, in S2, the Hudson formula is used to calculate the stabilizing weight W of the prefabricated revetment block, as follows:

[0029]

[0030] In the above formula, W is the stable weight (t) of a single stone block or block; γ b The unit weight (kN / m³) of boulders and block materials 3 ); H F Design wave height (m); K D α is the block stability coefficient; α is the angle between the slope and the horizontal plane (°); γ is the unit weight of water (kN / m³). 3 ).

[0031] Furthermore, in S3, the physical model test time is longer than that of λ. t Wave height ratio λ H Wave period ratio λ T Mass ratio λ m The calculation formulas are as follows:

[0032] λ=l p / l m (3)

[0033] λ t =λ 1 / 2 (4)

[0034] λ H =λ (5)

[0035] λ T =λ 1 / 2 (6)

[0036] λ m =λ 3 (7)

[0037] In the above formula, l p The prototype length; l m λ represents the model length; λ represents the geometric scale of the physical model experiment.

[0038] Furthermore, in S5, the model experiment uses a regular wave, and the calibrated model design wave height H′ F And the model design wave period T′ F The permissible deviation is ±5%. H′ F 、T′ F The formula for calculating the initial value is as follows:

[0039] H′ F =H F / λ (8)

[0040] T′ F =T F / λ T (9)

[0041] Among them, H F For design wave height; TF The design wave period; λ is the geometric scale of the physical model experiment; λ T The scale is the wave period ratio for the physical model.

[0042] Furthermore, in S6, the formula for calculating h′2 is as follows:

[0043] h′2=h2 / λ (10)

[0044] Among them, h2 is the prototype design low water level.

[0045] Furthermore, in S7, the formula for calculating h′1 is as follows:

[0046] h′1=h1 / λ (11)

[0047] Among them, h1 is the high water level of the prototype design.

[0048] Furthermore, in S9, the prototype wave height H0 and prototype wave period T0 are calculated using the following formulas:

[0049] H0=λ H H′ F (12)

[0050] T0=λ T T′ F (13)

[0051] Furthermore, in S10, the formula for calculating P0 is:

[0052]

[0053] The unit of P0 is kW / m.

[0054] The method for determining the stability of prefabricated revetment blocks for sloping breakwaters, using the technical solution of this invention, achieves the following beneficial effects:

[0055] Based on the similarity theory of model tests, this method conducts wave section tests on prefabricated revetment blocks to determine the critical instability conditions of the prefabricated revetment blocks under wave action. It comprehensively considers the influence of wave height and wave period on the stability of the prefabricated revetment blocks, solving the problem of the inability to determine the wave resistance performance and critical instability conditions of prefabricated revetment blocks for sloping breakwaters, and making up for the theoretical deficiencies in the design methods of prefabricated revetment blocks for sloping breakwaters. Attached Figure Description

[0056] Figure 1 This is a flowchart of the stability determination method for prefabricated revetment blocks of sloping breakwaters in an embodiment of the present invention;

[0057] Figure 2This is a comparison chart of the critical instability state function curve of the prefabricated retaining block in the experimental example of this invention and the experimental results; Detailed Implementation

[0058] To better understand the present invention, the present invention will be further described below with reference to specific embodiments and accompanying drawings.

[0059] Example

[0060] like Figure 1 As shown, a stability determination method for prefabricated revetment blocks of sloping breakwaters is presented. This method is used in engineering projects to quantify the critical instability conditions of prefabricated revetment blocks by measuring the wave power at the critical instability point. The method includes:

[0061] S1. Based on the "Hydrological Specifications for Ports and Waterways (JTS 145-2015)," determine the design high water level h1, design low water level h2, design wave height cumulative frequency F, and design wave height H for the project area. F Design wave period T F ;

[0062] Specifically, in S1, when H F Greater than or equal to the shallow water limiting wave height H b Take H F =H b H b The shallow water limiting wave height is determined according to the "Port and Waterway Hydrology Code (JTS 145-2015)"; the design wave period T F Take as the average wave period

[0063] S2. Calculate the stable weight W of the precast facing block;

[0064] Specifically, in S2, the Hudson formula is used to calculate the stabilizing weight W of the prefabricated revetment block, as follows:

[0065]

[0066] In the above formula, W is the stable weight (t) of a single stone block or block; γ b The unit weight (kN / m³) of boulders and block materials 3 ); H F Design wave height (m); K D α is the block stability coefficient; α is the angle between the slope and the horizontal plane (°); γ is the unit weight of water (kN / m³). 3 ).

[0067] S3. Determine the geometric scale λ of the physical model test based on the site conditions and engineering plan dimensions.

[0068] Specifically, in S3, the physical model test time is longer than that of the scale λ. t Wave height ratio λ H Wave period ratio λ T Mass ratio λ m The calculation formulas are as follows:

[0069] λ=l p / l m (3)

[0070] λ t =λ 1 / 2 (4)

[0071] λ H =λ (5)

[0072] λ T =λ 1 / 2 (6)

[0073] λ m =λ 3 (7)

[0074] In the above formula, l p The prototype length; l m λ represents the model length; λ represents the geometric scale of the physical model experiment.

[0075] S4. Construct a physical model and deploy wave height meters. The model construction includes sloping embankments and prefabricated revetment blocks.

[0076] Specifically, the sloping embankment and precast revetment blocks must be geometrically similar to the prototype, with a geometric scale not exceeding 40. In addition to geometric similarity, the precast revetment blocks must also be similar in mass and center of gravity.

[0077] S5. Conduct model design of wave element H′ F and T′ F The rate is fixed;

[0078] Specifically, further, in S5, the model experiment uses a regular wave, and the calibrated model design wave height H′ F And the model design wave period T′ F The permissible deviation is ±5%. H′ F 、T′ F The formula for calculating the initial value is as follows:

[0079] H′ F =H F / λ (8)

[0080] T′ F =T F / λ T (9)

[0081] Among them, H F For design wave height; T F The design wave period; λ is the geometric scale of the physical model experiment; λ T The scale is the wave period ratio for the physical model.

[0082] S6. Conduct a low-water-level test using the model design. The test water level is taken as the model design low water level h′2. First, run wavelets for 1 hour to compact the blocks, then run wavelets at the model design wave height H′. F With the model design wave period T′ F To simulate wave action, the simulated prototype wave action time must be greater than 2 hours. After wave generation, determine whether any blocks become unstable within a range of one wave height from the still water level. Repeat this process three times, and the blocks are rearranged after each test.

[0083] If one group of the three tests shows no block instability, then the group of blocks is determined to be instable under the low water level h′2 designed in the model, and proceeds to S7;

[0084] If the block becomes unstable in every test, it is determined that the block is unstable under the low water level h′2 designed by the model, and enters S9;

[0085] Specifically, further, in S6, the formula for calculating h′2 is as follows:

[0086] h′2=h2 / λ (10)

[0087] Among them, h2 is the prototype design low water level.

[0088] The instability determination methods are as follows: For a single-layer paved precast revetment block, instability occurs when the cumulative displacement exceeds the thickness of a single block; for a single-layer randomly placed precast revetment block, instability occurs when the width of the gap generated after displacement exceeds half of the maximum geometric dimension of the block; for a randomly placed precast revetment block, instability occurs when the cumulative displacement exceeds the maximum geometric dimension of a single block; and for a large precast revetment block where strength plays a controlling role, instability occurs when the cumulative displacement exceeds half of the maximum geometric dimension of the block.

[0089] S7. Conduct a high-water-level test of the model design. Adjust the test water level to the high water level h′1 designed for the model, repeat the test three times, and rearrange the blocks after each test;

[0090] If one group of the three tests shows no block instability, then the group of blocks is determined to be instable under the high water level h′1 designed in the model, and proceeds to S8;

[0091] If the block becomes unstable in every test, it is determined that the block group is unstable at the high water level h′1 designed by the model, and enters S9;

[0092] Furthermore, in S7, the formula for calculating h′1 is as follows:

[0093] h′1=h1 / λ (11)

[0094] Among them, h1 is the high water level of the prototype design.

[0095] The instability determination method is the same as that in S6.

[0096] S8, Model Design Wave Height H′ F Keeping constant, the model design wave period T′ F Increase by 0.1s, then return to S5;

[0097] S9. Design wave height H′ of the block at critical instability. F And the model design wave period T′ F According to wave height ratio λ H Sum of wave period ratio λ T Reverse calculation to the prototype wave height H0 and prototype wave period T0;

[0098] Specifically, in S9, the prototype wave height H0 and prototype wave period T0 are calculated using the following formulas:

[0099] H0=λ H H′ F (12)

[0100] T0=λ T T′ F (13)

[0101] S10. Calculate the critical instability power P0, where P0 is the wave resistance performance of the prefabricated revetment block.

[0102] Furthermore, in S10, the formula for calculating P0 is:

[0103]

[0104] The unit of P0 is kW / m.

[0105] S11. Determine the critical instability state function of the precast revetment block, as shown in the following expression:

[0106] TH 2 =2P0 (1)

[0107] S12, The stability judgment condition for precast facing blocks is TH 2 <2P0.

[0108] Experimental Example

[0109] This typical example model has a geometric scale of 5, a slope of 1:3, and a height of 1m. The revetment blocks are laid in a single layer on the slope of the embankment. The specific implementation steps for the technical solutions in section 4 above are as follows:

[0110] S1: In this typical example, the design high water level h1 = 4.5m, the design low water level h2 = 1.5m, and the design wave height H F =0.5m, design wave period T F =6s.

[0111] S2: The stable weight W is calculated using formula (2). Where γ b =24kN / m 3 γ=9.8kN / m 3 K D =5.5, cotα=3, so W=5.98kg.

[0112] S3: Determine the geometric scale λ=5 and time scale of the model test based on the test site conditions and engineering plan dimensions. Wave height ratio λ H =5. Wave period ratio Mass scale λ m =125.

[0113] S4: Construct the model and arrange the wave height instrument.

[0114] S5~S8: Sequentially carry out model design of wave element H′ F and T′ F Calibration, low-water-level test, and high-water-level test were conducted using the model design. Based on the instability judgment method, the model design wave height H′ at the critical instability of the precast revetment block was obtained. F =0.1m and wave period T′ F =2.98s.

[0115] S9: Design wave height H′ at critical instability. F Sum wave period T′ F According to wave height ratio λ H Sum of wave period ratio λ T By recalculating back to the prototype wave height H0 and wave period T0, we get H0 = 0.5m and T0 = 6.66s.

[0116] S10: Calculate the critical instability power P0 according to formula (14) to determine the wave resistance performance of the precast facing blocks. The calculated P0 = 0.83kW / m.

[0117] S11: The critical instability state function of the prefabricated retaining wall block is determined by formula (1) as TH. 2 =1.66.

[0118] S12: The stability criterion for prefabricated revetment blocks is TH. 2 <1.66.

[0119] After the above steps, the wave resistance performance value of the precast revetment blocks of the sloping breakwater, P0 = 0.83 kW / m, and the critical instability state function TH of the precast revetment blocks can be obtained. 2 =1.66. Further experiments were conducted using 20 sets of regular wave model tests, as shown in Table 1, with wave periods ranging from 3 to 6 seconds and wave heights ranging from 0.5 to 0.9 meters. The prototype wave height and wave period under the 20 experimental schemes were compared with the critical instability state function TH. 2 =1.66 for comparison, such as Figure 2 As shown, it can be observed that all 13 test schemes in which the facing block exhibited instability during the test were located on the critical instability state function curve TH. 2 =Above 1.66, satisfying TH 2 >1.66; During the experiment, all 7 test schemes in which the facing block remained stable were located at the critical instability state function curve TH. 2 =Below 1.66, satisfying TH 2 <1.66 indicates that the critical instability state function TH 2 =1.66 and the stability criterion TH of precast facing blocks 2 Reliability <1.66.

[0120] Table 1. Verification Test Plan and Phenomena

[0121]

[0122] The above technical solutions only embody the preferred technical solutions of the present invention. Any modifications that may be made by those skilled in the art to certain parts thereof embody the principles of the present invention and fall within the protection scope of the present invention.

Claims

1. A method for determining the stability of prefabricated revetment blocks for sloping breakwaters, characterized in that, This method is used in engineering applications to quantify the critical instability conditions of precast retaining blocks by measuring the wave power at the critical instability point. The method includes: S1. Determine the design high water level h1, design low water level h2, design wave height cumulative frequency F, and design wave height H of the engineering area. F Design wave period T F ; S2. Calculate the stable weight W of the precast facing block; S3. Determine the geometric scale λ of the physical model test based on the site conditions and engineering plan dimensions. S4. Construct a physical model and deploy wave height meters. The model construction includes sloping embankments and prefabricated revetment blocks. S5. Conduct model design of wave element H′ F and T′ F The rate is fixed; S6. Conduct a low-water-level test using the model design; the test water level is taken as the model design low water level h′2. First, run wavelets for 1 hour to compact the blocks, then run wavelets at the model design wave height H′. F With the model design wave period T′ F To simulate wave action, the simulated prototype wave action time must be greater than 2 hours. After wave generation, it is determined whether there is block instability within a range of one wave height of still water level. This is repeated three times, and the blocks are rearranged after each test. If one group of the three tests shows no block instability, then the group of blocks is determined to be instable under the low water level h′2 designed in the model, and proceeds to S7; If the block becomes unstable in every test, it is determined that the block is unstable under the low water level h′2 designed by the model, and enters S9; S7. Conduct a high-water-level test of the model design; adjust the test water level to the high water level h′1 designed for the model, repeat the test three times, and rearrange the blocks after each test; If one group of the three tests shows no block instability, then the group of blocks is determined to be instable under the high water level h′1 designed in the model, and proceeds to S8; If the block becomes unstable in every test, it is determined that the block group is unstable at the high water level h′1 designed by the model, and enters S9; S8, Model Design Wave Height H′ F Keeping constant, the model design wave period T′ F Increase by 0.1s, then return to S5; S9. Design wave height H′ of the block at critical instability. F And the model design wave period T′ F According to wave height ratio λ H Sum of wave period ratio λ T Reverse calculation to the prototype wave height H0 and prototype wave period T0; S10. Calculate the critical instability power P0, where P0 is the wave resistance performance of the prefabricated revetment block. S11. Determine the critical instability state function of the precast revetment block, as shown in the following expression: TH 2 =2P0 (1); S12, The stability judgment condition for precast facing blocks is TH 2 <2P0.

2. The method for determining the stability of prefabricated revetment blocks of a sloping breakwater according to claim 1, characterized in that, In S1, when H F Greater than or equal to the shallow water limiting wave height H b Take H F =H b ; Design wave period T F Take as the average wave period 3. The method for determining the stability of prefabricated revetment blocks of a sloping breakwater according to claim 1, characterized in that, In S2, the stabilizing weight W of the prefabricated revetment block is calculated using the Hudson formula, as follows: In the above formula, W is the stable weight (t) of a single stone block or block; γ b The unit weight (kN / m³) of boulders and block materials 3 ); H F Design wave height (m); K D α is the block stability coefficient; α is the angle between the slope and the horizontal plane (°); γ is the unit weight of water (kN / m³). 3 ).

4. The method for determining the stability of prefabricated revetment blocks of a sloping breakwater according to claim 1, characterized in that, In S3, the physical model test time is compared to the scale λ. t Wave height ratio λ H Wave period ratio λ T Mass ratio λ m The calculation formulas are as follows: λ=l p / l m (3) l t =λ 1 / 2 (4) l H =λ (5) l T =λ 1 / 2 (6) l m =λ 3 (7) In the above formula, l p The prototype length; l m λ represents the model length; λ represents the geometric scale of the physical model experiment.

5. The method for determining the stability of prefabricated revetment blocks of a sloping breakwater according to claim 4, characterized in that, In S5, the model experiment uses a regular wave, and the calibrated model design wave height H′ F And the model design wave period T′ F The permissible deviation is ±5%; H′ F 、T′ F The formula for calculating the initial value is as follows: H′ F =H F / λ (8) T′ F =T F / λ T (9) Among them, H F For design wave height; T F The design wave period; λ is the geometric scale of the physical model experiment; λ T The scale is the wave period ratio for the physical model.

6. The method for determining the stability of prefabricated revetment blocks of a sloping breakwater according to claim 1, characterized in that, In S6, the formula for calculating h′2 is as follows: h′2=h2 / λ (10) Among them, h2 is the prototype design low water level.

7. The method for determining the stability of prefabricated revetment blocks of a sloping breakwater according to claim 1, characterized in that, In S7, the formula for calculating h′1 is as follows: h′1=h1 / λ (11) Among them, h1 is the high water level of the prototype design.

8. The method for determining the stability of prefabricated revetment blocks of a sloping breakwater according to claim 1, characterized in that, In S9, the prototype wave height H0 and prototype wave period T0 are calculated using the following formulas: H0=λ H H′ F (12) T0=λ T T′ F (13)。 9. The method for determining the stability of prefabricated revetment blocks of a sloping breakwater according to claim 1, characterized in that, In S10, the formula for calculating P0 is: The unit of P0 is kW / m.

Images