A design method for polyurethane crushed stone frame slope protection structure

Abstract

The present invention proposes a polyurethane crushed stone grid slope protection structure design method, which relates to the field of embankment engineering design. According to the wave physics model test, the effective action coefficient of the fluctuating pressure of the polyurethane crushed stone protective layer with different porosities is established, and further the calculation method of the maximum effective fluctuating pressure on the top and bottom of the polyurethane crushed stone protective structure with different porosities is obtained, and combined with the force balance principle and structural strength theory, a design method for the protective surface thickness and lattice spacing of the polyurethane crushed stone grid slope protection structure is proposed. The present invention takes into account the rationality and economy of the polyurethane crushed stone slope protection structure, overcomes the empiricism and subjectivity of the scale design of the slope protection structure, and can provide a reference for similar projects.

Description

Technical Field

[0001] The invention belongs to the field of embankment engineering design, and in particular relates to a polyurethane crushed stone frame slope protection structure design method. Background Art

[0002] The design of slope protection structure is very important in embankment projects, especially in areas affected by wind and wave dynamics. For embankments with wind and wave heights less than 3m, the more common slope protection structures are: 1) block stone slope protection; 2) fence board structure slope protection; 3) reinforced gabion; 4) small artificial blocks (twisted W-shaped blocks, twisted I-shaped blocks, four-legged hollow blocks, etc.).

[0003] Polyurethane gravel grid slope protection is a new type of seawall slope protection. It uses concrete grids to provide support for polyurethane gravel slope protection. While giving full play to the advantages of polyurethane gravel slope protection such as good wave dissipation performance and high structural strength, it can effectively solve the defect of easy fracture of non-grid all-polyurethane gravel slope protection structure. From the perspective of engineering application, polyurethane gravel grid slope protection has the advantages of 1) good wave dissipation performance and strong wind and wave resistance; 2) ecological and environmental protection; 3) flat slope surface, beautiful appearance, good landscape; 4) high structural strength and high stability. Compared with block stone slope protection, its block stone weight is much smaller and the surface flatness is high; compared with fence board slope protection, its environmental protection and beauty are improved; compared with gabion slope protection, its durability and beauty are improved; compared with small artificial block slope protection, its construction is simple, the cost is reduced, and the surface flatness is improved.

[0004] Polyurethane crushed stone is a new type of embankment material that began to appear in slope protection engineering applications at the beginning of this century. At present, the design experience of polyurethane crushed stone slope protection is still very limited, especially for polyurethane crushed stone frame slope protection structure, there is no relevant report on how to calculate its design size. Only in the "Code for Slope Design of Water Conservancy and Hydropower Engineering" is it stipulated that "the spacing of mortar-laid stone lattice should not be greater than 3m, and the spacing of cast-in-place reinforced concrete lattice should not be greater than 5m" for frame slope protection structure.

[0005] In summary, polyurethane crushed stone frame slope protection is a new type of seawall slope protection with outstanding advantages, but no clear design method is given for key dimensions such as lattice spacing and polyurethane crushed stone surface thickness. Summary of the invention

[0006] Purpose of the invention: The purpose of the present invention is to provide a new design method for seawall slope protection structure, which meets the wave resistance performance requirements of the protective structure, takes into account the structural safety and economy, and provides guidance for similar projects. The polyurethane crushed stone frame slope protection structure includes a cast-in-place reinforced concrete grid and a polyurethane crushed stone surface layer. The cast-in-place reinforced concrete grid is a criss-crossed square grid, and the grid is a polyurethane crushed stone surface layer. The polyurethane crushed stone surface layer is a mixture of polyurethane and crushed stone, and is a porous and air-permeable structure.

[0007] Technical solution, in order to achieve the above-mentioned invention object, the present invention proposes a polyurethane crushed stone grid slope protection structure design method, the method comprising the following steps:

[0008] Step 1, collect basic design parameters;

[0009] Step 2, establish a wave physics model and simultaneously measure the wave pressure on the top and bottom surfaces of the polyurethane gravel protective structure;

[0010] Step 3, changing the porosity of the polyurethane gravel protective structure, repeating step 2, and extracting the synchronous fluctuating pressure on the top and bottom surfaces of the protective layer;

[0011] Step 4, according to the difference in the fluctuating pressure on the top and bottom surfaces of the protective structure measured simultaneously in the test, the effective action coefficient k of the fluctuating pressure of the polyurethane crushed stone protective layer with different porosities is established;

[0012] Step 5: Using the effective action coefficient k of the fluctuation pressure of the polyurethane crushed stone protective layer, calculate the vertical maximum effective fluctuation pressure P on the bottom surface of the polyurethane crushed stone protective layer with different porosities. u , the maximum effective vertical fluctuation pressure P on the top surface d ;

[0013] Step 6: The maximum effective vertical fluctuation pressure P on the bottom surface of the polyurethane crushed stone protective structure with different porosities u The minimum thickness h of the polyurethane gravel protective surface is determined based on the principle of force balance;

[0014] Step 7: The maximum effective vertical fluctuation pressure P on the top surface of the polyurethane crushed stone protective structure with different porosities d And material tensile strength parameters, determine the maximum width B of the polyurethane gravel facing frame.

[0015] Furthermore, the basic design parameters in step 1 include: wave height H, wave period T, slope gradient m, and maximum allowable tensile strength S of the armor structure material.

[0016] Furthermore, the specific method of step 2 is as follows:

[0017] S1 model design, using normal model, determine the geometric scale, design wave physics model according to gravity similarity, and determine the scale relationship of each physical quantity in the model;

[0018] S2 Calibration of test wave elements: waves are simulated according to the gravity similarity criterion, prototype values ​​of test wave elements are converted into model values ​​according to geometric scale, and then the model values ​​are input into the wave making software to generate wave making signals, and the wave making machine is controlled to generate corresponding wave simulation sequences. The error between the simulated value and the model value of the test wave height and wave period is controlled within ±2%;

[0019] S3 test model making: making a test section model in a wave tank, with each part of the test section reduced in scale compared to the prototype, and measuring the porosity of the polyurethane gravel face structure of the test model;

[0020] For the measurement of the fluctuating pressure on the top and bottom surfaces of the S4 armour layer, no less than 20 fluctuating pressure measuring points are installed along the slope surface, and the distance between the measuring points is controlled between 5 and 10 cm. Pressure sensors are installed on the top and bottom surfaces of the armour layer at each measuring point to synchronously measure the fluctuating pressure on the top and bottom surfaces of the polyurethane gravel armour layer that changes with time under the action of different waves. The sampling frequency of the fluctuating pressure is not less than 100 Hz.

[0021] Furthermore, the calculation method of the effective action coefficient k of the fluctuating pressure in step 4 is as follows:

[0022]

[0023] Where △P is the maximum absolute value of the difference between the synchronous wave pressures of the top and bottom surfaces of the polyurethane protective structure, H is the wave height, γ is the gravity of water, f(n) represents a function related to n, and n is the porosity of the polyurethane protective structure;

[0024] According to the wave physics model test, when n=0.4, k=0.1; when n=0.2, k=0.2.

[0025] Furthermore, in step 5, the maximum effective vertical fluctuation pressure P on the bottom surface is u The calculation method is as follows:

[0026] P u = k·γ·H

[0027] The maximum effective vertical fluctuation pressure P on the top surface d The calculation method is as follows:

[0028] P d = k·λ·γ·H

[0029] Where λ is the wave impact pressure coefficient, and λ=4.0.

[0030] Further, using the principle of force balance, in step 6, the method for determining the minimum thickness h of the polyurethane gravel face is as follows:

[0031]

[0032] In the above formula, m is the slope rate; γ b is the weight of polyurethane gravel slope protection, take 2.45kN / m 3 .

[0033] Furthermore, in step 7, it is assumed that there is a cavity at the bottom of the polyurethane and the edge overlaps the concrete frame, and the maximum width B of the polyurethane crushed stone facing frame is calculated according to the simply supported beam;

[0034] Calculate the uniformly distributed pressure q on the protective structure:

[0035]

[0036] Calculation of the maximum tensile strength σ of polyurethane crushed stone protective surface max :

[0037]

[0038] According to the tensile strength theory of materials, if the protective structure is to not break, the maximum tensile stress σ max Not greater than the maximum allowable tensile strength S, and then the maximum width B of the polyurethane crushed stone face grid that meets the strength requirements satisfies the following conditions:

[0039]

[0040] Beneficial effects: Compared with the prior art, the technical solution of the present invention has the following beneficial technical effects:

[0041] (1) Overcomes the empiricism and subjectivity of structural scale design. Polyurethane crushed stone frame slope protection is a new type of seawall slope protection. There is currently no mature design method for the thickness of the protective layer and the spacing of the lattice. Most of the design is based on the "Design Code for Embankment Engineering" and "Design Code for Slopes of Water Conservancy and Hydropower Engineering". The design of the structural scale is highly empirical and subjective. Based on the basic parameters such as the hydrodynamic conditions of the protective structure, the embankment structure, and the structural strength of the protective material, the present invention obtains an accurate design method for the thickness of the polyurethane crushed stone protective surface and the spacing of the lattice, making the structure safer and more economical.

[0042] (2) The wave dissipation performance of polyurethane crushed stone slope protection structures with different porosities is clarified. Traditional protective surfaces are mostly made of impermeable concrete slabs or mortar-laid blocks. There are few research results on the wave pressure distribution of polyurethane crushed stone slope protection structures with a certain porosity, and the influence of the pore structure of the protective surface on the wave dissipation effect is unclear. The present invention provides the effective action coefficient of the wave pressure of polyurethane crushed stone slope protection with different porosities through wave physics model tests. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 This is a schematic diagram of a polyurethane crushed stone frame slope protection structure in an embodiment of the present invention;

[0044] Figure 2 The specific process of the polyurethane crushed stone frame slope protection structure design method in the embodiment of the present invention;

[0045] Figure 3 The fluctuating pressure process line of the polyurethane crushed stone slope protection in the embodiment of the present invention;

[0046] Figure 4 is the test value of the effective action coefficient k of the polyurethane gravel fluctuation pressure in the embodiment of the present invention (n=0.4);

[0047] Figure 5 is the test value of the effective action coefficient k of the polyurethane gravel fluctuation pressure in the embodiment of the present invention (n=0.2);

[0048] Figure 6 It is a schematic diagram of the force on the protective surface structure during the receding process of the wave water body in the embodiment of the present invention;

[0049] Figure 7 The figure is a schematic diagram of the forces acting on the protective surface structure during the wave water impact process in the embodiment of the present invention. DETAILED DESCRIPTION

[0050] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0051] like Figure 1 As shown, an embodiment of the present invention provides a polyurethane crushed stone lattice slope protection structure design method, wherein the polyurethane crushed stone lattice slope protection structure comprises a polyurethane crushed stone protective layer and a cast-in-place reinforced concrete lattice, wherein the polyurethane crushed stone protective layer is a structure with a certain porosity formed by mixing blocks and polyurethane. The cast-in-place reinforced concrete lattice is a criss-crossed square structure, and a polyurethane crushed stone protective layer is laid inside the lattice. The thickness of the polyurethane crushed stone protective layer and the lattice spacing are the key to the design.

[0052] like Figure 2 As shown, the present invention provides a polyurethane crushed stone grid slope protection structure design method, the method comprising the following steps:

[0053] Step 1: Collection of basic design parameters, including wave height H, wave period T, slope gradient m, and maximum allowable tensile strength S of the protective structure material.

[0054] Step 2, establish a wave physics model and simultaneously measure the wave pressure on the top and bottom surfaces of the polyurethane gravel protective structure;

[0055] The wave pressure on the top and bottom surfaces of the polyurethane gravel protective structure is obtained by a test method. The test method is a wave physical model test method, which includes the following steps:

[0056] S1 model design, using normal model, determine the geometric scale, design wave physics model according to gravity similarity, and determine the scale relationship of each physical quantity in the model;

[0057] S2 Calibration of test wave elements: waves are simulated according to the gravity similarity criterion, prototype values ​​of test wave elements are converted into model values ​​according to geometric scale, and then the model values ​​are input into the wave making software to generate wave making signals, and the wave making machine is controlled to generate corresponding wave simulation sequences. The error between the simulated value and the model value of the test wave height and wave period is controlled within ±2%;

[0058] S3 test model production: a test section model is produced in a wave tank. All parts of the test section are geometrically similar to the prototype, and all structural parts are reduced in scale. The model error does not exceed 1mm. The porosity of the polyurethane gravel face structure of the test model is measured.

[0059] S4 The top and bottom surfaces of the protective layer are subjected to fluctuating pressure measurement. No less than 20 fluctuating pressure measuring points are installed along the slope surface, and the distance between the measuring points is controlled between 5 and 10 cm. Each measuring point is equipped with a pressure sensor on the top and bottom surfaces of the protective layer, which can synchronously measure the fluctuation pressure of the top and bottom surfaces of the polyurethane gravel protective layer under different wave effects over time. The sampling frequency of the fluctuating pressure is not less than 100Hz to avoid missing large wave impact pressure. Figure 3 As shown, the fluctuation pressure on the top and bottom surfaces of the armour layer changes with time.

[0060] Step 3, changing the porosity of the polyurethane gravel protective structure, repeating step 2, and extracting the synchronous fluctuating pressure on the top and bottom surfaces of the protective layer;

[0061] Step 4, according to the difference in the fluctuating pressure on the top and bottom surfaces of the protective structure measured simultaneously in the test, the effective action coefficient k of the fluctuating pressure of the polyurethane crushed stone protective layer with different porosities is established;

[0062] Step 5: Using the effective action coefficient k of the fluctuation pressure of the polyurethane crushed stone protective layer, calculate the vertical maximum effective fluctuation pressure P on the bottom surface of the polyurethane crushed stone protective layer with different porosities. u , the maximum effective vertical fluctuation pressure P on the top surface d ;

[0063] Step 6: The maximum effective vertical fluctuation pressure P on the bottom surface of the polyurethane crushed stone protective structure with different porosities u The minimum thickness h of the polyurethane gravel protective surface is determined based on the principle of force balance;

[0064] Step 7: The maximum effective vertical fluctuation pressure P on the top surface of the polyurethane crushed stone protective structure with different porosities d and material tensile strength parameters, determine the maximum width B of the polyurethane crushed stone facing frame;

[0065] In step 4, the calculation method of the effective effect coefficient k of the fluctuating pressure is as follows:

[0066]

[0067] Where △P is the maximum absolute value of the difference between the synchronous wave pressures of the top and bottom surfaces of the polyurethane face structure, H is the wave height, γ is the gravity of water, f(n) represents a function related to n, and n is the porosity of the polyurethane face structure.

[0068] like Figure 4 and Figure 5 As shown in the figure, the coefficient k of different porosities n measured in the test, T is the wave period, and H is the wave height. When the porosity n = 0.4, the effective coefficient k of the wave pressure under different incident wave conditions is between 0.07 and 0.11, of which about 86% of the test values ​​are below 0.1, and it is recommended that k be 0.1. When the porosity n = 0.2, the effective coefficient k of the wave pressure under different incident wave conditions is between 0.12 and 0.25, of which about 71% of the test values ​​are below 0.2, and it is recommended that k be 0.2. In practical applications, the porosity n of the polyurethane crushed stone armour layer is basically between 0.2 and 0.4.

[0069] Table 1 Effective coefficient k of fluctuating pressure of polyurethane crushed stone armour layer

[0070]

[0071] Note: When n = 0.2 ~ 0.4, the coefficient k can be obtained by interpolating the values ​​in the table.

[0072] In step 5, the maximum effective vertical fluctuation pressure P on the bottom surface is u The calculation method is as follows:

[0073] P u = k·γ·H

[0074] The maximum effective vertical fluctuation pressure P on the top surface d The calculation method is as follows:

[0075] P d = k·λ·γ·H

[0076] Where λ is the wave impact pressure coefficient, and λ=4.0.

[0077] In step 6, if Figure 6 As shown in the figure, the force distribution of the protective layer during the water receding stage. During the water receding stage, the protective layer is most likely to fall off due to unbalanced force. Based on the principle of force balance, the method for determining the minimum thickness h of the polyurethane crushed stone protective surface is as follows:

[0078]

[0079] In the above formula, m is the slope rate; γ bis the weight of polyurethane gravel slope protection, take 2.45kN / m 3 .

[0080] In step 7, it is assumed that there is a cavity at the bottom of the polyurethane and the edge overlaps the concrete frame. The maximum width B of the polyurethane gravel facing frame is calculated according to the simply supported beam;

[0081] like Figure 7 As shown in the figure, the force distribution of the armour layer during the wave impact stage. During the wave impact stage, the armour layer is most likely to break and be damaged due to insufficient strength. The gravity and wave impact force on the armour structure are considered as uniformly distributed loads.

[0082] Calculate the uniformly distributed pressure q on the protective structure:

[0083]

[0084] Calculation of the maximum tensile strength σ of polyurethane crushed stone protective surface max :

[0085]

[0086] According to the tensile strength theory of materials, if the protective structure is to not break, the maximum tensile stress σ max Not greater than the maximum allowable tensile strength S, and then the maximum width B of the polyurethane crushed stone face grid that meets the strength requirements satisfies the following conditions:

[0087]

[0088] At this point, the design parameters of the polyurethane crushed stone frame slope protection structure, such as the thickness and maximum width, can be determined. For example, when the wave height H is 3.0m, S is 0.52Mpa, the slope ratio m is 3, the impact wave pressure coefficient λ is 4.0, the porosity of the polyurethane crushed stone protection structure n=0.4, and the polyurethane crushed stone protection wave pressure reduction coefficient k is 0.1, after calculation, the polyurethane protection thickness h is 0.33m, and the polyurethane crushed stone protection width B is 2.1m.

Claims

1. A polyurethane crushed stone grid slope protection structure design method, characterized in that: The method comprises the following steps: Step 1, collect basic design parameters; Step 2, establish a wave physics model and simultaneously measure the wave pressure on the top and bottom surfaces of the polyurethane gravel protective structure; Step 3, changing the porosity of the polyurethane gravel protective structure, repeating step 2, and extracting the synchronous fluctuating pressure on the top and bottom surfaces of the protective layer; Step 4, according to the difference in the fluctuating pressure on the top and bottom surfaces of the protective structure measured simultaneously in the test, the effective action coefficient k of the fluctuating pressure of the polyurethane crushed stone protective layer with different porosities is established; Step 5: Using the effective action coefficient k of the fluctuation pressure of the polyurethane crushed stone protective layer, calculate the vertical maximum effective fluctuation pressure P on the bottom surface of the polyurethane crushed stone protective layer with different porosities. u , the maximum effective vertical fluctuation pressure P on the top surface d ; Step 6: The maximum effective vertical fluctuation pressure P on the bottom surface of the polyurethane crushed stone protective structure with different porosities u The minimum thickness h of the polyurethane gravel protective surface is determined based on the principle of force balance; Step 7: The maximum effective vertical fluctuation pressure P on the top surface of the polyurethane crushed stone protective structure with different porosities d and material tensile strength parameters, determine the maximum width B of the polyurethane crushed stone face grid; The basic design parameters in step 1 include: wave height H, wave period T, slope gradient m, and maximum allowable tensile strength S of the armor structure material; The specific method of step 2 is as follows: S1 model design, using normal model, determine the geometric scale, design wave physics model according to gravity similarity, and determine the scale relationship of each physical quantity in the model; S2 Calibration of test wave elements: waves are simulated according to the gravity similarity criterion, prototype values ​​of test wave elements are converted into model values ​​according to geometric scale, and then the model values ​​are input into the wave making software to generate wave making signals, and the wave making machine is controlled to generate corresponding wave simulation sequences. The error between the simulated value and the model value of the test wave height and wave period is controlled within ±2%; S3 test model making: making a test section model in a wave tank, with each part of the test section reduced in scale compared to the prototype, and measuring the porosity of the polyurethane gravel face structure of the test model; For the measurement of the fluctuating pressure on the top and bottom surfaces of the S4 armour layer, no less than 20 fluctuating pressure measuring points are installed along the slope surface, and the distance between the measuring points is controlled between 5 and 10 cm. Pressure sensors are installed on the top and bottom surfaces of the armour layer at each measuring point to synchronously measure the fluctuating pressure on the top and bottom surfaces of the polyurethane gravel armour layer that changes with time under the action of different waves. The sampling frequency of the fluctuating pressure is not less than 100 Hz.

2. A polyurethane crushed stone grid slope protection structure design method according to claim 1, characterized in that: In step 4, the calculation method of the effective effect coefficient k of the fluctuating pressure is as follows: Where △P is the maximum absolute value of the difference between the synchronous wave pressures of the top and bottom surfaces of the polyurethane protective structure, H is the wave height, γ is the gravity of water, f(n) represents a function related to n, and n is the porosity of the polyurethane protective structure; According to the wave physics model test, when n=0.4, k=0.1; when n=0.2, k=0.

2.

3. A polyurethane crushed stone grid slope protection structure design method according to claim 2, characterized in that: In step 5, the maximum effective vertical fluctuation pressure P on the bottom surface is u The calculation method is as follows: P u =k·γ·H The maximum effective vertical fluctuation pressure P on the top surface d The calculation method is as follows: P d =k·λ·γ·H Where λ is the wave impact pressure coefficient, and λ=4.

0.

4. A polyurethane crushed stone grid slope protection structure design method according to claim 3, characterized in that: Using the principle of force balance, in step 6, the method for determining the minimum thickness h of the polyurethane gravel face is as follows: In the above formula, m is the slope rate; γ b is the weight of polyurethane gravel slope protection, take 2.45kN / m 3 .

5. A polyurethane crushed stone grid slope protection structure design method according to claim 4, characterized in that: In step 7, it is assumed that there is a cavity at the bottom of the polyurethane and the edge overlaps the concrete frame. The maximum width B of the polyurethane gravel facing frame is calculated according to the simply supported beam; Calculate the uniformly distributed pressure q on the protective structure: Calculation of the maximum tensile strength σ of polyurethane crushed stone protective surface max : According to the tensile strength theory of materials, if the protective structure is to not break, the maximum tensile stress σ max Not greater than the maximum allowable tensile strength S, and then the maximum width B of the polyurethane crushed stone face grid that meets the strength requirements satisfies the following conditions:

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