A method for determining the slope gradient of dredged waterway in sea areas

Abstract

The present invention discloses a method for determining the slope of a dredged channel slope in a sea area. The method comprises: determining the maximum wave dynamic load on the dredged channel slope surface and the maximum stress caused by waves within the dredged channel slope; determining the soil strength index under the maximum wave dynamic load through an indoor vibration triaxial test; establishing a soil mechanics stability calculation model for the dredged channel slope, inputting the soil vibration strength index value obtained from the indoor vibration triaxial test and the maximum wave dynamic load on the channel slope surface, and calculating the stability safety factor of the dredged channel slope under the wave dynamic load under several slope schemes for the proposed dredged channel slope; selecting the steepest slope of the several slope schemes that meets the stability safety factor required by the specification as the slope value of the proposed dredged channel slope. On this basis, the slope can also be appropriately slowed down based on the calculation of the scouring of the slope surface of the proposed dredged channel slope by waves and / or tidal currents, and the slope can be used as the slope value of the proposed dredged channel slope.

Description

Technical Field

[0001] The present invention belongs to the field of water transport engineering industry research and construction, and in particular relates to a method for determining the slope of a dredged sea channel. Background Art

[0002] Determining the slope gradient of dredged channels not only affects their stability and the proper operation of the channel, but also the dredging workload and investment. This is particularly true for shallow, deep-ditch channels, where excavation depths are substantial and dredging efforts are substantial. The slope gradient accounts for approximately 20-30% of the total dredging effort, making the impact of dredging slope gradient even more pronounced. Furthermore, in open waters lacking the protection of breakwaters, natural islands, and other structures, offshore waves can directly enter and impact the surface soil. Previous studies have qualitatively demonstrated that waves have a certain softening and scouring effect on the surface soil, a factor that warrants attention when waves are high. Furthermore, previous studies have qualitatively demonstrated that tidal currents have a certain scouring effect on fine-grained soils. However, the current specifications only determine the slope of the dredged channel slope based on geological data using a table lookup method, without considering factors such as excavation thickness, tides, waves, and slope stability. This affects the accuracy and economy of determining the slope of the dredged channel slope in the sea area, especially for deep-dug channels in shallow waters in open seas.

[0003] In recent years, many ports have conducted observational studies on dredged channel slopes. The first research method is to use the soil mechanics stability of the slope (i.e., the overall stability of geotechnical mechanics) to calculate the stability safety factor of the dredged channel slope under different slope conditions based on still water conditions, using the shear strength index of the soil after unloading. This is combined with on-site local dredging tests to observe the stability of the dredged slope and then determine the slope of the dredged channel slope. The second research method is to use qualitative analysis and on-site observation to study the effects of water flow and waves on the scouring of the dredged channel slope from the perspective of hydrodynamic scouring. However, existing research still has the following deficiencies:

[0004] 1. When calculating the safety factor of channel dredging slope stability using slope soil mechanics, the adverse effects of wave dynamic loads on the stability of channel dredging slopes have not been considered, and the need to determine the slope of channel dredging slopes under wave action conditions in open sea areas cannot be met.

[0005] 2. The research on the influence of water flow and waves on the scour of the waterway dredging slope is still at the qualitative level and has not yet reached the quantitative level.

[0006] 3. There is no systematic design method for determining the slope of channel dredging slopes. Summary of the Invention

[0007] The present invention provides a method for determining the slope of a dredged channel in a sea area, which solves the problem that the prior art does not consider the adverse effects of wave dynamic loads on the soil mechanical stability of the dredged channel slope, and cannot quantitatively consider the effects of water flow and waves on the scouring of the slope surface of the dredged channel slope. A systematic method for determining the slope of a dredged channel slope is formed to meet the needs of determining the slope of a dredged channel in a sea area, provide a scientific basis for reasonably determining the slope of a dredged channel in a sea area, and achieve the coordinated unity of dredging slope stability and saving waterway project investment.

[0008] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0009] A method for determining the slope of a dredged channel in a sea area, the method comprising:

[0010] S0: Based on the geology of the proposed waterway and engineering practice experience, several slope schemes for the dredged slope of the proposed waterway are initially proposed; or based on the geology of the proposed waterway, in accordance with the provisions of the "Seaport General Design Code" (such as Table 6.4.9 "Slopes of Waterway Slopes for Different Geotechnical Types" of JTS165-2013), combined with engineering practice experience, several slope schemes for the dredged slope of the proposed waterway are initially proposed;

[0011] S1: Based on the design service life of the dredged slope of the proposed channel, determine the design wave return period standard and corresponding design wave elements of the dredged slope of the proposed channel, and then determine the maximum wave load under different preset water level conditions;

[0012] S2: Determine the soil strength index under the maximum wave dynamic load through indoor vibration triaxial test;

[0013] S3: Establish a soil mechanics stability calculation model for the channel dredging slope. Input the soil vibration intensity index value obtained from the indoor vibration triaxial test and the maximum wave dynamic load value on the channel slope surface into the model to calculate the stability safety factor of the channel dredging slope under wave dynamic load for several slope schemes of the proposed channel dredging slope.

[0014] S4: Select the steepest slope of several slope schemes that meet the stability safety factor required by the specification as the slope value of the proposed channel dredging slope.

[0015] Optionally, step S1 specifically includes:

[0016] S11: Determine the design wave recurrence period standard of the dredged slope of the proposed waterway according to the design service life of the dredged slope of the proposed waterway (e.g., if the design service life of the dredged slope is 6 months, 1 year, 5 years, 10 years, and 20 years, the design wave recurrence period standard is 1 year, 1 to 5 years, 5 to 10 years, 10 to 20 years, and 20 to 50 years, respectively), and the combination with different preset water level conditions, where the water levels of the different preset water level conditions include extreme low water level, design low water level, design high water level, extreme high water level, and medium water level;

[0017] S12: Determine the design wave elements corresponding to different preset water level conditions under the design wave recurrence period standard for the proposed waterway based on the measured wave statistical method, or by using one of the methods of the "Hydrological Code for Ports and Waterways", the Putian wave formula, or the wave mathematical model. The design wave elements include water depth h, seawater density γ, and the like. w , effective wave height A series of wave heights H 1％ ~Wave height H 100％ , wavelength L, wave period T, and wave action time D u ;

[0018] S13: Determine the wave dynamic load on the surface of the dredged channel slope according to the design wave elements corresponding to different preset water level conditions under the design wave return period standard, and select the maximum wave dynamic load on the surface of the dredged channel slope under different preset water level conditions.

[0019] Optionally, in step S13, the wave dynamic load on the surface of the proposed channel dredging slope is determined, which can be obtained through on-site measurement or indoor physical model testing, or calculation using computational fluid dynamics software.

[0020] Optionally, in step S13, the wave dynamic load on the surface of the dredged slope of the proposed channel is determined, which can be obtained by calculation using a relevant calculation formula, specifically:

[0021] The formula for calculating the wave dynamic load on the surface of the dredged channel slope is:

[0022] p=p0sin2π(x / Lt / T) (1)

[0023]

[0024] Where: p is the wave dynamic load on the surface of the channel dredged slope; p0 is the pressure; x is the horizontal coordinate relative to the wave node; L is the wavelength; T is the wave period; t is the time; H is the wave height or the series wave height H of a wave train. 1％ ~H 100％ , or the effective wave height H s ; γw is the density of water; h is the water depth.

[0025] Optionally, step S2 specifically includes:

[0026] S21: Through geological survey, obtain representative soil samples on the proposed channel section. The sampling must cover all major soil layers related to soil mechanical stability. Each major soil layer must include at least two upper and lower soil samples. The soil samples must be undisturbed samples.

[0027] S22: Based on the design wave elements corresponding to different design water levels under the design wave return period standard and the maximum wave dynamic load obtained at the specific section of the proposed channel, the maximum stress caused by waves at different depths and locations inside the dredged slope at the soil sample is determined. Together with the wave period and wave action time of the design wave elements, this stress is used as the load for the indoor vibration triaxial test.

[0028] Optionally, in step S22, the maximum stress caused by waves at different depths and positions inside the dredged slope of the soil sample is determined, which can be obtained through on-site measurement or indoor physical model testing.

[0029] Optionally, in step S22, the maximum stress caused by waves at different depths and positions inside the dredged slope at the soil sample is determined, which can be calculated using the finite element method and relevant theoretical formulas based on the wave dynamic load on the surface of the dredged slope of the proposed channel obtained in S13.

[0030] S23: Conduct indoor triaxial vibration tests to obtain the dynamic strength index of each soil sample under wave dynamic load. For silt, silty soil, clay soil, and silty soil, the shear strength index can be the triaxial unconsolidated undrained shear index after vibration or the unconfined compressive strength index after vibration.

[0031] Optionally, for a proposed waterway with a relatively large to high frequency of waves, the scouring effect of waves on the dredged slope surface of the proposed waterway is considered; for a proposed waterway with a large tidal force, the scouring effect of the tidal force on the dredged slope surface of the proposed waterway is considered. After step S4, the following steps are further included:

[0032] S5.1: Establish mathematical models for the wind and wave fields in the project area, as well as a three-dimensional tidal and sediment scour mathematical model with fine local grid division. Use measured wind, wave, current, and sediment concentration data to verify and calibrate the model.

[0033] S5.2: Use the verified and calibrated three-dimensional wind, wave, tidal and sediment coupling mathematical model to simulate typical high wind, high wave and / or high tide processes, as well as the dynamic field and sediment concentration field of the project sea area;

[0034] S5.3: Using a validated and calibrated three-dimensional wind, wave, tidal and sediment coupling mathematical model, quantitatively calculate the scour thickness of the proposed channel slopes at different beach water depths during typical high winds, high waves and high tides. Considering the frequency of typical high winds and high waves in a year, analyze whether the impact of scour caused by waves and tidal currents on the proposed channel slope surface maintenance is within an acceptable range.

[0035] S5.4: The slope value of the proposed dredged channel slope shall be determined comprehensively based on the calculation of scour of the proposed dredged channel slope surface by considering waves and tidal currents, and the feasible slope value of the proposed dredged channel slope based on the soil mechanics stability calculation of the proposed dredged channel slope under the action of wave dynamic loads.

[0036] Optionally, in step S5.4, the specific method for comprehensively determining the slope of the proposed channel dredging slope is as follows:

[0037] S5.4.1: For waterways with a short design life of dredged channel slopes (e.g., less than 5 years), the steepest slope with a stability safety factor that meets the requirements of the Code for Design of Foundations for Water Transport Engineering, obtained from geomechanical stability calculations of the proposed waterway dredged channel slope under wave dynamic loads, may be used as the slope of the proposed dredged channel slope;

[0038] S5.4.2: For waterways with a long design service life (e.g., greater than or equal to 5 years) of the proposed channel dredging slope, the slope can be appropriately slowed down based on the calculation of the scouring of the proposed channel dredging slope surface by waves and / or tidal currents on the basis of S5.4.1, and the slope can be used as the slope of the proposed channel dredging slope.

[0039] Beneficial effects of the present invention:

[0040] 1. When calculating the safety factor of the dredged channel slope stability using slope soil mechanics stability, the system quantitatively considers the reduction in the strength index of the channel slope soil under the action of wave loads, and thus the adverse effect on the mechanics stability of the channel dredged channel slope soil. This solves the problem that the existing technology does not quantitatively consider the adverse effect of wave dynamic loads on the mechanics stability of the channel dredged channel slope soil;

[0041] 2. Using a wind, wave, and three-dimensional tidal current sediment coupling mathematical model, the impact of waves and currents on the scouring of the channel dredging slope surface is quantitatively calculated, solving the problem that existing technologies cannot quantitatively consider the impact of waves and currents on the scouring of the channel dredging slope surface;

[0042] 3. A systematic method for determining the slope of dredged channel slopes has been formed, which can meet the needs of determining the slope of dredged channel slopes in sea areas, solve the problem that the current table lookup method for determining dredged slopes lacks clear theoretical support and does not consider the adverse effects of wave and tidal dynamic loads on the stability of dredged channel slopes, and provide a scientific basis for the reasonable determination of the slope of dredged channel slopes in open sea areas, achieve the coordination and unity of ship navigation safety and saving waterway project investment, and make the determination of dredged channel slopes more comprehensive and reasonable.

[0043] The technical solution and method of the present invention are applicable to the research and construction fields of coastal waterway projects in the water transport engineering industry, and are particularly applicable to the determination of the slope gradient of dredged waterway dredging in sea areas, and are particularly applicable to the determination of the slope gradient of dredged waterway dredging in deep trenches constructed on shallows with fine-grained soil in open sea areas with significant wave influences. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 This is the calculation result of the channel dredging slope stability without considering the influence of wave dynamic load (slope gradient 1:8).

[0045] Figure 2 This is the sample point arrangement diagram for the triaxial vibration test of the channel dredging slope.

[0046] Figure 3 It is a schematic diagram of the soil mechanics stability calculation model for channel dredging slopes.

[0047] Figure 4 It is the result of soil mechanics stability calculation of channel dredging slope considering the influence of wave dynamic load (slope gradient 1:8).

[0048] Figure 5 It is the soil mechanics stability calculation result of the channel dredging slope considering the influence of wave dynamic load (slope gradient 1:7).

[0049] Figure 6 It is the lateral distribution diagram of the scouring thickness of the dredged channel slope under the action of waves and tidal currents. DETAILED DESCRIPTION

[0050] The present invention provides a method for determining the slope of a dredged sea channel, the method comprising:

[0051] S0: Several slope options for the dredged channel slope are initially proposed;

[0052] S1: Based on the design service life of the dredged slope of the proposed channel, determine the design wave recurrence period standard and corresponding design wave elements of the dredged slope of the proposed channel, and then determine the maximum wave load on the surface of the dredged slope of the channel under different preset water level conditions. The details are as follows:

[0053] S11: Determine the design wave recurrence period standard of the dredged slope of the proposed waterway according to the design service life of the dredged slope of the proposed waterway, and its combination with different preset water level conditions, wherein the water levels of the different preset water level conditions include extreme low water level, design low water level, design high water level, extreme high water level and medium water level.

[0054] In step S11, the design service life of the dredged slope can be 6 months, 1 year, 5 years, 10 years, and 20 years, and the design wave recurrence period standards are 1 year, 1 to 5 years, 5 to 10 years, 10 to 20 years, and 20 to 50 years respectively.

[0055] S12: Determine the design wave elements corresponding to different preset water level conditions under the design wave recurrence period standard for the proposed waterway based on the measured wave statistical method, or by using one of the methods of the "Hydrological Code for Ports and Waterways", the Putian wave formula, or the wave mathematical model. The design wave elements include water depth h, seawater density γ, and the like. w , effective wave height H s , the series wave height H of a series of waves 1％ ~Wave height H 100％ , wavelength L, wave period T, and wave action time D u .

[0056] S13: Determine the wave dynamic load on the surface of the dredged channel slope under the design wave return period standard according to the design wave elements corresponding to different preset water level conditions, and obtain the maximum wave dynamic load on the surface of the dredged channel slope under different preset water level conditions.

[0057] In step S13, the wave dynamic load on the surface of the proposed channel dredging slope is determined, which can be obtained through field measurement or indoor physical model testing, calculation using computational fluid dynamics software, or calculation using a relevant calculation formula, which is:

[0058] p=p0sin2π(x / Lt / T) (1)

[0059]

[0060] Where: p is the wave dynamic load on the surface of the channel dredged slope; p0 is the pressure; x is the horizontal coordinate relative to the wave node; L is the wavelength; T is the wave period; t is the time; H is the wave height or the series wave height H of a wave train. 1％ ~H 100％ , or the effective wave height H s ; γ w is the density of water; h is the water depth.

[0061] The wave dynamic load on the surface of the dredged channel slope under different preset water level conditions is calculated, and the preset water level with the maximum wave dynamic load on the surface of the dredged channel slope and its corresponding design wave element combination are obtained, which is the most unfavorable preset water level and design wave element combination.

[0062] S2: Determine the soil strength index under the maximum wave dynamic load through indoor vibration triaxial test. The details are as follows:

[0063] S21: Through geological survey, obtain representative soil samples on the proposed channel section. The sampling must cover all major soil layers related to soil mechanical stability. Each major soil layer must include at least two upper and lower soil samples. The soil samples must be undisturbed samples.

[0064] S22: Based on the design wave elements corresponding to different preset water level conditions under the design wave return period standard and the maximum wave dynamic load on the dredged channel slope surface at the specific section of the proposed channel, the maximum stress caused by waves at different depths and locations inside the dredged channel at the soil sample is determined. Together with the wave period and wave action time of the design wave elements, this stress is used as the load for the indoor vibration triaxial test;

[0065] Optionally, in step S32, the maximum stress caused by waves at different depths and positions inside the dredged slope of the soil sample is determined, which can be obtained through field measurements or indoor physical model tests;

[0066] Optionally, in step S32, the maximum stress caused by waves at different depths and positions inside the dredged slope at the soil sample is determined, which can be calculated using the finite element method and relevant theoretical formulas based on the wave dynamic load on the surface of the dredged slope of the proposed channel obtained in S23;

[0067] S23: Conduct indoor triaxial vibration tests to obtain the dynamic strength index of each soil sample under wave dynamic load. For silt, silty soil, clay soil, and silty soil, the shear strength index can be the triaxial unconsolidated undrained shear index after vibration or the unconfined compressive strength index after vibration.

[0068] S3: Establish a soil mechanics stability calculation model for the dredged channel slope. Input the soil vibration intensity index value obtained from the indoor vibration triaxial test and the maximum wave dynamic load value on the surface of the dredged channel slope into the model to calculate the stability safety factor of the dredged channel slope under wave dynamic load under several slope schemes of the proposed dredged channel slope. In this embodiment, based on the geology of the proposed waterway and engineering practice experience, several slope schemes for the proposed dredged channel slope are initially proposed. Alternatively, based on the geology of the proposed waterway, in accordance with the provisions of the "General Design Code for Seaports" (such as Table 6.4.9 "Slopes of Channel Slopes for Different Geotechnical Categories" of JTS165-2013), combined with engineering practice experience, several slope schemes for the dredged channel slope are initially proposed. The above model is used to calculate the stability safety factor of the dredged channel slope under wave dynamic load under several slope schemes of the proposed dredged channel slope.

[0069] S4: Select the steepest slope of several slope schemes that meet the stability safety factor required by the specification as the slope value of the proposed channel dredging slope.

[0070] S5: For a proposed waterway with a high frequency of relatively large to very large waves, consider the scouring effect of waves on the slope of the proposed dredged waterway slope; for a proposed waterway with a large tidal force, consider the scouring effect of the tidal force on the slope of the proposed dredged waterway slope, and combine the slope value of the dredged waterway slope in step S4 to comprehensively determine the slope value of the proposed dredged waterway slope. The specific steps are as follows:

[0071] S5.1: Establish mathematical models for the wind and wave fields in the project area, as well as a three-dimensional tidal and sediment scour mathematical model with fine local grid division. Use measured wind, wave, current, and sediment concentration data to verify and calibrate the model.

[0072] S5.2: Use the verified and calibrated three-dimensional wind, wave, tidal and sediment coupling mathematical model to simulate typical high wind, high wave and / or high tide processes, as well as the dynamic field and sediment concentration field of the project sea area;

[0073] S5.3: Using a validated and calibrated three-dimensional wind, wave, tidal and sediment coupling mathematical model, quantitatively calculate the scour thickness of the proposed channel slopes at different beach water depths during typical high winds, high waves and high tides. Considering the frequency of typical high winds and high waves in a year, analyze whether the impact of scour caused by waves and tidal currents on the proposed channel slope surface maintenance is within an acceptable range.

[0074] S5.4: The slope value of the proposed dredged channel slope shall be determined comprehensively based on the calculation of scour of the proposed dredged channel slope surface by considering waves and tidal currents, and the feasible slope value of the proposed dredged channel slope based on the soil mechanics stability calculation of the proposed dredged channel slope under the action of wave dynamic loads.

[0075] In step S5.4, the specific method for comprehensively determining the slope of the proposed dredged channel slope is as follows: for waterways with a short design service life of the proposed dredged channel slope (e.g., less than 5 years), the steepest slope whose stability safety factor meets the requirements of the "Code for Design of Foundations for Water Transport Engineering" obtained from the geomechanical stability calculation of the proposed dredged channel slope under wave dynamic load can be used as the slope of the proposed dredged channel slope; for waterways with a long design service life of the proposed dredged channel slope (greater than or equal to 5 years), on the basis of S5.4.1, combined with the calculation of the scouring of the slope surface of the proposed dredged channel slope by waves and / or tidal currents, the slope can be appropriately slowed down to serve as the slope of the proposed dredged channel slope.

[0076] The technologies mentioned above, including field observations, field measurements, indoor physical model tests, Putian wave formula, wave mathematical model, computational fluid dynamics software, finite element method, indoor vibration triaxial test, triaxial unconsolidated undrained shear test after vibration, unconfined compression test after vibration, and three-dimensional wind, wave, tidal and sediment coupling mathematical model, are all mature technologies and will not be elaborated on here.

[0077] The present invention will be further described below with reference to the accompanying drawings and examples, but the embodiments of the present invention are not limited thereto.

[0078] Engineering conditions: A certain channel is located in the open sea, outside the breakwater entrance. The natural seabed elevation of Section A is -8m (i.e. 8m below the local theoretical lowest tide level) and the length is 1km. Section A already has a lower-level channel, a 150,000-ton channel with a navigable width of 230m and a bottom elevation of -16.5m (i.e. 16.5m below the local theoretical lowest tide level). The proposed channel for Section A is a 300,000-ton channel with a navigable width of 350m and a channel bottom elevation of -22m (i.e. 22m below the local theoretical lowest tide level). The design service life of the dredged slope is tentatively set at 5 years. The channel geology of Section A is silt with low shear strength. The bottom elevation of the silt layer is -22.0m, and below it is a hard clay layer with very high shear strength. The design high water level is 5.36m.

[0079] Step 1: The channel geology is silt. According to Table 6.4.9 “Slope gradients of channel sides for different rock and soil types” of the “General Design Code for Seaports” (JTS165-2013), the dredged side slope gradients for the proposed 300,000-ton channel are planned to be 1:8 and 1:7.

[0080] Step 2: On-site observation of the dredged slope of the existing lower-level waterway at the proposed waterway was carried out. The observation results showed that the overall slope of the dredged slope of the existing lower-level waterway was stable at 1:6.

[0081] Step 3: From the perspective of slope soil mechanics stability, the stability of the proposed channel dredging slope is verified. Due to the large waves, the softening effect of waves on the soil mechanics strength of the proposed channel dredging slope should also be considered, as should the adverse effects of wave dynamic loads on the stability of the channel dredging slope. The specific steps include the following:

[0082] Step 3-1, according to the geological survey report, obtain the physical and mechanical indicators of the soil of the proposed channel dredging slope before excavation, including soil weight and shear strength index. For silt, silty soil, clay soil, and silty soil, the shear strength index can be selected from the unconfined compressive strength index or the triaxial unconsolidated undrained shear index after unloading, and the direct shear quick shear index. The required physical indicators selected in this embodiment are shown in Table 1. The slope stability calculation formula in the "Water Transport Engineering Foundation Design Code" (such as JTS147-2017) is used. The slope soil mechanics stability calculation formula is used to calculate the slope stability safety factor of 2.878 when the dredged slope is 1:8 without considering the influence of wave dynamic load (the calculation results are shown in the table). Figure 1 ).

[0083] Table 1 Physical and mechanical indexes of soil layers

[0084]

[0085] Step 3-2: Based on the design service life of the proposed channel dredging slope, determine the design wave recurrence period standard of the channel dredging slope as once in 5 years, and combine it with the extreme low water level, design low water level, design high water level, extreme high water level, and medium water level;

[0086] Step 3-3, based on the measured wave statistics and wave mathematical model calculations, determine the design wave elements (unexcavated state) of the proposed channel under different design water levels of the design wave return period standard as shown in Table 2 below;

[0087] Table 2 Design wave elements at various characteristic water levels

[0088]

[0089]

[0090] Step 3-4: Based on the design wave elements corresponding to different design water levels under a 5-year return period (i.e., Table 2), the wave dynamic load values ​​on the beach are determined according to linear wave theory based on formulas (1) and (2): 8.4 kPa for the extreme low water level condition, 9.1 kPa for the design low water level condition, 9.2 kPa for the design high water level condition, and 9.0 kPa for the extreme high water level condition. Therefore, the design high water level and its corresponding design wave element are the most unfavorable design water level and design wave element combination.

[0091] According to the method of "Hydrological Code for Ports and Waterways", the design wave elements and wave action time corresponding to the design high water level under the 5-year return period of this section are determined. Figure 2 ) are shown in Table 3 below.

[0092] Table 3 Wave parameters of each area of ​​the slope

[0093]

[0094] Step 3-5: Based on the wave parameters of each area of ​​the dredged slope in Table 3, use formulas (1) to (2) to calculate the wave dynamic load on the surface of the dredged slope of the proposed channel under the action of the design wave element corresponding to the design high water level under a return period of 5 years. The calculation results are shown in Table 4.

[0095] Table 4 Dynamic wave loads on the surface of the dredged channel slope

[0096]

[0097] According to the wave dynamic load on the surface of the dredged slope of the proposed channel (Table 4), the finite element method is used to calculate the internal stress of the soil caused by the waves.

[0098] Table 5 Internal stress amplitude of the soil mass of the proposed channel dredging slope caused by waves

[0099]

[0100] Step 3-6: First, obtain representative soil samples on the proposed channel section through geological survey. The sampling must cover all major soil layers related to soil mechanical stability. Each major soil layer must contain at least two soil samples, one above and one below. The soil samples must be undisturbed. Typical sampling points are as follows: Figure 2 As shown;

[0101] Secondly, the stress caused by waves calculated in Table 5, together with the wave period and wave action time of the design wave element, is used as the loading for the indoor vibration triaxial test;

[0102] Finally, an indoor vibration triaxial test (vibration triaxial unconsolidated undrained test) was conducted to obtain the dynamic strength index of each soil sample under wave dynamic load, that is, the dynamic cohesion c at each location. d and dynamic internal friction angle See Table 6 for details.

[0103] Table 6 Dynamic strength index of soil in each area of ​​slope

[0104]

[0105] Step 3-7: Calculate the soil mechanical stability safety factor of the proposed channel dredging slope. The specific steps are:

[0106] First, a calculation model for the stability of the waterway dredging slope is established, and the soil dynamic parameter indicators in Table 6 are assigned to the corresponding model areas;

[0107] Secondly, add the maximum wave dynamic load on the channel slope surface, such as Figure 4 As shown;

[0108] Finally, the slope stability calculation formula in the "Water Transport Engineering Foundation Design Code" (such as JTS147-2017) is used to calculate the stability safety factor of the channel dredging slope under wave dynamic load. The calculation results show that when the slope of the channel dredging slope is 1:8, the results are as follows: Figure 4 As shown in the figure, the minimum stability safety factor of the dredged channel slope is 1.536, which is about 45% lower than the stability safety factor under still water conditions, but greater than the 1.3 required in the "Code for Design of Foundations for Water Transport Engineering" (JTS147-2017); when the slope of the dredged channel slope is 1:7, the soil mechanics stability coefficient of the dredged channel slope is 1.398, which is still greater than the 1.3 required in the "Code for Design of Foundations for Water Transport Engineering" (JTS147-2017).

[0109] Step 4: Establish a three-dimensional wind, wave, tidal and sediment coupling mathematical model to simulate the dynamic field (flow field, wave field) related to the stability of the dredged slope under the action of typical strong winds, strong waves and high tides, reproduce the sediment movement process, and quantitatively calculate the scouring amplitude of the proposed channel dredging slope. The specific sub-steps include the following:

[0110] Step 4-1: Establish mathematical models of the wind and wave fields in the engineering sea area, as well as a three-dimensional tidal and sediment scouring mathematical model with fine grid division in the local area (navigation channel and dredged slope waters), to form a three-dimensional tidal and sediment coupling mathematical model of wind and wave. Typhoon "Wepa" was selected as a typical process of high winds, high waves and high tides, and the model was verified using the measured wind, wave, current, sediment content and other hydrological data of Typhoon "Wepa", the 150,000-ton channel scale at that time, and the water depth and topography of the sea area.

[0111] Step 4-2: Use the verified three-dimensional wind, wave, tidal and sediment coupling mathematical model to simulate the typical strong wind and wave superimposed high tide process, the dynamic field (wind field, wave field, flow field) and sediment content field of the engineering sea area.

[0112] In step 4-3, the verified three-dimensional wind, wave, tidal and sediment coupling mathematical model was used to quantitatively calculate the scouring of the proposed channel dredging slope caused by a typical strong wind and wave superimposed on a high tide process. The calculation results show that the maximum scouring thickness does not exceed 0.07m. Since the typical strong wind and wave process does not occur more than twice in a year, the impact of scouring caused by waves and tidal currents on the proposed channel slope is within an acceptable range.

[0113] Step 5: The design service life of the proposed channel dredging slope is relatively long (5 years), and the scouring range of the channel dredging slope under the action of waves and tidal currents is very limited. The steepest slope of 1:7, which meets the requirements of the water transport industry standard "Water Transport Engineering Foundation Design Code" for the soil mechanics stability safety factor of the proposed channel dredging slope under the action of wave dynamic loads and is 1.3, is selected as the slope value of the proposed channel dredging slope.

[0114] The above description of the embodiments is intended to facilitate understanding and use of the present invention by those skilled in the art. It will be apparent that those skilled in the art can readily make various modifications to these embodiments and apply the general principles described herein to other embodiments without requiring inventive effort. Therefore, the present invention is not limited to the above-described embodiments. Improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. A method for determining the slope of a dredged channel in a sea area, characterized in that: The method comprises: S0: Several slope options for the dredged channel slope are initially proposed; S1: Based on the design service life of the dredged slope of the proposed channel, determine the design wave return period standard and corresponding design wave elements of the dredged slope of the proposed channel, and then determine the maximum wave dynamic load on the surface of the dredged slope of the channel under different preset water level conditions; S2: Determine the soil strength index under the maximum wave dynamic load through indoor vibration triaxial test; specifically including: S21: Obtain representative soil samples on the proposed channel section through geological survey. The sampling must cover all soil layers related to soil mechanical stability. Each soil layer must contain at least two upper and lower soil samples, and the soil samples must be original samples; S22: According to the design wave elements corresponding to different design water levels under the design wave recurrence period standard, and according to the maximum wave dynamic load on the dredged channel slope surface at the specific section of the proposed channel, determine the maximum stress caused by waves at different depths and positions inside the dredged slope at the soil sample, together with the wave period and wave action time of the design wave elements, as the loading for the indoor vibration triaxial test; S23: Conduct indoor vibration triaxial test to obtain the dynamic strength index of each soil sample under wave dynamic load. For silt, silty soil, clay soil and silty soil, the shear strength index can be the triaxial unconsolidated undrained shear index after vibration or the unconfined compressive strength index after vibration; S3: Establish a soil mechanics stability calculation model for the channel dredging slope. Input the soil vibration intensity index value obtained from the indoor vibration triaxial test and the maximum wave dynamic load value on the channel slope surface into the model to calculate the stability safety factor of the channel dredging slope under wave dynamic load for several slope schemes of the proposed channel dredging slope. S4: Select the steepest slope of several slope schemes that meet the stability safety factor required by the specification as the slope value of the proposed channel dredging slope.

2. The method for determining the slope of dredging slope in sea area and waterway according to claim 1, characterized in that: Step S1 specifically includes: S11: determining a design wave return period standard for the dredged slope of the proposed waterway based on the design service life of the dredged slope of the proposed waterway, and a combination thereof with different preset water level conditions, wherein the water levels of the different preset water level conditions include an extreme low water level, a design low water level, a design high water level, an extreme high water level, and a medium water level; S12: Determine the design wave elements corresponding to different preset water level conditions under the design wave recurrence period standard for the proposed waterway based on the measured wave statistical method, or by using one of the methods of the "Hydrological Code for Ports and Waterways", the Putian wave formula, or the wave mathematical model. The design wave elements include water depth, h , seawater weight , effective wave height , a series of wave heights H 1% ~Wave height H 100% ,wavelength L , wave period T , and wave action time ; S13: Determine the wave dynamic load on the surface of the dredged channel slope under the design wave return period standard according to the design wave elements corresponding to different preset water level conditions, and obtain the maximum wave dynamic load on the surface of the dredged channel slope under different preset water level conditions.

3. The method for determining the slope of dredging slope in sea area and waterway according to claim 2, characterized in that: In step S13, the wave dynamic load on the surface of the dredged slope of the proposed channel is obtained through on-site measurement or indoor physical model testing and calculation using computational fluid dynamics software.

4. The method for determining the slope of dredging slope in sea area and waterway according to claim 2, characterized in that: In step S13, the wave dynamic load on the surface of the dredged slope of the proposed channel is calculated using the relevant calculation formula, specifically: The formula for calculating the wave dynamic load on the surface of the dredged channel slope is: Where: p The dynamic wave load on the surface of the dredged channel slope; is pressure; is the horizontal coordinate relative to the wave node; is the wavelength; is the wave period; For time; is the wave height or the series wave height H of a wave 1% ~H 100% , or the effective wave height ; is the weight of water; For water depth.

5. The method for determining the slope of dredging slope in sea area and waterway according to claim 1, characterized in that: In step S22, the maximum stress caused by waves at different depths and positions inside the dredged slope of the soil sample is determined by field measurement or indoor physical model test.

6. The method for determining the slope of dredging slope in sea area and waterway according to claim 2, characterized in that: In step S22, the maximum stress caused by waves at different depths and positions inside the dredged slope at the soil sample is determined, and the maximum stress is calculated using the finite element method and relevant theoretical formulas based on the wave dynamic load on the surface of the dredged slope of the proposed channel obtained in S13.

7. The method for determining the slope of dredging slope in sea area and waterway according to claim 1, characterized in that: After step S4, the method further includes: S5.1: Establish mathematical models for the wind and wave fields in the project area, as well as a three-dimensional tidal and sediment scour mathematical model with fine local grid division. Use measured wind, wave, current, and sediment concentration data to verify and calibrate the model. S5.2: Use the verified and calibrated three-dimensional wind, wave, tidal and sediment coupling mathematical model to simulate typical high wind, high wave and / or high tide processes, as well as the dynamic field and sediment concentration field of the project sea area; S5.3: Using a validated and calibrated three-dimensional wind, wave, tidal and sediment coupling mathematical model, quantitatively calculate the scour thickness of the proposed channel slopes at different beach water depths during typical high winds, high waves and high tides. Considering the frequency of typical high winds and high waves in a year, analyze whether the impact of scour caused by waves and tidal currents on the proposed channel slope surface maintenance is within an acceptable range. S5.4: The slope value of the proposed dredged channel slope shall be determined comprehensively based on the calculation of scour of the proposed dredged channel slope surface by considering waves and tidal currents, and the feasible slope value of the proposed dredged channel slope based on the soil mechanics stability calculation of the proposed dredged channel slope under the action of wave dynamic loads.

8. The method for determining the slope of dredging slope in sea area and waterway according to claim 7, characterized in that: In step S5.4, the specific method for comprehensively determining the slope of the proposed channel dredging slope is as follows: S5.4.1: For waterways with a proposed dredged channel slope with a design life of less than 5 years, the steepest slope with a stability safety factor that meets the requirements of the "Code for Design of Foundations for Water Transport Engineering" obtained from the geomechanical stability calculation of the proposed dredged channel slope under wave dynamic loads may be used as the slope of the proposed dredged channel slope; S5.4.2: For waterways with a design service life of 5 years or more, the slope of the proposed dredged channel slope may be appropriately slowed down based on the calculation of the scouring of the slope surface by waves and / or tidal currents on the basis of S5.4.1, and the slope may be used as the slope of the proposed dredged channel slope.

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