A method for predicting the maximum depth of a cliff top crack in an extreme sea state

Abstract

The application discloses a method for predicting the maximum depth of a cliff top crack of a sea cliff under extreme sea conditions, which comprises the following steps: obtaining the gravity of a cliff top structure; obtaining the height of the structure above the ground; obtaining the maximum wind speed; obtaining the wind force acting on the structure; obtaining the average water depth, wave height and wave duration in front of the sea cliff; obtaining the trough height, trough depth and sea cliff height of a sea erosion trough; calculating the average wave pressure of waves acting on the cliff face above the average water depth; calculating the seawater infiltration rate of the sea cliff soil; calculating the seawater infiltration distance of the sea cliff above and below the average water depth; obtaining the natural and saturated specific gravity of the cliff soil; obtaining the cohesion and internal friction angle of the cliff soil; calculating the seawater infiltration volume in the cliff; calculating the weight of the cliff after seawater intrusion; obtaining the cohesive friction strength of the cliff soil; obtaining the maximum crack depth provided by the cohesive friction strength and tensile strength; and calculating the maximum depth of the cliff top crack.

Description

Technical Field

[0001] This invention relates to the field of marine geological disasters, and in particular to a method for predicting the maximum depth of cracks at the top of sea cliffs under extreme sea conditions. Background Technology

[0002] Sea cliffs are a common geological feature, formed by crustal movement and wave erosion. Long-term wave action often results in sea grooves at the base of the cliff, and sometimes structures at the summit. The weight of these structures and the horizontal wind forces threaten the cliff's stability. When signs of instability appear, cracks first appear at the summit. These cracks deepen under extreme sea conditions and wind forces, eventually leading to cliff instability. Determining the maximum depth of these cracks is crucial for preventing cliff disasters. To date, no theoretical method has been found to calculate the maximum depth of these cracks. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for predicting the maximum depth of sea cliff top cracks under extreme sea conditions, which has the advantages of being easy to use, reliable results, and highly operable.

[0004] To achieve the above objectives, the technical solution of the present invention is a method for predicting the maximum depth of sea cliff crest cracks under extreme sea conditions, comprising:

[0005] (1) Obtain the gravity G1 of the structure at the top of the cliff;

[0006] (2) Obtain the height H1 of the structure above the ground;

[0007] (3) Calculate the maximum wind speed v under extreme sea states. max ;

[0008] (4) Calculate the wind force W acting on the structure under extreme sea states. p ,as follows:

[0009]

[0010] Where ρ1 is the air density, taken as 1.29 kg / m³. 3 l0 is the calculation length, taken as 1.0m.

[0011] (5) Obtain the average depth d, wave height H and wave duration t0 of the water in front of the cliff under extreme sea conditions;

[0012] (6) Obtain the height H2, depth d1, and cliff height H3 of the sea trough;

[0013] (7) Calculate the average wave pressure p1 acting on the sea cliff surface above the average rise in elevation, as follows:

[0014] p1=0.5γ w H

[0015] Where, γ w The specific gravity of seawater is taken as 10.25 kN / m. 3 ;

[0016] (8) Calculate the seawater infiltration rate v of the sea cliff soil as follows:

[0017]

[0018] Where p0 is the reference pressure, taken as 1.0 kPa; t represents the seawater infiltration time;

[0019] (9) Calculate the seawater infiltration distance x1 above the average elevation of the sea cliff, as follows:

[0020]

[0021] (10) Calculate the seawater infiltration distance x2 below the average elevation of the sea cliff, as follows:

[0022]

[0023] (11) Obtain the natural unit weight γ1 and saturated unit weight γ1 of the cliff soil. sat ;

[0024] (12) Obtain the cohesion c and internal friction angle of the cliff soil.

[0025] (13) Calculate the infiltration volume V1 of seawater within the cliff body, as follows:

[0026] V1=[0.5x1H+x2(d-H2)]l0

[0027] (14) Calculate the weight G2 of the cliff after seawater intrusion, as follows:

[0028] G2=[(H3-H2)d1l0-V1]γ1+V1γ sat

[0029] (15) Obtain the cohesive frictional strength τ of the cliff soil u ;

[0030] (16) The maximum crack depth D1 provided by the cohesive friction strength of the cliff soil is obtained as follows:

[0031]

[0032] (17) Calculate the maximum crack depth D2 provided by the tensile strength of the cliff soil, as follows:

[0033]

[0034] (18) Calculate the maximum depth D of the crack at the top of the sea cliff. max ,as follows:

[0035] D max =min{D1,D2}

[0036] Where min is a function that takes the minimum value.

[0037] Preferably, the natural unit weight γ1 and saturated unit weight γ1 of the cliff soil are obtained. sat Specifically, it includes:

[0038] Typical undisturbed soil samples were collected from the sea cliff. The density ρ1 of the undisturbed soil samples was measured using the ring cutter method, and then multiplied by the gravitational acceleration to obtain the natural unit weight γ1. The undisturbed soil samples were then immersed in water until fully saturated, and the saturated density ρ1 was measured using the ring cutter method. sat Then multiply by the acceleration due to gravity to obtain its saturated specific weight γ. sat .

[0039] Preferably, the cohesion c and internal friction angle of the cliff soil are obtained. Specifically, it includes:

[0040] Using typical undisturbed soil samples taken from sea cliffs, direct shear tests were conducted in the laboratory to determine their cohesion (c) and internal friction angle.

[0041] Preferably, the cohesive frictional strength τ of the cliff soil is obtained. u Specifically, it includes:

[0042] The cohesive friction strength τ was measured within the cliff using an in-situ vane shear apparatus. u .

[0043] As can be seen from the above description of the present invention, compared with the prior art, the present invention has the following beneficial effects:

[0044] This invention provides a method for predicting the maximum depth of sea cliff crest cracks under extreme sea conditions, which has the advantages of being easy to use, providing reliable results, and being highly operable.

[0045] The present invention will be further described in detail below with reference to the embodiments, but the method for predicting the maximum depth of sea cliff top cracks under extreme sea conditions is not limited to the embodiments. Detailed Implementation

[0046] The technical solutions in the embodiments of the present invention will be described and discussed in detail below. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0047] This invention provides a method for predicting the maximum depth of sea cliff crest cracks under extreme sea conditions, comprising:

[0048] (1) Obtain the gravity G1 of the structure on the cliff top.

[0049] Based on the design data of the structure, obtain the gravity G1 of the structure at the top of the cliff.

[0050] (2) Obtain the height H1 of the structure above the ground.

[0051] Use a tape measure to measure the height H1 of the structure above the ground.

[0052] (3) Calculate the maximum wind speed v under extreme sea states. max .

[0053] Based on historical meteorological observation data, the maximum wind speed v during extreme sea states was obtained. max .

[0054] (4) Calculate the wind force W acting on the structure under extreme sea states. p .

[0055]

[0056] Where ρ1 is the air density, taken as 1.29 kg / m³. 3 l0 is the calculation length, taken as 1.0m.

[0057] (5) Obtain the average depth d, wave height H and wave duration t0 of the water in front of the cliff under extreme sea conditions.

[0058] The above three parameters were obtained based on empirical observation data of hydrodynamics in front of the cliff under extreme sea conditions.

[0059] (6) Obtain the height H2, depth d1, and cliff height H3 of the sea trough.

[0060] Using a measuring tape, the height H2 of the sea trough, the depth d1 of the trough, and the height H3 of the sea cliff were measured in front of the cliff.

[0061] (7) Calculate the average wave pressure p1 acting on the sea cliff surface above the average water depth elevation.

[0062] p1=0.5γ w H

[0063] Where, γ w The specific gravity of seawater is taken as 10.25 kN / m. 3 .

[0064] (8) Calculate the seawater infiltration rate v of the sea cliff soil.

[0065]

[0066] Where p0 is the reference pressure, taken as 1.0 kPa; t represents the seawater infiltration time.

[0067] (9) Calculate the seawater infiltration distance x1 above the average water depth elevation of the sea cliff.

[0068]

[0069] (10) Calculate the seawater infiltration distance x2 below the average water depth elevation of the sea cliff.

[0070]

[0071] (11) Obtain the natural unit weight γ1 and saturated unit weight γ1 of the cliff soil. sat .

[0072] Typical undisturbed soil samples were collected from the sea cliffs and transported back to the laboratory. The density ρ1 of the undisturbed soil samples was measured using the ring cutter method, and then multiplied by the gravitational acceleration to obtain its natural unit weight γ1. The undisturbed soil samples were then immersed in water until fully saturated, and the saturated density ρ was measured using the ring cutter method. sat Then multiply by the acceleration due to gravity to obtain its saturated specific weight γ. sat .

[0073] (12) Obtain the cohesion c and internal friction angle of the cliff soil.

[0074] Using typical undisturbed soil samples taken from sea cliffs, direct shear tests were conducted in the laboratory to determine their cohesion (c) and internal friction angle.

[0075] (13) Calculate the infiltration volume V1 of seawater within the cliff body.

[0076] V1=[0.5x1H+x2(d-H2)]l0

[0077] (14) Calculate the weight of the cliff after seawater intrusion into the cliff body, G2.

[0078] G2=[(H3-H2)d1l0-V1]γ1+V1γ sat

[0079] (15) Obtain the cohesive frictional strength τ of the cliff soil u .

[0080] The cohesive friction strength τ was measured within the cliff using an in-situ vane shear apparatus. u .

[0081] (16) Obtain the maximum crack depth D1 provided by the cohesive friction strength of the cliff soil.

[0082]

[0083] (17) Calculate the maximum crack depth D2 provided by the tensile strength of the cliff soil.

[0084]

[0085] (18) Calculate the maximum depth D of the crack at the top of the sea cliff. max .

[0086] D max =min{D1,D2}

[0087] Here, min is a function that takes the minimum value of the latter parameter.

[0088] In this embodiment, the term "extreme sea state" refers to the meaning disclosed in the prior art, specifically the storm surge phenomenon caused by typhoons. Due to severe atmospheric disturbances, such as strong winds and sudden changes in air pressure, the sea level rises and falls abnormally, causing the tide level in the affected sea area to greatly exceed the normal tide level.

[0089] The working principle of this invention is that the soil at the top of the cliff is damaged along the bottom of the sea trough under the weight of the superstructure, wind force, and the gravity of the seawater. Based on the limit equilibrium principle of the cliff soil, the most unfavorable depth of the crack, i.e. the maximum depth, is obtained.

[0090] Due to long-term wave erosion, typical sea caves have developed on the sea cliffs of a certain coastline in southeastern my country. In order to ensure the safety of the facilities above the sea caves, the cave entrances are sealed with rammed earth. In order to obtain the safety of the cave entrances under extreme sea conditions, the method of this invention is used to predict them.

[0091] Concrete structures are distributed on a sea cliff in northern my country. Due to long-term wave erosion, sea grooves have developed on the lower part, and cracks are distributed on the top of the cliff. In order to use the depth of the cracks to determine the stability of the cliff, it is necessary to determine the maximum depth of the cracks on the top of the sea cliff. The method of this invention is used to predict it.

[0092] Concrete structures are distributed on a sea cliff in northern my country. Due to long-term wave erosion, sea grooves have developed on the lower part, and cracks are distributed on the top of the cliff. In order to use the depth of the cracks to determine the stability of the cliff, it is necessary to determine the maximum depth of the cracks on the top of the sea cliff. The method of this invention is used to predict it.

[0093] Based on the design data of the concrete structure at the cliff top, the weight G1 of the structure is obtained as 17.8 kN. Using a measuring tape, the height H1 of the structure above the ground is measured to be 1.75 m. Based on historical meteorological observation data, the maximum wind speed v under extreme sea conditions is obtained. max The wind speed is 21.3 m / s. Calculate the wind force W acting on the structure under extreme sea states. p The mean elevation difference is 0.51 kN. Based on empirical observation data of hydrodynamics in front of the sea cliff under extreme sea states, the average water rise depth d in front of the sea cliff under extreme sea states is obtained as 2.92 m, wave height H as 1.21 m, and wave duration t0 as 2.4 h. Using a measuring tape, the trench height H2 of the sea erosion channel is measured as 1.15 m, trench depth d1 as 1.53 m, and sea cliff height H3 as 6.72 m. The average wave pressure p1 acting on the sea cliff surface above the average water rise depth elevation is calculated to be 6.20 kPa. The seawater infiltration rate of the sea cliff soil is calculated as v = 1.72 × 10⁻⁶. -2 exp(-0.0374t). The seawater infiltration distance x1 is calculated to be 0.46m above the average elevation of the sea cliff. The seawater infiltration distance x2 is calculated to be 0.92m below the average elevation of the sea cliff. Typical undisturbed soil samples were taken from the sea cliff and transported back to the laboratory. The density ρ1 of the undisturbed soil samples was measured using the ring cutter method. Then, multiplied by the gravitational acceleration, the natural unit weight γ1 of the cliff soil was obtained as 17.8 kN / m³. 3 The undisturbed soil sample was immersed in water until fully saturated, and then its saturated density ρ was measured using the ring sampler method. sat Then multiply by the acceleration due to gravity to obtain the saturated specific weight γ. sat 19.2 kN / m 3 Using typical undisturbed soil samples taken from the sea cliff, direct shear tests were conducted in the laboratory, and the cohesion c of the cliff soil was measured to be 32.7 kPa and the internal friction angle was determined. The angle is 16.4°. The calculated infiltration volume of seawater within the cliff body, V1, is 1.91 m³. 3 The weight of the cliff face after seawater intrusion, G2, was calculated to be 154.4 kN. The cohesive frictional strength τ of the cliff face soil was measured using an in-situ vane shear tester within the cliff body. u The maximum crack depth D1, determined by the cohesive frictional strength of the cliff soil, is 0.49 m. The maximum crack depth D2, determined by the tensile strength of the cliff soil, is 0.31 m. The maximum crack depth D at the top of the sea cliff under extreme sea conditions is then determined. max It is 0.31m.

[0094] The above is merely a preferred embodiment of the present invention. However, the present invention is not limited to the above embodiment. Any equivalent changes and modifications made according to the present invention, provided that the resulting functional effects do not exceed the scope of the present invention, shall fall within the protection scope of the present invention.

Claims

1. A method for predicting the safety of sea cave entrances under extreme sea conditions, characterized in that, include: (1) Obtain the gravity G1 of the structure at the top of the cliff; (2) Obtain the height H1 of the structure above the ground; (3) Calculate the maximum wind speed v under extreme sea states. max ; (4) Calculate the wind force W acting on the structure under extreme sea states. p ,as follows: Where ρ1 is the air density, taken as 1.29 kg / m³. 3 l0 is the calculated length, taken as 1.0m; (5) Obtain the average depth d, wave height H and wave duration t0 of the water in front of the cliff under extreme sea conditions; (6) Obtain the height H2, depth d1, and cliff height H3 of the sea trough; (7) Calculate the average wave pressure p1 acting on the sea cliff surface above the average rise in elevation, as follows: p1=0.5γ w H Where, γ w The specific gravity of seawater is taken as 10.25 kN / m. 3 ; (8) Calculate the seawater infiltration rate v of the sea cliff soil as follows: Where p0 is the reference pressure, taken as 1.0 kPa; t represents the seawater infiltration time; (9) Calculate the seawater infiltration distance x1 above the average elevation of the sea cliff, as follows: ; (10) Calculate the seawater infiltration distance x2 below the average elevation of the sea cliff, as follows: ; (11) Obtain the natural unit weight γ1 and saturated unit weight γ1 of the cliff soil. sat ; (12) Obtain the cohesion c and internal friction angle of the cliff soil. (13) Calculate the infiltration volume V1 of seawater within the cliff body, as follows: V1 = [0.5x1H + x2(d-H2)]l0; (14) Calculate the weight G2 of the cliff after seawater intrusion, as follows: G2=[(H3-H2)d1l0-V1]γ1+V1γ sat ; (15) Obtain the cohesive frictional strength τ of the cliff soil u ; (16) The maximum crack depth D1 provided by the cohesive friction strength of the cliff soil is obtained as follows: ; (17) Calculate the maximum crack depth D2 provided by the tensile strength of the cliff soil, as follows: ; (18) Calculate the maximum depth D of the crack at the top of the sea cliff. max ,as follows: D max =min{D1,D2} Where min is a function that takes the minimum value.

2. The method for predicting the safety of sea cave entrances under extreme sea conditions as described in claim 1, characterized in that, Obtain the natural unit weight γ1 and saturated unit weight γ of the cliff soil. sat Specifically, it includes: Typical undisturbed soil samples were collected from the sea cliff. The density ρ1 of the undisturbed soil samples was measured using the ring cutter method, and then multiplied by the gravitational acceleration to obtain the natural unit weight γ1. The undisturbed soil samples were then immersed in water until fully saturated, and the saturated density ρ1 was measured using the ring cutter method. sat Then multiply by the acceleration due to gravity to obtain its saturated specific weight γ. sat .

3. The method for predicting the safety of sea cave entrances under extreme sea conditions as described in claim 1, characterized in that, Obtain the cohesion c and internal friction angle of the cliff soil. Specifically, it includes: Using typical undisturbed soil samples taken from sea cliffs, direct shear tests were conducted in the laboratory to determine their cohesion (c) and internal friction angle.

4. The method for predicting the safety of sea cave entrances under extreme sea conditions as described in claim 1, characterized in that, Obtain the cohesive frictional strength τ of the cliff soil u Specifically, it includes: The cohesive friction strength τ was measured within the cliff using an in-situ vane shear apparatus. u .

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