A prediction method for the stability of weathered grooves in submarine tunnels under the action of typhoon waves

Abstract

The present invention relates to a method for predicting the stability of weathered troughs in submarine tunnels under the action of typhoon waves. The working principle of this method is that when waves continuously act on the weathered trough soil mass, on the one hand, the wave pressure causes a landslide force in the weathered trough, and on the other hand, the self-weight of the weathered trough also constitutes a landslide force. The cyclic pressure causes the strength of the weathered trough soil mass to decay. The strength of the decayed soil mass has the ability to resist the landslide force and prevent the weathered trough from sliding. If the landslide resistance force is less than the landslide force, the weathered trough will experience a landslide and lose stability. The present invention has the advantages of simple structure, reliable results, and convenient use.

Description

Technical Field

[0001] The present invention relates to the field of infrastructure construction, and particularly to a method for predicting the stability of weathered troughs of submarine tunnels under the action of typhoon waves. Background Art

[0002] A submarine tunnel is a common form of underground structure. The surrounding rock of some submarine tunnels is located in the submarine weathered trough, and its engineering properties are poor. Under normal sea conditions, the weathered trough covering the top of the tunnel can maintain self-stability. However, when a typhoon occurs, the waves exert a cyclic pressure on the seabed, causing disturbance to the soil mass in the weathered trough and gradually decreasing its strength. In addition, when the waves are at the crest, the soil mass on the surface of the weathered trough is subjected to the wave pressure. Before the tunnel is supported, the soil mass in the weathered trough may collapse due to its own weight and other effects, resulting in engineering accidents. So far, no method has been seen to judge the stability of the weathered trough of submarine tunnels under typhoons. Summary of the Invention

[0003] The purpose of the present invention is to provide a method for predicting the stability of weathered troughs of submarine tunnels under the action of typhoon waves, which has the advantages of simple structure, reliable results and convenient use.

[0004] To achieve the above purpose, the technical solution of the present invention is: A method for predicting the stability of weathered troughs of submarine tunnels under the action of typhoon waves includes the following steps:

[0005] (1) Determine the width B of the submarine tunnel, the single-cycle advance L0 and the thickness H0 of the weathered trough;

[0006] (2) Determine the hydrodynamic parameters at the weathered trough when encountering a once-in-a-century typhoon wave, including the water depth d, wave height H, wave length L, period T0 and continuous action time T;

[0007] (3) Determine the saturated unit weight γ of the soil mass underwater at the weathered trough sat ;

[0008] (4) Determine the wave peak pressure p0 generated by the once-in-a-century typhoon wave on the seabed surface of the weathered trough;

[0009] (5) Determine the number of wave cycle actions N;

[0010] (6) Determine the decay cohesion c', decay internal friction angle and excess pore water pressure u of the soil mass when the number of actions under the wave cyclic load is N;

[0011] (7) Determine the sliding collapse force T1 caused by gravity of the weathered trough before the tunnel is supported after excavation;

[0012] (8) Determine the sliding collapse force T2 caused by wave pressure of the weathered trough before the tunnel is supported after excavation;

[0013] (9) Determine the total landslide force T of the weathered trough when the tunnel excavation has not been supported yet.

[0014] (10) Determine the anti-landslide force R of the weathered trough when the tunnel excavation has not been supported yet.

[0015] (11) Judge the stability of the weathered trough of the submarine tunnel under the action of typhoon waves.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The working principle of the present invention is that when the waves continuously act on the weathered trough soil mass, on the one hand, the wave pressure causes a landslide force in the weathered trough, and on the other hand, the self-weight of the weathered trough also constitutes a landslide force. The cyclic pressure causes the strength of the weathered trough soil mass to decay, and the anti-landslide force of the decayed soil mass strength prevents the weathered trough from landsliding. If the anti-landslide force is less than the landslide force, the weathered trough will experience landsliding and lose stability. The present invention has the advantages of simple structure, reliable results and convenient use. Specific Embodiments

[0017] Next, the technical solution of the present invention will be specifically described.

[0018] A method for predicting the stability of the weathered trough of a submarine tunnel under the action of typhoon waves according to the present invention includes the following steps:

[0019] (1) Define the width B of the submarine tunnel, the single-cycle advance L0 and the thickness H0 of the weathered trough.

[0020] Determine the above three parameters according to the tunnel design and construction plan.

[0021] (2) Determine the hydrodynamic parameters at the weathered trough when encountering a once-in-a-century typhoon wave, including the water depth d, wave height H, wave length L, period T0 and continuous action time T.

[0022] Determine the above parameters at the tunnel weathered trough according to the marine meteorological and hydrological data.

[0023] (3) Determine the saturated unit weight γ of the soil mass underwater at the weathered trough sat .

[0024] Use a drill rig to take undisturbed soil samples in the weathered trough, transport them back to the laboratory, measure the density of the soil mass using the cutting ring method, and then multiply it by the acceleration of gravity to obtain its saturated unit weight γ sat .

[0025] (4) Determine the wave peak pressure p0 generated by the once-in-a-century typhoon wave on the seabed surface of the weathered trough.

[0026]

[0027] Among them, ρ wis the seawater density, taking 1.025 g / cm 3 ; g is the acceleration due to gravity.

[0028] (5) Determine the number of wave cycle actions N.

[0029] N = T / T0

[0030] (6) Determine the attenuated cohesion c', attenuated internal friction angle and excess pore water pressure u when the number of actions of the soil under cyclic wave load is N.

[0031] Using undisturbed soil samples taken by a drill rig, three soil samples are used to conduct dynamic triaxial tests in the laboratory. ① For the first soil sample, the magnitudes of the applied static confining pressure and static axial pressure are both σ1, σ1 = 0.75(ρ w gd + 0.5γ sat H0). After consolidation is completed, a sinusoidal dynamic load σ d , σ d = 0.5p0 is applied axially. After cycling N times with a period of T0, the dynamic load is stopped, and then a static load is applied axially until the soil sample fails, and the axial pressure σ1' at failure is measured;

[0032] ② For the second soil sample, the magnitudes of the applied static confining pressure and static axial pressure are both σ2, σ2 = ρ w gd + 0.5γ sat H0. After consolidation is completed, a sinusoidal dynamic load σ d , σ d = 0.5p0 is applied axially. After cycling N times with a period of T0, the dynamic load is stopped, the excess pore water pressure u at this time is measured, and then a static load is applied axially until the soil sample fails, and the axial pressure σ2' at failure is measured;

[0033] ③ For the third soil sample, the magnitudes of the applied static confining pressure and static axial pressure are both σ3, σ3 = 1.25(ρ w gd + 0.5γ sat H0). After consolidation is completed, a sinusoidal dynamic load σ d , σ d = 0.5p0 is applied axially. After cycling N times with a period of T0, the dynamic load is stopped, and then a static load is applied axially until the soil sample fails, and the axial pressure σ3' at failure is measured.

[0034] When testing with three soil samples, using the applied static confining pressure and failure axial pressure, i.e., (σ1, σ1'), (σ2, σ2'), (σ3, σ3'), draw Mohr circles to obtain the attenuated cohesion c' and attenuated internal friction angle

[0035] (7) Determine the landslide force T1 caused by gravity of the weathered trough before support after tunnel excavation.

[0036] T1 = BL0H0γ sat

[0037] (8) Determine the landslide force T2 caused by wave pressure of the weathered trough before support after tunnel excavation.

[0038] T2 = p0BL0

[0039] (9) Determine the total landslide force T of the weathered trough before support after tunnel excavation.

[0040] T = T1 + T2

[0041] (10) Determine the anti - landslide force R of the weathered trough before tunnel excavation and support.

[0042]

[0043] (11) Determine the stability of the weathered trough of the subsea tunnel under typhoon waves.

[0044] Compare the magnitudes of the landslide force T and the anti - landslide force R. If T < R, the weathered trough is in a stable state; if T = R, the weathered trough is in a critical state of instability; if T > R, the weathered trough is in an unstable state.

[0045] Implementation case

[0046] For the construction of a subsea highway tunnel in a province in the eastern part of China, the preliminary exploration report shows that the tunnel passes through the weathered trough area. To determine the stability of the weathered trough under typhoon waves, the method of the present invention is used for prediction. First, according to the tunnel design and construction plan, the width B of the subsea tunnel is determined to be 14.0 m, the single - cycle advance L0 is 3.0 m, and the thickness H0 of the weathered trough is 27.6 m. According to the marine meteorological and hydrological data, when determining the typhoon waves once in a hundred years, the hydrodynamic parameters at the weathered trough are determined, including the water depth d of 9.9 m, the wave height H of 4.1 m, the wave length L of 52.4 m, the period T0 of 5.9 s, and the continuous action time T of 2.7 h. Undisturbed soil samples are taken from the weathered trough by a drill rig and transported back to the laboratory. The density of the soil is measured by the ring - cutter method and then multiplied by the acceleration of gravity to obtain the underwater saturated unit weight γ of the soil at the weathered trough sat is 19.4 kN / m 3 . Determine that the peak wave pressure p0 generated by the typhoon waves once in a hundred years on the seabed surface of the weathered trough is 11.5 kPa. Determine that the number of wave cycles N is 1647.

[0047] Using the undisturbed soil samples taken by the drill rig, dynamic triaxial tests were carried out on three soil samples in the laboratory. ① For the first soil sample, the static confining pressure and the static axial pressure σ1 applied were both 275 kPa. After consolidation was completed, a sinusoidal dynamic load σ d of 5.75 kPa was applied axially, with a period of 5.9 s. After cyclic action for 1,647 times, the dynamic load was stopped, and then a static load was applied axially until the soil sample failed. The axial pressure σ1' at failure was measured to be 428 kPa;

[0048] ② For the second soil sample, the static confining pressure and the static axial pressure σ2 applied were both 367 kPa. After consolidation was completed, a sinusoidal dynamic load σ d of 5.75 kPa was applied axially, with a period of 5.9 s. After cyclic action for 1,647 times, the dynamic load was stopped, and the excess pore water pressure at this time was measured to be 272 kPa. Then a static load was applied axially until the soil sample failed, and the axial pressure at failure was measured to be 563 kPa;

[0049] ③ For the third soil sample, the static confining pressure and the static axial pressure σ3 applied were both 459 kPa. After consolidation was completed, a sinusoidal dynamic load of 5.75 kPa was applied axially, with a period of 5.9 s. After cyclic action for 1,647 times, the dynamic load was stopped, and then a static load was applied axially until the soil sample failed, and the axial pressure at failure was measured to be 681 kPa.

[0050] When testing with the three soil samples, the static confining pressures and the failure axial pressures applied, namely (275 kPa, 428 kPa), (367 kPa, 563 kPa), (459 kPa, 681 kPa), were used to draw the Mohr circle. The attenuated cohesion c' after cyclic action for 1,647 times was obtained as 25 kPa, the attenuated internal friction angle was 9°, and the excess pore water pressure u was 275 kPa. The landslide force T1 caused by gravity in the weathered trough before support after tunnel excavation was determined to be 22,488 kN. The landslide force T2 caused by wave pressure in the weathered trough before support after tunnel excavation was determined to be 483 kN. The total landslide force T in the weathered trough before support after tunnel excavation was determined to be 22,971 kN. The anti-landslide force R of the weathered trough before support during tunnel excavation was determined to be 37,158 kN. Since T < R, the weathered trough is in a stable state under the once-in-a-century typhoon waves.

[0051] The above are the preferred embodiments of the present invention. All changes made according to the technical solution of the present invention, when the functions and effects generated do not exceed the scope of the technical solution of the present invention, shall fall within the protection scope of the present invention.

Claims

1. A method for predicting the stability of weathered grooves in a submarine tunnel under the action of typhoon waves, characterized in that, It includes the following steps: (1) Determine the width B of the subsea tunnel, the single-cycle advance L0, and the weathered trough thickness H0; (2) Determine the hydrodynamic parameters at the weathered trough when encountering a once-in-a-century typhoon wave, including the water depth d, wave height H, wave length L, period T0, and the continuous action time T'; (3) Determine the saturated unit weight γ of the soil underwater at the weathering trough sat ; (4) Determine the wave peak pressure p0 generated by the once-in-a-century typhoon wave on the seabed surface of the weathered trough; (5) Determine the number of wave cycle actions N; (6) Determine the attenuated cohesive force c' and attenuated internal friction angle of the soil mass when the number of actions under cyclic wave loading is N, and the excess pore water pressure u. The specific method is as follows: and Use the undisturbed soil samples taken by the drill rig and conduct dynamic triaxial tests on three soil samples in the laboratory: ①For the first soil sample, the magnitudes of the applied initial confining pressure and initial axial pressure are both σ1, and σ1 = 0.75(ρ w gd + 0.5γ sat H0), where ρ w is the seawater density. After consolidation is completed, a dynamic load σ d in the form of a sine wave is applied axially, and σ d = 0.5p0, with a period of T0. After cyclic action for N times, the dynamic load is stopped, and then a static load is applied axially until the soil sample fails, and the axial pressure σ1' at failure is measured; ②For the second soil sample, the magnitudes of the applied static confining pressure and static axial pressure are both σ2, and σ2 = ρ w gd + 0.5γ sat H0. After consolidation is completed, a dynamic load σ d in the form of a sine wave is applied axially, σ d = 0.5p0, with a period of T0. After cyclic action for N times, the dynamic load is stopped, and the excess pore water pressure u at this time is measured. Then, a static load is applied axially until the soil sample fails, and the axial pressure σ2' at failure is measured; ③ For the third soil sample, the magnitudes of the applied static confining pressure and static axial pressure are both σ3, and σ3 = 1.25(ρ w gd + 0.5γ sat H0). After consolidation is completed, a dynamic load σ d in the form of a sine wave is applied axially. σ d = 0.5p0, with a period of T0. After cyclic action for N times, the dynamic load is stopped, and then a static load is applied axially until the soil sample fails, and the axial pressure σ3' at the time of failure is measured; When testing with three soil samples, the applied static confining pressure and the failure axial pressure, namely (σ1, σ1'), (σ2, σ2'), (σ3, σ3'), are used to draw the Mohr circle, and the attenuated cohesion c' and the attenuated internal friction angle after N cycles of action are obtained. (7) Determine the landslide force T1 caused by gravity in the weathered trough before the tunnel excavation is supported; (8) Determine the landslide force T2 caused by wave pressure in the weathered trough before the tunnel excavation is supported; (9) Determine the total landslide force T in the weathered trough before the tunnel excavation is supported; (10) Determine the anti-landslide force R in the weathered trough before the tunnel excavation is supported. The calculation formula is: (11) Judge the stability of the weathered trough of the subsea tunnel under the action of typhoon waves in the following way: Compare the magnitudes of the landslide force T and the anti-landslide force R. If T < R, the weathered trough is in a stable state; if T = R, the weathered trough is in a critical state of instability; if T > R, the weathered trough is in an unstable state.

2. The method for predicting the stability of weathered grooves in a submarine tunnel under the action of typhoon waves according to claim 1, characterized in that, In step (3), the saturated unit weight γ of the soil mass underwater at the weathering trough is determined sat by the following method: Use a drilling rig to take undisturbed soil samples in the weathering trough, transport them back to the laboratory, measure the density of the soil mass by the cutting ring method, and then multiply it by the acceleration of gravity to obtain its saturated unit weight γ sat .

3. The method for predicting the stability of weathered grooves in a submarine tunnel under the action of typhoon waves according to claim 1, characterized in that, In step (4), the calculation formula for the wave peak pressure p0 generated by the once-in-a-century typhoon wave on the seabed surface of the weathered trough is: where ρ w is the seawater density; g is the acceleration due to gravity.

4. The method for predicting the stability of weathered grooves in a submarine tunnel under the action of typhoon waves according to claim 1, characterized in that, In step (5), the calculation formula for the number of wave cycle actions N is: N = T' / T0.

5. The method for predicting the stability of weathered grooves in a submarine tunnel under the action of typhoon waves according to claim 1, characterized in that, In step (7), the calculation formula for the landslide force T1 caused by gravity in the weathered trough before the tunnel excavation is supported is: T1 = BL0H0γ sat .

6. The method for predicting the stability of weathered grooves in a submarine tunnel under the action of typhoon waves according to claim 1, characterized in that, In step (8), the calculation formula for the landslide force T2 caused by wave pressure in the weathered trough before the tunnel excavation is supported is: T2 = p0BL0.

7. A method for predicting the stability of weathered troughs in submarine tunnels under the action of typhoon waves, characterized in that, In step (9), the calculation formula for the total landslide force T in the weathered trough before the tunnel excavation is supported is: T = T1 + T2.

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