CN111157699B - Indoor test-based submarine landslide evaluation method - Google Patents

Indoor test-based submarine landslide evaluation method Download PDF

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Publication number
CN111157699B
CN111157699B CN201911400359.7A CN201911400359A CN111157699B CN 111157699 B CN111157699 B CN 111157699B CN 201911400359 A CN201911400359 A CN 201911400359A CN 111157699 B CN111157699 B CN 111157699B
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box
soil
test
slope
landslide
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CN111157699A (en
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窦玉喆
国振
王立忠
朱从博
芮圣洁
周文杰
李雨杰
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Zhejiang University ZJU
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Zhejiang University ZJU
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    • GPHYSICS
    • G01MEASURING; TESTING
    • G01NINVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N33/00Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
    • G01N33/24Earth materials

Abstract

The invention discloses a submarine landslide evaluation method based on indoor tests, which comprises the steps of preparing structural soft clay and carrying out the indoor tests; the preparation of the structural soft clay can be obtained by doping portland cement 525 into marine soft soil and adding water to 2 times of the liquid limit of a soil body, and then uniformly stirring under a vacuum condition; wherein, the addition of the silicate 525 cement is 2% of the mass of the soft soil particles; indoor test realize based on the novel indoor test device of simulation seabed landslide, the device includes mold box main part, false slope, funnel, soil cutting board, sensor support and portal frame lifting device. The method can realize the test simulation of the multi-slope angle and multi-working condition submarine landslide, and the method can also be combined with an indoor large-scale section wave water channel to systematically study the influence of the coupling effect of waves, slope toe scouring and rapid sedimentation on the submarine landslide, thereby obtaining a systematic method for evaluating the stability of the submarine landslide.

Description

Indoor test-based submarine landslide evaluation method
Technical Field
The invention relates to a set of test device capable of realizing multi-slope-angle and multi-working-condition simulation of submarine landslide, in particular to a submarine landslide evaluation method based on an indoor test, which is suitable for the field of ocean engineering research.
Background
As is well known, the reserves of conventional energy sources such as petroleum, natural gas and the like in the ocean are quite abundant, and according to incomplete statistics, the reserves of the ocean petroleum are about 1450 hundred million tons and account for 34 percent of the total reserves of the global petroleum, wherein the ascertained reserves are about 380 hundred million tons; in continental shelf areas only, the current discovery of hydrocarbon-bearing basins has areas of up to 1500 million square kilometers, and over 800 hydrocarbon-bearing basins, over 1600 hydrocarbon fields, and geological reserves of natural gas of up to about 140 billions of cubic meters have been discovered.
China is a large ocean country with a long coastline, and the awareness of ocean resource development and utilization is gradually strengthened. However, due to the large-scale development and utilization of oceans by human beings, the massive construction and use of seabed engineering facilities such as seabed platforms, seabed pipelines, cables and the like, and the drastic change of the environment of the seabed itself caused by external force, the malignant damage events of the seabed itself or seabed structures are increasing, causing a great amount of economic property loss and personal casualties, which makes the research of human beings on the oceanic geological disasters more urgent and more practical, and the importance of understanding the oceanic geological disasters is also becoming more prominent. China is a typical coastal large country, and the offshore area of the east is close to several large earthquake zones of the pacific of the northwest, so that the loss is easily caused by the spread of the submarine earthquake; the south China sea area is located in an intersection zone of a large land slope and a sea chest area, so that the depth of seawater in the area is greatly changed, the geological conditions (multi-sea chest) and water body flow (ocean current) in the area are changed violently, the geological conditions are complex and changeable, and submarine geological disasters are easy to occur. Therefore, great attention should be paid to the research on the submarine geological disaster.
The submarine landslide is a main form in marine geological disasters, a large amount of sediments can be conveyed to a far distance along with the occurrence of the submarine landslide, the conveying process can seriously threaten marine oil and gas engineering facilities and submarine cables, and the submarine landslide is also considered as an important inducing factor causing the distortion failure or the cut-off of submarine oil pipelines; large-scale sea-bottom landslides are also frequently accompanied by very destructive tsunamis; frequent occurrence of the landslide on the sea bottom seriously threatens the life safety of ocean engineering structures and ocean related personnel. Therefore, research on the stability of the submarine slope and the trigger mechanism of the submarine landslide becomes a hot research problem in the field of current marine engineering and marine geological disasters.
However, theoretical analysis and numerical technical calculation are mostly adopted in the current research, and the influence of the coupling effect of slope angle change, slope toe scouring and rapid sedimentation on the seabed landslide can hardly be considered simultaneously by the indoor test evaluation method. The invention patent with the application number of CN108894182A provides a landslide triggering device and a landslide triggering method applied to submarine landslide flume test research, and only the influence of a slope angle on the stability of a slope is considered in the landslide triggering device; the utility model with application number CN207764186U provides a test device for simulating seabed landslide, which mainly researches the flow sliding process after landslide triggering and only considers the influence of the slope angle.
Disclosure of Invention
Aiming at the defects of the prior art, the invention further explores the damage mechanism of the submarine landslide. The invention provides a set of test device capable of realizing the simulation of seabed landslide under multiple slope angles and multiple working conditions. The device can realize the lifting of the box body at any angle within the range of 0-20 degrees through the portal frame lifting device, particularly, the device can excavate soil bodies at different positions through the variable-length soil cutting plate and simulate the scouring phenomenon of slope toe at different degrees; in addition, the hopper is lifted by the lifting device, the top of the slope is loaded, and landslide caused by rapid deposition can be simulated; meanwhile, the device can be adopted, and the stability of the seabed slope under the action of the wave load is simulated and evaluated by combining an indoor water tank test. Meanwhile, the evaluation method also carries out the preparation of artificial structural soft clay, combines a large-scale section wave water channel, and systematically studies the influence of wave load, slope toe scouring and rapid sedimentation on the submarine landslide, thereby obtaining a set of submarine landslide evaluation method induced by multiple trigger factors.
The invention adopts the following technical scheme:
a method for evaluating the landslide of the sea floor based on indoor test, this method is realized on the basis of large-scale section wave flume and new indoor test device to imitate the landslide, can study the influence on the landslide of the sea floor by the coupling action of three of wave load, foot scouring and fast deposition systematically, thus get a set of submarine landslide evaluation method induced by many trigger factors; the test can monitor the whole process of underwater terrain evolution, wave nonlinear form and pressure, soil body pore pressure and displacement field and measure the intensity change of landslide soil body by arranging a three-dimensional terrain laser imaging system, a Doppler current meter array, a non-contact wave height instrument, a laser displacement meter, a micro pore pressure sensor and a pressure meter;
the novel indoor test device model box main body also comprises a false slope, a funnel, a soil cutting plate, a sensor bracket and a portal frame lifting device;
the model box main body consists of a box body and a base, wherein the box body comprises flashboards, side plates and a bottom plate which are positioned at two ends; the top of the box body is a slope, and the front end of the box body is lower than the rear end; the two ends of the box body are also provided with rotating shafts, the rotating shaft at the rear end can enable the box body to simulate multi-angle landslide, and the rotating shaft at the front end is used for lifting the front end of the box body in the soil consolidation process, so that the top of the box body is in a plane state, the box body cannot flow out when the soil body strength is too low, and consolidation can be better completed;
the false slope comprises a slope section, a horizontal section positioned at the front end of the box body and a horizontal section positioned at the rear end of the box body, wherein the slope section is connected with the horizontal section positioned at the front end of the box body; the horizontal section at the rear end of the box body is consistent with the rear end of the box body in height; the horizontal section and the slope section are both arranged for stabilizing the waveform, so that the wave reaches a stable state before ascending;
the funnel comprises a cylindrical section and a trapezoidal section, and the trapezoidal section is connected to the lower part of the cylindrical section through a screw; during the test, the funnel filled with the structural soft clay is integrally lifted and placed on the box body through the lifting device, and then the structural soft clay falls down from the funnel to load the slope top so as to simulate the rapid deposition effect; in order to ensure that the bevel edge of the trapezoidal section is completely attached to the box body, the angle of the bevel edge of the trapezoidal section is completely the same as the lifting angle of the box body; the function of the funnel is as follows: firstly, sanding: preparing a sand slope by a rain falling method; secondly, simulating a slope rapid deposition effect;
the soil cutting plate comprises a top rod and a steel plate for cutting soil; one end of the ejector rod is connected with the flashboard positioned at the front end, the other end of the ejector rod is connected with the steel plate, and the length of the ejector rod is variable; the soil cutting plate can cut and excavate soil along different positions of the slope, and the slope toe scouring phenomenon of the slope in different degrees is simulated; when the soil body is excavated, firstly inserting a steel plate for cutting the soil body into a specified position of the soil body, then adjusting the length of the ejector rod to prop the ejector rod on a flashboard at the front end of the model box, and finally excavating the cut soil body by using a shovel;
the sensor bracket comprises a sensor fixing device and a sensor protecting device; the sensor support is used for mounting a sensor, the specific type of the sensor can be selected according to the requirement, and the sensor protection device is sleeved outside the sensor and used for protecting the sensor from being damaged; the sensor fixing device is used for fixing the sensor on the bottom plate;
the portal frame lifting device comprises two portal frames and a control device, the two portal frames are respectively arranged at two ends of the box body and used for lifting the box body through a rotating shaft, and the portal frame positioned at the rear end can lift the box body at any angle within the range of 0-20 degrees; the portal frame positioned at the front end is used for lifting the front end of the box body in the soil consolidation process; the control device is used for controlling the movement of the portal frame and adjusting the position and the lifting height of the portal frame.
The evaluation method can simultaneously consider the influence of wave load, slope toe scouring and rapid sedimentation on the seabed landslide, and specifically comprises the following steps:
(1) determining test scale
The determination of the test scale is determined according to field conditions and laboratory equipment conditions. The test scale is based on the principle of similar gravity with equal Flode numbersDetermining the geometric scale as nLThe wave height H scale, the wave period T scale and the flow velocity v scale are as follows:
nH=nL
nT=nL 0.5
nv=nL 0.5
(2) novel hoisting indoor experiment device
And hoisting the novel indoor test device to the specified position of the large-scale section wave flow water tank by adopting a gantry crane lifting device.
(3) Wave height rate determination for fixed bed test
In order to obtain stable and accurate wave flow conditions, a fixed bed test model needs to be built before the beginning of a formal experiment. Arranging a false slope, a model box and the like at specified positions in a large-sized section wave water channel, and then fixing a rigid plate cut according to the size of the box body on the inclined plane of the box body to form a closed rigid body, so that a fixed bed test model can be obtained, and the wave shallow hydration effect is realized; then carrying out calibration debugging on wave flow conditions required by the test; after calibration and debugging are finished, the upper rigid plate is removed to prepare for the subsequent filling of the structural soft clay;
(4) preparation of structured soft clay
Adding silicate 525 cement into the ocean soft soil, adding water to 2 times of the liquid limit of the soil body, and then uniformly stirring under a vacuum condition to obtain the marine soft soil; wherein, the addition of the silicate 525 cement is 2% of the mass of the soft soil particles;
(5) calibration and arrangement of sensors
And calibrating, arranging and installing the sensors used in the test.
(6) Structural soft soil filling and maintenance
Filling the prepared structural soft clay into a box body, and injecting water into a large-sized section wave water tank after filling until the structural soft clay is completely submerged, so that the structural soft clay is solidified for 2 days under the self weight of water, thereby achieving higher sensitivity.
(7) The test is started after the maintenance is finished
1) Opening a data acquisition instrument and camera equipment; 2) measuring the strength of the structural soft clay; 3) adjusting the slope angle through a portal frame lifting device; 4) and applying wave loads with different water depths, wave heights and periods or carrying out tests on working conditions such as slope toe excavation, rapid sedimentation and the like.
In the technical scheme, furthermore, in the novel indoor test device, the flashboard positioned at the front end of the box body can be detached; when soil is filled in the box body, the flashboard is in a locked state, and when the soil is solidified and tested, the front end flashboard is lifted to prevent the slope from sliding; the base adopts the # -shaped structure, can make box stability higher.
Furthermore, the side plates are made of transparent organic glass, so that the damage process of the landslide can be clearly observed.
Furthermore, the bottom plate is made of stainless steel and is uniformly provided with the drain holes, so that drainage consolidation of soil in the box body can be completed.
Furthermore, the two horizontal sections are connected with the box body, the heights of the two horizontal sections are respectively consistent with the front end and the rear end of the box body, and the lengths of the two horizontal sections can be adjusted according to wave conditions.
Further, the trapezoidal section of funnel can be according to the angle modulation size of model slope, in order to make trapezoidal section and box laminate completely, the inclination of trapezoidal section lower limb is the same with the angle that the box was lifted completely.
Furthermore, the sensor fixing device is formed by vertically welding a flat steel bar and a hollow round pipe, the sensor is fixed on the hollow round pipe, and the height of the hollow round pipe needs to be determined according to the position of the hollow round pipe placed on the box body because the box body is a slope; for more convenient and fast fixed sensor, cut off 1/2 with hollow pipe along direction of height, then according to the different positions of experimental monitoring division bolt hole in the different height departments of hollow pipe, can manually fix the sensor of division screw in advance on the bolt hole of different positions like this.
Further, sensor protection device form by 3 layers of organic glass carving, embedded filter screen and permeable stone, the probe outside of sensor is permeable stone, the permeable stone opposite side is the filter screen to prevent to lead to the sensor to damage because soil particle is too thin. The filter screen is ICr18Nig of 400 meshes/inch, and the thickness of the permeable stone is 5 mm.
The invention has the following advantages:
the invention provides a submarine landslide evaluation method based on an indoor test, which can realize a test of simulating submarine landslide under multiple slope angles and multiple working conditions. The method can realize the lifting of the box body at any angle within the range of 0-20 degrees through the portal frame lifting device, and particularly can simulate the scouring phenomenon of slope toe at different degrees by excavating soil bodies at different positions through the variable-length soil cutting plate; the hopper filled with the slurry is lifted by the lifting device, the top of the slope is loaded, and the landslide caused by the rapid sedimentation effect can be simulated; the preparation method of the structural soft clay is simple, the prepared soil body is low in initial strength and high in sensitivity, and the seabed landslide phenomenon can be simulated well. The indoor test-based submarine landslide evaluation method is combined with an indoor large-section wave water tank, and the influence of coupling of waves, slope toe scouring and rapid sedimentation on submarine landslide can be systematically researched.
Drawings
FIG. 1 is a schematic illustration of a test apparatus;
FIG. 2 is a three-dimensional view of the mold box body and funnel;
FIG. 3 is a three-dimensional view of a mold box body;
FIG. 4 is a front view of the mold box body and funnel;
FIG. 5 is a top view of the mold box body and funnel;
FIG. 6 is a three-dimensional view of a cutting board;
FIG. 7 is a diagram showing the positional relationship between the soil cutting plate and the mold box
FIG. 8 is a view of a construction of a false slope;
FIG. 9 is a three-dimensional view of the funnel and closure plate;
FIG. 10 is a front view of the funnel and closure plate;
FIG. 11 is a view of the shutter structure;
FIG. 12 a sensor mount;
the device comprises a model box main body 1, a false slope 2, a funnel 3, a soil cutting plate 4, a sensor support 5, a gantry lifting device 6, a box 7, a base 8, a rotating shaft 9, a gate plate 10, a side plate 11, a bottom plate 12, a slope section 13, horizontal sections 14 and 15, a cylinder section 16, a trapezoidal section 17, a push rod 18, a steel plate 19 for cutting soil, a sensor fixing device 20, a sensor protecting device 21, a filter screen 22 and permeable stones 23, wherein the model box main body is a model box main body, the false slope 2 is a false slope, the gate plate 10 is a gate plate, the side plate 11 is a side plate, the bottom plate 12 is.
Detailed Description
A submarine landslide evaluation method based on indoor tests is realized based on a large-scale section wave flume and a novel indoor test device for simulating submarine landslide. The novel indoor test device is shown in figure 1 and comprises a model box main body 1, a false slope 2, a funnel 3, a soil cutting plate 4, a sensor bracket 5 and a portal frame lifting device 6; the model box main body 1 consists of a box body 7 and a base 8, wherein the box body 7 comprises a gate plate 10, a side plate 11 and a bottom plate 12.
The two ends of the box body 7 are also provided with rotating shafts 9, the rotating shafts 9 at the rear ends can enable the box body 7 to simulate multi-angle landslide, and the rotating shafts 9 at the front ends are used for lifting the front end of the box body in the soil consolidation process, so that the bevel edge of the box body 7 keeps a plane, the box body 7 cannot flow out when the soil strength is too low, and the consolidation can be better completed. The false slope 2 comprises a slope section 13 and two horizontal sections 14 and 15. The funnel 3 comprises a cylinder section 16 and a trapezoid section 17, and the size of the trapezoid section 17 can be adjusted according to the angle of a model slope; the soil cutting plate 4 comprises a top rod 18 and a steel plate 19 for cutting soil; the sensor holder 5 includes a sensor fixing unit 20 and a sensor protecting unit 21.
The slope section 13 and the horizontal section 14 of the false slope 2 are arranged at the front end of the box body 7, the horizontal section 15 is arranged at the rear end of the box body 7, the heights of the horizontal section 14 and the horizontal section 15 are respectively consistent with the front end and the rear end of the box body 7, and the lengths of the horizontal sections 14 and 15 can be adjusted according to specific test working conditions.
The funnel 3 comprises a cylindrical section 16 and a trapezoidal section 17. The trapezoidal section 17 is screwed to the underside of the cylindrical section 16. During the test, the hopper 3 filled with the structural soft clay is integrally lifted and placed on the box body 7 through the lifting device 6, then the structural soft clay falls down from the hopper 3, and the slope top is loaded to simulate the rapid deposition effect; in order to make the trapezoidal section 17 completely fit with the box body 7, the lower edge of the trapezoidal section 17 is inclined at the same angle as the box body is lifted. Function of the funnel 3: firstly, sanding: preparing a sand slope by a rain falling method; and secondly, simulating a slope rapid deposition effect.
The soil cutting plate 4 comprises a top rod 18 and a steel plate 19 for cutting soil, one end of the top rod 18 is connected with the flashboard 10 positioned at the front end, the other end of the top rod is connected with the steel plate 19, and the length of the top rod 18 is variable; the soil cutting plate 4 can cut and excavate soil bodies at different positions along the slope through the ejector rod 18, and is used for simulating the slope toe scouring phenomenon of the slope in different degrees.
The sensor bracket 5 comprises a sensor fixing device 20 and a sensor protecting device 21; the sensor fixing device 20 is used for fixing the sensor on the bottom plate 12; the fixing device 20 is formed by vertically welding a flat steel bar and a hollow circular tube, and the height of the hollow circular tube needs to be determined according to the position of the hollow circular tube placed on the box body 7 because the top end of the box body 7 is a slope. For more convenient and fast fixed sensor, cut off 1/2 with hollow pipe along direction of height, then according to the different positions of experimental monitoring division bolt hole in the different height departments of hollow pipe, can manually fix the sensor of division screw in advance on the bolt hole of different positions like this. Meanwhile, the arrangement position of the sensor bracket 5 can be determined according to the specific working condition of the test; sensor protection device 21 form by 3 layers of organic glass carving, embedded ICr18Nig filter screen 22 and the permeable stone 23 that thickness is 5mm of 400 mesh/inch, the probe outside of sensor is permeable stone 23, the permeable stone 23 opposite side is the filter screen. The sensor protection device 21 is sleeved outside the sensor to prevent the sensor from being damaged due to the fact that soil particles are too fine. The sensors used in this embodiment include an aperture sensor, a pressure sensor, and an acceleration sensor.
The two gantry cranes of the gantry lifting device 6 are respectively arranged at the front end and the rear end of the box body 7, the gantry crane at the rear end can lift the box body at any angle within the range of 0-20 degrees, and the gantry crane at the front end is used for lifting the front end of the box body 7 to keep the bevel edge of the box body 7 on a plane so as to prevent a slope soil body from flowing out.
The gate plate 10 is positioned at the front end of the box body 7, and the gate plate 10 is detachable; when soil is filled in the box body 7, the gate plate 10 is in a locked state, and when the soil is solidified and tested, the front gate plate 10 is lifted to prevent the slope from sliding; the base 8 is located the bottom of box 7, adopts the # -shaped structure can make box 7 stability higher. The pivot 9 is located box 7 both ends, and the effect of box 7 rear end pivot 9 is in order to realize that box 7 can simulate multi-angle landslide, and box 7 front end pivot 9 then uses in the soil mass consolidation process, lifts up the box front end and can make the hypotenuse of box 7 keep a plane to guarantee that the soil mass can not flow out box 7, thereby better completion concreties. The side plate 11 is made of transparent organic glass, so that the damage process of the landslide can be clearly observed. The bottom plate 12 is made of stainless steel and is uniformly provided with drain holes with the diameter of 5mm, so that the soil in the box body 7 can be drained and consolidated.
The preparation of the structural soft clay specifically comprises the following steps: firstly, stirring natural soft soil uniformly at a rotating speed of 30-40r/min, then measuring the water content of the soft soil, and determining the quality of added cement and water according to the water content of the soil body; firstly, adding water to the liquid limit of 2 times of the soft soil, stirring for 3 hours at the rotating speed of 30-40r/min under the vacuum condition, then adding Portland 525 cement with the mass being 2% of the mass of soft soil particles, and stirring for 1 hour at the rotating speed of 30-40r/min under the vacuum condition to obtain the structural soft clay.
The influence of wave load, slope toe scouring and rapid sedimentation on the seabed landslide can be considered simultaneously by the combination of the seabed landslide evaluation method. The specific implementation steps are as follows:
(1) determining test scale
The determination of the test scale is determined according to field conditions and laboratory equipment conditions. The test scale is based on the principle of similar gravity with equal Flode numbersDetermining the geometric scale as nLThe wave height H scale, the wave period T scale and the flow velocity v scale are as follows:
nH=nL
nT=nL 0.5
nv=nL 0.5
(2) hoisting the novel experimental device
And hoisting the test device to the specified position of the large-sized section wave flow water tank by adopting a gantry crane lifting device.
(3) Wave height rate determination for fixed bed test
In order to obtain stable and accurate wave flow conditions, a fixed bed test model needs to be built before the beginning of a formal experiment. The method comprises the steps that a false slope, a model box and the like are arranged at a designated position in a large-section wave water tank, and then a rigid plate cut according to the size of a box body is fixed on the inclined plane of the box body to form a closed rigid body, so that a test bed model can be obtained; then carrying out calibration debugging on wave flow conditions required by the test;
(4) preparation of structured soft clay
Firstly weighing natural soft clay, uniformly stirring natural soft soil at a rotating speed of 30-40r/min, then measuring the water content of the soft soil, and calculating and determining the mass of added cement and water according to the water content of the soil body. Firstly, adding water to 2 times of the liquid limit of a soil sample, stirring for 3 hours at the rotating speed of 30-40r/min under the vacuum condition, then adding Portland 525 cement accounting for 2% of the mass of dry soft soil particles, and stirring for 1 hour at the rotating speed of 30-40r/min under the vacuum condition to obtain the structural soft soil.
(5) Calibration and arrangement of sensors
And calibrating, arranging and installing the sensors used in the test.
(6) Structural soft soil filling and maintenance
The prepared structural soft clay is filled into the novel indoor testing device, and water is injected into the water tank after filling is completed until the soft clay is completely submerged, so that the soft clay is solidified for 2 days under the self weight of water, and higher sensitivity is achieved.
(7) The test is started after the maintenance is finished
1) Opening a data acquisition instrument and camera equipment; 2) measuring the strength of the structural soft clay; 3) adjusting the slope angle through a portal frame lifting device; 4) and applying wave loads with different water depths, wave heights and periods or carrying out tests on working conditions such as slope toe excavation, rapid sedimentation and the like.
The evaluation method can simultaneously consider the influence of the mutual coupling effect of wave shallow hydration, slope toe scouring and rapid sedimentation on the seabed landslide, and is a set of evaluation method capable of systematically researching the induction of the seabed landslide by multiple trigger factors.

Claims (9)

1. A submarine landslide evaluation method based on indoor test is characterized in that the method is realized based on a large section wave flume and a novel indoor test device for simulating submarine landslide;
the novel indoor test device comprises a model box main body (1), a false slope (2), a funnel (3), a soil cutting plate (4), a sensor bracket (5) and a portal frame lifting device (6), wherein the model box main body (1) consists of a box body (7) and a base (8), and the box body (7) comprises flashboards (10), side plates (11) and a bottom plate (12) which are positioned at two ends; the top of the box body (7) is a slope, and the front end of the box body is lower than the rear end; the two ends of the box body (7) are also provided with rotating shafts (9), the rotating shaft (9) at the rear end can enable the box body (7) to simulate multi-angle landslide, and the rotating shaft (9) at the front end is used for lifting the front end of the box body in the soil consolidation process, so that the top of the box body (7) is in a plane state, the box body (7) cannot flow out when the soil strength is too low, and the consolidation is finished;
the false slope (2) comprises a slope section (13), a horizontal section (14) positioned at the front end of the box body (7) and a horizontal section (15) positioned at the rear end of the box body (7); the slope section (13) is connected with the horizontal section (14) to achieve the purpose of stabilizing waves; the height of the horizontal section (15) is consistent with that of the rear end of the box body (7) so as to stably reflect waves and prevent the waves from generating vortexes at the rear end of the box body (7);
the funnel (3) comprises a cylinder section (16) and a trapezoid section (17), and the trapezoid section (17) is connected to the lower part of the cylinder section (16) through screws; during the experiment, the portal frame lifting device (6) integrally lifts the funnel (3) filled with the structural soft clay and puts the funnel on the box body (7), then the structural soft clay falls down from the funnel (3) and loads the slope top to simulate the rapid deposition effect;
the soil cutting plate (4) comprises a push rod (18) and a steel plate (19) for cutting soil, one end of the push rod (18) is connected with the flashboard (10) positioned at the front end, and the other end of the push rod (18) is connected with the steel plate (19); the length of the ejector rod (18) is variable, so that the soil cutting plate (4) can cut and excavate soil along different positions of the slope, and the slope toe scouring phenomenon of the slope in different degrees is simulated;
the sensor bracket (5) comprises a sensor fixing device (20) and a sensor protecting device (21); the sensor protection device (21) is sleeved outside the sensor and used for protecting the sensor from being damaged; the sensor fixing device (20) is used for fixing the sensor on the bottom plate (12);
the portal frame lifting device (6) comprises two portal frames and a control device, the two portal frames are respectively arranged at the front end and the rear end of the box body (7), and the box body is lifted through the rotating shaft (9); the control device is used for controlling the movement of the portal frame and adjusting the position and the lifting height of the portal frame;
the evaluation method comprises the following steps:
1) determining test scale
The determination of the test scale is determined according to field conditions and laboratory equipment conditions; the test scale is based on the principle of similar gravity with equal Flode numbersDetermining the geometric scale as nLThe wave height H scale, the wave period T scale and the flow velocity v scale are as follows:
nH=nL
nT=nL 0.5
nv=nL 0.5
2) novel hoisting indoor experiment device
Hoisting the novel indoor test device to a specified position of a large-scale section wave current water tank by adopting a gantry crane lifting device (6);
3) wave height rate determination for fixed bed test
In order to obtain stable and accurate wave flow conditions, a fixed bed test model needs to be built before a formal experiment is started; arranging the false slope (2) and the model box (1) at specified positions in a section wave flow water tank, and then fixing a rigid plate cut according to the size of the box body (7) on the inclined plane of the box body (7) to form a closed rigid body, thus obtaining a fixed bed test model; then carrying out calibration debugging on wave flow conditions required by the test; after calibration and debugging are finished, the upper rigid plate is removed to prepare for the subsequent filling of the structural soft clay;
4) preparation of structured soft clay
Adding silicate 525 cement into the ocean soft soil, adding water to 2 times of the liquid limit of the soil body, and then uniformly stirring under a vacuum condition to obtain the marine soft soil; wherein, the addition of the silicate 525 cement is 2% of the mass of the soft soil particles;
5) calibration and arrangement of sensors
Calibrating, arranging and installing sensors used in the test;
6) filling and maintaining of structural soft clay
Filling the structural soft clay into the box body (7), and after filling, injecting water into the section wave water tank until the structural soft clay is completely submerged, so that the structural soft clay is solidified for 2 days under the self weight of water;
7) the test is started after the maintenance is finished
And opening data acquisition and camera equipment, testing the strength of the structural soft clay, adjusting the slope angle through a portal frame lifting device, and applying wave loads of different water depths, wave heights and periods or carrying out tests on slope toe excavation and rapid deposition working conditions.
2. The method for evaluating the landslide based on the lab test as claimed in claim 1, wherein in the novel lab test device, the shutter (10) at the front end of the box body (7) is detachable; when soil is filled in the box body (7), the flashboard (10) at the front end is in a locked state, and when the soil is solidified and tested, the flashboard (10) at the front end is lifted to prevent the slope from sliding; the base (8) adopts a # -shaped structure, so that the stability of the box body (7) is higher.
3. The submarine landslide evaluation method based on indoor tests according to claim 1, wherein the side plates (11) are made of transparent organic glass, and the damage process of landslide can be clearly observed.
4. The submarine landslide evaluation method based on indoor test according to claim 1, wherein the bottom plate (12) is made of stainless steel and has drain holes uniformly distributed thereon, so that drainage consolidation of soil in the box body (7) can be achieved.
5. The method for evaluating sea bottom landslide based on laboratory test as claimed in claim 1, wherein the horizontal section (14) at the front end of the box body (7) and the horizontal section (15) at the rear end of the box body (7) are connected with the box body (7) and the heights of the horizontal section and the horizontal section are respectively consistent with the front end and the rear end of the box body (7).
6. The method for evaluating sea bottom landslide based on laboratory test as claimed in claim 1, wherein the inclined angle of the lower edge bevel of the trapezoidal section (17) is the same as the angle of the box body lifted.
7. The method for evaluating the landslide of the sea floor based on the laboratory test as claimed in claim 1, wherein the sensor fixing means (20) is formed by vertically welding a flat steel bar and a hollow circular tube, and the sensor is fixed on the hollow circular tube.
8. The method for evaluating sea bottom landslide based on indoor test as claimed in claim 1, wherein the sensor protection device (21) is carved with 3 layers of organic glass, and a filter screen (22) and a permeable stone (23) are embedded; the filter screen (22) is ICr18Nig of 400 meshes/inch, and the thickness of the permeable stone (23) is 5 mm.
9. The method for evaluating the landslide based on the laboratory test according to claim 1, wherein the preparation of the structural soft clay specifically comprises the following steps: firstly, uniformly stirring ocean soft soil at a rotating speed of 30-40r/min, then measuring the water content of the soft soil, and determining the quality of added cement and water according to the water content of the soft soil; then adding water to the liquid limit of 2 times of the soft soil, stirring for 3 hours at the rotating speed of 30-40r/min under the vacuum condition, finally adding portland cement 525, and stirring for 1 hour at the rotating speed of 30-40r/min under the vacuum condition to obtain the structural soft clay.
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KR101376092B1 (en) * 2013-02-13 2014-03-21 한국지질자원연구원 Laboratory flume for examining water wave propagation due to submarine landslides
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