CN110082502B - Three-dimensional visual test device and method for seabed deformation induced by hydrate decomposition - Google Patents
Three-dimensional visual test device and method for seabed deformation induced by hydrate decomposition Download PDFInfo
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- CN110082502B CN110082502B CN201910371663.7A CN201910371663A CN110082502B CN 110082502 B CN110082502 B CN 110082502B CN 201910371663 A CN201910371663 A CN 201910371663A CN 110082502 B CN110082502 B CN 110082502B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/16—Measuring arrangements characterised by the use of optical techniques for measuring the deformation in a solid, e.g. optical strain gauge
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/84—Systems specially adapted for particular applications
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
- G01N33/24—Earth materials
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/84—Systems specially adapted for particular applications
- G01N2021/8411—Application to online plant, process monitoring
Abstract
The invention provides a three-dimensional visual test device and a three-dimensional visual test method for seabed deformation induced by hydrate decomposition. The laser displacement sensor comprises a transparent model box, wherein a deposition layer is arranged in the transparent model box, a laser and a CCD camera are arranged on the side surface of the transparent model box, a laser displacement meter is arranged at the top of the transparent model box, and a temperature sensor and a pressure sensor are also arranged in the deposition layer; the settled layer comprises a transparent marine soft clay layer and a natural gas hydrate layer; the transparent marine soft clay layer is prepared by mixing and stirring lithium magnesium silicate and distilled water according to a mass ratio of 3.5-6.5: 100, and the natural gas hydrate layer is prepared by trichlorofluoromethane and distilled water according to a volume ratio of 1: 2-1: 4 under normal pressure. The invention can simulate seabed response under the natural gas hydrate decomposition condition under normal pressure, and the fluid migration path in the seabed sediment and the crack propagation in the soil body can be seen by naked eyes, and a three-dimensional displacement field can be obtained through image processing.
Description
Technical Field
The invention relates to the technical field of marine geology, in particular to a three-dimensional visual test device and a three-dimensional visual test method for seabed deformation induced by hydrate decomposition.
Background
The natural gas hydrate is mostly present in sediment pores under the low-temperature and high-pressure environment of the seabed, and when the temperature of the seabed rises or the pressure is reduced, the natural gas hydrate is decomposed into gas and water, so that the pore pressure is increased. As pore pressure builds, the seabed can deform, such as by heaving. Meanwhile, the decomposition of the natural gas hydrate leads to the gradual reduction of the cementation strength of the sediment, the effective stress is reduced, and the seabed landslide is easy to occur under the triggering action of external force such as earthquake and the like.
At present, the research on seabed deformation induced by natural gas hydrate decomposition mainly takes marine geophysical survey as a main part, and mostly stays on qualitative description, and simulation is carried out in a laboratory by adopting a device, namely a physical model test is a better method, and the physical model test is an important research means for exploring a fluid migration and seabed deformation mechanism formed by natural gas hydrate decomposition. The geological model containing the natural gas hydrate layer is subjected to physical model test research to collect test data such as pore pressure, seabed surface deformation and the like in the test process, and the process and mechanism of fluid migration and seabed deformation induced by decomposition of the natural gas hydrate can be revealed. These physical model tests usually require the study of changes in the soil, such as two-dimensional or three-dimensional displacements in the soil, fluid migration paths in the soil, and crack propagation in the soil.
Because the synthesis of the natural gas hydrate requires high-pressure and low-temperature conditions, the indoor physical model test is difficult to meet the conditions. Chinese patent CN107589235A discloses a simulation test device for inducing seabed landslide by natural gas hydrate decomposition, which comprises a transparent water tank, a soil slope arranged in the transparent water tank, seawater located on the soil slope, a first air compressor, a second air compressor, a trigger disc, a pore pressure meter and a data acquisition instrument; the simulation test device can effectively simulate the seabed landslide induced by the decomposition of the natural gas hydrate, and can observe the processes of water pressure, air pressure change and landslide after the decomposition; however, in the simulation test device, hydrate is not formed, only air is injected into the model by using an air compressor to simulate the decomposition of the hydrate, and the actual situation that the seabed deformation is induced by the decomposition of the natural gas hydrate in the nature is greatly different; moreover, the soil slope is invisible, so that the simulation test device cannot directly observe the internal fluid migration path of the soil body, cannot observe crack propagation and the like in the soil body, and cannot know the three-dimensional displacement change condition in the soil body.
Disclosure of Invention
The invention provides a three-dimensional visual test device and a three-dimensional visual test method for seabed deformation induced by hydrate decomposition, which solve the problem that the three-dimensional displacement change conditions of a fluid migration path inside a soil body and crack propagation inside the soil body cannot be visually observed in the prior art.
The invention discloses a three-dimensional visual test device for inducing seabed deformation by hydrate decomposition, which adopts the technical scheme that: the laser displacement sensor comprises a transparent model box, wherein a deposition layer is arranged in the transparent model box, a laser is arranged on one side of the transparent model box, a CCD camera is arranged on one side of the transparent model box perpendicular to the laser, a laser displacement meter is arranged at the top of the transparent model box, and a temperature sensor and a pressure sensor are further arranged in the deposition layer; the sedimentary layers comprise a transparent marine soft clay layer and a natural gas hydrate layer, the natural gas hydrate layer is positioned inside the transparent marine soft clay layer, the transparent marine soft clay layer comprises an underlayer and an overlayer, the underlayer is positioned at the bottom of the natural gas hydrate layer, and the overlayer is positioned at the top of the natural gas hydrate layer; the transparent marine soft clay layer is prepared by mixing and stirring lithium magnesium silicate and distilled water according to a mass ratio of 3.5-6.5: 100, and the natural gas hydrate layer is prepared by trichloromonofluoromethane and distilled water according to a volume ratio of 1: 2-1: 4 under normal pressure.
Under the submarine high-pressure low-temperature environment, the natural gas hydrate reservoir keeps stable; when the temperature and pressure condition changes and the natural gas hydrate is decomposed, a large amount of gas and water are generated, the pore pressure is increased, and the strength of seabed sediments is reduced, so that marine geological disasters are caused. At present, the preparation of the natural gas hydrate needs a high-pressure (MPa-level) low-temperature environment, the test conditions of a laboratory are difficult to meet, and the high pressure easily brings about potential safety hazards such as bursting. The transparent marine soft clay is adopted to simulate the soft clay layer in the seabed sediment, the natural gas hydrate substitute material is adopted to simulate the natural gas hydrate in the seabed sediment, the transparent marine soft clay has high transparency and high visualization degree, and the natural gas hydrate substitute material can decompose gas and water along with the rise of temperature under normal pressure, so that the test conditions are simplified. The laser emits a light beam from the side surface of the sedimentary deposit, vertically illuminates a longitudinal plane of the sedimentary deposit, and forms different stratum sections; the CCD camera is used for collecting pictures of different stratum sections in the test process and obtaining a three-dimensional displacement field through computer analysis. The laser displacement meter is erected at the top of the settled layer to collect the surface deformation of the seabed in the test process, and a coating layer is required to be sprayed on the top of an upper cladding of the settled layer under normal conditions so as to effectively reflect an optical signal from the laser displacement meter above the settled layer; and a temperature sensor and a pressure sensor are also arranged in the deposition layer and used for collecting the temperature and pressure change in the test process. The test device consists of a transparent model box, a laser, a CCD camera, a laser displacement meter, a temperature sensor and a pressure sensor, the test device can simulate the decomposition process of the natural gas hydrate under normal pressure, and directly observe the test phenomena of fluid migration path, crack propagation and the like formed by the decomposition of the natural gas hydrate in the stratum, thereby realizing the visualization of the simulation test process; the three-dimensional displacement change condition of the seabed is obtained through image analysis of different stratum sections, the three-dimensional visual test device for inducing seabed deformation through hydrate decomposition is obtained, the conditions of a simulation test are simplified, the terrain change of the inside and the surface of the seabed and the temperature and pressure data of the inside of the stratum in the test process can be collected, scientific theoretical guidance is provided for prevention and control of marine geological disasters, and the device is high in operability and convenient to popularize.
As a preferred embodiment, the laser comprises a laser source and a lens set, the laser source and the lens set are located in a first plane vertically arranged, and the first plane is vertically arranged with the side surface of the transparent mold box. The laser irradiates the interior of the settled layer through the transparent model box and irradiates a certain plane in the settled layer to form different stratum sections; under the action of a CCD camera, photos of soil deformation on different stratum sections are timely and continuously shot, so that fluid migration paths, crack propagation and seabed three-dimensional displacement change conditions formed by decomposition of the natural gas hydrate in the stratum are recorded.
As a preferred embodiment, the transparent mold box is located on an operation platform, the bottom of the laser light source is provided with a first slide rail, the operation platform is provided with a first slide rail adapted to the first slide rail, the bottom of the lens group is provided with a second slide rail, and the operation platform is provided with a second slide rail adapted to the second slide rail. The invention can synchronously move the laser light source and the lens group under the matching action of the first slide rail, the second slide rail and the second slide rail, so that the laser light source and the lens group are always kept in a plane vertical to the side surface of a settled layer, the positions of the laser light source and the lens group are conveniently dragged, the section of a picture is shot by changing the CCD camera, and the three-dimensional displacement change conditions of fluid migration paths and crack expansion on different sections in the stratum are obtained.
The invention discloses a three-dimensional visual test method for inducing seabed deformation by hydrate decomposition, which adopts the technical scheme that: the method comprises the following steps: A. preparation of natural gas hydrate substitute material 1) taking trichlorofluoromethane, placing at-18-4 ℃, and refrigerating for later use; 2) respectively placing distilled water at 2-4 ℃, and refrigerating for later use; 3) adding the trichloromonofluoromethane obtained in the step 1) into the distilled water obtained in the step 2), and stirring to uniformly mix the trichloromonofluoromethane and the distilled water to obtain a mixture; 4) continuously stirring the mixture obtained in the step 3) at the temperature of-18-4 ℃ for 8-20 min until solid hydrate begins to be formed, thus obtaining the natural gas hydrate substitute material; B. preparation of transparent marine soft clay 5) taking lithium magnesium silicate and distilled water, wherein the weight ratio of the lithium magnesium silicate to the distilled water is 3.5-6.5: 100, slowly adding the lithium magnesium silicate into the distilled water, and stirring the distilled water all the time in the process of adding the lithium magnesium silicate into the distilled water; continuously stirring at the stirring speed of 800-1200 r/min for 5-20 min to obtain transparent marine soft clay; C. preparing an underlayer 6) preparing transparent marine soft clay according to the method in the step 5), placing the transparent marine soft clay in a transparent model box, standing and solidifying to obtain the transparent marine soft clay, namely forming the underlayer; D. preparing an upper cladding 7) preparing transparent marine soft clay according to the method in the step 5), placing the transparent marine soft clay in an upper cladding soft clay preparation device, standing and solidifying to obtain transparent marine soft clay; the preparation device for the soft clay of the upper cladding comprises a base, wherein one end of the base is provided with an opening end, a forming sleeve used for containing the transparent marine soft clay is connected to the inside of the base in a sleeved mode, the two ends of the forming sleeve are provided with the opening ends, and the forming sleeve is connected with a push plate capable of pushing out the transparent marine soft clay; E. preparation of a settled layer 8) putting the natural gas hydrate substitute material obtained in the step 4) into the middle position of the top of the underlying layer obtained in the step 6), namely forming a natural gas hydrate layer; 9) removing the base of the upper coating layer soft clay preparation device in the step 7), slowly pushing the transparent marine soft clay obtained in the step 7) downwards by adopting a push plate, and covering the formed natural gas hydrate layer obtained in the step 8) to obtain a settled layer stored in a transparent model box; 10) placing a temperature sensor and a pressure sensor in the deposition layer, placing a laser on one side of a transparent model box, placing a CCD camera on one side of the transparent model box perpendicular to the laser, and placing a laser displacement meter on the top of the transparent model box; 11) starting a laser and a CCD camera, and collecting photos in the CCD camera; starting a temperature sensor, a pressure sensor and laser displacement to perform real-time acquisition; 12) and (4) changing the position of the laser, and obtaining photos of different cross sections of the seabed through a CCD camera.
Firstly, preparing a substitute material of a natural gas hydrate and a transparent substitute material of marine soft clay respectively, organically combining the substitute material of the natural gas hydrate and the transparent substitute material of the marine soft clay together in a transparent model box to form a visual transparent geological model which is a sedimentary layer and is similar to a natural seabed structure, and forming a three-dimensional visual test device under the coordination action of a laser, a CCD camera, a laser displacement meter, a temperature sensor and a pressure sensor; the natural gas hydrate layer in the sediment layer in the three-dimensional visual test model is prepared under normal pressure and through effective temperature control, high-pressure operation is not needed, the preparation method is simple, the conditions are mild, special requirements on equipment are not needed, and the cost is low; the upper cladding in the visual test model is stood and consolidated in the upper cladding soft clay preparation device in advance, the upper cladding is an organic whole, air bubbles are prevented from being introduced, and the transparency of the deposition layer is guaranteed. The settled layer in the visual test model prepared by the invention is usually stored in a refrigerator, wherein in the standing consolidation process and the consolidation completion storage of the transparent marine soft clay in the settled layer, wet thin gauze is required to be covered on the surface of the transparent marine soft clay, and the transparent marine soft clay is sealed by a preservative film to prevent the obtained transparent marine soft clay from being dried and cracked. The temperature of a deposition layer in the visual test model can be naturally and gradually increased under the influence of the ambient temperature, and is finally the same as the room temperature, in the temperature increasing process, a natural gas hydrate layer can be gradually decomposed into gas and water, and the gas and the water are transported under the action of the super-pore pressure to form a transportation channel, or the decomposition process can be accelerated in a manual mode, so that the time required by the test is shortened, for example, a hot air blower is used for heating the outer wall of a transparent model box containing the deposition layer or a water bath heating mode is adopted. In order to facilitate observation of the internal fluid migration channel of the settled layer in the visual test model, the transparent model box is made of a transparent material with higher strength, such as colorless organic glass (acrylic).
As a preferred embodiment, in the step 7), a transparent waterproof film is arranged at the bottom opening end of the forming sleeve, the transparent waterproof film is detachably connected with the outside of the forming sleeve through a fixing band, and in the step 9), the transparent waterproof film is detached while the base is removed. The bottom of the forming sleeve is wrapped by a waterproof transparent film, the fixing band can be a rubber band which is tightened to prevent water leakage in the standing and fixing process, the height from the tightening position to the bottom is slightly larger than the height of the base, if the height of the base is 1.5cm, the height from the tightening position to the bottom can be 2cm, and the waterproof transparent material can be plastic wrap, oil paper and the like. If the preparation method of the upper cladding is improper, a large number of bubbles are generated inside the upper cladding, so that the transparency of a deposited layer is influenced, and the visualization effect of a test model is further influenced; the invention adopts the device for preparing the soft clay of the upper cladding, which consists of the base, the forming sleeve and the push plate, the size of the forming sleeve is matched with that of the transparent model box, and the transparent ocean soft clay in the base and the forming sleeve is fully cured and formed, so that the upper cladding forms an organic whole, the generation of air bubbles in the upper cladding is avoided, and the transparency of the upper cladding is greatly improved.
As a preferable embodiment, the standing temperature is 1-4 ℃, and the standing time is 24-48 h. After stirring, the mixture of lithium magnesium silicate and distilled water is poured into a corresponding container, for example: the transparent model box and the upcoating soft clay preparation device are stood for consolidation indoors to form a soft clay transparent substitute material, and if a small amount of bubbles are contained in the soft clay transparent substitute material, the soft clay transparent substitute material can be consolidated and dissipated after being stood for about 24-48 hours; if the mixture contains bubbles with larger volume, the mixture can be sucked out by a syringe with a slender needle; usually, it is allowed to stand at room temperature or low temperature.
In a preferred embodiment, the stirring speed of the lithium magnesium silicate added into the distilled water is 500-1000 r/min. The distilled water is required to be continuously stirred in the process of adding the lithium magnesium silicate into the distilled water, the lithium magnesium silicate added into the distilled water is quickly dispersed and uniformly stirred, and meanwhile, the stirring speed is not too high, so that the lithium magnesium silicate is prevented from being carried out by the too high stirring speed in the adding process, and the waste of materials and the change of the viscosity of the obtained transparent soft clay are prevented; after the lithium magnesium silicate is completely added into the distilled water, the stirring speed is increased, and the stirring speed is preferably that the mixture of the lithium magnesium silicate and the distilled water does not overflow and bubbles are not generated in the mixture.
In a preferred embodiment, the adding speed of the lithium magnesium silicate to the distilled water is 5-15 g/s. The addition speed of the lithium magnesium silicate in the finishing water is not suitable to be too fast, and the lithium magnesium silicate needs to be added while stirring, poured quickly or completely and then stirred, so that the stirring is not uniform, and the transparency is reduced finally.
As a preferable embodiment, the stirring speed in the step 3) and the stirring speed in the step 4) are both 500-1000 r/min, and the stirring time in the step 3) is 1-5 min. The invention adopts a stirring method to fully mix the liquid trichlorofluoromethane and the distilled water, thereby preventing the demixing, fully ensuring the mixing uniformity of the two substances by high-speed stirring, and strictly avoiding the demixing phenomenon.
In a preferred embodiment, the lithium magnesium silicate has a particle size of 20 to 30nm and a density of 0.9 to E1.1g/cm3The refractive index is 1.3 to 1.8. Distilled water is used in the preparation process of the transparent soft clay in the test model, the distilled water does not contain various impurities such as electrolyte and the like, and the transparency is not influenced by reaction in the preparation process, so that the transparency of the obtained transparent soft clay is high and far exceeds that of the transparent soft clay prepared by tap water; according to the type of the natural soft clay to be replaced, the mass ratio of the lithium magnesium silicate to the distilled water is adjusted, so that the natural soft clay with different strengths is obtained; when the soft clay strength is high, the consumption of lithium magnesium silicate is large; when the strength of the soft clay is low, the dosage of the lithium magnesium silicate is small.
Compared with the prior art, the invention has the beneficial effects that: according to the invention, transparent marine soft clay is adopted in the settled layer to simulate a soft clay layer in the seabed sediment, and natural gas hydrate substitute materials are adopted to simulate natural gas hydrate in the seabed sediment, so that the obtained settled layer has high transparency and high visualization degree, and a three-dimensional visualization test device is formed under the cooperation of a laser, a CCD camera, a laser displacement meter, a temperature sensor and a pressure sensor, so that the three-dimensional visualization test device for inducing seabed deformation by natural gas hydrate decomposition is obtained; the natural gas hydrate layer of the settled layer in the three-dimensional visual test device is prepared under normal pressure, and can decompose gas and water along with the rise of temperature; the three-dimensional visual test device can simulate the decomposition process of the natural gas hydrate, has a visual structure, can directly observe the test phenomena of fluid migration paths, crack propagation and the like in the submarine sediments, and realizes the visualization of the internal displacement of the submarine sediments; the temperature and pressure change in the seabed and the deformation conditions in the seabed and on the surface in the test process can be collected, the three-dimensional visual test device for inducing the seabed deformation by hydrate decomposition is obtained, the conditions of a simulation test are simplified, scientific theoretical guidance is provided for prevention and control of marine geological disasters, the cost performance is high, and the popularization is convenient; the invention completes the preparation of hydrate and the visualization of submarine sediments under normal pressure, does not need high pressure, has simple preparation method, mild conditions, no special requirements on equipment and low cost.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
FIG. 1 is a schematic perspective view of a three-dimensional visual testing apparatus according to the present invention;
FIG. 2 is a schematic exploded view of an apparatus for preparing soft clay for an overburden according to the present invention;
FIG. 3 is a schematic cross-sectional view of a deposited layer of the present invention;
FIG. 4 is a photograph showing the appearance of a deposition layer of the present invention;
FIG. 5 is a photograph taken by a CCD camera during testing according to the present invention;
FIG. 6 is a schematic perspective view of a transparent mold box used in the present invention;
in the figure: 100-a base; 200-forming a sleeve; 300-push plate; 4-an underlying layer; 5-natural gas hydrate layer; 6-an upper cladding layer;
900-an operating platform; 101-a deposition layer; 111-laser displacement meter; 112-a scaffold; 113-a lens group; 114-a laser light source; 115-CCD camera; 116-transparent mold box.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Referring to fig. 1, fig. 2, fig. 3, fig. 4, fig. 5 and fig. 6, the three-dimensional visualization test device for inducing seabed deformation by hydrate decomposition according to the present invention includes a transparent model box 116, a deposition layer 101 is disposed in the transparent model box 116, a laser is disposed on one side of the transparent model box 116, a CCD camera 115 is disposed on one side of the transparent model box 116 perpendicular to the laser, a laser displacement meter 111 is disposed on the top of the transparent model box 116, and a temperature sensor and a pressure sensor are further disposed in the deposition layer 101; the sedimentary layer 101 comprises a transparent marine soft clay layer and a natural gas hydrate layer 5, wherein the natural gas hydrate layer 5 is positioned inside the transparent marine soft clay layer, the transparent marine soft clay layer comprises an underlayer 4 and an overlayer 6, the underlayer 4 is positioned at the bottom of the natural gas hydrate layer 5, and the overlayer 6 is positioned at the top of the natural gas hydrate layer 5; the transparent marine soft clay layer is prepared by mixing and stirring lithium magnesium silicate and distilled water according to a mass ratio of 3.5-6.5: 100, and the natural gas hydrate layer 5 is prepared by trichlorofluoromethane and distilled water according to a volume ratio of 1: 2-1: 4 under normal pressure. For simplicity, transparent mold box 116 is not shown in FIG. 1, and the temperature sensor, pressure sensor, and their associated wires are not shown; the CCD camera 115 is connected with a computer, and the CCD camera 115 can carry out automatic continuous shooting; a laser section of a laser is vertically hit into the deposition layer 101 to form a speckle field; the laser displacement meter 111 is erected on the top of the transparent model box 116 through a bracket 112; in the test process, photo images shot by the CCD camera 115 are collected by the computer at proper time, and the obtained speckle field images are analyzed by using image processing software of the computer, so that a three-dimensional displacement field of the soil body in the deposition layer 101 is obtained.
Referring to fig. 1, in the present invention, the laser includes a laser source 114 and a lens set 113, the laser source 114 and the lens set 113 are located in a first plane vertically disposed, and the first plane is perpendicular to a side surface of a transparent mold box 116. In the invention, the laser is positioned at the right side of the deposition layer 101, the CCD camera 115 is positioned at the front side of the deposition layer 101, the CCD camera 115 just shoots the test phenomena of fluid migration path, crack propagation and the like vertically driven into a vertical plane in the deposition layer 101 by the laser light source 114 through the lens group 113, and the change condition of the internal displacement of the deposition layer 101 is recorded. In this embodiment, the transparent mold box 116 is located on an operation platform 900, a first slide rail is disposed at the bottom of the laser source 114, a first slide rail adapted to the first slide rail is disposed on the operation platform 900, a second slide rail is disposed at the bottom of the lens set 113, and a second slide rail adapted to the second slide rail is disposed on the operation platform 900. According to the invention, under the matching action of the first slide rail and the first slide rail as well as the second slide rail and the second slide rail, the laser light source 114 and the lens group 113 can be synchronously moved, so that the laser light source 114 and the lens group 113 are always kept in a plane vertical to the side surface of the settled layer 101, the positions of the laser light source 114 and the lens group 113 are dragged, and the plane of pictures taken by the CCD camera 115 is changed, so that the three-dimensional displacement change conditions of a fluid migration path and crack propagation on different planes in the settled layer 101 are obtained.
The invention discloses a three-dimensional visual test method for inducing seabed deformation by hydrate decomposition, which comprises the following steps:
A. preparation of natural gas hydrate substitute material
1) Taking trichlorofluoromethane, placing at-18-4 ℃, and refrigerating for later use;
2) respectively placing distilled water at 2-4 ℃, and refrigerating for later use;
3) adding the trichlorofluoromethane obtained in the step 1) into the distilled water obtained in the step 2), and stirring at the stirring speed of 500-1000 r/min for 1-5 min to uniformly mix the trichlorofluoromethane and the distilled water to obtain a mixture;
4) continuously stirring the mixture obtained in the step 3) at the temperature of-18-4 ℃, wherein the stirring speed is 500-1000 r/min, and the stirring time is 8-20 min, until a solid hydrate begins to be formed, so as to obtain a natural gas hydrate substitute material;
B. preparation of transparent marine soft clay
5) Taking lithium magnesium silicate and distilled water, wherein the weight ratio of the lithium magnesium silicate to the distilled water is 3.5-6.5: 100, the particle size of the lithium magnesium silicate is 20-30 nm, and the density is 0.9-1.1 g/cm3Slowly adding lithium magnesium silicate into distilled water, wherein the adding speed of the lithium magnesium silicate to the distilled water is 5-15 g/s, the distilled water is always in a stirring state in the process of adding the lithium magnesium silicate into the distilled water, and the stirring speed in the process of adding the lithium magnesium silicate into the distilled water is 5001000 r/min; continuously stirring at the stirring speed of 800-1200 r/min for 5-20 min to obtain transparent marine soft clay;
C. preparation of the underlayer 4
6) Preparing transparent marine soft clay according to the method in the step 5), placing the transparent marine soft clay in a transparent model box 116, standing at the temperature of 1-4 ℃ for 24-48 h, and solidifying to obtain transparent marine soft clay, namely forming a bottom stratum 4;
D. preparation of the overlying layer 6
7) Preparing transparent marine soft clay according to the method in the step 5), placing the transparent marine soft clay in an overburden soft clay preparation device, standing and solidifying to obtain transparent marine soft clay; the preparation device of the soft clay of the upper cladding comprises a base 100 with an opening end at one end, a forming sleeve 200 used for containing the soft clay of the transparent ocean is connected to the inside of the base 100 in a sleeved mode, the opening ends are arranged at two ends of the forming sleeve 200, the forming sleeve 200 is connected with a push plate 300 capable of pushing the soft clay of the transparent ocean out, a transparent waterproof film is arranged at the opening end of the bottom of the forming sleeve 200, and the transparent waterproof film is detachably connected with the outside of the forming sleeve 200 through a fixing band;
E. preparation of the deposit 101
8) Placing the natural gas hydrate substitute material obtained in the step 4) in the middle position of the top of the underlayer 4 obtained in the step 6), namely forming a natural gas hydrate layer 5;
9) removing the base 100 of the upper coating layer soft clay preparation device in the step 7), simultaneously detaching the transparent waterproof film, slowly pushing the transparent ocean soft clay obtained in the step 7) downwards by adopting a push plate 300, and covering the formed natural gas hydrate layer 5 obtained in the step 8) to obtain a settled layer 101 stored in a transparent model box 116;
10) placing a temperature sensor and a pressure sensor inside the deposition layer 101, placing a laser on one side of a transparent model box 116, placing a CCD camera 115 on one side of the transparent model box 116 perpendicular to the laser, placing a laser displacement meter 111 on the top of the transparent model box 116, wherein the plane where the lens of the CCD camera 115 is located is parallel to one outer vertical surface of the transparent model box 116;
11) starting a laser and a CCD camera 115, and after the power of the laser is stable, adjusting the angle of a laser section to vertically drive the laser section into the deposition layer 101 to form a speckle field; adjusting the test field of the CCD camera 115 to cover the whole speckle field picture, setting the test field into an automatic continuous shooting mode, and collecting the pictures in the CCD camera 115; starting a temperature sensor, a pressure sensor and laser displacement, and acquiring data of the temperature sensor, the pressure sensor and the laser displacement meter 111 in real time;
12) and at regular intervals, the position of the laser is changed, the data of the temperature sensor, the pressure sensor and the laser displacement on other planes in the sedimentary layer 101 are continuously collected, the photos in the CCD camera 115 are collected, and the photos of different cross sections of the seabed are obtained through the CCD camera.
Compared with the prior art, the invention has the beneficial effects that: according to the invention, transparent marine soft clay is adopted in the sediment layer 101 to simulate a soft clay layer in the seabed sediment, natural gas hydrate substitute material is adopted to simulate natural gas hydrate in the seabed sediment, the obtained sediment layer 101 has high transparency and high visualization degree, a three-dimensional visualization test device is formed under the cooperation of a laser, a CCD camera 115, a laser displacement meter 111, a temperature sensor and a pressure sensor, and the three-dimensional visualization test device for seabed deformation induced by natural gas hydrate decomposition is obtained; the natural gas hydrate layer 5 of the sediment layer 101 in the three-dimensional visual test device is prepared under normal pressure, and can decompose gas and water along with the rise of temperature; the three-dimensional visual test device can simulate the decomposition process of the natural gas hydrate, has a visual structure, can directly observe the test phenomena of fluid migration paths, crack propagation and the like in the submarine sediments, and realizes the visualization of the internal displacement of the submarine sediments; the temperature and pressure change in the seabed and the deformation conditions in the seabed and on the surface in the test process can be collected, the three-dimensional visual test device for inducing the seabed deformation by hydrate decomposition is obtained, the conditions of a simulation test are simplified, scientific theoretical guidance is provided for prevention and control of marine geological disasters, the cost performance is high, and the popularization is convenient; the invention completes the preparation of hydrate and the visualization of submarine sediments under normal pressure, does not need high pressure, has simple preparation method, mild conditions, no special requirements on equipment and low cost.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.
Claims (7)
1. A three-dimensional visual test method for seabed deformation induced by hydrate decomposition is characterized in that:
the testing method is carried out on a three-dimensional visual testing device for inducing seabed deformation by hydrate decomposition, the three-dimensional visual testing device for inducing seabed deformation by hydrate decomposition comprises a transparent model box, a deposition layer is arranged in the transparent model box, a laser is arranged on one side of the transparent model box, the laser comprises a laser source and a lens group, the laser source and the lens group are positioned in a first plane which is vertically arranged, the first plane is vertically arranged with the side surface of the transparent model box, a CCD (charge coupled device) camera is arranged on one side of the transparent model box which is vertical to the laser, a laser displacement meter is arranged at the top of the transparent model box, and a temperature sensor and a pressure sensor are also arranged in the deposition layer;
the transparent model box is positioned on an operation platform, a first slide rail is arranged at the bottom of the laser light source, a first slide rail matched with the first slide rail is arranged on the operation platform, a second slide rail is arranged at the bottom of the lens group, and a second slide rail matched with the second slide rail is arranged on the operation platform;
the sedimentary layers comprise a transparent marine soft clay layer and a natural gas hydrate layer, the natural gas hydrate layer is positioned inside the transparent marine soft clay layer, the transparent marine soft clay layer comprises an underlayer and an overlayer, the underlayer is positioned at the bottom of the natural gas hydrate layer, and the overlayer is positioned at the top of the natural gas hydrate layer;
the transparent marine soft clay layer is prepared by mixing and stirring lithium magnesium silicate and distilled water according to a mass ratio of 3.5-6.5: 100, and the natural gas hydrate layer is prepared by trichloromonofluoromethane and distilled water according to a volume ratio of 1: 2-1: 4 at normal pressure;
the test method comprises the following steps:
A. preparation of natural gas hydrate substitute material
1) Taking trichlorofluoromethane, placing at-18-4 ℃, and refrigerating for later use;
2) respectively placing distilled water at 2-4 ℃, and refrigerating for later use;
3) adding the trichloromonofluoromethane obtained in the step 1) into the distilled water obtained in the step 2), and stirring to uniformly mix the trichloromonofluoromethane and the distilled water to obtain a mixture;
4) continuously stirring the mixture obtained in the step 3) at the temperature of-18-4 ℃ for 8-20 min until solid hydrate begins to be formed, thus obtaining the natural gas hydrate substitute material;
B. preparation of transparent marine soft clay
5) Taking lithium magnesium silicate and distilled water, wherein the weight ratio of the lithium magnesium silicate to the distilled water is 3.5-6.5: 100, slowly adding the lithium magnesium silicate into the distilled water, and stirring the distilled water all the time in the process of adding the lithium magnesium silicate into the distilled water; continuously stirring at the stirring speed of 800-1200 r/min for 5-20 min to obtain transparent marine soft clay;
C. preparation of underlying layers
6) Preparing transparent marine soft clay according to the method in the step 5), placing the transparent marine soft clay in a transparent model box, standing and solidifying to obtain transparent marine soft clay, namely forming an underlying layer;
D. preparation of an overlying layer
7) Preparing transparent marine soft clay according to the method in the step 5), placing the transparent marine soft clay in an overburden soft clay preparation device, standing and solidifying to obtain transparent marine soft clay;
the preparation device for the soft clay of the upper cladding comprises a base, wherein one end of the base is provided with an opening end, a forming sleeve used for containing the transparent marine soft clay is connected to the inside of the base in a sleeved mode, the two ends of the forming sleeve are provided with the opening ends, and the forming sleeve is connected with a push plate capable of pushing out the transparent marine soft clay;
E. preparation of the deposit
8) Placing the natural gas hydrate substitute material obtained in the step 4) in the middle position of the top of the underlying layer obtained in the step 6), namely forming a natural gas hydrate layer;
9) removing the base of the upper coating layer soft clay preparation device in the step 7), slowly pushing the transparent marine soft clay obtained in the step 7) downwards by adopting a push plate, and covering the natural gas hydrate layer obtained in the step 8) to obtain a settled layer stored in a transparent model box;
10) placing a temperature sensor and a pressure sensor in the deposition layer, placing a laser on one side of a transparent model box, placing a CCD camera on one side of the transparent model box perpendicular to the laser, and placing a laser displacement meter on the top of the transparent model box;
11) starting a laser and a CCD camera, and collecting photos in the CCD camera; starting a temperature sensor, a pressure sensor and laser displacement to perform real-time acquisition;
12) and (4) changing the position of the laser, and obtaining photos of different cross sections of the seabed through a CCD camera.
2. The three-dimensional visualization test method of hydrate dissociation induced seabed deformation according to claim 1, wherein:
in the step 7), a transparent waterproof film is arranged at the bottom opening end of the forming sleeve and detachably connected with the outside of the forming sleeve through a fixing band, and the transparent waterproof film is detached while the base is removed in the step 9).
3. The three-dimensional visualization test method of hydrate dissociation induced seabed deformation according to claim 1, wherein:
the standing temperature is 1-4 ℃, and the standing time is 24-48 h.
4. The three-dimensional visualization test method of hydrate dissociation induced seabed deformation according to claim 1, wherein:
the stirring speed of the lithium magnesium silicate in the process of adding distilled water is 500-1000 r/min.
5. The three-dimensional visualization test method of hydrate dissociation induced seabed deformation according to claim 1, wherein:
the adding speed of the lithium magnesium silicate to the distilled water is 5-15 g/s.
6. The three-dimensional visualization test method of hydrate dissociation induced seabed deformation according to claim 1, wherein:
the stirring speed in the step 3) and the stirring speed in the step 4) are both 500-1000 r/min, and the stirring time in the step 3) is 1-5 min.
7. The three-dimensional visualization test method of hydrate dissociation induced seabed deformation according to claim 1, wherein:
the lithium magnesium silicate has a particle size of 20-30 nm and a density of 0.9-1.1 g/cm3The refractive index is 1.3 to 1.8.
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