Model test device and method for testing resistance rate effect of missile penetrating into seabed soil at high speed

Abstract

The invention belongs to the technical field of indoor tests of marine geotechnical engineering, and discloses a model test device for testing the resistance rate effect of a missile penetrating into a seabed soil body at a high speed, which comprises a model box system, a reaction frame system, a missile excitation device and a data acquisition module. The invention further provides a model test method for testing the resistance rate effect of the guided missile penetrating into the seabed soil body at the high speed. Through cooperation of all parts of the test device system, the data acquisition module is finally used for extracting the speed and counter-force changes of the missile passing through a water layer and a soil layer at different penetration speeds and soil layer thicknesses, and finally a complete penetration speed-depth curve and a penetration resistance-depth curve of the missile are drawn. According to the curve and a penetration resistance calculation formula, soil body strength parameters are reversely bulldozed, the mechanism that the undrained shear strength of the soil body is influenced by the soil body rate effect is analyzed, and a set of simple, convenient and efficient indoor test device and method are provided for research on the high-speed soil body resistance and rate effect of the cohesive soil of the seabed.

Description

Technical Field

[0001] The present invention relates to the field of indoor test technology for marine geotechnical engineering, and in particular to the study of soil velocity effect in the high-speed interaction process between clay seabed and structure. By collecting the velocity and resistance fluctuations of missiles penetrating into the clay layer during the test, the mechanism by which the undrained shear strength of clay is affected by the soil velocity effect is analyzed. The present invention proposes a model test device and method for testing the resistance velocity effect of missiles penetrating into the seabed soil at high speed. Background Art

[0002] The undrained shear strength of clay soil is used to describe its ability to resist shear failure perpendicular to the shear plane under saturated undrained conditions. It is one of the key indicators for evaluating the strength of clay soil seabed in the field of marine engineering. In actual engineering, in addition to the characteristics of the seabed itself (such as composition, water content and sensitivity, etc.), the influence of external forces on the strength of clay soil cannot be ignored. For example, during the installation of a dynamic anchor, the anchor body is 10 1 to 10 2 s -1 The ultra-high speed of the anchor contacts the clay seabed and penetrates downwards. This high-speed penetration process will significantly increase the undrained shear strength of the clay. If this effect is ignored, the dynamic anchor will be unable to reach the predetermined depth due to insufficient kinetic energy, and will not be able to provide sufficient tension for the anchor chain, which will ultimately endanger the service safety of the marine structure.

[0003] However, the commonly used test methods such as triaxial test, ring shear test, cross plate shear test, etc. cannot meet the high-speed shear test requirements of 10-50m / s during the dynamic anchor penetration process, so it is difficult to carry out the shear process research of the structure-cohesive seabed during the dynamic anchor penetration process. In addition, the lack of measurement element accuracy and acquisition frequency of traditional test methods also makes it difficult for this method to collect accurate and efficient test data.

[0004] In summary, accurately evaluating the mechanism of soil velocity effect on the undrained shear strength of clay soil is of great significance for the study of high-speed penetration of dynamic anchors, but the existing test devices and methods are difficult to meet the research needs. Therefore, it is necessary to propose a research device and method that is targeted and accurate in studying the influence of soil velocity effect on the undrained shear strength of clay seabed. Summary of the invention

[0005] In order to make up for the shortcomings of existing research methods and accurately evaluate the influence mechanism of soil velocity effect on the undrained shear strength of clay soil, the first problem to be solved by the present invention is to provide a model test device for testing the velocity effect of missiles penetrating the seabed soil resistance at high speed, and to draw the penetration velocity-depth curve by using the velocity and resistance fluctuations of missiles penetrating soils of different thicknesses, and then analyze the influence mechanism of soil velocity effect on penetration resistance. To this end, the present invention adopts the following technical solutions:

[0006] A model test device for testing the resistance rate effect of missiles penetrating into seabed soil at high speed, characterized in that it comprises four parts: a model box system, a reaction frame system, an excitation device and a data acquisition module. The model box system consists of a model box, a support frame and a soil sample box; the reaction frame system consists of a bracket, a horizontal fixer and an excitation device fixer; the excitation device consists of a nail gun, a nail and a missile; and the data acquisition module consists of a spoke dynamometer, a high-speed camera, a data acquisition device and a computer.

[0007] The bottom of the model box is square, with an outer side length of 200 mm, a height of 500 mm, and a wall thickness of 5 mm, and is made of a transparent acrylic plate material. The opening at the bottom ensures that the missile can pass freely during the test, so that the spoke dynamometer only records the reaction force fluctuations during the missile's penetration and ejection of the soil sample.

[0008] The support frame is composed of left and right halves, which lift the soil sample box and place it in the middle of the model box to facilitate the visualization collection of data during the missile penetration and ejection of soil samples. A cylindrical area with a diameter of 100 mm and a height of 200 mm is reserved in the middle to place the soil sample box.

[0009] The soil sample box has an inner diameter of 100mm and a height of 200mm. It is made of transparent acrylic material, with a hole at the bottom and a thin plastic film to ensure the waterproofness of the soil sample box before the missile penetrates. The bottom of the soil sample box is used to place soil samples in the lower layer of 0-100mm with the bottom surface as the zero point, and the upper layer of 100-200mm is set as the water layer to restore the in-situ penetration process of the dynamic anchor. Four sets of concentric ring-shaped hollow supports with an outer diameter of 100mm, an inner diameter of 20mm, and a height of 20mm are also provided to adjust the thickness of the soil sample.

[0010] The reaction frame system adopts a portal frame form, which is welded from a square hollow steel pipe, with a total height of 1100mm, a horizontal width of 360mm, an outer length of the hollow steel pipe of 40mm, an outer length of the upper bracket of 60mm, and sliding grooves are provided on the upper and both sides of the bracket. Horizontal fixtures are installed on both sides to limit the horizontal displacement of the model box during the test process. An excitation device fixture is installed above the bracket for installing the excitation device. The bottom surface of the excitation device fixture is a square with an outer wall of 40mm, an inner wall of 36mm, and a total length of 150mm.

[0011] The excitation device is improved from a commercial small nail gun and nails. A nail gun with an outer diameter of 36mm and a total length of 120mm and a standard capless nail with a length of 42mm are used. The missile shell with a length of 30mm and an outer diameter of 7.6mm is processed according to the shape of the nail tip. During the test, the nail and the missile are fired together. The nail gun can provide an excitation speed of 10-40m / s for the missile, breaking through the speed limit of the existing test method and solving the problem that it is difficult to carry out the study of the velocity effect of clay soil.

[0012] The spoke dynamometer can monitor the reaction force fluctuations caused by the soil velocity effect during the model missile entering the water and the soil in real time. The spoke dynamometer has a diameter of 143mm and is in the shape of concentric rings. During the test, the missile can pass through it with a range of 0-100N and an accuracy of 0.01N, which meets the test load and accuracy requirements. The data output frequency is 12.8KHz.

[0013] The high-speed camera uses a 100,000-frame-class high-speed black-and-white camera to record the relative position of the missile during the entire process of excitation, penetration into the soil sample, and even ejection of the soil sample, and calculates the missile speed change process in each stage of the entire test process in conjunction with the duration. The corresponding data output frequency is 12.8KHz, corresponding to the spoke-type dynamometer. The input frequency of the data acquisition device is 12.8KHz, corresponding to the high-speed camera and the spoke-type dynamometer, and is used to input the data collected by the two into a computer for analysis and research.

[0014] The test principle is as follows: ensure that the initial missile penetration speed, the water layer height in the soil sample box and the top surface height of the soil sample remain unchanged, carry out penetration tests on five groups of soil samples with different thicknesses of 20mm, 40mm, 60mm, 80mm and 100mm, use the shooting results of a high-speed camera to calculate the speed fluctuations of the missile entering the water, penetrating and ejecting the soil sample in soil samples of different thicknesses, draw a complete speed-depth curve, and use the resistance-depth curve drawn according to the reaction force of the spoke dynamometer and the resistance calculation formula to jointly analyze the influence mechanism of the undrained shear strength on the soil velocity effect.

[0015] Another technical problem to be solved by the present invention is to propose a model test method for testing the resistance rate effect of a missile penetrating into seabed soil at high speed in combination with the above test device.

[0016] A model test method for testing the resistance rate effect of a missile penetrating into seabed soil at high speed, characterized by comprising the following steps:

[0017] Step (1) soil sample preparation: saturated and consolidated kaolin is used in sequence in the order of 20 mm, 40 mm, 60 mm, 80 mm and 100 mm, the inner diameter of the soil sample is 100 mm, and the initial undrained shear strength of the soil sample at a low shear rate is determined by a triaxial test or a ring shear test.

[0018] Step (2) Equipment installation: Place the spoke dynamometer on a flat and stable ground, and place the model box on top so that the opening on the bottom of the model box is aligned with the center hole of the spoke dynamometer. Place the support frame and soil sample box in the box in turn. Stick plastic cloth on the bottom of the soil sample box for waterproofing, and place the support and soil sample on top to ensure that the total height of the two is 100mm, and then add water to make the total height reach 180mm. Place a high-speed camera and a matching tripod in front of the model box and adjust the window and resolution. Then place the reaction frame system on the model box system and the spoke dynamometer in turn, fit the two sides of the horizontal fixture model box, and adjust the excitation device fixture so that the bottom circular hole is in line with the center of the soil sample.

[0019] Step (3) Data acquisition device calibration: Connect the spoke dynamometer and the high-speed camera to the control device and initialize the data, and apply a small pressure to the model box system to verify the sensitivity and accuracy of the data acquisition module.

[0020] Step (4) Installation of firing device: Put the missile on the outside of the nail and insert it into the firing port of the nail gun. Place the excitation device on the excitation device holder, and make sure that the movement path of the nail is in line with the center of the soil sample and the opening of the model box before officially starting the test.

[0021] Step (5) Penetration test: launch the missile, penetrate the soil sample and pierce out, and collect data in the test.

[0022] Step (6) Repeat the test: Starting from the 20 mm thick soil sample, repeat the test in order of 40 mm, 60 mm, 80 mm and 100 mm until the missile cannot be fired or the test ends after 100 mm. This is considered as one group. Then adjust the parameters such as the firing speed of the nail or the initial strength of the clay soil and repeat the test.

[0023] Step (7) Data processing: Calculate the speed of the missile when entering the water, penetrating and ejecting soil samples of different thicknesses from the shooting results of the high-speed camera. Combined with the speed of ejection at depths of 20 mm, 40 mm, 60 mm, 80 mm and 100 mm, draw a penetration speed-depth curve. In addition, draw a penetration resistance-depth curve in combination with the resistance fluctuation curve of the spoke dynamometer. According to the penetration resistance calculation formula (1):

[0024] ma=W b -F tip -F s -F D -F b (1)

[0025] In formula (1), m is the mass of the missile, a is the acceleration, and W is b is the missile's own weight, F tip is the vertical penetration resistance, F s is the lateral resistance, F D is the drag resistance, Fs The buoyancy of soil.

[0026] The specific calculation method is as follows:

[0027]

[0028] In formula (2), ρ s is the saturated density of clay soil, measured before the test; C d is the drag resistance coefficient, which is 0.22 for clay soil; A t is the missile cross-sectional area, and the calculation formula is Where d is the missile diameter, 7.6 mm; v is the real-time penetration velocity, obtained from the results captured by a high-speed camera.

[0029] F b =ρ′V s g (3)

[0030] In formula (3), ρ′ is the floating density of clay soil, which can be calculated using the saturated density of clay soil: s -1 is calculated approximately; ′V s is the missile volume, and the calculation formula is Where z is the missile length 30mm; g = 9.8m / s 2 is the acceleration due to gravity.

[0031] The calculation formulas for end resistance and side friction resistance are:

[0032] F tip =R f (s u N kt A t ) (4)

[0033] F s =R f (αs u A s ) (5)

[0034] In formula (4) and formula (5), R f is the strain rate coefficient, and the calculation formula is Among them, β is the soil rate effect parameter, which is the focus of this study; s u A is the undrained shear strength of clay soil, measured before the test; t is the missile cross-sectional area; A s is the missile side surface area, calculated as A s =πdz; α is the friction coefficient on the interface side; thus, the calculation method of the strain rate coefficient can be summarized as formula (6):

[0035]

[0036] Formula (6) can analyze the trend of the strain rate coefficient changing with different parameters and reveal the development mechanism of the resistance effect with soil velocity during high-speed penetration.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] (1) This test method uses a nail gun to launch missiles, which solves the problem of low loading rate in traditional shear test methods and overcomes the defects of existing high-speed test schemes such as unsatisfactory shear effect and difficult data collection. In traditional shear tests, the loading rate can usually only reach 0.05m / s, while this test method can increase the loading rate by nearly three orders of magnitude (providing an excitation speed of 10-40m / s), greatly improving the shear rate and carrying out targeted indoor high-speed shear test research.

[0039] (2) The total height of this test device is 1100mm and the total area is about 1m 2 The device is simple, the steps are simple, and the safety is high. The shear interaction process between the missile and the clay soil sample is sufficient and can provide sufficient shear deformation. This method can be effectively applied to indoor experimental research on high-speed penetration interaction of clay seabed represented by the installation problem of dynamic anchors.

[0040] (3) Data collection is performed using a spoke-type dynamometer with a high acquisition frequency and a high-speed camera. The velocity-depth and velocity-resistance curves of the missile penetration process can be plotted. The soil velocity effect correlation coefficient can be inferred by combining the calculation formula. The test principle is clear and the test method is feasible. After further optimization, it can be used for the analysis of actual engineering dynamic anchor penetration operations. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 It is an overall schematic diagram of an indoor dynamic anchor high-speed penetration test device that takes into account the soil velocity effect;

[0042] Figure 2 This is a schematic diagram of the model box system of the test device;

[0043] Figure 3 It is a schematic diagram of the reaction frame system of the test device;

[0044] Figure 4 This is a schematic diagram of the triggering device and missile;

[0045] Figure 5 It is a schematic diagram of the data acquisition module;

[0046] Figure 6 Schematic diagram of soil sample box filling and velocity-depth curve drawing during the test process.

[0047] The numbers in the figure are: model box system (100); model box (101); support frame (102); soil sample box (103); reaction frame system (200); support (201); horizontal fixer (202); excitation device fixer (203); excitation device (300); nail gun (301); nail (302); missile (303); data acquisition module (400); spoke dynamometer (401); high-speed camera (402); data acquisition device (403); computer (404). DETAILED DESCRIPTION

[0049] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work belong to the protection scope of the present invention.

[0050] The bottom surface (101) of the model box is square, with an outer side length of 200 mm, a height of 500 mm, and a wall thickness of 5 mm, and is made of a transparent acrylic plate material. The opening at the bottom ensures that the missile can pass freely during the test, so that the spoke-type dynamometer (402) only records the reaction force fluctuations during the process of the missile penetrating and ejecting the soil sample.

[0051] The support frame (102) is composed of left and right halves, and lifts the soil sample box (103) to place it in the middle of the model box, so as to facilitate the visual data collection of the process of the missile (303) penetrating and ejecting the soil sample, and a cylindrical area with a diameter of 100 mm and a height of 200 mm is reserved in the middle to place the soil sample box (103).

[0052] The soil sample box (103) has an inner diameter of 100 mm and a height of 200 mm. It is made of a transparent acrylic material, and has a hole at the bottom and a thin plastic film to ensure that the soil sample box (103) is waterproof before the missile (303) penetrates. The bottom surface of the soil sample box (103) is used to place the soil sample in the range of 0-100 mm below the zero point, and the upper layer of 100-200 mm is set as a water layer to restore the in-situ penetration process of the power anchor. Four sets of concentric ring-shaped hollow supports with an outer diameter of 100 mm, an inner diameter of 20 mm, and a height of 20 mm are provided to adjust the thickness of the soil sample.

[0053] The reaction frame system (200) is in the form of a portal frame, welded from a square hollow steel pipe, with a total height of 1100 mm and a horizontal width of 360 mm. The outer side of the hollow steel pipe is 40 mm long, the outer side of the upper bracket is 60 mm long, and sliding grooves are provided on the upper and both sides of the bracket. Horizontal fixtures are installed on both sides to limit the horizontal displacement of the model box (102) during the test process. An excitation device fixture 203 is installed above the bracket (201) for installing the excitation device. The bottom surface of the excitation device fixture is a square with an outer wall of 40 mm, an inner wall of 36 mm, and a total length of 150 mm.

[0054] The excitation device (300) is improved from a commercial small-sized nail gun (301) and a nail (302). The nail gun (301) with an outer diameter of 36 mm and a total length of 120 mm and a standard capless nail (302) with a length of 42 mm are used. A missile shell with a length of 30 mm and an outer diameter of 7.6 mm is processed according to the shape of the nail tip. During the test, the nail (302) and the missile (303) are fired together. The nail gun (301) can provide an excitation speed of 10-40 m / s for the missile (303), breaking through the speed limit of the existing test method and solving the problem that it is difficult to carry out the study of the velocity effect of clay soil.

[0055] The spoke dynamometer (401) can monitor in real time the reaction force fluctuation caused by the soil velocity effect during the process of the model missile (303) entering water and soil. The spoke dynamometer (401) has a diameter of 143 mm and is in the shape of concentric rings. During the test, the missile can pass through it with a range of 0-100N and an accuracy of 0.01N, meeting the test load and accuracy requirements, and the data output frequency is 12.8KHz.

[0056] The high-speed camera (402) uses a 100,000-frame high-speed camera to record the relative position of the missile (303) during the whole process of excitation, penetration into the soil sample and even ejection from the soil sample, and calculates the speed change process of the missile (303) in each stage of the whole test process in conjunction with the duration. The corresponding data output frequency is 12.8KHz, corresponding to the spoke-type dynamometer. The input frequency of the data acquisition device (403) is 12.8KHz, corresponding to the high-speed camera and the spoke-type dynamometer, and is used to input the data collected by the two into a computer for analysis and research.

[0057] The test principle is as follows: ensure that the initial missile (303) penetration speed, the water layer height in the soil sample box (103) and the top surface height of the soil sample are constant, and after conducting missile penetration tests on five groups of soil samples with different thicknesses of 20 mm, 40 mm, 60 mm, 80 mm and 100 mm, respectively, use the shooting results of a high-speed camera (402) to merge the speed interpolation of the missile (303) in the soil samples with different thicknesses during the process of entering the water, penetrating the soil sample and ejecting the soil sample, draw a complete speed-depth curve, and reversely infer the influence mechanism of the undrained shear strength on the soil velocity effect through the fluctuation difference of the spoke dynamometer (401) and the calculation formula of the penetration resistance.

[0058] Another technical problem to be solved by the present invention is to propose a model test method for testing the resistance rate effect of a missile penetrating into seabed soil at high speed in combination with the above test device.

[0059] A model test method for testing the resistance rate effect of a missile penetrating into seabed soil at high speed, characterized in that it comprises the following steps:

[0060] Step (1) soil sample preparation: kaolin is used to prepare soil samples, and saturated and consolidated samples are prepared in the order of 20 mm, 40 mm, 60 mm, 80 mm and 100 mm. The initial undrained shear strength of the soil samples at a low shear rate is determined by a triaxial test or a ring shear test.

[0061] Step (2) Equipment installation: Place the spoke dynamometer (401) on a flat and stable ground, place the model box (101) above the dynamometer and align the opening on the bottom with the center hole of the spoke dynamometer (401). Place the support frame (102) and the soil sample box (103) in the box in sequence. The bottom of the soil sample box (103) is covered with plastic cloth for waterproofing, and the support and fully saturated and consolidated soil samples are placed on the top according to the test grouping, ensuring that the total height of the two is 100 mm, and then add water to make the total height reach 180 mm. According to the relative height of the soil sample, a high-speed camera (401) and a matching tripod are placed in front of the model box (101) to ensure that the soil samples on the path of the missile (303) penetration and the upper and lower cavities can be completely captured in the picture. Then, the reaction frame system (200) is placed on the model box system (100) and the spoke dynamometer (401) in turn, the horizontal fixture (202) is fitted to both sides of the model box (101), and the excitation device fixture (203) is adjusted so that the bottom circular hole is in line with the center of the soil sample.

[0062] Step (3) Data acquisition device calibration: Connect the spoke dynamometer (401) and the high-speed camera (402) to the control device and initialize the data. Apply a small pressure to the model box system (100) and verify the sensitivity and accuracy of the spoke dynamometer (401) according to the reaction force fluctuation curve. Adjust the position of the high-speed camera (402) according to the camera view.

[0063] Step (4) Installation of firing device: After the missile (303) is placed on the outside of the nail (302), it is inserted into the firing port of the nail gun (301). The excitation device (300) is placed on the excitation device holder (203), and the test is officially started after the movement path of the nail (302) is confirmed to be in line with the center of the soil sample and the opening of the model box (101).

[0064] Step (5) Penetration test: The missile (303) is launched from the hole of the excitation device holder (203), penetrates into the soil sample through the cavity above the soil sample, and pierces out from the bottom of the soil sample. After passing through the cavity below, the test device is ejected from the hole on the bottom of the model box.

[0065] Step (6) Repeat the test: Starting from the soil sample with a thickness of 20 mm, repeat the test in the order of 40 mm, 60 mm, 80 mm and 100 mm, until the missile cannot be fired or the test ends after 100 mm, which is considered as one group. Thereafter, adjust the firing speed of the gun nail (303) or the initial strength of the clay soil, and repeat the test again according to the above soil sample thickness.

[0066] Step (7) Data processing: The speed of the missile (303) when entering the water, penetrating and ejecting soil samples of different thicknesses is calculated from the shooting results of the high-speed camera (402). The penetration speed-depth curve is plotted in combination with the ejection speeds at depths of 20 mm, 40 mm, 60 mm, 80 mm and 100 mm. In addition, the penetration resistance-depth curve is plotted in combination with the resistance fluctuation curve of the spoke-type dynamometer (401).

[0067] In summary, the present invention proposes a model test device and method for testing the resistance rate effect of missiles penetrating into seabed soil at high speed. The soil rate coefficient is inferred based on the test results under different penetration speeds and soil sample strengths, and the influence mechanism of soil sample on soil rate effect is evaluated.

Claims

1. A model test device for testing the resistance rate effect of a missile penetrating into seabed soil at high speed, comprising: The model box system (100) comprises a model box (101), a support frame (102) and a soil sample box (103) for placing soil samples, the model box (101) and the soil sample box (103) are made of transparent acrylic material, and the support frame (102) leaves a movement path for the missile to penetrate and shoot out, so as to complete a visual penetration test; The reaction frame system (200) comprises a bracket (201), a horizontal fixer (202) and an excitation device fixer (203): the horizontal fixer (202) is fitted to the outer wall of the model box (101) to reduce the error caused by the horizontal disturbance during the model box experiment; the excitation device fixer (203) is used to fix the excitation device (300); The excitation device (300) comprises a nail gun (301), nails (302) and a missile (303), which are used to provide kinetic energy for launching the missile (303); The data acquisition module (400) includes a spoke-type dynamometer (401), a high-speed camera (402), a data acquisition device (403) and a computer (404). The input and output frequencies of the spoke-type dynamometer (401), the high-speed camera (402) and the data acquisition device (403) are all 12.8KHz to ensure the data acquisition accuracy of the missile (303) during the ultra-high-speed penetration process.

2. A model test device for testing the resistance rate effect of a missile penetrating into seabed soil at high speed according to claim 1, characterized in that: The model box (101) in the model box system (100) has a hole at the bottom to ensure that the missile (303) penetration path is not blocked by anything other than the soil sample; the support frame (102) is used to place the soil sample box (103); the soil sample box (103) is placed with a support, soil sample and water from bottom to top according to test requirements.

3. A model test device for testing the resistance rate effect of a missile penetrating into seabed soil at high speed according to claim 1, characterized in that: The support (201) is used to fix a horizontal fixer (202) and an excitation device fixer (203); the horizontal fixer (202) is connected to the outer wall of the model box (101) to ensure the stability of the model box system (100); the excitation device fixer (203) is used to provide the excitation device (300) with the reaction force required for excitation, and to ensure that the missile (303) can accurately pass through the bottom of the soil sample box (103), the model box (101) and the center hole of the spoke-type dynamometer (401) in sequence during the whole movement process, and be photographed by a high-speed camera (402).

4. A model test device for testing the resistance rate effect of a missile penetrating into seabed soil at high speed according to claim 3, characterized in that: The data acquisition system corresponding to the spoke-type dynamometer (401) and the high-speed camera (402) has an acquisition frequency of 12.8 KHz, so as to meet the requirements of drawing a missile penetration speed-depth curve and a penetration resistance-depth curve.

5. A model test device for testing the resistance rate effect of a missile penetrating into seabed soil at high speed according to claim 4, characterized in that: The model box (101) and the soil sample box (102) are both made of transparent acrylic material to ensure that the high-speed camera (402) can smoothly capture the movement image of the missile during the entire penetration process.

6. A model test method for testing the resistance rate effect of a missile penetrating into seabed soil at high speed, which uses the model test device for testing the resistance rate effect of a missile penetrating into seabed soil at high speed as described in claims 1-5, characterized in that: The specific steps are as follows: S01 Soil sample preparation: Kaolin was used to prepare soil samples, and saturated and consolidated samples were prepared in the order of 20mm, 40mm, 60mm, 80mm and 100mm. The initial undrained shear strength of the soil samples at low shear rate was determined by triaxial test or ring shear test; S02 Equipment installation: Place the spoke dynamometer (100) on a flat and stable ground, place the model box (101) on top and align the opening on the bottom of the model box (101) with the center hole of the spoke dynamometer (401); place the support frame (102) and the soil sample box (103) in the model box (101) in sequence; stick plastic cloth on the bottom of the soil sample box (103) to prevent water leakage, place the support and the fully saturated and consolidated soil sample on top in sequence and ensure that the total height is 100 mm, then add water to make the total height reach 180 mm; according to the relative height of the soil sample, a high-speed camera (402) and a matching tripod are placed in front of the model box (101) to ensure that the soil sample on the path of the missile (303) and the upper and lower cavities can be completely captured in the picture; then the reaction frame system (300) is placed on the model box system (100) and the spoke dynamometer (401) in turn, the horizontal fixture 302 is fitted on both sides of the model box 201, and the excitation device fixture (303) is adjusted so that the bottom circular hole is in line with the center of the soil sample; S03 Data acquisition device calibration: connect the spoke dynamometer (401) and the high-speed camera (402) to the control device and initialize the data; apply a small pressure to the model box system (100) and verify the sensitivity and accuracy of the spoke dynamometer 100 according to the reaction force fluctuation curve; adjust the position of the high-speed camera 500 according to the camera view; S04: Installation of firing device: After the missile (303) is placed on the outside of the nail (302), it is inserted into the firing port of the nail gun (301); and the excitation device (300) is placed on the excitation device holder (203), and the test is officially started after the movement path of the nail (302) is confirmed to be in line with the center of the soil sample and the opening of the model box (101); S05 penetration test: launching the missile (303) so that the missile (303) is ejected from the hole of the excitation device holder (203), penetrates into the soil sample through the cavity above the soil sample, and pierces out from the bottom of the soil sample; after passing through the cavity below, the missile (303) is ejected from the test device through the hole on the bottom surface of the model box (101); S06 Repeat the test: starting from the soil sample with a thickness of 20 mm, repeat in the order of 40 mm, 60 mm, 80 mm and 100 mm, until the missile (303) cannot be fired or ends after 100 mm, which is considered as one group; thereafter, adjust the firing speed of the gun nail (402) or the initial strength of the clay soil, and repeat the test again according to the above soil sample thickness; S07 Data processing: The data extracted by the data acquisition equipment (403) to the computer (404) include high-speed photos of the whole process of the missile (203) penetration and the reaction force fluctuation of the spoke-type dynamometer (401); the speed of the missile (303) when entering the water, penetrating and ejecting soil samples of different thicknesses is calculated from the shooting results of the high-speed camera (402); and the penetration speed-depth curve is plotted in combination with the speed of ejection at depths of 20mm, 40mm, 60mm, 80mm and 100mm; in addition, the penetration resistance-depth curve is plotted in combination with the resistance fluctuation curve of the spoke-type dynamometer (401), and the penetration resistance calculation formula (1) is used: at=W b -F tip -F s -F D -F b (1) In formula (1), m is the mass of the missile (303), a is the acceleration, and W b is the missile (303)’s own weight, F tip is the vertical penetration resistance, F s is the lateral resistance, F D is the drag resistance, F s for soil buoyancy; The specific calculation method is as follows: In formula (2), ρ s is the saturated density of clay soil, measured before the test; C d is the drag resistance coefficient, which is 0.22 for clay soil; A t is the cross-sectional area of ​​the missile (303), and the calculation formula is Where d is the missile diameter 7.6mm; v is the real-time penetration velocity, obtained from the results of high-speed camera shooting; F b =ρ′V s g (3) In formula (3), ρ′ is the floating density of clay soil, which can be calculated using the saturated density of clay soil: s -1 is calculated approximately; ′V s is the volume of the missile (303), and the calculation formula is Where z is the length of the missile (303) 30 mm; g = 9.8 m / s 2 is the acceleration due to gravity; The calculation formulas for end resistance and side friction resistance are: F tip =R f (s u N kt A t ) (4) F s =R f (αs u A s ) (5) In formula (4) and formula (5), R f is the strain rate coefficient, and the calculation formula is Among them, β is the soil rate effect parameter, which is the focus of this study; s u A is the undrained shear strength of clay soil, measured before the test; t is the cross-sectional area of ​​the missile (303), A s is the side surface area of ​​the missile (303), calculated by the formula A s =πdz; α is the friction coefficient on the interface side; thus, the calculation method of the strain rate coefficient can be summarized as formula (6): Formula (6) can analyze the trend of the strain rate coefficient changing with different parameters and reveal the development mechanism of the resistance effect with soil velocity during high-speed penetration.

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