A simulated offshore bucket foundation test model device and a penetration test method

Abstract

The invention discloses a simulated offshore bucket foundation test model device and a penetration test method, the device comprises three parts: a test system, a water supply system and a negative pressure regulating system; the test system comprises a model box, a suction bucket foundation installation device, a bucket foundation and a wave-breaking plate; the water supply system comprises an automatic water level control device and a water supply device; the negative pressure regulating system comprises a water-gas separation device and a vacuum pump; wherein the automatic water level control device can maintain the water level in the model box, objectively simulating the situation that the sea level is stable and unchanged; the water-gas separation device provides a stable negative pressure environment for the inside of the suction bucket foundation installation device, and can avoid directly sucking water and sand into the vacuum pump; the invention can be used to simulate the offshore bucket foundation penetration process under the marine environment, study the offshore bucket foundation penetration speed, the friction resistance between the bucket wall and the soil body and the negative pressure required for penetration, and improve the excavation-free design calculation method and related construction technology.

Description

Technical Field

[0001] The invention relates to an offshore barrel foundation penetration test device, which can be used to simulate the offshore barrel foundation penetration process in a marine environment, study the offshore barrel foundation penetration speed, the friction between the barrel wall and the soil, and the negative pressure required for penetration, and improve the excavation-free design calculation method and related construction technology. Background Art

[0002] In recent years, offshore barrel foundations have been widely used in marine projects such as oil platform foundations, wind turbine tower foundations, breakwater foundations, and port construction in the offshore oil industry. The suction bucket technology used has realized the excavation-free installation of offshore barrel foundations in complex marine environments. It can be used to prevent and control the damage of seabed liquefaction to offshore barrel foundation projects, while also speeding up construction, reducing construction costs, and shortening construction periods.

[0003] In current marine engineering, suction buckets have not yet been put into use as piling devices in trenchless construction, but are more often used as the foundation form of fixed structures or temporary structures. Therefore, the relevant trenchless design calculation methods and related construction technologies need to be improved. Compared with the established models used in the research of theoretical analytical methods and numerical methods, the calculated data are more dependent on the selection of calculation parameters; and the engineering measurement method is difficult to achieve real-time monitoring of the dynamic changes of the seabed, and the measurement cost is high, the technical requirements are high, the monitoring is difficult, and it is highly dependent on environmental conditions. Given that the model test under normal gravity does not affect the microstructure of the soil, and the penetration speed of the bucket foundation and the suction bucket foundation installation device and the friction between the bucket wall and the soil are consistent with the test conditions, it can effectively simulate the sinking process of the bucket foundation and the suction bucket foundation installation device in actual engineering to achieve the test purpose.

[0004] Therefore, in order to improve the trenchless design calculation method and related construction technology, determine the negative pressure required for the offshore bucket foundation penetration, the penetration speed, the frictional resistance between the bucket wall and the soil, and the distance between the bucket foundation and the suction bucket foundation installation device, a model test device simulating the offshore bucket foundation and a penetration test method are urgently needed. Summary of the invention

[0005] In order to overcome the above-mentioned deficiencies of the prior art, the present invention provides a simulated offshore barrel foundation test model device and a penetration test method.

[0006] The technical solution adopted by the present invention to solve its technical problem is:

[0007] On one hand, the present invention provides a simulated offshore bucket foundation test model device, comprising a test system, a water supply system and a negative pressure regulating system; the test system comprises a model box, a suction bucket foundation installation device, a bucket foundation and a wave-breaking plate; the water supply system comprises an automatic water level control device and a water supply device; the negative pressure regulating system comprises a water-gas separation device and a vacuum pump;

[0008] The model box is composed of five pieces of organic glass at the front, back, left, right and bottom, so that the test situation in the model box can be observed in real time. The organic glass is sealed and connected by glass glue; a water inlet valve is provided at the bottom of the side of the model box, so that water can be supplied from bottom to top into the model box to prepare saturated soil; a sand and gravel layer, a steel wire mesh and a geotextile of a certain thickness are arranged in sequence from bottom to top in the model box; saturated soil is located above the geotextile; air-free water at a certain height from the surface of the saturated soil is filled into the model box; the saturated soil simulates the seabed; and the air-free water simulates the seawater environment;

[0009] The suction type barrel foundation installation device is a PVC barrel composed of a cover plate and a suction barrel body; the cover plate is provided with a through vent hole and a first vacuum gauge valve; the vent hole is provided with an air extraction valve, and the vent hole is used to connect the suction type barrel foundation installation device and the negative pressure regulating system; the bottom of the first vacuum gauge valve is provided with a water and mud blocking protection device, and the first vacuum gauge valve is used to monitor the air pressure state in the suction type barrel foundation installation device in real time;

[0010] The barrel foundation is a PVC barrel without a bottom or a cover; the barrel foundation can be fixed on the outside of the suction barrel body by mechanical buckles and abut against the cover plate of the suction barrel foundation installation device; the central axes of the suction barrel foundation installation device and the barrel foundation coincide and are both placed in the central area of ​​the model box; at least one row of micro pore water pressure sensors is fixed on the outer wall of the barrel foundation at a certain distance in the vertical direction;

[0011] The wave-breaking plate is installed parallel to and close to one side of the model box, inserted into the soil layer to a certain depth, and the bottom of the grid opening is slightly higher than the saturated soil surface, so as to eliminate the influence of the violent water level fluctuation generated during water supply on the test; an automatic water level control device is installed on the upper part of the side of the model box parallel to and close to the wave-breaking plate, and the automatic water level control device penetrates into the airless water to a certain depth;

[0012] The water-gas separation device consists of a second vacuum gauge valve, an air inlet, an air outlet and a water-gas separation bottle; the water-gas separation bottle is provided with an air inlet valve and a water and mud discharge valve; the second vacuum gauge valve is used to monitor the negative pressure state in the water-gas separation bottle in real time; the air inlet is connected to the air vent of the suction-type barrel foundation installation device through an air pipe; the air outlet is connected to the vacuum pump through an air pipe; the negative pressure value of the vacuum pump is controlled by a negative pressure regulating gauge valve.

[0013] Furthermore, if the strength of the connection between the five pieces of plexiglass at the front, back, left, right and bottom of the model box is insufficient, angle steel can be used for reinforcement; the wire mesh is made of stainless steel; the volume of saturated soil and airless water in the test system is determined by the volume of the model box, the height of the barrel foundation and the penetration depth; the size of the suction barrel foundation installation device can be determined by the size of the barrel foundation prototype using a similar principle; the cover plate of the suction barrel foundation installation device is made integrally with the suction barrel body; the cover plate diameter of the suction barrel foundation installation device must be larger than the outer diameter of the barrel foundation; the upper end surface of the barrel foundation is against the cover plate of the suction barrel foundation installation device and then fixed by mechanical buckles, so that the two are fixed and penetrate into the saturated soil together; the vent is connected to the air inlet through an air pipe, so that the suction barrel foundation installation device is sealed and connected to the water-gas separation device; the suction barrel foundation installation device and the barrel foundation are both PVC barrels, and the deformation of the soil in the barrel can be observed, and there is a certain distance between the barrel foundation and the suction barrel body.

[0014] Furthermore, the wave-breaking plate is a steel plate, and the distance between the wave-breaking plate and the organic glass plate parallel and close thereto is determined by the water inlet demand, so as to reduce the adverse effect of the violent fluctuation of the water level caused by the water inlet into the model box on the test; the wave-breaking plate has a long grid opening and a short grid opening, and the upper and lower short grid openings constitute a group, which are evenly distributed on the wave-breaking plate with the long grid openings.

[0015] Furthermore, the water supply device in the water supply system is used to replenish air-free water in the model box; a float is provided in the automatic water level control device, and the height of the float changes with the water level line in the model box; when the water level line drops, the height of the float drops with the water level line, and when the water level line is lower than the preset water level, the automatic water level control device is turned on, and the water supply device supplies water; when the water level line slowly rises, the height of the float rises with the water level line, and when the water level line reaches the preset water level, the automatic water level control device is turned off, and the water supply device stops supplying water.

[0016] Furthermore, the length of the air inlet pipe in the water-gas separation device in the negative pressure regulating system that penetrates into the bottle should be longer than the length of the air outlet pipe that penetrates into the bottle. The second vacuum gauge valve is installed on the top of the water-gas separation device to monitor the negative pressure value in the water-gas separation device. During the entire test process, the mud and liquid height in the water-gas separation bottle should be lower than the height of the air outlet pipe outlet in the bottle.

[0017] Another aspect of the present invention provides a method for simulating an offshore bucket foundation penetration test using the above device, the method comprising the following steps:

[0018] (1) Assemble the test device: fix at least one row of micro pore water pressure sensors at a certain distance along the vertical direction on the outer wall of the barrel foundation and arrange displacement monitoring points on the cover plate of the suction barrel foundation installation device; set up a wave-breaking plate on one side of the model box; assemble the automatic water level control device and the water supply device into a water supply system; and seal the air outlet of the water-gas separation device with the vacuum pump to form a negative pressure regulation system.

[0019] (2) Preparation of saturated soil: A sand and gravel layer, wire mesh and geotextile of a certain thickness are laid from the bottom of the model box from bottom to top to form a cushion layer with a larger porosity than the upper sand and soil; then a certain height of sand and soil is laid into the model box, and airless water passes through the water inlet valve and the cushion layer into the sand and soil to prepare airless saturated soil; the total height of the saturated soil depends on the height of the model box, and the wave-breaking plate must be penetrated to a certain depth in the soil layer; after the saturated soil is prepared, the water inlet valve is closed, and displacement monitoring points are set on the surface of the saturated soil.

[0020] (3) Connect the automatic water level control device to the water supply device, and fill water into the model box. When the preset water level is reached, the automatic water level control device is turned off and the water supply device automatically stops supplying water.

[0021] (4) Use mechanical clips to fix the outer bottom of the cover plate of the suction bucket foundation installation device to the upper end surface of the bucket foundation, and then slowly put the two buckets into the water. The buckets sink evenly under the action of gravity and insert into the saturated soil to a certain depth, so that the interior of the suction bucket foundation installation device becomes a sealed space to ensure a good sealing effect between the inside and outside of the two buckets during the subsequent suction process, and avoid the soil flow at the skirt end of the bucket body at the initial stage of suction, resulting in sinking and tilting.

[0022] (5) Use a sealed air pipe to connect the vent hole of the suction-type barrel foundation installation device and the air inlet of the water-gas separation device, turn on the vacuum pump, and make the suction-type barrel foundation installation device and the water-gas separation bottle in a vacuum state. Then continuously apply negative pressure to ensure that the barrel foundation and the suction-type barrel foundation installation device penetrate the soil stably and uniformly until the barrel foundation sinks to the designed elevation. Stop pumping, close the exhaust valve on the vent hole, and record the corresponding pressure.

[0023] (6) Use a data acquisition instrument to collect and record the readings of the micro pore water pressure sensor, soil surface displacement sensor and vacuum gauge in real time at the initial state of the test and during the penetration process. At the same time, monitor the displacement of the bucket after stopping the vacuum until the collected data gradually reaches a stable state. The stable state can be determined according to relevant specifications.

[0024] (7) After data collection, open the mechanical buckle that fixes the suction bucket foundation installation device, connect the air pipe on the vent hole to the air injection device and open the air extraction valve, inflate the suction bucket foundation installation device and pull it out. During the pulling-out process, monitor the displacement of the soil surface in the model box. After the suction bucket foundation installation device is pulled out, perform a verticality test on the bucket foundation.

[0025] (8) To ensure the accuracy of the test and avoid contingency, the above steps (1) to (7) are repeated, and the collected data are calculated and analyzed to complete the simulated offshore bucket foundation penetration test, and determine the negative pressure required for bucket foundation penetration, penetration speed, friction between the bucket wall and the soil, and the distance between the bucket foundation and the suction bucket foundation installation device.

[0026] Furthermore, in the step (1), at least one row of micro pore water pressure sensors are arranged at a certain interval along the vertical direction of the outer wall of the barrel foundation, wherein the number and spacing of the micro pore water pressure sensors are determined by the depth of the barrel foundation into the soil; when the suction-type barrel foundation installation device and the barrel foundation reach a preset elevation, all the micro pore water pressure sensors are located in the soil.

[0027] Furthermore, in step (4), the negative pressure loss rate can be obtained by comparing the first vacuum gauge valve, the second vacuum gauge valve and the negative pressure regulating gauge valve on the vacuum pump.

[0028] Furthermore, in step (5), the range of negative pressure applied is determined by controlling the barrel penetration speed in a preliminary test and the magnitude of the frictional resistance measured in the preliminary test.

[0029] Furthermore, during the test, when the mud and liquid level in the water-gas separation bottle reaches the warning height, the vacuum pump is turned off and the air inlet valve is opened to connect to the atmospheric pressure, and the mud and liquid in the bottle are discharged through the water and mud discharge valve, wherein the warning height is determined by the depth of the air outlet pipe into the bottle; in order to speed up the water and mud discharge speed, the valve connected to the air outlet pipe on the water-gas separation device can be closed while opening the air inlet valve, and air can be injected into the water-gas separation bottle through the air inlet valve.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] 1. The automatic water level control device used in the present invention can maintain the water level in the model box, objectively simulate the stable and unchanged sea level, ensure that the model test fully simulates the actual situation of the installation of the trenchless offshore bucket foundation, and is conducive to further improving the offshore bucket foundation trenchless design calculation method and related construction technology;

[0032] 2. The present invention uses air-free water in the model box to prepare saturated test soil, which prevents bubbles in the water from entering the weakly permeable soil layer and causing the unsaturated soil (compared with saturated soil, the mechanical properties of unsaturated soil are greatly different and uncertain), and can also prevent bubbles in the water from interfering with the micro pore pressure sensor and affecting its measurement accuracy;

[0033] 3. In the present invention, a gravel layer, a steel wire mesh and a geotextile with a certain thickness are sequentially arranged from bottom to top in the model box to form a cushion layer with a large porosity ratio. The airless water enters the sandy soil through the cushion layer from the water inlet valve, which is beneficial to the preparation of high-quality airless saturated soil.

[0034] 4. The present invention fixes a wave-breaking plate on one side of the model box, which can eliminate the influence of violent fluctuations generated during water supply on the stability of the water surface in the model test, avoid interfering with the test process and affecting the test results;

[0035] 5. The present invention adopts a water-gas separation device, which can provide a stable negative pressure environment inside the suction-type bucket-shaped foundation installation device, and can temporarily store a small portion of water and sand sucked out from the suction-type bucket-shaped foundation installation device in the water-gas separation device to avoid directly sucking water and sand into the vacuum pump; the negative pressure in the suction-type bucket-shaped foundation installation device can be accurately controlled by the vacuum gauge in the sealing valve of the water-gas separation device;

[0036] 6. The present invention uses the suction-type bucket foundation installation device as a pile driving device for trenchless installation, which enriches the application scope of the suction-type bucket foundation installation device, and at the same time improves the trenchless calculation formula and related construction technology for installing bucket foundations using the suction-type bucket foundation installation device in actual marine engineering. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 This is a schematic diagram of the structure of the test model device simulating an offshore barrel foundation;

[0038] Figure 2 This is the appearance diagram of the suction barrel foundation installation device;

[0039] Figure 3 It is a schematic diagram of the wave-breaking plate structure;

[0040] In the figure: model box 1, water inlet valve 1-1, gravel layer 1-2, wire mesh 1-3, geotextile 1-4, saturated soil 1-5, airless water 1-6, suction barrel foundation installation device 2, cover plate 2-1, suction barrel body 2-2, vent 2-3, first vacuum gauge valve 2-4, barrel foundation 3, micro pore water pressure sensor 3-1, wave-breaking plate 4, long grille opening 4-1, short grille opening 4-2, automatic water level control device 5, water supply device 6, water-gas separation device 7, second vacuum gauge valve 7-1, air inlet 7-2, air outlet 7-3, vacuum pump 8. DETAILED DESCRIPTION

[0041] The present invention is further described in detail below with reference to the accompanying drawings and embodiments.

[0042] like Figure 1 As shown, a simulated offshore bucket foundation test model device provided in this embodiment includes three parts: a test system, a water supply system and a negative pressure regulation system; the test system includes a model box 1, a suction bucket foundation installation device 2, a bucket foundation 3 and a wave-breaking plate 4; the water supply system includes an automatic water level control device 5 and a water supply device 6; the negative pressure regulation system includes a water-gas separation device 7 and a vacuum pump 8;

[0043] The model box 1 is composed of five pieces of organic glass at the front, back, left, right and bottom, so that the test situation in the model box 1 can be observed in real time, and the organic glass is sealed and connected by glass glue; a water inlet valve 1-1 is provided at the bottom of the side of the model box 1, which can supply water from bottom to top into the model box 1 to prepare saturated soil 1-5; a sand and gravel layer 1-2, a steel mesh 1-3 and a geotextile 1-4 of a certain thickness are arranged in sequence from bottom to top in the model box 1; saturated soil 1-5 is located above the geotextile 1-4; air-free water 1-6 at a certain height from the surface of the saturated soil 1-5 is filled in the model box 1; the saturated soil 1-5 simulates the seabed; and the air-free water 1-6 simulates the seawater environment;

[0044] like Figure 2 As shown, the suction barrel foundation installation device 2 is a PVC barrel composed of a cover plate 2-1 and a suction barrel body 2-2; the cover plate 2-1 is provided with a through vent hole 2-3 and a first vacuum gauge valve 2-4; the vent hole 2-3 is provided with an exhaust valve, and the vent hole 2-3 is used to connect the suction barrel foundation installation device 2 and the negative pressure regulating system; the bottom of the first vacuum gauge valve 2-4 is provided with a water-blocking and mud-blocking protective device, and the first vacuum gauge valve 2-4 is used to monitor the air pressure state in the suction barrel foundation installation device 2 in real time;

[0045] The barrel-shaped foundation 3 is a PVC barrel without a bottom or a cover; the barrel-shaped foundation 3 can be fixed to the outside of the suction barrel body 2-2 by mechanical buckles, and abuts against the cover plate 2-1 of the suction barrel-shaped foundation installation device 2; the central axes of the suction barrel-shaped foundation installation device 2 and the barrel-shaped foundation 3 coincide and are both placed in the central area of ​​the model box 1; at least one row of micro pore water pressure sensors 3-1 are fixed on the outer wall of the barrel-shaped foundation 3 at a certain distance in the vertical direction;

[0046] The wave-breaking plate 4 is installed parallel to and close to one side of the model box 1, inserted into the soil layer to a certain depth, and the bottom of the grid opening is slightly higher than the surface of the saturated soil 1-5, so as to eliminate the influence of the violent water level fluctuation generated during water supply on the test; an automatic water level control device 5 is installed on the upper part of the side of the model box 1 parallel to and close to the wave-breaking plate 4, and the automatic water level control device 5 penetrates into the air-free water 1-6 to a certain depth;

[0047] The water-gas separation device 7 consists of a second vacuum gauge valve 7-1, an air inlet 7-2, an air outlet 7-3 and a water-gas separation bottle; the water-gas separation bottle is provided with an air inlet valve 7-4 and a water and mud discharge valve 7-5; the second vacuum gauge valve 7-1 is used to monitor the negative pressure state in the water-gas separation bottle in real time; the air inlet 7-2 is connected to the air vent 2-3 of the suction barrel foundation installation device 2 through an air pipe; the air outlet 7-3 is connected to the vacuum pump 8 through an air pipe; the negative pressure value of the vacuum pump 8 is controlled by a negative pressure regulating gauge valve.

[0048] Specifically, if the strength of the connection between the front, back, left, right and bottom five pieces of plexiglass of the model box 1 is insufficient, angle steel can be used for reinforcement; the wire mesh 1-3 is made of stainless steel; the volume of the saturated soil 1-5 and the airless water 1-6 in the test system is determined by the volume of the model box 1, the height of the barrel foundation 3 and the penetration depth; the size of the suction barrel foundation installation device 2 can be determined by the size of the barrel foundation prototype using the similarity principle; the cover plate 2-1 of the suction barrel foundation installation device 2 is made integrally with the suction barrel body 2-2; the suction barrel foundation installation device The diameter of the cover plate 2-1 of the device 2 needs to be larger than the outer diameter of the barrel foundation 3; the upper end surface of the barrel foundation 3 is pressed against the cover plate 2-1 of the suction barrel foundation installation device 2 and then fixed by mechanical snaps, so that the two are fixed and penetrate into the saturated soil 1-5 together; the air vent 2-3 is connected to the air inlet 7-2 through an air pipe, so that the suction barrel foundation installation device 2 is sealed with the water-gas separation device 7; the suction barrel foundation installation device 2 and the barrel foundation 3 are both PVC barrels, and the deformation of the soil in the barrel can be observed, and there is a certain distance between the barrel foundation 3 and the suction barrel body 2-2.

[0049] Specifically, the wave-breaking plate 4 is a steel plate, and the distance between the wave-breaking plate 4 and the organic glass plate parallel and close thereto is determined by the water inlet demand, so as to reduce the adverse effect of the violent fluctuation of the water level caused by the water inlet into the model box 1 on the test; Figure 3 As shown, the wave-breaking plate 4 has long grille openings 4 - 1 and short grille openings 4 - 2 , and the upper and lower short grille openings 4 - 2 form a group and are evenly and alternately distributed on the wave-breaking plate 4 with the long grille openings 4 - 1 .

[0050] Specifically, the water supply device 6 in the water supply system is used to replenish the air-free water 1-6 in the model box 1; the automatic water level control device 5 is provided with a float, and the height of the float changes with the water level line in the model box 1; when the water level line drops, the height of the float drops with the water level line, and when the water level line is lower than the preset water level, the automatic water level control device 5 is turned on, and the water supply device 6 supplies water; when the water level line slowly rises, the height of the float rises with the water level line, and when the water level line reaches the preset water level, the automatic water level control device 5 is closed, and the water supply device 6 stops supplying water.

[0051] Specifically, the length of the air inlet pipe in the water-gas separation device 7 in the negative pressure regulating system that penetrates into the bottle should be longer than the length of the air outlet pipe that penetrates into the bottle. The second vacuum gauge valve 7-1 is installed on the top of the water-gas separation device 7 to monitor the negative pressure value in the water-gas separation device 7. During the entire test process, the mud liquid height in the water-gas separation bottle should be lower than the height of the air outlet pipe outlet in the bottle.

[0052] This embodiment provides a method for simulating an offshore bucket foundation penetration test using the above device, the method comprising the following steps:

[0053] (1) Figure 1 The test device is assembled as shown: at least one row of micro pore water pressure sensors 3-1 are fixed at a certain distance along the vertical direction on the outer wall of the barrel foundation 3, and displacement monitoring points are arranged on the cover plate 2-1 of the suction barrel foundation installation device 2; a wave-breaking plate 4 is set up on one side of the model box 1; the automatic water level control device 5 and the water supply device 6 are assembled into a water supply system; the air outlet 7-3 of the water-gas separation device 7 is sealed and connected with the vacuum pump 8 to form a negative pressure regulation system.

[0054] The number and spacing of the micro pore water pressure sensors 3-1 are determined by the depth of the bucket foundation 3 into the soil; when the suction bucket foundation installation device 2 and the bucket foundation 3 reach the preset elevation, all the micro pore water pressure sensors 3-1 are located in the soil.

[0055] (2) Preparation of saturated soil 1-5: A gravel layer 1-2, a wire mesh 1-3 and a geotextile 1-4 of a certain thickness are laid from the bottom of the model box 1 from bottom to top to form a cushion layer with a larger porosity than the upper sand; a certain height of sand is laid in the model box 1, and airless water 1-6 passes through the water inlet valve 1-1 and the cushion layer into the sand to prepare airless saturated soil 1-5; the total height of the saturated soil 1-5 depends on the height of the model box 1, and the wave-breaking plate 4 must penetrate a certain depth into the soil layer; after the saturated soil 1-5 is prepared, the water inlet valve 1-1 is closed, and a displacement monitoring point is set on the surface of the saturated soil 1-5.

[0056] (3) The automatic water level control device 5 is connected to the water supply device 6, and water is poured into the model box 1. When the preset water level is reached, the automatic water level control device 5 is closed, and the water supply device 6 automatically stops supplying water.

[0057] (4) Use mechanical clips to fix the outer bottom of the cover plate 2-1 of the suction-type bucket foundation installation device 2 to the upper end surface of the bucket foundation 3, and then slowly put the two buckets into the water. The bucket body sinks evenly under the action of gravity and is inserted into the saturated soil 1-5 to a certain depth, so that the interior of the suction-type bucket foundation installation device 2 becomes a sealed space to ensure that a good sealing effect is formed between the inside and outside of the two buckets during the subsequent suction process, thereby avoiding the flow of soil at the skirt end of the bucket body at the initial stage of suction, resulting in sinking and tilting.

[0058] (5) Use a sealed air pipe to connect the air vent 2-3 of the suction-type barrel foundation installation device 2 and the air inlet 7-2 of the water-gas separation device 7, turn on the vacuum pump 8, so that the suction-type barrel foundation installation device 2 and the water-gas separation bottle are both in a vacuum state, and then continuously apply negative pressure to ensure that the barrel foundation 3 and the suction-type barrel foundation installation device 2 are stably and uniformly penetrated into the soil until the barrel foundation 3 is sunk to the designed elevation, stop pumping, close the air pump valve on the air vent 2-3 and record the corresponding pressure; wherein, the range of negative pressure applied can be determined by controlling the barrel penetration speed in the preliminary test and the friction resistance measured in the preliminary test.

[0059] (6) The data acquisition instrument is used to collect and record the readings of the micro pore water pressure sensor 3-1, the soil surface displacement sensor and the vacuum gauge in real time at the initial state of the test and during the penetration process. At the same time, the displacement of the bucket is monitored after the air extraction is stopped until the collected data gradually reaches a stable state. The stable state can be determined according to relevant specifications.

[0060] (7) After data collection, open the mechanical buckle that fixes the suction-type bucket foundation installation device 2, connect the air pipe on the vent hole 2-3 to the air injection device and open the air extraction valve, inflate the suction-type bucket foundation installation device 2 to pull it out, monitor the displacement of the soil surface in the model box 1 during the pulling-out process, and perform a verticality test on the bucket foundation 3 after the suction-type bucket foundation installation device 2 is pulled out.

[0061] (8) To ensure the accuracy of the test and avoid contingency, the above steps (1) to (7) are repeated, and the collected data are calculated and analyzed to complete the simulated offshore bucket foundation penetration test, and the negative pressure required for the bucket foundation penetration, the penetration speed, the frictional resistance between the bucket wall and the soil, and the distance between the bucket foundation 3 and the suction bucket foundation installation device 2 are determined. At the same time, by comparing the first vacuum gauge valve 2-4, the second vacuum gauge valve 7-1 and the negative pressure regulating gauge valve on the vacuum pump 8, the negative pressure loss rate can be obtained.

[0062] During the test, when the mud and liquid level in the water-gas separation bottle reaches the warning height, the vacuum pump 8 is turned off and the air inlet valve 7-4 is opened to connect to the atmospheric pressure, and the mud and liquid in the bottle are discharged through the water and mud discharge valve 7-5, wherein the warning height is determined by the depth of the air outlet pipe into the bottle; in order to speed up the water and mud discharge speed, the valve connected to the air outlet pipe on the water-gas separation device 7 can be closed while opening the air inlet valve 7-4, and air can be injected into the water-gas separation bottle through the air inlet valve 7-4.

[0063] The above description is only for explaining the principle of the present invention and cannot be interpreted as limiting the protection scope of the present invention in any way. Based on the explanation here, those skilled in the art can associate other specific implementations of the present invention without creative work, and these methods will fall within the protection scope of the present invention.

Claims

1. A simulated offshore bucket foundation test model device, characterized in that: The invention comprises three parts: a test system, a water supply system and a negative pressure regulating system; the test system comprises a model box (1), a suction bucket foundation installation device (2), a bucket foundation (3) and a wave-breaking plate (4); the water supply system comprises an automatic water level control device (5) and a water supply device (6); the negative pressure regulating system comprises a water-gas separation device (7) and a vacuum pump (8); The model box (1) is composed of five pieces of organic glass at the front, back, left, right and bottom sides; a water inlet valve (1-1) is provided at the bottom of the side of the model box (1), which can supply water from the bottom to the top of the model box (1) to prepare saturated soil (1-5); a sandstone layer (1-2), a steel mesh (1-3) and a geotextile (1-4) are arranged in sequence from the bottom to the top in the model box (1); the saturated soil (1-5) is located above the geotextile (1-4); the model box (1) is filled with air-free water (1-6) above the surface of the saturated soil (1-5); the saturated soil (1-5) simulates the seabed; and the air-free water (1-6) simulates the seawater environment; The suction bucket-type foundation installation device (2) is a PVC bucket composed of a cover plate (2-1) and a suction bucket body (2-2); the cover plate (2-1) is provided with a through vent hole (2-3) and a first vacuum gauge valve (2-4); the vent hole (2-3) is provided with an air extraction valve; the bottom of the first vacuum gauge valve (2-4) is provided with a water-blocking and mud-blocking protective device for real-time monitoring of the air pressure state in the suction bucket-type foundation installation device (2); The barrel-shaped foundation (3) is a PVC barrel without a bottom or a cover; the barrel-shaped foundation (3) can be fixed to the outside of the suction barrel body (2-2) by means of a mechanical buckle, and abuts against the cover plate (2-1) of the suction barrel-shaped foundation installation device (2); the central axes of the suction barrel-shaped foundation installation device (2) and the barrel-shaped foundation (3) coincide with each other and are both placed in the central area of ​​the model box (1); at least one row of micro pore water pressure sensors (3-1) are fixed to the outer wall of the barrel-shaped foundation (3) at a certain distance in the vertical direction; The wave-breaking plate (4) is installed parallel to and close to a side of the model box (1), inserted into the soil layer to a certain depth, and the bottom of the grille opening is slightly higher than the surface of the saturated soil (1-5), so as to eliminate the influence of the violent water level fluctuation generated during water supply on the test; an automatic water level control device (5) is installed on the upper part of the side of the model box (1) parallel to and close to the wave-breaking plate (4), and the automatic water level control device (5) penetrates into the airless water (1-6) to a certain depth; The water-gas separation device (7) is composed of a second vacuum gauge valve (7-1), an air inlet (7-2), an air outlet (7-3) and a water-gas separation bottle; the water-gas separation bottle is provided with an air inlet valve (7-4) and a water and mud discharge valve (7-5); the second vacuum gauge valve (7-1) is used to monitor the negative pressure state in the water-gas separation bottle in real time; the air inlet (7-2) is connected to the air vent (2-3) of the suction bucket-type foundation installation device (2) through an air pipe; the air outlet (7-3) is connected to a vacuum pump (8) through an air pipe; the negative pressure value of the vacuum pump (8) is controlled by a negative pressure regulating gauge valve; The water supply device (6) in the water supply system is used to replenish the air-free water (1-6) in the model box (1); a float is provided in the automatic water level control device (5), and the height of the float changes with the water level line in the model box (1); when the water level line drops, the height of the float drops along with the water level line; when the water level line is lower than a preset water level, the automatic water level control device (5) is turned on, and the water supply device (6) supplies water; when the water level line slowly rises, the height of the float rises along with the water level line; when the water level line reaches the preset water level, the automatic water level control device (5) is turned off, and the water supply device (6) stops supplying water.

2. The simulated offshore bucket foundation test model device according to claim 1, characterized in that: The wave-breaking plate (4) is a steel plate, and the distance between the wave-breaking plate (4) and the organic glass plate parallel to and close to the wave-breaking plate (4) is determined by the water inflow requirement, so as to reduce the adverse effect of the violent fluctuation of the water level caused by the water inflow into the model box (1) on the test; the wave-breaking plate (4) has a long grille opening (4-1) and a short grille opening (4-2), and the upper and lower short grille openings (4-2) form a group and are evenly distributed on the wave-breaking plate (4) in an alternating manner with the long grille opening (4-1).

3. The simulated offshore bucket foundation test model device according to claim 1 is characterized in that: The length of the air inlet pipe in the water-gas separation device (7) in the negative pressure regulating system extending into the bottle should be longer than the length of the air outlet pipe extending into the bottle; during the entire test process, the height of the mud liquid in the water-gas separation bottle should be lower than the height of the outlet pipe opening in the bottle.

4. A method for simulating an offshore bucket foundation penetration test using the device according to any one of claims 1 to 3, characterized in that: The method comprises the following steps: (1) Assembling the test device: fixing at least one row of micro pore water pressure sensors (3-1) at a certain distance along the vertical direction on the outer wall of the bucket foundation (3) and arranging displacement monitoring points on the cover plate (2-1) of the suction bucket foundation installation device (2); setting up a wave-breaking plate (4) on one side of the model box (1); assembling the automatic water level control device (5) and the water supply device (6) into a water supply system; and sealingly connecting the air outlet (7-3) of the water-gas separation device (7) with the vacuum pump (8) to form a negative pressure regulation system; (2) preparing saturated soil (1-5): laying a sand and gravel layer (1-2), a steel wire mesh (1-3) and a geotextile (1-4) from the bottom of the model box (1) in order to form a cushion layer with a larger porosity than the upper sand; then laying a certain height of sand in the model box (1), and allowing airless water (1-6) to pass through the water inlet valve (1-1) and the cushion layer into the sand to prepare airless saturated soil (1-5); the total height of the saturated soil (1-5) depends on the height of the model box (1), and the wave-breaking plate (4) must penetrate a certain depth into the soil layer; after the saturated soil (1-5) is prepared, closing the water inlet valve (1-1) and setting a displacement monitoring point on the surface of the saturated soil (1-5); (3) water is poured into the model box (1) through the water supply system, and when the preset water level is reached, the automatic water level control device (5) is closed, and the water supply device (6) automatically stops supplying water; (4) Using mechanical buckles, fix the outer bottom of the cover plate (2-1) of the suction bucket foundation installation device (2) to the upper end surface of the bucket foundation (3), and then slowly put the two buckets into the water. The bucket bodies sink evenly under the action of gravity and are inserted into the saturated soil (1-5) to a certain depth, so that the interior of the suction bucket foundation installation device (2) becomes a sealed space, so as to ensure that a good sealing effect is formed between the inside and outside of the two buckets during the subsequent suction process; (5) Use a sealed air pipe to connect the vent (2-3) of the suction bucket foundation installation device (2) and the air inlet (7-2) of the water-gas separation device (7), turn on the vacuum pump (8), so that the suction bucket foundation installation device (2) and the water-gas separation bottle are both in a vacuum state, and then continuously apply negative pressure to ensure that the bucket foundation (3) and the suction bucket foundation installation device (2) are stably and uniformly penetrated into the soil until the bucket foundation (3) sinks to the designed elevation, stop pumping, close the air pumping valve on the vent (2-3), and record the corresponding pressure; (6) Using a data acquisition instrument, collect and record the readings of the micro pore water pressure sensor (3-1), the soil surface displacement sensor and the vacuum gauge in real time at the initial state of the test and during the penetration process. At the same time, monitor the displacement of the bucket after stopping the vacuum until the collected data gradually reaches a stable state; (7) After data collection, the mechanical buckle fixing the suction bucket foundation installation device (2) is opened, the air pipe on the vent hole (2-3) is connected to the air injection device and the air extraction valve is opened, air is inflated into the suction bucket foundation installation device (2) to pull it out, and the displacement of the soil surface in the model box (1) is monitored during the pulling out process. After the suction bucket foundation installation device (2) is pulled out, the verticality of the bucket foundation (3) is tested; (8) Repeat steps (1) to (7) to perform calculations and analysis on the collected data to complete the simulated offshore bucket foundation penetration test and determine the negative pressure required for the bucket foundation (3) to penetrate, the penetration speed, the frictional resistance between the bucket wall and the soil, and the distance between the bucket foundation (3) and the suction bucket foundation installation device (2).

5. The method according to claim 4, characterized in that In the step (1), the number and spacing of the micro pore water pressure sensors (3-1) are determined by the depth of the bucket foundation (3) buried in the soil; when the suction bucket foundation installation device (2) and the bucket foundation (3) reach a preset elevation, all the micro pore water pressure sensors (3-1) are located in the soil.

6. The method according to claim 4, characterized in that In the step (4), the negative pressure loss rate can be obtained by comparing the first vacuum gauge valve (2-4), the second vacuum gauge valve (7-1) and the negative pressure regulating gauge valve on the vacuum pump (8).

7. The test method according to claim 4, characterized in that: In the step (5), the range of negative pressure applied is determined by controlling the barrel penetration speed in the preliminary test and the frictional resistance measured in the preliminary test.

8. The method according to claim 4, characterized in that During the test, when the mud and liquid level in the water-gas separation bottle reaches the warning height, the vacuum pump (8) is turned off and the air inlet valve (7-4) is opened to connect to the atmospheric pressure, and the mud and liquid in the bottle are discharged through the water and mud discharge valve (7-5); in order to speed up the water and mud discharge speed, the valve connected to the air outlet pipe on the water-gas separation device (7) can be closed while opening the air inlet valve (7-4), and air can be injected into the water-gas separation bottle through the air inlet valve (7-4).

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