CN112195986A - Offshore barrel type foundation simulation test model device and penetration test method - Google Patents
Offshore barrel type foundation simulation test model device and penetration test method Download PDFInfo
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- CN112195986A CN112195986A CN202011065205.XA CN202011065205A CN112195986A CN 112195986 A CN112195986 A CN 112195986A CN 202011065205 A CN202011065205 A CN 202011065205A CN 112195986 A CN112195986 A CN 112195986A
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Abstract
The invention discloses a test model device for simulating an offshore bucket foundation and a penetration test method, wherein the device comprises a test system, a water supply system and a negative pressure regulating system; the test system comprises a model box, a suction type barrel-shaped foundation mounting device, a barrel-shaped foundation and a wave-absorbing 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 separating device and a vacuum pump; the automatic water level control device can maintain the water level height in the model box and objectively simulate the situation that the sea level is stable and unchanged; the water-gas separation device provides a stable negative pressure environment for the interior of the suction type barrel-shaped foundation installation device, and can prevent water and sand from being directly sucked into the vacuum pump; the invention can be used for simulating the penetration process of the offshore bucket foundation in the marine environment, researching the penetration speed of the offshore bucket foundation, the frictional resistance between the bucket wall and the soil body and the negative pressure required by penetration, and perfecting the excavation-free design calculation method and the related construction technology.
Description
Technical Field
The invention relates to an offshore bucket foundation penetration test device which can be used for simulating the penetration process of an offshore bucket foundation in a marine environment, researching the penetration speed of the offshore bucket foundation, the frictional resistance between a bucket wall and a soil body and the negative pressure required by penetration, and perfecting a non-excavation design calculation method and related construction technologies.
Background
In recent years, the offshore bucket foundation is widely applied to ocean engineering such as an oil extraction platform foundation, a wind power tower foundation, a breakwater foundation, harbor construction and the like in the marine oil industry, the adopted suction bucket technology realizes the excavation-free installation of the offshore bucket foundation in a complex ocean environment, can be used for preventing and treating the damage of seabed liquefaction to the offshore bucket foundation engineering, and can also accelerate the construction speed, reduce the construction cost and shorten the construction period.
In the current ocean engineering, a suction barrel is not used as a piling device in excavation-free construction, and is more used as a basic form of a fixed structure or a temporary structure, so that a relevant excavation-free design calculation method and a relevant construction technology are still to be perfected, and compared with a theoretical analytical method and a numerical method, a set model is adopted for research, and calculated data has greater dependence on calculation parameters; the real-time monitoring of the dynamic change of the seabed is difficult to realize by the method of engineering actual measurement, and the method has the advantages of high actual measurement cost, high technical requirement index, high monitoring difficulty and great dependence on environmental conditions. In view of the fact that the soil body microstructure is not influenced by the normal gravity lower model test, the penetration speed of the installation device of the bucket foundation and the suction bucket foundation and the frictional resistance between the bucket wall and the soil body are consistent with the test condition, the sinking and penetrating process of the installation device of the bucket foundation and the suction bucket foundation in the actual engineering can be effectively simulated, and therefore the test purpose is achieved.
Therefore, in order to perfect a non-excavation design calculation method and a related construction technology and determine the negative pressure and the penetration speed required by the penetration of the offshore bucket foundation, the magnitude of the frictional resistance between the bucket wall and the soil body and the distance between the bucket foundation and the suction bucket foundation installation device, a simulation offshore bucket foundation model test device and a penetration test method are urgently needed.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention provides a test model device for simulating an offshore bucket foundation and a penetration test method.
The technical scheme adopted by the invention for solving the technical problems is as follows:
the invention provides a test model device for simulating an offshore bucket foundation, which comprises a test system, a water supply system and a negative pressure adjusting system; the test system comprises a model box, a suction type barrel-shaped foundation mounting device, a barrel-shaped foundation and a wave-absorbing plate; the water supply system comprises an automatic water level control device and a water supply device; the negative pressure adjusting system comprises a water-gas separating device and a vacuum pump;
the model box consists of five pieces of organic glass at the front, the back, the left and the right and at the bottom, so that the test condition in the model box can be observed in real time, and the organic glass is connected with each other in a sealing way through glass cement; a water inlet valve is arranged at the bottom of the side surface of the model box and can supply water into the model box from bottom to top to prepare saturated soil; a sandstone layer, a steel wire mesh and geotextile with certain thickness are sequentially arranged in the model box from bottom to top; saturated soil is arranged above the geotextile; airless water with a certain height from the surface of saturated soil is injected into the model box; the saturated soil simulates a seabed; the waterless simulation seawater environment;
the suction type barrel-shaped foundation mounting device is a PVC barrel formed by combining a cover plate and a suction barrel body; the cover plate is provided with a through air vent and a first vacuum meter valve; the air vent is provided with an air exhaust valve and is used for communicating the suction type barrel-shaped foundation mounting device with the negative pressure adjusting 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 for monitoring the air pressure state in the suction type bucket foundation installation device in real time;
the barrel-shaped foundation is a PVC barrel without a bottom and a cover; the bucket foundation can be fixed on the outer side of the suction bucket body through a mechanical buckle and abuts against a cover plate of the suction bucket foundation mounting device; the suction type barrel-shaped foundation mounting device is superposed with the central axis of the barrel-shaped foundation and is placed in the central area of the model box; at least one row of micro pore water pressure sensors are fixed on the outer wall of the barrel-shaped foundation along the vertical direction at a certain distance;
the wave-absorbing plate is arranged in parallel and close to one side surface of the model box, is inserted into a soil layer for a certain depth, and the bottom of the opening of the grating is slightly higher than the surface of saturated soil, so that the influence of severe water level fluctuation generated during water supply on a test is eliminated; installing an automatic water level control device on the upper part of the side surface of the model box which is parallel to and close to the wave-absorbing plate, wherein the automatic water level control device is deeply inserted into the airless water to a certain depth;
the water-gas separation device consists of a second vacuum meter valve, a gas inlet, a gas outlet and a water-gas separation bottle; the water-gas separation bottle is provided with an air inlet valve and a water and sludge discharge valve; the second vacuum meter valve is used for monitoring the negative pressure state in the water-gas separation bottle in real time; the air inlet is communicated with the air vent of the suction type barrel-shaped foundation mounting device through an air pipe; the air outlet is communicated with a vacuum pump through an air pipe; the vacuum pump is controlled by a negative pressure regulating meter valve to control the negative pressure value.
Furthermore, if the strength of the joints of the five organic glasses at the front, the rear, the left, the right and the bottom of the model box is insufficient, angle steel can be adopted for reinforcement; the steel wire mesh is made of stainless steel; the volume of saturated soil and water-free in the test system is determined according to the volume of the model box, the height of the bucket foundation and the penetration depth; the size of the suction type barrel-shaped foundation mounting device can be determined by the size of a barrel-shaped foundation prototype by utilizing a similar principle; the cover plate of the suction type barrel-shaped foundation mounting device and the suction type barrel body are integrally manufactured; the diameter of a cover plate of the suction type bucket foundation mounting device is required to be larger than the outer diameter of the bucket foundation; the upper end surface of the barrel-shaped foundation props against a cover plate of the suction barrel-shaped foundation mounting device and then is fixed by a mechanical buckle, so that the barrel-shaped foundation and the cover plate are fixed and then are together penetrated into saturated soil; the air vent is connected with an air inlet through an air pipe, so that the suction type barrel-shaped foundation mounting device is hermetically connected with the water-air separation device; the suction type bucket foundation installation device and the bucket foundation are both PVC buckets, the deformation of soil in the buckets can be observed, and a certain distance exists between the bucket foundation and the suction bucket body.
Furthermore, the wave absorbing plate is a steel plate, and the distance between the wave absorbing plate and the organic glass plate which is parallel to and close to the wave absorbing plate is determined by the water inlet requirement, so that the adverse effect of severe fluctuation of the water level caused by water inlet in the model box on the test is reduced; the wave-absorbing plate is provided with long grating openings and short grating openings, and the upper short grating openings and the lower short grating openings form a group and are uniformly distributed on the wave-absorbing plate at intervals with the long grating openings.
Further, a water supply device in the water supply system is used for supplementing airless water to the model box; a floater is arranged in the automatic water level control device, and the height of the floater changes along with the water level line in the model box; when the water level line descends, the height of the floater descends along with the water level line, and when the water level line is lower than a preset water level, the automatic water level control device is started to supply water to the water supply device; when the water level line rises slowly, the height of the floater rises along with the water level line, and when the water level line reaches a preset water level, the automatic water level control device is closed, and the water supply device stops supplying water.
Furthermore, the length of the air inlet pipe in the water-gas separation device in the negative pressure adjusting system extending into the bottle is longer than the length of the air outlet pipe in the bottle, and a second vacuum meter valve is arranged at the top of the water-gas separation device and used for monitoring the negative pressure value in the water-gas separation device; in the whole test process, the height of mud liquid in the water-gas separation bottle is lower than the height of the pipe orifice of the air outlet pipe in the bottle.
The invention also provides a method for simulating an offshore barrel type foundation penetration test by using the device, which comprises the following steps:
(1) assembling a test device: fixing at least one row of micro pore water pressure sensors on the outer wall of the barrel-shaped foundation along the vertical direction at a certain distance, and arranging displacement monitoring points on a cover plate of the suction type barrel-shaped foundation mounting device; erecting a wave-absorbing plate on one side of the model box; assembling the automatic water level control device and the water supply device into a water supply system; and the air outlet of the water-gas separation device is hermetically connected with a vacuum pump to form a negative pressure regulating system.
(2) Preparing saturated soil: sequentially laying a sandstone layer, a steel wire mesh and geotextile with certain thickness from bottom to top of the bottom of the model box to form a cushion layer with a pore ratio larger than that of sandy soil on the upper part; then sand with a certain height is paved in the model box, and airless water enters the sand through the water inlet valve and the cushion layer to prepare airless saturated soil; the total height of the saturated soil is determined according to the height of the model box, and the wave-absorbing plate is required to be embedded into the soil layer for a certain depth; and after the saturated soil is prepared, closing the water inlet valve, and arranging a displacement monitoring point on the surface of the saturated soil.
(3) And connecting the automatic water level control device with the water supply device, injecting water into the model box, closing the automatic water level control device when the preset water level is reached, and automatically stopping water supply of the water supply device.
(4) Utilize mechanical buckle to fix the outer edge bottom of the apron of barrel-shaped basic installation device of suction formula with the up end of barrel-shaped basis, then slowly put into the aquatic with two buckets, the staving evenly sinks under the action of gravity and inserts the certain degree of depth of saturated soil for the inside confined space that becomes of barrel-shaped basic installation device of suction formula, form better sealed effect with the outside between inside two buckets of suction in-process after guaranteeing, avoid leading to sinking to run through the slope at suction initial stage staving skirt end soil body flow.
(5) A sealed air pipe is adopted to connect an air vent of the suction type bucket foundation installation device and an air inlet of the water-gas separation device, a vacuum pump is started to enable the interior of the suction type bucket foundation installation device and the interior of the water-gas separation bottle to be in a vacuum state, then negative pressure is continuously applied to ensure that the bucket foundation and the suction type bucket foundation installation device stably and uniformly penetrate into a soil body until the bucket foundation is sunk to a designed elevation, air suction is stopped, an air suction valve on the air vent is closed, and corresponding pressure intensity is recorded.
(6) And (3) acquiring and recording the readings of the micro pore water pressure sensor, the soil body surface displacement sensor and the vacuum meter in real time by using a data acquisition instrument in an initial test state and in a penetration process, and simultaneously monitoring the displacement of the barrel after stopping pumping until the acquired data gradually reach a stable state, wherein the stable state can be determined according to relevant specifications.
(7) And after data are collected, opening a mechanical buckle of the fixed suction type barrel-shaped foundation mounting device, connecting an air pipe on the air vent with the air injection device, opening an air extraction valve, inflating the suction type barrel-shaped foundation mounting device to extract the suction type barrel-shaped foundation mounting device, monitoring the surface displacement of soil in the mold box in the extraction process, and detecting the verticality of the barrel-shaped foundation after the suction type barrel-shaped foundation mounting device is extracted.
(8) In order to ensure the accuracy of the test and avoid the contingency, the steps (1) to (7) are repeated, the collected data are calculated and analyzed, the penetration test for simulating the offshore bucket foundation is completed, and the negative pressure, the penetration speed, the frictional resistance between the bucket wall and the soil body and the distance between the bucket foundation and the suction bucket foundation installation device are determined.
Further, in the step (1), at least one row of micro pore water pressure sensors are arranged along the vertical direction of the outer wall of the barrel-shaped foundation at certain intervals, wherein the number and the intervals of the micro pore water pressure sensors are determined by the soil penetration depth of the barrel-shaped foundation; when the suction type barrel-shaped foundation installation device and the barrel-shaped foundation reach the preset elevation, all the micro pore water pressure sensors are positioned in the soil body.
Further, in the step (4), the loss rate of the negative pressure 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.
Further, in the step (5), the range of the applied negative pressure is determined by controlling the barrel body penetration speed in the pre-test and the measured frictional resistance in the pre-test.
Further, in the test process, when the height of the mud liquid in the water-gas separation bottle reaches the warning height, the vacuum pump is closed, the air inlet valve is opened to communicate with the atmospheric pressure, the mud liquid in the bottle is discharged through the water and mud discharging valve, and the warning height is determined by the depth of the air outlet pipe penetrating into the bottle; in order to accelerate the speed of water and mud drainage, the air inlet valve is opened and the valve communicated with the air outlet pipe on the water-gas separation device is closed at the same time, and air is injected into the water-gas separation bottle through the air inlet valve.
Compared with the prior art, the invention has the beneficial effects that:
1. the automatic water level control device adopted by the invention can maintain the water level height in the model box, can objectively simulate the situation that the sea level is stable and unchanged, ensures that the model test fully simulates the real situation of the installation of the excavation-free offshore bucket foundation, and is favorable for further perfecting the excavation-free design calculation method and the related construction technology of the offshore bucket foundation;
2. according to the invention, the saturation test soil body is prepared in the model box by adopting the non-air water, so that the problem of non-saturation of the soil body caused by the fact that air bubbles in water enter a weak water permeability soil layer is avoided (compared with saturated soil, the mechanical properties of the unsaturated soil have larger difference and uncertainty), and the influence of the air bubbles in water on the measurement precision of the micro pore pressure sensor can also be avoided;
3. according to the invention, a gravel layer, a steel wire mesh and geotextile with certain thickness are sequentially arranged in the model box from bottom to top to form a cushion layer with a larger pore-gap ratio, and airless water enters sand soil from a water inlet valve and penetrates through the cushion layer, so that high-quality airless saturated soil can be prepared;
4. according to the invention, the wave-absorbing plate is fixed on one side in the model box, so that the influence of severe fluctuation generated in water supply on the stability of the water surface in the model test can be eliminated, the test process is prevented from being interfered, and the test result is prevented from being influenced;
5. the invention adopts the water-gas separation device, and the water-gas separation device can provide a stable negative pressure environment for the interior of the suction type barrel-shaped foundation installation device, and can temporarily store a small part of water and sand sucked out from the suction type barrel-shaped foundation installation device in the water-gas separation device, thereby avoiding directly sucking the water and the sand into the vacuum pump; the vacuum gauge in the sealing valve of the water-gas separation device can accurately control the negative pressure in the suction type barrel-shaped foundation installation device;
6. the invention takes the suction type barrel-shaped foundation installation device as the excavation-free pile driving device, enriches the application range of the suction type barrel-shaped foundation installation device, and simultaneously perfects the excavation-free calculation formula and the related construction technology for installing the barrel-shaped foundation by using the suction type barrel-shaped foundation installation device in the actual ocean engineering.
Drawings
FIG. 1 is a schematic structural diagram of a test model device for simulating an offshore bucket foundation;
FIG. 2 is an external view of a suction bucket foundation mounting device;
FIG. 3 is a schematic structural view of a wave-absorbing plate;
in the figure: the device comprises a model box 1, a water inlet valve 1-1, a sand layer 1-2, a steel wire mesh 1-3, geotextile 1-4, saturated soil 1-5, airless water 1-6, a suction type barrel-shaped foundation installation device 2, a cover plate 2-1, a suction type barrel body 2-2, a vent hole 2-3, a first vacuum meter valve 2-4, a barrel-shaped foundation 3, a micro pore water pressure sensor 3-1, a wave-absorbing plate 4, a long grid opening 4-1, a short grid opening 4-2, an automatic water level control device 5, a water supply device 6, a water-gas separation device 7, a second vacuum meter valve 7-1, a gas inlet 7-2, a gas outlet 7-3 and a vacuum pump 8.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings and examples.
As shown in fig. 1, the test model device for simulating an offshore bucket foundation provided by the embodiment includes a test system, a water supply system and a negative pressure regulating system; the test system comprises a model box 1, a suction type barrel-shaped foundation installation device 2, a barrel-shaped foundation 3 and a wave-absorbing 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 separating device 7 and a vacuum pump 8;
the model box 1 consists of five pieces of organic glass at the front, the back, the left and the right and at the bottom, the test condition in the model box 1 can be observed in real time, and the organic glass is connected in a sealing way through glass cement; a water inlet valve 1-1 is arranged at the bottom of the side surface of the model box 1 and can supply water into the model box 1 from bottom to top to prepare saturated soil 1-5; sequentially arranging a sandstone layer 1-2, a steel wire mesh 1-3 and geotextile 1-4 with certain thickness in the model box 1 from bottom to top; 1-5 parts of saturated soil is arranged above the geotextile 1-4; the model box 1 is filled with airless water 1-6 with a certain height from the surface of saturated soil 1-5; the saturated soil 1-5 simulates a seabed; the waterless 1-6 simulates a seawater environment;
as shown in fig. 2, the suction bucket foundation mounting 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 air vent 2-3 and a first vacuum meter valve 2-4; an air suction valve is arranged on the vent hole 2-3, and the vent hole 2-3 is used for communicating the suction type barrel-shaped foundation installation device 2 with the negative pressure adjusting system; the bottom of the first vacuum gauge valve 2-4 is provided with a water and mud blocking protection device, and the first vacuum gauge valve 2-4 is used for monitoring the air pressure state in the suction type barrel-shaped foundation installation device 2 in real time;
the barrel-shaped foundation 3 is a PVC barrel without a bottom and a cover; the barrel-shaped foundation 3 can be fixed on the outer side of the suction barrel body 2-2 through 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 type barrel-shaped foundation installation device 2 and the barrel-shaped foundation 3 are superposed and are 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 along the vertical direction at a certain distance;
the wave-absorbing plate 4 is arranged in parallel and close to one side surface of the model box 1, is inserted into a soil layer for a certain depth, and the bottom of the opening of the grating is slightly higher than the surface of saturated soil 1-5 so as to eliminate the influence of severe water level fluctuation generated in water supply on the test; an automatic water level control device 5 is arranged on the upper part of the side surface of the model box 1 which is parallel to and close to the wave-absorbing plate 4, and the automatic water level control device 5 is deeply inserted into the water-free 1-6 for a certain depth;
the water-gas separation device 7 consists of a second vacuum meter valve 7-1, a gas inlet 7-2, a gas 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 sludge discharge valve 7-5; the second vacuum meter valve 7-1 is used for monitoring the negative pressure state in the water-gas separation bottle in real time; the air inlet 7-2 is communicated with an air vent 2-3 of the suction type barrel-shaped foundation installation device 2 through an air pipe; the air outlet 7-3 is communicated with a vacuum pump 8 through an air pipe; the vacuum pump 8 is controlled by a negative pressure regulating meter valve to control the negative pressure value.
Specifically, if the strength of the joints of the five organic glasses at the front, the rear, the left, the right and the bottom of the model box 1 is insufficient, angle steel can be adopted for reinforcement; the steel wire meshes 1-3 are made of stainless steel; the volume of saturated soil 1-5 and non-aqueous water 1-6 in the test system is determined according to the volume of the model box 1, the height and the penetration depth of the bucket foundation 3; the size of the suction type barrel-shaped foundation mounting device 2 can be determined by the size of a barrel-shaped foundation prototype by utilizing a similar principle; the cover plate 2-1 of the suction type barrel-shaped foundation installation device 2 is integrally manufactured with the suction barrel body 2-2; the diameter of a cover plate 2-1 of the suction type barrel-shaped foundation installation device 2 is required to be larger than the outer diameter of the barrel-shaped foundation 3; the upper end surface of the barrel-shaped foundation 3 props against a cover plate 2-1 of the suction barrel-shaped foundation installation device 2 and then is fixed by a mechanical buckle, so that the two parts are fixed and then are together penetrated into saturated soil 1-5; the air vent 2-3 is connected with the air inlet 7-2 through an air pipe, so that the suction type barrel-shaped foundation installation device 2 is hermetically connected with the water-gas separation device 7; the suction type bucket foundation installation device 2 and the bucket foundation 3 are both PVC buckets, the deformation of soil in the buckets can be observed, and a certain distance exists between the bucket foundation 3 and the suction bucket body 2-2.
Specifically, the wave-absorbing plate 4 is a steel plate, and the distance between the wave-absorbing plate 4 and the organic glass plate which is parallel to and close to the wave-absorbing plate is determined by the water inlet requirement, so that the adverse effect of severe fluctuation of the water level caused by water inlet in the model box 1 on the test is reduced; as shown in FIG. 3, the wave-absorbing plate 4 has long grating openings 4-1 and short grating openings 4-2, and the upper and lower short grating openings 4-2 form a group and are uniformly distributed on the wave-absorbing plate 4 at intervals with the long grating openings 4-1.
Specifically, a water supply device 6 in the water supply system is used for supplementing airless water 1-6 into the model box 1; a floater is arranged in the automatic water level control device 5, and the height of the floater changes along with the water level line in the model box 1; when the water level line descends, the height of the floater descends along 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 started, and the water supply device 6 supplies water; when the water level line rises slowly, the height of the floater rises along with the water level line, and when the water level line reaches a preset water level, the automatic water level control device 5 is closed, and the water supply device 6 stops supplying water.
Specifically, the length of the air inlet pipe penetrating into the bottle in the water-gas separation device 7 in the negative pressure regulation system is longer than the length of the air outlet pipe penetrating into the bottle, and a second vacuum meter valve 7-1 is installed at the top of the water-gas separation device 7 and used for monitoring the negative pressure value in the water-gas separation device 7; in the whole test process, the height of mud liquid in the water-gas separation bottle is lower than the height of the pipe orifice of the air outlet pipe in the bottle.
The method for simulating the penetration test of the offshore bucket foundation by using the device provided by the embodiment comprises the following steps:
(1) the test apparatus was assembled as shown in fig. 1: fixing at least one row of micro pore water pressure sensors 3-1 on the outer wall of the barrel-shaped foundation 3 along the vertical direction at a certain distance, and arranging displacement monitoring points on a cover plate 2-1 of the suction type barrel-shaped foundation installation device 2; erecting a wave-absorbing 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 an air outlet 7-3 of the water-gas separation device 7 is hermetically connected with a vacuum pump 8 to form a negative pressure regulating system.
Wherein, the number and the spacing of the micro pore water pressure sensors 3-1 are determined by the depth of the barrel-shaped foundation 3; when the suction type barrel-shaped foundation installation device 2 and the barrel-shaped foundation 3 reach the preset elevation, all the micro pore water pressure sensors 3-1 are positioned in the soil body.
(2) Preparing saturated soil 1-5: sequentially arranging a sand-stone layer 1-2, a steel wire mesh 1-3 and geotextile 1-4 with certain thickness from bottom to top at the bottom of the model box 1 to form a cushion layer with a sand-soil pore ratio larger than that of the upper part; then, sand with a certain height is paved in the model box 1, and airless water 1-6 enters the sand through the water inlet valve 1-1 and the cushion layer to prepare airless saturated soil 1-5; the total height of the saturated soil 1-5 is determined according to the height of the model box 1, and the wave-absorbing plate 4 is required to be embedded into the soil layer for a certain depth; and after the saturated soil 1-5 is prepared, closing the water inlet valve 1-1, and arranging a displacement monitoring point on the surface of the saturated soil 1-5.
(3) And connecting the automatic water level control device 5 with the water supply device 6, injecting water into the model box 1, closing the automatic water level control device 5 when the preset water level is reached, and automatically stopping water supply of the water supply device 6.
(4) The bottom of the outer edge of a cover plate 2-1 of a suction type barrel-shaped foundation installation device 2 is fixed with the upper end face of a barrel-shaped foundation 3 through a mechanical buckle, then two barrels are slowly put into water, the barrel bodies sink uniformly under the action of gravity and are inserted into saturated soil by a certain depth of 1-5, so that the inside of the suction type barrel-shaped foundation installation device 2 becomes a sealed space, a better sealing effect is formed between the inside and the outside of the two barrels in the later suction process, and the problem that the skirt end of the barrel body is sunk and inclined due to soil body flowing in the suction initial stage is avoided.
(5) Connecting an air vent 2-3 of a suction type barrel-shaped foundation installation device 2 and an air inlet 7-2 of a water-gas separation device 7 by adopting a sealed air pipe, starting a vacuum pump 8 to ensure that the interior of the suction type barrel-shaped foundation installation device 2 and a water-gas separation bottle are in a vacuum state, continuously applying negative pressure to ensure that the barrel-shaped foundation 3 and the suction type barrel-shaped foundation installation device 2 stably and uniformly penetrate into a soil body until the barrel-shaped foundation 3 sinks to a designed elevation, stopping air suction, closing an air suction valve on the air vent 2-3 and recording the corresponding pressure intensity; wherein, the range of the applied negative pressure can be determined by controlling the barrel body penetration speed in the pre-test and the friction resistance measured in the pre-test.
(6) The data acquisition instrument is used for acquiring and recording the readings of the micro pore water pressure sensor 3-1, the soil body surface displacement sensor and the vacuum meter in real time in the initial test state and the penetration process, and meanwhile, after the air exhaust is stopped, the displacement monitoring on the barrel is carried out until the acquired data gradually reach a stable state, wherein the stable state can be determined according to relevant specifications.
(7) After data acquisition is finished, a mechanical buckle of the fixed suction type barrel-shaped foundation installation device 2 is opened, an air pipe on the air vent 2-3 is connected with an air injection device, an air extraction valve is opened, the suction type barrel-shaped foundation installation device 2 is inflated and pulled out, the surface displacement of soil in the model box 1 is monitored in the pulling-out process, and the barrel-shaped foundation 3 is subjected to perpendicularity detection after the suction type barrel-shaped foundation installation device 2 is pulled out.
(8) In order to ensure the accuracy of the test and avoid the contingency, the steps (1) to (7) are repeated, the collected data are calculated and analyzed, the penetration test for simulating the offshore barrel-shaped foundation is completed, the negative pressure, the penetration speed, the frictional resistance between the barrel wall and the soil body and the distance between the barrel-shaped foundation 3 and the suction-type barrel-shaped foundation installation device 2 required by the penetration of the barrel-shaped foundation are determined, and the loss rate of the negative pressure can be obtained by comparing the first vacuum meter valve 2-4, the second vacuum meter valve 7-1 and the negative pressure adjusting meter valve on the vacuum pump 8.
In the test process, when the height of the mud liquid in the water-gas separation bottle reaches the warning height, the vacuum pump 8 is closed, the air inlet valve 7-4 is opened to communicate with the atmospheric pressure, the mud liquid in the bottle is discharged through the water and mud discharging valve 7-5, wherein the warning height is determined by the depth of the air outlet pipe penetrating into the bottle; in order to accelerate the speed of water and sludge drainage, the air inlet valve 7-4 is opened, the valve communicated with the air outlet pipe on the water-gas separation device 7 is closed at the same time, and air is injected into the water-gas separation bottle through the air inlet valve 7-4.
The foregoing description is only for the purpose of illustrating the principles of the invention and is not to be construed in any way as limiting the scope of the invention. Based on the explanations herein, those skilled in the art will be able to conceive of other embodiments of the present invention without inventive effort, which would fall within the scope of the present invention.
Claims (10)
1. A test model device for simulating an offshore bucket foundation is characterized by comprising a test system, a water supply system and a negative pressure adjusting system; the test system comprises a model box (1), a suction type barrel-shaped foundation mounting device (2), a barrel-shaped foundation (3) and a wave-absorbing plate (4); the water supply system comprises an automatic water level control device (5) and a water supply device (6); the negative pressure adjusting system comprises a water-gas separating device (7) and a vacuum pump (8);
the model box (1) is composed of five organic glasses at the front, back, left and right sides and the bottom; a water inlet valve (1-1) is arranged at the bottom of the side surface of the model box (1) and can supply water into the model box (1) from bottom to top to prepare saturated soil (1-5); a sandstone layer (1-2), a steel wire mesh (1-3) and geotextile (1-4) are sequentially distributed in the model box (1) from bottom to top; saturated soil (1-5) is arranged above the geotextile (1-4); the model box (1) is filled with airless water (1-6) higher than the surface of saturated soil (1-5); the saturated soil (1-5) simulates a seabed; the water-free (1-6) simulates a seawater environment;
the suction type barrel-shaped foundation installation device (2) is a PVC barrel formed by combining 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 meter valve (2-4); an air extraction valve is arranged on the vent hole (2-3); the bottom of the first vacuum meter valve (2-4) is provided with a water and mud blocking protection device for monitoring the air pressure state in the suction type barrel-shaped foundation installation device (2) in real time;
the barrel-shaped foundation (3) is a PVC barrel without a bottom and a cover; the barrel-shaped foundation (3) can be fixed on the outer side of the suction barrel body (2-2) through a mechanical buckle and abuts against the cover plate (2-1) of the suction barrel-shaped foundation mounting device (2); the central axes of the suction type barrel-shaped foundation mounting device (2) and the barrel-shaped foundation (3) are superposed and are 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) along the vertical direction at a certain distance;
the wave absorbing plate (4) is arranged in parallel and close to one side surface of the model box (1), is inserted into a soil layer for a certain depth, and the bottom of the opening of the grating is slightly higher than the surface of saturated soil (1-5) so as to eliminate the influence of severe water level fluctuation generated during water supply on a test; an automatic water level control device (5) is arranged on the upper part of the side surface of the model box (1) which is parallel to and close to the wave-absorbing plate (4), and the automatic water level control device (5) extends into the water (1-6) without air to a certain depth;
the water-gas separation device (7) consists of a second vacuum meter valve (7-1), a gas inlet (7-2), a gas outlet (7-3) and a water-gas separation bottle; an air inlet valve (7-4) and a drainage mud valve (7-5) are arranged on the water-gas separation bottle; the second vacuum meter valve (7-1) is used for monitoring the negative pressure state in the water-gas separation bottle in real time; the air inlet (7-2) is communicated with an air vent (2-3) of the suction type barrel-shaped foundation installation device (2) through an air pipe; the air outlet (7-3) is communicated with a vacuum pump (8) through an air pipe; the vacuum pump (8) is controlled by a negative pressure regulating meter valve to control the negative pressure value.
2. A simulated offshore bucket foundation test model set up as claimed in claim 1 wherein the volume of saturated soil (1-5) and water (1-6) in the test system is determined by the volume of the model box (1), the height and penetration depth of the bucket foundation (3); the size of the suction type barrel-shaped foundation mounting device (2) can be determined by the size of a barrel-shaped foundation prototype by utilizing a similar principle; the cover plate (2-1) of the suction type barrel-shaped foundation installation device (2) is integrally manufactured with the suction type barrel body (2-2); the diameter of a cover plate (2-1) of the suction type barrel-shaped foundation mounting device (2) needs to be larger than the outer diameter of the barrel-shaped foundation (3); the upper end surface of the barrel-shaped foundation (3) props against a cover plate (2-1) of the suction barrel-shaped foundation installation device (2) and then is fixed by a mechanical buckle, so that the two parts are fixed and then are together penetrated into saturated soil (1-5); a certain distance is reserved between the bucket foundation (3) and the suction bucket body (2-2).
3. A simulated offshore bucket foundation test model installation as claimed in claim 1, wherein the wave-absorbing plate (4) is a steel plate, the distance between the wave-absorbing plate (4) and the organic glass plate parallel and close to the wave-absorbing plate is determined by the water inlet requirement, so as to reduce the adverse effect of the severe fluctuation of the water level caused by the water inlet in the model box (1) on the test; the wave absorbing plate (4) is provided with long grating openings (4-1) and short grating openings (4-2), the upper short grating opening and the lower short grating opening (4-2) form a group, and the short grating openings and the long grating openings (4-1) are uniformly distributed on the wave absorbing plate (4) at intervals.
4. A simulated offshore bucket foundation test model installation as claimed in claim 1, wherein the water supply means (6) in the water supply system is used to replenish the model box (1) with non-aerated water (1-6); a floater is arranged in the automatic water level control device (5), and the height of the floater changes along with the water level line in the model box (1); when the water level line descends, the height of the floater descends along 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 started, and the water supply device (6) supplies water; when the water level line rises slowly, the height of the floater rises along with the water level line, when the water level line reaches a preset water level, the automatic water level control device (5) is closed, and the water supply device (6) stops supplying water.
5. A simulated offshore bucket foundation test model installation as claimed in claim 1, wherein the length of the air inlet pipe penetrating into the bottle in the water-gas separation device (7) in the negative pressure regulating system is longer than the length of the air outlet pipe penetrating into the bottle; in the whole test process, the height of mud liquid in the water-gas separation bottle is lower than the height of the pipe orifice of the air outlet pipe in the bottle.
6. A method of simulating an offshore bucket foundation penetration test using the apparatus of any one of claims 1 to 5, the method comprising the steps of:
(1) assembling a test device: at least one row of micro pore water pressure sensors (3-1) are fixed on the outer wall of the barrel-shaped foundation (3) along the vertical direction at a certain distance, and displacement monitoring points are arranged on a cover plate (2-1) of the suction type barrel-shaped foundation installation device (2); erecting a wave-absorbing 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 an air outlet (7-3) of the water-gas separation device (7) is hermetically connected with a vacuum pump (8) to form a negative pressure regulating system.
(2) Preparation of saturated soil (1-5): sequentially arranging a sandstone layer (1-2), a steel wire mesh (1-3) and geotextile (1-4) from bottom to top from the bottom of the model box (1) to form a cushion layer with a sand-soil pore ratio larger than that of the upper part; then sand at a certain height is paved in the model box (1), and airless water (1-6) enters the sand through the water inlet valve (1-1) and the cushion layer to prepare airless saturated soil (1-5); the total height of the saturated soil (1-5) is determined according to the height of the model box (1), and the wave-absorbing plate (4) needs to be deeply inserted into the soil layer for a certain depth; and after the saturated soil (1-5) is prepared, closing the water inlet valve (1-1), and arranging a displacement monitoring point on the surface of the saturated soil (1-5).
(3) Water is injected into the model box (1) through a water supply system, when a 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) The bottom of the outer edge of a cover plate (2-1) of a suction type barrel-shaped foundation installation device (2) is fixed with the upper end face of a barrel-shaped foundation (3) by a mechanical buckle, then the two barrels are slowly put into water, and the barrel bodies sink uniformly under the action of gravity and are inserted into saturated soil (1-5) to a certain depth, so that the inside of the suction type barrel-shaped foundation installation device (2) becomes a sealed space, and a better sealing effect is formed between the inside and the outside of the two barrels in the later suction process.
(5) A sealed air pipe is adopted to connect an air vent (2-3) of a suction type barrel-shaped foundation installation device (2) and an air inlet (7-2) of a water-gas separation device (7), a vacuum pump (8) is started to enable the interior of the suction type barrel-shaped foundation installation device (2) and the interior of a water-gas separation bottle to be in a vacuum state, then negative pressure is continuously applied to ensure that the barrel-shaped foundation (3) and the suction type barrel-shaped foundation installation device (2) stably and uniformly penetrate into a soil body until the barrel-shaped foundation (3) is sunk to a designed elevation, air suction is stopped, an air suction valve on the air vent (2-3) is closed, and corresponding pressure intensity is recorded.
(6) And (3) acquiring and recording the readings of the micro pore water pressure sensor (3-1), the soil surface displacement sensor and the vacuum meter in real time by using a data acquisition instrument in an initial test state and in a penetration process, and simultaneously monitoring the displacement on the barrel after stopping pumping till the acquired data gradually reaches a stable state.
(7) After data acquisition is finished, a mechanical buckle of the fixed suction type barrel-shaped foundation installation device (2) is opened, an air pipe on the air vent (2-3) is connected with an air injection device, an air extraction valve is opened, the suction type barrel-shaped foundation installation device (2) is inflated to be extracted, the surface displacement of soil in the model box (1) is monitored in the extracting process, and after the suction type barrel-shaped foundation installation device (2) is extracted, perpendicularity detection is carried out on the barrel-shaped foundation (3).
(8) And (3) repeating the steps (1) to (7), calculating and analyzing the collected data, completing the penetration test of the offshore bucket foundation, and determining the negative pressure and the penetration speed required by the penetration of the bucket foundation (3), the frictional resistance between the bucket wall and the soil body and the distance between the bucket foundation (3) and the suction bucket foundation installation device (2).
7. The method according to claim 6, wherein in the step (1), the number and the spacing of the micro pore water pressure sensors (3-1) are determined by the depth of the barrel-shaped foundation (3) into the soil; when the suction type barrel-shaped foundation installation device (2) and the barrel-shaped foundation (3) reach the preset elevation, all the micro pore water pressure sensors (3-1) are positioned in the soil body.
8. The method according to claim 6, characterized in that in step (4), the loss rate of negative pressure 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).
9. The test method according to claim 6, wherein in the step (5), the range of the negative pressure to be applied is determined by controlling the barrel penetration rate in the pre-test and the magnitude of the frictional resistance measured in the pre-test.
10. The method according to claim 6, characterized in that during the test, when the mud level in the water-gas separation bottle reaches the warning level, the vacuum pump (8) is closed, the air inlet valve (7-4) is opened to communicate with the atmospheric pressure, and the mud in the bottle is discharged through the water and mud discharging valve (7-5); in order to accelerate the speed of water and sludge drainage, the air inlet valve (7-4) is opened, the valve communicated with the air outlet pipe on the water-gas separation device (7) is closed, and air is injected into the water-gas separation bottle through the air inlet valve (7-4).
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| CN202011065205.XA CN112195986A (en) | 2020-09-30 | 2020-09-30 | Offshore barrel type foundation simulation test model device and penetration test method |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114894510A (en) * | 2022-03-24 | 2022-08-12 | 清华大学 | Centrifuge test model in suction bucket foundation installation and operation process |
| CN114894509A (en) * | 2022-03-24 | 2022-08-12 | 清华大学 | Centrifuge test model for testing suction bucket foundation |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114894510A (en) * | 2022-03-24 | 2022-08-12 | 清华大学 | Centrifuge test model in suction bucket foundation installation and operation process |
| CN114894509A (en) * | 2022-03-24 | 2022-08-12 | 清华大学 | Centrifuge test model for testing suction bucket foundation |
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