MICP reinforcing flexible protection device suitable for suction anchor foundation and construction method

Abstract

The invention discloses an MICP reinforcing flexible protection device suitable for a suction anchor foundation and a construction method. The device comprises a suction anchor and a flexible protection block, the upper side of the flexible protection block is of a mushroom-umbrella-shaped structure, the lower side face of the flexible protection block is a plane, and the flexible protection block is arranged on the upper middle portion of the suction anchor in a sleeving mode during installation; a plurality of pressure sensors are fixedly installed on the lower side face of the flexible protection block, a plurality of grouting guide pipes are installed on the flexible protection block in a penetrating mode, the bottom ends of all the grouting guide pipes are located on the same horizontal plane, and the top ends of the grouting guide pipes are distributed along a mushroom-umbrella-shaped structure on the upper side of the flexible protection block. Biomineralization and structure bionic technologies are fused, MICP microorganism grouting is injected into the seabed around the suction anchor through the grouting guide pipe, the bearing performance of sand around the suction anchor is successfully enhanced, the limitation of traditional rigid reinforcement is broken through, the construction precision is improved, and the life cycle stability of the deep sea suction anchor foundation is guaranteed.

Description

Technical Field

[0001] The present invention belongs to the technical field of marine engineering, and in particular relates to a MICP reinforced flexible protective device suitable for a suction anchor foundation and a construction method. Background Art

[0002] Deep-sea suction anchor foundations face stability challenges under multiple coupling effects during long-term service: First, the soft soil layer on the seabed has the significant characteristics of high water content, high porosity and low density. Its spatial distribution heterogeneity leads to deviations between the theoretical model of soil parameters and the actual working conditions, which directly affects the accuracy of bearing capacity calculations; second, during service, the suction anchor must simultaneously withstand the static load of the superstructure and the scouring effects of dynamic processes such as deep-sea currents, internal waves, tidal currents, and extreme events such as turbidity currents, tsunamis, and deep-sea storms, which lead to the loss of surrounding soil and thus reduce its pull-out bearing capacity. At present, the design of suction anchors has not fully considered protective measures. Therefore, they are prone to tilting or pulling out under the action of scouring, causing the suction anchor to fail. Third, the penetration speed, pressure difference control and verticality deviation during the construction phase can easily destroy the integrity of the original soil structure, resulting in insufficient final penetration accuracy and stress concentration problems. Especially in complex and changeable marine environments, suction anchors are prone to tilting. Tilt not only reduces the pull-out bearing capacity of the suction anchor, but also increases its risk of scouring, thereby further exacerbating its instability and potential failure risk.

[0003] Existing reinforcement methods generally suffer from problems such as poor adaptability of rigid materials, high construction costs, and the risk of marine ecological damage. For example, traditional grouting materials are prone to brittle fracture under dynamic loads and are difficult to adapt to the rheological properties of deep-sea soils. Processes such as steel sheet pile enclosures rely on large ship engines, resulting in low economic efficiency and construction efficiency. The highly alkaline hydration reaction of cement-based materials also causes continuous damage to the marine microbial environment. The currently widely used MICP microbial-induced calcium carbonate precipitation reinforcement technology mainly focuses on the solidification treatment of shallow soils. This technology has a significant drawback when applied to suction anchor structures: the lack of a specially designed directional grouting device. Due to the lack of such a device, the slurry penetration effect during construction is uneven, which not only affects the reinforcement effect but also greatly reduces the efficiency of construction. Summary of the Invention

[0004] In order to solve the above technical problems, the present invention provides a MICP reinforcement flexible protection device suitable for suction anchor foundation and a construction method.

[0005] The technical solution of the present invention to solve the above technical problems is: A MICP reinforced flexible protective device suitable for a suction anchor foundation comprises a suction anchor and a flexible protective block. The upper side of the flexible protective block is a mushroom-shaped structure, and the lower side is a plane. The flexible protective block is sleeved on the upper middle part of the suction anchor during installation. A plurality of pressure sensors are fixedly mounted on the lower side of the flexible protective block. A plurality of grouting tubes are interspersed and installed on the flexible protective block. The bottom ends of all the grouting tubes are in the same horizontal plane, and the top ends of the grouting tubes are distributed along the mushroom-shaped structure on the upper side of the flexible protective block.

[0006] Preferably, the surface layer of the flexible protective block is made of salt-corrosion-resistant polymer composite material.

[0007] Preferably, the side wall of the grouting conduit is provided with a plurality of rows of staggered grouting holes.

[0008] Preferably, the bottom of the grouting conduit is designed to be a pointed cone.

[0009] Preferably, a plurality of pressure sensors are evenly and fixedly mounted on the bottom of the flexible protective block along its circumference.

[0010] Preferably, the method comprises the following steps: S1. sleeve the flexible protective block on the upper middle portion of the suction anchor so that the bottom horizontal surface of the flexible protective block is aligned with the pre-installed mark of the suction anchor; S2. The flexible protective block is firmly connected to the outer wall of the suction anchor; S3. Use floating crane equipment to hoist the suction anchor, equipped with a flexible device, to the designed area. Start the negative pressure penetration system. Initially, penetrate at a low speed, using the contact surface between the bottom horizontal surface of the flexible protective block and the seabed to correct verticality. Once the device reaches a depth of one-third of the anchor height, switch to high-speed penetration mode to the designed elevation. Use the built-in pressure sensor at the bottom of the flexible protective block to provide real-time feedback on the contact stress between the flexible protective block and the soil, dynamically adjusting the pressure differential.

[0011] S4. Connect a high-pressure grouting pump to the vertical grouting conduit and perform phased pressurized injection of the microbial slurry. Strictly control the grouting pressure and gradually increase it to the preset value. S5. After grouting is completed, the soil is allowed to stand for curing to allow the microorganisms in the soil to induce the production of calcium carbonate crystals, thereby achieving in-situ gradient strengthening of the soil.

[0012] Preferably, the specific process of correcting verticality is: using the initial contact between the horizontal surface of the bottom of the flexible protective block and the seabed, the contact stress distribution is fed back in real time through the pressure sensor built into the bottom of the flexible protective block. If the stress distribution is uneven, indicating that there is a tilt, the pressure difference in different areas of the negative pressure penetration system is dynamically adjusted to assist in correcting the verticality of the suction anchor.

[0013] Preferably, during the grouting process of the microbial slurry, a grouting liquid formed by mixing a deep-sea acclimated Bacillus pasteurianus liquid and a binder is used, and citric acid solution and artificial seawater-based flushing liquid are used for pretreatment before grouting. A gradient binder is used during grouting. In the first stage, a mixture of 0.6-0.9 M CaCl2 and 0.3-0.5 M urea is injected, and the salinity is adapted to ±5‰. In the second stage, a mixture of 1.0-1.4 M urea and 0.5-0.7 M CaCl2 is injected. The grouting pressure is reduced and maintained for 20-40 minutes. After completing the unilateral grouting, a nitrogen mixture containing trace oxygen is injected through the grouting pipe, and the oxygen content is 0.5%-1.0%. Pressure is applied for 10-16 hours.

[0014] Preferably, the grouting head adopts a spiral shear nozzle with a rotation speed of 10-20rpm. The grouting liquid temperature is managed before grouting to maintain the slurry temperature at 8-10°C, which is higher than the soil temperature.

[0015] The technical effects of the present invention are: (1) The upper side of the flexible protective block of the present invention is a mushroom-shaped structure, which effectively disperses the impact force of waves and currents, reduces the scouring of the suction anchor foundation soil by the current, and thus significantly improves the pull-out bearing capacity of the suction anchor.

[0016] (2) The present invention uses microbial induced calcium carbonate precipitation MICP grouting reinforcement technology to successfully enhance the bearing capacity of sand around the suction anchor, improve the mechanical properties and stability of the soil, and effectively reduce the failure probability of the suction anchor in a complex marine environment.

[0017] (3) The present invention specifically designs a MICP microbial grouting formula and construction process for sand in deep-sea low-temperature and high-pressure environments, which enhances the grouting effect, ensures the uniformity and strength of the reinforcement layer, and takes into account the protection of the marine ecological environment, not only avoiding the environmental pollution problems that may be caused by traditional reinforcement methods. The grouting process of the present invention avoids the release of harmful chemicals into the marine environment during the reinforcement process, thereby maintaining the balance and health of the marine ecosystem. In addition, by precisely controlling the grouting volume and grouting rate, the interference with the surrounding biological habitats is further reduced, achieving the dual goals of engineering safety and environmental protection. Finally, the present invention integrates the interdisciplinary technology of biomineralization and structural bionics, which not only breaks through the limitations of traditional rigid reinforcement methods, but also improves the construction accuracy, providing a full life cycle stability guarantee for deep-sea suction anchor foundations. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a structural schematic diagram of the present invention; Figure 2 It is a bottom view of the present invention; Figure 3 It is a schematic diagram of the expansion of the side holes of the small grouting tube.

[0019] In the figure, 1, suction anchor; 2, flexible protective block; 21, pressure sensor; 22, grouting catheter; 221, grouting hole. DETAILED DESCRIPTION

[0020] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0021] like Figure 1 、 2 As shown in Figure 3, a suction anchor 1 and a flexible protective block 2, the upper side of the flexible protective block 2 is a mushroom-shaped structure, and the lower side thereof is a plane. The flexible protective block 2 is sleeved on the upper middle part of the suction anchor 1 during installation; a plurality of pressure sensors 21 are fixedly installed on the lower side of the flexible protective block 2, and a plurality of grouting tubes 22 are interspersed and installed on the flexible protective block 2. The bottom ends of all the grouting tubes 22 are in the same horizontal plane, and the top ends of the grouting tubes 22 are distributed along the mushroom-shaped structure on the upper side of the flexible protective block 2. According to the principles of fluid mechanics, the mushroom-shaped structure on the upper side of the flexible protective block 2 can change the flow direction of the fluid wave flow, so that the fluid flows along the curved surface when passing through the structure, thereby effectively dispersing the impact force of the wave flow, reducing the overall impact force borne by the structure, and improving the pull-out resistance of the suction anchor 1.

[0022] A plurality of pressure sensors 21 are evenly fixedly installed along the circumference of the bottom of the flexible protective block 2; the pressure sensors 21 on the lower side of the flexible protective block 2 can provide real-time feedback on the soil contact stress. According to the data fed back by the pressure sensors 21, the installation depth and angle of the suction anchor 1 are adjusted to ensure that the suction anchor 1 always maintains the best posture during the installation process, thereby further improving the installation accuracy and stability.

[0023] Several grouting tubes 22 are installed on the flexible protective block 2. The bottom ends of all the grouting tubes 22 are in the same horizontal plane. The top ends of the grouting tubes 22 are distributed along the mushroom-shaped structure on the upper side of the flexible protective block 2. The side walls of the grouting tubes 22 are provided with several rows of staggered grouting holes 221, and the bottom of the grouting tubes 22 is designed to be a pointed cone.

[0024] Several rows of staggered grouting holes 221 opened on the side wall of the grouting conduit 22 can ensure uniform penetration of the slurry and enhance the overall strength and anti-scouring ability of the soil; the grouting conduit 22 is made of corrosion-resistant, high-strength alloy material to adapt to long-term operation requirements in complex marine environments.

[0025] A construction method for a MICP reinforced flexible protective device suitable for a suction anchor foundation comprises the following steps: S1, sleeve the flexible protection block 2 on the upper middle part of the suction anchor 1, so that the bottom horizontal surface of the flexible protection block 2 is aligned with the pre-installed mark of the suction anchor 1.

[0026] S2, use flanges or buckles to firmly connect the flexible protective block 2 to the outer wall of the suction anchor 1, so as to achieve accurate construction positioning.

[0027] S3: The suction anchor equipped with the flexible device is hoisted to the designed area through floating crane equipment, and the negative pressure penetration system is started. In the initial stage, the device penetrates at a low speed, and the verticality is automatically corrected by using the contact surface between the bottom horizontal surface of the flexible protective block 2 and the seabed. After the device is inserted into the mud to a depth of 1 / 3 of the anchor height, it is switched to high-speed penetration mode until it reaches the designed elevation. The contact stress between the flexible protective block 2 and the soil is fed back in real time through the built-in pressure sensor 21 at the bottom of the protective device 2, and the pressure difference is dynamically adjusted.

[0028] In step S4, a high-pressure grouting pump is connected to the evenly spaced grouting conduits 22 to perform a phased pressurized injection of a mixture of a microbial slurry consisting of deep-sea acclimated Bacillus pasteurianus and a cementing fluid. During the grouting process, the grouting pressure must be strictly controlled and gradually increased to a preset value to ensure that the slurry evenly penetrates deep into the soil, forming an effective reinforcement layer.

[0029] S5. After the grouting is completed, the soil is left to stand for a period of time to allow the microorganisms in the soil to induce the production of calcium carbonate crystals, thereby achieving in-situ gradient strengthening of the soil.

[0030] MICP grouting uses a grouting fluid composed of a deep-sea-acclimated Bacillus pasteurianus bacteria solution and a cementing fluid. First, the grouting is pretreated with a citric acid solution and an artificial seawater-based flushing solution. Grouting is then performed using a gradient cementing fluid. In the first stage, a mixture of 0.8 M CaCl₂ and 0.4 M urea is injected, with a salinity adjusted to ±5‰ and a higher grouting pressure. In the second stage, a mixture of 1.2 M urea and 0.6 M CaCl₂ is injected, at which point the grouting pressure is slightly reduced and maintained for 30 minutes. Single-sided grouting is then completed. Finally, a nitrogen mixture containing trace oxygen (0.5% to 1.0%) is injected through the grouting pipe at a low pressure for 12 hours to activate the anaerobic-aerobic coupled metabolic process, thereby increasing calcium carbonate yield.

[0031] During grouting, the grouting head uses a spiral shear nozzle with a rotation speed of 10-20rpm to prevent sand particles from clogging the grouting holes.

[0032] The main advantages of the present invention are reflected in the following points: First, by designing a composite functional flexible protective block 2, the impact force of waves and currents is effectively dispersed, the scouring and loss of the suction anchor foundation soil is reduced, and the pull-out bearing capacity of the suction anchor is significantly improved. Secondly, by using microbial induced calcium carbonate precipitation MICP grouting reinforcement technology, the bearing capacity of the soft sand around the suction anchor is successfully enhanced, the mechanical properties and stability of the soil are improved, and the failure probability of the suction anchor in a complex marine environment is effectively reduced. Third, for sand in the low temperature and high pressure environment of the deep sea, the present invention specially designs a MICP microbial grouting formula and construction process to enhance the grouting effect, ensure the uniformity and strength of the reinforcement layer, and take into account the protection of the marine ecological environment, not only avoiding the environmental pollution problems that may be caused by traditional reinforcement methods. The grouting process of the present invention avoids the release of harmful chemicals into the marine environment during the reinforcement process, thereby maintaining the balance and health of the marine ecosystem. In addition, by precisely controlling the grouting volume and grouting rate, the interference with the surrounding biological habitats is further reduced, achieving the dual goals of engineering safety and environmental protection. Finally, the present invention integrates the interdisciplinary technologies of biomineralization and structural bionics, which not only breaks through the limitations of traditional rigid reinforcement methods, but also improves construction accuracy and provides stability guarantee for the deep-sea suction anchor foundation throughout its life cycle.

Claims

1. A MICP reinforced flexible protective device suitable for suction anchor foundation, characterized in that: The invention comprises a suction anchor (1) and a flexible protective block (2), wherein the upper side of the flexible protective block (2) is a mushroom-shaped structure, and the lower side thereof is a plane. The flexible protective block (2) is sleeved on the upper middle part of the suction anchor (1) during installation; a plurality of pressure sensors (21) are fixedly installed on the lower side of the flexible protective block (2); a plurality of grouting conduits (22) are inserted and installed on the flexible protective block (2), the bottom ends of all the grouting conduits (22) are in the same horizontal plane, and the top ends of the grouting conduits (22) are distributed along the mushroom-shaped structure on the upper side of the flexible protective block (2).

2. The MICP reinforced flexible protective device suitable for suction anchor foundation according to claim 1, characterized in that: The surface layer of the flexible protective block (2) is made of salt corrosion resistant polymer composite material.

3. The MICP reinforced flexible protective device suitable for suction anchor foundation according to claim 1, characterized in that: The side wall of the grouting conduit (22) is provided with a plurality of rows of staggered grouting holes (221).

4. The MICP reinforced flexible protective device suitable for suction anchor foundation according to claim 1, characterized in that: The bottom of the grouting conduit (22) is designed to be a pointed cone.

5. The MICP reinforced flexible protective device suitable for suction anchor foundation according to claim 1, characterized in that: A plurality of pressure sensors (21) are evenly and fixedly mounted on the bottom of the flexible protective block (2) along its circumference.

6. A construction method for a MICP reinforced flexible protective device suitable for a suction anchor foundation, characterized in that: The following steps are involved: S1. The flexible protective block (2) is set on the upper middle part of the suction anchor (1), so that the bottom horizontal surface of the flexible protective block (2) is aligned with the pre-installed mark of the suction anchor (1); S2. The flexible protective block (2) is firmly connected to the outer wall of the suction anchor (1); S3. The suction anchor with the flexible device is hoisted to the designed area by floating crane equipment, and the negative pressure penetration system is started. In the initial stage, the device is penetrated at a low speed, and the verticality is automatically corrected by the contact surface between the bottom horizontal surface of the flexible protection block (2) and the seabed. After the device is inserted into the mud to a depth of 1 / 3 of the anchor height, it is switched to a high-speed penetration mode until it reaches the designed elevation. The contact stress between the flexible protection block (2) and the soil is fed back in real time by the built-in pressure sensor (21) at the bottom of the flexible protection block (2), and the pressure difference is dynamically adjusted; S4. Connecting a high-pressure grouting pump to a vertical grouting conduit (22), performing staged pressurized injection of the microbial slurry, strictly controlling the grouting pressure, and gradually increasing it to a preset value; S5. After grouting is completed, the soil is allowed to stand for curing to allow the microorganisms in the soil to induce the production of calcium carbonate crystals, thereby achieving in-situ gradient strengthening of the soil.

7. The construction method of the MICP reinforcement flexible protection device applicable to the suction anchor foundation according to claim 6 is characterized in that: During the grouting process of the microbial slurry, a grouting fluid is used that is a mixture of deep-sea acclimated Bacillus pasteurianus bacteria liquid and a cementing fluid, and is pretreated with a citric acid solution and an artificial seawater-based flushing fluid before grouting. A gradient cementing fluid is used during grouting. In the first stage, a mixture of 0.6-0.9 M CaCl2 and 0.3-0.5 M urea is injected, and the salinity adaptation range is ±5‰. In the second stage, a mixture of 1.0-1.4 M urea and 0.5-0.7 M CaCl2 is injected. The grouting pressure decreases and is maintained for 20-40 minutes. After completing the single-side grouting, a nitrogen mixture containing trace oxygen is injected through the grouting pipe, and the oxygen content is 0.5%-1.0%. Pressure is applied and continued for 10-16 hours.

8. The construction method of the MICP reinforcement flexible protection device applicable to the suction anchor foundation according to claim 5 is characterized in that: During grouting, the grouting head uses a spiral shear nozzle with a rotation speed of 10-20rpm. Before grouting, the grouting liquid temperature is managed to maintain 8-10℃, so that it is higher than the soil temperature.

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