A MICP-reinforced flexible protection device suitable for suction anchor foundations and a construction method thereof

Abstract

The application discloses a MICP reinforced 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 in a mushroom type structure, and the lower side is a plane. The flexible protection block is sleeved on the upper part of the suction anchor during installation. A plurality of pressure sensors are fixedly installed on the lower side of the flexible protection block. A plurality of grouting pipes are inserted and installed on the flexible protection block. The bottom ends of all the grouting pipes are on the same horizontal plane. The top ends of the grouting pipes are distributed along the mushroom type structure of the upper side of the flexible protection block. The application combines biological mineralization and structural bionics technology. The suction anchor surrounding seabed is injected with MICP microbial grouting through the grouting pipes. The bearing capacity of the sand soil surrounding the suction anchor is successfully enhanced. The application breaks through the limitation of traditional rigid reinforcement, improves the construction precision, and guarantees the stability of the whole life cycle of the deep-sea suction anchor foundation.

Description

Technical Field

[0001] This invention belongs to the field of marine engineering technology, specifically relating to a MICP-reinforced flexible protection device and construction method suitable for suction anchor foundations. Background Technology

[0002] Deep-sea suction anchor foundations face stability challenges under multiple coupled effects during long-term service: First, the soft soil strata on the seabed are characterized by high water content, high porosity, and low density. Their spatial heterogeneity leads to discrepancies between theoretical models of soil parameters and actual working conditions, directly affecting the accuracy of bearing capacity calculations. Second, during service, suction anchors must simultaneously withstand the static load of the superstructure and the dynamic processes of deep-sea currents, internal waves, and tidal currents, as well as the scouring effects of extreme events such as turbidity currents, tsunamis, and deep-sea storms, resulting in the loss of surrounding soil and a reduction in their pull-out bearing capacity. Currently, suction anchor designs do not adequately consider protective measures, making them prone to tilting or pull-out under scouring, leading to anchor failure. Third, deviations in settlement speed, pressure differential control, and verticality during construction can easily damage the integrity of the undisturbed soil structure, resulting in insufficient final settlement accuracy and stress concentration problems. Especially in complex and ever-changing 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 erosion, thereby further exacerbating its instability and potential failure risk.

[0003] Existing reinforcement methods generally suffer from poor compatibility with rigid materials, high construction costs, and risks 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; sheet pile retaining structures rely on large vessels and machinery, resulting in low economic efficiency and construction cost; and the highly alkaline hydration reaction of cement-based materials can cause continuous damage to the marine microbial environment. Currently, the widely used MICP (microbial-induced calcium carbonate precipitation) reinforcement technology mainly focuses on the solidification of shallow soils. However, when applied to suction anchor structures, this technology has a significant drawback: the lack of a specially designed directional grouting device. Due to the absence of such a device, the grout penetration during construction is uneven, which not only affects the reinforcement effect but also significantly reduces construction efficiency. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a MICP-reinforced flexible protection device and construction method suitable for suction anchor foundations.

[0005] The technical solution of the present invention to solve the above-mentioned technical problems is:

[0006] A MICP-reinforced flexible protective device suitable for suction anchor foundations includes a suction anchor and a flexible protective block. The upper side of the flexible protective block has a funnel-shaped structure, and its lower side is flat. During installation, the flexible protective block is fitted onto the upper part of the suction anchor. Multiple pressure sensors are fixedly installed on the lower side of the flexible protective block. Several grouting conduits are inserted and installed on the flexible protective block. The bottom ends of all grouting conduits are at the same horizontal plane, and the top ends of the grouting conduits are distributed along the funnel-shaped structure on the upper side of the flexible protective block.

[0007] Preferably, the surface layer of the flexible protective block is made of a salt-resistant polymer composite material.

[0008] Preferably, the sidewall of the grouting conduit has several rows of staggered grouting holes.

[0009] Preferably, the bottom of the grouting conduit is designed to be a pointed cone shape.

[0010] Preferably, multiple pressure sensors are uniformly fixedly installed on the bottom of the flexible protective block along its circumference.

[0011] Preferably, it includes the following steps:

[0012] S1. Place the flexible protective block on the upper middle part of the suction anchor, aligning the bottom horizontal plane of the flexible protective block with the pre-installation mark of the suction anchor;

[0013] S2. Securely connect the flexible protective block to the outer wall of the suction anchor;

[0014] S3. The suction anchor with the flexible device is hoisted to the design area by a floating crane. The negative pressure sinking system is started. In the initial stage, the sinking is carried out at a low speed. The verticality is corrected by using the bottom horizontal plane of the flexible protective block to contact the seabed. After the device is inserted into the mud to a depth of 1 / 3 of the anchor height, the sinking mode is switched to high speed sinking mode until the design elevation is reached. The pressure sensor built into the bottom of the flexible protective block provides real-time feedback on the contact stress between the flexible protective block and the soil, and the pressure difference is dynamically adjusted.

[0015] S4. Connect the high-pressure grouting pump to the vertical grouting pipe to inject the microbial grout in stages under pressure, strictly control the grouting pressure, and gradually increase it to the preset value;

[0016] S5. After grouting is completed, allow the soil to cure statically, allowing microorganisms in the soil to induce calcium carbonate crystals and achieve in-situ gradient reinforcement of the soil.

[0017] Preferably, the specific process of correcting the verticality is as follows: the bottom horizontal plane of the flexible protective block is initially in contact with the seabed, and the contact stress distribution is fed back in real time by the pressure sensor built into the bottom of the flexible protective block. If the stress distribution is uneven, it indicates that there is tilt. Then, the verticality of the suction anchor is corrected by dynamically adjusting the pressure difference in different areas of the negative pressure sinking system.

[0018] Preferably, during the grouting process of the microbial slurry, a grouting solution is prepared by mixing deep-sea-acclimated Bacillus pasteurellium bacterial solution with a cementing solution. Before grouting, the solution is pretreated with citric acid solution and artificial seawater-based flushing solution. During grouting, a gradient cementing solution is used. In the first stage, a mixture of 0.6-0.9 M CaCl2 and 0.3-0.5 M urea is injected, with a salinity of ±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 unilateral grouting is completed, a nitrogen mixture containing trace amounts of oxygen (0.5%-1.0%) is injected through the grouting pipe and pressure is applied for 10-16 hours.

[0019] Preferably, the grouting head uses a spiral shear nozzle with a rotation speed of 10-20 rpm. Before grouting, the temperature of the grout is managed to maintain the grout temperature at 8-10℃, which is higher than the soil temperature.

[0020] The technical advantages of this invention are as follows:

[0021] (1) The upper side of the flexible protective block of the present invention has a fungal umbrella-shaped structure, which effectively disperses the impact force of the wave current, reduces the scouring of the suction anchor foundation soil by the ocean current, and thus significantly improves the pull-out bearing capacity of the suction anchor.

[0022] (2) The present invention utilizes the microbial induced calcium carbonate precipitation (MICP) grouting reinforcement technology to successfully enhance the bearing capacity of the 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 the complex marine environment.

[0023] (3) This invention specifically designs a MIP (microbial grouting) formula and construction process for sandy soil in the low-temperature and high-pressure environment of deep sea, enhancing the grouting effect, ensuring the uniformity and strength of the reinforced layer, and taking into account the protection of the marine ecological environment. It not only avoids the environmental pollution problems that may be caused by traditional reinforcement methods, but also prevents 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 disturbance to the surrounding biological habitat is further reduced, achieving the dual goals of engineering safety and environmental protection. Finally, this invention integrates interdisciplinary technologies of biomineralization and structural biomimicry, which not only breaks through the limitations of traditional rigid reinforcement methods, but also improves the construction accuracy, providing a life-cycle stability guarantee for deep-sea suction anchor foundations. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the structure of the present invention;

[0025] Figure 2 This is a bottom view of the present invention;

[0026] Figure 3 This is a schematic diagram of the unfolded side hole of the grouting guide pipe.

[0027] In the figure, 1 is the suction anchor; 2 is the flexible protective block; 21 is the pressure sensor; 22 is the grouting conduit; and 221 is the grouting hole. Detailed Implementation

[0028] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0029] like Figure 1 , 2 As shown in Figure 3, the suction anchor 1 and the flexible protective block 2 are arranged in a fungal umbrella-shaped structure on the upper side and a flat surface on the lower side. The flexible protective block 2 is fitted onto the upper part of the suction anchor 1 during installation. Multiple pressure sensors 21 are fixedly installed on the lower side of the flexible protective block 2. Several grouting conduits 22 are inserted and installed on the flexible protective block 2. The bottom ends of all grouting conduits 22 are at the same horizontal plane, and the top ends of the grouting conduits 22 are distributed along the fungal umbrella-shaped structure on the upper side of the flexible protective block 2. According to the principle of fluid mechanics, the fungal umbrella-shaped structure on the upper side of the flexible protective block 2 can change the flow direction of the fluid wave, so that the fluid flows along the curved surface when passing through the structure, thereby effectively dispersing the impact force of the wave, reducing the overall impact force borne by the structure, and improving the pull-out resistance of the suction anchor 1.

[0030] Multiple pressure sensors 21 are evenly fixedly installed on the bottom of the flexible protective block 2 along its circumference; the pressure sensors 21 on the lower side of the flexible protective block 2 can provide real-time feedback on the soil contact stress. Based on 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.

[0031] Several grouting conduits 22 are inserted and installed on the flexible protective block 2. The bottom ends of all grouting conduits 22 are at the same horizontal plane. The top ends of the grouting conduits 22 are distributed along the umbrella-shaped structure on the upper side of the flexible protective block 2. Several rows of staggered grouting holes 221 are opened on the side wall of the grouting conduits 22. The bottom of the grouting conduits 22 is designed as a pointed cone.

[0032] The grouting pipe 22 has several rows of staggered grouting holes 221 on its sidewall to ensure uniform grout penetration and enhance the overall strength and erosion resistance of the soil. The grouting pipe 22 is made of corrosion-resistant and high-strength alloy material to meet the long-term operation requirements in complex marine environments.

[0033] A construction method for a MICP-reinforced flexible protective device suitable for suction anchor foundations includes the following steps:

[0034] S1, the flexible protective block 2 is fitted onto the upper middle part of the suction anchor 1, so that the bottom horizontal plane of the flexible protective block 2 is aligned with the pre-installed mark of the suction anchor 1.

[0035] S2, the flexible protective block 2 is firmly connected to the outer wall of the suction anchor 1 using flanges or clips, thereby achieving precise construction positioning.

[0036] S3. The suction anchor with the flexible device is hoisted to the design area by a floating crane. The negative pressure sinking system is started. In the initial stage, it is driven in at a low speed. The verticality is automatically corrected by the contact surface between the bottom horizontal plane of the flexible protective block 2 and the seabed. After the device is driven into the mud to a depth of 1 / 3 of the anchor height, it is switched to high-speed sinking mode until the design elevation is reached. The pressure sensor 21 built into the bottom of the flexible protective block 2 provides real-time feedback on the contact stress between the flexible protective block 2 and the soil, and the pressure difference is dynamically adjusted.

[0037] S4 connects the high-pressure grouting pump to the evenly distributed grouting conduit 22 to inject a mixture of deep-sea acclimatized Bacillus pasteurellium bacterial solution and cementing solution in stages under pressure. During the grouting process, the grouting pressure must be strictly controlled and gradually increased to the preset value to ensure that the grout can penetrate evenly into the depths of the soil and form an effective reinforcement layer.

[0038] S5. After grouting is completed, the soil is left to cure for a period of time to induce the formation of calcium carbonate crystals by microorganisms, thereby achieving in-situ gradient reinforcement of the soil.

[0039] The MICP grouting technology uses a grouting solution made from a mixture of deep-sea-acclimated Bacillus pasteurellium culture and a cementing fluid. First, pretreatment is performed using citric acid solution and artificial seawater-based flushing fluid, followed by grouting 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 of ±5‰, at a relatively high 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, completing unilateral grouting. Finally, a nitrogen mixture containing trace amounts of oxygen (0.5%–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 the yield of calcium carbonate.

[0040] During grouting, the grouting head uses a spiral shear nozzle with a rotation speed of 10-20 rpm to prevent sand particles from clogging the grouting hole.

[0041] The main advantages of this invention are as follows: First, by designing a composite functional flexible protective block 2, the impact force of wave currents is effectively dispersed, reducing erosion and loss of the soil in the suction anchor foundation, thereby significantly improving the pull-out bearing capacity of the suction anchor. Second, by employing microbial induced calcium carbonate precipitation (MICP) grouting reinforcement technology, the bearing capacity of the soft sand surrounding the suction anchor is successfully enhanced, improving the mechanical properties and stability of the soil and effectively reducing the probability of suction anchor failure in complex marine environments. Third, for sandy soils in the low-temperature, high-pressure environment of deep seas, this invention specifically designs a MIP microbial grouting formula and construction process, enhancing the grouting effect, ensuring the uniformity and strength of the reinforcement layer, while also taking into account marine ecological environment protection, avoiding the environmental pollution problems that may be caused by traditional reinforcement methods. The grouting process of this 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 disturbance to the surrounding biological habitat is further reduced, achieving the dual goals of engineering safety and environmental protection. Finally, this invention integrates interdisciplinary technologies of biomineralization and structural biomimicry, which not only breaks through the limitations of traditional rigid reinforcement methods, but also improves construction accuracy, providing stability assurance for deep-sea suction anchor foundations throughout their entire life cycle.

Claims

1. A MICP-reinforced flexible shield suitable for use with a suction anchor foundation, characterized in that, Includes a suction anchor (1) and a flexible protective block (2). The upper side of the flexible protective block (2) is a fungal umbrella-shaped structure, and its lower side is a plane. The flexible protective block (2) is fitted onto the upper part of the suction anchor (1) during installation. Multiple pressure sensors (21) are fixedly installed on the lower side of the flexible protective block (2). Several grouting conduits (22) are inserted and installed on the flexible protective block (2). The bottom ends of all grouting conduits (22) are at the same horizontal plane, and the top ends of the grouting conduits (22) are distributed along the fungal umbrella-shaped structure on the upper side of the flexible protective block (2).

2. The MICP-reinforced flexible shield suitable for use with a suction anchor foundation of claim 1, wherein, The surface of the flexible protective block (2) is made of salt-resistant polymer composite material.

3. The MICP-reinforced flexible shield suitable for use with a suction anchor foundation of claim 1, wherein, The sidewall of the grouting conduit (22) has several rows of staggered grouting holes (221).

4. The MICP-reinforced flexible shield suitable for use with a suction anchor foundation of claim 1, wherein, The bottom of the grouting conduit (22) is designed to be conical.

5. The MICP-reinforced flexible shield suitable for use with a suction anchor foundation of claim 1, wherein, Multiple pressure sensors (21) are uniformly fixedly installed on the bottom of the flexible protective block (2) along its circumference.

6. A method of construction of a MICP-reinforced flexible shield suitable for use with a suction anchor foundation as claimed in claim 5, characterised in that, Includes the following steps: S1. Place the flexible protective block (2) on the upper middle part of the suction anchor (1) so that the bottom horizontal plane of the flexible protective block (2) is aligned with the pre-installed mark of the suction anchor (1); S2. Securely connect the flexible protective block (2) to the outer wall of the suction anchor (1); S3. The suction anchor with the flexible device is hoisted to the design area by a floating crane. The negative pressure sinking system is started. In the initial stage, the sinking is carried out at a low speed. The verticality is automatically corrected by the bottom horizontal plane of the flexible protective block (2) and the seabed contact surface. After the device is inserted into the mud to a depth of 1 / 3 of the anchor height, the sinking mode is switched to high speed sinking mode until the design elevation is reached. The pressure sensor (21) built into the bottom of the flexible protective block (2) provides real-time feedback on the contact stress between the flexible protective block (2) and the soil, and the pressure difference is dynamically adjusted. S4. Connect the high-pressure grouting pump to the vertical grouting pipe (22) to inject the microbial slurry in stages under pressure, strictly control the grouting pressure, and gradually increase it to the preset value; S5. After grouting is completed, allow the soil to cure statically, allowing microorganisms in the soil to induce calcium carbonate crystals and achieve in-situ gradient reinforcement of the soil.

7. The construction method of the MICP-reinforced flexible protection device for suction anchor foundations according to claim 6, characterized in that, During the grouting process of the microbial slurry, a grouting solution made of pasteurized bacteria solution and cementing solution is used. Before grouting, the solution is pretreated with citric acid solution and artificial seawater-based flushing solution. Gradient cementing solution 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, with a salinity range of ±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 grouting on one side is completed, a nitrogen mixture containing trace amounts of oxygen (0.5%-1.0%) is injected through the grouting pipe and pressure is applied for 10-16 hours.

8. The construction method of the MICP-reinforced flexible protection device for suction anchor foundations according to claim 7, characterized in that, During grouting, a spiral shear nozzle is used with a rotation speed of 10-20 rpm. Before grouting, the temperature of the grout is managed to maintain the grout temperature at 8-10℃, which is higher than the soil temperature.

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