A method for reinforcing marine saturated sandy soil foundation by using micro-bubble assisted EICP to control the cementation between sand particles

Abstract

The present application relates to a kind of microbubble assisted EICP regulation cementation between sand particles Marine saturated sand ground reinforcement method, comprising the following steps: S1, preparation microbubble water: using air, nitrogen, inert gas any one or more than two mixed gas, with water or EICP reaction liquid is prepared by microbubble generating device liquid containing microbubble, containing microbubble liquid is microbubble water or EICP reaction liquid containing microbubble;S2, multi-phase interface construction and particle cementation reinforcement: EICP reaction liquid containing microbubble, or microbubble water and EICP reaction liquid is introduced into the marine saturated sand ground to be reinforced inside, microbubble and pore water and sand particles form multi-phase interface together;EICP reaction liquid fills to the target sand soil pore region of multi-phase interface, forms solid cementation bridge connected adjacent sand particles, completes the reinforcement treatment of marine saturated sand ground.By microbubble construction gas-liquid-solid multi-phase interface, realize the effective regulation of calcium carbonate deposition position.

Description

Technical Field

[0001] This invention relates to the field of marine engineering technology, and in particular to a method for reinforcing marine saturated sandy soil foundations by regulating intergranular cementation using microbubble-assisted EICP. Background Technology

[0002] In marine engineering construction, a large number of foundation structures need to be laid in the seabed surface or shallow foundations. Marine sandy soil foundations are usually in a saturated state, and under the action of waves, currents, cyclic loads, foundation construction disturbances, and long-term service loads, problems such as strength reduction, pore water pressure accumulation, local liquefaction, insufficient bearing capacity, or weakening of the surrounding soil may occur. Therefore, low-disturbance, environmentally friendly, and controllable in-situ reinforcement of saturated marine sandy soil foundations is an important technical requirement for the safe construction and long-term service of marine foundation engineering.

[0003] Traditional foundation reinforcement methods include cement grouting, chemical grout injection, compaction grouting, and high-pressure jet grouting. These methods are widely used in terrestrial foundations, but when applied to marine saturated sandy soil foundations, they may suffer from problems such as difficulty in controlling grout diffusion, large material consumption, significant environmental disturbance, and insufficient construction adaptability. In recent years, soil reinforcement technologies based on biomineralization or enzymatic mineralization have gradually attracted attention. Among them, EICP technology utilizes urease to catalyze the hydrolysis of urea, causing calcium ions to react with carbonate ions to form calcium carbonate precipitate, thereby cementing sand particles and improving the strength of the sandy soil. Compared with cement-based reinforcement, EICP has advantages such as lower grout viscosity, better injectability, milder reaction conditions, and better environmental friendliness, thus showing potential for reinforcement of marine saturated sandy soil foundations.

[0004] The basic approach to EICP reinforcement of sandy soils involves injecting a reaction solution containing urease, urea, and calcium salts into the pores of the sand. This causes an enzymatic reaction within the pores, generating calcium carbonate precipitate. The precipitate fills the pores, adheres to the surface of sand particles, or forms cement at particle contact points, thereby increasing the strength of the sand. Studies have found that the deposition location and morphology of calcium carbonate significantly affect the reinforcement effect: if calcium carbonate is mainly deposited on the surface of sand particles, in the particle contact area, and in the pore throat region, it is conducive to effective cementation; if calcium carbonate mainly exists as random pore filling or localized precipitation, its contribution to the mechanical bonding between sand particles is limited, and it can also easily affect the diffusion of subsequent reaction solutions. Therefore, in EICP reinforcement of marine saturated sandy soil foundations, it is not only necessary to generate calcium carbonate precipitate, but also to increase the proportion of calcium carbonate deposited at effective cementation sites.

[0005] Compared to the aforementioned requirements, conventional EICP grouting reinforcement methods primarily influence the reaction process by adjusting urease concentration, urea concentration, calcium salt concentration, injection rounds, and injection sequence. They lack effective means to control the deposition location of calcium carbonate on sand particle surfaces, in contact zones, and in pore throat regions. The generated calcium carbonate often fills random pores, resulting in low reinforcement efficiency per unit amount of calcium carbonate deposit. To improve deposition efficiency, some methods introduce nucleation induction fluids, mineral seeds, or calcium powders into the reaction system as nucleation or attachment carriers to promote calcium carbonate precipitation and deposition. While these methods can improve nucleation efficiency or alter deposition morphology to some extent, they mainly rely on liquid-phase chemical induction or the addition of solid particles for deposition regulation. Limited by the dispersibility, transport, and spatial distribution of the added materials, it is difficult to form a gas-liquid-solid multiphase interface in the sand pores that can migrate and distribute with the injected fluid and interact with sand particles, thus limiting interface control capabilities. Summary of the Invention

[0006] (a) Technical problems to be solved

[0007] In view of the above-mentioned shortcomings and deficiencies of the prior art, the present invention provides a method for reinforcing marine saturated sandy soil foundations by regulating the cementation between sand particles using microbubble-assisted EICP. This method solves the technical problem that when reinforcing marine saturated sandy soil foundations using existing EICP technology, the effective deposition location of calcium carbonate is difficult to control, resulting in a low effective cementation ratio between sand particles and low reinforcement efficiency.

[0008] (II) Technical Solution

[0009] To achieve the above objectives, the main technical solutions adopted by the present invention include:

[0010] This invention provides a method for reinforcing marine saturated sandy soil foundations by regulating interparticle cementation using microbubble-assisted EICP, comprising the following steps:

[0011] S1. Preparation of microbubble water: Using any one or more of the following gases, namely air, nitrogen, and inert gas, and a mixture of two or more gases, water or EICP reaction solution is used to prepare a liquid containing microbubbles through a microbubble generator. The liquid containing microbubbles is microbubble water or EICP reaction solution containing microbubbles.

[0012] S2. Multiphase Interface Construction and Particle Cementation Reinforcement: An EICP reaction solution containing microbubbles, or a mixture of microbubbles, water, and EICP reaction solution, is introduced into the marine saturated sand foundation to be reinforced. The microbubbles in the microbubble-containing liquid remain within the sand's pore structure, forming a gas-liquid-solid multiphase interface together with pore water and sand particles, creating a stable gas-bearing environment within the local pores of the sand. Simultaneously, the EICP reaction solution fills the target sand pore area with the microbubble multiphase interface. Under the regulation of this gas-bearing environment, the EICP reaction solution forms liquid bridges at or near the contact points of adjacent sand particles. Subsequently, through the continuous nucleation, precipitation, and deposition of calcium carbonate within the liquid bridge area, the liquid bridges gradually solidify, ultimately forming a solid cemented bridge connecting adjacent sand particles, thus completing the reinforcement treatment of the marine saturated sand foundation.

[0013] Preferably, the parameters of the liquid containing microbubbles can be adjusted according to the particle size, void ratio, permeability coefficient, target reinforcement depth, and construction injection conditions of the sand to be reinforced. The purpose is to allow the microbubbles to enter the target reinforcement area with the injected liquid, reduce their concentration and retention near the injection port, and form a gas-liquid-solid multiphase interface on the surface of sand particles, in the pore throat area, and in the particle contact neighborhood that can be used for subsequent EICP reactions.

[0014] In a preferred embodiment of the present invention, in step S1, the characteristic particle size of the microbubbles is 50nm-100μm, and the concentration of the microbubbles is 10. 6 -10 10 per mL.

[0015] In a preferred embodiment of the present invention, in step S1, the characteristic particle size of the microbubbles is 200 nm-30 μm, and the concentration of the microbubbles is 10. 7 -10 9 per mL.

[0016] Furthermore, the characteristic particle size of the microbubbles is preferably 200 nm-10 μm to balance pore migration ability and local retention to form interfaces.

[0017] The concentration range of microbubbles is used to provide a sufficient number of gas-liquid interfaces while avoiding excessive concentration that could lead to concentrated stagnation near the injection port. Higher concentrations are beneficial for increasing the number of interfaces and improving the control of calcium carbonate nucleation and deposition; lower or moderate concentrations are beneficial for maintaining the injectability and diffusivity of microbubble water.

[0018] In a preferred embodiment of the present invention, nitrogen is preferably used as the gas in step S1. Nitrogen has relatively stable chemical properties and causes less interference to the EICP reaction system.

[0019] In a preferred embodiment of the present invention, in step S1, the EICP reaction solution includes a urease solution and a cementing solution;

[0020] The microbubble-containing EICP reaction solution is microbubble water, microbubble-containing urease solution, or microbubble-containing cementing solution.

[0021] In a preferred embodiment of the present invention, step S2 is one of the following methods:

[0022] (a) When the liquid containing microbubbles is microbubble water, the microbubble water is first injected into the marine saturated sandy soil foundation to be reinforced. After the microbubbles are retained and form a gas-containing environment, EICP reaction liquid is then injected.

[0023] (b) When the microbubble-containing liquid is microbubble water, the microbubble water and the premixed EICP reaction solution are injected together into the marine saturated sand foundation to be reinforced;

[0024] (c) When the liquid containing microbubbles is a urease solution containing microbubbles, the urease solution containing microbubbles is first injected into the marine saturated sandy soil foundation to be reinforced. After the microbubbles are retained and form a gas-containing environment, the cementing liquid is then injected.

[0025] (d) When the liquid containing microbubbles is a cementing solution containing microbubbles, the cementing solution containing microbubbles is first injected into the marine saturated sandy soil foundation to be reinforced. After the microbubbles are retained and form a gas-containing environment, the urease solution is then injected.

[0026] All of the above methods enable microbubbles to be retained in the pores of sand, forming a gas-bearing environment and guiding the EICP reaction liquid to form liquid bridges at particle contact points, ultimately transforming into solid cemented bridges. Method (a) is the optimal implementation method, suitable for general marine saturated sandy soil foundations, ensuring sufficient retention of microbubbles and stable formation of the gas-bearing environment, with the highest deposition ratio of calcium carbonate at particle contact points, resulting in the best reinforcement effect. Method (b) is suitable for sandy soil foundations with good permeability, shortening the construction period. Methods (c) and (d) are suitable for sandy soil foundations with poor permeability or high fine particle content, ensuring sufficient retention of microbubbles and formation of the gas-bearing environment.

[0027] In a preferred embodiment of the present invention, when mode (a) is used, the microbubble water is left to stand for 5 min-6 h after injection; more preferably, it is left to stand for 10 min-60 min.

[0028] The microbubble water and / or EICP reaction solution are injected in multiple rounds of low-volume injection, intermittent injection, or segmented injection.

[0029] The purpose of allowing the microbubble water to settle after injection is to provide a time window for microbubble diffusion, local retention, and interface formation. If the waiting time is too short, the microbubbles may not have fully diffused into the target area; if the waiting time is too long, it may reduce the continuity of construction.

[0030] Intermittent injection refers to setting a time interval during the injection process to allow the liquid to fully diffuse in the pores before continuing the injection; segmented injection refers to dividing the target reinforcement area into multiple segments along the depth direction and injecting into each segment separately by moving the injection pipe to ensure longitudinal uniformity.

[0031] In a preferred embodiment of the present invention, when mode (a) is used, the volume of the microbubble water injected each time is 0.2-3.0 times the pore volume of the target reinforcement zone, and the volume of the EICP reaction solution injected each time is 0.2-1.0 times the pore volume of the target reinforcement zone.

[0032] It should be noted that the injection volume per instance refers to the volume of liquid injected in a single, continuous injection. For multiple rounds of low-volume injection, the injection volume per instance is the volume injected in each round; for intermittent injection, the injection volume per instance is the volume injected in a single, continuous injection within each injection period; for segmented injection, the injection volume per instance is the volume injected in a single segment. Regardless of the injection method used, the injection volume per instance refers to the volume of liquid injected in a single, uninterrupted injection.

[0033] The injection volume of microbubble water in each step is used to ensure that the microbubble water can cover the target reinforcement area. If the injection volume is too small, the microbubbles may have difficulty reaching the target depth or covering the target area; if the injection volume is too large, it may cause ineffective diffusion or material waste. The single injection volume of the EICP reaction solution is used to improve the distribution of microbubbles and the uniformity of subsequent cementation reactions.

[0034] Preferably, the volume of microbubble water injected each time is 0.5-1.5 times the pore volume of the target reinforcement area, so as to balance the coverage of the target area and the economic efficiency of construction.

[0035] In a preferred embodiment of the present invention, in step S2, the EICP reaction solution is injected in 1-10 rounds. Multiple injection rounds help reduce localized concentrated retention and rapid localized precipitation, and improve the treatment uniformity within the target reinforcement area. Preferably, the EICP reaction solution is injected in 2-5 rounds.

[0036] In a preferred embodiment of the present invention, the injection pressure and injection flow rate are determined based on the target reinforcement depth, soil permeability, and pore structure. These parameters are used to propel microbubble water into the target reinforcement depth while avoiding excessively rapid injection that could cause localized channeling or concentrated stagnation near the injection port. For highly permeable soils, the injection flow rate is appropriately increased; for soils with low permeability or high fine particle content, a lower flow rate, multiple low-volume injections, or intermittent injection methods are used.

[0037] In a preferred embodiment of the present invention, in step S2, the cementing solution includes urea and a calcium source;

[0038] The urea concentration is 0.1-1.5 mol / L, and the calcium source concentration is 0.1-1.5 mol / L; the calcium source is selected from at least one of calcium chloride, calcium lactate, or calcium acetate. The urease solution concentration can be determined according to the enzyme activity and the target reaction rate, preferably with an activity of 2.0-8.0 U / mL, more preferably 4.0-8.0 U / mL.

[0039] When it is necessary to improve the uniformity of reinforcement, multiple rounds of low-concentration injection can be used; when it is necessary to form a localized reinforcement with higher strength, the amount of injection per injection or the concentration of the cementing solution can be increased.

[0040] In a preferred embodiment of the present invention, in method (a), the urease solution is injected first, followed by the cementing solution; the cementing solution is injected first, followed by the urease solution; or the urease solution and the cementing solution are mixed before injection. In a preferred embodiment of the present invention, in step S1, the microbubble water is prepared using fresh water, seawater, or artificial seawater.

[0041] In a preferred embodiment of the present invention, in step S1, microbubbles are generated by a shear-type microbubble generator, a swirling microbubble generator, a pressurized dissolved gas release device, a microporous aeration device, or a gas-liquid mixing pump.

[0042] As a preferred embodiment of the present invention, at least one of the following is included: the sandy soil foundation surrounding the marine engineering foundation, the sandy soil foundation below the marine engineering foundation, the surface sandy soil foundation of the seabed, the erosion protection reinforcement zone, and the locally weakened seabed reinforcement zone.

[0043] Specifically, the marine saturated sandy soil foundation includes at least one of the following: offshore wind power foundation, offshore photovoltaic foundation, subsea equipment foundation, subsea pipeline foundation, gravity foundation, suction foundation, pile foundation, slab foundation, offshore platform foundation, and cross-sea structure foundation, as well as the surrounding or underlying sandy soil foundation of artificial islands, seawall revetments, and near-shore port area backfilled sandy soil foundation.

[0044] (III) Beneficial Effects

[0045] The beneficial effects of this invention are as follows: This invention provides a microbubble-assisted EICP method for reinforcing marine saturated sandy soil foundations by regulating intergranular cementation. By constructing a gas-liquid-solid multiphase interface using microbubbles, the deposition location of calcium carbonate is effectively regulated. In existing EICP reinforcement methods, calcium carbonate precipitation mainly fills the pores between sand particles randomly, making it difficult to preferentially form effective cementation at particle contact points. This invention introduces a liquid containing microbubbles into the saturated sandy soil foundation. The microbubbles remain on the surface of sand particles, in the pore throat region, and in the vicinity of particle contact areas, forming a stable gas-liquid-solid multiphase interface and a local gas-bearing region. This gas-bearing region can regulate the distribution of the subsequent EICP reaction liquid. Under injection pressure, the gas accumulates in the pores between sand particles in the EICP reaction liquid, causing the reaction liquid to preferentially distribute at or near the contact points of adjacent sand particles, forming liquid bridges. This induces calcium carbonate nucleation, precipitation, and deposition within the liquid bridge region. The liquid bridges at or near the sand particle contact points then gradually transform into solid cementation bridges between particles. In this way, calcium carbonate is guided to the location most conducive to the transmission of interparticle forces, significantly improving the contribution efficiency of unit calcium carbonate deposition to soil strength and reducing ineffective pore filling.

[0046] By creating a gas-bearing environment within the pores through microbubbles, soil saturation can be effectively reduced, increasing soil compressibility and buffering capacity. This suppresses the rapid rise in pore water pressure under earthquakes or cyclic loading, thereby improving the liquefaction resistance of sandy soil foundations. Simultaneously, calcium carbonate solid cement bridges form stable mechanical connections between particles, significantly improving the shear strength and bearing stability of the soil. Furthermore, the cementing products exhibit stable chemical properties and good durability.

[0047] Because calcium carbonate preferentially deposits at effective cementation sites, the amount of EICP reaction solution and the number of reaction cycles required to achieve the same strength target can be significantly reduced. Compared with conventional EICP methods, this invention can achieve higher shear strength and liquefaction resistance of sand with the same amount of calcium carbonate generated, or reduce the amount of reaction solution injected and the number of cycles with the same reinforcement effect, thereby reducing engineering material and construction costs. Traditional microbial induced calcium carbonate deposition (MICP) methods rely on living microorganisms, which are easily inhibited in the high-salt, high-pressure, and complex chemical environment of the ocean, and their activity is difficult to maintain. This invention uses plant urease-induced calcium carbonate deposition (EICP) technology. Urease is a cell-free enzyme preparation, which is not affected by the high-salt environment of the ocean and can maintain catalytic activity under seawater conditions.

[0048] Furthermore, this invention employs an externally pre-generated microbubble water method. By adjusting the parameters of the microbubble generator, the particle size, concentration, and distribution characteristics of the microbubbles can be precisely controlled. Compared to in-situ microbial metabolic gas production, this invention does not rely on microbial activity and is unaffected by fluctuations in environmental temperature, pH, salinity, nutrient concentration, etc. The bubble generation rate and total amount can be actively adjusted according to engineering requirements.

[0049] The microbubble water and EICP reaction solution injected in this invention are both low-viscosity fluids, causing minimal disturbance to the original sandy soil structure and generating no high temperature, high pressure, or harmful chemicals. The microbubbles dissipate slowly after reinforcement, causing no lasting impact on the marine ecosystem. Furthermore, the injection method can be flexibly selected based on site conditions (soil permeability, saturation, reinforcement depth, etc.). The injection pressure, volume, and number of injection cycles of the microbubble water and EICP reaction solution can all be adjusted according to the target reinforcement effect, making it suitable for marine saturated sandy soil foundations of different types and complexities. Simultaneously, the microbubble water can be prepared on-site using seawater, eliminating the need for an additional freshwater supply, thus exhibiting strong construction adaptability, and is particularly suitable for the reinforcement of saturated sandy soil foundations in marine engineering projects such as offshore wind power, offshore photovoltaic, and subsea pipelines. Attached Figure Description

[0050] Figure 1 A frontal view of a microbubble water injection system into a marine saturated sandy soil foundation;

[0051] Figure 2 A top-view diagram illustrating the injection of microbubble water into a marine saturated sandy soil foundation;

[0052] Figure 3 A schematic diagram illustrating the principle of using microbubble water to assist EICP reaction solution in promoting the bonding between sand particles. Detailed Implementation

[0053] To better explain and facilitate understanding of the present invention, the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0054] To better understand the above technical solutions, exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present invention are shown in the drawings, it should be understood that the present invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that the present invention can be understood more clearly and thoroughly, and that the scope of the present invention can be fully conveyed to those skilled in the art.

[0055] Example 1

[0056] This embodiment provides a method for reinforcing marine saturated sandy soil foundations by regulating interparticle cementation using microbubble-assisted EICP, including the following steps:

[0057] (1) Preparation of microbubble water: Nitrogen gas was used as the gas source to prepare nitrogen-containing microbubble water and nitrogen micro-nano bubble water using a microbubble generator. The concentration of the microbubbles was 10... 8 The microbubble water is prepared using seawater with a salinity matching that of the foundation to be reinforced.

[0058] (2) Inject microbubble water: such as Figure 1 , Figure 2 and Figure 3 As shown, the microbubble water obtained in step (1) is injected into the target reinforcement area of ​​the marine saturated sandy soil foundation to be reinforced through the injection pipe interface. The injection pressure is higher than the pore water pressure at the target location, and the injection flow rate is set to 3L / min according to the sand permeability coefficient.

[0059] After microbubble water enters saturated sand, it diffuses along the pore channels of the sand towards the target reinforcement area. Some microbubbles are retained on the surface of sand particles, in the pore throat region, and in the particle contact area. The retained microbubbles, together with pore water and sand particles, form a gas-liquid-solid multiphase interface, creating a gas-bearing environment in the local pores. After injection, the mixture is allowed to stand for 30 minutes to allow the microbubbles to be fully retained and to form a stable multiphase interface.

[0060] (3) Injection of EICP reaction solution: The EICP reaction solution is injected into the target reinforcement area through the same injection tube. The EICP reaction solution contains urease solution and cementing solution, wherein the cementing solution contains urea and calcium chloride, with the urea concentration being 0.5 mol / L and the calcium chloride concentration being 0.5 mol / L. The urease solution is prepared by extracting soybean flour and water at a mass ratio of 1:10, and the urease activity is approximately 8.0 U / mL.

[0061] In this embodiment, a sequential injection method is adopted, first injecting urease solution and then injecting cementing liquid. The single-round injection volume of both urease solution and cementing liquid is 0.5 times the pore volume of the target reinforcement area. After injection, the mixture is allowed to stand for 24 hours to allow urease to catalyze the hydrolysis of urea. The resulting carbonate ions react with calcium ions to form calcium carbonate precipitate, such as... Figure 3 As shown.

[0062] (4) Multiple rounds of reinforcement: Based on the target reinforcement effect, step (3) is repeated 3 times. Before each round of injection, the injection parameters are adjusted according to the monitoring results.

[0063] After treatment using the above method, the gas-bearing environment formed by microbubbles in the pores of the sand effectively regulated the distribution of the EICP reaction liquid, causing it to preferentially form liquid bridges at the contact points of adjacent sand particles. Within the liquid bridge area, calcium carbonate nucleates, precipitates, and deposits, and the liquid bridging gradually transforms into solid cemented bridges between particles. Test results show that the shear strength of the reinforced sandy soil foundation increased by approximately 85% compared to the unreinforced state, its liquefaction resistance was significantly improved, and the proportion of calcium carbonate deposited at particle contact points reached 65% of the total deposition.

[0064] Example 2

[0065] This embodiment provides a method for reinforcing marine saturated sandy soil foundations by regulating intergranular cementation using microbubbles-assisted EICP. The difference from Embodiment 1 is that the liquid containing microbubbles is a urease solution containing microbubbles. The specific steps include:

[0066] (1) Preparation of urease solution containing microbubbles: Nitrogen gas is used as the gas source, and microbubbles are introduced into the urease solution (the urease solution is prepared by extracting soybean flour and water at a mass ratio of 1:10, and the urease activity is about 8.0 U / mL) through a microbubble generator to form a urease solution containing microbubbles.

[0067] (2) Injecting urease solution containing microbubbles: The enzyme solution containing microbubbles prepared in step (1) is injected into the target reinforcement area of ​​the marine saturated sandy soil foundation to be reinforced through the injection tube, and left to stand for 20 minutes after injection.

[0068] (3) Injection of cementing solution: The cementing solution (containing urea and calcium chloride, with a urea concentration of 0.5 mol / L and a calcium chloride concentration of 0.5 mol / L) is injected into the target reinforcement area through the same injection tube, and then left to stand for 24 hours after injection. After the cementing solution enters the pore area containing microbubbles and urease, urea hydrolysis occurs under the catalysis of urease, and the generated carbonate ions react with calcium ions to form calcium carbonate precipitate. Since the microbubbles pre-occupy the particle contact area, calcium carbonate preferentially nucleates and deposits in this area, forming a solid cementing bridge between particles.

[0069] (4) Multiple rounds of reinforcement: Based on the target reinforcement effect, step (3) is repeated 3 times.

[0070] In this embodiment, urease is injected together with microbubbles, allowing the urease to be pre-distributed within the microbubble-affected area, resulting in a more concentrated reaction after the subsequent cementitious liquid is introduced. Compared to Example 1, this embodiment increases the shear strength by approximately 78% (slightly lower than the 85% in Example 1) with the same amount of cementitious liquid, while shortening the construction period by approximately 10%, making it suitable for sandy soil foundations with tight schedules or poor permeability.

[0071] Example 3

[0072] This embodiment provides a method for reinforcing marine saturated sandy soil foundations by regulating intergranular cementation using microbubbles-assisted EICP. The difference from Embodiment 1 is that the liquid containing microbubbles is a urease solution containing a cementing solution. The specific steps include:

[0073] (1) Preparation of cementing solution containing microbubbles: Nitrogen gas is used as the gas source, and microbubbles are introduced into the cementing solution through a microbubble generator to form a cementing solution containing microbubbles. The cementing solution contains urea and calcium chloride, with a urea concentration of 0.5 mol / L and a calcium chloride concentration of 0.5 mol / L. The cementing solution is prepared using seawater with a salinity matching that of the foundation to be reinforced.

[0074] (2) Injecting the cementing liquid containing microbubbles: Inject the cementing liquid containing microbubbles obtained in step (1) into the target reinforcement area through the injection tube, and let it stand for 20 minutes after the injection is completed.

[0075] (3) Injection of urease solution: The urease solution (the urease solution is prepared by extracting soybean flour and water at a mass ratio of 1:10, and the urease activity is about 8.0 U / mL) is injected into the target reinforcement area of ​​the marine saturated sandy soil foundation to be reinforced through the same injection tube, and then left to stand for 24 hours after injection.

[0076] (4) Multiple rounds of reinforcement: Based on the target reinforcement effect, step (3) is repeated 3 times.

[0077] This embodiment improves reaction efficiency by co-injecting calcium source and urea with microbubbles, allowing the reactants to directly reach the particle contact interface region via the microbubbles. Shear strength is increased by approximately 75%, while reducing the risk of premature sedimentation within the injection pipeline, making it more suitable for continuous on-site construction.

[0078] Example 4

[0079] This embodiment provides a method for reinforcing marine saturated sandy soil foundations by regulating interparticle cementation using microbubble-assisted EICP. The difference from Embodiment 1 lies in the simultaneous injection of microbubble water and premixed EICP reaction solution. Specifically, it includes the following steps:

[0080] (1) Preparation of microbubble water: Same as step (1) in Example 1.

[0081] (2) Preparation of EICP mixed reaction solution: Mix urease solution (soybean flour to water mass ratio 1:10, activity about 8.0 U / mL) and cementing solution (urea 0.5 mol / L, calcium chloride 0.5 mol / L) at a volume ratio of 1:1 to obtain premixed EICP reaction solution. Use immediately after mixing.

[0082] (3) Synchronous injection: After mixing the microbubble water and the premixed EICP reaction solution at the injection port, the mixture is synchronously injected into the target reinforcement area of ​​the marine saturated sandy soil foundation to be reinforced. After injection, the mixture is left to stand for 24 hours.

[0083] (4) Multiple rounds of reinforcement: Repeat step (3) for 3 rounds.

[0084] This embodiment simplifies the construction process, increases shear strength by about 70% (lower than Embodiment 1), but shortens construction time by about 30%, making it suitable for marine engineering projects with good permeability and short construction windows.

[0085] Comparative Example 1

[0086] This comparative example provides a conventional EICP sandy soil foundation reinforcement method that does not introduce microbubbles, for comparison with the effects of Examples 1-4. Specific steps:

[0087] (1) Preparation of EICP reaction solution: urease solution (soybean flour to water mass ratio 1:10, activity about 8.0 U / mL) and cementing solution (urea 0.5 mol / L, calcium chloride 0.5 mol / L).

[0088] (2) Injection of EICP reaction solution: Urease solution and cementing solution are sequentially injected into the marine saturated sand foundation to be reinforced. The injection pressure, injection flow rate, single-round injection volume, and settling time are all consistent with those in Example 1. No pre-injection or accompanying injection of microbubble water is performed.

[0089] (3) Multiple rounds of reinforcement: Repeated injection of EICP reaction solution for 3 rounds, with each round left to stand for 24 hours.

[0090] Testing revealed that the shear strength of the reinforced sandy soil foundation in Comparative Example 1 increased by approximately 35% compared to the unreinforced foundation. The proportion of calcium carbonate deposited at particle contact points was only about 25% of the total deposit, with most calcium carbonate existing in the form of random pores. The improvement in liquefaction resistance was significantly lower than in Examples 1-4.

[0091] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

[0092] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0093] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0094] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0095] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, for example, sequentially. For instance, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For instance, the method may also include step (c), indicating that step (c) may be added to the method in any order; for example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0096] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0097] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

Claims

1. A method for reinforcing marine saturated sandy soil foundations by regulating interparticle cementation using microbubble-assisted EICP, characterized in that, Includes the following steps: S1. Preparation of microbubble water: Using any one or more of the following gases, namely air, nitrogen, and inert gas, and a mixture of two or more gases, water or EICP reaction solution is used to prepare a liquid containing microbubbles through a microbubble generator. The liquid containing microbubbles is microbubble water or EICP reaction solution containing microbubbles. S2. Multiphase Interface Construction and Particle Cementation Reinforcement: An EICP reaction solution containing microbubbles, or a mixture of microbubbles, water, and EICP reaction solution, is introduced into the marine saturated sand foundation to be reinforced. The microbubbles in the microbubble-containing liquid remain within the sand's pore structure, forming a gas-liquid-solid multiphase interface together with pore water and sand particles, creating a stable gas-bearing environment within the local pores of the sand. Simultaneously, the EICP reaction solution fills the target sand pore area with the microbubble multiphase interface. Under the regulation of this gas-bearing environment, the EICP reaction solution forms liquid bridges at or near the contact points of adjacent sand particles. Subsequently, through the continuous nucleation, precipitation, and deposition of calcium carbonate within the liquid bridge area, the liquid bridges gradually solidify, ultimately forming a solid cemented bridge connecting adjacent sand particles, thus completing the reinforcement treatment of the marine saturated sand foundation.

2. The method for reinforcing marine saturated sandy soil foundations by regulating interparticle cementation using microbubble-assisted EICP as described in claim 1, characterized in that, In step S1, the characteristic particle size of the microbubbles is 50 nm-100 μm, and the concentration of the microbubbles is 10. 6 -10 10 per mL.

3. The method for reinforcing marine saturated sandy soil foundations by regulating interparticle cementation using microbubble-assisted EICP as described in claim 2, characterized in that... In step S1, the characteristic particle size of the microbubbles is 200 nm-30 μm, and the concentration of the microbubbles is 10. 7 -10 9 per mL.

4. The method for reinforcing marine saturated sandy soil foundations by regulating interparticle cementation using microbubble-assisted EICP as described in claim 1, characterized in that... In step S1, the EICP reaction solution includes a urease solution and a cementing solution; The microbubble-containing EICP reaction solution is a microbubble-containing urease solution or a microbubble-containing cementing solution.

5. The method for reinforcing marine saturated sandy soil foundations by regulating interparticle cementation using microbubble-assisted EICP as described in claim 4, characterized in that, Step S2 can be one of the following methods: (a) When the liquid containing microbubbles is microbubble water, the microbubble water is first injected into the marine saturated sandy soil foundation to be reinforced. After the microbubbles are retained and form a gas-containing environment, EICP reaction liquid is then injected. (b) When the microbubble-containing liquid is microbubble water, the microbubble water and the premixed EICP reaction solution are injected together into the marine saturated sand foundation to be reinforced; (c) When the liquid containing microbubbles is a urease solution containing microbubbles, the urease solution containing microbubbles is first injected into the marine saturated sandy soil foundation to be reinforced. After the microbubbles are retained and form a gas-containing environment, the cementing liquid is then injected. (d) When the liquid containing microbubbles is a cementing solution containing microbubbles, the cementing solution containing microbubbles is first injected into the marine saturated sandy soil foundation to be reinforced. After the microbubbles are retained and form a gas-containing environment, the urease solution is then injected.

6. The method for reinforcing marine saturated sandy soil foundations by regulating interparticle cementation using microbubble-assisted EICP as described in claim 5, characterized in that... When using method (a), the microbubble water is allowed to stand for 5 min-6 h after injection; The microbubble water and / or EICP reaction solution are injected in multiple rounds of low-volume injection, intermittent injection, or segmented injection.

7. The method for reinforcing marine saturated sandy soil foundations by regulating interparticle cementation using microbubble-assisted EICP as described in claim 6, characterized in that... When mode (a) is used, the volume of the microbubble water injected each time is 0.2-3.0 times the pore volume of the target reinforced area, and the volume of the EICP reaction solution injected each time is 0.2-1.0 times the pore volume of the target reinforced area.

8. The method for reinforcing marine saturated sandy soil foundations by regulating interparticle cementation using microbubble-assisted EICP as described in claim 5, characterized in that, When in mode (a), the urease solution is injected first and then the cementing liquid is injected, the cementing liquid is injected first and then the urease solution is injected, or the urease solution and the cementing liquid are mixed and then injected.

9. The method for reinforcing marine saturated sandy soil foundations by regulating interparticle cementation using microbubble-assisted EICP as described in claim 4, characterized in that, In step S2, the cementing solution includes urea and a calcium source; The urea concentration is 0.1-1.5 mol / L, and the calcium source concentration is 0.1-1.5 mol / L; the calcium source is selected from at least one of calcium chloride, calcium lactate, or calcium acetate.

10. The method for reinforcing marine saturated sandy soil foundations by microbubble-assisted EICP regulation of interparticle cementation as described in any one of claims 1-9, characterized in that, The marine saturated sandy soil foundation refers to at least one of the following: sandy soil foundation surrounding marine engineering foundations, sandy soil foundation below marine engineering foundations, surface sandy soil foundation of the seabed, erosion protection reinforcement zone, and locally weakened seabed reinforcement zone.

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