Sand liquefaction prevention and treatment method based on biomimetic mineralization

Abstract

The application provides a sand liquefaction prevention and treatment method based on biomimetic mineralization, and belongs to the technical field of geotechnical engineering. The sand liquefaction prevention and treatment method comprises the following steps: (1) exploring a region to be reinforced, dividing a liquefaction risk level of the region to be reinforced based on an exploration result, and determining a treatment range and depth; (2) configuring a reinforcement system comprising an ultrasonic vibration device, a grouting system and a distributed optical fiber sensor, and preparing cementing liquid A and cementing liquid B; (3) arranging hole positions in a quincunx shape in the region to be reinforced, performing drilling construction, and installing the grouting system, the ultrasonic vibration device and the distributed optical fiber sensor in the grouting hole; (4) starting the ultrasonic vibration device to pre-vibrate the region to be reinforced, and then sequentially injecting the cementing liquid A and the cementing liquid B through the grouting system; (5) after grouting is completed, starting the ultrasonic vibration device again to perform cyclic vibration, so as to promote the cementing liquid A and the cementing liquid B to generate cementing crystals; and (6) verifying a reinforcement effect.

Description

Technical Field

[0001] This application belongs to the field of geotechnical engineering technology, specifically relating to a method for preventing sand liquefaction based on biomimetic mineralization. Background Technology

[0002] Soil liquefaction refers to the sudden breakdown and liquefaction of saturated sand under vibrational loads. When loose saturated sand is subjected to horizontal vibrational loads, the sand particles detach from their original positions and, without forming a new stable state, remain suspended. The load on the sand particles is then borne by pore water. When the vibrational load is strong, the pore water pressure cannot dissipate in time and continues to rise. When the pore water pressure approaches the total stress, the soil enters a flow state, i.e., soil liquefaction occurs. Soil liquefaction can easily trigger numerous engineering disasters, specifically manifested as water spraying and sand eruption, lateral expansion and sliding of the soil, and can also lead to reduced foundation stiffness, building tilting, and deterioration of site geological conditions due to the floating of sand particles. It can cause serious damage not only to public buildings but also to water conservancy structures such as building collapses and dam erosion. Currently, the main methods for treating sand liquefaction include vibration compaction technology, crushed stone pile drainage system, cement-based grouting and silicate grouting. However, these methods all have drawbacks such as limited treatment depth, treatment effect greatly affected by geological conditions, high engineering cost and environmental pollution risk. Therefore, there is an urgent need to introduce greener, more economical and effective sand liquefaction treatment technologies. Summary of the Invention

[0003] To address the aforementioned technical problems, this application provides a method for preventing and controlling sand liquefaction based on biomimetic mineralization, aiming to at least partially solve the above-mentioned technical problems. The specific technical solution provided by this application is as follows.

[0004] This application provides a method for preventing sand liquefaction based on biomimetic mineralization, which includes the following steps:

[0005] Step (1): Conduct an exploration of the area to be reinforced, classify the liquefaction risk level of the area to be reinforced based on the exploration results, and determine the scope and depth of treatment;

[0006] Step (2): Configure a reinforcement system including ultrasonic vibration equipment, grouting system and distributed optical fiber sensors, and prepare cementing liquid A and cementing liquid B to induce biomimetic mineralization reaction;

[0007] Step (3): Drill holes in a quincunx pattern in the area to be reinforced, install a grouting system in the grouting holes, implant an ultrasonic vibration device in the predetermined position, and deploy distributed fiber optic sensors at the same time.

[0008] Step (4): Start the ultrasonic vibration equipment to pre-vibrate the area to be reinforced, and then inject cementing liquid A and cementing liquid B in sequence through the grouting system;

[0009] Step (5): After grouting is completed, the ultrasonic vibration equipment is restarted to perform cyclic vibration, so as to promote the migration, mixing and biomimetic mineralization reaction of ions in cementing solution A and cementing solution B, and generate colloidal crystals.

[0010] Step (6): Verification of reinforcement effect.

[0011] In this embodiment, by first exploring and classifying the liquefaction risk level and then determining the treatment scope and depth, precise and targeted treatment of sand liquefaction is achieved. By combining ultrasonic vibration technology with biomimetic mineralization technology, ultrasonic pre-vibration effectively breaks through the capillary water film on the surface of sand particles and opens up pore permeation channels. Cyclic vibration further promotes the migration and mixing of cementing liquid ions. Combined with a plum blossom-shaped pore layout, the cementing liquid is diffused more evenly. Distributed fiber optic sensors ensure the controllability of the construction process. The final generated calcium carbonate gel crystals can fully fill and cement the pores of sand, significantly improving the liquefaction resistance and mechanical strength of sand. Moreover, the process is green and environmentally friendly, adaptable to sand layers with different geological conditions, effectively overcoming the application shortcomings of traditional treatment technologies, and achieving better treatment depth and reinforcement effect. Attached Figure Description

[0012] Figure 1 This is a schematic flowchart of the sand liquefaction prevention method based on biomimetic mineralization in the embodiments of this application;

[0013] Figure 2 This is a schematic cross-sectional view of the sand liquefaction prevention process in the embodiments of this application;

[0014] Figure 3 for Figure 2 A magnified view of a portion of region A in the middle;

[0015] Figure 4 for Figure 2 The diagram shows a planar structure of the sand liquefaction prevention process.

[0016] In the above figures, the reference numerals are as follows:

[0017] 1. Grouting hole for cementing fluid A; 2. Grouting hole for cementing fluid B; 3. Ultrasonic probe; 4. Sleeve valve tube; 5. Sealing ring; 6. Rubber stopper; 7. Grouting port; 8. Grouting core tube; 9. Shell material; 10. Rubber check valve; 11. Storage container for cementing fluid A; 12. Storage container for cementing fluid B; 13. Battery and control system; 14. Area to be reinforced; 15. Pre-tightening bolts; 16. Transducer; 17. Diffuser; 18. Distributed fiber optic sensor. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with specific embodiments and the accompanying drawings.

[0019] Biomimetic-chemically induced carbonate precipitation (BCICP) is based on the biomimetic mineralization of calcium carbonate. It involves directly regulating the metathesis reaction between calcium chloride and sodium carbonate between soil particles by adding an external regulator. The resulting calcium carbonate crystals can effectively fill soil pores and cement soil particles, thereby improving soil properties.

[0020] Specifically, the application of biomimetic mineralization technology can reduce the permeability coefficient of sand and block the development path of excess pore water pressure; it can also reduce the porosity of sand to the critical porosity, allowing the sand to enter the non-liquefaction zone. In addition, biomimetic mineralization treatment can regulate the formation of three cementation modes of calcium carbonate, optimizing the dynamic load response of sand; improving the strength index of sand; and optimizing drainage performance. Furthermore, this technology has good adaptability to different environments and is less affected by freeze-thaw cycles and wet-dry cycles. In summary, biomimetic mineralization technology, through the synergistic effect of crystals and sand particles, breaks through the bottlenecks of traditional technologies in three aspects: pore filling, cementation strengthening, and drainage control, achieving a dual-pathway blockage of sand liquefaction prevention and control based on the "structure-permeability" pathway.

[0021] Currently, the application of biomimetic mineralization technology faces the challenge of addressing the numerous micropores (0.1mm-0.5mm) present in soil (especially in silt and fine sand sites). The cementing fluid is hindered from penetrating these pores by the capillary water film on the surface of soil particles. Ultrasonic vibration technology, however, can utilize the micro-jet effect generated by low-frequency vibration to break through the capillary water film on the surface of sand particles, creating channels within the 0.1mm-0.5mm micropores. Mid-frequency vibration drives the sand particles to vibrate, loosening the interlocking relationship between them, reducing the flow friction resistance of the cementing fluid, and promoting its diffusion. Finally, the cavitation effect is utilized; the bursting of microbubbles formed by vibration releases instantaneous energy, accelerating the diffusion of cementing fluid molecules and the circulation within the pores.

[0022] Based on this, this application provides a method for preventing and controlling sand liquefaction based on biomimetic mineralization. By combining biomimetic mineralization technology with ultrasonic vibration technology, the bottleneck of cementing liquid penetration is overcome, and the pore-filling and cementing strengthening effect of calcium carbonate crystals is fully utilized to achieve efficient prevention and control of sand liquefaction.

[0023] Figure 1 This is a schematic flowchart of the sand liquefaction prevention method based on biomimetic mineralization in the embodiments of this application; Figure 2 This is a schematic cross-sectional view of the sand liquefaction prevention process in the embodiments of this application; Figure 3 for Figure 2 A magnified view of a portion of region A in the middle; Figure 4 for Figure 2 The diagram shows a planar structure of the sand liquefaction prevention process.

[0024] Specifically, such as Figures 1-4 As shown, the method for preventing sand liquefaction based on biomimetic mineralization provided in this application includes steps (1) to (6).

[0025] Step (1): Conduct an exploration of the area 14 to be reinforced, and classify the liquefaction risk level of the area 14 to be reinforced based on the exploration results, and determine the scope and depth of treatment.

[0026] Step (2): Configure a reinforcement system including an ultrasonic vibration device, a grouting system and a distributed optical fiber sensor 18, and prepare cementing liquid A and cementing liquid B for inducing biomimetic mineralization reaction.

[0027] Step (3): Drill holes in the area to be reinforced 14 in a quincunx pattern, install the grouting system in the grouting holes, implant the ultrasonic vibration equipment in the predetermined position, and deploy the distributed fiber optic sensor 18.

[0028] Step (4): Start the ultrasonic vibration equipment to pre-vibrate the area 14 to be reinforced, and then inject the cementing liquid A and cementing liquid B in sequence through the grouting system.

[0029] Step (5): After grouting is completed, the ultrasonic vibration equipment is restarted for cyclic vibration to promote the migration, mixing and biomimetic mineralization reaction of ions in cementing solution A and cementing solution B, and generate colloidal crystals.

[0030] Step (6): Verification of reinforcement effect.

[0031] In this embodiment, by first exploring and classifying the liquefaction risk level, accurately locking the treatment scope and depth, and then configuring a collaborative reinforcement system consisting of ultrasonic vibration equipment, grouting system, and distributed fiber optic sensors, combined with quincunx-shaped hole layout and drilling construction, the equipment is precisely deployed. After ultrasonic pre-vibration breaks through the capillary water film to open a permeation channel, cementing liquid A and cementing liquid B are injected, and cyclic vibration promotes ion migration and mixing and biomimetic mineralization reaction to generate uniform colloidal crystals. Finally, the reinforcement quality is guaranteed by effect verification. The whole process realizes "precise positioning - efficient permeation - enhanced reaction - controllable quality", effectively filling sand pores and cementing particles, blocking liquefaction paths, significantly improving the sand's anti-liquefaction performance, and overcoming the shortcomings of single technology.

[0032] In some embodiments, step (1) specifically includes classifying the liquefaction risk level of the area to be reinforced 14 by: calculating the liquefaction resistance safety factor FL and liquefaction index IL of the area to be reinforced 14 based on the exploration results, and classifying the liquefaction risk level of the area to be reinforced based on the liquefaction index IL. The exploration results include soil structure and hydrological conditions, basic physical state indicators of sandy soil, and liquefaction index related parameters.

[0033] For example, this application provides an exploration scheme: using a Standard Penetration Test (SPT) device, a Static Cone Penetration Test (CPT) device, and a ground-penetrating radar system to conduct exploration in the area to be reinforced. Specifically, exploration boreholes are laid out in a (8m-12m) × (8m-12m) grid within the area to be reinforced. A combined method of "SPT + CPT + ground-penetrating radar scanning" is used to identify key indicators of the liquefiable sand layer within a depth range of 30m-50m, specifically including:

[0034] Soil structure and hydrological conditions: distribution range, number of layers, thickness, burial depth, unit weight of sandy soil layers, groundwater level, saturation state, pore water pressure, and groundwater head height;

[0035] Basic physical properties of sandy soil: void ratio (e), relative density (D) r Particle size distribution characteristics (particle size distribution and D) 10 D 30 D 50 D 60 (The corresponding sand particle size when the cumulative distribution ratio in the system reaches 10%, 30%, 50%, and 60%).

[0036] Liquefaction index related parameters: raw blow count N, cone tip resistance q c wait.

[0037] In some embodiments, the calculation process of the liquefaction resistance safety factor FL includes: calculating the cyclic liquefaction resistance ratio CRR of the sand and the cyclic shear stress ratio CSR of the sand under seismic action, wherein CRR is based on the original blow count N and is determined after correction for overlying stress, fine grain content, magnitude and effective stress, and CSR is determined based on the peak ground acceleration, total soil stress, effective stress and depth reduction factor; and finally, it is calculated by FL=CRR / CSR.

[0038] Specifically, the cyclic liquefaction resistance ratio (CRR) of sandy soil is calculated using the following steps:

[0039] 1. Correct the original hit count N to the effective hit count N 60 The calculation formula is shown in equation (1):

[0040] Equation (1);

[0041] Among them, C E C B C R C S These are all empirical parameters and their values ​​need to be determined based on actual exploration results. Specifically, the energy correction coefficient C... E The value ranges from 0.6 to 1.2, and the aperture correction factor C BThe value of is 0.85 - 1.15, and the rod length correction coefficient C R The value of is 0.75 - 1.10, and the sampler correction coefficient C S The value of is 0.8 - 1.2.

[0042] 2. For the effective blow count N 60 Perform overburden stress normalization to obtain the normalized blow count , and the calculation formula is shown in Equation (2):

[0043] Equation (2);

[0044] where C N is the overburden stress correction coefficient (empirical parameter), and the value range is 0.5 - 2.0.

[0045] 3. Based on the fine - grain content FC, correct to obtain the corrected normalized blow count , and the calculation formula is shown in Equation (3):

[0046] Equation (3);

[0047] where FC (fine - grain content) is determined by the soil sample screening test, which refers to the proportion of the mass of sand particles with a particle size less than 0.075 in the total mass of sand particles. Determine the value of the correction coefficient C FC : When FC ≤ 5%, the correction coefficient C FC is 0.95 - 1.05; when 5% < FC ≤ 15%, the correction coefficient C FC is 1.05 - 1.15; when 15% < FC ≤ 35%, the correction coefficient C FC is 1.15 - 1.30.

[0048] 4. Calculate the cyclic resistance ratio to liquefaction CRR of the sand in each soil layer i , and the calculation formula is shown in Equation (4):

[0049] Equation (4);

[0050] where CRR 7.5,i varies monotonically with , when is 5 - 10, CRR 7.5 is 0.05 - 0.10; when is 10 - 20, CRR 7.5 wis 0.10 - 0.25; when it is greater than 20, CRR 7.5Greater than 0.25. MSF is the magnitude correction factor, with values ​​determined by magnitude: 0.8-1.0 for strong earthquakes, 1.0-1.3 for moderate earthquakes, and 1.3-1.8 for minor earthquakes. K σ The effective stress correction factor is 1.0-1.2 for shallow soil (0-20m) and 0.8-1.0 for deep soil (20m and below).

[0051] Specifically, the cyclic shear stress ratio (CSR) of sand under seismic loading is calculated using the following steps:

[0052] 1. Calculate the total stress This value is taken as the cumulative total stress of the overlying soil layers, and the calculation formula is shown in equation (5):

[0053] Equation (5);

[0054] Where γ is the unit weight of groundwater and Δz is the thickness of the soil layer.

[0055] 2. Calculate the pore pressure With effective stress The calculation formulas are shown in equations (6) and (7):

[0056] Equation (6),

[0057] Equation (7);

[0058] Where, γ w The empirical value is 9.8-10 kN / m 3 h w,i The water head height from the midpoint of the soil layer to the water level line (calculated from the water level depth).

[0059] 3. Calculate the depth reduction factor r d,i According to the depth of the midpoint of the soil layer Piecewise linear interpolation determines the depth; the greater the depth, the better. The smaller the value, the more appropriate the values ​​for each depth segment are:

[0060] ;

[0061] ;

[0062] ;

[0063] .

[0064] 4. Calculate the cyclic shear stress ratio (CSR) of sand under seismic action for each soil layer. The calculation formula is shown in equation (8):

[0065] Equation (8);

[0066] Among them, a max The peak seismic acceleration under design seismic loading is taken in the range of 0.05g-0.40g, and the specific value is determined according to the seismic fortification requirements of the project site. g is the acceleration due to gravity.

[0067] In some embodiments, the calculation process of the liquefaction index IL includes: dividing the area to be reinforced into continuous calculation units along the depth direction, and calculating the liquefaction contribution value of the calculation units in which the liquefaction safety factor FL is less than 1.0. , of which FL i h represents the liquefaction resistance safety factor for a calculation unit with a liquefaction resistance safety factor less than 1.0. i For the thickness of the calculation unit with a liquefaction safety factor less than 1.0, w i The depth weighting coefficient varies with the depth of the computational cell; the liquefaction contribution value IL of all computational cells that satisfy FL < 1.0. i The summation yields the liquefaction index IL.

[0068] Specifically, the liquefaction resistance safety factor FL of each soil layer is first determined. i Calculate them one by one, when FL i A value less than 1.0 indicates a high probability of liquefaction in the sand at that depth, necessitating reinforcement and treatment of the soil layer. To further determine key parameters such as the treatment scope and depth, a liquefaction index (IL) is obtained by weighted integration of the liquefaction layer thickness and liquefaction degree, thereby delineating liquefaction zones. The process for determining the IL index is as follows:

[0069] 1. Divide the liquefiable sand layer into several calculation units along the depth direction, with each unit having a thickness of 0.5m-1.0m. In practice, the liquefiable sand layer is continuously divided according to the depth range recorded in the grouting hole logs and in-situ tests, ensuring that each calculation unit covers the sand state within its corresponding depth range. The midpoint depth of the calculation unit is used as the representative depth of that unit, which is used for the liquefaction safety factor FL. i and liquefaction index IL i The calculation.

[0070] 2. For FL i For computational units with a value <1.0, their liquefaction contribution value IL is defined. i As shown in equation (9):

[0071] Equation (9);

[0072] Among them, FL i h is the liquefaction resistance safety factor for the i-th calculation unit; iw is the thickness of the i-th computational unit; i The depth weighting coefficient varies with the depth of the computational unit (w) within the range from the surface to a depth of 20m. i Take 1.0-1.5; within the depth range of 20m-30m, w i Take 0.5-1.0; below 30m, w i Take 0.2-0.5).

[0073] 3. The final liquefaction index IL is the sum of all FL values. i Liquefaction contribution value IL of computational units <1.0 i The sum, i.e., IL = ∑IL i .

[0074] In some embodiments, the liquefaction risk level of the area to be reinforced is divided according to the liquefaction index IL. Specifically, when the liquefaction index IL ≥ 15, the area to be reinforced is classified as a high liquefaction risk area, and its treatment depth covers the area to be reinforced and extends downward to a preset depth (e.g., 5m-10m); when 5 ≤ IL < 15, the area to be reinforced is classified as a medium liquefaction risk area, and its treatment depth covers the area to be reinforced; when IL < 5, the area to be reinforced is classified as a low liquefaction risk area, and selective reinforcement is carried out on the local weak areas of the area to be reinforced.

[0075] In some embodiments, in step (2), the reinforcement system configured for the treatment construction includes an ultrasonic vibration device, a grouting system, and distributed fiber optic sensors. Optionally, the specific configuration and parameters of each system are as follows:

[0076] Ultrasonic vibration device: It consists of an ultrasonic probe 3 and a battery and control system 13; the ultrasonic probe has a diameter of 45mm-55mm and a length of 30m-55m, and the battery and control system 13 has a frequency range of 18kHz-55kHz and a power of 50w-220W.

[0077] Grouting System: The core of the grouting system is the sleeve valve pipe system, which works in conjunction with supporting construction equipment, including a crawler rotary drilling rig, a high-precision metering pump, and a hydraulic implanter. For example, such as... Figure 3 As shown, the specific configuration and parameters of the sleeve valve pipe system are as follows:

[0078] (1) Main sleeve valve tube 4: Made of high-density polyethylene (PE100) or rigid unplasticized polyvinyl chloride (PVC-U), with an outer diameter of 70mm-80mm, a wall thickness of about 5mm, a valve port spacing of 0.3m-0.6m, and a 70-120 mesh nylon filter screen attached to the outside;

[0079] (2) Matching pipe fittings and accessories: Grouting core pipe 8 with an outer diameter of 32mm-38mm and a wall thickness of about 3mm; rubber check valve 10 with a thickness of 3mm-3.5mm and an opening pressure difference of 0.05MPa-0.15MPa; bidirectional sealing rings 5 ​​with a width of 12mm and a thickness of 6mm are installed every 0.3m-0.6m on the pipe body, and the bottom of the bidirectional sealing rings 5 ​​is sealed with rubber plugs 6 with a length of 60mm-80mm and a pressure resistance of ≥2.0MPa; the pipe body is equipped with grouting ports 7 made of 304 stainless steel with a diameter of about 20mm and a pressure resistance of 2.5MPa.

[0080] (3) Filling material: The sleeve valve pipe 4 and the grouting hole wall are selectively filled with shell material 9. The shell material can be bentonite or low-strength shell material according to the actual working conditions. The low-strength shell material includes cement, bentonite and water.

[0081] In some embodiments, in step (2), cementing solution A is an aqueous solution containing water-soluble calcium salt, preferably a mixed aqueous solution containing water-soluble calcium salt, nucleation regulator and dispersant, and cementing solution B is an aqueous solution containing water-soluble carbonate. The concentrations of cementing solution A and cementing solution B are determined according to the particle size distribution characteristics and liquefaction risk level of the sand.

[0082] For example, the water-soluble calcium salt includes calcium chloride; the nucleation regulator includes any one of carboxymethyl chitosan, sodium carboxymethyl cellulose, hydroxypropyl methyl cellulose, and polyacrylic acid; the dispersant includes a polycarboxylic acid-based dispersant to reduce the probability of ionic aggregation; and the water-soluble carbonate includes sodium carbonate. The cementing solution should be prepared and used immediately, and stored for no more than 10 hours. After preparation, cementing solution A and cementing solution B are placed in storage container 11 (cementing solution A) and storage container 12 (cementing solution B), respectively, for later use.

[0083] In some embodiments, step (3), the drilling operation of arranging holes in a quincunx pattern in the area to be reinforced 14 specifically includes: such as Figure 4 As shown, in the area to be reinforced 14, grouting holes 1 for cementitious liquid A and grouting holes 2 for cementitious liquid B are arranged in a staggered, quincunx pattern for drilling. Specifically, in the high liquefaction risk zone, the distance between grouting holes 1 for cementitious liquid A and grouting holes 2 is 1.0m-1.4m; in the medium liquefaction risk zone, the distance is 1.4m-1.8m; and in the low liquefaction risk zone, the distance is 1.8m-2.2m.

[0084] It should be noted that, unless otherwise specified, the term "grouting hole" mentioned in this application includes grouting hole 1 for cementing liquid A and grouting hole 2 for cementing liquid B.

[0085] For example, after drilling holes in a quincunx pattern in the area to be reinforced 14, a crawler-type rotary drilling rig is used for drilling. In high-liquefaction risk areas, a casing follow-up process is used to prevent borehole wall collapse, while in medium- and low-liquefaction risk areas, a mud wall protection process is used. After drilling to the designed depth, the sediment at the bottom of the hole is cleaned. By designing the spacing between the cementing fluid A injection hole 1 and the cementing fluid B injection hole 2, combined with the synergistic control of the above drilling process, cementing fluid A and cementing fluid B are fully contacted in both spatial and temporal dimensions, significantly improving the integrity and uniformity of the biomimetic mineralization reaction.

[0086] In some embodiments, in step (3), the prefabricated sleeve valve pipe 4 is lowered into the grouting hole and the bottom of the pipe is sealed; filling material is injected into the gap between the grouting hole wall and the sleeve valve pipe. The filling material is selected according to the depth zone. Bentonite is used in the depth range of 0-10m, and low-strength shell material is used in the depth range of 10m-50m; after the filling operation is completed, clean water is injected for sealing test. The test qualification standard is no leakage. If leakage is found, the corresponding filling part needs to be refilled.

[0087] In some embodiments, step (3) involves implanting the ultrasonic vibration device into a predetermined position and simultaneously deploying the distributed fiber optic sensor 18. Specifically, this includes: using a hydraulic implanter to vertically implant the ultrasonic probe 3 into the outside of the sleeve valve tube 4 in the grouting system, wherein the ultrasonic probe 3 is arranged in a cross shape inside the grouting hole, and at the same time, the distributed fiber optic sensor 18 is deployed along the axial direction of the grouting hole outside the grouting hole. Then, the grouting hole is backfilled with fine sand and lightly compacted.

[0088] For example, such as Figures 2-4 As shown, an ultrasonic probe 3 (including pre-tightening bolt 15, transducer 16, and diffuser 17) is vertically implanted into the outer side of the sleeve valve tube 4, 5cm-20cm above the rubber plug 6, using a hydraulic implantation machine. This placement facilitates the vertical movement of the ultrasonic probe 3 along with the sleeve valve tube 4. The hydraulic implantation machine's advancing speed is controlled at 0.15m / s-0.25m / s, with a pause of 8s-12s every 4m-6m to prevent excessive compaction of the sand. After the ultrasonic probe 3 is implanted, the grouting hole is backfilled with fine sand in layers (4cm-6cm per layer) and lightly compacted to ensure close contact between the ultrasonic probe 3 and the sand, allowing for full propagation of vibration energy. Simultaneously, the ultrasonic probe 3 is arranged in a cross shape within the grouting hole. Utilizing the principle of liquid movement from high-pressure to low-pressure areas, the diffusion efficiency of the cementing fluid is improved. Furthermore, the ultrasonic vibration energy acts radially on the grouting influence area, effectively overlapping with the cementing fluid diffusion range, thereby enhancing the uniformity of the biomimetic mineralization reaction.

[0089] Furthermore, to achieve continuous monitoring of strain, temperature, and micro-vibration changes within the area to be reinforced 14, distributed optical fiber sensors 18 are laid parallel to the grouting hole axis in the sand outside the grouting holes, with a spacing of 5cm-15cm. The deployment depth of the distributed optical fiber sensors 18 is differentiated according to the liquefaction risk level. In high liquefaction risk areas, they are deployed along the entire length of the treatment range, while in medium and low liquefaction risk areas, the deployment depth covers the treatment range and extends 5m-10m below the treatment range. The optical fibers are fixed with fine sand or low-modulus grouting material to ensure good coupling with the undisturbed sand and guarantee the monitoring effect.

[0090] In some embodiments, during steps (4) and (5), the vibration parameters are adjusted according to the liquefaction risk level of the area 14 to be reinforced during the pre-vibration and cyclic vibration using an ultrasonic vibration device. Specifically, in the high liquefaction risk area, the ultrasonic frequency is 18kHz-24kHz, the ultrasonic power is 110W-160W, and the vibration time is 30min-60min; in the medium liquefaction risk area, the ultrasonic frequency is 20kHz-26kHz, the ultrasonic power is 90W-130W, and the vibration time is 20min-40min; in the low liquefaction risk area, the ultrasonic frequency is 24kHz-30kHz, the ultrasonic power is 70W-110W, and the vibration time is 10min-50min.

[0091] In some embodiments, in step (5), the number of cycles during cyclic vibration is determined by the liquefaction risk level, specifically: in the high liquefaction risk zone, the number of cycles is 12-14; in the medium liquefaction risk zone, the number of cycles is 10-12; and in the low liquefaction risk zone, the number of cycles is 8-10. During cyclic vibration, the distribution of the generated crystals is monitored (e.g., an ultrasonic imager can be used), and when crystal agglomeration is detected, the ultrasonic parameters are adjusted for fragmentation, for example, the ultrasonic frequency is increased to 43kHz-50kHz, and vibration is performed for 8-12 minutes to break up the agglomerates.

[0092] In some embodiments, the operation of sequentially injecting cementitious liquid A and cementitious liquid B through the grouting system in step (4) needs to be carried out in stages according to the design depth; wherein the concentration of cementitious liquid is determined according to the particle size distribution characteristics and liquefaction risk level of sand, and the grouting pressure, flow rate and single injection volume are determined according to the grouting depth range. The specific parameter calculation, selection and operation requirements are as follows:

[0093] 1. Based on the preliminary exploration results, the particle size distribution and D... 10 D 30 D 50 D 60(The corresponding sand particle sizes when the cumulative distribution ratio in the system reaches 10%, 30%, 50%, and 60%), and calculate the gradation coefficient: uniformity coefficient C. u and curvature coefficient C c Both can be determined by equations (10) and (11):

[0094] Equation (10);

[0095] Equation (11);

[0096] 2. Based on the above calculation results, classify the sand into particle sizes and determine the quality of the gradation:

[0097] Particle size classification: Fine sand is classified as D. 50 <0.25mm or D 10 <0.05mm and with low permeability; medium sand is 0.25. <D 50 <0.5mm; coarse sand is D 50 >0.5mm;

[0098] Judging the quality of gradation: When C u >6 and 1 <C c A value less than 3 indicates a good gradation; when C... u <6 or C c Deviations from the above range are considered to indicate poor gradation.

[0099] 3. Based on the particle size distribution characteristics and liquefaction risk level of the sand, determine the concentrations of cementing solution A and cementing solution B and the addition ratio of polycarboxylate dispersant according to the standards shown in Table 1.

[0100] Table 1. Concentration standards of cementitious solution A and cementitious solution B, and the addition ratio of polycarboxylate dispersant.

[0101]

[0102] 4. Based on the grouting depth range, determine the corresponding grouting pressure, grouting flow rate, and single injection volume. The specific parameters are shown in Table 2.

[0103] Table 2 Grouting pressure, flow rate, and single injection volume

[0104]

[0105] 5. According to the determined cementitious liquid concentration and grouting process parameters, first inject cementitious liquid A into the cementitious liquid A injection hole 1, and monitor the changes in grouting flow rate and pressure in real time during the injection process; after the cementitious liquid A is injected, clean the grouting pipeline, and then move the grouting equipment to the adjacent cementitious liquid B injection hole 2 to inject cementitious liquid B.

[0106] In some embodiments, in step (6), after the cyclic vibration ends, the reinforcement effect is verified. The specific operation includes: setting up test holes in the reinforcement area according to a grid of (4m-6m)×(4m-6m) and drilling core samples. The three core indicators of the soil in the reinforcement area, namely unconfined compressive strength (UCS), permeability coefficient and crystal distribution, are detected by the core samples. For areas with high reinforcement requirements, in-situ tests such as standard penetration test (SPT), static cone penetration test (CPT), and shear wave velocity (Vs) test can be carried out to achieve comprehensive and accurate verification of the reinforcement effect.

[0107] In summary, this application provides a biomimetic mineralization-based method for preventing and controlling sand liquefaction. By coupling biomimetic mineralization-induced calcium carbonate precipitation technology with intelligent ultrasonic vibration technology, and using ultrasonic vibration to enhance the biomimetic mineralization reaction as the core, it specifically solves the problems of uneven cementing fluid penetration, unstable deep treatment effect, and reduced reinforcement efficiency caused by crystal agglomeration in existing sand liquefaction prevention and control technologies. It is particularly suitable for the treatment of deep and complex sand liquefaction. This application relies on a combined process of "plum blossom-shaped pore layout + layered filling + ultrasonic circulation enhancement". Ultrasonic pre-vibration breaks up the capillary water film in the sand, and ultrasonic circulation vibration enhances the ion reaction efficiency, ensuring the reinforcement efficiency and effect of biomimetic mineralization. Furthermore, the process parameters are customized according to the sand liquefaction risk level and depth gradient, and dynamic monitoring by distributed fiber optic sensors is combined to achieve precise reinforcement of different soil layers. The biomimetic mineralization material used in this application can be prepared and used immediately and is environmentally friendly. It is highly compatible with construction equipment. Furthermore, a comprehensive verification method is employed, combining short-term verification by drilling core samples to test unconfined compressive strength and permeability coefficients with in-situ experiments such as SPT, CPT, and shear wave velocity tests, to ensure the reinforcement effect meets standards. The overall technical solution balances construction efficiency and safety, effectively improving the strength of sandy soil, eliminating sand liquefaction, and achieving the reinforcement of sandy soil foundations. It is particularly suitable for the liquefaction control of deep and complex sandy soils, and is a sandy soil liquefaction prevention and control method that integrates biomimetic mineralization implementation, sandy soil liquefaction elimination, and sandy soil foundation reinforcement.

[0108] The present application is further illustrated below through embodiments and related test experiments. In the detailed description below, numerous specific details are set forth for ease of explanation to provide a comprehensive understanding of the embodiments of the present application. However, it is apparent that one or more embodiments may be implemented without these specific details. Moreover, the details in the following embodiments can be arbitrarily combined to form other feasible embodiments without conflict. All instruments, consumables, and reagents used in the following embodiments are commercially available unless otherwise specified.

[0109] Example 1

[0110] Along the port container yard area to be reinforced, exploration boreholes were laid out in a 10m×10m grid. A combination of standard penetration test (SPT), static cone penetration test (CPT) and ground-penetrating radar scanning was used to systematically explore the sand layer within a depth range of 5m-30m underground to determine the engineering geological conditions of the liquefiable sand layer.

[0111] Exploration results indicate that the area mainly consists of saturated fine sand and silty fine sand layers formed by marine sedimentation, with fine sand accounting for approximately 82% and fine grains (particle size less than 0.075 mm) comprising approximately 18%. The measured particle size parameter D... 10 Approximately 0.04 mm, D 30 Approximately 0.11 mm, D 50 Approximately 0.21 mm, D 60 Approximately 0.26 mm, uniformity coefficient C u Approximately 6.5, curvature coefficient C c The density is approximately 1.2, classifying it as fine sand with moderate gradation deviation. The groundwater level is at a depth of approximately 1.3m, indicating the sand layer is in a long-term saturated state with a natural water content of 28%-32% and a relative density D. r Approximately 28%.

[0112] Based on the grouting hole logging results and the variation characteristics of SPT and CPT profiles, the sand layer within the depth range of 5m-30m is divided into three layers. The stratification conditions and in-situ test parameters are shown in Table 3.

[0113] Table 3. Layering conditions and in-situ test parameters of sandy soil in Example 1

[0114]

[0115] In this embodiment, the design peak ground acceleration a is taken. max The specific gravity of water is 0.30g. w Take 9.8 kN / m 3 The unit weight of the soil layer above the water level is taken as 18 kN / m. 3 The unit weight of saturated sand below the water level is taken as 19 kN / m³. 3 The empirical parameters used in the liquefaction resistance analysis were all strictly selected according to the range given in step (1), and their specific values ​​are: energy correction coefficient (C E =0.90), aperture correction factor (C) B =1.00), rod length correction factor (C) R =0.85), sampler correction factor (C S =1.00), overburden stress correction factor (C N =1.20), fine-grain correction factor (C FC =1.20) and magnitude correction factor (MSF=1.00). Effective stress correction factor (Kσ The value of ) varies with depth: it is 1.10 when the depth is less than or equal to 20m and 0.90 when the depth is greater than 20m.

[0116] The cyclic shear stress ratio (CSR), cyclic liquefaction resistance ratio (CRR), and liquefaction safety factor (FL) of each soil layer were calculated. Representative calculation units at different depths were selected within the main liquefiable sand layers ranging from 5m to 25m. The depth reduction factor (r) was used for the calculations. d Values ​​were taken in segments of 0-10m, 10m-20m, and 20m-30m. Calculation results show that the representative value of CSR within this depth range is approximately 0.30-0.34. Based on the original SPT blow count N=6-9, after corrections using energy, aperture, rod length, and sampler correction factors, and further corrections for overburden stress and fine grain content, (N1) 60CS The representative value is approximately 7.5-9.0, corresponding to CRR. 7.5 We set it to 0.08. This is combined with the magnitude correction factor MSF and the effective stress correction factor K. σ Subsequently, the CRR was approximately 0.088 in the 0-20m depth range and approximately 0.072 in the 20m-25m depth range.

[0117] Based on this calculation, the liquefaction safety factor FL of each representative calculation unit in the depth range of 5m-25m is about 0.24-0.30, all less than 1.0, indicating a high probability of liquefaction. However, in the depth range of 25m-30m, due to the significant increase in the number of SPT blows, the CRR increases significantly after the same correction, and the FL can approach or exceed 1.0, significantly reducing the probability of liquefaction.

[0118] The liquefiable sand layer within the range of 5m-25m is divided into several calculation units with a thickness of 0.5m, and units with FL<1.0 are further divided into... Perform a weighted integral, where h i Taking a depth of 0.5m, the depth weighting coefficient is set at 1.2 for 0-20m and 0.8 for 20m-25m, resulting in a liquefaction index (IL) of 22.6. Based on the criterion of IL ≥ 15, this area is classified as a high-liquefaction risk zone, and the treatment depth is determined to cover the entire liquefiable layer (5m-25m), while extending downwards by 5m to form a treatment range of 5-30m.

[0119] The ultrasonic vibration equipment uses an array-type intelligent ultrasonic probe with a diameter of 50mm and a length of 28m. The operating frequency range is 18kHz-55kHz, and the power range is 50W-220W. It is equipped with an ultrasonic control system. The grouting system uses a tracked rotary drilling rig with grouting holes of 120mm in diameter and a verticality deviation of less than 1%. The grouting pipeline uses PE sleeve valve pipes with an outer diameter of 75mm and a valve spacing of 0.4m. A 100-mesh nylon filter is attached to the outside of the pipe, and a high-precision metering pump is provided. Distributed fiber optic sensors are deployed along the axial direction of the grouting holes, covering a treatment depth range of 5m-28m, and extend appropriately below the reinforced area, with a monitoring point every 1m along the depth direction.

[0120] Based on the aforementioned exploration and screening test results, the particle size distribution characteristics of the sandy soil targeted for treatment in this embodiment are as follows: the sandy soil satisfies D 50 <0.25mm and D 10 Sand with a diameter <0.05mm is classified as fine sand; simultaneously, C u >6 and 1 <C c A value <3 indicates that the gradation is in a state of moderate deviation. Combined with the aforementioned liquefaction index calculation result of IL=22.6, this area is classified as a high liquefaction risk zone. Cementing solution A uses a 1.5 mol / L calcium chloride solution (approximately 166.5 g / L), with 8 g / L carboxymethyl chitosan (CMCS) added as a regulator, and the pH adjusted to approximately 7.0 using a 1 mol / L sodium hydroxide solution. The solution is stirred thoroughly and set aside. A polycarboxylate-based dispersant is added to cementing solution A at a concentration of 0.5%-0.8% to reduce the risk of ionic aggregation under high concentration conditions. Cementing solution B uses a 1.5 mol / L sodium carbonate solution (approximately 159 g / L), and is stirred thoroughly and set aside. The filling materials include low-strength shelling material (cement:bentonite:water = 1:2:3) and fine sand with a particle size of 0.1 mm-0.2 mm.

[0121] Grouting holes were arranged in a "quincunx" pattern within the reinforcement area, with cementing liquid A grouting holes and cementing liquid B grouting holes arranged alternately at 1m intervals. A crawler-type rotary drilling rig was used to drill at the designed hole positions, and a casing follow-up process was adopted during construction. The drilling reached a depth of 28m. After drilling was completed, the sediment at the bottom of the hole was cleaned.

[0122] The prefabricated sleeve valve pipe is lowered into the grouting hole and the bottom of the pipe is sealed. The filling material between the sleeve valve pipe and the hole wall is set according to depth zones: low-strength casing material is filled in the fine sand layer range of 5m-25m, and bentonite is filled in the 25m-28m section. After installation, clean water is injected into the sleeve valve pipe for a leak test. If the pressure drop is less than 0.02MPa within 30 minutes, it is considered qualified. Any leaking holes are refilled.

[0123] An ultrasonic probe was vertically implanted into the grouting hole using a hydraulic implantation machine (approximately 20kN thrust). The implantation position was controlled to be about 5cm-10cm above the rubber stopper and outside the sleeve valve tube. The advancement speed was controlled at 0.2m / s, with a 10s pause every 5m of implantation. After implantation, the area around the ultrasonic probe was backfilled with fine sand in layers, each layer approximately 5cm thick, and compacted using a small tamping device to ensure close contact between the ultrasonic probe and the sand. Distributed fiber optic sensors were laid parallel to the grouting hole axis in the sand outside the grouting hole, with a spacing of 5cm.

[0124] The ultrasonic vibration equipment was started to pre-vibrate the saturated fine sand layer in the high liquefaction risk zone. The ultrasonic vibration parameters were set as follows: frequency 20kHz, power 140W, and duration 45min. During the pre-vibration process, the cementitious liquid penetration response was monitored in real time using distributed fiber optic sensors. The pre-vibration was stopped when the monitoring signal tended to stabilize.

[0125] Turn on the high-precision metering pump and inject cementing liquid A into the sand layer corresponding to the grouting hole. Set the grouting parameters according to depth gradients: within the 5m-10m depth range, grouting pressure 0.4MPa, flow rate 6L / min, and single injection volume 80L; within the 10m-20m depth range, grouting pressure 1.0MPa, flow rate 80L / min, and single injection volume 120L; within the 20m-25m depth range, grouting pressure 1.6MPa, flow rate 10L / min, and single injection volume 180L. Monitor pressure and flow rate changes in real time during the grouting process.

[0126] After the cementing liquid A is injected, the grouting pipeline is cleaned and moved to the adjacent cementing liquid B grouting hole. Cementing liquid B is injected at the corresponding depth section with the same parameters as cementing liquid A. The grouting process follows the principle of "skipping holes".

[0127] After the cementing fluid injection is completed, the ultrasonic vibration equipment is restarted to promote the migration of ions in the cementing fluid within the soil and to induce a biomimetic mineralization reaction. In this embodiment, based on the characteristics of the high liquefaction risk area, it is preferable to implement 12 ultrasonic cycle enhancement treatments, with a settling time of 150 minutes for each cycle, followed by ultrasonic vibration after the settling period. After each cycle, the crystal distribution is detected using an ultrasonic imager; when local crystal agglomeration is found, the ultrasonic vibration frequency is temporarily increased to 50 kHz and vibrated continuously for 10 minutes to break up the crystal agglomerates.

[0128] After reinforcement, core samples were drilled in a 6m × 6m grid within the reinforced area. The unconfined compressive strength (UCS), permeability coefficient, and crystal distribution were tested. The results showed that the unconfined compressive strength of the reinforced sand core samples was 120kPa-260kPa, an increase of approximately 1.5-3.0 times compared to before reinforcement; the permeability coefficient was within 1.0 × 10⁻⁶ kPa. -4 m / s - 3.5 × 10-4 Within the range of m / s, this indicates that while significantly improving mechanical properties, it did not adversely affect the overall seepage conditions of the site. Crystal distribution testing results show that carbonate mineralization products are uniformly distributed at the sand grain contact points and within the pores, with no obvious large-scale aggregates found. The equivalent crystal size is mainly concentrated in the range of 10μm-80μm. Based on the comprehensive test results, the mechanical properties and structural stability of the reinforced sand in the reinforced area meet the design requirements.

[0129] Example 2

[0130] Construction was carried out in sections along the highway subgrade to be reinforced, with a subgrade width of approximately 26m and a single section length of approximately 1000m. Exploration boreholes were laid out in a 9m × 9m grid within the reinforcement area, with a total of 45 boreholes per section. A combination of standard penetration tests (SPT), static cone penetration tests (CPT), and ground-penetrating radar scanning was used to systematically explore the saturated sandy soil layer of the alluvial plain within a depth range of 0-15m to determine the engineering geological conditions of the liquefiable sandy soil layer.

[0131] Exploration results indicate that the sandy soil in this area is an alluvial saturated fine sand layer with a fine particle content (particle size less than 0.075 mm) of less than 10%. The groundwater level is about 1.5 m deep, and the sand layer is in a long-term saturated state with a natural water content of 30%-33% and a relative density D. r Approximately 32%. Sieving and particle size analysis results show that the sand has a relatively uniform particle size distribution, with the measured particle size parameter D... 10 Approximately 0.06 mm, D 30 Approximately 0.10 mm, D 50 Approximately 0.18mm, D 60 The uniformity coefficient C is approximately 0.22 mm. u =D 60 / D 10 ≈3.7, curvature coefficient C c =D 30 2 / (D 10 ·D 60 )≈0.76, satisfying D 50 <0.25mm and C u The condition <6 indicates fine sand with gradation deviation (uniform gradation limits permeability and diffusion uniformity). In-situ test results show that the standard penetration test blow count N is mainly distributed between 4 and 6, and the static cone tip resistance q... c It is approximately 3.5MPa-5.0MPa.

[0132] Based on the grouting hole logging results and the variation characteristics of SPT and CPT profiles, the soil layer within the 0-18m depth range is divided into three layers: 0-10m is a saturated fine sand layer, 10-15m is a saturated fine sand interbedded with silt layer, and 15-18m is a relatively dense fine sand transition layer. The stratification conditions and in-situ test parameters are shown in Table 4.

[0133] Table 4. Sand layer stratification and in-situ test parameters in Example 2

[0134]

[0135] In this embodiment, the design peak ground acceleration a is taken. max The specific gravity of water is 0.25g. w Take 9.8 kN / m 3 The unit weight of the soil layer above the water level is taken as 18 kN / m. 3 The unit weight of saturated sand below the water level is taken as 19 kN / m³. 3 The empirical parameters used in the liquefaction resistance analysis all strictly fall within the range given in step (1), and the energy correction coefficient C... E Take 0.90, aperture correction factor C B Take 1.00, rod length correction factor C R Take 0.85, sampler correction factor C S Take 1.00, overburden stress correction factor C N Set the fine-grain correction factor to 1.20. FC The magnitude correction factor (MSF) is set to 1.05; the effective stress correction factor (K) is set to 1.00. σ Take a value of 1.10 within the depth range of 0-18m. Calculate the cyclic shear stress ratio CSR, cyclic liquefaction resistance ratio CRR, and liquefaction safety factor FL, where the depth reduction factor r... d The CSR is taken as 0.95-1.00 in the 0-10m range and 0.85-0.95 in the 10-18m range. Calculation results show that the representative value of CSR in the main liquefiable sand layer in the 0-15m range is approximately 0.22-0.28, which is corrected by SPT to obtain (N1). 60CS The representative value is approximately 5.8-7.5, corresponding to CRR. 7.5 Take a value between 0.07 and 0.10, and combine MSF with K. σ The corrected CRR value is approximately 0.08-0.11, from which the FL value is approximately 0.35-0.50, which is significantly less than 1.0, indicating a high probability of liquefaction.

[0136] The liquefiable sand layer within the 0-15m range is divided into several calculation units with a thickness of 0.5m, and units with FL < 1.0 are further divided into... Perform a weighted integral, where h i Take 0.5m, wi Taking 1.2 for 0-15m, the final liquefaction index IL = 12.8 was obtained. Based on the criterion of 5≤IL<15, this area was classified as a medium liquefaction risk zone, and the treatment depth was determined to cover the main liquefiable layer (0-15m), while extending downwards by 3m to form a treatment range of 0-18m.

[0137] The ultrasonic vibration equipment employs an array-type intelligent ultrasonic probe and a matching control system. The probe diameter is 50mm, the length is 30m, the operating frequency range is 20kHz-55kHz, and the output power range is 50W-220W. The grouting system includes a tracked rotary drilling rig, PVC sleeve valve pipes, and a high-precision metering pump. It is also equipped with a wellpoint dewatering system and distributed fiber optic sensors for construction monitoring. The distributed fiber optic sensors are deployed along the axial direction of the grouting holes, parallel to the outer side of the holes, with a sensor spacing of 10cm, covering a treatment depth range of 0-18m. They also extend appropriately below the reinforced area to monitor deeper responses.

[0138] Based on the aforementioned particle size distribution and risk level assessment results, the sand in this embodiment meets the requirements for fine sand (D). 50 <0.25mm) and gradation deviation (C u <6) conditions, and is located in the medium liquefaction risk zone. Based on the above principles, cementing liquid A (Ca 2+ ) and cementing solution B (CO3) 2- The concentrations of all cementing solutions were selected within the range of 0.80 mol / L to 1.30 mol / L. Simultaneously, 0.35% to 0.6% (by mass) of a polycarboxylate-based dispersant was added to cementing solution A to reduce the probability of ion aggregation. Considering the uniform gradation of the sand and soil, the relatively simple pore channels, and the need to balance permeability and reaction rate in this embodiment, cementing solution A was preferably a 1.2 mol / L calcium chloride solution, with 0.45% (by mass of cementing solution A) of polycarboxylate-based dispersant added, along with 5 g / L sodium carboxymethyl cellulose as a viscosity and dispersibility regulator. Cementing solution B used a 1.2 mol / L sodium carbonate solution, matching the concentration level of cementing solution A. The filling materials included low-strength casing material and fine sand. The low-strength casing material used a cement, bentonite, and water mass ratio of 1:2.5:3 to meet the requirements for casing isolation and grout stoppage.

[0139] Grouting holes were laid out in a quincunx pattern within the reinforcement area, with cementing fluid A grouting holes and cementing fluid B grouting holes arranged alternately at a spacing of 1.4m. This spacing falls within the recommended range of 1.4m-1.8m for medium liquefaction risk areas and corresponds to the ultrasonic pre-vibration frequency requirement of 20kHz-26kHz for medium liquefaction risk areas. Existing roadbed drainage pipes were avoided during the hole placement process. Before construction, the wellpoint dewatering system was activated to lower the groundwater level to below 2.5m. Drilling was then carried out using a mud-wall protection process, drilling to a depth of 18m. After drilling, the bottom of the hole was flushed with high-pressure clean water, and the sediment thickness was controlled to be no more than 4cm.

[0140] The prefabricated sleeve valve pipe is lowered into the grouting hole and the bottom of the pipe is sealed. The filling material between the sleeve valve pipe and the hole wall is set according to depth zones: bentonite is filled in the 0-10m depth range, and low-strength casing material is filled in the 10m-18m depth range. After installation, clean water is injected into the sleeve valve pipe for a sealing test. If the pressure drop is less than 0.018MPa within 30 minutes, it is considered qualified. For any leaking holes, casing material is added and the pressure test is repeated.

[0141] The ultrasonic probe was vertically implanted into the outer side of the sleeve valve tube, approximately 5-10 cm above the rubber stopper, using a hydraulic implantation machine. The advancement speed was controlled at 0.18 m / s, with a 10-second pause every 4.5 m of implantation. After implantation, the area around the probe was backfilled with fine sand in layers and lightly compacted to ensure close contact between the ultrasonic probe and the sand, thereby improving vibration propagation efficiency.

[0142] The ultrasonic vibration equipment was started to pre-vibrate the saturated fine sand layer in the medium liquefaction risk zone. The pre-vibration parameters were set to an ultrasonic frequency of 24 kHz, a power of 120 W, and a duration of 30 min. This parameter combination is within the recommended range for pre-vibration in the medium liquefaction risk zone, in order to reduce the capillary water pressure of the sand and improve the cementing liquid infiltration conditions.

[0143] Subsequently, the high-precision metering pump was activated, and cementing liquid A and cementing liquid B were injected sequentially according to the designed depth. Grouting was controlled in segments based on depth: within the 0-10m depth range, the grouting pressure was controlled at 0.45MPa, the flow rate at 6L / min, and the single injection volume at 80L-100L; within the 10m-18m depth range, the grouting pressure was controlled at 1.0MPa, the flow rate at 8L / min, and the single injection volume at 120L-150L. During construction, cementing liquid A was first injected into the cementing liquid A injection hole according to the above parameters, and the pressure and flow rate changes were monitored in real time. After injection, the grouting pipeline was cleaned to prevent premature reaction within the pipeline. Then, the process was moved to the adjacent cementing liquid A injection hole, and cementing liquid B was injected at the corresponding depth segment using the same pressure, flow rate, and injection volume parameters. The grouting process followed the principle of "skipping holes".

[0144] After the cementing solution is injected, the ultrasonic vibration equipment is restarted to promote ion migration and induce a biomimetic mineralization reaction. Based on the characteristics of the liquefaction risk zone, this embodiment preferably implements 10 cycles of ultrasonic enhancement treatment, and after each cycle, an ultrasonic imager is used to detect the crystal distribution. When local crystal agglomerations are found, the ultrasonic vibration frequency is increased to 45 kHz and maintained for 10 minutes to break up the agglomerates and improve mineralization uniformity.

[0145] After reinforcement, core samples were drilled in a 5m × 5m grid within the reinforced area to test the unconfined compressive strength, permeability coefficient, and crystal distribution. The test results showed that the unconfined compressive strength of the reinforced sand core samples was 160kPa-320kPa, an increase of approximately 1.5-2.5 times compared to before reinforcement; the permeability coefficient was 8.0 × 10⁻⁶. -5 m / s - 2.5 × 10 -4 Within the range of m / s; crystal distribution test results show that carbonate mineralization products are continuously and uniformly distributed at the contact points of sand grains and inside the pores, with no obvious large-scale aggregates found, and the equivalent particle size of the crystals is mainly concentrated in the range of 10μm-70μm. Based on the comprehensive test results, the mechanical properties and structural stability of the roadbed sand in the reinforced area meet the design requirements, and its liquefaction resistance is significantly improved.

[0146] Example 3

[0147] Foundation treatment was carried out along the area to be reinforced during the construction of factory buildings in the industrial park. The column grid spacing of the factory buildings was 9m, and the reinforcement area of ​​a single zone was approximately 180m × 120m. Exploration boreholes were laid out in an 8m × 8m grid within the area to be reinforced, totaling 40 boreholes. A combination of standard penetration tests (SPT), static cone penetration tests (CPT), and ground-penetrating radar scanning was used to systematically explore the saturated silty fine sand layer of fluvial and lacustrine facies within a depth range of 3m-20m to determine the engineering geological conditions of the liquefiable sand layer.

[0148] Exploration results indicate that the sandy soil in this area is mainly a saturated fine sand layer formed by fluvial and lacustrine sedimentary deposits, with a fine-grained (particle size less than 0.075 mm) content of 12%-18%, a natural water content of 29%-32%, and a relative density D. r Approximately 29% of the sand layer is at a groundwater level of about 1.2m, indicating that the sand layer is in a state of long-term saturation. In-situ testing results show that the standard penetration test blow count N is mainly distributed between 5 and 7, and the static cone tip resistance q... c The pressure is approximately 4.0 MPa to 6.0 MPa. Particle size analysis results show that this fine sand layer is mainly composed of fine sand particles with a relatively high content. The measured particle size parameter D... 50 Less than 0.25mm, and D 10 Less than 0.05mm, combined with C u With C cThe calculation results indicate that the sand is fine with poor gradation and relatively low permeability.

[0149] Based on the grouting hole logging results and the variation characteristics of SPT and CPT profiles, the soil layer within the depth range of 3m-23m is divided into three layers: 3m-10m is a saturated fine sand layer, 10m-20m is a saturated fine sand interbedded with silt layer, and 20m-23m is a relatively stable transition layer. The stratification conditions and in-situ test parameters are shown in Table 5.

[0150] Table 5. Sand layer stratification and in-situ test parameters in Example 3

[0151]

[0152] In this embodiment, the design peak ground acceleration a is taken. max The specific gravity of water is 0.30g. w Take 9.8 kN / m 3 The unit weight of the soil layer above the water level is taken as 18 kN / m. 3 The unit weight of saturated sand below the water level is taken as 19 kN / m³. 3 The empirical parameters used in the liquefaction resistance analysis all strictly fell within the given range, and the energy correction factor C... E Take 0.90, aperture correction factor C B Take 1.00, rod length correction factor C R Take 0.85, sampler correction factor C S Take 1.00, overburden stress correction factor C N Set the fine-grain correction factor to 1.20. FC Based on FC = 12%-18%, take 1.15-1.20; the magnitude correction factor MSF is taken as 1.00; the effective stress correction factor K σ Take 1.10 for depths between 0-20m and 0.90 for depths below 20m. Calculate the cyclic shear stress ratio (CSR), cyclic liquefaction resistance ratio (CRR), and liquefaction safety factor (FL) using the formulas, where the depth reduction factor (r) is... d The CSR is taken as 0.95-1.00 in the 0-10m range and 0.85-0.95 in the 10m-20m range. Calculation results show that the representative value of CSR in the main liquefiable fine sand layer (3m-20m) is approximately 0.28-0.34, which is corrected by SPT to obtain (N1). 60CS The representative value is approximately 6.5-9.5, corresponding to CRR. 7.5 Take a value between 0.06 and 0.10, and combine MSF with K. σ The corrected CRR has a representative value of approximately 0.07-0.11, from which the representative value of FL is approximately 0.22-0.40. Most of the calculation units are less than 1.0, indicating a high probability of liquefaction.

[0153] The liquefiable sand layer within the range of 3m-20m is divided into several calculation units with a thickness of 0.5m, and units with FL<1.0 are further divided into... Perform a weighted integral, where h i Take 0.5m, depth weighting coefficient w i The liquefaction index (IL) was set at 1.2 for the 0-20m range and 0.8 for the extended control section below 20m, resulting in an IL of 21.3. Based on the criterion of IL ≥ 15, the area was classified as a high-liquefaction risk zone, and the treatment depth was determined to cover the main liquefiable layer (3m-20m) and extend downwards by 3m to form a treatment range of 3m-23m.

[0154] The ultrasonic vibration equipment employs an array-type intelligent ultrasonic probe and a matching control system, with a working frequency range of 18kHz-55kHz and an output power range of 50W-220W. The grouting system includes a hydraulic crawler-type rotary drilling rig, PE sleeve valve pipes, and dual-path high-precision metering pumps; it is also equipped with a well dewatering system, distributed fiber optic sensors, and stratified pore water pressure gauges for monitoring the construction process. The distributed fiber optic sensors are deployed along the axial direction of the grouting holes, parallel to the outer side of the holes, with a sensor spacing of 5cm, covering a treatment depth range of 3m-23m, and extending appropriately below the reinforced area to monitor deeper responses.

[0155] Based on the aforementioned particle size distribution and risk level determination results, the treatment target in this embodiment meets the fine sand criterion (D). 50 <0.25mm and D 10 <0.05mm), while the fine particle content (FC) is in the range of 12%-18%, the permeability is relatively low, and IL=21.3 is classified as a high liquefaction risk zone. According to the selection rule of "fine sand or poor gradation - high risk", the cementing solution A (Ca 2+ ) and cementing solution B (CO3) 2- The concentrations of all components were selected within the range of 1.00 mol / L to 1.50 mol / L. Simultaneously, 0.5% to 0.8% (by mass) of a polycarboxylate-based dispersant was added to cementing solution A to reduce the probability of ionic agglomeration. Considering the high fine sand particle content and the need to ensure the integrity and uniformity of the deep reaction in this embodiment, cementing solution A was preferably a 1.45 mol / L calcium chloride solution, with 0.65% (by mass of cementing solution A) of a polycarboxylate-based dispersant added, along with 8 g / L hydroxypropyl methylcellulose as a dispersant and regulator. Cementing solution B used a 1.45 mol / L sodium carbonate solution, matching the concentration level of cementing solution A. The filling materials included layered low-strength shell material, pH buffer, and graded fine sand. The shell material for the 3m-20m section used a cement, bentonite, and water mass ratio of 1:2.1:3.1 to meet the requirements for grout stopping and isolation under fine sand conditions.

[0156] Grouting holes were laid out in a quincunx pattern within the reinforcement area, with cementing fluid A grouting holes and cementing fluid B grouting holes arranged alternately at intervals of 1.2m. This interval falls within the recommended range of 1.0m-1.4m for high liquefaction risk areas, and the holes were laid out to avoid pre-buried pipelines in the plant foundation. Before construction, the well dewatering system was activated to stabilize the groundwater level below 2.8m and allowed to stand for 36 hours to allow the strata to stabilize. Drilling was then carried out using a combined casing-following and mud-walling process. The casing-following process (casing diameter 130mm) was used for the 3m-10m fine sand layer, while the mud-walling process (mud viscosity approximately 27s) was used for the 10m-23m section, drilling to a depth of 23m. After drilling, the bottom of the hole was flushed in stages with high-pressure cleaning water, and the thickness of the sediment in the fine sand layer was controlled to be no more than 3cm.

[0157] The prefabricated sleeve valve pipe is lowered into the grouting hole and the bottom of the pipe is sealed. The filling material between the sleeve valve pipe and the hole wall is set according to depth zones. The 3m-20m fine sand layer is filled with high-viscosity, low-strength casing material, and the 20m-23m section is filled with bentonite and compacted to no less than 90%. After installation, clean water is injected into the sleeve valve pipe for a sealing test. If the pressure drop is less than 0.015MPa within 30 minutes, it is considered qualified. For leakage holes, casing material or bentonite is added according to the corresponding depth, and the pressure test is repeated.

[0158] The ultrasonic probe was vertically implanted into the outer side of the sleeve valve tube, approximately 5-10 cm above the rubber stopper, using a hydraulic implantation machine. The advancement speed was controlled at 0.16 m / s, with a 12-second pause every 4 m in the 3-10 m section and a 10-second pause every 3.5 m in the 10-20 m section. After implantation, the area around the ultrasonic probe was backfilled in layers with graded fine sand and lightly compacted, with a compaction degree of not less than 85%, to ensure that the ultrasonic vibration energy was effectively transferred to the 3-20 m reinforcement layer.

[0159] The ultrasonic vibration equipment was started to pre-vibrate the saturated fine sand layer in the high liquefaction risk area. The pre-vibration parameters were selected within the recommended range for the high liquefaction risk area. Specifically, the ultrasonic frequency was 22kHz, the power was 140W, and the duration was 40min in the 3m-10m range, and the ultrasonic frequency was 24kHz, the power was 120W, and the duration was 45min in the 10m-20m range, in order to reduce capillary water pressure and improve the cementitious liquid penetration conditions.

[0160] Subsequently, dual-channel high-precision metering pumps were activated, and cementing liquid A and cementing liquid B were injected sequentially according to the designed depth. Grouting parameters were controlled in segments based on depth: within the 3m-8m depth range, the grouting pressure was controlled at 0.5MPa, the flow rate at 7L / min, and the single injection volume at 90L; within the 8m-15m depth range, the grouting pressure was controlled at 1.2MPa, the flow rate at 8L / min, and the single injection volume at 135L; and within the 15m-20m depth range, the grouting pressure was controlled at 1.8MPa, the flow rate at 9L / min, and the single injection volume at 180L. During construction, cementing liquid A was first injected into the cementing liquid A injection hole according to the above parameters. After injection, the pipeline was flushed in segments with clean water to prevent premature reaction within the pipeline. Then, the process was moved to the adjacent cementing liquid B injection hole, and cementing liquid B was injected at the corresponding depth segment using the same pressure, flow rate, and injection volume parameters. The grouting process followed the principle of "skipping holes".

[0161] After the cementing solution was injected, the ultrasonic vibration equipment was restarted to promote ion migration and induce a biomimetic mineralization reaction. Based on the characteristics of the high liquefaction risk zone, 12 ultrasonic cycle strengthening treatments were implemented, and the crystal distribution was detected using an ultrasonic imager after each cycle. When a tendency for crystal aggregation was detected, the ultrasonic vibration frequency was increased to 43kHz-50kHz and vibrated continuously for 8-12 minutes to break up the agglomerates, thereby improving the uniformity of mineralization product distribution in the pore structure and increasing the reinforcement efficiency.

[0162] After reinforcement, core samples were drilled in a 5m × 5m grid within the reinforced area for testing. Core samples were taken at approximately 3m intervals within a depth range of 3m-20m to obtain representative data in the depth direction. The test results showed that the unconfined compressive strength of the reinforced sand core samples was 180kPa-360kPa, an increase of approximately 2.0-3.0 times compared to before reinforcement; the permeability coefficient was 6.0 × 10⁻⁶. -5 m / s - 2.0 × 10 -4 Within the range of m / s; crystal distribution test results show that carbonate mineralization products are continuously and uniformly distributed at the contact points of sand grains and inside the pores, with a coverage of not less than 88%. The equivalent particle size of the crystals is mainly concentrated in the range of 10μm-90μm, and no obvious large-scale agglomerates are observed. At the same time, standard penetration tests and shear wave velocity tests were conducted in the core load-bearing area of ​​the plant. The results show that after reinforcement, the standard penetration blow count N is not less than 18, and the shear wave velocity Vs is not less than 250m / s. Overall, it is evident that the bearing capacity and liquefaction resistance of the treated foundation meet the design requirements of the plant foundation.

[0163] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of this application. It should be understood that the above descriptions are merely specific embodiments of this application and are not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for preventing and controlling soil liquefaction based on biomimetic mineralization, characterized in that, Includes the following steps: Step (1): Conduct an exploration of the area to be reinforced, classify the liquefaction risk level of the area to be reinforced based on the exploration results, and determine the scope and depth of treatment; Step (2): Configure a reinforcement system including ultrasonic vibration equipment, grouting system and distributed optical fiber sensors, and prepare cementing liquid A and cementing liquid B to induce biomimetic mineralization reaction; Step (3): Drill holes in a quincunx pattern in the area to be reinforced, install the grouting system in the grouting holes, implant the ultrasonic vibration device in the predetermined position, and deploy the distributed optical fiber sensor at the same time. Step (4): Start the ultrasonic vibration device to pre-vibrate the area to be reinforced, and then inject the cementing liquid A and the cementing liquid B in sequence through the grouting system; Step (5): After the grouting is completed, the ultrasonic vibration device is restarted to perform cyclic vibration, so as to promote the migration, mixing and biomimetic mineralization reaction of ions in the cementing liquid A and the cementing liquid B, and generate colloidal crystals. Step (6): Verification of reinforcement effect.

2. The method for preventing soil liquefaction according to claim 1, characterized in that, Based on the exploration results, the liquefaction risk level of the area to be reinforced is classified as follows: Based on the exploration results, the liquefaction safety factor FL and liquefaction index IL of the area to be reinforced are calculated, and the liquefaction risk level of the area to be reinforced is classified according to the liquefaction index IL. The exploration results include soil structure and hydrological conditions, basic physical state indicators of sandy soil, and liquefaction index-related parameters.

3. The method for preventing soil liquefaction according to claim 2, characterized in that, The calculation process for the liquefaction resistance safety factor FL includes: The cyclic liquefaction resistance ratio (CRR) and the cyclic shear stress ratio (CSR) of sand under seismic loading are calculated. The CRR is based on the original blow count N and is determined after corrections for overlying stress, fine grain content, magnitude, and effective stress. The CSR is determined based on the peak ground acceleration, total soil stress, effective stress, and depth reduction factor. The final result is calculated using FL = CRR / CSR.

4. The method for preventing soil liquefaction according to claim 3, characterized in that, The calculation process for the liquefaction index IL includes: The area to be reinforced is divided into continuous calculation units along the depth direction. For calculation units with a liquefaction resistance safety factor FL less than 1.0, their liquefaction contribution value is calculated. , of which FL i h is the liquefaction safety factor corresponding to the calculation unit with a liquefaction safety factor less than 1.

0. i w represents the thickness of the calculation unit with a liquefaction safety factor less than 1.

0. i This refers to the depth weighting coefficient, which varies with the depth of the computing unit. The liquefaction contribution value IL of all computational units that satisfy FL < 1.0 i The summation yields the liquefaction index IL.

5. The method for preventing soil liquefaction according to claim 4, characterized in that, The classification of the liquefaction risk level of the area to be reinforced based on the liquefaction index includes: When the liquefaction index IL≥15, the area to be reinforced is classified as a high liquefaction risk zone, and its treatment depth covers the area to be reinforced and extends downward to a preset depth; When 5≤IL<15, the area to be reinforced is classified as a medium liquefaction risk zone, and its treatment depth covers the area to be reinforced. When IL < 5, the area to be reinforced is classified as a low liquefaction risk zone, and selective reinforcement is carried out on the local weak areas of the area to be reinforced.

6. The method for preventing and controlling soil liquefaction according to claim 5, characterized in that, The drilling operation, which involves arranging holes in a quincunx pattern in the area to be reinforced, includes: In the area to be reinforced, cementitious liquid A injection holes and cementitious liquid B injection holes are arranged in a staggered quincunx pattern for drilling construction. The distance between the grouting holes of cementing liquid A and cementing liquid B in the high liquefaction risk zone is 1.0m-1.4m. The distance between the grouting holes of cementing liquid A and cementing liquid B in the medium liquefaction risk zone is 1.4m-1.8m; The distance between the grouting holes of cementing liquid A and cementing liquid B in the low liquefaction risk zone is 1.8m-2.2m.

7. The method for preventing soil liquefaction according to claim 5, characterized in that, During the pre-vibration and cyclic vibration processes, the vibration parameters are as follows: In the high liquefaction risk area, the ultrasonic frequency is 18kHz-24kHz, the ultrasonic power is 110W-160W, and the vibration time is 30min-60min. In the medium liquefaction risk zone, the ultrasonic frequency is 20kHz-26kHz, the ultrasonic power is 90W-130W, and the vibration time is 20min-40min. In the low liquefaction risk zone, the ultrasonic frequency is 24kHz-30kHz, the ultrasonic power is 70W-110W, and the vibration time is 10min-50min.

8. The method for preventing soil liquefaction according to claim 7, characterized in that, The number of cycles during the cyclic vibration is determined by the liquefaction risk level. In the high liquefaction risk zone, the number of cycles of the cyclic vibration is 12-14. In the medium liquefaction risk zone, the number of cycles of the cyclic vibration is 10-12. In the low liquefaction risk zone, the number of cycles of the cyclic vibration is 8-10. During the cyclic vibration process, the distribution of the generated crystals is monitored, and when crystal agglomeration is detected, the ultrasonic parameters are adjusted to break them up.

9. The method for preventing soil liquefaction according to claim 5, characterized in that, The cementing solution A is an aqueous solution containing water-soluble calcium salt, and the cementing solution B is an aqueous solution containing water-soluble carbonate. The cementing solution A is a mixed aqueous solution containing water-soluble calcium salt, nucleation regulator and dispersant; The concentrations of cementing solution A and cementing solution B are determined based on the particle size distribution characteristics of the sand and the liquefaction risk level.

10. The method for preventing soil liquefaction according to claim 1, characterized in that, The step of implanting the ultrasonic vibration device at a predetermined location and simultaneously deploying the distributed fiber optic sensors includes: An ultrasonic probe is vertically implanted into the outside of the sleeve valve tube in the grouting system using a hydraulic implantation machine. The ultrasonic probe is arranged in a cross shape inside the grouting hole. At the same time, the distributed optical fiber sensor is arranged along the axial direction of the grouting hole outside the grouting hole. Then, the grouting hole is backfilled with fine sand and lightly compacted.

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