A design method of urease-induced calcium carbonate precipitation solidification soil

Abstract

The application discloses a design method of urease-induced calcium carbonate precipitation solidified soil, which comprises the following steps: setting up orthogonal test of the solidified soil sample, and measuring the volume content of calcium carbonate; and carrying out a static water disintegration test to obtain a disintegration time curve, adopting a three-parameter hyperbolic curve model to fit the curve, establishing a design grade classification standard according to the volume content of calcium carbonate and the model fitting parameters, and reversely determining the EICP content and the curing age according to the target design grade. The application firstly introduces the disintegration time evolution law into the design process of the solidified soil, realizes the change from the experience design to the quantitative design, and proposes a three-level design system of the dangerous grade, the safe grade and the conservative grade, so that the engineering performance and the economic cost can be considered, and the optimal design interval of the solidified soil can be conveniently determined. The application is suitable for the EICP solidification design of various kinds of easily disintegrated soil bodies, and can provide technical support for the application of the green biological solidification technology in the slope protection, the roadbed reinforcement and other engineering projects.

Description

Technical Field

[0001] This invention belongs to the field of bio-geotechnical engineering, specifically relating to a design method for urease-induced calcium carbonate precipitation (EICP) solidification of soil, which can be applied to slope protection, roadbed reinforcement and other projects of easily disintegrating soils such as granite residual soil, loess, and red soil. Background Technology

[0002] Enzyme-Induced Calcium Carbonate Precipitation (EICP) is a green and low-carbon bio-solidification technology. Its principle involves urease catalyzing the hydrolysis of urea to generate carbonate ions, which combine with calcium ions in a calcium source to form calcium carbonate crystals. This cements soil particles, fills soil pores, and improves soil strength and water stability. Compared to traditional solidification materials such as cement and lime, EICP technology has advantages such as environmental friendliness, convenient construction, and minimal disturbance to the soil structure, making it promising for applications in scenarios such as the treatment of water-damaged granite residual soil slopes in southern China.

[0003] Currently, multi-directional technical research has been carried out both domestically and internationally on EICP-stabilized soil. Related patented technologies mainly focus on the development of stabilization devices, optimization of construction processes, material compounding and modification, and synergy with engineering structures. (1) Solidification testing device type: For example, patent CN119688410A discloses an EICP combined with polymer reinforced soil sample preparation and performance testing device, which integrates sample preparation, wind erosion, rain erosion, water stability testing and other functions, and realizes multi-performance integrated testing. However, this type of technology only focuses on performance testing methods and does not establish a quantitative correlation between anti-disintegration performance and calcium carbonate generation, and cannot provide a theoretical basis for parameter selection for engineering design; (2) Material compounding: For example, patent CN119735394A uses EICP technology to improve the compressive strength of geopolymers and enhances mechanical properties by filling the pores of geopolymers with calcium carbonate. However, its application scenario is in the field of building materials and does not involve the evaluation and design method of soil anti-disintegration performance. Patent CN119956759A proposes a bacterial enzyme alternating injection sand fixation process, which improves the uniformity of sand solidification by alternating operation of MICP and EICP. However, it is only for non-cohesive sand and does not consider the time history characteristics of cohesive soil disintegration when exposed to water, nor does it form a systematic parameter design method. (3) Engineering Applications: For example, patent CN122147922A proposes a directional filling method for reinforcing expansive soil slopes using microbial technology, applying MIP / EICP-treated soil to areas above the sliding surface. However, this method relies solely on experience to determine treatment parameters and lacks a quantitative design method based on the characteristics of the entire disintegration process, making it difficult to accurately balance the reinforcement effect and engineering cost. Patent CN121853429A discloses a method for synergistic reinforcement of embankment structures using geogrids and EICP, focusing on three-dimensional force transmission structures and reaction liquid diversion construction, without addressing the quantitative design criteria for the anti-disintegration performance of EICP-solidified soil. Patent CN119145397A proposes a powder-mixed EICP method for solidifying sandy soil, optimizing the urease application process, but without establishing a graded evaluation and design system for the anti-disintegration performance of the soil.

[0004] In summary, existing EICP-based soil-stabilizing technologies share the following common shortcomings: lack of unified design indicators; inability to reflect the evolution characteristics of the entire soil disintegration process; lack of quantitative correlation between EICP dosage, curing age, and calcium carbonate formation; and difficulty in determining the optimal design parameters that balance engineering performance and economy.

[0005] To address the aforementioned issues, this invention proposes a design method for urease-induced calcium carbonate precipitation (EICP) solidified soil. By constructing a disintegration time history evolution model, a quantitative relationship between calcium carbonate generation and disintegration characteristic parameters is established, and an optimal engineering design range is defined, thereby achieving accurate evaluation and parameter optimization design of the disintegration resistance performance of EICP solidified soil. Summary of the Invention

[0006] The purpose of this invention is to provide a design method for urease-induced calcium carbonate precipitation (EICP) solidified soil. By establishing a quantitative relationship between the amount of calcium carbonate generated and the parameters of the disintegration time history model, the disintegration resistance performance of EICP solidified soil can be predicted and the design parameters optimized.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: A design method for urease-induced calcium carbonate precipitation and solidification soil includes the following steps: S1. Based on the engineering characteristics of the target solidified soil, multiple sets of solidified soil samples with different EICP solution dosages and curing ages were set up according to the orthogonal test principle. S2. The amount of CaCO3 generated in each group of solidified soil samples was determined by the drainage method, and the volume content of CaCO3 V was calculated. C ; S3. Conduct static water disintegration tests on each group of solidified soil samples, continuously record the mass change of the solidified soil samples after immersion in water, and calculate the disintegration rate R. S The disintegration time history curve of the disintegration rate as a function of time was obtained. S4. A three-parameter hyperbolic model was used to fit the disintegration time history curve: ; In the formula: The disintegration rate; This refers to the disintegration time; The final collapse rate; To achieve a disintegration rate of 0.5R Sf The corresponding characteristic time; This refers to the time interval parameter; The fitting function representing the change in disintegration rate with disintegration time; S5. Based on the final collapse rate Time interval parameters Find the maximum disintegration rate ; S6. The final disintegration rate was obtained by fitting the data using regression analysis. Maximum disintegration rate Regarding the volume content of CaCO3 The fitting relationship; S7. According to V C Based on the corresponding anti-disintegration performance and the aforementioned fitting relationship, a design level classification standard is established: (1) Hazard level: <YV1, >YR1, >YK1 indicates that the soil still has a significant risk of collapse; (2) Safety level: YV1≤ ≤YV2,YR2< ≤YR1, YK2< ≤YK1 indicates that the soil has good resistance to disintegration; (3) Conservative level: >YV2, ≤YR2, ≤YK2 indicates that the soil has excellent resistance to disintegration; Among them, YV1 and YV2 are respectively The thresholds; YR1 and YR2 are respectively The thresholds; YK1 and YK2 are respectively The threshold; S8. Based on the design grade classification standard, determine the EICP solution dosage and curing age in reverse according to the target design grade.

[0008] Furthermore, in step S1, the EICP solution dosage ranges from 9% to 16%, with at least 4 groups set up; the curing age ranges from 1 hour to 14 days (i.e., 1 hour to 14 days), with the time interval between curing ages increasing as the curing age progresses, with at least 7 groups set up; the sample compaction degree is consistent with the target solidified soil compaction degree; and the sample curing adopts a moisturizing and constant temperature environment.

[0009] Further, in step S2, the amount of CaCO3 generated in the sample is determined by the water displacement method, including the following steps: Weigh a number of samples and place them in a titration bottle. Add hydrochloric acid to the titration bottle to react with the CaCO3 in the sample. Calculate the volume of CO2 based on the volume of water displaced, and then calculate the amount (mass) of CaCO3 produced.

[0010] Further, the CaCO3 volume content mentioned in step S2 Calculate using the following formula: ; In the formula: This represents the mass of CaCO3 in the solidified soil sample. This represents the volume ratio of CaCO3 in the solidified soil sample. This represents the specific gravity of soil particles in the plain soil sample. This represents the mass of dry soil in the plain soil sample. The specific gravity of CaCO3 is taken as 2.71.

[0011] Furthermore, in step S3, the disintegration rate R S Calculate using the following formula: ; In the formula: The disintegration rate; This refers to the voltage change of the force sensor. The force sensor calibration coefficient is 200 g / V. The initial mass of the sample is denoted as .

[0012] Furthermore, in step S5, the maximum disintegration rate The slope of the tangent at the inflection point of the disintegration time history curve is calculated using the following formula: .

[0013] Furthermore, in step S6, the final disintegration rate is obtained by fitting the data using an exponential function. Maximum disintegration rate Regarding the volume content of CaCO3 The fitting relationship.

[0014] Furthermore, in step S7, for the residual soil of granite, YV1=2% and YV2=4%; YR1=50%, YR2=20%; YK1=0.6% / s, YK2=0.3% / s.

[0015] Furthermore, the original soil (plain soil) of the target solidified soil is one of granite residual soil, loess, red soil, or expansive soil.

[0016] In summary, compared with the prior art, the present invention has the following beneficial technical effects: This invention is the first to introduce the disintegration time history evolution law into the design process of EICP-stabilized soil, realizing the transformation from empirical design to quantitative design. It establishes a unified relationship model between CaCO3 generation and disintegration time history parameters, realizing a quantitative correlation between EICP solution dosage, curing age, and disintegration resistance. A three-level design system of hazardous zone, safe zone, and conservative zone is proposed, which can balance engineering performance and economic cost, and determine the optimal design range for EICP-stabilized soil. This invention is applicable to the EICP stabilization design of various easily disintegrating soils such as granite residual soil, loess, red soil, and expansive soil, and provides systematic technical support for the application of green biological stabilization technology in slope protection, roadbed reinforcement, and other projects. Attached Figure Description

[0017] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the detailed embodiments of the invention to explain the invention and do not constitute a limitation thereof.

[0018] Figure 1 A schematic diagram of the EICP solidified soil design process; Figure 2 This is a schematic diagram illustrating sample curing, calcium carbonate determination, and disintegration test; in which... Figure 2 (a) For maintenance, Figure 2 (b) The amount of CaCO3 produced is determined by the water displacement method. Figure 2 (c) is a disintegration test; Figure 3 This is a schematic diagram illustrating the evolution of the sample disintegration rate over immersion time. Figure 4 This is a schematic diagram of fitting the disintegration time history curve model. Figure 5 Time interval parameter Maximum disintegration rate With CaCO3 production Relationship diagram; in which Figure 5 (a) is – , Figure 5 (b) is – ; Figure 6 For the final collapse rate The disintegration rate reached 0.5R. Sf The corresponding characteristic time With CaCO3 production Relationship diagram; in which Figure 6 (a) is – , Figure 6 (b) is – ; Figure 7 To speed up the time Deceleration point time With CaCO3 production Relationship diagram; in which Figure 7 (a) is – , Figure 7 (b) is – ; Figure 8 A schematic diagram illustrating the design grade classification of EICP-stabilized soil; Figure 9 Schematic diagram of fitting time history curve models for the collapse of other types of solidified soil; where Figure 9 (a) is residual soil from granite (Fujian). Figure 9 (b) is loess (Shaanxi). Figure 9 (c) is red soil (Yunnan). Figure 9 (d) is MICP-modified soil (Fujian). Detailed Implementation

[0019] The present invention will be further described below with reference to the accompanying drawings and embodiments. It should be emphasized that the following description is merely exemplary and is not intended to limit the scope and application of the present invention.

[0020] Example 1: This embodiment uses granite residual soil as an example to illustrate in detail the EICP solidified soil design method provided by the present invention.

[0021] S1. Based on the engineering characteristics of the target solidified soil, multiple groups of solidified soil samples with different EICP solution dosages and curing ages were set up according to the orthogonal test principle; at the same time, plain soil samples were set up as a control group.

[0022] The soil used in the experiment was taken from the residual granite slope of the Guiyang-Chenzhou Expressway in Hunan Province. Its liquid limit was 32.5%, plastic limit was 18.2%, plasticity index was 14.3, and specific gravity was 2.69. An EICP solution was prepared and sprayed onto the dry soil instead of water, based on the maximum dry density corresponding to a saturation of 70%, to control the EICP solution dosage. Cylindrical specimens with a diameter of 70 mm and a height of 56 mm were prepared by static pressing using a press. The specimens were then placed on a porous plate in a curing tank for curing. Distilled water was placed below the porous plate. Figure 2 (a). The residual granite soil used in this embodiment is at a saturation level S. rThe maximum dry density is reached at 70% saturation. The moisture content, i.e., the EICP solution dosage, is controlled based on this saturation. Four compaction degrees (EICP solution dosages) were set: 85% (15.7%), 90% (12.9%), 95% (10.8%), and 100% (9.0%). 85% was set as the lower limit of compaction, and 100% as the upper limit. Seven curing ages were set: 1 hour, 10 hours, 24 hours, 72 hours, 168 hours, 336 hours, and 672 hours (28 days), resulting in a total of 28 solidified soil samples. Simultaneously, plain soil samples of granite residual soil were prepared. Too low an EICP solution dosage would not achieve the desired reinforcement effect, while too high a dosage would lead to excessively high engineering costs.

[0023] S2. The amount of CaCO3 generated in each group of solidified soil samples was determined by the drainage method, and the volume content of CaCO3 V was calculated. C .

[0024] Specifically, weigh approximately 20g of dry soil from the solidified soil sample and place it in a titration flask. Add 200ml of 1mol / L hydrochloric acid dropwise through a burette to the titration flask to react with the calcium carbonate precipitate in the soil sample. Collect the generated CO2 through a gas collecting bottle and calculate the CO2 volume based on the volume of water displaced. Figure 2 (b) and then calculate the amount (mass) of CaCO3 produced.

[0025] CaCO3 volume content Calculate using the following formula: (1); In the formula: This represents the mass of CaCO3 in the solidified soil sample. This represents the volume ratio of CaCO3 in the solidified soil sample. This represents the specific gravity of soil particles in the plain soil sample. This represents the mass of dry soil in the plain soil sample. The specific gravity of CaCO3 is taken as 2.71.

[0026] Plain soil samples were prepared from original soil samples of solidified soil using the same preparation method as solidified soil samples.

[0027] S3. Conduct static water disintegration tests on each group of solidified soil samples, continuously record the mass change of the solidified soil samples after immersion in water, and calculate the disintegration rate R. S The disintegration time history curve of the disintegration rate as a function of time was obtained.

[0028] The static water disintegration test was conducted as follows: Solidified soil samples were placed on a 1cm mesh metal frame and immersed in distilled water. A force sensor (range 2kg, accuracy 0.1g) was used to monitor the disintegration rate in real time, and data was collected over 24 hours using a data acquisition system. The temperature was controlled at 20±2℃. Figure 2 (c)).

[0029] Disintegration rate R S Calculate using the following formula: (2); In the formula: The disintegration rate; This refers to the voltage change of the force sensor. The force sensor calibration coefficient is 200 g / V. The initial mass of the sample is denoted as .

[0030] The evolution of sample disintegration rate with immersion time is as follows: Figure 3 The disintegration test results show that the disintegration rate exhibits an S-shaped development pattern with disintegration time on a semi-logarithmic coordinate system. Figure 4 ): Disintegration rate Initial growth is slow, followed by accelerated collapse, and finally stabilizes. From this, the final collapse rate can be obtained. Therefore, it can be characterized by a hyperbolic model. MATLAB fitting revealed that the three-parameter hyperbolic model provided the best fit; therefore, the three-parameter hyperbolic model was used to fit the disintegration time history curves of each group. The model expression is as follows: (3); In the formula: The disintegration rate; This refers to the disintegration time; The final collapse rate; To achieve a disintegration rate of 0.5 The corresponding characteristic time, The time interval parameter is obtained through best fitting.

[0031] The specific fitting model in this embodiment is as follows: ; .

[0032] S5. Based on the final collapse rate Time interval parameters Find the maximum disintegration rate .

[0033] In semi-logarithmic coordinates, The first and second derivatives are as follows: (4); (5); In equation (5), let Equation (6) is obtained. Substituting equation (6) into equation (3) yields equation (7): (6); (7); In the formula: The breakdown rate at the inflection point.

[0034] Therefore, the coordinates of the inflection point are ( , ).consider The value corresponding to the maximum rate of collapse is the slope of the tangent line passing through the inflection point, which can be obtained by substituting equation (6) into equation (4): (8); In the formula: This represents the maximum disintegration rate.

[0035] Next, this embodiment introduces acceleration point time. Deceleration point time Let's discuss the changing patterns of the disintegration time history curve.

[0036] Combining equations (6), (7), and (8), the equation of the tangent line passing through the inflection point can be obtained as follows: (9); At the initial moment of sample immersion in water, both the disintegration rate and the disintegration percentage were 0; after the disintegration stabilized, the disintegration percentage reached... .

[0037] Therefore, the boundary conditions of the disintegration time history can be expressed as: (10); (11); In Equation (9), the two horizontal lines correspond to the initial disintegration rate and the final disintegration rate of the experiment, respectively.

[0038] Considering that both boundaries are horizontal lines, a tangent is drawn at the point of maximum speed. The intersection of the tangent with the two horizontal lines determines two turning points, namely the acceleration point and the deceleration point. Substituting equation (11) into equation (9), the coordinates of the two turning points are obtained as follows: (12); (13); (14); (15); In the formula: and They are respectively and The disintegration rate at that time.

[0039] The coordinates of the acceleration point are ( , The coordinates of the deceleration point are ( , ).

[0040] Substituting the x-coordinates of the two points into equation (4) yields the disintegration rates of the two points: (16); (17); In the formula: and They are respectively and The disintegration rate at that time, after simplification, can be obtained as follows: .

[0041] There is a correlation between the two turning points and the inflection point, as shown in equations (18) to (20): (18); (19); (20).

[0042] Considering the three inflection points of the collapse time history curve, the collapse time history can be divided into four stages: initial collapse stage (S1), accelerated collapse stage (S2), decelerated collapse stage (S3), and stable collapse stage (S4). In stage S1, the sample disintegration rate increases from 0 to... The disintegration rate slowly increased to ( for (corresponding disintegration rate); when During phase S2, the collapse rate from Accelerated increase to 0.5 The disintegration rate rapidly increases to its peak value. ( for (corresponding disintegration rate); when achieve Then it enters phase S3, where the disintegration rate drops from 0.5%. Deceleration increased to The disintegration rate decreased rapidly from its peak value to ( for (corresponding disintegration rate); when When entering phase S4, the collapse rate from Slowly rise to The disintegration rate approaches 0. The goodness of fit R for all samples is... 2 All values ​​are greater than 0.95, indicating that the model can accurately describe the disintegration evolution. Taking a sample with 85% compaction and 24 hours of curing as an example (…), Figure 4 ), and the fitting yielded: =20.38%, t sc =1314s, α=2.08; Calculated maximum disintegration rate: =0.24% / s, acceleration point time =502s, deceleration point time =3437s.

[0043] S6. The final disintegration rate was obtained by fitting the data using regression analysis. Maximum disintegration rate Regarding the volume content of CaCO3 The fitting relationship.

[0044] The exponential function was used to regress multiple parameters of 28 groups of solidified soil samples with four compaction degrees and seven ages, yielding the results. The exponential relationship with each model parameter ( Figures 5-7 The results show that, with Increase, reduce, The collapse time is reduced, and the soil's resistance to collapse is increased. =143.2exp(-25.7 -0.3, =1.49exp(-22.1 -0.38. The volumetric CaCO3 content of commonly used lime-improved soil. Generally, within the range of 2% to 4% (Chen Kang, Liu Xianfeng, Jiang Guanlu, et al. Study on the deterioration law of mechanical properties of lime-modified red mudstone filler under wet-dry cycles [J]. Rock and Soil Mechanics, 2025, 46(1):43-54.), CaCO3 cementation plays a certain role in lime-modified soil, which is similar to the core of EICP solidified soil. Therefore, this range can also be used as a selection criterion for EICP solidified soil. From Figure 5-7 It can be seen that when When <2%, >50%, >0.6% / s, significant disintegration will still occur at this rate, and the disintegration rate will be relatively fast; when 2% < When <4%, 20% < <50%, 0.3% / s< <0.6% / s, and Significantly reduced; when When >4%, <20%, <0.3% / s indicates that EICP-stabilized soil only undergoes minor disintegration. Therefore, the range of 2% to 4% was selected as the threshold. The safe range is reasonable.

[0045] S7. According to V C Corresponding anti-disintegration performance and , and The fitting relationship between them is used to establish design level classification standards (such as...). Figure 8 ): when When <2%, >50%, >0.6% / s indicates a dangerous range, suggesting that the soil still has a significant risk of collapse; When 2%≤ When ≤4%, 20% < ≤50%, 0.3% / s < ≤0.6% / s is within the safe range, indicating that the soil has good resistance to disintegration; when When >4%, ≤20%, ≤0.3% / s is a conservative range, indicating that the soil has excellent resistance to disintegration.

[0046] S8. Based on the design grade classification standard, determine the EICP solution dosage and curing age in reverse according to the target design grade.

[0047] according to Figure 8 In accordance with the requirements for highway slope protection, the three-level section standard of this invention is adopted as follows: For projects requiring rapid protection (such as temporary slope protection during the rainy season), a combination of high dosage and short curing period within the safety level can be selected; for projects requiring long-term stability (such as permanent roadbed slopes), a combination of curing period and dosage within the conservative level is recommended.

[0048] During construction, the combination of EICP solution dosage and curing time can be adjusted according to the on-site schedule to ensure that the target calcium carbonate volume ratio is achieved, thus achieving the optimal balance between anti-disintegration performance and project cost.

[0049] Besides the granite residual soils in Hunan Province, other regions' granite residual soils (Xiamen, Fujian) (LIU XY, ZHANG XW, KONG LW, et al. Disintegration of granite residual soils with varying degrees of weathering[J]. Engineering Geology, 2022. 305: 106723.) or other soil types including red soil (Kunming, Yunnan) (SUN Y, LI Z, LIN XC, et al. Anti-disintegration property of red soil treated with building gypsum powder[J]. Applied Clay Science, 2025, 273: 107832.), Loess (Xianyang, Shaanxi) (Chu Feng, Zhang Dandong, Luo Jingbo, et al. Strength, Deformation and Water Stability Characteristics of Abaca Fiber Reinforced Loess and Its Modified Duncan-Chang Model Test Study [J / OL]. Chinese Journal of Rock Mechanics and Engineering, 1-20 [2026-04-06]), Improved Soil (Fuzhou, Fujian) (Ding Xingzhi, Lai Hanjiang, Cui Mingjuan. Optimization of Process Parameters and Its Disintegration Resistance of Biomineralized Granite Residual Soil [J / OL]. Chinese Journal of Geotechnical Engineering, 1-9 [2026-04-06].), etc., the disintegration time history curve model proposed in this invention can be applied to all of them ( Figure 7 Similarly, the design grade classification standard for EICP solidified soil can be obtained by following the method in Example 1.

[0050] Granite residual soil (Xiamen, Fujian): , ; Red soil (Kunming, Yunnan): , ; Loess (Xianyang, Shaanxi): , ; MICP-modified soil (Fuzhou, Fujian): , .

[0051] The EICP-based soil solidification design method provided by this invention can be widely applied in engineering fields such as granite residual soil slope protection. Through this method, engineers can scientifically determine the curing age and dosage of the EICP solution based on specific engineering needs (rapid protection or long-term stability) and soil conditions, ensuring both reinforcement effectiveness and economic efficiency, thus demonstrating promising prospects for widespread application.

[0052] Finally, it is necessary to state that the above embodiments are only used to further illustrate the technical solution of the present invention in detail, and should not be construed as limiting the scope of protection of the present invention. Any non-essential improvements and adjustments made by those skilled in the art based on the above content of the present invention shall fall within the scope of protection of the present invention.

Claims

1. A design method for urease-induced calcium carbonate precipitation and solidification soil, characterized in that: Includes the following steps: S1. Based on the engineering characteristics of the target solidified soil, multiple sets of solidified soil samples with different EICP solution dosages and curing ages were set up according to the orthogonal test principle. S2. The amount of CaCO3 generated in each group of solidified soil samples was determined by the drainage method, and the volume content of CaCO3 V was calculated. C ; S3. Conduct static water disintegration tests on each group of solidified soil samples, continuously record the mass change of the solidified soil samples after immersion in water, and calculate the disintegration rate R. S The disintegration time history curve of the disintegration rate as a function of time was obtained. S4. A three-parameter hyperbolic model was used to fit the disintegration time history curve: ； In the formula: The disintegration rate; This refers to the disintegration time; The final collapse rate; To achieve a disintegration rate of 0.5R Sf The corresponding characteristic time; This refers to the time interval parameter; S5. Based on the final collapse rate Time interval parameters Find the maximum disintegration rate ; S6. The final disintegration rate was obtained by fitting the data using regression analysis. Maximum disintegration rate Regarding the volume content of CaCO3 The fitting relationship; S7. According to V C Based on the corresponding anti-disintegration performance and the aforementioned fitting relationship, a design level classification standard is established: (1) Hazard level: <YV1, >YR1, >YK1; (2) Safety level: YV1≤ ≤YV2,YR2< ≤YR1, YK2< ≤YK1; (3) Conservative level: >YV2, ≤YR2, ≤YK2; Among them, YV1 and YV2 are respectively The thresholds; YR1 and YR2 are respectively The thresholds; YK1 and YK2 are respectively The threshold; S8. Based on the design grade classification standard, determine the EICP solution dosage and curing age in reverse according to the target design grade.

2. The design method for urease-induced calcium carbonate precipitation and solidification soil according to claim 1, characterized in that: In step S1, the EICP solution dosage ranges from 9% to 16%, with at least 4 groups; the curing age ranges from 1 hour to 14 days, with at least 7 groups; the sample compaction degree is consistent with the target solidified soil compaction degree; and the sample curing adopts a moist and constant temperature environment.

3. The design method for urease-induced calcium carbonate precipitation and solidification soil according to claim 1, characterized in that: In step S2, the amount of CaCO3 generated in the sample is determined by the water displacement method, including the following steps: Weigh a number of samples and place them in a titration bottle. Add hydrochloric acid to the titration bottle to react with the CaCO3 in the sample. Calculate the volume of CO2 based on the volume of water displaced, and then calculate the amount of CaCO3 generated.

4. The design method for urease-induced calcium carbonate precipitation and solidification soil according to claim 1, characterized in that: In step S2, the volume content of CaCO3 Calculate using the following formula: ； In the formula: This represents the volume ratio of CaCO3 in the solidified soil sample. This represents the mass of CaCO3 in the solidified soil sample. This represents the specific gravity of soil particles in the plain soil sample. This represents the mass of dry soil in the plain soil sample. This represents the specific gravity of CaCO3.

5. The design method for urease-induced calcium carbonate precipitation and solidification soil according to claim 1, characterized in that: In step S3, the disintegration rate is calculated using the following formula: ； In the formula: The disintegration rate of the solidified soil sample; This refers to the voltage change of the force sensor. For force sensor calibration coefficients; This represents the initial mass of the solidified soil sample.

6. The design method for urease-induced calcium carbonate precipitation and solidification soil according to claim 1, characterized in that: In step S5, the maximum disintegration rate Calculate using the following formula: 。 7. The design method for urease-induced calcium carbonate precipitation and solidification soil according to claim 1, characterized in that: In step S6, the final disintegration rate is obtained by fitting the data using an exponential function. Maximum disintegration rate Regarding the volume content of CaCO3 The fitting relationship.

8. The design method for urease-induced calcium carbonate precipitation and solidification soil according to claim 1, characterized in that: In step S7, for the residual soil of granite, YV1=2%, YV2=4%; YR1=50%, YR2=20%; YK1=0.6% / s, YK2=0.3% / s.

9. The design method for urease-induced calcium carbonate precipitation and solidification soil according to any one of claims 1-8, characterized in that: The original soil of the target solidified soil is one of the following: granite residual soil, loess, red soil, or expansive soil.

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