Method for preparing high-strength low-shrinkage fluid soil

Abstract

The invention belongs to the technical field of building materials, and provides a method for preparing high-strength low-shrinkage fluid soil, which comprises the following steps: respectively researching the influence of different oyster shell powder substitution rates on the strength and shrinkage of the prepared fluid soil under the condition of fixed water-solid ratio by setting the oyster shell powder substitution rate gradient; the method comprises the following steps: analyzing an oyster shell powder, determining an optimal oyster shell powder substitution rate interval according to an analysis result, further determining an optimal oyster shell powder substitution rate, setting a water-solid ratio gradient, determining an optimal water-solid ratio, and taking the optimal water-solid ratio as a preparation parameter under the condition that the optimal oyster shell powder substitution rate is fixed, so as to finally prepare the fluid soil with high strength and low shrinkage characteristics. The oyster shell waste is used for replacing part of cement, so that the cost is reduced, the carbon emission of cement production is reduced, the comprehensive performance of the fluid soil is improved through scientific parameter optimization, and remarkable economic benefits and environmental protection benefits are achieved.

Description

Technical Field

[0001] This invention belongs to the field of building materials technology, specifically a method for preparing high-strength, low-shrinkage fluid soil. Background Technology

[0002] Fluid soil is a type of soil material with special rheological properties. Under certain conditions, it exhibits fluid-like characteristics, enabling it to self-level and self-compact. It is widely used in foundation engineering, diaphragm wall construction, pipeline backfilling, and other fields. It features convenient construction, good filling effect, and minimal disturbance to the surrounding soil. Traditional fluid soil is made by mixing cement, aggregates (sand, stone, etc.), water, and admixtures in a certain proportion. Cement, as a cementing material, is used in large quantities, which not only results in high costs but also consumes a large amount of energy and emits a large amount of carbon dioxide during cement production, which is inconsistent with the concept of green and low-carbon development.

[0003] Oyster shells are waste products from marine aquaculture, primarily composed of calcium carbonate. They are widely available and inexpensive. Grinding oyster shells into powder can be used as an auxiliary cementitious material or aggregate to replace part of the cement, reducing cement usage and achieving resource utilization of waste. However, the proportion of oyster shell powder replacing cement significantly affects key properties of fluid soils, such as strength and shrinkage rate. An inappropriate replacement ratio may lead to decreased strength and increased shrinkage, impacting project quality.

[0004] Therefore, the present invention provides a method for preparing high-strength, low-shrinkage fluid soil. Summary of the Invention

[0005] In order to overcome the shortcomings of the prior art, at least one technical problem raised in the background art is solved.

[0006] The technical solution adopted by this invention to solve its technical problem is:

[0007] Step 1: Obtain the parameters for preparing fluidized soil and set the gradient of oyster shell powder replacement rate;

[0008] Step 2: Obtain the corresponding fluid soil strength based on the oyster shell powder replacement rate gradient, analyze the relationship between the oyster shell powder replacement rate and the fluid soil strength, and determine the oyster shell powder replacement rate corresponding to the maximum strength of the fluid soil based on the analysis results;

[0009] Step 3: Obtain the corresponding shrinkage rate of fluid soil based on the oyster shell powder replacement rate gradient, analyze the relationship between oyster shell powder and fluid soil shrinkage rate, and determine the oyster shell powder replacement rate corresponding to the lowest shrinkage rate based on the analysis results;

[0010] Step 4: Based on the oyster shell powder replacement rate corresponding to the highest strength and lowest shrinkage rate, obtain the optimal oyster shell powder replacement rate range, and then determine the optimal oyster shell powder replacement rate;

[0011] Step 5: Analyze the strength and shrinkage of fluid soil prepared with different water-solid ratios under the optimal oyster shell powder substitution rate, and determine the optimal water-solid ratio.

[0012] Furthermore, the oyster shell powder replacement rate gradient is set as follows:

[0013] The starting point is 0%, and the endpoint is set to r based on the activity of oyster shell powder and engineering requirements. e ;

[0014] Based on the midpoint, separate low substitution rate intervals and high substitution rate intervals are set, with the midpoint being (0+r). e ) / 2;

[0015] For the low substitution rate range between the starting point and the midpoint, an interval Δr is used, and dense intervals can accurately capture the performance inflection point.

[0016] For the high substitution rate range between the midpoint and the endpoint, an interval of 2Δr is used, and the performance change trend tends to be gradual, so that the overall pattern can be reflected without too dense an interval.

[0017] Furthermore, the process of analyzing the relationship between oyster shell powder and the strength of fluid soil is as follows:

[0018] Based on the set oyster shell powder replacement rate gradient, fluid soil samples were prepared, and the strength of each sample was measured using the standard compressive strength test method to obtain the corresponding fluid soil strength sequence.

[0019] Using the oyster shell powder replacement rate as the independent variable and the corresponding fluid soil strength as the dependent variable, a quadratic function was fitted using the least squares method to obtain the fitted function.

[0020] Furthermore, the method for determining the oyster shell powder replacement rate corresponding to the maximum strength is as follows:

[0021] The fitting function of oyster shell powder replacement rate and fluid soil strength is differentiated, and the derivative is set to 0 to obtain the oyster shell powder replacement rate corresponding to the highest strength of fluid soil.

[0022] Furthermore, the process of analyzing the relationship between oyster shell powder and the shrinkage rate of fluidized soil is as follows:

[0023] Fluid soil samples were prepared according to the set oyster shell powder replacement rate gradient, and the shrinkage rate was calculated by measuring the change in length of the sample during the curing process.

[0024] Three parallel samples were prepared for each substitution rate, and the average value was taken as the shrinkage rate value for that substitution rate.

[0025] With the substitution rate as the independent variable and the contraction rate as the dependent variable, the data were fitted using the least squares method as a polynomial.

[0026] The initial polynomial order is set to 2. For each additional order, the coefficient of determination is calculated. The polynomial with the coefficient of determination closest to 1 is selected as the fitting model for the oyster shell powder replacement rate and the shrinkage rate of fluid soil.

[0027] Furthermore, the shrinkage rate is calculated as follows:

[0028] Shrinkage is calculated by measuring the change in length of the sample during curing, using the following formula: Where L0 is the initial length of the sample, L t The length of the sample at time t during curing;

[0029] Furthermore, the process of determining the oyster shell powder substitution rate corresponding to the minimum shrinkage rate based on the analysis results is as follows:

[0030] For the fitted curve, calculate the second derivative, set the second derivative to 0, and solve for all possible extreme points;

[0031] Substitute the obtained extreme points into the fitted curve function to calculate the corresponding shrinkage rate value;

[0032] Find the minimum value among the calculated shrinkage rates; the corresponding oyster shell powder replacement rate is the replacement rate with the lowest shrinkage rate in fluid soil.

[0033] Furthermore, the process of determining the optimal oyster shell powder substitution rate range includes:

[0034] Obtain the oyster shell powder replacement rate r corresponding to the highest strength and lowest shrinkage rate of the fluid soil. 强度 r 收缩 And compare them;

[0035] If r 强度 =r 收缩 This substitution rate is directly taken as the optimal substitution rate, and the optimal substitution rate range is [r]. 强度 ,r 收缩 ];

[0036] If r 强度 <r 收缩 , [r 强度 ,r 收缩 [This represents the initial oyster shell powder replacement rate range;]

[0037] If r 强度 >r 收缩 , [r 收缩 r 强度 [ ] represents the initial oyster shell powder replacement rate range.

[0038] Furthermore, the optimal oyster shell powder substitution rate is determined as follows:

[0039] Based on the determined optimal oyster shell powder substitution rate range, a response surface methodology-specific experimental design method was used to fit the response surface model of strength and shrinkage rate.

[0040] Set an objective function, substitute the fitted response surface models of strength and shrinkage rate into the objective function, take the derivative of the objective function, and set the derivative to 0. The oyster shell powder substitution rate obtained is the optimal oyster shell powder substitution rate.

[0041] Furthermore, the optimal water-to-solid ratio is determined as follows:

[0042] Under the optimal oyster shell powder replacement rate, the conventional water-solid ratio of pure cement fluid soil is used as the initial benchmark, and the water-solid ratio gradient is set in combination with the porosity of oyster shell powder.

[0043] For each water-to-solid ratio, fluid soil was prepared according to the optimal oyster shell powder substitution rate, and the strength and shrinkage rate of the fluid soil were tested sequentially.

[0044] The comprehensive preparation index corresponding to each water-to-solid ratio is calculated according to the weighting formula. The water-to-solid ratio with the largest comprehensive preparation index is the optimal water-to-solid ratio.

[0045] The beneficial effects of this invention are as follows:

[0046] By setting a gradient of oyster shell powder replacement rate, the effects of this rate on the strength and shrinkage of fluid soil were studied. The optimal replacement rate range was determined, which can reduce the shrinkage rate while ensuring the strength of fluid soil, significantly improving its comprehensive performance and durability. Replacing part of the cement with oyster shell powder realizes the resource utilization of waste, reduces cement usage, and reduces energy consumption and carbon emissions in the cement production process, which is in line with the concept of green and low-carbon development. At the same time, it reduces the preparation cost of fluid soil, which has significant economic and environmental benefits. By optimizing the water-solid ratio within the optimal replacement rate range, the prepared fluid soil is ensured to have good workability (flowability and workability), which facilitates engineering construction and improves construction efficiency and project quality. Attached Figure Description

[0047] The invention will now be further described with reference to the accompanying drawings.

[0048] Figure 1 This is a flowchart of the steps in a method for preparing high-strength, low-shrinkage fluid soil as described in Embodiment 1 of the present invention;

[0049] Figure 2 This is a logic diagram of a method for preparing high-strength, low-shrinkage fluid soil as described in Embodiment 1 of the present invention. Detailed Implementation

[0050] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below in conjunction with specific embodiments.

[0051] Example 1

[0052] Please see Figure 1 As shown in the embodiment of the present invention, a method for preparing high-strength, low-shrinkage fluid soil includes the following steps:

[0053] Step 1: Obtain the parameters for preparing fluidized soil and set the gradient of oyster shell powder replacement rate;

[0054] In step one, the fluid soil is a soil material with special rheological properties. Under certain conditions, it exhibits fluid-like characteristics and can self-level and self-compact. It is widely used in foundation engineering, underground continuous wall construction, pipeline backfilling and other fields. It has the characteristics of convenient construction, good filling effect and small disturbance to the surrounding soil. The fluid soil is made by mixing cement, aggregate (sand, stone, etc.), water and admixtures in a certain proportion.

[0055] The fluid soil preparation parameter is the water-to-solid ratio, which refers to the ratio of the mass of water in the fluid soil to the total mass of all solids. The solid materials include cement, oyster shell powder, sand / stone and other aggregates. The mass of the aggregates is fixed. The water-to-solid ratio directly reflects the ratio of water to solid particles in the system, which determines the fluidity (constructability), the degree of hydration reaction (strength basis) and the pore structure after hardening (shrinkage performance core) of the material.

[0056] The oyster shells mentioned are waste products from marine aquaculture, mainly composed of calcium carbonate. After being ground into powder, they can be used as auxiliary cementing materials or aggregates to replace part of the cement. The functions of using powdered oyster shells to replace part of the cement include:

[0057] Function 1: Reduce cement usage, save costs and resources. Oyster shells are low-cost waste materials, which reduces energy consumption and carbon emissions in cement production, in line with the concept of green and low-carbon development.

[0058] Function 2: Improve the workability of fluid soil. Oyster shell powder particles are usually irregularly shaped or porous with a large specific surface area. In fluid soil, they can adsorb some free water and adjust the viscosity of the slurry. Their particle shape can reduce the friction between aggregates. When combined with an appropriate amount of water, it can improve the fluidity and water retention of the mixture, avoid bleeding or segregation, and optimize the construction performance.

[0059] Function 3: During the cement hydration process, the CaCO3 in oyster shell powder can react with the cement hydration products to generate products such as calcium carbonate aluminate, which fill the pores of cement stone, improve the microstructure, and thus enhance the strength of fluid soil within a certain range of oyster shell powder replacement rate.

[0060] Function 4: During the cement hydration process, shrinkage occurs due to water evaporation and volume changes of hydration products, while the inert particles of oyster shell powder can inhibit the shrinkage of cement paste.

[0061] In step one, the process of setting the oyster shell powder substitution rate gradient includes:

[0062] The starting point is 0% (benchmark group, to ensure performance comparison with pure cement), and the endpoint is set to r based on the activity of oyster shell powder and engineering requirements. e ;

[0063] Based on the midpoint, separate low substitution rate intervals and high substitution rate intervals are set, with the midpoint being (0+r). e ) / 2:

[0064] For the interval between the starting point and the midpoint, the interval Δr is used because oyster shell powder may significantly improve performance (such as increased strength and decreased shrinkage) within this interval through the filling effect and active reaction. Dense intervals can accurately capture the performance inflection point.

[0065] For the interval between the midpoint and the end point, an interval of 2Δr is used because the "dilution effect" of the reduction in cement usage gradually dominates in this interval, and the trend of performance change tends to be gradual (such as the continuous decrease in strength and the narrowing of the shrinkage rate). The overall pattern can be reflected without too dense an interval.

[0066] Among them, the interval gradient interval Δr is based on the characteristics of oyster shell powder. A preliminary experiment was conducted to fit the trend curve of the change of the strength and shrinkage rate of the fluid soil with the oyster shell powder replacement rate. The average value of the interval between each inflection point in the curve of the change of the strength and shrinkage rate of the fluid soil with the oyster shell powder replacement rate was calculated as Δr.

[0067] Understandably, a 0% substitution rate represents the original performance benchmark of a pure cement system, with the endpoint r... e The essence of this design is to balance the boundary between material properties and engineering practicality. By using differentiated intervals, it can accurately capture key performance changes (low range) and efficiently reflect the overall trend (high range), ultimately achieving the goal of "neither missing performance inflection points nor wasting experimental resources". This provides experimental evidence at the physical mechanism level for the rational application of oyster shell powder in cement systems (such as the selection of the optimal substitution rate).

[0068] Setting up a gradient of oyster shell powder replacement rates is to systematically investigate the impact of oyster shell powder replacing cement on the properties of fluid soil. The oyster shell powder replacement rate represents the proportion of oyster shell powder mass to the original cement mass. By setting a series of different oyster shell powder replacement rates (such as multiple gradients from low to high), the performance changes of fluid soil under different replacement degrees can be comprehensively examined. This step provides diverse samples for subsequent research and forms the basis for subsequent analysis and optimization. Its beneficial effect is that by systematically changing variables, it creates conditions for finding the optimal oyster shell powder replacement rate, avoids blind experimentation, and improves research efficiency.

[0069] Step 2: Obtain the corresponding strength of the fluid soil based on the oyster shell powder replacement rate gradient, analyze the relationship between the oyster shell powder replacement rate and the strength of the fluid soil, and determine the oyster shell powder replacement rate corresponding to the maximum strength of the fluid soil based on the analysis results;

[0070] In step two, the process of analyzing the relationship between oyster shell powder and the strength of fluid soil includes:

[0071] Maintain aggregate type (sand, stone chips), particle size distribution, and mass (m). 骨料 With the initial cement mass fixed, the oyster shell powder replacement rate gradient (r1, r2, ..., r) is set. n ), calculate the mass of oyster shell powder (m) 壳粉 =r×m 水泥 ) and remaining cement mass (m' 水泥 =m 水泥 ×(1-r)), ensuring consistent total mass of solid material (m) 固 =m 骨料 +m' 水泥 +m 壳粉 );

[0072] According to the set oyster shell powder replacement rate gradient (r1, r2, ..., r n Fluid soil samples were prepared, and using a fixed water-to-solid ratio, the strength of each sample was measured using standard compressive strength testing methods to obtain the corresponding fluid soil strength sequence (f1, f2, ..., f...). n ), where f n Let r be the replacement rate of oyster shell powder for the nth time. n The strength of the prepared fluid soil;

[0073] Among them, the strength of fluid soil is an important indicator for measuring its ability to resist external damage. In practical engineering applications, higher strength can ensure that fluid soil does not fail when subjected to load, thus ensuring the safety and stability of the engineering structure.

[0074] According to the set oyster shell powder replacement rate gradient (r1, r2, ..., r n) and fluid soil strength sequence (f1, f2, ..., f n Using the oyster shell powder substitution rate as the abscissa and the intensity as the ordinate, a scatter plot was drawn and a curve was fitted to visually present the change law of intensity with the oyster shell powder substitution rate.

[0075] When the oyster shell powder substitution rate is low, the fine particle filling effect of the oyster shell powder increases the density of the solid material, or a small amount of active ingredients participate in the hydration reaction, making the strength slightly higher than that of pure cement. As the oyster shell powder substitution rate increases, the cement content decreases, resulting in insufficient cementitious ability, and the strength decreases with the increase of the oyster shell powder substitution rate.

[0076] The substitution rate of oyster shell powder (r1, r2, ..., r n ) is the independent variable, and the fluid strength (f1, f2, ..., f) is the independent variable. n (a1x2 + b1x + c1) is the dependent variable. The least squares method is used to fit a quadratic function, f = a1x2 + b1x + c1.

[0077] Taking the derivative of the intensity function, we get y' = 2a1x + b1. Setting the derivative to 0, we can find the critical point of the oyster shell powder substitution rate: x intensity = -b1 / (2a1).

[0078] It is understandable that by analyzing the relationship between the oyster shell powder replacement rate and the strength of fluid soil, the effect is as follows:

[0079] Function 1: Clarify the influence mechanism of oyster shell powder substitution rate on strength, reveal the role of oyster shell powder in the cementitious system (filling effect, active reaction or negative dilution effect), provide a basis for material modification (such as calcination treatment to improve activity), identify the "strength sensitive range", and guide the subsequent shrinkage rate test to focus on the performance coupling effect of this range;

[0080] Function 2: Screening the optimal oyster shell powder replacement rate for strength, determining the optimal solution under a single strength index, ensuring that the fluid soil meets the engineering strength requirements while maximizing the utilization rate of oyster shell powder (reducing cement usage and taking into account economy), providing basic data for multi-objective optimization (strength and shrinkage balance), and avoiding the inclusion of oyster shell powder replacement rates that clearly do not meet the strength requirements in subsequent steps (such as strength falling below the design standard after exceeding a certain threshold);

[0081] Step 3: Calculate the corresponding shrinkage rate of fluid soil based on the oyster shell powder replacement rate gradient, analyze the relationship between oyster shell powder and fluid soil shrinkage rate, and determine the oyster shell powder replacement rate corresponding to the lowest shrinkage rate based on the analysis results;

[0082] In step three, the process of analyzing the relationship between oyster shell powder and the shrinkage rate of fluidized soil includes:

[0083] Maintain aggregate type (sand, stone chips), particle size distribution, and mass (m).骨料 With the initial cement mass fixed, the oyster shell powder replacement rate gradient (r1, r2, ..., r) is set. n ), calculate the mass of oyster shell powder (m) 壳粉 =r×m 水泥 ) and remaining cement mass (m' 水泥 =m 水泥 ×(1-r)), ensuring consistent total mass of solid material (m) 固 =m 骨料 +m' 水泥 +m 壳粉 );

[0084] According to the set oyster shell powder replacement rate gradient (r1, r2, ..., r n To prepare fluid soil samples, a fixed water-to-solid ratio was used. A high-precision displacement sensor (such as a dial gauge or laser rangefinder) was employed to calculate the shrinkage rate by measuring the change in length of the sample during curing. The formula is as follows: Where L0 is the initial length of the sample, L t The length of the sample at time t during curing;

[0085] Among them, the shrinkage rate of fluid soil is the proportion of volume reduction caused by factors such as water loss and cementitious material hydration during the hardening process of fluid soil. It is usually expressed as a percentage. The shrinkage rate is a key indicator for measuring the volume stability of fluid soil. Excessive shrinkage rate can easily cause cracking and reduce material durability and engineering quality.

[0086] Three parallel samples were prepared for each substitution rate, and the average value was taken as the shrinkage rate value for that substitution rate to reduce measurement error;

[0087] Using the substitution rate (r) as the independent variable and the shrinkage rate ε as the dependent variable, the data were fitted using the least squares method with a polynomial, and the fitted polynomial was ε = a. n r n +a n-1 r n-1 +...+a1r+a0, by solving the normal equation system R T Ra = R T ε yields the coefficient vector a = (a0, a1, ..., a n ) T , where R is the design matrix composed of powers of the independent variable r, and ε is the dependent variable vector;

[0088] During the fitting process, the initial polynomial order was set to 2, and the coefficients of determination were recalculated for each additional order. Where m is the number of data points. These are the fitted values. The mean of the dependent variable is used, and the residual plot is analyzed to determine the degree of deviation between the data points and the fitted curve, thus judging whether overfitting has occurred. R is selected. 2 The polynomial closest to 1 that avoids overfitting is used as the fitting model;

[0089] For the fitted curve, calculate the first derivative ε'. When ε'>0, the shrinkage rate increases with the increase of the substitution rate; when ε'<0, the shrinkage rate decreases with the increase of the substitution rate. The absolute value of the derivative reflects the speed of the trend change. The larger the absolute value, the more drastic the trend change.

[0090] Calculate the second derivative ε” and determine the concavity of the curve by the sign of ε”. ε”>0 indicates that the curve is concave downward and may have a minimum value. ε”<0 indicates that the curve is concave upward and may have a maximum value. Set ε”=0 to obtain the possible extreme points. Combine the sign of ε” to determine whether it is a maximum or a minimum value, so as to accurately locate the inflection point of the shrinkage rate change.

[0091] By calculating the numerical solution of derivative ε” = 0, all possible extreme points are obtained. These extreme points are substituted into the fitted curve function ε to calculate the corresponding shrinkage rate value, and compared with the boundary points (i.e. the shrinkage rate when the replacement rate is 0 and the maximum replacement rate).

[0092] Find the minimum shrinkage rate value among the calculated values. The corresponding oyster shell powder replacement rate is the replacement rate that minimizes the shrinkage rate of the fluidized soil under a fixed curing time. If multiple replacement rates correspond to the same minimum shrinkage rate, then further calculate the variance of the shrinkage rate under these replacement rates. Choose the oyster shell powder replacement rate with the smallest variance to ensure optimal stability of shrinkage rate;

[0093] It is understandable that the analysis of the shrinkage rate of fluid soil under different replacement rates has the following effect:

[0094] Function 1: To reveal the mechanism of shrinkage rate influence, and to clarify the role of oyster shell powder in inhibiting or promoting the shrinkage of fluid soil by systematically studying the shrinkage characteristics of fluid soil under different replacement rates, such as whether it affects shrinkage by improving pore structure and regulating hydration process, so as to provide a theoretical basis for optimizing material performance;

[0095] Function 2: Screening for low-shrinkage replacement rates, determining the oyster shell powder replacement rate that minimizes the shrinkage of fluid soil, providing key parameters for the preparation of low-shrinkage fluid soil, reducing quality problems such as cracks caused by shrinkage, and improving the durability and stability of fluid soil in engineering applications;

[0096] Step 4: Based on the oyster shell powder replacement rate corresponding to the highest strength and lowest shrinkage rate, obtain the optimal oyster shell powder replacement rate range, and then determine the optimal oyster shell powder replacement rate;

[0097] In step four, the process of determining the optimal oyster shell powder substitution rate range includes:

[0098] Obtain the oyster shell powder replacement rate r corresponding to the highest strength and lowest shrinkage rate of the fluid soil. 强度 r 收缩 And compare them:

[0099] If r 强度 =r 收缩 If the two are equal, it means that the substitution rate can simultaneously meet the requirements of high strength and low shrinkage, and this substitution rate can be directly taken as the optimal substitution rate. In this case, the optimal substitution rate range is a single value, i.e., [r 强度 ,r 收缩] ;

[0100] If r 强度 <r 收缩 The maximum strength occurs at lower oyster shell powder substitution rates, while the minimum shrinkage occurs at higher oyster shell powder substitution rates. The range between the two is [r] 强度 ,r 收缩 [This represents the initial oyster shell powder replacement rate range;]

[0101] If r 强度 >r 收缩 The maximum strength occurs at higher oyster shell powder substitution rates, while the minimum shrinkage occurs at lower oyster shell powder substitution rates. The range between the two is [r] 收缩 r 强度 [This represents the initial oyster shell powder replacement rate range;]

[0102] In step four, the process of determining the optimal oyster shell powder substitution rate includes:

[0103] Based on the determined optimal oyster shell powder substitution rate range [r] l ,r u The sample points were selected using a design of experimental methods specific to response surface methodology to ensure coverage of key locations within the interval while also taking into account the model fitting accuracy.

[0104] Sample point selection includes interval endpoints [r] l ,r u ], Center point r0 = (r l +r u ) / 2, and the midpoints within the interval: rl+Δx, ru-Δx, where Δx is the step size;

[0105] The fluid soil was prepared based on each sample point, and the strength Y1 and shrinkage Y2 of the prepared fluid soil were tested.

[0106] The response surface model of strength and shrinkage rate is fitted. The strength model is fitted with the substitution rate x as the independent variable and the strength Y1 as the dependent variable using the least squares method, and the coefficients are calculated using sample point data.

[0107] Shrinkage rate model: with the replacement rate x as the independent variable and the shrinkage rate Y2 as the dependent variable, the least squares method is used for fitting, and the coefficients are calculated through sample point data;

[0108] The strength and shrinkage rate of the fluid soil are standardized to obtain Y*1 and Y*2 respectively. The objective function is F(x) = w1×Y*1 + w2×Y*2, where w1 and w2 are weight coefficients.

[0109] Substituting the expressions for Y1 and Y2 into F(x), and simplifying, we get F(x) as a quadratic function. Taking the derivative, we get F'(x) = 0. Solving for x0, we find that x0 is the optimal oyster shell powder substitution rate.

[0110] It is understandable that determining the optimal oyster shell powder substitution rate serves several purposes:

[0111] By determining the optimal oyster shell powder replacement rate, the prepared fluid soil can achieve a good balance in terms of strength and shrinkage rate. This ensures the structural stability of the material under load and reduces the possibility of defects such as cracks caused by shrinkage. It significantly improves the comprehensive performance and durability of the fluid soil and meets the engineering requirements for high-performance materials.

[0112] Oyster shell powder, as a recycled waste material, is cheaper than cement. Under the premise of meeting engineering performance requirements, by reasonably determining the replacement rate range, the proportion of oyster shell powder used can be increased and the amount of cement used can be reduced. This can not only reduce production costs, but also promote resource recycling, reduce energy consumption and carbon emissions from cement production, and achieve a win-win situation for both economic and environmental benefits.

[0113] Step 5: Analyze the strength and shrinkage of fluid soil prepared with different water-solid ratios under the optimal oyster shell powder substitution rate, and determine the optimal water-solid ratio;

[0114] In step five, the process of analyzing the strength and shrinkage of the fluid soil prepared with the water-solid ratio corresponding to the optimal oyster shell powder substitution rate range includes:

[0115] Under the optimal oyster shell powder replacement rate, the conventional water-solid ratio of pure cement fluid soil is used as the initial benchmark. The water-solid ratio gradient is set by taking into account the porosity of oyster shell powder (large specific surface area, requiring more adsorption of free water to maintain fluidity).

[0116] For each water-to-solid ratio, fluid soil was prepared according to the optimal oyster shell powder substitution rate, and the strength and shrinkage rate of the fluid soil were tested sequentially.

[0117] According to the weighting formula F=w1×Y1+w2×Y2, calculate the comprehensive preparation index corresponding to each water-solid ratio, where w1 and w2 are weighting coefficients, Y1 is the strength of the fluid soil, and Y2 is the shrinkage rate of the fluid soil.

[0118] It is understandable that the physical meaning of the comprehensive preparation index is: a comprehensive performance evaluation index obtained by integrating the strength and shrinkage rate of fluid soil through a weighting formula. It quantitatively reflects the comprehensive performance of fluid soil under a specific water-solid ratio. The weighting coefficient reflects the relative importance of strength and shrinkage rate in practical applications. Therefore, the larger the value of the comprehensive preparation index, the higher the degree to which the strength and shrinkage rate of fluid soil under that water-solid ratio meet the engineering requirements.

[0119] The water-to-solid ratio with the highest comprehensive preparation index is taken as the optimal water-to-solid ratio.

[0120] The physical meaning of the optimal water-solid ratio is: under the optimal oyster shell powder substitution rate, the water-solid ratio that maximizes the comprehensive preparation index and matches the optimal proportioning parameters that are compatible with the porous characteristics of oyster shell powder, achieves the best balance between the strength and shrinkage rate of the fluid soil at this water-solid ratio: ensuring that the fluid soil has sufficient strength to meet the bearing requirements, while controlling the shrinkage rate at a low level to avoid structural defects (such as cracks) caused by excessive volume deformation, and ultimately achieving the optimal comprehensive performance (bearing capacity + volume stability) of the fluid soil.

[0121] By comprehensively preparing the index to integrate strength and shrinkage rate, the performance imbalance caused by optimizing a single index is avoided (such as pursuing only high strength may lead to excessive shrinkage rate, or pursuing only low shrinkage rate may sacrifice strength). This ensures that the fluid soil can both bear load and stabilize volume in engineering applications. The optimal water-solid ratio determined at the end provides clear process parameters for the actual preparation of oyster shell powder modified fluid soil, ensuring that the comprehensive performance of the fluid soil meets the design requirements under the optimal substitution rate, and providing a guarantee for the feasibility of engineering construction and the reliability of the structure.

[0122] The technical solution and advantages of this application embodiment are as follows: Parameters for preparing fluidized soil are obtained; a gradient of oyster shell powder replacement rate is set; the corresponding strength of the fluidized soil is obtained based on the oyster shell powder replacement rate gradient; the relationship between the oyster shell powder replacement rate and the strength of the fluidized soil is analyzed; the oyster shell powder replacement rate corresponding to the maximum strength of the fluidized soil is determined based on the analysis results; the corresponding shrinkage rate of the fluidized soil is obtained based on the oyster shell powder replacement rate gradient; the relationship between oyster shell powder and the shrinkage rate of the fluidized soil is analyzed; the oyster shell powder replacement rate corresponding to the minimum shrinkage rate is determined based on the analysis results; the optimal oyster shell powder replacement rate range is obtained based on the oyster shell powder replacement rates corresponding to the highest strength and the lowest shrinkage rate; the optimal oyster shell powder replacement rate is then determined; and the strength and shrinkage rate of fluidized soil prepared with different water-solid ratios under the optimal oyster shell powder replacement rate are analyzed to determine the optimal water-solid ratio. This application investigates the effects of oyster shell powder substitution rate gradients on the strength and shrinkage of fluidized soil, determines the optimal substitution rate range, and optimizes the water-to-solid ratio within this range. Ultimately, this yields fluidized soil with both high strength and low shrinkage. By utilizing oyster shell waste to replace part of the cement, not only are costs and carbon emissions from cement production reduced, but the comprehensive performance of the fluidized soil is also improved through scientific parameter optimization, resulting in significant economic and environmental benefits. Through systematic experiments and data analysis, the optimal water-to-solid ratio is precisely determined within the optimal oyster shell powder substitution rate range, achieving the best balance between the strength and shrinkage of the fluidized soil. This meets the stringent requirements of engineering for material performance, providing clear water-to-solid ratio parameters for the actual preparation of fluidized soil, avoiding blind experimentation and resource waste during production, and improving production efficiency and product quality stability.

[0123] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing high-strength, low-shrinkage fluid soil, characterized in that: include: Step 1: Obtain the parameters for preparing fluidized soil and set the gradient of oyster shell powder replacement rate; Step 2: Obtain the corresponding strength of the fluid soil based on the oyster shell powder replacement rate gradient, analyze the relationship between the oyster shell powder replacement rate and the strength of the fluid soil, and determine the oyster shell powder replacement rate corresponding to the maximum strength of the fluid soil based on the analysis results; Step 3: Obtain the corresponding shrinkage rate of fluid soil based on the oyster shell powder replacement rate gradient, analyze the relationship between oyster shell powder and fluid soil shrinkage rate, and determine the oyster shell powder replacement rate corresponding to the lowest shrinkage rate based on the analysis results; Step 4: Based on the oyster shell powder replacement rate corresponding to the highest strength and lowest shrinkage rate, obtain the optimal oyster shell powder replacement rate range, and then determine the optimal oyster shell powder replacement rate; Step 5: Analyze the strength and shrinkage of fluid soil prepared with different water-solid ratios under the optimal oyster shell powder substitution rate, and determine the optimal water-solid ratio.

2. The method for preparing high-strength, low-shrinkage fluid soil according to claim 1, characterized in that: The oyster shell powder replacement rate gradient is set as follows: The starting point is 0%, and the endpoint is set to r based on the activity of oyster shell powder and engineering requirements. e ; Based on the midpoint, separate low substitution rate intervals and high substitution rate intervals are set, with the midpoint being (0+r). e ) / 2; For the low substitution rate range between the starting point and the midpoint, an interval Δr is used, and dense intervals can accurately capture the performance inflection point. For the high substitution rate range between the midpoint and the endpoint, an interval of 2Δr is used, and the performance change trend tends to be gradual, so that the overall pattern can be reflected without too dense an interval.

3. The method for preparing high-strength, low-shrinkage fluid soil according to claim 1, characterized in that: The process of analyzing the relationship between oyster shell powder and the strength of fluid soil is as follows: Based on the set oyster shell powder replacement rate gradient, fluid soil samples were prepared, and the strength of each sample was measured using the standard compressive strength test method to obtain the corresponding fluid soil strength sequence. Using the oyster shell powder replacement rate as the independent variable and the corresponding fluid soil strength as the dependent variable, a quadratic function was fitted using the least squares method to obtain the fitted function.

4. The method for preparing high-strength, low-shrinkage fluidized soil according to claim 1, characterized in that: The method for determining the oyster shell powder replacement rate corresponding to the maximum strength is as follows: The fitting function of oyster shell powder replacement rate and fluid soil strength is differentiated, and the derivative is set to 0 to obtain the oyster shell powder replacement rate corresponding to the highest strength of fluid soil.

5. The method for preparing high-strength, low-shrinkage fluidized soil according to claim 1, characterized in that: The process of analyzing the relationship between oyster shell powder and the shrinkage rate of fluidized soil is as follows: Fluid soil samples were prepared according to the set oyster shell powder replacement rate gradient, and the shrinkage rate was calculated by measuring the change in length of the sample during the curing process. Three parallel samples were prepared for each substitution rate, and the average value was taken as the shrinkage rate value for that substitution rate. With the substitution rate as the independent variable and the contraction rate as the dependent variable, the data were fitted using the least squares method as a polynomial. The initial polynomial order is set to 2. For each additional order, the coefficient of determination is calculated. The polynomial with the coefficient of determination closest to 1 is selected as the fitting model for the oyster shell powder replacement rate and the shrinkage rate of fluid soil.

6. The method for preparing high-strength, low-shrinkage fluidized soil according to claim 5, characterized in that: The shrinkage rate of the fluid soil is calculated as follows: Shrinkage is calculated by measuring the change in length of the sample during curing, using the following formula: Where ε is the shrinkage rate, L0 is the initial length of the sample, and L t The length of the sample at time t during curing.

7. The method for preparing high-strength, low-shrinkage fluid soil according to claim 1, characterized in that: The process of determining the oyster shell powder replacement rate corresponding to the minimum shrinkage rate based on the analysis results is as follows: For the fitted curve, calculate the second derivative, set the second derivative to 0, and solve for all possible extreme points; Substitute the obtained extreme points into the fitted curve function to calculate the corresponding shrinkage rate value; Find the minimum value among the calculated shrinkage rates; the corresponding oyster shell powder replacement rate is the replacement rate with the lowest shrinkage rate in fluid soil.

8. The method for preparing high-strength, low-shrinkage fluid soil according to claim 1, characterized in that: The process of determining the optimal oyster shell powder replacement rate range includes: Obtain the oyster shell powder replacement rate r corresponding to the highest strength and lowest shrinkage rate of the fluid soil. 强度 r 收缩 And compare them; If r 强度 =r 收缩 This substitution rate is directly taken as the optimal substitution rate, and the optimal substitution rate range is [r]. 强度 ,r 收缩] ; If r 强度 <r 收缩 , [r 强度 ,r 收缩 [This represents the initial oyster shell powder replacement rate range;] If r 强度 >r 收缩 , [r 收缩 r 强度 [ ] represents the initial oyster shell powder replacement rate range.

9. The method for preparing high-strength, low-shrinkage fluid soil according to claim 1, characterized in that: The optimal oyster shell powder substitution rate is determined as follows: Based on the determined optimal oyster shell powder substitution rate range, a response surface methodology-specific experimental design method was used to fit the response surface model of strength and shrinkage rate. Set an objective function, substitute the fitted response surface models of strength and shrinkage rate into the objective function, take the derivative of the objective function, and set the derivative to 0. The oyster shell powder substitution rate obtained is the optimal oyster shell powder substitution rate.

10. The method for preparing high-strength, low-shrinkage fluid soil according to claim 1, characterized in that: The optimal water-to-solid ratio is determined as follows: Under the optimal oyster shell powder replacement rate, the conventional water-solid ratio of pure cement fluid soil is used as the initial benchmark, and the water-solid ratio gradient is set in combination with the porosity of oyster shell powder. For each water-to-solid ratio, fluid soil was prepared according to the optimal oyster shell powder substitution rate, and the strength and shrinkage rate of the fluid soil were tested sequentially. The comprehensive preparation index corresponding to each water-to-solid ratio is calculated according to the weighting formula. The water-to-solid ratio with the largest comprehensive preparation index is the optimal water-to-solid ratio.

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