Cured soil capillary water rising height prediction method based on porosity change

Abstract

The invention provides a solidified soil capillary water rising height prediction method based on porosity change, and belongs to the technical field of capillary water height testing. The method comprises the following steps: obtaining a to-be-detected soil sample; preparing a capillary water height sample and a cutting ring sample under the condition of the same compaction degree; a capillary water rising test is carried out, capillary water rising height data at different time nodes in the corresponding solidification period are recorded, the contact angle of the solidified soil in the corresponding solidification period is measured through the cutting ring sample, and the pore radius of the solidified soil is measured through a mercury intrusion method; selecting a soil sample with a flat surface in the middle from the cutting ring sample, and carrying out a microscopic test to obtain a microstructure image; the porosity under the same parameters is identified through PCAS, and porosity data are obtained; and according to the change rule of the porosity data, parameters of the capillary water rising height calculation formula are corrected. According to the method, the porosity change and capillary water rising height calculation are combined, so that the prediction precision of the capillary water rising height of the soil under different solidification degrees is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of capillary water height testing, and in particular to a cured soil capillary water rise height prediction method based on porosity change. BACKGROUND

[0002] As a soil improvement method, cured soil with solidifying agent has broad application prospects in engineering construction. This technology mixes solidifying agent with soil to promote physical and chemical reactions, changing the structure and properties of the soil, thereby improving its strength, stability, and permeability. The application of cured soil can effectively solve the problems of low soil strength, poor shear strength, easy collapse, and high permeability, and has good adaptability to the environment. This technology plays an important role in infrastructure construction such as roads, bridges, channels, and dams, and also has significant application value in slope control, soil pollution remediation, and waste disposal.

[0003] Capillary water rise directly affects the strength decay, settlement deformation, and long-term stability of the soil, so accurate prediction of capillary water rise height is crucial for engineering design and safety evaluation. Existing capillary water rise height prediction methods, such as fractal theory models and homogeneous / laminated soil calculation methods, all take undisturbed soil, natural homogeneous soil, or specific natural soil types (silty clay, loess) as the research object, and rely on the initial physical parameters of the soil. The core feature of cured soil is that the addition of solidifying agent leads to dynamic evolution of soil particle arrangement, pore size distribution, and connectivity. Since the internal pore structure of the soil changes after curing, traditional undisturbed soil prediction models cannot adapt to the capillary water rise law of cured soil, resulting in low prediction accuracy and difficulty in meeting the design and long-term stability evaluation needs of cured soil engineering. SUMMARY

[0004] The purpose of the present application is to provide a cured soil capillary water rise height prediction method based on porosity change, which addresses the problem of low prediction accuracy of capillary water rise height due to changes in pore radius after soil curing. By quantifying the dynamic change law of porosity and correcting the capillary water rise height prediction model, the prediction error problem caused by ignoring the change in porosity due to soil curing in traditional prediction methods is solved.

[0005] To achieve the above purpose, the present application proposes a cured soil capillary water rise height prediction method based on porosity change, comprising the following steps: Step S1: Obtain the soil sample to be tested, and add inorganic solidifying agent to the soil sample to be tested for curing; Step S2: Using the cured soil sample to be tested as raw material, prepare capillary water height samples and cutting ring samples under the same compaction degree conditions: Step S3: Perform a capillary water rise test on the capillary water height sample, record the capillary water rise height data at different time nodes under the corresponding curing age, use the cutting ring sample, measure the contact angle of the cured soil under the corresponding curing age by a contact angle measuring instrument, and use the mercury intrusion method to measure the pore radius of the cured soil; Step S4: Select the soil sample in the middle region and with a flat surface from the cutting ring sample for micro-test to obtain the microstructure image of the cured soil; Step S5: Based on the obtained microstructure image, use the PCAS image analysis software to identify the porosity under the same parameter conditions, and obtain the porosity data of the cured soil under the corresponding curing age; Step S6: Derive the capillary water rise height calculation formula, introduce the pore diameter correction parameter according to the variation law of the porosity data, correct the parameters of the capillary water rise height calculation formula, obtain the corrected capillary water rise height calculation formula, and derive the equation of the liquid motion velocity in the capillary tube after parameter correction.

[0006] Preferably, in step S1, the inorganic curing agent is a mixture of Portland cement and fly ash, and the mass of the soil sample to be tested is used as the basis to replace part of the soil sample to be tested according to the corresponding mass ratio.

[0007] Preferably, in step S2, the amount of ingredients is determined by referring to the maximum dry density and the optimum moisture content of the soil during preparation, the compaction coefficient is set to confirm the compaction degree, and additional water is added according to the mass of the curing agent to meet the water content required for hydration.

[0008] Preferably, in step S2, the capillary water height sample is prepared using a transparent tubular container, the soil is layered and filled to form a soil column, the curing age is set, and the capillary water height sample is obtained, and the diameter and height of the cutting ring sample are set to obtain the cutting ring sample.

[0009] Preferably, in step S6, the pore diameter correction parameter is the porosity reduction ratio of the cured soil compared to the uncured soil.

[0010] Preferably, in step S6, the following steps are included: Step S61: Calculate the volume of liquid flowing through a certain distance in the capillary tube per unit time, and the calculation formula is: ; wherein, is the volume of liquid flowing through a certain distance in the capillary tube per unit time, is the effective pore diameter of the capillary tube, is the distance of liquid flowing in the capillary tube per unit time; Step S62: considering the length of the liquid in the capillary, the effective aperture of the capillary, the viscosity of the liquid, the slip coefficient and the total effective pressure, the volume of the liquid flowing through a certain distance in the capillary per unit time is calculated, and the calculation formula is: ; ; wherein, is the total effective pressure, is the viscosity of the liquid, is the length of the liquid in the capillary, is the slip coefficient, is the unit time, is the unbalanced atmospheric pressure, is the hydrostatic pressure, is the capillary pressure; Step S63: the liquid motion velocity in the capillary is calculated, and the calculation formula is: ; Step S64: the liquid motion velocity formula in the capillary is integrated to obtain the length formula of the liquid in the capillary, which is specifically: ; wherein, is the time of the liquid motion in the capillary; Step S65: the parameter is set to zero, and is true for all liquids that can wet the inner wall of the capillary, the value of is calculated, and the formula is: ; wherein, is the surface tension of the liquid, is the contact angle; Step S66: based on the setting and simplification processing, the capillary water rising height calculation formula is obtained, which is specifically: ; Step S67: considering the change of the soil porosity, the aperture correction parameter is introduced, the capillary water rising height calculation formula is parameter corrected, and the equation of the liquid motion velocity in the capillary after parameter correction is derived, and the corrected capillary water rising height calculation formula is: ; wherein, is the aperture correction parameter.

[0011] Preferably, in step S67, the equation of the liquid motion velocity in the capillary after parameter correction is obtained by differentiating the corrected capillary water rising height calculation formula, the rising rate of the capillary water is calculated, and the equation is: .

[0012] Therefore, this invention proposes a method for predicting the capillary rise height of solidified soil based on porosity changes, with the following beneficial effects: (1) This invention is the first to focus on the dynamic evolution of porosity of solidified soil, and specifically solves the technical pain point that the original soil model is not suitable for solidified soil, filling the gap in the field of capillary water prediction of solidified soil.

[0013] (2) This invention uses multiple microscopic testing technologies such as mercury intrusion porosimetry, contact angle measuring instrument, and PCAS software to accurately quantify pore structure parameters, introduce pore size correction parameters to establish a quantitative correlation model, and significantly improve the prediction accuracy of the model.

[0014] (3) This invention closely integrates with the actual needs of solidified soil engineering, and can accurately predict the capillary water rise height under different solidifying agent dosages and different ages. It provides key technical support for solidifying agent ratio optimization, compaction control and long-term stability assessment of engineering, effectively solves the practical problems of strength attenuation and settlement deformation caused by capillary water rise in solidified soil engineering, and realizes the closed loop from theoretical model to engineering application. Attached Figure Description

[0015] Figure 1 A flowchart of a method for predicting capillary rise height in solidified soil based on porosity variation; Figure 2 This is a schematic diagram of the results of the solidified soil pore identification process, where (a) is an SEM image, (b) is a binarized image, and (c) is a result vector image; Figure 3 A schematic diagram of the fitted curve for predicting the capillary rise height in solidified soil; Figure 4 This is a schematic diagram of the capillary water rise rate curve for solidified soil. Detailed Implementation

[0016] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0017] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0018] Example 1 like Figure 1 As shown, this invention provides a method for predicting the capillary rise height of solidified soil based on porosity changes, comprising the following steps: Step S1: Using sulfated soil as the treatment object, silicate cement and fly ash were selected as solidification materials to carry out solidification tests on the soil. The mixing ratio of silicate cement and fly ash in the solidification material was set to 5:5. Based on the mass of the original sulfated soil, the solidification material replaced part of the original sulfated soil at a mass ratio of 10%, 20%, and 30% respectively, and the solidification performance of sulfated soil under different replacement ratios was tested.

[0019] Step S2: The maximum dry density of the sulfate-saline soil was determined to be 1.91 g / cm³ through experiments. 3 The optimal moisture content was 16.8%, and the compaction coefficient was 0.9. To ensure the required moisture content for hydration, 20% more water by weight of the corresponding curing agent was added during sample preparation. Uncured soil (C0) and three groups of cured soil samples with different curing agent dosages (CF1, CF4, CF7) were prepared for testing. The mix proportions of the cured soil samples are shown in Table 1. Table 1 Sample Mix Proportions An acrylic tube with an inner diameter of 5 cm and a height of 150 cm was selected as the soil column container. The soil to be tested was filled into the acrylic tube in a five-layer filling method, so that the soil inside the tube eventually formed a soil column structure with a height of 100 cm. After the soil column was filled, it was placed in a cool environment for a 7-day curing treatment. After curing, the capillary water height sample was obtained. The diameter of the ring sample was set to 61.8 mm and the height to 20 mm to obtain the ring sample. Step S3: Begin the capillary rise test, continuously monitor and record the capillary rise height data at each preset time point within 10 days after the start of the test. The capillary rise height is shown in Table 2. Table 2. Water rise height in capillary tubes Next, the contact angle of the solidified soil at 7 days of age was measured using a ring sample and a contact angle measuring instrument. The specific data of the contact angle of the sample are shown in Table 3. Table 3. Sample contact angle Finally, the pore radius of the solidified soil was determined using mercury intrusion porosimetry.

[0020] Step S4: After the experiment, select a soil sample with a flat surface from the middle area at the same height from the ring sampler for microscopic testing to obtain a microscopic structure image of the solidified soil.

[0021] Step S5: Based on the obtained microstructure image, quantitative analysis of the sample is performed using the Particle (Pore) and Crack Image Recognition and Analysis System (PCAS). The solidified soil pore identification process is as follows:Figure 2 As shown. Under the same set parameter conditions, porosity identification was performed to obtain the porosity data of the solidified soil at the corresponding solidification age, specifically: The pore characteristics of solidified and unsolidified soil were detected and analyzed using PCAS pore analysis software. Specifically, the porosity of three groups of solidified soil samples with an age of 7 days was compared with that of unsolidified soil samples. After calculation and analysis by the software, it was found that compared with the porosity of unsolidified soil sample C0, the porosity of solidified soil samples CF1, CF4 and CF7 decreased by 0.29, 0.42 and 0.49, respectively.

[0022] Step S6: The formula for calculating the capillary water rise height is derived. Based on the variation law of porosity data, a pore size correction parameter is introduced to correct the formula for calculating the capillary water rise height, resulting in the corrected formula. The equation for the liquid velocity in the capillary after parameter correction is then derived, including the following steps: Step S61: Calculate the volume of liquid flowing through a certain distance in the capillary per unit time. The calculation formula is: ; in, It is the volume of liquid flowing through a certain distance in a capillary per unit time. The effective pore size of the capillary. This is the distance the liquid flows through the capillary per unit time. Step S62: Considering the length of the liquid in the capillary, the effective pore size of the capillary, the viscosity of the liquid, the slip coefficient, and the total effective pressure, calculate the volume of liquid flowing through a certain distance in the capillary per unit time. The calculation formula is as follows: ; ; in, The total effective pressure, The viscosity of the liquid. The length of the liquid in the capillary tube. The slip coefficient, For a unit of time, Unbalanced atmospheric pressure, For hydrostatic pressure, For capillary pressure; Step S63: Calculate the velocity of the liquid in the capillary tube. The calculation formula is as follows: ; Step S64: Integrate the formula for the velocity of the liquid in the capillary tube to obtain the formula for the length of the liquid in the capillary tube, specifically: ; in, The time it takes for the liquid to move in the capillary tube; Step S65: Assume and If the parameter is negligible compared to the others, then it is considered to be a parameter. The value is zero. This assumption holds true for all liquids capable of wetting the inner wall of a capillary. Calculation The value is given by the formula: ; in, The surface tension of the liquid, Contact angle; Step S66: Based on the settings and simplification process, the formula for calculating the capillary rise height is obtained, specifically: ; Step S67: Considering the change in porosity of the solidified soil, a pore size correction parameter is introduced. This parameter is the percentage decrease in porosity of the solidified soil compared to the unsolidified soil. The capillary rise height calculation formula is then modified accordingly. Specifically: The revised formula for calculating the capillary rise height is as follows: ; in, For aperture correction parameters; Differentiating the modified formula for calculating the capillary rise height, we obtain the equation for the velocity of the liquid in the capillary after parameter correction. The rise rate of the capillary water is then calculated using the following equation: ; By using the modified formula for calculating the capillary rise height and the equation for the capillary rise rate, a fitting analysis was performed on the relevant test data of the solidified soil samples. The results are as follows: Figure 3 and Figure 4 As shown, the accuracy of all fitting results is at a high level, specifically reflected in the coefficient of determination R of each fitted curve. 2 All values ​​reached above 0.93, which fully and reliably proves the scientific nature of the data fitting process and the credibility of the fitting results in this experiment.

[0023] It is worth noting that all contents not described in detail in this invention are existing technologies and are well known to those skilled in the art.

[0024] Therefore, this invention provides a method for predicting capillary rise height in solidified soil based on porosity changes. Taking the key engineering problem of soil porosity changes during solidification as its core starting point, this method, based on traditional capillary rise height prediction models, incorporates porosity variation patterns obtained through microscopic testing at different solidification ages to specifically modify the porosity-related parameters in the model, forming a capillary rise height prediction model adapted to the characteristics of solidified soil. Related experiments are conducted, and the actual data obtained from the experiments are compared and analyzed with the prediction results of the modified model to verify the universality of the modified model under different solidification degrees, significantly improving the prediction accuracy of capillary rise height in soil at different solidification degrees. This invention, by considering the correlation mechanism between dynamic changes in porosity and capillary rise height, accurately reflects the actual effect of pore structure changes on capillary seepage, thereby improving the scientific nature of solidified soil engineering design and long-term service safety.

[0025] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for predicting capillary rise height in solidified soil based on porosity variation, characterized in that, Includes the following steps: Step S1: Obtain the soil sample to be tested and add an inorganic solidifying agent to solidify the soil sample; Step S2: Using the solidified soil sample to be tested as raw material, capillary water height samples and ring samplers are prepared under the same compaction conditions: Step S3: Conduct a capillary rise test on the capillary height sample, record the capillary rise height data at different time points under the corresponding curing age, use a ring sample, measure the contact angle of the cured soil under the corresponding curing age using a contact angle measuring instrument, and use mercury intrusion porosimetry to determine the pore radius of the cured soil. Step S4: Select a soil sample with a smooth surface from the middle area of ​​the ring sampler for microscopic testing to obtain a microscopic structure image of the solidified soil. Step S5: Based on the obtained microstructure image, use PCAS image analysis software to identify porosity under the same set parameter conditions to obtain the porosity data of the solidified soil at the corresponding solidification age. Step S6: The formula for calculating the capillary water rise height is derived. Based on the variation law of porosity data, a pore size correction parameter is introduced to correct the formula for calculating the capillary water rise height, resulting in the corrected formula for calculating the capillary water rise height. The equation for the velocity of the liquid in the capillary after parameter correction is also derived.

2. The method for predicting capillary rise height in solidified soil based on porosity variation according to claim 1, characterized in that: In step S1, the inorganic curing agent is a mixture of silicate cement and fly ash. Based on the mass of the soil sample to be tested, a portion of the soil sample to be tested is replaced according to the corresponding mass ratio.

3. The method for predicting capillary rise height in solidified soil based on porosity variation according to claim 1, characterized in that: In step S2, the amount of ingredients is determined by referring to the maximum dry density and optimum moisture content of the soil during the preparation process, the compaction coefficient is set to confirm the compaction degree, and water is added in addition to meet the moisture content required for hydration based on the mass of the curing agent.

4. The method for predicting capillary rise height in solidified soil based on porosity variation according to claim 1, characterized in that: In step S2, the capillary water height sample is prepared using a transparent tubular container, and soil is layered and filled to form a soil column. The solidification age is set to obtain the capillary water height sample. The diameter and height of the ring sample are set to obtain the ring sample.

5. The method for predicting capillary rise height in solidified soil based on porosity variation according to claim 1, characterized in that: In step S6, the pore size correction parameter is the rate of reduction in porosity of the solidified soil compared to the unsolidified soil.

6. The method for predicting capillary rise height in solidified soil based on porosity variation according to claim 1, characterized in that: Step S6 includes the following steps: Step S61: Calculate the volume of liquid flowing through a certain distance in the capillary per unit time. The calculation formula is: ； in, It is the volume of liquid flowing through a capillary tube over a certain distance per unit time. The effective pore size of the capillary. This is the distance the liquid flows through the capillary per unit time. Step S62: Considering the length of the liquid in the capillary, the effective pore size of the capillary, the viscosity of the liquid, the slip coefficient, and the total effective pressure, calculate the volume of liquid flowing through a certain distance in the capillary per unit time. The calculation formula is as follows: ； ； in, The total effective pressure, The viscosity of the liquid. The length of the liquid in the capillary tube. The slip coefficient, For a unit of time, Unbalanced atmospheric pressure, For hydrostatic pressure, For capillary pressure; Step S63: Calculate the velocity of the liquid in the capillary tube. The calculation formula is as follows: ； Step S64: Integrate the formula for the velocity of the liquid in the capillary tube to obtain the formula for the length of the liquid in the capillary tube, specifically: ； in, The time it takes for the liquid to move in the capillary tube; Step S65: Set parameters The value is zero, and this holds true for all liquids capable of wetting the inner wall of the capillary. Calculation The value of is given by the formula: ； in, The surface tension of the liquid, Contact angle; Step S66: Based on the settings and simplification process, the formula for calculating the capillary rise height is obtained, specifically: ； Step S67: Considering the change in porosity of the solidified soil, a pore size correction parameter is introduced to correct the formula for calculating the capillary rise height. The equation for the liquid velocity in the capillary after parameter correction is then derived. The corrected formula for calculating the capillary rise height is: ； in, These are the aperture correction parameters.

7. The method for predicting capillary rise height in solidified soil based on porosity variation according to claim 6, characterized in that: In step S67, the modified formula for calculating the capillary rise height is differentiated to obtain the equation for the velocity of the liquid in the capillary after parameter correction. The rise rate of the capillary water is then calculated, and the equation is as follows: 。

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