Preparation method of hydroxypropyl methyl cellulose solution for centrifugal model test

Abstract

The invention relates to a preparation method of a hydroxypropyl methyl cellulose solution for a centrifugal model test. The method comprises the following steps: calculating the total mass of required HPMC powder and the total mass of water; water accounting for 5-10% of the total mass of the water and HPMC powder accounting for 15-30% of the total mass of the HPMC powder are added into a preparation container in a stirring state, and a gel or paste base material is formed; scattering the residual HPMC powder into the base material to form a mixture; and adding the residual water into the mixture to prepare an initial HPMC solution, and sealing and standing at room temperature to obtain the HPMC solution. The process is simplified, the operation is convenient, the whole process can be carried out at normal temperature, the operation process is simplified, the requirement on special equipment is reduced, the energy consumption and the test cost are also remarkably reduced, and the method is particularly suitable for rapidly preparing large-batch solutions under laboratory or field conditions. The device is specially designed for an application scene in which a large batch of polymer solutions with fixed viscosity are required in a rock-soil centrifugal model test, and can be used for flexibly preparing solutions with different viscosities so as to meet centrifugal model test requirements under different conditions.

Description

Technical Field

[0001] This invention belongs to the field of polymer solution preparation technology, and specifically relates to a method for preparing a hydroxypropyl methylcellulose solution for centrifugation model tests, which is used to prepare a high-viscosity pore fluid required for saturated sand models in soil and rock centrifugation model tests. Background Technology

[0002] Hydroxypropyl methyl cellulose (HPMC) is a non-toxic, odorless, and chemically stable non-ionic cellulose ether. Its aqueous solution exhibits controllable thickening properties, excellent water retention, and chemical stability. It also possesses a density and compressibility close to water, as well as rheological properties similar to Newtonian fluids. It is a commonly used material in geotechnical centrifuge model tests to simulate pore fluids in soil and to prepare saturated media for saturated sand models. In geotechnical centrifuge model tests, based on the design requirements of the seepage velocity similarity law, HPMC solutions of specific viscosities are often required to match the model conditions. Due to the scale requirements of the test models, the demand for this solution in a single test typically reaches tens to hundreds of kilograms. Simultaneously, centrifuge model tests require extremely high accuracy in simulating seepage patterns. The HPMC solution needs to ensure uniform overall viscosity and good batch-to-batch repeatability; even small fluctuations in solution properties directly affect the accuracy and reliability of the seepage characteristics of the saturated sand model. Currently, common methods for preparing HPMC solutions include the hot water method, powder mixing method, and organic solvent wetting method. For example, Chinese patent application number 201210476359 discloses a method for preparing a methylcellulose solution, which involves dispersing the powder in hot water (70-100°C), then adding cold water and cooling and stirring in an ice-water bath. While this method can accelerate dissolution, it mainly relies on temperature control to achieve powder dispersion, requiring heating and cooling equipment, making the process complex and energy-intensive. When applied to the preparation of large batches of HPMC solution required for geotechnical centrifuge model tests, the existing methods have the following shortcomings: (1) They rely on temperature control equipment, and the process is complicated and energy-intensive: The method requires heating, cooling and temperature control equipment to achieve water temperature regulation. Heating and cooling large batches of liquid takes a long time and consumes a lot of energy. It is also difficult to ensure the overall temperature uniformity of the solution. The uneven dissolution of powder due to local temperature differences will affect the performance of the solution. (2) The uniformity and stability of the solution are difficult to meet the standards: After HPMC particles come into contact with water, the surface will quickly swell to form a viscous gel film that wraps the undissolved powder inside, forming fish-eye-shaped lumps or flocculents that are difficult to disperse. Even with temperature control, the existing methods still cannot completely solve the agglomeration problem in large batches due to insufficient coverage of stirring shear force and untimely powder dispersion. This results in uneven viscosity distribution inside the prepared solution. After standing, local viscosity differences and slight stratification are likely to occur, which cannot meet the requirements of model tests for the uniformity of solution viscosity. (3) Small single-batch preparation volume and inability to guarantee batch repeatability: Existing methods are limited by the performance of temperature control equipment, resulting in a limited single-batch preparation volume. When preparing large batches of solutions, multiple batches need to be prepared. However, during the batch operation, it is difficult to ensure that the process parameters such as temperature and dispersion time are completely consistent for each batch. This can easily lead to significant differences in viscosity and uniformity between different batches of solutions, failing to meet the technical requirements for batch repeatability in centrifugation model tests. Therefore, it is urgent to develop a new method for preparing HPMC solutions that is suitable for large-scale preparation, easy to operate, and can ensure uniform solution viscosity. Summary of the Invention

[0003] To address the aforementioned problems, the present invention aims to provide a simple method for preparing hydroxypropyl methylcellulose solution that requires no water temperature control and is suitable for centrifugal model experiments. This method effectively prevents powder agglomeration and ensures complete dissolution, guaranteeing uniform viscosity in large batches of solution and exhibiting good batch repeatability.

[0004] To achieve the above objectives, the method for preparing a hydroxypropyl methylcellulose solution for centrifugation model tests provided by the present invention includes the following steps performed in sequence:

[0005] 1) Based on the similarity ratio of the centrifugal model test design, determine the target viscosity of the HPMC solution. Then, based on the internal dimensions of the model box and the soil parameters, calculate the total amount of solution to be prepared. After that, based on the target viscosity of the HPMC solution, determine the specifications of the HPMC powder and the corresponding concentration. Finally, based on the total amount of solution to be prepared and the concentration, calculate the total mass of HPMC powder and the total mass of water required.

[0006] 2) Add water to the preparation container in sequence, which is 5-10% of the total mass of water. Start the stirring device equipped with a high-shear stirring head for continuous high-intensity stirring. Then slowly and evenly add HPMC powder, which accounts for 15-30% of the total mass of HPMC powder, until a high-concentration gel or paste base without flocculent matter is formed.

[0007] 3) Maintain high-speed stirring and sprinkle the remaining HPMC powder into the base material. If the base material is too viscous, add a small amount of water to dilute it until a uniform mixture is formed.

[0008] 4) Continue stirring at high speed and add the remaining water to the mixture until the base material is evenly dispersed, thereby preparing the initial HPMC solution;

[0009] 5) Stop stirring and seal the initial HPMC solution at room temperature to obtain the HPMC solution.

[0010] In step 1), the method for determining the target viscosity of the HPMC solution based on the similarity ratio designed for the centrifugal model test, then calculating the total amount of solution to be prepared based on the internal dimensions of the model box and the soil parameters, followed by determining the specifications and corresponding concentration of the HPMC powder based on the target viscosity of the HPMC solution, and finally calculating the required total mass of HPMC powder and total mass of water based on the total amount of solution prepared and the concentration is as follows:

[0011] 1.1) Based on the similarity ratio N, expressed as model size / prototype size, designed for centrifugal model experiments, the target viscosity of the HPMC solution is determined to be 1 / N;

[0012] 1.2) Calculate the total amount of solution to be prepared based on the internal dimensions of the model box and the soil parameters;

[0013] 1.3) Compare the target viscosity determined in step 1.1) with the specifications of commercial HPMC powder, where the HPMC powder specification is the viscosity value of its 2.00% mass fraction aqueous solution at 20℃. If an HPMC powder specification with the same target viscosity exists, select that specification of HPMC powder and directly determine the preparation concentration as 2.00%. If no matching HPMC powder specification exists, the preparation concentration needs to be determined through multiple preliminary experiments and interpolation based on the concentration-viscosity relationship curve.

[0014] 1.4) Based on the total amount of solution prepared determined in step 1.2) and the concentration determined in step 1.3), calculate the total mass of HPMC powder and the total mass of water required.

[0015] In steps 2) to 4), the stirring speed is 500-1500 rpm.

[0016] In step 5), the settling time is 12-24 hours.

[0017] The advantages and positive effects of this invention are: simplified process, convenient operation, and complete elimination of reliance on temperature control steps such as heating and cooling. The entire process can be carried out at room temperature, which not only simplifies the operation process and reduces the requirements for specialized equipment (such as heaters and ice baths), but also significantly reduces energy consumption and experimental costs. It is particularly suitable for the rapid preparation of large batches of solutions under laboratory or field conditions. Furthermore, by preparing a high-concentration gel or paste base, this invention provides a high-viscosity, high-shear-resistance medium environment for subsequent HPMC powder. Combined with the high-intensity shear force field generated by a high-efficiency stirring tool, the subsequently added HPMC powder can be instantly dispersed and wetted, fundamentally avoiding the formation of "fish-eye" insoluble substances and ensuring the viscosity uniformity of the final solution in different liquid layers. Since the process parameters such as water-to-powder ratio, feeding sequence, stirring intensity, and settling time are clear and easy to control, the method of this invention has excellent batch-to-batch repeatability. Testing showed that the viscosity deviation of multiple batches of HPMC solutions of the same concentration prepared using the method of this invention could be controlled within ±1.0%, fully meeting the requirements of uniformity and accuracy of pore fluid viscosity in geotechnical centrifuge model tests. This invention is specifically designed for applications requiring large-volume, fixed-viscosity polymer solutions in geotechnical centrifuge model tests, allowing for the flexible preparation of solutions of different viscosities to meet the needs of centrifuge model tests under various conditions. Attached Figure Description

[0018] Figure 1 This is a process flow diagram of the method for preparing hydroxypropyl methylcellulose solution for centrifugation model tests provided by the present invention. Detailed Implementation

[0019] To further understand the invention's content, features, and effects, the following application examples are provided, along with detailed descriptions in conjunction with the accompanying drawings:

[0020] Example 1:

[0021] like Figure 1 As shown, the method for preparing the hydroxypropyl methylcellulose solution for centrifugation model tests provided in this embodiment includes the following steps performed in sequence:

[0022] 1) Based on the similarity ratio of the centrifugal model test design, determine the target viscosity of the HPMC solution. Then, based on the internal dimensions of the model box and the soil parameters, calculate the total amount of solution to be prepared. After that, based on the target viscosity of the HPMC solution, determine the specifications of the HPMC powder and the corresponding concentration. Finally, based on the total amount of solution to be prepared and the concentration, calculate the total mass of HPMC powder and the total mass of water required.

[0023] The specific method is as follows:

[0024] 1.1) In this embodiment, the similarity ratio N of the centrifugation model test design is 1 / 50, so the target viscosity of the HPMC solution is 50 mPa·s;

[0025] 1.2) The internal dimensions of the model box used in the experiment were 80cm long * 35cm wide. The sand model consisted of two layers of soil, with the upper layer being 24cm thick and having a dry density of 1.623 g / cm³. 3 The lower layer is fine sand with a porosity of 33.33%, and is 4 cm thick with a dry density of 1.494 g / cm³. 3 For medium-grade sand with a porosity of 42.20%, the pore fluid volume V in the sand model can be calculated. 孔隙流体 =80*35*(24*33.33%+4*42.20%)=27124.16cm 3 The density ρ of HPMC solution at room temperature HPMC溶液 ≈1.000g / cm 3 The pore fluid mass m in the sand model can be obtained. 孔隙流体 =V 孔隙流体 *ρ HPMC溶液 =27124.16g. Considering factors such as losses during the saturation process, the total amount of solution prepared in this embodiment is m. HPMC溶液 =2*m 孔隙流体 =54248.32g;

[0026] 1.3) Compare the target viscosity of 50 mPa·s determined in step 1.1) with the specifications of commercial HPMC powder. Since there is commercial HPMC powder with a specification of 50 mPa·s, directly select HPMC powder of this specification and determine the concentration to be 2.00%.

[0027] 1.4) Based on the total amount of solution determined in step 1.2) and the concentration determined in step 1.3), calculate the required total mass m of HPMC powder. HPMC =m HPMC溶液 *2.00%=1084.97g, total mass of water required: m 水 =m HPMC溶液 -m HPMC =53163.35g.

[0028] 2) Add 2658.17g of water, which accounts for 5% of the total water mass, to the preparation container. Start the stirring device equipped with a high-shear stirring head and stir continuously at a speed of 1000rpm. Then slowly and evenly add 216.99g of HPMC powder, which accounts for 20% of the total HPMC powder mass, until a high-concentration gel or paste base without flocculent matter is formed.

[0029] 3) Maintain high-speed stirring and sprinkle the remaining HPMC powder into the base material. If the base material is too viscous, add a small amount of water to dilute it until a uniform mixture is formed.

[0030] 4) Continue stirring at high speed and add the remaining water to the mixture until the base material is evenly dispersed, thereby preparing an HPMC solution;

[0031] 5) Stop stirring and let the above HPMC solution stand in a sealed container at room temperature for 12 hours to obtain the target HPMC solution.

[0032] Example 2:

[0033] The method for preparing a hydroxypropyl methylcellulose solution for centrifugation model tests provided in this embodiment includes the following steps performed in sequence:

[0034] 1) Based on the similarity ratio of the centrifugal model test design, determine the target viscosity of the HPMC solution. Then, based on the internal dimensions of the model box and the soil parameters, calculate the total amount of solution to be prepared. After that, based on the target viscosity of the HPMC solution, determine the specifications of the HPMC powder and the corresponding concentration. Finally, based on the total amount of solution to be prepared and the concentration, calculate the total mass of HPMC powder and the total mass of water required.

[0035] The specific method is the same as in Example 1.

[0036] 2) Add 5316.34g of water (10% of the total mass of water) to the preparation container in sequence. Start the stirring device equipped with a high-shear stirring head and stir continuously at a speed of 1500rpm. Then slowly and evenly add 325.50g of HPMC powder (30% of the total mass of HPMC powder) until a high-concentration gel or paste base without flocculent matter is formed.

[0037] 3) Maintain high-speed stirring and sprinkle the remaining HPMC powder into the base material. If the base material is too viscous, add a small amount of water to dilute it until a uniform mixture is formed.

[0038] 4) Continue to maintain high-speed stirring, add the remaining water to the above mixture, and adjust the position of the stirring head up and down during the stirring process to ensure that the high-concentration base material does not accumulate at the bottom of the container until the base material is evenly dispersed, thereby preparing the HPMC solution;

[0039] 5) Stop stirring and let the above HPMC solution stand in a sealed container at room temperature for 24 hours to obtain the target HPMC solution.

[0040] Example 3:

[0041] The method for preparing a hydroxypropyl methylcellulose solution for centrifugation model tests provided in this embodiment includes the following steps performed in sequence:

[0042] 1) Based on the similarity ratio of the centrifugal model test design, determine the target viscosity of the HPMC solution. Then, based on the internal dimensions of the model box and the soil parameters, calculate the total amount of solution to be prepared. After that, based on the target viscosity of the HPMC solution, determine the specifications of the HPMC powder and the corresponding concentration. Finally, based on the total amount of solution to be prepared and the concentration, calculate the total mass of HPMC powder and the total mass of water required.

[0043] The specific method is the same as in Example 1.

[0044] 2) Add 4253.07g of water (8% of the total mass of water) to the preparation container in sequence. Start the stirring device equipped with a high-shear stirring head and stir continuously at a speed of 1200rpm. Then slowly and evenly add 271.25g of HPMC powder (25% of the total mass of HPMC powder) until a high-concentration gel or paste base without flocculent matter is formed.

[0045] 3) Maintain high-speed stirring and sprinkle the remaining HPMC powder into the base material. If the base material is too viscous, add a small amount of water to dilute it until a uniform mixture is formed.

[0046] 4) Continue stirring at high speed and add the remaining water to the mixture until the base material is evenly dispersed, thereby preparing an HPMC solution;

[0047] 5) Stop stirring and let the above HPMC solution stand in a sealed container at room temperature for 20 hours to obtain the target HPMC solution.

[0048] In the above embodiments, the inventors used a syringe and a catheter to extract 450 ml of the target HPMC solution from the bottom and the surface, respectively, and used a digital viscometer to test the viscosity. The bottom and surface viscosities were 50.37 and 50.12 mPa·s, respectively, and the errors from the target viscosity were both less than 1.00%, indicating that the method of the present invention is suitable for the large-scale preparation of saturated media for geotechnical centrifuge model tests.

Claims

1. A method for preparing a hydroxypropyl methylcellulose solution for centrifugation model tests, characterized in that: The method for preparing the hydroxypropyl methylcellulose solution includes the following steps performed in sequence: 1) Based on the similarity ratio of the centrifugal model test design, determine the target viscosity of the HPMC solution. Then, based on the internal dimensions of the model box and the soil parameters, calculate the total amount of solution to be prepared. After that, based on the target viscosity of the HPMC solution, determine the specifications of the HPMC powder and the corresponding concentration. Finally, based on the total amount of solution to be prepared and the concentration, calculate the total mass of HPMC powder and the total mass of water required. 2) Add water to the preparation container in sequence, which is 5-10% of the total mass of water. Start the stirring device equipped with a high-shear stirring head for continuous high-intensity stirring. Then slowly and evenly add HPMC powder, which accounts for 15-30% of the total mass of HPMC powder, until a high-concentration gel or paste base without flocculent matter is formed. 3) Maintain high-speed stirring and sprinkle the remaining HPMC powder into the base material. If the base material is too viscous, add a small amount of water to dilute it until a uniform mixture is formed. 4) Continue stirring at high speed and add the remaining water to the mixture until the base material is evenly dispersed, thereby preparing the initial HPMC solution; 5) Stop stirring and seal the initial HPMC solution at room temperature to obtain the HPMC solution.

2. The method for preparing hydroxypropyl methylcellulose solution for centrifugation model tests according to claim 1, characterized in that: In step 1), the method for determining the target viscosity of the HPMC solution based on the similarity ratio designed for the centrifugal model test, then calculating the total amount of solution to be prepared based on the internal dimensions of the model box and soil parameters, followed by determining the specifications and corresponding concentration of the HPMC powder based on the target viscosity of the HPMC solution, and finally calculating the required total mass of HPMC powder and total mass of water based on the total amount of solution prepared and the concentration is as follows: 1.1) Based on the similarity ratio N, expressed as model size / prototype size, designed for centrifugal model experiments, the target viscosity of the HPMC solution is determined to be 1 / N; 1.2) Calculate the total amount of solution to be prepared based on the internal dimensions of the model box and the soil parameters; 1.3) Compare the target viscosity determined in step 1.1) with the specifications of commercial HPMC powder, where the HPMC powder specification is the viscosity value of its 2.00% mass fraction aqueous solution at 20℃. If an HPMC powder specification with the same target viscosity exists, select that specification of HPMC powder and directly determine the preparation concentration as 2.00%. If no matching HPMC powder specification exists, the preparation concentration needs to be determined through multiple preliminary experiments and interpolation based on the concentration-viscosity relationship curve. 1.4) Based on the total amount of solution prepared determined in step 1.2) and the concentration determined in step 1.3), calculate the total mass of HPMC powder and the total mass of water required.

3. The method for preparing hydroxypropyl methylcellulose solution for centrifugation model tests according to claim 1, characterized in that: In steps 2) to 4), the stirring speed is 500-1500 rpm.

4. The method for preparing hydroxypropyl methylcellulose solution for centrifugation model tests according to claim 1, characterized in that: In step 5), the settling time is 12-24 hours.

Images