A method for calculating the amount of soil conditioner used in earth pressure balance shield

Abstract

The present invention discloses a method for calculating the amount of earth pressure balance shield slag improver, comprising the following steps: based on bentonite particles, the improved soil particles are layered and wrapped, and the number of wrapped layers is obtained by a slump test; based on the number of wrapped layers, the number of bentonite particles required to wrap a single improved soil particle is obtained; the number of improved soil particles in a sandy and gravel soil body is obtained; based on the functional relationship between the number of bentonite particles required to wrap a single improved soil particle and the number of improved soil particles, the number of bentonite particles required to improve the sandy and gravel soil body is obtained, and then the required bentonite mass is obtained. The present invention utilizes the microstructure of the improved soil particles and bentonite particles in the sandy and gravel soil body combined by various inter-particle forces, and derives a formula for calculating the injection mass of the bentonite improved sandy and gravel soil body, thereby solving the problem of selecting the amount and proportion of the bentonite improved sandy and gravel soil body in principle, and the amount and proportion obtained are more accurate.

Description

Technical Field

[0001] The invention belongs to the technical field of slag improvement in shield engineering, and in particular relates to a method for calculating the amount of an earth pressure balance shield slag improver. Background Art

[0002] In order to meet the requirements of relative safety and speed of construction, shield method has become the main construction method for underground projects such as urban tunnels. The earth pressure balance shield machine has very high requirements for the improvement of slag, which directly affects the smooth and safe excavation of the shield. In order to improve the stratum adaptability of the earth pressure balance shield, facilitate soil discharge and control the pressure of the soil bin, it is often necessary to improve the shield slag to make the slag have good fluidity. However, the main contradiction nowadays is that the geological conditions of underground construction are complex and changeable, and the contradiction between the difference in construction level of personnel and the lack of standardization and scientificization of slag improvement related products is becoming increasingly prominent. The specific steps to determine the amount of bentonite required for slag improvement are to take soil samples at the construction site, use different ratios of bentonite and water, mix them with slag, and then conduct field tests to check whether the ratio meets the requirements of shield excavation. The construction site usually adopts a slump test to determine the fluidity of the improved slag. For sand and gravel strata, the slump of the slag reaches 150mm-200mm, which can be considered that the improvement effect meets the excavation requirements. However, this method of determining the improvement effect by field tests is not suitable for the project cost budget estimation before the construction team enters the site. When the existing slag improvement scheme does not meet the advancement requirements, the field test requires the shield to be shut down and the mix ratio to be readjusted, which affects the construction progress and causes time and economic losses. Therefore, it is urgent to propose a method for calculating the amount of slag improver for earth pressure balance shield. Summary of the invention

[0003] In order to solve the above technical problems, the present invention proposes a method for calculating the amount of earth pressure balance shield slag improver to solve the above problems in the prior art.

[0004] To achieve the above object, the present invention provides a method for calculating the amount of earth pressure balance shield slag improver, comprising the following steps:

[0005] The bentonite particles are used to wrap the improved soil particles layer by layer, and the slump test is used to obtain the number of wrapping layers;

[0006] Based on the number of wrapping layers, obtaining the number of bentonite particles required to wrap a single soil particle to be improved;

[0007] Obtain the number of soil particles to be improved in the sandy gravel soil;

[0008] Based on the functional relationship between the number of bentonite particles required to encapsulate a single soil particle to be improved and the number of soil particles to be improved, the number of bentonite particles required to improve the sand and gravel soil is obtained, and then the required bentonite mass is obtained.

[0009] Optionally, the process of obtaining the number of coating layers using a slump test includes: determining the viscosity of a slag improver, using the viscosity of the slag improver to improve a sand and gravel soil of a single particle size, performing a slump test on the improved sand and gravel soil of a single particle size, presetting a target slump, and calculating the corresponding number of bentonite particle coating layers based on the amount of bentonite used when the target slump is reached.

[0010] Optionally, the process of determining the concentration of the slag improver includes: using a funnel viscometer to measure the viscosity of bentonite slurries with different soil-water ratios, using a stirring rod to stir to determine the state of the bentonite slurry, and determining the viscosity of the slag improver based on the obtained viscosity value and the slurry state.

[0011] Optionally, the process of obtaining the number of bentonite particles required to wrap a single soil particle to be improved includes: obtaining the surface area of ​​the bentonite particles wrapping the single soil particle to be improved, and obtaining the number of bentonite particles required to wrap the single soil particle to be improved based on the ratio of the surface area wrapping the single soil particle to be improved to the projected area of ​​the single bentonite particle.

[0012] Optionally, the relationship for obtaining the surface area of ​​a single soil particle to be improved that is wrapped by bentonite particles is as follows:

[0013]

[0014] Among them, S n is the surface area of ​​a single improved soil particle wrapped by bentonite particles, n is the number of wrapping layers, D is the particle size of the improved soil particle, and d is the particle size of the bentonite particle after volume expansion by puffing.

[0015] Optionally, the process of obtaining the number of soil particles to be improved in the sand and gravel soil body includes: obtaining the total mass of the sand and gravel soil body, the mass percentage of the soil particles to be improved in the sand and gravel soil body, and the mass of a single soil particle to be improved, and based on the functional relationship between the total mass of the sand and gravel soil body, the mass percentage of the soil particles to be improved in the sand and gravel soil body, and the mass of a single soil particle to be improved, obtaining the number of soil particles to be improved in the sand and gravel soil body.

[0016] Optionally, the process of obtaining the mass of a single soil particle to be improved is: multiplying the volume of the single soil particle to be improved by the density of the sand and gravel soil body to obtain the mass of the single soil particle to be improved.

[0017] Optionally, before obtaining the required bentonite mass, the method further includes: obtaining the volume of a single bentonite particle, and multiplying the volume of the single bentonite particle by the number of bentonite particles required for improving the sand and gravel soil to obtain the required volume of the bentonite particles.

[0018] Optionally, the process of obtaining the required bentonite mass includes: multiplying the required bentonite particle volume by the bentonite density to obtain the required bentonite mass.

[0019] Compared with the prior art, the present invention has the following advantages and technical effects:

[0020] The present invention is based on the process of wrapping the soil particles to be improved layer by layer with bentonite particles, and adopts a slump test to obtain the number of wrapping layers; based on the number of wrapping layers, the number of bentonite particles required to wrap a single soil particle to be improved is obtained; the number of soil particles to be improved in a sandy and gravel soil body is obtained; based on the functional relationship between the number of bentonite particles required to wrap a single soil particle to be improved and the number of soil particles to be improved, the number of bentonite particles required to improve the sandy and gravel soil body is obtained, and then the required bentonite mass is obtained.

[0021] The present invention utilizes the microstructure of the soil particles to be improved and the bentonite particles in the sand and gravel soil body combined by various inter-particle forces, theoretically derives a formula for calculating the injection mass of the bentonite improved sand and gravel soil body, and solves the problem of selecting the amount and proportion of the bentonite improved sand and gravel soil body in principle, so that the amount and proportion obtained are more accurate and more reliable; and solves the randomness and hysteresis of the amount of on-site slag improvement, and can arrange the slag improvement plan in advance according to the engineering geological survey report, which is of great help to cost control and engineering progress arrangement. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The drawings constituting a part of the present application are used to provide a further understanding of the present application. The illustrative embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0023] Figure 1 Graph showing the test results of bentonite slurry funnel viscosity at different soil-water ratios according to an embodiment of the present invention;

[0024] Figure 2 A flow chart of a method for calculating the amount of an earth pressure balance shield slag improver according to an embodiment of the present invention;

[0025] Figure 3 This is a schematic diagram of bentonite particles wrapped with sand and pebble particles according to an embodiment of the present invention;

[0026] Figure 4 Schematic diagram of the relationship between the ratio of the number of coating layers and the particle size of bentonite particles according to an embodiment of the present invention and the particle size. DETAILED DESCRIPTION

[0027] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0028] It should be noted that the steps shown in the flowcharts of the accompanying drawings can be executed in a computer system such as a set of computer executable instructions, and that, although a logical order is shown in the flowcharts, in some cases, the steps shown or described can be executed in an order different from that shown here.

[0029] Embodiment 1

[0030] The present embodiment provides a method for calculating the amount of earth pressure balance shield slag improver, comprising the following steps: selecting a suitable slag improver viscosity based on the viscosity measurement of bentonite slurry and the evaluation of the slurry state; wrapping the soil particles to be improved layer by layer with bentonite particles, and obtaining the number of wrapping layers by using a slump test; obtaining the number of bentonite particles required to wrap a single soil particle to be improved based on the number of wrapping layers; obtaining the number of soil particles to be improved in a sandy and gravel soil body; obtaining the number of bentonite particles required to improve the sandy and gravel soil body based on the functional relationship between the number of bentonite particles required to wrap a single soil particle to be improved and the number of soil particles to be improved, and then obtaining the required bentonite mass.

[0031] Calculation principle:

[0032] When bentonite slurry is injected into the sandy gravel soil for improvement, the bentonite undergoes a hydration reaction. A large number of bentonite hydration film molecules and clay particles with a network structure are dispersed in the slurry. Some particles aggregate to form a spherical particle with the surface wrapped in mud. A large number of spherical particles are dispersed among the soil particles and adsorbed on the surface of the sandy soil particles in coordination with the hydration film. Macroscopically, the bentonite slurry wraps the surface of the soil particles. The presence of the hydration film also increases the cohesion between the particles. This fine-grained wrapping effect reduces the porosity of the sandy gravel soil, makes the particle grading more uniform, reduces the friction between the particles relatively, and enhances the workability of the sandy gravel soil.

[0033] The viscosity of bentonite slurries with different soil-water ratios was measured using a funnel viscometer. The results are as follows: Figure 1 The bentonite slurry with a funnel viscosity of 20-30s has a suitable viscosity, and the viscosity is moderate when stirred with a stirring rod. When the slump test is carried out, no agglomeration or excessive filtration will occur. Therefore, the viscosity value in this range is selected as the suitable viscosity of the slag improver.

[0034] According to the particle size differences of the sandy and gravel soil, all the soil particles in the sandy and gravel soil to be improved can be divided into two parts: one part is the large-diameter particles (D>0.5mm) that need to be improved; the other part is the small-diameter particles (D<0.5mm) that can be improved only by bentonite particles that are filtered out between large particles.

[0035] The particle size of bentonite particles is usually less than 2μm. After hydration reaction with water, the volume expands to more than 10 times the original volume. Theoretically, when the added bentonite particles completely cover the surface of large-size sand and gravel particles after swelling with water, the workability and plasticity of the sand and gravel soil are the best, and the improvement effect of sand and gravel soil is the best. According to the particle grading of sand and gravel soil, the surface area of ​​soil particles is calculated. Based on the mechanism of slag improvement, the bentonite particles required to cover these surface areas are calculated to quantitatively calculate the bentonite mass required for slag improvement. The calculation steps are as follows: Figure 2 shown.

[0036] Bentonite mass calculation process:

[0037] The shapes of the soil particles in the gravel soil and the bentonite particles injected into the soil sample are simplified to spheres, so the surface area and volume calculation formulas of a single soil particle are as follows:

[0038] S 土颗粒 =πD 2 (1)

[0039]

[0040] Where: S 土颗粒 is the surface area of ​​a single soil particle, in mm 2 ; V 土颗粒 is the volume of a single soil particle, in mm 3 ; D is the particle size of the soil to be improved, in mm.

[0041] To calculate the amount of bentonite required, we need to first find out the number of soil particles to be improved. If the mass, density and gradation curve of the sand and gravel soil are known, we can calculate the number of soil particles of each graded soil. 土体 The calculation is as follows:

[0042] V 土体 =m 土体 / ρ 土体 (3)

[0043] The total mass of the sandy gravel soil is m 土体 , ρ 土体 is the density of gravel soil.

[0044] According to the particle grading curve, the mass percentage P of the corresponding particle size in the sandy gravel soil can be known. D , we can get the number of soil particles N to be improved in the sandy gravel soil D :

[0045]

[0046] The particle size of bentonite particles is usually close to 1μm. After hydration reaction with water, the volume expands to more than 10 times the original volume. The particle size of the expanded bentonite particles is about 2μm. Since the particle size difference between sand and gravel particles and bentonite particles is too large, the bentonite particles and the outer surface of the particles to be improved can be simplified as a point connection between a sphere and a plane. After the bentonite is injected, the bentonite particles will wrap the soil particles to be improved. When calculating, the point connection is approximated as the projection of the small-size particles on the surface area direction of the soil particle sphere, such as Figure 3 shown.

[0047] When the bentonite particles wrap a layer of the soil particles to be improved, the surface area that needs to be wrapped by the next layer of bentonite particles will increase. Therefore, the surface area S that needs to be wrapped by the bentonite particles can be obtained. n The relationship with the number of wrapping layers n:

[0048]

[0049] Where d is the particle size of bentonite particles after volume expansion by bulking.

[0050] Therefore, the number of bentonite particles N required to encapsulate one soil particle to be improved is 总 is the surface area S of bentonite particles that need to be coated n The ratio of the projected area of ​​a single bentonite particle is shown in formula (6):

[0051]

[0052] According to the number of all particles with a particle size greater than 0.5 mm, the total number of bentonite particles required to improve the entire sand and gravel soil can be obtained:

[0053]

[0054] According to the above formula, the number of bentonite particles N required to improve the sand and gravel soil 膨润土 and bentonite density ρ 膨润土 The mass of bentonite to be added can be obtained 膨润土 :

[0055]

[0056] where d 膨化前 is the particle size of bentonite particles before expansion. According to the relationship between the mass of bentonite and the mass of the sandy gravel soil to be improved obtained from formula (8), the mass of bentonite required to achieve the improvement effect can be calculated when the grading curve of the soil to be improved is known. The number of coating layers of a single soil particle to be improved is a necessary parameter that needs to be solved.

[0057] The process of obtaining the number of coating layers using a slump test includes: improving a sand and gravel soil of a single particle size using bentonite slurries with different soil-water ratios and injection rates, conducting a slump test on the improved sand and gravel soil of a single particle size, presetting a target slump, and calculating the corresponding number of bentonite particle coating layers based on the amount of bentonite used when the target slump is reached.

[0058] Specifically, the process of measuring the number of coating layers of bentonite particles includes:

[0059] The number of layers of bentonite particles is an important indicator of whether the soil has achieved a good improvement effect. As the number of bentonite particle layers changes, the porosity between large particles changes, and the contact mode and friction between particles also change dramatically. At the same time, the number of coating layers also determines the amount of bentonite used in improving the soil.

[0060] In order to determine the optimal number of bentonite particle coating layers, this embodiment uses bentonite slurries with different soil-water ratios and injection rates to improve single-particle-size sand and gravel soil, and conducts a slump test on the improved single-particle-size sand and gravel soil. The target slump of the improved soil is set to 175 mm, and the corresponding number of bentonite particle coating layers is calculated by the amount of bentonite used to reach the target slump.

[0061] The slump of the improved gravel soil has been significantly improved, meeting the slump requirements of the improved slag soil, and there is no large filtration loss, and the influence of water is small. According to the test results, it can be found that with the increase of the single particle size, the mass of bentonite required for the improved soil body also increases accordingly. When the slump standard is reached, the slurry soil-water ratio and injection rate of each single gradation and the specific amount of bentonite and water are shown in Table 1. The slump of the improved soil body has an error of less than 5mm from the target slump, which is within a reasonable range.

[0062] Table 1

[0063]

[0064] Based on the mass of bentonite used, the number of bentonite particle layers wrapped around each particle can be calculated when the improvement effect of single-size sand and gravel soil is good. The amount of bentonite and water required to achieve the target improvement effect is shown in Table 2. Table 2 also calculates the number of layers wrapped around bentonite particles and the ratio of the number of layers to the particle size under the corresponding bentonite dosage. Based on the calculated number of layers of wrapped bentonite particles, it can be found that as the particle size of the large particles to be improved increases, the number of bentonite layers required to wrap a single particle to achieve the improvement effect increases, and the ratio of the number of layers to the particle size also increases with the increase in particle size. Figure 4 Shown is the relationship between the ratio of the number of bentonite particle coating layers to the particle size and the particle size.

[0065] Table 2

[0066]

[0067] Calculation results verification:

[0068] In order to verify the accuracy of the calculation formula, different soil-water ratios and different injection rates of bentonite slurries were used to improve the sandy and gravel soils with different particle sizes. After the improvement, a slump test was carried out to compare the slump when the slurry ratio closest to the calculated mass was used for improvement with the ideal improved slag slump value. The bentonite mass required to improve the sandy and gravel soils with various fine particle contents calculated by the above formula, as well as the slump value closest to the theoretical mass, are shown in Table 3.

[0069] Table 3

[0070]

[0071] It has been verified that the sand and gravel soil improved by bentonite slurry with actual mass closest to the theoretical mass meets the slump requirements of ideal improved slag soil, so the theoretical calculation is feasible.

[0072] This embodiment proposes a suitable relationship between bentonite slurry soil-water ratio and slurry viscosity, and determines the slurry viscosity suitable for slag improvement based on the viscosity value measured by the funnel viscometer and the slurry state of the bentonite slag improver.

[0073] This embodiment proposes the relationship between the number of bentonite coating layers and the particle size, and finds a specific method to test the number of coating layers. Through the experiment, the relationship between the particle size of sand and gravel soil and the number of coating layers is obtained, which provides a reference for the improvement of slag in sand and gravel formations.

[0074] In this embodiment, based on the geological survey report of the stratum conditions, the required amount of bentonite can be calculated when the soil gradation curve and the excavation volume in the excavation area are known.

[0075] This embodiment can formulate corresponding slag improvement ratios according to the project construction geological survey report, which has advanced predictiveness. When excavating to the soil layer of corresponding grade, corresponding improvement plans can be adopted, which can greatly save time costs and is of great help to the early cost estimation.

[0076] The above are only preferred specific implementations of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A method for calculating the amount of earth pressure balance shield slag improver, characterized in that: The following steps are involved: Based on the bentonite particles, the improved soil particles are wrapped layer by layer, and the slump test is used to obtain the number of wrapping layers; Based on the number of wrapping layers, obtaining the number of bentonite particles required to wrap a single soil particle to be improved; Obtain the number of soil particles to be improved in the sandy gravel soil; Based on the functional relationship between the number of bentonite particles required to encapsulate a single soil particle to be improved and the number of soil particles to be improved, the number of bentonite particles required to improve the sandy gravel soil is obtained, thereby obtaining the required bentonite mass; The process of obtaining the number of coating layers by using the slump test includes: determining the viscosity of the slag improver, improving the sand and gravel soil of a single particle size by using the viscosity of the slag improver, performing a slump test on the improved sand and gravel soil of a single particle size, presetting a target slump, and calculating the corresponding number of bentonite particle coating layers based on the amount of bentonite used when the target slump is reached; The process of obtaining the number of bentonite particles required to wrap a single soil particle to be improved includes: obtaining the surface area of ​​the bentonite particles wrapping the single soil particle to be improved, and obtaining the number of bentonite particles required to wrap the single soil particle to be improved based on the ratio of the surface area wrapping the single soil particle to be improved to the projected area of ​​the single bentonite particle; The process of obtaining the number of soil particles to be improved in the sandy gravel soil body includes: obtaining the total mass of the sandy gravel soil body, the mass percentage of the soil particles to be improved in the sandy gravel soil body, and the mass of a single soil particle to be improved, and obtaining the number of soil particles to be improved in the sandy gravel soil body based on the functional relationship between the total mass of the sandy gravel soil body, the mass percentage of the soil particles to be improved in the sandy gravel soil body, and the mass of a single soil particle to be improved; Before obtaining the required bentonite mass, the method further includes: obtaining the volume of a single bentonite particle, multiplying the volume of the single bentonite particle by the number of bentonite particles required for improving the sand and gravel soil, and obtaining the required volume of the bentonite particles; The process of obtaining the desired mass of bentonite includes multiplying the desired volume of bentonite particles by the density of bentonite to obtain the desired mass of bentonite.

2. The method for calculating the amount of earth pressure balance shield slag improver according to claim 1, characterized in that: The process of determining the viscosity of the slag improver includes: using a funnel viscometer to measure the viscosity of bentonite slurries with different soil-water ratios, using a stirring rod to stir the bentonite slurry to determine the state of the slurry, and determining the viscosity of the slag improver based on the obtained viscosity value and the slurry state.

3. The method for calculating the amount of earth pressure balance shield slag improver according to claim 1, characterized in that: The relationship for obtaining the surface area of ​​a single soil particle to be improved by bentonite particles is as follows: Among them, Sn is the surface area of ​​a single improved soil particle wrapped by bentonite particles, n is the number of wrapping layers, D is the particle size of the improved soil particle, and d is the particle size of the bentonite particle after volume expansion by puffing.

4. The method for calculating the amount of earth pressure balance shield slag improver according to claim 1, characterized in that: The process of obtaining the mass of a single soil particle to be improved is as follows: multiplying the volume of a single soil particle to be improved by the density of the sand and gravel soil to obtain the mass of the single soil particle to be improved.

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