Preparation method of engineering residue soil precast pile and variable-frequency micro-amplitude vibration bidirectional compaction device

Abstract

The invention discloses a preparation method and device of an engineering muck precast pile, muck is screened according to the particle size, according to the muck particle size composition, the compaction characteristics of muck with different particle sizes in an ideal state are simulated by adopting particle flow numerical simulation, and the maximum compaction density and gradation are obtained; according to the maximum compaction density gradation and the characteristic particle size of the cementing material in the ideal state, different amounts of the cementing material are doped to prepare a muck mixture, and according to an evolution model of the compaction density along with the pressure, the tight packing gradation of the muck and the cementing material mixture is obtained; the method comprises the following steps: carrying out tests on the change of the compaction dry density along with the water content, the clay mineral content and the water demand of a cementing material under different pressure conditions, constructing a model of the dry density along with the water content, the clay mineral content and the water demand of the cementing material based on a multi-parameter artificial neural network machine learning model, and obtaining the optimal water content and the maximum dry density under different pressure conditions; a variable-frequency micro-amplitude vibration two-way compaction device is adopted, and a static pressure-strong vibration-weak vibration-static pressure four-stage process is adopted for compaction forming.

Description

Technical Field

[0001] The invention belongs to the technical field of geotechnical engineering, and in particular relates to a method for preparing a prefabricated pile of engineering slag and a variable frequency micro-amplitude vibration bidirectional compacting device. Background Art

[0002] Waste slag has a wide range of sources, a large stock, a fast growth rate, and a low utilization rate. It is mainly disposed of by landfill, which has become an important problem restricting the rapid economic development and urbanization process. Waste slag has the properties of a multi-phase medium (water, soil, organic matter, microorganisms, etc.), and the interface action process is complex. During the recycling process, the structure is easy to become unstable and the skeleton is easy to compress. The efficiency of curing interface modification and regulation is low, resulting in low strength of the solidified slag product, easy agglomeration, difficult compaction, and low degree of recycling.

[0003] Traditional slag solidification technology fails to fully understand the complex interface interactions between water, soil, and curing agents in multiphase media, which makes it difficult to effectively regulate these interactions during the modification process, affecting the stability and structural integrity of the slag. In terms of particle size regulation, existing technologies and processes have considered the impact of particle size on the performance of recycled products (ZL201910143702.8, ZL201910535360.4, 201810290666.3), but have not yet made a breakthrough in slag particle size regulation technology from a theoretical and model perspective, and cannot meet the optimal grading requirements for high-strength products.

[0004] In addition, in compaction molding, using traditional geotechnical engineering test methods, under constant compaction work conditions (light, heavy, variable work ZL 202322163609.8), the compaction parameters obtained are difficult to guide the preparation of slag solidification products by strong pressure (>600kN) process, and when the curing agent dosage is greater than 5%, the effect of curing agent particle size on the gradation of slag solidification products is not considered. In terms of moisture content control, the long-used critical moisture content provides an empirical reference for soil treatment and construction in geotechnical engineering construction. However, based on the critical moisture content, the optimal moisture content obtained by compaction fails to consider the influence of slag components, particle gradation, moisture form between interfaces, moisture required in the hydration process of cementitious materials, and the relationship between hydration products at interfaces, and cannot meet the requirements of high-strength slag products formed by solidification and compaction. How to finely control the moisture content of slag solidification materials and the influence of interparticle ion concentration and type on interfacial repulsion has become a key problem.

[0005] In terms of prefabricated product compaction, traditional processes include static pressure and vibration compaction. Among them, static pressure (CN202410134060.6, ZL 202211024430.8) often relies on gravity and mold pressure, and cannot apply pressure evenly in all directions. The unidirectional pressure due to friction leads to uneven density inside the product, affecting the overall performance. Although vibration compaction (CN202410468285.5) can help the close arrangement of material particles and reduce porosity through vibration, excessive vibration or improper process will cause microcracks inside the structure, affecting the stability of the cured product.

[0006] In summary, as a type of environmental soil, in the process of modification and solidification of construction waste soil for resource utilization, the existing technology has not paid attention to the interface properties such as the interaction relationship between multiphase media, particle grading optimization, moisture content regulation, and adjustment of particle spacing by external force. It is urgent to develop a regulation method and equipment to solve the key problems of low compaction degree, low strength and poor stability of construction waste soil prefabricated products, which is of great significance to improving the resource utilization and high value utilization of construction waste soil. Summary of the invention

[0007] In view of the technical limitations of the existing slag solidification and modification, such as poor particle size gradation, improper moisture control, and poor control of the solidification and compaction molding process and equipment, which lead to loose structure, low strength and poor stability of the slag product, the present invention provides a method for preparing prefabricated piles of engineering slag. Based on the "environmental soil interface mechanical modification and regulation technology", innovative particle flow numerical simulation and compaction density evolution model with pressure are introduced to construct the most dense stacking gradation of slag and cementitious materials; a multi-parameter artificial neural network machine learning model in which water content varies with clay mineral content, particle size gradation quality fractal dimension, cementitious material dosage and water requirement, and compaction density is established to finely control the free water between slag particles, satisfy the physical reconstruction of cementitious materials between slag particles, and further reduce the repulsion between slag particles; a variable frequency micro-vibration bidirectional compaction device and a static pressure-strong earthquake-weak earthquake-static pressure process are developed to form a new technology system for foundation treatment of prefabricated solidified soil piles by interface modification and regulation.

[0008] In order to achieve the above purpose, the technical solutions adopted are as follows:

[0009] A method for preparing engineering slag prefabricated piles, comprising gradation optimization, moisture content control, variable frequency micro-amplitude vibration bidirectional compaction molding;

[0010] (1) The gradation optimization includes: pre-treating the slag and screening the slag according to the particle size; according to the particle size components of the slag, using particle flow numerical simulation to simulate the compaction characteristics of slag with different particle sizes under ideal conditions to obtain the maximum compaction density and gradation; according to the gradation of the maximum compaction density under ideal conditions and the characteristic particle size of the cementitious material, adding different amounts of cementitious material to prepare the slag mixture, and obtaining the close stacking gradation of the slag and cementitious material mixture according to the evolution model of compaction density with pressure;

[0011] (2) The moisture content control includes: conducting tests on the change of compacted dry density with moisture content, clay mineral content, and water requirement of cementitious materials under different pressure conditions, establishing a dry density change model with moisture content, clay mineral content, and water requirement of cementitious materials based on a multi-parameter artificial neural network machine learning model, and obtaining the optimal moisture content and maximum dry density under different pressure conditions;

[0012] (3) The variable frequency micro-amplitude vibration bidirectional compaction molding includes: according to the compaction resistance characteristics of the slag, the negative feedback control system controls the variable frequency alternating coil, and the alternating electromagnetic induction under the action of pressure generates a micro-amplitude high-frequency vibration to act on the slag-soil mixture, and the same frequency amplitude rods are arranged on the upper and lower parts of the compaction barrel, and the bidirectional vibration is used for compaction molding; the specific compaction molding process includes a four-level molding process of static pressure-strong vibration-weak vibration-static pressure.

[0013] According to the above scheme, the pretreatment of the slag in step 1, screening the slag according to the particle size, includes the following steps:

[0014] The slag is dried and a double-roll crusher is used to control the maximum particle size of the slag to less than 4.75mm. The crushed slag is screened with a multi-stage vibrating screen. The screening particle group ranges are as follows: coarse-grained soil is 4.75-2.36mm, 2.36-1.18mm, 1.18-0.6mm, 0.6-0.15mm, 0.15-0mm; medium-grained soil is 2.36-1.18mm, 1.18-0.6mm, 0.6-0.15mm, 0.15-0mm; fine-grained soil is 1.18-0.6mm, 0.6-0.15mm, 0.15-0mm.

[0015] According to the above scheme, the particle flow numerical simulation described in step 1 is used to simulate the compaction characteristics of soil with different particle sizes under ideal conditions to obtain the maximum compaction density and gradation, including the following steps:

[0016] The particles are set as rigid clusters (clumps). According to the single interval components after the slag is screened, the logarithmic normal distribution mode in the interval is used to generate a model with a particle number greater than 1 million. The ideal compaction density of each single component under the ideal state is calculated. The ideal compaction density of the slag under the full particle size component can be calculated by formula (1);

[0017] ρ0′=a∑ki ·ρ i ' (1)

[0018] Where: ρ0' is the ideal compaction density of different graded slag, g / cm 3 ; a is the correction factor, dimensionless; k i is the mass proportion of each single component, dimensionless; ρ i ' is the ideal compaction density of each single component g / cm 3 .

[0019] The ideal compaction density and the ideal compaction degree of each single component are known, the maximum value of ρ0' is solved iteratively, and the mass proportion of each component is determined, so as to determine the gradation. According to the proportion of each component, the above-mentioned single-component simulation method is used to determine the correction coefficient a, and then the maximum compaction degree under the optimal gradation of the slag is obtained. (When the slag gradation is poor, the dosage of a certain particle size component can be fixed, and the above-mentioned method can be used to determine the optimal gradation under special conditions to ensure the utilization rate of slag for different types of slag precast piles).

[0020] According to the above scheme, the characteristic particle size of the cementitious material in step 1 is coarse-grained soil: d 90 ≤100μm, medium-grained soil: d 90 ≤45μm, fine-grained soil: d 90 ≤10μm; the amount of cementitious material added to coarse-grained soil is 5-15% of the dry weight of the soil, medium-grained soil is 8-18% of the dry weight of the soil, and fine-grained soil is 12-24% of the dry weight of the soil. The pressure range is 10-15MPa for coarse-grained soil, 12-16MPa for medium-grained soil, and 13-17MPa for fine-grained soil.

[0021] According to the above scheme, the evolution model of compaction density with pressure in step 1 is fitted according to the general formula of density-pressure curve relationship as shown in formula (2):

[0022] ρ(p)=a+1 / (b+c -p ) (2)

[0023] In the formula: ρ is the compaction density value of different cementitious material dosages, p is the pressure value, c is the fitting parameter, a+1 / (b+1) is the loose bulk density value, a+1 / b is the maximum compaction density value, and the above formula is a general fitting formula for dimensionless values.

[0024] According to the above scheme, the different pressure conditions used in step 2 are: 9, 11, 13, and 15 MPa for coarse-grained soil, 10, 12, 14, and 16 MPa for medium-grained soil, and 11, 13, 15, and 17 MPa for fine-grained soil.

[0025] According to the above scheme, the moisture content in step 2 is in the range of w0-4% to w0+4%, where w0 is the base moisture content at which all the pores of the slag are filled with water in the particle flow simulation calculation.

[0026] According to the above scheme, the water requirement of the cementitious material in step 2 is determined according to the material category slurry test. The cementitious material is a hydraulic inorganic cementitious material, and the 28d slurry strength is greater than 32.5MPa.

[0027] According to the above scheme, the artificial neural network machine learning model described in step 2 has two hidden layers, the first hidden layer has 7 neurons, and the second hidden layer has 2 neurons; the input vector of the first hidden layer is calculated using formula (3):

[0028] z1=W1x+b1 (3)

[0029] Wherein, x in Formula 3 is the input vector from the input layer, is the weight matrix of the first hidden layer, W1 and b1 are training parameters, and b1 is the bias vector;

[0030] The activation of neurons is passed to the next layer through the nonlinear function (4):

[0031] a1=f(z1) (4)

[0032] a1 represents the output vector of the hidden layer, and the nonlinear activation function represented by f is the rectified linear unit (ReLU) function.

[0033] According to the above scheme, the four-stage forming process of static pressure-strong vibration-weak vibration-static pressure described in step 3 includes: the first-stage static pressure range is 8-13MPa for coarse-grained soil, 10-14MPa for medium-grained soil, and 11-15MPa for fine-grained soil, and the static pressure time is 10-15s for coarse-grained soil, 15-20s for medium-grained soil, and 20-25s for fine-grained soil; the second-stage strong vibration frequency is 100-300Hz; the third-stage weak vibration frequency is 10-30Hz; the fourth-stage static pressure range is 10-15MPa for coarse-grained soil, 12-16MPa for medium-grained soil, and 13-17MPa for fine-grained soil, and the static pressure time is 30-40s for coarse-grained soil, 40-60s for medium-grained soil, and 60-90s for fine-grained soil. The first-level static pressure is used to initially expel the air between the particles; the second-level strong earthquake adjusts the position of the particles, and the fine particles quickly fill the pores between the coarse particles; the third-level weak earthquake fine-tunes the position of the particles, adjusting the point-to-surface contact of the particles of each component to surface-to-surface contact, and densifying the matrix; the fourth-level static pressure dissipates the pore water pressure and further stabilizes the high-density matrix.

[0034] A variable frequency micro-amplitude vibration bidirectional compaction device for engineering slag precast piles, comprising a negative feedback mode control system 1, an alternating coil generator 2, an amplitude rod 3, a blowing and suction hole 4, a resistance reduction sleeve 5, a vibration chamber 6, a hydraulic pressure plate 7, and a cable 8;

[0035] The two sides of the resistance reduction sleeve 5 are slidably connected to two amplitude rods 3, the other end of the amplitude rod 3 is coaxially threadedly connected to the vibration chamber 6, and the other end of the vibration chamber 6 is welded to the hydraulic pressure plate 7 to form a whole;

[0036] The negative feedback mode control system 1 is connected to the vibration chamber 6 via a cable 8 to control the alternating coil generator 2;

[0037] A blowing and suction hole 4 connected to a blowing and suction device is provided at the middle position ±0.5m of the drag reducing sleeve 5, and the blowing and suction hole 4 is connected to the conduit of the external additional blowing and suction device by a snap-fit ​​connection.

[0038] According to the above scheme, the alternating coil generator 2 includes an alternating coil 201, a winding iron block 202, and a magnetic guide disk 203; the alternating coil 201 is bonded to the iron columns on both sides of the winding iron block 202 by sealing wax according to the right-hand screw rule, and one end of the winding iron column 202 is riveted to the upper part of the inner cavity of the vibration chamber 6, and the other end is welded to the magnetic guide disk 203.

[0039] According to the above scheme, the amplitude rod 3 includes an amplitude rod outer body 301, a magnetic disk 302, a spring 303, a movable pad 304, a fixed disk 305, and an amplitude rod inner impact rod 306; the amplitude rod outer body 301, the spring 303 and the movable pad 304 are arranged to be in sliding contact with the amplitude rod inner impact rod 306, the magnetic disk 302 and the amplitude rod inner impact rod 306 are threadedly connected, and the fixed disk 305 and the amplitude rod inner impact rod 306 are formed into a whole by welding.

[0040] The control system with negative feedback mode adopts an adaptive control algorithm with a response time of less than 20ms. The electromagnetic force generated by the alternating coil is 0.3 to 0.5 times the pressure. The limit of the amplitude rod connecting the spring is 1 to 10mm. The resistance reduction sleeve and the compaction cavity include a porous design, and the porous structure is arranged at ±0.5m in the middle of the pile length. The blowing and suction device is used to blow in lubricating oil or release agent, and negative pressure sucks out the air generated during the compaction of the precast pile. The aperture range of the blowing and suction device is 0.1-2mm.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] As a kind of environmental soil, engineering slag soil is modified and solidified for resource utilization. The interaction relationship between multiphase media, particle grading optimization, moisture content regulation, and intergranular spacing adjustment by external force are considered. The present invention discloses a grading optimization, moisture content regulation, variable frequency micro-vibration bidirectional compaction device, and a preparation method and device for prefabricated piles by static pressure-strong earthquake-weak earthquake-static pressure four-stage forming process. In the grading optimization process, crushing and screening are first carried out to classify different types of slag soil, which provides a premise for the regulation of particle size. The particle flow numerical simulation method is used to obtain the optimal grading and ideal compaction degree, which makes up for the traditional In order to make up for the shortcomings of the empirical trial mixing technology, the compaction density evolution model of different gradations under constant pressure was further used. The influence of the particle size and dosage of cementitious materials in the mixed materials on compaction was considered, and the particle size and dosage of cementitious materials required for different types of slag were clarified to provide support for the subsequent mixture compaction molding process. In the process of moisture content regulation, a multi-parameter artificial neural network machine learning model of the optimal moisture content with clay mineral content, particle size gradation quality fractal dimension, and cementitious material water requirement was constructed to finely control the free water between slag particles, and further reduce the repulsion between slag particles while satisfying the physical reconstruction of cementitious materials between slag particles. The method not only considers the influence of clay mineral content and particle morphology on moisture content, but also combines the amount of water required for hydration of cementitious materials, and finely controls the moisture required for densified products. Compared with the traditional experience, the compaction curve is obtained through compaction test, and the optimal moisture content and maximum dry density obtained are more scientific. The variable frequency micro-amplitude vibration bidirectional compaction device developed by the company overcomes the disadvantages of the traditional molding method that it is impossible to apply pressure evenly in all directions, and the internal density of the product is uneven due to unidirectional pressure due to friction resistance, which affects the overall performance. The proprietary high-frequency micro-amplitude device design not only improves the compactness between particles and reduces porosity, but also solves the problems of excessive vibration or working The problem of micro cracks inside the structure caused by improper processing is solved. The porous structure discharges gas, reduces energy consumption, and improves the economy of the preparation of precast slag piles. The supporting four-stage forming process of static pressure-strong earthquake-weak earthquake-static pressure uses the first-stage static pressure to initially discharge the gas between the particles; the second-stage strong earthquake adjusts the position of the particles, and the fine particles quickly fill the pores between the coarse particles; the third-stage weak earthquake fine-tunes the position of the particles, and adjusts the point-to-surface contact of the particles of each component to surface-to-surface contact to form a dense matrix; the fourth-stage static pressure dissipates the pore water pressure, further stabilizes the high-density matrix modification and regulation to prepare high-performance slag piles, which solves the key problems of low compaction, low strength and poor stability of slag prefabricated products. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 : Compaction density curve and fitting curve under different pressure ranges.

[0044] Figure 2 : Artificial neural network machine learning model.

[0045] Figure 3: Schematic diagram of the structure of the variable frequency micro-amplitude vibration bidirectional compaction device.

[0046] Figure 4 : Schematic diagram of the alternating coil generator structure.

[0047] Figure 5 : Schematic diagram of the amplitude rod structure.

[0048] Figure numerals: 1-negative feedback mode control system; 2-alternating coil generator; 3-amplitude rod; 4-blowing and suction holes; 5-resistance reduction sleeve; 6-vibration chamber; 7-hydraulic pressure plate; 8-cable; 201-alternating coil; 202-winding iron block; 203-conducting magnetic disk; 301-amplitude rod outer body; 302-magnetic disk; 303-spring; 304-movable pad; 305-fixed disk; 306-impact rod inside the amplitude rod. DETAILED DESCRIPTION

[0049] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0050] A specific implementation method provides a method for preparing prefabricated piles of engineering slag based on the mechanical modification and control technology of the environmental soil interface. The engineering slag used is sampled at the construction site. According to the soil properties, the slag is coarse-grained soil. The slag is pretreated, the slag is screened according to the particle size, and the slag is dried on a laboratory scale. A double-roll crusher is used to control the maximum particle size of the slag to be less than 4.75 mm. A multi-stage vibrating screen is used to screen the crushed slag. The screened particle groups are 4.75-2.36 mm, 2.36-1.18 mm, 1.18-0.6 mm, 0.6-0.15 mm, and 0.15-0 mm, respectively, and the mass proportions of each component are 0.11, 0.18, 0.33, 0.20, and 0.18, respectively.

[0051] The particle flow numerical simulation is used to simulate the compaction characteristics of slag with different particle sizes under ideal conditions. The particles are set as rigid clusters (clumps). According to the single interval components after slag screening, the logarithmic normal distribution mode in the interval is used to generate a model with a particle number greater than 1 million. The ideal compaction density of each single component under ideal conditions is calculated. The ideal compaction density of slag under full particle size components can be calculated by formula (1).

[0052] ρ0′=a∑k i ·ρ i ' (1)

[0053] Where: ρ0' is the ideal compaction density of different graded slag, a is the correction coefficient, k i is the mass proportion of each single component, ρ i ' is the ideal compaction density of each single component.

[0054] Through the above simulation calculation, the ρ0' of the five groups of single components of 4.75-2.36mm, 2.36-1.18mm, 1.18-0.6mm, 0.6-0.15mm, and 0.15-0mm are 2.23g / cm 3 , 2.26g / cm 3 , 2.44g / cm 3 , 2.21g / cm 3 , 2.12g / cm 3 , the correction coefficient a is 1.07, and the ideal compaction density ρ0' of the slag under the full particle size component is 2.44.

[0055] The characteristic particle size of cementitious material is d 90 The density of the sample is 85 μm, the amount of cementitious material added is 12%, and the compaction density curve and fitting curve under different pressure ranges (10-15 MPa) are as follows: Figure 1 As shown. The maximum compacted density is 2.51g / cm 3 .

[0056] In the particle flow simulation calculation, the pores of the slag are completely filled with water, with a baseline moisture content of 21.3%. The moisture content range used in the test is 17.3-24.3%, and the constant pressure is 9, 11, 13, and 15 MPa. The cementitious material is 425 cement, with a 28d net slurry strength of 44.3 MPa, and the water requirement is 26.5% of the cementitious material.

[0057] The specific implementation method provides an artificial neural network machine learning model, see Attachment Figure 2 As shown. (0 cementitious material dosage, 1 clay mineral content, 2 required water content of cementitious material, 3 input vector (3), 4-10, first hidden layer nodes, 11 nonlinear activation function, 12-13, second hidden layer nodes, 14 output function)

[0058] The artificial neural network machine learning model has two hidden layers, the first hidden layer has 7 neurons, and the second hidden layer has 2 neurons; the input vector of the first hidden layer is calculated using formula (3):

[0059] z1=W1x+b1 (3)

[0060] Wherein, x in Formula 3 is the input vector from the input layer, is the weight matrix of the first hidden layer, W1 and b1 are training parameters, and b1 is the bias vector;

[0061] The activation of neurons is passed to the next layer through the nonlinear function (4):

[0062] a1=f(z1) (4)

[0063] a1 represents the output vector of the hidden layer, and the nonlinear activation function represented by f is the rectified linear unit (ReLU) function.

[0064] The training process is as follows: First, when the pressure is 9MPa, a set of input data is given to the neural network. The data in this model are: 5% cementitious material content, 2.3% clay mineral content, and 12% water required for cementitious material. Let it propagate forward to obtain an output result, the optimal moisture content. Then, compare the output optimal moisture content with the expected result and calculate an error value; then, propagate the error value back along the network, and calculate the gradient value of each node and connection according to the contribution of each node and connection to the error value (input vector); finally, according to the gradient value of each node and connection, update the weight value and bias value of each node and connection to reduce the error value. When the error is controlled within the acceptable range, output the prediction result.

[0065] The optimal moisture content and maximum dry density predicted by the artificial neural network model at various pressure levels are shown in Table 1.

[0066] Table 1

[0067] Pressure(MPa) Optimum moisture content (%) <![CDATA[Maximum dry density (g / cm 3 )]]> 9 22.4 2.48 11 21.3 2.53 13 19.7 2.55 15 18.6 2.56

[0068] In order to more conveniently realize the process of variable frequency micro-amplitude vibration bidirectional compaction molding, a specific implementation method provides a variable frequency micro-amplitude vibration bidirectional compaction device, refer to the attached Figures 3 to 5 The device comprises a negative feedback mode control system 1, an alternating coil generator 2, an amplitude rod 3, a blowing and suction hole 4, a resistance reduction sleeve 5, a vibration chamber 6, a hydraulic pressure plate 7, and a cable 8;

[0069] The two sides of the resistance reduction sleeve 5 are slidably connected to two amplitude rods 3, the other end of the amplitude rod 3 is coaxially threadedly connected to the vibration chamber 6, and the other end of the vibration chamber 6 is welded to the hydraulic pressure plate 7 to form a whole;

[0070] The negative feedback mode control system 1 is connected to the vibration chamber 6 via a cable 8 to control the alternating coil generator 2;

[0071] A blowing and suction hole 4 connected to a blowing and suction device is provided at the middle position ±0.5m of the drag reducing sleeve 5, and the blowing and suction hole 4 is connected to the conduit of the external additional blowing and suction device by a snap-fit ​​connection.

[0072] Reference Figure 4The alternating coil generator 2 includes an alternating coil 201, a winding iron block 202, and a conductive magnetic disk 203; the alternating coil 201 is bonded to the iron columns on both sides of the winding iron block 202 by sealing wax according to the right-hand screw rule, and one end of the winding iron column 202 is riveted to the upper part of the inner cavity of the vibration chamber 6, and the other end is welded to the conductive magnetic disk 203.

[0073] Reference Figure 5 The amplitude rod 3 includes an amplitude rod outer body 301, a magnetic disk 302, a spring 303, a movable pad 304, a fixed disk 305, and an amplitude rod inner impact rod 306; the amplitude rod outer body 301, the spring 303 and the movable pad 304 are arranged to be in sliding contact with the amplitude rod inner impact rod 306, the magnetic disk 302 and the amplitude rod inner impact rod 306 are threadedly connected, and the fixed disk 305 and the amplitude rod inner impact rod 306 are formed into a whole by welding.

[0074] The specific method of using this device includes the following steps:

[0075] (1) Before preparing the prefabricated pile, lubricating oil or mold release agent is injected into the inner wall of the resistance reduction sleeve 5 through the blowing and suction hole 4. The injection time is 1s-2s, and the amplitude rod 3 is moved to promote the uniform distribution of the lubricating oil or mold release agent. The blowing and suction hole 4 is located at the middle position of the pile length ±0.5m, and the hole diameter ranges from 0.1-2mm;

[0076] (2) When the prefabricated pile is prepared, the bulk construction waste soil material which has been optimized in gradation and regulated in optimal moisture content is placed in the cavity of the resistance reduction sleeve 5 coated with lubricating oil or a release agent, and the hydraulic pressure plate 7 is opened to push the amplitude rod 3 into the cavity of the resistance reduction sleeve 5 until it touches the bulk construction waste soil material;

[0077] (3) During the punching and compacting process of the precast piles, the high-pressure gas generated during the preparation of the precast piles is discharged through the blowing and suction holes 4 until the amplitude rods 3 on both sides of the resistance reduction sleeve 5 can no longer be pressed in;

[0078] (4) During the micro-amplitude high-frequency vibration of the precast pile, the alternating coil 201 is controlled by the negative feedback mode control system 1 to generate a changing magnetic field around the winding iron block 202, and the magnetic disk 302 is driven by the magnetic disk 203 to drive the impact rod 306 in the amplitude rod to perform micro-amplitude high-frequency simple harmonic motion in the outer body 301 of the amplitude rod to generate an axial additional force, wherein the magnetic disk 203 and the magnetic disk 302 are limited to 10 mm, and the negative feedback mode control system adopts an adaptive control algorithm with a response time of less than 20 ms. The axial additional force generated by the vibration of the alternating coil generator is 0.3 to 0.5 times the set pressure;

[0079] (5) After the prefabricated pile is prepared through bidirectional impact extrusion and slight high-frequency vibration, the resistance-reducing sleeve 5 is placed in a demoulding machine for demoulding, and the prefabricated pile is prepared.

[0080] According to the different pressure conditions in Table 1, the moisture content of the slag soil is controlled, the prefabricated pile mixture is prepared and put into the pressure chamber, the variable frequency micro-vibration bidirectional compaction device is turned on, the electromagnetic force generated by the alternating coil generator is 0.35 times the set pressure, the limit of the amplitude rod connecting the spring is 8mm, the resistance reduction sleeve and the compaction cavity hole are designed to be in the middle of the pile length, and the hole diameter is 1.5mm. Bidirectional compaction vibration molding, the first-level static pressure is 11MPa, the static pressure time is 12s for coarse-grained soil, the second-level strong vibration frequency is 150Hz, the third-level weak vibration frequency is 15Hz, the fourth-level static pressure is 13MPa, and the static pressure time is 35s for coarse-grained soil. After demoulding, maintenance is carried out, and the strength of the single pile at 7d is 15.6MPa.

[0081] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing prefabricated piles of engineering slag, characterized in that Including gradation optimization, moisture content control, variable frequency micro-vibration bidirectional compaction molding; (1) The gradation optimization includes: pre-treating the slag and screening the slag according to the particle size; using particle flow numerical simulation to simulate the compaction characteristics of slag with different particle sizes under ideal conditions according to the slag particle size components, and obtaining the maximum compaction density and gradation; adding different amounts of cementitious materials to prepare the slag mixture according to the gradation of the maximum compaction density under ideal conditions and the characteristic particle size of the cementitious material, and obtaining the tightly packed gradation of the slag and cementitious material mixture according to the evolution model of the compaction density with pressure; (2) The moisture content control includes: conducting experiments on the change of compacted dry density with moisture content, clay mineral content, and water requirement of cementitious materials under different pressure conditions, establishing a dry density change model with moisture content, clay mineral content, and water requirement of cementitious materials based on a multi-parameter artificial neural network machine learning model, and obtaining the optimal moisture content and maximum dry density under different pressure conditions; (3) The variable frequency micro-amplitude vibration bidirectional compaction molding includes: using a variable frequency micro-amplitude vibration bidirectional compaction device to perform a four-stage molding process of static pressure-strong vibration-weak vibration-static pressure.

2. The method for preparing prefabricated piles of construction waste soil according to claim 1, characterized in that The pretreatment of the slag in step 1, wherein the slag is screened according to particle size, comprises the following steps: The slag is dried and a double-roll crusher is used to control the maximum particle size of the slag to less than 4.75mm. The crushed slag is screened with a multi-stage vibrating screen. The screening particle group ranges are as follows: coarse-grained soil is 4.75-2.36mm, 2.36-1.18mm, 1.18-0.6mm, 0.6-0.15mm, 0.15-0mm; medium-grained soil is 2.36-1.18mm, 1.18-0.6mm, 0.6-0.15mm, 0.15-0mm; fine-grained soil is 1.18-0.6mm, 0.6-0.15mm, 0.15-0mm.

3. The method for preparing prefabricated piles of construction waste soil according to claim 1, characterized in that The particle flow numerical simulation described in step 1 simulates the compaction characteristics of soil with different particle sizes under ideal conditions to obtain the maximum compaction density and gradation, including the following steps: The particles are set as rigid clusters (clumps). According to the single interval components after slag screening, the log-normal distribution mode within the interval is used to generate a model with a particle number greater than 1 million. The ideal compaction density of each single component under ideal conditions is calculated. The ideal compaction density of slag under full particle size components can be calculated using formula (1); ρ0'=a∑k i ·r i ' (1) Where: ρ0' is the ideal compaction density of different graded soil, g / cm 3 ; a is the correction coefficient, dimensionless; k i is the mass ratio of each single component, dimensionless; ρ i ' is the ideal compaction density of each single component g / cm 3 . Given the ideal compaction density and ideal compaction degree of each single component, the maximum value of ρ0' is solved iteratively, and the mass proportion of each component is determined, thereby determining the gradation. According to the proportion of each component, the above-mentioned single-component simulation method is used to determine the correction coefficient a, and then the maximum compaction degree under the optimal gradation of the slag is obtained.

4. The method for preparing prefabricated piles of construction waste soil according to claim 1, characterized in that The characteristic particle size of the cementitious material described in step 1 is coarse-grained soil: d90≤100μm, medium-grained soil: d90≤45μm, and fine-grained soil: d90≤10μm; the cementitious material dosage of coarse-grained soil is 5-15% of the dry weight of the soil, medium-grained soil is 8-18% of the dry weight of the soil, and fine-grained soil is 12-24% of the dry weight of the soil; the pressure range of coarse-grained soil is 10-15MPa, medium-grained soil is 12-16MPa, and fine-grained soil is 13-17MPa.

5. The method for preparing prefabricated piles of construction waste soil according to claim 1, characterized in that The evolution model of compaction density with pressure in step 1 is fitted with a general formula based on the density-pressure curve relationship as shown in formula (2): ρ(p)h+1 / (b+c -p ) (2) Where: ρ is the compacted density value of different cementitious material dosages, p is the pressure value, c is the fitting parameter, a+1 / (b+1) is the loose bulk density value, a+1 / b is the maximum compacted density value, and the above formula is a general fitting formula for dimensionless values.

6. The method for preparing prefabricated piles of construction waste soil according to claim 1, characterized in that The different pressure conditions used in step 2 are: 9, 11, 13, and 15 MPa for coarse-grained soil, 10, 12, 14, and 16 MPa for medium-grained soil, and 11, 13, 15, and 17 MPa for fine-grained soil; the moisture content range is w0-4% to w0+4%, where w0 is the baseline moisture content at which all the pores of the slag are filled with water in the particle flow simulation calculation.

7. The method for preparing prefabricated piles of construction waste soil according to claim 1, characterized in that The water requirement of the cementitious material in step 2 is determined according to the material type slurry test. The cementitious material is a hydraulic inorganic cementitious material, and the 28d slurry strength is greater than 32.5MPa.

8. The method for preparing prefabricated piles of construction waste soil according to claim 1, characterized in that The artificial neural network machine learning model described in step 2 has two hidden layers, the first hidden layer has 7 neurons, and the second hidden layer has 2 neurons; the input vector of the first hidden layer is calculated using formula (3): z1=W1x+b1 (3) Where x in Equation 3 is the input vector from the input layer, is the weight matrix of the first hidden layer, W1 and b1 are training parameters, and b1 is the bias vector; The activation of neurons is passed to the next layer through the nonlinear function (4): a1=f(z1) (4) a1 represents the output vector of the hidden layer, and the nonlinear activation function represented by f is the rectified linear unit (ReLU) function.

9. The method for preparing prefabricated piles of construction waste soil according to claim 1, characterized in that The four-stage forming process of static pressure-strong vibration-weak vibration-static pressure described in step 3 includes: the first-stage static pressure range is 8-13MPa for coarse-grained soil, 10-14MPa for medium-grained soil, and 11-15MPa for fine-grained soil, and the static pressure time is 10-15s for coarse-grained soil, 15-20s for medium-grained soil, and 20-25s for fine-grained soil; the second-stage strong vibration frequency is 100-300Hz; the third-stage weak vibration frequency is 10-30Hz; the fourth-stage static pressure range is 10-15MPa for coarse-grained soil, 12-16MPa for medium-grained soil, and 13-17MPa for fine-grained soil, and the static pressure time is 30-40s for coarse-grained soil, 40-60s for medium-grained soil, and 60-90s for fine-grained soil.

10. A variable frequency micro-amplitude vibration bidirectional compacting device, characterized in that It includes a negative feedback mode control system 1, an alternating coil generator 2, an amplitude rod 3, a blowing and suction hole 4, a resistance reduction sleeve 5, a vibration chamber 6, a hydraulic pressure plate 7, and a cable 8; The two sides of the resistance reduction sleeve 5 are slidably connected to two amplitude rods 3, the other end of the amplitude rod 3 is coaxially threadedly connected to the vibration chamber 6, and the other end of the vibration chamber 6 is welded to the hydraulic pressure plate 7 to form a whole; The negative feedback mode control system 1 is connected to the vibration chamber 6 via a cable 8 to control the alternating coil generator 2; A blowing and suction hole 4 for connecting to a blowing and suction device is provided at the middle position ±0.5m of the resistance reducing sleeve 5 , and the blowing and suction hole 4 is connected to the conduit of the external additional blowing and suction device by a snap connection.

11. The variable frequency micro-amplitude vibration bidirectional compacting device according to claim 10, characterized in that The alternating coil generator 2 includes an alternating coil 201, a winding iron block 202, and a conductive magnetic disk 203; the alternating coil 201 is bonded to the iron columns on both sides of the winding iron block 202 by sealing wax according to the right-hand screw rule, and one end of the winding iron column 202 is riveted to the upper part of the inner cavity of the vibration chamber 6, and the other end is welded to the conductive magnetic disk 203.

12. The variable frequency micro-amplitude vibration bidirectional compacting device according to claim 10, characterized in that The amplitude rod 3 includes an amplitude rod outer body 301, a magnetic disk 302, a spring 303, a movable pad 304, a fixed disk 305, and an amplitude rod inner impact rod 306; the amplitude rod outer body 301, the spring 303 and the movable pad 304 are arranged to be in sliding contact with the amplitude rod inner impact rod 306, the magnetic disk 302 and the amplitude rod inner impact rod 306 are threadedly connected, and the fixed disk 305 and the amplitude rod inner impact rod 306 are formed into a whole by welding.

13. The method for preparing prefabricated piles of construction waste soil according to claim 1, characterized in that Step 3 adopts the variable frequency micro-amplitude vibration bidirectional compacting device described in any one of claims 10-12.

Images