Method for preparing porosity-controllable gangue gelling filling body based on response surface method

Abstract

The invention discloses a method for preparing a porosity-controllable gangue gelling filling body based on a response surface method, and relates to the technical field of mineral engineering. According to the method, coal gangue is used as a main raw material and matched with a cementing material composed of thermal activation coal gangue powder, slag powder and cement, meanwhile, an exciting agent is introduced for excitation, the average particle size of coal gangue aggregate, the mixing amount of the cementing material and the water-solid ratio of the cementing material are used as core influence factors, and a porosity and 28-day uniaxial compressive strength response surface model is constructed; and the optimal preparation parameters can be quickly determined. According to the method, the resource utilization rate of the coal gangue can exceed 90%, meanwhile, the problems that the porosity is difficult to regulate and control, the mechanical property is unstable and the production efficiency is low in a traditional filling technology can be solved, and a key technical support is provided for safety, high efficiency and ecological environmental protection of mine filling mining.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of mining engineering, in particular to a controllable porosity gangue cemented filling body preparation method based on a response surface method. BACKGROUND

[0002] With large-scale exploitation of coal resources, goaf treatment has become a key problem to ensure mine safety and ecological environment, and filling mining technology is widely used because it can effectively dispose goaf. Gangue, as the main waste of coal mining, is used to prepare filling materials, which can realize solid waste resource utilization and reduce costs. However, the traditional gangue filling has obvious shortcomings: on the one hand, the porosity control and mechanical property optimization ability are lacking, which is difficult to meet the needs of different geological conditions, such as areas with high control requirements for rock strata, which require filling materials with high strength and appropriate porosity to support overburden rock, and goaf with special requirements for air permeability, which also requires precise control of the pore structure; on the other hand, the traditional technology consumes a lot of materials and relies on ramming mechanism to compact repeatedly 3-6 times, which has low filling efficiency and seriously restricts the advancing speed of the coal mining face.

[0003] The new gangue cemented high-porosity filling technology provides an innovative path to solve these problems, which is to fill broken gangue into the goaf and use the rear jetting mechanism of the filling hydraulic support to spray fast coagulation material onto the surface of the gangue, so that the two are cemented to form a high-porosity bearing structure, which can form a filling body with certain strength without repeated ramming, efficiently dispose solid waste and control rock movement and ground deformation. However, this technology still lacks precise control means for porosity, and the quantitative relationship between preparation parameters and porosity and mechanical properties has not been established, resulting in insufficient stability of the filling body performance and difficulty in adapting to complex engineering scenarios.

[0004] Therefore, it is of great significance to develop a gangue cemented filling body preparation method that can precisely control porosity and has good mechanical properties to promote the development of filling mining technology and ensure safe and efficient production of mines. SUMMARY

[0005] The purpose of the present application is to provide a controllable porosity gangue cemented filling body preparation method based on a response surface method to solve the problems existing in the prior art. The method can effectively control the porosity of the filling body to meet different engineering requirements, optimize the mechanical properties of the filling body, and improve the safety and effectiveness of filling mining.

[0006] To achieve the above purpose, the present application provides the following solutions:

[0007] The present application provides a controllable porosity gangue cemented filling body preparation method based on a response surface method, which uses coal gangue (also known as gangue) as aggregate and a mixture of hot-activated coal gangue powder, slag powder and cement as cementing material.

[0008] The preparation method comprises the following steps:

[0009] Step 1, response surface experiment design:

[0010] Based on the response surface method, taking the average particle size of coal gangue aggregate, the cementitious material content and the cementitious material water solid ratio as independent variables, taking the filling body porosity and the 28d compressive strength as response values, a three-factor three-level response surface model is constructed by using the Box-Behnken design method;

[0011] Step 2, preparation of filling body:

[0012] The activator is added to the cementitious material, the alkali equivalent is adjusted to 6%, and then the coal gangue aggregate and water are added to prepare the filling body;

[0013] Step 3, performance test and model optimization: the mass-volume method is used to test the porosity of the filling body, and the pressure testing machine is used to test the 28-day uniaxial compressive strength; the test data is substituted into the response surface model, the mathematical relationship between the independent variables and the response values is fitted through multiple regression analysis, and the Design-Expert software is used to analyze the interaction of each factor, and the optimal preparation parameters meeting the target performance are obtained.

[0014] The present application uses coal gangue as the main raw material, and the cementitious material composed of hot activated coal gangue powder, slag powder and ordinary portland cement is matched, the activator is introduced for activation, and through the whole process technical route of "raw material precise pretreatment-Box-Behnken response surface experiment design-controllable preparation-multidimensional performance test-mathematical model optimization", the synergistic regulation of the porosity and mechanical properties of the filling body is realized.

[0015] Further, the hot activated coal gangue powder is obtained by calcining the coal gangue powder with a particle size of ≤200 mesh.

[0016] Further, the specific surface area of the slag powder is ≥440 m² / kg.

[0017] Further, the slag powder is obtained by ball milling the slag, and the coal gangue powder is obtained by ball milling the coal gangue.

[0018] Further, the coal gangue aggregate uses medium coal gangue with a particle size of 5-10 mm and coarse coal gangue with a particle size of 10-15 mm.

[0019] Further, the activator is water glass. More preferably, the modulus of the water glass is 1.4.

[0020] Further, the calcining temperature is 800℃.

[0021] The present application takes the average particle size of coal gangue aggregate, the cementitious material dosage, and the water-solid ratio of cementitious material as core influencing factors, constructs a response surface model of porosity and 28-day uniaxial compressive strength, and can quickly determine the optimal preparation parameters suitable for different engineering scenarios.

[0022] Further, the porosity calculation formula is as follows:

[0023] ;

[0024] Wherein, m1 is the total mass of coal gangue, m2 is the total mass of coal gangue cemented high-porosity filling body; ρ1 is the density of coal gangue; V0 is the volume of coal gangue; ρ2 is the density of rapid coagulation cementitious material;

[0025] The uniaxial compressive strength calculation formula is as follows:

[0026] ;

[0027] Wherein, A is the compression area of the test piece, and F is the pressure value.

[0028] Further, the cement is ordinary portland cement.

[0029] Further, the mass ratio of the hot-activated coal gangue powder, the slag powder and the cement is 56%:24%:20% in terms of mass percentage.

[0030] The present application realizes coal gangue resource utilization rate of more than 90%, and solves the problems of traditional filling technology, such as difficult porosity control, unstable mechanical properties, and low production efficiency, thereby providing key technical support for safe and efficient and ecological and environmental protection of mine filling mining.

[0031] The present application discloses the following technical effects:

[0032] The mathematical model established by the present application through the response surface method can accurately analyze the influence of factors such as the average particle size of coal gangue aggregate, the cementitious material dosage, and the water-solid ratio on the porosity of the filling body, so as to realize the control of the porosity and meet the special requirements of different engineering scenarios on the porosity structure of the filling body, such as preparing high-porosity filling body in goaf requiring good air permeability, and preparing low-porosity and high-strength filling body in areas requiring high rock control.

[0033] While controlling the porosity, the method of the present application can comprehensively consider the influence of various factors on the uniaxial compressive strength of the filling body, optimize the raw material ratio and the preparation process, improve the mechanical properties of the filling body, enhance the support capacity of the filling body to the overburden rock of the goaf, and ensure the safety of mine mining.

[0034] The coal gangue is largely used as a main raw material, realizes the resource utilization of coal mining waste, reduces the environmental pollution caused by the gangue accumulation, reduces the cost of the filling material, and has significant economic and environmental benefits.

[0035] The application can quickly determine the optimal preparation process parameters through the response surface experiment design and model optimization, reduces the large number of experiment times and time required by the traditional trial and error method, improves the research and development and production efficiency of the filling material, and is beneficial to the popularization and application of the technology in the actual engineering. BRIEF DESCRIPTION OF DRAWINGS

[0036] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the drawings needed to be used in the embodiments will be briefly introduced as follows. Obviously, the drawings in the following description only constitute some embodiments of the application, and other drawings can be obtained by those skilled in the art without any creative effort on the basis of these drawings.

[0037] Figure 1 is a preparation process schematic diagram of the controllable porosity filling body of the application;

[0038] Figure 2 is a response surface of the influence of the average particle size of the gangue aggregate and the cementitious material content on the porosity;

[0039] Figure 3 is a response surface of the influence of the average particle size of the gangue aggregate and the water-solid ratio of the cementitious material on the porosity;

[0040] Figure 4 is a response surface of the influence of the cementitious material content and the water-solid ratio of the cementitious material on the porosity;

[0041] Figure 5 is a normal probability distribution diagram of the porosity residual error;

[0042] Figure 6 is a response surface of the influence of the average particle size of the gangue aggregate and the cementitious material content on the 28d compressive strength;

[0043] Figure 7 is a response surface of the influence of the average particle size of the gangue aggregate and the water-solid ratio of the cementitious material on the 28d compressive strength;

[0044] Figure 8 is a response surface of the influence of the cementitious material content and the water-solid ratio of the cementitious material on the 28d compressive strength;

[0045] Figure 9 is a normal probability distribution diagram of the 28d compressive strength residual error. DETAILED DESCRIPTION

[0046] The detailed description set forth above discloses certain implementations of the application, but the application is not limited to these implementations that can be practiced in a variety of embodiments. It is to be understood that the foregoing description is that of certain embodiments of the application and that numerous changes in the details of implementations disclosed can be made without departing from the spirit of the application, and the scope of the application is defined by the appended claims.

[0047] It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. Additionally, the use of the terms "including", "comprising", "having" and variations thereof herein is only to specify the presence of stated features, steps, or components and does not preclude the presence or addition of one or more other features, steps, components, or groups thereof. Further, unless otherwise specified, all ranges of values and / or amounts are to be interpreted as being inclusive of the other.

[0048] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present application, the preferred methods and materials are described. All documents mentioned herein are incorporated by reference to disclose and describe the methods and / or materials in connection with which the documents are cited. In case of conflict, the present specification will control.

[0049] Various modifications and changes can be made to the specific embodiments of the application described herein without departing from the scope or spirit of the application. Other embodiments of the application will be apparent to those of ordinary skill in the art from the description and examples presented herein. The description and examples are illustrative of the application and are not intended to limit the scope of the application.

[0050] As used herein, the terms "comprise", "comprising", "include", "including", "have", "having" and variants thereof are open-ended, and include one or more of the recited elements.

[0051] It should be noted that the present application does not describe in detail the conventional operation means in the art, and is not the focus of the present application.

[0052] The present application provides a preparation method of a controllable porosity gangue cementitious filling body, preferably adopting the following steps:

[0053] S1: raw material preparation: the gangue is coarsely crushed, secondarily crushed and classified and screened to obtain fine gangue with a particle size of 0-5 mm, medium gangue with a particle size of 5-10 mm and coarse gangue with a particle size of 10-15 mm; the fine gangue is ball milled to a particle size of less than 200 mesh and high-temperature calcined to prepare hot activated coal gangue powder; the hot activated coal gangue powder accounts for 56% by mass, the slag powder accounts for 24% by mass and the ordinary Portland cement accounts for 20% by mass, mixed to form a cementitious material; a water glass with a modulus of 1.4 is prepared as an activator, and the alkali equivalent of the cementitious material is adjusted to 6%;

[0054] S2: Response surface experiment design: Taking the average particle size of gangue aggregate, the dosage of cementitious material, and the water-solid ratio of cementitious material as independent variables, and taking the porosity of filling body and the 28-day uniaxial compressive strength as response values, a three-factor three-level response surface model was constructed by using the Box-Behnken design method to generate 17 test schemes (including 5 center repeated tests);

[0055] S3: Preparation of filling body: According to the test scheme, the gangue aggregate, cementitious material, and water glass activator were mixed to form a uniform slurry; the slurry was loaded into a 100mm x 100mm x 100mm cubic mold in multiple times, and after each loading, the slurry was vibrated for 15-20s using a vibration table, and then the surface was scraped and placed in a standard curing room with a temperature of 20℃ and a relative humidity of ≥95% for curing to the specified age;

[0056] S4: Performance testing and model optimization: The mass-volume method was used to test the porosity of the filling body, and the pressure testing machine was used to test the 28-day uniaxial compressive strength; the test data was substituted into the response surface model, and the mathematical relationship between the independent variables and the response values was fitted by multiple regression analysis, and the Design-Expert software was used to analyze the interaction of each factor, and the optimal preparation parameters that meet the target performance were obtained.

[0057] Further, the slag powder needs to be ball milled to a specific surface area of 440m² / kg to ensure the activity of the auxiliary cementitious material; during the crushing process of the coal gangue, the particle size deviation needs to be controlled to be ≤0.5mm to ensure the stability of the aggregate gradation.

[0058] Further, in step S3, according to the test scheme, first, the gangue aggregate, cementitious material, and water glass activator are added to the mixer in sequence, dry mixing for 2-3min, then adding the calculated amount of water and wet mixing for 3-5min to form a uniform slurry;

[0059] Further, in step S3, the mixer needs to have a speed adjustment function, with a dry mixing speed of 300-400r / min and a wet mixing speed of 500-600r / min, to ensure the uniformity of the slurry mixing and the consistency of the filling body density.

[0060] In step 4, the porosity is calculated using the formula:

[0061] ;

[0062] Wherein, m1 is the total mass of the gangue in the mold, m2 is the total mass of the gangue cementitious high-porosity filling body; ρ1 is the density of the coal gangue; v0 is the internal volume of the mold; ρ2 is the density of the rapid-setting cementitious material;

[0063] Uniaxial compressive strength test: the uniaxial compressive strength test of the filling body test piece after curing is carried out using a pressure testing machine, the loading rate is controlled at 0.5-1.0 kN / s, and the maximum load F at the destruction of the test piece is recorded.

[0064] The uniaxial compressive strength is calculated by the formula:

[0065] ;

[0066] Wherein, A is the compression area of the test piece, and F is the pressure value.

[0067] The porosity and uniaxial compressive strength data obtained by the experiment are substituted into the response surface model, and the mathematical relationship between the response value and the independent variable is fitted by multiple regression analysis. The model is analyzed by using software such as Design-Expert, response surface graph and contour graph are drawn, and the influence law of each factor and its interaction on porosity and uniaxial compressive strength is analyzed. Through model optimization, the best raw material ratio and preparation process parameters meeting the requirements of target porosity and mechanical properties are determined.

[0068] The method can realize that the porosity of the filling body is 9%-27% adjustable, the uniaxial compressive strength at 28 days is 0.5-3.5 MPa controllable, and the filling demand under different geological conditions is adapted, when the average particle size of the gangue aggregate is 7.5 mm, the cementing material content is 22%, and the water-solid ratio is 0.5, the porosity of the filling body is 19.5%±0.5%, and the uniaxial compressive strength at 28 days is 2.4±0.1 MPa, which meets the safety and environmental protection requirements of conventional mine filling.

[0069] The application will be further described in detail in combination with examples as follows:

[0070] Example 1

[0071] The application provides a controllable porosity gangue cementing filling body preparation method based on a response surface method, and the steps are as follows:

[0072] (1) Material preparation:

[0073] a. Material processing and crushing: collect the gangue and slag of a coal mine in Shandong province, sort and clean to remove dust, stone and other impurities and dry, and use a jaw crusher to coarsely crush the coal gangue to a particle size of less than 50 mm, so as to facilitate subsequent processing. Then, a cone crusher is used to further crush the gangue, so that most of the particle sizes of the gangue are in the range of 5-15 mm, to prepare for subsequent screening.

[0074] b. Gangue screening: The crushed gangue is screened by a vibrating screen to divide it into three grades, i.e., coarse gangue with a particle size of 10-15 mm (average particle size of 12.5 mm), medium gangue with a particle size of 5-10 mm (average particle size of 7.5 mm), and fine gangue with a particle size of less than 5 mm (average particle size of 2.5 mm).

[0075] (2) Preparation of filling material

[0076] a. Preparation of hot-activated coal gangue powder: The fine gangue obtained by screening is subjected to superfine treatment by a ball mill, with a ball milling time of 4 h and a ball-to-material ratio of 8:1, to ensure a particle size of ≤200 mesh (particle size ≤74 μm). The superfined gangue powder is calcined at a high temperature of 800°C in a muffle furnace for 2 h to activate the active SiO2 and Al2O3 in the coal gangue by high temperature, thereby obtaining hot-activated coal gangue powder.

[0077] b. Treatment of slag powder: After the slag is dried to remove water, it is ground by a ball mill for 3 h to make the specific surface area of the slag powder reach 440 m2 / kg, so that it has sufficient activity and can play a cementing role in cooperation with other cementitious components.

[0078] c. Preparation of cementitious material: According to the mass ratio of 56% hot-activated coal gangue powder, 24% slag powder, and 20% ordinary Portland cement (P・O 42.5), the three materials are put into a planetary mixer to ensure uniform mixing and form a cementitious material.

[0079] d. Preparation of filling material: Water glass with a modulus of 1.4 is used as an activator and is added to the cementitious material of step c to adjust the alkali equivalent of the basic cementitious material to 6% for activating the activity of the auxiliary cementitious material. After uniform stirring, different particle size graded gangue aggregates are added, and water is added to prepare the filling body.

[0080] (3) Response surface experimental design

[0081] A three-factor and three-level response surface experiment is designed to measure the porosity and 28d compressive strength of each test group.

[0082] a. The response surface experiment with three factors and three levels is established, and the factor level table is shown in Table 1. The factor level table is as follows:

[0083] Table 1 Box-Behnken response surface design influencing factors and levels

[0084]

[0085] A total of 17 groups of tests (including 5 groups of center repeated tests) were conducted to study the effects of gangue aggregate average particle size, cementitious material content and water solid ratio on 28d compressive strength and porosity. The design combinations and corresponding results are shown in Table 2.

[0086] Table 2 Box-Behnken response surface test design scheme

[0087]

[0088] b. Regression equation fitting and variance analysis

[0089] The regression equation was established by fitting data of porosity (X) with gangue aggregate average particle size (A), cementitious material content (B) and cementitious material water solid ratio (C) as independent variables:

[0090]

[0091] The variance analysis is shown in Table 3. According to Table 3, the P value of the regression equation model is extremely significant, indicating that the model has good fitting degree and the experimental method is feasible. The P value of the loss fitting term is not significant, indicating that the model error is small. The larger the factor F value and the smaller the P value, the greater the influence of the factor on the result.

[0092] Table 3 Variance analysis results of porosity quadratic model

[0093]

[0094] Note: ** indicates extremely significant difference (P<0.001); * indicates significant difference (P<0.05).

[0095] The significance of the influence of each factor variable on the response value in the regression equation can be determined by F test. Among them, the gangue aggregate average particle size (A), the cementitious material content (B) and the cementitious material water solid ratio (C) have extremely significant influence on the model (P<0.0001), the quadratic term of the gangue aggregate average particle size (A) has extremely significant influence on the model (P<0.0001), and the quadratic term of the cementitious material water solid ratio (C) has significant influence on the model (P<0.05). The test result of the experimental regression model is P<0.0001, indicating that the model test result is at an extremely significant level and has statistical significance. According to the F value, the order of the influence of the three factors on the porosity is the gangue aggregate average particle size > the cementitious material water solid ratio > the cementitious material content.

[0096] The response surface experiment curve surface diagram is shown in Figures 2-4 , Figure 5 The normal probability distribution diagram of the porosity residual error is shown in

[0097] c. Regression equation fitting and variance analysis of 28d compressive strength

[0098] The regression equation of 28d compressive strength Y is established by data fitting with gangue aggregate average particle size (A), cementitious material dosage (B) and cementitious material water-solid ratio (C) as independent variables:

[0099]

[0100] The variance analysis is shown in Table 4.

[0101] Table 4 Variance analysis results of 28d compressive strength quadratic model

[0102]

[0103] Note: ** is extremely significant difference (P<0.001); * is significant difference (P<0.05).

[0104] The significance of the influence of each factor variable on the response value in the regression equation can be determined by F test, wherein the gangue aggregate average particle size (A) and the cementitious material water-solid ratio (C) have extremely significant influence on the model (P<0.001), the quadratic term of the cementitious material water-solid ratio (C) has extremely significant influence on the model (P<0.001), and the quadratic term of the cementitious material dosage (B) has significant influence on the model (P<0.05). The test result of the experimental regression model is P<0.0001, indicating that the model test result is at an extremely significant level and has statistical significance. According to the F value, the influence order of the three factors on the 28d compressive strength is the gangue aggregate average particle size > the cementitious material water-solid ratio > the cementitious material dosage.

[0105] The response surface experiment curve diagram is shown in Figures 6-8 , Figure 9 is the normal probability distribution diagram of 28d compressive strength residual error.

[0106] The above-described embodiments are only descriptions of the preferred modes of the present application, and do not limit the scope of the present application. Without departing from the design spirit of the present application, various modifications and improvements of the technical solutions of the present application made by those skilled in the art shall fall within the protection scope determined by the claims of the present application.

Claims

1. A controllable porosity gangue cemented filling body preparation method based on a response surface method, characterized by, Coal gangue is used as aggregate, and a mixture of hot-activated coal gangue powder, slag powder and cement is used as cementitious material; The preparation method comprises the following steps: Step 1, response surface experiment design: Based on the response surface method, the average particle size of coal gangue aggregate, the cementitious material dosage and the water-solid ratio of the cementitious material are used as independent variables, the porosity of the filling body and the 28d compressive strength are used as response values, and a three-factor three-level response surface model is constructed by using the Box-Behnken design method; Step 2, preparation of the filling body: An activator is added to the cementitious material, and then coal gangue aggregate and water are added to prepare the filling body; Step 3, performance test and model optimization: the porosity and 28-day uniaxial compressive strength of the filling body are tested; the test data are substituted into the response surface model, the mathematical relationship between the independent variables and the response values is fitted through multiple regression analysis, the interaction of each factor is analyzed by using Design-Expert software, and the optimal preparation parameters meeting the target performance are obtained.

2. The method for preparing controllable porosity gangue cemented filling body based on response surface method according to claim 1, characterized in that, The hot-activated coal gangue powder is obtained by calcining coal gangue powder with a particle size of ≤200 mesh.

3. The method for preparing controllable porosity gangue cemented filling body based on response surface method according to claim 1, characterized in that, The specific surface area of the slag powder is ≥440 m² / kg.

4. The method for preparing controllable porosity gangue cemented filling body based on response surface method according to claim 2, characterized in that, The slag powder is obtained by ball milling of slag, and the coal gangue powder is obtained by ball milling of coal gangue.

5. The method for preparing controllable porosity gangue cemented filling body based on response surface method according to claim 1, characterized in that, The coal gangue aggregate uses medium coal gangue with a particle size of 5-10 mm and coarse coal gangue with a particle size of 10-15 mm.

6. The method for preparing controllable porosity gangue cemented filling body based on response surface method according to claim 1, characterized in that, The activator is water glass; the water glass is added to adjust the alkali equivalent of the system to 6%.

7. The method for preparing controllable porosity gangue cemented filling body based on response surface method according to claim 2, characterized in that, The calcination temperature is 800℃.

8. The method for preparing controllable porosity gangue cemented filling body based on response surface method according to claim 1, characterized in that, The porosity calculation formula is as follows: ； Wherein, m1 is the total mass of coal gangue, m2 is the total mass of coal gangue cemented high-porosity filling body; ρ1 is the density of coal gangue; V0 is the volume of coal gangue; ρ2 is the density of fast-setting cementitious material; The uniaxial compressive strength calculation formula is as follows: ； Wherein, A is the compression area of the test piece, and F is the pressure value.

9. The method for preparing controllable porosity gangue cemented filling body based on response surface method according to claim 1, characterized in that, The cement is ordinary Portland cement.

10. The method for preparing controllable porosity gangue cemented filling body based on response surface method according to claim 1, characterized in that, The mass ratio of the hot-activated coal gangue powder, the slag powder and the cement is 56%:24%:20% by mass percentage.

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