Method for analyzing oxidation-hydrolysis characteristics of sulfide minerals under different oxygen concentrations and application of method in stability evaluation of high-speed rail roadbed

Abstract

The invention belongs to the technical field of geotechnical engineering and geochemistry, and particularly discloses a method for analyzing oxidation-hydrolysis characteristics of sulfide minerals under different oxygen concentrations and application of the method in high-speed rail roadbed stability evaluation. The method comprises the following steps: firstly, carrying out mineral component analysis on sulfide minerals to determine the pyrite content and other mineral compositions; then, the sulfide minerals are placed in water-containing environments with different oxygen concentrations to be subjected to a simulation test, water is sampled at different time points, the ion concentration, the pH value, the conductivity and the mineral surface appearance and components in a sample are measured, and the oxidation-hydrolysis characteristics of the sulfide minerals under different oxygen concentrations are obtained. The problem that there is no system research for reaction characteristics in different oxygen concentration environments at present and the problem that it is difficult to accurately evaluate the influence of oxygen concentration on the stability of a rock-soil body are solved.

Description

Technical Field

[0001] The invention relates to the technical field of geotechnical engineering and geochemistry, and in particular to a method for analyzing oxidation-hydrolysis characteristics of sulfide minerals under different oxygen concentrations and an application thereof in evaluating the stability of high-speed railway subgrades. Background Art

[0002] In high-speed railway subgrade projects, sulfide minerals (such as pyrite) in fillers and parent rocks undergo oxidation-hydrolysis reactions during weathering to generate acidic substances (such as sulfuric acid) and soluble ions (such as Fe 2+ 、SO4 2 -), leading to reduced rock and soil strength, foundation settlement, environmental pollution and other problems. In the prior art, the research on oxidation-hydrolysis of sulfide minerals is mostly focused on the condition of a single oxygen concentration, and there is a lack of systematic research on the reaction characteristics under different oxygen concentration environments.

[0003] In addition, it is difficult for existing methods to accurately evaluate the impact of oxygen concentration on rock and soil stability, resulting in a lack of pertinence in engineering design and reinforcement measures. Therefore, how to provide a method for analyzing the oxidation-hydrolysis characteristics of sulfide minerals under different oxygen concentrations and its application in the assessment of high-speed railway subgrade stability, improve the systematic research on the reaction characteristics of sulfide minerals under different oxygen concentration environments, and construct a high-speed railway subgrade stability assessment method are the problems that need to be solved in this field. Summary of the invention

[0004] In view of this, the present invention provides a method for analyzing the oxidation-hydrolysis characteristics of sulfide minerals under different oxygen concentrations and its application in the stability assessment of high-speed railway subgrades, so as to solve the problem that there is no systematic study on the reaction characteristics under different oxygen concentration environments and it is difficult to accurately assess the impact of oxygen concentration on the stability of rock and soil.

[0005] In order to achieve the above object, the present invention adopts the following technical solution:

[0006] A method for analyzing oxidation-hydrolysis characteristics of sulfide minerals under different oxygen concentrations comprises the following steps:

[0007] 1) Conduct mineral composition analysis on sulfide minerals to determine the pyrite content and other mineral compositions;

[0008] 2) Place sulfide minerals in water-containing environments with different oxygen concentrations for simulation tests, sample water at different time points, measure the ion concentration, pH value, conductivity, and mineral surface morphology and composition in the samples, and obtain the oxidation-hydrolysis characteristics of sulfide minerals under different oxygen concentrations;

[0009] The ion concentration includes sulfate ion concentration;

[0010] The different oxygen concentrations include a low oxygen concentration environment, a medium oxygen concentration environment, and a high oxygen concentration environment;

[0011] The low oxygen concentration environment is as follows: Immerse the sulfide minerals in water, and then adjust the oxygen concentration in the water to 0 - 1 mg / L;

[0012] The medium oxygen concentration environment is as follows: Immerse the sulfide minerals in water, and then adjust the oxygen concentration in the water to 8 - 10 mg / L;

[0013] The high oxygen concentration environment is as follows: Partially immerse the sulfide minerals in water and partially expose them to the air, and then adjust the oxygen concentration in the water to 8 - 10 mg / L.

[0014] Preferably, the particle size of the sulfide minerals in step 2) is 2 - 5 mm.

[0015] Preferably, the environmental temperature of the simulation test in step 2) is 25°C and the humidity is 60%.

[0016] Another object of the present invention is to provide an application of the above - mentioned analysis method in the evaluation of the stability of high - speed railway subgrades, including the following steps:

[0017] S1: Obtain the oxidation rate based on the sulfate ion concentration obtained from the test;

[0018] S2: Calculate the chemical damage factor according to the oxidation rate;

[0019] S3: Calculate the elastic modulus, compressive strength, and swelling strain according to the chemical damage factor;

[0020] S4: Calculate the subgrade deformation amount according to the elastic modulus and swelling strain;

[0021] S5: Calculate the subgrade safety factor according to the subgrade deformation amount and compressive strength;

[0022] When the subgrade safety factor ≥ 1.3, it is judged that the subgrade is stable; when 1 ≤ subgrade safety factor < 1.3, it is judged that the subgrade needs to be reinforced; when the subgrade safety factor < 1, it is judged that the subgrade is unstable;

[0023] The calculation formula for the oxidation rate is: R = k×C×S;

[0024] Wherein, R is the oxidation rate, k is the reaction rate constant, C is the effective oxygen concentration, and S is the initial specific surface area of the sulfide minerals;

[0025] The calculation formula for the chemical damage factor is: D = α×R×t;

[0026] Wherein, D is the chemical damage factor; α is the material sensitivity coefficient; t is the oxidation time, and the unit of t is days;

[0027] The calculation formula for the elastic modulus is: E = E0×(1 - D);

[0028] where E is the elastic modulus, E0 is the initial elastic modulus of the sulfide mineral, and D is the chemical damage factor;

[0029] The calculation formula for the compressive strength is: σ = σ0×(1 - 0.8D);

[0030] where σ is the compressive strength, σ0 is the initial compressive strength of the sulfide mineral, and D is the chemical damage factor;

[0031] The calculation formula for the swelling strain is: p = 0.1×D;

[0032] where p is the swelling strain and D is the chemical damage factor;

[0033] The calculation formula for the subgrade deformation amount is: Δh = h0×(p - q / E×D);

[0034] where Δh is the subgrade deformation amount, h0 is the thickness of the subgrade filling layer, p is the swelling strain, q is the subgrade load, E is the elastic modulus, and D is the chemical damage factor;

[0035] The calculation formula for the subgrade safety factor is:

[0036] where F s is the subgrade safety factor, σ is the compressive strength, γ is the bulk density of the filler, h0 is the thickness of the subgrade filling layer, angle of internal friction.

[0037] Preferably, the high - speed railway subgrade includes sulfide minerals.

[0038] Preferably, when the high - speed railway subgrade is in deep geotechnical body or closed environment, the test in step S1 is carried out in a low oxygen - concentration environment;

[0039] When the high - speed railway subgrade is in groundwater immersion environment, the test in step S1 is carried out in a medium oxygen - concentration environment;

[0040] When the high - speed railway subgrade is in surface or near - surface open environment, the test in step S1 is carried out in a high oxygen - concentration environment.

[0041] Through the above - mentioned technical solutions, compared with the prior art, the present invention has the following beneficial effects:

[0042] Through precise control of oxygen concentration, establishment of a quantitative oxidation kinetics model, and multi-scale data linkage analysis, seamless connection from the laboratory to the engineering site is achieved, key problems such as single environmental simulation, low data reliability, and weak engineering guidance in traditional methods are solved, and a scientific, efficient, and low-cost technical solution is provided for the long-term stability evaluation and disease prevention of high-speed railway subgrades.

[0043] Systematically simulate different oxygen environments to cover actual engineering scenarios. Through three working conditions of low oxygen, medium oxygen, and high oxygen, accurately simulate the oxidation environments at different depths and positions of high-speed railway subgrades. Different oxygen concentration conditions are directly related to actual engineering parameters such as subgrade filling height and groundwater level change, providing a basis for targeted design. Through multi-index linkage analysis of microscopic indexes such as scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) and macroscopic indexes such as ion concentration, pH value, and conductivity, the comprehensive action mechanism of micro-macro can be systematically revealed from multiple scales. Establish a simple and practical quantitative oxidation kinetics model to directly guide engineering decisions, making engineering applications efficient, accurate, and cost controllable. Brief Description of the Drawings

[0044] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained according to the provided drawings.

[0045] Figure 1 Schematic diagram of the setting of different oxygen concentration environments in Embodiment 1 of the present invention;

[0046] Figure 2 For SO4 in high, medium, and low oxygen concentration environments in Embodiment 1 of the present invention 2- 、Ca 2+ Concentration change curves over time;

[0047] Figure 3 Solution pH value and pH value change rate at different times in high, medium, and low oxygen concentration environments in Embodiment 1 of the present invention;

[0048] Figure 4 Conductivity change curves over time in high, medium, and low oxygen concentration environments in Embodiment 1 of the present invention;

[0049] Figure 5 Mineral surface morphology of the sample after 52 days of reaction in the high oxygen concentration environment in Embodiment 1 of the present invention. Detailed Embodiments

[0050] The present invention provides a method for analyzing the oxidation-hydrolysis characteristics of sulfide minerals under different oxygen concentrations, comprising the following steps:

[0051] 1) Analyze the mineral composition of the sulfide minerals to determine the content of pyrite and other mineral compositions;

[0052] 2) Place the sulfide minerals in an aqueous environment with different oxygen concentrations for simulation tests, sample the water at different time points, and measure the ion concentration, pH value, conductivity, and mineral surface morphology and composition in the samples to obtain the oxidation-hydrolysis characteristics of the sulfide minerals under different oxygen concentrations.

[0053] In the present invention, the sulfide minerals include high-speed railway subgrade fillers and / or parent rock samples.

[0054] In the present invention, the ion concentration includes sulfate ion concentration and calcium ion concentration.

[0055] In the present invention, the significance of determining the content of pyrite and other mineral compositions is as follows: If there are carbonate minerals in the sulfide minerals, the carbonate minerals will dissolve in the acidic environment generated after the oxidation-hydrolysis reaction of pyrite, exposing the encapsulated pyrite further, increasing the specific surface area of pyrite, and promoting the occurrence of the oxidation-hydrolysis reaction of pyrite. Exclude the existence of clay minerals, as clay minerals will expand when exposed to water, affecting the judgment of the deformation of the high-speed railway subgrade in engineering applications.

[0056] In the present invention, the different oxygen concentrations include a low oxygen concentration environment, a medium oxygen concentration environment, and a high oxygen concentration environment;

[0057] The low oxygen concentration environment is: Immerse the sulfide minerals in water, and then adjust the oxygen concentration in the water to 0 - 1 mg / L, specifically it can be 0.1 mg / L, 0.2 mg / L, 0.4 mg / L, 0.5 mg / L, 0.6 mg / L, 0.8 mg / L;

[0058] The medium oxygen concentration environment is: Immerse the sulfide minerals in water, and then adjust the oxygen concentration in the water to 8 - 10 mg / L, specifically it can be 8 mg / L, 8.2 mg / L, 8.5 mg / L, 8.8 mg / L, 9 mg / L, 9.2 mg / L, 9.5 mg / L, 9.8 mg / L, 10 mg / L;

[0059] The high-oxygen-concentration environment is as follows: partially immerse sulfide minerals in water and partially expose them to air, and then adjust the oxygen concentration in the water to 8-10 mg / L, specifically, it can be 8 mg / L, 8.2 mg / L, 8.5 mg / L, 8.8 mg / L, 9 mg / L, 9.2 mg / L, 9.5 mg / L, 9.8 mg / L, 10 mg / L; the volume concentration of oxygen in the air is 20.95% (298.5 mg / L).

[0060] In the present invention, the volume ratio of the immersed part to the exposed part of the sulfide minerals is 1-2:1, preferably 1.2-1.8:1, further preferably 1.4-1.6:1, and still further preferably 1.5:1.

[0061] In the present invention, the particle size of the sulfide minerals in step 2) is 2-5 mm, specifically, it can be 2 mm, 2.5 mm, 3 mm, 3.5 mm, 4 mm, 4.5 mm, 5 mm.

[0062] In the present invention, the environmental temperature of the simulation test in step 2) is 25 °C and the humidity is 60%.

[0063] The present invention also provides an application of the above analysis method in the evaluation of the stability of high-speed railway subgrades, including the following steps:

[0064] S1: Obtain the oxidation rate based on the sulfate ion concentration obtained by testing;

[0065] S2: Calculate the chemical damage factor according to the oxidation rate;

[0066] S3: Calculate the elastic modulus, compressive strength and swelling strain according to the chemical damage factor;

[0067] S4: Calculate the subgrade deformation amount according to the elastic modulus and swelling strain;

[0068] S5: Calculate the subgrade safety factor according to the subgrade deformation amount and compressive strength;

[0069] When the subgrade safety factor ≥ 1.3, it is judged that the subgrade is stable; when 1 ≤ subgrade safety factor < 1.3, it is judged that the subgrade needs to be reinforced; when the subgrade safety factor < 1, it is judged that the subgrade is unstable.

[0070] In the present invention, the reinforcement measures include reinforcement measures such as isolation, drainage, grouting, etc., and passivation treatment of high-speed railway subgrade fillers and parent rocks using modified materials (such as phosphates, lignin, acetylacetone) to inhibit the further occurrence of sulfide mineral oxidation-hydrolysis reactions.

[0071] In the present invention, the calculation formula for the oxidation rate is: R = k × C × S;

[0072] Wherein, R is the oxidation rate (mmol / (kg·day)), k is the reaction rate constant, C is the effective oxygen concentration (mg / L), and S is the initial specific surface area of the sulfide mineral (m 2 / g).

[0073] In the present invention, the reaction rate constant is obtained by non-linear fitting of the test result data of the sulfate ion concentration. The reaction curve is divided into an initial acceleration stage, a middle deceleration stage, and a later stable stage. The reaction rate constant k is the curve slope of the later stable stage of the fitting curve.

[0074] In the present invention, when testing in a low / medium oxygen concentration environment, the effective oxygen concentration is the oxygen concentration in water; when testing in a high oxygen concentration environment, the calculation formula for the effective oxygen concentration is: C = (V 空气 / V 水 ) × C 空气 + (1 - V 空气 / V 水 ) × C 水 ; where V 空气 is the volume of the exposed part of the sulfide mineral, V 水 is the volume of the immersed part of the sulfide mineral; C 空气 is the oxygen concentration in the air; C 水 is the oxygen concentration in water.

[0075] In the present invention, the calculation formula for the chemical damage factor is: D = α × R × t;

[0076] where, D is the chemical damage factor; α is the material sensitivity coefficient; t is the oxidation time, and the unit of t is days.

[0077] In the present invention, the material sensitivity coefficient is obtained by calibrating the sample through indoor mechanical tests (in accordance with GB / T 50123-2019 "Standard for Geotechnical Test Methods").

[0078] In the present invention, the calculation formula for the elastic modulus is: E = E0 × (1 - D);

[0079] where, E is the elastic modulus (kPa), E0 is the initial elastic modulus of the sulfide mineral (kPa), and D is the chemical damage factor.

[0080] In the present invention, the calculation formula for the compressive strength is: σ = σ0 × (1 - 0.8D);

[0081] where, σ is the compressive strength, σ0 is the initial compressive strength of the sulfide mineral, and D is the chemical damage factor.

[0082] In the present invention, the calculation formula for the expansion strain is: p = 0.1 × D;

[0083] Among them, p is the swelling strain and D is the chemical damage factor.

[0084] In the present invention, the calculation formula for the subgrade deformation amount is: Δh = h0×(p - q / E×D);

[0085] Among them, Δh is the subgrade deformation amount (m), h0 is the thickness of the subgrade filling layer (m), p is the swelling strain, q is the subgrade load (kPa), E is the elastic modulus (kPa), and D is the chemical damage factor.

[0086] In the present invention, the calculation formula for the subgrade safety factor is:

[0087] Among them, F s is the subgrade safety factor, σ is the compressive strength (kPa), γ is the bulk density of the filler (kN / m 3 ), h0 is the thickness of the subgrade filling layer (m), the internal friction angle (°).

[0088] In the present invention, the high-speed railway subgrade includes sulfide minerals.

[0089] In the present invention, when the high-speed railway subgrade is in deep geotechnical bodies or a closed environment, the test in step S1 is carried out in an environment with a low oxygen concentration.

[0090] In the present invention, when the high-speed railway subgrade is in an environment of groundwater immersion, the test in step S1 is carried out in an environment with a medium oxygen concentration.

[0091] In the present invention, when the high-speed railway subgrade is in a surface or near-surface open environment, the test in step S1 is carried out in an environment with a high oxygen concentration.

[0092] Next, the technical solutions in the embodiments of the present invention will be described clearly and completely. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without making creative efforts shall fall within the protection scope of the present invention.

[0093] Example 1

[0094] 1. Sample preparation and test method:

[0095] (1) Sample selection and preparation:

[0096] Select sulfide minerals (high-speed railway subgrade filler sample L-1), and screen granular samples with a particle size of 2 - 5 mm to ensure that the samples have a consistent specific surface area and reactivity.

[0097] Mineral composition analysis (X-ray diffraction analysis, XRD) was carried out on the samples to determine the pyrite content and other mineral compositions. Quartz 34.76%, illite 19.55%, chlorite 5.78%, calcite 16.9%, dolomite 10.77%, microcline 3.22%, albite 5.52%, pyrite 1.25%, gypsum 2.25%. It was determined that pyrite was present, and the contents of carbonate minerals calcite and dolomite were relatively high, which promoted the continuous and sufficient progress of the reaction, and the influence of expansive clay minerals (montmorillonite) on the results was excluded.

[0098] (2) Test condition control:

[0099] In a constant temperature and humidity laboratory, the test environment temperature was controlled at 25 °C and the humidity was 60% to maintain the consistency of environmental conditions, avoid relative errors between different groups of tests caused by environmental conditions, and at the same time, the environmental conditions were set to simulate actual engineering conditions.

[0100] Three oxygen concentration environments, namely low oxygen concentration environment, medium oxygen concentration environment and high oxygen concentration environment, were set respectively to conduct sulfide mineral oxidation-hydrolysis tests. Three parallel tests were set under each oxygen concentration environment to ensure the reliability and repeatability of the data.

[0101] (3) Oxygen concentration environment setting:

[0102] Low oxygen concentration environment: An equal amount of test sample (100 g) was placed in a beaker, a constant amount of deionized water (300 mL) was added, the sample was completely immersed in the deionized water, the beaker was placed in a vacuum bucket, and a vacuum environment was formed in the vacuum bucket using a vacuum pump for the test. The oxygen concentration was 0.6 mg / L, simulating the oxidation-hydrolysis conditions in deep geotechnical bodies or closed environments.

[0103] Medium oxygen concentration environment: An equal amount of test sample (100 g) was placed in a beaker, a constant amount of deionized water (300 mL) was added, the sample was completely immersed in the deionized water, and the beaker was placed on the operating table in a constant temperature and humidity laboratory for the test. The oxygen was provided by dissolved oxygen in the water (dissolved oxygen concentration was 9.5 mg / L), simulating the oxidation-hydrolysis conditions under groundwater saturation conditions.

[0104] High oxygen concentration environment: Place an equal amount of test samples (100 g) in a porous cylindrical glass cylinder. The diameter of the porous glass cylinder is 1 / 4 of that of the beaker, and the diameter of the small holes on the porous glass cylinder should be less than 1 / 3 of the minimum particle size of the sample. Then place the porous glass cylinder containing the sample in the center of the beaker, add a constant amount of deionized water (300 mL) to the beaker, partially immerse the sample in the porous glass cylinder in the deionized water, and partially expose it to the air. Place the beaker on the operating table in a constant temperature and humidity laboratory for testing. The exposed part is directly in contact with the oxygen in the air, and the immersed part reacts with the sample through the diffusion of dissolved oxygen. The oxygen concentration of the exposed part is 298.5 mg / L (standard atmospheric conditions), and the dissolved oxygen concentration in the water is 9.5 mg / L, simulating the oxidation-hydrolysis conditions in the surface or near-surface open environment. The schematic diagram of different oxygen concentration environment settings is as shown in Figure 1 shown.

[0105] (4) Monitoring of the reaction process:

[0106] Sampling is carried out at different time points (5 hours, 11 hours, 26 hours, 51 hours, 76 hours, 101 hours, 125 hours, 150 hours, 176 hours, 200 hours, 227 hours, 246 hours, 13 days, 16 days, 23 days, 26 days, 29 days, 32 days, 35 days, 38 days, 42 days, 47 days, 52 days) to measure indicators such as the ion concentration, pH value, and conductivity of the solution. The sampling interval is more intensive during the early stage of the chemical reaction when it is intense.

[0107] Use a syringe to make a sampler, and install a filter with a pore size of 0.45 μm at the front end of the syringe to eliminate the influence of suspended particles, ensure the purity of the sampled solution, and at the same time avoid damage to subsequent testing instruments (such as ion chromatographs, etc.) caused by impurities in the solution.

[0108] 2. Testing and data analysis:

[0109] Select the anion and cation concentrations in the solution, the pH value of the solution, the conductivity of the solution, the surface morphology and composition indicators of the sample minerals for the analysis of the results of the sulfide mineral oxidation-hydrolysis test, reveal the characteristics of the hydrolysis-oxidation multi-stage reaction of sulfide minerals and the generation, diffusion, and accumulation laws of key ions, systematically study the regulation effect of oxygen concentration conditions on the reaction rate and erosion effect, and analyze the microscopic structural damage of the filler and parent rock induced by the erosion of sulfide minerals and the cumulative macroscopic expansion effect.

[0110] (1) Determination of ion concentration:

[0111] Use an ion chromatograph (Anhui Wanyi IC6210 type) to measure anions (such as SO4 2- , Cl - ) and cations (such as Fe 2+ , Ca2+ , Mg 2+ concentration.

[0112] By diluting the sample (400-fold dilution) and plotting a standard curve, the measurement accuracy is ensured. The curves of the concentrations of SO4 2- , Ca 2+ varying with time under high (H), medium (M), and low (L) oxygen concentration environments are as Figure 2 shown. By Figure 2 it can be seen that the concentrations of SO4 2- , Ca 2 + show the same change trend, increasing rapidly in the early stage of the reaction, gradually slowing down in the middle stage of the reaction, and tending to be stable in the late stage of the reaction.

[0113] (2) pH value measurement:

[0114] Use a precision pH meter (Mettler-Toledo FE-28 type) to measure the pH value of the solution and evaluate the generation of acidic substances during the reaction.

[0115] Before each measurement, calibrate the pH meter using standard buffer solutions (pH 4.0, 7.0, 10.0).

[0116] The pH values and the change rates of the pH values of the solution at 5 h, 51 h, 312 h, 696 h, and 1128 h under high (H), medium (M), and low (L) oxygen concentration environments are as Figure 3 shown. By Figure 3 it can be seen that under the three oxygen concentration conditions, the pH value shows a downward trend with time. Especially under high oxygen concentration, the pH drops most significantly. The change rate of the pH value is relatively large in the initial stage of the reaction and then tends to be stable.

[0117] (3) Conductivity measurement:

[0118] Use a conductivity meter (Leici DDS-11A type) to measure the conductivity of the solution and analyze the quantity and types of mobile ions in the solution.

[0119] Eliminate the influence of temperature on the conductivity measurement through the manual temperature compensation function.

[0120] The curves of the conductivity varying with time under high (H), medium (M), and low (L) oxygen concentration environments are as Figure 4 shown. By Figure 4 it can be seen that under the three oxygen concentration conditions, the conductivity increases rapidly in the early stage of the reaction, gradually slows down in the middle stage of the reaction, and tends to be stable in the late stage of the reaction.

[0121] (4) Mineral surface morphology and composition analysis:

[0122] The surface morphology changes of minerals before and after the reaction were observed using a scanning electron microscope (SEM) and energy-dispersive spectroscopy (EDS), and the composition of the oxidation products was analyzed. After 52 days of reaction of the samples under a high oxygen concentration, the surface morphology and composition of the sample minerals were as shown in Figure 5 which showed that many microcracks and micropores were generated due to the dissolution of chemical reactions between the sample mineral particles.

[0123] X-ray photoelectron spectroscopy (XPS) was used to analyze the changes in the chemical states of the mineral surface, revealing the microscopic mechanism of the oxidation-hydrolysis reaction. The characteristics of the multi-stage oxidation-hydrolysis reaction of sulfide minerals and the generation, diffusion, and accumulation laws of key ions were revealed, systematically reflecting the regulatory effects of different oxygen concentration environmental conditions on the reaction rate and erosion effect.

[0124] Example 2

[0125] Subgrade fillers for high-speed railway lines were selected. The particle size of the filler sample was 2.5 mm, the subgrade filling thickness h0 = 3 m, and the groundwater level was high in the subgrade section, corresponding to an environment with a medium oxygen concentration.

[0126] S1: Calculation of the oxidation rate R:

[0127] XRD analysis showed that the pyrite content in the sample was 1.2%, and the specific surface area S = 1.2 mm 2 / g. The effective oxygen concentration C = 8.5 mg / L and the reaction rate constant k = 0.0025 were obtained through testing.

[0128] The oxidation rate R = k × C × S = 0.0025 × 8.5 × 1.2 = 0.0255 mmol / (kg·day) was calculated.

[0129] S2: Calculation of the chemical damage factor D:

[0130] The material sensitivity coefficient α = 0.06 was calibrated through indoor mechanical tests, and the oxidation time t = 1 year = 365 days.

[0131] The chemical damage factor D = α × R × t = 0.06 × 0.0255 × 365 = 0.558.

[0132] S3: The elastic modulus E, compressive strength σ, and swelling strain p were calculated based on the chemical damage factor:

[0133] The initial elastic modulus E0 of the sulfide mineral was 120000 kPa, and the initial compressive strength σ0 was 800 kPa.

[0134] The elastic modulus E = E0 × (1 - D) = 120000 × (1 - 0.558) = 53040 kPa;

[0135] The compressive strength σ = σ0×(1 - 0.8D) = 800×(1 - 0.8×0.558) = 443 kPa;

[0136] The swelling strain p = 0.1×D = 0.1×0.558 = 0.0558

[0137] S4: Calculate the subgrade deformation Δh based on the elastic modulus and swelling strain:

[0138] The subgrade load q = 150 kPa.

[0139] The subgrade deformation Δh = h0×(p - q / E×D) = 3×(0.0558 - 150 / 53040×0.558) = 0.16 m, that is, when the sulfide minerals are completely oxidized - hydrolyzed, the subgrade produces an expansion deformation of 160 mm.

[0140] S5: Calculate the subgrade safety factor F based on the subgrade deformation and compressive strength s :

[0141] The bulk density of the filler γ = 20 kN / m 3 , the internal friction angle

[0142] The subgrade safety factor

[0143] At this time, the subgrade safety factor F s = 12.8 ≥ 1.3, it is judged that the subgrade is stable.

[0144] In this specification, each embodiment is described in a progressive manner. Each embodiment focuses on the differences from other embodiments. For the same and similar parts between each embodiment, reference can be made to each other.

[0145] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art. The general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for analyzing the oxidation-hydrolysis characteristics of sulfide minerals under different oxygen concentrations, characterized in that, It includes the following steps: 1) Analyze the mineral composition of sulfide minerals to determine the pyrite content and other mineral compositions; 2) Place the sulfide minerals in an aqueous environment with different oxygen concentrations for simulation tests, sample the water at different time points, and measure the ion concentration, pH value, conductivity, and mineral surface morphology and composition in the samples to obtain the oxidation-hydrolysis characteristics of the sulfide minerals under different oxygen concentrations; The ion concentration includes the sulfate ion concentration; The different oxygen concentrations include a low oxygen concentration environment, a medium oxygen concentration environment, and a high oxygen concentration environment; The low oxygen concentration environment is: Immerse the sulfide minerals in water, and then adjust the oxygen concentration in the water to 0 - 1 mg / L; The medium oxygen concentration environment is: Immerse the sulfide minerals in water, and then adjust the oxygen concentration in the water to 8 - 10 mg / L; The high oxygen concentration environment is: Partially immerse the sulfide minerals in water and partially expose them to the air, and then adjust the oxygen concentration in the water to 8 - 10 mg / L.

2. The method for analyzing the oxidation-hydrolysis characteristics of sulfide minerals under different oxygen concentrations according to claim 1, wherein In step 2), the particle size of the sulfide minerals is 2 - 5 mm.

3. The method for analyzing the oxidation-hydrolysis characteristics of sulfide minerals at different oxygen concentrations according to claim 2, wherein In step 2), the environmental temperature of the simulation test is 25 °C and the humidity is 60%.

4. Use of the analysis method according to any one of claims 1 to 3 in the assessment of the stability of high-speed railway subgrades, characterized in that, It includes the following steps: S1: Obtain the oxidation rate based on the measured sulfate ion concentration; S2: Calculate the chemical damage factor according to the oxidation rate; S3: Calculate the elastic modulus, compressive strength, and swelling strain according to the chemical damage factor; S4: Calculate the subgrade deformation amount according to the elastic modulus and swelling strain; S5: Calculate the subgrade safety factor according to the subgrade deformation amount and compressive strength; When the subgrade safety factor ≥ 1.3, it is judged that the subgrade is stable; when 1 ≤ subgrade safety factor < 1.3, it is judged that the subgrade needs to be reinforced; when the subgrade safety factor < 1, it is judged that the subgrade is unstable; The calculation formula for the oxidation rate is: R = k × C × S; Where, R is the oxidation rate, k is the reaction rate constant, C is the effective oxygen concentration, and S is the initial specific surface area of the sulfide minerals; The calculation formula for the chemical damage factor is: D = α × R × t; Where, D is the chemical damage factor; α is the material sensitivity coefficient; t is the oxidation time, and the unit of t is days; The calculation formula for the elastic modulus is: E = E0 × (1 - D); Where, E is the elastic modulus, E0 is the initial elastic modulus of the sulfide minerals, and D is the chemical damage factor; The calculation formula for the compressive strength is: σ = σ0 × (1 - 0.8D); Where, σ is the compressive strength, σ0 is the initial compressive strength of the sulfide minerals, and D is the chemical damage factor; The calculation formula for the swelling strain is: p = 0.1 × D; Where, p is the swelling strain and D is the chemical damage factor; The calculation formula for the subgrade deformation amount is: Δh = h0 × (p - q / E × D); Where, Δh is the subgrade deformation amount, h0 is the thickness of the subgrade filling layer, p is the swelling strain, q is the subgrade load, E is the elastic modulus, and D is the chemical damage factor; The calculation formula for the subgrade safety factor is as follows: Among them, F s is the subgrade safety factor, σ is the compressive strength, γ is the unit weight of the filling material, h0 is the thickness of the subgrade filling layer, and φ is the internal friction angle.

5. The application of the analysis method according to claim 4 in the assessment of high-speed railway subgrade stability, characterized in that, The high-speed railway subgrade includes sulfide minerals.

6. Use of the analysis method according to claim 5 in the assessment of high-speed railway subgrade stability, characterized in that, When the high-speed railway subgrade is in deep geotechnical bodies or a closed environment, the test in step S1 uses a low oxygen concentration environment; When the high-speed railway subgrade is in an environment soaked by groundwater, the test in step S1 is carried out in an environment with a medium oxygen concentration; When the high-speed railway subgrade is in a surface or near-surface open environment, the test in step S1 is carried out in an environment with a high oxygen concentration.

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