Method for blocking migration of soil petroleum pollutants based on source head temperature compensation

Abstract

The present application is suitable for the field of oil-contaminated soil treatment technology, and provides a viscosity-temperature compensation method based on source blocking of migration of oil pollutants in soil, which comprises extracting oil from soil and determining asphaltene content, adjusting water content parameter of contaminated soil, adding a first modifier epoxy acrylate (AESO) and stirring uniformly, adding a second modifier polymethyl acrylate (T602HB) and stirring uniformly, continuously adding lime and fly ash and stirring uniformly, compacting and curing, and conducting wide-temperature-range simulated rainfall test. Through the method of hierarchical and staged synergistic solidification, on the one hand, the first modifier AESO and the second modifier T602HB are added hierarchically according to asphaltene content to construct a composite active interface of "increasing viscosity and reducing viscosity in parallel", and the adsorption effect between soil particles and oil is enhanced; on the other hand, the modifiers are added in stages with lime and fly ash, so as to solve the phenomenon of competitive adsorption of composite modifiers and prevent the compatibility problem of organic-inorganic materials.

Description

Technical Field

[0001] This invention relates to the field of oil-contaminated soil remediation technology, and more specifically, to a viscosity-temperature compensation method based on blocking the migration of oil pollutants in soil at the source. Background Technology

[0002] The viscosity-temperature properties of petroleum influence the adsorption performance between the medium and petroleum, and are key to inducing the dynamic evolution of petroleum pollutants in soil. Petroleum mainly consists of oil, gum, asphaltenes, and carbonaceous matter. Asphaltenes, as an important polar macromolecular component of petroleum, have a decisive influence on the temperature sensitivity of petroleum due to their content and structure. At high temperatures, asphaltenes exhibit enhanced thermal motion, micelle depolymerization, and a loose network, leading to a decrease in the overall viscosity of petroleum molecules and increased fluidity. At low temperatures, asphaltenes form a three-dimensional network through polar groups and aromatic ring structures, encapsulating oil and gum, significantly increasing petroleum viscosity. Once the network structure is damaged, it is difficult to recover. Asphaltenes dominate the temperature-sensitive behavior of petroleum through changes in molecular aggregation state, thereby affecting the dynamic desorption-adsorption behavior of petroleum molecules in contaminated soil. Lime-fly ash can improve the adsorption of petroleum pollutants in soil to a certain extent. However, it has also been found that the change in the occurrence form of petroleum in soil caused by ambient temperature is the internal cause of the fluctuation of related properties of petroleum-contaminated soil. The amount of petroleum desorption will continue to change with temperature fluctuations. The reasonable control of the viscosity-temperature property of petroleum-contaminated soil determines its stability and environmental safety in the process of engineering reuse. This is a key scientific issue that needs to be solved in the process of promoting the engineering reuse of petroleum-contaminated soil.

[0003] Currently, the remediation of petroleum-contaminated soil generally suffers from two major drawbacks: poor adaptability over a wide temperature range and insufficient bidirectional stability of petroleum-soil particles. Traditional single modification methods cannot simultaneously meet the needs of high-temperature viscosity enhancement and low-temperature flow, while lime-fly ash has limitations in suppressing the temperature sensitivity of asphaltene, thus triggering secondary migration of petroleum pollutants. Therefore, based on the above problems, a viscosity-temperature compensation method based on blocking the migration of petroleum pollutants in soil at the source is proposed, and a complex structural system of graded, phased and synergistic solidification is constructed. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a viscosity-temperature compensation method based on blocking the migration of petroleum pollutants in soil at the source, which solves the phenomenon of competitive adsorption of composite modifiers and prevents the compatibility problem of organic-inorganic materials.

[0005] To achieve the above objectives, the present invention provides the following technical solution: A viscosity-temperature compensation method based on blocking the migration of petroleum pollutants in soil at their source includes the following steps: Step S1: Extract petroleum from the soil and determine the asphaltene content; Step S2: Adjust the moisture content parameters of the contaminated soil; Step S3: Add the first modifier, epoxidized acrylate (AESO), and stir until homogeneous; Step S4: Add the second modifier, polymethyl methacrylate (T602HB), and stir until homogeneous; Step S5: Continue adding lime and fly ash and mix well; Step S6 involves compaction and curing, followed by a wide-temperature-range simulated rainfall test.

[0006] The present invention is further configured such that: in step S1, the content of asphaltene in petroleum is determined by solvent precipitation method, which is beneficial to dynamically control the dosage ratio of modifier and achieve precise viscosity-temperature compensation.

[0007] The present invention is further configured such that: in step S2, the water content of the petroleum-contaminated soil is controlled at 17.7%, and after being stirred evenly, it is sealed and cured at room temperature for 24 hours to achieve oil-water competitive adsorption equilibrium.

[0008] The present invention is further configured such that: in step S3, the first modifier, epoxidized acrylate soybean oil (AESO), is added at 12% of the asphaltene content. After mixing and stirring evenly, the mixture is covered with a film and sealed at room temperature for 24 hours. This facilitates full contact between AESO and petroleum contaminants, and enhances petroleum viscosity through pre-crosslinking of the epoxy groups with the asphaltene.

[0009] The present invention is further configured such that: in step S4, a second modifier, polymethyl methacrylate (T602HB), is added at 6% of the asphalt content, mixed and stirred evenly, and then covered and sealed at room temperature for 7 days.

[0010] The present invention is further configured as follows: in step S5, lime and fly ash are added according to the concentration of petroleum pollution. When the concentration of petroleum pollution is ≤60mg / g, the amount of lime and fly ash added is 8% and 20% of the dry soil mass percentage, respectively; when the concentration of petroleum pollution is 60mg / g-90mg / g, the amount of lime and fly ash added is 10% and 25% of the dry soil mass percentage, respectively; when the concentration of petroleum pollution is >90mg / g, the amount of lime and fly ash added is 12% and 25% of the dry soil mass percentage, respectively. After mixing and stirring evenly, the mixture is compacted and cured for 28 days under constant temperature and humidity conditions.

[0011] The present invention is further configured such that: in step S6, the petroleum-contaminated soil containing the first modifier, the second modifier, lime and fly ash is compacted and cured, and a wide-temperature-range simulated rainfall test is conducted to determine the blocking effect.

[0012] The advantages of this invention are: This invention employs a graded, phased, and synergistic solidification method. On one hand, it constructs a composite active interface that combines "adhesion-reduction" by adding a first modifier AESO and a second modifier T602HB according to the asphaltene content, thereby enhancing the adsorption effect between soil particles and petroleum. On the other hand, it adds modifiers and lime-fly ash in stages to solve the phenomenon of competitive adsorption of composite modifiers and prevent compatibility issues between organic and inorganic materials. This ensures that the remediated contaminated soil meets the standards for road and transportation construction land (Class II land) in the "Soil Environmental Quality Standard for Construction Land Soil Pollution Risk Control" (GB36600-2018), and can be directly reused as roadbed material. The first modifier, epoxidized acrylate soybean oil (AESO), the second modifier, polymethyl methacrylate (T602HB), lime, and fly ash have advantages such as low price, easy availability, and environmental friendliness, avoiding excessively high operating costs and conforming to current engineering implementation prospects. Attached Figure Description

[0013] Figure 1 This is a flowchart of the viscosity-temperature compensation method for blocking the migration of petroleum pollutants in soil at the source, as per the present invention. Figure 2 This is a distribution diagram of oil content in contaminated soil after filtration under different treatment methods according to the present invention; Figure 3 This is a comparison diagram of the filtrate phenomena of contaminated soil under different treatment methods according to the present invention; Figure 4 This is a comparison diagram of the filtrate phenomena of solidified contaminated soil under different treatment methods according to the present invention; Figure 5 These are microscopic comparison images of contaminated soil under different treatment methods according to the present invention; Figure 6 This is a microscopic comparison of solidified contaminated soil under different treatment methods according to the present invention. Detailed Implementation

[0014] The present application will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, only the parts relevant to the invention are shown in the accompanying drawings.

[0015] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0016] Please see Figure 1-6 The present invention provides the following technical solutions: Specifically, this refers to a viscosity-temperature compensation method based on blocking the migration of petroleum pollutants in soil at their source. The specific operational steps are as follows: This experiment selected three types of petroleum-contaminated soil with concentrations of 30 mg / g, 90 mg / g, and 150 mg / g. Corresponding control groups were set up for petroleum-contaminated soil with different concentrations.

[0017] Example 1 To ensure accurate viscosity compensation, the asphaltene content in petroleum was determined using the solvent precipitation method. An appropriate amount of dry soil was taken, and the moisture content of the contaminated soil was controlled to be 17.7% of its dry weight. After thorough mixing, the soil was covered with a film and sealed for curing at room temperature for 24 hours. Based on the dry weight percentage, the petroleum concentration in the contaminated soil was controlled to be 30 mg / g. To simulate a realistic contaminated environment, the petroleum-contaminated soil was sealed and stored for 24 hours after preparation.

[0018] Add 12% of the asphalt content as the first modifier, epoxidized acrylate soybean oil (AESO). After mixing and stirring evenly, cover and cure at room temperature for 24 hours. Then add 6% of the second modifier, polymethyl methacrylate (T602HB). After mixing and stirring evenly, cover and cure at room temperature for 7 days to allow the modifier to fully contact the petroleum.

[0019] Based on the dry soil mass as a percentage, control the ratio of lime and fly ash to 8% and 20% respectively. After mixing evenly, cure in a constant temperature and humidity environment. The curing temperature is 20±2℃, the curing humidity is ≥90%, and the curing period is 28 days.

[0020] Specific procedures for soil column fabrication: Using a mold, compact the soil sample with a manual lightweight compactor. Fill the cured soil sample into the column. The cured sample is then subjected to wide-temperature-range simulated rainfall tests at 0℃, 20℃, 40℃, 60℃, and 80℃. The column is made of stainless steel, with a total height of 230 mm and an inner diameter of 70 mm.

[0021] Example 2 To ensure accurate viscosity compensation, the asphaltene content in petroleum was determined using the solvent precipitation method. An appropriate amount of dry soil was taken, and the moisture content of the contaminated soil was controlled to be 17.7% of the dry soil mass. After thorough mixing, the soil was covered with a film and sealed for 24 hours at room temperature. Based on the dry soil mass percentage, the petroleum concentration in the contaminated soil was controlled to be 90 mg / g. To simulate an actual contaminated environment, the petroleum-contaminated soil was sealed and stored for 24 hours after preparation.

[0022] Based on the dry soil mass as a percentage, control the ratio of lime and fly ash to 10% and 25% respectively. After mixing evenly, cure in a constant temperature and humidity environment. The curing temperature is 20±2℃, the curing humidity is ≥90%, and the curing period is 28 days.

[0023] The remaining steps are the same as in Example 1.

[0024] Example 3 To ensure accurate viscosity compensation, the asphaltene content in petroleum was determined using the solvent precipitation method. A suitable amount of dry soil was taken, and the moisture content of the contaminated soil was controlled to be 17.7% of the dry soil mass. After thorough mixing, the soil was covered with a film and sealed for 24 hours at room temperature. Based on the dry soil mass percentage, the petroleum concentration in the contaminated soil was controlled to be 150 mg / g. To simulate an actual contaminated environment, the petroleum-contaminated soil was sealed and stored for 24 hours after preparation.

[0025] Based on the dry soil mass as a percentage, control the ratio of lime and fly ash to 12% and 25% respectively. After mixing evenly, cure in a constant temperature and humidity environment. The curing temperature is 20±2℃, the curing humidity is ≥90%, and the curing period is 28 days.

[0026] The remaining steps are the same as in Example 1.

[0027] Comparative Example 1 Take an appropriate amount of dry soil and control the moisture content of the contaminated soil to 17.7% of the dry soil mass. After mixing evenly, cover with a film and seal at room temperature for 24 hours. Based on the dry soil mass percentage, control the oil concentration in the contaminated soil to 30 mg / g. To achieve the actual contaminated environment, seal and store the oil-contaminated soil for 24 hours after preparation.

[0028] Specific procedures for soil column fabrication: Using a mold, compact the soil sample with a manual lightweight compactor. Fill the cured soil sample into the column. The cured sample is then subjected to wide-temperature-range simulated rainfall tests at 0℃, 20℃, 40℃, 60℃, and 80℃. The column is made of stainless steel, with a total height of 230 mm and an inner diameter of 70 mm.

[0029] Comparative Example 2 Take an appropriate amount of dry soil and control the moisture content of the contaminated soil to 17.7% of the dry soil mass percentage. After mixing evenly, cover with a film and seal at room temperature for 24 hours. Based on the dry soil mass percentage, control the oil concentration in the contaminated soil to 90 mg / g. To achieve the actual contaminated environment, seal and store the oil-contaminated soil for 24 hours after preparation.

[0030] The remaining steps are the same as in Comparative Example 1.

[0031] Comparative Example 3 Based on the percentage of dry soil mass, the concentration of petroleum in the contaminated soil was controlled at 150 mg / g, and the remaining steps were the same as those in Comparative Example 1.

[0032] Comparative Example 4 To ensure accurate viscosity compensation, the asphaltene content in petroleum was determined using the solvent precipitation method. A suitable amount of dry soil was taken, and the moisture content of the contaminated soil was controlled to be 17.7% of the dry soil mass. After thorough mixing, the soil was covered with a film and sealed for 24 hours at room temperature. Based on the dry soil mass percentage, the petroleum concentration in the contaminated soil was controlled to be 30 mg / g. To simulate an actual contaminated environment, the petroleum-contaminated soil was sealed and stored for 24 hours after preparation.

[0033] Add 12% of the asphalt content as the first modifier, epoxidized acrylate soybean oil (AESO). After mixing and stirring evenly, cover and cure at room temperature for 24 hours. Then add 6% of the second modifier, polymethyl methacrylate (T602HB). After mixing and stirring evenly, cover and cure at room temperature for 7 days to allow the modifier to fully contact the petroleum.

[0034] Specific procedures for soil column fabrication: Using a mold, compact the soil sample with a manual lightweight compactor. Fill the cured soil sample into the column. The cured sample is then subjected to wide-temperature-range simulated rainfall tests at 0℃, 20℃, 40℃, 60℃, and 80℃. The column is made of stainless steel, with a total height of 230 mm and an inner diameter of 70 mm.

[0035] Comparative Example 5 To ensure accurate viscosity compensation, the asphaltene content in petroleum was determined using the solvent precipitation method. An appropriate amount of dry soil was taken, and the moisture content of the contaminated soil was controlled to be 17.7% of its dry weight. After thorough mixing, the soil was covered with a film and sealed for curing at room temperature for 24 hours. Based on the dry weight percentage, the petroleum concentration in the contaminated soil was controlled to be 90 mg / g. To simulate a realistic contaminated environment, the petroleum-contaminated soil was sealed and stored for 24 hours after preparation.

[0036] The remaining steps are the same as in Comparative Example 4.

[0037] Comparative Example 6 Based on the percentage of dry soil mass, the concentration of petroleum in the contaminated soil was controlled at 150 mg / g, and the remaining steps were the same as those in Comparative Example 4.

[0038] Comparative Example 7 Take an appropriate amount of dry soil, controlling the moisture content of the contaminated soil to 17.7% of its dry soil mass. After mixing evenly, cover with a film and seal for curing at room temperature for 24 hours. Based on the dry soil mass percentage, control the petroleum concentration in the contaminated soil to 30 mg / g. To achieve an actual contaminated environment, seal and store the petroleum-contaminated soil for 24 hours after preparation.

[0039] Based on the dry soil mass as a percentage, control the ratio of lime and fly ash to 8% and 20% respectively. After mixing evenly, cure in a constant temperature and humidity environment. The curing temperature is 20±2℃, the curing humidity is ≥90%, and the curing period is 28 days.

[0040] Specific procedures for soil column fabrication: Using a mold, compact the soil sample with a manual lightweight compactor. Fill the cured soil sample into the column. The cured sample is then subjected to wide-temperature-range simulated rainfall tests at 0℃, 20℃, 40℃, 60℃, and 80℃. The column is made of stainless steel, with a total height of 230 mm and an inner diameter of 70 mm.

[0041] Comparative Example 8 Take an appropriate amount of dry soil, controlling the moisture content of the contaminated soil to 17.7% of its dry soil mass. After mixing evenly, cover with a film and seal for curing at room temperature for 24 hours. Based on the dry soil mass percentage, control the petroleum concentration in the contaminated soil to 90 mg / g. To achieve an actual contaminated environment, seal and store the petroleum-contaminated soil for 24 hours after preparation.

[0042] Based on the dry soil mass as a percentage, control the ratio of lime and fly ash to 10% and 25% respectively. After mixing evenly, cure in a constant temperature and humidity environment. The curing temperature is 20±2℃, the curing humidity is ≥90%, and the curing period is 28 days.

[0043] The remaining steps are the same as in Comparative Example 7.

[0044] Comparative Example 9 Take an appropriate amount of dry soil and control the moisture content of the contaminated soil to 17.7% of the dry soil mass. After mixing evenly, cover with a film and seal at room temperature for 24 hours. Based on the dry soil mass percentage, control the oil concentration in the contaminated soil to 150 mg / g. To achieve the actual contaminated environment, seal and store the oil-contaminated soil for 24 hours after preparation.

[0045] Based on the dry soil mass as a percentage, control the ratio of lime and fly ash to 12% and 25% respectively. After mixing evenly, cure in a constant temperature and humidity environment. The curing temperature is 20±2℃, the curing humidity is ≥90%, and the curing period is 28 days.

[0046] The remaining steps are the same as in Comparative Example 7.

[0047] like Figure 2The comparison shows that the maximum fluctuation rate of oil content in petroleum-contaminated soil was as high as 75%, 83.59%, and 84.03% respectively. The filtered oil content of modified petroleum-contaminated soil at various temperatures was between that of petroleum-contaminated soil and solidified petroleum-contaminated soil. In terms of improving the temperature sensitivity of asphalt, its effect was lower than that of the solidification effect of lime and fly ash. At high temperatures, the fluctuation rate of solidified petroleum-contaminated soil was as high as 57%. The modifier, in combination with lime and fly ash, significantly improved the temperature sensitivity of asphalt, making the solidified petroleum-contaminated soil less affected by temperature. The filtered oil content in the studied temperature range was always close to the initial oil content, with a change rate of 0.79%-4.19% compared to the initial oil content, which meets the standard for road and transportation construction land (Class II land) in the "Soil Environmental Quality Construction Land Soil Pollution Risk Control Standard" (GB36600-2018).

[0048] like Figure 3 For example Figure 4 As shown, thick oil layers were observed in petroleum-contaminated soil over a wide temperature range. The oil concentration and clarity of the filtrate from modified petroleum-contaminated soil were improved compared to the original petroleum-contaminated soil, with the best control effect at an ambient temperature of 60℃. However, a significant oil layer still existed, and the filtration phenomenon even intensified at 80℃. Although the modifier could passivate the viscosity-temperature properties of asphaltene to some extent, it was not effective in enhancing the stability of petroleum adsorption in the soil. At high temperatures (>40℃), the combined effect of lime and fly ash was not ideal. Figure 3 The data shown indicate that the desorption performance of petroleum pollutants in solidified petroleum-contaminated soil remains positively correlated with temperature. The filtrate from petroleum-contaminated soil solidified by the modifier in synergy with lime and fly ash remained clear under all study conditions, confirming that the synergistic solidification effect of the modifier and lime and fly ash can enhance the adsorption stability of petroleum pollutants in the soil, mitigate the influence of temperature on its desorption performance, and achieve the goal of blocking the migration and diffusion of petroleum pollutants in the soil at the source.

[0049] like Figure 5The comparison shows that the distribution of petroleum in soil under temperature is closely related to the temperature sensitivity of the asphaltene it contains. Under low temperature (≤20℃), asphaltene molecular chains aggregate to form a three-dimensional crystal network, which encapsulates other oil components and increases petroleum viscosity. Strongly bound petroleum increases, and petroleum is mostly distributed in an irregular thick oil film state on the surface and pores of soil particles. As the temperature rises (≥40℃), the thermal motion of asphaltene increases, the network structure loosens, leading to a decrease in petroleum viscosity and the disappearance of the thick oil film state. Accompanied by an increase in the content of free and weakly bound states, the fluid petroleum is mostly distributed in the pores of the soil. The combined use of two modifiers plays a viscosity-reducing role at low temperatures. The modified petroleum is mostly distributed in a uniform thin oil film state on the surface and pores of soil particles. Under high temperature conditions (>60℃), although the modifier can play a certain viscosity-increasing role, its viscosity value still shows an overall downward trend. Moreover, the thin film is more susceptible to temperature effects than the thick oil film, and the clarity of the soil particle outline decreases.

[0050] like Figure 6 As shown in the comparison, affected by the temperature-sensitive fluctuations of asphaltene, the morphology of the solidified products gradually changed from rod-like to flocculent. Free petroleum and flocculent products filled the pores of the soil. The change in the aggregation morphology of asphaltene under temperature influence affects the rheology of petroleum, directly weakening the solidification effect of lime and fly ash. This is precisely why the control effect of lime and fly ash is limited. Epoxidized acrylate soybean oil (AESO) and polymethyl methacrylate (T602HB) were used in conjunction with lime and fly ash for the temperature-sensitive treatment of petroleum-contaminated soil. Through the complementary and mutually reinforcing effects of modifiers, lime, and fly ash in viscosity-temperature compensation, the dynamic desorption-adsorption effect at the oil-soil interface was enhanced, forming a composite structure of "viscosity enhancement and viscosity reduction," which strengthened the persistence of the thin oil film.

[0051] This patent utilizes penetration and dispersion to allow the modifier to enter the pores of the asphaltene structure. AESO, through its long functional chain and abundant hydroxyl groups (-OH), extends fully within the asphaltene pores, exerting a cross-linking effect and encapsulating other oil components, thereby enhancing the cohesive force of the asphaltene and increasing the viscosity of petroleum at high temperatures. T602HB, through its alkyl side chain, co-crystallizes with the asphaltene, changing the direction of crystal growth and generating uniform, loose grains. This prevents the formation of a three-dimensional network between the asphaltene and aromatic ring structures, thus reducing the viscosity of petroleum at low temperatures and ensuring the low-temperature fluidity of the oil. The combined use of these two viscosity index improvers helps to achieve bidirectional viscosity-temperature compensation control at both high and low temperatures, thereby achieving stable petroleum viscosity over a wide temperature range.

[0052] The above description is merely a preferred embodiment of this application and an explanation of the technical principles employed. Those skilled in the art should understand that the scope of the invention involved in this application is not limited to technical solutions formed by specific combinations of the above-described technical features, but should also cover other technical solutions formed by arbitrary combinations of the above-described technical features or their equivalents without departing from the inventive concept. For example, technical solutions formed by substituting the above features with (but not limited to) technical features with similar functions disclosed in this application.

Claims

1. A viscosity-temperature compensation method based on preventing the migration of petroleum pollutants in soil at the source, characterized in that: Includes the following steps: Step S1 involves extracting petroleum from the soil and determining the asphaltene content. The determination of asphaltene content in petroleum using the solvent precipitation method is beneficial for dynamically controlling the dosage ratio of modifiers and achieving precise viscosity-temperature compensation. Step S2: Adjust the moisture content parameter of the contaminated soil to control the moisture content of the petroleum contaminated soil to 17.7%. After stirring evenly, seal and cure at room temperature for 24 hours to achieve oil-water competitive adsorption equilibrium. In step S3, add the first modifier, epoxidized acrylate soybean oil (AESO), at 12% of the asphalt content. After mixing and stirring evenly, cover with a film and seal at room temperature for 24 hours. This is beneficial for AESO and petroleum contaminants to fully contact each other and enhance the viscosity of petroleum through pre-crosslinking of the asphalt with its epoxy groups. Step S4: Add the second modifier polymethyl methacrylate (T602HB) at 6% of the asphalt content, mix and stir evenly, then cover and seal at room temperature for 7 days. Step S5: Add lime and fly ash according to the concentration of petroleum pollution. For petroleum pollution concentration < 60 mg / g, the amount of lime and fly ash added is 8% and 20% of the dry soil mass, respectively; for petroleum pollution concentration 60 mg / g-90 mg / g, the amount of lime and fly ash added is 10% and 25% of the dry soil mass, respectively; for petroleum pollution concentration > 90 mg / g, the amount of lime and fly ash added is 12% and 25% of the dry soil mass, respectively. After mixing evenly, compact the mixture and cure it under constant temperature and humidity for 28 days. Step S6 involves compacting and curing petroleum-contaminated soil containing the first modifier, the second modifier, lime, and fly ash, followed by a wide-temperature-range simulated rainfall test to determine the blocking effect.

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