A method and apparatus for in-situ fine-grained remediation of soil and groundwater

Abstract

A soil and groundwater in-situ fine agent injection repair method and device, using high-pressure rotary jet in-situ injection method, comprising: 1) obtaining plot information; 2) stratum generalization layering; 3) presetting injection thickness H0, calculating agent infiltration diffusion distance L; 4) back calculating the soil layer thickness H of the high-pressure injection section of a layer; 5) comparing H and H0, if the difference is within the predetermined threshold range, then H+L is set as the soil layer thickness of the injection diffusion unit of the layer, and the layer is vertically divided into multiple injection diffusion units in turn; otherwise, return to step 3); 6) repeating steps 2) to 5) to divide all strata into injection diffusion units; 7) carrying out pilot test to obtain diffusion effect evaluation parameters; 8) optimizing and adjusting to obtain the best process and equipment operation parameters of each layer of the plot. Realize the fine injection of the agent in the soil and groundwater in-situ repair process.

Description

TECHNICAL FIELD

[0001] The application relates to a soil and underground water in-situ fine agent injection remediation method and device and belongs to the technical field of soil and underground water in-situ remediation. BACKGROUND

[0002] For soil contaminated by organic pollutants, especially soil contaminated by benzene series, petroleum hydrocarbon, chlorinated hydrocarbon and the like, in-situ chemical oxidation and reduction technology is widely applied in in-situ treatment technology due to its good treatment effect and economic advantages. The remediation effect of in-situ chemical oxidation and reduction technology is mainly affected by factors such as the type of remediation agent, the adding ratio, the uniformity of agent diffusion and the like. Under the condition that the type of remediation agent and the adding concentration are certain, how to ensure that the remediation agent can uniformly diffuse into the target soil layer (or aquifer) and fully contact with the pollutants to further cause biological and chemical reactions becomes the key to affecting the remediation effect.

[0003] At present, the mainstream in-situ agent injection methods on the market include well construction injection, high-pressure splitting injection, in-situ mixing injection and high-pressure rotary jet injection. Among them, well construction injection is suitable for injection in low-pressure and high-permeability strata because the diffusion of the agent is affected by the well construction material, the lithology of the soil layer, the soil permeability and the like. The adaptability of the strata is poor. High-pressure splitting injection uses a straight push drill to press the grouting pipe into the target stratum and then relies on a surface high-pressure injection pump to pump high-pressure jets to crack the soil around the grouting pipe to form fine cracks and inject the remediation agent into the surrounding soil. However, the construction efficiency is low and the uniformity of the agent injection is greatly affected by the lithology of the strata, so it is not suitable for remediation and treatment of large and complex contaminated land blocks. In-situ mixing injection uses a shallow and deep mixing drill to inject the agent while mixing the soil and the agent uniformly by using the drill bit after penetrating the target depth. This agent adding method has the advantage of uniform mixing, but the mixing process mixes the soil at different depths up and down, which is difficult to meet the needs of differential remediation of soil at different depths. Improper operation may even cause cross-contamination of soil at different depths. Therefore, it is only suitable for land blocks with uniform pollution and single pollution type.

[0004] The high-pressure jet grouting in-situ injection technology is to drill a grouting pipe (drill rod) with a special nozzle to a predetermined depth of a soil layer, then spray the prepared medicament from the nozzle, and the grouting pipe with the nozzle is lifted upward while spraying, the high-pressure jet flow cuts and stirs the soil, fully mixes the medicament with the soil, and the medicament solution further diffuses in the aquifer due to the high injection pressure, and the diffusion radius is relatively large compared with the traditional deep stirring, and the high-pressure jet grouting injection technology is suitable for treating silt, silt soil, clay, silt, sandy soil, loess, plain soil and gravel soil, and is especially suitable for treating silt or clay with wet and sticky soil, strong plasticity and low diffusion coefficient. The high-pressure jet grouting injection technology can also realize the requirement of different medicament injection at different depths of soil by changing the lifting speed of the drill rod and the injection flow of the medicament, and is the most widely used method for repairing medicament injection in the industry at present.

[0005] Although the high-pressure jet grouting injection method has the advantages of wide soil suitability, good medicament injection and diffusion effect, and fixed-depth repair, etc., the current injection method adopts the operation method of rotating and lifting the drill rod upward while injecting the medicament from the bottom to the top, and the medicament concentration, injection pressure and injection flow of a single hole are fixed values, so that for low-permeability and low-porosity soil layers, under the condition that the medicament concentration and the medicament injection ratio are determined, for the soil layer with large medicament solution injection amount per unit length, the slurry amount during the medicament injection process is large (more than 50%), which causes great waste of the medicament; and for the soil layer with small medicament injection amount, the lifting speed of the injection drill rod is limited by the influence of the lifting speed on the medicament injection effect, for example, if the equipment is lifted too fast, the medicament cannot be uniformly stirred with the surrounding soil, and if the equipment is lifted too slowly, the medicament is over-injected. In addition, for a complex contaminated land with large vertical distribution difference, due to the difference in soil physical properties, the diffusion radius of the medicament is different during the injection process (under the condition that the injection pressure and flow are constant), which causes the difference in the injection concentration, and the situation that the unit volume medicament injection amount is lower than the set concentration ratio and the repair effect cannot be achieved. SUMMARY

[0006] In view of the above problems, the present application provides a soil and groundwater in-situ fine medicament injection repair method, which realizes the fine medicament injection in the soil and groundwater in-situ repair by the slice-type medicament segmented injection method and the layered differential medicament injection method on the basis of the high-pressure jet grouting injection technology. The purpose of the present application is achieved by the following technical scheme:

[0007] A soil and groundwater in-situ fine medicament injection repair method, which adopts the high-pressure jet grouting in-situ injection method, drills a drill rod with a nozzle to a predetermined depth of a soil layer, sprays the prepared medicament from the nozzle, and the high-pressure jet flow cuts and stirs the soil, including the following steps:

[0008] Step 1: Obtain site information: by collecting and analyzing the relevant information of the contaminated site, or by field investigation, the site information includes: site pollutant characteristics and stratum soil conditions;

[0009] Step 2: Stratify the stratum: according to the collected site information, the stratum of the site is vertically divided into multiple layers;

[0010] Step 3: Estimate the distance of the reagent infiltration and diffusion in a layer: when using high-pressure jet grouting technology to inject solution into the soil, the vertical diffusion and leakage distance of the solution in the soil is affected by many factors, including the permeability of the soil, the properties of the solution (such as viscosity, density), injection pressure, injection rate, reagent injection amount, and the thickness of the injection soil layer, and the porosity of the soil layer. Among them, the diffusion of the reagent itself, the amount of injected reagent, the thickness of the soil layer, and the permeability of the soil are the key factors. Darcy's law is a basic law for describing the flow of fluid in porous media, which can be expressed as:

[0011] q = k i (1)

[0012] Where q is the flow rate per unit area per unit time (volume / time / area), k is the permeability coefficient (length / time), and i is the hydraulic gradient (dimensionless).

[0013] However, when estimating the diffusion distance of the solution, the actual concern is the horizontal or vertical diffusion distance, rather than the flow rate. Therefore, the problem can be simplified to consider one-dimensional diffusion, and it is assumed that the hydraulic gradient is proportional to the diffusion distance. Since it is relatively complex to directly apply Darcy's law to calculate the diffusion distance, a simplified method can be used, which is based on empirical formulas or experimental results under similar conditions. The formula for calculating the reagent infiltration and diffusion distance L is simplified to formula (2). According to the pollutant characteristics and stratum soil conditions of a layer, a pre-estimated injection thickness H0 is determined, and then formula (2) is used to estimate the reagent infiltration and diffusion distance:

[0014]

[0015] Where L represents the vertical distance of the reagent infiltration and diffusion segment, m; k represents the permeability coefficient, m / d (measured or taken from experience); t represents the effective diffusion time, d (7-25 d); Δp represents the pressure difference between the reagent solution injected to the thickness H0 and the lower layer of soil, which is approximately the pressure head difference kg·g / m 2 (obtained through laboratory testing), where g represents the acceleration of gravity; ρs represents the density of the solution, kg / m 3 ; g represents the acceleration of gravity;

[0016] Step four: reverse calculation of the high-pressure injection section soil layer thickness: according to the solubility of the reagent and the preset injection thickness, the reagent original liquid concentration C0 of a layer is given, and the soil layer thickness H of the high-pressure injection section of the reagent of a layer is calculated by using formula (3);

[0017]

[0018] In the formula, C0 represents the concentration of the prepared reagent original liquid, kg / m 3 ; C1 represents the required concentration of the reagent in a certain layer, kg / m 3 ; D e represents the influence radius of high-pressure jet grouting in a certain layer under certain working conditions, m (measured or taken according to experience); θ1 represents the filling rate of the reagent in the high-pressure injection section soil (the experience value is 0.75-0.9, and the actual value can be optimized according to the measured reverse slurry ratio); H represents the thickness of the high-pressure injection section soil layer, m; β represents the loss ratio of the reagent in the high-pressure injection section (the experience interval value is 0.1-0.25, which can be measured according to the experiment); θ2 represents the filling rate of the reagent in the soil of the downward diffusion section (the experience value is 0.5-0.75), and L represents the vertical distance of the reagent downward diffusion section, m;

[0019] Step five: compare H and H0, if the difference is within the predetermined threshold range, set H+L as the soil layer thickness of the injection diffusion unit of the layer, and vertically divide the layer into multiple injection diffusion units in turn (equivalent to slicing); if the difference is not within the predetermined threshold range, return to step three to give a new estimated H0;

[0020] Step six: repeat steps two to five to divide all layers into injection diffusion units;

[0021] Step seven: determine the reagent injection amount of each layer (i.e. ) according to the high-pressure injection section soil layer thickness H in each injection diffusion unit of each layer, and determine the equipment operation parameters in combination with the soil conditions of each layer to carry out reagent injection pilot test and obtain the diffusion effect evaluation parameters in the pilot test results;

[0022] Step eight: optimize and adjust according to the diffusion effect evaluation parameters obtained in step seven, and then obtain the final best high-pressure injection section soil layer thickness H, reagent downward diffusion section vertical distance L, influence radius R, reagent injection amount and equipment operation parameters under the condition of each layer of the plot.

[0023] Further optimization, in step one, the plot pollutant characteristics include pollutant type, pollutant spatial distribution and pollutant concentration; and the soil conditions of the layer include soil type, soil water content, soil porosity, soil vertical permeability coefficient, soil organic matter content and soil reducing mineral content.

[0024] Further, in step two, strata with similar soil quality and similar types and concentrations of pollutants are generalized as one layer.

[0025] Further, in step four, the required concentration C1 of each stratum is obtained by analyzing and calculating the types and concentrations of pollutants in the soil or by small-scale test experiments.

[0026] Further, in step five, the predetermined threshold range is ±10%.

[0027] Further, in step seven, the equipment operating parameters include injection pressure, lifting speed, drill pipe rotation speed and reagent flow rate; and the diffusion effect evaluation parameters include diffusion time, diffusion influence radius, reagent infiltration diffusion distance and average concentration after reagent diffusion.

[0028] Further, in step seven, the pilot test adopts a triangular point distribution method for drilling hole distribution, and the number of drilling hole distribution is not less than 3; within the effective diffusion time of the reagent, soil in the injection and diffusion range is collected at multiple positions in the triangular injection range at fixed time and depth, and the diffusion effect evaluation parameters of the reagent are obtained by measuring the concentrations of the tracer and the reagent; the tracer is bromide ion, and the sampling time is taken at equal intervals, and the sampling interval is 3-5 days.

[0029] The high-pressure jetting device of the remediation method, the high-pressure jetting device comprises a reagent feeding assembly, an air feeding assembly and a jetting assembly; the reagent feeding assembly comprises a reagent configuration device, a high-pressure grouting pump connected to the output end of the reagent configuration device through a pipeline and a high-pressure grouting pipe connected to the output end of the high-pressure grouting pump; the reagent configuration device comprises at least three independent reagent barrels, an independent electronic liquid outlet control valve is arranged on the liquid outlet pipeline of each reagent barrel, the liquid outlet pipelines of the reagent barrels are communicated to a total pipeline at the ends, an electromagnetic flow meter is arranged on the total pipeline, and the output end of the total pipeline is connected to the high-pressure grouting pump; the air feeding assembly comprises an air compressor, a fresh air inlet port arranged on one side of the air compressor and a compressed air pipeline connected to the output end of the air compressor; the jetting assembly comprises a jetting drilling machine, a high-pressure jetting drill pipe connected to the jetting drilling machine and a drill pipe automatic lifting device for controlling the lifting of the high-pressure jetting drill pipe; the high-pressure jetting drill pipe is composed of an inner pipe and an outer pipe, a reagent jetting nozzle is arranged on the inner pipe, an air jetting nozzle is arranged on the outer pipe, the output end of the high-pressure grouting pipe is communicated with the inner pipe, and the output end of the compressed air pipeline is communicated with the outer pipe; a drill bit is mounted at the bottom of the jetting drill pipe.

[0030] The beneficial effects of the present application are as follows:

[0031] 1) The present application improves the construction efficiency, reduces the agent gushing amount of each stratum, especially the low permeability stratum, improves the agent utilization efficiency, and reduces the construction cost by adopting the combination of injection section and downward diffusion section.

[0032] 2) The present application improves the application range of high-pressure rotary jet injection by adopting slice type agent injection (i.e. dividing the land into different strata, and dividing each stratum into multiple injection and downward diffusion units) according to the injection requirements of different strata. For example, for the stratum with low injection requirement, the slice type injection is adopted, the downward diffusion is relied on to increase the agent diffusion range, and the residence time of the agent injection section is prolonged, so that the uneven mixing of the agent caused by the low injection requirement per unit length, the fast lifting speed of the drill pipe, and the poor agent diffusion effect can be effectively solved.

[0033] 3) According to the different influence radius of different strata and soil, in order to ensure the different injection requirements of different strata and agent concentration, the present technical solution adopts different concentrations of agent supply, and the operation is more refined.

[0034] The present application will be further described in detail below in combination with the drawings and specific embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 The present application is a high-pressure rotary jet equipment and principle diagram.

[0036] Figure 2 The present application is a high-pressure rotary jet slicing injection principle diagram.

[0037] Figure 3 The present application is a high-pressure rotary jet injection method schematic diagram.

[0038] Figure 4 The present application is a test injection hole and sampling hole arrangement schematic diagram in Example 1.

[0039] Figure 5 The present application is a comparison of back slurry under different injection methods of high-pressure rotary jet (left side is the prior art, and right side is the present application).

[0040] Figure 6 The present application is a comparison of agent injection uniformity under different injection methods of high-pressure rotary jet.

[0041] Figure 7 The present application is a high-pressure rotary jet agent configuration device schematic diagram in Example 2.

[0042] Figure 8 The present application is a difference diagram of agent requirement concentration of different strata of high-pressure rotary jet in Example 2.

[0043] Reference signs:

[0044] 1, medicament configuration device; 2, high-pressure grouting pump; 3, high-pressure grouting pipe; 4, fresh air inlet port; 5, air compressor; 6, compressed air pipeline; 7, rotary jet drilling machine; 8, automatic lifting device of drill pipe; 9, high-pressure jet drill pipe; 101, medicament barrel; 102, electronic liquid outlet control valve; 103, electromagnetic flowmeter. DETAILED DESCRIPTION

[0045] Example 1

[0046] A soil and groundwater in-situ fine medicament injection remediation method, using a high-pressure rotary jet in-situ injection method, by drilling a drill pipe with a nozzle to a predetermined depth of the soil layer, and spraying the prepared medicament from the nozzle, the drill pipe is lifted upward at the same time of jetting, the high-pressure jet cuts and stirs the soil, comprising the following steps:

[0047] Step one: Obtain plot information: by collecting and analyzing the relevant data of the contaminated plot, or by on-site investigation, the plot information includes: plot pollutant characteristics and stratum soil conditions; the plot pollutant characteristics include pollutant type, pollutant spatial distribution and pollutant concentration; the stratum soil conditions include soil type, soil water content, soil porosity, soil vertical permeability coefficient, soil organic matter content and soil reducing mineral content.

[0048] Step two: stratify the stratum: according to the collected plot information, the plot stratum is vertically divided into multiple layers; strata with similar soil conditions and similar pollutant types and concentrations are generalized into a layer. In this example, the stratum is divided into 4 layers, S1, S2, S3, S4, as shown in Figure 1 .

[0049] Step three: estimate the medicament infiltration and diffusion distance of S1 layer: according to the pollutant characteristics and stratum soil conditions of a certain layer, a pre-estimated injection thickness H0 is determined, and then formula (2) is used to estimate the medicament infiltration and diffusion distance:

[0050]

[0051] In the formula: L represents the blowing distance of the medicament infiltration and diffusion section, m; k represents the permeability coefficient, m / d (measured or taken according to experience, the empirical value is referred to Table 1); t represents the effective diffusion time, d (7-25d); Δp represents the pressure difference between the medicament solution of the injection thickness H0 and the lower layer soil, which is approximately the pressure of the water head difference kg·g / m 2 (available through laboratory detection), wherein g represents the acceleration of gravity; ρs represents the density of the solution, kg / m 3 ; g represents the acceleration of gravity.

[0052] Table 1

[0053] Soil Class K (cm / s) Soil Class K (cm / s) Coarse Gravel 1～0.5 Loess (Sandy) 1 x 10 -3 ~ 1 x 10 -4 ]]> Sandy Gravel 0.1～0.01 Loess (Clayey) 1 x 10 -5 ~ 1 x 10 -6 ]]> Coarse Sand 5 x 10 -2 ~ 1 x 10 -2 ]]> Clay Loam 1 x 10 -4 ~ 1 x 10 -6 ]]> Fine Sand 5 x 10 -3 ~ 1 x 10 -3 ]]> Silt Loam 1 x 10 -6 ~ 1 x 10 -7 ]]> Clayey Sand 2 x 10 -3 ~ 1 x 10 -4 ]]> Clay [1 x 10 -6 ~1 x 10 -8 ]]> Sandy Loam 1 x 10 -3 ~ 1 x 10 -4 ]]> Uniformly Fertile Clay 1 x 10 -8 ~ 1 x 10 -10 ]]>

[0054] Step four: reverse calculation of the soil thickness of the high-pressure injection section: given the concentration C0 of the prepared agent solution of a certain layer, the soil thickness H of the high-pressure injection section of the agent of the certain layer is calculated by using formula (3);

[0055]

[0056] In the formula: C0 represents the concentration of the prepared agent solution, kg / m 3 ; C1 represents the required concentration of the agent of a certain layer, kg / m 3 ; D e represents the influence radius of the high-pressure jet grouting of a certain layer under certain working conditions, m (measured or taken according to experience, and the experience value is shown in Table 2); θ1 represents the filling rate of the agent in the soil of the high-pressure injection section (the experience value is 0.75-0.9, and the actual value can be optimized according to the measured reverse slurry ratio); H represents the soil thickness of the high-pressure injection section, m; β represents the loss ratio of the agent in the high-pressure injection section (the experience value is 0.1-0.25, and the actual value can be measured according to the experiment); θ2 represents the filling rate of the agent in the soil of the downward diffusion section (the experience value is 0.5-0.75), and L represents the vertical distance of the downward diffusion section, m; the required concentration C1 of each layer is obtained by analyzing and calculating the type and concentration of the pollutants in the soil or by a small test experiment.

[0057] Table 2

[0058]

[0059] Note: N in the table is the vertical impact number measured by standard penetration. The reference value of the diameter of the jet grouting pile in the table is m.

[0060] Step five: compare H and H0, if the difference is within the predetermined threshold range (±10%), set H+L as the soil thickness of the injection diffusion unit of S1 layer, and vertically divide S1 layer into multiple injection diffusion units in turn, and the injection principle diagram of the layer is shown in FIG. 2, and the existing high-pressure jet grouting agent injection schematic diagram is shown in FIG. Figure 3 ; compare H and H0, if the difference is not within the predetermined threshold range, return to step three and give a new estimated H0.

[0061] Step six: repeat steps two to five to divide S2, S3 and S4 layers into injection diffusion units.

[0062] Step seven: determine the amount of medicament injection of each layer according to the high-pressure injection section soil layer thickness H in each layer of the injection diffusion unit, and determine the equipment operation parameters in combination with the soil conditions of each layer, carry out the pilot test of medicament injection, and obtain the diffusion effect evaluation parameters in the pilot test results; the equipment operation parameters include: injection pressure, lifting speed, drill pipe rotation speed and medicament flow. The pilot test adopts a triangular distribution method to distribute the drilling holes, and the number of drilling holes is not less than 3. Within the effective diffusion time of the medicament, the soil in the injection and diffusion range is collected at multiple positions within the triangular injection range at regular time intervals and depths, the concentration of the tracer and the medicament is determined, the medicament diffusion effect evaluation parameters are obtained, and the diffusion effect evaluation parameters include diffusion time, diffusion influence radius, medicament infiltration and diffusion distance, and average concentration after medicament diffusion; the determination of the tracer is bromide ion, and the sampling time is taken at equal intervals, and the sampling interval is 3-5 days. The injection hole and the sampling hole are arranged as shown in Figure 4 ,

[0063] Step eight: optimize and adjust according to the diffusion effect evaluation parameters obtained in step seven, and then obtain the final best high-pressure injection section soil layer thickness H, medicament infiltration and diffusion section vertical distance L, influence radius R, medicament injection amount and equipment operation parameters under the condition of each layer of the plot.

[0064] By determining the best medicament injection section H and medicament diffusion section L, the thickness of the soil layer for medicament injection is reduced, the slurry return ratio is reduced, and the medicament injection effect under low dosage is ensured. In the low-permeability formation, the slurry return ratio can be reduced from 10%-40% to 4%-20% under the condition of large grouting amount. In the case of low grouting amount, the injection layer thickness is adjusted, the drill pipe lifting speed of the grouting section is changed, and the medicament stirring and diffusion are more uniform. As shown in Figure 5 , 6

[0065] Example 2

[0066] A high-pressure rotary jet device for the repair method described in example 1, the high-pressure rotary jet device comprising a medicament feeding assembly, an air feeding assembly and a rotary jet assembly; as shown in Figure 1 .

[0067] The medicament feeding assembly comprises: a medicament configuration device 1, a high-pressure grouting pump 2 connected to the output end of the medicament configuration device 1 through a pipeline, and a high-pressure grouting pipe 3 connected to the output end of the high-pressure grouting pump 2; as shown in Figure 7 , the medicament configuration device 1 comprises at least three independent medicament barrels 101, an independent electronic liquid outlet control valve 102 is arranged on the liquid outlet pipeline of each medicament barrel 101, the liquid outlet pipelines of the medicament barrels 101 are communicated to a total pipeline, an electromagnetic flowmeter 103 is arranged on the total pipeline, and the output end of the total pipeline is connected to the high-pressure grouting pump 2.​

[0068] The air intake assembly comprises an air compressor 5, a fresh air intake port 4 arranged on one side of the air compressor 5, and a compressed air pipeline 6 connected with the output end of the air compressor 5.

[0069] The rotary jetting assembly comprises a rotary jetting drilling machine 7, a high-pressure jetting drill rod 9 (triple pipe) connected with the rotary jetting drilling machine 7, and a drill rod automatic lifting device 8 for controlling the lifting of the high-pressure jetting drill rod 9; the high-pressure jetting drill rod 9 is composed of an inner pipe and an outer pipe, the inner pipe is provided with a medicament jetting nozzle, the outer pipe is provided with an air jetting nozzle, the output end of the high-pressure grouting pipe 3 is communicated with the inner pipe, and the output end of the compressed air pipeline 6 is communicated with the outer pipe; a drill bit is mounted at the bottom of the jetting drill rod 9.

[0070] According to different generalized stratification influence radii, the demand for medicament dosage and medicament dosage concentration is different, the medicament configuration unit can supply C01, C02 and C03 concentration medicaments according to the injection requirements of different medicaments, and the supply switching of the medicaments relies on the automatic switching of the electromagnetic valves. In addition, an automatic control unit is arranged, and the injection is automatically performed according to the medicament dosage and influence radius of different strata at different depths. Figure 8 It is a schematic view of the different strata medicament requirement concentration difference in the embodiment.

[0071] The above embodiment is only a part of the embodiment of the present application, and cannot cover all the embodiments of the present application. Based on the above embodiment and the accompanying drawings, more embodiments can be obtained by those skilled in the art without creative labor, and therefore the embodiments obtained without creative labor should be included in the protection scope of the present application.

Claims

1. A remediation method of soil and groundwater in-situ fine-grained agent injection, using a high-pressure jet grouting in-situ injection method, by drilling a drill rod with a nozzle to a predetermined depth of the soil layer, and spraying a prepared agent from the nozzle, the high-pressure jet cutting and mixing the soil, characterized in that: The method comprises the following steps: Step one: obtaining plot information: collecting and analyzing relevant information of the contaminated plot, or obtaining through field investigation, the plot information including plot pollutant characteristics and stratum soil conditions; Step two: stratum generalization and stratification: according to the collected plot information, the plot stratum is vertically divided into multiple layers; Step three: estimating the reagent infiltration and diffusion distance of a layer: according to the pollutant characteristics and stratum soil conditions of the layer, the injection thickness H0 is estimated, and then the reagent infiltration and diffusion distance is estimated by using formula (2): （2） In the formula, L represents the vertical distance of the downward infiltration and diffusion section of the agent, m; k represents the permeability coefficient, m / d; t represents the effective diffusion time, d; and Δp represents the difference between the pressure of the injection H0-thick agent solution and the lower soil, kg·g / m 2 ; ρ s represents the density of the solution, kg / m 3 ; and g represents the acceleration of gravity. In the formula, L represents the vertical distance of the downward infiltration and diffusion section of the agent, m; k represents the permeability coefficient, m / d; t represents the effective diffusion time, d; and Δp represents the difference between the pressure of the injection H0-thick agent solution and the lower soil, kg·g / m 2 ; ρ s represents the density of the solution, kg / m 3 ; and g represents the acceleration of gravity. Step four: inverse calculation of high-pressure injection section soil thickness: preset the concentration of the prepared agent stock solution of a layer The soil thickness H of the high-pressure injection section of the agent in a certain layer is calculated by using formula (3). = （3） In the formula: represents the concentration of the agent stock solution, kg / m 3 ; represents the demand concentration of the agent for a certain formation, kg / m 3 ; represents the influence radius of high-pressure jetting in a certain formation under certain working conditions, m; represents the filling rate of the agent in the soil in the high-pressure injection section; H represents the thickness of the soil in the high-pressure injection section, m; represents the loss proportion of the agent in the high-pressure injection section; represents the filling rate of the agent in the soil in the infiltration and diffusion section; Step five: comparing H and H0, if the difference is within the predetermined threshold range, setting H+L as the soil layer thickness of the injection and diffusion unit of the layer, and vertically dividing the layer into multiple injection and diffusion units in turn; comparing H and H0, if the difference is not within the predetermined threshold range, returning to step three to give a new estimated H0; Step six: repeating steps two to five to divide all strata into injection and diffusion units; Step seven: determining the reagent injection amount of each layer according to the high-pressure injection section soil layer thickness H in each injection and diffusion unit of the layer, and determining the equipment operation parameters in combination with the stratum soil conditions of each layer, carrying out reagent injection pilot test, and obtaining the diffusion effect evaluation parameters in the pilot test results; Step eight: optimizing and adjusting according to the diffusion effect evaluation parameters obtained in step seven, and then obtaining the final plot best high-pressure injection section soil layer thickness H, reagent infiltration and diffusion section vertical distance L, influence radius R, reagent injection amount and equipment operation parameters under the condition.

2. The method of in-situ fine-grained remediation of soil and groundwater according to claim 1, characterized in that: In step one, the plot pollutant characteristics include pollutant type, pollutant spatial distribution and pollutant concentration; the stratum soil conditions include soil type, soil water content, soil porosity, soil vertical permeability coefficient, soil organic matter content and soil reducing mineral content.

3. The method of in-situ fine-grained remediation of soil and groundwater according to claim 2, characterized in that: In step two, strata with similar soil quality and similar pollutant type and concentration are generalized into one layer.

4. The method of in-situ fine-grained remediation of soil and groundwater according to claim 1, characterized in that: The required concentration of each layer in step four C 1 is obtained by analyzing and calculating the type and concentration of pollutants in the soil or by small-scale test experiments.

5. The method of soil and groundwater in-situ fine-grained remediation according to claim 1, characterized in that: In step five, the predetermined threshold range is ±10%.

6. The method of in-situ fine-grained remediation of soil and groundwater according to claim 1, characterized in that: In step seven, the equipment operation parameters include injection pressure, lifting speed, drill pipe rotation speed and reagent flow; the diffusion effect evaluation parameters include diffusion time, diffusion influence radius, reagent infiltration and diffusion distance and average concentration after reagent diffusion.

7. The method of soil and groundwater in-situ fine-grained remediation according to claim 1, characterized in that: In step seven, the pilot test adopts the triangular point distribution method for drilling point distribution, and the number of drilling points is not less than 3; within the effective diffusion time of the reagent, soil in the injection and diffusion range is collected at multiple positions in the triangular injection range at regular intervals, the concentrations of the tracer and the reagent are determined, the reagent diffusion effect evaluation parameters are obtained, the tracer is bromide ion, and the sampling time is taken at equal intervals, and the sampling interval is 3-5 days.

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