A slurry stratified permeation grouting method for powder fine sand layer based on dynamic proportioning regulation

Abstract

The application discloses a kind of based on dynamic proportioning regulation and control's powder fine sand layer slurry stratified permeation grouting method, determine the particle size distribution of target reinforcement area;Further, the target reinforcement area is divided into coarse particle zone, medium particle zone and fine particle zone;And calculate the design grouting amount of each area;Each area determines the corresponding composite slurry respectively, composite slurry is made by strong permeability slurry and weak permeability slurry proportioning, and determine the design reference particle size after each area grouting;Coarse particle zone, medium particle zone and fine particle zone are sequentially grouted and reinforced;During the grouting process in each area, if it meets the termination grouting condition, then the grouting of the area is completed;And during the grouting process, according to the deviation of measured particle size and design reference particle size in a certain area, the proportioning of the composite slurry of the area is dynamically adjusted, so that the measured particle size after grouting is as close to the design reference particle size as possible;So as to ensure that different particle size powder fine sand layer reaches the required effect after grouting and reinforcement.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of tunnel and underground engineering disaster grouting treatment, in particular to a layered permeation grouting method for silt-sand layer based on dynamic proportioning regulation. BACKGROUND

[0002] Silt-sand stratum is a common soft and poor stratum and exists universally in many regions. The silt-sand particles have small particle size and low cohesion, resulting in loose stratum structure and poor cementation. After excavation disturbance, the self-stability of the silt-sand stratum is poor, which can easily lead to accidents such as surface subsidence, soil cracking and face instability. The silt-sand stratum is plastic and rheological when meeting water, which can easily induce disasters such as collapse, piping and water and mud inrush. As a common method for tunnel and underground engineering geological disaster treatment, grouting reinforcement technology has the advantages of strong geological adaptability, flexible construction operation, controllable construction period and cost, and is widely used in a large number of projects.

[0003] In actual grouting reinforcement projects, cement particles have large particle size and are difficult to enter fine-grained soil and sand layers with small permeability coefficient, resulting in small diffusion radius of cement grout in silt-sand layers and limited reinforcement range, which seriously affects the poor grouting reinforcement effect. Ultra-fine cement and water glass grouting materials can solve the deficiency of cement grout to a certain extent due to their smaller particles and better permeability. Chemical grouting materials have the advantages of low viscosity, high permeability and good injectability, and can be stably injected into silt-sand layers to achieve stratum reinforcement. However, they are limited in practical application due to defects such as high price, low strength, easy aging and poor durability. In addition, the stratum is not composed of one particle size in actual situations, but generally exists in composite particle size stratum with different particle size distribution. In summary, the use of a single type of grout (such as cement-water glass double-liquid grout) cannot effectively meet the complex permeation requirements of composite particle size stratum, resulting in excessive reinforcement in coarse particle regions and insufficient reinforcement in fine particle regions.

[0004] In addition, the calculation of grouting amount in the grouting process mainly depends on the empirical coefficient method, which lacks accurate consideration of stratum particle size distribution and porosity, resulting in a high calculation error of grouting amount of up to 20-30%. This not only causes material waste, but also may lead to poor reinforcement effect.

[0005] Therefore, how to provide a new grouting method that can use different grouts for grouting according to the particle size distribution of silt-sand layers and accurately control the grouting amount to ensure that the silt-sand layers achieve the required effect after grouting reinforcement, and facilitate subsequent construction of silt-sand layers, is the research direction of the present application. SUMMARY

[0006] In view of the problems in the prior art, the present application provides a slurry stratified permeation grouting method for powder fine sand layer based on dynamic proportioning regulation, which can adopt different slurries for grouting according to the particle size distribution of the powder fine sand layer, and can fully exert the performance of each slurry by matching the slurry with the corresponding powder fine sand layer of the particle size, and can accurately control the grouting amount, so as to ensure that the powder fine sand layer of different particle sizes reaches the required effect after grouting and reinforcement, and facilitate subsequent construction of the stratum.

[0007] In order to achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows: a slurry stratified permeation grouting method for powder fine sand layer based on dynamic proportioning regulation, comprising the following steps:

[0008] Step one: according to the geotechnical investigation data and the related design documents, the target reinforcement area of the powder fine sand layer in front of the tunnel face is determined; then the particle size distribution and the porosity of the target reinforcement area are determined by geological drilling core taking.

[0009] Step two: according to the particle size distribution, the target reinforcement area is divided into a coarse particle zone, a medium particle zone and a fine particle zone, and the volume of each zone is determined.

[0010] Step three: according to the volume and the porosity of each zone, the design grouting amount of each zone is calculated.

[0011] Step four: according to the division of step two, the corresponding composite slurry of each zone is determined, the composite slurry is made by proportioning a slurry with strong permeability and a slurry with weak permeability, and the design reference particle size after grouting of each zone is determined.

[0012] Step five: grouting holes and grouting pipes are arranged in the target reinforcement area.

[0013] Step six: according to the slurry and the proportioning determined in step four, the coarse particle zone, the medium particle zone and the fine particle zone are sequentially grouted and reinforced.

[0014] Step seven: during the grouting process of each zone, the grouting pressure, the flow and the grouting amount are monitored in real time, if the termination grouting condition is met, the grouting of the zone is completed; and during the grouting process, the proportioning of the composite slurry of a zone is dynamically adjusted according to the deviation of the measured particle size from the design reference particle size in the zone, so that the measured particle size after grouting is as close as possible to the design reference particle size.

[0015] Step eight: after the grouting of all zones is completed, the grouting and reinforcement effect is evaluated by geophysical exploration, if the requirement is met, the grouting work of the target reinforcement area is completed; if the requirement is not met, the grouting and reinforcement is repeated again by repeating steps five to seven, until the requirement is met, and the grouting work of the target reinforcement area is completed.

[0016] Further, the specific division criteria in step two are as follows: the particle size d≥0.5 mm is determined as the coarse particle zone; the particle size 0.1

[0017] Further, the design grouting amount in step three is specifically calculated according to the following formula:

[0018] Q 总 =α·V·n·β;

[0019] In the formula, Q 总 is the design grouting amount of the current zone; V is the volume of the current zone, n is the porosity of the current zone; α is a loss coefficient, which is 1.2-1.5; and β is a compactness correction coefficient, which is 0.8-1.2.

[0020] Further, the corresponding composite grout of each zone is determined in step four, specifically: the coarse particle zone uses ordinary cement grout and ultra-fine cement grout, and the initial ratio of the two is 6:4; the medium particle zone uses ultra-fine cement grout and cement-silicate double liquid grout, and the initial ratio of the two is 7:3; and the fine particle zone uses polyurethane chemical grout and acrylate chemical grout, and the initial ratio of the two is 5:5.

[0021] Further, step five is specifically: according to the range of the target reinforcement zone, grouting holes are arranged at an interval of 1.5-2.0 m, the grouting hole depth penetrates the silty sand layer and enters the stable stratum by 0.5 m; the grouting pipe is inserted into the grouting hole to the designed depth, the orifice is sealed by a stopper to ensure the stability of the grouting pressure.

[0022] Further, in the grouting reinforcement process in step six, the grouting pressure is controlled to be not greater than 2.0 MPa, and the grouting flow is controlled to be not greater than 30 L / min.

[0023] Further, the termination condition of grouting in step seven is specifically: the grouting flow control is the main, the grouting amount control is the auxiliary, when the grouting flow of a certain zone is less than 2 L / min, or the grouting amount reaches 1.2 times of the designed grouting amount of the zone and the grouting flow is less than 6 L / min, the grouting is terminated.

[0024] Further, the ratio of the composite grout of the zone is dynamically adjusted in step seven, specifically:

[0025] When it is detected that the actual particle size of a certain zone deviates from the designed reference particle size by ≥10%, the dynamic adjustment is triggered, and the specific adjustment method is as follows: when the measured particle size is less than the designed reference particle size, the amount of the grout with stronger permeability in the composite grout is increased on the basis of the initial ratio; when the measured particle size is greater than the designed reference particle size, the amount of the grout with stronger permeability in the composite grout is reduced on the basis of the initial ratio; and the calculation formula of the specific adjustment amount is:

[0026] ;

[0027] In the formula: is the adjusted amount of the current area; d i is the measured particle size of the current area, d i0 is the design reference particle size of the current area, Q 总 is the design grouting amount of the current area; k is the adjustment coefficient, and is 0.03-0.05.

[0028] Further, in the grouting process of the seventh step, in order to ensure the safety of the grouting process, the ground deformation is monitored through the surface settlement observation point and the tunnel convergence observation point, and if there is an abnormality, the grouting is stopped in time.

[0029] Compared with the prior art, the present application can realize the precision and high efficiency of the grouting reinforcement of the silty sand layer through the synergistic penetration and dynamic proportioning regulation of multiple slurries; first, according to the particle size distribution of the target reinforcement area, the area is divided into multiple areas, wherein the ordinary cement slurry and the ultra-fine cement slurry form a strength gradient reinforcement system in the coarse particle zone and the medium particle zone, and the compressive strength is significantly improved to more than 2.0MPa, while the polyurethane / acrylate chemical slurry realizes nano-level penetration in the fine particle zone, and the penetration radius is expanded to 0.6-1.0m, which is more than 50% higher than that of traditional chemical grouting. In the initial proportioning of the composite slurry in each area, the design reference particle size is first determined, and the actual particle size and the design reference particle size are compared during the grouting process, if the deviation exceeds the threshold value, the initial proportioning of the composite slurry is adjusted through the dynamic proportioning adjustment algorithm, so that the particle size after grouting is as close as possible to the design reference particle size, which can control the grouting amount calculation error within 15%, improve the material utilization rate to more than 85%, and reduce the comprehensive cost by 20-40%. In addition, the present application breaks through the material adaptation bottleneck of the traditional grouting process in the silty sand layer, forms a particle size grading matching, grouting parameter closed-loop control and reinforcement effect quantitative improvement technical system, and is especially suitable for efficient treatment of silty sand layer in urban underground engineering. And it has the advantages of strong pertinence, wide applicability, good reinforcement effect, high material utilization rate, significant economic benefit and the like, and provides an efficient solution for silty sand layer grouting reinforcement. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 is the overall flowchart of the present application.

[0031] Figure 2 is the schematic diagram of dividing different areas and corresponding composite slurries in the embodiment of the present application.

[0032] Figure 3 is the schematic diagram of grouting reinforcement in the embodiment of the present application. DETAILED DESCRIPTION

[0033] The application will be further described below.

[0034] As Figure 1 shown, the application comprises the following steps:

[0035] Step one, according to the geotechnical investigation data and related design documents, determine the target reinforcement area of the fine sand layer in front of the tunnel face; then through geological drilling core, use the particle size analyzer to analyze the particle size distribution of the core sample, draw the particle size distribution curve, and determine the particle size distribution and porosity of the target reinforcement area.

[0036] Step two, according to the particle size distribution, divide the target reinforcement area into coarse particle zone, medium particle zone and fine particle zone, and determine the volume of each zone, the specific division standard is: the particle size d≥0.5 mm is determined as the coarse particle zone; the particle size in 0.1

[0037] Step three, according to the volume and porosity of each zone, calculate the design grouting amount of each zone, the specific formula is:

[0038] Q 总 =α·V·n·β

[0039] In the formula, Q 总 is the design grouting amount of the current area; V is the volume of the current area, n is the porosity of the current area; α is the loss coefficient, taking 1.2~1.5, β is the compactness correction coefficient, taking 0.8~1.2.

[0040] Step four, according to the division of step two, determine the corresponding composite grout for each zone, the composite grout is made by mixing the grout with strong permeability and the grout with weak permeability, as Figure 2 shown, specifically: the coarse particle zone uses ordinary cement grout and ultra-fine cement grout, and the initial ratio of the two is 6:4; the medium particle zone uses ultra-fine cement grout and cement-silicate double liquid grout, and the initial ratio of the two is 7:3; the fine particle zone uses polyurethane chemical grout and acrylic ester chemical grout, and the initial ratio of the two is 5:5. And determine the design reference particle size after grouting of each zone. The above composite grout all passes the compatibility test, which includes that the viscosity change rate after mixing the grout is ≤5%, and the compressive strength loss rate is ≤10%. In this way, the subsequent grouting reinforcement requirements can be met.

[0041] Step five, according to the range of the target reinforcement area, arrange the grouting holes with an interval of 1.5~2.0 m, the annular arrangement angle of the grouting drill hole is 15°~30°, the drill hole subsection length is 3~5 m, the grouting hole depth penetrates the fine sand layer and enters the stable stratum 0.5 m; insert the grouting pipe into the grouting hole to the designed depth, seal the hole with the stopper, and ensure the stability of the grouting pressure.

[0042] Step six, according to the slurry and the proportioning determined in step four, the coarse particle zone, the medium particle zone and the fine particle zone are sequentially grouted and reinforced as shown in Figure 3 ; and the grouting pressure is controlled to be not greater than 2.0 MPa, the grouting flow is controlled to be not greater than 30 L / min, and the single-hole grouting amount is 1.5-3.0 m 3 .

[0043] Step seven, during the grouting of each zone, the grouting pressure, flow and amount are monitored in real time, and if the termination condition of grouting is met, the grouting of the zone is completed, specifically, the grouting flow control is mainly used and the grouting amount control is used as a supplement, when the grouting flow of a certain zone is less than 2 L / min or the grouting amount reaches 1.2 times of the designed grouting amount of the zone and the grouting flow is less than 6 L / min, the grouting is terminated. During the grouting process, according to the deviation of the actual particle size from the designed reference particle size in a certain zone, the proportioning of the composite slurry in the zone is dynamically adjusted, so that the actual particle size after grouting is as close as possible to the designed reference particle size, specifically,

[0044] When it is detected that the actual particle size of a certain zone deviates from the designed reference particle size by ≥10%, the dynamic adjustment is triggered, and the specific adjustment method is as follows: when the actual particle size is less than the designed reference particle size, the use amount of the slurry with strong permeability in the composite slurry is increased based on the initial proportioning; when the actual particle size is greater than the designed reference particle size, the use amount of the slurry with strong permeability in the composite slurry is reduced based on the initial proportioning; the calculation formula of the specific adjustment amount is:

[0045] ;

[0046] In the formula, is the adjustment amount of the current zone; d i is the actual particle size of the current zone, d i0 is the designed reference particle size of the current zone, Q 总 is the designed grouting amount of the current zone; k is an adjustment coefficient, and is taken as 0.03-0.05.

[0047] In order to ensure the safety of the grouting process, the settlement observation points and the vertical displacement observation points are arranged above the surface of the grouting and reinforcement zone and around the adjacent buildings, the tunnel permanent monitoring section and the newly buried lining convergence observation points are arranged, the ground deformation is monitored through the surface settlement observation points and the tunnel convergence observation points, and if there is an abnormality, the grouting is stopped in time.

[0048] Step eight, after grouting all the areas, evaluate the grouting reinforcement effect through geophysical exploration, the evaluation methods include but are not limited to water pressure test, drilling core, drilling television, geophysical exploration technology, elastic wave test; if the requirement is met, the grouting work of the target reinforcement area is completed; if the requirement is not met, repeat steps five to seven to grout again until the requirement is met, and the grouting work of the target reinforcement area is completed.

[0049] Example 1: subway tunnel passes through composite fine sand layer.

[0050] A subway tunnel is 8 m deep, and the collapse of the fine sand layer is exposed at the tunnel face, with the risk of water and mud bursting. In the early stage, cement slurry was used for grouting reinforcement treatment. During construction, it was found that the fine sand layer was dense, the grouting treatment effect was poor, and the construction progress was slow. Therefore, the above-mentioned grouting method of the application is used for treatment.

[0051] Firstly, collect the geotechnical investigation data and related design documents, and determine the main location of the fine sand layer in the area 15 m in front of the tunnel face through the drilling core results and the collapse of the fine sand layer, form a preliminary grouting construction scheme, determine to use advanced curtain grouting, and the grouting reinforcement area is within the area within the contour line 2 m outside the tunnel. The grouting holes are arranged at a ring spacing of 1.5 m and a hole bottom spacing of 2.0 m, and the drilling depth penetrates the fine sand layer and enters the stable stratum 0.5 m.

[0052] The particle size distribution of the fine sand layer is analyzed by geological drilling core analysis and the porosity is measured. The reinforcement area is divided into coarse particle area (volume 600 m 3 , average particle size 0.6 mm, porosity 38%) and fine particle area (volume 400 m 3 , average particle size 0.1 mm, porosity 30%).

[0053] The coarse particle area selects ordinary cement slurry (water-cement ratio W / C=0.8) and ultra-fine cement slurry (particle size 5 μm, W / C=1.0) for collaborative grouting at a volume ratio of 6:4; the fine particle area adopts polyurethane (A:B=1:1) and acrylate (A:B=1:1) chemical slurry for composite grouting at a volume ratio of 7:3. The design grouting amount of the coarse particle area is calculated as 326.0 m 3 (Q=1.3×600×0.38×1.1), and the design grouting amount of the fine particle area is calculated as 171.6 m 3 (Q=1.3×400×0.30×1.1).

[0054] During the grouting construction process, the grouting pressure is controlled within 1.5 MPa, and the grouting flow is controlled within 30 L / min.

[0055] The actual average particle size of the fine particle zone was monitored during the grouting process, which was 0.07 mm (the design reference particle size was 0.1 mm), triggering the dynamic adjustment formula ΔQ = 0.05 × |0.07-0.1| / 0.1 × 171.6 = 2.6 m 3 , the proportion of polyurethane was reduced to 68.5% (117.5 m 3 ), and the proportion of acrylate was increased to 31.5% (54.1 m 3 ).

[0056] During the grouting process, settlement observation points and vertical displacement observation points were arranged on the surface above the target grouting reinforcement area and around the adjacent buildings. Every 10 m, an observation point was arranged. Six convergence observation points (top arch center line, left arch abutment, right arch abutment, left side wall, right side wall) were observed at the tunnel permanent monitoring section and newly buried lining side wall. Analyze the ground monitoring data and feedback to adjust the grouting parameters. When the maximum uplift value caused by grouting exceeds 2 mm, the designed grouting amount should be reduced. The actual maximum uplift value of the ground is less than 2 mm, so the single-hole grouting amount is not adjusted. After reaching the grouting termination condition, grouting is terminated. After grouting is completed, the blockage is released, the pipe is pulled out and the hole is swept, and the two water inlet pipes of the grouting pump are taken out and washed with clean water to prevent pipe blockage caused by slurry solidification.

[0057] After the slurry solidifies and the strength of the reinforced body grows, the grouting hole is subjected to water pressure test, core drilling and borehole television to test the permeability coefficient of the reinforced fine sand layer and analyze the grouting reinforcement effect. The measured compressive strength of the reinforced coarse particle zone is 4.8 MPa, the permeability coefficient is 5×10 -6 cm / s, the compressive strength of the fine particle zone is 3.6 MPa, and the permeability coefficient is 2×10 -7 cm / s, meeting the requirements, and the material cost is reduced by 38% and the construction period is shortened by 15 days.

[0058] Example 2: Crossing composite particle size fine sand layer of a river-crossing tunnel.

[0059] A certain river-crossing tunnel crosses a composite particle size fine sand layer with a thickness of 50 m, and there are coarse particle zones (volume 800 m 3 , d=0.8 mm, n=30%), medium particle zones (volume 1200 m 3 , d=0.3 mm, n=35%) and fine particle zones (volume 1000 m 3, d = 0.06 mm, n = 40%) three types of strata. The grouting holes are arranged in a quincunx shape with a ring spacing of 1.2 m and a hole bottom spacing of 1.8 m, and the drilling section length is 6 m. In the coarse particle zone, ordinary cement slurry (W / C = 1.0) and ultra-fine cement slurry (particle size 8 μm, W / C = 1.2) are grouted in a volume ratio of 7:3; in the medium particle zone, ultra-fine cement-water glass double slurry (C:S = 1:1) and acrylic ester chemical slurry (A:B = 1:1) are compounded in a volume ratio of 8:2; and in the fine particle zone, epoxy resin chemical slurry and acrylic ester chemical slurry (A:B = 1:1) are synergistically grouted in a volume ratio of 5:5.

[0060] The design grouting amount of each area is calculated: the coarse particle zone is 288 m 3 (Q1 = 1.2 x 800 x 0.30 x 1.0 = 288 m 3 ), the medium particle zone is 504 m 3 (Q2 = 1.2 x 1200 x 0.35 x 1.0 = 504 m 3 ), and the fine particle zone is 480 m 3 (Q3 = 1.2 x 1000 x 0.4 x 1.0 = 480 m 3 ). During grouting, the actual particle size d = 1.2 mm (design reference particle size d0 = 0.8 mm) is detected in the coarse particle zone, triggering adjustment ΔQ1 = 0.05 x |1.2-0.8| / 0.8 x 288 = 7.2 m 3 , so the proportion of ordinary cement slurry is increased from 70% to 72.5%; the actual particle size d = 0.03 mm (design reference particle size d0 = 0.06 mm) is detected in the fine particle zone, ΔQ3 = 0.05 x |0.03-0.06| / 0.06 x 480 = 12 m 3 , and the proportion of acrylic ester is increased to 52.5%. The grouting pressure is controlled in stages: ≤2.0 MPa in the coarse particle zone, ≤1.8 MPa in the medium particle zone, and ≤1.5 MPa in the fine particle zone, and the grouting flow is limited to 30 L / min.

[0061] After reinforcement, the compressive strength of the coarse particle zone is 4.1 MPa, the permeability coefficient is 3 x 10 -6 cm / s, the compressive strength of the medium particle zone is 3.3 MPa, the permeability coefficient is 5 x 10 -7 cm / s, the compressive strength of the fine particle zone is 2.5 MPa, and the permeability coefficient is 8 x 10 -8 cm / s, meeting the requirements, and the comprehensive material cost is reduced by 41%, and the permeation radius is increased by 60% compared with the traditional process.

[0062] The above merely describes the preferred embodiments of the present application, and it should be pointed out that those skilled in the art can make several improvements and refinements without departing from the principles of the present application, and these improvements and refinements should also be considered as the protection scope of the present application.

Claims

1. A method for layered permeation grouting of fine sand layers based on dynamic proportion control, characterized in that, Includes the following steps: Step 1: Based on the geotechnical investigation data and relevant design documents, determine the target reinforcement area of ​​the silty fine sand layer in front of the tunnel face; then, determine the particle size distribution and porosity of the target reinforcement area by core sampling through geological drilling. Step 2: Based on the particle size distribution, divide the target reinforcement area into coarse particle area, medium particle area and fine particle area, and determine the volume of each area; Step 3: Calculate the design grouting volume for each region based on its volume and porosity; Step 4: Based on the division in Step 2, determine the corresponding composite grout for each area. The composite grout is made by mixing a grout with strong permeability and a grout with weak permeability, and determine the design reference particle size after grouting in each area. Step 5: Install grouting holes and grouting pipes in the target reinforcement area; Step 6: Based on the grout and mix ratio determined in Step 4, perform grouting reinforcement on the coarse-particle zone, medium-particle zone, and fine-particle zone in sequence. Step 7: During the grouting process in each area, monitor the grouting pressure, flow rate, and grouting volume in real time. If the grouting termination conditions are met, the grouting of that area is completed. Furthermore, during the grouting process, if the actual particle size in a certain area deviates from the design reference particle size by ≥10%, dynamically adjust the ratio of the composite grout for that area. The specific adjustment method is as follows: when the measured particle size is smaller than the design reference particle size, increase the amount of highly permeable grout in the composite grout based on the initial ratio; when the measured particle size is larger than the design reference particle size, decrease the amount of highly permeable grout in the composite grout based on the initial ratio. This ensures that the measured particle size after grouting is as close as possible to the design reference particle size. Step 8: After completing grouting in all areas, evaluate the grouting reinforcement effect through geophysical exploration. If the required requirements are met, the grouting work in the target reinforcement area is completed; if the required requirements are not met, repeat steps 5 to 7 to perform grouting reinforcement again until the requirements are met and the grouting work in the target reinforcement area is completed.

2. The method for layered penetration grouting of fine sand layers based on dynamic proportion control according to claim 1, characterized in that, The specific classification criteria in step two are as follows: particles with a diameter d ≥ 0.5 mm are defined as coarse particles; particles with a diameter 0.1 < d < 0.5 mm are defined as medium particles; and particles with a diameter d ≤ 0.1 mm are defined as fine particles.

3. The method for layered penetration grouting of fine sand layers based on dynamic proportion control according to claim 1, characterized in that, The specific formula for designing the grouting volume in step three is as follows: Q 总 =α·V·n·β In the formula, Q 总 V is the design grouting volume for the current area; n is the volume of the current area; α is the loss coefficient; β is the density correction coefficient.

4. The method for layered penetration grouting of fine sand layers based on dynamic ratio control according to claim 1, characterized in that, In step four, each region is assigned a corresponding composite slurry. Specifically, the coarse-particle region uses ordinary cement slurry and ultrafine cement slurry with an initial ratio of 6:4; the medium-particle region uses ultrafine cement slurry and cement-water glass dual-liquid slurry with an initial ratio of 7:3; and the fine-particle region uses polyurethane chemical slurry and acrylic chemical slurry with an initial ratio of 5:

5.

5. The method for layered penetration grouting of fine sand layers based on dynamic proportion control according to claim 1, characterized in that, Step five specifically involves: arranging grouting holes at a spacing of 1.5 to 2.0 m according to the target reinforcement area, with the grouting hole depth penetrating the fine sand layer and entering the stable stratum by 0.5 m; inserting the grouting pipe into the grouting hole to the designed depth, and sealing the hole opening with a plug to ensure stable grouting pressure.

6. The method for layered penetration grouting of fine sand layers based on dynamic proportion control according to claim 1, characterized in that, During the grouting reinforcement process in step six, the grouting pressure should be controlled to be no greater than 2.0 MPa and the grouting flow rate should be no greater than 30 L / min.

7. The method for layered penetration grouting of fine sand layers based on dynamic proportion control according to claim 1, characterized in that, The termination condition in step seven is as follows: with grouting flow rate control as the main factor and grouting volume control as the secondary factor, grouting is terminated when the grouting flow rate in a certain area is less than 2 L / min, or when the grouting volume reaches 1.2 times the designed grouting volume in that area and the grouting flow rate is less than 6 L / min.

8. The method for layered penetration grouting of fine sand layers based on dynamic proportion control according to claim 1, characterized in that, The specific calculation formula for adjusting the amount of slurry in step seven is as follows: In the formula: Adjustment amount for the current region; d i d represents the measured particle size of the current region. i0 Q is the design baseline particle size for the current region. 总 is the design grouting volume for the current area; k is the adjustment coefficient.

9. The method for layered penetration grouting of fine sand layers based on dynamic proportion control according to claim 1, characterized in that, During the grouting process in step seven, the deformation of the strata is monitored through surface settlement observation points and tunnel convergence observation points. If any abnormality is found, grouting is stopped immediately.

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