Design method of tunnel-soil body rigidity coordinated soft stratum classification and partition reinforcement system

Abstract

The invention relates to a tunnel-soil body rigidity coordinated soft stratum classification and partition reinforcing system design method which is suitable for reinforcing soft stratums around a proposed tunnel and an existing tunnel. According to the method, a double-pipe jet grouting pile and a ground sleeve valve pipe grouting technology are combined, and a reinforcing area is divided into a resistance area and a stress blocking area. The resistance areas are located on the two sides of the tunnel, horizontal resistance is provided through inclined gridding pile distribution, and stress release caused by excavation is reduced. The range is determined according to a beam-spring model constructed according to shield construction parameters, and the reinforcing width and depth are optimized through rigidity coordination of a tunnel and a resistance area; the stress blocking area is located outside the resistance area and aims at blocking additional dynamic and static stress transmission and optimizing mechanical response, and the range of the stress blocking area is determined by the soft stratum proportion and the resistance coefficient. The method makes up for the theoretical defects of the prior art, provides a safe and efficient reinforcing system for the tunnel to be built around the existing tunnel, ensures the stability and normal operation of the tunnel structure, and has wide engineering application prospects.

Description

Technical Field

[0001] The invention relates to the technical field of soft stratum reinforcement, and in particular to a design method for a soft stratum classification and zoning reinforcement system with coordinated tunnel-soil stiffness. Background Art

[0002] As my country's urban modernization process accelerates, urban population density increases, and traffic pressure intensifies. In order to ease traffic congestion, more and more cities are expanding transportation resources by building subways. However, when the proposed subway tunnel is located in soft strata and needs to cross over an existing tunnel, the construction will face severe technical challenges.

[0003] On the other hand, when building tunnels in soft strata, the high water content, high compressibility, high sensitivity, low strength, low density, and low permeability of the soil may lead to serious geological problems. In particular, when shield construction crosses over existing tunnels, it may cause redistribution of stratum stress, resulting in displacement, settlement, or even damage to the existing tunnel. In addition, construction disturbances may cause deformation of the surrounding strata, affecting the stability of the existing tunnel. If the settlement exceeds the safety range, the normal operation of the existing tunnel will be at risk. During long-term operation, the dynamic stress of the train is transmitted through the soft strata. Since the soft strata have poor absorption capacity for dynamic stress, the dynamic load may accumulate over a long period of time, posing a threat to the structural safety of the existing tunnel.

[0004] Existing soft strata reinforcement technology has been applied to control strata settlement and deformation. The Chinese invention patent with application number 201810721619.X discloses a reinforcement structure and method for a soft soil, water-rich, large-section tunnel group underpass structure, including existing structures above the tunnel and dark-cut tunnel group structure below it; the invention is conducive to the safe construction of dark-cut tunnels, and is also very effective in controlling the settlement and deformation of structures above the tunnels. However, when the proposed tunnel crosses the existing tunnel, the effectiveness of the reinforcement scheme of the above invention is insufficient, which may cause settlement or deformation of the existing tunnel. A Chinese invention patent with application number 201811258850.6 discloses a ground reinforcement system and method for reinforcing an existing tunnel, including a tunnel and pull-out piles. A plurality of pull-out piles arranged in rows are provided on both sides of the tunnel, thereby improving the reinforcement of the existing tunnel. However, the reinforcement technology of the invention focuses on the static control of the ground during construction, and does not fully consider the long-term transmission effect of the dynamic stress of the train during the operation of the tunnel, which may cause a cumulative impact on the structural stability of the existing tunnel and increase safety hazards.

[0005] Therefore, the existing technology still has obvious limitations in dealing with the construction of the proposed tunnel and ensuring the safety during the operation period. An effective soft stratum reinforcement technology is urgently needed to improve the bearing capacity of the foundation, reduce the settlement and deformation of the stratum during construction and operation, and ensure the safety and normal operation of the proposed and existing tunnels. Summary of the invention

[0006] In view of the above problems, the present invention provides a design method for a soft stratum classification and zoning reinforcement system with coordinated tunnel-soil stiffness.

[0007] The technical solution of the present invention is as follows: A design method for a tunnel-soil stiffness coordinated soft stratum classification and zoning reinforcement system comprises the following steps: Step 1: Obtain the stratigraphic profile parameters of the proposed tunnel and the existing tunnel based on the geological survey data; obtain the design parameters of the proposed tunnel based on the construction design data; Step 2: Based on the design parameters of the proposed tunnel obtained in step 1, determine the reinforcement range of the reinforcement system along the longitudinal direction of the proposed tunnel according to the design direction of the proposed tunnel and the direction of the existing tunnel; the reinforcement system divides the reinforcement area into a "resistance zone" and a "stress isolation zone", where: The resistance zone is located on both sides of the tunnel. The horizontal resistance is provided by inclined grid piles to reduce the stress release caused by excavation. Its range is determined by the beam-spring model constructed based on the shield construction parameters. The reinforcement width and depth are optimized by coordinating the stiffness of the tunnel and the resistance zone. The stress isolation zone is located outside the resistance zone, aiming to isolate the transmission of additional dynamic and static stresses and optimize the mechanical response. Its range is determined by the proportion of weak formations and the resistance coefficient. Step 3: Based on the stratum profile parameters obtained in step 1, determine the reinforcement depth of the resistance zone in the reinforcement system according to the proportion of soft soil layers in the stratum where the proposed tunnel is located. H k and reinforcement depth of stress isolation area H y ; Step 4: Construct a beam-spring model based on the tunnel design parameters obtained in step 1 to simulate the cross-sectional deformation of the tunnel structure; Step 5: Based on step 4, change the surrounding loading and unloading conditions to obtain the changes in the lateral convergence deformation of the tunnel structure as the two sides of the proposed tunnel arch are located within the scope of the reinforcement system, and then determine the layout position and lateral range of the resistance zone on both sides of the proposed tunnel arch L k ; Step 6: Based on step 5, according to the tunnel stiffness of the proposed tunnel K 1 and resistance zone stiffness K k Adjust the lateral extent of the resistance zone L k2 and reinforcement depth H k2 ; Step 7: Obtain the resistance coefficient Δ( Q), determine the relationship between the width of the stratum reinforcement on both sides of the proposed tunnel and the resistance it can provide, and determine the lateral range of the stress isolation zone L y .

[0008] Furthermore, in step 1, the stratigraphic profile parameters of the proposed tunnel and the existing tunnel at the location obtained from the geological survey data include the horizontal stratification of the strata and the weight of each soil layer. γ , compression modulus E, Poisson's ratio μ , base bed coefficient m , Cohesion c and internal friction angle φ .

[0009] Furthermore, in step 1, the design parameters of the proposed tunnel obtained from the construction design data include the tunnel burial depth H , Lining outer diameter , Lining inner diameter , Lining width and design trends.

[0010] Furthermore, in the step 2, according to the design direction of the proposed tunnel and the direction of the existing tunnel, the overlapping section of the proposed tunnel and the existing tunnel and the section 50 m before and after should be set as the ground grouting reinforcement range.

[0011] Furthermore, in the step three, the definition of soft soil layers may include clay layers in soft plastic and fluid plastic states, sand layers in loose states, and fill and highly compressible soil layers that have not been treated in any way. According to the proportion of soft soil layers in the stratum where the proposed tunnel is located, the longitudinal reinforcement section of the upper span interval is divided into two categories: half-section reinforcement and full-section reinforcement.

[0012] Furthermore, in the step 3, the half-section reinforcement adopts double-tube rotary jet piles, and the reinforcement depth is 2 m below the half-section of the proposed tunnel; the full-section reinforcement adopts double-tube rotary jet piles combined with the reinforcement measures of the ground sleeve valve pipe, and the reinforcement depth is 2 m below the soft soil layer. The reinforcement systems of the above two types of sections are divided into resistance zone and stress isolation zone, that is, the reinforcement depth of the resistance zone of the half-section reinforcement section H k and stress isolation area reinforcement depth H y The reinforcement depth of the resistance zone of the proposed tunnel is 2m below the half section and the full section reinforcement section. H k and stress isolation area reinforcement depth H y It is 2m below the soft soil layer.

[0013] Furthermore, in step four, the main section model of the tunnel segment is simplified into a beam unit, springs are used to simulate the force between the soil and the tunnel structure, a spring model is used to simulate the internal force and deformation of the tunnel structure, an elastic foundation beam method is used to analyze the internal force of the tunnel structure, and a beam-spring model is constructed using finite element software.

[0014] Furthermore, in step 4, the axial stiffness of the spring is determined K s and tunnel structure loads, specifically: The spring axial stiffness K s for: in, m is the elastic base coefficient of the surrounding rock around the proposed tunnel. For the resistance zone on both sides of the arch waist of the proposed tunnel, it is taken as the base coefficient of the reinforced soil layer. m k , the base bed coefficient of the soft soil layer is taken in the area around the tunnel except the arch waist; s It is 1 / 2 of the sum of the lengths of adjacent lining units.

[0015] The tunnel structure load includes vertical earth pressure P 1. Horizontal soil pressure and lining deadweight G and foundation reaction P v Four parts, including: The vertical soil pressure is: The horizontal earth pressure includes the horizontal earth pressure at the top of the tunnel Q 1 and the horizontal earth pressure at the bottom of the tunnel Q 1 +Q 2, where: The deadweight of the lining is: The foundation reaction force is: In the formula, P 0 is the ground load, K 0 is the static lateral pressure coefficient of the surrounding soil layer, γ h The tunnel lining is heavy.

[0016] Furthermore, in step 5, the horizontal arrangement position of the first row of jet grouting piles in the resistance zone adjacent to the center line of the proposed tunnel is through the central angle of the tunnel located in the resistance zone on both sides of the arch waist. In the beam-spring model, by changing the static lateral pressure coefficient of the soil layer around the proposed tunnel K 0Simulate the loading and unloading conditions around the tunnel to obtain different tunnel center angles The corresponding lateral convergence deformation is then used to determine the horizontal layout position of the resistance zone when the lateral convergence meets the reinforcement design requirements.

[0017] Lateral extent of the resistance zone L k The calculation formula is: Furthermore, in step 6, according to the stiffness of the proposed tunnel K 1 and the equivalent stiffness of the resistance zone K k Adjusted lateral range of resistance zone L k2 and reinforcement depth H k2 They are: in, K 1 is the stiffness of the proposed tunnel, which can be obtained from the construction design data in step 1. K k is the stiffness of the resistance zone, that is ; and They are correction coefficients for lateral range and reinforcement depth, respectively, and are determined based on relevant engineering experience.

[0018] Furthermore, in step 7, the resistance exertion coefficient Δ( Q ) and the horizontal reinforcement width of the stress isolation area L y It is related to the degree of reinforcement, which can be expressed as: When the resistance coefficient Δ( Q ) = 1, the minimum horizontal reinforcement width of the stress isolation area can be obtained L y_min : Compared with the prior art, the present invention has the following advantages and beneficial effects: 1. Through theoretical derivation combined with simplified numerical analysis, the present invention has developed a classification and zoning reinforcement system design method suitable for soft strata. This method is based on solid theoretical support, is easy to operate, and has higher efficiency and accuracy than traditional engineering judgment and complex numerical simulation.

[0019] 2. The tunnel-soil stiffness coordinated soft stratum classification and zoning reinforcement system design method provided by the present invention can effectively ensure the structural safety and normal operation of the planned and existing tunnels. Its design scheme has strong engineering applicability, not only can it meet the deformation control requirements of shield construction, but also can significantly reduce the subsequent construction costs, and has wide potential for promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of a tunnel-soil stiffness coordinated soft stratum classification and zoning reinforcement system of the present invention.

[0021] Figure 2 The present invention is a flowchart of the steps of a design method for a soft stratum classification and zoning reinforcement system with coordinated tunnel-soil stiffness.

[0022] Figure 3 This is a schematic diagram of the classification and zoning of the longitudinal reinforcement section of the proposed tunnel in the embodiment.

[0023] Figure 4 Schematic diagram of a beam-spring model constructed according to tunnel design parameters in the embodiment.

[0024] Figure 5 Schematic diagram of tunnel structure load calculation in the beam-spring model constructed in the embodiment.

[0025] Figure 6 : is the relationship between the lateral convergence deformation of the tunnel structure and the central angle of the tunnel located in the reinforced soil in the embodiment.

[0026] Figure 7 Schematic diagram of the value of the tunnel center angle in the embodiment where the tunnel structure is located in the reinforced soil.

[0027] Figure 8 It is a schematic diagram of the design of the soft stratum classification and zoning reinforcement system with coordinated tunnel-soil stiffness in the embodiment. DETAILED DESCRIPTION

[0028] The technical solution provided by the present application will be further described below in conjunction with specific embodiments and accompanying drawings. The advantages and features of the present application will become more apparent with the following description.

[0029] Example: A proposed subway line crosses over an existing operating line. The distance between the left and right lines of the proposed subway line is 15.3 - 17.2 m, the diameter of the tunnel is 6 m, and it crosses over the existing operating line at an angle of 8° to 17°. The buried depth of the proposed subway line tunnel is 7 -9 m, and the buried depth of the existing line tunnel is 15 - 17 m. The minimum vertical clearance between the proposed tunnel and the existing tunnel is only 2.0 m, and the length of the overlapping section with a vertical clearance of less than 3.0 m is about 70 m. The strata where the tunnel is located mainly include miscellaneous fill, silt, silty clay and sand. In order to ensure the construction safety during the excavation of the proposed shield tunnel and the normal operation of the existing line, this method is used to carry out classified and zoned reinforcement measures for the strata around the proposed and existing tunnels to coordinate the stiffness of the tunnel and soil, such as Figure 1 , Figure 2 As shown, the specific steps include: Step 1: Obtain the stratigraphic profile parameters of the proposed tunnel and the existing tunnel based on geological survey data; obtain the design parameters of the proposed tunnel based on construction design data.

[0030] Step 2: Based on the design parameters of the proposed tunnel obtained in step 1, determine the reinforcement range of the reinforcement system along the longitudinal direction of the proposed tunnel according to the design direction of the proposed tunnel and the direction of the existing tunnel; the reinforcement system divides the reinforcement area into a "resistance zone" and a "stress isolation zone", where: The resistance zone is located on both sides of the tunnel. The horizontal resistance is provided by inclined grid piles to reduce the stress release caused by excavation. Its range is determined by the beam-spring model constructed based on the shield construction parameters. The reinforcement width and depth are optimized by coordinating the stiffness of the tunnel and the resistance zone. The stress isolation zone is located outside the resistance zone, aiming to isolate the transmission of additional dynamic and static stresses and optimize the mechanical response. Its range is determined by the proportion of soft formations and the resistance coefficient.

[0031] Step 3: Based on the stratum profile parameters obtained in step 1, determine the reinforcement depth of the resistance zone in the reinforcement system according to the proportion of soft soil layers in the stratum where the proposed tunnel is located. H k and reinforcement depth of stress isolation area H y .

[0032] Step 4: Construct a beam-spring model based on the tunnel design parameters obtained in step 1 to simulate the cross-sectional deformation of the tunnel structure.

[0033] Step 5: Based on step 4, change the surrounding loading and unloading conditions to obtain the changes in the lateral convergence deformation of the tunnel structure as the two sides of the proposed tunnel arch are located within the scope of the reinforcement system, and then determine the layout position and lateral range of the resistance zone on both sides of the proposed tunnel arch L k .

[0034] Step 6: Based on step 5, according to the tunnel stiffness of the proposed tunnel K 1 and resistance zone stiffness K k Adjust the lateral extent of the resistance zone L k2 and reinforcement depth H k2 .

[0035] Step 7: Obtain the resistance coefficient Δ( Q ), determine the relationship between the width of the stratum reinforcement on both sides of the proposed tunnel and the resistance it can provide, and determine the lateral range of the stress isolation zone L y .

[0036] Step 1 specifically includes the following sub-steps: (1) The stratigraphic parameters of the proposed tunnel and the existing tunnel were obtained based on the geological survey data: the proposed tunnel is located in the silt reclamation stratum, with the underlying strata consisting of silt and sandy clay; the existing operating line tunnel is located in the sandy clay and fully weathered gneissic mixed granite, with the underlying strata consisting of sandy clay and fully weathered gneissic mixed granite. The interlayer between the proposed tunnel and the existing tunnel is mainly composed of organic sand, silt and plastic sandy clay. The density of each soil layer is 2.34 kg / m2. γ , compression modulus E, Poisson's ratio μ , base bed coefficient m , Cohesion c and internal friction angle φ See Table 1 below.

[0037] Table 1 Physical and mechanical parameters of each stratum (2) Obtain the design parameters of the proposed tunnel based on the construction design data: the proposed tunnel burial depth H is 7-9 m; the outer diameter of the lining = 6 m, inner diameter of lining = 5.4 m, lining width = 1.5 m. The proposed tunnel will cross the existing tunnel at an angle of 8° to 17°, and there will be an overlapping section within the mileage range of DK17+77.87 to DK17+268.17.

[0038] Step 2 specifically includes the following: According to the directions of the proposed tunnel and the existing tunnel, the section within the mileage range of DK17+27 ~ DK17+318 of the proposed tunnel is set as the ground grouting reinforcement treatment range.

[0039] Step 3 specifically includes the following: (1) Classification of reinforcement sections: Silt, muddy clay, organic sand, medium sand and coarse sand within the proposed tunnel area are classified as soft soil layers. According to the proportion of soft soil layers in the stratum where the proposed tunnel is located, the ground grouting reinforcement section DK17+27 to DK17+318 is divided into two categories: half-section reinforcement and full-section reinforcement. Figure 3 As shown, specifically: DK17+27 ~DK17+114.3 are half-section reinforcements, and DK17+114.3 ~ DK17+318 are full-section reinforcements.

[0040] (2) Regional stratum reinforcement measures: The above-mentioned half-section reinforcement adopts double-tube jet grouting piles, and the reinforcement depth is 2 m below the half-section of the proposed tunnel. The full-section reinforcement adopts double-tube jet grouting piles combined with ground sleeve valve pipe reinforcement measures, and the reinforcement depth is 2 m below the soft soil layer. The reinforcement systems of the above two types of sections are divided into resistance zones and stress isolation zones, that is, the reinforcement depth of the resistance zone of the half-section reinforcement section is H k and stress isolation area reinforcement depth H y The reinforcement depth of the resistance zone of the proposed tunnel is 2m below the half section and the full section reinforcement section. H k and stress isolation area reinforcement depth H y It is 2m below the soft soil layer.

[0041] Step 4 specifically includes the following: (1) Establishing the beam-spring model: Based on the tunnel design parameters obtained in step 1, construct the beam-spring model as shown in the attached figure. Figure 4 As shown in the figure, the main section model of the tunnel segment is simplified into a beam unit, the spring is used to simulate the force between the soil and the tunnel structure, the local spring model is used to simulate the internal force and deformation of the tunnel structure, the elastic foundation beam method is used to analyze the internal force of the tunnel structure, and the above beam-spring model is constructed by finite element software. The soil resistance effect is not considered in the above tunnel structure load calculation.

[0042] (2) Determine the axial stiffness of the spring K s : (3) The tunnel structure load includes vertical earth pressure P 1. Horizontal soil pressure and lining deadweight G and foundation reaction P v Four parts, as attached Figure 5 As shown in the picture.

[0043] Since there is no surface load, P 0 = 0, severe γ The value is 18 (according to the geological survey data, there are miscellaneous fill and silt above the tunnel, so the embodiment is heavy γ The value is 18), the tunnel depth H is 8, then the vertical soil pressure P 1 is: in, K 0 takes the value of 0.6, then: The horizontal earth pressure at the top of the tunnel is: Q 1=86.4kPa The horizontal earth pressure at the bottom of the tunnel is: Q 1 +Q 2 = 86.4 + 64.8 = 151.2 kPa in, γ h The value is 25, the lining weight G for: Among them, the foundation reaction P v for: The specific contents of step five are as follows: (1) Analysis of the lateral convergence deformation of the proposed tunnel: The lateral convergence deformation of the proposed tunnel is based on the beam-spring model in step 4 by changing the static lateral pressure coefficient of the soil layer around the proposed tunnel. K 0Simulate the loading and unloading situation around the tunnel. Figure 6 Shows the base coefficient of the reinforced soil m = 20 MPa / m, static side pressure coefficient K When 0 = 0.6, the lateral convergence deformation of the tunnel structure of the proposed tunnel changes with the central angle of the tunnel located in the resistance zone on both sides of the arch waist. of changes.

[0044] (2) Determine the horizontal layout position of the resistance zone: According to the construction requirements, in order to control the lateral convergence deformation of the tunnel to less than 10 mm, the central angle of the tunnel on both sides of the arch waist within the resistance zone is Should not be less than 50°. Figure 7 At this time, the horizontal layout position of the first row of jet grouting piles in the resistance zone near the tunnel centerline can be determined by the central angle of the tunnel on both sides of the arch waist in the resistance zone. By reverse calculation, it is 2.7 m away from the tunnel centerline. Figure 8 shown.

[0045] (3) Determine the lateral extent of the resistance zone Lk , to facilitate construction guidance, only one decimal place is retained: The specific contents of step six are as follows: According to the design parameters of the proposed tunnel in step 1, the stiffness of the tunnel can be known. K 1 is about 35MN / m, and the stiffness of the resistance zone can be Obtain, in accordance with the geological conditions of this project, the correction coefficient and Taken as 0.3 and 0.35 respectively. According to the coordination of the stiffness of the tunnel and the resistance zone, the lateral range of the adjusted resistance zone L k2 and reinforcement depth H k2 They are: The specific contents of step seven are as follows: Minimum horizontal width of stress barrier area L y_min : To facilitate construction guidance, the reinforcement depth of the stress isolation area is consistent with that of the resistance area, and the lateral range of the stress isolation area is L y Take it as 2.6 m.

[0046] In summary, in this case, a half-section reinforcement scheme mainly based on double-tube jet grouting piles is adopted in the range of DK17+27 ~ DK17+114.3, and the reinforcement depth is 2.6 m below the half-section of the proposed tunnel; a full-section reinforcement scheme of double-tube jet grouting piles combined with ground sleeve valve pipes is adopted in the range of DK17+114.3 ~ DK17+318, and the reinforcement depth is 2.6 m below the coarse sand layer. The reinforcement width of the outer side of the proposed double-line tunnel (the left side of the left-line tunnel and the right side of the right-line tunnel) is 7.3 m, of which the horizontal reinforcement width of the resistance zone is 4.7 m, and the horizontal reinforcement width of the stress isolation zone is 2.6 m; the horizontal reinforcement width of the stress isolation zone in the middle area of ​​the proposed double-line tunnel is obtained by subtracting the width of the resistance zone from the actual left and right tunnel interval, specifically 1.6 m, as shown in the attached figure. Figure 8 shown.

[0047] The above description is only a description of the preferred embodiments of the present application, and is not intended to limit the scope of the present application. Any changes or modifications made by any person skilled in the art based on the above disclosed technical contents shall be deemed as equivalent effective embodiments and shall fall within the scope of protection of the technical solution of the present application.

Claims

1. A design method for a soft stratum classification and zoning reinforcement system with coordinated tunnel-soil stiffness, characterized in that: The following steps are involved: Step 1: Obtain the stratigraphic profile parameters of the proposed tunnel and the existing tunnel based on the geological survey data; obtain the design parameters of the proposed tunnel based on the construction design data; Step 2: Based on the design parameters of the proposed tunnel obtained in step 1, determine the reinforcement range of the reinforcement system along the longitudinal direction of the proposed tunnel according to the design direction of the proposed tunnel and the direction of the existing tunnel; the reinforcement system divides the reinforcement area into a "resistance zone" and a "stress isolation zone", where: The resistance zone is located on both sides of the tunnel. The horizontal resistance is provided by inclined grid piles to reduce the stress release caused by excavation. Its range is determined by the beam-spring model constructed based on the shield construction parameters. The reinforcement width and depth are optimized by coordinating the stiffness of the tunnel and the resistance zone. The stress isolation zone is located outside the resistance zone, aiming to isolate the transmission of additional dynamic and static stresses and optimize the mechanical response. Its range is determined by the proportion of weak formations and the resistance coefficient. Step 3: Based on the stratum profile parameters obtained in step 1, determine the reinforcement depth of the resistance zone in the reinforcement system according to the proportion of soft soil layers in the stratum where the proposed tunnel is located. H k and reinforcement depth of stress isolation area H y ; Step 4: Construct a beam-spring model based on the tunnel design parameters obtained in step 1 to simulate the cross-sectional deformation of the tunnel structure; Step 5: Based on step 4, change the surrounding loading and unloading conditions to obtain the changes in the lateral convergence deformation of the tunnel structure as the two sides of the proposed tunnel arch are located within the scope of the reinforcement system, and then determine the layout position and lateral range of the resistance zone on both sides of the proposed tunnel arch L k ; Step 6: Based on step 5, according to the tunnel stiffness of the proposed tunnel K 1 and resistance zone stiffness K k Adjust the lateral extent of the resistance zone L k2 and reinforcement depth H k2 ; Step 7: Obtain the resistance coefficient Δ( Q ), determine the relationship between the width of the stratum reinforcement on both sides of the proposed tunnel and the resistance it can provide, and determine the lateral range of the stress isolation zone L y .

2. A tunnel-soil stiffness coordinated soft stratum classification and zoning reinforcement system design method as claimed in claim 1, characterized in that: In step one: The stratigraphic profile parameters of the proposed tunnel and the existing tunnel obtained from geological survey data include the horizontal stratification of the strata and the weight of each soil layer. γ , compression modulus E, Poisson's ratio μ , base bed coefficient m , Cohesion c and internal friction angle φ .

3. The method for designing a tunnel-soil stiffness coordinated soft stratum classification and zoning reinforcement system according to claim 1, characterized in that: In step one: The design parameters of the proposed tunnel obtained from the construction design data include the tunnel burial depth H , Lining outer diameter , Lining inner diameter , Lining width and design trends.

4. The method for designing a tunnel-soil stiffness coordinated soft stratum classification and zoning reinforcement system according to claim 1, characterized in that: In step 2: According to the design direction of the proposed tunnel and the direction of the existing tunnel, the overlapping section of the proposed tunnel and the existing tunnel and the section 50 m before and after should be set as the scope of ground grouting reinforcement.

5. The method for designing a tunnel-soil stiffness coordinated soft stratum classification and zoning reinforcement system according to claim 1, characterized in that: In step three: The definition of soft soil layers includes clay layers in soft plastic and fluid plastic states, sand layers in loose states, and untreated fill and highly compressible soil layers. According to the proportion of soft soil layers in the stratum where the proposed tunnel is located, the longitudinal reinforcement section of the upper span is divided into two categories: half-section reinforcement and full-section reinforcement.

6. A tunnel-soil stiffness coordinated soft stratum classification and zoning reinforcement system design method as claimed in claim 5, characterized in that: The half-section reinforcement adopts double-tube jet grouting piles, and the reinforcement depth is 2 m below the half-section of the proposed tunnel; the full-section reinforcement adopts double-tube jet grouting piles combined with ground sleeve valve pipe reinforcement measures, and the reinforcement depth is 2 m below the soft soil layer; The reinforcement systems of the above two types of sections are divided into resistance zone and stress isolation zone, that is, the reinforcement depth of the resistance zone of the half-section reinforcement section is H k and stress isolation area reinforcement depth H y The reinforcement depth of the resistance zone of the proposed tunnel is 2m below the half section and the full section reinforcement section. H k and stress isolation area reinforcement depth H y It is 2m below the soft soil layer.

7. The method for designing a tunnel-soil stiffness coordinated soft stratum classification and zoning reinforcement system according to claim 1, characterized in that: In step 4: The main section model of the tunnel segment is simplified into a beam unit, the spring is used to simulate the force between the soil and the tunnel structure, the spring model is used to simulate the internal force and deformation of the tunnel structure, the elastic foundation beam method is used to analyze the internal force of the tunnel structure, and the beam-spring model is constructed through finite element software; Determine the axial stiffness of the spring K s and tunnel structure loads, specifically: The spring axial stiffness K s for: in, m is the elastic base coefficient of the surrounding rock around the proposed tunnel. For the resistance zone on both sides of the arch waist of the proposed tunnel, it is taken as the base coefficient of the reinforced soil layer. m k , the base bed coefficient of the soft soil layer is taken in the area around the tunnel except the arch waist; s 1 / 2 of the sum of the lengths of adjacent lining units; The tunnel structure load includes vertical earth pressure P 1. Horizontal soil pressure and lining deadweight G and foundation reaction P v Four parts, including: The vertical soil pressure is: The horizontal earth pressure includes the horizontal earth pressure at the top of the tunnel Q 1 and the horizontal earth pressure at the bottom of the tunnel Q 1 +Q 2, where: The deadweight of the lining is: The foundation reaction force is: In the formula, P 0 is the ground load, K 0 is the static lateral pressure coefficient of the surrounding soil layer, γ h The tunnel lining is heavy.

8. The method for designing a tunnel-soil stiffness coordinated soft stratum classification and zoning reinforcement system according to claim 6, characterized in that: In step five: The horizontal layout position of the first row of jet grouting piles near the center line of the proposed tunnel in the resistance zone passes through the central angle of the tunnel located in the resistance zone on both sides of the arch waist. Reverse calculation to obtain; In the beam-spring model, the static lateral pressure coefficient of the soil layer around the proposed tunnel is changed K 0Simulate the loading and unloading conditions around the tunnel to obtain different tunnel center angles The corresponding lateral convergence deformation is used to determine the horizontal layout position of the resistance zone when the lateral convergence meets the reinforcement design requirements; Lateral extent of the resistance zone L k The calculation formula is: 。 9. The method for designing a tunnel-soil stiffness coordinated soft stratum classification and zoning reinforcement system according to claim 1, characterized in that: In step six: According to the proposed tunnel stiffness K 1 and the equivalent stiffness of the resistance zone K k Adjusted lateral range of resistance zone L k2 and reinforcement depth H k2 They are: in, K 1 is the stiffness of the proposed tunnel, K k is the stiffness of the resistance zone, that is ; and are the correction factors for lateral range and reinforcement depth respectively.

10. The method for designing a tunnel-soil stiffness coordinated soft stratum classification and zoning reinforcement system according to claim 1, characterized in that: In step seven: Resistance exertion coefficient Δ( Q ) and the horizontal reinforcement width of the stress isolation area L y It is related to the degree of reinforcement, which can be expressed as: When the resistance coefficient Δ( Q ) = 1, the minimum horizontal reinforcement width of the stress isolation area is obtained L y_min : 。

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