Method for determining vertical parallel double-circle tunnel excavation influence area range

Abstract

The invention discloses a vertical parallel double-circle tunnel excavation influence area range determination method, which belongs to the technical field of rock soil and tunnel engineering, and comprises the following steps of: obtaining the maximum displacement delta max of an excavation surface corresponding to a stratum loss rate caused by construction of an engineering tunnel to be evaluated and the length Lp of a part of a pile group embedded into a soil body; and calculating a difference value delta Lp between the length Lp of the part of the current engineering pile group embedded into the soil body and # imgabs0 # corresponding to the given influence area range, and then calculating a three-level control standard influence area expression of the influence of tunnel excavation at different positions on the settlement of the existing pile group based on the ratio of the settlement value SP of the pile group to delta max by adopting the method disclosed by the invention. The method solves the problems of large modeling and calculation workload, low convergence and the like when the influence range of pile group settlement caused by double-tunnel excavation is determined through numerical simulation, can quickly determine the influence of tunnel excavation at different positions on the existing pile group settlement, and has the advantages of simple and convenient calculation process, reasonable result, high applicability and the like.

Description

Technical Field

[0001] The invention relates to the technical field of rock, soil and tunnel engineering, and in particular to a method for determining the range of an excavation influence zone of a vertical parallel double-circular tunnel. Background Art

[0002] With the continuous development of urban underground space, the construction of vertical parallel double tunnels adjacent to the pile foundation of existing buildings is inevitable during the shield tunnel construction process. Engineering practice shows that tunnel excavation will cause disturbance of the soil around the pile foundation, resulting in deformation and additional internal force of the pile foundation, affecting the bearing capacity of the pile foundation and seriously affecting the safety of the upper building. Therefore, predicting the influence of tunnel excavation at different positions on the settlement of adjacent existing pile groups has important guiding significance for tunnel design. At present, the prediction of the settlement of adjacent existing pile groups caused by the excavation of vertical parallel double circular tunnels is mainly carried out through numerical simulation. However, this method still has problems such as large modeling workload, poor convergence of numerical calculation, and long calculation time when designing the optimal tunnel layout to control the settlement of pile groups and determining the influence range of double tunnel excavation.

[0003] A Chinese invention patent application with publication number CN116227267A discloses a method for predicting the displacement of an existing tunnel outside a foundation pit excavation influence zone and the pit. The main steps include analyzing the maximum displacement of the tunnel outside the pit under different working conditions using numerical simulation and drawing contour line cloud maps based on the information of the project to be evaluated, determining the influence zone corresponding to different tunnel positions with reference to the specifications, and obtaining the influence zone determination parameters under different foundation pit excavation depths and different maximum lateral displacements of the retaining structures. By analyzing the change law of the influence zone determination parameters, a method for predicting the range of the influence zone under arbitrary conditions based on the interpolation method is proposed. According to the actual position of the tunnel and the prediction results of the influence zone range, the influence zone of the tunnel is determined, and then the displacement that may be caused by the tunnel is predicted.

[0004] The above invention patent application has the following shortcomings in the prediction method of the influence zone of foundation pit excavation and the displacement of existing tunnels outside the pit: 1. Compared with the foundation pit project, the influence of double tunnel excavation on pile groups cannot be simplified into a two-dimensional model for analysis. Therefore, the above method fails to solve the shortcomings of traditional numerical simulation prediction methods such as complex modeling, large model calculation, and long time consumption, and cannot quickly determine the influence of tunnel excavation at different positions on the settlement of pile groups; 2. The current specifications do not clearly stipulate the standard value of pile group settlement control. Therefore, the influence zone division method in the above method is not applicable to pile group deformation, and a new basis for influence zone division needs to be proposed; 3. The change law of the parameters determined in the influence zone in the above method still needs to be summarized and analyzed through numerical simulation, and there is a lack of summary of the change law of the parameters determined in the influence zone under general working conditions. To this end, the present invention proposes a method for determining the influence zone range of vertical parallel double circular tunnel excavation at different positions on the settlement of adjacent existing pile groups. Summary of the invention

[0005] The technical problem to be solved by the present invention is: how to solve the problems existing in the existing method for predicting the settlement and deformation of adjacent existing pile groups caused by the excavation of vertical parallel double circular tunnels, such as large modeling workload, poor convergence of numerical calculation, and long calculation time. A method for determining the range of the influence zone of the excavation of a vertical parallel double circular tunnel is provided.

[0006] like Fig. 9 As shown, the present invention solves the above technical problems through the following technical solutions, and the present invention comprises the following steps:

[0007] Step S1: Determine whether the soil type is sandy soil, and then determine the physical and mechanical parameters of the soil; then determine whether the tunnel construction conditions meet the requirements. When the above tunnel construction conditions are met and the physical and mechanical parameters of the soil are within the preset range, proceed to step S2;

[0008] Step S2: Obtain the geometric dimensions of the tunnel and pile group of the project to be evaluated, including the maximum displacement of the excavation surface corresponding to the stratum loss rate caused by tunnel construction, δ max and the length of the pile group buried in the soil L p ;

[0009] Step S3: According to the pile group settlement value S P The maximum displacement of the excavation surface corresponding to the ground loss rate caused by tunnel construction is δ max ratio, set the third-level control standard for pile group settlement, and use the pile group settlement influence area corresponding to the third-level control standard as the basis for determining the influence area corresponding to the project to be evaluated; the influence area is divided into two cases, with the vertical center axis of the pile group as the dividing line, and the double tunnels are both located on one side of the vertical center axis of the pile group as case one, and the double tunnels are located on both sides of the vertical center axis of the pile group as case two;

[0010] Step S4: Based on the engineering related parameters of the given impact area, calculate the length L of the current engineering pile group buried in the soil p The length of the pile group embedded in the soil in the engineering-related parameters of the given influence area The difference ΔL p ;

[0011] Step S5: In case one, the expressions of the influence zones under various levels of control standards are calculated according to the first calculation formula; in case two, the expressions of the influence zones at various levels are calculated according to the second calculation formula; and the work of determining the scope of the influence zones is thus completed.

[0012] Furthermore, in step S1, when the soil type is sandy soil, the preset ranges of its physical and mechanical parameters are as follows:

[0013] The soil modulus is 10-30 MPa;

[0014] The effective cohesion is 0-3kPa;

[0015] Poisson's ratio is 0.20-0.30;

[0016] The effective internal friction angle is 20-35°.

[0017] Furthermore, in step S1, the tunnel construction conditions are: the upper first tunnel is used as the leading tunnel, and the center of the first tunnel is located at the length L of the buried part of the pile group. p The center of the upper and lower parts is L p / 3 length range, and the distance between the center of the first tunnel and the center of the pile foundation close to the tunnel side is within the range of 1.5 to 2 times the tunnel diameter; the lower second tunnel serves as the rear tunnel, and the center of the second tunnel is located below the horizontal axis of the pile toe.

[0018] Furthermore, in step S2, the maximum displacement of the excavation surface δ max The calculation formula is as follows:

[0019] δ max =2(R-R0)

[0020] Among them, R0 is the radius of the contraction surface; R is the radius of the excavation surface.

[0021] Furthermore, in step S3, the third-level control standard S for pile group settlement corresponding to the affected area is P / δ max They are 12%, 17% and 27% respectively, and the influence areas defined according to the three-level control standard of pile groups are: Control standard S P / δ max The area with a rate greater than 27% is the main affected area; control standard S P / δ max The area with a rate greater than 17% and less than or equal to 27% is a secondary impact area; control standard S P / δ max The area with a rate greater than 12% and less than or equal to 17% is a general impact area; control standard S P / δ max The area with a rate of influence less than or equal to 12% is a weakly affected area.

[0022] Furthermore, in step S3, the shape of the influence zone is a right-angled trapezoid formed by a broken line, and the influence zone ranges from the horizontal distance L between the center of the lower second tunnel and the center of the pile group toe. x The ratio of the diameter of the tunnel to the tunnel diameter D is used as the horizontal coordinate, and the vertical distance L between the center of the lower second tunnel and the center of the pile toe is used as the horizontal coordinate. yThe ratio of the value of the diameter of the tunnel to the tunnel diameter D is determined as a linear function group in the coordinate system composed of the ordinate; when the double tunnel is in situation one, the abscissa is a negative value, and when the double tunnel is in situation two, the abscissa is a positive value. In both cases, the ordinate is always positive.

[0023] Furthermore, the linear function group for determining the influence area includes two parts. The first part is the lower oblique line of the influence area, which is determined by the intersection point Q2 of the two broken lines in the influence area and the intersection point Q3 of the broken line and the vertical coordinate, and the expression is y=kx+b. The second part is the vertical line of the influence area, which is determined by the intersection point Q2 of the two broken lines in the influence area and the intersection point Q1 of the broken line and the horizontal coordinate, and the expression is x=b2. The range of the influence area can be determined by limiting the horizontal and vertical coordinate values ​​of the linear function group for determining the influence area.

[0024] Furthermore, in step S4, the engineering parameters of the given impact area include the tunnel diameter D, the maximum displacement of the excavation surface corresponding to the stratum loss rate caused by tunnel construction, and Length of pile group buried in soil

[0025] Furthermore, in step S5, at different lengths L of pile groups buried in the soil p Under these conditions, the first calculation formula of the first case is as follows:

[0026] Control StandardS P / δ max Equal to 12%:

[0027]

[0028] Control StandardS P / δ max Equals 17%:

[0029]

[0030] Control StandardS P / δ max Equals 27%:

[0031]

[0032] Where x is the horizontal distance L between the center of the tunnel and the center of the pile toe x and the tunnel diameter D, y is the vertical distance L from the center of the second tunnel to the center of the pile group toe y The ratio of m1 to the tunnel diameter D, m1, m2, and m3 are the ordinates of the intersection of the two straight lines in the expression of the influence area.

[0033] Furthermore, in step S5, at different lengths L of pile groups buried in the soil pUnder these conditions, the second calculation formula of the second case is as follows:

[0034] Control StandardS P / δ max Equal to 12%:

[0035]

[0036] Control StandardS P / δ max Equals 17%:

[0037]

[0038] Control StandardS P / δ max Equals 27%:

[0039]

[0040] Where x is the horizontal distance L between the center of the tunnel and the center of the pile toe x and the tunnel diameter D, y is the vertical distance L from the center of the second tunnel to the center of the pile group toe y The ratio of m4 to the tunnel diameter D, m4, m5, and m6 are the ordinates of the intersection of the two straight lines in the expression of the influence area.

[0041] Compared with the prior art, the present invention has the following advantages:

[0042] The method for determining the scope of the influence zone of vertical parallel double circular tunnel excavation solves the problems of large model calculation amount and high professional requirements in the existing numerical simulation technology for the influence range of pile group settlement caused by double tunnel excavation. It can quickly and accurately calculate the scope of the influence zone of pile group settlement caused by vertical parallel double tunnel excavation under the third-level control standard, and has the advantages of simple calculation process, reasonable results and strong applicability. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 is a schematic diagram of a non-uniform boundary shrinkage model in Embodiment 1 of the present invention;

[0044] Figure 2 is a schematic diagram of the tunnel position in the first embodiment of the present invention;

[0045] Figure 3 1 is a simplified schematic diagram of the settlement influence area of ​​a pile group when the double tunnels are located on the same side of the pile group in the first embodiment of the present invention (case 1);

[0046] Figure 4 It is the simplified pile group settlement influence area when the double tunnels are located on both sides of the pile group in the first embodiment of the present invention (case 2);

[0047] Figure 5Schematic diagram of coordinates for determining the expression of the pile group settlement influence zone in the first embodiment of the present invention;

[0048] Figure 6a This is a comparison diagram of the vertical deformation influence area of ​​the pile group in the second embodiment of the present invention (the length of the buried part of the pile foundation is equal to 25m);

[0049] Figure 6b 1 is a comparison diagram of the vertical deformation influence area of ​​the pile group under the second situation in the second embodiment of the present invention (the length of the buried part of the pile foundation is equal to 25m);

[0050] Figure 7a This is a comparison diagram of the vertical deformation influence area of ​​the pile group in the second embodiment of the present invention (the length of the buried part of the pile foundation is equal to 19.6m);

[0051] Figure 7b 1 is a comparison diagram of the vertical deformation influence area of ​​the pile group under the second situation in the second embodiment of the present invention (the length of the buried part of the pile foundation is equal to 19.6m);

[0052] Figure 8a This is a comparison diagram of the vertical deformation influence area of ​​the pile group in the second embodiment of the present invention (the length of the buried part of the pile foundation is equal to 15m);

[0053] Figure 8b 1 is a comparison diagram of the vertical deformation influence area of ​​the pile group under the second situation in the second embodiment of the present invention (the length of the buried part of the pile foundation is equal to 15m);

[0054] Fig. 9 It is a schematic flow chart of a method for determining the scope of the influence zone of excavation of a vertical parallel double-circular tunnel according to the present invention. DETAILED DESCRIPTION

[0055] The following is a detailed description of an embodiment of the present invention. This embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation method and a specific operation process are given, but the protection scope of the present invention is not limited to the following embodiment.

[0056] Embodiment 1

[0057] This embodiment provides a technical solution: a method for determining the range of the influence zone of vertical parallel double-circle tunnel excavation, comprising the following steps:

[0058] S1: First, determine whether the soil type is sandy soil, and then determine the physical and mechanical parameters of the soil; then determine whether the tunnel construction conditions meet the requirements. When the above conditions are met and the physical and mechanical parameters of the soil are within the preset range, proceed to step S2;

[0059] S2: Obtain the geometric dimensions of the tunnel and pile groups of the project to be evaluated, including the maximum displacement δ of the excavation surface corresponding to the stratum loss rate caused by tunnel constructionmax and the length of the pile group buried in the soil L p ;

[0060] S3: According to the pile group settlement value S P The maximum displacement of the excavation surface corresponding to the ground loss rate caused by tunnel construction is δ max Ratio, set the third-level control standard for pile group settlement, and use the pile group settlement influence area range corresponding to the third-level control standard for pile group settlement as the basis for determining the influence area corresponding to the project to be evaluated;

[0061] S4: Based on the engineering parameters of the given impact area, calculate the length L of the current engineering pile group buried in the soil p The length of the pile group embedded in the soil in the engineering-related parameters of the given influence area The difference ΔL p ;

[0062] S5: In case one, the expressions of the influence zone under various levels of control standards are calculated according to the first calculation formula; in case two, the expressions of the influence zone under various levels of control standards are calculated according to the second calculation formula; and the work of determining the scope of the influence zone is then completed.

[0063] In step S1, when the soil type is sandy soil, the preset ranges of its physical and mechanical parameters are as follows:

[0064] The soil modulus is 10-30 MPa;

[0065] The effective cohesion is 0-3kPa;

[0066] Poisson's ratio is 0.20-0.30;

[0067] The effective internal friction angle is 20-35°.

[0068] In step S1, the tunnel construction conditions are: the upper first tunnel is used as the leading tunnel, and the center of the first tunnel is located at the length L of the buried part of the pile group in the soil. p The center of the upper and lower parts is L p / 3 length, and the distance between the center of the first tunnel and the center of the pile foundation close to the tunnel side is within 1.5 to 2 times the diameter of the tunnel; the lower second tunnel is used as the rear tunnel, and the center of the second tunnel is located below the horizontal axis of the pile toe;

[0069] In step S2, the maximum displacement of the excavation surface δ max Calculated by formula (1):

[0070] δ max =2(R-R0) (1)

[0071] Where R0 is the radius of the contraction surface; R is the radius of the excavation surface (e.g. Figure 1shown).

[0072] Furthermore, in step S3, the third-level control standard S for pile group settlement corresponding to the affected area is P / δ max They are 12%, 17%, and 27% respectively, and the impact areas defined according to the three-level control standards are: Control standard S P / δ max The area greater than 27% is the main impact area (I); control standard S P / δ max The area greater than 17% and less than or equal to 27% is the secondary impact area (II); control standard S P / δ max The area with a rate greater than 12% and less than or equal to 17% is the general impact area (III); control standard S P / δ max The area with a rate of less than or equal to 12% is the weakly affected area (IV)

[0073] In step S3, the influence area is divided into two cases. With the vertical center axis of the pile group as the dividing line, the double tunnels are both located on one side of the vertical center axis of the pile group, which is defined as case one, and the double tunnels are located on both sides of the vertical center axis of the pile group, which is defined as case two. Figure 2 shown.

[0074] In step S3, the shape of the influence area is a right-angled trapezoid composed of broken lines, such as Figure 3 and Figure 4 As shown in the figure, the affected area is the horizontal distance L between the center of the second tunnel and the center of the pile group toe. x The ratio of the tunnel diameter D (hereinafter referred to as the horizontal offset distance of the tunnel) is used as the horizontal coordinate, and the vertical distance L between the center of the second tunnel circle and the center of the pile group toe is used as the horizontal coordinate. y The ratio of the vertical displacement distance of the tunnel to the diameter D (hereinafter referred to as the vertical displacement distance of the tunnel) is determined as a linear function group in the coordinate system composed of the ordinates; when the double tunnels are in situation one, the abscissa is a negative value, and when the double tunnels are in situation two, the abscissa is a positive value. In both cases, the ordinate is always positive.

[0075] In step S3, the linear function group for determining the influence area includes two parts. The first part is the lower oblique line of the influence area, which is determined by the intersection point Q2 of the two broken lines in the influence area and the intersection point Q3 of the broken line and the ordinate, and the expression is y=kx+b. The second part is the vertical line of the influence area, which is determined by the intersection point Q2 of the two broken lines in the influence area and the intersection point Q1 of the broken line and the abscissa, and the expression is x=b2. The influence area range can be determined by limiting the horizontal and vertical coordinate values ​​of the linear function group for determining the influence area, as shown in the following example. Figure 5 shown.

[0076] In step S4, the engineering parameters of the given impact area are: the tunnel diameter D is equal to 6m, the maximum displacement of the excavation surface corresponding to the stratum loss rate caused by tunnel construction Equal to 30.48mm, the length of the pile group buried in the soil =19.6m, based on this, the difference ΔL p As shown in formula (2):

[0077] ΔL p =L p –19.6 (2)

[0078] In step S5, the expression form of the given influence area under each level of control standard is as follows:

[0079]

[0080] In step S5, the coefficients of the given influence zone expression under the three-level control standard are shown in Table 3 and Table 4:

[0081] Table 3 Determination coefficients of given influence area expressions under the three-level control standard in case 1

[0082]

[0083] Table 4 Determination coefficients of given influence area expressions under the third-level control standard in case 2

[0084]

[0085] In step S5, at different lengths L of pile groups buried in the soil p Under these conditions, the first calculation formula of the first case is as follows:

[0086] Control StandardS P / δ max Equal to 12%:

[0087]

[0088] Control StandardS P / δ max Equals 17%:

[0089]

[0090] Control StandardS P / δ max Equals 27%:

[0091]

[0092] In step S5, at different lengths L of pile groups buried in the soil pUnder these conditions, the second calculation formula of the second case is as follows:

[0093] Control StandardS P / δ max Equal to 12%:

[0094]

[0095] Control StandardS P / δ max Equals 17%:

[0096]

[0097] Control StandardS P / δ max Equals 27%:

[0098]

[0099] In the step S5, the vertical line ordinate value range of the first calculation formula in the case 1 and the second calculation formula in the case 2 determines the coefficients m1 to m6 as the ordinates of the intersection of the two straight lines in the impact area.

[0100] Embodiment 2

[0101] In this embodiment, the foundation soil is a sandy foundation, the effective cohesion of the soil is c'=0.1 kPa, the effective internal friction angle is φ'=37°, and the Poisson's ratio is ν=0.2; the first tunnel in the upper part is used as a leading tunnel, and the center of the first tunnel is located at the length L of the part of the pile group buried in the soil. p The center of the upper and lower parts is L p / 3 length, and the distance between the center of the first tunnel and the center of the pile foundation close to the tunnel side is within 1.5 to 2 times the diameter of the tunnel; the lower second tunnel is used as the rear tunnel, and the center of the second tunnel is located below the horizontal axis of the pile toe;

[0102] This embodiment uses PLAXIS 3DA three-dimensional numerical model of the influence of vertical parallel shield tunnel excavation on the deformation of adjacent pile groups is established. In the numerical model, the foundation soil is simulated using the small strain hard soil model (HSS model). The HSS model is a small strain constitutive model that not only takes into account the shear hardening and compression hardening of the soil, but also takes into account the characteristics of the shear modulus of the soil in a small strain range that decays with the increase of shear strain. It is suitable for describing the failure and deformation behavior of various soil types (including soft soil and hard soil). The numerical simulation calculation process includes two stages: in the first stage, the pile groups and pile top loads are activated after the initial foundation stress is generated, and the calculation is performed until the numerical model reaches mechanical equilibrium and deformation stability; in the second stage, the model displacement is reset to zero, and then the simulation of the excavation of three pile group lengths adjacent to the double tunnel is realized by passivating the corresponding soil unit, so as to calculate the vertical deformation of the pile top under three different pile group lengths, which is used to verify the reliability of the calculation method of the present invention.

[0103] In this embodiment, numerical simulation is used to calculate the length L of different pile groups buried in the soil. p , different second tunnel horizontal offset distance (L x / D=-5, -4, -3, -2.5, -2, -1.5, -1, -0.5, 0, 0.5, 1, 1.5, 2, 2.5, 3, 4, 5) and different second tunnel vertical translation distances (L y The maximum vertical deformation of the pile top caused by the double tunnel construction under the working conditions of / D=0, 1, 2, 3, 4) and other conditions. The detailed parameters of each working condition are shown in Table 5, with a total of 246 groups of models.

[0104] Table 5 Simulated construction conditions of vertical parallel twin tunnels adjacent to existing pile groups

[0105]

[0106] For the above numerical simulation working conditions, the first calculation formula of the present invention and the first calculation formula are used to calculate the vertical deformation influence area of ​​the existing pile top caused by the double tunnel construction under different pile foundation lengths to determine the linear function group, and compare it with the numerical simulation calculation results. p , calculate the length L of the pile group buried in the soil p Corresponding to the given impact area The difference ΔL p ; Then the difference ΔL p Substitute the first calculation formula of case one and the second calculation formula of case two respectively to obtain the linear function group for determining the range of the vertical deformation influence zone of the pile group. The function graph drawn by the function group in the corresponding coordinate system is the vertical deformation influence zone of the pile group corresponding to the third-level control standard.

[0107] The comparison between the calculation influence area range of the first calculation formula and the second calculation formula of the present invention and the calculation influence area range of the numerical simulation is as follows: Figure 6a and Figure 6b , Figure 7a and Figure 7b , Figure 8a and Figure 8b It can be seen that the influence area of ​​the maximum vertical deformation of the pile top of the pile group in this embodiment is consistent with the influence area calculated by numerical simulation.

[0108] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A method for determining the scope of the influence zone of vertical parallel double-circle tunnel excavation, characterized in that: According to the influence of tunnel excavation on the settlement of existing pile groups at different locations, the tunnel excavation influence area is determined, including the following steps: Step S1: Determine whether the soil type is sandy soil, and then determine the physical and mechanical parameters of the soil; then determine whether the tunnel construction conditions meet the requirements. When the above tunnel construction conditions are met and the physical and mechanical parameters of the soil are within the preset range, proceed to step S2; Step S2: Obtain the geometric dimensions of the tunnel and pile group of the project to be evaluated, including the maximum displacement of the excavation surface corresponding to the stratum loss rate caused by tunnel construction, δ max and the length of the pile group buried in the soil L p ; Step S3: According to the pile group settlement value S P The maximum displacement of the excavation surface corresponding to the ground loss rate caused by tunnel construction is δ max ratio, set the third-level control standard for pile group settlement, and use the pile group settlement influence area corresponding to the third-level control standard as the basis for determining the influence area corresponding to the project to be evaluated; the influence area is divided into two cases, with the vertical center axis of the pile group as the dividing line, and the double tunnels are both located on one side of the vertical center axis of the pile group as case one, and the double tunnels are located on both sides of the vertical center axis of the pile group as case two; Step S4: Based on the engineering parameters of the given impact area, calculate the length L of the current engineering pile group buried in the soil p The length of the pile group embedded in the soil L in the engineering-related parameters of the given influence area 1 P The difference ΔL p ; Step S5: In case one, the expressions of the influence zones under various levels of control standards are calculated according to the first calculation formula; in case two, the expressions of the influence zones at various levels are calculated according to the second calculation formula; and the work of determining the scope of the influence zones is thus completed.

2. A method for determining the range of the influence zone of vertical parallel double-circle tunnel excavation according to claim 1, characterized in that: In step S1, when the soil type is sandy soil, the preset ranges of its physical and mechanical parameters are as follows: The soil modulus is 10-30 MPa; The effective cohesion is 0-3kPa; Poisson's ratio is 0.20-0.30; The effective internal friction angle is 20-35°.

3. The method for determining the range of the influence zone of vertical parallel double-circle tunnel excavation according to claim 1 is characterized in that: In step S1, the tunnel construction conditions are: the upper first tunnel is used as the leading tunnel, and the center of the first tunnel is located at the length L of the buried part of the pile group in the soil. p The center of the upper and lower parts is L p / 3 length range, and the distance between the center of the first tunnel and the center of the pile foundation close to the tunnel side is within the range of 1.5 to 2 times the tunnel diameter; the lower second tunnel serves as the rear tunnel, and the center of the second tunnel is located below the horizontal axis of the pile toe.

4. A method for determining the range of the influence zone of vertical parallel double-circle tunnel excavation according to claim 1, characterized in that: In step S2, the maximum displacement of the excavation surface δ max The calculation formula is as follows: d max =2(R-R0) Among them, R0 is the radius of the contraction surface; R is the radius of the excavation surface.

5. The method for determining the range of the excavation influence zone of a vertical parallel double-circle tunnel according to claim 1, characterized in that: In step S3, the third-level control standard S for pile group settlement corresponding to the affected area P / δ max They are 12%, 17% and 27% respectively, and the influence areas defined according to the three-level control standard of pile groups are: Control standard S P / δ max The area with a rate greater than 27% is the main affected area; control standard S P / δ max The area with a rate greater than 17% and less than or equal to 27% is a secondary impact area; control standard S P / δ max The area with a rate greater than 12% and less than or equal to 17% is a general impact area; control standard S P / δ max The area with a rate of influence less than or equal to 12% is a weakly affected area.

6. A method for determining the range of the influence zone of vertical parallel double-circle tunnel excavation according to claim 5, characterized in that: In step S3, the shape of the affected area is a right-angled trapezoid formed by a broken line, and the affected area ranges from the horizontal distance L between the center of the lower second tunnel and the center of the pile toe of the pile group. x The ratio of the diameter of the tunnel to the tunnel diameter D is used as the horizontal coordinate, and the vertical distance L between the center of the lower second tunnel and the center of the pile toe is used as the horizontal coordinate. y The ratio of the value of the diameter of the tunnel to the tunnel diameter D is determined as a linear function group in the coordinate system composed of the ordinate; when the double tunnel is in situation one, the abscissa is a negative value, and when the double tunnel is in situation two, the abscissa is a positive value. In both cases, the ordinate is always positive.

7. A method for determining the range of the influence zone of vertical parallel double-circle tunnel excavation according to claim 6, characterized in that: The linear function group for determining the influence area includes two parts. The first part is the lower oblique line of the influence area, which is determined by the intersection point Q2 of the two broken lines in the influence area and the intersection point Q3 of the broken line and the vertical coordinate, and the expression is y=kx+b. The second part is the vertical line of the influence area, which is determined by the intersection point Q2 of the two broken lines in the influence area and the intersection point Q1 of the broken line and the horizontal coordinate, and the expression is x=b2. The range of the influence area can be determined by limiting the horizontal and vertical coordinate values ​​of the linear function group for determining the influence area.

8. A method for determining the range of the influence zone of vertical parallel double-circle tunnel excavation according to claim 7, characterized in that: In step S4, the engineering parameters of the given impact area include the tunnel diameter D, the maximum displacement of the excavation surface corresponding to the stratum loss rate caused by tunnel construction, Length of pile group buried in soil 9. A method for determining the range of the influence zone of vertical parallel double-circle tunnel excavation according to claim 8, characterized in that: In step S5, at different lengths L of pile groups buried in the soil p Under these conditions, the first calculation formula of the first case is as follows: Control StandardS P / δ max Equal to 12%: Control StandardS P / δ max Equals 17%: Control StandardS P / δ max Equals 27%: Where x is the horizontal distance L between the center of the tunnel and the center of the pile toe x and the tunnel diameter D, y is the vertical distance L from the center of the second tunnel to the center of the pile group toe y The ratio of m1 to the tunnel diameter D, m1, m2, and m3 are the ordinates of the intersection of the two straight lines in the expression of the influence area.

10. A method for determining the range of the influence zone of vertical parallel double-circle tunnel excavation according to claim 9, characterized in that: In step S5, at different lengths L of pile groups buried in the soil p Under these conditions, the second calculation formula of the second case is as follows: Control StandardS P / δ max Equal to 12%: Control StandardS P / δ max Equals 17%: Control StandardS P / δ max Equals 27%: Where x is the horizontal distance L between the center of the tunnel and the center of the pile toe x and the tunnel diameter D, y is the vertical distance L from the center of the second tunnel to the center of the pile group toe y The ratio of m4 to the tunnel diameter D, m4, m5, and m6 are the ordinates of the intersection of the two straight lines in the expression of the influence area.

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