A method for determining the scope of an excavation influence zone of a vertical parallel double-circle tunnel

Abstract

The application discloses a vertical parallel double-circular tunnel excavation influence area range determination method and belongs to the technical field of geotechnical and tunnel engineering. max And the length L of the group pile buried in the soil p The difference AL between the length L of the group pile buried in the soil p And the given influence area range p Then, the application calculates the three-level control standard influence area expression of different position tunnel excavation on existing group pile settlement based on the ratio of the group pile settlement value S P And the maximum displacement δ max Of the excavation face. The application solves the problems of large modeling and calculation workload and low convergence in determining the group pile settlement influence range caused by double-tunnel excavation through numerical simulation, can quickly determine the influence of different position tunnel excavation on existing group pile settlement, and has the advantages of simple calculation process, reasonable result and strong applicability.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of geotechnics and tunnel engineering, and particularly relates to a method for determining the influence area range of vertical parallel double circular tunnel excavation. BACKGROUND

[0002] With the continuous development of urban underground space, it is inevitable to appear the situation of vertical parallel double tunnel adjacent to existing building pile foundation construction in the process of shield tunnel construction. Engineering practice shows that tunnel excavation will cause disturbance of 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 vertical parallel double circular tunnel excavation mainly relies on numerical simulation, but this method still has problems such as large modeling workload, poor numerical calculation convergence, long calculation time, etc. when designing the best tunnel arrangement mode to control the settlement of the pile group and determining the influence range of double tunnel excavation.

[0003] The Chinese invention patent application with the publication number CN116227267A discloses a method for predicting the influence area of foundation pit excavation and the displacement of existing tunnel outside the pit, and the main steps include: according to the engineering information to be evaluated, using numerical simulation to analyze the maximum displacement of the tunnel outside the pit under different working conditions and drawing an isogram cloud map, referring to the specification to determine the influence area corresponding to different tunnel positions, obtaining the influence area determination parameters under different foundation pit excavation depths and different maximum displacements of the enclosure structure, analyzing the variation law of the influence area determination parameters, proposing an influence area range prediction method under arbitrary conditions based on the interpolation method, determining the influence area where the tunnel is located according to the actual position of the tunnel and the prediction result of the influence area range, and then predicting the displacement that the tunnel may produce.

[0004] The method for predicting the influence area of foundation pit excavation and the displacement of existing tunnel outside the pit in the above-mentioned invention patent application has the following deficiencies: 1. Compared with foundation pit engineering, the influence of double tunnel excavation on pile groups cannot be simplified as a two-dimensional model for analysis, therefore, the above-mentioned method cannot solve the shortcomings of traditional numerical simulation prediction methods such as complex modeling, large model calculation amount, and long time consumption, and cannot quickly determine the influence of tunnel excavation at different positions on the settlement of pile groups; 2. There is no clear specification of the control standard value of pile group settlement in the current specification, therefore, the influence area division method in the above-mentioned method is not applicable to the deformation of pile groups, and a new influence area division basis needs to be proposed; 3. The variation law of the influence area determination parameters in the above-mentioned method still needs to be summarized and analyzed through numerical simulation, and there is a lack of summary of the variation law of the influence area determination parameters under general working conditions. Therefore, the present application proposes a method for determining the influence area range of vertical parallel double circular tunnel excavation at different positions on the settlement of adjacent existing pile groups. SUMMARY

[0005] The technical problem to be solved by the present invention is: how to solve the problems existing in the existing method of 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 numerical calculation convergence, and long calculation time. A method for determining the scope of the influence zone of the excavation of vertical parallel double circular tunnels is provided.

[0006] like Figure 9 As shown, the present invention solves the above technical problems through the following technical solutions, which include 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. If 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 The three-level control standard for pile group settlement is set, and the range of the pile group settlement influence zone corresponding to the three-level control standard is used as the basis for determining the influence zone of the project to be evaluated. The influence zone is divided into two cases. The vertical center axis of the pile group is used as the dividing line. Case 1 is defined as the case where both tunnels are located on one side of the vertical center axis of the pile group, and case 2 is defined as the case where both tunnels are located on both sides of the vertical center axis of the pile group.

[0010] 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 among the engineering-related parameters of the given influence area The difference ΔL p ;

[0011] Step S5: In case one, the influence zone expressions under each level of control standards are calculated according to the first calculation formula; in case two, the influence zone expressions at each level are calculated according to the second calculation formula; and thus the work of determining the scope of the influence zone is 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 0-3 kPa;

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

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

[0017] Further, in the step S1, the tunnel construction conditions are: the upper first tunnel as the preceding tunnel, the first tunnel center located at the group pile embedded in the soil part length L p The upper and lower L p / 3 length range of the center, and the first tunnel center distance from the pile foundation center near the tunnel side in the range of 1.5-2 times the tunnel diameter; the lower second tunnel as the following tunnel, the second tunnel center located below the pile toe horizontal axis.

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

[0019] δ max = 2(R-R0)

[0020] Wherein, R0 is the radius of the shrinked surface; R is the radius of the excavation surface.

[0021] Further, in the step S3, the three-level control standards S P / δ max of the group pile settlement of the influence area are respectively 12%, 17%, and 27%, and the influence area defined according to the three-level control standards of the group pile settlement are: the area with the control standard S P / δ max greater than 27% is the main influence area; the area with the control standard S P / δ max greater than 17% and less than or equal to 27% is the secondary influence area; the area with the control standard S P / δ max greater than 12% and less than or equal to 17% is the general influence area; and the area with the control standard S P / δ max less than or equal to 12% is the weak influence area.

[0022] Further, in the step S3, the influence area shape is a right trapezoid formed by a broken line, and the range of the influence area is taken as the abscissa by the ratio of the horizontal distance L x of the lower second tunnel center from the group pile toe center and the tunnel diameter D, and taken as the ordinate by the vertical distance L y of the lower second tunnel center from the group pile toe center.The linear function group in the coordinate system with the ratio of the distance L between the pile toe of the group pile and the center of the second tunnel to the tunnel diameter D as the ordinate and the ratio of the distance L between the pile toe of the group pile and the center of the first tunnel to the tunnel diameter D as the abscissa is determined.

[0023] Further, the linear function group of the influence area comprises two parts, the first part is the oblique line in the lower part of the influence area, which is determined by the intersection point Q2 of the two fold lines of the influence area and the intersection point Q3 of the fold line and the ordinate, and the expression is y=kx+b, and the second part is the vertical line in the influence area, which is determined by the intersection point Q2 of the two fold lines of the influence area and the intersection point Q1 of the fold line and the abscissa, and the expression is x=b2; the range of the influence area can be determined by limiting the value of the abscissa and the ordinate of the linear function group.

[0024] Further, in the step S4, the engineering related parameters of the given influence area include the tunnel diameter D, the maximum displacement of the excavation surface corresponding to the stratum loss rate caused by the tunnel construction The length of the group pile buried in the soil

[0025] Further, in the step S5, the engineering related parameters of the given influence area include the tunnel diameter D, the maximum displacement of the excavation surface corresponding to the stratum loss rate caused by the tunnel construction p Under the condition that the length of the group pile buried in the soil L

[0026] Control standard S P / δ max is equal to 12%:

[0027]

[0028] Control standard S P / δ max is equal to 17%:

[0029]

[0030] Control standard S P / δ max is equal to 27%:

[0031]

[0032] wherein x is the horizontal distance L x between the pile toe of the group pile and the center of the second tunnel, and y is the vertical distance L y between the pile toe of the group pile and the center of the second tunnel, and m1, m2 and m3 are the ordinate of the intersection point of the two straight lines of the expression of the influence area.

[0033] Further, in the step S5, the engineering related parameters of the given influence area include the tunnel diameter D, the maximum displacement of the excavation surface corresponding to the stratum loss rate caused by the tunnel construction pUnder the condition, the second calculation formula of the case two is as follows:

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

[0035]

[0036] Control standard S P / δ max Equal to 17%:

[0037]

[0038] Control standard S P / δ max Equal to 27%:

[0039]

[0040] Wherein, x is the horizontal distance L of the second tunnel center from the pile toe center of the group pile x And the ratio of the tunnel diameter D, y is the vertical distance L of the second tunnel center from the pile toe center of the group pile y And the ratio of the tunnel diameter D, m4, m5, m6 are the longitudinal coordinates of the intersection points of the two straight lines of the influence zone expression.

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

[0042] The vertical parallel double-circle tunnel excavation influence area range determination method solves the problems of large model calculation amount and high professional requirement of the numerical simulation technology in the existing double-tunnel excavation caused group pile settlement influence range, can quickly and accurately calculate the group pile settlement influence area range caused by vertical parallel double-tunnel excavation under the three-level control standard, has the advantages of simple calculation process, reasonable result, strong applicability and the like. BRIEF DESCRIPTION OF DRAWINGS

[0043] Figure 1 It is a non-uniform boundary shrinkage model schematic diagram in the embodiment one of the present application;

[0044] Figure 2 It is a tunnel position schematic diagram in the embodiment one of the present application;

[0045] Figure 3 It is a simplified group pile settlement influence area schematic diagram when the double tunnel is located on the same side of the group pile (case one) in the embodiment one of the present application;

[0046] Figure 4 It is a simplified group pile settlement influence area when the double tunnel is located on the two sides of the group pile (case two) in the embodiment one of the present application;

[0047] Figure 5 is a coordinate schematic diagram for determining the expression of the influence area of group piles sinking in embodiment one of the present application;

[0048] Figure 6a is a comparison diagram of the influence area range of vertical deformation of group piles in case one in embodiment two (the length of the buried part of the pile foundation is equal to 25m);

[0049] Figure 6b is a comparison diagram of the influence area range of vertical deformation of group piles in case two in embodiment two (the length of the buried part of the pile foundation is equal to 25m);

[0050] Figure 7a is a comparison diagram of the influence area range of vertical deformation of group piles in case one in embodiment two (the length of the buried part of the pile foundation is equal to 19.6m);

[0051] Figure 7b is a comparison diagram of the influence area range of vertical deformation of group piles in case two in embodiment two (the length of the buried part of the pile foundation is equal to 19.6m);

[0052] Figure 8a is a comparison diagram of the influence area range of vertical deformation of group piles in case one in embodiment two (the length of the buried part of the pile foundation is equal to 15m);

[0053] Figure 8b is a comparison diagram of the influence area range of vertical deformation of group piles in case two in embodiment two (the length of the buried part of the pile foundation is equal to 15m);

[0054] Figure 9 is a flowchart of the method for determining the influence area range of vertical parallel double-circle tunnel excavation. DETAILED DESCRIPTION

[0055] The embodiments of the present application will be described in detail below, and the embodiments are implemented on the premise of the technical scheme of the present application, and detailed implementation manners and specific operation processes are given, but the protection scope of the present application is not limited to the following embodiments.

[0056] Embodiment one

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

[0058] S1: first, determine whether the soil type is sand, and then determine the physical and mechanical parameters of the soil; and then determine whether the tunnel construction conditions meet the requirements, and when the above conditions are met and the physical and mechanical parameters of the soil are within the preset range, then step S2 is performed;

[0059] S2: Obtain the geometric dimensions of the tunnel and pile group of the project to be evaluated, including the maximum excavation surface displacement δ corresponding to the stratum loss rate caused by tunnel construction max 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 three-level control standard for pile group settlement, and use the pile group settlement influence area range corresponding to the three-level control standard 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 among 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 the control standards at all levels are calculated according to the first calculation formula; in case two, the expressions of the influence zone under the control standards at all levels are calculated according to the second calculation formula; and then the work of determining the scope of the influence zone is 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 to 35°.

[0068] In step S1, the tunnel construction conditions are: the upper first tunnel is used as the leading tunnel, 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, 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;

[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] wherein R0 is the radius of the shrinked surface; R is the radius of the excavated surface (as shown in Figure 1 ).

[0072] Further, in the step S3, the group pile settlement three-level control standards S P / δ max are 12%, 17%, and 27% respectively, and the influence zones defined according to the three-level control standards are as follows: the zone with a control standard S P / δ max greater than 27% is the main influence zone (I); the zone with a control standard S P / δ max greater than 17% and less than or equal to 27% is the secondary influence zone (II); the zone with a control standard S P / δ max greater than 12% and less than or equal to 17% is the general influence zone (III); and the zone with a control standard S P / δ max less than or equal to 12% is the weak influence zone (IV).

[0073] In the step S3, the influence zone is divided into two cases, with the vertical central axis of the group pile as the dividing line, the case one is defined as the double tunnels being located on one side of the vertical central axis of the group pile, and the case two is defined as the double tunnels being located on both sides of the vertical central axis of the group pile, as shown in Figure 2 .

[0074] In the step S3, the shape of the influence zone is a right trapezoid composed of broken lines, as shown in Figure 3 and Figure 4 , the range of the influence zone is determined by a linear function group in a coordinate system with the ratio of the horizontal distance L x between the center of the lower second tunnel and the center of the pile toe of the group pile and the tunnel diameter D (hereinafter referred to as the horizontal offset distance of the tunnel) as the horizontal coordinate and the ratio of the vertical distance L y between the center of the lower second tunnel and the center of the pile toe of the group pile and the tunnel diameter D (hereinafter referred to as the vertical offset distance of the tunnel) as the vertical coordinate; in the case one, the horizontal coordinate is negative, in the case two, the horizontal coordinate is positive, and in both cases, the vertical coordinate is always positive.

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

[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 Equal to 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 standards 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 the given influence area expression under the three-level control standard in case 1

[0082]

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

[0084]

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

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

[0087]

[0088] Control Standard S P / δ max Equal to 17%:

[0089]

[0090] Control Standard S P / δ max Equal to 27%:

[0091]

[0092] In the step S5, the length L of the different group piles embedded in the soil body p Under the condition, the second calculation formula of the case two is as follows:

[0093] Control standard S P / δ max is equal to 12%:

[0094]

[0095] Control standard S P / δ max is equal to 17%:

[0096]

[0097] Control standard S P / δ max is equal to 27%:

[0098]

[0099] In the step S5, the vertical line ordinate value range determining coefficients m1-m6 of the first calculation formula of the case one and the second calculation formula of the case two are the intersection point ordinates of the two straight lines in the influence area.

[0100] Embodiment two

[0101] In the embodiment, the foundation soil is sand ground, the effective cohesion of the soil body is c'=0.1 kPa, the effective internal friction angle is φ'=37°, and the Poisson's ratio is v=0.2; the upper first tunnel is as a preceding tunnel, the first tunnel center is located in the length L p of the group piles embedded in the soil body, and the lower second tunnel is as a subsequent tunnel, the second tunnel center is located below the pile toe horizontal axis. p / 3 length range of the upper and lower group pile embedded in the soil body, and the interval between the first tunnel center and the pile foundation center close to the tunnel side is in the range of 1.5-2 times of the tunnel diameter.

[0102] In the embodiment, the PLAXIS 3DA three-dimensional numerical model is established to study the influence of vertical parallel shield tunnel excavation on adjacent pile groups. The ground soil in the numerical model is simulated by the Hardening-Soil Small-Strain (HSS) model. The HSS model is a small-strain constitutive model that not only considers the shear and compression hardening of soil, but also considers the characteristics of the shear modulus of soil in the small-strain range, which is suitable for the description of the failure and deformation behavior of various soils (including soft and hard soils). The numerical simulation process includes two stages: the first stage is to activate the pile group and the pile top load after the initial ground stress is generated, and the calculation is carried out until the numerical model reaches mechanical equilibrium and deformation stability; the second stage is to reset the model displacement to zero, and then simulate the excavation of three pile groups adjacent to the double tunnels by blunting the corresponding soil elements, in order 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.

[0103] In this embodiment, the numerical simulation is used to calculate the maximum vertical deformation of the pile top caused by the double tunnel construction under different pile group lengths L p , different second tunnel horizontal offset distances (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 / D = 0, 1, 2, 3, 4), and the detailed parameters of each condition are shown in Table 5, a total of 246 groups of models.

[0104] Table 5 Simulation conditions of vertical parallel double tunnel adjacent to existing pile groups

[0105]

[0106] For the above numerical simulation conditions, the first calculation formula and the first calculation formula are used to calculate the linear function group of the vertical deformation influence area range of the existing pile group under different pile foundation lengths caused by the double tunnel construction under two conditions, and the calculation results are compared with the numerical simulation results. According to the different pile foundation lengths L p under each condition, the difference ΔL p between the length L p of the pile group buried in the soil and the given influence area range is calculated. ; then the difference ΔL p is brought into the first calculation formula of the first condition and the second calculation formula of the second condition, respectively, to obtain the linear function group of the vertical deformation influence area range of the pile group, and the function graph is drawn in the corresponding coordinate system, which is the vertical deformation influence area of the pile group corresponding to the three-level control standard.

[0107] The comparison between the calculation influence area range of the first calculation formula and the second calculation formula and the numerical simulation calculation influence area range is shown in Figure 6a and Figure 6b , Figure 7a and Figure 7b , Figure 8a and Figure 8b It can be seen that the group pile top maximum vertical deformation influence area range in the embodiment is in good agreement with the numerical simulation calculation influence area range.

[0108] Although the embodiments of the present application have been shown and described above, it should be understood by those skilled in the art that the above-mentioned embodiments are exemplary and cannot be understood as limiting the present application, and those skilled in the art can make changes, modifications, replacements and modifications to the above-mentioned embodiments within the scope of the present application.

Claims

1. A method for determining the range of influence of the excavation of a vertically parallel double-circular tunnel, characterized by, According to the size of the influence of tunnel excavation on the settlement of the existing pile group in different positions, the influence area of the tunnel excavation is determined, including the following steps: Step S1: determining whether the soil type is sand, and then determining the physical and mechanical parameters of the soil; then determining whether the tunnel construction conditions meet the requirements; when the tunnel construction conditions are met and the physical and mechanical parameters of the soil are within the preset range, step S2 is performed; Step S2: Obtain the geometric dimensions of the engineering tunnel and group pile to be evaluated, including the maximum displacement δ of the excavation surface corresponding to the stratum loss rate caused by tunnel construction max and the length L of the group pile buried in the soil p ; Step S3: determining the group pile settlement value S according to the group pile settlement value S P and the maximum displacement δ of the excavation face corresponding to the stratum loss rate caused by the tunnel construction max The ratio is set to three levels of group pile settlement control standards, and the range of the group pile settlement influence area corresponding to the three levels of group pile settlement control standards is determined as the influence area corresponding to the to-be-evaluated project; wherein, the influence area is divided into two cases, with the vertical central axis of the group pile as the dividing line, the double tunnels located on one side of the vertical central axis of the group pile are defined as case one, and the double tunnels located on both sides of the vertical central axis of the group pile are defined as case two; Step S4: calculating the current pile group buried in soil part length L based on the engineering related parameters of the given influence area p The difference AL of the pile group buried in soil part length in the engineering related parameters of the given influence area p ;​ Step S5: in case one, the influence area expression under each control standard is calculated according to the first calculation formula; in case two, the influence area expression is calculated according to the second calculation formula; and then the influence area range determination work is completed; In the step S1, the tunnel construction condition is that the upper first tunnel is a preceding tunnel, the first tunnel center is located in the group pile embedded in the soil part with a length L p The upper and lower centers of the group pile are within the range of L p / 3, and the first tunnel center is within the range of 1.5-2 times the tunnel diameter from the pile foundation center close to the tunnel side; the lower second tunnel is a following tunnel, and the second tunnel center is located below the pile toe horizontal axis; In the step S3, the shape of the influence zone is a right trapezoid formed by broken lines, and the range of the influence zone is determined by the horizontal distance L between the center of the lower second tunnel and the center of the pile toe of the group pile x and the ratio of the vertical distance L between the center of the lower second tunnel and the center of the pile toe of the group pile y and the tunnel diameter D as the longitudinal coordinate in the coordinate system composed of the linear function group; when the double tunnel is in case one, the horizontal coordinate is negative, when the double tunnel is in case two, the horizontal coordinate is positive, and in both cases, the longitudinal coordinate is always positive; The linear function group for determining the influence area includes two parts, the first part is the lower inclined line of the influence area, which is determined by the intersection point Q2 of the two fold lines of the influence area and the intersection point Q3 of the fold line and the longitudinal 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 fold lines of the influence area and the intersection point Q1 of the fold line and the horizontal coordinate, 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; In the step S5, the different groups of piles are embedded into the soil body with a length L p Under the condition, the first calculation formula of the case one is shown as follows: Control standard S P / δ max equal to 12%: Control standard S P / δ max equal to 17%: Control standard S P / δ max equal to 27%: wherein x is a horizontal distance L of the second tunnel center from the pile toe center of the group pile x and a ratio of the tunnel diameter D, y is a vertical distance L of the second tunnel center from the pile toe center of the group pile y and a ratio of the tunnel diameter D, m1, m2, m3 are longitudinal coordinates of intersection points of the 2 lines of the influence zone expression; In the step S5, the different groups of piles are embedded into the soil body with a length L p Under the condition, the second calculation formula of the case two is shown as follows: Control standard S P / δ max equal to 12%: Control standard S P / δ max equal to 17%: Control standard S P / δ max equal to 27%: wherein x is a horizontal distance L of the second tunnel center from the pile toe center of the group pile x and a ratio of the tunnel diameter D, y is a vertical distance L of the second tunnel center from the pile toe center of the group pile y and a ratio of the tunnel diameter D, m4, m5, m6 are longitudinal coordinates of the intersection point of the two lines of the impact zone expression.

2. The method according to claim 1, wherein, In the step S1, when the soil type is sand, the preset range of the physical and mechanical parameters is as follows: The soil modulus is 10-30 MPa; The effective cohesion is 0-3 kPa; The Poisson's ratio is 0.20-0.30; The effective internal friction angle is 20-35°.

3. The method according to claim 1, wherein, The step S3, the group pile settlement corresponding to the influence area three level control standard S P / δ max Respectively 12%, 17%, 27%, and according to the group pile settlement three level control standard defined influence area respectively: control standard S P / δ max Greater than 27% of the area is the main influence area; control standard S P / δ max Greater than 17%, less than or equal to 27% of the area is the secondary influence area; control standard S P / δ max Greater than 12%, less than or equal to 17% of the area is the general influence area; control standard S P / δ max Less than or equal to 12% of the area is the weak influence area.

4. The method according to claim 1, wherein, In the step S2, the maximum displacement δ of the excavation surface max The calculation formula is as follows: delta max = 2(R-R0) Wherein, R0 is the radius of the shrinkage surface; R is the radius of the excavation surface.

5. The method according to claim 1, wherein, In the step S4, the engineering related parameters of the given influence zone include the tunnel diameter D, the maximum displacement of the excavation face corresponding to the stratum loss rate caused by the tunnel construction Length of the group pile buried in the soil

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