A calculation method for the maximum ground settlement caused by the construction of a double-track tunnel

Abstract

The present invention belongs to the technical field of underground engineering, and specifically relates to a calculation method for the maximum ground settlement caused by the construction of a double-track tunnel. The present invention provides a calculation method for the maximum ground settlement caused by the construction of a double-track tunnel, which includes the following steps: First step, consult the design materials to obtain the tunnel structure information; consult the geological exploration materials to obtain the groundwater and formation information. Second step, establish a finite element analysis model for the construction of the double-track tunnel using numerical simulation software. Third step, simulate the tunnel excavation according to the on-site construction process, set the ground loss rates of the two tunnels to vary within a certain range respectively, and obtain the corresponding relationship between the maximum ground settlement during the construction of the double-track tunnel and the ground loss rate through a series of numerical simulations. The maximum ground settlement of any cross-section during the construction of the double-track tunnel can be calculated by using the method of linear interpolation, and the calculation process is convenient and fast.

Description

Technical Field

[0001] The present invention relates to the technical field of underground engineering, and specifically, to a calculation method for the maximum surface settlement caused by the construction of a double-track tunnel. Background Art

[0002] With the continuous development of underground engineering in China, a large number of tunnel projects are under construction. The surface settlement problem caused by tunnel construction has always been a key concern, and the monitoring and control of the maximum surface settlement are one of the key points of environmental protection in tunnel construction. At present, the surface settlement is usually monitored by a tracking monitoring scheme during tunnel construction, that is, the change in the surface elevation is monitored within a certain range before and after the tunnel excavation face (such as 50m before and after the excavation face). This monitoring scheme is effective in the construction of a single-track tunnel. However, in the double-track tunnel project constructed successively, the first-constructed tunnel not only causes surface settlement above it, but also causes surface settlement above the second-constructed tunnel. The surface settlement caused by the construction of the double-track tunnel is actually the superposition of the influence effects of the two tunnels. When the distance between the two tunnels is relatively close, the maximum surface settlement often occurs at the middle position between the two tunnels. The monitoring data provided by the direct tracking monitoring cannot reflect this actual maximum surface settlement. Therefore, it is necessary to provide a calculation method for the maximum surface settlement caused by the construction of a double-track tunnel based on the existing monitoring scheme and data.

[0003] After retrieving the existing technical documents, no description of the calculation method for the maximum surface settlement caused by the construction of a double-track tunnel based on the existing monitoring scheme and data has been found. Summary of the Invention

[0004] Aiming at the defects in the prior art, the present invention provides a calculation method for the maximum surface settlement caused by the construction of a double-track tunnel, which overcomes the defect that the monitoring data directly provided by the existing monitoring scheme in the past cannot accurately reflect the maximum surface settlement caused by the construction of a double-track tunnel, gives specific calculation methods and steps, and realizes the determination of the maximum surface settlement caused by the construction of a double-track tunnel.

[0005] To achieve the above object, the present invention provides a calculation method for the maximum surface settlement caused by the construction of a double-track tunnel, including the following steps:

[0006] First step, consult the design materials to obtain the tunnel structure information; consult the geological exploration materials to obtain the groundwater and formation information.

[0007] Second step, establish a finite element analysis model for the construction of the double-track tunnel by using numerical simulation software.

[0008] Step 3: Simulate the tunnel excavation according to the on-site construction process, set the ground loss rates of the two tunnels to vary within a certain range respectively, and obtain the corresponding relationship between the maximum ground settlement caused by the construction of the double-track tunnel and the ground loss rates of the two tunnels.

[0009] Step 4: Determine the ground loss rate by using the linear interpolation method according to the maximum ground settlement measured during the tunnel construction.

[0010] Step 5: Determine the maximum ground settlement during the construction of the double-track tunnel by using the linear interpolation method according to the ground loss rates of the two tunnels.

[0011] In Step 1, the design data refers to the official tunnel structure design blueprints.

[0012] In Step 1, the tunnel structure information includes the tunnel diameter, tunnel burial depth, tunnel spacing, and tunnel lining parameters.

[0013] The tunnel diameter refers to the inner diameter of the tunnel, the tunnel burial depth refers to the burial depth at the center line of the tunnel, and the tunnel spacing refers to the distance between the center lines of the two tunnels; the tunnel lining parameters include the compression stiffness, flexural stiffness, thickness, unit weight, and Poisson's ratio of the tunnel lining.

[0014] In Step 1, the geological exploration data refers to the official detailed geological exploration report of the tunnel construction site.

[0015] In Step 1, the groundwater information refers to the buried depth of the groundwater level within the tunnel construction site.

[0016] In Step 1, the stratum information includes the stratum layer thickness and soil parameters.

[0017] The soil parameters include the natural unit weight, saturated unit weight, vertical permeability coefficient, horizontal permeability coefficient, elastic modulus, cohesion, internal friction angle, dilatancy angle, Poisson's ratio, and coefficient of lateral earth pressure at rest of the soil.

[0018] The following formula should be satisfied between the Poisson's ratio of the soil and the coefficient of lateral earth pressure at rest of the soil:

[0019]

[0020] Where: ν is the Poisson's ratio of the soil; K0 is the coefficient of lateral earth pressure at rest of the soil.

[0021] In Step 2, the finite element analysis model for the construction of the double-track tunnel means that: horizontally, the model is centered on the midpoint of the two tunnels, and the range is not less than the sum of 4 times the tunnel burial depth and 1 time the tunnel spacing; vertically, the range of the model is not less than the sum of 1 time the tunnel burial depth and 2 times the tunnel diameter; mesh the model, input the groundwater level, tunnel parameters, and soil parameters, and set the initial conditions and boundary conditions of the model.

[0022] The initial conditions of the model are as follows: the initial in-situ stress of the model is in balance, and the initial excess pore water pressure of the model is zero; the boundary conditions of the model are as follows: the horizontal displacements of both side boundaries of the model are zero, the horizontal and vertical displacements of the bottom boundary of the model are zero, and the displacement of the top boundary of the model is not restricted.

[0023] In the third step, the formation loss rate refers to the ratio between the difference between the actual excavated soil volume and the completed tunnel volume during tunnel construction and the completed tunnel volume, and is simulated by setting the shrinkage rate of the tunnel volume in the numerical simulation software.

[0024] In the third step, the range of variation of the formation loss rate means: select n formation loss rates, denoted as R1, R2, R3, ……, R n , and the difference between adjacent two formation loss rates is α; where, R1 = 0, R i = (i - 1)α, i = 2, 3, ……, n.

[0025] In the third step, the corresponding relationship between the maximum ground settlement caused by the construction of the double-track tunnel and the formation loss rates of the two tunnels is obtained by the following method: during the simulation of the tunnel excavation process, set the formation loss rates of the two tunnels as R i and R j (i = 1, 2, 3, ……, n; j = 1, 2, 3, ……, n), calculate the corresponding maximum ground settlement through the numerical simulation software, denoted as S ij , summarize the calculation results, and obtain the corresponding relationship shown in Table 1, where: S ij = S ji (i = 1, 2, 3, ……, n; j = 1, 2, 3, ……, n).

[0026] Table 1 Maximum ground settlement (mm)

[0027]

[0028] In the fourth step, the linear interpolation method used to determine the formation loss rate means: given the measured maximum ground settlement S r during tunnel construction, search the second row of the said Table 1, and find two adjacent maximum ground settlements S 1k and S 1(k+1) such that S 1k ≤ Sr ≤ S 1(k+1) , and calculate the formation loss rate R r using the following formula:

[0029]

[0030] Where: R kis the formation loss rate of the k-th layer, R k+1 is the formation loss rate of the (k + 1)-th layer. By using this method, the formation loss rates of the two tunnels are obtained respectively, denoted as R r1 , R r2 .

[0031] In the fifth step, the linear interpolation method for determining the maximum ground settlement during the construction of a double-track tunnel means: Given the formation loss rates R r1 , R r2 of the two tunnels, look up the first row of Table 1 and find two adjacent formation loss rates R m and R m+1 such that R m ≤ R r1 ≤ R m+1 . Then look up the first column of Table 1 and find two adjacent formation loss rates R n and R n+1 such that R n ≤ R r2 ≤ R n+1 . Calculate two auxiliary maximum ground settlements S f1 and S f2 through the following formula:

[0032]

[0033] The maximum ground settlement S during the construction of a double-track tunnel is calculated through the following formula:

[0034]

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] The present invention overcomes the drawback that the monitoring data provided by the existing monitoring scheme directly used in the past cannot accurately reflect the maximum ground settlement caused by the construction of a double-track tunnel. Considering the superposition effect of the ground settlement caused by the construction of a double-track tunnel, it can accurately determine the maximum ground settlement caused by the construction of a double-track tunnel. The present invention does not need to change the existing ground settlement monitoring scheme for tunnel construction, so that the existing ground settlement monitoring data can be effectively utilized. The present invention obtains the corresponding relationship between the maximum ground settlement during the construction of a double-track tunnel and the formation loss rate through a finite number of numerical simulations, and the maximum ground settlement of any cross-section during the construction of a double-track tunnel can be calculated by using the linear interpolation method, and the calculation process is convenient and fast. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] By reading the detailed description of the non-restrictive embodiments with reference to the following 1-4 drawings, other features, objects and advantages of the present invention will become more obvious.

[0038] Figure 1Finite element analysis model diagram for the construction of a double-track tunnel in an embodiment of the present invention.

[0039] Figure 2 Relationship diagram between the maximum surface settlement and the ground loss rate during the construction of a double-track tunnel in an embodiment of the present invention.

[0040] Figure 3 Measured surface settlement distribution diagram of Tunnel 1 at the calculation section in a double-track tunnel project of an embodiment of the present invention.

[0041] Figure 4 Measured surface settlement distribution diagram of Tunnel 2 at the calculation section in a double-track tunnel project of an embodiment of the present invention. Detailed implementation manners

[0042] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

[0043] Embodiment

[0044] The present invention will be described in detail below in conjunction with specific embodiments. The following embodiments are helpful for those skilled in the art to further understand the present invention, but do not limit the present invention in any form. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can be made, and these all fall within the protection scope of the present invention. For the content not specifically described in this embodiment, refer to the methods already given in the content of the invention, and will not be repeated here.

[0045] A certain tunnel project is a double-track parallel shield tunnel, and a tracking monitoring scheme is adopted to monitor the surface settlement caused by tunnel construction. In this embodiment, the maximum surface settlement caused by its construction is calculated, and the specific steps are as follows:

[0046] First step, consult the design materials to obtain the tunnel structure information; consult the geological exploration materials to obtain the groundwater and formation information. Specifically:

[0047] 1) Consult the official tunnel structure design blueprints to obtain that the inner diameter of the tunnel is 8m, the buried depth at the tunnel center line is 24m, the distance between the center lines of the two tunnels is 20m, and the tunnel lining parameters are shown in Table 2.

[0048] Table 2 Tunnel lining parameter table

[0049] Structure Name EA (kN / m) EI (kN·m2 / m) d (m) ω (kN / m / m) v Tunnel Lining 1.38×107 1.84×105 0.40 8.4 0.15

[0050] Note: EA = compressive stiffness; EI = flexural stiffness; d = thickness; w = unit weight; ν = Poisson's ratio.

[0051] 2) Consult the detailed geological exploration report of the tunnel construction site, and it is obtained that the buried depth of the groundwater level in the construction site is 0 m. The layered thickness of the strata and the soil parameter information are shown in Table 3.

[0052] Table 3 Strata Parameter Table

[0053]

[0054]

[0055] Note: γunsat = natural unit weight; γsat = saturated unit weight; K0 = coefficient of earth pressure at rest; kv = vertical permeability coefficient; kh =

[0056] horizontal permeability coefficient; E = elastic modulus; c = cohesion; ψ = dilation angle; ν = Poisson's ratio.

[0057] Step 2: Use numerical simulation software to establish a finite element analysis model for the construction of a double-track tunnel as shown in Figure 1 Specifically:

[0058] 1) The horizontal direction of the model is centered on the midpoint of Tunnel 1 and Tunnel 2, with a range of 140 m; the vertical direction of the model has a range of 40 m.

[0059] 2) The model is meshed using triangular elements. The buried depth of the groundwater level is input as 0 m, and the tunnel and soil parameters are input corresponding to Table 2 and Table 3 above.

[0060] 3) Set the initial conditions of the model: the initial in-situ stress of the model is balanced, and the initial excess pore water pressure of the model is zero; set the boundary conditions of the model: the horizontal displacement of the two side boundaries of the model is zero, the horizontal and vertical displacements of the bottom boundary of the model are zero, and the displacement of the top boundary of the model is not restricted.

[0061] Step 3: Simulate the tunnel excavation according to the on-site construction process, set the formation loss rates of the two tunnels to vary within a certain range respectively, and obtain the corresponding relationship between the maximum surface settlement caused by the construction of the double-track tunnel and the formation loss rates of the two tunnels. Specifically:

[0062] 1) Select 5 formation loss rates, denoted as R1, R2, R3, R4, R5 respectively, and the difference between adjacent two formation loss rates is 0.5%; among them, R1 = 0%, R2 = 0.5%, R3 = 1.0%, R4 = 1.5%, R5 = 2.0%.

[0063] 2) During the simulation of the tunnel excavation process, the ground loss rates of the two tunnels are set to vary between R1 and R5 respectively. The corresponding maximum ground settlement is calculated by a numerical simulation software and denoted as S ij . The corresponding relationship between the maximum ground settlement caused by the construction of the double-track tunnel and the ground loss rates of the two tunnels is as Figure 2 shown. The calculation results are summarized to obtain the corresponding relationship shown in Table 4 below.

[0064] Table 4 Maximum Ground Settlement during Double-Track Tunnel Construction (mm)

[0065]

[0066]

[0067] Fourth step: According to the maximum ground settlement measured during the tunnel construction, the ground loss rate is determined by the linear interpolation method. Specifically:

[0068] 1) As Figure 3 and Figure 4 shown, the measured ground settlement distribution diagrams of Tunnel 1 and Tunnel 2 at the cross-section to be calculated are obtained. The maximum ground settlements can be obtained as S r1 = 17.25 mm and S r2 = 25.39 mm respectively. For Tunnel 1, look up the second row in Table 4 above, and find two adjacent maximum ground settlements S 12 = 7.92 mm, S 13 = 18.47. There is S 12 ≤ S r1 ≤ S 13 . Calculate the ground loss rate R r1 of Tunnel 1 at the calculated cross-section to be 0.94%, and the calculation process is as follows:

[0069]

[0070] 2) For Tunnel 2, using the same method, the ground loss rate R r2 at the calculated cross-section is calculated to be 1.31%.

[0071] Fifth step: According to the ground loss rates of the two tunnels, the maximum ground settlement during the construction of the double-track tunnel is determined by the linear interpolation method. Specifically:

[0072] 1) It is known from the fourth step that the ground loss rates of the two tunnels at the calculated cross-section are R r1 = 0.94% and R r2 = 1.31% respectively. Look up the first row in Table 4 above, and find two adjacent ground loss rates R2 = 0.5% and R3 = 1.0%. There is R2 ≤ R r1≤R3; Search the first column of Table 4 above to find two adjacent ground loss rates R3 = 1.0% and R4 = 1.5%, with R3 ≤ R r2 ≤R4. Calculate two auxiliary maximum ground settlement amounts S f1 = 30.09 mm, S f2 = 39.40 mm. The calculation process is as follows:

[0073]

[0074]

[0075] 2) Calculate the maximum ground settlement amount S = 35.86 mm during the construction of a double-track tunnel. The calculation process is as follows:

[0076]

[0077] The present invention can effectively determine the maximum ground settlement amount caused by the construction of a double-track tunnel, and the calculation process is convenient and fast; it can make full use of the ground settlement monitoring data of tunnel construction provided by the existing monitoring scheme; to solve the problem that the existing ground settlement monitoring scheme for tunnel construction cannot accurately reflect the maximum ground settlement amount caused by the construction of a double-track tunnel, the present invention has high popularization and application value.

[0078] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various deformations or modifications within the scope of the claims, which does not affect the essence of the present invention.

Claims

1. A method for calculating the maximum surface settlement caused by double-track tunnel construction, comprising the following steps: The first step is to consult the design data to obtain tunnel structure information; consult the geological survey data to obtain groundwater and stratum information; The second step is to use numerical simulation software to establish a finite element analysis model for double-track tunnel construction; The third step is to simulate tunnel excavation based on the on-site construction process, setting the ground loss rate of the two tunnels to vary within a certain range, and obtain the corresponding relationship between the maximum surface settlement caused by the dual-track tunnel construction and the ground loss rate of the two tunnels; Step 4: Determine the stratum loss rate using linear interpolation based on the maximum surface settlement measured during tunnel construction; Step 5: Based on the ground loss rates of the two tunnels, the maximum ground settlement during the construction of the double-track tunnel is determined using the linear interpolation method. In the first step, the design data refers to the official tunnel structure design blueprint. The tunnel structure information includes tunnel diameter, tunnel depth, tunnel spacing, and tunnel lining parameters. The tunnel diameter refers to the tunnel inner diameter, the tunnel depth refers to the depth at the tunnel centerline, and the tunnel spacing refers to the distance between two tunnel centerlines. The tunnel lining parameters include the compression stiffness, bending stiffness, thickness, weight, and Poisson's ratio of the tunnel lining. In the first step, the geological survey data refers to the official detailed geological survey report for the tunnel construction site. The groundwater information refers to the depth of the groundwater level within the tunnel construction site. In the first step, the stratum information includes stratum layer thickness and soil parameters, wherein the soil parameters include natural density, saturated density, vertical permeability, horizontal permeability, elastic modulus, cohesion, internal friction angle, dilatancy angle, Poisson's ratio, and static lateral pressure coefficient; The Poisson's ratio of the soil and the static lateral pressure coefficient of the soil should satisfy the following formula: Where: ν is the Poisson's ratio of the soil; K0 is the static lateral pressure coefficient of the soil; The finite element analysis model for the dual-track tunnel construction is as follows: the model horizontally extends from the midpoint of the two tunnels to a range of no less than four times the sum of the tunnel depth and one times the tunnel spacing; the model vertically extends to a range of no less than one times the sum of the tunnel depth and two times the tunnel diameter; the model is meshed, the groundwater level, tunnel parameters, and soil parameters are input, and the initial and boundary conditions of the model are set; The initial conditions of the model are: the initial ground stress of the model is balanced, and the initial excess pore water pressure of the model is zero; the boundary conditions of the model are: the horizontal displacement of the boundaries on both sides of the model is zero, the horizontal and vertical displacements of the bottom boundary of the model are zero, and the displacement of the top boundary of the model is unconstrained; In the third step, the formation loss rate refers to the ratio of the difference between the actual excavated soil volume and the completed tunnel volume during tunnel construction to the completed tunnel volume. The simulation is performed by setting the tunnel volume shrinkage rate in the numerical simulation software. In the third step, the range of the formation loss rate is as follows: n formation loss rates are selected and recorded as R1, R2, R3, ..., R n , the difference between the loss rates of two adjacent formations is α; where R1=0, R i =(i-1)α, i=2, 3,...,n; In the third step, the corresponding relationship between the maximum surface settlement caused by the construction of the double-track tunnel and the stratum loss rate of the two tunnels is obtained by the following method: during the simulated tunnel excavation process, the stratum loss rates of the two tunnels are set to R i and R j (i=1, 2, 3, ..., n; j=1, 2, 3, ..., n), the corresponding maximum surface settlement is calculated by numerical simulation software and recorded as S ij , summarizing the calculation results, we get the corresponding relationship shown in Table 1, where: S ij =S ji (i=1, 2, 3,..., n; j=1, 2, 3,..., n); Table 1 Maximum surface settlement (mm) In the fourth step, the linear interpolation method used to determine the formation loss rate is: given the maximum surface settlement S measured during tunnel construction, r , find the second row in Table 1 and find the maximum surface settlement S of two adjacent surfaces 1k and S 1(k+1) , so that S 1k ≤S r ≤S 1(k+1) , the formation loss rate R is calculated using the following formula r : Where: R k is the kth formation loss rate, R k+1 For the kth +1 The formation loss rate of the two tunnels is obtained by this method, which is recorded as R r1 、R r2 ; In the fifth step, the linear interpolation method for determining the maximum surface settlement during construction of a double-track tunnel is: given the ground loss rate R of the two tunnels, r1 、R r2 , look up the first row of Table 1 and find the loss rate R of two adjacent formations m and R m+1 , so that R m ≤R r1 ≤R m+1 , look up the first column of Table 1 and find the loss rate R of two adjacent formations n and R n+1 , so that R n ≤R r2 ≤R n+1 ; Calculate the maximum settlement of the two auxiliary surfaces S by the following formula f1 and S f2 : The maximum surface settlement S during double-track tunnel construction is calculated using the following formula:

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