Method for calculating lateral pressure of shallow tunnel

Abstract

The invention belongs to the field of geotechnical engineering, and particularly relates to a shallow tunnel lateral pressure calculation method which comprises the following steps: setting model parameters; the confining pressure of the confining pressure top is calculated; calculating a fracture surface A; b, calculating a fracture surface; calculating the total soil pressure on the AD wall; calculating the soil pressure at any height h on the straight wall AD; the problems that in the prior art, the result of lateral soil pressure is too large, so that tunnel lateral structure supporting is too conservative, engineering materials are wasted, and the engineering cost is increased can be solved; the problems of complex parameters and tedious modeling in the traditional calculation process are solved; in addition, the method has the advantages of being high in calculation accuracy, accurate in result and high in reliability.

Description

Technical Field

[0001] The invention belongs to the field of geotechnical engineering, and in particular relates to a method for calculating the lateral pressure of a shallow buried tunnel. Background Art

[0002] At present, my country is vigorously promoting the construction of urban subways, highways and other projects, and the tunnel projects involved, especially shallow buried tunnels, are an important part of them. In the analysis and calculation process of shallow buried tunnels in soft soil strata, the calculation of tunnel lateral earth pressure is an important reference indicator for tunnel excavation and support design.

[0003] In the traditional soil pressure calculation process, the lateral soil pressure of the tunnel is often calculated according to the Rankine active soil pressure theory; the size of the lateral pressure of a shallow tunnel depends on the top pressure and the Rankine lateral pressure coefficient; the Rankine theory assumes that the wall is rigid, the wall back is vertical, the surface of the backfill behind the wall is horizontal, the wall back is smooth, and there is no friction between the wall back and the backfill; because the Rankine theory ignores the fact that the actual wall back is not smooth and there is friction, the calculated active soil pressure is too large, that is, when the top pressure is constant, the result of the lateral soil pressure is too large, which makes the lateral structural support of the tunnel conservative, wastes engineering materials, and increases the project cost; therefore, in order to make the construction of shallow tunnels economical and reasonable and to ensure safety, a shallow tunnel lateral pressure calculation method is needed. Summary of the invention

[0004] The purpose of the present invention is to provide a method for calculating the lateral pressure of a shallow tunnel, so as to solve the problem that the lateral soil pressure result in the prior art is too large, resulting in conservative support of the tunnel lateral structure, wasting engineering materials and increasing the engineering cost.

[0005] The technical solution of the present invention to solve the above technical problem is as follows: a method for calculating the lateral pressure of a shallow buried tunnel, characterized in that the method for calculating the lateral pressure of a shallow buried tunnel comprises:

[0006] S1: Model parameter setting;

[0007] S2: Calculate the confining pressure at the top of the confining pressure;

[0008] S3: the slope h' of the rupture surface EF in region a a calculate;

[0009] S4:b The slope h′ of the fracture surface AF in region b calculate;

[0010] S5: Calculation of total earth pressure on AD wall:

[0011] S6: Calculation of earth pressure at any height h on the vertical wall AD.

[0012] In step S1, the model assumes that the ground surface is horizontal, and the soil block ADEF is analyzed in detail. The soil block ADEF is divided into two areas a and b for consideration. The fracture surface is assumed to be a plane-to-plane fracture surface. The plane-to-plane fracture surface is characterized by starting from point A of the tunnel arch foot, extending the failure surface to point F at the top, and then extending from point F to point E on the ground surface.

[0013] In step S3, the slope h of the fracture surface EF in region a is a The calculation of the tunnel lateral soil is divided into two areas, a and b, and the fracture surface EF is:

[0014] z=h′ a (x+b),

[0015] Where: h′ a is the slope of the rupture surface EF in area a, x is the X coordinate value of any point on the entire rupture surface; z is the Z coordinate value of any point on the entire rupture surface, and b is the range of the surface damage zone, that is, the length of DE on the diagram;

[0016] have:

[0017]

[0018] In the formula, γ is the density of soil, q is the surface load of soil, c is the cohesion of soil, is the internal friction angle of the soil, h1 is the z coordinate of a point on AD, and E1 is the soil pressure at a point at any height of EF.

[0019] In step S4, the slope h′ of the fracture surface AF in region b is b Calculation, in area b, the fracture surface AF is:

[0020] z=h+h′ b x,

[0021] Where: h′ b is the slope of the fracture surface AF in region b, x is the X coordinate value of any point on the entire fracture surface; z is the Z coordinate value of any point on the entire fracture surface, h is the Z coordinate of a point on AD, and in order to make the fracture surface of region b close to the real fracture surface, h′ can be taken b =0.5(h′ a +h′0), h′0=λ, then:

[0022]

[0023] In the formula, E h is the earth pressure at any point on the AF height.

[0024] In step S5, the total earth pressure on the AD wall is calculated by substituting the wall boundary conditions into the wall surface and obtaining The total earth pressure E at any height h on the vertical wall AD is obtained h for:

[0025]

[0026] In the formula, K q is the load earth pressure coefficient, K c is the cohesive earth pressure coefficient, K γ is the gravity earth pressure coefficient, γ is the gravity of the soil, q is the surface load of the soil, c is the cohesion of the soil, is the internal friction angle of the soil, and h is any height on the straight wall AD.

[0027] In step S6, the soil pressure e at any height h on the vertical wall AD is h for:

[0028] e h =γhK γ -2cK c +qK q ,

[0029] Where:

[0030]

[0031] In the formula, K q is the load earth pressure coefficient, K c is the cohesive earth pressure coefficient, K γ is the gravity earth pressure coefficient, γ is the gravity of the soil, q is the surface load of the soil, c is the cohesion of the soil, is the internal friction angle of the soil, h is any height on the vertical wall AD, and h′ b =0.5(h′ a +h′0), h′0=λ.

[0032] The present invention is mainly used in the analysis and calculation of tunnel lateral pressure during the construction of shallow buried tunnel projects such as urban subway tunnels and mountain highway tunnels. The present invention assumes that the ground surface is horizontal and divides the potential failure surface into plane-type failure surfaces. By analyzing the corresponding soil pressure on the AD surface when x=0 and at any depth h, the tunnel lateral surrounding rock pressure can be obtained.

[0033] Compared with the prior art, the present invention has the following beneficial effects: (1) It solves the problem in the prior art that the lateral earth pressure result is too large, which makes the tunnel lateral structure support conservative, wastes engineering materials, and increases the engineering cost; (2) It solves the problem of complex parameters and cumbersome modeling in the traditional calculation process; (3) The present invention has the advantages of accurate calculation, accurate results, and high reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a model calculation diagram of a shallow tunnel lateral pressure calculation method of the present invention;

[0035] Figure 2 The present invention is a flow chart of a method for calculating the lateral pressure of a shallow tunnel. DETAILED DESCRIPTION

[0036] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0037] Example

[0038] like Figure 2 A method for calculating the lateral pressure of a shallow tunnel is shown, which specifically includes the following steps:

[0039] S1: Model parameter setting, given that the tunnel depth is H = 10m, tunnel span 2a = 10m, and soil layer weight is 20kN / m 3 , ground level, surface load q = 0, soil cohesion C = 10kPa / 50kPa / 100kPa, internal friction angle Calculate the lateral confining pressure of the tunnel;

[0040] S2: Calculate the confining pressure at the top of the confining pressure, q1 = 10 * 20 = 200 kPa;

[0041] S3:A fracture surface calculation, such as Figure 1 The lateral soil of the tunnel is divided into two areas, a and b. The fracture surface of A is: z = h′ a (x+b), we have:

[0042]

[0043] S4: In zone B, the fracture surface is: z = h + h' b x, and in order to make the fracture surface of zone B close to the real fracture surface, it is possible to take: h′ b =0.5(h′ a +h′0), we have:

[0044]

[0045] S5: Calculate the total earth pressure on the AD wall, substituting the wall boundary conditions into the calculation, and The total earth pressure at any height h on the vertical wall AD is obtained as:

[0046]

[0047] S6: The earth pressure at any height h on the vertical wall AD is:

[0048] e h =γhK γ -2cK c +qK q ,

[0049]

[0050] Where:

[0051] During the calculation process, the earth pressure coefficient K γ , K c and K q The calculation results of the tunnel lateral confining pressure are shown in Table 1. From the comparison results, it can be seen that the tunnel lateral surrounding rock pressure calculated by the method proposed in the present invention is smaller than the lateral surrounding rock pressure calculated by the Rankine earth pressure calculation theory, which makes the force calculation of the tunnel lateral support structure more reasonable.

[0052] Table 1 Comparison of lateral confining pressure calculated by Rankine earth pressure theory and the algorithm of the present invention

[0053]

Claims

1. A method for calculating the lateral pressure of a shallow tunnel, characterized in that: The method for calculating the lateral pressure of a shallow tunnel comprises: S1: Model parameter setting; S2: Calculate the confining pressure at the top of the confining pressure; S3: the slope h' of the rupture surface EF in region a a calculate; S4:b The slope h′ of the fracture surface AF in region b calculate; S5: Calculation of total earth pressure on AD wall: S6: Calculation of earth pressure at any height h on the vertical wall AD.

2. A method for calculating lateral pressure of a shallow tunnel according to claim 1, characterized in that: In step S1, the model assumes that the ground surface is horizontal, and the soil block ADEF is analyzed in detail. The soil block ADEF is divided into two areas a and b for consideration. The fracture surface is assumed to be a plane-to-plane fracture surface. The plane-to-plane fracture surface is characterized by starting from point A of the tunnel arch foot, extending the failure surface to point F at the top, and then extending from point F to point E on the ground surface.

3. A method for calculating lateral pressure of a shallow tunnel according to claim 1, characterized in that: In step S3, the slope h′ of the fracture surface EF in region a is a The calculation of the tunnel lateral soil is divided into two areas, a and b, and the fracture surface EF is: z=h a (x+b), Where: h′ a is the slope of the rupture surface EF in area a, x is the X coordinate value of any point on the entire rupture surface; z is the Z coordinate value of any point on the entire rupture surface, and b is the range of the surface damage zone, that is, the length of DE on the diagram; have: In the formula, γ is the density of soil, q is the surface load of soil, c is the cohesion of soil, is the internal friction angle of the soil, h1 is the z coordinate of a point on AD, and E1 is the soil pressure at a point at any height of EF.

4. A method for calculating lateral pressure of a shallow tunnel according to claim 1, characterized in that: In step S4, the slope h′ of the fracture surface AF in region b is b Calculation, in area b, the fracture surface AF is: z=h+h′ b x, Where: h′ b is the slope of the fracture surface AF in region b, x is the X coordinate value of any point on the entire fracture surface; z is the Z coordinate value of any point on the entire fracture surface, h is the Z coordinate of a point on AD, and in order to make the fracture surface of region b close to the real fracture surface, it can be taken h′ b =0.5(h′ a +h′0), h′0=λ, then: In the formula, E h is the earth pressure at any point on the AF height.

5. A method for calculating lateral pressure of a shallow tunnel according to claim 1, characterized in that: In step S5, the total earth pressure on the AD wall is calculated by substituting the wall boundary conditions into the wall surface and obtaining The total earth pressure E at any height h on the vertical wall AD is obtained h for: In the formula, K q is the load earth pressure coefficient, K c is the cohesive earth pressure coefficient, K γ is the gravity earth pressure coefficient, γ is the gravity of the soil, q is the surface load of the soil, c is the cohesion of the soil, is the internal friction angle of the soil, and h is any height on the straight wall AD.

6. A method for calculating lateral pressure of a shallow tunnel according to claim 1, characterized in that: In step S6, the soil pressure e at any height h on the vertical wall AD is h for: yes h =γhK γ -2cK c +qK q , Where: In the formula, K q is the load earth pressure coefficient, K c is the cohesive earth pressure coefficient, K γ is the gravity earth pressure coefficient, γ is the gravity of the soil, q is the surface load of the soil, c is the cohesion of the soil, is the internal friction angle of the soil, h is any height on the vertical wall AD, and

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