CN106644206A - Method for calculating surrounding rock pressure of shallow tunnel - Google Patents

Abstract

The invention relates to the technical field of tunnel engineering. A method for calculating surrounding rock pressure for shallow buried tunnels of the present invention comprises the steps of: selecting a monitoring point for convergent deformation of surrounding rock; constructing a structural mechanics model at the monitoring point; deriving a calculation relational expression between the convergent deformation and surrounding rock pressure ; Bring the actual engineering data and convergence monitoring data into the relationship formula to calculate the displacement on the left and right sides of the monitoring point, and the convergence deformation of the monitoring point; calculate the friction angle and pressure of the surrounding rock. This method establishes a structural mechanics model by analyzing the relationship between the convergence deformation of the surrounding rock of the side wall and the pressure of the surrounding rock in the tunnel construction of the double-side-wall pilot tunnel method, and then calculates the surrounding rock pressure from the on-site monitoring data. There is a calculation method that relies on empirical parameters, which is more accurate and can better represent the actual surrounding rock pressure of the tunnel, and the convergence deformation data of the tunnel is easier to obtain and the calculation is convenient and accurate.

Description

A Calculation Method of Surrounding Rock Pressure for Shallow Buried Tunnels

technical field

The invention relates to the technical field of tunnel engineering, in particular to a method for calculating surrounding rock pressure for shallow buried tunnels.

Background technique

Surrounding rock pressure is the pressure generated on the contact surface between the support and the surrounding rock when the deformation of the surrounding rock is blocked by the support structure during the stress redistribution process caused by the disturbance of the rock mass. It directly affects the structural design and construction of the tunnel. Choice of method. Due to the shallow buried depth of shallow tunnels, the impact caused by excavation will more directly affect the surface and surrounding buildings.

The surrounding rock pressure caused by tunnel excavation is affected by many factors, not only related to geological factors such as rock mass structure, geological structure, rock physical and mechanical properties, groundwater, initial in-situ stress, but also related to the shape, size, and excavation pressure of the cavern. It is related to human factors caused by engineering activities such as construction methods and support forms. In tunnel engineering practice, accurate prediction of surrounding rock pressure caused by tunnel excavation is of great significance for the smooth progress of tunnel construction.

The empirical formula method is a widely used and relatively mature method for determining the surrounding rock pressure. It is based on a large number of actual engineering data and is based on experience summed up according to different surrounding rock levels. It is convenient for engineering and technical personnel to obtain the surrounding rock pressure quickly and conveniently. The magnitude and distribution pattern of the pressure. For example, the calculation formulas of surrounding rock pressure in "Code for Design of Highway Tunnel" and "Code for Design of Railway Tunnel" which are widely used in China at present are calculated based on the empirical parameters obtained from the analysis of a large number of previous engineering examples to obtain the surrounding rock pressure. However, the empirical formula method still has some limitations: the engineering examples referred to in the empirical formula method can only represent limited engineering geological conditions, and with the development and progress of design and construction technology, the geological conditions of tunnel construction are getting worse. The engineering geological conditions in engineering practice are more and more complex, and the engineering geological conditions in engineering practice have their own particularities. In this case, it is impossible to obtain more accurate surrounding rock pressure values by using the traditional empirical formula method.

Contents of the invention

The purpose of the present invention is to overcome the technical problem that when the empirical formula method is used to determine the surrounding rock pressure of the tunnel, the empirical parameters based on it cannot well represent the mechanical properties of the tunnel, so the traditional empirical formula method cannot obtain accurate surrounding rock pressure values. , providing a calculation method for surrounding rock pressure in shallow tunnels, the method establishes a structural mechanics model by analyzing the relationship between the convergence deformation of the side wall surrounding rock and the pressure of the surrounding rock in the tunnel construction of the double side wall pilot tunnel method, Compared with the existing calculation methods that rely on empirical parameters, the surrounding rock pressure obtained by inverse calculation from on-site monitoring data is more accurate and can better represent the actual surrounding rock pressure of the tunnel, and the convergence deformation data of the tunnel is easier to obtain and the calculation is convenient and accurate.

In order to realize the above-mentioned purpose of the invention, the present invention provides the following technical solutions:

A method for calculating surrounding rock pressure for shallow buried tunnels, comprising the following steps:

(1) Select the convergence deformation monitoring point of the surrounding rock: conduct research and analysis on the tunnel constructed by the double-side-wall pilot tunnel method, and select the point on the pilot tunnel excavated first according to the excavation sequence as the convergence deformation monitoring point;

(2) Construct a structural mechanics model at the monitoring point; construct a structural mechanics model at the pilot tunnel according to the actual situation;

(3) Deduce the calculation relationship between the convergence deformation and the surrounding rock pressure;

(4) Bring the actual engineering data and the convergence monitoring data into the relational formula in step (3), and calculate the displacement on the left and right sides of the monitoring point and the convergence deformation of the monitoring point respectively;

(5) Calculate the calculated friction angle and surrounding rock pressure of surrounding rock;

This method analyzes the relationship between the convergence deformation of the side wall surrounding rock and the pressure of the surrounding rock in the tunnel construction of the double side wall pilot pit method, establishes a structural mechanics model, and obtains the horizontal surrounding rock pressure and the vertical surrounding rock pressure from the on-site monitoring data. Compared with the existing calculation methods that rely on empirical parameters, the pressure is more accurate and can better represent the actual surrounding rock pressure of the tunnel, and the convergence deformation data of the tunnel is easier to obtain and the calculation is convenient and accurate.

As a preference, in step (2), the upper step of the left pilot pit or the upper step of the right pilot pit is selected for analysis and a mechanical model is constructed. According to actual construction experience, after the construction of the first left pilot pit or right pilot pit, the convergence deformation increases steadily within a week, the convergence speed slows down after one week, and basically stabilizes after two weeks. Therefore, the left pilot pit and the right pilot pit can be taken as At a monitoring point in the middle of the face of the right pilot pit, the convergence deformation after the monitoring data is basically stable within one to two weeks can represent the deformation convergence caused by the surrounding rock pressure.

As a preference, the following assumptions are made when building the model: the upper step of the left pilot pit or the upper step of the right pilot pit is regarded as a sector; the right wall and round arch of the upper step are simplified as rigid materials; each node of the simplified model is regarded as a rigid connection.

Preferably, both sides of the monitoring point are regarded as statically indeterminate beams and statically indeterminate arches for analysis, and the displacements of the statically indeterminate beams and statically indeterminate arches are calculated respectively to obtain the convergent deformation of the monitoring points.

Preferably, the displacement calculation of the statically indeterminate beam at the monitoring point includes the following steps:

(1) First analyze the load on the statically indeterminate beam: the load on the statically indeterminate beam q _l is the sum of the components of the horizontal load q _s and the vertical load q _c in the direction perpendicular to the beam, that is, q _l = q _s sinα +q _c ·cosα, and divide the load q _l into uniform load q _l1 and linear load q _l2 , where α is the angle between the two radii of the sector; since both ends of the beam are consolidated, no axial load Therefore, only the effect of horizontal load and vertical load on the load perpendicular to the beam direction is considered;

(2) List the calculation formulas of loads q _l1 and q _l2 respectively;

(3) Using the force method principle of structural mechanics to calculate the calculation formula of the bending moment on the statically indeterminate beam;

(4) Combining the load and bending moment calculation formulas to obtain the displacement calculation formulas of the monitoring point under the load q _l1 and q _l2 respectively, and bring the measured tunnel pressure data into the calculation formula to obtain the displacement of the load respectively;

(5) Obtain the total displacement ω _l of the statically indeterminate beam.

As preferably, when calculating in the above-mentioned step (2): the direction along the statically indeterminate beam is defined as the x direction, and the direction perpendicular to it is the y direction;

(1) When calculating q _l1 :

According to the force method principle of structural mechanics, calculate the bending moment of the statically indeterminate beam at any position in the x direction:

In the formula, r is the radius of the sector, and M(x) is the bending moment in the x direction;

According to the relationship between bending moment and deflection in material mechanics: Where EI is a constant, ω is the amount of deformation;

Double integrating the bending moment yields:

ω _l1 (x)·EI＝∫∫[M(x)dx]dx+C ₁ x+D ₁ , where ω _l1 (x) is the displacement of the monitoring point in the y direction under the q _l1 load, because the beam It is consolidated with the arch, so ω(0)=0, ω(r)=0, which can be calculated by substituting into the above formula:

And q _l1 = q _c ·cosα+e ₁ sinα, where e ₁ is the horizontal lateral pressure of the tunnel top/kPa, the value of q _l1 is obtained, and then the displacement of the statically indeterminate beam under the load q _l1 is obtained ω _l1 ;

(2) Calculate the value of q _l2 :

Calculate the bending moment at any position x on the statically indeterminate beam according to the force method principle of structural mechanics:

Taking the double integral over the bending moment gives:

In the formula, ω _l2 (x) is the displacement of the monitoring point in the y direction under the q _l2 load; and q _l2 = (e ₂ -e ₁ ) sinα, where e ₂ is the horizontal side pressure of the tunnel bottom/kPa, Get the displacement of the statically indeterminate beam under the action of load q _l2 ;

In this calculation process, the displacements of q _l1 and q _l2 are obtained by inverse calculation from the measured tunnel data, that is, the measured horizontal lateral pressure at the top _of the tunnel at e1 and the horizontal lateral pressure at the bottom of the tunnel at _e2 are brought into the derivation formula to obtain the load q _l1 and q _l2 values, and then obtain the displacement of the super statically indeterminate beam under the load q _l1 and q _l2 respectively, and obtain the displacement of the super statically indeterminate beam, which lays the foundation for calculating the displacement of the monitoring point. The measured data is used to calculate the super static The displacement of the fixed beam is more accurate and reliable than the traditional calculation method relying on empirical formulas, and has wider adaptability.

Preferably, the displacement calculation of the hyperstatically indeterminate arch at the monitoring point includes the following steps:

(1) decompose the horizontal load on the statically indeterminate arch into uniform load q ₁ , linear load q ₂ , and also include the vertical load q ₃ ; The restraint load is recorded as x ₃ , the vertical load is recorded as x ₂ , and the torque received at the intersection point is recorded as x ₁ ;

(2) According to the intersection of the statically indeterminate arch and the horizontal plane as a rigid connection node, the displacement relationship of the intersection point under the action of unit load in three directions is obtained;

(3) List the displacement relational expressions of the intersection of the statically indeterminate arch and the horizontal plane under loads in three directions;

(4) List the calculation formula of bending moment at any point on the statically indeterminate arch;

(5) Since the beam and the arch are consolidated, bring the data of the coordinate points into the above formula to obtain the displacement ω _g of the statically indeterminate arch.

As preferably, in the above-mentioned step (2), it can be drawn according to the rigid connection point of the model:

In the formula, _Δiq is the displacement along the direction of x _i produced by the load q, and δ _ij is the displacement along the direction of x _i produced by the unit force x _j =1, where i=1, 2 or 3, j=1, 2 or 3, and according to the characteristics of the rigid connection point, δ ₁₂ =δ ₂₁ , δ ₁₃ =δ ₃₁ , δ ₂₃ =δ ₃₂ ;

And when calculating the displacement δ _ij of any point of the statically indeterminate arch:

In the formula, r is the radius of the sector, and α is the angle between the two radii of the sector;

And calculate the displacement _Δiq under the action of loads q ₁ , q ₂ , q ₃ respectively:

The constraints x ₁ , x ₂ , x ₃ under the loads q ₁ , q ₂ , q ₃ can be obtained by using the above formula, and then the bending moment at any point on the arch can be obtained:

,

The double integral of the bending moment M(x) can be obtained:

In the formula ( which is is a value between 0 and α), C ₂ and D ₂ are constant coefficients generated during the double integral process of bending moment;

By substituting ω(0)=0 and ω(α)=0 into the above formula, C ₂ and D ₂ can be obtained, and the displacement ω _g of the hyperstatic definite arch can be obtained.

Preferably, the convergent deformation of the monitoring point is the sum of the displacement deformations of the statically indeterminate beam and the statically indeterminate arch: ω=ω _l ·sinα+ω _g .

As a preference, when calculating the friction angle:

(1) First judge whether the tunnel is a shallow buried tunnel, and determine the surrounding rock level according to the convergence deformation ω and field data;

(2) For shallow tunnels, calculate the vertical surrounding rock pressure q: In the formula, q is the vertical uniform load/kN m ^-2 , γ is the weight of surrounding rock over the tunnel/kN m ^-3 ; H is the buried depth of the tunnel/m; B _t is the tunnel width/m, and λ is the lateral pressure Coefficient, θ is the friction angle of surrounding rock/°;

(3) Among them, the lateral pressure coefficient λ:

In the formula: β is the angle/° between the rupture surface and the horizontal plane, Calculating the friction angle/° for the surrounding rock yields:

The horizontal lateral pressure is:

In the formula, H is the buried depth of the tunnel/m, and h is the tunnel height/m;

(4) γ, and λ value, the θ degree is calculated according to the design drawings, and finally the horizontal surrounding rock pressure and vertical surrounding rock pressure are obtained.

The grade of the surrounding rock is determined according to the convergent deformation of the monitoring point obtained from the actual measurement data of the tunnel, and the correlation coefficient and the calculated friction angle value of the surrounding rock are obtained from the grade of the surrounding rock according to the value recommended by the code, and the horizontal surrounding rock pressure and the vertical surrounding rock pressure are taken into account. The calculation formula of pressure obtains the pressure value.

Compared with prior art, the beneficial effect of the present invention:

This calculation method analyzes the relationship between the convergence deformation of the surrounding rock of the side wall and the pressure of the surrounding rock in the tunnel construction of the double-side-wall pilot pit method, establishes a structural mechanics model, and calculates the horizontal surrounding rock pressure and the vertical surrounding rock pressure from the on-site monitoring data. Compared with the existing calculation method that relies on empirical parameters, the rock pressure is more accurate and can better represent the actual surrounding rock pressure of the tunnel, and the convergence deformation data of the tunnel is easier to obtain and the calculation is convenient and accurate.

Description of drawings:

Figure 1 is a schematic diagram of the construction of the existing double-side-wall pilot pit method.

Fig. 2 is a simplified model diagram of the steps on the left pilot pit of the present invention.

Figure 3 is a model diagram of a statically indeterminate beam subjected to horizontal loads.

Fig. 4 Model diagram of statically indeterminate beam subjected to vertical load.

Figure 5 is a model diagram of the statically indeterminate arch subjected to horizontal loads.

Fig. 6 The vertical load model diagram of the statically indeterminate arch.

Figure 7 is a statically indeterminate beam load calculation model diagram.

Fig. 8 Calculation model diagram of statically indeterminate arch load.

Markings in the picture: 1-step up the left guide pit, 2-step down the left guide pit, 3-step up the right guide pit, 4-step down the right guide pit, 5-up the step in the middle guide pit, 6-down the step in the middle guide pit, 7- Observation point for the convergence of the upper steps of the left pilot pit, 8- the boundary line between the upper and lower steps, 9- the initial support of the first layer, 10- the initial support of the second layer.

detailed description

The present invention will be further described in detail below in conjunction with test examples and specific embodiments. However, it should not be understood that the scope of the above subject matter of the present invention is limited to the following embodiments, and all technologies realized based on the content of the present invention belong to the scope of the present invention.

Example

As shown in Figures 1 to 8, this embodiment takes a certain urban highway tunnel as an example for calculation. The pit method is excavated in parts, and the calculation method of the surrounding rock pressure of the tunnel includes the following steps:

(1) Select the monitoring points for the convergence deformation of the surrounding rock: as shown in Figure 1, the tunnel is divided into six parts for excavation in sequence, namely, the upper step 1 of the left pilot pit, the lower step 2 of the left pilot pit, and the upper step of the right pilot pit. Step 3, the lower step 4 of the right pilot pit, the upper step 5 of the middle pilot pit, the lower step 6 of the middle pilot pit, and the boundary line 8 of the upper and lower steps. In this embodiment, the convergence observation point 7 of the upper step of the left pilot pit is selected as the detection position. The first layer of primary support 9 of the outer layer and the second layer of primary support 10 of the inner layer are arranged in the middle. Point is the monitoring point for convergence deformation. The excavation width of the pilot tunnel is 5.16m, that is, the tunnel width B _t =5.16m. According to the load equivalent height, the tunnel is shallow or deep:

H _p ＝(2～2.5)h _q , where H _p is the shallow tunnel boundary depth/m, h _q load equivalent height/m, and h _q =0.45×2 ^s-1 ω, where S is the surrounding rock Level, this embodiment S=5, ω is the width influence coefficient, ω=1+i(B-5), B is the tunnel width/m, this embodiment is B _t =5.16m, i is every increase or decrease of B by 1m The increase and decrease rate of the surrounding rock pressure is based on the vertical uniform pressure of the surrounding rock with B=5m. When B<5m, take i=0.2; when B>5m, take i=0.1; , H _p =2.5h _q , thus:

h _q =0.45×2 ^s-1 ω=7.32m, H _p =2.5h _q =18.29m, so the tunnel is a shallow buried tunnel.

(2) Construct a structural mechanics model at the monitoring point:

The following assumptions are made when building the model: the upper step of the left pilot pit is regarded as a fan shape; the right wall and round arch of the upper step are simplified as rigid materials; each node of the simplified model is regarded as a rigid connection.

Therefore, as shown in Figure 2, the two sides of the monitoring point are regarded as statically indeterminate beams and statically indeterminate arches for analysis, and the displacements of the statically indeterminate beams and statically indeterminate arches are calculated to obtain the convergent deformation of the monitoring points.

The displacement calculation of the statically indeterminate beam at the monitoring point includes the following steps:

1) As shown in Figure 3 and Figure 4, first analyze the load on the statically indeterminate beam: the load q _l on the statically indeterminate beam is the sum of the components of the horizontal load q _s and the vertical load q _c in the direction perpendicular to the beam, That is, q _l = q _s ·sinα+q _c ·cosα, and the load q _l is divided into uniform load q _l1 and linear load q _l2 , where α is the angle between the two radii of the sector; since the two ends of the beam are Consolidation is not affected by axial load, so only the effect of horizontal load and vertical load on the load perpendicular to the beam direction is considered;

2) List the calculation formulas of loads q _l1 and q _l2 respectively:

When calculating q _l1 :

As shown in Figure 3 and Figure 4, the bending moment of the statically indeterminate beam at any position in the x direction is calculated according to the force method principle of structural mechanics: In the formula, r is the radius of the sector, and M(x) is the bending moment in the x direction;

According to the relationship between bending moment and deflection in material mechanics: Where EI is a constant, ω is the amount of deformation;

Double integrating the bending moment yields:

ω _l1 (x)·EI＝∫∫[M(x)dx]dx+C ₁ x+D ₁ , where ω _l1 (x) is the displacement of the monitoring point in the y direction under the q _l1 load, because the beam It is consolidated with the arch, so ω(0)=0, ω(r)=0, which can be calculated by substituting into the above formula:

And q _l1 = q _c ·cosα+e ₁ sinα, where e1 is the horizontal lateral pressure of the tunnel top/kPa, the value of q _l1 is obtained, and then the displacement of the statically indeterminate beam under the load q _l1 is obtained ω _l1 ;

Calculate the value of q _l2 :

Calculate the bending moment at any position x on the statically indeterminate beam according to the force method principle of structural mechanics:

Taking the double integral over the bending moment gives:

In the formula, ω _l2 (x) is the displacement of the monitoring point in the y direction under the q _l2 load; and q _l2 = (e ₂ -e ₁ ) sinα, where e ₂ is the horizontal side pressure of the tunnel bottom/kPa, Calculate the displacement of the statically indeterminate beam under the action of load q _l2 , and then obtain the total displacement of the statically indeterminate beam ω _l .

The displacement calculation of the hyperstatically indeterminate arch at the monitoring point includes the following steps:

(a) As shown in Fig. 5 to Fig. 8, decompose the horizontal load on the statically indeterminate arch into uniform load q ₁ , linear load q ₂ , and vertical load q ₃ ; The horizontal restraint load received by the intersection with the horizontal plane is recorded as x ₃ , the vertical load is recorded as x ₂ , and the torque received by the intersection point is recorded as x ₁ ;

(b) According to the characteristic that the intersection point of the statically indeterminate arch and the horizontal plane is a rigid connection node, the displacement relationship of the intersection point under the unit load in three directions is obtained:

According to the rigid connection point, it can be obtained that:

In the formula, _Δiq is the displacement along the direction of x _i produced by the load q, and δ _ij is the displacement along the direction of x _i produced by the unit force x _j =1, where i=1, 2 or 3, j=1, 2 or 3, and according to the characteristics of the rigid connection point, δ ₁₂ =δ ₂₁ , δ ₁₃ =δ ₃₁ , δ ₂₃ =δ ₃₂ ;

And when calculating the displacement δ _ij of any point of the statically indeterminate arch:

In the formula, r is the radius of the sector, and α is the angle between the two radii of the sector;

And calculate the displacement _Δiq under the action of loads q ₁ , q ₂ , q ₃ respectively:

The constraints x ₁ , x ₂ , x ₃ under the loads q ₁ , q ₂ , q ₃ can be obtained by using the above formula, and then the bending moment at any point on the arch can be obtained:

, the double integral of the bending moment M(x) can be obtained:

In the formula C ₂ and D ₂ are the constant coefficients generated in the process of calculating the double integral of the bending moment;

Substituting ω(0)=0 and ω(α)=0 into the above formula, C ₂ and D ₂ can be obtained, and the displacement ω _g of the statically indeterminate arch can be obtained. The convergence deformation of the monitoring point is the statically indeterminate beam and The sum of displacement and deformation of statically definite arch: ω＝ω _l sinα+ω _g ;

When the tunnel is judged to be shallow buried, calculate its vertical surrounding rock pressure q: In the formula, q is the vertical uniform load/kN m ^-2 , γ is the weight of surrounding rock over the tunnel/kN m ^-3 ; H is the buried depth of the tunnel/m; B _t is the tunnel width/m, and λ is the lateral pressure Coefficient, θ is the friction angle of surrounding rock/°;

Among them, the lateral pressure coefficient λ:

In the formula: β is the angle/° between the rupture surface and the horizontal plane, Calculating the friction angle/° for the surrounding rock yields:

The horizontal lateral pressure is:

In the formula, H is the buried depth of the tunnel/m, and h is the tunnel height/m;

Bringing in the data of this example, the accumulated deformation during the excavation process ω(x)=15.5mm, the buried depth of the tunnel H=13.31m, EI=7.354×10 ⁶ N·m ² , and the tunnel is of Class V enclosure. According to the value recommended by the code, the weight of surrounding rock on the tunnel is γ=19kN·m ^-3 , and the angle between the right wall of the model and the horizontal plane is θ=71.68° calculated by referring to the design drawings, which can be obtained by substituting the above calculation formula:

λ = 0.19, q = 199.41kPa, e ₁ = 47.35kPa, e ₂ = 17.22kPa,

Calculation of Friction Angle of Level Ⅴ Surrounding Rock in Code for Design of Highway Tunnel The recommended range of values is 40°～50°, the table below is The values of vertical surrounding rock pressure and horizontal surrounding rock pressure calculated according to the code when taking 40°, 45° and 50° respectively:

It can be seen from the table that the surrounding rock pressure obtained by the calculation method of this scheme is within the range of calculation results according to the "Code for Design of Highway Tunnels", which proves that the method is feasible and has high accuracy.

The calculation method of this embodiment establishes a structural mechanics model by analyzing the relationship between the convergence deformation of the surrounding rock of the side wall and the pressure of the surrounding rock in the tunnel construction of the double-side pilot pit method, and obtains the horizontal surrounding rock pressure by back-calculating the on-site monitoring data. Compared with the existing calculation method relying on empirical parameters, it is more accurate and can better represent the actual surrounding rock pressure of the tunnel, and the convergence deformation data of the tunnel is easier to obtain and the calculation is convenient and accurate.

All features disclosed in this specification, or steps in all methods or processes disclosed, may be combined in any manner, except for mutually exclusive features and/or steps.

Any feature disclosed in this specification (including any appended claims, abstract and drawings), unless expressly stated otherwise, may be replaced by alternative features which are equivalent or serve a similar purpose. That is, unless expressly stated otherwise, each feature is one example only of a series of equivalent or similar features.

Claims (10)

1. a kind of pressure from surrounding rock computational methods for shallow tunnel, it is characterised in that comprise the following steps：

(1) the convergent deformation monitoring point of country rock is chosen：Tunnel to being constructed using two side-wall pilot tunnel is researched and analysed, and is chosen It is convergent deformation monitoring point by the point on the pilot tunnel that sequence of excavation is excavated at first；

(2) in monitoring point structural texture mechanical model；

(3) calculation relational expression between convergent deformation and pressure from surrounding rock is derived；

(4) engineering real data and convergence monitoring data are brought into the relational expression of step (3), monitoring point is calculated respectively left and right The displacement of both sides, and the convergent deformation of monitoring point；

(5) calculate country rock and calculate angle of friction and pressure from surrounding rock.

2. pressure from surrounding rock computational methods according to claim 1, it is characterised in that left base tunnel is chosen in step (2) and is appeared on the stage Rank or right base tunnel top bar are analyzed, tectonic dynamics model.

3. pressure from surrounding rock computational methods according to claim 2, it is characterised in that do when setting up model it is assumed hereinafter that：Will Left base tunnel top bar or right base tunnel top bar are considered as sector；Top bar right wall and circular arch part are reduced to rigid material；Simplify mould The each node of type is considered as and is rigidly connected.

4. pressure from surrounding rock computational methods according to claim 3, it is characterised in that be respectively seen as monitoring point both sides super quiet Determine beam and indeterminate arch is analyzed, the convergence that the displacement of statically indeterminate beam and indeterminate arch is calculated respectively to obtain monitoring point becomes Shape.

5. pressure from surrounding rock computational methods according to claim 4, it is characterised in that the displacement meter of the statically indeterminate beam of monitoring point Comprise the following steps：

(1) statically indeterminate beam load is analyzed first：Statically indeterminate beam load q_lFor horizontal loading q_sHanging down with vertical load qc Directly in the component sum in beam direction, i.e. q_l=q_s·sinα+q_cCos α, and by load q_lIt is divided into evenly load q_l1, linear load q_l2, wherein α is the angle between fan-shaped two radius；

(2) load q is listed respectively_l1、q_l2Calculating formula；

(3) the calculation of Bending Moment formula on statically indeterminate beam is calculated using the force method principle of structural mechanics；

(4) with reference to load and calculation of Bending Moment formula monitoring point is respectively obtained by load q_l1、q_l2Displacement calculating formula, will actual measurement tunnel Pressure data brings calculating formula into, respectively obtains the displacement of load；

(5) total displacement amount ω of statically indeterminate beam is obtained_l。

6. pressure from surrounding rock computational methods according to claim 5, it is characterised in that when calculating in step (2)：Will be along super quiet The direction for determining beam is defined as x directions, and perpendicular direction is y directions；

(1) q is calculated_l1When：

The moment of flexure of statically indeterminate beam optional position in the x direction is calculated by the force method principle of structural mechanics：

R is fan-shaped radius in formula, and M (x) is the moment of flexure in x directions；

According to moment of flexure in the mechanics of materials and the relational expression of amount of deflection：Wherein EI is constant, and ω is deflection；

Double integral is asked to obtain moment of flexure：

ω_l1(x) EI=∫ ∫ [M (x) dx] dx+C₁x+D₁, ω in formula_l1X () is that q is received in monitoring point_l1Load displacement in y-direction Amount, C₁For, D₁It is to seek moment of flexure the constant coefficient produced during double integral, because beam and arch are consolidation, so ω (0)=0, ω (r)=0, substitutes into above formula and can be calculated：

And q_l1=q_c·cosα+e₁Sin α, wherein e₁For tunnel Top lateral pressure/kPa, draws q_l1Value, and then draw in load q_l1The displacement ω of the lower statically indeterminate beam of effect_l1；

(2) q is calculated_l2Value：

The moment of flexure on statically indeterminate beam at the x of optional position is calculated by the force method principle of structural mechanics：

Double integral is asked moment of flexure to obtain：

ω in formula_l2X () is that q is received in monitoring point_l2 Load displacement in y-direction；And q_l2=(e₂-e₁) sin α, e in formula₂For tunnel bottom lateral pressure/kPa, draw Load q_l2The displacement of the lower statically indeterminate beam of effect.

7. pressure from surrounding rock computational methods according to claim 4, it is characterised in that the displacement meter of the indeterminate arch of monitoring point Comprise the following steps：

(1) it is evenly load q by horizontal direction load decomposition suffered by indeterminate arch₁, linear load q₂, also including vertical direction Load q₃；The constraint load of the horizontal direction that indeterminate arch is subject to the intersection point of horizontal plane is designated as x₃, vertical direction load is designated as x₂, the moment of torsion that the intersection point is received is designated as x₁；

(2) intersection point according to indeterminate arch and horizontal plane is rigid connection node, draws intersection point unit in three directions Displacement relation under load action；

(3) displacement relation formula of the indeterminate arch with the intersection point of horizontal plane under three direction load actions is listed；

(4) the calculation of Bending Moment formula of arbitrfary point on indeterminate arch is listed；

(5) because beam is consolidation with arch, the data of coordinate points are brought into displacement ω that above formula obtains indeterminate arch_g。

8. pressure from surrounding rock computational methods according to claim 7, it is characterised in that according to being rigidly connected a little in step (2) Can draw：

Δ in formula_iqBe by load q produce along x_iThe position in direction Move, δ_ijIt is by unit force x_j=1 produce along x_iThe displacement in direction, wherein i=1,2 or 3, j=1,2 or 3, and according to the rigidity The characteristic of tie point, δ₁₂=δ₂₁、δ₁₃=δ₃₁、δ₂₃=δ₃₂；

And calculate the displacement δ of indeterminate arch arbitrfary point_ijWhen：

R is fan-shaped radius in formula, and α is fan-shaped two radius Between angle；

And calculate respectively in load q₁、q₂、q₃Displacement under effect_iq：

$\left\{\begin{array}{c}{\mathrm{EI\&Delta;}}_{1q_1}=\&lsqb;\frac{1}{4}\mathrm{\&alpha;}-\frac{1}{8}\sin \left(2\mathrm{\&alpha;}\right)\&rsqb;q_1{r}^3\\ {\mathrm{EI\&Delta;}}_{2q_1}=\&lsqb;\frac{1}{6}{\sin }^3\mathrm{\&alpha;}+\frac{1}{8}\sin \left(2\mathrm{\&alpha;}\right)-\frac{1}{4}\mathrm{\&alpha;}\&rsqb;q_1{r}^4\\ {\mathrm{EI\&Delta;}}_{3q_1}=\left(-\frac{1}{6}{\cos }^3\mathrm{\&alpha;}+\frac{1}{2}\cos \mathrm{\&alpha;}-\frac{1}{3}\right)q_1{r}^4\end{array}\right.,$

$\left\{\begin{array}{c}{\mathrm{EI\&Delta;}}_{1q_2}=\left(\frac{\mathrm{\&alpha;}}{4}-\frac{{\cos }^3\mathrm{\&alpha;}}{18\sin \mathrm{\&alpha;}}-\frac{\sin \left(2\mathrm{\&alpha;}\right)}{8}+\frac{\cos \mathrm{\&alpha;}}{6\sin \mathrm{\&alpha;}}-\frac{1}{9\sin \mathrm{\&alpha;}}\right)q_2{r}^3\\ {\mathrm{EI\&Delta;}}_{2q_2}=\left(\frac{{\cos }^3\mathrm{\&alpha;}-3cos\mathrm{\&alpha;}+2}{18sin\mathrm{\&alpha;}}-\frac{\mathrm{\&alpha;}}{4}+\frac{{\sin }^3\mathrm{\&alpha;}+sin\left(2\mathrm{\&alpha;}\right)}{8}\right)q_2{r}^4\\ {\mathrm{EI\&Delta;}}_{3q_2}=\left(\frac{19\cos \mathrm{\&alpha;}}{48}-\frac{{\cos }^3\mathrm{\&alpha;}}{8}+\frac{\mathrm{\&alpha;}}{16sin\mathrm{\&alpha;}}-\frac{1}{3}\right)q_2{r}^4\end{array}\right.,$

$\left\{\begin{array}{c}{\mathrm{EI\&Delta;}}_{1q_3}=\&lsqb;\frac{\sin \left(2\mathrm{\&alpha;}\right)}{8}+\frac{3\mathrm{\&alpha;}}{4}-\sin \mathrm{\&alpha;}\&rsqb;q_3{r}^3\\ {\mathrm{EI\&Delta;}}_{2q_3}=\&lsqb;2\sin \mathrm{\&alpha;}-\frac{{\sin }^3\mathrm{\&alpha;}}{6}-\frac{3\sin \left(2\mathrm{\&alpha;}\right)}{8}-\frac{5}{4}\mathrm{\&alpha;}\&rsqb;q_3{r}^4\\ {\mathrm{EI\&Delta;}}_{2q_3}=\&lsqb;\frac{{\cos }^3\mathrm{\&alpha;}}{6}-\frac{{\cos }^2\mathrm{\&alpha;}}{2}+\frac{\cos \mathrm{\&alpha;}}{2}-\frac{1}{6}\&rsqb;q_3{r}^4\end{array}\right.,$

Load q can be tried to achieve using above formula₁、q₂、q₃Constraint x under effect₁、x₂、x₃, then can try to achieve the moment of flexure of the upper arbitrfary point of arch：

,

Double integral is asked moment M (x) to obtain：

In formula C₂ For, D₂It is to seek moment of flexure the constant coefficient produced during double integral；

ω (0)=0, ω (α)=0 are substituted into above formula, C can be tried to achieve₂、D₂, draw the displacement ω of indeterminate arch_g。

9. pressure from surrounding rock computational methods according to claim 8, it is characterised in that the convergent deformation of monitoring point is indeterminate The displacement deformation sum of beam and indeterminate arch：ω=ω_l·sinα+ω_g。

10. pressure from surrounding rock computational methods according to claim 9, it is characterised in that when calculating angle of friction：

(1) first determine whether whether tunnel is shallow tunnel, Grades of Surrounding Rock is determined according to convergent deformation ω and field data；

(2) for shallow tunnel when, calculate its vertical pressure from surrounding rock q：Q is vertical equal in formula Cloth load/kNm^-2, γ is tunnel above rock severe/kNm^-3；H is edpth of tunnel/m；B_tFor tunnel width/m, λ is side Pressure coefficient, θ be country rock angle of friction/°；

(3) wherein, lateral pressure coefficient λ：

In formula：β is the plane of fracture and water The angle of plane/°,For country rock calculate angle of friction/°, and then draw：

Lateral pressure is：

H is edpth of tunnel/m in formula, and h is tunnel height/m；

(4) according to Grades of Surrounding Rock by specification recommend value obtain γ,And λ value, finally try to achieve horizontal adjoining rock pressure and enclose with vertical Rock pressure power.