A method and system for determining the ultimate support pressure of shallow shield tunnel excavation face

Abstract

The invention relates to the technical field of tunnel engineering, and discloses a method and system for determining the ultimate support pressure of an excavation face of a shallow buried shield machine in a tunnel. The method and system include: constructing a numerical model of a shallow buried shield machine and a combined curved surface model of a tunnel excavation process; constructing a first model based on a truncated cone area model, and constructing a second model of multi-layer soil and considering the vertical soil pressure of a groundwater level on the basis of the first model; constructing a third model based on an arc swivel area model, and calculating the internal energy loss power in the arc swivel area model according to the third model, and calculating the arc swivel internal force and external force power in the arc swivel area model according to the third model; calculating the vertical pressure power in the truncated cone area model based on the second model, and calculating the regional penetration force power in the arc swivel area model based on the numerical model; and calculating the ultimate support pressure of the shallow buried shield machine through the arc swivel internal force, external force power, vertical pressure power and regional penetration force power.

Description

Technical Field

[0001] The present invention relates to the technical field of tunnel engineering, and in particular to a method and system for determining the ultimate support pressure of a shallow shield excavation face in a tunnel. Background Art

[0002] With the promotion of the new urbanization strategy, the reconstruction and expansion of urban roads has become an important measure to improve the traffic capacity of urban roads, adapt to the growth of traffic volume and the demand for urban roads. In recent years, due to factors such as the shortage of urban land and the gradual improvement of landscape requirements, there are more and more plans and designs for the layout of urban roads along the river adjacent to flood control dikes. With the continuous increase in road traffic pressure, the construction of underground comprehensive pipeline corridors can effectively improve the overall layout of the urban ground, improve the cleanliness of the city, and make urban roads wider. As a kind of dark excavation construction method, the shield method will become the first choice for pipeline corridor construction considering the prohibition of excavation and filling in the flood season in the riverside area. During the shield tunneling process, the shield excavation changes the original stratum seepage field, and the groundwater seeps, resulting in an increase in the permeability on the excavation surface, which poses a great threat to the stability of the excavation surface. In addition, affected by the changes in the tidal level of the Yangtze River, the water level change has also become a key factor affecting the stability of the shield excavation surface in the riverside area. Therefore, exploring the impact of water level changes on the permeability and stability of the shield excavation face is of great significance to the design and construction of shield tunnels along the river. The excavation face stability engineering mainly considers that when the support pressure is too small, the surface will undergo a large settlement, resulting in the collapse of the excavation face. At present, the evaluation of the failure model and the accurate calculation of the ultimate support pressure have always been important research contents of the stability of the shield excavation face. However, most of the existing calculation methods only consider specific soil layers and do not consider the influence of groundwater. The proposed calculation models are also mostly based on the improvement of the traditional wedge failure model, which is somewhat different from the actual situation, resulting in low calculation accuracy. It can be seen that the existing calculation method of the ultimate support pressure of the shallow buried shield excavation face has the problem of low calculation accuracy. Summary of the invention

[0003] The invention provides a method and system for determining the ultimate support pressure of a shallow buried shield excavation face in a tunnel, so as to solve the problem of low calculation accuracy in the existing method for calculating the ultimate support pressure of a shallow buried shield excavation face.

[0004] In order to achieve the above object, the present invention is implemented by the following technical solutions:

[0005] In a first aspect, the present invention provides a method for determining the ultimate support pressure of a shallow shield tunnel excavation face, comprising:

[0006] Acquire first structural data of a shallow buried shield during tunnel excavation, and construct a numerical model of the shallow buried shield based on the first structural data;

[0007] Determine the second structural data of the excavation failure surface based on the numerical model, and construct a combined curved surface model of the tunnel excavation process based on the second structural data, wherein the combined curved surface model includes: a truncated cone area model and an arc rotation area model;

[0008] Constructing a first model based on the truncated cone area model, and constructing a second model of multi-layer soil and considering the vertical earth pressure of groundwater level on the basis of the first model;

[0009] Constructing a third model based on the arc rotation area model, calculating the internal energy loss power in the arc rotation area model according to the third model, and calculating the arc rotation internal force and external force power in the arc rotation area model according to the third model;

[0010] Calculating the vertical pressure power in the frustum area model based on the second model, and calculating the regional penetration power in the arc rotation area model based on the numerical model;

[0011] The ultimate support pressure of the shallow buried shield is calculated by the internal force of the arc rotation, the external force power, the vertical pressure power and the regional penetration power.

[0012] Optionally, the construction of the first model includes:

[0013] By analyzing the micro-element force of the truncated cone area model, the micro-element force expression is obtained, which is as follows:

[0014] ;

[0015] Solving the differential equation yields in y And consider the vertical stress expression of the bottom of the cone under the condition of single soil layer:

[0016] ;

[0017] According to the boundary conditions of the established model, we can obtain C 1 , substituting into the vertical stress expression, and according to the geometric relationship, the first model can be obtained:

[0018] ;

[0019] Where: in y is the vertical effective stress at the top of the microelement, c' is the buoyancy density of soil, y is the average vertical penetration force on the microelement, T yi is the first value of the cone in the numerical model. iPartial penetration, r i For the i The radius corresponding to each part is r i = r 0 -2 oh / n tan α , n is the uniform number of grids on the excavation surface, c' For effective cohesion, f' is the effective friction angle, the is the friction force on the sliding body, r 0 is the top radius of the cone, K' is the effective lateral coefficient, the value is 1-sin f' , y For depth, C 1 is a constant, indicating q ,in q Additional load on the ground surface. h The tunnel depth, D is the diameter of the excavation surface, e is the natural logarithm, f is the internal friction angle.

[0020] Optionally, the construction of the second model includes:

[0021] In the first model, the vertical earth pressure in the truncated cone area model is considered to obtain the second model, in which the vertical earth pressure includes: the vertical earth pressure of multi-layer soil and the vertical earth pressure of groundwater level. The expression of the second model is shown as follows:

[0022] ;

[0023] Where: α In case of active destruction, the angle between the sliding surface and the horizontal direction is α =π / 4+ f / 2, D is the excavation surface diameter, is the average value of the friction angle above the water level, is the average weight above the water level, kN / m 3 , is the average cohesion above the water level, is the average value of the effective friction angle below the water level, is the average buoyancy value below the water level, is the average cohesion above the water level, H is the distance between the water level and the top arch, h The tunnel depth, dis the thickness of the soil layer, represents the average effective side pressure coefficient, represents the average lateral pressure coefficient, q is the additional load on the ground surface, e is the natural logarithm, f is the internal friction angle.

[0024] Optionally, the construction of the third model includes:

[0025] ;

[0026] In the formula, A is the surface area of ​​the rigid body, V is the rigid body volume, T i , F i are the surface force and body force on the rigid body, is the velocity field, s ij is a static field, For virtual strain;

[0027] ;

[0028] Where: D represents the power consumed by internal energy, is the static field of the plastic critical failure state, is the virtual strain of the critical plastic failure state.

[0029] Optionally, calculating the internal energy loss power in the arc rotation area model according to the third model includes:

[0030] ;

[0031] ;

[0032] Where: D 外表面 represents the power consumed by the internal energy of the outer surface, D 上表面 represents the power consumed by the internal energy of the outer surface, oh For around O Angular velocity when point selection is made, β is the angle between the microelement on the arc rotation and the horizontal plane, r' ( β ) is the distance between the boundary of the microelement and the axis of the microelement, Indicates the angle of deviation from the O1 and O2 axes. represents effective cohesion, D represents tunnel diameter, α is the angle between the sliding surface and the horizontal direction during active failure, r0 is the top radius of the cone, represents the distance between the boundary of the microelement and the center of the microelement, x represents the horizontal coordinate of the microelement, z represents the vertical coordinate of the microelement, and l represents the distance between the microelement and the axis. O 1 The distance between them.

[0033] Optionally, the calculating the arc rotation internal force and external force power in the arc rotation area model according to the third model includes:

[0034] ;

[0035] ;

[0036] ;

[0037] ;

[0038] Where: W G is the gravitational power, W σT is the support pressure power, W Tz Arc rotation horizontal penetration power, W σ'y is the pressure power at the top of the arc swivel, D is the internal energy consumption power, r is the distance from the infinitesimal body to the center of the circle, i For deviation O 1. O The angle of the 2 axes, D is the excavation surface diameter, s T is the excavation face support pressure, represents the angle between the microelement on the arc rotation and the horizontal plane, Indicates effective cohesion, α is the angle between the sliding surface and the horizontal direction during active failure, r 0 is the top radius of the cone, c' is the buoyancy density of soil, oh For around O The angular velocity of the point when it rotates, It represents the distance between the boundary of the microelement and the axis of the microelement. represents the vertical penetration force of the n-1th grid in the numerical model, represents the vertical penetration force of the nth grid in the numerical model, x represents the abscissa of the microelement, z represents the ordinate of the microelement, and l represents the distance between the microelement and O 1 distance, y represents the distance between the microelement and the ground surface, rn-1 represents the radius of the cylinder corresponding to the n-1th truncated cone, r n represents the radius of the cylinder corresponding to the nth truncated cone, n represents the number of truncated cones, Represents the vertical effective stress at the top of the microelement.

[0039] Optionally, the calculation of the ultimate support pressure of the shallow shield through the arc rotation internal force, external force power, vertical pressure power and regional penetration power includes:

[0040] W G - W σT + W Tz + W σ'y = D ;

[0041] Where: W G is the gravitational power, W σT is the support pressure power, W Tz Arc rotation horizontal penetration power, W σ'y is the pressure power at the top of the arc swivel, D The power consumed is the internal energy.

[0042] In a second aspect, an embodiment of the present application provides a system for determining the ultimate support pressure of a shallow shield excavation face in a tunnel, characterized in that it includes a processor and a memory;

[0043] Memory, used to store computer programs;

[0044] The processor is used to implement any method step described in the first aspect when executing a program stored in the memory.

[0045] Beneficial effects:

[0046] The method for determining the ultimate support pressure of the excavation face of a shallow buried shield machine in a tunnel provided by the present invention constructs a numerical model of a shallow buried shield machine, and determines a truncated cone area model and an arc swivel area model of the tunnel excavation process, thereby constructing a first model based on the truncated cone area model, and constructing a second model of multi-layer soil and considering the vertical soil pressure of the groundwater level on the basis of the first model, and constructing a third model based on the arc swivel area model, and calculating the internal energy loss power in the arc swivel area model according to the third model, and calculating the arc swivel internal force and external force power in the arc swivel area model according to the third model, and finally calculating the ultimate support pressure of the shallow buried shield machine through the arc swivel internal force, external force power, vertical pressure power and regional penetration force power; based on the above method, a new calculation method for solving the ultimate support pressure by bringing the penetration force in the numerical model into the virtual power equation is used, thereby avoiding the complexity of the theoretical calculation of the penetration force, and the model force analysis is comprehensive and the calculation method is simple. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 It is a flow chart of a method for determining the ultimate support pressure of a shallow shield tunnel excavation face according to a preferred embodiment of the present invention;

[0048] Figure 2 It is a schematic diagram of the destruction form of the excavation surface in the preferred embodiment of the present invention;

[0049] Figure 3 It is a schematic diagram of the frustum-arc rotation failure model in the preferred embodiment of the present invention;

[0050] Figure 4 It is a schematic diagram of the force analysis of the truncated cone part in the preferred embodiment of the present invention;

[0051] Figure 5 It is a schematic diagram of calculating the average penetration force of the truncated cone part in the preferred embodiment of the present invention;

[0052] Figure 6 It is a schematic diagram of force analysis of the arc rotating part in the preferred embodiment of the present invention;

[0053] Figure 7 It is a schematic diagram of calculating the gravity power of arc rotation in a preferred embodiment of the present invention;

[0054] Figure 8 It is a schematic diagram of calculating the internal energy consumption power of the upper surface of the arc swivel in the preferred embodiment of the present invention;

[0055] Figure 9 It is a schematic diagram of the calculation of the arc rotating penetration power in the preferred embodiment of the present invention;

[0056] Figure 10 It is a schematic diagram for comparing support pressure calculation in a preferred embodiment of the present invention. DETAILED DESCRIPTION

[0057] The technical solution of the present invention is described clearly and completely below. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0058] Unless otherwise defined, the technical terms or scientific terms used in the present invention shall have the usual meanings understood by persons with ordinary skills in the field to which the present invention belongs. The words "first", "second" and similar words used in the present invention do not indicate any order, quantity or importance, but are only used to distinguish different components. Similarly, words such as "one" or "one" do not indicate quantity restrictions, but indicate the existence of at least one. Words such as "connect" or "connected" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the object being described changes, the relative positional relationship also changes accordingly.

[0059] Example 1

[0060] See also Figure 1-10 The present application provides a method for determining the ultimate support pressure of a shallow shield tunnel excavation face, comprising:

[0061] Acquire first structural data of a shallow buried shield during tunnel excavation, and construct a numerical model of the shallow buried shield based on the first structural data;

[0062] Determine the second structural data of the excavation failure surface based on the numerical model, and construct a combined curved surface model of the tunnel excavation process based on the second structural data, wherein the combined curved surface model includes: a truncated cone area model and an arc rotation area model;

[0063] Constructing a first model based on the truncated cone area model, and constructing a second model of multi-layer soil and considering the vertical earth pressure of groundwater level on the basis of the first model;

[0064] Constructing a third model based on the arc rotation area model, calculating the internal energy loss power in the arc rotation area model according to the third model, and calculating the arc rotation internal force and external force power in the arc rotation area model according to the third model;

[0065] Calculating the vertical pressure power in the frustum area model based on the second model, and calculating the regional penetration power in the arc rotation area model based on the numerical model;

[0066] The ultimate support pressure of the shallow buried shield is calculated by the internal force of the arc rotation, the external force power, the vertical pressure power and the regional penetration power.

[0067] In the above embodiment, by constructing a numerical model of a shallow buried shield, and determining the truncated cone area model and the arc swivel area model of the tunnel excavation process, a first model is constructed based on the truncated cone area model, and a second model of multi-layer soil and vertical soil pressure considering the groundwater level is constructed on the basis of the first model, and a third model is constructed based on the arc swivel area model, and the internal energy loss power in the arc swivel area model is calculated according to the third model, and the arc swivel internal force and external force power in the arc swivel area model are calculated according to the third model. Finally, the ultimate support pressure of the shallow buried shield can be calculated by the arc swivel internal force, external force power, vertical pressure power and regional penetration power; based on the above method, the effect of penetration force under water level change of the shallow buried shield is considered, and the relationship between the ultimate support pressure and the water level change is obtained. By bringing the penetration force in the numerical model into the virtual power equation to solve the ultimate support pressure, the complexity of the penetration force theory calculation is avoided, the model force analysis is comprehensive, and the calculation method is simple.

[0068] The above embodiment is further described in detail, and the steps are as follows:

[0069] Step 1: Construct a three-dimensional fluid-solid coupling numerical model of a shallow shield considering seepage. According to the failure form of the excavation surface in the numerical model, such as Figure 2 As shown in the figure, a combined surface model consisting of a truncated cone area and an arc rotation area is established, as shown in Figure 3 As shown;

[0070] Step 2: Establish a vertical pressure model of a single soil body above the vault. The first model is obtained by taking a microelement stress analysis of the truncated cone part.

[0071] ;

[0072] Solving the differential equation yields in y The vertical stress expression of the bottom of the cone considering only a single soil layer is:

[0073] ;

[0074] According to the boundary conditions of the established model, we can obtain C 1 , and according to the geometric relationship, we can get:

[0075] ;

[0076] In the above formula: in yis the vertical effective stress at the top of the microelement, in kPa; c' is the buoyancy density of soil, in kN / m 3 ; y is the average vertical penetration force on the microelement, in kN / m 3 ; T yi is the first value of the cone in the numerical model. i The permeability of the part, in kPa; r i For the i The radius corresponding to each part, r i = r 0 -2 oh / n tan α , n is the uniform number of grids on the excavation surface; c' is the effective cohesion, in kPa, f' is the effective friction angle, in degrees; the is the friction force on the sliding body; ∑F y =0 means the sum of the vertical forces of the entire model is 0; r 0 is the top radius of the cone, K' is the effective lateral coefficient, the value is 1-sin f' ; y is the depth, in m; C 1 is a constant, indicating q ,in q is the additional surface load, in kPa, h The tunnel depth, D is the diameter of the excavation surface, e is the natural logarithm, f is the internal friction angle.

[0077] Step 3: Establish a second model of multi-layer soil and considering the vertical earth pressure of the groundwater level, wherein the second model is obtained from the first model.

[0078] ;

[0079] Where: α In case of active destruction, the angle between the sliding surface and the horizontal direction is α =π / 4+ f / 2, unit is °; D is the excavation surface diameter; is the average value of the friction angle above the water level, in degrees; is the average weight above the water level, in kN / m 3 ; is the average value of cohesion above the water level, in kPa; is the average value of the effective friction angle below the water level, in degrees; The average buoyancy value below the water level, in kN / m 3 ; is the average value of cohesion above the water level, in kPa; H is the distance between the water level and the top arch, in m; h is the tunnel burial depth, in m, represents the average effective side pressure coefficient, represents the average lateral pressure coefficient, q is the additional load on the ground surface, e is the natural logarithm, f is the internal friction angle.

[0080] It should be noted that the above formula is obtained by analyzing a single soil layer. The calculation can be performed according to the weighted average value of the parameters of each soil layer. Taking bulk density as an example, c = ∑γ n d n / ∑d n , c n For the n The bulk density of the soil layer, d is the thickness of the soil layer.

[0081] Step 4: Obtain the average penetration force on the cone according to the numerical model and substitute in y In the expression, the calculation is in y

[0082] ;

[0083] Step 5: Calculate the third model by performing power analysis on the internal forces and external forces in the arc rotation model in the combined curved surface model to establish a virtual power equation.

[0084] W G - W σT + W Tz + W σ'y = D ;

[0085] Where: W G is the gravitational power,W σT is the support pressure power, W Tz Arc rotation horizontal penetration power, W σ'y is the pressure power at the top of the arc swivel, D The power consumed is the internal energy.

[0086] Step 6: Calculate the power generated by the internal and external forces of each part of the arc rotation.

[0087] The power generated by gravity, change the coordinate system to spherical coordinate system, and take the microelement as Figure 7 , and integrate the internal microelement of the arc swivel to obtain the calculation result of gravity power:

[0088] ;

[0089] In the formula, W G is the gravitational power, c' is the buoyancy density of soil, oh For around O The angular velocity of the point when it rotates, It represents the distance between the boundary of the microelement and the axis of the microelement. r is the distance from the infinitesimal body to the center of the circle, i For deviation O 1. O The angle of the 2 axes, represents the angle between the microelement on the arc rotation and the horizontal plane, α is the angle between the sliding surface and the horizontal direction during active failure, D The power consumed is the internal energy.

[0090] The power generated by the internal energy is composed of the upper surface and the outer surface of the arc rotating body. When calculating the internal energy power generated by the outer surface, the coordinate system is changed to the spherical coordinate system. The micro-element selected for calculation is similar to that for gravity calculation. The micro-element on the outer surface is integrated to obtain the calculation result of the outer surface power:

[0091] ;

[0092] The power generated by the internal energy surface can be expressed in polar coordinates according to Figure 8 Calculate and integrate the microelement to obtain the power calculation results in the table above:

[0093] ;

[0094] In the above formula, D 外表面 represents the power consumed by the internal energy of the outer surface, D 上表面represents the power consumed by the internal energy of the outer surface, oh For around O Angular velocity when point selection is made, β is the angle between the microelement on the arc rotation and the horizontal plane, r' ( β ) is the distance between the boundary of the microelement and the axis of the microelement, Indicates the angle of deviation from the O1 and O2 axes. represents effective cohesion, D represents tunnel diameter, α is the angle between the sliding surface and the horizontal direction during active failure, r 0 is the top radius of the cone, represents the distance between the boundary of the microelement and the center of the microelement, x represents the horizontal coordinate of the microelement, z represents the vertical coordinate of the microelement, and l represents the distance between the microelement and the axis. O 1 The distance between them.

[0095] The calculation method of support pressure power is the same as that of upper surface internal energy consumption power, which can be referred to Figure 9 Shown

[0096] ;

[0097] The calculation method of the permeability of the arc rotation part is to assume that the arc rotation of the adjacent grid is a regular cylinder, and the average permeability of the upper and lower surfaces of the cylinder is the permeability of the cylinder, such as Figure 9 Shown

[0098] ;

[0099] The calculation method of the top vertical pressure power is the same as the upper surface internal energy consumption power, which can be referred to Figure 9 Shown

[0100] ;

[0101] In the above formula, W σT is the support pressure power, W Tz Arc rotation horizontal penetration power, W σ'y is the pressure power at the top of the arc swivel, D is the internal energy consumption power, r is the distance from the infinitesimal body to the center of the circle, i For deviation O 1. O The angle of the 2 axes, s T is the excavation face support pressure, represents the angle between the microelement on the arc rotation and the horizontal plane, Indicates effective cohesion, α is the angle between the sliding surface and the horizontal direction during active failure, r 0 is the top radius of the cone, c' is the buoyancy density of soil, oh For around O The angular velocity of the point when it rotates, It represents the distance between the boundary of the microelement and the axis of the microelement. represents the vertical penetration force of the n-1th grid in the numerical model, represents the vertical penetration force of the nth grid in the numerical model, x represents the abscissa of the microelement, z represents the ordinate of the microelement, and l represents the distance between the microelement and O 1 distance, y represents the distance between the microelement and the ground surface, r n-1 represents the radius of the cylinder corresponding to the n-1th truncated cone, r n represents the radius of the cylinder corresponding to the nth truncated cone, n represents the number of truncated cones, Represents the vertical effective stress at the top of the microelement.

[0102] Step 7: Use the calculation results of the internal and external forces in step 6 to construct the equilibrium equation according to step 5, and solve it to obtain the ultimate support pressure.

[0103] Step 8: Based on the equation established in step 7, the law of how the ultimate support pressure changes with water level, cohesion, and friction angle can be analyzed.

[0104] Example 2

[0105] See also Figure 1-10 The setting of the soil bin pressure of the shield machine is an important application of the excavation face support pressure. In this embodiment, the calculation result of the active limit active pressure is compared with the average value of the soil bin pressure during the actual excavation process. The soil layer parameters related to the excavation face are as follows.

[0106] The shield is buried at a depth of 6m and has a diameter of 6m. The covering soil above the arch is 3m of silty clay mixed with silty sand and 3m of silty silty clay mixed with silty sand. The corresponding soil in front of the excavation face is 3m of silty silty clay mixed with silty sand and 3m of silty sand.

[0107]

[0108] Calculate the soil volume in the cylindrical area c' = or c ∑c' n d n / ∑d n =3kPa, f' = or φ' ∑φ' n d n / ∑d n = 10 ° .

[0109] From the information given in the shield excavation report, it can be known that the corresponding water level during the shield section excavation is 11.6m~14.7m. First, a numerical model corresponding to the water level of 12m is established, and the permeability in the numerical model is extracted as shown in the following table. The grid unit of the numerical model is 1m×1m×1m. According to the shield burial depth and radius, the cone part and the arc rotation part are 6 grids respectively.

[0110]

[0111] ;

[0112] ;

[0113] The calculated arc corner area soil c' = or c ∑c' n d n / ∑d n = 4kPa, f' = or φ' ∑φ' n d n / ∑d n = 15 ° .

[0114] ;

[0115] ;

[0116] ;

[0117] ;

[0118] The penetration required for calculation on the extracted arc rotation is as follows:

[0119]

[0120] ;

[0121] ;

[0122] ;

[0123] In this embodiment, 1.5 times the calculated result of the active limit active pressure is taken and compared with the set value of the soil tank pressure, and 1.5σ is obtained. T =70kPA, compared with Figure 10 The soil bin pressure corresponding to the absolute shield pressure is available, and 1.5 times the calculated result of the active limit active pressure has a good fit. Therefore, setting the 1.5 times calculated result as the soil bin pressure can meet the stability requirements.

[0124] The embodiment of the present application also provides a system for determining the ultimate support pressure of a shallow shield excavation face in a tunnel, including a processor and a memory;

[0125] Memory, used to store computer programs;

[0126] The processor is used to implement any method step in the method for determining the ultimate support pressure of the excavation face of a shallow buried shield tunnel when executing the program stored in the memory.

[0127] The preferred specific embodiments of the present invention are described in detail above. It should be understood that a person skilled in the art can make many modifications and changes based on the concept of the present invention without creative work. Therefore, any technical solution that can be obtained by a person skilled in the art through logical analysis, reasoning or limited experiments based on the concept of the present invention on the basis of the prior art should be within the scope of protection determined by the claims.

Claims

1. A method for determining the ultimate support pressure of a shallow shield tunnel excavation face, characterized in that: include: Acquire first structural data of a shallow buried shield during tunnel excavation, and construct a numerical model of the shallow buried shield based on the first structural data; Determine the second structural data of the excavation failure surface based on the numerical model, and construct a combined curved surface model of the tunnel excavation process based on the second structural data, wherein the combined curved surface model includes: a truncated cone area model and an arc rotation area model; Constructing a first model based on the truncated cone area model, and constructing a second model of multi-layer soil and considering the vertical earth pressure of groundwater level on the basis of the first model; Constructing a third model based on the arc rotation area model, calculating the internal energy loss power in the arc rotation area model according to the third model, and calculating the arc rotation internal force and external force power in the arc rotation area model according to the third model; Calculating the vertical pressure power in the frustum area model based on the second model, and calculating the regional penetration power in the arc rotation area model based on the numerical model; The ultimate support pressure of the shallow buried shield is calculated by the internal force of the arc rotation, the external force power, the vertical pressure power and the regional penetration power.

2. The method for determining the ultimate support pressure of a shallow shield tunnel excavation face according to claim 1 is characterized in that: The step of constructing a first model based on the frustum region model comprises: By analyzing the micro-element force of the truncated cone area model, the micro-element force expression is obtained, which is as follows: ； Solving the force expression of the microelement, we can get σ' y The vertical stress expression at the bottom of the truncated cone model under the condition of a single soil layer is: ； According to the boundary conditions of the established frustum region model, we can obtain C 1. C 1 is introduced into the vertical stress expression at the bottom of the truncated cone area model, and the first model is obtained according to the geometric relationship: ； Where: σ' y is the vertical effective stress at the top of the microelement, γ' is the buoyancy density of soil, y is the average vertical penetration force on the microelement, T yi is the first value of the cone in the numerical model. i Partial penetration, α is the angle between the sliding surface and the horizontal direction during active failure, α =π / 4+ φ / 2, r i For the i The radius corresponding to each part, r i = r 0-2 i / n tan α , n is the uniform number of grids on the excavation surface, c' For effective cohesion, φ' is the effective friction angle, τ' is the friction force on the sliding body, r 0 is the top radius of the cone, K' is the effective lateral coefficient, the value is 1-sin φ' , y For depth, C 1 is a constant, indicating q ,in q Additional load on the ground surface. h The tunnel depth, D is the diameter of the excavation surface, e is the natural logarithm, φ is the internal friction angle.

3. The method for determining the ultimate support pressure of a shallow shield tunnel excavation face according to claim 1 is characterized in that: The second model of multi-layer soil and considering the vertical earth pressure of groundwater level is constructed on the basis of the first model, including: In the first model, the vertical earth pressure in the truncated cone area model is considered to obtain the second model, in which the vertical earth pressure includes: the vertical earth pressure of multi-layer soil and the vertical earth pressure of groundwater level. The expression of the second model is shown as follows: ； Where: σ' y is the vertical effective stress at the top of the microelement, y is the average vertical penetration force on the microelement, α is the angle between the sliding surface and the horizontal direction during active failure, α =π / 4+ φ / 2, D is the excavation surface diameter, is the average value of the friction angle above the water level, is the average weight above the water level, is the average cohesion above the water level, is the average value of the effective friction angle below the water level, is the average buoyancy value below the water level, is the average cohesion above the water level, H is the distance between the water level and the top arch, h The tunnel depth, d is the thickness of the soil layer, represents the average effective side pressure coefficient, represents the average lateral pressure coefficient, q is the additional load on the ground surface, e is the natural logarithm, φ is the internal friction angle.

4. The method for determining the ultimate support pressure of a shallow shield tunnel excavation face according to claim 1 is characterized in that: The third model satisfies the following relationship: ； In the formula, A is the surface area of ​​the rigid body, V is the rigid body volume, T i , F i are the surface force and body force on the rigid body, is the velocity field, σ ij is a static field, For virtual strain; ； Where: D represents the power consumed by internal energy, is the static force field of the critical plastic failure state, is the virtual strain of the critical plastic failure state.

5. The method for determining the ultimate support pressure of a shallow shield tunnel excavation face according to claim 1 is characterized in that: The internal energy loss power in the arc rotation area model is calculated according to the third model, including: ； ； Where: D 外表面 represents the power consumed by the internal energy of the outer surface, D 上表面 represents the power consumed by the internal energy of the outer surface, ω For around O Angular velocity when point selection is made, β is the angle between the microelement on the arc rotation and the horizontal plane, r' ( β ) is the distance between the boundary of the microelement and the axis of the microelement, Indicates the angle of deviation from the O1 and O2 axes. represents effective cohesion, D represents tunnel diameter, α is the angle between the sliding surface and the horizontal direction during active failure, r 0 is the top radius of the cone, represents the distance between the boundary of the microelement and the center of the microelement, x represents the horizontal coordinate of the microelement, z represents the vertical coordinate of the microelement, and l represents the distance between the microelement and the axis. O 1 distance.

6. The method for determining the ultimate support pressure of a shallow shield tunnel excavation face according to claim 1, characterized in that: The arc rotation internal force and external force power in the arc rotation area model are calculated according to the third model, including: ； ； ； ； Where: W G is the gravitational power, W σT is the support pressure power, W Tz Arc rotation horizontal penetration power, W σ'y is the pressure power at the top of the arc swivel, D is the internal energy consumption power, ρ is the distance from the infinitesimal body to the center of the circle, θ For deviation O 1. O The angle of the 2 axes, σ T is the excavation face support pressure, represents the angle between the microelement on the arc rotation and the horizontal plane, Indicates effective cohesion, α is the angle between the sliding surface and the horizontal direction during active failure, r 0 is the top radius of the cone, γ' is the buoyancy density of soil, ω For around O The angular velocity of the point when it rotates, It represents the distance between the boundary of the microelement and the axis of the microelement. represents the vertical penetration force of the n-1th grid in the numerical model, represents the vertical penetration force of the nth grid in the numerical model, x represents the abscissa of the microelement, z represents the ordinate of the microelement, and l represents the distance between the microelement and O 1 distance, y represents the distance between the microelement and the ground surface, r n-1 represents the radius of the cylinder corresponding to the n-1th truncated cone, r n represents the radius of the cylinder corresponding to the nth truncated cone, n represents the number of truncated cones, Represents the vertical effective stress at the top of the microelement.

7. The method for determining the ultimate support pressure of a shallow shield tunnel excavation face according to claim 1 is characterized in that: The ultimate support pressure of the shallow shield is calculated through the arc rotation internal force, external force power, vertical pressure power and regional penetration power, including: W G - W σT + W Tz + W σ'y = D ； Where: W G is the gravitational power, W σT is the support pressure power, W Tz Arc rotation horizontal penetration power, W σ'y is the pressure power at the top of the arc swivel, D The power consumed is the internal energy.

8. A system for determining the ultimate support pressure of a shallow shield tunnel excavation face, characterized in that: Including processor and memory; Memory, used to store computer programs; A processor, for implementing the method steps described in any one of claims 1 to 7 when executing a program stored in a memory.

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