Tunnel stratum grouting reinforcement design method considering vertical jacking construction load

Abstract

The invention discloses a tunnel stratum grouting reinforcement design method considering a vertical jacking construction load, and belongs to the technical field of underground tunnel engineering. The prediction method comprises the steps that the value range of the grout injection rate beta is determined, the value range of the thickness D of a grouting reinforcement ring is determined, the design range of the grouting reinforcement ring is determined, and the range of the grouting reinforcement ring and the value range of grouting pressure P are further determined; according to the foundation bearing capacity requirements of a grouting reinforcement ring and an undisturbed stratum and the maximum floating displacement threshold value of local segments caused by the grouting lifting effect, a theoretical basis is provided for design of the range and thickness D of the grouting reinforcement ring, the grout injection rate beta and the grout pressure P, and control over design parameters of the grouting reinforcement ring is achieved; the theory based on the method is more reasonable, the calculation process is simple, and the method can be used for tunnel stratum grouting reinforcement design in actual vertical jacking construction.

Description

Technical Field

[0001] The invention belongs to the technical field of underground tunnel engineering and relates to a tunnel stratum grouting reinforcement design method considering vertical jacking construction load. Background Art

[0002] Drainage tunnels are important supporting buildings for large nuclear power plants in coastal areas. The drainage head structure of a drainage tunnel usually consists of a horizontal shield tunnel and multiple vertical jacking pipes. The vertical jacking method is widely used in the jacking pipe construction of the drainage head structure of a drainage tunnel due to its advantages such as short construction period, small impact on the environment and high economic benefits.

[0003] The lifting force during the vertical jacking construction will cause a concentrated load downward vertically on the horizontal shield tunnel. When the lifting force is large, it may cause excessive settlement of the underlying stratum of the horizontal shield tunnel, or even damage the bearing capacity of the foundation. In order to ensure the structural safety of the horizontal shield tunnel and the stability of the underlying stratum during the vertical jacking construction, the split grouting method is often used to reinforce the underlying stratum. However, since the drainage head structure of the drainage tunnel is usually located on the seabed, the seabed geological environment is complex and there are few related studies. In the existing schemes for strengthening the foundation of the shield tunnel when considering the vertical jacking construction load, the grouting parameters such as grouting range, grouting pressure and slurry injection rate are determined by experience, lacking a theoretical basis, resulting in poor grouting effect and even possible safety accidents. Summary of the invention

[0004] In view of the shortcomings of the prior art, the present invention proposes a tunnel stratum grouting reinforcement design method considering the vertical jacking construction load, which provides a theoretical basis for the calculation of the grouting reinforcement circle range and thickness D, slurry injection rate β, and slurry pressure P, and can effectively reduce the subjectivity of the horizontal shield tunnel stratum grouting reinforcement design at the drainage head of the drainage tunnel, and improve the structural safety of the horizontal shield tunnel during the vertical jacking construction. The method described in the present invention is suitable for the horizontal shield tunnel stratum splitting grouting reinforcement design when the vertical jacking construction load is considered, and the stratum around the tunnel approximately meets the assumption of the Winkler elastic foundation beam theory, that is, the stratum reaction force under the grouting reinforcement working condition is approximately proportional to the vertical deformation of the tunnel.

[0005] The present invention provides the following technical solution: a tunnel stratum grouting reinforcement design method considering vertical jacking construction load, specifically comprising the following steps:

[0006] S100, determine the value range of slurry injection rate β: according to the foundation bearing capacity of the grouting reinforcement ring is not less than the maximum lifting force F pmax The compressive stress acting on the vertical jacking arc diffusion base and the slurry injection rate β satisfy the following expression:

[0007]

[0008] Among them, E s0 E is the compression modulus of the cement used for grouting after solidification into stone body. s2 is the compression modulus of the original formation, f ak is the characteristic value of the foundation bearing capacity of the original stratum, F pmax is the maximum lifting force in vertical lifting construction, b b It is the side length of the vertical lifting arc diffusion base;

[0009] After determining the slurry injection rate β, the compression modulus of the grouting reinforcement ring can be determined according to the following formula:

[0010]

[0011] Among them, E s1 is the compression modulus of the grouting reinforcement ring;

[0012] S200, determine the value range of the grouting reinforcement ring thickness D: for the maximum lifting force F pmax The compressive stress that reacts on the vertical jacking arc diffusion base and diffuses to the original stratum should meet the foundation bearing capacity requirements, so the thickness D of the grouting reinforcement ring satisfies the following expression:

[0013]

[0014] Where α is the pressure diffusion angle;

[0015] According to the solution of Yegorov's plane problem and combined with the relevant provisions of the Code for Design of Building Foundations (GB50007-2011), the pressure diffusion angle α satisfies the following expression:

[0016]

[0017] Among them, b b is the side length of the vertical lifting arc diffusion base, E s2 is the compression modulus of the original formation;

[0018] S300, determine the design range of the grouting reinforcement ring: the grouting reinforcement ring is arranged in the underlying stratum of the shield tunnel and is distributed with equal thickness on the outer side of the shield tunnel segment. According to the principle that the range of the grouting reinforcement ring is not less than the pressure diffusion range of the vertical jacking construction load, the grouting reinforcement ring range corresponds to the shield tunnel center angle θ to satisfy the following expression:

[0019]

[0020] Among them, r o is the outer contour radius of the shield tunnel, t p is the shield tunnel lining thickness;

[0021] S400, further determine the range of the grouting reinforcement circle and the range of the grouting pressure P: During the construction of the drainage head structure of the drainage tunnel, the shield tunnel stratum grouting reinforcement construction step precedes the vertical jacking construction in sequence, so it is necessary to consider the problem of excessive floating displacement of the local pipe segment caused by the stratum grouting reinforcement construction; in the most unfavorable case, the shield tunnel buoyancy F w Satisfies the following expression:

[0022] F w =F w1 +F w2 -G o

[0023] Among them, F w1 is the static buoyancy, F w2 is the dynamic buoyancy, G o It is the deadweight of shield tunnel lining;

[0024] The dynamic buoyancy force F w2 The following expressions are satisfied:

[0025]

[0026] Where P is the grouting pressure;

[0027] The floating displacement of the local segment caused by the grouting reinforcement construction of the shield tunnel can be calculated according to the Winkler elastic foundation beam theory. The floating displacement S(x) satisfies the following differential equation expression:

[0028]

[0029] Where EI is the longitudinal stiffness of the shield tunnel, η is the correction factor for considering the reduction effect of the transverse joint when calculating the longitudinal stiffness of the shield tunnel, and k s is the vertical bed coefficient of the original stratum;

[0030] After solving the above differential equation, the maximum floating displacement S max Satisfies the following expression:

[0031]

[0032] Among them [S max ] is the floating displacement limit;

[0033] The scope of the grouting reinforcement circle and the range of the grouting pressure P are further determined, and the design of the grouting reinforcement of the horizontal shield tunnel stratum is completed.

[0034] Furthermore, in step S200, the lifting force F pIt changes with the progress of vertical lifting construction and reaches the maximum lifting force F at a certain state. pmax , and the lifting force F p Satisfies the following expression:

[0035] F p =G p +F f +F h

[0036] Among them, G p F is the deadweight of the jacking pipe, f is the friction resistance of the pipe wall, F h For the head-on resistance.

[0037] Further, in step S400, the static buoyancy F w1 is the hydrostatic pressure on the horizontal shield tunnel structure, satisfying the following expression:

[0038] F w1 =πr o 2 γ w

[0039] Among them, γ w The weight of water.

[0040] The present invention is based on the following principle analysis: During the vertical lifting construction process of the drainage head structure of the drainage tunnel, the purpose of the design of the grouting reinforcement ring of the horizontal shield tunnel stratum is to bear the vertical lifting construction load, so as to avoid insufficient foundation bearing capacity of the underlying stratum of the horizontal shield tunnel or settlement that will affect the safety of the structure. When the horizontal shield tunnel stratum is reinforced by splitting grouting, the range and thickness D of the grouting reinforcement ring, the slurry injection rate β and the slurry pressure P are the design parameters that need to be focused on. The problems of insufficient foundation bearing capacity or excessive settlement should be avoided in the design, and the anti-floating stability problems caused by the grouting lifting effect should also be paid attention to. Among them, for the problem of insufficient foundation bearing capacity, in addition to checking the foundation bearing capacity of the grouting reinforcement ring, the original soil layer below the grouting reinforcement ring should also be regarded as a weak underlying layer and the foundation bearing capacity should be checked; for the anti-floating stability problem caused by the grouting lifting effect, the maximum floating displacement S of the local segment can be calculated according to the Winkler elastic foundation beam theory. max , and requires the maximum floating displacement S max Not greater than the floating displacement limit [S max ], thereby realizing the control of the design parameters of the grouting reinforcement ring.

[0041] Compared with the prior art, the beneficial effects of the present invention are: a tunnel stratum grouting reinforcement design method considering the vertical jacking construction load is proposed, and according to the foundation bearing capacity requirements of the grouting reinforcement circle and the original stratum, and the threshold value of the maximum floating displacement of the local segment caused by the grouting lifting effect, a theoretical basis is provided for the design of the grouting reinforcement circle range and thickness D, slurry injection rate β, and slurry pressure P, solving the problem of determining the grouting design parameters based on experience in the prior art, which leads to poor grouting effect and possible safety hazards. The theory on which the present invention is based is more reasonable and the calculation process is relatively simple, which can be used for the tunnel stratum grouting reinforcement design in actual vertical jacking construction, and has strong practicality. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 Flow chart of the tunnel grouting reinforcement design method considering vertical jacking construction load;

[0043] Figure 2 Schematic diagram of tunnel stratum grouting reinforcement considering vertical jacking construction load;

[0044] Figure numerals: 1-horizontal shield tunnel, 2-vertical jacking arc diffusion base, 3-grouting reinforcement ring. DETAILED DESCRIPTION

[0045] The following is combined with Figure 1-2 The embodiments of the present invention are described in more detail with reference to the accompanying drawings so that a person skilled in the art can implement the present invention after reading the present description. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0046] The specific application project is the integrated design and construction project of drainage tunnels for units 3 and 4 of the Zhangzhou Nuclear Power Plant. The project adopts the drainage scheme of "shield starting pit + drill and blast tunnel + shield tunnel + drainage head". The drainage head structure of the drainage tunnel consists of a horizontal shield tunnel 1 and 10 vertical reinforced concrete jacking pipes. The horizontal shield tunnel 1 is a steel structure with an outer contour radius r o 3.65m, lining thickness t p is 0.4m, and the longitudinal moment of inertia I c 51.775m 4 The elastic modulus E of the steel material is 200 GPa. The correction coefficient η for the reduction of the transverse joints in the calculation of the longitudinal stiffness of the horizontal shield tunnel 1 is 0.7. The force-bearing surface of the vertical jacking arc diffusion base 2 is a square with a side length of 4 m. The original stratum under the horizontal shield tunnel 1 is sandy clay, and the compression modulus E s2 is 7.86MPa, vertical bed coefficient k s is 14.7MPa / m, and the characteristic value of bearing capacity f akThe maximum lifting force F in vertical lifting construction is 230kPa. pmax It is 6736.6kN.

[0047] S100, determine the value range of the grout injection rate β: according to the foundation bearing capacity of the grouting reinforcement ring 3 is not less than the maximum lifting force F pmax The compressive stress acting on the vertically lifted arc-shaped diffusion base 2 and the slurry injection rate β satisfy the following expression:

[0048]

[0049] Among them, E s0 E is the compression modulus of the cement used for grouting after solidification into stone body. s2 is the compression modulus of the original formation, b b is the side length of the vertically lifted arc-shaped diffusion base 2, f ak is the characteristic value of the foundation bearing capacity of the original stratum, F pmax It is the maximum lifting force in vertical lifting construction;

[0050] According to the calculation results of formula (1), the slurry injection rate β is required to be ≥ 16.3%. In the actual grouting reinforcement construction, in order to avoid human factors or accidental factors that cause the actual slurry injection rate to fail to reach 16.3%, the design document considers the surplus and requires the slurry injection rate β to reach 20%;

[0051] Compression modulus E of grouting reinforcement ring 3 s1 It can be determined according to formula (2);

[0052]

[0053] S200, determine the value range of the grouting reinforcement ring thickness D: for the maximum lifting force F pmax The compressive stress that reacts on the vertical jacking arc diffusion base 2 and diffuses to the original stratum, the original stratum should meet the foundation bearing capacity requirements, so the thickness D of the grouting reinforcement ring 3 satisfies the following expression:

[0054]

[0055] Among them, t p is the lining thickness of horizontal shield tunnel 1, α is the pressure diffusion angle;

[0056] According to the solution of Yegorov's plane problem and combined with the relevant provisions of the Code for Design of Building Foundations (GB50007-2011), the pressure diffusion angle α satisfies the following expression:

[0057]

[0058] Among them, E s1is the compression modulus of the grouting reinforcement ring 3, E s2 is the compression modulus of the original formation;

[0059] After substituting the actual engineering design parameters into equations (3) and (4) and performing joint iterative solutions, we obtain that the pressure diffusion angle α ≥ 20° and the thickness of the grouting reinforcement ring 3 D ≥ 2.06 m;

[0060] S300, determine the design range of the grouting reinforcement ring 3: the grouting reinforcement ring 3 is arranged in the underlying stratum of the horizontal shield tunnel 1, and is distributed with equal thickness on the outer side of the horizontal shield tunnel 1 segment. According to the principle that the range of the grouting reinforcement ring 3 is not less than the pressure diffusion range of the vertical jacking construction load, the grouting reinforcement ring 3 range corresponding to the center angle θ of the horizontal shield tunnel 1 satisfies the following expression:

[0061]

[0062] Among them, b b is the side length of the vertical lifting arc diffusion base 2, t p is the lining thickness of horizontal shield tunnel 1, r o is the outer contour radius of the horizontal shield tunnel 1;

[0063] In the actual tunnel stratum grouting reinforcement design, the determination of the center angle θ of the horizontal shield tunnel 1 corresponding to the range of the grouting reinforcement circle 3 needs to be further calculated in combination with the relevant expressions in step S400, and the engineering surplus should be fully considered;

[0064] S400, further determine the range of the grouting reinforcement ring 3 and the value range of the grouting pressure P: During the construction of the drainage head structure of the drainage tunnel, the horizontal shield tunnel 1 stratum grouting reinforcement construction step precedes the vertical jacking construction in sequence, so it is necessary to consider the problem of excessive floating displacement of the local pipe segment caused by the stratum grouting reinforcement construction; in the most unfavorable case, the shield tunnel buoyancy F w Satisfies the following expression:

[0065] F w =F w1 +F w2 -G o (6)

[0066] Among them, F w1 is the static buoyancy, F w2 is the dynamic buoyancy, G o F is the deadweight of the lining of horizontal shield tunnel 1; w 、F w1 、F w2 and G o All are values ​​per meter along the longitudinal direction of the tunnel;

[0067] The static buoyancy F w1Satisfies the following expression:

[0068] F w1 =πr o 2 γ w =418.5kN / m (7)

[0069] The horizontal shield tunnel 1 lining deadweight G o It can be determined as 685kN / m according to the lining mass calculation formula;

[0070] The dynamic buoyancy force F w2 The following expressions are satisfied:

[0071]

[0072] Where P is the grouting pressure;

[0073] The floating displacement of the local segment caused by the grouting reinforcement construction of the horizontal shield tunnel 1 can be calculated according to the Winkler elastic foundation beam theory. The floating displacement S(x) satisfies the following differential equation expression:

[0074]

[0075] Where EI is the longitudinal stiffness of the horizontal shield tunnel 1, η is the correction factor considering the reduction effect of the transverse joint when calculating the longitudinal stiffness of the horizontal shield tunnel 1, k s is the vertical bed coefficient of the original stratum;

[0076] After solving the differential equation (9), the maximum floating displacement S max Satisfies the following expression:

[0077]

[0078] Among them [S max ] is the floating displacement limit. According to the requirements of relevant standards and specifications of hydraulic tunnels and the actual situation of the project, the floating displacement limit [S max ] is 11mm;

[0079] After substituting the actual engineering design parameters into equations (6) and (10) and performing joint iterative solutions, it is calculated that the range of the grouting reinforcement ring 3 corresponds to the horizontal shield tunnel 1 center angle θ≤60°, the grouting pressure P≤0.5MPa, and the maximum floating displacement S at this time max =10.9mm, and S max ≤[S max ].

[0080] In the actual engineering design, the proposed grouting rate β is 20%, the thickness D of the grouting reinforcement ring 3 is 4m, the angle θ of the center of the horizontal shield tunnel 1 corresponding to the range of the grouting reinforcement ring 3 is 60°, and the grouting pressure P is 0.3-0.5MPa. Substituting the above-mentioned design parameters of the grouting reinforcement ring 3 into equations (1), (3), (5) and (10) for verification, the verification results show that all parameters meet the requirements of the value range. This means that under the condition of considering the vertical jacking construction load, the foundation bearing capacity of the grouting reinforcement ring 3 and the original stratum meets the requirements, and the maximum floating displacement of the local segment caused by the grouting lifting effect meets the requirements.

[0081] The above are one or more embodiments of the present invention, and the description is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be based on the attached claims.

Claims

1. The tunnel grouting reinforcement design method considering vertical jacking construction load is characterized by The following steps are involved: S100, determining the value range of the slurry injection rate β: the slurry injection rate β satisfies the following expression: Among them, E s0 E is the compression modulus of the cement used for grouting after solidification into stone body. s2 is the compression modulus of the original formation, f ak is the characteristic value of the foundation bearing capacity of the original stratum, F pmax is the maximum lifting force in vertical lifting construction, b b It is the side length of the vertical lifting arc diffusion base; S200, determining the value range of the grouting reinforcement ring thickness D: the grouting reinforcement ring thickness D satisfies the following expression: Where α is the pressure diffusion angle; S300, determine the design range of the grouting reinforcement ring: the grouting reinforcement ring is arranged in the underlying stratum of the shield tunnel and is distributed with equal thickness outside the shield tunnel segment; the grouting reinforcement ring range corresponds to the shield tunnel center angle θ that satisfies the following expression: Among them, r o is the outer contour radius of the shield tunnel, t p is the shield tunnel lining thickness; S400, further determine the range of the grouting reinforcement ring and the value range of the grouting pressure P: the buoyancy F of the shield tunnel w Satisfies the following expression: F w =F w1 +F w2 -G o The dynamic buoyancy force F w2 Satisfies the following expressions: Where P is the grouting pressure; Maximum floating displacement S max Satisfies the following expression: Among them [S max ] is the floating displacement limit; EI is the longitudinal stiffness of the shield tunnel, η is the correction coefficient considering the reduction effect of the transverse joint when calculating the longitudinal stiffness of the shield tunnel, k s is the vertical bed coefficient of the original stratum; The scope of the grouting reinforcement circle and the range of the grouting pressure P are further determined, and the design of the grouting reinforcement of the horizontal shield tunnel stratum is completed.

2. The tunnel stratum grouting reinforcement design method considering vertical jacking construction load according to claim 1 is characterized in that: In step S100, the compression modulus E of the grouting reinforcement ring s1 It can be determined according to the following formula: Among them, E s1 is the compression modulus of the grouting reinforcement ring.

3. The tunnel stratum grouting reinforcement design method considering vertical jacking construction load according to claim 1 is characterized in that: In step S200, the pressure diffusion angle α satisfies the following expression: Among them, b b is the side length of the vertical lifting arc diffusion base, E s2 is the compression modulus of the original formation.

4. The tunnel stratum grouting reinforcement design method considering vertical jacking construction load according to claim 1 is characterized in that: In step S200, the lifting force F p It changes with the progress of vertical lifting construction and reaches the maximum lifting force F at a certain state. pmax , and the lifting force F p Satisfies the following expression: F p =G p +F f +F h Among them, G p F is the deadweight of the jacking pipe, f is the friction resistance of the pipe wall, F h For the head-on resistance.

5. The tunnel stratum grouting reinforcement design method considering vertical jacking construction load according to claim 1 is characterized in that: In step S400, the static buoyancy F w1 is the hydrostatic pressure on the horizontal shield tunnel structure, satisfying the following expression: F w1 =πr o 2 c w Among them, γ w The weight of water.

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