Tunnel Ground Grouting Reinforcement Design Method Considering Vertical Jacking Construction Load

Abstract

The present invention discloses a design method for grouting reinforcement of tunnel strata considering vertical jacking construction loads, belonging to the technical field of underground tunnel engineering. The prediction method of the present invention includes determining the value range of the slurry injection rate β, determining the value range of the thickness D of the grouting reinforcement ring, determining the design range of the grouting reinforcement ring, further determining the range of the grouting reinforcement ring and the value range of the grouting pressure P; according to the foundation bearing capacity requirements of the grouting reinforcement ring and the original formation, and the threshold value of the maximum floating displacement of the local segment caused by the grouting lifting effect, it provides a theoretical basis for the design of the range and thickness D of the grouting reinforcement ring, the slurry injection rate β, and the slurry pressure P, and realizes the control of the design parameters of the grouting reinforcement ring; the theory on which the present invention is based is more reasonable and the calculation process is relatively simple, and it can be used for the design of grouting reinforcement of tunnel strata in actual vertical jacking construction.

Description

Technical Field

[0001] The present invention belongs to the technical field of underground tunnel engineering, and relates to a design method for grouting reinforcement of tunnel strata considering vertical jacking construction loads. Background Technique

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

[0003] The jacking force during the construction of the vertical jacking method will cause a vertically downward concentrated load on the shield tunnel with a horizontal orientation. When the jacking force value is large, it may cause excessive settlement of the underlying strata of the horizontal shield tunnel, and even cause the failure of the bearing capacity of the foundation. In order to ensure the structural safety of the horizontal shield tunnel and the stability of its underlying strata during the construction of the vertical jacking method, the method of split grouting is often used to reinforce the underlying strata. However, since the drainage head structure of the drainage tunnel is usually located under the sea, the seabed geological environment is complex and there is little relevant research. In the existing schemes for the foundation reinforcement of shield tunnels considering vertical jacking construction loads, grouting parameters such as the grouting range, grouting pressure, and slurry injection rate are determined by experience, lacking theoretical basis, resulting in poor grouting effect and even possible induction of safety accidents. Summary of the Invention

[0004] Aiming at the deficiencies of the existing technology, the present invention proposes a design method for grouting reinforcement of tunnel strata considering vertical jacking construction loads, providing a theoretical basis for the calculation of the range and thickness D of the grouting reinforcement circle, the slurry injection rate β, and the slurry pressure P, which can effectively reduce the subjectivity of the design of the grouting reinforcement of the strata of the horizontal shield tunnel 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 of the present invention is applicable to the design of split grouting reinforcement of the strata of the horizontal shield tunnel considering vertical jacking construction loads, and the strata around the tunnel approximately satisfy the assumptions of the Winkler elastic foundation beam theory, that is, the magnitude of the strata reaction force under the grouting reinforcement condition is approximately proportional to the vertical deformation of the tunnel.

[0005] The present invention provides the following technical solutions: A design method for grouting reinforcement of tunnel strata considering vertical jacking construction loads, specifically including the following steps:

[0006] S100. Determine the value range of the slurry injection rate β: According to the bearing capacity of the foundation of the grouting reinforcement circle not less than the maximum jacking force F pmax The compressive stress acting on the vertical jacking arc-shaped diffusion base, the slurry injection rate β satisfies the following expression:

[0007]

[0008] Among them, E s0 is the compression modulus after the cement used for grouting solidifies into a stone body, and E s2 is the compression modulus of the original formation, and f ak is the characteristic value of the bearing capacity of the original formation's foundation, and F pmax is the maximum jacking force in the vertical jacking construction, and b b is the side length of the vertical jacking arc-shaped diffusion base;

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

[0010]

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

[0012] S200. Determine the value range of the thickness D of the grouting reinforcement circle: For the maximum jacking force F pmax The compressive stress that acts on the vertical jacking arc-shaped diffusion base and spreads to the original formation, and the original formation should meet the requirements of the bearing capacity of the foundation. Therefore, the thickness D of the grouting reinforcement circle satisfies the following expression:

[0013]

[0014] Among them, α is the pressure diffusion angle;

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

[0016]

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

[0018] S300. Determine the design range of the grouting reinforcement circle: The grouting reinforcement circle is arranged in the underlying formation of the shield tunnel and is evenly distributed in thickness outside the shield tunnel segment. According to the principle that the range of the grouting reinforcement circle is not less than the pressure diffusion range of the vertical jacking construction load, the central angle θ of the grouting reinforcement circle corresponding to the shield tunnel satisfies the following expression:

[0019]

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

[0021] S400. Further determine the range of the grouting reinforcement circle and the value range of the grouting pressure P: During the construction of the drainage head structure of the drainage tunnel, the construction steps of the shield tunnel strata grouting reinforcement precede the vertical jacking construction in sequence. Therefore, it is necessary to consider the problem of excessive local segment floating displacement caused by the shield tunnel strata grouting reinforcement construction. In the most unfavorable case, the buoyancy force F of the shield tunnel w satisfies the following expression:

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

[0023] Among them, F w1 is the static buoyancy force, F w2 is the dynamic buoyancy force, and G o is the self-weight of the shield tunnel lining;

[0024] The dynamic buoyancy force F w2 satisfies the following expression:

[0025]

[0026] Among them, P is the grouting pressure;

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

[0028]

[0029] Among them, EI is the longitudinal stiffness of the shield tunnel, η is the correction coefficient considering the reduction effect of the transverse joint in the calculation of the longitudinal stiffness of the shield tunnel, and k s is the vertical subgrade coefficient of the original formation;

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

[0031]

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

[0033] Further determine the range of the grouting reinforcement circle and the value range of the grouting pressure P, and complete the design of the shield tunnel strata grouting reinforcement.

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

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

[0036] where G p is the self-weight of the pipe jacking, F f is the frictional resistance of the pipe wall, and F h is the face resistance.

[0037] Furthermore, in step S400, the static buoyancy force F w1 is the hydrostatic pressure on the horizontal shield tunnel structure and satisfies the following expression:

[0038] F w1 = πr o 2 γ w

[0039] where γ w is the unit weight of water.

[0040] The principle analysis of the present invention is as follows: During the vertical jacking construction of the drainage head structure of the drainage tunnel, the purpose of the grouting reinforcement ring design of the horizontal shield tunnel stratum is to bear the vertical jacking construction load and avoid insufficient bearing capacity of the foundation layer under the horizontal shield tunnel or settlement that will affect the structural safety. When the horizontal shield tunnel stratum is reinforced by split grouting, the range and thickness D of the grouting reinforcement ring, the grout injection rate β, and the grout pressure P are design parameters that need to be focused on. In the design, problems such as insufficient bearing capacity of the foundation or excessive settlement should be avoided. At the same time, attention should also be paid to the anti-floating stability problem caused by the grouting lifting effect. Among them, for the problem of insufficient bearing capacity of the foundation, in addition to checking the bearing capacity of the grouting reinforcement ring, the original soil layer under the grouting reinforcement ring should also be regarded as a weak underlying layer and the bearing capacity of the foundation should be checked; for the anti-floating stability problem caused by the grouting lifting effect, the maximum upward displacement S max of the local segment can be calculated according to the Winkler elastic foundation beam theory, and it is required that the maximum upward displacement S max shall not be greater than the upward displacement limit value [S max , so as to realize 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 as follows: A design method for grouting reinforcement of tunnel strata considering the construction load of vertical jacking is proposed. According to the requirements of the foundation bearing capacity of the grouting reinforcement circle and the original formation, and the threshold value of the maximum floating displacement of the local segment caused by the grouting uplift effect, it provides a theoretical basis for the design of the range and thickness D of the grouting reinforcement circle, the grout injection rate β, and the grout pressure P, and solves the problems in the prior art that the grouting design parameters are determined by experience, resulting in poor grouting effect and potential safety hazards. The theory on which the present invention is based is more reasonable and the calculation process is relatively simple. It can be used for the grouting reinforcement design of tunnel strata in actual vertical jacking construction, and has strong practicability. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 FIG. is a flow chart of a design method for grouting reinforcement of tunnel strata considering the construction load of vertical jacking;

[0043] Figure 2 FIG. is a schematic diagram of grouting reinforcement of tunnel strata considering the construction load of vertical jacking;

[0044] Reference numerals: 1 - horizontal shield tunnel, 2 - vertical jacking arc-shaped diffusion base, 3 - grouting reinforcement circle. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0045] The following further elaborates on the embodiments of the present invention in conjunction with the Figure 1-2 accompanying drawings and reference numerals, enabling those skilled in the art to implement it after studying this specification. 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 the drainage tunnels for Units 3 and 4 of Zhangzhou Nuclear Power Plant. The project adopts a drainage scheme of "shield launching foundation pit + drill-and-blast tunnel + shield tunnel + drainage head". The drainage head structure of the drainage tunnel consists of 1 horizontal shield tunnel 1 and 10 vertically oriented reinforced concrete jacking pipe conduits. The horizontal shield tunnel 1 is made of steel, with an outer contour radius r o of 3.65 m, a lining thickness t p of 0.4 m, a longitudinal moment of inertia I c of 51.775 m 4 , the elastic modulus E of the steel material is 200 GPa, and the correction coefficient η considering the reduction effect of transverse joints is taken as 0.7 when calculating the longitudinal stiffness of the horizontal shield tunnel 1. The stress surface of the vertical jacking arc-shaped diffusion base 2 is a square with a side length of 4 m. The original formation underlying the horizontal shield tunnel 1 is sandy clay, with a compression modulus E s2 of 7.86 MPa, a vertical subgrade reaction coefficient k s of 14.7 MPa / m, and a characteristic value of bearing capacity f akis 230 kPa. The maximum jacking force F that appears during the vertical jacking construction pmax is 6736.6 kN.

[0047] S100. Determine the value range of the grout injection rate β: According to the bearing capacity of the foundation of the grouting reinforcement zone 3 is not less than the maximum jacking force F pmax The compressive stress acting on the vertical jacking arc-shaped diffusion base 2, the grout injection rate β satisfies the following expression:

[0048]

[0049] Among them, E s0 is the compression modulus of the cement used for grouting after solidifying into a stone body, E s2 is the compression modulus of the original formation, b b is the side length of the vertical jacking arc-shaped diffusion base 2, f ak is the characteristic value of the bearing capacity of the original formation, F pmax is the maximum jacking force during the vertical jacking construction;

[0050] According to the calculation results of formula (1), it is required that the grout injection rate β≥16.3%. In the actual formation grouting reinforcement construction, in order to avoid the actual grout injection rate not reaching 16.3% due to human factors or accidental factors, therefore, a surplus is considered in the design document and it is required that the grout injection rate β reaches 20%;

[0051] The compression modulus E of the grouting reinforcement zone 3 s1 can be determined according to formula (2);

[0052]

[0053] S200. Determine the value range of the thickness D of the grouting reinforcement zone: For the maximum jacking force F pmax The compressive stress acting on the vertical jacking arc-shaped diffusion base 2 and spreading to the original formation, the original formation should meet the bearing capacity requirements, so the thickness D of the grouting reinforcement zone 3 satisfies the following expression;

[0054]

[0055] Among them, t p is the lining thickness of the horizontal shield tunnel 1, and 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 Foundation" (GB50007-2011), the pressure diffusion angle α satisfies the following expression:

[0057]

[0058] Among them, E s1is the compression modulus of the grouting reinforcement zone 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 solution, the pressure diffusion angle α≥20° and the thickness D of the grouting reinforcement zone 3≥2.06 m are obtained;

[0060] S300. Determine the design scope of the grouting reinforcement zone 3: The grouting reinforcement zone 3 is arranged in the underlying formation of the horizontal shield tunnel 1 and is evenly distributed with equal thickness outside the segments of the horizontal shield tunnel 1. According to the principle that the scope of the grouting reinforcement zone 3 is not less than the pressure diffusion range of the vertical jacking construction load, the central angle θ of the grouting reinforcement zone 3 corresponding to the horizontal shield tunnel 1 satisfies the following expression:

[0061]

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

[0063] In the actual design of tunnel formation grouting reinforcement, the determination of the central angle θ of the grouting reinforcement zone 3 corresponding to the horizontal shield tunnel 1 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 zone 3 and the value range of the grouting pressure P: During the construction of the drainage head structure of the drainage tunnel, the construction step of the formation grouting reinforcement of the horizontal shield tunnel 1 is prior to the vertical jacking construction in sequence. Therefore, the problem of excessive local segment floating displacement caused by the formation grouting reinforcement construction needs to be considered; in the most unfavorable case, the buoyancy force F of the shield tunnel w satisfies the following expression:

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

[0066] where F w1 is the static buoyancy force, F w2 is the dynamic buoyancy force, G o is the self-weight of the lining of the horizontal shield tunnel 1; F w 、F w1 、F w2 and G o are all values per meter along the longitudinal direction of the tunnel;

[0067] The static buoyancy force F w1Satisfy the following expression:

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

[0069] The self-weight G of the lining of the horizontal shield tunnel 1 o can be determined to be 685 kN / m according to the lining quality calculation formula;

[0070] The dynamic buoyancy force F w2 satisfies the following expression:

[0071]

[0072] where P is the grouting pressure;

[0073] The local segment floating displacement caused by the construction of the ground grouting reinforcement 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 coefficient considering the reduction effect of the transverse joint in the calculation of the longitudinal stiffness of the horizontal shield tunnel 1, and k s is the vertical subgrade coefficient of the original formation;

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

[0077]

[0078] where [S max is the limit value of the floating displacement. Combining the relevant code standards of the hydraulic tunnel and the actual situation of the project, it is required that the limit value of the floating displacement [S max is 11 mm;

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

[0080] In the actual engineering design, the slurry injection rate β is set to 20%, the thickness D of the grouting reinforcement ring 3 is 4m, the central angle θ corresponding to the range of the grouting reinforcement ring 3 for the horizontal shield tunnel 1 is 60°, and the grouting pressure P is 0.3 - 0.5MPa. Substitute the above design parameters of the grouting reinforcement ring 3 into equations (1), (3), (5) and (10) for checking. The checking 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 capacities of the grouting reinforcement ring 3 and the original formation meet the requirements, and the maximum local segment floating displacement 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 should not be construed as a limitation to the scope of the present invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several deformations and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention patent shall be subject to the appended 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 Among them, F w1 is the static buoyancy, F w2 is the dynamic buoyancy, G o It is the deadweight of shield tunnel lining; 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 2 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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