Reinforcement design and evaluation method for surrounding stratum of vertical jacking pipeline of subsea tunnel

Abstract

The invention discloses a reinforcement design and evaluation method for a surrounding stratum of a vertical jacking pipeline of a subsea tunnel, and belongs to the technical field of underground tunnel engineering. The design method comprises the steps of grouting reinforcement body strength checking calculation, grouting pressure calculation, establishment of a prediction model of permeability coefficients, seepage analysis, back calculation of the grout injection rate according to the average leakage amount and selection of reasonable design parameter values. According to the design method, reasonable design parameter values are selected for reinforcement design of the stratum around the vertical jacking pipeline of the subsea tunnel, and the problems that the grouting effect is poor and even safety accidents are induced due to the fact that grouting parameters are determined according to experience in construction are solved; the evaluation method comprises the steps of grouting pressure evaluation, grout injection rate evaluation, grouting reinforcement body permeability coefficient evaluation and grouting reinforcement overall effect evaluation. According to the evaluation method, overall grouting reinforcement effect evaluation is achieved, and it is ensured that the grouting reinforcement scheme reaches the designed expected effect.

Description

Technical Field

[0001] This invention belongs to the field of underground tunnel engineering technology, and relates to the design and evaluation method of strengthening the strata around the vertical jacking pipeline of the submarine tunnel. Background Technology

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

[0003] During vertical jacking construction, a certain gap is usually reserved between the jacking pipe and the reserved opening of the horizontal tunnel. After the vertical jacking construction is completed, the junction of the vertically oriented jacking pipe and the horizontal tunnel will become the weak point of the drainage head structure of the drainage tunnel. On the one hand, the lining segments and jacking segments of the horizontal tunnel in this weak section suffer from stress concentration. Furthermore, during operation, the change in water momentum as the water flows from the horizontal tunnel into the jacking pipe translates into pressure acting on the sidewalls of the jacking segments. This pressure exacerbates the stress concentration problem in this weak section. Additionally, the surrounding strata of the pipeline corresponding to this weak section are likely to undergo excessive deformation during the load-bearing process, leading to excessive inclination of the jacking pipe and affecting the safety of the drainage tunnel's drainage head structure and the reliability of its drainage function during operation. On the other hand, this weak section also poses a risk of leakage. Because large nuclear power plants in coastal areas typically use larger jacking segments to improve drainage efficiency, the potential seepage area increases. If the construction quality of the anti-leakage structure in this weak section is poor, or if structural cracking occurs during operation due to excessive inclination of the jacking pipe, high-pressure water and sediment from the seabed may flow into the jacking pipe, causing personal injury and rendering the water diversion project unusable.

[0004] These common and serious construction quality problems necessitate that the surrounding strata at the junction of the jacking pipeline and the horizontal tunnel possess excellent load-bearing and seepage-proof capabilities. However, the vertical jacking construction process requires overcoming the oncoming resistance of the overlying strata and the friction between the sidewall of the jacking pipeline and the surrounding strata. This results in the surrounding strata of the jacking pipeline being in a loose state after the vertical jacking construction, making it difficult to provide the necessary load-bearing and seepage-proof functions for the jacking pipeline. Therefore, it is necessary to reinforce the surrounding strata at the junction of the jacking pipeline and the horizontal tunnel.

[0005] Because the drainage head structure of drainage tunnels is usually located on the seabed, the seabed geological environment is complex and related research is limited. In existing methods for grouting reinforcement of the surrounding strata at the junction of the jacking pipe and the horizontal tunnel, grouting parameters such as grouting pressure and grout injection rate are determined empirically, lacking theoretical basis. This results in poor grouting effects and may even induce safety accidents. Furthermore, the complex seabed environment makes it difficult to inspect the strata surrounding the jacking pipe, thus making it difficult to evaluate the effectiveness of grouting reinforcement. Therefore, it is necessary to establish a practical and accurate evaluation method for grouting reinforcement effects to ensure that the grouting reinforcement scheme achieves the expected design results. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention proposes a method for designing and evaluating the reinforcement of the surrounding strata of vertical jacking pipes in submarine tunnels. This method is applicable to the design and evaluation of grouting reinforcement of the surrounding strata near the junction of the horizontal tunnel and the jacking pipe in the drainage head structure of submarine drainage tunnels. It provides a theoretical basis for grouting reinforcement design and offers a practical and accurate method for evaluating the grouting reinforcement effect, thereby improving the safety and reliability of the drainage head structure of submarine drainage tunnels.

[0007] The first aspect of this application discloses a method for reinforcing the surrounding strata of a vertically jacking pipeline in a submarine tunnel, specifically including the following steps:

[0008] S101. Strength verification of grouting reinforcement: Based on the principle that the bearing capacity of the foundation of the grouting reinforcement ring is not less than the sum of the water pressure inside the pipe during operation and the impact pressure of water flow acting on the side wall of the jacking pipe segment, the grout injection rate R... i Satisfy the following expression:

[0009]

[0010] Among them, E s0 E is the compression modulus of the cement used in grouting after it has solidified into a stone mass. s2 f is the compressibility modulus of the original strata. ak ρ represents the characteristic value of the bearing capacity of the original strata. w S is the density of water. w v is the cross-sectional area of ​​the jacking pipe. w H represents the average water flow velocity during the operation of the jacking pipeline. c ρ represents the vertical thickness of the grouting reinforcement, and p represents the water pressure inside the pipe during operation.

[0011] S102. Grouting Pressure Calculation: To ensure that the grout can penetrate into the formation and maintain formation stability, the design grouting pressure P for grouting reinforcement of the formation around the jacking pipeline is calculated. c It should be greater than the active earth pressure strength E at the grouting hole. aAnd less than the passive earth pressure intensity E at the grouting hole. p That is, the design grouting pressure P c Satisfy the following expression:

[0012]

[0013] Where, σ z θ is the vertical stress of the formation at the grouting hole, θ is the internal friction angle of the formation at the grouting hole, and c is the cohesion of the formation at the grouting hole.

[0014] S103. Establish a predictive model for the permeability coefficient: For the surrounding strata samples collected during the exploration period near the junction of the horizontal tunnel and the jacking pipeline, grouting reinforcement samples were prepared with reference to the "Specification for Cement-Soil Mix Proportion Design" (JGJ / T 233—2011). The grout injection rate R of the grouting reinforcement sample was... i Satisfy the following expression:

[0015]

[0016] Among them, V c V is the volume of cement slurry incorporated into the sample. r Where n is the volume of the grouting solid, n is the porosity of the formation, and α is the grout loss rate.

[0017] To establish the permeability coefficient as a function of grout injection rate R i The predictive model for the changes was developed using a variable head test method for various grout injection rates R. i The permeability coefficient of the grouting-reinforced samples was measured, and regression analysis was performed on the permeability coefficient test data to obtain the permeability coefficient k of the grouting-reinforced body in the stratum surrounding the jacking pipe. c With grout injection rate R i The regression model uses a log-linear model, as shown in the following expression:

[0018]

[0019] Where b1 and b2 are both parameters of the fitted model;

[0020] S104. Seepage Analysis: The junction between the horizontal tunnel and the jacking pipe is the most unfavorable point for seepage prevention. The seepage analysis conservatively assumes that the entire seepage prevention capacity is provided by the grouting and solidification of the surrounding strata. Therefore, the shortest seepage path is the vertical distance from the seabed surface to this junction. According to Darcy's law, the equivalent permeability coefficient k of the grouting and solidification and the undisturbed strata... e Satisfy the following expression:

[0021]

[0022] Where H is the vertical distance between the seabed surface and the junction. c k represents the vertical thickness of the grouting reinforcement. c H is the permeability coefficient of the grouting solids. s k represents the thickness of the original formation above the grouting solidification. s The permeability coefficient of the original formation above the grouting solidification;

[0023] S105. Calculate the grout injection rate based on the average leakage rate: The average leakage rate at this junction is Q. w Satisfy the following expression:

[0024] Q w =k e ·A e ·i≤[Q w ]

[0025] Where A e Let i be the cross-sectional area of ​​the seepage flow, and i be the hydraulic gradient. w [This refers to the average leakage limit;]

[0026] The equivalent permeability coefficient k is determined based on the range of average leakage. e The range of values ​​for k is then used to calculate the permeability coefficient k of the grouting reinforcement. c The range of values ​​for [k] cmin ,k s Finally, the slurry injection rate R was calculated. i The range of values ​​for [R] imin ,R imax ];

[0027] S106. Select reasonable design parameter values: Based on the value range required for each parameter in steps S101 to S105, select reasonable design parameter values ​​for the reinforcement design of the surrounding strata of the vertical jacking pipeline of the submarine tunnel.

[0028] The second aspect of this application discloses a method for evaluating the reinforcement of the surrounding strata of a vertically jacking pipeline in a submarine tunnel, which specifically includes the following steps:

[0029] S201. Grouting Pressure Evaluation: The grouting pressure during the grouting reinforcement construction of the strata surrounding the jacking pipeline is tracked and recorded in real time to obtain the actual average grouting pressure P. ca Grouting pressure evaluation index I p Satisfy the following expression:

[0030]

[0031] Among them, E a E represents the active earth pressure at the grouting hole. p P represents the passive earth pressure at the grouting hole.c To design the grouting pressure;

[0032] S202. Grout Injection Rate Evaluation: The actual total volume V of cement grout during the grouting and reinforcement construction of the strata surrounding the jacking pipe. ca Record the data to calculate the actual grout injection rate R. ia Actual slurry injection rate R ia Satisfy the following expression:

[0033]

[0034] Grout injection rate evaluation index I r Satisfy the following expression:

[0035]

[0036] Among them, R imin and R imax The slurry injection rate R i The lower and upper limits of the value;

[0037] S203. Evaluation of the permeability coefficient of the grouting reinforcement: The permeability coefficient of the grouting reinforcement is tested through a water injection test. During the test, the permeability section and the rubber sealing section are determined inside the water injection borehole. Based on the water injection test conditions and results, the actual permeability coefficient k of the grouting reinforcement is determined. ca Satisfy the following expression:

[0038]

[0039] Among them, l w s is the length of the water injection borehole test section. w r is the water head height of the water injection borehole. w Q is the radius of the water injection borehole. w To ensure a stable water injection rate for the water injection borehole;

[0040] Evaluation index of grouting solidification permeability coefficient I k Satisfy the following expression:

[0041]

[0042] Where, k cmin The permeability coefficient k of the grouting solids c The lower limit of the value;

[0043] S204. Overall effect evaluation of grouting reinforcement: Evaluation index I of grouting pressure calculated based on steps S201 to S203. p Evaluation index of grout injection rate I r Evaluation index I of grouting solidification permeability coefficient kThe overall effect of grouting reinforcement is evaluated, and the evaluation index I0 of the overall effect of grouting reinforcement satisfies the following expression:

[0044]

[0045] The qualification standard of the overall effect evaluation index I0 of grouting reinforcement is determined according to the actual engineering requirements, and then the overall effect of grouting reinforcement is evaluated based on the overall effect evaluation index I0.

[0046] Compared with existing technologies, the beneficial effects of this invention are as follows: For the top-level grouting reinforcement project around the jacking pipe in the vertical jacking construction of the drainage head structure of a submarine drainage tunnel, a design method for reinforcing the strata around the vertically jacking pipe of a submarine tunnel is disclosed. This design method includes strength verification of the grouting reinforcement body, grouting pressure calculation, establishing a predictive model for the permeability coefficient, seepage analysis, back-calculation of the grout injection rate based on the average leakage, and selection of reasonable design parameter values. Specifically, the strength verification of the grouting reinforcement body ensures the strength requirements of the grouting reinforcement body; the design of the grouting pressure ensures that the grout can penetrate into the strata without causing strata instability; subsequently, based on the predictive model of the change in strata permeability coefficient with grout injection rate, the range of the equivalent permeability coefficient is determined according to the range of the average leakage, and then the permeability coefficient of the grouting reinforcement body is back-calculated. The range of values ​​is determined by reverse calculation to obtain the range of grout injection rate values, thereby selecting reasonable design parameter values ​​for the reinforcement design of the strata surrounding the vertical jacking pipeline of the submarine tunnel. This avoids the problem of poor grouting effect or even safety accidents caused by determining grouting parameters based on experience during construction. In addition, this invention also discloses an evaluation method for the reinforcement of the strata surrounding the vertical jacking pipeline of the submarine tunnel. This evaluation method includes evaluation of grouting pressure, evaluation of grout injection rate, evaluation of the permeability coefficient of the grouting reinforcement, and evaluation of the overall effect of grouting reinforcement. Among them, the actual average grouting pressure and actual grout injection rate are obtained by real-time tracking and recording of the grouting reinforcement construction process around the jacking pipeline. The actual permeability coefficient of the grouting reinforcement is obtained through water injection test, and finally the overall effect of grouting reinforcement is evaluated to ensure that the grouting reinforcement scheme achieves the expected design effect. Attached Figure Description

[0047] Figure 1 This is a flowchart of the design method for reinforcing the surrounding strata of the vertical jacking pipeline in a submarine tunnel according to the present invention;

[0048] Figure 2 This is a flowchart of the evaluation method for strengthening the surrounding strata of the vertical jacking pipeline in a submarine tunnel according to the present invention;

[0049] Figure 3 This is a schematic diagram of the ground reinforcement around the vertical lifting pipeline of the submarine tunnel according to the present invention;

[0050] Figure 4This is a graph showing the relationship between the permeability coefficient of the grouting solids and the grout injection rate in an embodiment of the present invention.

[0051] Attached reference numerals: 1-Lifting pipe, 2-Horizontal tunnel, 3-Grouting solidified body, 4-Seabed surface, 5-Sea level. Detailed Implementation

[0052] The following is in conjunction with the appendix Figure 1-4 The accompanying drawings and reference numerals provide a more detailed description of the embodiments of the present invention, enabling those skilled in the art to implement it after reading this specification. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of the invention.

[0053] The specific application project is the integrated design and construction project of drainage tunnels for Units 3 and 4 of Zhangzhou Nuclear Power Plant. The project adopts a drainage scheme of "shield starting pit + drill and blast tunnel + shield tunnel + drainage head". The drainage head structure of the drainage tunnel consists of one horizontal shield tunnel and ten vertical reinforced concrete jacking pipes.

[0054] The first aspect of this application provides as follows: Figure 1-4 The method for reinforcing the surrounding strata of the vertical jacking pipeline for the subsea tunnel, as shown, specifically includes the following steps:

[0055] S101. Strength verification of grouting reinforcement: Based on the principle that the bearing capacity of the foundation of the grouting reinforcement ring is not less than the sum of the water pressure inside the pipe during operation and the impact pressure of water flow acting on the side wall of the jacking pipe segment, the grout injection rate R... i Satisfy the following expression:

[0056]

[0057] Among them, E s0 E is the compression modulus of the cement used in grouting after it has solidified into a stone mass. s2 f is the compressibility modulus of the original strata. ak ρ represents the characteristic value of the bearing capacity of the original strata. w S is the density of water. w v is the cross-sectional area of ​​the jacking pipe. w H represents the average water flow velocity during the operation of the jacking pipeline. c ρ represents the vertical thickness of the grouting reinforcement, and p represents the water pressure inside the pipe during operation.

[0058] In practice, the compression modulus E of the cement used for grouting after it solidifies into a stone mass is... s0 The compressibility modulus of the original formation is 40 MPa, and the compressibility modulus E is... s2 The characteristic value of the bearing capacity f of the undisturbed strata is 7.86 MPa. ak The pressure is 230 kPa, and the density ρ of water is... w 1000 kg / m3 The cross-sectional area S of the jacking pipe w It is 3.61m 2 The average water flow velocity v during the operation of the jacking pipeline w The flow rate is 10 m / s, and the water pressure p in the pipe during operation is 200 kPa. The slurry injection rate R is calculated according to formula (1). i ≥0.051;

[0059] S102. Grouting Pressure Calculation: To ensure that the grout can penetrate into the formation and maintain formation stability, the design grouting pressure P for grouting reinforcement of the formation around the jacking pipeline is calculated. c It should be greater than the active earth pressure strength E at the grouting hole. a And less than the passive earth pressure intensity E at the grouting hole. p That is, the design grouting pressure P c Satisfy the following expression:

[0060]

[0061] Where, σ z θ is the vertical stress of the formation at the grouting hole, θ is the internal friction angle of the formation at the grouting hole, and c is the cohesion of the formation at the grouting hole.

[0062] In practice, the grouting hole is located near the junction of horizontal tunnel 2 and jacking pipe 1. The internal friction angle θ of the stratum at the grouting hole is 12°, the cohesion c of the stratum at the grouting hole is 24.6 kPa, the vertical distance H between the seabed surface 4 and the junction is 8 m, and the unit weight of the stratum is 19.4 kN / m³. 3 The vertical distance between the seabed surface 4 and the sea level 5 is 8m, and the specific gravity of seawater is 10kN / m³. 3 The vertical stress σ of the stratum at the grouting hole is then... z The active earth pressure intensity E at the grouting hole is 235.2 kPa; according to equation (1), the active earth pressure intensity E at the grouting hole is 235.2 kPa. a The calculation is as follows:

[0063]

[0064] According to equation (1), the passive earth pressure intensity E at the grouting hole is... p The calculation is as follows:

[0065]

[0066] Based on equations (2), (3), and (4), the grouting pressure P is designed. c The value range is [114.4 kPa, 419.4 kPa];

[0067] S103. Establish a predictive model for the permeability coefficient: For the surrounding strata samples collected during the exploration period near the junction of the horizontal tunnel and the jacking pipeline, grouting reinforcement samples were prepared with reference to the "Specification for Cement-Soil Mix Proportion Design" (JGJ / T 233—2011). The grout injection rate R of the grouting reinforcement sample was... i Satisfy the following expression:

[0068]

[0069] Among them, V c V is the volume of cement slurry incorporated into the sample. r Where n is the volume of the grouting solid, n is the porosity of the formation, and α is the grout loss rate.

[0070] To establish the permeability coefficient as a function of grout injection rate R i The predictive model for the changes was developed using a variable head test method for various grout injection rates R. i The permeability coefficient of the grouting-reinforced samples was measured, and regression analysis was performed on the permeability coefficient test data to obtain the permeability coefficient k of the grouting-reinforced body in the stratum surrounding the jacking pipe. c With grout injection rate R i The regression model uses a log-linear model, as shown in the following expression:

[0071]

[0072] Where b1 and b2 are both parameters of the fitted model;

[0073] In practical implementation, the grout injection rate R of a typical grouting reinforcement sample is... i The value was set to 0.32, and the volume of the grouting reinforced sample was 1942 cm³. 3 The formation porosity n is 0.3, and the slurry loss rate α is 0.1; according to equation (4), the volume V of cement slurry incorporated into the sample is... c The calculation is as follows:

[0074] V c =V r ·n·(1+α)·R ia =1941×0.3×(1+0.1)×0.32=205cm 3 (7)

[0075] To establish the permeability coefficient as a function of grout injection rate R i The predictive model for the change uses the variable head test method to measure the grout injection rate R. i The permeability coefficients of grouting reinforced samples with values ​​of 0, 0.16, 0.32, 0.48, 0.64, and 0.8 were measured. The permeability coefficient k of the grouting reinforced sample was determined. c With grout injection rate Ri Relationship diagram as follows Figure 4 As shown; according to equation (5), the corresponding prediction model is calculated as follows:

[0076]

[0077] The correlation coefficient R corresponding to this prediction model 2 The value is 0.9235, which indicates that the prediction model has a good fit.

[0078] S104. Seepage Analysis: The junction between the horizontal tunnel and the jacking pipe is the most unfavorable point for seepage prevention. The seepage analysis conservatively assumes that the entire seepage prevention capacity is provided by the grouting solidified body 3 surrounding the jacking pipe. Therefore, the shortest seepage path is the vertical distance from the seabed surface to this junction. According to Darcy's law, the equivalent permeability coefficient k of the grouting solidified body and the undisturbed strata... e Satisfy the following expression:

[0079]

[0080] Where H is the vertical distance between the seabed surface and the junction. c k represents the vertical thickness of the grouting reinforcement. c H is the permeability coefficient of the grouting solids. s k represents the thickness of the original formation above the grouting solidification. s The permeability coefficient of the original formation above the grouting solidification;

[0081] In practice, the vertical distance H between the seabed surface and the junction is 8m, and the vertical thickness H of the grouting solidification is... c The initial estimate is 2m, and the permeability coefficient k of the undisturbed strata above the grouting solid is... s The value is 0.000053 cm / s; the grout injection rate R i Taking a grouting reinforcement sample with a permeability coefficient of 0.32 as an example, the corresponding permeability coefficient k c The permeability is 0.00000017 cm / s. According to equation (8), the equivalent permeability coefficient k of the grouting solid and the undisturbed stratum is... e The calculation is as follows:

[0082]

[0083] S105. Calculate the grout injection rate based on the average leakage rate: The average leakage rate at this junction is Q. w Satisfy the following expression:

[0084] Q w =k e ·A e ·i≤[Q w (11)

[0085] Where A e Let i be the cross-sectional area of ​​the seepage flow, and i be the hydraulic gradient. w [This refers to the average leakage limit;]

[0086] The equivalent permeability coefficient k is determined based on the average leakage limit. e The range of values ​​for k is then used to calculate the permeability coefficient k of the grouting reinforcement. c The range of values ​​for [k] cmax ,k cmin Finally, the slurry injection rate R was calculated. i The range of values ​​for [R] imin ,R imax ];

[0087] In practice, the average leakage limit [Q] w ] is 0.05L / (m 2 ·d), A e Taking a unit seepage cross-sectional area and a hydraulic gradient i of 2, the equivalent permeability coefficient k is... e The calculation is as follows:

[0088]

[0089] According to equation (9), the upper limit value of the permeability coefficient of the grouting solid is k. cmax The calculated value is 7.24 × 10⁻⁶. -9 cm / s; According to equation (8), the slurry injection rate R i Approaching R i When k = 1, the permeability coefficient of the grouting solidification is k. c 2.34×10 -10 cm / s, it can be considered that at this point it is difficult to further reduce the permeability coefficient k of the grouting solidification. c The value of , therefore the lower limit of the permeability coefficient of the grouting reinforcement is k. cmin The value is 2.34 × 10. -10 cm / s, at which point the upper limit of the grout injection rate R imax =1; In summary, the permeability coefficient k of the grouting reinforcement is... c The value range is [2.34×10]. -10 cm / s, 7.24×10 -9 [cm / s];

[0090] According to equation (8), the upper limit of the permeability coefficient of the grouting solid is k. cmax The corresponding lower limit value R of grout injection rate imin The calculation is as follows:

[0091]

[0092] Combining formula (1), the slurry injection rate R i The value range is [0.708, 1];

[0093] S106. Select reasonable design parameter values: Based on the value range required for each parameter in steps S101 to S105, select reasonable design parameter values ​​for the reinforcement design of the surrounding strata of the vertical jacking pipeline of the submarine tunnel.

[0094] The second aspect of this application discloses, as follows: Figure 1-4 The method for evaluating the reinforcement of the surrounding strata of a vertically jacking pipeline for a submarine tunnel, as shown, specifically includes the following steps:

[0095] S201. Grouting Pressure Evaluation: The grouting pressure during the grouting reinforcement construction of the strata surrounding the jacking pipeline is tracked and recorded in real time to obtain the actual average grouting pressure P. ca Grouting pressure evaluation index I p Satisfy the following expression:

[0096]

[0097] Among them, E a E represents the active earth pressure at the grouting hole. p P represents the passive earth pressure at the grouting hole. c To design the grouting pressure;

[0098] In practice, the designed grouting pressure P c The actual average grouting pressure P was set at 300 kPa and recorded in real time. ca The grouting pressure is 262.1 kPa. According to equation (14), the grouting pressure evaluation index I... p The calculation is as follows:

[0099]

[0100] It can be considered that the grouting pressure control level during the grouting reinforcement construction of the strata around the jacking pipeline is relatively good;

[0101] S202. Grout Injection Rate Evaluation: The actual total volume V of cement grout during the grouting and reinforcement construction of the strata surrounding the jacking pipe. ca Record the data to calculate the actual grout injection rate R. ia Actual slurry injection rate R ia Satisfy the following expression:

[0102]

[0103] Grout injection rate evaluation index I r Satisfy the following expression:

[0104]

[0105] Among them, R imin and R imax The slurry injection rate R i The lower and upper limits of the value;

[0106] In specific implementation, based on the actual total volume V of cement slurry ca The actual grout injection rate R was calculated. ia The value is 0.75. According to formula (17), the grout injection rate evaluation index I is... r The calculation is as follows:

[0107]

[0108] It can be considered that although the grout injection rate during the grouting reinforcement construction of the strata around the jacking pipeline meets the standard, it needs to be improved.

[0109] S203. Evaluation of the permeability coefficient of the grouting reinforcement: The permeability coefficient of the grouting reinforcement is tested through a water injection test. During the test, the permeability section and the rubber sealing section are determined inside the water injection borehole. Based on the water injection test conditions and results, the actual permeability coefficient k of the grouting reinforcement is determined. ca Satisfy the following expression:

[0110]

[0111] Among them, l w s is the length of the water injection borehole test section. w r is the water head height of the water injection borehole. w Q is the radius of the water injection borehole. w To ensure a stable water injection rate for the water injection borehole;

[0112] Evaluation index of grouting solidification permeability coefficient I k Satisfy the following expression:

[0113]

[0114] Where, k cmin The permeability coefficient k of the grouting solids c The lower limit of the value;

[0115] In practice, the actual permeability coefficient k of the grouting solidified material is calculated based on the water injection test conditions and results. ca 5.0×10 -9 cm / s, according to equation (20), the evaluation index I of the grouting solidification permeability coefficient. k The calculation is as follows:

[0116]

[0117] It can be considered that although the grout injection rate during the grouting reinforcement construction of the strata around the jacking pipeline meets the standard, it needs to be improved.

[0118] S204. Overall effect evaluation of grouting reinforcement: Evaluation index I of grouting pressure calculated based on steps S201 to S203. p Evaluation index of grout injection rate I r Evaluation index I of grouting solidification permeability coefficient k The overall effect of grouting reinforcement is evaluated, and the evaluation index I0 of the overall effect of grouting reinforcement satisfies the following expression:

[0119]

[0120] The qualification standard of the overall effect evaluation index I0 of grouting reinforcement is determined according to the actual engineering requirements, and then the overall effect of grouting reinforcement is evaluated according to the overall effect evaluation index I0.

[0121] In specific implementation, according to formula (22), the overall effect evaluation index I0 of grouting reinforcement is calculated as follows:

[0122]

[0123] It can be concluded that although the overall effect of grouting reinforcement during the construction of the grouting reinforcement of the strata around the jacking pipeline meets the standards, it needs to be improved.

[0124] The above describes one or more embodiments of the present invention in a relatively specific and detailed manner, but it should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this patent should be determined by the appended claims.

Claims

1. A method for reinforcing the surrounding strata of a vertically jacking pipeline in an undersea tunnel, characterized in that... Includes the following steps: S101. Strength verification of grouting reinforcement: Based on the principle that the bearing capacity of the foundation of the grouting reinforcement ring is not less than the sum of the water pressure inside the pipe during operation and the impact pressure of water flow acting on the side wall of the jacking pipe segment, the grout injection rate R... i Satisfy the following expression: Among them, E s0 E is the compression modulus of the cement used in grouting after it has solidified into a stone mass. s2 f is the compressibility modulus of the original strata. ak ρ represents the characteristic value of the bearing capacity of the original strata. w S is the density of water. w v is the cross-sectional area of ​​the jacking pipe. w H represents the average water flow velocity during the operation of the jacking pipeline. c ρ represents the vertical thickness of the grouting reinforcement, and p represents the water pressure inside the pipe during operation. S102, Grouting Pressure Calculation: Design Grouting Pressure P c Satisfy the following expression: Where, σ z E represents the vertical stress of the formation at the grouting hole, θ represents the internal friction angle of the formation at the grouting hole, and c represents the cohesion of the formation at the grouting hole. a E represents the active earth pressure intensity at the grouting hole. p The passive earth pressure intensity at the grouting hole; S103. Establish a predictive model for the permeability coefficient: For the surrounding strata samples collected during the exploration period near the junction of the horizontal tunnel and the jacking pipeline, grouting reinforcement samples were prepared with reference to the "Specification for Cement-Soil Mix Proportion Design" (JGJ / T 233—2011). The grout injection rate R of the grouting reinforcement sample was... i Satisfy the following expression: Among them, V c V is the volume of cement slurry incorporated into the sample. r Where n is the volume of the grouting solid, n is the porosity of the formation, and α is the grout loss rate. The variable head test method was used to test the injection rates R of various grouts. i The permeability coefficient of the grouting-reinforced samples was measured, and regression analysis was performed on the permeability coefficient test data to obtain the permeability coefficient k of the grouting-reinforced body in the stratum surrounding the jacking pipe. c With grout injection rate R i The regression model uses a log-linear model, as shown in the following expression: Where b1 and b2 are both parameters of the fitted model; S104. Seepage Analysis: Equivalent permeability coefficient k of grouting solidified body and undisturbed strata e Satisfy the following expression: Where H is the vertical distance between the seabed surface and the junction. c k represents the vertical thickness of the grouting reinforcement. c H is the permeability coefficient of the grouting solids. s k represents the thickness of the original formation above the grouting solidification. s The permeability coefficient of the original formation above the grouting solidification; S105. Calculate the grout injection rate based on the average leakage rate: The junction of the horizontal tunnel and the jacking pipe is the most unfavorable point for seepage prevention. The average leakage rate at this junction is Q. w Satisfy the following expression: Q w =k e ·A e ·i≤[Q w ] Where A e Let i be the cross-sectional area of ​​the seepage flow, and i be the hydraulic gradient. w [This refers to the average leakage limit;] The equivalent permeability coefficient k is determined based on the range of average leakage. e The range of values ​​for k is then used to calculate the permeability coefficient k of the grouting reinforcement. c The range of values ​​for [k] cmin ,k s Finally, the slurry injection rate R was calculated. i The range of values ​​for [R] imin ,R imax ]; S106. Select reasonable design parameter values: Based on the value range required for each parameter in steps S101 to S104, select reasonable design parameter values ​​for the reinforcement design of the surrounding strata of the vertical jacking pipeline in the submarine tunnel.

2. An evaluation method, characterized in that, The evaluation method for reinforcing the surrounding strata of a vertically jacking pipeline in a submarine tunnel as described in claim 1 includes the following steps: S201. Grouting Pressure Evaluation: The grouting pressure during the grouting reinforcement construction of the strata surrounding the jacking pipeline is tracked and recorded in real time to obtain the actual average grouting pressure P. ca Grouting pressure evaluation index I p Satisfy the following expression: Among them, E a E represents the active earth pressure at the grouting hole. p P represents the passive earth pressure at the grouting hole. c To design the grouting pressure; S202. Grout Injection Rate Evaluation: The actual total volume V of cement grout during the grouting and reinforcement construction of the strata surrounding the jacking pipe. ca Record the data to calculate the actual grout injection rate R. ia Actual slurry injection rate R ia Satisfy the following expression: Grout injection rate evaluation index I r Satisfy the following expression: Among them, R imin and R imax The respective slurry injection rates R i The lower and upper limits of the value; S203. Evaluation of the permeability coefficient of the grouting reinforcement: The permeability coefficient of the grouting reinforcement is tested through water injection tests, and the actual permeability coefficient k of the grouting reinforcement is obtained. ca Evaluation index I of grouting solidification permeability coefficient k Satisfy the following expression: Where, k cmin The permeability coefficient k of the grouting solids c The lower limit of the value; S204. Overall effect evaluation of grouting reinforcement: Evaluation index I of grouting pressure calculated according to steps S201 to S203. p Evaluation index of grout injection rate I r Evaluation index I of grouting solidification permeability coefficient k The overall effect of grouting reinforcement is evaluated, and the evaluation index I0 of the overall effect of grouting reinforcement satisfies the following expression: The qualification standard of the overall effect evaluation index I0 of grouting reinforcement is determined according to the actual engineering requirements, and then the overall effect of grouting reinforcement is evaluated based on the overall effect evaluation index I0.

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