Method for reinforcing inverted arch of tunnel in collapsible loess zone
Through combined reinforcement design and intelligent monitoring technology, the problem of structural instability of traditional tunnel arches in wet loess is solved, and the safety and economics of the tunnel are improved.
Patent Information
- Application Number
- CN202510440895.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-09
- Publication Date
- 2025-07-18
AI Technical Summary
The traditional tunnel arch reinforcement method is difficult to fully cope with the complex characteristics of wet loess, and it lacks systematic and accurate reinforcement scheme design and monitoring methods, resulting in instability of tunnel structure and operational safety hazards.
Combined reinforcement design is adopted, including grouting reinforcement, prestressed anchor rod reinforcement, steel frame reinforcement and other combinations. Through segmented grouting and hollow grouting anchor rods and other technologies, it combines intelligent algorithms for real-time monitoring and evaluation to optimize the reinforcement plan.
It significantly improves the bearing capacity of the tunnel arch in a wet loess environment, reduces settlement deformation, ensures the long-term stability and safety of the tunnel structure, and reduces construction and operation costs.
Smart Images
Figure QLYQS_5 
Figure QLYQS_19 
Figure QLYQS_23
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of tunnel invert reinforcement, and specifically to a method for reinforcing the tunnel invert in collapsible loess areas. Background Art
[0002] When carrying out tunnel engineering construction in collapsible loess areas, the tunnel invert faces many severe challenges. The special geological properties of collapsible loess, such as loose soil texture and large pores between particles, cause the soil structure to be rapidly damaged and the strength to be sharply reduced after being soaked in water, which is extremely likely to cause settlement deformation of the tunnel invert. Moreover, under the action of external forces such as earthquakes, the collapsible loess may also undergo liquefaction, further threatening the stability of the tunnel structure and posing a serious hidden danger to the operation safety of the tunnel.
[0003] Traditional methods for reinforcing tunnel inverts have many limitations. On the one hand, a single reinforcement method is difficult to comprehensively deal with the complex properties of collapsible loess. For example, only using grouting reinforcement can, to a certain extent, fill the soil pores and improve the soil strength, but it cannot fundamentally solve the structural deformation problem caused by loose soil texture; while simply relying on bolt reinforcement, in areas with strong collapsibility and large soil deformation, its reinforcement effect is limited and it is difficult to effectively prevent the settlement of the tunnel invert. On the other hand, the existing technology lacks systematicness and accuracy in formulating and adjusting reinforcement plans. During the construction process, the monitoring and evaluation methods for reinforcement effects are relatively backward, mostly manual regular sampling inspections, and it is impossible to obtain real-time and comprehensive data on the deformation, stress, etc. of the tunnel invert. Once it is found that the reinforcement effect is not ideal, it is also difficult to quickly and accurately optimize and adjust the reinforcement plan, resulting in delays in the project progress, increased costs, and it is difficult to ensure the long-term stability and safety of the tunnel structure. Summary of the Invention
[0004] Aiming at the deficiencies of the existing technology, the present invention provides a method for reinforcing the tunnel invert in collapsible loess areas to solve the problems raised in the above background art.
[0005] To achieve the above objectives, the present invention is realized through the following technical solutions: A method for reinforcing the tunnel invert in collapsible loess areas, including the following steps:
[0006] S1. Drill and sample the collapsible loess in the tunnel area, measure the soil collapsibility coefficient, void ratio, permeability coefficient and seismic liquefaction index, and divide the strata into collapsibility grades of first, second, and third levels according to the collapsibility coefficient, and determine the priority of reinforcement;
[0007] S2. Adopt a combined reinforcement design. For the first-level collapsible loess area, adopt the combination of grouting reinforcement + invert filling reinforcement. The depth of grouting reinforcement is 3 - 5 m below the invert, and the thickness of the filling layer is 0.8 - 1.2 m. For the second-level collapsible loess area, adopt the combination of grouting reinforcement + prestressed anchor rod reinforcement. The length of the anchor rod is 6 - 8 m, the diameter is 28 - 32 mm, and the prestress loading value is 70% - 80% of the design bearing capacity. For the third-level collapsible loess area, adopt the combination of steel frame reinforcement + grouting reinforcement + anchor rod reinforcement. The spacing of the steel frames is increased to 0.5 - 0.8 m, and the grouting pressure is increased to 1.5 - 2.0 MPa;
[0008] S3. Adopt a composite slurry. Through the segmented grouting process, the length of each grouting section is 1.2 - 1.5 m, and the cyclic grouting interval time is 30 - 40 min;
[0009] S4. Adopt hollow grouting anchor rods, arranged in a plum blossom shape, with a longitudinal spacing of 1.2 - 1.5 m and a circumferential spacing of 0.8 - 1.0 m;
[0010] S5. Select H-shaped steel frames. The steel frames are welded with Φ22 longitudinal connecting bars, and the spacing is less than or equal to 1.0 m. The invert filling is poured in layers with lightweight concrete with a density of 1600 - 1800 kg / m³ and a compressive strength of 30 - 42, and the thickness of each layer is 0.45 - 0.5 m. It is vibrated with a vibrating pump with a frequency of 8000 - 10000 times / min, and the curing humidity is 90% - 96%;
[0011] S5. Collect settlement data every 8 h, control the settlement rate to be less than or equal to 0.2 mm / d, and when the cumulative settlement is greater than 10 mm, start supplementary grouting or anchor rod supplementary tensioning, and monitor the settlement data, evaluate the results, and optimize and adjust the reinforcement plan.
[0012] Preferably, in the step S1, the value range of the coefficient of the first-level collapsibility is , the value range of the coefficient of the second-level collapsibility is , the value range of the coefficient of the third-level collapsibility is , where is the coefficient of collapsibility.
[0013] Preferably, in the step S3, the composite slurry is cement slurry and chemical slurry, and the ratio of cement slurry to chemical slurry is 7:3. After grouting is completed, the diffusion radius of the slurry is detected to be more than 1.2 m, and the bearing capacity of the soil in the reinforcement area is increased to more than 150 kPa.
[0014] Preferably, in the step S4, the diameter of the hollow grouting anchor rod is 32 mm, the wall thickness is 3.5 mm. After the anchor rod is installed, prestress is applied to 60 - 80 kN, and the prestress loss rate is monitored to be less than or equal to 5%.
[0015] Preferably, in the step S6, the equipment for collecting settlement data includes, but is not limited to, a level, a total station, and a GPS locator.
[0016] Preferably, in the step S6, to evaluate the results and optimize and adjust the reinforcement plan includes the following steps:
[0017] S61. Collect the arch settlement data after the reinforcement signature approval every 4 hours, and calculate the relative settlement difference. The calculation formula is: , where in the formula, is the settlement difference, n is the number of detection points, and are the settlement values before and after the reinforcement of the i-th monitoring point respectively. When is greater than 10 mm, it is determined that the settlement control fails, and an emergency plan needs to be initiated;
[0018] S62. Predict the settlement trend. Define the time series settlement data as , and calculate the smoothed value. The calculation formula is: , where in the formula, is the smoothed value at the current moment, is the smoothed value at the previous moment, is the smoothing coefficient, and the value range is [0.2 - 0.5];
[0019] S63. Establish the relationship between the settlement and the time t. The calculation formula is: , where in the formula, is a constant, that is, the basic settlement value that does not depend on the historical settlement and historical error. p is the number of terms of the historical settlement, q is the number of terms of the historical error, is the autoregressive coefficient, is the historical settlement data, is the moving average coefficient, is the error term at the j-th moment before the moment t, is the error term at the moment t;
[0020] S4. When the cumulative settlement is greater than 10 mm, supplement the grouting volume. The calculation formula is: , where in the formula, is the initial grouting volume, is the supplementary grouting volume, is the cumulative settlement. When the settlement rate is greater than 0.2 mm / d, increase the prestress value proportionally. The calculation formula is: , where in the formula, is the original designed prestress, is the adjusted prestress, and v is the settlement rate at the current moment.
[0021] The present invention provides a method for strengthening the inverted arch of a tunnel in collapsible loess areas, with the following beneficial effects:
[0022] 1. By innovatively adopting a combined strengthening design, the present invention organically combines various strengthening methods, gives full play to their respective advantages, comprehensively improves the stability of the tunnel inverted arch, significantly enhances the bearing capacity of the tunnel inverted arch in the collapsible loess environment, reduces the occurrence of settlement deformation. In view of the diversity and complexity of the geological conditions in collapsible loess areas, the combined strengthening design can flexibly adjust the combination and parameters of the strengthening methods. In areas with strong collapsibility and serious soil looseness, the dosage and strength of the grouting material are increased, and at the same time, the layout of the steel frames is densified. In relatively stable areas, the strengthening parameters are appropriately adjusted to achieve reasonable resource allocation and ensure the best strengthening effect under different geological conditions.
[0023] 2. By real-time and accurately monitoring parameters such as deformation and stress during the strengthening process and after the operation of the tunnel inverted arch, through intelligent algorithms, the present invention can quickly and accurately evaluate the strengthening effect, timely discover potential safety hazards, provide reliable data support for scheme optimization, and ensure that the tunnel inverted arch is always in a safe and stable state. This dynamic optimization mechanism can effectively cope with the uncertainties during the construction process and the changes in geological conditions during the operation process, greatly improving the quality and safety of the tunnel project and reducing the later maintenance cost. Specific implementation manners
[0024] The technical solutions in the embodiments of the present invention are clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.
[0025] The embodiments of the present invention provide a method for strengthening the inverted arch of a tunnel in collapsible loess areas, including the following steps:
[0026] S1. Drill and sample the collapsible loess in the tunnel area, measure the soil collapsibility coefficient, void ratio, permeability coefficient and seismic liquefaction index, and divide the strata into collapsibility grades of grade one, grade two and grade three according to the collapsibility coefficient to determine the priority of strengthening;
[0027] S2. Adopt a combined reinforcement design. For the first-level collapsible loess area, adopt the combination of grouting reinforcement + invert filling reinforcement. The depth of grouting reinforcement is 3 - 5 m below the invert, and the thickness of the filling layer is 0.8 - 1.2 m. For the second-level collapsible loess area, adopt the combination of grouting reinforcement + prestressed anchor reinforcement. The length of the anchor is 6 - 8 m, the diameter is 28 - 32 mm, and the prestress loading value is 70% - 80% of the design bearing capacity. For the third-level collapsible loess area, adopt the combination of steel frame reinforcement + grouting reinforcement + anchor reinforcement. The spacing of the steel frames is increased to 0.5 - 0.8 m, and the grouting pressure is increased to 1.5 - 2.0 MPa;
[0028] S3. Adopt a composite slurry. Through the segmented grouting process, the length of each grouting section is 1.2 - 1.5 m, and the cyclic grouting interval time is 30 - 40 min;
[0029] S4. Adopt hollow grouting anchors, arranged in a plum blossom pattern, with a longitudinal spacing of 1.2 - 1.5 m and a circumferential spacing of 0.8 - 1.0 m;
[0030] S5. Select H-shaped steel frames. Use Φ22 longitudinal connecting bars for welding between the steel frames, with a spacing less than or equal to 1.0 m. The invert filling is poured in layers with lightweight concrete having a density of 1600 - 1800 kg / m³ and a compressive strength of 30 - 42, and the thickness of each layer is 0.45 - 0.5 m. Vibration pumps with a frequency of 8000 - 10000 times / min are used for vibration compaction, and the curing humidity is 90% - 96%;
[0031] S5. Collect settlement data every 8 h, control the settlement rate to be less than or equal to 0.2 mm / d, and when the cumulative settlement exceeds 10 mm, start supplementary grouting or anchor supplementary tensioning, monitor the settlement data, evaluate the results, and optimize and adjust the reinforcement plan.
[0032] In this embodiment, in step S1, the value range of the coefficient of primary collapsibility is , the value range of the coefficient of secondary collapsibility is , the value range of the coefficient of tertiary collapsibility is , where is the coefficient of collapsibility.
[0033] In this embodiment, in step S3, the composite slurry is cement slurry and chemical slurry, and the ratio of cement slurry to chemical slurry is 7:3. After grouting, the diffusion radius of the slurry is detected to be more than 1.2 m, and the bearing capacity of the soil in the reinforcement area is increased to more than 150 kPa.
[0034] In this embodiment, in step S4, the diameter of the hollow grouting anchor is 32 mm, the wall thickness is 3.5 mm. After the anchor is installed, prestress is applied to 60 - 80 kN, and the prestress loss rate is monitored to be less than or equal to 5%.
[0035] Specifically, through the innovative adoption of a combined reinforcement design, multiple reinforcement methods are organically combined to give full play to their respective advantages, comprehensively enhancing the stability of the tunnel invert, significantly improving the bearing capacity of the tunnel invert in the collapsible loess environment, reducing the occurrence of settlement deformation. In view of the diversity and complexity of the geological conditions in the collapsible loess area, the combined reinforcement design can flexibly adjust the combination and parameters of the reinforcement methods. In areas with strong collapsibility and serious soil looseness, the dosage and strength of the grouting material are increased, and at the same time, the layout of the steel frames is densified. In relatively stable areas, the reinforcement parameters are appropriately adjusted to achieve the rational allocation of resources and ensure the best reinforcement effect under different geological conditions.
[0036] In this embodiment, in step S6, the equipment for collecting settlement data includes, but is not limited to, a level, a total station, and a GPS locator.
[0037] In this embodiment, in step S6, for the result evaluation and optimization and adjustment of the reinforcement plan, the following steps are included:
[0038] S61. Collect the settlement data of the arch after reinforcement signing every 4 hours, and calculate the relative settlement difference. The calculation formula is: , where is the settlement difference, n is the number of detection points, and are the settlement values before and after reinforcement at the i-th monitoring point respectively. When is greater than 10 mm, it is determined that the settlement control fails, and an emergency plan needs to be activated;
[0039] S62. Predict the settlement trend. Define the time series settlement data as , and calculate the smoothed value. The calculation formula is: , where is the smoothed value at the current moment, is the smoothed value at the previous moment, is the smoothing coefficient, and its value range is [0.2 - 0.5];
[0040] S63. Establish the relationship between the settlement and time t. The calculation formula is: , where is a constant, that is, the basic settlement value that does not depend on the historical settlement and historical error, p is the number of terms of the historical settlement, q is the number of terms of the historical error, is the autoregressive coefficient, is the historical settlement data, is the moving average coefficient, is the error term at the j-th moment before time t, is the error term at time t;
[0041] S4. When the cumulative settlement is greater than 10 mm, the supplementary grouting volume is replenished, and the calculation formula is: , where is the initial grouting volume, is the supplementary grouting volume, is the cumulative settlement. When the settlement rate is greater than 0.2 mm / d, the prestress value is increased proportionally, and the calculation formula is: , where is the original designed prestress, is the adjusted prestress, and v is the settlement rate at the current moment.
[0042] Specifically, by monitoring parameters such as deformation and stress during the reinforcement process of the tunnel invert and after operation in real time and accurately, through intelligent algorithms, the reinforcement effect can be quickly and accurately evaluated, potential safety hazards can be discovered in time, reliable data support can be provided for scheme optimization, and it is ensured that the tunnel invert is always in a safe and stable state. This dynamic optimization mechanism can effectively cope with the uncertainties during the construction process and the changes in geological conditions during operation, greatly improving the quality and safety of the tunnel project, and at the same time reducing the later maintenance cost.
[0043] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.
Claims
1. A method for strengthening the invert of a tunnel in collapsible loess areas, characterized in that It includes the following steps: S1. Drill and sample the collapsible loess in the tunnel area, measure the soil collapsibility coefficient, void ratio, permeability coefficient and seismic liquefaction index, divide the strata into collapsibility grades of first, second and third levels according to the collapsibility coefficient, and determine the reinforcement priority; S2. Adopt a combined reinforcement design. For the first-level collapsible area, use the combination of grouting reinforcement + invert filling reinforcement. The depth of grouting reinforcement is 3 - 5 m below the invert, and the thickness of the filling layer is 0.8 - 1.2 m. For the second-level collapsible area, use the combination of grouting reinforcement + prestressed anchor reinforcement. The length of the anchor is 6 - 8 m, the diameter is 28 - 32 mm, and the prestress loading value is 70% - 80% of the design bearing capacity. For the third-level collapsible area, use the combination of steel frame reinforcement + grouting reinforcement + anchor reinforcement. The spacing of the steel frames is increased to 0.5 - 0.8 m, and the grouting pressure is increased to 1.5 - 2.0 MPa; S3. Adopt a composite slurry and use a segmented grouting process. The length of each grouting segment is 1.2 - 1.5 m, and the cyclic grouting interval time is 30 - 40 min; S4. Adopt hollow grouting anchors, arranged in a plum blossom shape, with a longitudinal spacing of 1.2 - 1.5 m and a circumferential spacing of 0.8 - 1.0 m; S5. Select H-shaped steel frames, weld Φ22 longitudinal connecting bars between the frames, with a spacing less than or equal to 1.0 m. The invert filling is poured in layers with lightweight concrete with a density of 1600 - 1800 kg / m³ and a compressive strength of 30 - 42, and the thickness of each layer is 0.45 - 0.5 m. Vibration pumps with a frequency of 8000 - 10000 times / min are used for vibration, and the curing humidity is 90% - 96%; S6. Collect settlement data every 8 h, control the settlement rate to be less than or equal to 0.2 mm / d, and when the cumulative settlement is greater than 10 mm, start supplementary grouting or anchor supplementary tensioning, monitor the settlement data, evaluate the results, and optimize and adjust the reinforcement plan.
2. The method for reinforcing the inverted arch of a tunnel in collapsible loess area according to claim 1, characterized in that, In the step S1, the value range of the coefficient of primary collapsibility is , the value range of the coefficient of secondary collapsibility is , and the value range of the coefficient of tertiary collapsibility is , where is the coefficient of collapsibility.
3. The method for reinforcing the inverted arch of a tunnel in collapsible loess area according to claim 1, characterized in that, In the step S3, the composite slurry is cement slurry and chemical slurry, and the ratio of cement slurry to chemical slurry is 7:
3. After grouting is completed, the diffusion radius of the slurry is detected to be more than 1.2 m, and the bearing capacity of the soil in the reinforcement area is increased to more than 150 kPa.
4. The method for reinforcing the inverted arch of a tunnel in collapsible loess area according to claim 1, characterized in that, In the step S4, the diameter of the hollow grouting anchor is 32 mm, the wall thickness is 3.5 mm, prestress is applied to the anchor to 60 - 80 kN after installation, and the prestress loss rate is monitored to be less than or equal to 5%.
5. The method for reinforcing the inverted arch of a tunnel in collapsible loess area according to claim 1, characterized in that, In the step S6, the equipment for collecting settlement data includes but is not limited to levels, total stations and GPS locators.
6. The method for reinforcing the inverted arch of a tunnel in collapsible loess area according to claim 1, characterized in that, In the step S6, evaluating the results and optimizing and adjusting the reinforcement plan includes the following steps: S6.
1. Collect the settlement data of the arch after reinforcement and signature verification every 4 hours, and calculate the relative settlement difference. The calculation formula is: , where is the settlement difference, n is the number of detection points, and are the settlement values before and after reinforcement at the i-th monitoring point respectively. When is greater than 10 mm, it is determined that the settlement control fails and the emergency plan needs to be activated; S6.
2. Predict the settlement trend, define the time series settlement data as , calculate the smoothed value, and the calculation formula is: , where is the smoothed value at the current moment, is the smoothed value at the previous moment, is the smoothing coefficient, and the value range is [0.2 - 0.5]; S6.
3. Establish the settlement versus time t, and the calculation formula is: , where is a constant, that is, the foundation settlement value that does not depend on historical settlement and historical error. p is the number of terms of historical settlement, q is the number of terms of historical error, is the autoregressive coefficient, is the historical settlement data, is the moving average coefficient, is the error term at the j-th moment before time t, is the error term at time t; S6.
4. When the cumulative settlement is greater than 10 mm, the supplementary grouting volume is replenished, and the calculation formula is: , where is the initial grouting volume, is the supplementary grouting volume, is the cumulative settlement. When the settlement rate is greater than 0.2 mm / d, the prestress value is increased proportionally, and the calculation formula is: , where is the original designed prestress, is the adjusted prestress, and v is the settlement rate at the current moment.