Shield muck wall external grouting construction process

Abstract

The application relates to a shield muck wall external grouting construction process, which comprises the following steps: detecting the water content, particle size distribution and slump of the muck discharged by a shield; determining the additive amount according to a grading ratio table according to the muck type; removing coarse particles by vibrating screening of the muck; preparing grouting slurry by quantitative stirring according to the proportioning ratio; setting the grouting pressure to be 1.1-1.3 times of the stratum water and soil pressure, and setting the grouting coefficient to be 120-150%, so that synchronous grouting is carried out; taking 10-20 rings of tunneling as an adjustment period, and dynamically adjusting the grouting proportioning, pressure and grouting amount according to monitoring data such as stratum settlement and segment ellipticity; and the final acceptance index is that the surface settlement is less than 10 mm, and the segment ellipticity is less than 3 ‰. The application realizes full-process closed-loop control of muck grouting, significantly improves the control precision of surface settlement, reduces the grouting cost, and is suitable for shield tunnel construction under different stratum conditions.

Description

Technical Field

[0001] This application relates to the field of shield tunnel construction, and in particular to a grouting construction process for the external wall of shield tunnel excavation. Background Technology

[0002] In shield tunnel construction, external grouting is a core and critical process for filling the natural structural voids between the tunnel segments and the ground after the shield machine has excavated, controlling uneven surface settlement, stabilizing the precast segment structure, and blocking groundwater seepage channels. It directly determines the safety and quality of tunnel construction. With the continuous expansion of urban rail transit and underground space development in my country, the amount of excavated soil generated during shield tunneling is increasing year by year. Traditional methods of transporting and disposing of excavated soil are not only costly and occupy large amounts of land resources, but also easily cause environmental problems such as dust and soil erosion. Against this backdrop, utilizing the original excavated soil generated during shield tunneling to prepare grouting materials and achieve on-site resource utilization of excavated soil has become an important development direction for green construction in the industry.

[0003] After years of development, existing shield tunnel wall grouting technology has formed three mainstream application modes: The first is the traditional synchronous grouting process, in which pre-prepared commercial cement mortar is injected into the gaps on the outside of the tunnel segments through 4-6 grouting holes reserved at the tail of the shield while the shield machine is excavating. In the industry, the grouting pressure is usually set at 0.2-0.3MPa based on experience, the grouting coefficient is controlled at 110%-130%, and a fixed grout mix ratio is used throughout the process; The second is the grouting process based on the resource utilization of shield excavation waste, which mixes the excavated waste with cement and admixtures to make grouting material to replace part of the commercial mortar injected into the gaps behind the tunnel wall. However, in actual application, a fixed amount of waste and grouting parameters are still used, without adjustment according to changes in waste characteristics; The third is the passive adjustment process based on surface settlement monitoring. By setting up leveling monitoring points along the tunnel to obtain surface settlement data, the amount of grouting for subsequent construction is adjusted according to the settlement situation. This is currently the quality control method commonly used in the industry.

[0004] The above methods all lack a dynamic correlation and a closed-loop control mechanism for the entire process between soil quality, geological conditions and grouting parameters, resulting in poor matching between grouting parameters and actual working conditions. This not only fails to effectively solve the problem of low accuracy in controlling surface settlement. Summary of the Invention

[0005] In order to improve the matching between grouting parameters and actual working conditions, thereby improving the accuracy of surface settlement control, this application provides a grouting construction process for the external wall of shield tunneling excavation.

[0006] This application provides a grouting construction process for the external wall of tunnel boring machine (TBM) slag walls, which adopts the following technical solution: A method for external grouting construction of shield tunnel muck walls includes the following steps: S1 Slag Quality Inspection: Samples of slag discharged from the tunnel boring machine are taken and tested for three quality indicators: moisture content, particle size distribution, and slump. S2 Graded Proportion Lookup Table: Based on the type and quality indicators of the slag obtained from the test, the amount of additives for the grouting material is determined by looking up the preset graded proportion table. S3 Vibrating Screen: Vibrating screen is used to process slag and soil to remove coarse particles with a diameter greater than 10mm. S4 quantitative mixing: According to the proportion determined by referring to the table, the slag, cementitious materials, functional regulators and water are put into the mixer and mixed to prepare the grouting slurry; S5 Pressure Grouting: Calculate the soil and water pressure P0 at the current ring location, set the grouting pressure P to be 1.1-1.3 times the soil and water pressure P0, and the grouting coefficient to be 120-150%. Simultaneously grout into the construction gap between the segments and the ground through the grouting holes at the shield tail. S6 Dynamic Adjustment: Every 10-20 rings of tunneling constitutes an adjustment cycle. Based on surface settlement monitoring data, segment ellipticity detection data, and grouting pressure and flow records, feedback is provided to adjust the grouting mix ratio, grouting pressure, and grouting volume for the next cycle.

[0007] By adopting the above technical solutions, a complete closed-loop process system was constructed, which includes real-time detection of slag quality, graded proportion lookup, quantitative mixing and grouting, grouting with ground pressure matching, and multi-parameter collaborative dynamic adjustment. This system replaces the extensive mode of fixed proportions, experience-based pressure, and passive post-event adjustments, achieving refined and standardized control of the entire grouting process. Compared with traditional processes, the accuracy of surface settlement control is improved by more than 60%, and the settlement fluctuation range is reduced from ±5-15mm to within ±3mm. At the same time, it realizes the on-site resource utilization of shield tunnel slag, reducing the amount of slag transported by more than 80%, eliminating the need to rely on expensive commercial cement mortar, and reducing the overall grouting cost by 45-55%. It ensures the compactness and uniformity of grout filling from the source, effectively avoiding engineering quality problems such as segment floating, cracking, and groundwater leakage, and significantly improving the long-term stability of the tunnel structure.

[0008] Optionally, in step S1, the excavated soil is sampled once for each ring of excavation. The moisture content is tested using the drying method with an accuracy of ±0.5%. The particle size distribution is tested using the sieve method with sieve aperture sizes of 0.075mm, 0.25mm, 0.5mm, 1mm, 2mm, 5mm, and 10mm respectively. The slump is tested using the standard slump cone method.

[0009] By adopting the above technical solutions, the standardized methods, testing frequency, and accuracy requirements for slag quality testing were clarified, providing reliable data support for the accurate implementation of subsequent grading and proportioning. This solved the problem of proportioning deviation caused by non-standard testing and inaccurate data. Sampling was mandated once per ring of tunneling, enabling timely capture of subtle changes in the moisture content and particle size distribution of the slag in each ring, avoiding the proportioning lag caused by sampling only once per multiple ring. The drying method was used to test the moisture content, ensuring the accuracy of the moisture content data. A 1% deviation in moisture content will result in a change of approximately 15mm in slurry fluidity, directly affecting the pumpability and filling effect of the grout. Simultaneously, a multi-stage sieving method from 0.075mm to 10mm was used to test the particle size distribution, comprehensively covering the key particle size range affecting slurry cohesion, water retention, and strength. Combined with the standard slump cone method, the consistency characteristics of the slag were visually reflected, providing a comprehensive basis for the accurate determination of additive dosage.

[0010] Optionally, in step S2, the amount of additives in the graded proportion table is calculated as a percentage of the dry weight of the slag, wherein the amount of additives for silty clay slag is 8-12%, the amount of additives for silty soil slag is 6-10%, and the amount of additives for sandy soil slag is 10-15%.

[0011] By adopting the above technical solutions, differentiated additive dosage ranges were set for the three most common types of shield tunneling excavated soil in engineering projects: silty clay, silt, and sand. Based on their physical properties such as liquid limit, plasticity index, and fineness modulus, the additive dosage ranges were set for each type. Silty clay has a high clay content and good water retention, so the additive dosage is 8-12%. Silt has finer particles and moderate cohesion, so the additive dosage is 6-10%. Sand has coarse particles, poor water retention, and is prone to segregation, so the additive dosage is 10-15%. This graded proportion table has been verified by a large number of indoor tests and field tests, which can ensure that the slurry prepared from different types of excavated soil has stable fluidity, setting time, and early strength, thus solving the problem of unstable slurry quality from the source.

[0012] Optionally, in step S3, a double-layer vibrating screen is used for screening, with the upper screen aperture size being 30mm and the lower screen aperture size being 10mm, and the screening efficiency being no less than 90%. After screening, the moisture content of the undersize material is detected. When the moisture content deviation is greater than 3%, the slag is dehydrated or replenished with water for adjustment.

[0013] By adopting the above technical solution, and through standardized vibrating screening and moisture content adjustment processes, harmful particles that affect the pumpability of the slurry are effectively removed, further stabilizing the basic properties of the slag and providing a guarantee for the subsequent slurry quality. A double-layer vibrating screen with an upper layer of 30mm and a lower layer of 10mm is used for grading and screening. The upper screen first removes large-diameter stones, concrete blocks and other debris mixed in the slag to prevent them from damaging the subsequent mixing and grouting equipment. The lower screen removes coarse particles with a diameter >10mm to avoid clogging the grouting pump and conveying pipeline. At the same time, the screening efficiency is specified to be ≥90% to ensure that the vast majority of harmful particles are effectively removed. When the moisture content of the undersize material deviates by >3%, dehydration or water replenishment is performed, because a moisture content fluctuation of more than 3% will cause the slurry flowability to change by more than 20mm, which will seriously affect the grouting effect. This step controls the fluctuation of slurry performance to a minimum.

[0014] Optionally, in step S4, a forced mixer is used for mixing for 3-5 minutes; after mixing, the slurry properties are tested, and the fluidity is controlled to be 180-220 mm and the density to be 1.5-1.8 g / cm³; if any indicator fails to meet the requirements, the mixing is increased for 1-2 minutes or the water addition is finely adjusted. If the slurry still fails to meet the requirements after adjustment, the batch of slurry is discarded and the batch is re-prepared.

[0015] By adopting the above technical solution, the preparation process and performance control standards of the grout were clarified, ensuring the uniformity, workability, and stability of the grout. This solved the problems of insufficient mixing and large fluctuations in grout performance. A forced mixer was used for mixing, which, compared to ordinary mixers, ensures thorough mixing of slag, cementitious materials, and admixtures, avoiding cement clumping and uneven additive distribution. The specified mixing time is 3-5 minutes, avoiding both uneven mixing due to insufficient mixing time and damage to the grout structure due to excessive mixing time. Segregation is caused by the slurry. At the same time, the slurry fluidity is strictly controlled at 180-220mm and the density at 1.5-1.8g / cm³. When the fluidity is below 180mm, the pumpability of the slurry is poor and it is easy to clog the pipeline. When the fluidity is above 220mm, the slurry is prone to bleeding and segregation, resulting in poor filling effect. The density index directly reflects the solid content and later strength of the slurry. The established non-conforming product handling mechanism can adjust or discard slurries that do not meet the performance standards, thereby eliminating the injection of inferior slurry into the formation from the process and avoiding quality hazards such as surface subsidence and voids in the later stage.

[0016] Optionally, in step S5, the grouting flow rate is controlled at 10-30 L / min; the grout is injected evenly through 4-6 grouting holes set at the shield tail, and the grouting volume per hole is evenly distributed according to the grouting coefficient and the number of grouting holes.

[0017] By adopting the above technical solutions, controlling the grouting flow rate and using a multi-hole uniform grouting method, the uniform distribution of grout around the tunnel segments is ensured, improving the integrity and uniformity of the grouting filling. Controlling the grouting flow rate at 10-30 L / min avoids turbulence caused by excessive flow rate, which leads to grout segregation and stratification. It also prevents excessive flow rate from scouring the surrounding soil and causing ground disturbance, while avoiding excessive flow rate, which prolongs the grouting time and affects the tunnel boring progress. By uniformly injecting grout through 4-6 grouting holes set at the tail of the shield, the grout volume of each hole is evenly distributed, avoiding problems such as local deformation and cracking of tunnel segments due to excessive grouting pressure in a single hole, or insufficient filling due to insufficient grouting in certain areas. This effectively reduces the ellipticity of the tunnel segments and ensures the circularity of the tunnel structure.

[0018] Optionally, in step S6, the specific rules for dynamic adjustment are as follows: if the surface settlement is greater than 8mm, increase the grouting coefficient by 5-10% or increase the amount of additive by 1-2%; if the surface settlement is less than 3mm and the segments tend to float, reduce the grouting pressure coefficient by 0.05-0.1; if the grout bleeding rate is greater than 3%, increase the amount of thickening and water-retaining agent by 0.2-0.5 parts.

[0019] By adopting the above technical solution, clear, quantifiable, and operable dynamic adjustment rules were formulated, solving the problems of single adjustment methods, lack of standards, and delayed response. This enabled precise and rapid adjustment of grouting parameters, significantly shortening the adjustment cycle from 50-100 rings to 10-20 rings. It allows for timely correction of construction deviations before surface settlement reaches excessive levels, preventing further settlement. Specific adjustment ranges are given for the three most common abnormal situations during construction. For example, when surface settlement > 8mm, it indicates that the grouting... If the tail voids are not filled sufficiently, increasing the grouting coefficient by 5-10% or increasing the amount of additives by 1-2% can quickly increase the amount of grout filling, improve the early strength of the grout, and inhibit the development of settlement. When the surface settlement is <3mm and the segments tend to float, it indicates that the grouting pressure is too high. Reducing the grouting pressure coefficient by 0.05-0.1 can prevent the grout pressure from continuing to push up the segments. When the grout bleeding rate is >3%, it indicates that the grout has poor water retention. Increasing the amount of thickening and water-retaining agent by 0.2-0.5 parts can effectively improve the cohesiveness of the grout and prevent segregation and bleeding.

[0020] Optionally, step S7, quality acceptance, is also included: after the tunneling is completed, an overall acceptance is carried out. The acceptance indicators include the maximum surface settlement along the tunnel axis being less than 10 mm, the ellipticity of the tunnel segments being less than 3‰, and the grouting filling rate being greater than 95%.

[0021] By adopting the above technical solutions, a three-dimensional comprehensive acceptance standard was established, which includes surface settlement, segment ellipticity, and grouting filling rate. This standard can comprehensively, objectively, and accurately evaluate the grouting construction quality. The maximum surface settlement along the tunnel axis is <10mm, which meets the highest requirements of my country's urban rail transit engineering construction and acceptance specifications. This standard can effectively protect the buildings, pipelines, and municipal facilities around the tunnel. The segment ellipticity is <3‰, which prevents the segments from cracking and leaking due to excessive deformation, ensuring the integrity and durability of the tunnel structure. The grouting filling rate is >95%, which ensures that the building gaps between the segments and the ground are completely filled, leaving no voids, and fundamentally eliminating the hidden dangers of later surface settlement and tunnel leakage.

[0022] Optionally, in step S5, the grouting method adopts a combination of synchronous grouting and secondary grouting. The grouting coefficient of synchronous grouting is set to 100-120%, and the secondary grouting is carried out through the grouting holes of the segments 5-10 rings behind the shield tail. The amount of grouting is 20-40% of the theoretical void volume of the structure, and the grouting pressure is 1.0-1.1 times the soil and water pressure of the stratum.

[0023] By adopting the above technical solution, synchronous grouting mainly fills the immediate structural voids generated during shield tunneling. The grouting coefficient is set to 100-120%, avoiding the problem of segment floating caused by excessive grouting volume during pure synchronous grouting. Secondary grouting is carried out 5-10 rings behind the shield tail. At this time, the synchronous grouting slurry has initially solidified and produced a certain shrinkage. Grouting is injected through the grouting holes of the segments, which can effectively fill the tiny voids caused by shrinkage. The grouting volume is 20-40% of the theoretical void volume, and the grouting pressure is controlled at 1.0-1.1 times the soil and water pressure of the stratum to avoid excessive pressure disturbing the solidified grout. This combined process is particularly suitable for sensitive areas with strict surface settlement control requirements, such as urban core areas, important buildings, and underground pipelines, and can further control surface settlement within 5mm.

[0024] Optionally, in step S1, the quality testing of the slag and soil adopts an online automatic testing system, including an online moisture meter, an online particle analyzer, and an online consistency meter. The test data is transmitted to the control system in real time, and the grouting material ratio is automatically determined by looking up a table.

[0025] By adopting the above technical solution and replacing manual sampling and testing with an online automatic detection system, the detection efficiency and real-time performance are greatly improved, and manual intervention and human error are reduced. This lays the foundation for the full automation control of the grouting process. The online moisture content meter, online particle analyzer, and online consistency meter can continuously and in real-time detect the quality of the slag and soil. The detection frequency is increased from once per cycle to once per second, and the ratio response time is shortened from 20-30 minutes to less than 5 minutes. The detection data is transmitted to the control system in real time, and the grouting material ratio is automatically determined by looking up the table without manual calculation and intervention, thus avoiding human error and improving the accuracy of the ratio. This solution is particularly suitable for construction conditions with complex geological conditions and frequent changes in strata. It can respond promptly to rapid changes in slag and soil characteristics and ensure the stability of grouting quality.

[0026] In summary, this application includes at least one of the following beneficial technical effects: A closed-loop control system was constructed to achieve dynamic matching of grouting parameters with soil quality and geological conditions. This improved surface settlement control accuracy by over 60%, reduced settlement fluctuation range from ±5-15mm to within ±3mm, controlled segment ellipticity within 3‰, and achieved a grouting filling rate of over 95%. This effectively prevented segment cracking and leakage, enhancing the long-term stability of the tunnel structure. It enables the on-site resource utilization of tunnel boring machine excavation soil, replacing high-priced commercial cement mortar, reducing the overall grouting cost by 45-55%; it reduces the amount of excavation soil transported by more than 80%, lowering transportation and disposal costs, while avoiding dust and noise pollution caused by excavation soil transportation, meeting the requirements of green construction. The combined process of synchronous grouting and secondary grouting can control surface settlement in sensitive areas to within 5mm, making it suitable for complex conditions such as urban core areas. The online automatic detection system reduces the mix proportioning response time to within 5 minutes, minimizing manual intervention and errors, improving construction efficiency, and laying the foundation for fully automated construction. Attached Figure Description

[0027] Figure 1 This is a flowchart of the external grouting construction process for shield tunneling muck walls in Example 1.

[0028] Figure 2 This is a flowchart of the external grouting construction process for shield tunneling muck walls in Example 1.

[0029] Figure 3 This is a flowchart of the external grouting construction process for shield tunneling muck walls in Example 1. Detailed Implementation

[0030] The following is in conjunction with the appendix Figure 1-2 This application will be described in further detail.

[0031] The embodiment uses the silty clay soil layer of Section 11 of Beijing Metro Line 22 as an example to illustrate the construction process of the present invention in detail. Example

[0032] Reference Figure 1 , This application discloses a construction process for external grouting of shield tunnel slag walls, which specifically includes the following steps: The geological parameters in this embodiment are: burial depth 12-18m, soil type is silty clay, natural moisture content 24%, liquid limit 36%, plasticity index 19, and the calculated value of soil and water pressure P0 is 0.18MPa.

[0033] S1: During the tunnel boring machine (TBM) excavation, the excavated soil was sampled once per ring. The moisture content of the soil was determined to be 23.5% using the drying method (accuracy ±0.5%). The particle size distribution was determined using the sieving method (sieve aperture sizes 0.075mm, 0.25mm, 0.5mm, 1mm, 2mm, 5mm, 10mm), with particles <5mm accounting for 82%. The slump was determined to be 6cm using the standard slump cone method.

[0034] S2: Graded Proportion Lookup Table Based on the test results, the type of slag was determined to be silty clay slag. Referring to the preset grading and proportioning table, the total additive dosage (based on the dry weight percentage of the slag) for silty clay slag is 8-12%. Considering the specific quality indicators, the additive dosage in this embodiment was determined to be 10%.

[0035] S3: Vibrating screen The slag was conveyed to a double-layer vibrating screen, with the upper screen having a 30mm aperture and the lower screen having a 10mm aperture, removing coarse particles larger than 10mm (accounting for approximately 8%), achieving a screening efficiency of 92%. After screening, the moisture content of the undersize material was measured to be 22.8%, which is less than 3% different from the required moisture content for mixing, so no dehydration or water replenishment adjustment is necessary.

[0036] S4: Quantitative stirring According to the proportions determined by referring to the table, the following components were added sequentially to the forced mixer: 65 parts of slag, 12 parts of slag powder, 9 parts of calcium carbide slag, 4 parts of cement, functional regulators (including water-reducing agents, thickening and water-retaining agents, etc.), and 28 parts of water. The mixing time was 4 minutes. After mixing, samples were taken for testing: the slurry fluidity was measured to be 195 mm using the spread method, and the slurry density was measured to be 1.62 g / cm³ using the volumetric cylinder method, both meeting the control requirements of fluidity 180-220 mm and density 1.5-1.8 g / cm³.

[0037] S5: Pressure grouting This embodiment employs a synchronous grouting method. Before grouting, the soil and water pressure P0 = 0.18 MPa is calculated based on the current ring depth and soil weight, and the grouting pressure is set to P = 1.2 × P0 = 0.22 MPa. The grouting coefficient K = 135% (the ratio of grouting volume to the theoretical void volume). Grout is injected evenly through four grouting holes set at the shield tail. The grouting volume per hole is evenly distributed according to the total grouting volume and the number of holes, and the grouting flow rate is controlled at 20 L / min to avoid grout segregation due to excessive flow rate.

[0038] S6: Dynamic Adjustment A set adjustment cycle was established after every 15 rings of tunneling. Analysis of monitoring data from rings 1-15 revealed a maximum surface settlement of 6.2 mm and a segment ellipticity of 1.9‰, both within controllable ranges. Based on this analysis, to further optimize settlement control, the grouting coefficient for rings 16-30 was adjusted to 130%. After the adjustment, the maximum surface settlement was 5.8 mm, demonstrating improved control effectiveness.

[0039] S7: Quality Acceptance After the tunneling of this section was completed, an overall acceptance inspection was conducted. The inspection results were as follows: the maximum surface settlement along the tunnel axis was 7.1 mm, which is less than the control target of 10 mm; the maximum ellipticity of the tunnel segments was 2.1‰, which is less than the control target of 3‰; and the grouting filling rate detected by radar was 96.5%, which is greater than 95%. All indicators met the acceptance requirements.

[0040] The implementation principle of Example 1: The fine-particle components of the silty clay slag are used as the main framework of the grouting material. By adding cementing materials such as slag powder and carbide slag, a thixotropic suspension slurry is formed under the action of water. The amount of additives is controlled at 8-12% of the dry weight of the slag, which can maintain the slurry flowability at 180-220 mm and the density at 1.5-1.8 g / cm³, ensuring pumpability while preventing slurry segregation. The grouting pressure is set at 1.1-1.3 times the ground water and soil pressure. The mechanical principle is that the grouting pressure must overcome the ground water and soil pressure to fully fill the voids in the structure, but excessive pressure will split the strata or cause the tunnel segments to float. This multiple range is obtained through mechanical balance calculations to ensure that the slurry fills the voids without disrupting the original stress field of the strata. The grouting coefficient of 120-150% takes into account factors such as over-excavation, ground shrinkage, and slurry shrinkage due to water loss during shield tunneling. The dynamic adjustment cycle of 15 rings (approximately 22.5m) is matched with the stress release rate of the silty clay strata, effectively capturing the development trend of stratum subsidence and correcting parameters. Ultimately, deformation coordination between the grouting material and the stratum was achieved, and surface subsidence was controlled within 7.1mm. Example

[0041] The difference between Example 2 and Example 1 is that: (Refer to...) Figure 2 The pressure grouting in S5 adopts a combined grouting process of synchronous grouting and secondary grouting.

[0042] Synchronous grouting: The grouting pressure is set to P = 1.15 × P0 = 1.15 × 0.25 = 0.29MPa. The grouting coefficient K is set to 110%, which is lower than the 120-150% of pure synchronous grouting. Synchronous grouting is carried out through four grouting holes at the shield tail.

[0043] Secondary grouting: Secondary grouting is performed 5-10 rings behind the shield tail through the grouting holes on the segments. The grouting volume is 30% of the theoretical void volume, and the grouting pressure is set to 1.05 times the soil and water pressure of the stratum, i.e., 0.26 MPa.

[0044] The implementation principle of Example 2 is as follows: The grouting process is divided into two stages—the first stage (synchronous grouting) completes the rapid filling of the main voids, and the second stage (secondary grouting) supplements and reinforces the shrinkage and defects after synchronous grouting. The synchronous grouting coefficient is reduced to 100-120%, only ensuring the basic filling of the gap between the tunnel segment and the stratum, avoiding the pressure accumulation caused by injecting too much grout at once, which could lead to the floating of the tunnel segment. Secondary grouting is carried out 5-10 rings after the shield tail passes. At this time, the tunnel segment has been initially stabilized and the stratum stress has been partially released. Grout is injected through the grouting holes of the tunnel segment at a lower pressure (1.0-1.1 times the soil and water pressure). The purpose is to: compensate for the volume shrinkage of the synchronous grout during the solidification process; fill the voids formed by the leakage of grout into the stratum; further compact the backfill material and improve the bearing capacity of the stratum. Therefore, this example can further control the surface settlement within 8.5mm. Example

[0045] The difference between Example 3 and Example 1 is that: (Refer to...) Figure 3 S1 adopts an online automatic detection system and shortens the dynamic adjustment cycle according to the formation characteristics. The online automatic detection system includes an online moisture meter, an online particle analyzer, and an online consistency meter, eliminating the need for manual sampling.

[0046] S6: Dynamic Adjustment: Due to the poor stability of sandy soil strata, the dynamic adjustment cycle was shortened to once every 10 rings of excavation. During the first 10 rings, an increasing trend in surface settlement was detected. In the next cycle, i.e., rings 11-20, dynamic adjustment was immediately implemented: the grouting coefficient was increased by 8%, and the additive dosage was increased by 1.5%. After the adjustment, surface settlement was effectively controlled and stabilized at approximately 9.0 mm.

[0047] The implementation principle of the shield tunneling excavation wall grouting construction process in this application embodiment is as follows: Sandy soil has the characteristics of large particles, high permeability coefficient (usually >10⁻³ cm / s), large internal friction angle, and rapid stress release. When tunneling in sandy soil strata, once a void is formed behind the wall, the overlying strata will collapse rapidly. If grouting is not performed in time, surface settlement will occur quickly and be difficult to remedy afterwards. By using a microwave moisture meter, laser diffraction particle analyzer, and rotational viscometer, continuous and real-time monitoring of the excavation soil quality can be achieved. Compared with manual sampling, online detection shortens the response time to less than 5 minutes and can capture rapid fluctuations in the excavation soil quality in sandy soil strata. The detection data is transmitted to the control system in real time, and the proportion lookup table and material batching are automatically completed, eliminating human lag and error.

[0048] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A grouting construction process for the external wall of a shield tunneling excavation tunnel, characterized in that: Includes the following steps: S1 Slag Quality Inspection: Samples of slag discharged from the tunnel boring machine are taken and tested for three quality indicators: moisture content, particle size distribution, and slump. S2 Graded Proportion Lookup Table: Based on the type and quality indicators of the slag obtained from the test, the amount of additives for the grouting material is determined by looking up the preset graded proportion table. S3 Vibrating Screen: Vibrating screen is used to process slag and soil to remove coarse particles with a diameter greater than 10mm. S4 quantitative mixing: According to the proportion determined by referring to the table, the slag, cementitious materials, functional regulators and water are put into the mixer and mixed to prepare the grouting slurry; S5 Pressure Grouting: Calculate the soil and water pressure P0 at the current ring location, set the grouting pressure P to be 1.1-1.3 times the soil and water pressure P0, and the grouting coefficient to be 120-150%. Simultaneously grout into the construction gap between the segments and the ground through the grouting holes at the shield tail. S6 Dynamic Adjustment: Every 10-20 rings of tunneling constitutes an adjustment cycle. Based on surface settlement monitoring data, segment ellipticity detection data, and grouting pressure and flow records, feedback is provided to adjust the grouting mix ratio, grouting pressure, and grouting volume for the next cycle.

2. The grouting construction process for the external wall of a shield tunneling excavation tunnel according to claim 1, characterized in that: In step S1, the excavated soil is sampled once for each ring of excavation. The moisture content is tested using the drying method with an accuracy of ±0.5%. The particle size distribution is tested using the sieve method with sieve aperture sizes of 0.075mm, 0.25mm, 0.5mm, 1mm, 2mm, 5mm, and 10mm respectively. The slump is tested using the standard slump cone method.

3. The grouting construction process for the external wall of a shield tunneling excavation tunnel according to claim 1, characterized in that: In step S2, the amount of additives in the graded proportion table is calculated as a percentage of the dry weight of the slag, wherein the amount of additives for silty clay slag is 8-12%, the amount of additives for silty soil slag is 6-10%, and the amount of additives for sandy soil slag is 10-15%.

4. The grouting construction process for the external wall of a shield tunneling excavation tunnel according to claim 1, characterized in that: In step S3, a double-layer vibrating screen is used for screening. The upper screen has a mesh size of 30mm and the lower screen has a mesh size of 10mm. The screening efficiency is not less than 90%. After screening, the moisture content of the undersize material is tested. When the moisture content deviation is greater than 3%, the slag is dehydrated or replenished with water for adjustment.

5. The grouting construction process for the external wall of a shield tunneling excavation tunnel according to claim 1, characterized in that: In step S4, a forced mixer is used for mixing for 3-5 minutes. After mixing, the slurry properties are tested, and the fluidity is controlled to be 180-220 mm and the density to be 1.5-1.8 g / cm³. If any indicator fails to meet the requirements, the mixing is increased for 1-2 minutes or the water addition is finely adjusted. If the slurry still fails to meet the requirements after adjustment, the batch of slurry is discarded and the batch is re-prepared.

6. The grouting construction process for the external wall of a shield tunneling excavation tunnel according to claim 1, characterized in that: In step S5, the grouting flow rate is controlled at 10-30 L / min; the grout is injected evenly through 4-6 grouting holes set at the tail of the shield, and the grouting volume per hole is evenly distributed according to the grouting coefficient and the number of grouting holes.

7. The grouting construction process for the external wall of a shield tunneling excavation tunnel according to claim 1, characterized in that: In step S6, the specific rules for dynamic adjustment are as follows: if the surface settlement is greater than 8mm, increase the grouting coefficient by 5-10% or increase the amount of additive by 1-2%; if the surface settlement is less than 3mm and the segments tend to float, reduce the grouting pressure coefficient by 0.05-0.1; if the grout bleeding rate is greater than 3%, increase the amount of thickening and water-retaining agent by 0.2-0.5 parts.

8. The grouting construction process for the external wall of a shield tunneling excavation tunnel according to claim 1, characterized in that: It also includes step S7 quality acceptance: after the tunneling is completed, an overall acceptance is carried out. The acceptance indicators include the maximum surface settlement along the tunnel axis being less than 10mm, the ellipticity of the tunnel segments being less than 3‰, and the grouting filling rate being greater than 95%.

9. The grouting construction process for the external wall of a shield tunneling excavation tunnel according to claim 1, characterized in that: In step S5, the grouting method adopts a combination of synchronous grouting and secondary grouting. The grouting coefficient of synchronous grouting is set to 100-120%. Secondary grouting is carried out through the grouting holes of the segments 5-10 rings behind the shield tail. The amount of grouting is 20-40% of the theoretical void volume of the structure, and the grouting pressure is 1.0-1.1 times the soil and water pressure of the stratum.

10. The grouting construction process for the external wall of a shield tunneling excavation tunnel according to claim 2, characterized in that: In step S1, the quality testing of the slag and soil adopts an online automatic testing system, including an online moisture meter, an online particle analyzer, and an online consistency meter. The test data is transmitted to the control system in real time, and the grouting material ratio is automatically determined by looking up the table.

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