Back grouting process

Abstract

The invention relates to the field of tunnel engineering construction, in particular to a backfill grouting technology. Firstly, construction preparation is conducted, stratum parameters are obtained, and a stratum parameter-slurry ratio-grouting parameter mapping relation library is established; in the synchronous grouting stage, a multi-dimensional pressure equalizing system with a six-pipeline eight-grouting-hole four-main and four-auxiliary layout is adopted, and the pressure and the grouting amount are dynamically regulated and controlled based on a grouting pressure-void ratio model; a short-distance water stop ring is constructed on the third ring behind the shield tail, and rapid-hardening micro-expansion double-liquid slurry is injected to form a closed-loop water stop ring; secondary reinforcing grouting is conducted on the fifth ring to the eighth ring behind the shield tail, and risk points are recognized through sensor data and accurately filled; and by combining real-time monitoring and a dynamic grout supplementing mechanism, the quality is finally verified through a drilling grouting method. According to the method, the stratum self-adaption capacity, grouting uniformity and water stop reinforcing efficiency of grout are remarkably improved, the deformation and leakage risks of the duct piece are reduced, the construction efficiency is improved by 40%, and the method is suitable for complex stratum shield tunnel engineering.

Description

Technical Field

[0001] This invention relates to the field of tunnel engineering construction, and specifically to a backfill grouting process. Background Technology

[0002] In shield tunnel construction, backfill grouting is a core process for filling the circumferential void between the tunnel segments and the ground, controlling ground settlement, preventing groundwater leakage, and ensuring the stability of the tunnel structure. Its construction quality directly determines the long-term service safety of the tunnel. Existing backfill grouting technologies mainly include synchronous grouting and secondary reinforcement grouting. However, in complex geological formations, limitations in technical architecture and parameter control methods result in insurmountable defects, specifically:

[0003] Poor grout compatibility and delayed adjustment: Existing synchronous grouting methods mostly use cement mortar with fixed mix proportions, while secondary grouting uses a single type of single-component or double-component grout. The mix proportions need to be adjusted through field tests to adapt to different geological formations, resulting in long adjustment cycles (≥24 hours) and insufficient flexibility. According to GB / T 50446-2017 "Code for Construction and Acceptance of Shield Tunnels", the grout density should be ≥85%, but the permeability coefficient should be > In highly permeable formations, the setting time of fixed-ratio grout is too long (46h), resulting in a grout loss rate of 25%-30% and a filling density of only 65%-75% (lower than the standard requirements).

[0004] Poor grouting uniformity: Current synchronous grouting mostly adopts a dual-pump, four-pipeline symmetrical grouting method, with a relatively simple grouting hole layout (90° interval) and a lack of dynamic control mechanism for the pressure and flow of each grouting hole. The circumferential pressure difference exceeds 0.05MPa, which leads to uneven stress on the segments, insufficient filling of voids, and easy formation of through-seepage channels.

[0005] Water-stopping and reinforcement are not synchronized: In the existing process, the construction of the water-stopping ring is mostly carried out on the 5th ring after the shield tail. The length of the groundwater channel is up to 7.5m. The grout solidification time is 30-60s. Groundwater can easily seep into the soil chamber and cause the slag discharge accident of the screw conveyor. Summary of the Invention

[0006] To address the problems of existing technologies, this invention provides a post-wall grouting process.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A wall-mounted grouting process includes the following steps:

[0009] Step 1, Construction Preparation: Obtain the geological parameters of the tunnel crossing section, embed density sensors and seepage pressure sensors at the preset positions of the segments, install pressure-flow dual sensors in the grouting holes at the shield tail, and establish a mapping relationship library of "geological parameters-grout ratio-grouting parameters" containing a dynamic mathematical correlation model.

[0010] Step 2, Synchronous Grouting: During the tunnel boring process, the central control system uses the stratum adaptation algorithm to process real-time stratum parameters, calls the adjustable coagulation micro-expansion composite grout formula from the mapping relationship library, and starts the multi-dimensional pressure equalization grouting system.

[0011] Step 3, Construction of the close-range water-stop ring: When the shield tunneling reaches the position of the third ring segment after the shield tail, inject the fast-setting micro-expansion double-liquid grout through the grouting hole, and control the initial setting time of the grout to form a closed-loop water-stop ring.

[0012] Step 4, Secondary reinforcement grouting: When the shield tunneling reaches the 5th to 8th ring after the shield tail, the central control system identifies unfilled areas and leakage risk points based on sensor feedback data, prepares a two-liquid grout containing nano-reinforcing agent, and controls the grouting pressure based on the grouting pressure-void ratio model.

[0013] Step 5, Real-time monitoring and dynamic grouting: The central control system generates PQts multidimensional curves based on sensor data. When the density is detected to be <95% or the seepage pressure exceeds the set threshold, the directional grouting device is automatically activated.

[0014] Step 6, Quality Verification: After grouting is completed, the drilling grouting method is used for verification in combination with sensor data. Under the specified pressure, the injection volume should not exceed 10L in the first 10 minutes, and the density should be ≥9. When the seepage pressure stabilizes at 5%, it is judged to be qualified.

[0015] In step 2, the grouting pressure is controlled at 0.1~0.25MPa and the grouting volume is 1.5~1.8 times the building voids based on the grouting pressure-void ratio model. The opening of the electric regulating valve is dynamically adjusted to ensure that the circumferential pressure difference is ≤0.02MPa.

[0016] The adjustable setting micro-expansion composite slurry mentioned in step 2 has the following components and mass ratio: P·O42.5 cement, modified fly ash, nano-bentonite, graded sand, micro-expansion agent, intelligent setting regulator and water.

[0017] The rapid-setting micro-expansion two-component slurry described in step 3 consists of cement slurry, water glass diluent, and micro-expansion agent.

[0018] In the two-component slurry containing nano-reinforcing agent described in step 4, the nano-reinforcing agent is a composite of nano-silica and nano-calcium carbonate in a mass ratio of 1:1.

[0019] The multi-dimensional pressure equalization grouting system mentioned in step 2 includes a variable frequency hydraulic grouting pump and a six-pipeline eight-grouting-hole system built into the shield tail.

[0020] The eight grouting holes are arranged in a layout of four main holes and four auxiliary holes.

[0021] Compared with existing technologies, based on case studies of innovative tunnel construction technologies, this invention significantly improves the ability of grout to adapt to different strata, the uniformity of grouting, and the efficiency of water-stopping and reinforcement. It effectively reduces the risk of segment deformation and leakage, and increases construction efficiency by 40%. It is particularly suitable for shield tunnel projects in complex strata. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of synchronous grouting according to the present invention.

[0023] Figure 2 This is a flowchart of the secondary grouting construction process of the present invention.

[0024] Figure 3 This is a schematic diagram of the grouting holes for the segments of the present invention.

[0025] Figure 4 This is a flowchart of the present invention. Detailed Implementation

[0026] The present invention will be further described in detail below through embodiments. These embodiments are only used to illustrate the present invention and do not limit the scope of the present invention.

[0027] A wall-mounted grouting process includes the following steps:

[0028] (1) Construction preparation: Obtain the core parameters of the strata in the tunnel crossing section, embed fiber optic grating density sensors and seepage pressure sensors at the preset positions of the segments, and install pressure-flow dual sensors in the grouting holes at the shield tail. Establish a mapping relationship library of "strata parameters - grout ratio - grouting parameters" containing a dynamic mathematical correlation model; the specific construction preparation includes the following steps:

[0029] A detailed geological survey was conducted on the tunnel section, and the water content, permeability coefficient (K), and at-rest earth pressure of the strata were obtained using the borehole sampling method (sampling depth ≥30m). Core parameters such as porosity are verified for accuracy using ground-penetrating radar and then input into the central control system.

[0030] During segment production, fiber optic compaction sensors (model FGB-100, measurement range 0-100%, accuracy ±1%) and pressure sensors (model YSJ-200, measurement range 0-1.0MPa, accuracy ±0.01MPa) are embedded at preset positions on the segments. The sensors are wirelessly connected to the data acquisition terminal. Pressure-flow dual sensors (sampling frequency 10Hz, pressure measurement range 0-2.0MPa, flow measurement range 0-50L / min) are built into the grouting holes at the tail of the shield to ensure real-time acquisition of grouting process parameters.

[0031] A mapping database of "formation parameters - grout mix ratio - grouting parameters" with dynamic mathematical correlation models was established. Based on 500 sets of indoor test data (grout fluidity, setting time, compressive strength tests) under different formation conditions and 300 sets of field construction data (density, leakage, segment deformation) through monitoring data, four core dynamic mathematical models were constructed. The correlation coefficients (R²) of these models are all ≥0.90, which can effectively ensure prediction accuracy and provide a reliable basis for intelligent control. Through this mapping database, the optimal grout mix formula, grouting pressure, flow rate, and grouting timing under different formation conditions are clarified, including four dimensions: formation parameters, grout mix formula parameters, grouting process parameters, and effect evaluation parameters, realizing the full-chain correlation of "formation - grout - process - effect".

[0032] Stratigraphic parameters (4 items) are the basic characteristic data of the underground soil layers, including:

[0033] Moisture content (soil moisture), permeability coefficient (K, water permeability), and earth pressure at rest ( The soil layer's own pressure and porosity (the proportion of spaces between soil particles) serve as the "original basis" for the design of all subsequent parameters, and can be compared to a "stratum health check report".

[0034] Grout formulation parameters (7 items for simultaneous grouting + 5 items for secondary grouting)

[0035] The composition and proportion of grouting materials are customized according to formation parameters: For simultaneous grouting: the dosage of seven components needs to be determined (e.g., 80-220 parts cement, 460-620 parts water, etc.). For secondary grouting: the two-component grout formula containing nano-reinforcing agents needs to be adjusted, including five parameters such as the volume ratio of cement grout to water glass diluent and the amount of nano-reinforcing agent added. Its purpose is to ensure that the grout is "suitable for formation characteristics." For example, fast-setting grout should be used in highly permeable formations, while high-flowability grout should be used in soft soil formations.

[0036] Setting agent addition ratio - permeability coefficient model: Expression: λ = × [1 + (0.3 0.5)× Parameter definition: λ is the actual proportion (%) of setting regulator added. The basic addition ratio for setting agent (default 2.5%), where K is the formation permeability coefficient (cm / s). This is a commonly used logarithmic function; its fitting basis is based on experimental data of slurry setting time under 500 different K values, yielding R² ≥ 0.92, and the applicable range of K is... cm / s. Function: Through experimental research and application cases, it enables precise control of the slurry setting time in formations with different permeability coefficients, in order to avoid slurry loss in highly permeable formations and insufficient fluidity in soft plastic formations.

[0037] Two-component grout mix design - static earth pressure model: Expression:

[0038] ;

[0039] Parameter definition: V is the volume ratio of water glass diluent to cement slurry. The static earth pressure (MPa) is used; the fitting basis is based on 300 different... Based on the grouting effect test data, R² ≥ 0.91 was obtained, and the formula is applicable. The range is 0.1-0.8 MPa. Its function is to dynamically adjust the ratio of the two-component grout according to the magnitude of the earth pressure, thereby balancing the early strength of the grout with the risk of seepage damage to the soil, and thus ensuring the quality of the waterstop ring formation. Grouting process parameters:

[0040] The key data guiding the construction operation are as follows: In terms of pressure, based on porosity, the calculation is performed using a model (simultaneous grouting P = 0.42×n + 0.08, secondary grouting P = 0.85×n + 0.12).

[0041] Flow rate: dynamically balanced by an electric regulating valve (main orifice accounts for 60%–70%, auxiliary orifice 30%–40%).

[0042] In terms of timing, synchronous grouting needs to be carried out in real time along with the tunnel boring machine, while secondary grouting is carried out 5-8 rings behind the shield tail.

[0043] Its function is to ensure that the grout can be filled evenly without damaging the tunnel segments or the formation.

[0044] Grouting pressure-void ratio model: Expression: P = 0.42×n + 0.08 (simultaneous grouting); P = 0.85×n +0.12 (secondary grouting)

[0045] Parameter definitions: P is the grouting pressure (MPa), and n is the formation porosity (%); Fitting basis: Based on fitting of 300 sets of field construction data, R²≥0.90, applicable n range 30%~50%; Provides differentiated pressure calculation basis for synchronous and secondary grouting, adapts to the functional requirements of different grouting stages, and takes into account both filling density and structural safety. Effect evaluation parameters:

[0046] Key indicators for verifying grouting quality:

[0047] Density: Monitored by a fiber Bragg grating sensor, must be ≥95%;

[0048] Isobaric pressure: Monitored by osmotic pressure sensors, it must be stable and not exceed the standard;

[0049] Deformation: Monitors whether the tunnel segments deform due to excessive grouting pressure. Its function is to determine whether the grouting meets the standards; if not, the preceding parameters need to be adjusted in reverse.

[0050] The pressure-setting time model is expressed as follows: when u > 0.2 MPa, t_c = -5 × u + 25; when u ≤ 0.2 MPa, t_c = -3.3 × u + 26.6. The parameters are defined as follows: t_c represents the initial setting time of the two-liquid slurry, in seconds (s); u represents the formation pressure, in megapascals (MPa). The fitting is based on 200 sets of matching test data of pressure and setting time, with an R² value not less than 0.90. This model is applicable to u values ​​ranging from 0.05 to 0.5 MPa. Its function is to achieve the linkage control between leakage risk level and slurry setting rate, enabling rapid sealing of high-pressure leakage points and uniform filling of low-pressure areas.

[0051] The operational logic of each model: formation parameters (such as K, Using (n, u) as inputs, the model directly correlates the grout formulation (setting agent ratio, two-liquid grout mix ratio) and process parameters (grouting pressure). Finally, the model output is verified using performance evaluation parameters (density, seepage pressure, deformation), forming a closed-loop control system from "bottom-level input to model calculation to parameter output to performance feedback."

[0052] (2) Synchronous grouting: During the shield tunneling process, the central control system processes real-time ground parameters through a ground adaptation algorithm (a fusion model of multiple linear regression and BP neural network).

[0053] This algorithm balances the stability of linear fitting with the accuracy of neural networks, achieving optimal matching between formation parameters and grouting parameters. The system retrieves the adjustable-coagulation micro-expansion composite grout formula from the mapping database and simultaneously activates a multi-dimensional pressure-equalizing grouting system. This system employs a symmetrical "four main, four auxiliary" layout with six pipelines and eight grouting holes. Compared to the traditional four-pipeline layout, this significantly improves circumferential grouting uniformity and avoids deformation caused by uneven stress on the segments. The grouting pressure is determined based on a grouting pressure-porosity model, with the formula P = 0.42×n + 0.08 (where n is the formation porosity, %). Its core function is to quantitatively match the grouting pressure according to the formation porosity, avoiding segment deformation caused by excessive pressure and incomplete filling due to insufficient pressure. The final pressure is 0.1. Grouting pressure of 0.25 MPa, theoretical building void ratio of 1.5. Grouting is performed with a 1.8 times grouting volume. This redundant design effectively compensates for grout loss and shrinkage, ensuring dense filling of voids. Dual pressure and flow sensors provide real-time feedback of pressure data from each grouting hole, offering a real-time data source for pressure control. The central control system dynamically adjusts the opening of the electric regulating valve to achieve millisecond-level precise flow control, thereby balancing the pressure in each grouting hole and ensuring a circumferential pressure difference ≤0.02MPa. This achieves adaptive closed-loop control of "formation sensing – grout adaptation – pressure balancing." The grouting pressure model is based on fitting 300 sets of field construction data, with a correlation coefficient R²≥0.90. It is applicable to a porosity range of 30%–50%, ensuring prediction accuracy within the mainstream formation porosity range and improving process applicability.

[0054] The specific central control system uses a formation adaptation algorithm (a fusion model of multiple linear regression and BP neural network) to process real-time formation parameters: First, the formation parameters and the grout base formula are linearly fitted using a multiple linear regression model to obtain a preliminary formula; then, the preliminary formula, real-time sensor data, and historical construction effect data are input into the BP neural network model, with "compaction ≥95% and grout loss rate ≤5%" as the optimization objective, to output the optimal grout formula and grouting parameters, which are then verified and corrected by a random forest algorithm before being sent to the intelligent grout preparation module;

[0055] The intelligent slurry preparation module automatically completes slurry stirring, ensuring stirring time ≥5 minutes and slurry uniformity ≥98%; at the same time, the slurry storage tank maintains self-stirring mode with a stirring speed of 30 rpm to prevent sedimentation.

[0056] During shield tunneling, a multi-dimensional pressure equalization grouting system is activated. Two variable frequency hydraulic grouting pumps perform symmetrical grouting through a six-pipeline, eight-grouting-hole system ("four main, four auxiliary") built into the shield tail. The initial grouting pressure is set at 0.1-0.2 MPa, and the grouting volume is 1.5-1.8 times the theoretical building voids. Specifically, the multi-dimensional pressure equalization grouting system includes two variable frequency hydraulic grouting pumps (grouting capacity of 2×15 cubic meters / hour, pressure adjustment range of 0.1-1.0 MPa) and a six-pipeline, eight-grouting-hole system built into the shield tail. The eight grouting holes adopt a "four main holes + four auxiliary holes" layout. The main holes are located at the arch top, arch bottom, and both sides of the waist (at 90-degree intervals), and the auxiliary holes are located at 45-degree intervals between the main holes. The flow rate is precisely distributed through an electric regulating valve, with the main holes accounting for 60%-70% of the flow rate. With auxiliary holes accounting for 30% to 40%, and combined with real-time feedback from pressure and flow dual sensors, a pressure balancing algorithm (PID closed-loop control) is used to achieve a circumferential pressure difference of ≤0.02MPa, solving the problem of uneven circumferential pressure (difference >0.05MPa) in traditional four-pipe grouting.

[0057] Each grouting hole is equipped with pressure and flow dual sensors that collect data in real time. The central control system adjusts the opening of the electric regulating valve through a pressure balancing algorithm (PID closed-loop control) to ensure that the flow rate of the main hole accounts for 60% to 70%, the auxiliary hole accounts for 30% to 40%, and the circumferential pressure difference is ≤0.02MPa. When tunneling to a highly permeable stratum (K>10⁻³cm / s);

[0058] The system automatically adds the setting regulator according to the formula:

[0059] ( Increasing the dosage of intelligent setting regulator shortens the grout setting time from 4-6 hours to 2-3 hours, while simultaneously increasing the grouting pressure to 0.2. 0.25MPa further reduces slurry loss.

[0060] Following the principle of "simultaneous tunneling and grouting, no tunneling without grouting", the grouting volume for that ring is completed simultaneously when the shield tunneling completes one ring (1.5m) of tunneling, ensuring that the gaps are filled in a timely manner.

[0061] Specifically, the components and mass ratio of the adjustable-setting micro-expansion composite grout are as follows: 80-220 parts of P·O42.5 cement (to provide core cementing strength for the grout, adapting to the bearing capacity requirements of different strata), 240-390 parts of modified fly ash (which can replace part of the cement, reduce the heat of hydration, and improve the fluidity and later strength of the grout), 50-65 parts of nano-bentonite (which can optimize the water retention and impermeability of the grout, avoid filling voids due to bleeding, and this ratio range can balance water retention and fluidity), and 600-780 parts of graded sand (which can improve the skeleton strength of the grout and reduce solidification shrinkage). The mixture contains 5-8 parts of a micro-expansion agent (to compensate for grout solidification shrinkage and ensure tight adhesion between the grout body and the segments and formation), 2-5 parts of a smart setting regulator (to dynamically control the setting time of the grout to adapt to formations with different permeability coefficients), and 460-620 parts of water (to adjust the fluidity of the grout and ensure its diffusion). The smart setting regulator is a composite system of lithium carbonate and potassium aluminum sulfate (mass ratio 2:1, its function is to improve the sensitivity of setting time control, making it easier to achieve precise setting over a wide range compared to other ratios). Its addition ratio is dynamically adjusted according to the formation permeability coefficient K using a dynamic mathematical model. The adjustment formula is as follows:

[0062] Function: To establish a quantitative correlation between permeability coefficient and setting agent dosage, enabling targeted adaptation to formations with different permeability. Here, λ is the actual addition ratio of the setting agent (%), λ0 is the base addition ratio of the setting agent (2.5%), and K is the formation permeability coefficient (cm / s). 10 The function used is a commonly used logarithmic function. This model is based on 500 sets of intermediate test data on slurry setting under different permeability coefficients (correlation coefficient R² ≥ 0.92), and is applicable to a K range of 10⁻. 5 -10⁻²cm / s; when K>10⁻³cm / s, the setting time is shortened from 4~6h to 2~3h (adapting to the rapid filling requirements of highly permeable strata and reducing slurry loss); when K≤10⁻ 4 When the flow rate is cm / s, the proportion of setting regulator added should be reduced by 20% to 30% (to ensure the fluidity of the slurry and avoid localized incomplete filling) to ensure both the fluidity of the slurry and the density of the filling.

[0063] (3) Construction of close-range water-stop ring: When the shield tunneling reaches the position of the third ring segment after the shield tail, inject quick-setting micro-expansion double-liquid grout through the grouting hole of the water-stop ring, control the initial setting time of the grout to 20-30s, and quickly form a closed-loop water-stop ring; specifically, when the shield tunneling reaches the position of the third ring segment after the shield tail, inject quick-setting micro-expansion double-liquid grout through the grouting pipe of the water-stop ring;

[0064] The central control system is based on the static earth pressure of the strata. Through the dual-liquid slurry ratio-static earth pressure model ( hour, hour, Adjusting the two-component slurry ratio: Under these conditions, to improve the early strength of the grout (1-day compressive strength ≥ 1.5 MPa), a volume ratio of water glass diluent to cement grout of 1:1 to 1.2:1 is used. However, In cases where the grout is insufficient to reduce the risk of seepage damage to the soil (seepage failure gradient ≤ 10), a volume ratio of 1.5:1 to 2:1 is recommended. The amount of micro-expansion agent added should be 3% to 5% of the cement mass, which can effectively compensate for grout shrinkage (shrinkage rate ≤ 0.5%).

[0065] The initial setting time of the grout is controlled at 20-30 seconds, which quickly forms a closed-loop water-stopping ring. Compared with the traditional fifth ring arrangement, the length of the groundwater channel is shortened by more than 50%, significantly reducing the risk of groundwater infiltration.

[0066] The rapid-setting micro-expansion two-component grout consists of cement grout, water glass diluent, and a micro-expansion agent. The cement grout has a water-cement ratio of 1:1 (balancing grout fluidity and early strength, providing basic bonding capacity for rapid setting). The volume ratio of the water glass diluent (water glass to water volume ratio of 1:1, reducing water glass concentration and preventing grout clumping and pipe blockage due to excessively rapid reaction) to the cement grout is dynamically adjusted based on the static earth pressure P0 using a pressure-proportioning correlation model. The model formula is as follows:

[0067] ;

[0068] This formula achieves precise matching between earth pressure and grout strength, avoiding grout compression and damage under high earth pressure and excessive grout permeation under low earth pressure. V represents the volume ratio of water glass diluent to cement grout, and P0 represents the static earth pressure (MPa). This model is optimized based on 300 sets of grouting effect test data (compressive strength and permeability coefficient tests) under different static earth pressures, with R² ≥ 0.91, and is applicable to… Range 0.1 0.8MPa; the corresponding adjustment rule is: when When the pressure is >0.3 MPa, it is recommended that the volume ratio of water glass diluent to cement slurry be 1:1. A 1.2:1 ratio enhances the early strength of the grout to resist high earth pressure, thus ensuring the stability of the waterstop ring formation; when For pressures ≤0.3 MPa, the recommended volume ratio of water glass diluent to cement slurry is 1.5:1. The 2:1 ratio reduces the curing speed of the grout, thereby minimizing its penetration and damage to the soil, while ensuring uniform diffusion of the grout. The amount of micro-expansion agent added is 3% to 5% of the cement mass (to compensate for the grout's solidification shrinkage, ensure the water-stop ring is tight and crack-free, and block groundwater channels).

[0069] (4) Secondary reinforcement grouting: When the shield tunneling reaches the tail of the shield, the 5th... At the 8th ring, the synchronous grouting body has initially stabilized, and the gap between the tunnel segments and the stratum has not excessively widened. This condition balances reinforcement effect and construction efficiency. Based on feedback data from fiber optic grating density sensors (when the monitored value is <95%) and seepage pressure sensors (when the monitored value exceeds the standard), the central control system can accurately identify unfilled areas and leakage risk points. It intelligently prepares a cement-water glass dual-liquid grout containing nano-reinforcing agents using a dual-liquid grout ratio optimization algorithm. The grouting pressure is determined based on a grouting pressure-porosity model, with the formula P = 0.85×n + 0.12 (where n is the stratum porosity, %). This pressure is higher than that of synchronous grouting, ensuring grout penetration into deep gaps while allowing for adjustment based on porosity to avoid damaging the formed grouting body. Ultimately, the grouting pressure is controlled between 0.3 and 0.5 MPa, precisely filling the shrinkage voids, unfilled areas, and separation gaps between the tunnel segments and the stratum, compensating for synchronous grouting defects, and improving the overall integrity and impermeability of the tunnel structure. This model is derived from the synchronous grouting model, and is applicable to a porosity range of 30% to 50% with R² ≥ 0.90. It can maintain model consistency, reduce system computational complexity, and improve control stability.

[0070] Specific reinforcement grouting steps:

[0071] When the tunnel boring machine (TBM) reaches the 5th to 8th ring after the shield tail, the central control system uses data from fiber optic grating density sensors (monitoring value <95%) and seepage pressure sensors (monitoring value exceeding the standard) to intelligently proportion a two-liquid slurry containing nano-reinforcing agent through a two-liquid slurry ratio optimization algorithm: cement slurry water-cement ratio 1:1, water glass diluent to cement slurry volume ratio 1:13:1, and nano-reinforcing agent (nano-silica and nano-calcium carbonate compound, mass ratio 1:1) added at 2% to 4% of the cement mass;

[0072] Connect the grouting pipe using an intelligent sealing grouting joint, first inject pure cement grout for 1 minute (injection volume not less than 5L), then open the water glass valve for mixing and injection, controlling the grouting pressure at 0.3-0.5MPa. Adjust the initial setting time using the seepage pressure-setting time model: when seepage pressure > 0.2MPa, control the initial setting time to 15-20s according to the formula t_c = -5×u + 25 to quickly seal the leakage channel; when seepage pressure ≤ 0.2MPa, control the initial setting time to 20-30s according to the formula t_c = -3.3×u + 26.6 to ensure uniform grout diffusion.

[0073] After grouting a single grouting hole is completed, wait 5 to 10 minutes, open the grouting head to check the injection effect. If the effect is not good (the mud content of the grout flowing out is >10%), inject again until only a small amount of clear water flows out (mud content ≤2%). After depressurization, remove the grouting head, seal the grouting hole with quick-setting cement mortar and install plastic screws.

[0074] The nano-reinforcing agent in the two-liquid grout is a 1:1 mass ratio of nano-silica and nano-calcium carbonate, which synergistically improves the compressive strength and impermeability of the grout aggregate and fills micropores. The addition amount is 2%–4% of the cement mass. This ratio maximizes the reinforcing effect without affecting the grout's fluidity. The initial setting time of the two-liquid grout is controlled by a seepage pressure-setting time correlation model in the central control system. The model formula is: t_c = -5×u + 25 (u>0.2MPa); t_c = -3.3×u + 26.6 (When u≤0.2MPa) Function: To establish a quantitative relationship between seepage pressure and setting time, achieving rapid sealing under leakage risk and uniform reinforcement under normal working conditions, where t_c is the initial setting time of the two-liquid grout (s), and u is the formation seepage pressure (MPa); This model is constructed based on 200 sets of seepage pressure and setting time matching tests, with a goodness of fit R²≥0.90, and is applicable to a u range of 0.05~0.5MPa; The corresponding control rules are: when seepage pressure>0.2MPa, the initial setting time is controlled at 15~20s to quickly solidify and seal the seepage channels, preventing continuous groundwater infiltration; when seepage pressure≤0.2MPa, the initial setting time is controlled at 20~30s to prolong the grout diffusion time, ensuring that shrinkage voids and peeling gaps are fully filled.

[0075] (5) Real-time monitoring and dynamic grouting: The central control system generates a PQts multidimensional curve (P: grouting pressure, Q: grouting volume, t: time, s: density / permeability) based on sensor data. When the density is detected to be <95% or the permeability exceeds the set threshold, the system automatically starts the directional grouting device to synchronously inject grout at a pressure of 1.05. The value is 1.1 times the standard value. Precise grouting is carried out according to the principle of "small amount and multiple times". After grouting, the indicators are re-monitored until they meet the standard.

[0076] Specifically, the central control system receives sensor data in real time (sampling frequency 5Hz), generates PQts multidimensional curves through the data processing unit, and combines this with the tunnel boring machine's attitude data (measurement accuracy ±0.1°) to comprehensively analyze the grouting effect. The parameter control unit incorporates a machine learning algorithm (based on a random forest optimization model). This algorithm continuously optimizes the mapping relationship library based on historical construction data (≥100 sets), gradually improving the grout matching accuracy and grouting effect compliance rate as construction progresses (improvement ≥5% / 10 rings). For example, when accumulating a certain type of soft soil layer (porosity n=45%, permeability coefficient K=10⁻), 4 After obtaining 50 sets of construction data (cm / s), the model will automatically correct the grouting pressure formula corresponding to the stratum (original P=0.42×n+0.08), making the pressure calculation more in line with the actual filling requirements, thereby reducing the risk of segment deformation.

[0077] When the density is detected to be below 95% or the seepage pressure exceeds the set threshold (which is set based on the formation water pressure, usually 0.2MPa), the directional grouting device is automatically activated: using a location positioning algorithm (based on the spatial distribution data of the fiber optic density sensor and combined with the triangulation principle) to determine the coordinates of the unfilled area (positioning accuracy ≤ ±5cm), the telescopic grouting pipe (telescopic range 0 - 500mm) and angle adjustment mechanism (adjustment angle ±30°) are used to accurately align with the target area, and grouting is carried out at a synchronous grouting pressure of 1.05 - 1.1 times the pressure, following the principle of "small amount, multiple times" (single grouting volume ≤ 0.5m³, interval time ≥ 5min).

[0078] After the grouting is completed, the system re-collects sensor data to carry out verification work until the density reaches 95% or above and the seepage pressure is stable (fluctuation ≤0.02MPa within 30 minutes).

[0079] (6) Quality Verification: Seven days after grouting is completed, a comprehensive verification is conducted using borehole grouting method combined with sensor data. Grout with a water-cement ratio of 2:1 is injected into the hole. Under the specified pressure, the injection volume should not exceed 10L within the first 10 minutes, and the density sensor monitoring value should reach 95% or above, and the seepage pressure should be stable, which is considered qualified. Specifically, the quality inspection is carried out using the borehole grouting method: one inspection hole (diameter φ50mm, hole depth ≥50cm) is arranged at the arch top, arch bottom, and both sides of the waist of the segment, and grout with a water-cement ratio of 2:1 is injected into the hole;

[0080] Under the specified pressure (0.5MPa), if the injection volume does not exceed 10L within the initial 10 minutes, and the density is ≥95% and the seepage pressure is stable as monitored by the sensor, it is considered qualified; if it is not qualified, the directional grouting device is started for secondary grouting, and the test is repeated after grouting.

[0081] Project Case 1: Grouting Construction Behind the Wall of a Shield Tunnel in Water-Rich and Highly Permeable Geological Formations

[0082] The formation parameters are as follows: water cut 35%, permeability coefficient The earth pressure at rest, P0 = 0.35 MPa, and the porosity is 40%.

[0083] Construction preparation: Drilling sampling method was used to obtain formation parameters, and ground-penetrating radar was used for detection and verification; FGB-100 type compaction sensor and YSJ-200 type seepage pressure sensor were embedded in the tunnel segments, and pressure-flow dual sensor was installed in the grouting hole at the shield tail; the parameters of highly permeable formations were called from the mapping relationship library.

[0084] Synchronous grouting: The proportion of adjustable-setting micro-expansion composite grout is as follows: 200 parts P·O42.5 cement, 380 parts modified fly ash, 60 parts nano-bentonite, 750 parts graded sand, 6 parts micro-expansion agent, 4 parts intelligent setting regulator (the addition ratio is calculated according to the formula and is 1.4 times the base ratio), and 580 parts water; the grouting pressure is 0.22 MPa, and the grouting volume is 1.7 times the theoretical building voids; the multi-dimensional pressure equalization grouting system controls the flow rate of the main hole to 65% and the auxiliary hole to 35%, with a circumferential pressure difference of 0.015 MPa; the incorporation of bentonite helps to improve the performance of the grout, such as fluidity and final setting time.

[0085] Construction of the close-range waterstop ring: The third ring behind the shield tail is injected with a rapid-setting, micro-expansion dual-liquid grout, with a water glass diluent to cement grout volume ratio of 1.1:1 (according to...). (Determined through a pressure-proportion correlation model), the amount of micro-expansive added is 4%, and the initial setting time is 25 seconds;

[0086] Secondary reinforcement grouting: At the 6th ring behind the shield tail, the density was monitored by the sensor to be 92% (less than 95%). Intelligent proportioning dual-liquid grout (nano-reinforcing agent added at 3%) was used. The grouting pressure was 0.4MPa and the initial setting time was 18s (determined by the seepage pressure-setting time correlation model based on a seepage pressure of 0.22MPa).

[0087] Real-time monitoring and dynamic grouting: The PQts curve showed a local density of 93%. The directional grouting device was activated, and the coordinates of the unfilled area were determined by the location positioning algorithm. Grouting was performed at a pressure of 0.23 MPa for 0.3 m³, and the density reached 98% after grouting.

[0088] Quality verification: After 7 days, the drilling grouting inspection was carried out. The injection volumes of the three test holes in the first 10 minutes were 7.8L, 8.2L and 7.5L respectively, with an average injection volume of 8.0L, which met the requirement of ≤10L. The density was 98%, and the seepage pressure was stable below 0.05MPa, so it was judged as qualified.

[0089] Project Case 2: Grouting Construction Behind the Wall of a Shield Tunnel in Soft Plastic Soil

[0090] Formation parameters: water cut 40%, permeability coefficient Earth pressure at rest Porosity 45%;

[0091] Construction preparation: The formation parameters were obtained by drilling and sampling, and the soft plastic formation adaptation parameters were called from the mapping relationship library;

[0092] Synchronous grouting: The proportion of adjustable-setting micro-expansion composite grout is as follows: 150 parts P·O42.5 cement, 350 parts modified fly ash, 55 parts nano-bentonite, 680 parts graded sand, 5 parts micro-expansion agent, 3 parts intelligent setting regulator (added at 0.8 times the base ratio), and 520 parts water; grouting pressure is 0.15 MPa, grouting volume is 1.6 times the theoretical building voids; the main hole flow rate accounts for 60%, the auxiliary hole for 40%, and the circumferential pressure difference is 0.01 MPa;

[0093] Construction of close-range waterstop rings: In the rapid-setting micro-expansion two-component grout, the volume ratio of water glass diluent to cement grout is 1.8:1 (according to...). (Confirmed), micro-expansion agent addition amount 3%, initial setting time 22s;

[0094] Secondary reinforcement grouting: At the 5th ring position after the shield tail, the seepage pressure monitoring value is 0.18 MPa (meets the standard), the density is 93%, the amount of nano-reinforcing agent added in the two-liquid grout is 2%, the grouting pressure is 0.35 MPa, and the initial setting time is 28s;

[0095] Real-time monitoring and dynamic slurry replenishment: No abnormal data, no additional slurry replenishment required;

[0096] Quality verification: After 7 days, the grouting inspection of the boreholes showed that the injection volumes in the first 10 minutes of the three test holes were 5.8L, 6.2L, and 5.5L, respectively, with an average of 5.8L ≤ 10L. The compaction was 97%, and the ground settlement was controlled within the range of -15mm to -5mm, which met the specifications.

Claims

1. A wall-mounted grouting process, characterized in that, Includes the following steps: Step 1, Construction Preparation: Obtain the geological parameters of the tunnel crossing section, embed density sensors and seepage pressure sensors at the preset positions of the segments, install pressure-flow dual sensors in the grouting holes at the shield tail, and establish a mapping relationship library of "geological parameters-grout ratio-grouting parameters" containing a dynamic mathematical correlation model. Step 2, Synchronous Grouting: During the tunnel boring machine excavation, the central control system processes real-time geological parameters through a geological adaptation algorithm, calls the adjustable micro-expansion composite grout formula from the mapping relationship library, and starts the multi-dimensional pressure equalization grouting system. Step 3, Construction of the close-range water-stop ring: When the shield tunneling reaches the position of the third ring segment after the shield tail, inject the fast-setting micro-expansion double liquid grout through the grouting hole, and control the initial setting time of the grout to form a closed-loop water-stop ring. Step 4, Secondary reinforcement grouting: When the shield tunneling reaches the 5th to 8th ring after the shield tail, the central control system identifies unfilled areas and leakage risk points based on sensor feedback data, prepares a two-liquid grout containing nano-reinforcing agent, and controls the grouting pressure based on the grouting pressure-void ratio model. Step 5, Real-time monitoring and dynamic grouting: The central control system generates PQts multidimensional curves based on sensor data. When the density is detected to be <95% or the seepage pressure exceeds the set threshold, the directional grouting device is automatically activated. Step 6, Quality Verification: After grouting is completed, the drilling grouting method is used for verification in combination with sensor data. Under the specified pressure, the injection volume should not exceed 10L in the first 10 minutes, and the compaction degree should not be less than 95% and the seepage pressure should be stable to be considered qualified.

2. The wall-mounted grouting process according to claim 1, characterized in that, In step 2, the grouting pressure is controlled at 0.1~0.25MPa and the grouting volume is 1.5~1.8 times the building voids based on the grouting pressure-void ratio model. The opening of the electric regulating valve is dynamically adjusted to ensure that the circumferential pressure difference is ≤0.02MPa.

3. The wall-mounted grouting process according to claim 2, characterized in that, The components and mass ratio of the adjustable setting micro-expansion composite slurry mentioned in step 2 are: P·O42.5 cement, modified fly ash, nano-bentonite, graded sand, micro-expansion agent, intelligent setting regulator and water.

4. The wall-mounted grouting process according to claim 3, characterized in that, In step 3, the quick-setting micro-expansion two-component slurry consists of cement slurry, water glass diluent, and micro-expansion agent.

5. The wall-mounted grouting process according to claim 4, characterized in that, In step 4, the nano-reinforcing agent in the two-liquid slurry is a composite of nano-silica and nano-calcium carbonate in a mass ratio of 1:

1.

6. The wall-mounted grouting process according to claim 1, characterized in that, In step 2, the multi-dimensional pressure equalization grouting system includes a variable frequency hydraulic grouting pump and a six-pipeline eight-grouting-hole system built into the shield tail.

7. The wall-mounted grouting process according to claim 6, characterized in that, The eight grouting holes adopt a layout of four main holes and four auxiliary holes.

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