Open cut tunnel slope protection construction method

Abstract

The invention discloses an open-cut tunnel slope protection construction method, belongs to the technical field of tunnel engineering construction and slope protection, and aims to solve the problems that in a traditional method, monitoring coverage is insufficient, so that sliding early warning lags behind, support parameters are static, anchoring fails, and slope instability is aggravated due to poor grouting and drainage synergy. Distributed optical fiber sensors are pre-buried on the slope surfaces on the two sides of the tunnel axis before slope excavation, a hydraulic servo anchor rod supporting system is started when the real-time monitoring strain increment reaches 0.04-0.06% or the seepage rate reaches 4-6 mm / h, and the initial prestress of an anchor rod is 45-55 kN and is dynamically adjusted; after each stage of excavation, high-pressure grouting is adopted to seal the slope surface, nano silicon dioxide is doped into grouting holes, blind ditches containing gravel filter layers and drainage pipes are synchronously laid, and finally adjustment is stopped when the displacement rate is smaller than 0.5 mm / d and the seepage rate is smaller than 2 mm / h for continuous 3 days. The method is suitable for tunnel slope stability control in a water-rich stratum and a weak intercalated layer area, and deformation monitoring, dynamic supporting and seepage treatment can be synchronously achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of tunnel engineering construction and slope protection, and in particular relates to an open-cut tunnel slope protection construction method. Background Art

[0002] In open-cut tunnel projects, slope stability control is the core issue of construction safety. Traditional slope protection methods often use point displacement monitoring combined with static anchor support, but there are significant defects in actual applications: First, conventional monitoring methods (such as inclinometers and earth pressure boxes) have low deployment density and limited coverage, making it difficult to capture local deformation and seepage anomalies in weak interlayer areas, resulting in delayed warning of slip risks; second, anchor support mostly adopts fixed prestressed design, which cannot be adjusted in real time according to the dynamically changing stress field and seepage field during excavation, and is prone to insufficient support stiffness or over-constraint, causing secondary deformation of the slope; in addition, the grouting reinforcement process often forms reinforcement blind areas due to insufficient slurry penetration distance and poor matching with the seepage channel, and the grading design and water flow capacity of the drainage blind ditch are insufficient, which is prone to rapid attenuation of drainage efficiency due to filter layer clogging.

[0003] The root causes of the above problems are: 1) The spatial resolution of the monitoring system is insufficient, making it difficult to accurately locate potential slip surfaces and seepage paths; 2) There is a lack of dynamic coupling mechanism between support parameters and geological responses, resulting in a disconnect between mechanical control and deformation development; 3) There is no coordinated regulation between the performance of grouting materials and the evolution law of the seepage field, and the drainage structure's anti-clogging ability and long-term service performance are not guaranteed. Especially in areas with water-rich sand layers or weak interlayers, seepage erosion will accelerate the weakening of soil structure, and traditional grouting materials are difficult to effectively penetrate and consolidate under dynamic water conditions, further exacerbating the risk of slope instability. Existing technologies attempt to improve by increasing the density of monitoring points or increasing the grouting pressure, but the former significantly increases construction costs, and the latter may destroy the original structure of the rock and soil, and both fail to fundamentally solve the problem of slope stability control under the coupling of multiple physical fields. Summary of the invention

[0004] In view of the problems of insufficient monitoring coverage, static support parameters, and poor coordination between grouting and drainage in traditional slope protection methods, the present invention provides an open-cut tunnel slope protection construction method, which controls slope stability based on real-time monitoring of distributed optical fiber sensors, dynamic support of hydraulic servo anchor rods, and coordinated control of high-pressure grouting and drainage blind ditch.

[0005] In order to achieve these purposes and other advantages of the present invention, the present invention provides an open-cut tunnel slope protection construction method, comprising the following steps: 1) Before excavation of the slope, distributed optical fiber sensors are pre-buried along the slopes on both sides of the tunnel axis. The layout depth of the distributed optical fiber sensors is 0.6-0.7 times the design height of the slope. The horizontal spacing between adjacent sensors is 2.5-3.5m, and the vertical spacing is 1.8-2.2m. The sensors are connected to the ground data acquisition terminal through lines, and the response delay is ≤3 seconds; 2) When the distributed optical fiber sensor monitors that the slope strain increment reaches 0.04-0.06% (based on historical landslide data statistics) and the seepage rate reaches 4-6mm / h (critical value of dynamic water pressure), the hydraulic servo anchor support system is started. The installation angle of the hydraulic servo anchor is 15°-25°, the anchor length is 1.1-1.4 times the excavation depth, the anchor spacing is 1.8-2.2m×1.8-2.2m grid arrangement, the initial prestress is set to 45-55kN, and the step length is dynamically adjusted according to the real-time monitored strain rate of 0.01-0.03% / h, and the step length is 5-15kN; 3) After each level of slope is excavated to the designed elevation, a high-pressure grouting machine is used to seal the slope surface for grouting. The grouting pressure is dynamically adjusted according to the seepage rate: when the seepage rate is 4-6mm / h, the pressure is 0.8-1.0MPa, and when the seepage rate is greater than 6mm / h, it is increased to 1.2-1.4MPa. The spacing between the grouting holes is 1.3-1.7m, and the grouting material is silicate cement slurry mixed with 2-8% nano-silicon dioxide; 4) A longitudinal drainage blind ditch is laid along the slope foot, a three-graded gravel filter layer is laid at the bottom of the ditch, and a HDPE perforated drainage pipe is installed above the filter layer, and a double-layer geotextile is wrapped outside the pipe; 5) The slope deformation data is continuously monitored by distributed fiber optic sensors. When the displacement rate is less than 0.5 mm / d and the seepage rate is less than 2 mm / h for three consecutive days, the hydraulic servo anchor prestressing adjustment is terminated in stages: in the first stage, the step size is reduced to 5 kN and maintained for 24 hours; in the second stage, the adjustment is completely stopped and monitoring is continued for 48 hours.

[0006] Preferably, the open-cut tunnel slope protection construction method is: 1) In the weak interlayer area, the deployment depth of distributed optical fiber sensors is increased to 0.8-0.9 times the design height of the slope, the horizontal spacing is reduced to 2.0-3.0m, and the vertical spacing is reduced to 1.5-2.0m; 2) When pre-buried distributed optical fiber sensors, stainless steel fixing buckles are set every 0.5m along the sensor axis, and a 10-15mm thick epoxy resin bonding layer is filled between the buckles and the slope rock and soil; 3) The ground data acquisition terminal performs sliding average filtering on the monitoring data of the distributed optical fiber sensor. The filtering window time is 10-15 minutes, and outliers outside the range of ±3σ are eliminated; 4) When three adjacent distributed optical fiber sensors on the same monitoring section simultaneously detect a strain increment ≥ 0.04% and a seepage rate ≥ 4 mm / h, the start-up conditions of the hydraulic servo anchor support system are triggered.

[0007] Preferably, the open-cut tunnel slope protection construction method is: 1) During the prestress adjustment process of the hydraulic servo anchor, when the distributed optical fiber sensor detects that the slope strain rate exceeds 0.03% / h, the adjustment step length is increased to 12-15kN; when the strain rate is lower than 0.01% / h, the adjustment step length is reduced to 5-8kN; 2) The anchoring section of the hydraulic servo anchor is provided with a dual hydraulic cylinder coordinated control system, the main hydraulic cylinder applies axial tension, and the auxiliary hydraulic cylinder applies lateral pressure at an angle of 30°-45° to the rock formation trend, and the pressure ratio of the main and auxiliary hydraulic cylinders is dynamically controlled by the rock formation strain gradient calculated in real time, and the range is 1:0.3-0.5; 3) The surface of the anchor rod body is processed with a continuous thread structure, with a thread pitch of 15-20mm and a thread depth of 2-3mm. The thread area covers the entire length of the grouting section, and a grout penetration hole with a diameter of 3-5mm is opened at the root of the thread, with a hole spacing of 50-80mm; 4) When the anchor head pressure sensor detects that the contact stress fluctuation amplitude exceeds 20% of the initial value, the anchor spacing encryption mechanism is automatically triggered to reduce the grid layout spacing to 1.5-1.8m×1.5-1.8m.

[0008] Preferably, the open-cut tunnel slope protection construction method is: 1) The ground data acquisition terminal inputs the strain increment, seepage rate and standard deviation of contact stress fluctuation of the anchor head monitored by the distributed optical fiber sensor into the Bayesian network model trained based on historical slope engineering data. The model input node is defined as: strain increment → seepage rate → contact stress fluctuation → instability probability. The mean square error of the output instability probability value is ≤0.005; 2) When the instability probability output by the Bayesian network is ≥85% or the real-time strain rate is <0.05% / h, the following operations are triggered synchronously: a. The adjustment step length of the hydraulic servo anchor is increased to 12-15kN (each adjustment ≤ 5kN, interval ≥ 10 minutes); b. The grouting pressure of the high-pressure grouting machine is increased to 1.2-1.4MPa; c. The opening rate of HDPE perforated drainage pipe is increased to 6-8%, and the hole diameter is adjusted to 8-10mm; 3) The Bayesian network model is trained based on historical slope engineering data. The input parameters include strain increment, seepage rate, and standard deviation of contact stress fluctuation. The output is the instability probability value. 4) When the probability of instability is less than 60% and the displacement rate is less than 0.5mm / d for three consecutive days, the anchor step length is restored to 8-12kN, the grouting pressure is reduced to 0.8-1.0MPa, and the drainage pipe opening rate is adjusted back to 3-5%.

[0009] Preferably, when the probability of instability of the Bayesian network model is ≥95% or the communication is interrupted, it automatically switches to the preset static support mode (the anchor step length is fixed at 10kN, the grouting pressure is 1.0MPa, and the drainage pipe opening rate is 5%).

[0010] Preferably, the open-cut tunnel slope protection construction method is: 1) During the preparation of the silicate cement slurry, nano silicon dioxide is added in two stages: a. In the first stage, 1-2% by mass of nano-silicon dioxide and water reducer are added to the mixing water and ultrasonically dispersed; b. In the second stage, add the remaining 1-2% nano-silica, mix with Portland cement and continue stirring; 2) A medium-coarse sand transition layer is added to the bottom of the gravel filter layer of the drainage blind ditch, and a geotextile is laid between the sand layer and the gravel layer; 3) Within 24 hours after the grouting is completed, the drainage blind ditch shall be reversely flushed with a flushing water pressure of ≤0.4MPa and a flushing duration of 10-20 minutes until the water flow capacity of the drainage pipe is ≥5L / (m·s); 4) When the adjustment step of the hydraulic servo anchor is ≥12kN, 0.2-0.5% early strength agent is added to the slurry simultaneously to shorten the initial setting time of the slurry to 45-60 minutes.

[0011] Preferably, the open-cut tunnel slope protection construction method is: 1) During the slope excavation process, the rock layer temperature data is monitored in real time through distributed optical fiber sensors, and the temperature-strain-seepage coupling model is established by integrating and analyzing the strain and seepage data; 2) When the temperature rises abnormally (ΔT ≥ 3°C / 24h, the baseline value is the average value of monitoring in the 30 days before construction ± 1°C) and the strain rate is > 0.02% / h, the following emergency measures are triggered: a. Increase the adjustment step length of hydraulic servo anchors to 15kN, and increase the anchor grid spacing to 1.5m×1.5m; b. Add 0.5-1.0% expansion agent to the grouting slurry so that the volume expansion rate of the slurry after solidification is ≥5%; c. The opening rate of HDPE perforated pipes in drainage blind ditch is increased to 8-10%, and the hole diameter is expanded to 10-12mm; 3) The temperature-strain-seepage coupling model is constructed based on finite element analysis, with input parameters including rock thermal conductivity, porosity, and seepage path curvature radius, and the output is the potential thermally induced slip risk level; 4) After the emergency measures are implemented, if the temperature returns to the baseline value ±1°C and the strain rate is less than 0.01% / h within 48 hours, the anchor step length, grouting pressure and drainage pipe opening rate are gradually restored to the initial set values.

[0012] Preferably, the open-cut tunnel slope protection construction method is: 1) After the construction is completed, a graded early warning mechanism for slope stability is established based on the long-term monitoring data of distributed optical fiber sensors: when the displacement rate is stable at 0.3-0.5mm / d for 7 consecutive days, it is judged as a first-level early warning, and a manual inspection is initiated once a week to check whether the anchor prestress loss exceeds 10%; when the daily displacement rate is greater than 0.6mm / d or the seepage rate is greater than 6mm / h, it is judged as a second-level early warning, and local grouting and anchor prestress compensation are immediately carried out; when the displacement rate is greater than 0.8mm / d and the seepage rate is greater than 8mm / h for 3 consecutive days, it is judged as a third-level early warning, and the anchor grid is fully encrypted to 1.5m×1.5m, and a temporary drainage well is added; 2) The following parameters need to be recorded during manual inspection: the fluctuation amplitude of contact stress on the anchor bolt head, the crack width of the grouting body, and the drainage capacity of the drainage blind ditch, and the subsequent construction parameters should be dynamically adjusted according to the inspection results; 3) The grouting material is quick-setting silicate cement slurry with an initial setting time of ≤1 hour, mixed with 4-6% nano-silicon dioxide, and the grouting holes are preferentially selected at the nodes with the largest strain increment area; 4) Conditions for lifting the warning: After maintenance, the displacement rate is less than 0.3mm / d and the seepage rate is less than 2mm / h for 7 consecutive days, and the anchor prestress loss is ≤5%.

[0013] Preferably, the open-cut tunnel slope protection construction method is: 1) Dynamically adjust anchor support parameters according to different geological conditions: Water-rich sand layer area (seepage rate of about 7.2mm / h): the anchor length is increased to 1.3-1.5 times the excavation depth, the initial prestress is increased to 55-65kN, and the grouting pressure is set to 1.2-1.5MPa; Weak interlayer area: the anchor grid spacing is increased to 1.5m×1.5m, the grouting hole depth is increased to 0.6-0.7 times the slope design height, and 6-8% nano-silicon dioxide is added to improve the grout impermeability; In the area with developed rock fractures: the bolt installation angle is adjusted to be orthogonal to the fracture trend (error ≤ ±5°), and the spacing between slurry penetration holes is reduced to 30-50mm; 2) During the rainy season or when the groundwater level rises, perform the following preventive maintenance measures: Increase the porosity of HDPE perforated pipes in drainage blind ditch to 8-10%, expand the hole diameter to 10-12mm, and perform reverse flushing once a week (water pressure 0.6-0.8MPa, lasting 20-30 minutes); The monitoring frequency of anchor prestressing is increased from once a day to three times a day. When a single monitoring finds that the prestressing loss is ≥5%, an immediate compensation step of 5-8kN is applied. Add a temporary diversion ditch (depth 200-300mm, slope ≥5%) in the intercepting ditch on the top of the slope to prevent surface runoff from seeping into the slope; 3) The matching relationship between the nano-silicon dioxide dosage and the grouting pressure is: When the grouting pressure is 0.8-1.0MPa, 4-5% nano-silica is added; when the grouting pressure is 1.2-1.5MPa, 6-8% nano-silica is added.

[0014] The present invention has at least the following beneficial effects: 1. The distributed optical fiber sensors of the present invention are deployed all over the area and combined with sliding average filtering, which makes the monitoring data completeness rate exceed 98%, shortens the warning response time to within 5 minutes, and controls the missed detection rate within 3%. Compared with traditional point sensors, the accuracy of landslide warning is improved by 40%.

[0015] 2. The hydraulic servo anchor of the present invention is based on the step-by-step adjustment of the strain rate (5-15kN) and the coordinated control of the dual hydraulic cylinders (pressure ratio 1:0.3-0.5), which enables the support stiffness to match the formation deformation in real time, reduces the anchor fracture rate from 12% to below 5%, and reduces the interface slip to within 0.5mm.

[0016] 3. The nano-silicon dioxide of the present invention is added in stages to make the slurry compressive strength reach 20.8Mpa (ASTMC109) after 28 days; the three-graded gravel filter layer and the dynamic opening rate adjustment (3-10%) stabilize the drainage efficiency at more than 5L / (m·s), and reduce the risk of seepage erosion by 60%.

[0017] 4. The Bayesian network of the present invention integrates multiple parameters (strain, seepage, temperature) to achieve linkage control, and the false trigger rate is reduced from 15% to 5%. The graded early warning mechanism (displacement 0.3-0.8mm / d) significantly enhances the adaptability of the project to weak interlayers, water-rich layers and seasonal changes.

[0018] 5. The dynamic parameter adjustment of the present invention reduces ineffective grouting by 30%, saving 1.2 tons of cement per 100 linear meters; the intelligent termination conditions (displacement + seepage + contact stress) reduce the need for hidden maintenance, reduce the full-cycle cost by 25%, and improve construction efficiency by 20%.

[0019] Other advantages, objectives and features of the present invention will be embodied in part through the following description, and in part will be understood by those skilled in the art through study and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The present invention is a process framework diagram of the open-cut tunnel slope protection construction method. DETAILED DESCRIPTION

[0021] The present invention is further described in detail below in conjunction with embodiments so that those skilled in the art can implement the invention with reference to the description.

[0022] like Figure 1 As shown, a construction method for slope protection of an open-cut tunnel of the present invention comprises the following steps: 1) Before excavation of the slope, distributed optical fiber sensors are pre-buried along the slopes on both sides of the tunnel axis. The deployment depth of the distributed optical fiber sensors is 0.6-0.7 times the design height of the slope. The horizontal spacing between adjacent sensors is 2.5-3.5m, and the vertical spacing is 1.8-2.2m. The sensors are connected to the ground data acquisition terminal; 2) When the distributed optical fiber sensor monitors that the slope strain increment reaches 0.04-0.06% and the seepage rate reaches 4-6mm / h, the hydraulic servo anchor support system is started. The installation angle of the hydraulic servo anchor is 15°-25°, the anchor length is 1.1-1.4 times the excavation depth, the anchor spacing is 1.8-2.2m×1.8-2.2m grid arrangement, the initial prestress is set to 45-55kN, and the step length is dynamically adjusted according to the real-time monitored strain rate of 0.01-0.03% / h, and the step length is 5-15kN; 3) After each level of slope is excavated to the designed elevation, a high-pressure grouting machine is used to seal the slope surface with grouting. The grouting pressure is dynamically adjusted according to the seepage rate: when the seepage rate is 4-6mm / h, the pressure is 0.8-1.0MPa, and when the seepage rate is greater than 6mm / h, it is increased to 1.2-1.4MPa. The spacing of the grouting holes is 1.3-1.7m, and the row spacing is 0.866 times the hole spacing. The drilling direction is at an angle of 5°-10° with the slope normal. The grouting material is silicate cement slurry mixed with 2-8% nano-silicon dioxide; 4) A longitudinal drainage blind ditch is laid along the slope foot with a cross-sectional size of 280mm×280mm to 320mm×320mm. A three-graded gravel filter layer (lower layer 8-12mm, middle layer 12-18mm, upper layer 18-22mm) is laid at the bottom of the ditch. A HDPE perforated drainage pipe (diameter 140-160mm, open porosity 3-8%) is installed above the filter layer, and a double-layer geotextile is wrapped outside the pipe; (5) Distributed fiber optic sensors are used to continuously monitor slope deformation data. When the displacement rate is less than 0.5 mm / d and the seepage rate is less than 2 mm / h for three consecutive days, the hydraulic servo anchor prestressing adjustment is terminated in stages: in the first stage, the step size is reduced to 5 kN and maintained for 24 hours; in the second stage, the adjustment is completely stopped and monitoring is continued for 48 hours. Specifically, distributed fiber optic sensors can be pre-buried along the slopes on both sides of the tunnel axis, and the depth of the deployment can be selected as 0.6-0.7 times the design height of the slope. For example, when the slope height is 10 meters, the burial depth can be 6-7 meters. The horizontal spacing can be selected as 2.5-3.5 meters, and the vertical spacing can be selected as 1.8-2.2 meters. The sensor can be of MOI sm125 type and connected to a ground data acquisition terminal, such as Campbell CR6 type. The sensor can be installed at a position 0.5-1.0 meters from the edge of the slope, and the data acquisition terminal can be deployed in a temporary monitoring station at the top of the slope. The monitoring data includes strain increment and seepage rate. The strain increment threshold can be set to 0.04-0.06%, and the seepage rate threshold can be set to 4-6 mm / hour. The coverage of the inclinometer monitoring method is limited. This implementation scheme realizes continuous monitoring of the entire slope through distributed fiber optic sensors. The parameter setting method is based on the analysis of historical landslide data. For example, the strain increment before 10 landslides in a certain area exceeded 0.04%.

[0023] The installation angle of the hydraulic servo anchor can be selected as 15-25 degrees, and the anchor length can be selected as 1.1-1.4 times the excavation depth. For example, when the excavation depth is 8 meters, the anchor length can be 8.8-10.4 meters. The anchor spacing can be arranged in a grid of 1.8-2.2 meters × 1.8-2.2 meters, and the initial prestress can be set to 45-55 kN. The dynamic adjustment step size can be selected from 8-12 kN, for example, when the strain rate is 0.02% / hour, the step size is adjusted to 10 kN. The hydraulic system can use the Enerpac RC-106 pump station, and the anchor rod body can use HRB400 grade rebar. The anchor can be driven in perpendicular to the slope, the anchoring section is deep into the medium weathered rock layer, and the hydraulic control unit can be installed on the side of the construction platform. Compared with static anchor support, this implementation scheme adjusts the prestress through real-time data. In the functional test, the adjustment delay needs to be controlled within 3 minutes, for example, by simulating the input strain data to verify the response time.

[0024] The grouting pressure can be selected from 0.7-1.3 MPa, and the specific value is adjusted according to the seepage rate: when the seepage rate is 4-6 mm / h, the pressure can be selected from 0.8-1.0 MPa; when the seepage rate exceeds 6 mm / h, the pressure can be selected from 1.2-1.4 MPa. The hole spacing of the grouting holes can be selected from 1.3-1.7 meters. The grouting material can be a silicate cement slurry with a water-cement ratio of 0.4-0.5, such as Conch PO 42.5 cement, and mixed with 2-8% nano-silicon dioxide, such as Evonik AEROSIL 200.

[0025] The cross-sectional dimensions of the drainage blind ditch can be selected from 280 mm × 280 mm to 320 mm × 320 mm. A gravel filter layer with a thickness of 90-110 mm can be laid at the bottom of the ditch, and the gravel particle size can be selected from 8-22 mm. A HDPE perforated drainage pipe with a diameter of 140-160 mm can be installed above the filter layer, such as Liansu PE100 grade pipe. The outside of the pipe can be wrapped with a double-layer geotextile, and the specification can be selected as 200 g / m2. The drainage pipe can be laid along the toe line, and the slope can be set to 0.5%. Compared with the traditional grouting process, this implementation scheme dynamically adjusts the grouting pressure through the seepage rate. After grouting, the slurry diffusion radius reaches more than 1.5 meters, and the filling rate of cracks exceeds 85%.

[0026] To terminate the adjustment, the displacement rate must be less than 0.5 mm / day for three consecutive days, and the seepage rate must be less than 2 mm / hour. For example, the continuous monitoring data of a slope is 0.4 mm / day, 0.3 mm / day, and 0.4 mm / day, and the seepage rate is 1.8 mm / hour, 1.5 mm / hour, and 1.7 mm / hour, which is determined to be a stable state. The phased termination operation includes reducing the anchor step length to 5 kN and maintaining it for 24 hours in the first stage, and completely stopping the adjustment and continuously monitoring for 48 hours in the second stage. The fluctuation amplitude of contact stress can be calculated by the sliding standard deviation. For example, a standard deviation exceeding 0.8 kN within 6 hours is considered abnormal.

[0027] Compared with a single displacement rate threshold, this implementation scheme combines the seepage rate and contact stress data. In the experimental verification, the displacement rate of a certain project was stabilized below 0.3 mm / day within 48 hours after the termination and adjustment.

[0028] Preferably, when the distributed optical fiber sensor breaks or the data acquisition terminal fails, the backup monitoring module is activated: wireless inclination sensors (accuracy ±0.1°) and piezometers (range 0-100kPa) are arranged at intervals of 20m along the slope, and the data is transmitted to the emergency control terminal via LoRa, triggering the preset static anchor support plan (prestress is 80% of the design value).

[0029] Taking the slope project of K12+480 section of a tunnel as an example, the slope design height is 12m, the stratum is silty clay intercalated with sand, and the excavation depth is 9m. The specific steps are as follows: (1) Deployment of distributed optical fiber sensors A pipe drilling rig was used to drill holes (aperture 100mm), and PVC wall casings (wall thickness 2mm) were inserted. Distributed fiber optic sensors (MOI sm125) were embedded along the slopes on both sides of the tunnel axis. The sensors were laid out at a depth of 7.8m (0.65 times the slope height), with a horizontal spacing of 3.0m and a vertical spacing of 2.0m. After the sensors were installed, they were calibrated on-site using a standard strain beam (accuracy ±0.005%), and a constant temperature water bath (temperature fluctuation ±0.5℃) was used to compensate for temperature drift.

[0030] (2) Hydraulic servo anchor dynamic support The anchor installation angle is 20°, the length is 10.8m (1.2 times the excavation depth), the grid spacing is 2.0m×2.0m, and the initial prestress is 50kN; when the strain increment is monitored to be 0.05% and the seepage rate is 5.2mm / h, the anchor step length is triggered to adjust to 10kN; the hydraulic system (Enerpac RC-106) is equipped with a backup accumulator, which can maintain prestress for ≥30 minutes in the event of a power outage.

[0031] (3) High-pressure grouting and drainage blind ditch construction The grouting pressure is 1.0MPa, the hole spacing of the grouting holes is 1.5m, and the slurry mixed with 3% nano-silica (Evonik AEROSIL200) (water-cement ratio is 0.45, curing conditions are 20℃±2℃, humidity ≥95%) is tested according to ASTM C109 standard. The 28-day compressive strength is 20.8MPa (the control group without nano-materials is 16.5MPa). When the grouting pressure is 1.0MPa and the seepage rate is 4-6mm / h, the diffusion radius of the slurry mixed with 3% nano-silica is 1.5-3.5m (measured by dyeing tracer method), and the diffusion radius of the control group without nano-materials is 0.9-1.2m; the cross-section of the drainage blind ditch is 300mm×300mm, the thickness of the gravel filter layer is 100mm, the diameter of the HDPE drainage pipe (Liansu PE100) is 150mm, the open porosity is 6%, and the water flow capacity is 3L / (m·s).

[0032] (4) Termination of support adjustment The displacement rates were 0.4mm / d, 0.3mm / d, and 0.4mm / d for three consecutive days, and the seepage rate dropped to 1.8mm / h. In the first stage, the anchor step length was reduced to 5kN and maintained for 24 hours. In the second stage, the adjustment was completely stopped, and the displacement rate was stable at <0.5mm / d within 48 hours.

[0033] This implementation method realizes full slope monitoring through distributed fiber optic sensors, shortens the warning response time to within 5 minutes, and reduces the missed detection rate to below 3%. The dynamic adjustment of hydraulic servo anchors makes the support stiffness match the formation deformation, and the anchor fracture rate is reduced from 12% of the traditional method to less than 5%. The linkage control of grouting pressure and seepage rate reduces the reinforcement blind area by 80%, and the drainage blind ditch water diversion capacity is stabilized at more than 5 liters / (m·second). The multi-parameter termination condition reduces the misjudgment rate from the traditional single indicator of 20% to less than 8%. It effectively solves the technical problems of insufficient monitoring coverage of traditional slope protection methods resulting in delayed slip warning; static anchor support cannot dynamically match formation deformation; poor coordination between grouting and drainage systems leads to reinforcement blind areas and low drainage efficiency.

[0034] Further, in another embodiment, the open-cut tunnel slope protection construction method of the present invention: (1) In the weak interlayer area, the deployment depth of distributed optical fiber sensors is increased to 0.8-0.9 times the design height of the slope, the horizontal spacing is reduced to 2.0-3.0 m, and the vertical spacing is reduced to 1.5-2.0 m; (2) When pre-burying the distributed optical fiber sensor, a stainless steel fixing clip (SUS304, size 50 mm × 20 mm × 2 mm) is set every 0.5 m along the axial direction of the sensor, and a 10-15 mm thick epoxy resin bonding layer (Huntsman Araldite AW 106 type) is filled between the clip and the slope rock and soil; (3) The ground data acquisition terminal performs sliding average filtering on the monitoring data of the distributed optical fiber sensor, with a filtering window time of 10-15 minutes, and removes abnormal values ​​outside the range of ±3σ; (4) When three adjacent distributed optical fiber sensors on the same monitoring section simultaneously detect a strain increment ≥ 0.04% and a seepage rate ≥ 4 mm / h, the start-up conditions of the hydraulic servo anchor support system are triggered. Specifically, in the weak interlayer area, the deployment depth of the distributed optical fiber sensor can be selected as 0.8-0.9 times the design height of the slope. For example, when the slope height is 12 meters, the burial depth can be 9.6-10.8 meters. The horizontal spacing can be selected as 2.0-3.0 meters, and the vertical spacing can be selected as 1.5-2.0 meters. The sensor can be of MOI sm125 type, and the data acquisition terminal can be of Campbell CR6 type. The sensor can be buried along the potential slip surface, avoiding the rock fracture zone, and the data acquisition terminal can be installed in the monitoring station at the top of the slope. The deployment path can be determined by the geological exploration report. For example, when the thickness of a weak interlayer is 1.2 meters, the buried depth of the sensor is increased to 10 meters. Compared with the deployment of the inclinometer tube, this implementation scheme improves the monitoring accuracy by encrypting the deployment and adjusting the depth. The parameter setting method is based on the thickness of the weak interlayer. For example, when the thickness of the interlayer exceeds 1 meter, the deployment depth is increased to 0.85 times the height of the slope.

[0035] When pre-embedded sensors, stainless steel fixing clips can be set every 0.5 meters along the axial direction. The clip size can be selected as 50 mm × 20 mm × 2 mm, and the material can be selected as SUS304 stainless steel. An epoxy resin bonding layer can be filled between the clip and the rock and soil, and the thickness can be selected as 10-15 mm, such as Huntsman Araldite AW 106 epoxy resin. During installation, the clip can be fixed to the inner wall of the borehole by expansion bolts, and the epoxy resin is left to cure for 24 hours after filling. The ground data acquisition terminal can perform sliding average filtering on the sensor data, and the filtering window time can be selected as 10-15 minutes, such as 12 minutes. The ±3σ criterion can be used to eliminate outliers. For example, the original strain data for a certain period of time is: 105, 108, 250, 99, 104, 260, 98, 106, 255, 103. After filtering, the outliers of 250με, 260με, and 255με are eliminated, and the output mean is 109με. Compared with the sensor fixing method, this solution enhances coupling through buckles and epoxy resin. In the functional test, the sensor drift error can be controlled within ±0.005%.

[0036] The condition for triggering the start of the hydraulic servo anchor is that three adjacent sensors on the same section simultaneously detect a strain increment exceeding 0.04% and a seepage rate reaching 4 mm / h. For example, on a certain section, the horizontal spacing between sensors S07, S08, and S09 is 2.5 meters. When the strain increments detected are 0.05%, 0.06%, and 0.04%, respectively, and the seepage rates are 4.5 mm / h, 4.8 mm / h, and 5.2 mm / h, respectively, the triggering condition is met. Data verification requires at least three consecutive sampling cycles to exceed the standard, for example, sampling once per minute, and the data exceeds the threshold for three consecutive minutes. Compared with a single sensor trigger, this implementation reduces the false trigger rate through multi-sensor joint judgment. In an experiment, the false trigger rate of the traditional method was about 15%, and the false trigger rate of this solution was reduced to less than 1.5%.

[0037] Taking the K15+200 section slope project of a tunnel as an example, there is a weak interlayer (thickness 1.2m) in this area. The specific implementation steps are as follows: (1) Sensor layout in weak interlayer area A pipe drill (model Atlas Copco Diamec 262) was used to drill a hole with a diameter of 110 mm. A PVC wall casing (wall thickness 2.5 mm, externally coated with lubricant) was inserted, and a distributed optical fiber sensor (model MOI sm125) was embedded. The deployment depth was 0.85 times the slope height (the deployment depth was 12.75 m when the slope height was 15 m), with a horizontal spacing of 2.5 m and a vertical spacing of 1.8 m. Stainless steel clips were installed every 0.5 m along the axial direction of the sensor, and the clips were fixed to the hole wall by expansion bolts (M10×80 mm), and then epoxy resin (thickness 12 mm) was injected and left to cure for 24 hours.

[0038] (2) Data filtering and trigger condition verification The ground data acquisition terminal (Campbell CR6) performs sliding average filtering on the raw data (window time 12 minutes). For example, the strain data for a certain period is: 105, 108, 250, 99, 104, 260, 98, 106, 255, 103. After filtering, the abnormal values ​​of 250με, 260με, and 255με are eliminated, and the output mean is 109με; when sensors S07, S08, and S09 (horizontal spacing 2.5m) simultaneously detect strain increments of 0.05%, 0.06%, and 0.04%, and the seepage rates are 4.5mm / h, 4.8mm / h, and 5.2mm / h respectively, the anchor bolt is triggered to start.

[0039] (3) Emergency measures and reliability verification The hydraulic servo anchor system is equipped with a backup solar power supply module (output power 200W) to ensure that the data acquisition and hydraulic control unit continue to operate for ≥8 hours after power failure; monitoring 30 days after construction showed that the sensor data integrity rate was ≥97% and the false trigger rate was <1%.

[0040] In this implementation plan, the sensor deployment depth in the weak interlayer area is increased to 0.8-0.9 times the slope height, and the monitoring data integrity rate is increased from 85% to 98%. Stainless steel clips and epoxy resin fixation reduce the sensor drift error to ±0.005%, and improve data stability. The combined triggering conditions of multiple sensors reduce the false trigger rate from 15% to below 1.5%, and the support startup accuracy is improved. Therefore, it can effectively solve the problem of data distortion caused by insufficient deployment depth and spacing of sensors in the weak interlayer area; the problem of false triggering caused by the threshold of a single sensor is easily disturbed.

[0041] Further, in another embodiment, the open-cut tunnel slope protection construction method of the present invention: (1) During the prestress adjustment process of the hydraulic servo anchor, when the distributed optical fiber sensor detects that the slope strain rate exceeds 0.03% / h, the adjustment step length is increased to 12-15 kN (each adjustment is ≤5 kN, and the interval is ≥10 minutes); when the strain rate is lower than 0.01% / h, the adjustment step length is reduced to 5-8 kN; (2) The anchoring section of the hydraulic servo anchor is provided with a dual hydraulic cylinder coordinated control system, wherein the main hydraulic cylinder applies axial tension, and the auxiliary hydraulic cylinder applies lateral pressure at an angle of 30°-45° to the rock formation trend, and the pressure ratio of the main and auxiliary hydraulic cylinders is dynamically controlled by the rock formation strain gradient calculated in real time, and the range is 1:0.3-0.5; (3) A continuous thread structure (pitch 15-20 mm, depth 2-3 mm) is processed on the surface of the anchor rod body. The thread area covers the entire length of the grouting section, and grout penetration holes with a diameter of 3-5 mm are opened at the root of the thread, with a hole spacing of 50-80 mm. (4) When the bolt head pressure sensor detects that the contact stress fluctuation amplitude exceeds 20% of the initial value, the bolt spacing encryption mechanism is automatically triggered to reduce the grid layout spacing to 1.5-1.8m×1.5-1.8m.

[0042] Specifically, the adjustment step of anchor prestress can be 12-15 kN or 5-8 kN, which is determined according to the slope strain rate monitored by the distributed optical fiber sensor. When the strain rate is 0.03% / hour, the step length can be 12-15 kN; when the strain rate is 0.01% / hour, the step length can be 5-8 kN. The hydraulic servo system can use Enerpac RC-106 pump station (rated pressure 70MPa, flow rate 2.3L / min, suitable for the prestress loading range of HRB400 grade anchor 0-200kN), and the anchor rod body can use HRB400 grade rebar. The installation angle of the anchor can be 15-25 degrees. For example, when the rock formation inclination is 40 degrees, the installation angle can be set to 20 degrees. The adjustment process needs to respond within 3 minutes. For example, when the strain rate in a certain area is 0.035% / hour, the step length is increased to 14 kN, and the anchor prestress increases from 50 kN to 64 kN. Compared with the static loading of anchor bolts, this solution dynamically adjusts the step length through the strain rate. In the functional test, the adjustment delay needs to be verified by simulating the input strain data. When the input rate is 0.03% / hour, the system should complete the step length switching within 3 minutes.

[0043] The main hydraulic cylinder can apply axial tension, and the auxiliary hydraulic cylinder can apply lateral pressure at an angle of 30-45 degrees to the rock formation. The pressure ratio of the main and auxiliary hydraulic cylinders can be selected as 1:0.3-0.5. For example, when the pressure of the main cylinder is 20 MPa, the pressure of the auxiliary cylinder can be set to 6-10 MPa. The main hydraulic cylinder can be selected from Bosch Rexroth HED type, and the auxiliary hydraulic cylinder can be selected from Parker CDR series. The main cylinder is aligned with the axis of the anchor rod, and the auxiliary cylinder is installed at an angle through a universal joint. The direction is measured in real time by the total station. For example, when the rock formation trend is detected to be 35 degrees north-east, the direction of the auxiliary cylinder is adjusted to 30-40 degrees north-east.

[0044] For example, in a tunnel with granite fissure development, the slope height is 15m, the rock layer inclination is 40°, the fissures are developed (average spacing 0.5-1.2m), and there are seepage channels. It is necessary to dynamically control the anchor support stiffness to prevent shear slip in the fissure area. The hydraulic cylinder is deployed so that the main hydraulic cylinder is aligned with the anchor axis, the initial tension is 50kN, the auxiliary hydraulic cylinder is installed at an angle of 55° north-west, and the initial lateral pressure is 15kN (pressure ratio 1:0.3). Adjustment stage 1 (2 hours after excavation): real-time strain gradient ∇ε=0.018% / m → pressure ratio maintained at 1:0.3, auxiliary cylinder pressure 15kN; stage 2 (6 hours after excavation): real-time strain gradient ∇ε=0.032% / m → pressure ratio adjusted to 1:0.4, auxiliary cylinder pressure increased to 20kN; stage 3 (12 hours after excavation): real-time strain gradient ∇ε=0.048% / m → pressure ratio adjusted to 1:0.5, auxiliary cylinder pressure increased to 25kN. The displacement of the anchor head was measured by the total station, with a maximum slip of 0.4mm (the control group of the traditional static anchor was 1.2mm); when the grouting pressure was 1.2MPa, the slurry diffusion radius along the permeable hole reached 2.1m (measured by dye tracer method); the core drilling test showed that the crack filling rate was >85%, and the shear strength of the rock mass increased from 0.8MPa to 1.6MPa (ASTM D3080). Compared with the single hydraulic cylinder anchor system, this solution enhances the shear resistance through dual cylinder collaboration. The dual cylinder control reduces the slippage of the anchor interface from 1.2 mm to below 0.5 mm.

[0045] The bolt body can be processed with continuous threads (pitch 18±2mm, depth 2.5±0.5mm) by cold rolling or hot rolling forming process, and slurry penetration holes (diameter 4±1mm, hole spacing 60±10mm) can be opened at the root of the thread by laser cutting. The processing accuracy meets the GB / T 1499.2-2018 standard. The laser cutting equipment can be TRUMPF TruLaser 5030 (accuracy ±0.05mm). The pitch can be 15-20mm and the depth can be 2-3mm. The thread area covers the entire length of the grouting section. For example, when the length of the grouting section is 8 meters, the thread processing range is 0-8 meters. Slurry penetration holes can be opened at the root of the thread, the diameter can be 3-5mm, and the hole spacing can be 50-80mm. The penetration holes can be processed by laser CNC, the hole position error must be controlled within ±0.1mm, and the roughness of the inner wall of the hole can be selected as Ra≤1.6 microns. For example, the diameter of the penetration hole of a certain anchor is 4 mm, the hole spacing is 60 mm, and the slurry diffusion radius after grouting is 1.8 meters. Compared with ordinary threaded anchors, this solution optimizes slurry diffusion through penetration holes. The slurry filling rate was tested by drilling and coring, and the results showed that the filling rate increased from 70% to more than 85%.

[0046] A pressure sensor, such as Kistler 9067, can be installed on the head of the anchor to detect contact stress fluctuations. The fluctuation amplitude threshold can be set to 20% of the initial value. For example, when the initial contact stress is 50 kN, a fluctuation of more than 10 kN triggers densification. After densification, the anchor grid spacing can be reduced to 1.5-1.8 meters by 1.5-1.8 meters, for example, from 2.0 meters by 2.0 meters to 1.7 meters by 1.7 meters. The densification operation must be completed within 30 minutes. In one experiment, when the contact stress fluctuation in a certain area reached 32%, the fluctuation dropped to 8% after the new anchor was driven in. Compared with manual regular inspections, this solution automatically triggers densification through real-time data. The experimental object is a weak interlayer area. After densification, the displacement rate dropped from 0.6 mm / day to 0.3 mm / day.

[0047] Taking the slope project of K18+750 section of a tunnel as an example, the rock layer inclination is 40°. The specific implementation steps are as follows: (1) Dynamic adjustment of hydraulic servo anchor The bolt body is made of HRB400 threaded steel (28mm diameter), with continuous thread rolling on the surface (pitch 18mm, depth 2.5mm), and slurry penetration holes (4mm diameter, 60mm hole spacing) are laser-cut at the root of the thread. When the distributed optical fiber sensor detected a strain rate of 0.035% / h in a certain area, the trigger step was adjusted to 14kN, the hydraulic system (Enerpac RC-106) output pressure was 22MPa, and the anchor prestress was increased from 50kN to 64kN; The lateral pressure direction of the auxiliary hydraulic cylinder (Parker CDR series) matches the rock formation trend (35° north-east), and the pressure ratio is 1:0.4 (20MPa for the main cylinder and 8MPa for the auxiliary cylinder).

[0048] (2) Contact stress fluctuation and encryption mechanism A pressure sensor (Kistler 9067) was installed on the anchor head. The initial contact stress was 52 kN. During construction, a fluctuation range of 45-62 kN (fluctuation range of 32.7%) was detected, triggering an encryption command. The anchor grid spacing was reduced from 2.0m×2.0m to 1.7m×1.7m, and the contact stress fluctuation range was reduced to ±8% after the new anchors were driven in.

[0049] (3) Slurry penetration and grouting effect verification The grouting material is PO 42.5 cement slurry (water-cement ratio 0.45) mixed with 3% nano-silicon dioxide. When the grouting pressure is 1.0MPa, the diffusion radius of the slurry through the permeable holes reaches about 1.8m (measured by the dye tracer method); the core drilling test shows that the slurry filling rate of the cracks is ≥85%, and the shear strength of the rock mass is increased from 0.8MPa to 1.5MPa (ASTM D3080 standard).

[0050] This implementation plan is based on the step-by-step adjustment of the strain rate, the synergistic enhancement of shear resistance by dual hydraulic cylinders, and the optimization of slurry diffusion by thread and permeable hole design. It effectively solves the technical problems of stress lag caused by mismatch between anchor prestress adjustment and deformation rate; loss of anchoring force caused by slippage at the anchor-rock soil interface; and insufficient slurry diffusion range.

[0051] Further, in another embodiment, the open-cut tunnel slope protection construction method of the present invention: 1) The ground data acquisition terminal inputs the strain increment and seepage rate data monitored by the distributed optical fiber sensor and the contact stress data of the anchor head pressure sensor into the pre-trained Bayesian network model to calculate the probability of slope instability in real time; 2) When the instability probability of the Bayesian network output is ≥85%, the following operations are triggered synchronously: a. The adjustment step length of the hydraulic servo anchor is increased to 12-15kN; b. The grouting pressure of the high-pressure grouting machine is increased to 1.2-1.4MPa; c. The opening rate of HDPE perforated drainage pipe is increased to 6-8%, and the hole diameter is adjusted to 8-10mm; 3) The Bayesian network model is trained based on historical slope engineering data. The input parameters include strain increment (0.04-0.06%), seepage rate (4-6mm / h), contact stress fluctuation standard deviation (0-1.0kN), and the output is the instability probability value. The model training accuracy is ≥90%; (4) When the probability of instability is less than 60% and the displacement rate is less than 0.5 mm / d for three consecutive days, the anchor step length is restored to 8-12 kN, the grouting pressure is reduced to 0.8-1.0 MPa, and the drainage pipe opening rate is adjusted back to 3-5%.

[0052] Specifically, the strain increment range monitored by the distributed optical fiber sensor can be selected as 0.04-0.06%, the seepage rate range can be selected as 4-6mm / h, and the contact stress fluctuation standard deviation range can be selected as 0.5-1.0kN. The data can be input into the pre-trained Bayesian network model, and the model instability probability threshold is set to 85%, and the recovery threshold is set to 60%. The distributed optical fiber sensor can be MOI sm125, the contact stress sensor can be Kistler 9067, and the ground data acquisition terminal can be Campbell CR6. The Bayesian network model training can be implemented based on Python's pgmpy library, and the operating platform can be an industrial computer (such as Advantech UNO-2184G). The grouting material can be PO 42.5 silicate cement, and the nano-silicon dioxide can be Evonik AEROSIL 200. The distributed optical fiber sensor is pre-buried along the slope on both sides of the tunnel axis, 0.5-1.0m away from the edge of the slope, and the burial depth is 0.6-0.7 times the height of the slope. The data acquisition terminal is installed in the temporary monitoring station on the top of the slope and connected to the sensor through a fiber optic cable. The instability probability threshold of 85% is determined by historical data analysis: the data of 20 landslide events one hour before are counted, of which 17 have an instability probability of ≥85% before the event.

[0053] Compared with the traditional monitoring system, this implementation scheme uses Bayesian network to fuse multi-parameter data instead of single threshold judgment. In some cases, the traditional method only relies on displacement rate > 0.6mm / d to trigger an alarm, while this implementation scheme needs to meet the strain, seepage and contact stress conditions at the same time.

[0054] The bolt adjustment step can be 12-15kN, the grouting pressure can be 1.2-1.4MPa, and the drainage pipe opening rate can be 6-8%. In the recovery stage, the bolt step is adjusted back to 8-12kN, the grouting pressure is reduced to 0.8-1.0MPa, and the opening rate is adjusted back to 3-5%. The hydraulic servo system can use the Enerpac RC-106 pump station (rated pressure 70MPa, flow rate 2.3L / min, suitable for the prestressed loading range of HRB400 grade anchor rods 0-200kN), the grouting machine can use the Sany Heavy Industry SYC-2000 type, and the drainage pipe can use the Liansu PE100 grade HDPE pipe. The hydraulic pump station is deployed on the side of the construction platform, the grouting machine is arranged 5-10m behind the slope, and the drainage pipe is laid along the slope foot line. The anchor step adjustment delay needs to be controlled within 3 minutes. For example, after the excessive data is entered, the pressure of the hydraulic pump station is increased from 20 MPa to 24 MPa. The grouting pressure adjustment is automatically completed through the pressure control system of the high-pressure grouting machine, and the opening rate of the drainage pipe is achieved by replacing the pipe section with prefabricated holes.

[0055] When the probability of instability is less than 60% and the displacement rate is less than 0.5 mm / day for three consecutive days, the anchor step length can be restored to 8-12 kN, the grouting pressure can be reduced to 0.8-1.0 MPa, and the drainage pipe opening rate can be adjusted back to 3-5%. The model training data can contain more than 50 sets of historical slope engineering records, and the training accuracy is required to be ≥90%, and the mean square error (MSE) is ≤0.005. The verification method can use cross-validation, for example, divide the data into training sets (40 sets) and test sets (10 sets), and calculate the predicted displacement rate error. If the error exceeds 0.1 mm / day, the model needs to be retrained. Compared with traditional manual re-inspection, this scheme automatically evaluates the model performance through quantitative indicators. The experimental results show that the prediction error of the Bayesian network model is ±0.08 mm / day, which is 47% lower than the linear regression model error (±0.15 mm / day).

[0056] Taking the slope project of K21+300 section of a tunnel as an example, the rock layer is interbedded with sandstone and shale, and there are seepage channels. The specific implementation steps are as follows: (1) Bayesian network model construction and training Data collection: 50 sets of historical slope engineering data were collected, including strain increment (0.02-0.08%), seepage rate (2-8mm / h), standard deviation of contact stress fluctuation (0.5-1.2kN) and corresponding slope status (stable / instability); Model training: The Bayesian network was constructed using Python's pgmpy library, and the node dependency was defined as "strain increment → seepage rate → contact stress fluctuation → instability probability". A directed acyclic graph was used to represent the node dependency. The K2 algorithm was used for structural learning, and the number of parent nodes was constrained to not exceed 3 based on prior knowledge. The rationality of the final network structure was verified by the chi-square test (p value > 0.05).

[0057] The prior probability of the root node (strain increment, seepage rate) is determined based on historical data statistics; the intermediate node conditional probability table (CPT) is optimized by maximum likelihood estimation (MLE) combined with Laplace smoothing (α=0.1). The training goal is to minimize the cross entropy loss. The Adam optimizer (learning rate 0.001) is used for 500 rounds of training, and an early stopping mechanism is set (stop when the validation set loss does not decrease for 20 consecutive rounds). Five-fold cross validation is used, and the evaluation indicators include accuracy (92%), mean square error (0.0048) and ROC-AUC (0.95). Sensitivity analysis shows that the seepage rate has the greatest impact on the instability probability (weight 0.45), followed by strain increment (0.30) and contact stress fluctuation (0.25). The limit test shows that when the seepage rate is >8mm / h, the accuracy of the model predicting the instability probability ≥85% is 98%.

[0058] Model deployment: The trained model is integrated into the ground data acquisition terminal (industrial PC, model Advantech UNO-2484G), with a real-time calculation frequency of 1 time / minute.

[0059] (2) Real-time linkage control When the strain increment in a certain area is monitored to be 0.05%, the seepage rate is 5.8 mm / h, and the standard deviation of contact stress fluctuation is 0.9 kN, the probability of instability calculated by the Bayesian network is 88%; Trigger linkage command: a. The hydraulic servo anchor step length was increased from 10kN to 14kN (the pressure of the Enerpac RC-106 pump station was increased to 24MPa); b. The grouting pressure was adjusted from 1.0MPa to 1.25MPa (Sany SYC-2000 grouting machine); c. The opening rate of HDPE drainage pipe (Liansu PE100) increased from 5% to 7%, and the hole diameter expanded to 9mm; Monitoring data for 24 hours after adjustment: the strain rate dropped to 0.02% / h, the seepage rate dropped to 3.5mm / h, and the probability of instability dropped to 58%.

[0060] Parameter recovery mechanism When the displacement rate is 0.4mm / d, 0.3mm / d, and 0.4mm / d for three consecutive days, and the probability of instability is stable at 55%, the recovery operation is performed: The anchor step length is adjusted back to 10kN; Grouting pressure dropped to 0.9MPa; The drainage pipe opening rate was adjusted to 4%, and the hole diameter was reduced to 7mm; Within 48 hours after restoration, the slope deformation rate remained stable and the standard deviation of contact stress fluctuation was ≤0.6 kN.

[0061] This implementation method uses a Bayesian network model to fuse multi-parameter data, reducing the false trigger rate from 15% of the traditional method to less than 5%. The linkage control shortens the support response time to 3 minutes and reduces the reinforcement blind area by 60%. The parameter recovery mechanism avoids excessive support and saves about 1 ton / 100 linear meters of grouting materials. The model verification improves the prediction accuracy by 47% and the long-term stability through cross-error control. It can solve the technical problems of low synergy efficiency caused by independent regulation of multiple parameters in traditional methods and the lag in parameter adaptation under the action of seepage-stress coupling.

[0062] Further, in another embodiment, the open-cut tunnel slope protection construction method of the present invention: (1) During the preparation of the silicate cement slurry, nano-silicon dioxide is added in two stages: a. In the first stage, 1-2% by mass of nano-silicon dioxide and water reducer (polycarboxylic acid series, dosage 0.1-0.3%) are added to the mixing water and ultrasonically dispersed for 3-5 minutes (power 200-400W); b. In the second stage, add the remaining 1-2% nano-silicon dioxide, mix it with silicate cement (PO 42.5) and continue stirring for 2-3 minutes. The total stirring time is ≥5 minutes; (2) A medium-coarse sand transition layer (thickness 50-80mm, particle size 0.5-1mm) is added to the bottom of the gravel filter layer of the drainage blind ditch, and a geotextile (specification ≥200g / m²) is laid between the sand layer and the gravel layer; (3) Within 24 hours after the grouting is completed, the drainage blind ditch shall be reversely flushed with a flushing water pressure of ≤0.4MPa and a flushing duration of 10-20 minutes until the water flow capacity of the drainage pipe is ≥5L / (m·s); (4) When the adjustment step of the hydraulic servo anchor is ≥12 kN, 0.2-0.5% of early strength agent (triethanolamine) is injected into the slurry delivery pipe in real time through a metering pump (such as Prominent Gamma / X) to shorten the initial setting time of the slurry to 45-60 minutes.

[0063] Specifically, the preparation of silicate cement slurry can be divided into two stages by adding nano-silica. In the first stage, 1-2% by mass of nano-silica, such as Evonik AEROSIL 200, can be added to the mixing water together with the water reducer. The water reducer can be selected from polycarboxylic acid series, and the dosage can be selected from 0.1-0.3%, such as BASF MasterGlenium SKY 8233. After mixing, it can be treated by an ultrasonic disperser for 3-5 minutes, and the power can be selected from 200-400W, such as 300W. In the second stage, the remaining 1-2% of nano-silica can be added, mixed with PO 42.5 silicate cement, and then continued to stir for 2-3 minutes, and the total stirring time is not less than 5 minutes. The mixing equipment can be a twin-shaft mixer, such as SICOMA MAO 4500, and the speed can be selected from 60 rpm. Compared with the single-incorporation method, this solution improves dispersion uniformity through phased incorporation. The compressive strength of the slurry incorporating 3% nano-silicon dioxide reaches 18.5MPa, which is 50% higher than that of the unincorporated group.

[0064] The gravel filter layer of the drainage blind ditch can be filled in layers with three grades. The lower layer can be paved with gravel with a particle size of 8-12 mm, the middle layer can be paved with gravel with a particle size of 12-18 mm, and the upper layer can be paved with gravel with a particle size of 18-22 mm. The thickness of each layer can be selected to be 30-40 mm. A medium-coarse sand transition layer can be added to the bottom of the filter layer, with a thickness of 50-80 mm and a sand particle size of 0.5-1 mm, such as quartz sand (SiO2 content ≥ 95%). Geotextile can be laid between the sand layer and the gravel layer, with a specification of 200 g / m2 and a permeability coefficient of ≥ 0.1 cm / s. HDPE perforated pipes can be used for drainage pipes, such as Liansu PE100 grade, with a diameter of 140-160 mm and an open porosity of 3-8%. Compared with the single-graded filter layer, this solution reduces the risk of clogging through three-graded and sand transition layers, and the mixed graded filter layer stabilizes the drainage water flow capacity at more than 5 liters / (m·s).

[0065] The drainage blind ditch can be reverse flushed within 24 hours after the grouting is completed. The flushing water pressure can be selected to be below 0.4 MPa, and the duration can be selected to be about 10 minutes, for example, using a Grundfos CR 45 multi-stage centrifugal pump. After flushing, the water flow capacity of the drainage pipe needs to be tested, and the threshold can be set to 5 liters / (m·s), for example, using a Keyence FD-Q series flow meter for real-time monitoring. If the water flow capacity does not meet the standard, it is necessary to repeat the flushing until it is qualified. This solution ensures long-term performance through high-pressure flushing and quantitative thresholds, and the probability of filter layer clogging is reduced by 70% after flushing.

[0066] When the adjustment step length of the hydraulic servo anchor is ≥12 kN, 0.2-0.5% of the early strength agent can be added to the slurry. The early strength agent can be triethanolamine, such as Sika TEA-25. After addition, the initial setting time of the slurry can be shortened to 45-60 minutes. For example, when 0.3% of the early strength agent is added, the initial setting time is 52 minutes. The addition process can be controlled by a metering pump, such as the Prominent Gamma / X type, with an error of no more than ±0.2%. For example, when the step length of a certain anchor is increased to 14 kN, 0.3% of the early strength agent is added simultaneously, and the diffusion radius of the slurry under dynamic water conditions reaches 1.5 meters or more. Compared with the fixed early strength agent dosage, this scheme realizes dynamic control through step length linkage. After the early strength agent is added, the compressive strength of the slurry is increased by 30%.

[0067] Taking the K24+150 section slope project of a tunnel as an example, the groundwater level is high and the dynamic water pressure is significant. The specific implementation steps are as follows: (1) Preparation of nano-silica slurry Stage 1: Add 1.5% nano-silica (Evonik AEROSIL 200) and 0.2% polycarboxylate superplasticizer (BASF MasterGlenium SKY 8233) to the mixing water and treat it with an ultrasonic disperser (power 300 W, frequency 40 kHz) for 4 minutes; The second stage: PO 42.5 silicate cement was mixed with the remaining 1.5% nano-silicon dioxide using a twin-shaft mixer (model SICOMA MAO 4500) at 60 r / min for 3 minutes, and the slurry fluidity reached 260 mm (slump test ASTM C143); Performance verification: The slurry added with 3% nano-silica has an initial setting time of 2.5 hours (ASTM C191 standard) and a compressive strength of 20.8MPa after 28 days (the control group without addition is 16.5MPa).

[0068] (2) Optimization of drainage blind ditch construction A medium-coarse sand transition layer (60mm thick, 0.5-1mm particle size, quartz sand SiO2 content ≥95%) is laid at the bottom of the blind ditch, and a geotextile (specification 250g / m², permeability coefficient ≥0.1cm / s) is covered on the sand layer; A Grundfos CR 45 multistage centrifugal pump was used for back flushing, with a water pressure of 0.55 MPa for 18 minutes. The water flow capacity of the drain pipe was increased from 3.8 L / (m·s) to 5.3 L / (m·s).

[0069] (3) Synergistic control of early strength agents When the bolt adjustment step length was increased to 14 kN (corresponding to a grouting pressure of 1.25 MPa), 0.3% triethanolamine early strength agent (Sika TEA-25) was added to the slurry, and the initial setting time of the slurry was shortened to 52 minutes. Drilling and coring showed that after the early strength agent was added, the slurry had a diffusion radius of 1.5m or more under dynamic water conditions (seepage rate 6.5mm / h), and no segregation occurred.

[0070] The phased incorporation of nano-silica in this scheme increases the compressive strength of the slurry by 50% and reduces the permeability coefficient to 5×10⁻ 8 cm / s. The three-graded filter layer and sand transition layer design increased the drainage blind ditch's water flow capacity from 70% to 95%. The reverse flushing operation effectively removed the sediment, and the water flow capacity was maintained above 5 liters / (m·s). The dynamic addition of early strength agent shortened the initial setting time of the slurry to 52 minutes, and the filling rate exceeded 85% under dynamic water conditions, solving the technical problems of insufficient slurry penetration distance under high seepage conditions; unreasonable filter layer gradation leading to drainage blockage; and low curing strength of dynamic water grouting.

[0071] Further, in another embodiment, the open-cut tunnel slope protection construction method of the present invention: (1) During the slope excavation process, the rock layer temperature data (accuracy ±0.5°C) is monitored in real time through distributed optical fiber sensors, and the data is integrated with the strain and seepage data to establish a temperature-strain-seepage coupling model; (2) Abnormal temperature rise may be caused by accelerated groundwater runoff or frictional heating of rock mass, resulting in reduced shear strength of soil mass. When the temperature rises abnormally, the thermal infrared imager (accuracy ±0.1℃) is started to scan synchronously. If the temperature gradient is greater than 0.5℃ / m, it is judged as frictional heating, otherwise it is groundwater runoff acceleration. When the temperature rises abnormally (ΔT≥3℃ / 24h, the baseline value is the average value of monitoring 30 days before construction ±1℃, and the window period is 7 days) and accompanied by a strain rate greater than 0.02% / h, the following emergency measures are triggered: a. Increase the adjustment step length of hydraulic servo anchors to 15kN, and increase the anchor grid spacing to 1.5m×1.5m; b. Add 0.5-1.0% expansion agent (calcium sulphoaluminate) to the grouting slurry, so that the volume expansion rate of the slurry after solidification is ≥5%; c. The opening rate of HDPE perforated pipes in drainage blind ditch is increased to 8-10%, and the hole diameter is expanded to 10-12mm; (3) The temperature-strain-seepage coupling model is constructed based on finite element analysis (FEA). The input parameters include rock thermal conductivity (1.2-2.5 W / m·K), porosity (15-25%), and seepage path curvature radius (0.5-2.0 m). The output is the potential thermal slip risk level (low / medium / high). (4) After the emergency measures are implemented, if the temperature returns to the baseline value ±1°C and the strain rate is less than 0.01% / h within 48 hours, the anchor step length, grouting pressure and drainage pipe opening rate are gradually restored to the initial set values.

[0072] Specifically, distributed fiber optic sensors can monitor rock temperature data in real time, with an accuracy of ±0.5°C, such as the distributed temperature sensing system of LIOS Sensing GmbH. Temperature data can be integrated with strain increment (0.02-0.08%) and seepage rate (2-10 mm / hour) for analysis. The coupling model can be built based on finite element analysis software, such as COMSOL Multiphysics, and the input parameters can include rock thermal conductivity of 1.2-2.5 W / (m·Kelvin), porosity of 15-25%, and seepage path curvature radius of 0.5-2.0 m. The model output can be divided into low, medium, and high risk levels, for example, the temperature change rate ΔT ≥ 3°C / 24 hours is judged as high risk. Sensors can be pre-buried along the slope, and the data acquisition terminal can be installed in the monitoring station at the top of the slope. Compared with traditional temperature monitoring, this solution improves the risk prediction capability through a multi-parameter coupling model, and the model predicts the risk level and the actual landslide event. The coincidence rate is 90%.

[0073] When the temperature rises abnormally by ΔT ≥ 3°C / 24 hours and the strain rate is 0.02% / hour, emergency operation can be triggered. The adjustment step of the hydraulic servo anchor can be increased to 15 kN, and the anchor grid spacing can be increased to 1.5 m × 1.5 m, for example, from 2.0 m × 2.0 m to 1.5 m × 1.5 m. 0.5-1.0% expansion agent, such as calcium sulfoaluminate (BASF MasterLife CSA 30), can be added to the grouting slurry, and the volume expansion rate can reach 5-7% after curing. The opening rate of the HDPE perforated pipe of the drainage blind ditch can be increased to 8-10%, and the hole diameter can be expanded to 10-12 mm, such as Liansu PE100 grade pipe. Emergency operation must be started within 30 minutes. For example, when the temperature in a certain area rises by 3.5°C in 24 hours, the grouting pressure is increased from 1.0 MPa to 1.3 MPa. Compared with traditional grouting reinforcement, this solution enhances timeliness through temperature-strain linkage control, and emergency measures shorten the temperature drop time from 72 hours to 36 hours.

[0074] After the emergency measures are implemented, if the temperature returns to the baseline ±1°C within 48 hours and the strain rate is below 0.01% / hour, the parameters can be gradually restored. For example, the anchor step length is adjusted back from 15 kN to 12 kN and 8 kN in stages, the grouting pressure is reduced from 1.3 MPa to 0.9 MPa, and the drainage pipe opening rate is restored from 10% to 5%. Preventive maintenance can include increasing the frequency of flushing the drainage blind ditch to twice a week before the rainy season, and the water pressure can be selected to be 0.6-0.8 MPa, such as using a Grundfos CR 45 multi-stage centrifugal pump. Temporary diversion channels can be added to the top of the slope interception ditch, the depth can be selected to be 200-300 mm, and the slope can be set to 5-6%, such as using galvanized steel plates for on-site welding and installation. Compared with regular manual inspections, this solution dynamically adjusts quantitative indicators, and the diversion channel reduces the infiltration of surface runoff by 60%.

[0075] The temperature-seepage-strain coupling model of this implementation plan has increased the accuracy of thermal landslide warning to 90%, which is 35% higher than the traditional single parameter monitoring. Emergency response measures have increased the slurry filling rate in the temperature abnormality area to more than 85%, and the shear strength of the anchor rod has increased by 25%. The parameter recovery mechanism avoids excessive support and saves about 0.3 tons of expansion agent per 100 linear meters. Preventive maintenance stabilizes the water flow capacity of the drainage system at more than 5 liters / (m·s), and reduces the peak seepage rate in the rainy season by 50%, which can effectively solve the risk of thermal deformation caused by temperature anomalies. The problem of temperature coupling effect is not covered by traditional monitoring methods.

[0076] Taking the slope project of K27+600 section of a tunnel as an example, the rock layer is a granite fissure development area, and there is a geothermal anomaly risk. The specific implementation steps are as follows: (1) Construction of temperature-strain-seepage coupling model Data acquisition: Distributed fiber optic sensors (model LIOS Sensing GmbH) monitor temperature (resolution 0.1°C), strain (accuracy ±5με), and seepage rate (accuracy ±0.2mm / h) in real time; Model simulation: COMSOL Multiphysics software was used to establish a three-dimensional thermal-fluid-solid coupling model. The input parameters included the thermal conductivity of granite 1.8 W / m·K, porosity 18%, and the curvature radius of the seepage path 1.2 m. Risk grading: The model outputs risk level threshold (low: ΔT<1℃ / 24h; medium: ΔT=1-3℃ / 24h; high: ΔT≥3℃ / 24h).

[0077] (2) Emergency response to abnormal temperature Monitoring found that the temperature in a certain area rose from 25°C to 28.5°C (ΔT=3.5°C) within 24 hours, the strain rate was 0.025% / h, and the seepage rate was 6.8mm / h. The model determined that it was a high risk level; Emergency operation was triggered: the bolt step length was increased from 10kN to 15kN (the pressure of the Enerpac RC-106 pump station was increased to 26MPa), and the grid spacing was increased to 1.5m×1.5m; 0.8% calcium sulfoaluminate expansion agent (BASF MasterLifeCSA 30) was added to the slurry, and the volume expansion rate after curing was 6.2% (ASTM C878 standard); the open porosity of the HDPE drainage pipe (Liansu PE100) was increased from 5% to 9%, and the hole diameter was expanded to 11mm; 36 hours after the emergency measures were implemented, the temperature dropped to 26.2℃, the strain rate was 0.008% / h, and the seepage rate dropped to 3.1mm / h.

[0078] (3) Parameter recovery and effect verification The initial parameters were restored in stages: Stage 1 (24 hours): the bolt step length was adjusted back to 12 kN, and the grouting pressure was reduced from 1.3 MPa to 1.0 MPa; Stage 2 (24 hours): the drainage pipe opening rate was restored to 5%, and the hole diameter was reduced to 8 mm; Drilling and coring after recovery showed that the slurry filling rate in the area where the expansion agent was added was greater than 90%, and the compressive strength of the rock mass was increased to 28.5MPa (22.1MPa in the unadded area).

[0079] Further, in another embodiment, the open-cut tunnel slope protection construction method of the present invention: (1) After construction is completed, a graded early warning mechanism for slope stability is established based on the long-term monitoring data of distributed optical fiber sensors: a. When the displacement rate is stable at 0.3-0.5mm / d for 7 consecutive days, it is judged as a first-level warning and a manual inspection is initiated once a week to check whether the anchor prestress loss exceeds 10%; b. When the daily displacement rate is greater than 0.6mm / d or the seepage rate is greater than 6mm / h, it is judged as a second-level warning, and local grouting (grouting pressure 0.8-1.0MPa) and anchor prestress compensation (step length 5-8kN) are immediately performed; c. When the displacement rate is greater than 0.8mm / d and the seepage rate is greater than 8mm / h for three consecutive days, it is determined as a Level 3 warning, the anchor grid is fully encrypted to 1.5m×1.5m, and a temporary drainage well (diameter 500mm, depth 6-8m) is added; (2) The manual inspection shall record the following parameters: the fluctuation amplitude of contact stress of the anchor head, the crack width of the grouting body (≤2 mm), the drainage capacity of the drainage blind ditch (≥4 L / (m·s)), and dynamically adjust the subsequent construction parameters according to the inspection results; (3) The grouting material is quick-setting silicate cement slurry (initial setting time ≤ 1 hour, mixed with 4-6% nano-silicon dioxide), and the grouting holes are preferentially selected at the nodes with the largest strain increment area; (4) Conditions for lifting the warning: After maintenance, the displacement rate is less than 0.3 mm / d and the seepage rate is less than 2 mm / h for 7 consecutive days, and the anchor prestress loss is ≤5%.

[0080] Specifically, the displacement rate threshold monitored by the distributed optical fiber sensor can be set to three levels: the first-level warning is a displacement rate of 0.3-0.5 mm / day for 7 consecutive days; the second-level warning is a single-day displacement rate of >0.6 mm / day or a seepage rate of >6 mm / hour; the third-level warning is a displacement rate of >0.8 mm / day and a seepage rate of >8 mm / hour for 3 consecutive days. The sensor can be MOI sm125, and the data acquisition terminal can be Campbell CR6. The sensor can be pre-buried along the slope, and the data acquisition terminal can be installed in the monitoring station on the top of the slope and connected by optical fiber cable. For example, when the tunnel section monitors a displacement rate of 0.4 mm / day for 7 consecutive days, it is judged as a first-level warning, triggering a manual inspection once a week. Compared with a single threshold alarm, this solution achieves differentiated management through graded warnings. Parameter setting is based on historical data analysis. For example, the displacement rate before 10 landslides in a certain area exceeded 0.6 mm / day.

[0081] Manual inspections need to check anchor prestress loss, grout crack width, and drainage blind ditch water capacity. Anchor prestress loss threshold can be set to 10%, for example, when the initial prestress is 50 kN, the loss exceeds 5 kN and compensation is required. Grout crack width threshold can be set to ≤2 mm, measured by a crack width meter (such as Hilti PS 200). Drain blind ditch water capacity threshold can be set to ≥4 liters / (meter·second), detected by a flow meter (such as Keyence FD-Q series). Inspection results can be recorded in a digital log, for example, using a tablet (such as iPadPro) to enter on-site. Compared with conventional manual inspections, this solution guides maintenance through quantitative indicators. For example, during a certain inspection, it was found that the prestress of 3 anchors had lost 12%, which immediately triggered the compensation operation.

[0082] After the second-level warning is triggered, local grouting can be performed in the area with the largest strain increment. The grouting pressure can be selected as 0.8-1.0 MPa, and the grouting holes can be 1.3-1.7 meters apart. The grout can be a quick-setting silicate cement with an initial setting time of ≤1 hour and 4-6% nano-silicon dioxide (such as Evonik AEROSIL 200). The anchor compensation step can be selected from 5-8 kN. For example, the prestress of a certain anchor is compensated from 44 kN to 51 kN, and the Enerpac RC-106 hydraulic pump station is used for adjustment. The repair of drainage blind ditches includes clearing silt and backwashing. The water pressure can be selected as 0.5 MPa and the duration is 15 minutes. Compared with traditional grouting reinforcement, this solution locates the priority area through data. After grouting, the slurry diffusion radius reaches 1.5 meters or more, and the filling crack rate is greater than 85%.

[0083] The lifting of the early warning requires that the displacement rate is less than 0.3 mm / day for 7 consecutive days, the seepage rate is less than 2 mm / hour, and the anchor prestress loss is ≤5%. For example, after a slope is maintained, the displacement rate is 0.2-0.28 mm / day for 7 consecutive days, the seepage rate is 1.5-1.8 mm / hour, and the contact stress fluctuation is ≤3%, which is considered stable. The verification method includes coring to detect the slurry filling rate (≥85%) and pulling out test to verify the pull-out resistance of the anchor (≥110% of the design value). For example, 10 anchors were randomly sampled, and the pull-out resistance ranged from 418 to 435 kN (design value 400 kN), with a pass rate of 100%. Compared with manual sampling inspection, this plan ensures objectivity through quantitative indicators. Statistics show that the recurrence rate is less than 3% within 30 days after the early warning is lifted.

[0084] This implementation plan improves resource allocation efficiency by 40% through a graded early warning mechanism, and reduces the frequency of manual inspections for the first-level early warning to once a week. The quantitative inspection standard shortens the maintenance response time to within 2 hours, and reduces the anchor fracture rate from 8% to below 2%. Local grouting and anchor compensation operations save material costs of about 0.8 tons of cement / 100 linear meters. The multi-parameter release condition reduces the misjudgment rate from 15% of the traditional method to 5%, and significantly improves long-term stability. It can effectively solve the technical problems of easy misjudgment of single displacement rate criterion; lack of control over the recurrence of hidden deformation; and insufficient timeliness of maintenance response.

[0085] Taking the K30+900 section slope project of a tunnel as an example, after construction, it enters the stability maintenance stage. The specific implementation steps are as follows: (1) Long-term monitoring and early warning classification Monitoring data of distributed optical fiber sensor (MOI sm125): displacement rate was 0.4 mm / d and seepage rate was 3.2 mm / h on the 1st to 7th day, which was judged as no warning; on the 8th day, it suddenly increased to 0.7 mm / d and the seepage rate was 7.1 mm / h, triggering the second-level warning; Manual inspection found that: the prestressing force of three anchor rods lost 12% (initial 50kN→44kN); the drainage capacity of the slope foot drainage blind ditch dropped to 3.5L / (m·s); (2) Secondary warning response operations Local grouting: Drill grouting holes (diameter 42mm, depth 1.2m) in the area with the largest strain increment (coordinates X:125.34, Y:43.21), inject quick-setting slurry (water-cement ratio 0.4, mixed with 5% nano-silicon dioxide), grouting pressure 0.9MPa, initial setting time 50 minutes; Anchor compensation: The prestressed anchors are adjusted with a step size of 7kN to restore to 51kN (pressure of the hydraulic pump station is 21MPa); Repair of drainage blind ditch: remove sediment and reverse flush (water pressure 0.5MPa, 15 minutes), and the water flow capacity is restored to 4.8L / (m·s); (3) Warning release verification Monitoring data after maintenance: displacement rate 0.2-0.28mm / d, seepage rate 1.5-1.8mm / h on the 9th to 15th day; anchor prestress fluctuation ≤3% (48-52kN); Manual re-inspection confirmed that there were no visible cracks in the grouting body, and the drainage capacity of the blind drainage ditch was stable at more than 4.5L / (m·s), and the warning was lifted.

[0086] Further, in another embodiment, the open-cut tunnel slope protection construction method of the present invention: (1) Dynamically adjust anchor support parameters according to different geological conditions: a. Water-rich sand layer area: the anchor length is increased to 1.3-1.5 times the excavation depth, the initial prestress is increased to 55-65kN, and the grouting pressure is set to 1.2-1.5MPa (seepage rate 7.2mm / h); b. Weak interlayer area: the anchor grid spacing is increased to 1.5m×1.5m, the grouting hole depth is increased to 0.6-0.7 times the design height of the slope, and 4-8% nano-silicon dioxide is added to improve the grout impermeability; c. Rock fracture development area: the anchor installation angle is adjusted to be orthogonal to the fracture trend (error ≤ ±5°), and the spacing between slurry penetration holes is reduced to 30-50mm; (2) During the rainy season or when the groundwater level rises, perform the following preventive maintenance measures: a. Increase the porosity of the HDPE perforated pipe in the drainage blind ditch to 8-10%, expand the hole diameter to 10-12mm, and perform reverse flushing once a week (water pressure 0.6-0.8MPa, lasting 20-30 minutes); b. The monitoring frequency of anchor prestressing is increased from once a day to three times a day. When a single monitoring finds that the prestressing loss is ≥5%, an immediate compensation step of 5-8kN is applied; c. Add a temporary diversion ditch (depth 200-300mm, slope ≥5%) in the intercepting ditch on the top of the slope to prevent surface runoff from infiltrating into the slope; (3) The matching relationship between the nano-silica dosage and the grouting pressure is: a. When the grouting pressure is 0.8-1.0MPa, add 4-5% nano-silicon dioxide; (or replace with an equal amount of fly ash) b. When the grouting pressure is 1.2-1.5MPa, add 6-8% nano-silicon dioxide; (or replace with an equal amount of fly ash) (4) Construction records and effect verification: a. Record the support parameters, grouting pressure and seepage rate of each level of slope in real time and generate a digital log; b. After each level of slope protection is completed, the slurry filling rate is tested by coring (≥85% is qualified), and the pull-out test is used to verify the pull-out resistance of the anchor (≥110% of the design value).

[0087] Specifically, in the water-rich sand layer area, the anchor rod length can be selected as 1.3-1.5 times the excavation depth. For example, when the excavation depth is 10 meters, the anchor rod length can be 13-15 meters. The initial prestress can be set to 55-65 kN, and the grouting pressure can be selected to be 1.2-1.5 MPa (seepage rate is about 7.2 mm / h). The anchor rod body can be made of HRB400 grade rebar, and the hydraulic system can be Enerpac RC-106 pump station (rated pressure 70MPa, flow rate 2.3L / min, suitable for the prestressed loading range of HRB400 grade anchor rods 0-200kN). The anchor rod can be driven vertically to the slope, and the anchoring section is deep into the stable stratum (such as medium weathered rock strata). In the weak interlayer area, the anchor grid spacing can be increased to 1.5 meters by 1.5 meters, and the grouting hole depth can be set to 0.6-0.7 times the slope height. For example, when the slope height is 12 meters, the grouting hole depth can be 7.2-8.4 meters. Compared with traditional anchor support, this solution dynamically adjusts parameters according to geological conditions. After construction in a water-rich sand layer area, when the grouting pressure is about 1MPa, the diffusion radius is 1.5~3.5m, and the anchor pull-out resistance is 115% of the design value.

[0088] During the rainy season or when the groundwater level rises, the porosity of the HDPE perforated pipe in the drainage blind ditch can be increased to 8-10%, and the hole diameter can be expanded to 10-12 mm, such as Liansu PE100 grade pipe. The frequency of backwashing can be increased to once a week, the water pressure can be selected to be 0.6-0.8 MPa, and the duration can be 20-30 minutes, such as using a Grundfos CR 45 multi-stage centrifugal pump. The monitoring frequency of anchor prestressing can be increased from once a day to three times a day, for example, using a Kistler 9067 pressure sensor to collect data in real time. A temporary diversion trough can be added to the top of the slope intercepting ditch, the depth can be selected to be 200-300 mm, and the slope can be set to 5-6%, for example, by welding and installing galvanized steel plates. Compared with conventional drainage system inspections, this implementation scheme controls the peak seepage rate to less than 5 mm / hour during the rainy season of a certain project through quantitative threshold control operations.

[0089] The dosage of nano-silica (or fly ash) can be dynamically adjusted according to the grouting pressure. When the grouting pressure is 0.8-1.0 MPa, 4-5% nano-silica (such as Evonik AEROSIL 200) is added; when the pressure is 1.2-1.5 MPa, 6-8% is added. The slurry preparation can be carried out in two stages: in the first stage, the nanomaterials and water reducers (such as BASF Master Glenium SKY 8233) are added to the water and ultrasonically dispersed for 3-5 minutes (power 300W); in the second stage, it is mixed with cement for 2-3 minutes. For example, when the grouting pressure of a certain project was 1.3 MPa, 7% nano-silica was added, and the compressive strength of the slurry reached 20.8 MPa. Compared with the traditional grouting material ratio, this scheme optimizes the performance through the pressure-dosage linkage, and the permeability coefficient of the slurry with 7% nano-silica is reduced to 5×10⁻ 8 cm / s.

[0090] During the construction process, support parameters, grouting pressure and seepage rate can be recorded in real time to generate a digital log, for example, using an industrial tablet (such as iPad Pro) for on-site entry. After each level of slope protection is completed, the grout filling rate can be tested by drilling and coring, and the requirement is ≥85%. For example, coring in a weak interlayer area showed a filling rate of 88%. The pull-out resistance of the anchor can be verified by a pull-out test, for example, using a hydraulic jack (Enerpac P392) to load to 110% of the design value (such as 440 kN). Ten anchors were randomly sampled, and the pull-out resistance range could reach 418-435 kN (design value 400 kN), with a pass rate of 100%. Compared with traditional sampling inspection, this solution ensures construction quality through quantitative indicators. Statistics show that the anchor fracture rate has dropped from 8% in traditional methods to less than 2%.

[0091] The geological condition adaptation parameters of this implementation method increase the pull-out resistance of the anchor by 15%, and the slurry filling rate is stabilized at more than 85%. Rainy season maintenance measures keep the drainage capacity above 5 liters / (m·s), and reduce the risk of seepage erosion by 60%. The dynamic dosage of nano-silicon dioxide matches the grouting pressure, and the compressive strength of the slurry is increased by 50%. The construction record and verification system increases the quality pass rate from 90% to 98%, and the long-term stability is significantly enhanced. It can solve the problem of slope stability control under complex geology (water-rich layers, weak interlayers, and fissure areas) and seasonal hydrological changes (rainy season).

[0092] For example, take the slope project of K33+200 section of a tunnel as an example. The geological conditions are interlaced water-rich sand layers and weak interlayers. The specific implementation steps are as follows: Construction in water-rich sand layer area (seepage rate about 7.2mm / h) The anchor length is set to 1.4 times the excavation depth (excavation depth 10m, anchor length 14m), the initial prestress is 60kN, and the grouting pressure is 1.3MPa; the slurry is mixed with 7% nano-silicon dioxide (Evonik AEROSIL 200), the water-cement ratio is 0.4, and the slurry diffusion radius after grouting is more than 1.5m; drilling core testing shows that the slurry filling rate in the sand layer area is 88%, and the anchor pull-out force is 115% of the design value (standard HRB400 rebar, pull-out force ≥400kN).

[0093] The control group adopted traditional static anchor support (anchor length 10m, fixed prestressing force 50kN, point monitoring + conventional grouting).

[0094] Compared with traditional static anchor support, in the same water-rich sand layer area (excavation depth 10m), the anchor fracture rate of this technical solution is 4.2%, and the displacement rate is stable at 0.3mm / d; the fracture rate of the traditional method is 12.5%, and the peak displacement rate reaches 0.8mm / d.

[0095] Optimization of weak interlayer area The anchor grid spacing was increased to 1.5m×1.5m, and the grouting hole depth was 0.65 times the slope height (slope height 12m, grouting hole depth 7.8m); the permeability coefficient of the slurry mixed with 8% nano-silicon dioxide was reduced to 5×10⁻ after solidification. 8 cm / s (ASTM D5084 standard), the shear strength of the weak interlayer is increased from 0.5MPa to 1.2MPa; monitoring data: 30 days after construction, the displacement rate is stabilized at 0.2mm / d, and the seepage rate is ≤2mm / h.

[0096] Preventive maintenance during rainy season The porosity of the HDPE perforated pipe in the drainage blind ditch was increased to 9%, the hole diameter was 11mm, and the frequency of backwashing was increased to twice a week (water pressure 0.7MPa, 25 minutes each time). The anchor prestress monitoring found a daily loss of 6% (from 60kN to 56.4kN), and an immediate compensation step of 7kN was used to restore it to 63.4kN. The top diversion trough (depth 250mm, slope 6%) effectively intercepted surface runoff, and the peak seepage rate of the slope during the rainy season was ≤5mm / h.

[0097] Effect verification and recording Digital log records: grouting pressure of each slope is 1.2-1.5MPa, nano-silica content is 7-8%, and seepage rate is 2-5mm / h; Pull-out test results: 10 anchor rods were randomly sampled, with a pull-out force range of 418-435kN (design value 400kN), and a pass rate of 100%.

[0098] Although the embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and the embodiments. They can be applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily realized.

Claims

1. A construction method for slope protection of an open-cut tunnel, characterized in that: The following steps are involved: 1) Before excavation of the slope, distributed optical fiber sensors are pre-buried along the slopes on both sides of the tunnel axis. The deployment depth of the distributed optical fiber sensors is 0.6-0.7 times the design height of the slope. The horizontal spacing between adjacent sensors is 2.5-3.5m, and the vertical spacing is 1.8-2.2m. The sensors are connected to the ground data acquisition terminal; 2) When the distributed optical fiber sensor monitors that the slope strain increment reaches 0.04-0.06% and the seepage rate reaches 4-6mm / h, the hydraulic servo anchor support system is started. The installation angle of the hydraulic servo anchor is 15°-25°, the anchor length is 1.1-1.4 times the excavation depth, the anchor spacing is 1.8-2.2m×1.8-2.2m grid arrangement, the initial prestress is set to 45-55kN, and the step length is dynamically adjusted according to the real-time monitored strain rate of 0.01-0.03% / h, with a step length of 5-15kN; 3) After each level of slope is excavated to the designed elevation, a high-pressure grouting machine is used to seal the slope surface for grouting. The grouting pressure is dynamically adjusted according to the seepage rate: when the seepage rate is 4-6mm / h, the pressure is 0.8-1.0MPa, and when the seepage rate is greater than 6mm / h, it is increased to 1.2-1.4MPa. The spacing between grouting holes is 1.3-1.7m, and the grouting material is silicate cement slurry mixed with 2-8% nano-silicon dioxide; 4) A longitudinal drainage blind ditch is laid along the slope foot, a three-graded gravel filter layer is laid at the bottom of the ditch, and a HDPE perforated drainage pipe is installed above the filter layer, and a double-layer geotextile is wrapped outside the pipe; 5) The slope deformation data is continuously monitored by distributed fiber optic sensors. When the displacement rate is less than 0.5 mm / d and the seepage rate is less than 2 mm / h for three consecutive days, the hydraulic servo anchor prestressing adjustment is terminated in stages: in the first stage, the step size is reduced to 5 kN and maintained for 24 hours; in the second stage, the adjustment is completely stopped and monitoring is continued for 48 hours.

2. The open-cut tunnel slope protection construction method according to claim 1 is characterized by: 1) In the weak interlayer area, the deployment depth of distributed optical fiber sensors is increased to 0.8-0.9 times the design height of the slope, the horizontal spacing is reduced to 2.0-3.0m, and the vertical spacing is reduced to 1.5-2.0m; 2) When pre-buried distributed optical fiber sensors, stainless steel fixing buckles are set every 0.5m along the sensor axis, and a 10-15mm thick epoxy resin bonding layer is filled between the buckles and the slope rock and soil; 3) The ground data acquisition terminal performs sliding average filtering on the monitoring data of the distributed optical fiber sensor. The filtering window time is 10-15 minutes, and outliers outside the range of ±3σ are eliminated; 4) When three adjacent distributed optical fiber sensors on the same monitoring section simultaneously detect a strain increment ≥ 0.04% and a seepage rate ≥ 4 mm / h, the start-up conditions of the hydraulic servo anchor support system are triggered.

3. The open-cut tunnel slope protection construction method according to claim 2 is characterized by: 1) During the prestress adjustment process of the hydraulic servo anchor, when the distributed optical fiber sensor detects that the slope strain rate exceeds 0.03% / h, the adjustment step length is increased to 12-15kN; when the strain rate is lower than 0.01% / h, the adjustment step length is reduced to 5-8kN; 2) The anchoring section of the hydraulic servo anchor is provided with a dual hydraulic cylinder coordinated control system, the main hydraulic cylinder applies axial tension, and the auxiliary hydraulic cylinder applies lateral pressure at an angle of 30°-45° to the rock formation trend, and the pressure ratio of the main and auxiliary hydraulic cylinders is dynamically controlled by the rock formation strain gradient calculated in real time, and the range is 1:0.3-0.5; 3) The surface of the anchor rod body is processed with a continuous thread structure, with a thread pitch of 15-20mm and a thread depth of 2-3mm. The thread area covers the entire length of the grouting section, and a grout penetration hole with a diameter of 3-5mm is opened at the root of the thread, with a hole spacing of 50-80mm; 4) When the anchor head pressure sensor detects that the contact stress fluctuation amplitude exceeds 20% of the initial value, the anchor spacing encryption mechanism is automatically triggered to reduce the grid layout spacing to 1.5-1.8m×1.5-1.8m.

4. The open-cut tunnel slope protection construction method according to any one of claims 1 to 3, characterized in that: 1) The ground data acquisition terminal inputs the strain increment, seepage rate and standard deviation of contact stress fluctuation of the anchor head monitored by the distributed optical fiber sensor into the Bayesian network model trained based on historical slope engineering data. The model input node is defined as: strain increment → seepage rate → contact stress fluctuation → instability probability. The mean square error of the output instability probability value is ≤0.005; 2) When the instability probability output by the Bayesian network is ≥85% or the real-time strain rate is <0.05% / h, the following operations are triggered synchronously: a. The adjustment step length of the hydraulic servo anchor is increased to 12-15kN; b. The grouting pressure of the high-pressure grouting machine is increased to 1.2-1.4MPa; c. The opening rate of HDPE perforated drainage pipe is increased to 6-8%, and the hole diameter is adjusted to 8-10mm; 3) The Bayesian network model is trained based on historical slope engineering data. The input parameters include strain increment, seepage rate, and standard deviation of contact stress fluctuation. The output is the instability probability value. 4) When the probability of instability is less than 60% and the displacement rate is less than 0.5mm / d for three consecutive days, the anchor step length is restored to 8-12kN, the grouting pressure is reduced to 0.8-1.0MPa, and the drainage pipe opening rate is adjusted back to 3-5%.

5. The open-cut tunnel slope protection construction method according to claim 4 is characterized in that: 1) During the preparation of the silicate cement slurry, nano silicon dioxide is added in two stages: a. In the first stage, 1-2% by mass of nano-silicon dioxide and water reducer are added to the mixing water and ultrasonically dispersed; b. In the second stage, add the remaining 1-2% nano-silica, mix with Portland cement and continue stirring; 2) A medium-coarse sand transition layer is added to the bottom of the gravel filter layer of the drainage blind ditch, and a geotextile is laid between the sand layer and the gravel layer; 3) Within 24 hours after the grouting is completed, the drainage blind ditch shall be reversely flushed with a flushing water pressure of ≤0.4MPa and a flushing duration of 10-20 minutes until the water flow capacity of the drainage pipe is ≥5L / (m·s); 4) When the adjustment step of the hydraulic servo anchor is ≥12kN, 0.2-0.5% early strength agent is added to the slurry simultaneously to shorten the initial setting time of the slurry to 45-60 minutes.

6. The open-cut tunnel slope protection construction method according to claim 5 is characterized by: 1) During the slope excavation process, the rock temperature data is monitored in real time through distributed optical fiber sensors, and the temperature data is integrated and analyzed with the strain and seepage data to establish a temperature-strain-seepage coupling model; 2) When the temperature rises abnormally and the strain rate is greater than 0.02% / h, the following emergency measures are triggered: a. Increase the adjustment step length of hydraulic servo anchors to 15kN, and increase the anchor grid spacing to 1.5m×1.5m; b. Add 0.5-1.0% expansion agent to the grouting slurry so that the volume expansion rate of the slurry after solidification is ≥5%; c. The opening rate of HDPE perforated pipes in drainage blind ditch is increased to 8-10%, and the hole diameter is expanded to 10-12mm; 3) The temperature-strain-seepage coupling model is constructed based on finite element analysis, with input parameters including rock thermal conductivity, porosity, and seepage path curvature radius, and the output is the potential thermally induced slip risk level; 4) After the emergency measures are implemented, if the temperature returns to the baseline value ±1°C and the strain rate is less than 0.01% / h within 48 hours, the anchor step length, grouting pressure and drainage pipe opening rate are gradually restored to the initial set values.

7. The open-cut tunnel slope protection construction method according to claim 6 is characterized by: 1) After the construction is completed, a graded early warning mechanism for slope stability is established based on the long-term monitoring data of distributed optical fiber sensors: when the displacement rate is stable at 0.3-0.5mm / d for 7 consecutive days, it is judged as a first-level early warning, and a manual inspection is initiated once a week to check whether the anchor prestress loss exceeds 10%; when the daily displacement rate is greater than 0.6mm / d or the seepage rate is greater than 6mm / h, it is judged as a second-level early warning, and local grouting and anchor prestress compensation are immediately carried out; when the displacement rate is greater than 0.8mm / d and the seepage rate is greater than 8mm / h for 3 consecutive days, it is judged as a third-level early warning, and the anchor grid is fully encrypted to 1.5m×1.5m, and a temporary drainage well is added; 2) The following parameters need to be recorded during manual inspection: the fluctuation amplitude of contact stress on the anchor bolt head, the crack width of the grouting body, and the drainage capacity of the drainage blind ditch, and the subsequent construction parameters should be adjusted dynamically according to the inspection results; 3) The grouting material is quick-setting silicate cement slurry with an initial setting time of ≤1 hour, mixed with 4-6% nano-silicon dioxide, and the grouting holes are preferentially selected at the nodes with the largest strain increment area; 4) Conditions for lifting the warning: After maintenance, the displacement rate is less than 0.3mm / d and the seepage rate is less than 2mm / h for 7 consecutive days, and the anchor prestress loss is ≤5%.

8. The open-cut tunnel slope protection construction method according to claim 7 is characterized by: 1) Dynamically adjust anchor support parameters according to different geological conditions: Water-rich sand layer area: the anchor length is increased to 1.3-1.5 times the excavation depth, the initial prestress is increased to 55-65kN, and the grouting pressure is set to 1.2-1.5MPa; Weak interlayer area: the anchor grid spacing is increased to 1.5m×1.5m, the grouting hole depth is increased to 0.6-0.7 times the design height of the slope, and 2-8% nano-silicon dioxide is added to improve the grout impermeability; In the area with developed rock fractures: the bolt installation angle is adjusted to be perpendicular to the fracture direction, and the spacing between slurry penetration holes is reduced to 30-50mm; 2) During the rainy season or when the groundwater level rises, perform the following preventive maintenance measures: Increase the porosity of the HDPE perforated pipe of the drainage blind ditch to 8-10%, expand the hole diameter to 10-12mm, and perform backwashing once a week with a water pressure of 0.6-0.8MPa for 20-30 minutes; The monitoring frequency of anchor prestressing is increased from once a day to three times a day. When a single monitoring finds that the prestressing loss is ≥5%, an immediate compensation step of 5-8kN is applied. Add a temporary diversion ditch in the intercepting ditch on the top of the slope. The depth of the diversion ditch is 200-300mm and the slope is ≥5% to prevent surface runoff from infiltrating into the slope; 3) The matching relationship between the nano-silicon dioxide dosage and the grouting pressure is: When the grouting pressure is 0.8-1.0MPa, 4-5% nano-silica is added; when the grouting pressure is 1.2-1.5MPa, 6-8% nano-silica is added.

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