A shield construction and monitoring method for a dangerous river power tunnel

Abstract

The present invention discloses a shield construction and monitoring method for a power tunnel under a dangerous river, comprising the following steps: (1) reinforcing the tunnel hole under the river; (2) shield construction under the river; (3) shield construction under the power tunnel; (4) construction monitoring. The present invention has improved measures for each step, so that the shield section under the river and the power tunnel under the river can achieve the purpose of high-quality and safe underpass.

Description

Technical Field

[0001] The invention relates to the field of tunnel construction, and in particular to a shield construction and monitoring method for a dangerous source river power tunnel. Background Art

[0002] There are many sources of danger in the construction of underground tunnels in cities. For example, in the construction of power tunnels crossing underground dangerous rivers, innovative construction methods are required for special construction sections, and improvements should be made to the existing shield construction of power tunnels crossing dangerous rivers in order to achieve the goal of high-quality and safe construction. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a shield construction and monitoring method for a dangerous river power tunnel, which is an improved new construction method.

[0004] The technical problem to be solved by the present invention is achieved through the following technical solutions:

[0005] A shield construction and monitoring method for a dangerous river power tunnel comprises the following steps:

[0006] (1) Reinforcement of river channels; reinforcement of tunnels under rivers;

[0007] (2) Shield construction under the river;

[0008] (3) Shield construction under the power tunnel;

[0009] (4) Construction monitoring.

[0010] Preferably, the river channel reinforcement adopts sandbag cofferdam to stop water, and the water-facing surface of the cofferdam is fully covered with water-stop film, the film is flatly laid and compacted with sandbags, and the layers are overlapped and staggered, the riverbed is leveled, steel mesh is laid, and concrete is poured to seal the bottom.

[0011] Preferably, the shield construction under step (2) and step (3) includes the following steps: setting the construction stratum loss rate to within 2%, the shield pushing pressure to be greater than 0.8 times the theoretical water and soil pressure, timely synchronous grouting after the shield passes, and controlling the synchronous grouting volume and grouting pressure so that the unconfined uniaxial compressive strength should be greater than 1MPa;

[0012] Grouting is performed in time at the shield tail to fill the gap between the pipe segment and the soil, with the weight ratio of water to fly ash being (0.5-1.5): (0.5-1.5); the 28-day unconfined compressive strength of the soil reinforced by grouting is greater than 1MPa, and the permeability coefficient is less than 10cm / s; additional grouting holes are added on the pipe segment, and secondary grouting reinforcement is performed in the hole on the left and right construction lines;

[0013] During the shield tunneling process, grouting holes are drilled behind the wall for the corresponding segments. After the grouting flower pipe is inserted into the wall, deep hole grouting is carried out around the interval structure through the grouting holes behind the wall. The synchronous grouting volume and grouting pressure are controlled so that the unconfined uniaxial compressive strength should be greater than 1MPa and the effective diffusion radius of the grouting should be greater than 0.5m.

[0014] Preferably, the construction monitoring in step (4) comprises the following steps:

[0015] (1) Pipeline settlement: monitor the pipelines within the influence area; measurement point layout method: for pipelines within the shield influence area, a measurement point is arranged every 5 to 10 meters above the pipeline; or, a measurement point is arranged every 20 to 30 meters along the direction of the pipeline;

[0016] (2) River sedimentation: monitor the rivers within the affected area; measurement point layout method: for rivers within the shield influence area, a measurement point is laid out every 5 to 10 meters along the river bank direction;

[0017] Preferably, the monitoring, measurement and control measures include:

[0018] (1) Monitoring and measurement are carried out along the direction of the shield machine, 30 m in front and behind the shield machine, and 14 m in the horizontal direction;

[0019] (2) Displacement monitoring starts when the shield is pushed to 20 m away from the power tunnel or river, and is carried out every 3 hours until three months after the shield construction is completed.

[0020] Preferably, the construction monitoring in step (4) further comprises the following steps:

[0021] (1) Surface road settlement measurement points: They are arranged at an average of 50 m along the center line of the tunnel. When encountering cross-roads or overpasses, 5 to 7 cross-section measurement points are arranged; surface settlement measurement points are arranged on the surface of the square on both sides of the line and between the buildings within 30 m from the edge of the subway structure; measurement points are arranged on the roads, surfaces, and buildings within 30 m from the edge of the station entrances and exits.

[0022] (2) Underground pipeline settlement measurement points: arranged 40 to 50 meters along the pipeline direction;

[0023] (3) Settlement and inclination measuring points of buildings or structures: The measuring points are buried in the vertical structure of the building, with 4 to 6 points arranged for each building.

[0024] Preferably, the method for burying the underground pipeline settlement monitoring points (2) is as follows:

[0025] 1) Underground pipelines with inspection wells: Open the well cover and directly lay out the measuring points on the pipeline or on the pipeline carrier;

[0026] 2) Pipelines without inspection wells but with excavation conditions: Excavate and expose the pipelines, and place the measuring points directly on the pipelines;

[0027] 3) For pipelines without inspection wells or excavation conditions: bury indirect observation points on the corresponding surface;

[0028] 4) When laying out monitoring points on the pipeline, use a clamp-type buried point for closed pipelines; for open pipelines, make monitoring point supports on the pipeline or pipeline piers;

[0029] 5) Within the scope of the river section under the river, a section is set up every 10m, and a monitoring point is buried longitudinally in the center of the river, on the edges on both sides, and 3m outward.

[0030] Preferably, the control benchmark and alarm value of the monitored power tunnel shall not exceed the following values: vertical displacement 10mm, horizontal displacement 10mm; clearance convergence settlement / uplift 10mm; the control standard and alarm value of the monitored river section shall be: vertical displacement 20mm, horizontal displacement 20mm, clearance convergence settlement / uplift 30mm.

[0031] Preferably, the emergency measures for power tunnel construction are also included: grouting is used to reinforce the soil within 6.0m around the power tunnel, the ground grouting material is pure cement slurry, the grouting pressure is 1-2MPa, and the soil reinforcement depth is 8.0m; grouting reinforcement is carried out in the tunnel. Pure cement slurry is used, and the grouting pressure is 0.5-0.6MPa.

[0032] Compared with the prior art, the present invention has the following technical effects:

[0033] The shield construction and monitoring method of the power tunnel under the dangerous river of the present invention is improved by the following steps: (1) reinforcing the tunnel hole under the river; (2) shield construction under the river; (3) shield construction under the power tunnel; (4) construction monitoring. The present invention has improved measures for each step, so that the shield section under the river and the power tunnel under the river can achieve the purpose of safe underpass. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is the relationship diagram between the shield line and the river plane position of the present invention

[0035] Figure 2 This is the geological profile of the river in the present invention

[0036] Figure 3 This is a schematic diagram of the cross-sectional structure of the cofferdam treatment measures of the present invention.

[0037] Figure 4 This is the geological profile of the power tunnel of the present invention

[0038] Figure 5-1 Sectional diagram for arranging settlement observation points of the present invention

[0039] Figure 5-2 Plan view of the settlement observation point layout of the present invention

[0040] In the figure: 1- river channel, 2- small sand bags, 3- concrete slab, 4- film, 5- steel mesh, 6- sand bag cofferdam, 7- monitoring point. DETAILED DESCRIPTION

[0041] like Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5-1 , Figure 5-2 The shield construction and monitoring method of a dangerous river power tunnel shown includes construction implementation in the following engineering section.

[0042] Project Overview

[0043] The shield tunnel section mainly passes through the pebble layer, mudstone layer and sandstone layer. The maximum soil cover of the section is about 14m, the minimum soil cover is about 6m, the maximum curve radius of the line is 500m, and the minimum curve radius is 300m. The minimum slope is 5‰ and the maximum slope is 29.826‰.

[0044] The shield tunnel passes under the power tunnel and Shuanglong River in the Longdeng Mountain entry and exit section. The shield tunnel is covered with soil for about 15m and is 4.8m from the bottom of the power tunnel. The power tunnel is a rectangular reinforced concrete structure with a clearance of 2.5m×3.1m. It is constructed by open-cut method and has a buried depth of about 10m.

[0045] Shuanglong River is a mortar-laid rubble riverbank with no riverbed paving. The river is about 10m wide and 4m deep. The shield tunnel is covered with about 5.8m of soil.

[0046] Reinforcement along the way: river channel tile washing weir, buried 6.88 meters away from the tunnel, grouting in the tunnel, control excavation parameters, strengthen synchronous and secondary grouting, strengthen surface monitoring and inspection; rainwater pipe, buried 2.5-5 meters away from the tunnel, grouting in the tunnel; water supply pipe, buried 2-2.5 meters away from the tunnel, grouting in the tunnel; power pipe, buried 1.5-2 meters away from the tunnel, grouting in the tunnel; communication pipe, buried 1.5 meters away from the tunnel, grouting in the tunnel; gas pipe, buried 1.5 meters away from the tunnel, grouting in the tunnel; high-pressure gas pipe, buried 1.7 meters away from the tunnel, grouting in the tunnel. Sewage pipe, buried 3 meters away from the tunnel, grouting in the tunnel.

[0047] Engineering geology and hydrogeology:

[0048] The geology of the Longdengshan shield tunneling tunnel is sandstone strata for 1150 meters before it starts, and the strata it passes through after 1150 meters are pebble layers. The surrounding rock classification at the crossing is: Class V. The current status of the site is a municipal road with heavy traffic. According to the regional hydrogeological data and the occurrence conditions of groundwater, the groundwater is mainly pore groundwater in the Quaternary sand and pebble soil layers. The pebble soil layer on the site is thick and distributed in layers, with thin layers of sand in some parts, and a large amount of pore groundwater is stored in between. The water volume is large and the water level is high. Atmospheric precipitation and regional surface water are its main sources of replenishment. The pore water in the pebble soil layer forms a continuous free water surface.

[0049] Construction planning of the shield tunnel under the power tunnel and river in the Longdengshan entry and exit section: power tunnel exit line (C2), entry line one (R2); Shuanglong River exit line (C2), entry line one (R2), Shuanglong River bottom cover.

[0050] Resource Configuration

[0051] Equipment configuration: 3 tunnel boring machines DZ193, DZ194 and DZ368 of China Railway Construction Heavy Industry, starting base, reaction frame, gantry crane, cooling tower, slurry mixing system, ventilator, double-liquid grouting machine, geological drilling rig, battery car, fixed gas detector, handheld gas detector, etc.

[0052] Two Ф6280 composite earth pressure balance shield machines of China Railway Construction Heavy Industry are used in the shield section of this section. The main technical parameters of the shield machine are: excavation diameter Ф6280, cutterhead speed 0-3.18r / min, maximum propulsion speed 80mm / min, maximum thrust 3991.4T, the total length of the whole machine is about 82m, the total length of the main machine (including the cutterhead) is about 7.98 (excluding the cutterhead) m, the total weight (main machine + after-matching) is about 500t, the applicable segment specifications (outer diameter × inner diameter × width × division) Φ6000 / 5400~1200 / 1500 / 22.5°mm, the maximum design pressure is 6bar, the whole machine power is 1750KW, the horizontal turning radius is 250m, the longitudinal climbing ability is ±35‰, the rated torque is 6846KN·m, and the escape torque is 8687KN·m.

[0053] Construction steps for shield tunneling under risk sources:

[0054] Equipment preparation

[0055] Before the shield machine passes under the danger source, a comprehensive and detailed inspection and repair of the shield machine and its supporting equipment should be carried out. The focus should be on the grouting system, control circuit and hydraulic system, shield tail brush, gantry crane brake system, travel system, battery car brake and circuit of the shield machine. Damaged parts should be replaced immediately, and parts with hidden faults should be promptly eliminated. Grease or lubricating oil should be added to each lubrication part in time. In particular, the grouting pipeline should be cleaned and unblocked to prevent the conveying pipe from being blocked during the shield machine's passing under the risk source, resulting in interruption of slurry supply and thus causing the shield machine to shut down. At the same time, the shield tail sealing system should be monitored to ensure that there is no leakage during the pass, thereby ensuring the grouting volume.

[0056] Material preparation

[0057] The main materials for shield construction are reinforced concrete lining segments, special segments for passing under the Cheng-Zi-Lu elevated highway, waterproof materials, slurry mixing raw materials, including cement, sand, fly ash, and bentonite. Before passing under the Cheng-Zi-Lu elevated highway, the inventory of various raw materials is counted, including tracks, sleepers, plywood, water pipes, etc., to ensure sufficient quantity. During the shield crossing, the inventory of various raw materials is closely monitored, and the inventory of materials in the warehouse is counted every day. When the quantity is less than 1 / 2 of the warehouse capacity, it is immediately replenished, and the quality of raw materials is strictly controlled to resolutely prevent unqualified materials from entering the site. During the construction period, the impact of weather conditions on material supply is considered, and the weather conditions in the next two days are paid attention to every day. Raw materials affected by the weather should be reserved in advance.

[0058] Main measures for passing under the power tunnel

[0059] Shield construction control

[0060] When the shield machine is tunneling under the tunnel, minimizing the ground deformation caused by the shield construction process is an effective means to protect the power tunnel. When tunneling under the tunnel, the quality is mainly controlled by controlling the tunneling parameters, improving the grouting quality in the tunnel, and monitoring and measuring.

[0061] (1) Before the shield machine passes through the power tunnel, stop the machine 10 meters before the tunnel to check the machine condition. If necessary, open the machine to check the cutter to ensure continuous excavation when the shield machine passes the dangerous source.

[0062] (2) Strictly control the excavation parameters. Clarify the mileage of the power tunnel and its relationship with the interval tunnel;

[0063] (3) Ensure the improvement effect of the slag soil by increasing the amount of foaming agent and water added, strictly control the amount of slag discharged, reduce the cutter head speed and propulsion speed to ensure the shield passes at a uniform speed and appropriately increase the soil pressure;

[0064] (4) According to the surface settlement and excavation conditions, when the segment is dragged out of the shield tail 5 to 10 rings, choose the right time to use a double-liquid grouting machine to carry out secondary grouting reinforcement on the back of the upper part of the segment to fill the building gap behind the segment and shorten the solidification time of the synchronous grouting slurry;

[0065] (5) Use high-quality shield tail grease to improve the sealing effect and prevent leakage of shield tail;

[0066] (6) Apply flexible waterproof material to the seams inside the pipe.

[0067] (7) Monitor stress and strain in the crossing section and conduct surface inspections and monitoring.

[0068] (8) Carry out supplementary grouting to reinforce the stratum in a timely manner according to the monitoring situation.

[0069] Tunnel reinforcement measures

[0070] After the shield machine passes through the power tunnel, the grouting measures in the tunnel are strengthened, and the strata are reinforced by pre-reserved grouting holes in the segments. The reinforcement form is mainly double-liquid slurry and supplemented by single-liquid cement slurry to reduce the impact of the shield machine on the pipeline structure. Grouting reinforcement is carried out in the tunnel within a 3m range of the left and right tunnels, and the grouting reinforcement length is 9m. After the shield machine passes, it is decided whether to carry out tracking grouting based on the monitoring measurement results.

[0071] Key measures to be taken when shield tunnels pass under power tunnels

[0072] (1) Strictly control the shield tunneling parameters, mainly in terms of controlling the stratum loss rate within 2%, and the shield advancement pressure shall not be less than 0.8 times the theoretical water and soil pressure. After the shield passes through, synchronous grouting shall be carried out in a timely manner, and attention shall be paid to controlling the synchronous grouting volume and pressure. The unconfined uniaxial compressive strength shall not be less than 1MPa.

[0073] (2) Strengthen monitoring and measurement, implement fully informationized construction during the shield tunneling process, and closely monitor the displacement of the power tunnel and ground subsidence.

[0074] (3) Before the shield machine is used to pass through the power tunnel, a trial excavation construction should be carried out to obtain the necessary excavation parameters such as the shield machine's thrust pressure and ground settlement, so as to facilitate the construction.

[0075] (4) Additional grouting holes are added on the pipe segments, and secondary grouting reinforcement is carried out on the left and right lines. The length of the grouting reinforcement in the left line is 9 meters, and the length of the grouting reinforcement in the right line is 9 meters.

[0076] Shuanglong River Construction Measures

[0077] Shuanglong River situation

[0078] Shuanglong River belongs to the Minjiang River system in Sichuan Plain. It has been artificially modified. The riverbed depth, flow and flood level have been artificially controlled. The riverbed elevation is 478.82-478.624, the river bank elevation is 484.4, the river bank height is 5-5.5m, the water level is generally 0.5-1.5m, the water flow speed in this river section is slow, the water flow rate is 0.5m / s, the water level is relatively stable, the flood season is mainly in July and August, the water level is 3m, and the water flow rate is 2.5m / s. The cofferdam construction needs to be completed before mid-June.

[0079] Construction preparation before crossing

[0080] (1) Further investigate the geological drilling conditions in the river channel and determine whether there are any geological drilling holes and whether the drilling holes are blocked. If there are any unblocked holes, block them.

[0081] (2) Set up deep settlement measurement points on the ground around the river channel and carry out information-based monitoring and control of settlement.

[0082] (3) To ensure that the shield machine can cross the Shuanglong River smoothly, the mechanical and electrical equipment must be inspected and repaired before crossing, especially the water-stopping effect of the shield tail seal and the seal at the hinge between the middle body and the shield tail, to ensure that the shield machine is in good working condition.

[0083] (4) Adjust the entire monitoring system to ensure the accuracy of the collected data.

[0084] Measures for Crossing the Shuanglong River

[0085] A sandbag cofferdam 6 is used to stop the Shuanglong River, and a 0.8m concrete slab bottom seal 3 is applied to the river channel 1 that crosses the affected area.

[0086] (1) Prepare enough sandbags 6 for the cofferdam. To ensure the water-stop performance of the cofferdam, the water-facing surface of the cofferdam must be fully covered with water-stop film 4. The film is pressed tightly with small sandbags 2. A small sandbag is set for every two layers, with a spacing of one every 1.5m. The size of the small sandbag is 50*30*20cm;

[0087] (2) Start blocking the river upstream, first block the right half of the river along the direction of the river flow, divert the left half, place sandbags upstream of the river, and after the upstream is blocked, start blocking along the center line of the river, and finally block the downstream of the river. Use a water pump to pump the water within the cofferdam to the downstream.

[0088] According to the river flow during construction, Q = SV = (11 + 13.25) / 2 * 1.5 * 0.5 = 9.09m 3 / s, the cofferdam height H = Q*2 / 0.5 / (5.5+7.58) = 2.78m, so the cofferdam height of 3m meets the requirements during construction.

[0089] (3) After the water in the cofferdam is pumped out, the silt at the bottom of the river is first removed with an excavator, and then the silt at the bottom of the river is cleaned to the designed elevation. After the cleaning is completed, the riverbed is leveled, and after the leveling is completed, the Steel mesh 5, with a spacing of 0.4m, is tied and then poured with C25 plain concrete 2 for bottom sealing.

[0090] (4) Seven days after the right side is sealed, the left side is cofferdamed and the right side is diverted. The construction method is the same as that of sealing the right side.

[0091] (5) Seven days after the bottom sealing of the left half is completed, sandbags are piled up to a height of 1.5m. When the shield is pushed to the first two rings of the right half of the river, sandbags are piled up to a height of 1.5m on the right half of the river. The sandbags on the left half of the river are removed to divert the river.

[0092] Requirements for laying sandbags:

[0093] ① The sandbags are laid flat from the lowest point of the riverbed upwards layer by layer, with staggered seams between layers.

[0094] ② Each layer of newly laid sandbags needs to overlap with the completed sandbags by 0.2-0.3 meters to prevent large gaps from being left between the sandbags after the sand shrinks.

[0095] (6) The following measures should be considered during shield tunneling:

[0096] ① Before construction, based on the characteristics of environmental risk projects, predict possible accidents and formulate comprehensive emergency plans and construction plans;

[0097] ② Before crossing, the shield machine should be adjusted and ensured to perform well, and the excavation parameters should be strictly controlled to ensure uniform speed. During the construction process, the excavation soil pressure and the amount of excavation should be strictly controlled. Strict control of shield excavation parameters is mainly reflected in controlling the stratum loss rate within 2% and the shield advancement pressure is not less than 0.8 times the theoretical water and soil pressure. After the shield passes, synchronous grouting should be carried out in a timely manner, and attention should be paid to controlling the synchronous grouting volume and grouting pressure. The unconfined uniaxial compressive strength should be not less than 1MPa, such as 2-4MPa.

[0098] ③ The shield tail should be grouted in time to fill the gap between the pipe segment and the soil, and the grouting volume and grouting pressure should be strictly controlled. The cement slurry ratio, grouting pressure and other parameters should follow the principle of trial before doing, and the water-cement ratio is the best weight ratio of 1:1. The unconfined compressive strength of the grouting reinforced soil after 28 days is not less than 1MPa, if 2-4MPa is selected, the permeability coefficient is not greater than 10-6 / cm / s, such as 3-5cm / s. Add grouting holes on the pipe segment to carry out secondary grouting reinforcement in the double line.

[0099] ④ During the shield tunneling process, strengthen the settlement monitoring of the road surface and adjust the shield tunneling parameters in time according to the monitoring results to ensure safety.

[0100] ⑤ During the shield crossing process, the corresponding pipe segments are grouting holes behind the wall. After the grouting flower pipe is inserted into the wall, deep hole grouting is carried out around the interval structure through the grouting holes behind the wall. The grouting volume and grouting pressure are synchronized. The unconfined uniaxial compressive strength should be no less than 1MPa, such as 2-4MPa. Before large-scale deep hole grouting, grouting tests should be carried out in advance to determine reasonable slurry ratio, grouting pressure and other indicators. If necessary, the grouting pressure and other related parameters can be appropriately adjusted to ensure that the effective diffusion radius is greater than 0.5m, such as 0.6-1m, and meets the relevant requirements of the grouting reinforcement body.

[0101] Monitoring and control measures

[0102] The settlement and differential settlement of underground pipelines and rivers during shield construction are used to determine the safety of underground pipelines and rivers, as well as the reliability of the engineering protection measures adopted.

[0103] Monitoring items and requirements

[0104] 1. Before construction, conduct an investigation on the pipelines and rivers in the area. Based on the investigation, clarify the location, type and positional relationship of the pipelines and rivers and the tunnel. During the excavation construction process, inspect the pipelines in the shield excavation section.

[0105] 2. According to the excavation construction situation, monitoring and measurement are carried out 30m before and after the shield machine and 14m laterally along the direction of the shield machine, especially to increase the density of monitoring points near the pipeline.

[0106] 3. Measure and confirm the vertical and horizontal positions of the power tunnel and river in advance. Displacement monitoring starts when the shield is pushed to 20m away from the power tunnel and river, and monitoring is carried out every 3 hours until three months after the shield construction is completed.

[0107] Monitoring project content and layout principles

[0108] Pipeline settlement: monitor the pipelines within the affected area; the principles for the layout of measuring points are as follows: (1) For pipelines in the main affected area of ​​the shield, a measuring point is arranged every 5 to 10 m above the pipeline; (2) For pipelines in the secondary affected area of ​​the shield, based on the properties of the pipeline, a measuring point is arranged every 20 to 30 m along the direction of the pipeline.

[0109] River sedimentation: monitor rivers within the impact area; measurement point layout principles: (1) The shield mainly affects the rivers in the area, and a measurement point is arranged every 5 to 10 meters along the river bank.

[0110] Monitoring frequency

[0111] The determination of the frequency of project monitoring should meet the requirements of reflecting the important changes of the items measured by the monitored objects without missing the change moments. The monitoring frequency of shield engineering should be determined by comprehensively considering the shield type, different construction stages of shield and underground engineering, changes in the surrounding environment, natural conditions and local experience. In the absence of data anomalies and signs of accidents, the monitoring frequency can be determined according to the construction progress.

[0112] Principles and methods of measuring point layout

[0113] Measuring point layout principles

[0114] 1. Surface road settlement measurement points

[0115] In principle, they should be laid out at an average of 50 meters along the center line of the tunnel, 30 to 40 meters on important roads, and cross-section measuring points should be laid out when encountering cross-roads or overpasses, generally 5 to 7 measuring points. An appropriate number of surface settlement measuring points should be laid out on the surface of the square on both sides of the line and between the buildings within 30 meters of the edge of the subway structure. Measuring points should also be laid out on roads, surfaces, buildings, etc. within 30 meters of the edge line of the station entrance and exit.

[0116] 2. Pipeline settlement measurement points

[0117] According to the underground pipeline map and the control standard of the local inclination value between the two joints of the pipeline, the measuring points are arranged, and the properties of the pipelines such as gas, water supply, electricity, and sewage are distinguished. Generally, they are arranged 40 to 50 meters along the pipeline direction, and important pipelines are arranged at 30 meters. The location of the measuring points and the buried signs should be able to reflect the settlement changes of the pipeline.

[0118] 3. Building (structure) settlement and tilt measurement points

[0119] In principle, the measuring points should be arranged at locations that can control the settlement and tilt of buildings (structures), as well as locations where the shape of longer buildings changes. The measuring points are buried in the vertical structure of the building (structure), with 4 to 6 points arranged for each building. The number of points can be reduced appropriately for dense multi-story buildings. When the building (structure) tilts, generally a group of measuring points is arranged on the side close to the line first, and a group of measuring points is encrypted on the adjacent side if necessary.

[0120] Measurement point layout method

[0121] 1. The buried method of underground pipeline settlement monitoring points is as follows:

[0122] (1) For underground pipelines with inspection wells, the manhole covers should be opened and the measuring points should be directly laid out on the pipelines or on the pipeline carriers.

[0123] (2) For pipelines without inspection wells but with conditions for excavation, the pipelines should be exposed by excavation and the measuring points should be placed directly on the pipelines.

[0124] (3) For pipelines without inspection wells or excavation conditions, indirect observation points can be buried on the corresponding surface.

[0125] (4) When arranging monitoring points on the pipeline, for closed pipelines, clamp-type buried points can be used, and for open pipelines, monitoring point supports can be made on the pipeline or pipeline piers.

[0126] 2. Before and after the shield tunnel passes through the Shuanglong River, the ground monitoring and measurement shall be carried out. In the section under the Shuanglong River, a section shall be set up every 10m, and a monitoring point shall be buried longitudinally at the center of the Shuanglong River, the edges on both sides, and 3m outside. Figure 5-1 shown.

[0127] Calculation and observation methods and requirements

[0128] The underground pipeline settlement monitoring points adopt the geometric leveling method, using a precision level to measure the outbound and return routes. Its technical requirements and observation precautions are consistent with those of the surface settlement monitoring points. After the results are qualified, the height difference between each measuring point and the leveling origin is calculated. By counting and comparing the height difference values ​​of each time, the settlement value of each underground pipeline settlement monitoring point can be obtained.

[0129] The differential settlement of underground pipelines can be calculated through the observation results of pipeline settlement to obtain the uneven settlement (differential settlement). The settlement values ​​ΔS of points A and B can be obtained by leveling two adjacent points A and B on the structure (the distance b can be measured). A , ΔS B Finally, the uneven settlement (tilt) calculation is performed.

[0130]

[0131] The angle θ is the inclination angle produced by the object being sought.

[0132] When burying underground pipeline settlement monitoring points, attention should be paid to accurately investigate and verify the pipeline location to ensure that the measuring points can accurately reflect the deformation of the pipeline. Before burying the measuring points by drilling, it should be found out whether there are other pipelines to ensure the safety of burial. When burying the pipeline settlement monitoring points without inspection wells, the hole diameter of the buried indirect measuring points shall not be less than 150mm.

[0133] Control benchmark and alarm value

[0134] Monitoring and early warning is one of the purposes of monitoring work, and is an important measure to prevent engineering accidents and ensure the safety of engineering structures and surrounding environments. Monitoring control values ​​and early warning values ​​are the prerequisites for the implementation of monitoring work, and are important bases for judging whether the engineering structures and surrounding environments are in normal, abnormal, and dangerous states during the monitoring period. Therefore, it is necessary to determine monitoring control values ​​and alarm values. Monitoring control values ​​and alarm values ​​are generally controlled by the two indicators of monitoring variable accumulation value and change rate.

[0135] The monitoring control values ​​and alarm values ​​adopted in this project are as follows: the control benchmark and alarm values ​​of the power tunnel are: vertical displacement 10mm, horizontal displacement 10mm; clearance convergence settlement / uplift 10mm; the control standards and alarm values ​​of the monitored river section are: vertical displacement 20mm, horizontal displacement 20mm, clearance convergence settlement / uplift 30mm.

[0136] In order to ensure the authenticity, reliability and continuity of measurement data, quality assurance measures for the monitoring feedback procedure should be formulated.

[0137] Safety construction guarantee measures

[0138] The following measures should be taken when the shield tunnel passes under the power tunnel

[0139] (1) Strictly control the shield tunneling parameters, mainly in terms of controlling the stratum loss rate within 2%, and the shield advancement pressure shall not be less than 0.8 times the theoretical water and soil pressure. After the shield passes through, synchronous grouting shall be carried out in a timely manner, and attention shall be paid to controlling the synchronous grouting volume and pressure. The unconfined uniaxial compressive strength shall not be less than 1MPa.

[0140] (2) Strengthen monitoring and measurement, implement fully informationized construction during the shield tunneling process, and closely monitor the displacement of the power tunnel and ground subsidence.

[0141] (3) Before the shield machine is used to pass through the power tunnel, a trial excavation construction should be carried out to obtain the necessary excavation parameters such as the shield machine's thrust pressure and ground settlement, so as to facilitate the construction.

[0142] (4) Additional grouting holes are added on the pipe segments, and secondary grouting reinforcement is carried out on the left and right lines. The length of the grouting reinforcement in the left line is 9 meters, and the length of the grouting reinforcement in the right line is 9 meters.

[0143] The following measures should be taken during the shield tunneling period:

[0144] (1) Before construction, based on the characteristics of environmental risk projects, possible accidents should be predicted and a comprehensive emergency plan should be formulated. The construction plan and emergency plan should be submitted to the property rights unit for filing;

[0145] (2) Before crossing, the shield machine should be adjusted and ensured to perform well, and the excavation parameters should be strictly controlled to ensure uniform speed. During the construction process, the excavation soil pressure and the amount of excavation should be strictly controlled. Strict control of shield excavation parameters is mainly reflected in controlling the stratum loss rate within 2% and the shield thrust pressure to be no less than 0.8 times the theoretical water and soil pressure. After the shield passes, synchronous grouting should be carried out in a timely manner, and attention should be paid to controlling the synchronous grouting volume and grouting pressure. The unconfined uniaxial compressive strength should be no less than 1MPa.

[0146] (3) The shield tail should be grouted in time to fill the gap between the pipe segment and the soil, and the grouting volume and grouting pressure should be strictly controlled. The cement slurry ratio, grouting pressure and other parameters should follow the principle of trial before doing, and the water-cement ratio should be 1:1. The 28d unconfined compressive strength of the grouting reinforced soil should not be less than 1MPa, and the permeability coefficient should not be greater than 10-6 / cm / s. Add grouting holes on the pipe segment to carry out secondary grouting reinforcement for the double lines. The length of the C2 line grouting reinforcement in the tunnel is 40 meters, and the length of the R2 line grouting reinforcement in the tunnel is 50 meters.

[0147] (4) During the shield tunneling process, strengthen the settlement monitoring of the road surface and adjust the shield tunneling parameters in time according to the monitoring results to ensure safety.

[0148] (5) During the shield tunneling process, grouting holes are drilled behind the wall of the corresponding segments. After the grouting flower tube is inserted into the wall, deep hole grouting is carried out around the interval structure through the grouting holes behind the wall. The grouting volume and grouting pressure are synchronized. The unconfined uniaxial compressive strength should be no less than 1MPa. Before large-scale deep hole grouting, grouting tests should be carried out in advance to determine reasonable slurry ratio, grouting pressure and other indicators. If necessary, relevant parameters such as grouting pressure can be appropriately adjusted to ensure that the effective diffusion radius is greater than 0.5m and meets the relevant requirements of the grouting reinforcement body.

[0149] The present invention adopts the shield construction and monitoring method of the river power tunnel, and improves each step, so that the shield section underpasses the river and the power tunnel construction under the river achieves the purpose of high-quality and safe underpass.

Claims

1. A shield construction and monitoring method for a dangerous river power tunnel, comprising the following steps: (1) Reinforcement of river channels; reinforcement of power tunnels under rivers; (2) Shield construction under the river; (3) Construction of power tunnels under rivers using shield technology; (4) Construction monitoring; The shield construction under step (2) and step (3) includes the following steps: setting the construction stratum loss rate within 2%, the shield pushing pressure greater than 0.8 times the theoretical water-soil pressure, timely synchronous grouting after the shield passes, and controlling the synchronous grouting volume and grouting pressure so that the unconfined uniaxial compressive strength should be greater than 1MPa; timely grouting the shield tail to fill the gap between the pipe segment and the soil, the weight ratio of water to fly ash is (0.5-1.5): (0.5-1.5); grouting The 28-day unconfined compressive strength of the solid soil is greater than 1MPa, and the permeability coefficient is less than 10cm / s; additional grouting holes are added to the segments, and secondary grouting reinforcement is carried out in the tunnel for the left and right construction lines; during the shield crossing process, grouting holes are made behind the wall for the corresponding segments. After the grouting flower pipe is inserted into the wall, deep hole grouting is carried out around the interval structure through the grouting holes behind the wall. The synchronous grouting volume and grouting pressure are controlled so that the unconfined uniaxial compressive strength should be greater than 1MPa, and the effective diffusion radius of the grouting is greater than 0.5m.

2. According to the shield construction and monitoring method of the power tunnel in the dangerous river of claim 1, the step (1) adopts sandbag cofferdam to stop water for river channel reinforcement, and the water-facing surface of the cofferdam is fully covered with water-stop film, and the film is flatly laid and compacted with small sandbags, with overlapping and staggered seams between layers, the riverbed is leveled, steel mesh is laid, and concrete is poured to seal the bottom.

3. According to the shield construction and monitoring method for a dangerous river power tunnel according to claim 1 or 2, the step (4) construction monitoring comprises the following steps: (1) Pipeline settlement: monitor the pipelines within the affected area; measurement point layout method: for pipelines within the shield influence area, a measurement point is arranged every 5 to 10 meters above the pipeline; or, a measurement point is arranged every 20 to 30 meters along the direction of the pipeline; (2) River sedimentation: monitor the rivers within the impact area; measurement point layout method: for rivers within the shield impact area, a measurement point is arranged every 5 to 10 meters along the river bank.

4. According to the shield construction and monitoring method of the dangerous river power tunnel in claim 3, the monitoring measurement and control measures include: (1) Monitoring and measurement are carried out along the direction of the shield machine, 30 m in front and behind the shield machine, and 14 m in the horizontal direction; (2) Displacement monitoring starts when the shield is pushed to 20 m away from the power tunnel or river, and is carried out every 3 hours until three months after the shield construction is completed.

5. According to the shield construction and monitoring method for dangerous river power tunnels in claim 1, the step (4) construction monitoring further includes the following steps: (1) Surface road settlement measurement points: They are arranged at an average of 50 meters along the center line of the tunnel. When encountering cross-roads or overpasses, 5 to 7 cross-section measurement points are arranged; surface settlement measurement points are arranged on the surface of the square on both sides of the line and between the buildings within 30 meters of the edge of the subway structure; measurement points are arranged on the roads, surfaces, and buildings within 30 meters of the edge line of the station entrance and exit; (2) Underground pipeline settlement measurement points: arranged 40 to 50 meters along the pipeline direction; (3) Settlement and inclination measuring points of buildings or structures: The measuring points are buried in the vertical structure of the building, with 4 to 6 points arranged for each building.

6. According to the shield construction and monitoring method for dangerous river power tunnels in claim 5, the method for burying the underground pipeline settlement monitoring points (2) is as follows: 1) Underground pipelines with inspection wells: Open the well cover and directly lay out the measuring points on the pipeline or on the pipeline carrier; 2) Pipelines without inspection wells but with excavation conditions: Excavate and expose the pipelines, and place the measuring points directly on the pipelines; 3) For pipelines without inspection wells or excavation conditions: bury indirect observation points on the corresponding surface; 4) When laying out monitoring points on the pipeline, use a clamp-type buried point for closed pipelines; for open pipelines, make monitoring point supports on the pipeline or pipeline piers; 5) Within the scope of the river section under the river, a section is set up every 10m, and a monitoring point is buried longitudinally in the center of the river, on the edges on both sides, and 3m outward.

7. According to the shield construction and monitoring method of the dangerous river power tunnel in claim 1, the control benchmark and alarm value of the monitored power tunnel shall not exceed the following values: vertical displacement 10mm, horizontal displacement 10mm; clearance convergence settlement / uplift 10mm; the control standard and alarm value of the monitored river section shall be: vertical displacement 20mm, horizontal displacement 20mm, clearance convergence settlement / uplift 30mm.

8. The shield construction and monitoring method for power tunnels along dangerous rivers according to claim 4 also includes the following emergency measures for power tunnel construction: using grouting to reinforce the soil within 6.0m around the power tunnel, using pure cement slurry as the ground grouting material, with a grouting pressure of 1 to 2MPa, and a soil reinforcement depth of 8.0m; performing grouting reinforcement in the tunnel; using pure cement slurry with a grouting pressure of 0.5 to 0.6MPa.

Images