A construction method for a shield tunneling under dangerous pipelines

Abstract

The present invention discloses a construction method for a shield tunneling under pipelines, which includes the following steps: Step 1: On-site inspection; Step 2: Monitoring surface settlement and uplift; Step 3: Monitoring the deformation of buildings; Step 4: Monitoring the soil stratification and vertical displacement. The present invention has improved measures for each step, enabling the construction of a shield tunnel section under complex buildings to achieve the purpose of safe tunneling.

Description

Technical Field

[0001] The present invention relates to the field of tunnel construction, and in particular to a construction method for a shield tunneling under dangerous pipelines. Background Art

[0002] During the construction of crossing dangerous pipeline sources under the urban surface, an innovative construction method for special construction sections is required to improve the existing construction method of shield tunneling under dangerous pipelines around the existing tunnel, so as to achieve the purpose of fast and safe construction. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a construction method for a shield tunneling under dangerous pipelines, providing a new construction method.

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

[0005] A construction method for a shield tunneling under pipelines includes the following steps:

[0006] (1) Optimize the tunneling parameters, ground settlement control standards, and pipeline settlement control standards for crossing dangerous pipeline sources, find out the relative relationship between the construction environment and the tunneling parameters. The two types of geological formations in the lower side and the side-crossing dangerous pipeline source sections of the interval are the full-section mudstone formation and the composite formation of upper sand and gravel and lower mudstone. The optimized settings of the tunneling parameters are as follows:

[0007] The tunneling parameters for the shield tunneling under or through pipelines in the full-section mudstone formation are:

[0008]

[0009] The tunneling parameters for the shield tunneling under / through pipelines in the composite formation of upper gravel and lower mudstone are:

[0010]

[0011] The dangerous pipeline sources are rainwater pipes, power pipelines, high-pressure gas pipelines, and sewage pipes;

[0012] (2) Reinforce the dangerous pipeline sources to be crossed;

[0013] (3) Monitor the ground settlement;

[0014] (4) Monitor the settlement of underground pipelines;

[0015] (4) Set the monitoring control reference and alarm values.

[0016] Preferably, the reinforcement of the shield tunneling under rainwater pipes and power pipelines includes the following steps:

[0017] (1) Before the shield tunneling passes through the pipeline, stop the machine 10m ahead to check the machine condition, and open the chamber to check the cutters to ensure continuous tunneling when the shield passes through the hazard source;

[0018] (2) Control the tunneling parameters: clarify the mileage of the rainwater pipe and the power pipeline and their positional relationship with the interval tunnel. During the construction process, control the fluctuation of the tunneling earth pressure within the range of 0.1 bar, and use foam for soft soil pressure;

[0019] (3) Ensure the improvement of muck by increasing the amount of foam agent and water addition to control the muck output; during the shield tunneling process, evenly control the muck output according to the footage and earth pressure. At the same time, the muck output and the grouting volume should be matched;

[0020] (4) According to the surface settlement situation and the tunneling situation, when the segment is pulled out of the shield tail for 5 - 10 rings, use a double - liquid grouting machine to conduct secondary grouting reinforcement on the back of the upper part of the segment to fill the construction gap behind the segment and shorten the setting time of the synchronous grouting slurry; reinforce the formation through the reserved grouting holes in the segment. The reinforcement form is mainly double - liquid slurry and supplemented by single - liquid cement slurry. The reinforcement is carried out by in - tunnel grouting reinforcement within the range of 120° outward expansion of 1.5m at the crown of the left - line and right - line tunnels;

[0021] (5) Use high - quality shield tail grease to improve the sealing effect and prevent shield tail slurry leakage;

[0022] (6) Monitor the stress and strain of the crossing section;

[0023] (7) When the interval tunnel passes through this section, use segments with additional grouting holes, and supplement grouting to reinforce the formation in a timely manner according to the monitoring situation;

[0024] (8) Strengthen the monitoring and measurement, and monitor the displacement of the power tunnel and the ground settlement;

[0025] (9) Conduct test tunneling before the shield construction passes under the power tunnel to obtain the tunneling parameters for shield propulsion.

[0026] Preferably, the reinforcement for the shield to pass under the sewage pipeline includes the following steps:

[0027] (1) Before the shield passes under the pipeline, stop the machine 10m ahead to check the machine condition, and open the chamber to check the cutters to ensure continuous tunneling when the shield passes through the hazard source;

[0028] (2) Control the shield tunneling parameters: control the ground loss rate within 2%, and the shield propulsion earth pressure should not be less than 0.8 times the theoretical water and soil pressure; conduct synchronous grouting in a timely manner after the shield passes through, and control the synchronous grouting volume and grouting pressure. The unconfined uniaxial compressive strength should not be less than 1MPa; clarify the mileage of the drainage pipeline and its positional relationship with the interval tunnel;

[0029] (3) Ensure the improvement effect of muck by increasing the foaming agent and water addition, control the muck output, reduce the cutter head rotation speed and propulsion speed to ensure the shield tunneling smoothly and appropriately increase the soil pressure;

[0030] (4) According to the surface settlement situation and tunneling conditions, when the segment is pulled out of the shield tail for 5 - 10 rings, use a double - liquid grouting machine to conduct secondary grouting reinforcement on the back of the upper part of the segment to fill the construction gap behind the segment and shorten the setting time of the synchronous grouting slurry; strengthen the in - tunnel grouting measures, reinforce the formation through the reserved grouting holes on the segment, and mainly use double - liquid slurry and supplemented by single - liquid cement slurry for reinforcement to reduce the impact of the shield machine on the pipeline structure; the in - tunnel grouting reinforcement lengths for both the left and right lines are 30 meters; after the shield passes through, decide whether to conduct follow - up grouting according to the monitoring results. Reinforcement scope: The reinforcement scope for the straight - through section is to conduct in - tunnel secondary grouting within a range of 360° around the tunnel extended outwards by 1.5 m;

[0031] (5) Use high - quality shield tail grease to improve the sealing effect and prevent shield tail slurry leakage;

[0032] (6) Monitor the stress and strain during the crossing section;

[0033] (7) When the interval tunnel passes through this section, use segments with additional grouting holes and conduct supplementary grouting reinforcement on the formation in a timely manner according to the monitoring situation.

[0034] Preferably, the reinforcement for the shield tunneling under the buried high - pressure gas pipeline includes the following steps:

[0035] (1) Strictly control the shield tunneling parameters, mainly reflected in controlling the ground loss rate within 2% and the shield propulsion pressure not less than 0.8 times the theoretical water and soil pressure. Synchronous grouting shall be carried out in a timely manner after the shield passes through, and pay attention to controlling the synchronous grouting volume and grouting pressure. The unconfined uniaxial compressive strength should not be less than 1 MPa, and clarify the mileage of the gas pipeline and its positional relationship with the interval tunnel;

[0036] (2) Ensure the improvement effect of muck by increasing the foaming agent and water addition, strictly control the muck output, reduce the cutter head rotation speed and propulsion speed to ensure the shield tunneling smoothly and appropriately increase the soil pressure;

[0037] (3) According to the surface settlement situation and tunneling conditions, when the segment is pulled out of the shield tail for 5 - 10 rings, select an appropriate time to conduct secondary grouting reinforcement on the back of the upper part of the segment with a double - liquid grouting machine to fill the construction gap behind the segment and shorten the setting time of the synchronous grouting slurry; conduct secondary grouting reinforcement on the left and right in - tunnel segments by adding grouting holes on the segment. The reinforcement lengths for both the left and right lines are 10 meters. The reinforcement scope for the crossing section is to conduct in - tunnel secondary grouting within a range of 360° around the tunnel extended outwards by 1.5 m;

[0038] (4) Use high - quality shield tail grease to improve the sealing effect and prevent shield tail slurry leakage;

[0039] (5) Monitor the stress and strain of the crossing section.

[0040] (6) When the interval tunnel passes through this section, use segment linings with additional grouting holes and reinforce the formation by supplementary grouting in a timely manner according to the monitoring situation.

[0041] Preferably, the reinforcement for the shield tunneling passing by the sewage pipeline includes the following steps: For shield tunneling of the sewage pipe, take measures such as route adjustment, diversion, isolation or reinforcement. Through the centralized diversion method, submersible sewage pumps are used as drainage equipment, and the sewage is discharged by the submersible sewage pumps after the sewage main pipe is blocked.

[0042] (1) Strictly control the shield tunneling parameters, mainly reflected in controlling the ground loss rate within 2% and the shield propulsion pressure not less than 0.8 times the theoretical soil and water pressure. Synchronous grouting shall be carried out in a timely manner after the shield passes through, and attention shall be paid to controlling the synchronous grouting volume and grouting pressure. The unconfined uniaxial compressive strength shall not be less than 1 MPa.

[0043] (2) The cement slurry ratio and grouting pressure parameters shall follow the principle of "testing first and then doing". The water-cement ratio is 1:1; the unconfined compressive strength of the grouted and reinforced soil after 28 days shall not be less than 1 MPa, and the permeability coefficient shall not be greater than 10-6 / cm / s.

[0044] (3) Add grouting holes to the segment linings for secondary grouting reinforcement of the tunnel in the hole.

[0045] (4) Strengthen the monitoring and measurement. Implement information-based construction throughout the process of shield tunneling, and closely monitor the displacement of buildings and structures and the ground settlement.

[0046] (5) Conduct pilot tunneling construction before the shield tunnels pass by the buildings and structures on the side to obtain the shield tunneling parameters.

[0047] Preferably, the monitoring of the ground settlement includes the following steps:

[0048] Layout of ground settlement monitoring points: Drill holes in the soil layer, set threaded steel bar marking points in the holes. The length of the threaded steel bar marking points is greater than 90 cm. Fill coarse sand between the threaded steel bars and the soil layer. There is a protective cover above the drill hole; the drill hole penetrates the road surface structure layer, the drill hole diameter is about 80 - 130 mm, the depth is about 1 m, the length of the threaded steel bar is greater than 100 cm as the marking point, and it protrudes about 1 - 2 cm above the filled coarse sand surface. The diameter of the steel protective cover is greater than 110 mm; Cure for more than 15 days.

[0049] When the closed leveling route is adopted for observation, observe one-way; when the attached leveling route form is adopted, conduct round-trip observation, and take the average of the two observed elevation differences for adjustment; Observation sequence: Forward measurement: Rear, Front, Front, Rear; Return measurement: Front, Rear, Rear, Front.

[0050] Preferably, it includes the following steps: The underground pipeline monitoring points are arranged on the pipeline, at the positions corresponding to the project, or on the indirectly observed points buried on the corresponding ground surface. Specifically, they are arranged at the nodes, corner points of the pipeline, or the parts sensitive to displacement changes, and the layout spacing is 25m.

[0051] The embedding method of the underground pipeline settlement monitoring points: For the closed pipeline, use a water drill to penetrate the ground hardening layer, dig a hole to the outer retaining wall of the pipeline, put in the steel bar and fill the surrounding with fine sand. The position of the steel bar should be lower than the road surface, and cover the measuring point with a steel protection cover. At the same time, fill the measuring point with fine sand; For the open pipeline, make a monitoring point support on the pipeline or pipeline pier.

[0052] Preferably, the setting of the monitoring control reference and alarm value includes the following steps:

[0053] Adopt two control indicators, namely the cumulative value and the change rate of the monitoring variable, and the parameters are:

[0054]

[0055] Preferably, it also includes the following steps: Carry out monitoring feedback, reporting, disposal, and alarm cancellation emergency rescue measures, and the emergency measures for the power tunnel:

[0056] (1) Reinforce the power tunnel: Grout the soil within a range of 5.0m around the power tunnel. The grouting material on the ground is pure cement slurry, the grouting pressure is 0.2 - 0.4MPa, and the depth of soil reinforcement is 5.0m.

[0057] Grout reinforcement inside the power tunnel: Use pure cement slurry. The grouting pressure is 0.2 - 0.4MPa.

[0058] (2) Emergency measures for abnormal rain and sewage pipes: Take ground grouting and secondary grouting behind the segment in the tunnel.

[0059] (3) Emergency measures for gas pipeline accidents:

[0060] Reinforce the gas pipeline: Grout the soil within a range of 5.0m around the pipeline. The grouting material on the ground is pure cement slurry, the grouting pressure is 0.2 - 0.4MPa, and the depth of soil reinforcement is 8.0m.

[0061] Carry out grouting reinforcement inside the tunnel: Use pure cement slurry, and the grouting pressure is 0.2 - 0.4MPa.

[0062] In the present invention, being greater than or less than a certain value includes the preferred value of this numerical value.

[0063] The present invention has the following advantages compared with the prior art:

[0064] The present invention achieves the purpose of rapid and safe construction through the following steps: (1) optimizing the tunneling parameters, ground settlement control standards, and pipeline settlement control standards for crossing under dangerous source pipelines, and finding out the relative relationship between the construction environment and tunneling parameters; (2) strengthening the dangerous source pipelines to be crossed; (3) monitoring the ground settlement; (4) monitoring the settlement of underground pipelines; (5) setting monitoring control benchmarks and alarm values, etc., through repeated tests and explorations during the construction of underground dangerous source pipeline tunnels in cross-section mudstone strata and composite strata with sandy gravel in the upper part and mudstone in the lower part. Description of the Drawings

[0065] Figure 1-1 Example of the plan position relationship diagram of the shield tunnel section and the rainwater pipe and power pipeline

[0066] Figure 1-2 Example of the in-tunnel reinforcement schematic diagram of the interval tunnel crossing under the rainwater pipe

[0067] Figure 2-1 Example of the plan position relationship diagram of the shield tunnel section and the pipelines of the newly built sewage treatment plant

[0068] Figure 2-2 Cross-section diagram of the DN3200 sewage tunnel

[0069] Figure 2-3 Schematic diagram of the reinforcement of the shield tunneling under the pipelines of the newly built sewage treatment plant

[0070] Figure 3 Schematic diagram of the reinforcement of the shield tunneling under the DN1016 high-pressure gas pipeline

[0071] Figure 4 Schematic diagram of the reinforcement of the shield tunneling under the sewage pipe

[0072] Figure 5 Elevation layout diagram of the pumping from the sewage inspection well to the flat pipeline of the inspection well and the setting of the water pump

[0073] Figure 6 Schematic diagram of the structure of the ground settlement monitoring device of the present invention

[0074] Figure 7 Schematic diagram of the structure of the underground pipeline settlement monitoring device of the present invention

[0075] 1 - Pipeline, 2 - Soil layer, 3 - Sand layer, 4 - Steel pipe protection well, 5 - Rebar marking point with a diameter of 18 mm, 6 - Steel protection cover. Detailed Description of the Invention

[0076] Such as Figure 1-1 、 Figure 1-2 、 Figure 2-1 、 Figure 2-2 、 Figure 2-3 、 Figure 3 、 Figure 4 、Figure 5 , Figure 6 , Figure 7 A shield tunneling method for passing under pipelines, which is carried out in the shield tunnel section between Jinshilu Station and Sanselü Station in Chengdu. The strata passed through by the shield tunnel section are mainly mudstone.

[0077] In the shield tunnel section from Jinshilu Station to Sanselü Station to Zhonghe Station, the main pipelines passing under are: pipelines of the newly built sewage treatment plant, planned pipelines of high-pressure gas pipelines, and sewage pipes. The ground conditions along the line are complex. As Figure 1-1 shown.

[0078] In this bid section, 4 φ6280 earth pressure balance shield machines are adopted for the shield tunnel section. The construction steps for the shield to pass under the pipelines are as follows:

[0079] 1. Guarantee measures for construction preparation and ensuring continuous tunneling during passing under:

[0080] Before the shield machine passes under the hazard source, conduct a comprehensive and detailed overhaul of the shield machine and its trailing equipment. Focus on overhauling the grouting system, control circuit and hydraulic system, tail seal brush, gantry crane brake system, traveling system, battery car brake and circuit of the shield machine. Immediately replace the damaged parts, promptly eliminate the parts with potential faults, and timely add grease or lubricating oil to each lubricating part. Especially clean and dredge the grouting pipeline to avoid blockage of the conveying pipe during the shield passing under the risk source, resulting in interruption of slurry supply and causing the shield machine to stop. At the same time, monitor the tail seal system to ensure that there is no slurry leakage during passing under, so as to ensure the grouting volume.

[0081] The main materials for shield construction are reinforced concrete lining segments, which are special segments for passing under pipelines, waterproof materials, and raw materials for slurry mixing, including cement, sand, fly ash, and bentonite. Before passing under the pipelines, count the inventory quantities of various raw materials to ensure sufficient quantities, and closely monitor the inventory quantities of each raw material during the shield tunneling. Statistically count the material stock in the warehouse every day. When the quantity is lower than 1 / 2 of the warehouse capacity, immediately replenish it, and strictly control the quality of raw materials, resolutely preventing unqualified materials from entering the site. During the construction period, consider the impact of weather conditions on material supply, pay attention to the weather conditions in the next two days every day, and reserve the raw materials affected by the weather in advance.

[0082] Technical preparation

[0083] When the pipeline is penetrated from below / on the side in the Jin-San-Zhong section, the main technical work is to optimize the tunneling parameters, analyze the geological conditions, hydrological conditions, tunnel overburden thickness, relative positions with pipelines and buildings within the penetration range, establish reasonable tunneling parameters, and control the ground settlement and pipeline settlement to achieve the purpose of protecting the pipeline penetrated from below / on the side. In order to find out the relative relationship between the construction environment and tunneling parameters, the tunneling parameters and ground settlement monitoring values during the previous construction process were analyzed and summarized to determine the construction parameters in the tunneling project. The geology of the section where the pipeline is penetrated from below / on the side in this section is divided into two categories: the full-section mudstone formation and the composite formation with sand and gravel in the upper part and mudstone in the lower part. The optimization of tunneling parameters for these two types of formations is shown in the following table: Technical disclosure is provided to all on-site management personnel and the operation level, so that every construction worker can fully understand the technical requirements during the stage of the shield tunneling through the hazard source.

[0084] Optimization Table of Shield Tunneling Parameters for Penetrating Pipelines from Below / on the Side in the Mudstone Formation of the Jin-San-Zhong Section

[0085]

[0086] Optimization Table of Shield Tunneling Parameters for Penetrating Pipelines from Below / on the Side in the Composite Formation with Gravel in the Upper Part and Mudstone in the Lower Part of the Jin-San-Zhong Section

[0087]

[0088]

[0089] Meanwhile, during the stage of simultaneous tunneling from below, good muck improvement should be carried out, adopting the muck improvement method combining foam and bentonite, with double control of the muck output volume and weighing, having good fluidity; low permeability; reducing the cutter head torque, reducing tool wear, and having good lubricity. The position and quantity of muck improvement directly affect the state of the muck in the soil bin and the probability of mud cake formation.

[0090] Maintenance of Equipment

[0091] During the tunneling construction of penetrating pipelines from below / on the side, the continuity of construction is crucial. Before the shield tunnels through the pipeline from below / on the side, a comprehensive and systematic maintenance of the equipment is carried out 50m ahead, including the maintenance of gantry cranes, mixing plants, rear support equipment, electrical systems and hydraulic systems inside the shield machine, and the premature procurement of vulnerable parts as emergency spare parts to ensure smooth continuous tunneling through the pipeline from below / on the side without stopping the machine.

[0092] 2. Shield Tunneling under the Rainwater Pipe and Power Pipeline (Jin-San Section)

[0093] Spatial position relationship: In the range of mileage YDK42+813.00~840.000 (ZDK42+813.000~840.000), the left and right lines of the interval tunnel pass under the rainwater pipe and the 220kv power pipeline respectively. The size of the brick rainwater pipe is 2100mmx2300mm, and the size of the 220kv power pipeline is 2200mmx2000mm. Both the rainwater and power pipelines are laid along Jinjiang Avenue. The buried depth of the rainwater pipe is about 2m, and the buried depth of the power pipeline is about 4m. The overburden of the shield tunnel section is about 15m. The rainwater pipe is about 10.9m away from the top of the tunnel, and the power pipe is about 9.3m away from the top of the tunnel.

[0094] Such as Figure 1-2 , the shield construction protection measures:

[0095] Shield construction control:

[0096] When the shield is tunneling under, minimizing the ground deformation caused during the shield construction process is an effective means to protect the pipelines. During the underpass, the quality is mainly controlled from aspects such as controlling the tunneling parameters, improving the grouting quality in the tunnel, and monitoring and measurement.

[0097] (1) Before the shield passes through the pipeline, stop the machine 10m ahead to check the machine condition. If necessary, open the chamber to check the cutters to ensure continuous tunneling when the shield passes through the hazard source.

[0098] (2) Strictly control the tunneling parameters. Clearly define the mileage of the rainwater pipe and the power pipeline and their positional relationship with the interval tunnel. During the construction process, strictly control the tunneling earth pressure. During the shield tunneling process, strictly maintain the stability of the earth pressure on the tunneling face. The earth pressure fluctuation is within the range of 0.1bar. Reasonably use foam and other soft soil pressures to prevent the flow of groundwater, and ensure that the settlement caused by the shield tunneling excavation is within the allowable range. When the machine stops, send someone to closely monitor the change of the earth pressure. If it exceeds the predetermined value, take measures in time. Keep the earth pressure uniform to prevent it from being too high or too low. It is required that the shield machine driver should operate carefully during the operation, and the propulsion speed, screw rotation speed, and cutter head rotation speed should all have a smooth transition. The control of the earth pressure should be closely coordinated with the ground monitoring. If the ground monitoring finds that the ground in front of the cutter head always bulges beyond the warning value, at this time, the earth pressure should be appropriately reduced; on the contrary, the earth pressure should be increased. The ground monitoring of the earth pressure forms a good feedback channel to facilitate the shield driver to adjust the earth pressure control parameters in time.

[0099] (3) Ensure the effect of muck improvement by increasing the amount of foam agent and water addition, strictly control the muck output, reduce the cutter head rotation speed and propulsion speed to ensure the shield passes through evenly and appropriately increase the earth pressure. During the shield tunneling process, strictly control the muck output according to the footage and the earth pressure evenly, and at the same time, the muck output and the grouting volume should be matched.

[0100] (4) According to the surface settlement situation and tunneling conditions, when the segment is pulled out of the shield tail by 5 - 10 rings, select an appropriate time to conduct secondary grouting reinforcement on the back of the upper part of the segment with a double - liquid grouting machine to fill the construction voids behind the segment and shorten the setting time of the synchronous grouting slurry;

[0101] (5) Use high - quality shield tail grease to improve the sealing effect and prevent shield tail slurry leakage;

[0102] (6) Monitor the stress and strain of the crossing section, and arrange special personnel to conduct surface inspections and monitoring;

[0103] (7) When the interval tunnel passes through this section, use Type A segments with additional grouting holes, and conduct supplementary grouting to reinforce the formation in a timely manner according to the monitoring situation;

[0104] (8) Strengthen the monitoring and measurement. Implement full - information construction during the shield tunneling process, and closely monitor the displacement of the power tunnel and ground settlement;

[0105] (9) Conduct test tunneling before the shield machine tunnels under the power tunnel to obtain necessary tunneling parameters such as shield propulsion pressure and ground settlement, and implement information - based construction.

[0106] In - tunnel reinforcement measures

[0107] After the shield machine tunnels under the 220KV power pipe and rainwater pipe, strengthen the in - tunnel grouting measures. Reinforce the formation through the reserved grouting holes in the segments. The reinforcement form is mainly double - liquid grout supplemented by single - liquid cement grout to reduce the impact of the shield machine on the pipeline structure. Conduct in - tunnel grouting reinforcement in the range of 120° outward expansion of 1.5m at the crown of the left - hand and right - hand tunnels. The grouting reinforcement length is 27m for both the left - hand and right - hand tunnels (YDK42 + 813.000~840.000 (500 rings~519 rings), ZDK42 + 813.400~840.000 (497 rings~516 rings)).

[0108] 3. Tunneling under the DN2200 regeneration pipe, DN2400 tail water pipe, and DN3200 sewage tunnel (in the third - middle section), as Figure 2-1 、 Figure 2-2 、 Figure 2-3 shown.

[0109] Spatial position relationship

[0110] The shield tunnel passes under four pipelines of the newly built sewage treatment plant in the range of Y(Z)DK45+010~Y(Z)DK45+040. These four pipelines are: 1> Regeneration pipe DN2200, made of PCCP pipe, 300mm behind the wall, buried 5.4m deep; 2> Two tailwater pipes DN2400, made of PCCP pipe, 300mm behind the wall, buried 7.5m deep; 3> Sewage tunnel DN3200, made of reinforced concrete pipe, 320mm behind the wall, buried 12.4m deep. The shield tunnel is covered with soil for about 18.9m in the range of the pipeline, with a minimum distance of 6.4m from the bottom of the pipeline. The strata in the underpass area are mixed fill, pebbles, and mudstone from top to bottom, and the strata through which the tunnel passes are weathered mudstone.

[0111] Main protection measures for shield tunneling section:

[0112] Shield construction control

[0113] When the shield machine is tunneling underground, minimizing the ground deformation caused by the shield construction process is an effective means to protect the drainage pipe. When tunneling underground, the quality is mainly controlled from multiple aspects such as controlling the tunneling parameters, improving the quality of grouting in the tunnel, and strengthening monitoring and measurement.

[0114] (1) Before the shield machine passes through the pipeline, 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.

[0115] (2) Strictly control the shield tunneling parameters, mainly in terms of controlling the stratum loss rate within 2% and the shield advancement soil pressure not less than 0.8 times, such as 0.8-2 times the theoretical water and soil pressure. After the shield passes, timely synchronous grouting is carried out, and attention is paid to controlling the synchronous grouting volume and grouting pressure. The unconfined uniaxial compressive strength should be not less than 1MPa, such as 1-5MPa. Clarify the mileage of the drainage pipeline and its relationship with the interval tunnel;

[0116] (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;

[0117] (4) According to the surface settlement and excavation conditions, when the segment is dragged out of the shield tail 5-10 rings, choose the right time to use a double-liquid grouting machine to carry out secondary grouting reinforcement behind the segment (upper part) to fill the building gap behind the segment and shorten the solidification time of the synchronous grouting slurry;

[0118] (5) Use high-quality shield tail grease to improve the sealing effect and prevent leakage of shield tail;

[0119] (6) Monitor stress and strain in the crossing section and arrange special personnel to conduct surface inspections and monitoring;

[0120] (7) When the interval tunnel passes through this section, Type A segment linings with additional grouting holes are used, and supplementary grouting is carried out in a timely manner according to the monitoring situation to reinforce the formation.

[0121] Reinforcement measures inside the tunnel

[0122] After the shield tunneling machine passes under the pipelines of the newly built sewage treatment plant, strengthen the grouting measures inside the tunnel, and reinforce the formation through the reserved grouting holes in the segment linings. The main reinforcement form is double-fluid grout supplemented by single-fluid cement grout to reduce the impact of the shield tunneling machine on the pipeline structure. The length of the grouting reinforcement inside the tunnel for both the left line and the right line is 30 meters. After the shield tunneling machine passes through, it is decided whether to carry out follow-up grouting according to the results measured by the monitoring.

[0123] Reinforcement scope

[0124] (1) The reinforcement scope for the directly passing section is to carry out secondary grouting inside the tunnel within a range of 360° around the tunnel with an outward expansion of 1.5 m.

[0125] (2) The reinforced section inside the left-line tunnel is from ZDK45+010.000 to ZDK45+040.000 (ring 788 to ring 808), and the reinforced section inside the right-line tunnel is from YDK45+010.000 to YDK45+040.000 (ring 789 to ring 809).

[0126] 4. The shield tunneling machine passes under the planned DN1016 high-pressure gas pipeline (between section three and section middle), as Figure 3 shown.

[0127] Spatial position relationship

[0128] The shield interval tunnel passes under the planned DN1016 high-pressure gas pipeline from Y(Z)DK45+230.000 to Y(Z)DK45+240. The material of the DN1016 high-pressure gas pipeline is steel pipe, and the maximum buried depth at the pipe bottom is 9.1 m. The pipe material is D1016x19.5mm L415M longitudinal submerged arc welded steel pipe, and the design pressure is 4.0 MPa. It is required to consider protection measures during the pipeline construction to reduce the impact of the subway interval on it. If the pipeline is not buried when the shield tunneling machine passes through this range, the reinforcement measures inside the tunnel may not be implemented. The overburden of the shield interval tunnel is about 23.2 m, and the minimum distance from the pipeline bottom is 14.1 m.

[0129] Main treatment measures

[0130] When the pipeline is laid before the construction of the shield tunnel, the shield tunnel passes under the pipeline in this range. The overburden of the shield tunnel is about 23.2 m, and the minimum distance from the pipeline bottom is 14.1 m. When the shield tunnel passes under the DN1016 large-diameter high-pressure gas pipeline, the following key measures are adopted:

[0131] (1) Strictly control the shield tunneling parameters, mainly reflected in controlling the ground loss rate within 2% and the shield propulsion pressure not less than 0.8, such as 0.8 - 2 times the theoretical water and soil pressure. Synchronous grouting shall be carried out in a timely manner after the shield passes through, and attention shall be paid to controlling the synchronous grouting volume and grouting pressure. The unconfined uniaxial compressive strength shall not be less than 1MPa, such as 1 - 51MPa. Clearly define the mileage of the gas pipeline and its positional relationship with the interval tunnel;

[0132] (2) Ensure the muck improvement effect by increasing the foaming agent and water addition, strictly control the muck output, reduce the cutter head rotation speed and propulsion speed to ensure the shield passes through evenly and appropriately increase the soil pressure;

[0133] (3) According to the surface settlement situation and tunneling situation, when the segment is pulled out of the shield tail for 5 - 10 rings, select an appropriate time to carry out secondary grouting reinforcement on the back of the segment (upper part) with a double - liquid grouting machine to fill the building voids behind the segment and shorten the setting time of the synchronous grouting slurry;

[0134] (4) Use high - quality shield tail grease to improve the sealing effect and prevent shield tail slurry leakage;

[0135] (5) Monitor the stress and strain of the crossing section, arrange special personnel for surface inspection and monitoring;

[0136] (6) When the interval tunnel passes through this section, use segment type A with additional grouting holes, and carry out supplementary grouting in a timely manner according to the monitoring situation to reinforce the formation.

[0137] (7) Carry out secondary grouting reinforcement in the left and right line tunnels through adding grouting holes on the segments. The reinforcement length is 10 meters for both the left and right lines (Y(Z)DK45 + 230.000~Y(Z)DK45 + 240.000), from ring 935 to ring 942 for the left line and from ring 936 to ring 942 for the right line.

[0138] The reinforcement scope of the under - crossing section is to carry out in - tunnel secondary grouting within a range of 360° outward expansion of 1.5m around the tunnel. The specific reinforcement scope is shown in the following figure:

[0139] (8) Strengthen the monitoring and measurement, implement information - based construction throughout the process of shield passing through, and closely monitor the displacement of buildings and structures and the ground settlement.

[0140] 5. The shield passes by the DN1400 sewage main pipe and the street - side shops (between section three and section middle), as Figure 4 、 Figure 5 shown.

[0141] Spatial position relationship

[0142] The shield tunnel section passes under the DN1400 sewage pipe between Y(Z)DK46+040.000 and Y(Z)DK46+050.000. The DN1400 sewage pipe is made of reinforced concrete pipe with a wall thickness of 140mm, and the maximum buried depth is about 10.3m. During the pipeline design stage, it was connected with the subway, and a steel casing has been added to the area where the tunnel passes under. In the area where the shield tunnel section passes under the DN1400 sewage pipe, the overburden of the shield tunnel is about 17.1m, and the minimum distance from the bottom of the pipeline is about 6.8m.

[0143] Main treatment measures for passing under

[0144] The shield tunnel section passes under the DN1400 sewage pipe in the range between the third and the middle sections. The overburden of the shield tunnel is about 17.1m, and the minimum distance from the bottom of the pipeline is about 6.8m. When the shield tunnel passes closely under the large-diameter DN1400 sewage pipe, the key measures are as follows:

[0145] (1) The mileage of the No. 3 connection passage between Sanselulu Station and Zhonghe Station is YDK45+850.000 (ZDK45+848.957). At this mileage, it is 2047.506m away from the shield starting end, between rings 1363 and 1367. The connection passage will be used as a cutter changing point. Before passing under or beside the DN1400 sewage pipe, the cutters will be inspected and replaced at this cutter changing point, 137 rings away from the position of the pipeline to be passed under, to ensure the normal tunneling of the shield machine during passing under or beside the sewage pipeline.

[0146] (2) Strictly control the shield tunneling parameters, mainly reflected in controlling the ground loss rate within 2% and the shield propulsion pressure not less than 0.8 times the theoretical water and soil pressure. Synchronous grouting shall be carried out in a timely manner after the shield passes, and attention shall be paid to controlling the synchronous grouting volume and grouting pressure. The unconfined uniaxial compressive strength shall not be less than 1MPa. Clearly define the mileage of the sewage pipeline and its positional relationship with the tunnel section;

[0147] (3) Ensure the muck improvement effect by increasing the amount of foaming agent and water addition, strictly control the muck output, reduce the cutter head rotation speed and propulsion speed to ensure the shield passes through evenly and appropriately increase the soil pressure;

[0148] (4) According to the surface settlement situation and tunneling situation, when the segment is pulled out of the shield tail for 5 - 10 rings, select an appropriate time to carry out secondary grouting reinforcement on the back of the upper part of the segment with a double-fluid grouting machine to fill the construction gap behind the segment and shorten the setting time of the synchronous grouting slurry;

[0149] (5) Use high-quality shield tail grease to improve the sealing effect and prevent shield tail slurry leakage;

[0150] (6) Monitor the stress and strain of the crossing section, arrange special personnel for surface inspection and monitoring;

[0151] (7) When the interval tunnel passes through this section, Type A segment with additional grouting holes is used, and supplementary grouting is carried out in a timely manner according to the monitoring situation to reinforce the formation.

[0152] (8) Secondary grouting reinforcement is carried out in the left and right line tunnels by adding grouting holes on the segments. The reinforcement lengths of both the left and right lines are 10 meters (Y(Z)DK46 + 040.000~Y(Z)DK46 + 050.000), from Ring 1473 to Ring 1480 for the left line and from Ring 1476 to Ring 1482 for the right line. The reinforcement range for the undercrossing section is to carry out secondary grouting in the tunnel within the range of 180° outward expansion of 1.5 m from the tunnel crown.

[0153] (9) Strengthen the monitoring and measurement, implement information-based construction throughout the process of shield tunneling, and closely monitor the displacement of buildings and structures and the ground settlement.

[0154] 6. Main treatment measures for side passing, as Figure 5 shown.

[0155] For the DN1400 sewage pipe in the three - middle interval, the minimum horizontal distance from the tunnel is 2010 mm, and the minimum vertical distance from the tunnel is 2300 mm. The shield construction is relatively dangerous. Effective measures such as route adjustment, diversion, isolation or reinforcement should be taken to reduce the risk of sewage pipe bursting. After discussion with the design and geological exploration units, since the conditions for route adjustment, isolation or reinforcement are not available, the sewage in the 2# inspection well can be centrally diverted to the 3# inspection well through centralized diversion to ensure that there is no water in the DN1400 sewage pipe within this range during the shield undercrossing or side - passing construction.

[0156] Check calculation of the daily sewage flow of the DN1400 sewage pipe

[0157] The design flow of the sewage pipeline system is the maximum flow that the sewage pipeline and its appurtenances can ensure to pass through. Usually, the maximum daily maximum hourly flow is used as the design flow of the sewage pipeline system, and its unit is L / s. It includes two major parts: the design flow of domestic sewage and the design flow of industrial wastewater. After investigation, it is found that only domestic sewage is involved in the sewage pipeline within the construction area.

[0158] Check calculation of the full - pipe flow of the DN1400 sewage pipe: According to the Code for Design of Outdoor Wastewater Engineering (GB 50014 - 2006), the design flow velocity in the full - flow sewage pipe is 0.6~0.75 m / s. The cross - sectional area of the DN1400 sewage pipe S = ∏*R2 = 3.14*0.72 = 1.54 m2. The full - pipe flow Q = S*V = 1.54 m2*0.75 m / s = 1.155 m3 / s = 4158 m3 / h.

[0159] Pump configuration:

[0160] Under normal conditions: Two 50QW30-22-4 submersible sewage pumps are selected, one in standby and one in use. The designed flow rate is 30 m³ / h, the head is 22 m, the motor power is 4.5 kw, and the outlet pipe diameter is 125 mm, which is used as the main drainage equipment under normal conditions.

[0161] Under full-pipe conditions: Three WQ400-1800-32-250 submersible sewage pumps (one in standby) and two WQ300-600-20-55 submersible sewage pumps (one in standby) are selected as the main drainage equipment under full-pipe conditions.

[0162] Drainage system:

[0163] Temporary blockage of sewage pipe:

[0164] To ensure that there is no water within 80 m of the DN1400 sewage pipe between the two inspection wells during the drainage from the 2# inspection well to the 3# inspection well, it is necessary to block both ends in advance. A 240-mm brick wall is built inside the pipe, and the edge joint positions are sealed with leak stoppage agent. After the drainage pump and pipeline are installed and debugged, the blocking construction of this part is carried out.

[0165] Pipeline:

[0166] According to the water volume collected in the sewage pipe and combined with the selected pumping equipment, a set of pipelines are adopted under the normal flow state of the sewage in the pipe: with a diameter of φ125 mm, and all pipe materials are seamless steel pipes, which are used as the sewage drainage pipelines under normal conditions. When the sewage in the pipe is in a full-pipe state, three groups of φ400 mm drainage pipes are adopted, one of which is a standby pipeline, and one group of φ300 mm drainage pipes is used as the sewage drainage pipelines under full-pipe conditions.

[0167] Treatment measures for the side penetration inside the tunnel

[0168] The shield tunnel in the right line range of the three-middle section passes through the DN1400 sewage pipe on the side and is close to the street shops. The overburden of the shield tunnel is about 12 - 16 m, the distance from the bottom of the pipeline is about 2.3 - 6.26 m, and the minimum distance between the right line tunnel and the street shops is 2.0 m (mileage: DK46 + 270). For the shield tunnel passing through the large-diameter DN1400 sewage pipe at a close distance, the following key measures are adopted:

[0169] 1) Strictly control the shield tunneling parameters, mainly reflected in controlling the ground loss rate within 2% and the shield propulsion pressure not less than 0.8 times the theoretical soil and water pressure. After the shield passes through, synchronous grouting is 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 not be less than 1 MPa.

[0170] 2) Parameters such as the cement slurry ratio and grouting pressure should follow the principle of testing first and then doing. The water-cement ratio is 1:1. The unconfined compressive strength of the grouted and reinforced soil after 28 days should not be less than 1 MPa, and the permeability coefficient should not be greater than 10⁻⁶ / cm / s.

[0171] 3) Additional grouting holes are provided on the segment for secondary grouting reinforcement inside the tunnel. The reinforcement scope is (ZDK46 + 105~135, YDK46 + 205~295).

[0172] 4) Strengthen monitoring and measurement. Information-based construction is implemented throughout the process of shield tunneling, and closely monitor the displacement of buildings and structures and ground settlement.

[0173] 5) Conduct pilot tunneling construction before the shield machine passes through the side of buildings and structures to obtain necessary tunneling parameters such as shield propulsion pressure and ground settlement for information-based construction.

[0174] 6) Hazard source identification and evaluation: It is determined that the shield tunneling under the DN2200 regeneration pipe, DN2400 tail water pipe, and DN3200 sewage tunnel is a major hazard source. The shield tunneling under the DN1016 high-pressure gas pipeline (between the third and middle sections) is a major hazard source. It is determined that the shield passing through the side of the DN1400 water main pipe and street shops is a major hazard source.

[0175] 7. Monitoring purposes and items

[0176] The closure error of settlement observation shall be implemented according to the allowable error of Class II leveling measurement in the Code for Engineering Survey of Urban Rail Transit Engineering GB50308 - 2008. The horizontal displacement monitoring shall be implemented according to the Class II technical requirements and monitoring methods in the Code for Engineering Survey of Urban Rail Transit Engineering GB50308 - 2008.

[0177] Pipeline settlement monitoring: The monitoring objects are pipelines within the affected range. The principle for measuring point layout: 1) For pipelines within the main influence area of the shield, a measuring point is arranged every 5 - 10 m above the pipeline. Considering the attributes of the pipeline, the measuring point spacing for important pipelines is 5 m - 10 m, and the measuring point spacing for general pipelines is 5 m - 10 m; 2) For pipelines within the secondary influence area of the shield; considering the attributes of the pipeline, a measuring point is arranged every 20 - 30 m along the pipeline direction.

[0178] Monitoring frequency:

[0179] The determination of the engineering monitoring frequency should meet the requirement of being able to reflect the important change process of the monitored items of the monitored object without missing the change moment. The monitoring frequency of shield projects needs to be determined by comprehensively considering the shield type, different construction stages of the shield and underground engineering, as well as the changes in the surrounding environment, natural conditions and local experience. In the case of no data anomalies and accident signs, the on-site monitoring frequency after excavation can be determined according to the construction process. When any of the following situations occurs, monitoring should be strengthened, and the monitoring frequency or on-site inspection frequency should be appropriately increased:

[0180] (1) The monitoring data reaches the alarm value;

[0181] (2) The change amount of the monitoring data is relatively large or the rate accelerates;

[0182] (3) There are adverse geological conditions not found during the exploration;

[0183] (4) There is a large amount of accumulated water around the shield, continuous rainfall for a long time, and leakage in the municipal pipeline;

[0184] (5) The ground load near the shield suddenly increases or exceeds the design limit;

[0185] (6) There is a sudden large settlement or serious cracking on the surrounding ground;

[0186] (7) The adjacent buildings (structures) have sudden large settlements, uneven settlements or serious cracks;

[0187] (8) Other abnormal situations that affect the safety of the tunnel and the surrounding environment occur.

[0188] 7.1 Surface Settlement Monitoring

[0189] The monitoring purpose of this project is to monitor the displacement of the soil around the shield construction, understand the soil stability, and at the same time, indirectly judge the safety status of the retaining structure.

[0190] Measurement form and working principle:

[0191] For surface settlement monitoring, a vertical displacement monitoring network is established through closed and attached leveling routes with the elevation system of the first and second phases of Chengdu Metro Line 6 as the benchmark. The control points consist of reference points and working reference points. Generally, the reference points can use the survey control points provided by the design unit. If the survey control points provided by the design unit cannot be used, stable positions can be selected to make them by oneself.

[0192] Layout principle and method of measuring points: As Figure 5 shown.

[0193] The settlement monitoring points are arranged on the surface within the scope of construction influence according to the requirements in the design drawings. The principles are as follows: The surface settlement monitoring points are buried by means of manual excavation or drilling tools, and it is required to penetrate the road surface structure layer. The measuring points are covered with a protective cover 4, and the hole diameter shall not be less than 80 mm. The road and surface settlement monitoring measuring points should be buried flat, without affecting the passage of personnel and vehicles. At the same time, the measuring points are filled with coarse sand 2 to be stable, and clear marks are made for easy protection.

[0194] The surface settlement measuring points are buried by means of manual excavation or drilling tools, and the burying steps are as follows:

[0195] a. Use a Luoyang shovel for the soil surface and engineering drilling tools for the hard surface to excavate a hole with a diameter of about 130 mm and a depth of about 1 m, and tamp the bottom of the hole;

[0196] b. Remove the muck and inject an appropriate amount of clean water into the hole for maintenance;

[0197] c. Place a threaded steel bar No. 3 with a length of not less than 100 cm at the center of the hole. The steel bar marking point should protrude about 1 - 2 cm above the filling surface. The measuring point height should be lower than the road surface height to avoid the influence of traffic, and backfill and tamp it with coarse sand;

[0198] d. Install a steel protection cover No. 4 with a diameter of not less than 110 mm on the upper part;

[0199] e. Cure for more than 15 days. This method enables the measuring point to directly reflect the change of soil layer 1 in the form of end bearing.

[0200] The observation of reference points and working reference points shall be carried out in accordance with the technical requirements of the second-class vertical displacement monitoring network in the "Code for Engineering Survey" GB50026 - 2007. When using a closed leveling route for observation, only one-way observation can be carried out. When using an attached leveling route form, reciprocal observations must be carried out, and the average of the two observed height differences is taken for adjustment. Observation sequence:

[0201] Forward measurement: Rear, front, front, rear; Reverse measurement: Front, rear, rear, front;

[0202] Precautions for observation are as follows:

[0203] ① The level and leveling staff used should be inspected before the start and after the end of the project, and should also be inspected regularly during the project to ensure that the instruments are in good condition;

[0204] ② The observation should be carried out with three fixities, namely fixed personnel, fixed instrument, and fixed measuring station;

[0205] ③ Before observation, the storage location and method of the recording file should be correctly set, and the control limit difference parameters of the precise level should be checked and set to ensure compliance with the observation requirements;

[0206] ④ Observation should be carried out under the condition of no air wave and ensuring clear scale of the staff;

[0207] ⑤ Observation can only start when the instrument temperature is the same as the outside temperature;

[0208] ⑥ The number of measuring stations for both forward and reverse measurements of each measuring section should be even, otherwise the correction for the zero difference of the staff should be added;

[0209] ⑦ When changing from forward measurement to reverse measurement, the two staffs should be interchanged and the instrument should be reset;

[0210] ⑧ When completing a closed or attached route, pay attention to the closed or attached difference of the electronic record. After confirming that it is qualified, the measurement work can be completed. Otherwise, the reason should be found until the rework and retest are qualified.

[0211] 7.2 Pipeline settlement monitoring, as Figure 7 shown.

[0212] The settlement monitoring points of underground pipelines are set on the pipelines affected by construction. The principles for arranging the monitoring points are as follows:

[0213] ① In principle, the underground pipeline monitoring points are mainly arranged on gas pipelines, water supply pipelines, sewage pipelines, large rainwater pipelines and municipal pipeline culverts. When arranging the monitoring points, the relative position relationship between the underground pipelines and the project should be considered;

[0214] ② The monitoring points should be arranged at the nodes, turning points of the pipelines or the parts sensitive to displacement changes, and the layout spacing is 25m.

[0215] ③ According to the requirements of the design drawings, for pipelines with special requirements, the monitoring points are arranged at the top of the pipeline, and for those without special requirements, they are arranged at the corresponding surface monitoring points above the pipeline.

[0216] The embedding method of the settlement monitoring points of underground pipelines:

[0217] ① For underground pipelines with inspection wells, the manhole covers should be opened and the monitoring points should be directly arranged on the pipelines or pipeline carriers;

[0218] ② For pipelines without inspection wells but with excavation conditions, the pipelines should be excavated and exposed, and the monitoring points should be directly arranged on the pipelines;

[0219] ③ For pipelines without inspection wells and without excavation conditions, indirect observation points can be buried on the corresponding ground surface.

[0220] When arranging monitoring points on pipelines, for closed pipelines, a water drill with a diameter greater than Φ120 can be used to drill through the ground hardening layer to form a steel pipe protection well 4. Then, use a Luoyang shovel to dig a hole to the outer wall of the pipeline 1. Put the threaded steel bar 5 between the soil layer 2, and fill the surrounding with fine sand 3 to prevent the steel bar from changing with the change of the soil body. To avoid damage to the monitoring points by vehicles, the inserted steel bar 5 should be 2 cm below the road surface, and a steel protection cover 6 should be covered on it to protect the monitoring points. At the same time, fill the monitoring points with fine sand. For open pipelines, monitoring point supports can be made on the pipelines or pipeline piers.

[0221] The steps for monitoring the settlement of underground pipelines: The underground pipeline monitoring points are arranged on the pipelines, at the corresponding positions of the project or on the corresponding ground surface by burying indirect observation points. Specifically, they are arranged at the nodes, turning points of the pipelines or the parts sensitive to displacement changes, and the layout spacing is 25m;

[0222] Monitoring method: The settlement observation of underground pipelines can share the surface settlement leveling monitoring network, and the underground pipeline settlement monitoring points are incorporated into it to form closed circuits, attached circuits, etc. The settlement monitoring observation method, the instruments used, the observation accuracy and the data processing of underground pipelines are the same as those of surface settlement monitoring. When observing for the first time, the same observation object should be observed three times and the average value should be taken as the initial value.

[0223] 8. Control reference and alarm value

[0224] 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.

[0225] The monitoring control values and alarm values used in this project are as follows:

[0226]

[0227]

[0228] Monitoring feedback procedures: In order to ensure the authenticity, reliability and continuity of the measurement data, the following quality assurance measures are formulated:

[0229] (1) The monitoring team shall work closely with the supervising engineer, report situations and problems to the supervising engineer in a timely manner, and provide relevant practical and reliable data and records.

[0230] (2) The measurement points should be arranged reasonably and should be able to reflect the actual deformation and stress of the structure during the construction process and the degree of impact on the surrounding environment.

[0231] (3) Test components and monitoring instruments must be qualified products from regular manufacturers. Test components must have a certificate of conformity, and monitoring instruments must be checked and calibrated regularly.

[0232] (4) The buried measuring points should meet the quality requirements of the design. They should be accurately located, safe and stable, and have eye-catching protection signs.

[0233] (5) The monitoring work is carried out by engineers who have been engaged in monitoring work for many years and have experience in monitoring similar projects. Other members of the team are also engineers or surveyors with monitoring work experience, and they ensure that the monitoring personnel are relatively stable and the continuity of data is guaranteed.

[0234] (6) Monitoring data should be collated and analyzed in a timely manner. Generally, it should be reported once a week, and once a day in special cases. The monitoring report should include the stage deformation value, deformation rate, cumulative value, and draw the sedimentation trough curve, duration curve, etc., make necessary analysis, and evaluate the monitoring results.

[0235] (7) All test data shall be reported only after on-site inspection and verification; if any abnormal monitoring data is found, it shall be retested immediately, and the monitoring instruments, methods and calculation process shall be checked. After confirmation, it shall be reported immediately to Party A, the supervisor and the unit head so that measures can be taken.

[0236] (8) During the monitoring process of each monitoring item, the corresponding test implementation rules must be strictly followed.

[0237] (9) The rainy season is an adverse situation for construction, and the underground seepage is relatively serious. Therefore, to ensure the normal monitoring frequency during the rainy season, the measurement frequency of some weak links, main pipelines, and buildings should be strengthened.

[0238] Monitoring report, disposal, and alarm cancellation process:

[0239] When the monitoring values of each monitoring item exceed 70% of the control standard values specified in the design documents, specifications, and codes, the construction monitoring unit shall issue a pre-alarm report to relevant units and departments. And the monitoring should be strengthened to keep track of the deformation situation at any time until the deformation tends to be stable. After receiving the pre-alarm report submitted by the monitoring unit, the construction unit shall actively take corresponding technical measures to control the development of the deformation trend.

[0240] When the monitoring values reach the control standard values, the construction monitoring unit shall issue an alarm report to relevant units and departments. After receiving the alarm report submitted by the monitoring unit, the construction unit shall suspend construction, actively communicate with the design personnel and resident supervisors, organize relevant department personnel to discuss and analyze the reasons, formulate treatment plans and corresponding measures, and implement them within the shortest time to ensure the safety of the project. At the same time, the construction unit shall promptly report the determined plans, measures taken, and treatment effects to the construction headquarters.

[0241] 9. Emergency rescue measures

[0242] Emergency measures for power tunnels:

[0243] 1) When there are abnormal situations in the deformation monitoring of the power tunnel, the monitoring should be strengthened in a timely manner to grasp the deformation trend.

[0244] 2) When the deformation of the power tunnel tends to deteriorate, the emergency plan shall be immediately activated.

[0245] 3) Immediately organize the reinforcement of the power tunnel. Grouting is used to reinforce the soil within a range of 5.0 m around the power tunnel. The grouting material on the ground is pure cement slurry, the grouting pressure is 0.2 - 0.4 MPa, and the depth of soil reinforcement is 5.0 m.

[0246] 4) Conduct in-tunnel grouting reinforcement. Pure cement slurry is used. The grouting pressure is 0.2 - 0.4 MPa.

[0247] Emergency measures for rain and sewage pipes:

[0248] 1) Strengthen the monitoring of the deformation of rain and sewage pipes, and promptly report the monitoring data to the technical responsible person and project responsible person.

[0249] 2) Based on the on-site monitored pipeline deformation data, and on the basis of analyzing the shield tunneling parameters, the earth excavation volume, the geological exploration data and the relevant design data, it is determined to adopt ground grouting and secondary grouting behind the segment in the tunnel.

[0250] 3) Once a pipeline damage accident occurs, immediately notify the pipeline property unit, report the specific situation of the pipeline damage, and assist the pipeline property unit in rush repair.

[0251] Emergency measures for gas pipeline accidents:

[0252] 1) When there are abnormal situations in the monitored deformation of the gas pipeline, the monitoring should be strengthened in a timely manner to master the deformation trend.

[0253] 2) When the deformation of the gas pipeline tends to deteriorate, the emergency plan should be immediately activated.

[0254] 3) Immediately organize to reinforce the gas pipeline. Grout is used to reinforce the soil within a range of 5.0 m around the pipeline. The ground grouting material is pure cement slurry, the grouting pressure is 0.2 - 0.4 MPa, and the depth of soil reinforcement is 8.0 m.

[0255] 4) Conduct in-tunnel grouting reinforcement. Use pure cement slurry. The grouting pressure is 0.2 - 0.4 MPa.

[0256] 5) The on-site duty personnel should strengthen the on-site inspection.

Claims

1. A construction method for a shield tunneling under pipelines, comprising the following steps: (1) Optimize the tunneling parameters, ground settlement control standards, and pipeline settlement control standards for the pipelines passing under dangerous sources, find out the relative relationship between the construction environment and the tunneling parameters. The two types of geological strata in the lower side and side-passing sections of the dangerous source pipelines are the full-section mudstone stratum and the composite stratum with sand and gravel in the upper part and mudstone in the lower part. The optimized settings of the tunneling parameters are as follows: The tunneling parameters for the shield tunneling under or side-passing pipelines in the full-section mudstone stratum are: ， The tunneling parameters for the shield tunneling under / side-passing pipelines in the composite stratum with sand and gravel in the upper part and mudstone in the lower part are: ， The dangerous sources are rainwater pipes, power pipelines, high-pressure gas pipelines, and sewage pipes; (2) Reinforce the pipelines passing under dangerous sources; (3) Monitor the ground settlement; (4) Monitor the settlement of underground pipelines; (5) Set the monitoring control benchmark and alarm value; The reinforcement of the shield tunneling under rainwater pipes and power pipelines includes the following steps: (1) Before the shield passes through the pipeline, stop the machine at 10 m ahead to check the machine condition, and open the chamber to check the cutters to ensure continuous tunneling when the shield passes through the dangerous source; (2) Control the tunneling parameters: clarify the mileage of the rainwater pipe and the power pipeline and their positional relationship with the interval tunnel. During the construction process, control the fluctuation of the tunneling earth pressure within the range of 0.1 bar, and use foam soft soil pressure; (3) Ensure the improvement of muck by increasing the amount of foam agent and water addition, control the muck output. During the shield tunneling process, evenly control the muck output according to the footage and earth pressure, and at the same time, match the muck output and the grouting volume; (4) According to the ground settlement situation and the tunneling situation, when the segment is pulled out of the shield tail for 5 - 10 rings, use a double-fluid grouting machine to perform secondary grouting reinforcement on the back of the upper part of the segment to fill the construction voids behind the segment and shorten the setting time of the synchronous grouting slurry; reinforce the formation through the reserved grouting holes in the segment. The reinforcement form is mainly double-fluid slurry and supplemented by single-fluid cement slurry. Perform in-tunnel grouting reinforcement in the range of 120° outward expansion of 1.5 m at the crown of the left-line and right-line tunnels; (5) Use high-quality shield tail grease to improve the sealing effect and prevent shield tail slurry leakage; (6) Monitor the stress and strain of the crossing section; (7) When the interval tunnel passes through this section, use segments with additional grouting holes, and supplement grouting reinforcement of the formation in a timely manner according to the monitoring situation; (8) Strengthen the monitoring and measurement, and monitor the displacement of the power tunnel and the ground settlement; (9) Conduct test tunneling construction before the shield construction passes under the power tunnel to obtain the tunneling parameters for the shield propulsion. The reinforcement of the shield tunneling under sewage pipelines includes the following steps: (1) Before the shield passes under the pipeline, stop the machine at 10 m ahead to check the machine condition, and open the chamber to check the cutters to ensure continuous tunneling when the shield passes through the dangerous source; (2) Control the shield tunneling parameters: control the ground loss rate within 2%, and the shield propulsion earth pressure is not less than 0.8 times the theoretical water and soil pressure; perform synchronous grouting in a timely manner after the shield passes through, and control the synchronous grouting volume and grouting pressure. The unconfined uniaxial compressive strength should not be less than 1 MPa; clarify the mileage of the drainage pipeline and its positional relationship with the interval tunnel; (3) Ensure the improvement effect of muck by increasing the amount of foam agent and water addition, control the muck output, reduce the cutter head rotation speed and propulsion speed to ensure the shield passes through evenly and appropriately increase the earth pressure; (4) According to the surface settlement and excavation conditions, when the segment is dragged out of the shield tail for 5-10 rings, a double-liquid grouting machine is used 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; strengthen the grouting measures in the tunnel, and reinforce the stratum through the reserved grouting holes in the segment. 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; the grouting reinforcement length of the left and right lines is 30 meters; after the shield passes, decide whether to carry out tracking grouting based on the monitoring measurement results; reinforcement range: the reinforcement range of the forward section is 360° around the tunnel and 1.5m outside, and secondary grouting is carried out in the tunnel; (5) Use high-quality shield tail grease to improve the sealing effect and prevent leakage of shield tail; (6) Monitor stress and strain in the crossing section; (7) When the section tunnel passes through this area, additional grouting holes are used in the segment, and additional grouting is carried out in a timely manner to reinforce the stratum according to the monitoring situation; The shield tunneling and buried high-pressure gas pipeline reinforcement includes the following steps: (1) Strictly control the shield tunneling parameters, control 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; carry out synchronous grouting in a timely manner after the shield passes through, and pay attention to controlling the synchronous grouting volume and grouting pressure. The unconfined uniaxial compressive strength should be no less than 1MPa, and clearly define the mileage of the gas pipeline and its relationship with the interval tunnel; (2) 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; (3) According to the surface settlement and excavation conditions, when the segment is dragged out of the shield tail for 5-10 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; add grouting holes on the segment to carry out secondary grouting reinforcement in the left and right tunnels. The reinforcement length of the left and right lines is 10 meters. The reinforcement range of the underpass section is 360° around the tunnel and 1.5m outside for secondary grouting in the tunnel; (4) Use high-quality shield tail grease to improve the sealing effect and prevent leakage of shield tail; (5) Monitor stress and strain in the crossing section; (6) When the section tunnel passes through this area, additional grouting holes are used in the segment, and additional grouting is carried out in a timely manner to reinforce the stratum according to the monitoring situation; The shield side-through sewage pipeline reinforcement includes the following steps: sewage pipe shield construction adopts line adjustment, drainage, isolation or reinforcement, through centralized drainage, submersible sewage pump is the drainage equipment, and the sewage is discharged after the sewage main pipe is blocked by the submersible sewage pump; (1) Strictly control the shield tunneling parameters, control the stratum loss rate within 2% and the shield thrust pressure The upper limit should not be less than 0.8 times the theoretical water and soil pressure; after the shield passes through, synchronous grouting should be carried out in time, and attention should be paid to controlling the synchronous grouting volume and grouting pressure. The unconfined uniaxial compressive strength should not be less than 1MPa; (2) The cement slurry ratio and grouting pressure parameters should be based on the principle of trial before implementation, with a water-cement ratio of 1:1; the 28-day unconfined compressive strength of the grouting reinforced soil should be no less than 1 MPa, and the permeability coefficient should be no greater than 10-6 / cm / s; (3) Additional grouting holes are provided on the segment for secondary grouting reinforcement of the tunnel inside the tunnel; (4) Strengthen monitoring and measurement. Information-based construction is implemented throughout the process of shield tunneling, and the displacements of buildings and structures and ground settlement are closely monitored; (5) Pilot tunneling construction is carried out before the shield tunnels under the buildings and structures on the side of the shield construction to obtain shield tunneling parameters.

2. The shield tunneling construction method according to claim 1, wherein the monitoring of surface settlement includes the following steps: Layout of surface settlement monitoring points: Drill holes in the soil layer, set threaded steel bar marking points in the holes. The length of the threaded steel bar marking points is greater than 90 cm. Coarse sand is filled between the threaded steel bar and the soil layer. A protective cover is provided above the drill hole; The drill hole penetrates the road surface structure layer, the drill hole diameter is 80 - 130 mm, the depth is 1 m, the length of the threaded steel bar is greater than 100 cm as the marking point, and it exposes 1 - 2 cm above the coarse sand filling. The diameter of the steel protective cover is greater than 110 mm; Cure for more than 15 days; When the closed leveling route is adopted for observation, the one-way observation is carried out. When the attached leveling route form is adopted, the round-trip observation is carried out, and the average value of the elevation differences of the two observations is taken for adjustment; Observation sequence: Forward measurement: Rear, Front, Front, Rear; Reverse measurement: Front, Rear, Rear, Front.

3. The shield tunneling construction method according to claim 1, wherein the monitoring of underground pipeline settlement includes the following steps: The underground pipeline monitoring points are arranged on the pipeline, at the position corresponding to the project or on the indirectly observed points buried on the corresponding ground surface, specifically at the joints, corner points of the pipeline or the parts sensitive to displacement changes, and the layout spacing is 25 m; Burying method of underground pipeline settlement monitoring points: For closed pipelines, use a water drill to penetrate the ground hardening layer, dig a hole to the outer wall of the pipeline, put in the steel bar and fill the surrounding with fine sand. The position of the steel bar should be lower than the road surface and covered with a steel protective cover to protect the measuring point. At the same time, fill the measuring point with fine sand; For open pipelines, make monitoring point supports on the pipeline or pipeline pier.

4. The shield tunneling construction method according to claim 1, wherein the setting of monitoring control benchmarks and alarm values includes the following steps: Two control indicators of the cumulative value and change rate of monitoring variables are adopted, and the parameters are: 。 5. The shield tunneling construction method under pipelines according to claim 1 further includes the following steps: Carry out monitoring feedback, reporting, disposal and alarm elimination emergency rescue measures, emergency measures for power tunnels: (1) Emergency measures for power tunnels: Grout to reinforce the soil within 5.0 m around the power tunnel. The ground grouting material is pure cement slurry, the grouting pressure is 0.2 - 0.4 MPa, and the soil reinforcement depth is 5.0 m; Grouting reinforcement inside the power tunnel: Use pure cement slurry; The grouting pressure is 0.2 - 0.4 MPa; (2) Emergency measures for abnormal rain and sewage pipes: Adopt ground grouting and secondary supplementary grouting behind the segments inside the tunnel; (3) Emergency measures for gas pipeline accidents: Reinforce the gas pipeline: Grout to reinforce the soil within 5.0 m around the pipeline. The ground grouting material is pure cement slurry, the grouting pressure is 0.2 - 0.4 MPa, and the soil reinforcement depth is 8.0 m; Carry out grouting reinforcement inside the tunnel: Use pure cement slurry, and the grouting pressure is 0.2 - 0.4 MPa.

6. The shield tunneling method under pipelines according to claim 1 further includes the following steps: observation ， 1) The levels and leveling staffs used shall be inspected before and after the start and end of the project, and also regularly during the project to ensure that the instruments are in good condition; 2) The observations shall be carried out with three fixities, namely fixed personnel, fixed instrument, and fixed measuring station; 3) Before the observations, the storage location and method of the recording file shall be correctly set, and the control limit difference parameters of the precise level shall be checked and set to ensure compliance with the observation requirements; 4) The observations shall be carried out under the condition of no air wave and ensuring that the scale of the staff is clear; 5) The observations can only start when the instrument temperature is the same as the outside temperature; 6) The number of measuring stations for the forward and backward measurements of each survey section shall be even. Otherwise, the correction for the zero difference of the staff shall be added; 7) When changing from the forward measurement to the backward measurement, the two staffs shall be interchanged and the instrument shall be reset; 8) When completing the closed or connected route, attention shall be paid to the closed or connected difference of the electronic record. After confirming that it is qualified, the measurement work can be completed. Otherwise, the reasons shall be found until the rework and retest are qualified.

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