Construction method for pulling back and cleaning large-diameter concrete pipe in central urban area

Abstract

The invention provides a construction method for pulling back and cleaning a large-diameter concrete pipe in a central urban area, which comprises the following steps of: calculating the pipeline frictional resistance required for pulling back a whole section of pipeline according to the average frictional resistance of a pipe wall and a soil layer; s3, calculating the pipeline friction resistance, the working well allowable jacking force (F1), the pipeline front end pulling node allowable pulling force (F2) and the pipe allowable jacking force, when the pipeline friction resistance is larger than one of the working well allowable jacking force, the pipeline front end pulling node allowable pulling force and the pipe allowable jacking force, executing S3, and otherwise, executing S5; according to the method, a pull-back pigging scheme is calculated and determined according to the frictional resistance of the pipeline, the allowable jacking force of the working well, the allowable pulling force of the front-end pulling node of the pipeline and the allowable jacking force of the pipe, and then a segmented pull-back pigging system or a whole-section pull-back pigging system is configured according to the calculation result, so that the large-diameter underground pipeline is subjected to pull-back cleaning in a targeted manner; and the device is suitable for pulling back and removing composite curve, long-distance and large-diameter underground pipelines.

Description

Technical Field

[0001] The invention relates to a construction method, in particular to an environmentally friendly construction method for pulling back and cleaning large-diameter concrete pipes in a central urban area, belonging to the technical field of urban renewal construction. Background Art

[0002] As an important part of the country's spatial resources, the development and utilization of urban underground space plays an increasingly critical role in current urban development and land space management, and plays an important role in promoting high-quality urban development and enhancing the comprehensive carrying capacity of cities.

[0003] The underground space in typical areas such as historical conservation areas and old communities in the central city is occupied by various old and abandoned pipelines. It is also restricted by complex traffic and building (structure) conditions, making it difficult to transform underground space, which has become a shortcoming affecting the sustainable development of the city. It is an urgent problem to clean up large-diameter abandoned and old pipelines in the central city in an environmentally friendly way, release underground space, and help urban renewal construction.

[0004] For the technology of cleaning underground large-diameter pipelines, for example: Research on the environmental impact of the withdrawal method in the jacking project [J]. Construction, 2018: 989-991. Through numerical simulation, the impact of the jacking on the surrounding environment during the withdrawal process was analyzed. According to the calculation results of the withdrawal, the surface deformation along the axis of the jacking pipe has caused significant settlement deformation on the surface in front of the machine head, which poses a challenge to ensuring the safety of the complex surrounding environment of the central urban area; for example: the Chinese patent named a method for the withdrawal and correction of jacking pipes (publication number CN117267463A) discloses a jacking pipe withdrawal and correction construction technology, which uses fine-rolled threaded steel to connect with the machine head, and the large-diameter pipeline is pulled out in sections by the working well using a built-in relay room, and the mixed mud is filled in the front synchronously, but the following problems still exist:

[0005] 1. The fine-rolled threaded steel used for pullback is not suitable for curve pipe pullback;

[0006] 2. The finely rolled threaded steel used for pullback is connected to the steel structure of the pipe jacking machine, which is not suitable for connecting ordinary large-diameter underground pipelines;

[0007] 3. In the central urban area, the cavities formed by backfilling are not dense, which poses a great threat to the surrounding environment.

[0008] Therefore, a construction method that has little impact on the surrounding environment of the central urban area and is suitable for the removal of compound curves, long distances, and large-diameter underground pipelines has become an issue that needs to be studied and resolved urgently. To this end, a construction method for pulling back and cleaning large-diameter concrete pipes in the central urban area is proposed. Summary of the invention

[0009] In view of this, the present invention provides a construction method for pulling back and cleaning large-diameter concrete pipes in the central urban area to solve or alleviate the technical problems existing in the prior art and at least provide a beneficial choice.

[0010] The technical solution of the embodiment of the present invention is implemented as follows: a construction method for pulling back and cleaning large-diameter concrete pipes in a central urban area, comprising the following steps:

[0011] S1. Calculate the pipeline friction required to pull back the entire pipeline according to the average friction between the pipe wall and the soil layer;

[0012] S2, calculate the pipeline friction resistance, the allowable top force of the working well (F1), the allowable tension of the front end pull node of the pipeline (F2), and the allowable top force of the pipe. When the pipeline friction resistance is greater than the allowable top force of the working well, the allowable tension of the front end pull node of the pipeline, or the allowable top force of the pipe, execute S3, otherwise execute S5;

[0013] S3, adopting segmented pullback cleaning strategy;

[0014] S4. Configure a segmented back-pull pigging system, which includes a built-in anti-top system, a soil injection system, a grouting system, a back-pull system, a hole water stop system, a measurement system, a monitoring system, lighting, communication, monitoring and ventilation systems, and an emergency system;

[0015] S5, adopt the whole-section pullback cleaning strategy;

[0016] S6. Configure the whole section back-pull pigging system, which includes soil injection system, grouting system, back-pull system, hole water stop system, measurement system, monitoring system, lighting, communication, monitoring and ventilation system and emergency system;

[0017] S7. Installation and commissioning of the pullback pigging system;

[0018] S8. Start the pull-back cleaning system, start pull-back cleaning, separate the pipe sections, and transport them back to the factory for repair and reuse.

[0019] Further preferably, the average friction resistance between the pipe wall and the soil layer is f (KN / m 2 ) is obtained according to the type of soil layer and the material of the pipe.

[0020] Further preferably, the calculation formula of the pipeline friction resistance F (KN) is:

[0021] F=3.14×D×f1×L1×K1+3.14×D×f2×L2×K2+...+3.14×D×fn×Ln×Kn+3.14×D×fn+1×Ln+1×Kn+1;

[0022] Among them, the total length of the pipeline L (m) = L1 + L2 + ... + Ln + Ln + 1;

[0023] Where D(m) is the outer diameter of the pipe and K is the additional coefficient of curve tension.

[0024] Further preferably, the built-in anti-top system uses a built-in anti-top device to pull back the pipeline in sections, and the built-in anti-top device is a steel structure, including a front inner support ring, a water stop pressure ring, an outer retaining ring, an outer sealing ring, an inner retaining ring flange, an inner retaining ring body, an inner friction ring, a relay room jack, a cylinder clamp, a limit flange and a rear inner support ring;

[0025] Among them, the front inner support ring, the rear inner support ring and the pipe wall are connected with high-strength bolts, and the front inner support ring and the rear inner support ring are connected with a water-stop pressure ring, an outer retaining ring, an outer sealing ring, an inner retaining ring flange, an inner retaining ring body, an inner friction ring, a relay jack, a cylinder clamp and a limit flange by bolts to form a movable socket structure. A rubber ring is arranged between the movable socket structure and the pipe wall for water stopping, and the relay jack is used to jack up two adjacent sections of the pipe.

[0026] Further preferably, the soil injection system includes a primary soil mixer, a No. 1 soil injection pump, a soil delivery pipeline, a secondary soil mixer, a No. 2 soil injection pump, an upper soil injection pipe and a lower soil injection pipe;

[0027] The secondary soil mixer is connected to the feed end of the No. 2 soil injection pump, the upper soil injection pipe and the lower soil injection pipe are connected to the discharge end of the No. 2 soil injection pump, the soil delivery pipeline is connected between the discharge end of the No. 1 soil injection pump and the feed end of the secondary soil mixer, and the primary soil mixer is connected to the feed end of the No. 1 soil injection pump;

[0028] Among them, the primary soil mixer, No. 1 soil injection pump, soil delivery pipeline, secondary soil mixer and No. 2 soil injection pump are configured according to the pipeline length and matched with the pull-back speed a (m / h). The backfill volume V (m 3 / h) not less than the theoretical gap V1(m 3 / h), the specific calculation formula is as follows:

[0029] V≥V1, V1=3.14×R×R×a;

[0030] Where R(m) is the outer diameter of the pipe.

[0031] Further preferably, the grouting system is used to continuously inject lubricating slurry between the pipe wall and the soil layer during the back-pull cleaning process, the grouting material is composite bentonite, the grouting amount is not less than 2 cm gap on one side, and the grouting pressure (P) is:

[0032] P = krh;

[0033] Among them, P is the grouting pressure (kpa), k is the empirical coefficient, which is 0.8-1.2, and r is the soil density (KN / m 3 ), h is the buried depth of grouting point (m).

[0034] Further preferably, the anti-pull system is composed of an anti-pull beam including a steel sealing plate arranged in front of the pipeline, a steel strand, a bracket, an anti-pull cylinder and an anti-pull beam;

[0035] Among them, the anti-tension beam with steel sealing plate is used to create conditions for the front soil injection and pressure maintenance, and provide a tie point for the steel strand; the bracket is used to ensure that the steel strand is straight after bending and neatly distributed on both sides of the pipeline in a non-pre-tightened state; the anti-top beam is used to provide an anti-top force point and a steel strand tie point, and the anti-top cylinder is used to provide anti-top power;

[0036] The hole water-stopping system adopts packing water-stopping, and the packing material is graphite packing or stainless steel wire reinforced expanded graphite packing.

[0037] Further preferably, the measuring system includes a mileage measuring system, the measuring method is automatic measurement, and the mileage measuring system is composed of a guide prism, a rear-view prism, a total station, an automatic leveling base, a forced centering platform, an information control box, a display and software;

[0038] The forced centering platform is fixed at the turning point of the jacking tunnel, and ensures that it is always in sight with the guide prism in the front end of the pipeline and the rear-view prism in the working well;

[0039] The monitoring system monitors the surface and pipeline settlement in an automated manner, and the monitoring system includes an axial settlement sensor, a cross-sectional settlement sensor, a pipeline settlement sensor, and a reference sensor;

[0040] Among them, the axial settlement sensor is arranged just above the axis of the jacking pipe and arranged along the axis of the jacking pipe at intervals of 2.5m. The position of each axial settlement sensor is an axis monitoring point. A surface monitoring section is arranged every 10m. Each surface monitoring section contains 6 section monitoring points and 1 axis monitoring point. The section settlement sensor is arranged at the section monitoring point, and the distances between the section monitoring point and the axis monitoring point are 1.5m, 4.5m, and 11.5m respectively.

[0041] Further preferably, in the lighting, communication, monitoring and ventilation systems, the voltage used for lighting is not more than 36V, and the LED light strips with a voltage not more than 36V are set in the pipeline; the communication adopts wired telephone with intercom; the monitoring adopts high-definition camera; the ventilation volume is 3m of fresh air per person per minute. 3 , the minimum wind speed is not less than 0.15m / s;

[0042] The emergency system is used to open emergency holes inside the pipeline to inject soil to control the settlement when the building above the pipeline settles during the pull-back process; and to open pre-buried grouting holes on the surface above the pull-back clearing area before construction. When the settlement cannot be controlled, the pre-buried grouting holes are used to inject double liquid slurry to quickly control the settlement.

[0043] Further preferably, the installation sequence of the pullback pigging system is that large equipment is preferentially placed in a predetermined position in the pipe, and the debugging method is single system debugging followed by linkage debugging.

[0044] The embodiment of the present invention has the following advantages due to the adoption of the above technical solution:

[0045] 1. The present invention determines the pullback cleaning scheme by calculating according to the size of the pipeline friction resistance, the allowable top force of the working well, the allowable tension of the tie point in front of the pipeline, and the allowable top force of the pipe material, and then configures the segmented pullback cleaning system or the whole pullback cleaning system according to the calculation results, so as to carry out pullback cleaning of large-diameter underground pipelines in a targeted manner, and is suitable for pullback cleaning of compound curve, long-distance, and large-diameter underground pipelines.

[0046] Second, the present invention can ensure the safety and controllability of densely packed buildings (structures) and busy roads in the central urban area when pulling back to clear the pipeline.

[0047] 3. The present invention clears old and abandoned pipes by pulling back, thus releasing underground space. It can also be used for newly built underground excavated pipes. When they encounter obstacles or deviate from the axis, they can be re-laid by pulling back. In addition, the pipes cleared by pulling back can ensure the integrity of the pipe structure and can be reused as resources.

[0048] The above summary is for illustrative purposes only and is not limiting in any way. In addition to the illustrative aspects, embodiments and features described above, further aspects, embodiments and features of the present invention will be readily apparent by reference to the accompanying drawings and the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0050] Figure 1 is a flow chart of the steps of the present invention;

[0051] Figure 2 This is a schematic diagram of the installation of a built-in anti-top system according to the first embodiment of the present invention;

[0052] Figure 3 It is a schematic diagram of the installation of the soil injection system of the present invention;

[0053] Figure 4 It is a structural schematic diagram of the anti-pull system of the present invention;

[0054] Figure 5 It is a structural schematic diagram of the measurement system of the present invention;

[0055] Figure 6 It is a schematic diagram of the installation positions of the axial settlement sensor and the cross-sectional settlement sensor of the present invention;

[0056] Figure 7 This is a schematic diagram of the installation position of the pipeline settlement sensor of the present invention;

[0057] Figure 8 This is a schematic diagram of the installation of a built-in anti-top system according to the second embodiment of the present invention;

[0058] Fig. 9 This is a schematic diagram of debugging the steel strand in the second embodiment of the present invention;

[0059] Fig.10 It is a debugging schematic diagram of the retraction of the stop retreat device in the second embodiment of the present invention;

[0060] Fig.11 This is a schematic diagram of debugging the built-in anti-top 1 in the second embodiment of the present invention;

[0061] Fig.12 This is a schematic diagram of debugging the built-in anti-top 2 in the second embodiment of the present invention;

[0062] Fig.13 This is a schematic diagram of debugging a built-in subsequent anti-top system in Embodiment 2 of the present invention;

[0063] Fig.14 It is a schematic diagram of debugging the built-in reverse-lifting cylinder in the second embodiment of the present invention.

[0064] Figure numerals: 1. front inner support ring; 2. water stop pressure ring; 3. outer retaining ring; 4. outer sealing ring; 5. inner retaining ring flange; 6. inner retaining ring body; 7. inner friction ring; 8. relay room jack; 9. cylinder clamp; 10. limit flange; 11. rear inner support ring. DETAILED DESCRIPTION

[0065] In the following, only some exemplary embodiments are briefly described. As those skilled in the art will appreciate, the described embodiments may be modified in various ways without departing from the spirit or scope of the present invention. Therefore, the drawings and descriptions are considered to be exemplary and non-restrictive in nature.

[0066] It should be noted that the terms "first", "second", "symmetrical", "array", etc. are only used to distinguish between description and position description purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the definition of "first", "symmetrical", etc. can explicitly or implicitly include one or more of these features; similarly, when the number of certain features is not limited in the form of words such as "two" or "three", it should be noted that this feature also explicitly or implicitly includes one or more feature quantities.

[0067] The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0068] Embodiment 1

[0069] like Figure 1 As shown, an embodiment of the present invention provides a construction method for pulling back and cleaning a large-diameter concrete pipe in a central urban area, comprising the following steps:

[0070] S1. Calculate the pipeline friction required to pull back the entire pipeline according to the average friction between the pipe wall and the soil layer;

[0071] S2, calculate the pipeline friction resistance, the allowable top force of the working well (F1), the allowable tension of the front end pull node of the pipeline (F2), and the allowable top force of the pipe. When the pipeline friction resistance is greater than the allowable top force of the working well, the allowable tension of the front end pull node of the pipeline, or the allowable top force of the pipe, execute S3, otherwise execute S5;

[0072] S3, adopting segmented pullback cleaning strategy;

[0073] S4. Configure the segmented back-pull pigging system, which includes built-in anti-top system, soil injection system, grouting system, back-pull system, hole water stop system, measurement system, monitoring system, lighting, communication, monitoring and ventilation system and emergency system;

[0074] S5, adopt the whole-section pullback cleaning strategy;

[0075] S6. Configure the whole section back-pull pigging system, which includes soil injection system, grouting system, back-pull system, hole water stop system, measurement system, monitoring system, lighting, communication, monitoring and ventilation system and emergency system;

[0076] S7. Installation and commissioning of the pullback pigging system;

[0077] S8. Start the pull-back cleaning system, start pull-back cleaning, separate the pipe sections, and transport them back to the factory for repair and reuse.

[0078] In one embodiment, the average friction resistance between the pipe wall and the soil layer is f (KN / m 2) is obtained according to the type of soil layer and the material of the pipe; the specific values ​​are shown in the following table:

[0079]

[0080] The calculation formula of pipeline friction resistance F (KN) is:

[0081] F=3.14×D×f1×L1×K1+3.14×D×f2×L2×K2+...+3.14×D×fn×Ln×Kn+3.14×D×fn+1×Ln+1×Kn+1;

[0082] Among them, the total length of the pipeline L (m) = L1 + L2 + ... + Ln + Ln + 1;

[0083] Where D(m) is the outer diameter of the pipe, and K is the additional coefficient of curve tension, as shown in the following table:

[0084]

[0085] In one embodiment, Figure 2 As shown, the built-in anti-jacking system uses a built-in anti-jacking device to pull the pipeline back in sections. The built-in anti-jacking device is a steel structure, including a front inner support ring 1, a water stop pressure ring 2, an outer retaining ring 3, an outer sealing ring 4, an inner retaining ring flange 5, an inner retaining ring body 6, an inner friction ring 7, a relay room jack 8, a cylinder clamp 9, a limit flange 10 and a rear inner support ring 11;

[0086] Among them, the front inner support ring 1, the rear inner support ring 11 and the pipe wall are connected by high-strength bolts, and the front inner support ring 1 and the rear inner support ring 11 are connected by bolts to form a movable socket structure. A rubber ring is provided between the movable socket structure and the pipe wall for water stopping, and the relay jack 8 is used to reverse the two adjacent sections of the pipe.

[0087] By using the built-in anti-jacking equipment to pull back the pipeline in sections, sufficient pulling force is provided for long-distance pulling back. The tonnage and number of the jacks 8 can be adjusted according to the friction resistance and pipe material conditions of each section of the pipeline. When designed, the friction resistance of this section should be less than 80% of the total jacking force of the built-in anti-jacking. A travel meter can also be installed on the jack 8 and connected to the well control room.

[0088] In one embodiment, Figure 3 As shown, the soil injection system includes a primary soil mixer, a No. 1 soil injection pump, a soil delivery pipeline, a secondary soil mixer, a No. 2 soil injection pump, an upper soil injection pipe and a lower soil injection pipe;

[0089] Among them, the secondary soil mixer is connected to the feed end of the No. 2 soil injection pump, the upper soil injection pipe and the lower soil injection pipe are connected to the discharge end of the No. 2 soil injection pump, the soil delivery pipeline is connected between the discharge end of the No. 1 soil injection pump and the feed end of the secondary soil mixer, and the primary soil mixer is connected to the feed end of the No. 1 soil injection pump;

[0090] Among them, the primary soil mixer, No. 1 soil injection pump, soil delivery pipeline, secondary soil mixer and No. 2 soil injection pump are configured according to the pipeline length and matched with the pull-back speed a (m / h). The backfill volume V (m 3 / h) not less than the theoretical gap V1(m 3 / h), the specific calculation formula is as follows:

[0091] V≥V1, V1=3.14×R×R×a;

[0092] Where, R(m) is the outer diameter of the pipe;

[0093] To ensure the quality of filling the void in front of the pullback pipeline, the filling soil should have certain pumpability and self-sustaining properties, and the compression modulus of the soil's physical and mechanical properties should not be less than that of the original soil. The mix ratio is determined based on geotechnical tests in simulated underground environments. The raw materials for the mix ratio are yellow clay, curing agent, and pumping agent. When the pipeline is long, after being mixed by the primary soil mixer on the well, it is pumped to the secondary soil mixer at the front end of the pipeline by the No. 1 soil injection pump, and then the curing agent is added and mixed for the second time, and then it is pumped by the No. 2 soil injection pump, the upper soil injection pipe, and the lower soil injection pipe to fill the void in front of the pipeline to ensure that the injected soil is dense.

[0094] In one embodiment, the grouting system is used to continuously inject lubricating slurry between the pipe wall and the soil layer during the back-pull cleaning process. The grouting material is composite bentonite. The grouting amount is not less than 2 cm gap on one side. The grouting pressure (P) is:

[0095] P = krh;

[0096] Among them, P is the grouting pressure (kpa), k is the empirical coefficient, which is 0.8-1.2, and r is the soil density (KN / m 3 ), h is the buried depth of grouting point (m).

[0097] The grouting principle adopted by the grouting system is to inject a small amount of water multiple times to gradually restore the lubrication of the slurry sleeve. The performance indicators of the slurry are shown in the following table:

[0098]

[0099] In order to strengthen the grouting quality management during the grouting process, it is necessary to regularly check the slurry parameters, grouting volume, grouting pressure and actual average friction resistance, simultaneously check whether the grouting holes are unobstructed, and make grouting records.

[0100] In one embodiment, Figure 4As shown, the anti-pull system consists of an anti-pull beam with a steel cover plate arranged in front of the pipeline, a steel strand, a bracket, an anti-pull cylinder and an anti-pull beam;

[0101] Among them, the anti-tension beam is used to create conditions for the front soil injection and pressure maintenance, and provide a tie point for the steel strands; the bracket is used to ensure that the steel strands are straight when bending and neatly distributed on both sides of the pipeline in a non-prestressed state; the anti-top beam is used to provide an anti-top force point and a steel strand tie point, and the anti-top cylinder is used to provide anti-top power;

[0102] The hole water stop system adopts packing water stop, and the packing material is graphite packing or stainless steel wire reinforced expanded graphite packing;

[0103] Graphite packing or stainless steel wire reinforced expanded graphite packing has excellent wear resistance and is suitable for various high-wear working conditions. It can generate a certain radial force under the action of compression force and contact with the shaft tightly to achieve a good sealing effect. At the same time, it has excellent corrosion resistance and can resist the erosion of strong acids and alkalis, water and various organic solvents. The hole water-stopping system also has a tightening function. During use, if leakage occurs, it can be quickly tightened to achieve a compression and water-stopping effect.

[0104] In one embodiment, Figure 5 As shown, the measurement system includes a mileage measurement system, and the measurement method is automatic measurement. The mileage measurement system is composed of a guide prism, a rear-view prism, a total station, an automatic leveling base, a forced centering platform, an information control box, a display and software;

[0105] Among them, the forced centering platform is fixed at the turning point of the jacking tunnel, and it is ensured that it always has a line of sight with the guide prism in the front end of the pipeline and the rear-view prism in the working pit;

[0106] During initialization, manually determine the coordinates of the guiding prism, the coordinates of the forced centering station, the coordinates of the rear-view prism, the center coordinates of the pipe section where the forced centering station is located, and the center coordinates of the pipe section closest to the working well. By fine-tuning the position of the rear-view prism, the angle between the rear-view azimuth of the guiding total station and the existing axis azimuth of the pipeline section is no greater than 30°.

[0107] After initialization, the total station is driven to perform cyclic observations on the rear-view prism and the guide prism. The actual mileage and pullback distance of the front end of the pipeline are calculated based on the measured rear-view distance, guide distance and initialization parameters. The relevant information is transmitted via a wireless data link and displayed on the display in the pipe jacking machine operating room, which is convenient for construction control.

[0108] like Figure 6-Figure 7 As shown, the monitoring system uses an automated method to monitor the surface and pipeline settlement. The monitoring system includes an axial settlement sensor, a cross-sectional settlement sensor, a pipeline settlement sensor, and a reference sensor.

[0109] Among them, the axial settlement sensor is arranged just above the axis of the jacking pipe and arranged along the axis of the jacking pipe at intervals of 2.5m. The position of each axial settlement sensor is an axis monitoring point. A surface monitoring section is arranged every 10m. Each surface monitoring section contains 6 section monitoring points and 1 axis monitoring point. The section settlement sensor is arranged at the section monitoring point. The distances between the section monitoring point and the axis monitoring point are 1.5m, 4.5m, and 11.5m respectively.

[0110] Axial settlement sensors, cross-sectional settlement sensors, and pipeline settlement sensors are all automatic differential pressure sensors, such as Figure 7 As shown, a pipeline settlement sensor is arranged at each corner directly above the pipeline, and a pipeline settlement sensor is arranged every 10m in the straight section.

[0111] In one embodiment, in the lighting, communication, monitoring and ventilation systems, the voltage used for lighting is no more than 36V, and the LED light strips no more than 36V are set for lighting in the pipeline; communication uses wired telephones with intercoms; monitoring uses high-definition cameras; the ventilation volume is 3m of fresh air per person per minute. 3 , the minimum wind speed is not less than 0.15m / s;

[0112] The emergency system is used to control the settlement by injecting soil through emergency holes opened inside the pipeline when the building (structure) above the pipeline settles during the pullback process. The ratio of soil injection material is 1.5:1 yellow clay: water. Pre-buried grouting holes are opened on the surface above the pullback and cleaning area before construction. When the settlement cannot be controlled, the pre-buried grouting holes are used to inject double liquid slurry to quickly control the settlement.

[0113] In one embodiment, the installation sequence of the pullback pigging system is that large equipment is preferentially placed in a predetermined position in the pipe, and the debugging method is to perform linkage debugging after single system debugging.

[0114] In one embodiment, in S8, the pipeline is pulled back and cleaned, the pipe sections are separated, and the pipeline is hoisted back to the factory for repair and reuse. The pipeline is gradually pulled back to the working well. Due to the travel of the anti-jacking cylinder in the working well and the size of the working well, the steel strands need to be cut step by step, the pipeline is separated, and the steel strands are connected and pre-tightened after the pipeline is hoisted out, and the next pull-back process is entered. During the pull-back process, the number of built-in anti-jacking systems used can be reduced according to the actual friction resistance. The pipeline can be returned to the factory for repair and reuse.

[0115] Embodiment 2

[0116] This example is to lay a drainage pipeline in the central urban area. The reinforced concrete pipe with an outer diameter of 2.64m is constructed by jacking technology. The diameter of the jacking machine is 2.66m, and the jacking section is 301m. When it reaches 239m, it encounters the pile foundation of the overpass and cannot continue to jack. The solution of pulling back and cleaning the pipe and jacking back to bypass the pile foundation of the overpass without occupying underground space is adopted, and the pulling back and cleaning work of the deviated pipeline is successfully completed. The specific steps of pulling back and cleaning are as follows:

[0117] Step 1: Design of the pigging scheme. This section of the pipeline is located in the ②3-1 clayey silt layer, and the average friction between the pipe wall and the soil layer is 8KN / m 2 The allowable top force of the working well is 8000KN, the allowable top force of the pipe is 14000KN, the allowable tension of the front end of the pipeline is 8000KN, the curvature radius of the first 24m is 68D (D is the pipe diameter), the curvature radius of the middle 157.5m is 303D, and the back (near the working well end) 57.5m is a straight line. The 239m overall is divided into 5 sections for back-pull cleaning, and the maximum section resistance is 4001KN.

[0118] F=3.14×2.64×8×24×1.318+3.14×2.64×8×50×1.097+3.14×2.64×8×55×1.097+3.14×2.64×8×52.5×1.097+3.14×2.64×8×57.5=17369KN.

[0119] Step 2: Configure the pullback cleaning system based on the segmented pullback cleaning solution. The system includes a built-in anti-top system, a soil injection system, a grouting system, a pullback system, a tunnel water stop system, a measurement system, a monitoring system, lighting, communication, monitoring and ventilation systems, and an emergency system.

[0120] ① Built-in anti-top system, such as Figure 8 shown.

[0121] The back-pull cleaning scheme is divided into 5 sections, with a total of 4 anti-jacking devices. The front inner support ring 1 is connected to the pipe joint with high-strength bolts (180 bolts); the water stop ring 2 is connected to the front inner support ring 1 with bolts; the outer retaining ring 3 is inserted from the left; the outer sealing ring 4 is connected to the pipe joint and the outer retaining ring 3 with bolts; finally, 16 80t anti-jacking cylinders are installed at the bottom, and the cylinders are equipped with travel meters and connected to the control room.

[0122] ②Soil injection system

[0123] The pull-back pipeline is located in the ②3-1 clayey silt layer, and its compression modulus is 7.8MPa. After experiments, the final ratio of yellow clay: curing agent: water: pumping agent = 1000:100:1000:1. The average compression modulus after curing for 1 day is 1.9MPa, the average compression modulus after curing for 3 days is 2.6MPa, and the average compression modulus after curing for 28 days is 14.4MPa.

[0124] Because the pipeline is long, the soil is mixed on the well and pumped to the front end of the pipeline. Then, the curing agent is added and mixed for a second time before being pumped to fill the gap in front of the machine head to ensure that the soil is densely injected. The specific filling is as follows: Figure 3 shown.

[0125] ③ Grouting system

[0126] In order to continuously inject lubricating slurry between the pipe wall and the soil layer during the pullback cleaning process, on the one hand, the friction resistance between the pipe wall and the soil layer is reduced, and on the other hand, the disturbance of the pipe wall to the surrounding soil layer during the pullback process is reduced. The slurry holes are arranged with a section spacing of 5m, and 5 holes in each section. The grouting material is composite bentonite, with a ratio of bentonite and water of 1:12, a viscosity of 85s, and a specific gravity of 1.04. The initial grouting amount is 3 times the theoretical gap amount, and a small amount is injected multiple times. The grouting amount is adjusted according to the pullback resistance in the later stage, and the grouting pressure control is the same as in Example 1.

[0127] ④ Anti-pull system

[0128] The anti-pull system consists of an anti-pull beam (including a steel cover plate) in front of the pipeline, steel strands and brackets inside the pipe, a working well anti-pull cylinder and an anti-pull beam. The anti-pull beam (including a steel cover plate) creates conditions for soil injection and pressure maintenance in the front, and provides a tie point for the steel strands; the bracket inside the pipe ensures that the steel strands are straight when bending and neatly distributed on both sides of the pipeline in a non-pretightened state; the working well anti-pull beam provides an anti-pull force point and a steel strand tie point; the anti-pull cylinder provides anti-pull power. During operation, the anti-pull cylinder's jacking force should be controlled to be less than the total breaking force of the steel strands (considering the safety factor) and less than the bearing capacity of the working well, pipes, anti-pull beams, and anti-pull beams.

[0129] ⑤Tunnel water stop system

[0130] The soil layer at the entrance of the working well is ②3-1 clay silt layer with high permeability. During the pullback construction, 4 graphite packings are used to prevent leakage at the entrance. The water-stopping equipment has a tightening function. During use, if leakage occurs, the nut is quickly tightened to achieve a compression and water-stopping effect.

[0131] ⑥Measurement system

[0132] The mileage of the front end of the pull-back pipeline is automatically measured, which not only avoids interference with the construction but also collects data on the pull-back distance of the front end of the pipeline, so as to better control the settlement of the surrounding environment. Figure 5 shown.

[0133] ⑦ Monitoring system

[0134] In the pullback area, automatic means are used to monitor the surface and pipeline settlement. Figure 6 and Figure 7 shown.

[0135] ⑧Lighting, communication, monitoring and ventilation systems

[0136] Lighting: 36V LED light strips are installed in the pipeline; Communication: the underground signal is weak, and wired telephones are used in combination with walkie-talkies. The telephones are installed at important locations such as the front-end soil injection pump, built-in back-pull system, and working wells; Monitoring: high-definition cameras are installed at important locations such as the front-end soil injection pump, built-in back-pull system, and working wells, and connected to the well control room for real-time monitoring; Ventilation: ventilators are installed according to specifications, personnel carry four-in-one gas detection instruments, and an air real-time monitoring and alarm device is installed at the front end.

[0137] ⑨ Emergency System

[0138] During the pull-back process, a local gas pipeline above the pipeline had a settlement alarm, and emergency soil injection was carried out from the inside of the pipeline to effectively control the settlement of the modified pipeline. The ratio of soil injection materials was 1.5:1 for yellow clay: water, and the amount of soil injection was adjusted according to the monitoring data. At the same time, grouting holes were pre-buried on the surface of the pull-back range before the pull-back construction. Once the surrounding environment was affected and could not be controlled during the pull-back process, double liquid slurry was injected from the pre-buried grouting holes to control the settlement.

[0139] Step 3: Install and debug the pull-back cleaning system. The pull-back cleaning system is installed from the inside of the pipe to the outside. Large items are given priority to enter the predetermined position in the pipe to avoid transportation difficulties. After each system is installed and debugged, linkage debugging is carried out. The steel strands are stressed, the backstop device is retracted, the pipeline is moved in sections toward the working well, and the last built-in anti-top is slowly retracted. The machine head is pulled back by the steel strands while soil is injected synchronously, and friction-reducing slurry is injected synchronously during this period. The specific debugging steps are as follows:

[0140] ① Such as Fig. 9 The steel strand is subjected to the designed friction force Fn+1=3.14×D×fn+1×Ln+1×Kn+1 and is adjusted according to the actual friction force.

[0141] ② If Fig.10 , the stop device retracts, releasing the space for pulling the pipeline back in the working well, and the retraction distance is not greater than the protection stroke of the built-in anti-top jack.

[0142] ③If Fig.11 , the built-in anti-jack 1 is started, the jack cylinder extends, the extension distance is less than the cylinder protection stroke, and the cylinder pressure is less than the design value. Under the action of the built-in anti-jack 1, the L1 section is pushed into the working well.

[0143] ④ Such as Fig.12 , the built-in anti-jack 2 is started, the jack cylinder extends, the extension distance is less than the cylinder protection stroke, and the cylinder pressure is less than the design value. The L2 section moves toward the working well until the built-in anti-jack 1 jack cylinder stroke is retracted and closed.

[0144] ⑤ Such as Fig.13Similarly, the subsequent built-in anti-top systems are started in sequence, and the subsequent built-in anti-top systems in the direction of the working well are closed, so that the pipeline moves toward the working well section by section.

[0145] ⑥ Such as Fig.14 , the built-in anti-top n cylinder slowly retracts to match the synchronous soil injection rate in front, and the Ln+1 section is pulled back by the steel strand and moves toward the working well until the stroke of the built-in anti-top n cylinder is closed, and the synchronous soil injection in front fills the gap formed by the pullback.

[0146] Step 4: Pull back the pipe for cleaning, separate the pipe sections, and transport them back to the factory for repair and reuse. Pull the pipeline back to the working well gradually. Each time a section of the pipeline (2.5m long) is pulled back, the steel strand is cut once. After the steel strand is cut, it is coiled in the pipe. The pipe sections are separated by the pipe section lifting holes and the jack. After the pipe sections are separated, they are hoisted out and transported to the pipe factory for repair and reuse after they are qualified.

[0147] The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of various changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A construction method for pulling back and cleaning large-diameter concrete pipes in a central urban area, characterized in that: The following steps are involved: S1. Calculate the pipeline friction required to pull back the entire pipeline according to the average friction between the pipe wall and the soil layer; S2, calculate the pipeline friction resistance, the allowable top force of the working well (F1), the allowable tension of the front end pull node of the pipeline (F2), and the allowable top force of the pipe. When the pipeline friction resistance is greater than the allowable top force of the working well, the allowable tension of the front end pull node of the pipeline, or the allowable top force of the pipe, execute S3, otherwise execute S5; S3, adopting segmented pullback cleaning strategy; S4. Configure a segmented back-pull pigging system, which includes a built-in anti-top system, a soil injection system, a grouting system, a back-pull system, a hole water stop system, a measurement system, a monitoring system, lighting, communication, monitoring and ventilation systems, and an emergency system; S5, adopt the whole-section pullback cleaning strategy; S6. Configure the whole section back-pull pigging system, which includes soil injection system, grouting system, back-pull system, hole water stop system, measurement system, monitoring system, lighting, communication, monitoring and ventilation system and emergency system; S7. Installation and commissioning of the pullback pigging system; S8. Start the pull-back cleaning system, start pull-back cleaning, separate the pipe sections, and transport them back to the factory for repair and reuse.

2. The construction method for pulling back and cleaning large-diameter concrete pipes in the central urban area according to claim 1 is characterized in that: The average friction resistance between the pipe wall and the soil layer is f (KN / m 2 ) is obtained according to the type of soil layer and the material of the pipe.

3. The construction method for pulling back and cleaning large-diameter concrete pipes in the central urban area according to claim 2 is characterized in that: The calculation formula of the pipeline friction resistance F (KN) is: F=3.14×D×f1×L1×K1+3.14×D×f2×L2×K2+...+3.14×D×fn×Ln×Kn+3.14×D×fn+1×Ln+1×Kn+1; Among them, the total length of the pipeline L (m) = L1 + L2 + ... + Ln + Ln + 1; Where D(m) is the outer diameter of the pipe and K is the additional coefficient of curve tension.

4. The construction method for pulling back and cleaning large-diameter concrete pipes in the central urban area according to claim 1 is characterized in that: The built-in anti-top system uses a built-in anti-top device to pull the pipeline back in sections. The built-in anti-top device is a steel structure, including a front inner support ring, a water stop pressure ring, an outer retaining ring, an outer sealing ring, an inner retaining ring flange, an inner retaining ring body, an inner friction ring, a relay room jack, a cylinder clamp, a limit flange and a rear inner support ring; Among them, the front inner support ring, the rear inner support ring and the pipe wall are connected with high-strength bolts, and the front inner support ring and the rear inner support ring are connected with a water-stop pressure ring, an outer retaining ring, an outer sealing ring, an inner retaining ring flange, an inner retaining ring body, an inner friction ring, a relay jack, a cylinder clamp and a limit flange by bolts to form a movable socket structure. A rubber ring is arranged between the movable socket structure and the pipe wall for water stopping, and the relay jack is used to jack up two adjacent sections of the pipe.

5. The construction method for pulling back and cleaning large-diameter concrete pipes in the central urban area according to claim 1 is characterized in that: The soil injection system includes a primary soil mixer, a No. 1 soil injection pump, a soil delivery pipeline, a secondary soil mixer, a No. 2 soil injection pump, an upper soil injection pipe and a lower soil injection pipe; The secondary soil mixer is connected to the feed end of the No. 2 soil injection pump, the upper soil injection pipe and the lower soil injection pipe are connected to the discharge end of the No. 2 soil injection pump, the soil delivery pipeline is connected between the discharge end of the No. 1 soil injection pump and the feed end of the secondary soil mixer, and the primary soil mixer is connected to the feed end of the No. 1 soil injection pump; Among them, the primary soil mixer, No. 1 soil injection pump, soil delivery pipeline, secondary soil mixer and No. 2 soil injection pump are configured according to the pipeline length and matched with the pull-back speed a (m / h). The backfill volume V (m 3 / h) not less than the theoretical gap V1(m 3 / h), the specific calculation formula is as follows: V≥V1, V1=3.14×R×R×a; Where R(m) is the outer diameter of the pipe.

6. The construction method for pulling back and cleaning large-diameter concrete pipes in the central urban area according to claim 1 is characterized in that: The grouting system is used to continuously inject lubricating slurry between the pipe wall and the soil layer during the process of pulling back and cleaning the pipe. The grouting material is composite bentonite. The grouting amount is not less than 2 cm gap on one side. The grouting pressure (P) is: P = krh; Among them, P is the grouting pressure (kpa), k is the empirical coefficient, which is 0.8-1.2, and r is the soil density (KN / m 3 ), h is the buried depth of grouting point (m).

7. The construction method for pulling back and cleaning large-diameter concrete pipes in the central urban area according to claim 1 is characterized by: The anti-pull system is composed of an anti-pull beam with a steel cover plate arranged in front of the pipeline, a steel strand, a bracket, an anti-pull cylinder and an anti-pull beam; Among them, the anti-tension beam with steel sealing plate is used to create conditions for the front soil injection and pressure maintenance, and provide a tie point for the steel strand; the bracket is used to ensure that the steel strand is straight after bending and neatly distributed on both sides of the pipeline in a non-pre-tightened state; the anti-top beam is used to provide an anti-top force point and a steel strand tie point, and the anti-top cylinder is used to provide anti-top power; The hole water-stopping system adopts packing water-stopping, and the packing material is graphite packing or stainless steel wire reinforced expanded graphite packing.

8. The construction method for pulling back and cleaning large-diameter concrete pipes in the central urban area according to claim 1 is characterized by: The measuring system includes a mileage measuring system, the measuring method is automatic measurement, and the mileage measuring system is composed of a guide prism, a rear-view prism, a total station, an automatic leveling base, a forced centering platform, an information control box, a display and software; The forced centering platform is fixed at the turning point of the jacking tunnel, and ensures that it is always in sight with the guide prism in the front end of the pipeline and the rear-view prism in the working well; The monitoring system monitors the surface and pipeline settlement in an automated manner, and the monitoring system includes an axial settlement sensor, a cross-sectional settlement sensor, a pipeline settlement sensor, and a reference sensor; Among them, the axial settlement sensor is arranged just above the axis of the jacking pipe and arranged along the axis of the jacking pipe at intervals of 2.5m. The position of each axial settlement sensor is an axis monitoring point. A surface monitoring section is arranged every 10m. Each surface monitoring section contains 6 section monitoring points and 1 axis monitoring point. The section settlement sensor is arranged at the section monitoring point, and the distances between the section monitoring point and the axis monitoring point are 1.5m, 4.5m, and 11.5m respectively.

9. The construction method for pulling back and cleaning large-diameter concrete pipes in the central urban area according to claim 1 is characterized by: The lighting, communication, monitoring and ventilation systems use a voltage of no more than 36V, and the LED light strips in the pipelines are no more than 36V; communication uses wired telephones with intercoms; monitoring uses high-definition cameras; ventilation is 3m of fresh air per person per minute. 3 , the minimum wind speed is not less than 0.15m / s; The emergency system is used to open emergency holes inside the pipeline to inject soil to control the settlement when the building above the pipeline settles during the pull-back process; and to open pre-buried grouting holes on the surface above the pull-back clearing area before construction. When the settlement cannot be controlled, the pre-buried grouting holes are used to inject double liquid slurry to quickly control the settlement.

10. The construction method for pulling back and cleaning large-diameter concrete pipes in the central urban area according to claim 1 is characterized in that: The installation sequence of the pullback pigging system is that large equipment is given priority to enter the predetermined position in the pipe, and the debugging method is single system debugging followed by linkage debugging.

Images