CN113007611A

CN113007611A - Monitoring system for gas pipeline crossing river bottom

Info

Publication number: CN113007611A
Application number: CN202110187934.0A
Authority: CN
Inventors: 于斌; 尹生开; 崔庆春; 高艳秋
Original assignee: Hohhot China Gas Urban Gas Development Co ltd
Current assignee: Hohhot China Gas Urban Gas Development Co ltd
Priority date: 2021-02-18
Filing date: 2021-02-18
Publication date: 2021-06-22
Anticipated expiration: 2041-02-18
Also published as: CN113007611B

Abstract

A monitoring system for gas pipeline crossing river bottom, comprising: the multi-section gas pipeline penetrates through the river bottom from the working pit on one side of the river channel and extends to the receiving pit on the other side of the river channel; the plurality of soil layer detectors are buried around the plurality of sections of gas pipelines and used for measuring soil layer state parameters; the cathode connecting wire electrically connects the at least one soil layer detector with the at least one section of gas pipeline; and the anode connecting wire electrically connects the at least one soil layer detector with the at least one sacrificial anode cell. According to the monitoring system for the gas pipeline to penetrate through the river bottom, disclosed by the embodiment of the invention, the non-excavation horizontal directional drilling and pipe drawing construction is monitored in real time by adopting the soil layer detector, so that the environment is not polluted, the traffic is not influenced, the construction period is short, the comprehensive cost is low, the construction cost is saved, the construction period is shortened, and no potential safety hazard exists.

Description

Monitoring system for gas pipeline crossing river bottom

Technical Field

The invention relates to the field of gas pipeline laying, in particular to a monitoring system for gas pipelines to cross river bottoms.

Background

The urban underground gas pipe network is a system formed by all facilities from a door station to a user, and comprises a door station or plant pressure compressor, a gas storage facility, a pressure regulating device, a transmission and distribution pipeline, a metering device, a management facility, a monitoring system and the like. These gas pipelines are usually buried underground to isolate the corrosion of external oxygen and moisture to the pipelines, thereby improving the safety of gas supply. As a result, gas pipelines often face situations in which they encounter various other pipeline or geological conditions during the laying process, such as being parallel or intersecting with tap water, power supplies, communication networks, or needing to traverse rivers, subways, culverts, tunnels, and the like.

However, when the gas pipe network needs to cross the river channel, especially when the difference between the river surface and the actual ground is usually large (for example, more than 20 meters) and the soil layer hardness is high (for example, the river bottom and the river banks on both sides are cast-in-place concrete), the following common schemes have limitations:

1. and (5) suspension construction. A support may be laid or mounted generally beneath a bridge spanning a river channel, with the gas pipeline suspended from the support to span the river. However, the position distribution of the river channel bridge is often inconsistent with the position distribution of the gas pipeline, and the river crossing position is difficult to optimize aiming at the layout of the gas pipeline network. Further, the gas pipeline is hung outdoors for a long time, which is convenient for maintenance, but is easy to cause frost cracking or deviation of the pipeline when exposed to extreme weather (such as low temperature or strong wind), and has additional construction risks.

2. And (5) grooving construction. Because the fall between the river surface and the actual ground is more than 20 meters, the slope is greatly enlarged during construction, the construction range is enlarged, and the excavated earth volume far exceeds the actual earth volume to be excavated by the engineering; the concrete for breaking the river bottom of the small black river and the river banks at the two banks is difficult to remove, and river water needs to be drained or drained, so that the construction investment is huge; the grooving too deep can also cause certain potential safety hazard, the incident takes place easily, and the river course construction procedure is handled very complicacy simultaneously, and this scheme is difficult to adopt.

3. And (5) pipe jacking construction. Although the pipe jacking construction does not need to excavate a large amount of earthwork, two pits with the depth of 30 meters need to be excavated when entering and exiting due to the large drop height, and collapse prevention protection measures are taken for the pits, so that the construction difficulty and the potential safety hazard are increased, the pipe jacking operation with the depth of 30 meters needs to be effectively implemented by a very professional unit, the investment is huge, and the scheme is difficult to adopt.

Therefore, a construction method for gas pipeline crossing river bottom is needed to overcome the above technical difficulties.

Disclosure of Invention

Therefore, the present invention is directed to overcoming the above technical problems so as to enable efficient and safe penetration of a gas pipeline from a river bottom.

The invention provides a monitoring system for a gas pipeline to cross a river bottom, which comprises:

the multi-section gas pipeline penetrates through the river bottom from the working pit on one side of the river channel and extends to the receiving pit on the other side of the river channel;

the plurality of soil layer detectors are buried around the plurality of sections of gas pipelines and used for measuring soil layer state parameters;

the cathode connecting wire electrically connects the at least one soil layer detector with the at least one section of gas pipeline;

and the anode connecting wire electrically connects the at least one soil layer detector with the at least one sacrificial anode cell.

Wherein, the soil layer state parameters comprise the pressure, the humidity and the stray current of the soil layer.

The soil layer detector comprises a sensor and a controller, wherein the sensor is arranged on the surface of the shell, the controller is arranged in the shell, the sensor comprises a porous metal mesh which is in contact with the soil layer, a substrate which faces the porous metal mesh, a light emitter and a light receiver which are arranged on the substrate, and an air gap between the substrate and the porous metal mesh.

Wherein, the porous metal net is made of metal with good light reflection and difficult oxidation, and the aperture of the grid is smaller than 1 micron and larger than 50 nanometers.

The two or more sacrificial anode pools are respectively arranged on two sides of the river channel, and a plurality of sacrificial anode rods are inserted into each sacrificial anode pool and filled with insulating materials.

The density and the moisture-proof performance of the insulating material are superior to those of a soil layer in which the soil layer detector is located.

Wherein, a plurality of soil layer detectors are distributed on two sides and/or the upper and lower parts of the multi-section gas pipeline.

Wherein, every section of gas pipeline is stainless steel pipe, and the outer wall adopts three layer construction extrusion polyethylene in order to strengthen anticorrosive.

The soil layer detectors are electrically connected with the signal lines, and the side walls of the signal lines are reinforced and moistureproof and insulated by adopting MDPE or HDPE pipes.

Wherein the distance between each soil layer detector and the gas pipeline around the soil layer detector is within the range of 0.2 to 1 meter.

On the other hand, the invention provides a construction method for a gas pipeline to pass through a river bottom, which comprises the following steps:

step 1, measuring and positioning to determine the position parameters of the gas pipeline crossing the river bottom;

step 2, burying a plurality of soil layer detectors for measuring soil layer state parameters of the gas pipeline passing through the river bottom;

step 3, selecting and excavating a working pit and a receiving pit on the ground according to the position parameters and the soil layer state parameters;

step 4, positioning a drilling machine;

step 5, preparing slurry;

step 6, trial drilling;

step 7, drilling a guide hole;

step 8, back reaming;

step 9, dragging the pipe back, and dragging the multiple sections of gas pipelines from the working pit to the receiving pit;

step 10, on-site slurry treatment;

step 11, earth backfill;

and step 12, building the valve well.

Wherein, the position parameters comprise the position of the axis of the pipeline, and the elevation of the section, the ground and the water surface.

The soil layer detector in the step 2 comprises a sensor and a controller, wherein the sensor is arranged on the surface of the shell, the controller is arranged in the shell, the sensor comprises an expanded metal mesh which is contacted with the soil layer, a substrate which faces the expanded metal mesh, a light emitter and a light receiver which are arranged on the substrate, and an air gap between the substrate and the expanded metal mesh.

Wherein, in any one of the steps 7 to 9, the porous metal net is electrically connected with the fuel gas pipeline by adopting a cathode connecting wire.

Wherein, in any one of the steps 7 to 9, the soil layer detector is electrically connected with the sacrificial anode pool by adopting an anode connecting wire.

The sacrificial anode pool is two or more sacrificial anode pools respectively arranged on two sides of the river channel, a plurality of sacrificial anode rods are inserted into the sacrificial anode pools, and insulating materials are filled in the sacrificial anode pools.

Wherein, a plurality of soil layer detectors are distributed on both sides and/or the upper and lower parts of the gas pipeline to be paved.

Wherein, the gas pipeline is stainless steel pipe, and the outer wall adopts three layer construction extrusion polyethylene in order to strengthen anticorrosive.

After the technology of the invention is applied, the following effects can be achieved:

1) the construction process is simple, the operation is simple, and the organization and implementation are easy;

2) the safety is good, and constructor's operation all goes on subaerial, has avoided the influence of bad construction conditions such as deep basal pit operation, improves factor of safety.

3) The pipeline connection quality is good, because the pipeline connection is all carried out on the ground, the pipeline is pulled and laid once after being welded to be qualified, and the pipeline connection quality is improved.

4) Effectively reduces the cost and has good economic benefit.

5) The method has the advantages of no environmental pollution, no influence on traffic, small damage to ground bottom layers and capability of meeting the requirement of high environmental protection in urban underground pipe network construction.

6) The social benefit is obvious, and the administrative examination and approval of excavation can be reduced.

7) The construction period is short, and the transportation and the stacking of soil are not needed.

In conclusion, according to the monitoring system for the gas pipeline to penetrate through the river bottom, which is disclosed by the embodiment of the invention, the soil layer detector is adopted to monitor the trenchless horizontal directional drilling and pipe-pulling construction in real time, so that the environment is not polluted, the traffic is not influenced, the construction period is short, the comprehensive cost is low, the construction cost is saved, the construction period is shortened, and the potential safety hazard is avoided.

The stated objects of the invention, as well as other objects not listed here, are met within the scope of the independent claims of the present application. Embodiments of the invention are defined in the independent claims, with specific features being defined in the dependent claims.

Drawings

The technical solution of the present invention is explained in detail below with reference to the accompanying drawings, in which:

FIG. 1 is a schematic cross-sectional view of a monitoring system for gas pipeline crossing a river bottom according to an embodiment of the present invention;

FIG. 2 is a schematic top view of a monitoring system for gas pipeline crossing a river bottom according to an embodiment of the present invention;

FIG. 3 is a block diagram of the soil layer probe shown in FIGS. 1 and 2 in accordance with an embodiment of the present invention; and

fig. 4 is a flowchart of a construction method for a gas pipeline to cross a river bottom according to an embodiment of the present invention.

Detailed Description

The features and effects of the technical solution of the present invention will be described in detail below with reference to the accompanying drawings and illustrative embodiments, which disclose a construction method and a real-time monitoring system capable of efficiently and safely enabling a gas pipeline to pass through a river bottom. It is noted that like reference numerals refer to like structures and that the terms "first", "second", "upper", "lower", and the like as used herein may be used to modify various structures. These modifications do not imply a spatial, sequential, or hierarchical relationship to the structures being modified unless specifically stated.

The preferred embodiment of the invention takes the construction scheme of the under-small black river of the golden prevailing road gas pipeline called Mongolia and Haote as an example to explain the specific construction scheme. The project is located in the south of a golden bridge golden phoenix big hotel, two pipelines of medium pressure A phi 325 and secondary high pressure phi 457 pass through the north road of the silver river, the small black river and the south road of the silver river in a straight line distance of about 500 meters. The small black river is an extended landscape river, the fall between the river surface and the actual ground is larger and exceeds 20 m, the slope is greatly opened in grooving construction, the construction range is overlarge, and the river bottom and the river levees at the two banks of the small black river are cast-in-place concrete. Although the preferred embodiment of the present invention is exemplified by the engineering, it should be noted that the embodiment of the present invention can also be applied to the construction project of gas pipelines crossing other rivers, and only the process parameters need to be adaptively modified according to the geological conditions of the local river.

As shown in fig. 4, the construction method includes the steps of:

step 1), measuring and positioning, and determining the position parameters of the gas pipeline crossing the river bottom.

And (4) according to the design data, retesting all the wire points and the level points, and according to the result, lofting the pipeline and measuring the original ground. The position of the axis of the pipeline is marked by lime, the elevation of the section where the pipeline is to be laid, the ground and the water surface is measured, and an elevation section diagram is drawn, so that the elevation is accurately controlled during guiding construction.

The source of the design data may be based on the existing pipe network distribution diagram, such as the layout of the pipe burial depth and the GPS position. In addition, when the original pipe network distribution diagram is difficult to find or distinguish due to the long-term age, the original design data can be supplemented or modified through field measurement. Specifically, for an old pipe made of a metal material, particularly a magnetically conductive metal such as steel, etc., the distribution of the old pipe can be detected simply by using the earth magnetic change. However, for an old pipeline made of an insulating material (for example, polyethylene PE), since the old pipeline is non-conductive and non-magnetic, after the old pipeline is buried underground, no good method is available at present for directly detecting the spatial position of the old pipeline in the underground on the ground, and therefore, the existing geomagnetic change detection method cannot be applied. In order to track the buried insulated pipe, one or more tracing lines are laid around the old pipe (in the direction of the pipe extension) in parallel in the previous construction process, for example symmetrically on the left and right sides or on the top and bottom sides, or 3, 4, 6, 8, etc. in number and equiangularly/equidistantly around the circumference of the pipe. The tracing line has an exposed point at a valve of the pipeline and the like, and an alternating current signal with preset parameters (such as amplitude and/or phase) can be sent to the tracing line through the signal generator, so that the tracing line generates an electromagnetic field, and therefore the buried position of the pipeline can be determined by detecting the magnetic field generated by the underground tracing line by adopting the magnetic field detector on the ground, and construction is facilitated. And for the newly laid pipeline, the position parameters of the river channel passing through can be directly determined according to a pipe network distribution diagram submitted by a design unit.

It is noted that the construction project should be designed according to the town gas design Specification GB 50028-Bu 2006 and the town gas technical Specification GB 50494-Bu 2009. The valve installation should be under construction according to the valve product requirement, and the valve base should be placed on the stable layer. The gas pipeline project can be constructed after all buildings are dismantled within the range of 2.0m along the line. Because no underground corresponding pipe network facility data exists, the pipeline is required to strictly comply with the corresponding national standard when passing through and avoiding other pipelines. Before construction, a pit must be dug to recheck the pipe position, and construction can be carried out after meeting requirements. When the gas pipeline intersects with other pipelines, related protective measures or pipelines are required to be avoided and laid according to related standard space requirements or independent brick wall structure pipe ditches are required to be built.

Further, the engineering construction and acceptance are carried out according to the standard of 'urban gas distribution engineering construction and acceptance criteria' (CJJ 33-2005). If the road engineering is not constructed for a while, only the current road surface is taken as a reference, but the burial depth (from the pipe top to the road surface) of the gas pipeline after the road is formed must be ensured not to be lower than 1.6m (below a frozen soil layer so as to avoid the softening or hardening of the frozen soil to influence the safety of the gas pipeline).

And step 2), burying a soil layer detector for measuring soil layer state parameters of the gas pipeline passing through the river bottom.

Drilling holes around the old pipeline or the area where the new pipeline to be paved is located and embedding a soil layer detector according to the position parameters of the gas pipeline passing through the river bottom determined in the step 1). For shallow channels, the drill holes can be dug deeply by manpower, and for deeper channels, a mechanical construction mode of drilling by adopting a pile driver is needed to form a plurality of drill holes. As shown in fig. 1 and 2, the plurality of boreholes is distributed, for example, at least on both sides of the region of the gas pipeline to be laid, and preferably has a plurality of intermediate distribution points on both sides of the river channel, and optimally also has at least two boreholes reaching the river bottom below the river channel. Preferably, the boreholes extend from the centerline of the pipe to either side to form a plurality of rows or columns for measuring the geological conditions of the earth at different distances on either side of the pipe. As shown in fig. 1, the depth of the soil layer probe is determined according to the distribution of the pipes to be laid, for example, above and/or below the pipes, preferably at a distance in the range of 0.2 to 0.1 meters from the pipes, providing positional redundancy of the pipe construction to prevent the drill holes from penetrating the probe lines, while also reducing the wiring resistance of the signal connection lines between the probe and the pipes, reducing the RC delay. Subsequently, a plurality of soil layer probes are placed at the bottom of the borehole and the soil is preferably backfilled to completely cover the soil layer probes. Although not shown in detail in fig. 1, 2, the side walls of the bore are preferably reinforced and moisture-proof insulated with Medium Density Polyethylene (MDPE) or High Density Polyethylene (HDPE) tubing to ensure reliability of later routing of various signal lines.

Fig. 3 shows a schematic view of a soil layer probe according to an embodiment of the present invention, in which one side surface, i.e. the working surface or active surface, faces a pipeline, and a soil layer is sandwiched between the side surface and the pipeline. Specifically, the soil layer probe includes a housing (shown in the outermost box in fig. 3), a sensor (shown in the right side box in fig. 3) disposed on and exposed at a surface of the housing, a controller within the housing, and a bus connecting the controller to the sensor. The sensor comprises an expanded metal mesh arranged on the surface in direct contact with the soil layer, a substrate arranged opposite to the expanded metal mesh, at least a light emitter and a light receiver arranged on the substrate, and an air gap between the substrate and the expanded metal mesh.

The porous metal net is made of metals such as Pd, Pt, W, Ti, Ta and the like which have good light reflecting performance and are not easy to oxidize, the pore diameter of the grid is smaller than the minimum particle diameter of soil in the soil layer (for example, smaller than 1 micron, preferably smaller than or equal to 0.5 micron, and most preferably smaller than or equal to 0.1 micron) so as to block soil particles from entering the air gap, and the pore diameter is larger than 50 nanometers so as to allow enough water drops or water vapor to enter the air gap. The porous metal mesh is polished to the surface of the substrate until the surface roughness is 20 nm or less so as to obtain a sufficiently large surface reflectance, for example, 99.5% or more.

The light emitter may be an LED or a laser for emitting a radiant wave having a wavelength of 400 nm to 1200 nm to the expanded metal. Preferably, the light emitter is an array formed by arranging a plurality of LEDs or lasers, and can emit radiation with different wavelengths or emit radiation with the same wavelength from different positions so as to improve the range and the accuracy of measurement. The light receiver is, for example, an array of a plurality of photodiodes for receiving the radiation or light waves reflected by the expanded metal.

During the measurement, the side of the expanded metal mesh which is in contact with the soil layer is subjected to lateral pressure of the soil layer and is thus bent and deformed towards the air gap side, so that the optical path of one or more radiation waves emitted by the light reflector is changed, and therefore the amount of change in the optical path can be converted by measuring the radiation received by the light receiver, such as the amplitude and phase of the light, and the lateral pressure of the soil layer can be determined. Meanwhile, because a plurality of pores exist on the porous metal mesh used as the reflecting layer, water drops or water vapor can penetrate through the pores of the meshes and enter the air gap, the refractive index of a medium in the air gap is changed, namely, the existence of the water vapor enables the optical path to change, and therefore, the detector can be used for detecting the pressure of the soil layer, and can also be compared with a reference value measured under the condition of dry air so as to determine the relative humidity of the soil layer. Preferably, the distribution positions of the grid pores of the expanded metal are not overlapped with the light reflector and the light receiver, that is, the expanded metal comprises a central flat plate part and surrounding grid parts, so as to improve the reflectivity of radiation or light and improve the measurement accuracy. Therefore, the soil layer detector shown in the figure 3 is adopted to measure the pressure and the humidity of the soil layer at the same time, and the efficiency and the precision of detecting the geological conditions are improved.

In addition, the steel fuel gas pipeline needs to be provided with sacrificial anode/cathode protection, and the material selection of the sacrificial anode should meet the relevant regulations in buried steel pipeline cathode protection technical Specification GB/T21448-. Specifically, the soil layer detector can be used for additionally adding a cathode connecting line or a detection connecting line to one side of the pipeline, and the cathode connecting line or the detection connecting line extends to one side of the pipeline from the soil layer detector (for example, is electrically connected with the porous metal mesh and/or the gas pipeline), so that a detection signal can be applied under the control of the controller to detect the current distribution in the soil layer so as to obtain the distribution of stray current around the gas pipeline, and the influence of other nearby pipelines or the native stray current of the soil layer on the gas pipeline can be conveniently eliminated later. When a stray current exceeding a threshold value is detected, a cathode connection line coupled to the gas pipe may be electrically connected to the sacrificial anode pool shown in fig. 2 under the control of the controller, thereby conducting the stray current to the sacrificial anode pool. The sacrificial anode tanks are at least two and are respectively arranged in soil layers on two sides of the river and are connected with the soil layer detectors through anode cables. A plurality of sacrificial anode rods are inserted into the sacrificial anode pool and filled with insulating materials, and the density and the moisture resistance of the insulating materials are superior to those of a soil layer where the soil layer detector is located. The sacrificial anode rod is, for example, a magnesium alloy rod packed in bags, each bag is four, and the weight of a single sacrificial anode rod is 11 kg. The cathode connecting wire and the anode cable wire are copper-core cables VV22-1Kv/1x10mm, for example, and the lengths are based on the actual use amount.

Step 3), excavating working pits and receiving pits

And (3) selecting an inlet of the pipeline drilling hole, namely a working pit, and an outlet of the pipeline drilling hole, namely a receiving pit, according to the pipeline position parameter determined in the step (1) and the soil layer state parameter determined in the step (2). The working pit and the receiving pit are excavated by a machine to ensure the safety of the underground pipeline, and the gradient of the working pit and the receiving pit conforms to the curvature radius of the pipe 1200d-1500d to ensure the smooth pipe drawing. As shown in figure 1, the working pit and the receiving pit are arranged on the surface of the soil layer far away from the river bank, and the multiple sections of gas pipelines enter from the working pit and are connected out from the receiving pit. The pipeline depth can be controlled by controlling the horizontal distance and the gradient, so that the vertical deep hole operation can be effectively avoided, the construction position can be flexibly determined according to the distribution of ground buildings, and the pipeline joint is prevented from being cracked due to stress concentration by reducing the gradient. The horizontal distance is determined primarily according to the pipeline position parameters, and after soil layer state parameters are measured, adaptive modification is performed, for example, if soil layer humidity (namely water content) or pressure exceeds a certain threshold value, transverse deviation is considered, or additional waterproof sleeves or pressure-proof sleeves are added in subsequent steps 7-9, or if stray current in the soil layer exceeds a certain threshold value, additional sacrificial anode protection measures are added. Temporary or semi-permanent enclosure can be installed around the work pit and the receiving pit, so that the influence of foreign impurities such as gravel on the pipeline is avoided while the construction safety is guaranteed, and the pipeline laying quality is ensured.

Step 4), positioning the drilling machine

And (4) checking whether the drilling machine works normally, and accurately, horizontally and stably positioning the drilling machine. Preferably, the drill bit has a position sensor (e.g. gyroscope, GPS locator, etc.) thereon to reduce the amount of stepping to avoid damage to the soil detectors when the drill bit subsequently comes into proximity with previously buried soil detectors, and the specially made drill bit can be replaced for laying the cathode connection wires that electrically connect the gas pipeline with the expanded metal.

Step 5) preparation of slurry

According to geological survey of a construction site, the soil involved in the non-excavation traction pipe engineering is mainly pebbles and quicksand layers, bentonite slurry is selected, additives such as a diluent and the like are added, 100kg of bentonite is added into every 2 cubic degrees of water, the bentonite slurry is prepared, and the bentonite slurry is uniformly mixed by a ZT-25, ZT-33 and XZ-680 type non-excavation pipe-laying drilling machine slurry mixing system for later use.

Step 6), trial drilling

Starting the drilling machine, drilling 1-2 drill rods, checking whether equipment and instruments operate well, timely processing problems, and checking whether a slurry mixing system leaks during drilling trial.

Step 7), drilling a guide hole

And operating the directional drilling machine to drill horizontally according to the measured axis, controlling the direction of the drill bit by adopting a Drilltrack directional drilling guide system on the upper part of the road surface, and forming a guide hole according to a design curve strictly. If the drill deviates from the designed track or has the tendency of deviating from the track, the direction of the drill is changed by adjusting the parameters of the drill, such as the inclination angle, the rotation angle and the like. And after the pilot hole is finished, rechecking the elevation and the direction of the working pit soil inlet and the receiving pit soil outlet to ensure that the hole is formed according to the design curve. In the construction process, the abnormal conditions such as torque, bit pressure mutation, slurry leakage and the like exist in the drilling process, the construction is stopped immediately when a problem is found, and the construction is carried out after corresponding measures are taken after the reason is found out.

The directional drilling crossing part needs to be independently tested for strength and tightness, the test pressure is equal to the trunk test pressure, the directional drilling crossing part is connected with an adjacent section after being qualified, if no corresponding geological prospecting data of the crossing section is provided, geological prospecting needs to be carried out before construction, and the directional crossing length can be properly adjusted according to actual conditions in the actual construction process, and the specific method is shown in 'CDBZ-R07-2014/31'.

Step 8), pre (back) reaming

And after the pilot hole is finished, the starting rod and the pilot bit are dismounted, and the back-expanding bit is replaced for back expansion. And the liquid level in the slurry pit in the working pit is always kept higher than the underground water level elevation in the back expansion process. And (3) well using the slurry in the back reaming process, well controlling each performance parameter of the slurry during reaming, detecting irregularly, and adjusting the performance index of the slurry in time according to the construction requirement.

Because the construction soil layer near the river channel is usually pebbles and quicksand, a cone-type reamer is selected to be suitable, and the reamer extrudes the sludge to the periphery of the hole wall through rotation to play a good hole fixing role. According to the characteristics of the stratum, the back-expansion drilling speed is reasonably controlled so as to facilitate slag discharge. The corresponding squeezing and expanding type drill bit is reasonably adopted by the four times of back expansion and the last time of back expansion, if the back dragging force and the back expansion torque are large, the back expansion needs to be carried out for one more time, so that the hole wall is formed and stabilized.

In the drilling process, the original construction record is made in time, and the record content comprises drilling time, axis angle, torque, jacking force, soil condition and the like. In the back expansion process, the abnormal conditions such as torque, bit pressure mutation and the like exist in the drilling process, the construction is stopped immediately when a problem is found, and the construction is carried out after corresponding measures are taken after the reason is found out.

Step 9), back dragging the pipe

The pipe connection is welded and corrosion-resistant strictly according to the welding construction requirements. The engineering buried pipelines are all stainless steel pipes, and are extruded by a three-layer structure to have super-high-level corrosion resistance, so that the engineering buried pipelines conform to the relevant regulations in buried steel pipeline polyethylene anticorrosive coatings GB/T23257-2017. The circumferential weld joint patch adopts a radiation cross-linked polyethylene heat-shrinkable sleeve (belt) which is matched with an epoxy primer three-layer structure. The external corrosion prevention of the elbow adopts a corrosion prevention scheme of shrimp-shaped lap coating of a radiation crosslinking polyethylene heat shrinkage sleeve matched with epoxy primer. And (3) damage treatment of the anti-corrosion layer pipe section: when the diameter of the injury part is less than or equal to 30mm, the radiation cross-linked polyethylene can be adopted to repair the injury. And (3) filling the concave part with hot melt adhesive when the diameter of the damage is larger than 30mm, and then coating the damage by using a heat shrinkable tape, wherein the coating width exceeds the edge of the hole by 100mm. Before the pipeline is put into a ditch, 100 percent of appearance inspection and electric spark leakage detection must be carried out on the anticorrosive coating; 100% electric spark leakage detection is carried out before backfilling, the integrity of the anti-corrosion layer is required to be subjected to full-line inspection after backfilling, and the anti-corrosion layer is required to be reworked until the anti-corrosion layer is qualified after disqualification.

Before pulling back, the welding quality should be checked, and after the welding inspection is qualified, the pipe can be pulled. And (4) carrying out 100% appearance quality inspection on the weld joint of the steel pipe, and inspecting the internal quality of the weld joint according to 100% after the appearance quality inspection is qualified. The appearance quality of the welding gun is not lower than the level II in the national standard of construction quality acceptance standard of field equipment and industrial pipeline welding engineering GB 50683 plus 2011. The radiographic inspection of the internal quality of the metal pipeline is not lower than the II-level quality requirement in the nondestructive testing metal pipeline fusion welding annular butt joint radiographic inspection method GB/T12605-2008 of the current national standard.

And placing the connected pipes along a ramp of the receiving pit, arranging a pulley carriage below the pipes, and sequentially connecting a joint, a transfer case and a drill rod. The pipes are connected in advance according to the length of the well section. Before tube drawing, tube taking is started within 3-4 hours, and tube drawing is started immediately after tube taking is completed.

In the process of back dragging the pipeline, the condition in the hole is closely noticed, and a driller operator needs to closely notice the back dragging force and the change of torque of the driller. The back dragging should be smooth and steady, and the brutal dragging is prohibited. The pipe is dragged into the formed hole at one time, so that the pause is avoided as much as possible in the midway, and the drag resistance is reduced.

During construction, a newly-built gas pipeline is laid firstly, an interface piece is reserved, after the contact is completed, the original pipeline is respectively broken, and nitrogen purging is performed on the waste gas pipeline twice.

Step 10), on-site slurry treatment

In the construction process, mud entering and exiting the soil point is pumped into a mud tank by a mud pump, is discharged to a reasonable position by a mud truck in time, and cleans up waste mud and recovers the original appearance before construction as much as possible.

Step 11), earth backfill

And after the construction, the pavement structure layer is restored as the original state. When the excavation working pit meets the garbage soil, the garbage soil at the bottom of the pit is cleaned, and the pit is tamped after the garbage soil is backfilled; when the excavated working pit meets backfill soil, tamping the backfill soil; the soil piling at the edge of the trench is required to be carried out according to the standard.

Step 12), valve well masonry

After the horizontal directional drilling and pipe pulling construction of the two banks of the river channel is finished, valve wells are arranged on the two banks of the river channel, and sacrificial anodes are additionally arranged for protection so as to control and protect a gas pipeline penetrating through the river channel. The valve well can be arranged by using the enclosure in the step 3 so as to save material cost and shorten construction period. The sacrificial anode protection is for example a sacrificial anode cell as shown in fig. 2, the electrical connection to the individual soil detectors can be done simultaneously in steps 7-9, or can be added after the laying of the pipeline is completed, for example step 11.

As mentioned above, the monitoring system for the gas pipeline crossing the river bottom is additionally arranged in the construction process, and comprises: the multi-section gas pipeline penetrates through the river bottom from the working pit on one side of the river channel and extends to the receiving pit on the other side of the river channel; the plurality of soil layer detectors are buried around the plurality of sections of gas pipelines and used for measuring soil layer state parameters; the cathode connecting wire electrically connects the at least one soil layer detector with the at least one section of gas pipeline; and the anode connecting wire electrically connects the at least one soil layer detector with the at least one sacrificial anode cell. Wherein, the soil layer state parameters comprise the pressure, the humidity and the stray current of the soil layer. In this way, the change of state parameters of soil layers around the pipeline, such as pressure and humidity, can be detected in real time during the construction process to decide whether to modify the pipeline distribution design (particularly the positions of the working pit and the receiving pit and the downward-detecting and upward-ascending gradient of the pipeline) or to increase the pipeline protection measures, thereby improving the safety and reliability of construction. Further, these monitoring systems can remain in the soil horizon after the construction is accomplished, cooperate together with other monitoring facilities that add afterwards such as gas leakage detection system, improve the operation security of gas pipeline.

According to the monitoring system for the gas pipeline to penetrate through the river bottom, disclosed by the embodiment of the invention, the non-excavation horizontal directional drilling and pipe drawing construction is monitored in real time by adopting the soil layer detector, so that the environment is not polluted, the traffic is not influenced, the construction period is short, the comprehensive cost is low, the construction cost is saved, the construction period is shortened, and no potential safety hazard exists.

While the invention has been described with reference to one or more exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the disclosure without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the disclosed apparatus and methods will include all embodiments falling within the scope of the present invention.

Claims

1. A monitoring system for gas pipeline crossing river bottom, comprising:

2. The monitoring system for the gas pipeline crossing the river bottom according to claim 1, wherein the soil layer state parameters comprise the pressure, the humidity and the stray current of the soil layer.

3. The monitoring system for the gas pipeline crossing the river bottom according to claim 1, wherein the soil layer detector comprises a sensor disposed on the surface of the housing and a controller disposed in the housing, the sensor comprising an expanded metal mesh contacting the soil layer, a substrate facing the expanded metal mesh, a light emitter and a light receiver disposed on the substrate, and an air gap between the substrate and the expanded metal mesh.

4. The monitoring system for the gas pipeline to cross the river bottom according to claim 3, wherein the porous metal net is made of metal with good light reflection and difficult oxidation, and the mesh aperture is smaller than 1 micron and larger than 50 nanometers.

5. The monitoring system for the gas pipeline crossing the river bottom according to claim 1, wherein two or more sacrificial anode pools are respectively arranged at two sides of the river channel, and a plurality of sacrificial anode rods are inserted into each sacrificial anode pool and filled with insulating materials.

6. The monitoring system for the gas pipeline crossing the river bottom according to claim 5, wherein the density and the moisture-proof performance of the insulating material are superior to those of the soil layer where the soil layer detector is located.

7. The monitoring system for the crossing of the river bottom by the gas pipeline according to claim 1, wherein a plurality of soil detectors are distributed on two sides and/or above and below the plurality of sections of the gas pipeline.

8. The monitoring system for the gas pipeline crossing the river bottom according to claim 1, wherein each section of the gas pipeline is a stainless steel pipe, and the outer wall of the gas pipeline is made of three-layer structure extruded polyethylene to enhance corrosion resistance.

9. The monitoring system for the gas pipeline crossing the river bottom according to claim 1, wherein a plurality of signal lines are electrically connected with a plurality of soil detectors, and the side walls of the signal lines are reinforced and moisture-proof and insulated by MDPE or HDPE pipes.

10. A system for monitoring the crossing of a river bottom by a gas pipeline according to claim 1 wherein the spacing between each soil layer probe and its surrounding gas pipeline is in the range of 0.2 to 1 meter.