With the continuous acceleration of China's urbanization process, the scale of gas pipeline laying in cities and towns is also increasing. The construction of gas pipelines has high requirements for construction technology, and since the advent of directional crossing construction technology, it has brought great convenience to the construction of gas pipelines. At present, directional crossing construction technology has been widely used in China and has shown a relatively high value. In the actual gas pipeline directional crossing construction, in order to effectively ensure the construction quality, it is necessary to grasp the construction points of each link and not miss the details of any link.
This paper first introduces the directional crossing construction technology, then clarifies the application principle of the gas pipeline directional crossing construction technology, then introduces the application process of the gas pipeline directional crossing construction technology, then analyzes the specific application points of the gas pipeline directional crossing construction technology, and finally puts forward the optimization and control measures for the construction quality of the gas pipeline directional traversal.
01.An introduction to directional traversing construction techniques
Directional crossing construction technology is a new technology in modern gas pipeline construction, and it is also a commonly used technology. If you want to ensure the smooth development of construction operations and the construction quality standards, you must adopt some advanced, scientific and reasonable construction technologies, including directional crossing construction technology.
The basic principle of directional crossing construction technology is: relying on the pre-optimized design of 1-3 = 1-1 * 9 10 + 2 * 9-7 = 3 gas pipeline laying route, using professional drilling rig equipment for drilling, bypassing various underground obstacles in the drilling process and directly reaching the design destination, and then through the relevant treatment of the pilot hole in the track to make it meet the requirements of the diameter of the pipe, and finally the traction pipeline enters the track from the borehole to complete the gas pipeline laying work. In practical application, the directional crossing construction technology can complete the laying, detection, repair and replacement of complex underground pipelines without excavation. In general, the directional crossing construction technology mainly has the advantages of high construction accuracy, low environmental pollution, no obstruction of traffic, high safety and short construction period.
02.Principles of application of gas pipeline directional crossing construction technology
2.1 Standard Principles
Therefore, in the application of gas pipeline directional crossing construction technology, the standard principle should be fully followed, and the construction steps should be effectively guaranteed to meet the requirements of relevant standards, and ensure that the construction is carried out in strict accordance with the design drawings to continuously improve the level of construction standardization.
2.2 Safety Principles
Safety always comes first in any work, especially in construction. Therefore, in the application of gas pipeline directional crossing construction technology, the safety principle should be fully followed to maximize the construction safety and avoid the occurrence of various accidents. In order to effectively ensure the safety of construction, a comprehensive exploration survey should be done before construction, and effective plans should be formulated for these problems in advance according to geological data, environmental data, hydrological data, etc., and safety precautions should be effectively taken.
2.3 Quality principle
The quality of gas pipelines is directly related to the safety of people's lives and property and the sustainable development of towns, so in the application of gas pipeline directional crossing construction technology, the quality principle should be fully followed, the construction quality should be fully guaranteed, and any construction quality problems should be prevented. In particular, we should pay attention to the quality of details, because often details determine success or failure, and only by ensuring that every detail is up to standard, can we ensure that the overall construction quality meets the standard. In addition, some construction weaknesses are also the focus of quality monitoring objects, and the hidden quality hazards in these places should be minimized to better ensure the quality of construction.
03.The application process of gas pipeline directional crossing construction technology
The technical process of gas pipeline directional crossing construction is as follows: Measurement pay-off: Accurate measurement pay-off is carried out to reasonably determine the location of the leveling point and related data information; Understand the situation of underground pipelines: fully understand the situation of underground pipelines in the construction area through comprehensive investigation and field survey; Verify the location of the pipeline: verify the specific location of the pipeline according to the construction design drawings and related information; Equipment in place: send relevant construction equipment to the construction site; Equipment fixation and commissioning: fixation and commissioning of related construction equipment; Drilling pilot holes: Carry out effective drilling pilot hole operations; Reaming: Carry out effective reaming operations; Pipeline Dragback: Carry out effective pipeline pullback operations; Clearance and evacuation: Thoroughly clean up the construction site and evacuate it safely.
04.Key points of the specific application of gas pipeline directional crossing construction technology
4.1 Measure pay-off
The accuracy of the measurement pay-off results is directly related to the actual construction quality of the gas pipeline directional crossing construction. The main purpose of measuring pay-off is to reasonably determine the position of the leveling point and related data information. Normally, there are two main methods for measuring pay-off, one is the straight line segment method and the other is the curve method. Measuring pay-off is a manual work, and it is inevitable that there will be certain errors, but the error of measurement pay-off must be controlled within the allowable range. In order to obtain more accurate measurement pay-off data, repeated measurements should be carried out in practice. In addition, after the measurement pay-off is completed, the measurement data needs to be repeatedly checked based on relevant technical data to ensure the accuracy of the measurement pay-off results.
4.2 Understand the situation of underground pipelines
Before the directional crossing construction of the gas pipeline, a comprehensive investigation and on-site survey should be carried out to understand the situation of the underground pipeline clearly and avoid damage to the surrounding underground pipeline during the actual construction process. In the process of actual investigation and survey, it is necessary to strengthen the grasp of details, and not to omit any problems that may affect the actual construction operation.
4.3. Verify the location of the pipeline
In order to ensure that the gas pipeline is laid accurately in accordance with the design parameters, and to ensure that the bad bottom and underground in-service pipelines and structures can be effectively avoided in the actual construction process, the location of the pipeline should be effectively verified before the horizontal directional drilling construction, and the actual construction operation should be carried out on the premise of clearly grasping the specific location of the pipeline.
4.4. The equipment is in place
Under normal circumstances, the main equipment that needs to be used in the directional crossing construction of gas pipelines is directional drilling rigs, mud systems, motor units, etc., and the relevant construction equipment should be sent to the construction site in advance to avoid temporary deployment of equipment during the construction process and affect the construction progress.
4.5. Fixed debugging of the equipment
When the gas pipeline directional crossing construction equipment is in place, it is necessary to carry out effective equipment fixing and commissioning. In the process of fixed installation of equipment, it is necessary to ensure that the installation is standardized, such as all cables should be buried, and water pipelines and driving routes should be isolated from each other. In the debugging process after the equipment is fixed, it is necessary to carry out careful and comprehensive debugging, test the installation quality of the equipment, focus on the quality control of drilling tools, and find and deal with the problems in the equipment in a timely manner.
4.6. Drill pilot holes
4.6.1. Excavation into the soil work pit
Excavation into the soil work pit is a preliminary operation of drilling pilot hole in the construction of gas pipeline directional traversing, mud circulation pool can be set in the soil working pit, in the process of actual excavation into the soil work pit, pay attention to strictly control the depth, length, width and other parameters of the pit, to ensure that it is consistent with the construction design.
4.6.2 Prepare the slurry
The mud material used in the directional crossing construction of gas pipeline is a kind of bentonite mud composed of water, bentonite and admixtures, and the mud ratio must be scientifically carried out to ensure that the viscosity, dynamic shear force, static shear force and lubrication of the mud and other parameters meet the standard. For example, when the soil is mainly plain soil and sandy soil layer, it is advisable to control the mud viscosity at about 45s during the drilling pilot hole operation.
4.6.3. Pipeline pressure test
During the drilling of pilot holes in the construction of gas pipeline directional crossing, it is necessary to carry out effective pipeline pressure testing, especially pipeline strength test. In the specific pipeline pressure test process, the pressure gauge with specific accuracy requirements should be used and compressed air as the test medium, the pressure test pipeline interface should be effectively connected with the air compressor first, and then an appropriate amount of compressed air should be added to the pressure test pipeline in the environment of 40 temperature, during which it should be noted that the strength test pressure must be greater than the design pressure, when the test pressure reaches the relevant standards, then maintain the stable pressure for 1h and closely observe the pressure gauge for half an hour after that, if there is no air leakage at all, it can be proved qualified, Otherwise, the test pressure needs to be lowered to atmospheric pressure before being treated accordingly. Secondly, an effective air tightness test should be carried out to verify whether the air tightness of the pipeline meets the relevant standards.
4.6.4. Pilot hole drilling
In the process of drilling the formal pilot hole in the directional crossing construction of the gas pipeline, attention should be paid to the clear drilling trajectory (see Figure 2), according to the drilling diameter given in the design drawings and the specific specifications and models of the gas pipeline to determine the reasonable final soil angle, and in the whole process of drilling, the drilling direction, drilling speed and drilling depth should be fully controlled in accordance with the design drawings to ensure that the drilled pilot hole is clean and tidy. It should be noted that the phenomenon of slurry is very easy to occur during the drilling process, so we should attach great importance to this and take reasonable measures to deal with the problem of slurry in time.
In addition, during the pilot hole drilling process, the drilling parameters such as mud pressure, torque, and mud flow should be recorded in detail in real time. Generally speaking, it is required to control the mud pressure in a reasonable range, once the pressure increase problem occurs, the drilling should be stopped immediately and retreated 1-2m, and then the rotation state should be maintained for a certain time, and then slowly move forward to the previous position, and the drilling should be carried out again; Once the pressure drop occurs, the emergency rapid drilling breaks through this area and enters the mud pressure stability area in the shortest time. In addition, if there is a potential mud suffocating out of the formation during drilling, the relevant mud plugging agent should be used in time to optimize the performance of the mud, so as to improve the problem. The success of the final pilot hole drilling can be judged according to the actual drilling trajectory.
4.7 Reaming
Reaming is an operation link that is easy to be ignored in the directional crossing construction of gas pipelines. After the pilot hole has been drilled, an effective reaming is required. Under normal circumstances, the method of reaming should be graded and multi-reaming, in order to ensure the reaming effect to the greatest extent. It should be noted that in the actual reaming process, it is necessary to always maintain the tightness and coordination between the various processes, and if the reaming is not smooth, the hole should be cleaned immediately, that is, the sediment in the hole should be cleaned up, so as to play the role of correcting the hole. Generally speaking, it is advisable to carry out two hole cleaning treatments after the reaming is completed and before the pipeline backhauling operation is carried out. It is necessary to ensure that the final reaming diameter fully meets the requirements of geological conditions, pipe diameter and crossing length.
4.8 Pipe pullback
In the process of gas pipeline directional crossing construction, pipeline backhauling operation is a crucial operation. Before carrying out the pipeline towing operation, it is necessary to ensure the patency of each channel and mud nozzle of the reamer to ensure that the connection treatment is effective. In the actual pipeline towing process, it is necessary to place the rollers first to keep the distance between each roller appropriate, and also use a crane to cooperate with the operation, and place the rollers on the wet soil or sandbag bag, so as to protect the outer wall of the pipeline during the towing process. Secondly, it is necessary to keep the e-tube line coaxial with the gas pipeline through repeated calibration, so as to minimize the torque in the process of the e-tube, thereby reducing the drag resistance and preventing the friction damage of the gas pipeline. Furthermore, it is necessary to ensure that the reamer is carried out with a uniform rotation and a uniform speed of dragging, and control the pullback to carry out the operation continuously, so as to avoid interruption of the drag back due to the influence of various external factors.
4.9 Evacuation
After the completion of the gas pipeline directional crossing construction, the construction site needs to be thoroughly cleaned, all kinds of sundries and garbage left over from the construction should be cleaned up, and the relevant equipment should be transported away from the site, and then evacuated safely.
05.Optimization and control measures for the construction quality of gas pipeline directional crossing
5.1. Reasonable selection of pipeline materials
In the construction of gas pipeline directional crossing, pipeline materials are the most important construction materials, and it is necessary to reasonably select pipeline materials to ensure that the quality and performance of pipeline materials meet the standards, so as to ensure the construction quality. Generally speaking, the pipeline material is required to have a perfect three-layer structure, and at the same time, the length and wall thickness of the pipeline and other parameters must also meet the standard.
5.2. Strengthen the protection of the anti-corrosion layer outside the pipeline
If the external anti-corrosion layer of the pipeline is damaged, it will inevitably increase the corrosion risk of the pipeline and shorten the service life of the pipeline, so the protection of the anti-corrosion layer outside the pipeline should be strengthened in the directional crossing construction of the gas pipeline. Specifically, the main reasons to strengthen the protection of the anti-corrosion layer outside the pipeline are: to ensure the rationality of the position and depth of the pipe, to take 3PE reinforced anti-corrosion repair for the weld between the main pipe and the casing, to fill the flexible material around the nozzle of the main pipe and the steel casing, to try to reduce the impact of stones and debris in the sending ditch, and to strengthen the hole cleaning operation of the special geological section.
5.3. Adopt the whole process quality control mode
The traditional construction quality management mode only pays attention to the pre-event and post-event management and ignores the in-process management, which cannot effectively meet the quality control requirements of the gas pipeline directional crossing construction. To this end, the construction management should be improved, the whole process of quality control mode should be adopted, and the construction quality management work should run through all stages, including the design stage, the procurement stage, the construction stage, the completion acceptance stage, etc., and the human, material, financial and system and other quality influencing factors involved in the construction period should be effectively emphasized, pay attention to the specific changes of each element in real time, and coordinate the contradictions between different links and processes, so as to truly and effectively ensure the construction quality.
Wrapping up
In practice, it is necessary to carry out the construction work in strict accordance with the scientific and standardized construction process to ensure that the construction points of each link are grasped, and effective construction quality optimization and control measures are taken to effectively ensure the construction quality.