Method for pre-judging and quickly dredging blockage of hydraulic reclamation underwater pipeline

Abstract

The invention relates to a method for pre-judging and quickly dredging blockage of a hydraulic reclamation underwater pipeline. Comprising the following steps that S1, the pipe blocking position of a pipeline is pre-judged; s2, further pre-judging water blowing of the cutter suction dredger; s3, the pre-judged pipe blocking positions in the step S1 and the step S2 are mutually verified, and the initial position of pipe blocking is finally determined; s4, planning to perform hole cutting on the underwater pipeline; s5, hole cutting is conducted on the pipe blocking position; s6, after cutting of all the cutting holes is completed, the cutter suction dredger blows water to the pipeline at the maximum pressure, and blockages in the pipeline are sprayed out of the cutting holes under the action of the water blowing pressure; and S7, after pipeline dredging is completed, the diver dives to the underwater pipeline, and an underwater welding machine tool is adopted for conducting welding and hole patching on the pipeline. The invention provides the method for pre-judging and quickly dredging the blockage of the hydraulic reclamation underwater pipeline, so that the dredging workload and the dredging treatment cost are reduced, and the treatment time is shortened to avoid the influence on the hydraulic reclamation construction efficiency.

Description

Technical Field

[0001] The invention belongs to the technical field of filling construction, and in particular relates to a method for predicting and quickly clearing pipe blockage in a filling underwater pipeline. Background Art

[0002] Blowing sand reclamation project refers to using the pump (some with long pipes) of a dredger (some use sand dredging ships) to blow the sand and water from the seabed outside the circle into the target circle. The seawater flows out of the circle, and the sand remains in the circle. Gradually, the sea surface in the circle is filled with land by the sand that is continuously blown in. Blowing sand reclamation is to pile up sand and create land around the reclamation point. It is different from traditional soil excavation and transportation, and it is also different from sand excavation and transportation. Long-distance sand blowing requires pipes of different lengths. In the blowing reclamation project, underwater pipelines are used to transport the blowing mud over long distances. When the mud in the pipeline is composed of pilling clay, medium-coarse sand, rock and other soil materials, it is easy to cause underwater pipeline blockage due to poor fluidity. After the pipe is blocked, it needs to be dredged and cleaned to restore the mud transportation capacity of the pipeline.

[0003] The traditional dredging method is to use a high-powered anchor boat to lift the underwater pipeline section by section from underwater to the surface, place a buoy under the steel pipe section, and rely on the welfare effect of the buoy to make the steel pipe section float above the water surface, and then transport it to land by the anchor boat, and use air compressors and other equipment to dredge the section at the repair and maintenance site, and put it into use again after dredging and cleaning. The above-mentioned dredging method has significant defects: the workload of disassembly-transportation back to land-dredging and cleaning and then reuse is very large, requiring a large number of personnel and facilities to operate, and the dredging cost is too high; and the dredging process takes a long time, which affects the hourly rate of construction ships (such as suction dredgers, etc.) and reduces the construction efficiency of reclamation projects. In summary, it is necessary to develop and design a method for predicting and quickly dredging underwater pipelines in reclamation to solve the problems of existing methods. Summary of the invention

[0004] The purpose of the present invention is to provide a method for predicting and quickly clearing blockage of an underwater pipeline for filling and blowing, thereby reducing the workload and cost of clearing and shortening the processing time to avoid affecting the efficiency of filling and blowing construction.

[0005] The technical solution adopted by the present invention is: a method for predicting and quickly clearing pipe blockage in a blown-filled underwater pipeline, comprising the following steps:

[0006] Step S1, predicting the blockage position of the pipeline: setting a pressure gauge at a key position along the underwater pipeline to roughly predict the blockage position, which is located between the adjacent pressure gauge with readings and the pressure gauge without readings;

[0007] Step S2, the cutter suction ship blows water for further prediction: the cutter suction ship starts blowing water, and the average flow velocity V of the blowing water and the time T from the start of the blowing water to the decrease of the flow velocity are counted, so as to predict that the starting position of the pipe blockage is at a distance L=VT from the stern;

[0008] Step S3, mutually verifying the pipe blocking positions predicted in step S1 and step S2 and finally determining the starting position of the pipe blocking;

[0009] Step S4, planning to cut holes in the underwater pipeline: planning and designing the spacing of the cut holes and the hole diameter of the cut holes;

[0010] Step S5, cutting holes at the blocked pipe position: the diver dives to the underwater pipeline, and starts from the predicted starting position of the blocked pipe, and uses an underwater cutting tool to cut multiple holes on the pipeline according to the plan of step S4;

[0011] Step S6, after all the cutting holes are cut, the cutter suction vessel blows water to the pipeline at the maximum pressure, and the blockage in the pipeline is ejected from the cutting holes under the action of the blowing pressure;

[0012] Step S7, after the pipeline is cleared, the diver dives to the underwater pipeline and uses underwater welding equipment to weld and patch the holes in the pipeline.

[0013] Preferably, in step S4, the MIDAS GTS software finite element method is used based on the modified Mohr-Coulomb constitutive model, and key parameters of the pipeline and mud are input for verification to obtain the cut hole spacing and cut hole diameter size data.

[0014] Preferably, in step S5, each time a hole is cut, air is pumped into the pipeline using an air compressor downstream of the pipe blocking position on the pipeline, and bubbles are observed on the water surface to determine whether the hole has reached the pipe blocking end position. When bubbles are observed on the water surface, it means that the hole has reached the pipe blocking end position, and the hole cutting is stopped. When bubbles are not observed on the water surface, it means that the hole has not reached the pipe blocking end position, and the hole cutting is continued.

[0015] The advantages and positive effects of the present invention are:

[0016] The present invention provides a method for predicting and quickly clearing pipe blockage in a blown-filled underwater pipeline. Compared with the existing treatment method of using an anchor boat to lift the pipeline above the water surface and dismantle and transport it back to land for clearing, the present method is an in-situ clearing method that does not require displacement of the blown-filled underwater pipeline. The blockage position is judged through a pre-judgment step, and the spacing and size of the cut holes used for clearing are planned and designed. The method of cutting a plurality of cut holes on the pipeline is used in conjunction with the high-pressure water blowing of a suction dredger to clear the underwater pipeline. Therefore, the disturbance to the underwater pipeline by the present method is minimal and the workload is small. A large number of personnel and facilities do not need to be invested, and the cost of pipeline clearing is significantly reduced. The present method shortens the time required for pipeline clearing, thereby avoiding a significant impact on the hourly rate of the construction ship and avoiding affecting the efficiency of the blown-filled construction. DETAILED DESCRIPTION

[0017] In order to further understand the content, features and effects of the present invention, the following embodiments are given to explain in detail.

[0018] The method for predicting and quickly clearing pipe blockage in a blown-filled underwater pipeline of the present invention comprises the following steps:

[0019] Step S1, predicting the blockage position of the pipeline: setting a pressure gauge at a key position along the underwater pipeline to roughly predict the blockage position, which is located between the adjacent pressure gauge with readings and the pressure gauge without readings;

[0020] Step S2, the cutter suction ship blows water for further prediction: the cutter suction ship starts blowing water, and the average flow velocity V of the blowing water and the time T from the start of the blowing water to the decrease of the flow velocity are counted, so as to predict that the starting position of the pipe blockage is at a distance L=VT from the stern;

[0021] Step S3, mutually verifying the pipe blocking positions predicted in step S1 and step S2 and finally determining the starting position of the pipe blocking;

[0022] Step S4, planning to cut holes in the underwater pipeline: planning and designing the spacing of the cut holes and the hole diameter of the cut holes;

[0023] In this step, the MIDAS GTS software finite element method is used based on the modified Mohr-Coulomb constitutive model, and the key parameters of the pipeline and mud are input for verification to obtain the cut hole spacing and cut hole diameter size data.

[0024] The finite element method of MIDAS GTS software is based on the modified Mohr-Coulomb constitutive model. It is a calculation model configured by MIDAS GTS software and can be called directly. The key input parameters include but are not limited to: pipeline parameters such as pipeline diameter and maximum internal pressure of the pipeline, and mud parameters such as clay shear strength, adhesion, water content, liquid limit and plastic limit.

[0025] Two specific examples are given to illustrate the planning and design conclusions of cutting holes:

[0026] 1) Tiankun Ganyu project pipe plugging case: The diameter of the 1000mm pipeline is about 400m long. The maximum discharge pressure of Tiankun is 28.5bar. The planned design is a 40m cutting hole spacing and a 20cm cutting hole diameter.

[0027] 2) Tianji Ship Ganyu Project Pipe Blocking Case: The diameter of the 800mm pipeline is blocked for about 140m. The maximum discharge pressure of the Tianji Ship is 13bar. The planned design is a 15m cutting hole spacing and a 20cm cutting hole diameter.

[0028] Of course, it is conceivable that in step S4, the spacing between the cut holes and the hole diameters of the cut holes may be planned and designed based on construction experience.

[0029] Step S5, cutting holes at the blocked pipe position: the diver dives to the underwater pipeline, and starts from the predicted starting position of the blocked pipe, and uses an underwater cutting tool to cut multiple holes on the pipeline according to the plan of step S4;

[0030] In this step, each time a hole is cut, air is pumped into the pipeline using an air compressor downstream of the pipe plugging position on the pipeline, and bubbles are observed on the water surface to determine whether the hole has reached the pipe plugging end position. When bubbles are observed on the water surface, it means that the hole has reached the pipe plugging end position, and the hole cutting is stopped. When no bubbles are observed on the water surface, it means that the hole has not reached the pipe plugging end position, and the hole cutting is continued.

[0031] Step S6, after all the cutting holes are cut, the cutter suction vessel blows water to the pipeline at the maximum pressure, and the blockage in the pipeline is ejected from the cutting holes under the action of the blowing pressure;

[0032] Step S7, after the pipeline is cleared, the diver dives to the underwater pipeline and uses underwater welding equipment to weld and patch the holes in the pipeline.

Claims

1. A method for predicting and quickly clearing blockage in a blown-filled underwater pipeline, characterized by: The following steps are included: Step S1, predicting the blockage position of the pipeline: setting a pressure gauge at a key position along the underwater pipeline to roughly predict the blockage position, which is located between the adjacent pressure gauge with readings and the pressure gauge without readings; Step S2, the cutter suction ship blows water for further prediction: the cutter suction ship starts blowing water, and the average flow velocity V of the blowing water and the time T from the start of the blowing water to the decrease of the flow velocity are counted, so as to predict that the starting position of the pipe blockage is at a distance L=VT from the stern; Step S3, mutually verifying the pipe blocking positions predicted in step S1 and step S2 and finally determining the starting position of the pipe blocking; Step S4, planning to cut holes in the underwater pipeline: planning and designing the spacing of the cut holes and the hole diameter of the cut holes; Step S5, cutting holes at the blocked pipe position: the diver dives to the underwater pipeline, and starts from the predicted starting position of the blocked pipe, and uses an underwater cutting tool to cut multiple holes on the pipeline according to the plan of step S4; Step S6, after all the cutting holes are cut, the cutter suction vessel blows water to the pipeline at the maximum pressure, and the blockage in the pipeline is ejected from the cutting holes under the action of the blowing pressure; Step S7, after the pipeline is cleared, the diver dives to the underwater pipeline and uses underwater welding equipment to weld and patch the holes in the pipeline.

2. The method for predicting and quickly clearing blockage of an underwater pipeline during filling and blowing as claimed in claim 1 is characterized by: In step S4, the MIDAS GTS software finite element method is used based on the modified Mohr-Coulomb constitutive model, and the key parameters of the pipeline and the mud are input for verification to obtain the cut hole spacing and cut hole diameter size data.

3. The method for predicting and quickly clearing blockage of an underwater pipeline during filling and blowing as claimed in claim 2 is characterized by: In step S5, each time a hole is cut, air is pumped into the pipeline using an air compressor downstream of the pipe plugging position on the pipeline, and bubbles are observed on the water surface to determine whether the hole has reached the pipe plugging end position. When bubbles are observed on the water surface, it means that the hole has reached the pipe plugging end position, and the hole cutting is stopped. When no bubbles are observed on the water surface, it means that the hole has not reached the pipe plugging end position, and the hole cutting is continued.