The beira water supply project in mozambique is an international contracting project under construction by jiangsu international water resources management company.The main work of the pipeline is to bury a water pipeline about 10.5 kilometers long.This pipeline USES the Glass Reinforced Plastic sand-filled Pipe (GRP), and the embedding construction of the GRP Pipe is the key of the engineering construction.As a contractor, we attach great importance to the overall and whole-process control of the construction quality of GRP pipe embedding, which is also a problem that mofang and the supervision engineer are very concerned about.
GRP pipe is made of unsaturated polyester resin, glass fiber, quartz sand three main raw materials winding or centrifugal casting curing, with light weight, high strength, corrosion resistance, water resistance, etc., in the United States, Switzerland, Italy, Austria and other countries has been widely used.This new type of pipe has been introduced into China since the 1990s. It is a kind of flexible composite pipe that is being popularized in the fields of domestic urban water supply, sewage discharge and industrial water treatment system, and has a great development prospect.
The purpose of pipeline quality inspection is to ensure the quality of the project. Therefore, as the engineering contractor, we shall carry out strict inspection and acceptance of GRP pipes before packaging and transportation, after sea transportation and after the arrival of the goods at the construction site in accordance with the contract.
In the process of pipeline transportation, effective packaging measures should be taken to prevent damage.The packaging of pipes depends on the type of transportation. Pipes with different diameters are often transported in packages.The pipelines used in this project are imported from China by sea.When packing, the 600mm pipe set shall be placed in the 900mm pipe, and both ends of the pipe shall be fixed with wooden frames.Use forklift to remove small diameter pipe from large diameter pipe during unloading.GRP pipes are light and easy to assemble and disassemble, but be careful not to drag or roll on rough ground, let alone hammer them hard.The hoisting rope used for loading and unloading shall be flexible, wide belt or fiber rope, etc. It is strictly prohibited to use steel wire rope or chain hoisting pipe.Pipe stacking of the ground should be flat without sharp objects, and wood wedge should be added to prevent rolling.It is important to note that if the pipe is stowed in the open for a long time, the pipe joint should be covered with a sunshade to prevent the rubber ring and the inner wall of the pipe from being damaged by ultraviolet radiation.
The climate of the bela region of mozambique, where the project is being built, is different from that of jiangsu province, with only dry and rainy seasons.Due to the high water table during the rainy season, pipeline construction can only be arranged in the dry season.We carefully surveyed the entire site where the pipeline was laid and sampled the undisturbed soil within the excavation range of the pipeline.On the basis of accurately grasping the local meteorological and hydrological data and soil conditions, the detailed construction organization design is carried out.
Most GRP pipelines are laid in the ground, and the main construction procedures are as follows: grooving, foundation treatment, lower pipe, stabilizing pipe, interface, backfilling, pressure test and other major processes.The key points of quality control during the construction of main processes are as follows:
(1) trench excavationThe furrow distance and time should be as short as possible, and the construction of the next procedure should be carried out as soon as possible after the furrow is opened.Generally, at the end of each working day, no more than 50m of soil groove and open pipe shall be left.In addition, according to the original soil conditions and groundwater conditions, the rectangular groove or slope of the small groove, to consider the use of pillars, boards, branches and other methods of support, and have enough strength to prevent the collapse of the trench, to ensure the safety of the trench workers.
(2) pipeline foundation treatmentThe foundation form of the pipeline is determined according to the engineering geological conditions of soil, groundwater level, pipeline stiffness, buried depth requirements, the impact of ground dynamic load and the interface mode of the pipeline.When the bearing capacity of soil cannot meet the requirements of pipe strength and deformation rate, foundation treatment must be carried out.
The original soil in the pipeline excavation area of this project is clay or clay-crushed stone.The test results show that the soil bearing capacity of the trench is better, and the undisturbed soil can meet the needs of the project after being compacted and strengthened.The compaction degree shall be greater than 95%. After foundation treatment, 100mm sand cushion layer shall be laid, and the compaction degree shall be 90%.Sand cushion foundation construction should be very careful to prevent the sand extrusion from both sides, reduce the bearing capacity.Attention should also be paid to the need to treat sand foundations without groundwater seepage.
(3) pipe connectionThe quality of the pipeline connection reflects the quality of the pipeline system and is related to the normal operation of the pipeline.No matter take which kind of conduit connection form, must make sure to have enough intensity and rigidity, have the ability that alleviates axial force to a certain extent, still should make every effort to install convenient.Special attention should be paid to the following two points:
Correct use of lubricant.Do not use petroleum-based lubricants, which can deform the gasket. The lubricants used should be supplied by GRP tube manufacturers. Pipe fitting emplacement and connection to be completed with the help of the appropriate device.In particular, the elbow must be coaxially connected to the pipe and supported with appropriate devices to prevent possible displacement due to internal pressure impact.
(4) backfilling and tampingPipe and trench backfill materials constitute a unified "pipe-soil system".Groove backfilling is as important as piping installation.After the pipe is installed, the influence of the gravity and live load of the filled soil depends on the supporting force of the soil on both sides of the pipe to a great extent.If the backfill and compaction can not achieve enough support for the pipeline, the pipeline deformation will exceed the design allowable value.
(1) packing selectionUnder the premise of satisfying the requirements, the original trench soil material is the first choice for the pipe area backfilling material.This can not only ensure the compatibility of backfill materials with the original soil, but also save project funds.According to the terms of the contract and the drawings, the backfill in the pipe area of the project is made of granular materials including gravel and gravel.However, after our careful investigation and careful study on the site, we believe that this kind of packing is not suitable for the project back packing.However, the undisturbed soil material within the excavation scope of the pipeline has weak water permeability and high bearing capacity in the hard and plastic state. As long as the appropriate water content is controlled in the backfilling, the undisturbed soil material can achieve a high degree of compaction and be suitable as the backfilling material.After detailed demonstration, the supervision engineer approved the use of undisturbed soil material backfilling. (2) groove backfilling and tampingBefore backfilling, the sundries in the trench shall be removed and the trench shall be kept waterless.Backfill the armpits on both sides of the pipe with backfill, and both sides of the pipe should be tamped and rammed at the same time to form complete support.
3. The conclusionAs a new type of pipeline material, GRP pipe construction is relatively complex.In order to make the whole construction process reasonable and ensure the construction quality, the site should be thoroughly investigated before construction and hydrological and geological data should be collected as far as possible.Then, according to the flexible pipe design procedure specified in British industry code BS EN 1295-1, the structural selection and design of GRP pipes are carried out.For major construction processes such as grooving, foundation treatment, down pipe, steady pipe, interface, backfilling and pressure test, strict quality control shall be carried out for each step according to the above technical requirements.