1. The general provisions
1.1. Before the pipe laying, the construction unit should prepare, construction organization design.
1.2. Piping should be equipped in the undisturbed soil or through slot on post-processing backfill compacted foundation. When the pipe under the roadway, pipe roof covering should not be less than 0.7 m. When the pipe under the green way, pipe roof covering should not be less than 0.5 m.
1.3. Construction, the maximum allowable covering on the top of the tube, should be stipulated in the design of pipe ring stiffness, on both sides of groove and check the condition of undisturbed soil, when found in accordance with the design requirements, may be required to change the design or take appropriate technical measures to ensure the bearing capacity. 1.4. When polyethylene pipes across the railway, should be set of reinforced concrete, steel and cast iron materials, such as the protection of the casing, the casing inside diameter should be greater than polyethylene pipe diameter 300 mm. For buried pipeline under the railway, casing design should be governed by the provisions of the relevant railways. Polyethylene pipes shall not be on the basis of buildings and structures through below.
1.5. The underground water level is higher than the excavation groove groove bottom elevation area, the underground water level should be dropped to the bottom of the channel under the low. All the process of pipe laying, backfilling and drain water or cold is not allowed. Must be based on engineering is not affected by groundwater, to fulfill the requirements of strength and the pipeline to achieve anti-floating may stop lowering groundwater.
1.6. When polyethylene pipes for pipe line crossing inverted siphon pipe, when using the pressure of work, besides should comply with the product standard of the pipe should be less than 0.05 MPa. Polyethylene pipes should not be used to cross the river inverted siphon pipe.
1.7. Laying pipes should be straight line. When special circumstances need to use the flexible interface corner of flexible pipe line or arc, laying the deflection Angle and curve radian should comply with the value specified by the manufacturer.
1.8. Construction survey of the pipeline, the precipitation, grooving, trench and pipeline cross processing, pipeline technical requirements, such as the construction and so on should be according to the current national standard "water supply and drainage pipeline construction and acceptance norms" and regional drainage pipe to the relevant provisions of technical specification.
1.9. To adopt socket sleeve pipe, pin insertion direction should be consistent to the flow direction.
2. The groove
2.1. Net width of the groove groove bottom, according to local specific circumstances and according to the size of pipe diameter, buried depth, the construction technology, etc. When the pipe diameter less than 450 mm, pipe net width should not be less than 300 mm per side; When the pipe diameter greater than 450 mm, pipe net width should not be less than 500 mm per side.
2.2. Groove form should be based on the construction site environment, the groove depth, the underground water level, soil condition, construction equipment and seasonal effect.
2.3. Excavation groove should strictly control the basal elevation, shall not be disturbed basal undisturbed soil. Basement design elevation above 0.2 0.3 m of the undisturbed soil, should be in before laying with artificial clean up to the design elevation. In case of overbreak or disturbed, can fill in 10-15 mm natural grading application or maximum particle size less than 40 mm of rubble, and leveling compaction, the compaction should meet the requirements of base layer density, it is strictly forbidden to back fill earth with mixed soil. The bottom of the channel must be removed, if there is a sharp hard objects with sand backfill.
2.4. The bottom of the channel shall not be affected by water immersion, if using artificial rainfall, stability of underground water level should be fall to the bottom of the below grooves before excavation.
3. The pipeline foundation
3.1. Arc pipe should be adopted soil. Of common soil and undisturbed soil foundation of the following should be at the end of tube or the backfill compaction on the foundation of laying a layer thickness is 100 mm in the coarse sand base layer; Can be used when the foundation soil is poorer, bedding thickness not less than 200 mm of gravel base layer, can also be laid on the second floor, the lower use of gravel diameter is 5 ~ 32 mm, 100 ~ 100 mm thick, coarse sand in the upper, the thickness of not less than 50 mm. Basic density should comply with the provisions of the code table 3.2.4. For soft soil foundation, when the foundation bearing capacity is less than the design requirements or due to reasons such as construction of precipitation, foundation undisturbed soil disturbance id be theater ring foundation bearing capacity, must first to reinforcement of foundation, after meet the foundation bearing capacity, and laid in the coarse sand base layer.
3.2. In pipeline design based bearing soil arc Angle within the scope of the axillary Angle, must use the coarse sand or gravel backfill soil compaction. Backfill support Angle range should not be less than 2 alpha plus 30 o, backfill compaction shall comply with the provisions of the table 2.4.
3.3. Based in pipeline in the socket interface, socket connection groove, in areas such as the appropriate when laying pipes increases with the increasing spread (as shown in figure 1). The length of the groove, width and depth can be determined according to the size of pipe joint. Immediately after completion of the joint use of coarse sand backfill density.
3.4. Due to pipe load, the formation and change of soil factors may produce pipes longitudinal uneven settlement, should be in front of the pipe laying the foundation reinforcement.
3.5 polyethylene drainage pipe foundation treatment appropriate USES sand pile, stone piles composite foundation treatment method, etc. Shall not use driven pile, concrete block, rigid foundation treatment measures such as concrete foundation.
4. The pipe connection material
Sealing ring used in the splice elastic sealing rubber ring, should by pipe manufacturers supply, and shall meet the following requirements:
1 the appearance of the elastic sealing rubber ring should be smooth level off, can not have porosity, crack, roll fold, damaged, defects such as double skin;
2 elastic sealing rubber ring should use natural rubber. Shaw hardness of the rubber seal to appropriate USES 50 + 5, elongation should be greater than 400%; Tensile strength should not be less than 16 mpa.
5. Pipeline installation and connection
According to product standards must be taken before 5.1 steel tubes under section by appearance inspection, products do not conform to the standards, it is forbidden to laying.
5.2. Should according to pipe diameter size, the groove and construction machinery and equipment, to determine with artificial or mechanical pipe into the groove. Next pipe should use reliable sling, smooth groove, not with walls, groove fierce collision. When hoisting should have two support lifting point, it is forbidden to wear heart hanging.
5.3. Socket type sealing ring connection, the sleeve (or sets) connection, flange connection, the seals, sleeve parts, flange, flange connection with the fasteners with parts, must be supplied by pipe manufacturers. When the connection is need to use the auxiliary materials such as lubricant, providing relevant information by the pipe manufacturer.
5.4. Pipe connection must be connected parts, seals, casing accessories such as clean,
Soil and other impurities may be attached. Mechanical connection with steel sleeve, flange, bolts and other metal products, should according to the field soil and with reference to the corresponding standard measures to prevent corrosion.
5.5. The socket type sealing ring connection should be on when the environment temperature is higher, the socket end may not be inserted to the bottom of the socket, telescopic gap should be set aside not less than 10 mm. In front of the insert, should make insert depth markers in the socket end wall. After insert, insert circumferential length and socket empty seam should be uniform, and maintain a connection pipe axis straight.
5.6. After the pipe laying, the tube wall of local damage caused by accident, when local damage or circular aperture is not more than 60 mm, longitudinal cracks is not less than 1/12 of the pipe perimeter, welding torch can be used to repair. When local damage than the above range, removal of the damaged section, should be taken in tube or masonry inspection Wells, connection measures such as well.
5.7. The rain period construction of the floating measures should be taken to prevent pipes. When the pipe installation is not yet coverer by blisters, should be pipe center and bottom elevation survey and appearance inspection, such as found that displacement, floating, pull out the phenomenon such as mouth, should be timely rework processing.
Five, pipeline and the inspection shaft connection
1. The pipe or brick and concrete build by laying bricks or stones inspection shaft connection, appropriate USES rigid connection.
2. When the pipeline has been laid, the brick masonry wall of build by laying bricks or stones inspection Wells, appropriate USES cast-in-place concrete coating tube inserted into the casing. Concrete coating thickness library should not be less than l00mm, strength grade shall not be lower than C20 (FIG. 2, 3 in figure 2). 3. When pipe laying, when laying inspection Wells, should be on the wall according to the pipe axis of elevation and open the reserved hole diameter. Reserved the hole diameter should not be less than add l00mm pipe diameter. Connection is filled with cement mortar inserted into the pipe end and the gap between the mouth of the cave. The mixing ratio of cement mortar shall not be lower than 1:2 and mortar should be mixed with micro expansion agent. Brick wall on the hole should be reserved along the circumference of a circle brick masonry arch ring (figure 2, figure 3).
4. Of cast-in-situ concrete coating connection, appropriate USES the rubber sealing ring, but before pouring concrete, insert the rubber trap in the middle of the casing pipe end parts.
5. In the joint of shaft wall and inserted into the pipe end examination, concrete or filled mud slurry pipe end. May not appear twisted with circular cross section. When the larger diameter can be set up within the tube during the construction of temporary support. When using socket tube, the downstream outlet should not insert the socket part connected to the wall. As one like jack, socket can be removed. Using special pipe fittings and the inspection shaft connection, special pipe fittings shall be supplied by pipe manufacturers.
6. After the pipe connected to the inspection shaft must do waterproof layer in the internal and external wall of the pipe end connection, and meet the requirements of the overall inspection well leakage resistance.
7. When pipe laying on soft soil foundation or inhomogeneous formation, check the transition section can be used well and pipeline connection. Transition section by section of not less than 2 short tube flexible connection, and each section short length 600 ~ 800 mm. According to the geological conditions to determine the total length of transition section, 1500 ~ 2000 mm. Flexible joints can adopt socket type, sleeve (such as the flat tube) rubber seal joint. The transition period of inspection Wells with appropriate USES rigid connection.
8. Check the shaft connected to the upstream and downstream piping section of the pipe bottom overexcavation (hollow), after completion of the pipe connection must be immediately with sand and gravel backfilling, and according to the design based bearing soil arc Angle according to the procedure "pipe (PE) based on" the provisions of the backfill compacted.