Analysis on the Important Links of Quality Control of Drainage Pipeline Project

With the development of urbanization, the pace of infrastructure construction is accelerating, and with the increasing requirements for environmental protection, drainage pipeline engineering accounts for an increasing proportion of infrastructure construction. Drainage pipeline engineering is closely related to people’s production and life. The quality of its use function involves the vital interests of thousands of households, and it is related to the ecological problems of urban waterlogging prevention and groundwater and soil pollution. Therefore, strengthening the quality control of drainage pipeline engineering is of great significance for eliminating engineering quality defects and ensuring the quality of drainage pipeline engineering.

1. Quality control of drainage pipes (1) Common quality problems. Poor quality of pipes, cracks or local loose concrete, poor compression resistance and impermeability, easy to be crushed or water seepage: large deviation of pipe diameter size, easy installation of pipe error mouth. (2) Quality control measures 1. Pay attention to the inspection of pipe materials. The construction unit is required to select pipes produced by regular manufacturers, and check whether the delivery certificate of the pipes and the mechanical test report for inspection are complete. 2. Pay attention to the inspection of the appearance of the pipe. After the pipe enters the site, the engineering material staff shall inspect the appearance of the pipe. The pipe shall not be damaged, peeling, honeycomb exposed, cracked, etc., and the pipe that fails the appearance inspection shall not be used. 3. Strengthen the protection of pipes. The manufacturer should be required to strengthen the protection of the pipe during the transportation and installation of the pipe. 2. Quality control of measuring and laying-out (1) Common quality problems Measuring errors or accidentally avoiding the original structures, causing the pipeline to shift in position on the plane, and the slope on the elevation is not smooth. (2) Quality control measures 1. Re-test the pay-off. After the surveyor has determined the pipeline centerline and the location of the inspection well, re-measurement is required, and the next step of construction can only be allowed after the error meets the requirements of the specification. 2. More communication. During construction, if a structure is encountered accidentally and must be avoided, the supervision unit and the design unit should be required to negotiate to add a connecting well at an appropriate location, which is connected in a straight line, and the rotation angle of the connecting well should be greater than 135°. 3. Quality control of trench excavation (1) Common quality problems During trench excavation, there are often some quality problems such as slope collapse, water soaking at the bottom of the trench, over-excavation at the bottom of the trench, and non-compliance with the requirements of the trench section. (2) Quality control measures 1. Prevent slope collapse: determine the appropriate slope of the trench according to the soil type and the mechanical properties of the soil. The slope of the straight groove slope for supporting is generally 1:0. O5. For deeper trenches, it is advisable to excavate in layers. The earthwork for trenching should be properly arranged and stacked on both sides of the trench in general. The distance between the bottom of the pile of soil and the side of the trough is determined according to the depth, soil quality, and side slope of the trough. The minimum distance should be 1.0m. 2. Control of groove section: determine a reasonable groove section and groove bottom width. The slotting section is determined by factors such as the width of the bottom of the groove, the depth of the digging, the bottom of the groove, the slope of each layer, and the width of the reserved platform between the layers. The width of the groove bottom should be the width of the pipe structure plus the working width on both sides. Therefore, when determining the excavation section, it is necessary to consider production safety and engineering quality, so that the groove section is reasonable. 3. Prevent water from soaking at the bottom of the trough: During construction in the rainy season, a closed soil ridge should be built around the trench. When necessary, a drainage ditch should be excavated outside the ridge to prevent rainwater from flowing into the trough. To dig trenches below the groundwater level or in areas with shallow stagnant water, the construction unit shall be required to set up drainage ditches and collection wells to pump water. The next process should be carried out immediately after the bottom of the trench is reached, otherwise, a 20cm soil layer should be left at the bottom of the trench and not dug as a protective layer. 4. Prevent over-excavation of the bottom of the groove: when digging a groove, it should be tracked and the elevation of the bottom of the groove should be measured and inspected. When using mechanical trenching, reserve a 20cm soil layer above the designed trench bottom elevation for manual excavation. In case of over-excavation, the following measures should be taken: use gravel (or pebbles) to fill up to the design elevation, or fill soil to ram, and its density shall not be lower than the original natural foundation density. Fourth, the quality control of the flat base pipe seat (1) Common quality problems Some construction units pour flat base concrete when there is water and silt in the trench; the elevation deviation of the flat base is large, and the thickness cannot be guaranteed; Block concrete running formwork, concrete has honeycomb holes and other phenomena. (2) Quality control measures 1. Prevent the pouring of flat foundation concrete with muddy water. If rainwater or other passenger water flows into the trough, the trough should be thoroughly cleaned, the silt should be cleaned, and a sand cushion should be laid to ensure the construction of the dry trough; if there is groundwater in the trough, drainage measures should be taken. 2. Strictly control the thickness and elevation of the flat base. Before pouring the concrete flat foundation, when supporting the formwork, the bottom elevation of the groove and the top elastic line of the formwork should be checked. After the confirmation is correct, the concrete can be poured. 3. Check the strength, rigidity and stability of the pipe seat template. It should be particularly emphasized that the supporting points of the struts cannot be directly supported on the loose soil, and pads or piles should be added to enable the formwork to withstand the gravity and lateral thrust of concrete pouring and vibrating. 4. Strictly control the quality of concrete. It is required that the material should be cut according to the mix ratio, and the concrete should be vibrated and vibrated to be compact. 5. Quality control of pipe installation (1) Common quality problems In a circular inspection well, the pipe head is exposed to the wall of the well and is too long or retracted into the well wall; the local displacement of the pipe exceeds the standard and the straightness is poor; the pipe is reverse sloped and wrong. (2) Quality control measures 1. Correctly calculate the laying length of the pipeline: Determine the laying length of the pipeline between the two inspection wells, the length of the pipe extending into the inspection well and the reserved space between the ends of the two pipes according to the specifications. Strict control is required during the installation of pipes to prevent the pipe head from being exposed to the well wall and being too long or retracting into the well wall. 2. Strictly control the straightness and slope of the pipeline. The following measures can be taken and checked at any time: When installing the pipe, hang the edge line at the radius of the pipeline, and the line must be tightened without slack; when adjusting the centerline and elevation of each section of the pipe , It is necessary to use stones to support firmly, and the two adjacent pipes shall not be misaligned; before pouring the pipe seat, the triangle part where the two sides of the pipe and the flat foundation are connected should be filled with fine stone concrete with the same number as the pipe seat concrete. Pour solid, and then pour concrete on both sides at the same time. 6. Quality control of the interface (1) Common quality problems The quality of the wiper mortar is poor, and the interface wiper is hollow and cracked; the interface wiper mortar protrudes from the inner wall of the pipe; the wire mesh and the pipe seam are not aligned, the insertion depth of the pipe seat is insufficient, and the length of the wire mesh is insufficient . (2) Quality control measures 1. Strictly control the construction quality of the wipe tape. The cement mortar should be cut according to the mix ratio, the measurement should be accurate, the mixing should be uniform, and the strength and workability of the mortar should be ensured. Before wiping the tape, chisel the outer wall of the tube of the wiping tape, scrub it clean, and brush a line of cement slurry. When the pipe diameter is greater than 400mm, it can be wiped in two layers; when the pipe diameter is less than or equal to 400mm, it can be wiped at one time; for pipes with a pipe diameter greater than or equal to 700mm, when the pipe seam exceeds 10mm, thin bamboo should be used at the pipe joint when wiping the tape. Take off the pad, fill the mortar in the pipe joints and tamping, and then apply it in layers. After wiping, it should be covered and sprinkled with water to prevent it from hollowing and cracking. 2. Control the flatness between the inner pipe seam and the inner wall of the pipe. For pipes with a diameter less than or equal to 600mm, while wiping the tape, use sack balls or other tools to drag back and forth in the pipe to level the mortar flowing into the pipe; for pipes with a pipe diameter greater than 600mm, the internal pipe joints should be wiped. 3. Ensure the lap length of the barbed wire. For the wire mesh cement mortar wiper belt interface, it should be ensured that the wire mesh is aligned with the pipe seam and the overlap length of the wire mesh and the depth of insertion into the pipe seat should not be less than 10cm. 7. Quality control of inspection wells (1) Common quality problems: The foundation of the inspection well is poured with water and its size and elevation deviations are large; the well walls are cracked, the mortar is not full, and the plastering surface is bulging and cracked; no runners or The method does not meet the requirements; the installation of steps, well circle, and manhole cover does not meet the requirements. (2) Quality control measures 1. Strictly control the quality of the inspection well foundation. It is not allowed to pour the cushion and foundation with water. It is necessary to ensure that the geometric size and elevation of the foundation meet the design requirements, and bricks can only be laid when the concrete reaches a certain strength. 2. Strictly control the masonry quality of the well wall. The wall of the shaft must be vertical without any joints; the mortar must be full, and the joints must be smooth; the plastering surface must be calendered, and there must be no hollows, cracks, etc. 3. The practice of runners should be standardized. The height of the rainwater trough should be level with the radius of the main pipe, and the shape of the trough should be a semi-circular arc with the same radius as the main pipe; the height of the sewage trough should be level with the inner top of the main pipe, and the lower half should be the same half as the radius of the main pipe. The arc, the upper half is parallel to the well walls on both sides, and the width is the same as the diameter of the main pipe. 4. Strictly control the installation quality of steps, well circle and well cover. Gray cast iron steps must be used, the installation must be firm, and the steps of the sewage well must be painted with anti-rust paint: the installation of the well circle must be full of slurry, and the well cover and the well circle must be matched. Heavy-duty manhole covers must be installed on roads with heavy traffic. 8. Quality control of closed water test (1) Common quality problems Backfill the soil before the closed water test; insufficient preparation before the test; the water level of the closed water test and the measured water seepage time do not meet the requirements; the calculation of the seepage amount is wrong. (2) Quality control measures 1. Make it clear whether to do a closed water test. Sewage pipes, rain and sewage confluent pipes, and other drainage pipes whose design requires closed water must be tested for closed water. The closed water test should be carried out jointly by the owner, construction unit, supervision unit and relevant departments, and the backfill can only be carried out if the test is qualified. 2. Check the preparation work before the test. Before the test, it is necessary to use 1:3 cement mortar to build 240mm thick bricks to block the branch nozzles in the inspection well and the nozzles at both ends of the test pipe section, and to seal the surface. After curing for 3 to 4 days to reach a certain strength, go upstream Fill the well with water. When the water head reaches the required height, check the bricks, pipes, and wells for water leaks. If there are serious leaks, they should be plugged. After immersing for 24 hours, observe the water seepage again, and the time for measuring the water seepage should not be less than 30 minutes. 3. Control the water level of the closed water test. The test water level should be 2 meters above the top of the upstream pipe section of the test section. If the height from the top of the upstream pipe to the inspection well is less than 2 meters, the water level of the closed water test can reach the well head. 4. Calculate the amount of water seepage correctly. During the closed water test, various data should be recorded, and the seepage amount should be correctly calculated according to the specifications. If the test is qualified or unqualified, speak through the data. 9. Quality control of backfilled soil (1) Common quality problems Filled with water or the quality of backfilled soil does not meet the requirements; there is no layered backfill; the compactness of the backfilled soil is not strictly controlled. (2) Quality control measures 1. Strictly control the soil quality of the backfilled soil. The backfill shall not contain broken bricks, stones, concrete fragments and hard soil blocks larger than 10cm; the water content of the backfill should be close to the optimal water content. Before returning the soil, the returned soil should be subjected to a light standard compaction test to determine its optimal water content and maximum dry density; there should be no water in the trough during backfilling, and silt, humus, frozen soil and organic matter should not be backfilled. 2. Strictly control the thickness of each layer of backfill. The trench backfill should be compacted in layers, and the thickness of each layer is not