Introduction:

The municipal road drainage system is one of the important facilities for the normal use of urban municipal facilities, and it is very important to ensure the quality of its construction. The most common quality problems include four aspects: pipeline position deviation or water accumulation; pipeline leakage and unqualified closed water test; inspection well deformation, sinking, poor quality of components and backfill subsidence.

Problem 1: The position of the pipeline is offset or the water accumulates

cause:

Measurement errors, construction distortions and accidental avoidance of original structures have resulted in positional deviations on the plane, water accumulation or even falling slopes on the facade.

Precaution:

1. Measures to prevent diseases caused by measurement and construction mainly include:

(1) Before construction, re-test and protect the transfer piles in accordance with the construction survey specifications and regulations.

(2) Construction stakeout should be combined with hydrogeological conditions, stake out according to the embedding depth, design requirements and relevant regulations, and must be retested to verify that the error meets the requirements before the construction can be delivered;

(3) The construction should be carried out strictly in accordance with the sample piles, and the grooves and foundations should be well measured and accepted for the axis and longitudinal slope.

2. In the construction process, if you encounter a structure accidentally and need to avoid it, a connecting well should be added at an appropriate location, and the connecting well should be connected in a straight line. The rotation angle of the connecting well should be greater than 135°.

Problem 2: Water leakage in the pipeline, unqualified closed water test

cause:

Uneven foundation sinking, poor construction quality of pipes and their joints, improper sealing at the ends of closed water sections, and poor construction quality of wells can cause water leakage.

Prevention:

1. Poor pipeline foundation conditions will result in uneven settlement of the pipeline and foundation, which generally results in local water accumulation. In severe cases, pipeline fractures or joint cracks may occur.

The preventive measures are:

(1) Construct carefully according to the design requirements to ensure the strength and stability of the pipeline foundation. When the geological and hydrological conditions of the local foundation are poor, soil replacement and improvement treatment should be carried out to improve the bearing capacity of the bottom of the foundation trench.

(2) If the soil at the bottom of the trough is disturbed or soaked by water, the soft soil layer should be excavated first, and the over-excavated part should be backfilled with sandstone or gravel with good stability.

(3) When excavating earth below the groundwater level, effective measures should be taken to prevent drainage and precipitation at the bottom of the trench to ensure that the dry trench is excavated. If necessary, a 20cm thick soil layer can be reserved at the bottom of the trench. Dig and remove.

2. The quality of the pipe is poor, there are cracks or the local concrete is loose, the impermeability is poor, and the capacity leaks. Therefore require:

(1) The pipes used must have the quality department to provide the certificate and mechanical test report and other materials;

(2) The appearance quality of the pipe requires a smooth surface without loose bones and honeycomb hemp surface image;

(3) Check again section by section before installation. If you have found or have quality doubts, you should be ordered to leave the site or be used after effective treatment.

3. The pipe joint filler and construction quality are poor, and the pipe is damaged or joint cracked under the action of external force. Prevention:

(1) Select good quality interface fillers and organize construction according to the test mix ratio and reasonable construction technology;

(2) When wiping tape construction, the joint seam should be clean, if necessary, it should be chiseled, and then carefully constructed in accordance with the construction operation regulations.

4. The construction quality of the inspection well is poor, and the joint between the well wall and its connecting pipe is leaking. Preventive measures:

(1) The masonry mortar of the inspection well should be full, and the joints should not be missed; clean and moisten the surface before wiping, calender the mortar in time when wiping the surface, and maintain it; when there is groundwater, the troweling and jointing should be completed in time with the masonry. Do not carry out internal wiping or internal jointing after backfilling;

(2) The outer surface of the pipe connected to the inspection well should be moistened and evenly brushed with a layer of cement paste, and then the inside and outside surfaces should be painted to prevent leakage.

5. Planning reserved branch pipes are not tightly sealed and are often overlooked because they are in the well. If a brick wall is used for blockage, the following points should be paid attention to:

(1) Clean the inner wall of the pipe within 0.5m of the pipe mouth before plugging, and apply the cement paste while moistening the used bricks for later use;

(2) The marking of the plugging mortar should not be less than M7.5, and it should have a good consistency;

(3) The mark of cement mortar used for jointing and plastering shall not be lower than M15. When the pipe diameter is large, the inner and outer sides should be smaller and only the outer single-face jointing or plastering shall be done. The plastering surface should be constructed according to the waterproof 5-layer construction method.

(4) Generally, the inspection well shall be sealed before the construction of the inspection well to ensure the quality.

6. ​​The closed water test is a comprehensive inspection of the pipeline construction and material quality, during which it is inevitable that there will be three or two failures. At this time, you should mark the leaks one by one, and take care of them after draining the water in the pipe. For small gaps or pitted surface leakage, grout or waterproof coating can be used, and the more serious ones should be reworked. In addition to replacing pipes and refilling the joints, serious leakage can also be handled by professional and technical personnel. Do the test after the treatment, and repeat the process until the closed water is qualified.

Problem 3: The inspection well is deformed, sinking, and the quality of components is poor

cause:

Check the well deformation and sinking, the quality of the manhole cover and the installation quality is poor, and the installation of the ladder in the well is too random, which affects the appearance and the quality of use.

Prevention:

1. Check the base layer and cushion of the well carefully, and break the pipe to make the flow trough to prevent the well body from sinking.

2. The masonry quality of the inspection well should be well controlled to prevent the well body from deforming.

3. The inspection well cover and the seat should be matched; the slurry should be full during installation; the light and heavy models and the bottom of the surface should be good, and the iron climbing installation should control the position of the first step up and down, the deviation should not be too large, and the plane position should be accurate.

Problem 4: Backfill soil subsidence

cause:

Backfilling around the inspection well is not dense, not stratified and compacted as required, poor filler quality, poor water content control and other reasons affect the compaction effect and cause excessive settlement after construction.

Precaution:

(1) When the pipe groove is backfilled, suitable fillers and compaction (tamping) machinery must be selected according to the backfilling position and construction conditions. For example, the pits of the drainage facilities under the main roads of Nanning City are backfilled with mixed sand and gravel. Fill the tube groove from the thoracic cavity to 30cm from the top of the tube, and then irrigate and vibrate until the relative density is ≥0.7. Practice has proved that the effect is very good.

(2) When the trench is narrow, manual or frog-type rammer can be used to ram and fill. Different fillings and different filling thicknesses should choose different tamping tools to achieve the most economical compaction effect.

(3) The silt, tree roots, turf and decayed plants in the filler not only affect the compaction effect, but also shrink and rot in the soil to form holes. These materials should not be used as fillers to avoid sinking.

(4) Control the water content of the filler to be greater than about 2% of the optimum water content; in case of groundwater or after rain, the water must be drained first, and then stratified and compacted with the filling.

Treatment measures:

Take corresponding measures according to the degree of settlement damage:

(1) A small amount of settlement that does not affect other structures can be treated without treatment or only surface treatment, such as partial filling on the asphalt pavement to avoid accumulation of water;

(2) If the foundation of other structures is damaged, pump cement slurry can be used to fill;

(3) If the structure is damaged, the bad fillers should be excavated, replaced with materials with good stability, and restored to the damaged structure after compaction.

In summary, the pipeline project is a concealed project. When it is completed, only the inspection well is available for people to inspect. Therefore, the construction quality of inspection wells often influences the evaluation of the overall project quality. The excellence of drainage pipeline engineering must be established on the basis of the excellence of the main structural engineering. In the construction process, we must strive to overcome various common problems, ensure that the overall project construction quality is excellent, and then make the inspection well construction quality better, so as to achieve the goal of excellence.

Source | Pipe Gallery Construction