Inspection well construction guide

1. Foundation excavation

1. The pit should be excavated at the same time as the pipe trench, and the main line of the well base should be on the same axis as the pipe in the pipe trench during excavation. The pit slope is consistent with the trench slope. When the pit is excavated, the foundation soil should not be disturbed and the pit should be checked by rainwater in the dust and mud chamber, and the depth of the dust and mud chamber should be excavated locally according to the selected specifications. Pit excavation should consider the bias factor of the main line of the well block according to the selected specifications, and the pit wall at the bias end should be flush with the pipe trench. (2) In areas with high groundwater level or construction in the rainy season, there should be drainage and water level reduction measures.

Second, check the well installation

1. Check the installation sequence of the well seat and the pipeline connection. The installation should start from the upstream section of the household pipe, and be installed in the order of well → pipe → well → pipe, and gradually extend to the downstream branch pipe and main pipe. 2. The construction method of the well joint and the pipeline connection shall be consistent with the construction method of the pipeline connection of the same type joint. 3. Install the shaft immediately after the well base is installed, and the upper mouth should be temporarily blocked. 4, for the plastic well base and the bellows connection, the rubber seal should be placed at the first wave trough. 5. When the whole drainage system is constructed in sections, inspected and accepted, the interface connecting to the next pipe section should be temporarily blocked.

3. Shaft installation

1. The length of the wellbore shall be the height from the bottom of the socket connecting the wellbore to the design surface, minus the net distance from the wellbore to the surface. When the elevation of the ground or pavement is difficult to determine precisely, the shaft length can be appropriately reserved.
2. Shaft insertion into the well seat should be kept vertical. When inserting the shaft, do not use a heavy hammer to knock, should use a special tightening tool.

4. Backfill

1. Backfilling should be carried out after the acceptance of the drainage pipeline (including pipelines and inspection Wells), and at the same time as the backfilling of the pipeline trench. 2, before backfilling, the well base and shaft can be fixed with sand bags, steel and wood supports, and the water in the foundation pit and trench should be excluded. 3, the backfill shall not use silt, garbage and frozen soil, etc., and shall not include stones, bricks and other hard objects with edges and corners. 4, backfill using artificial layered symmetric backfill, each layer is applied wood tamping and other light tamping tools symmetrical compaction, its density is consistent with the pipeline backfill soil.

5. Check well installation

           The plastic inspection well can not be directly subjected to the concentrated action such as automobile wheel pressure, and it is necessary to set a reinforced concrete bearing ring to convert the concentrated force into a uniform load and transfer it to the soil around the inspection well, so as to avoid the inspection well directly bearing the concentrated force. When installing the pressure ring, a clearance of more than 300mm should be reserved between the pressure ring and the wellbore. To avoid the direct force of the inspection well due to the settlement of the bearing ring, the size of the settlement chamber is determined according to the mechanical strength of the soil. The pressure ring should be designed according to the size of the external load. A retaining ring should be set between the backfill material under the pressure ring and the inspection shaft body, and a sealing ring should be inserted between the retaining ring and the inspection shaft body to avoid the injection of impurities and road water into the surrounding of the inspection well, which will cause the soil to be soft and cause the well body to sink. The drainage pipe and the plastic inspection well are flexibly inserted and reinforced with cement cement.

Six, closed water test

           The closed water test should be carried out according to the current technical regulations for buried plastic drainage pipes.

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