Second, the foundation pit can be excavated mechanically or manually. When approaching the basement design elevation or replacement design elevation, manual excavation should be carried out at a height of 30cm, so as not to damage the structure of the basement soil, and the foundation should be laid as soon as possible to prevent the foundation pit from insufficient bearing capacity after long-term immersion.
Circular pipe culvert
1, pipeline foundation concrete can be poured in two times, first pouring the part below the bottom of the pipe. At this time, attention should be paid to reserve the thickness of the pipe wall and pour the mortar concrete of the pipe joint for 2~3cm. After the pipe joint is poured, the above part of the pipe bottom should be poured, and the combination of new and old concrete and the combination of the pipe foundation concrete and the pipe wall should be ensured.
2. When the height of the culvert top fill is more than 2m, the pre-camber shall be set according to the foundation soil conditions and relevant regulations.
3. Settlement joint setting: Culverts are symmetrically set every 4~6m along the center line of subgrade and perpendicular to the culvert axis. Settlement joint is set between the splayed wall and the end wall, which runs through the whole section and is 1~ 1.5cm wide, and asphalt wadding is filled in the joint.
4. Settlement joint treatment: the settlement joint is filled with asphalt cotton wool, wrapped with hemp rope with a diameter of 2cm for one week, and then wrapped with four layers of asphalt impregnated linen (the width is not less than 15cm). Finally, two pieces on each side shall be bound with thick lead wire, and the joint of the pipe joint shall be leveled with 1:3 cement mortar (width not less than 15cm), and the foundation concrete above the pipe joint shall be covered.
box culvert
1, the box culvert is constructed by cast-in-situ technology, and the whole box is poured twice, the first time is 30cm above the inner wall of the bottom plate, and the rest is poured for the second time after the final setting of concrete reaches 75% of the design strength. The joints poured twice should ensure a good joint surface.
2. Brush asphalt twice on the back of abutment and the outside of abutment as waterproof measures.
3. Settlement joint setting: Settlement joint (together with foundation and cushion) should be set every 4~6m on the whole length of culvert, and its position should be symmetrically set in the middle of subgrade (below the median) and perpendicular to the axis of box culvert.
4. Treatment of deformation joints: 4×6cm notches are set on the top plate, bottom plate and lateral wall of culvert deformation joints. The notch is filled with asphalt cotton wool, and the asphalt-coated plaster board is wrapped with three layers of asphalt and two layers of linoleum. The top surface of deformation joint of water tank culvert bottom plate can be filled with asphalt floc first, and then filled with hot asphalt.
5. The distance between the welded end of the steel bar and the bend is not less than 10d, and it cannot be located at the maximum bending moment of the member.
Filling treatment of subgrade on both sides of culvert
1. Both sides of culvert should be filled with 8% lime soil. When backfilling on both sides of culvert, backfill and tamp symmetrically in layers, and backfill the back of box culvert wall only after the concrete strength of box reaches 100%. According to different materials, the filling thickness of each layer is controlled at about 20cm.
2. The treatment scope of box culvert is 8m on both sides of culvert; The treatment range of both sides of the circular pipe culvert body shall not be less than twice the aperture, and the culvert abutment shall be compacted in layers, and the method of one-time compaction by large machinery shall not be adopted, nor shall only one side be compacted, and both sides must be symmetrical.
3. When filling, it should be overlapped with subgrade by steps, and the compaction degree should not be less than 96%. Within the range where the compaction quality is difficult to guarantee, materials such as sand and gravel should be filled.
4, each layer should be sampling compaction and lime dosage and other indicators.
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