2. Pouring foundation concrete and backfilling of foundation pit: sand, pebbles and cement that meet the design requirements shall be used as concrete materials, and the particle size of pebbles shall not exceed 1/4 of the minimum size of structures and 3/4 of the minimum clear distance of steel bars. 32.5R ordinary portland cement is used as cement to ensure the grade and quality of concrete. Settlement joints must be set at slab joints or foundation soil changes or at the junction of filling and excavation every 4~6 meters. The joint width is 1~2cm, and the center line of settlement joint is laid parallel to the road. After each layer is poured, it should be filled with materials that meet the design requirements. After the foundation concrete pouring, backfill the foundation pit according to the design requirements. Foundation concrete is poured at one time, leaving no construction joints.
3. Connection mode of foundation and wall: After the foundation concrete is poured, pebbles should be placed on the foundation surface immediately. The pebbles should penetrate into the foundation concrete not less than 5cm, and the exposed part should be not less than 5cm, and arranged in a plum blossom shape with a spacing of 30cm.
4. Culvert body pouring: The material requirements of culvert wall body concrete are the same as those of foundation concrete. The culvert wall is constructed with cast-in-place scaffolding and formwork. When shuttering, the accuracy of its position and the dimensions and specifications of verticality of each part must be strictly checked. After verification and firm support, concrete can be poured only after acceptance and signature by the supervision engineer. Settlement joints must be set at the joint of the slab or the change of foundation soil or the junction of filling and excavation every 4~6 meters. The joint width is 1~2cm, the center line of settlement joint is laid in parallel, and each layer should be filled with materials meeting the design requirements after pouring. The mixing, pouring, formwork removal and curing of concrete shall be carried out in strict accordance with the requirements of the specification.
5. Prefabrication of cover plate: In order to facilitate hoisting, the reinforced concrete cover plate is prefabricated nearby, and the cover plate is prefabricated in strict accordance with the size and requirements of the design documents. After the prefabrication strength reaches 65,438+000% and the strength of culvert abutment reaches 75% of the design strength, the cover plate and culvert abutment are installed by truck crane. Before installation, the dimensions of the cover plate and culvert abutment should be checked, and the cover plate and culvert wall should be tightly pressed, and then filled with cement mortar after installation.
6. Laying waterproof layer: As a waterproof layer, linoleum must have a test report of material inspection before construction and meet the design and specification requirements before it can be used. The asphalt is continuously stirred until it becomes liquid, and the hot asphalt in use is not lower than 150℃. Before painting, clean the masonry surface and keep it dry without dirt, water and other sundries. Before the hot asphalt is solidified, the linoleum is laid to make it stick together, so as to eliminate warping and hollowing.
7. Water inlet and outlet: The water inlet and outlet shall be constructed with masonry structure in strict accordance with the drawings, and the construction technology shall conform to the specifications. The trough bed of the inlet and outlet should be arranged straight to make the upstream and downstream water flow stable and smooth. When there are wells and rapids, the construction shall be carried out according to the drawings or the instructions of the supervision engineer.
8. Filling on both sides of culvert back: After the construction of culvert waterproof layer is completed and the concrete strength of cover plate meets the requirements, the culvert back shall be backfilled, and the filling construction shall be carried out symmetrically and evenly on both sides of culvert in layers, and symmetrically within the range of not less than 2 times the aperture on both sides of culvert. Behind the culvert abutment 1.0m is constructed by light tamping machinery. When the top filling thickness is greater than 1.0m, heavy construction machinery is allowed, and the back of culvert abutment is backfilled in layers.
9. Filling of top surface of culvert cover plate: The top surface of culvert cover plate shall be filled in layers after the strength of culvert cover plate meets the requirements. The loose laying thickness of the first layer shall not be less than 50cm, and the static pressure method shall be adopted when the roller is used for rolling. ? Culvert is a drainage tunnel under subgrade, which usually consists of two parts: tunnel body and portal building.
The tunnel body constitutes the main body of the water passage, and it should have the necessary aperture to ensure the design flow, and at the same time it should be firm and stable. On the one hand, the role of the tunnel body is to ensure the passage of water, on the other hand, it also directly bears the load pressure and fill pressure and transmits them to the foundation. Tunnel body is usually composed of load-bearing structures (such as arch ring, cover plate, etc.). ), culvert, foundation, waterproof layer, expansion joint and other parts. Reinforced concrete box culvert and circular pipe culvert are closed structures, culvert abutment, cover plate and foundation are integrated, and the section of culvert body is composed of box joints or pipe joints. In order to facilitate drainage, the culvert body should also have an appropriate longitudinal slope with a minimum slope of 0.3%.
The mouth of the cave is the connecting structure of the cave, subgrade and river. The entrance building consists of three parts: water inlet, water outlet and trench bed reinforcement. The function of the hole is: on the one hand, the culvert is connected with the river to make the water flow in and out smoothly; On the other hand, it ensures the stability of subgrade slope and prevents it from being washed by water. Gully bed reinforcement includes import and export adjustment structure, erosion reduction and corrosion prevention facilities, etc.
According to the structural form, culverts can be divided into circular tube culvert, arch culvert, slab culvert and box culvert.
Circular pipe culvert consists of two parts: the hole body and the mouth of the cave. The tunnel body is the main body of the water passage, which is mainly composed of pipe body, foundation and joint. The entrance of the cave is the connection part of the tunnel body, subgrade and water flow, which mainly has two forms: splayed wall and straight wall.
The pipe body of circular pipe culvert usually adopts reinforced concrete, and the pipe diameters are generally 0.5m, 0.75m, 1m, 1.25m,1.5m. The pipe diameters are selected according to the drainage requirements, and prefabricated installation is mostly adopted, and the prefabricated length is generally 2m. When the pipe diameter is 0.5 m or 0.75 m, single-layer reinforcement shall be used, and when the aperture is above 1 m and 1 m, the wall thickness shall be not less than 6 cm when the pipe diameter is 0.5 m, not less than 8 cm when the pipe diameter is 0.75 m, and not less than 10 cm when the pipe diameter is125m. ..