Retaining wall construction technology briefing
1. Foundation pit excavation
1. Before retaining wall construction, interception, drainage and anti-seepage should be done facility.
2. Foundation pit excavation should be carried out in stages.
3. When using a sloping base, the base elevation should be controlled according to the design, and over-excavation and filling should not be allowed. Mechanical excavation should be controlled to reserve 10 to 20cm, and the base should be cleared manually
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2. Masonry (foundation and wall)
1. When masonry, the poles or model hanging wires must be hung on both sides in sections. The outer sides should be straight and neat, one by one. The layers are sloped, and the inner surface lines can be generally smooth. The retaining wall at the bend should be smooth, sleek and beautiful.
2. When constructing the first layer of masonry, if the base is bedrock or concrete foundation, its surface should be cleaned, moistened, and mortared for masonry construction. When masonry work is resumed after an interruption, the surface of the masonry layer should be cleaned and moistened.
3. The masonry should be layered with staggered joints, and there should be no open joints. The caulking material and mortar for setting the masonry should be full and free of voids. When building the upper layer, the lower layer should not be vibrated. After the masonry is completed, jointing should be carried out.
4. The segmented positions of masonry work should be at expansion joints or settlement joints, and the horizontal joints of each section should be consistent. The slope of the drainage hole should be outward, without clogging, and should be set according to the requirements of the design drawings.
5. The two side walls of expansion joints and settlement joints should be vertical, flush, and non-overlapping; the waterproof materials in the joints should be constructed according to design requirements.
6. When the retaining wall foundation is set on the cross slope of the rock, the weathered layer on the surface should be removed and a step foundation should be made. The height-to-width ratio of the steps should not be greater than 2:1, and the width of the steps should not be Less than 0.5m.
7. The end of the retaining wall extending into the road or embedded in the ground should be constructed at the same time as the wall. The top of the retaining wall should be leveled, plastered or jointed, and the gaps between the slopes should be compacted and closed with clay.
3. Backfilling
1. The backfilling of the foundation pit should be backfilled and compacted in layers along with the masonry, and an outward slope of 3 meters should be reserved on the surface.
2. When the strength of the wall reaches 75% of the design strength, backfilling can be carried out. Backfilling at the back of the wall should be backfilled and compacted in layers. Within 0.5~1.0m from the back of the wall, it is not suitable to use a heavy-duty vibratory roller for rolling. It is suitable to use a vibrating rammer or an impact rammer, and compact it in a layer of 10-15CM.
Safety technical disclosure document
1. Material selection
Material procurement adheres to the principles of adapting measures to local conditions, ensuring quality, and reducing costs. Materials entering the site must have material certificates , certificates and related certificates, and unqualified products are prohibited from entering the construction site.
1.1 Masonry Stones
The MU30.0 stones (mainly stones) used for mortar masonry construction should be uniform, hard, crack-free, and not suitable for weathering. The stone surface There should be no weathered debris, mud marks, or dirt. Try to use larger stones for masonry. The stones should be roughly square and have no sharp edges. The top surface and the ground should be relatively flat. The thickness should not be less than 20cm, and the width should be consistent with the length. Less than its thickness, the flake stone should have two roughly parallel faces, its thickness should not be less than 15cm, and the length of one side should not be less than 30cm.
1.2 Masonry mortar
The masonry mortar is M7.5 cement mortar. First, qualified sand and cement are selected according to the design requirements. Tap water must be used for mixing the mortar. It is strictly prohibited to use water from anywhere. Sewage in ditch. The cement uses 32.5 ordinary Portland cement. The cement entering the site must have a factory certificate and re-inspection report. Its stability, setting time, strength and other indicators must meet the standards before it can be put into use.
Cement should be piled neatly at the construction site. The height of the bagged cement should generally not exceed 10 bags, and the pile width should be limited to 5-10 bags. Temporary open-air storage should be covered with a rainproof tarpaulin. The storage time of cement is generally not more than 3 months. If you are doubtful or unsure about the quality of cement, review the test before use and use it according to the test results. The sand and cement used on site should be piled up neatly and separately, and no mixing is allowed. The sand should be kept clean and mixed with soil.
Mortar for masonry masonry must have good fluidity and good workability to ensure that the mortar joints of the masonry are fully filled and compacted.
The easy on-site inspection method is to knead it into a small ball with your hands. If there is no pulp between the fingers and it does not loosen after letting go, it is considered qualified.
Masonry mortar should be quantitatively tested for strength in batches. A maximum of 100m3 of masonry should be used to test a set of mortar strength test pieces. When there are changes in the cement type, grade or mix ratio, another set of test specimens should be made and used as a basis for measuring the quality of the mortar.
2. Foundation pit excavation and protection
This project is planned to be mainly mechanical excavation, with manual cooperation. Measure the position of the positioning pile and the size of the structure according to the structure, use white ash to release the edge of the foundation pit, and then excavate the foundation pit. For details on earthwork excavation, please refer to the Earthwork Excavation Construction Technology Brief.
3. Mortar stone masonry
3.1 Technical requirements for masonry
Mortar masonry stone walls adopt the staggered construction method, and double lines are hung according to the shape of the stone. The first layer of stones is laid horizontally with the flat side facing down. The upper and lower stones are staggered with each other and overlapped inside and outside. The arrangement is stable and the layers are stacked.
The mortar masonry should be built using the mortar method. The mortar joints should be full and compacted. The mortar joints are generally 20-30mm and the thickness of the mortar is about 40-60mm. Gravel should be used for larger gaps. The blocks are embedded in mortar. It is not allowed to fill the gravel first and then fill it with mortar. Mortar masonry blocks shall not form horizontal or vertical joints, and shall not have knots or rubs. When filling the belly with stones, the horizontal filling width should not be greater than 4cm, and the ash joints of the filling stones should be staggered from each other. Flat joints are used for the joints on the surface of the masonry, and the grade of the mortar used for the joints is not lower than that of the masonry mortar.
3.2 Structural requirements
1) The retaining wall should be equipped with leakage holes. The spacing should not be greater than 3m, the external slope should be 5, and the hole diameter should not be less than φ100 or 100*100mm2, up, down, left and right. Arranged staggered into a plum blossom shape. A drainage bag with a diameter of not less than 500mm should be built behind the drainage hole. When the filler behind the wall is clay soil or silty clay, a sand and gravel drainage layer of not less than 300mm thick should be filled along the back of the wall. The bottom drainage hole should be The outlet should be 300mm higher than the ground or the water surface of the drainage ditch, and the bottom of the hole should be filled with a clay waterproof layer greater than 200mm thick.
2) The foundation burial depth should meet the foundation strength and stability requirements, and the minimum burial depth should not be less than 0.5m in soil foundations, and should not be less than 0.3m in soft rock foundations. The depth of foundation embedding should be calculated from the drainage ditch at the foot of the slope.
3) The width of the top of the retaining wall should not be less than 0.4m, and the wall should be equipped with expansion joints every 10-20m, with a joint width of 20-30mm. When there are changes in the foundation, settlement joints should be added, and the joint width should be 30-50mm.
4. Rainy season construction technical measures
4.1 When carrying out construction projects during the rainy season, the rainy season construction technical measures must be carefully prepared, and specific measures for implementation at each level should be formulated based on the actual construction conditions. and a regular inspection system to facilitate the implementation of technical measures during rainy season construction.
4.2 Carry out drainage work at the construction site in a timely manner according to the actual site layout.
4.3 Protection of temporary facilities and on-site construction equipment:
Temporary facilities on the construction site should be repaired and reinforced before the rainy season to ensure that they do not leak, collapse, or collapse, and that there are no surrounding areas. Standing water. All mechanical and electrical equipment at the construction site (switchboards, gate boxes, welding machines, water pumps, etc.) should have reliable protective measures (such as setting up awnings or setting up simple mechanical and electrical rooms, etc.). At the same time, the power cords of electrical equipment must be suspended and fixed and must not be dragged to the ground. The rainproof and leakage grounding protection devices of on-site electrical equipment should be sensitive and effective, and a dedicated person should be responsible for checking at any time. Before the arrival of the rainy season, you should check whether there are mixed lines, leakage of lighting and power lines, whether there is corrosion on the poles, whether the burial is secure, etc., to ensure normal power supply during the rainy season.
4.4 Masonry projects
When constructing masonry projects on rainy days, the foundation trench should be prevented from being filled with water and rainwater from washing away the mortar. The consistency of the mortar should be appropriately reduced, and construction joints should not be left during masonry construction. The masonry surface should be covered when work is completed. Mortar for masonry is ready to be mixed and used.
4.5 Rainwater construction mortar projects may cause the moisture content of construction raw materials (sand, cement, etc.) to increase due to rainfall. Therefore, the mortar mix ratio should be adjusted according to the rainfall. Mortar construction carried out after rainy days, The mortar mix ratio should be readjusted after measuring the moisture content of the raw materials. During the mortar transportation and masonry construction process, if the rainfall is too heavy, rainproof measures should be taken for the transportation equipment and pouring site to prevent the mortar from changing the fluidity and workability of the mortar due to rainfall during transportation and pouring.
5. On-site quality management system
5.1 Quality personnel observe, supervise and inspect quality-related activities on-site. Check whether the construction work on site is carried out according to approved procedures.
5.2 On-site inspection activities are random, without special reasons. In principle, they should be carried out every day, and any deficiencies or defects discovered during observation must be recorded.
5.3 Monthly inspections at the project site Convene a quality summary meeting attended by all departments and project managers. At the meeting, the technical department reported to everyone the operation of the quality system for the month, promptly identified existing problems, and urged the departments with problems to actively take corrective measures and make rectifications promptly.
5.4 All quality problems discovered on site and their corrective actions must be recorded in the format specified in the procedure document, and as the project progresses, they will be gradually transferred to the next stage as a completed state to prove that the quality meets the requirements. Log files.