Before construction, the pile head of CFG pile under the retaining wall should be cut off, and the elevation of the cut pile head should meet the design requirements, and the pile head should be cleaned up and reported to the testing unit for testing. After passing the inspection, the gravel cushion with a thickness of 0.2m shall be tamped and leveled first, and then the plain concrete cushion with a thickness of 0. 1m shall be poured to provide a working face for the foundation construction of the buttressed retaining wall.

2 measuring unreeling

According to the construction drawing, divide the construction section, measure the center line of subgrade at the toe of retaining wall slope, the main axis of foundation, the top axis of wall, the starting and ending points of retaining wall and cross section, and indicate the elevation and excavation depth. Each axis shall be provided with four pile points on the extension lines at both ends of the baseline, and protected by concrete encapsulation respectively; When measuring the pile position, the ground elevation of the middle pile and retaining wall foundation should be measured, and temporary leveling points should be set outside the construction interference area. The measurement results should meet the accuracy requirements and be closed with the leveling points of adjacent sections.

3 Foundation construction

After measuring and setting out to determine the foundation size, conduct steel binding and formwork erection, and embed wallboard steel bars and buttress steel bars at the same time. When binding foundation reinforcement, attention should be paid to the thickness of the protective layer of reinforcement, and the concrete cushion block with the same strength as the foundation should be used to ensure the quality of concrete. During the foundation construction of retaining wall, concrete can be poured at the same time according to three standard unit sections, which provides more working faces for the wallboard construction of retaining wall. Concrete shall be transported to the site by tanker in centralized mixing station, pumped into the mould, and vibrated with plug-in vibrating rod, without excessive vibration and vibration leakage.

4 wallboard and buttress structure

First, tie the wallboard reinforcement and buttress reinforcement. The formwork can only be poured after the steel bar is installed and inspected by the supervisor. In the process of construction, special attention should be paid to the verticality and flatness of the formwork. Set a cushion block between the reinforced concrete and the formwork, and tie the cushion block with steel bars. The pad should be made of fine stone concrete to ensure that the strength of the pad is the same as that of the concrete structure. The installation of the cushion block shall ensure that the thickness of the protective layer of reinforcement meets the design requirements, and at the same time, it shall ensure that it is 4 pieces /m2. In the process of concrete construction, always check whether the position of the cushion block is accurate.

5 Drainage hole construction

The drainage holes are staggered in plum blossom shape, with a spacing of 2m ~ 3m.

6 concrete curing

After the completion of concrete pouring, assign special personnel to cover the concrete surface before the initial setting of concrete, then carry out calendering treatment before the final setting of concrete, and then cover the geotextile with water to keep moisture. When the climate is hot or windy, you can water it after 2 to 3 hours to keep it fully moist. In humid climate, when the relative humidity of air is more than 60%, when ordinary cement is used, the wet curing time is not less than 7d.

7 template removal

The formwork removal period shall be determined according to the structural characteristics, formwork position and concrete strength. The side formwork of wallboard and pier is a non-load-bearing formwork, which can only be removed when the concrete strength can ensure that its surface and edges and corners are not damaged. Generally, the side formwork can only be removed when the compressive strength of concrete reaches 2.5MPa.

8 Backfilling of wall

Only when the concrete strength of retaining wall reaches 70% of the design strength can the wall be backfilled.