Before foundation pit excavation, ground drainage should be done well, and a drainage slope should be set at the top edge of foundation pit.

After setting out the footguard foundation pit, excavation shall be carried out immediately. The foundation pit is excavated manually or mechanically, and the slope of the four walls of the foundation pit is determined according to different soil quality and excavation depth to ensure the stability of the foundation pit slope. When the foundation pit is dug to 20cm above the design elevation, stop the excavation, select a representative section to dig to the design elevation, and do the foundation bearing capacity test. After the foundation bearing capacity meets the design requirements, continue to manually dig to the design elevation. After the supervision project is signed and recognized, the construction of mortar rubble foundation will be carried out immediately.

If the bearing capacity of the foundation can't meet the design requirements, the foundation treatment should be carried out after the approval of the supervision engineer, and the foundation construction can only be carried out after the design requirements are met and the supervision engineer is satisfied.

Step 2: Wall

Before laying, each stone should be washed with clear water and completely soaked. Masonry is constructed by grouting method and compacted with flat steel to make it full of slurry.

All stone materials should be laid in layers and sections, and a working face should be composed of 2 ~ 3 layers of blocks, which are laid in layers. The horizontal joints of each working layer should be roughly horizontal, and the vertical joints of each working layer should be staggered and not connected. The vertical joints of each working layer should be built by laying bricks or stones, the elevation difference of adjacent sections should not be greater than 1.2m, and the settlement joints should be set according to the construction drawing, and they should be perpendicular to the ground.

Before wall masonry, it is necessary to put segmented slope plates at both ends of each wall, hang horizontal lines along the wall direction to fix their plane position, and then correct the verticality of the slope plates with a plumb hammer.

The exposed surface of the wall should be made of processed face stones and arranged in sequence. Joints should be horizontal and vertical, the width of vertical joints should not be greater than 2cm, and the staggered distance between upper and lower vertical joints should not be less than 10cm. All face stone lines must be laid in one direction.

The wall should be equipped with drainage holes according to the design requirements and the actual situation on site.

3, pointing and expansion joints

The exposed surfaces of embankment retaining walls in this contract section are all hooked and serrated. The strength of jointing mortar should not be lower than that of masonry mortar.

The jointing of stone masonry should be embedded in jointing about 20mm deep. When the depth of the groove is not enough, it should be cut to a sufficient depth before the joint.

Mortar masonry should be cured within 7 ~ 14 days after the initial setting of mortar, and collision, vibration or bearing should be avoided during curing. The mixture ratio of masonry mortar is determined by laboratory trial mixing test.

Expansion joints are blocked with boards soaked with asphalt, and joints are filled with asphalt hemp.

4. Backfilling of the wall

Backfill on the back of the wall should be made of materials with good water permeability or fillers specified in the design.

Backfill on the back of the wall must overlap with excavation subgrade and fill subgrade effectively, and steps must be set for longitudinal joints.

Must be layered filling compaction, each layer thickness control within 15cm, hanging line construction.

Backfilling of the back of the wall should be rolled by roller as far as possible. If there are difficulties, you should choose a calendar machine to cooperate with manual work. When the roller is close to the wall, it should be statically pressed to avoid collision and vibration of the wall.

Only when the wall strength reaches more than 75% of the design strength, can the filling be started.

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