Underground diaphragm wallConstruction procedures

1Divide the unit slot segment

The main factors affecting the length of the groove are: geological conditions and the influence of adjacent buildings, wall shape, mechanical equipment lifting capacity, concrete supply capacity, continuous operation time.

The length of the slot segment is generally4m-6m.

2, guide wall construction

(1) Guide wall function: guide and calibrate the height, as the upper main retaining wall, to ensure the stability of the slurry level.

(2) Structural section: generally→PShape or-4Shaped cross section. The topsoil is well available4A shape. multi-purpose↓LShape. The structure is mostly cast-in-place reinforced concrete.

Mud overflow holes should be reserved in the outer guide wall.

(3) Construction sequence of cast-in-place guide wall

Level the site (change the soil first if the topsoil quality is poor)→Measuring lofting (the net distance of the guide wall is much thicker than the wall 40mm～60mm)→Dredging and disposal of abandoned soil→Tie bar→Supporting formwork (earth mold is used on the outside)→When pouring concrete, remove the mold and set the transverse support→The outer void of the guide wall is backfilled and compacted.

3, into a trough

Percussive drill is used to punch holes and grooves. When the soft soil thickness accounts for a large proportion, drilling can be performed first to improve the efficiency. The rock entry is changed to punching, and finally the groove is repaired.

In the process of punching, the mud is used by positive circulation after settling in the sedimentation tank.

(1) Selection of mud

The plastic index is usually used, except that some soil layers can meet the requirement of mud making by themselves≥20And clay content≥50％And sand ratio<5％The clay to pulping, and according to the geological conditions, trough method and use of the situation to decide whether to add additives.

Generally, tap water is used to configure mud. The salt content of mud should be measured and the water loss test should be carried out in projects near the coast.

(2) The amount of mud

The amount of new pulp is about the total amount of excavation 1.2～1.5 Times.

The volume of the slurry making pool and circulating mud pool is not less than the maximum excavation volume of the groove section 1. 5 Times.

Generally, a mud ditch is set along the outside of the guide wall for mud circulation. More brick masonry.

4And qing slot

When the soil quality is good, air mud suction and diving sand pump can be used to clear the tank. When it is poor, mud circulation or sand pumping cylinder can be used to clear the tank. Gravel soil layer can be used to clean the tank with diving sand pump or sand pumping cylinder.

5, the installation of the groove joint pipe

Common use of joint pipe 10mm～20mm The steel coil is welded to a diameter smaller than the design wall thickness 1mm~2cm The length of the tube is as deep as the wall.

6, the production and installation of steel cage

Steel cage is made on site. According to the capacity of the lifting equipment, whether to make and lift in sections or not, the cushion block controlling the thickness of the protective layer should be set on it, and it should be lifted immediately after the clearance acceptance.

7Install the catheter

General use 250mm Circular steel pipe. Catheter spacing should not be greater than 3m, the joint end of the off-slot segment is not greater than1.5m.

8, pouring concrete

After the steel cage is in place, the concealed works shall be checked and accepted, and the underwater concrete shall be poured immediately according to the specification requirements. If the interval is longer than 4h The thickness of sediment should be remeasured.

Underground diaphragm wallConstruction completion

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