Fully Rotating Steel Casing Cast-in-Place Pile Construction Method

The rotary full casing construction method is also known as the “BUROTO” method. The steel casing is used to protect the wall during the hole-forming process. It has the characteristics of good pile quality, no mud pollution, green ring, and reduced concrete filling coefficient. It can effectively solve the problems of hole collapse, neck shrinkage, and high filling coefficient that occur when ordinary methods are used for cast-in-place pile construction in urban high-fill and karst landforms. It is currently used in the construction fields of bridges, buildings, petrochemicals, etc.

1. Full-revolving cast-in-place pile construction machinery configuration

Main equipment and components:

1. Full-revolving drilling rig: hole forming

2. Steel casing: wall protection

3. Power station: provide power for the full-revolving main machine

4. Reaction fork: provide reaction force to prevent the main machine from shifting during full-revolving rotation

5. Operation room: operation platform,

Auxiliary equipment for personnel operation place:

1. Rotary drilling rig or impact grab: soil extraction, rock entry, hole cleaning

2. Pipe jacking machine: pull out the pipe to make full-revolving form a flow operation

3. Crawler crane: lift the main machine, power station, reaction fork, etc.; provide support for the reaction fork; lift steel cage, concrete conduit, and carry out impact grab to extract soil, etc.;

4. Excavator: level the site, remove slag, etc.

2. Construction process of fully rotary steel casing cast-in-place piles

1. Construction preparation

The main work of construction preparation is to level the site. Since the drilling rig is large and has many related auxiliary equipment, there are certain requirements for access channels and work platforms. Therefore, the construction preparation needs to consider the construction channels and work planes required for operations such as pile foundation steel cage processing and production, slag transportation, steel cage lifting and installation, and pile foundation concrete pouring.

2. Measurement and layout

First, carefully review the coordinates, elevation, and other relevant data provided by the design drawings. After confirming that they are correct, use the total station to lay out the pile position. After the pile center is laid out, draw a cross line along the pile center to 1.5m away and make a pile protection mark.

3. Full-revolving main engine in place

After the point is released, hoist the full-revolving chassis, and the center of the chassis should coincide with the center of the pile. Then hoist the main engine, install it on the chassis, and finally install the reaction fork.

4. Hoist and install the steel casing

After the main engine is in place, hoist and install the steel casing.

5. Measure and adjust verticality
After the rotary drilling machine is in place, perform rotary drilling. While rotating and driving the casing, press down the casing to achieve rapid drilling into the formation. When drilling the steel casing, use a plumb line to adjust the verticality of the casing in the XY directions.

6. Casing drilling and soil extraction
When the casing is drilled into the ground, a crane is used to release a grab bucket along the inner wall of the casing to the bottom of the hole to extract soil by grabbing or using a rotary drilling rig to extract soil.

7. Fabrication and installation of steel cages
After drilling to the designed elevation, clean the hole. After passing the inspection and acceptance by the geological survey, supervision, and Party A, install the steel cages.

8. Concrete pouring, casing extraction, and pouring into piles
After the steel cage is installed, pour concrete. After the concrete is poured to a certain height, pull out the casing. The casing can be pulled out using a pipe jacking machine or a full-rotation main machine.

3. Advantages of full-rotation construction:

1 It can solve the pile construction in special sites, special working conditions, and complex strata, with no noise, no vibration, and high safety performance;

2 No mud is used, the working surface is clean, and the possibility of mud entering the concrete can be avoided, which is conducive to improving the bond strength of concrete to the steel bars; it prevents soil backflow, and the hole wall will not be scratched when lifting the drill and lowering the steel cage, and there is less drilling debris;

3 The characteristics of the strata and rocks can be intuitively judged when the construction drill is in operation;

4 The drilling speed is fast, and for general soil layers, it can reach about 14m/h;

5 The drilling depth is large, and the maximum depth can reach about 80m according to the soil layer conditions;

6 The verticality of the hole is easy to grasp, and the verticality can be accurate to 1/1000;

7 It is not easy to cause hole collapse, the hole quality is high, the bottom is clean, the speed is fast, and the sediment can be cleared to about 30mm;

8 The hole diameter is standard and the filling coefficient is small. Compared with other hole-forming methods, a large amount of concrete can be saved.

 

The casing rotator is not only used for pile foundation construction in various complex strata such as quicksand, karst landforms, and ultra-high backfill, but can also be used for bite pile construction, subway steel columns, and pile removal construction.

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