Construction method of middle excavation type steel pipe pile

The middle excavation type steel pipe pile construction method refers to inserting a special drilling rig into the open type steel pipe pile, and pressing the steel pipe pile into the soil with a pressurized jack or a hoist while drilling and taking out soil. 1. Method of pile end treatment (cement slurry spraying and stirring to form an enlarged head, or final strike, or pouring concrete, etc.) to obtain a higher bearing capacity.

(1) Characteristics of TN. method Insert a long auger drill pipe into the steel pipe pile to make it drill into the soil; then use the door type hydraulic device (maximum pressure 1000kN) to press the pile into the soil; reach the bearing layer at the end of the pile After that, the cement slurry is sprayed out from the high pressure of the drill bit (the pressure is above 20MPa), and it is mixed with the pile end soil to form a cement-soil expansion head.

(2) The characteristics of the TBS construction method A drill with a special expansion mechanism is installed at the bottom end of the long helical drill bit; the steel pipe pile is sunk to the pile end bearing layer according to the middle excavation construction method; while the expansion knife is opened for cutting , Spray the cement slurry from the drill bit with low pressure, mix and stir with the soil at the end of the pile to form a cement-soil expansion head; finally, press the steel pipe pile into the depth of the expansion head 1D (D is the outer diameter of the steel pipe pile) and fix it. (3) The characteristics of the FB9 construction method The bottom end of the long helical drill is equipped with a device for removing the soil attached to the steel pipe and an enlarged drill with a wing expansion mechanism; according to the middle excavation construction method, the

After the steel pipe pile is sunk to the bearing layer of the pile end; while the expanding knife is opened for cutting, the cement slurry is sprayed from the drill bit with low pressure, and mixed with the pile end soil to form a cement-soil expansion head; finally, the steel pipe pile is Press into the expansion head 1D depth and fix it.

4.3 Rotary buried steel pipe pile construction method

This type of construction method refers to the pile construction method in which the steel pipe pile is rotated and pressed to the design depth by providing a rotary knife device. This kind of construction method does not produce impact when the pile penetrates into the soil, so it can be constructed without vibration, noise and soil dumping; in addition, it does not need to pour concrete or cement slurry, and does not need maintenance, so it can shorten the construction period. According to the characteristics of the shape of the steel pipe pile, this kind of construction method can be divided into the rotary press-in method (the bottom end of the steel pipe pile is provided with a helical blade), and the pile end wing rotary press-in method (the bottom end of the steel pipe pile is provided with two and a half pieces). Round wing plate), drill bit method (the bottom end of the steel pipe pile is provided with helical ribs) and wing pile method (the wings of different diameters are arranged at intervals on the side of the steel pipe pile). (1) The characteristics of the rotary press-in steel pipe pile construction method are provided with a helical blade at the bottom end of the steel pipe pile.

The steel pipe pile is rotated and pressed into the soil. When the diameter of the steel pipe pile is less than 500mm, use a three-point support type pile driver for construction; when the diameter of the steel pipe pile is greater than 500mm, use a casing azimuth jack for construction. The diameter of the helical blade is 1.5 times the diameter of the pile. (2) The characteristic of the pile end wing rotary press-in type steel pipe pile construction method The pile end wing is composed of two semicircular steel plates, the diameter of which is twice the diameter of the pile, and the semicircular steel plates are welded to the bottom end of the steel pipe in an alternating manner. Blocking steel sheets are installed at the intersections of the steel sheets to completely block the pile ends, thereby becoming closed piles. During construction, the end wings of the pile are like wood screws, and the pile can be rotated and pressed into the soil without being the king. In addition, the area of ​​the pile end wing is 4 times that of the pile, and since the pile end is completely closed, it can exert a large pile end resistance

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