Micro pile, also known as root pile, is a bored cast-in-place pile with a small diameter, the diameter is generally 10~30cm, and the slenderness ratio is generally greater than 30. The pile body is composed of pressure-poured cement mortar or small stone concrete and reinforcing materials, which usually use reinforcement bars, steel pipes or other steel sections.
1, micro pile introduction
Micro pile, also known as root pile, is a small diameter bored pile, the diameter is generally in10~30cm, the slenderness ratio is generally greater than30, the pile body is composed of pressure-infused cement mortar or small stone concrete and reinforcing materials, which are usually reinforced steel, steel pipe or other steel sections.
Its technology is simple, construction is convenient, flexible, adaptable to soil, and compared with the same volume of piles, bearing capacity is higher, has been widely applied in all kinds of civil construction projects, especially in deep foundation pit excavation support, ground subsidence, repair, roadbed reinforcement and slope reinforcement has been more successful applications.
2, construction technology
The construction of micro pile is generally carried out in the following steps:Into a hole→Hole cleaning→Place the reinforcing material→Grouting into piles.
(1) Rig in position
After the rig is set up on the work platform, move the rig so that the bit center is directly facing the pile position. The deviation of pile position should be controlled in20mmWithin, the vertical deviation of the straight pile should not be greater than1%. When drilling holes with inclined piles, the slope of inclined piles is adjusted by raising the drill foot to the required height.
(2) into a hole
Generally using geological drilling, can also be used to shovel impact into the hole, according to engineering geological conditions can also be used to dry hole or mud wall circulation into the hole. In order to avoid the phenomenon of perforation and slurry loss along the sand layer in the construction process, the construction methods such as hole jumping construction, intermittent construction and increasing the dosage of accelerating agent can be adopted.
(3) hole cleaning
The mud wall is used to form the hole, and then the hole is flushed with water. When drilling, the mud gravity is controlled in1.18About, the mud proportion after the hole is controlled in1.12The left and right sides.
(4) to place reinforcing material and backfill stone
The reinforcement material is generally made of steel bar, steel pipe or other steel sections, with long length configuration. The particle size of crushed stone used in micro pile should not exceed1/10The pile diameter. In order to avoid diameter reduction and hole collapse, the time of hoisting reinforcement material and grouting pipe should be shortened as much as possible. The amount of fill volume input of crushed stone is allowed10%~20%Change in theta.
(5) grouting
The water cement ratio of cement slurry should be controlled in0.4~0.6The slurry should be pulped with a high-speed mixer to ensure uniform mixing, reduce segregation, and then transferred to a low-speed mixing slurry storage barrel, while mixing while grouting. In general, the grouting time of pile body should not exceed2When small, multiple grouting technology can also be adopted to improve the effect of grouting.
Generally, the initial grouting slurry reaches the initial setting5~7After hours, the secondary grouting begins. The grouting pressure of secondary grouting is2~4Mpa. Generally from the bottom to the upper grouting side grouting side uniform pull. After extubation, the pile top should be filled with gravel immediately, and in1~2mSupplementary grouting within the scope.
3, micro pile erosion protection
The corrosion protection of micro pile mainly includes the following methods:
(1) galvanized treatment;
(2) coated with epoxy resin;
(3) use casing;
(4) Increase the size of reinforcement appropriately.
4, quality inspection
The static load test is used to test the bearing capacity and settlement characteristics of micro pile under vertical load.
The pulling force of micro pile is tested by static load test.
In addition to the bearing capacity of single pile, the static load of composite foundation should also be tested.
The integrity of pile body is generally tested by low strain.
Shanghai Strong Foundation Engineering Co., LTDThe business covers foundation pit engineering, pile foundation engineering, land and water Foundation treatment, slope treatment and other engineering fields. Around" Excellent technology, reliable process", construction fast "technical requirements,Is to provide customers with land, water foundation engineering technical consultation, construction services and other comprehensive solutions of the entity enterprise.Contact Number: 400-100-2850
