Self drilling anchor as a kind of simple, reliable, practical and efficient construction method.
The micro pile technique is a reliable system that can bear large axial or lateral loads.
And it has little interference on the the existing structure. The self drilling anchor bolt is used in the foundation engineering.
When the self drilling anchor used as the micro pile,whether it is the construction of new buildings or old buildings, the micro-piling method can reduce the impact of new buildings and existing buildings.The method is more and more popular.
The structure of the micro pile comprises a continuous thread hollow anchor rod and a OPC cement paste with a minimum strength of 25N/mm2, and the special surface of the cement slurry can transfer the tensile force and the pressure resistance to the ground. The micro pile can transfer the tensile and compressive load to the deeper soil layer.
First, compared with the traditional pile, the advantages of hollow bar micro pile:
1 It can withstand pressure and tensile strength
2 It does not require the use of temporary casing
3 It improves the internal mechanical effect of the ground / slurry
4 It is easy to install and improve production efficiency on a large extent
5 It can use a small rotary impact equipment
6 It can be installed in confined space
7 The bearing capacity of self drilling micro pile is 110kN~3660kN
8 It can be used without vibration drilling, low vibration, low noise, minimal damage to the adjacent building and it does not cause damage on building.
The installation of the mini pile method provides great benefits for excavation and concrete base plans, as well as providing great convenience for health and safety problems.
Two, engineering application:
In the vicinity of a private residence, the basement of the building takes advantage of the hollow micro pile, which is an integral part of the underlying structure of the foundation and the ground floor.
Due to the foundation of the ancient building,the oundation of the building without reinforced concrete support structure, the era of settlement, in order to inhibit the deformation, the use of micro pile for control and restrain the development of deformation.
Pile group for supporting structure supporting existing foundation
A new type of micro pile used in the new building and the use of rotary impact drilling machine. When the cement slurry is fixed, the annular area is not needed. The installation method has no vibration and low noise. Mini piles can be installed using a small rig and the need for smaller drilling, which means less damage, lower cost.
Three, the calculation of bearing capacity of micro pile
The bearing capacity of the self drilling micro pile is mainly determined by the length of L, the diameter of D, the limit of soil friction, the surface of cement paste and the safety factor.
The bearing capacity of the pile can be ignored.
Surface friction values should be obtained from field investigation and test.
Bonding length of tension pile or compression pile
Tw – safe working load
Fs – safety factor
D – drill diameter + enhancement factor
Tult – surface friction