Key Points of Construction and Treatment of Tower crane Suspension Foundation
Key Points of Construction and Treatment of Tower Suspension Foundation
1. Cases where the basis does not need to be addressed
When the base position of the tower is wide and the foundation layer is shallow, it can be directly constructed according to the base map of the tower. The base should meet the design requirements, generally 0.2-0 .3 MPa, which is easily satisfied or handled. In order to prevent groundwater flooding or safety, it is usually safer to place the base on a hard bottom.
The part that exceeds the depth of the foundation can be poured with C15 stone gongs. It should be noted that the tower hanging foundation is often used as a piece of stone grit because the owner saves investment requirements. There have been construction units that have used mudstone as a piece of stone to cause the tower to collapse. accident.
2. Deep soil layer.
(1) The thickness of the soil layer is more than 8M. That is, the rectangular tomb foundation is used as a support platform, and 800 suitable rocks are dug in each corner, and the requirements can be met by structural reinforcement. The cross-shaped foundation is to dig 5 piles and review the internal reinforcement of the foundation.
(2) If the thickness of the soil layer exceeds 8M and the excavation pile is more and safer, a smaller diameter drilling pile may be considered for solution. At this point, the construction unit is required to provide a balance moment calculation book for the tower crane for inspection.
The earlier manual did not provide data, and can only refer directly to the original foundation bearing capacity conversion of the anti-overturning moment as a basis, the calculation results are relatively conservative, and the requirements for the bearing capacity of the foundation are also high.
(3) The method of review calculates the anti-overturning moment according to the bearing capacity of the pile foundation and the distance between piles. This method has a clear form of force and is relatively simple to calculate.
3. Inadequate base positions.
This is generally the case where the base of the tower is just below the steep slope or the edge of the cliff, and its horizontal position can not be placed on the rectangular base of the tower(the cross-shaped foundation is not applicable). The construction unit reduces the foundation of the tower to ensure the mounting size of the tower body and places it on an enlarged independent pile foundation.
This basic form can also be used in places where the soil layer is deep and the soil quality is poor. The calculation of this basic form is more complex and should be used with caution. The calculation content is:
When calculating the balance moment and vertical load of tower crane, the influence of wind load should be considered.
To determine the pile diameter, usually take 1.2 ~ 1.5 M(25-63 tower hanging).
To determine the depth of the embedded rock and the size of the extended head, calculate the anchoring moment.
Calculate the required foundation bearing capacity and compare it with the ground survey data.
In calculating the reinforcement, the iterative method is used for direct calculation. When reviewing, the circular pile can be replaced with a square equivalent section to simplify the calculation, and the drawing test should also be performed.
The construction requirement is treated according to the pile foundation specification.
Such a scheme must strictly control the construction quality, such as rock depth, core test data, concrete quality, and the length of reinforced anchorman.
