Why subway steel support axial force value
Calculation of axial force of steel support in deep foundation pit:The first plus zero, the calculation of a cable tension, the anchor cable tension is able to ensure the stability of the foundation pit resistance, and then on the basis of the times on the basis of the standard 70~95%.Preload is generally not more than 450kN, because of the use of pile anchor structure is mostly sand, silt, or clay, anti pulling force of this stratum and anchor is limited, 450kN means that the prestressing design tension reaches 450/0.95~450/0.7, which is basically the ultimate anchor in this ordinary formation, if not met to consider the encryption of anchor spacing.
Prestressing loss inside soil anchor is amazing, which specification requirements of 10~15% super tension lock is not enough, in fact inside the prestressing Jack from soil drainage the moment gradually loss of anchorage problem, many problems of anchor soil creep, prestress loss after lock is terrible. Therefore, the general pre reinforcement will not add to the wife, because the actual role of the design and the lock is not so big.
The main reasons are as follows: 1. The deformation of foundation pit is too large;2, caused by high temperature;Generally, the foundation pit is supported by continuous wall (pile) and steel support. Support axial force monitoring, monitoring the foundation pit in the construction process of the support axial force changes, to avoid the bearing axial force beyond the design strength of the support failure caused by the instability of the whole support system.
