Numerical Simulation Of Combining Supporting Structure Of Idle Pile-anchor Foundation Pit Under Deepening Excavation

With the shortage of the land resources in ubran, development of undergroundspace is the current direction of the rational use of land resources. As a result, thefoundation pit in the city will be presented with a situation of "bigger and bigger,deeper and deeper. However, due to lack of funding, design changes, land transferand other reasons, resulting in many projects stop progress of the project after thecomplete of the foundation pit, leaving a lot of unused or unfinished foundation pit.Based on a engneering project of secondary excavation foundation pit, combined withcollecting literature, the analysis of field test and monitoring data, evaluating andanalysing the facters affecting the stability of idel pit. Besides, the numericalsimulation is applied to analyse the force and deformation characteristics in thedeepening excavation of foundation pit, and the impact parameter is also discussedhere. The main contents are as follows:1. The impact factors of durability and structural performance of retainingstructures are discussed by understanding the concrete carbonization, chloride ionerosion, mechanism of steel corrosion, combined with results of previous studies. Inaddition, based on on-site testing and displacement monitoring data, the stability ofidle pit project is evaluated.2. The plane strain numerical simulation model is established by software Z-Soilbased on the constitutive model of HSS (small strain hardening soil). The horizontaldisplacement, bending moment and the settlement outside the pit is discussed in theprogcess of deepening excavation. The results show that: In the process of deepeningexcavation, the setting of new supporting structure can be helpful to control thesecondary horizontal displacement and moment of the fisrt-stage pile.3. The basic analysis model of deepening excavation foundation pit isestablished to study the general trends of force and deformation characteristics of thetwo-stage pile-anchor combining supporting structure, the factors are as follows: thecoupling form, stiffness, length of coupling beams; the embedded ratio, spacing, stiffness of second-stage piles; the position of reinforment anchors; the height, widthof berms.