Study On The Critical Condition And Control Methods Of Anti-floating Failure Of Basement During Construction

With the rapid development of urban construction, the underground space isdeveloped and utilized effectively. The depth of embedded foundation is increasedwhich lead to the increasingly prominent anti-floating problem of basements. Structuredesigners at home and abroad adopt setting anti-floating anchor rod, increasing thestructural weight and other measures to ensure the anti-floating safety of basementwhen the anti-floating stability does not meet the requirements, while a few projectstake active anti-floating measures, such as drainage decompression. However, thesemeasures are designed on the premise that the basement has achieved the anti-floatingcapability, which didn’t consider the engineering practice that the anti-floating capabilityis different at different Construction Stage. In recent years, some accidents ofanti-floating failure happened due to improper dewatering measures and untimelybackfilling. Theoretical research and practical control methods are still deficient toprevent anti-floating failure of the basement during construction.This subject is mostly concentrated on the anti-floating problem of basement，according to the characteristics that the anti-floating capacity and groundwaterbuoyancy is dynamic during construction. The anti-floating failure mechanism ofbasement on different working conditions was studied to propose calculation methodsand control measures by theoretical analysis, engineering research and finite elementsimulation.Firstly, the anti-floating capability of basement during construction was analyzedand compared with the present codes, to expound the anti-floating calculation methodsof basement.Secondly, site observation upon a project accident was carried out, while statisticalanalysis on damage characteristic of basements and preliminary calculation were madeto analyze the accident causes and characteristics of structural damage.Thirdly, basement models were built with finite element software ABAQUS andSAP2000to analyze the change of internal forces with the growth of water level andmake sure the type and location of the component which was damaged firstly. Makesure the critical failure state of anti-floating and propose calculation methods andengineering measures of three kinds of anti-floating during construction.Finally, the variation of underground garage elevation was studied in the process of buildings’ subsidence to propose the key problem during artificial precipitation in orderto avoid man-made further destroy because of excessive settlement rate.Research and application of this subject showed that anti-floating head should bedetermined according to the critical condition of anti-floating failure duringconstruction. And take appropriate technical measures in order to prevent anti-floatingfailure effectively, and avoid economic losses.