The Research On Lime-soil Cushion Displacement Of Ground Defect

Basing on a large number of engineering practices, the reaserch of foundationtreatment achieved plenteous results and obtaind good practical value. Replacementcushion method have advantages of shorter construction period, lower cost, simpleequipment, etc, compared with others methods, therefore, it has been widely appliedin the country.Joining an engineering project, the auther explored the safety and economics onthe cushion method for multi-storey building, in the case of foundation defects.3-DFinite Element Analysis (FEA) models were formed to evaluate the influence ofpotential defect by ADINA, and the bottom displacement was chose as as influenceresult. The following factors were considered:3typical foundation defects (variedwith position&area),6load levels to simulate5~11storey building loads,3foundation forms, and cushion thickness. Among these,6defect areas from20㎡to120㎡,3defect positions as I, II, III. N was used to represent the total load ofbuilding, values were54000kN,63000kN,72000kN,81000kN,90000kN,99000kN.Strip foundation, grillage foundation, and raft foundation were chose to analysis theinfluence that foundation form and defect situation bring to the cushion displacementfield. To calculate the effect of elimination of level displacement which underdifferent cushion thickness, the cushion was made of two layers, the lower layer was3.0m thick pure soil, and the other layer was2:8lime-soil that the thickness wersrespectively1.5m,1.75m,2.0m,2.25m,2.5m.1620example results showed that, firstly, displacement of cushion under raftfoundation is raletively smaller, therefore, this foundation is better than other forms.Secondly, in the calculation of the3foundation forms, because double-defect did theleast harm to cushion, it illustrated that defects in sporadic distribution is better thanthe whole piece with the same defect area. Thirdly, although increasing the cushionthickness significantly enhanced the stability, the effect may decrease as thethickness gets larger, therefore, the integrity (Strength&Stiffness) of cushionmaterial can be considered as the primary factor.