Influence laws of excavation sequence and early stiffness of inner support on stability of foundation pit in soft soil
Deformation control of deep excavation is a difficult problem for deep foundation pit engineering in soft soil,and dense concrete inner supports are often used in engineering to improve support stiffness.However,the excavation sequence of deep foundation pit in soft soil and the early stiffness of concrete inner support are not reasonably considered in practice,which often cause the actual deformation of the foundation pit greater than the design value.According to the deep foundation pit in the Pearl River delta water resources allocation project,the verified numerical simulation method was used to study the influence laws of different excavation sequences and the early stiffness of concrete inner supports on the stress and deformation characteristics of soft soil foundation pit.The influence laws of asymmetric and/or symmetrical excavation on the diaphragm wall horizontal displacement and ground surface settlement were obtained.The results show that although asymmetric excavation will cause the displacement of diaphragm wall and surface settlement difference on both sides of foundation pit,asymmetric excavation can reduce time significantly compared with symmetrical excavation in the case of dense inner support.Moreover,due to the early stiffness of the concrete inner support,the earlier the next excavation is carried out after the applying inner support,the greater the diaphragm wall horizontal displacement and ground surface settlement will be.Considering the influence of the early stiffness of the inner support,the axial force of the inner support in the upper part of the foundation pit will increase,while the axial force of the inner support in the lower part will decrease,this trend will be more obvious at a lower early stiffness.Meanwhile,it is difficult to dynamically monitor the elastic modulus of concrete in real time during on-site construction,which is easy to cause the distortion of early monitoring data of inner support axial force,and even bring wrong decision-making to the project.
deep foundation pitsoft soilexcavation sequenceconcrete inner supportearly stiffnessdeformation characteristic
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维普
