轴力作用下软土基坑力学场演化规律的原位试验研究

In-situ Test Study on the Evolution Law of Mechanical Field of Soft Soil Foundation Excavation Under Axial Force

依托上海轨道交通14号线浦东南路站附属结构基坑,针对围护结构侧向变形、支撑轴力、迎土面土压力、坑内土体流变等,开展了轴力作用下基坑力学场演化规律的现场原位试验。试验结果表明,通过主动施加伺服轴力,可有效减小围护结构的侧向变形,并抵消因坑内流变产生的位移增量;根据钢支撑设置的“尽早”与“就近”原则,采用“分区控制原则”可更好地控制超深基坑围护结构侧向变形;而基于轴力相干性所提出的多目标动态控制法能提高轴力与变形关系的对应性。主动控制下支撑轴力的变化会引起围护结构迎土面土压力的变化,轴力增大时围护结构侧向变形减小、迎土侧土压力增大;温度变化可引起的轴力与围护结构侧向变形改变。研究证明通过主动调控支撑轴力能改变支护结构和土体的力学状态,基于轴力的围护结构侧向变形主动控制是可行的。

Based on the foundation excavation of the auxiliary structure of Pudong South Road Station of Shanghai Rail Transit Line 14,the field in-situ test of the evolution law of the mechanical field of the foundation excavation under the action of axial force was carried out for the lateral deformation of the retaining structure,the axial force of the support,the earth pressure on the soil surface,and the rheology of the soil in the foundation.The test results show that the lateral deformation of the retaining structure can be effectively reduced by actively applying the servo axial force,and the displacement increment caused by the rheology in the foundation can be offset.According to the‘early’and‘near’principles of steel support setting,the“zoning control principle”can better control the lateral deformation of the retaining structure of the ultra-deep foundation excavation.The multi-objective dynamic control method based on the coherence of axial force can improve the correspondence between axial force and deformation.Under the active control,the change of the axial force of the support will cause the change of the earth pressure on the soil surface of the retaining structure.When the axial force increases,the lateral deformation of the retaining structure decreases and the earth pressure on the soil surface increases.Temperature changes can cause changes in axial force and lateral deformation of the retaining structure.The research proves that the active control of the lateral deformation of the retaining structure based on the axial force is feasible by actively regulating the axial force of the support to change the mechanical state of the supporting structure and the soil.