Stresses and deformations of support structures of deep foundation pit based on centrifuge and numerical simulation
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摘要: 依据实际基坑开挖和支护结构工程特性进行模型概化，得出适合的离心模型试验方案，采用离心模型试验分析超深基坑开挖过程支护结构工程的受力和变形分布规律特征。同时建立三维有限元模型对圆形基坑开挖过程中支护结构的变形进行数值模拟，并将试验和数值计算结果进行对比分析。结果表明：支护结构水平位移模式为两头小，中间大的“涨肚型变形”；并且随着基坑深度的加深，地下连续墙水平位移最大值点逐渐下移；地表沉降呈凹槽形沉降形式，随着开挖的进行，沉降槽底部向着远离基坑的方向发展；地连墙背后土压力变化值呈非线性，开挖初期，土压力沿深度变化很小，但随着开挖的进行，土压力变化量逐渐增大；数值分析与离心模型试验的开挖支护结构变形特征结果较相近。研究成果可为基坑开挖设计切实有效的支护结构提供科学依据。Abstract: Based on the actual characteristics of excavation and support structures of foundation pit, a suitable centrifugal model test scheme is obtained, and the centrifugal model test is used to analyze the distribution characteristics of stress and deformation of the support structures of the ultra-deep foundation pit during the excavation process. Simultaneously a three-dimensional finite element model is established to simulate the deformation of the support structures during the excavation process of a circular foundation pit, and the test and numerical results are compared and analyzed. The results show that the horizontal displacement mode of the support structures is the "bulge shaped deformation" with small ends and large middle. As the depth of the foundation pit increases, the point with the maximum horizontal displacement of the underground diaphragm wall gradually moves downwards. The surface settlement is in the form of grooves, and as excavation continues, the bottom of the settlement groove develops towards the direction away from the foundation pit. The variation of soil pressure behind the diaphragm wall is non-linear. At the early stage of excavation, the variation of soil pressure along depth is small, but as excavation continues, the variation of soil pressure gradually increases. As the excavation continues, the bending moment value gradually increases, reaching the maximum positive bending moment near the depth of 17 m, about 2200 kN·m/m. The deformation characteristics of the support structures obtained from the numerical analysis and centrifugal model tests are relatively similar. The research results contribute to providing scientific basis for proposing practical and effective protection measures of the support structures for excavation of foundation pits.
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Keywords:
- deep foundation pit /
- excavation /
- support structure /
- deformation /
- centrifuge /
- numerical simulation
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图 1 圆形基坑离心模型和监测布置
Figure 1. Centrifugal model for circular foundation pit and monitoring layout
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图 3 圆形基坑地下连续墙侧向变形
Figure 3. Lateral deformations of diaphragm wall of circular foundation pit
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图 4 圆形闸门井基坑地表沉降
Figure 4. Surface settlements of circular foundation pit with gate well
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图 6 圆形闸门井地连墙X方向变形
Figure 6. Deformations of diaphragm wall of circular well gate in X direction
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