Model Experimental Study Of Interaction Between Deep Excavations And Adjacent Building Foundation

Surrounding buildings’deformation will be influenced by deep excavation, because the excavation of foundation pits may inform unloading effect, if the deformation is beyond the allowable values, it will endanger the safety and suitability of other buildings. At the same time, support structure design and construction of deep excavation projects in narrow site will be influenced directly by those surrounding buildings. There are many real failure cases of deep excavation projects for having not fully considered the influence of surrounding buildings. So it is the technology problem that must be faced and solved to control foundation excavation deformation effectively, keep the safety and suitability of surrounding buildings.Support structure of foundation pits support structure is designed as cantilever continuous underground wall. Some model experiments are conducted to simulate three foundation pits excavation:the foundation pits excavation situation without surrounding buildings is simulated in the first condition; the foundation pits excavation situation of strip foundation of surrounding buildings in the second condition; the foundation pits excavation situation of pile foundation of surrounding buildings in the third condition. Interaction and influence law between support structure’s deformation and surrounding buildings’different foundations settlement during excavation are researched, and some support structure’s design suggestions in different situation are given.The following results are showed after analyzing experimental data.(1) Under the influence of building load, earth pressure value varies dramatically, and distribution pattern of earth pressure value of support structure presents attached load superposition model, this is different from triangle distribution model.(2) Top earth pressure value will be transformed from stationary state into active state during foundation pits excavation without buildings, or there has strip foundation, while lower earth pressure value will be transformed from stationary state into passive state gradually. This means continuous underground wall rotates under a certain point during foundation pits excavation.(3) During foundation pits excavation, bend deformation of cantilever support structure is presented from top to button, main bend area distributes from1/6-1/2under the top of wall, and inflection point turns out in the bottom of support wall. The bend moment of middle and lower wall should be adjusted frequently, and bending moment along the wall will be tended to be stable in the later excavation.(4)Under regulatory effect of pile foundation, the earth pressure value of lower support will inform into active earth pressure gradually with excavating deeper, bending moment of wall would reach the minimum value, and this value will be more even, then the strength of bottom of support structure can perform better. (5)In terms of the building’s uneven settlement that is caused by foundation pits excavation with surrounding buildings, the uneven settlement of pile foundation is smaller than that happens in the strip foundation, so it should be paid enough attention that there has building with superficial foundation around pits, in case of it turns out structure failure for large deformation.