The Research On Behavior Of Adjacent Excavation With Changes Of The Forms Of Foundation

In recent years, China’s national economy develops rapidly, which directly led to limited ground space that is difficult to meet the material and cultural needs of the human, a large number of high-rise, high-rise buildings and underground construction grow rapidly. Deep excavation projects will be faced with many complex and uncertain factors, especially pit excavation in intensive buildings, often around the same excavation engineering met a different type of building structure, different forms of foundation and building loads, which impact the nearby pit excavation. In this paper, based on the large-scale finite element software ANSYS, a three-dimensional finite element model is established to simulate how the four different foundations forms of adjacent buildings affect the excavation, including natural ground with no adjacent building, raft shallow foundations, raft pile foundation as well as pile composite foundation. Conclusions are as follows:(1) The additional load of adjacent excavation affects the supporting structure. Compared the model without adjacent buildings to model with shallow foundation raft (model2), the results show that:under the same conditions, the supporting piles displacement and earth pressure of model2are greater than model1.(2) When the form of foundation with the neighboring building is pile foundation or pile composite ground, the constraints of horizontal displacement as well as the channeling function of the piles to soil, which bring beneficial influence to foundation pit supporting structures, become more apparent with the increase of cutting depth. Under such circumstances of rigid-pile composite foundation and piled raft foundation, the condition of the largest displacement of adjacent foundation pit supporting structure and the biggest earth pressure above the excavation surface are less than the raft of shallow foundation.(3) Rigid pile composite foundation and the pile raft foundation is similar on the influence to the behavior of adjacent foundation pit, as well as the trend of the displacement and earth pressure of retaining structure deformation, but the mattress layer in composite foundation adjustment will cause some forms of transmission of the loads:above the pile tip, pile foundation under the situation of displacement and earth pressure of retaining structure are less than pile composite foundation; the result of the pile end is just the opposite.(4) Rigid pile composite foundation and piled raft foundation are on the similar impacts to the excavation, but there are some differences:The impacts on unloading of soil between piles and losing of the pile side friction of the pile composite foundation are bigger than the pile foundation.