Numerical Analysis Of Deformation Of Foundation Excavation Considering Influences Of Spatial Effect

With development of foundation pit engineering, the space effect of foundation pit engineering is one problem that cannot be ignored during the design and construction of foundation pit engineering, which attracts more and more attention. Lots of engineering practice shows that foundation pit has obvious space effect, especially deep foundation pit in the dense area of city in which the space effect is even more obvious. For the foundation pit with different excavation sizes and angles, the deformation rule of different position is different, which needs to be taken into account during design and construction. For the foundation pit with different excavation size and angle, the development history of foundation pit engineering is reviewed, explanation of space effect of foundation pit is summarized and research status of space effect of foundation pit at home and abroad is studied and summarized in this paper. Combined with numerical simulation methods, the deformation rule and mechanism of foundation pit with different length-width ratios and excavation angles are studied considering space effect on the basis of theoretical analysis. The main research content is shown as follow:(1) Numerical analysis is used to study the space effect of foundation pits with different length-width ratios and analyze their deformation rule and mechanism. Result shows that when length-width ratio L/B is less than 2, horizontal displacement of enclosed structure along long sides of foundation pit and bottom heave of foundation pit are more obvious as length-width ratio L/B changes, but horizontal displacement of enclosed structure along short sides of foundation pit and surface subsidence of outside foundation pit are not obvious. When length-width ratio L/B is more than 2, considering the result of three-dimensional problem analysis of space effect is close to the result of two-dimension problem analysis, the deformation of foundation pit does not have obvious change as length-width ratio changes. It shows that the space effect along short side direction of foundation pit is more obvious, and space effect along long side direction of foundation pit is less obvious, especially the center area of long side direction can be analyzed as two-dimensional problem.(2) Numerical analysis is used to analyze deformation rule of foundation pit with different excavation angles. It is found that the deformation at corner is the smallest, and the deformation in the center is most obvious no matter excavation angle is acute angle or obtuse angle. Therefore, it is obvious that there is corner effect as well as space effect.When excavation angle is 60 °,the horizontal displacement of enclosed structure of foundation pit and bottom heave are smaller than horizontal displacement of enclosed structure and bottom heave when excavation angle is 180 °, and the change of excavation angle has obvious affect to the corner of foundation pit, but less affect to the central area.(3) The control of deformation of foundation pit with space effect taken into account is also studied in this paper. It finds out that excavation by layer, section and area is the common method to control the deformation of foundation pit, especially for long and narrow foundation pit. This excavation has an obvious effect on controlling the corner deformation of foundation pit, but has less effect on controlling the deformation of central area of foundation pit.