Study On The Mechanical Behavior Of Piles In Row In The Deep Foundation Pit Engineering Of Mountain Area

With the development of the economy, the big cities develop faster and faster and some mountain towns begin to rebuild. It makes the deep foundation pit engineering of the mountain area arise. There are many support measures used in foundation pit engineering, such as cement-soil gravity wall, inverse arch wall, soil nailing wall, anchoring and shotcreting, sheet-piles, piles in row, diaphragm wall. The deep foundation pit engineering of the mountain area is different from the general one. Due to the limitations of site topography, it is difficult to construct the interior bracing. It becomes particularly important to choose the proper support measures accordance with the different characteristics of foundation pit engineering.The dissertation takes the foundation excavation project of Langao County Cultural Square as an example. Based on the layout and design and the engineering geological conditions of the project, the support design is conducted.A numerical simulation of the geologically most complex section of the foundation pit engineering is also made by FLAC3 D. The analysis is mainly focused on the deformation of foundation soil and the stresses of manual dug piles. The results are as follows.(1) According to the results of numerical analysis, we can find that, with the increase of excavation depth, the soil displacement of foundation pit becomes larger gradually. The maximums of vertical and horizontal displacement of soil appear on the top of the foundation pit side wall. The vertical and horizontal displacements of side walls are both decreased gradually with the distance increasing from the top of foundation pit.(2) According to the stress analysis of manually dug piles, it has been found that the maximum stress of the soil, the maximum negative axial force and horizontal force appear at the depth of foundation pit excavation. And the maximum shear stress values appear at 1 metre below the bottom of the pit. The negative maximum values of the axial force gradually increase, the positive ones reduce, and the maximum shear stress values are almost the same. At the middle position of the piles, the horizontal force is always zero. But in the fourth excavation, when the level of excavation is lower than the middle of the pile, it is at 14 metres from the pile top position and the horizontal force fluctuations.(3)There are the maximum bending moment values of piles where the horizontal force values are zero. The maximum bending moment values and the zero value of horizontal force are always at the middle of the piles. The horizontal force shows centrosymmetric distribution and the bending moment is axisymmetric distributions at the center of the pile.The results of the numerical analysis with FLAC3 D can be compared with the monitoring data in the future in order to verify the accuracy of it. It also provides the experience for the deep foundation pit in mountain area.