Discrete Element Method For Deformable Bodies And Application On Underground Engineering

Along with the space development and the increased construction scale of underground structure, the importance and urgency of the seismic design and the safety evaluation for the underground structure is becoming more and more obvious. In this paper, combined with the project of Tianjin Subway No.1 Line, discrete element method (DEM) which bases on deformable bodies, the corresponding artificial viscous boundary, and the coupling method for infinite element and DEM are applied to the seismic problem of the metro tunnel and station. The dynamic response of the metro tunnel in artificial waves is analyzed and calculated, which may provide a basis for the tunnel design and the seismic fortification. The Tucheng Station in Tianjin Subway No.1 Line is discussed in DEM, and the earthquake response of the station frame structure in different earthquake waves is gotten. Also DEM is applied to analyze the bearing mechanics for rigid piled compound foundation. The main work is as follows:1. Based on the principle of deformation dynamics, a new element model for deformable bodies is established. From the side-side contact relation and the dynamic relaxation method, theoretical formulas are derived and the corresponding calculation program is worked out according to the DEM. From the analysis on a typical example, we get not only the distribution of the stress and the displacements, but also the convergence of the static solution, verify the validity of the calculation program and the selected parameters. The feasibility of this method used in the static analysis of geotechnical engineering is proved.2. Considered the features of earthquake disaster, the dynamic response of underground structure in artificial wave is gotten with DEM, which may provide a basis for the metro tunnel design and the seismic fortification.3. The corresponding theoretical formula of infinite element was deduced and in the boundary, the discrete element- infinite element coupling ware achieved. The analysis of the soil-underground structure interaction effects was carried out when the nearby soil was described as discrete elements and the soil beyond as infinite ones. The valid of the calculating program and the selection calculating parameters were tested. The dynamic reaction of underground structure was obtained under the earthquake waves.4. In this paper, the bearing capacity of rigid pile composite foundation under vertical loads and the law of variation of pile-soil bearing ratio among pile-soil interaction are calculated and analyzed on the basis of DEM of the deformable body model, which describes the bearing mechanism of pile-soil interaction of rigid pile composite foundation.5. In this paper, based on DEM, dynamic soil-underground structure interaction system is analyzed and calculated to practical project of Tucheng station of Tianjinsubway No.1 line. Seismic responses (including dynamic internal force and dynamic displacement) of Tianjin subway station frame, under action of Tianjin wave,artificial wave (middle earthquake) and man-made wave (small earthquake), are come out. Possible damage to subway station brought about seismic response is analyzed; some instructing suggestions about structure design of subway station are also indicated in this paper.