Applied Mechanics and Materials Vols. 256-259

Abstract: A coupled finite element–thin layer element (FE-TLE) model for the prediction of subway induced vibrations was developed. With this model, the soil-tunnel system is divided into two parts, i.e., the tunnel structure and layered soil with a tunnel type hole. The tunnel structure is simulated by finite elements and the layered soils with hole by thin layer elements. The model fully accounts for the dynamic interaction between the tunnel and the soil. The numerical models for train-induced ground-borne vibrations were validated by in-situ experiments.

Abstract: Ultra high toughness cementitious composites (UHTCC) demonstrates the properties of non-linear and hardening under load. Its tensile strain may reach over 3%, whereas its average fracture width is only about 60m which shows excellent ability in controlling crack. Tunnel lining is usually made of moulded concrete. One way it endure all the pressures from surrounding rock to guarantee tunnel stability, on the other hand also has low permeability to resist groundwater seepage, while UHTCC has the special advantages in this respect. By analyzing the pressures applied to tunnel lining in one tunnel section, discussion of how UHTCC is applied to lining is done, and some related questions about its application are explained by calculation.

Abstract: The tunnel project is a systems engineering problem. And it is very necessary to study on the system optimization method for supporting structure in order to promote the research about intelligent optimization of safety control for tunnel project. In this paper, the analytic hierarchy process is used to establish system model of supporting structure for urban tunnel and the SCORE function test method for non-linear drift (i.e., non-linear impact of factors) is also applied to simplify the model. This idea and method for the optimization of retaining structural system have important significance for optimization theory building of the tunnel support structure system.

Abstract: Three-dimensional finite element model of tunnel-soil-structures interaction was set up to analyze the causes of settlement and structural cracking when tunnel crossing complex gravelly soil area. It simulated the real tunnel excavation process of Chongqing Metro Line 3. Based on analysis and monitoring results, improved technical measures were used to control settlement, such as advance strengthening, excavation speed control and so on. The latest monitoring results indicate that vault and ground settlement are controlled, and convergence value is reduced significantly. The 3D numerical simulation analysis method provides reference for similar projects, and improvement of technical measures is conducive to settlement control.

Abstract: Rock burst will happened when the underground engineering is excavated in the hard and brittle rock mass because of high in situ stress or concentrated stress. The length of Qirehataer diversion tunnel is 15.639km,and the maximum over-depth is 1720m. With excavation of tunnel, lightly to moderate rock burst had taken place in 600m length about of tunnel, and moderate rock burst locally. The mainly lithology of tunnel is gneiss granite and the percent is 64.5%, uniaxial compressive strength of which is 63.5MPa so it should be classified hard rock. The maximum principle stress is 30MPa in the place of rock bust. This paper analysis engineering geology conditions of this area and the characters of rock burst, author concludes that posteriority and continuity for time and Traceability and continuity for place are different from others rock burst examples. The reason is that course of stress adjustment is continually and repetitive.

Abstract: This paper is used by the combined test technology of resistivity composite profile and high-density resistivity method. Regard Daiyuling the first tunnel engineering geology survey work area as a test site. Different physical parameters such as resistivity composite profile curve of transverse sectionⅠ~Ⅳ line and vertical profile and measured, fitting apparent resistivity quasi section measured by high-density resistivity method reflect geological phenomenon. Through mutual contrast verification, improve the accuracy and reliability of survey results. Provide necessary geophysical basis for engineering geological exploration.

Abstract: Using finite element principle, the numerical simulation analysis model of the tunnels with large-span, long and deep-depth was established. The killed cells excavated in part as, while supporting part as a unit was reactivated among the simulation analysis. The changing characteristics of the initial stress field, the circular soil excavation and supporting, the core soil excavation, as well as the down step excavation and supporting was simulated analysis during dynamic construction of the tunnel. Those will be provided a scientific basis for the safe construction.

Abstract: Combined with the project of an open cut metro tunnel passing through a viaduct, three- dimensional finite element method is applied to study the lateral deformation law of viaduct pile foundations induced by adjacent excavation in the pile foundations reinforcement and un-reinforcement conditions. The results show that the lateral deformation of pile foundations increases with the increasing of excavation depth. The closer distance and the larger deformation, the influence of pile foundations on excavation will be more obvious. The pile foundations deformation is significantly reduced when taking protection measures such as adding new piles, expanding the pile cap and strengthening stratum. Compared with the maximum deformation of the un-reinforcement condition, the reinforcement condition is only 27% to 30%, and the reinforcement measure is remarkably effective. In addition, the length of the piles, the depth of foundation pit, as well as the relative positions of walls and piles have significant influences on piles deformation forms, and it should be taken into account in the design and construction of foundation pit.

Abstract: This paper establishes the Finite Element Model of beam - spring method, and studies the influence of rotation, pressure and shear springs respectively, and analyses the sensitivity of the corresponding internal force curve by changing the spring stiffness value.

Abstract: With the development construction of subway in the city, the cross tunnel is becoming common. However, due to the geological conditions of the subway which limited the minimum depth of the shallow overburden of the tunnel is not the same. In this paper, according to the mechanical characteristics of the cross subway tunnel in several typical soil, a three-dimensional finite element mode is established. And to find out the discipline of minimum cover depth in vertical cross the tunnel by researching tunnel shield excavation the ground surface deformation characteristics.