Applied Mechanics and Materials Vols. 170-173

Abstract: The article analyzed the forced state of the surrounding rock and the tunnel lining for Fu longping double-decked tunnel by the Elasto-plastic finite element method. In the analysis, DP’s yield criterion was employed for the elasto-plastic characteristics of materials. It studied the construction method with the theory, and guided the construction for the double-decked tunnel ,too.

Abstract: GAP model will be modified and programmed by FISH language, which can be used in FLAC2D programs. The modified GAP model is used to study the variation of surface settlement shape with depth, the variation of the maximum settlement value with depth, and the variation of settlement gradient with depth. The results show that: the settlement shape is narrow and deep with the conditions of shallow buried depth of tunnel; on the contrary, the settlement shape is wide and shallow; When the tunnel depth is less than the critical value, the tunnel depth and the maximum surface settlement is approximately linear; when the tunnel depth is greater than the critical value, the curve of maximum surface settlement value with depth becomes flat and with the increase of the tunnel, the surface settlement gradient gradually decreases and eventually tends to zero. It is more reasonable to assess the influence of tunnel excavation near adjacent buildings, using the maximum surface settlement and the settlement gradient as a control standard.

Abstract: In order to analyze the different construction program under the tunnel surrounding rock stress, strain and plastic zone changes, we take water tunnel group of nuclear power plant as basic project and the application of software FLACIS3D numerical simulation.The results show that: During the tunnel excavation and support group process, the different rock tunnel construction program can produce different stress, displacement and plastic zone extended range of distribution and other aspects.To interval-type excavation program,although previously disturbing effect of the excavation of the tunnel construction and tunnel excavation of rock, it can generate less impact on the stability of surrounding rock. For the latter excavation of the tunnel, the tunnel project area affected by the first digging,the stress can be released, the stability of the first excavation of the tunnel effect is also small.Comparing to sequential and parallel program-type excavation program, the use of interval-style group of rock tunnel excavation will help stabilize the body.

Abstract: Based on the deep excavation engineering which used the common support design near the range of Suzhou Rail Transit Line 2, a 3-D numerical model was created to make the numerical simulation analysis of the deep foundation pit construction and obtain the comprehensive evaluation of the influence on the nearby subway tunnel stress and deformation when the 3 # and 4 # block foundation pits were excavated. The numerical results show that: when the pits are excavated to the basement, the total displacement value of the tunnel is 1.6mm. Because of the aspect ratio difference between the 3# and 4# block pits, the subway tunnel displacement of every direction trends to the 3# block. And the preserving soil area between the two blocks makes the tunnel stress present a symmetric distribution along the soil area's cross section. The surface settlements of soil behind enclosure structure lead to a great impact on the pipelines, whose maximum reaches 5mm. For comprehensive, the maximum displacement and spring back deformation of the subway tunnel meet the control requirements, with a certain margin of safety.

Abstract: Phenomenon of surrounding rock deformation and collapse, groundwater lowering, ground collapse and cracking appeared in a tunnel project. It is necessary to guaranty construction safety and ensure the reliability of supporting structures. This paper, using large-scale model, considers the surrounding rock deformations and stress adjustments caused by cavern excavation and tunnel support in the alteration zone. It suggests engineering protective measures by summarizing the major determinant of excavation deformation.

Abstract: In this thesis, considering the double-hole parallel tunnel engineering with super-small interval, the optimization of designed supporting parameters are studied by the strength reduction finite element method. The calculated safety factor by using the strength reduction finite element method was considered as the index of the tunnel surrounding rock stability, and by using the orthogonal finite element experimental method, the parameters are analyzed and the optimal values of bolt and spry cement are given. The excavation and supporting process under the optimal supporting parameters is simulated, and it indicates that the optimal parameters not only could ensure the stability of the tunnel surrounding rock, but also could decrease the cost of the engineering comparing with the original design project, and there is reference value for analogous engineering.

Abstract: With the excavation depth increase，the bursting stabilization had become a major factor affecting the security of foundation pit. On the base of research situation about foundation pit stabilization and a large number engineering practices，the factors and the complexity that affected the stability of foundation pit were analyzed. The new ideas about mechanism and determining methods of bursting in foundation pit were proposed，that with the “hydraulic fracturing” to explain the mechanism of bursting and the factors that affect the stability of foundation pit as a system to analyze the anti-bursting stability and the factors that affect bursting stability could be divided into two types, system strength and system stiffness.

Abstract: Coupled harmonic vibration of viscoelastic soil and fractional derivative type lining system with a deeply buried circular tunnel is investigated in the frequency domain. Based on theory of elastic and fractional derivative, steady state response of the viscoelastic soil and lining system is studied. Regarding the lining as a medium with fractional derivative constitutive behavior, and the analytical expressins of the displacement and stress of the soil and lining are respectively obtained by the continuity conditions on the inner boundary of lining and the interface between the soil and the lining. The order of fractional derivative model has a greater influence on system dynamic response, and it dependent on the material parameters of lining. With the frequency increasing, the resonance effects of system decrease.

Abstract: The building vibration induced by train loads has aroused people’s great attention. Many investigations have been carried out by many researches in order to evaluate the effect of train-induced vibration on environment. But they have not shown the reason why enlarged vibration region exist in front of a building. In this paper, building structure vibration induced by train loads was analyzed by numerical simulation method performed by ANSYS. Based on numerical results, it’s concluded that the reason for this phenomenon that enlarged vibration region may exist in front of a building is the result that incident wave and the reflected wave superpose mutually. Subsequently, the influence of barrier depth on the enlarged vibration region is also discussed.

Abstract: To acquire the stress distribution of surrounding rock is the important mean of stability analysis and the major task of numerical simulation. But the breaking probability cannot be expressed by the magnitude of single stress straightly. Based on the Mohr-Coulomb theory, coefficient S was deduced and used for further treatment of the result of numerical simulation. Models of parallel tunnel with different interval were building and analyzed. The different distributions of coefficient S were compared and analyzed after numerical calculation. The more reasonable tunnel interval was given, which can be a reference for optimization of design of similar projects.