Applied Mechanics and Materials Vols. 90-93

Abstract: Firstly, This paper applied the basic principle of composite material mechanics, saw the rock mass, anchor, mortar as a kind of composite material, established micromechanics equivalent model of bolted rock mass, deduced corresponding parameters formula of bolted rock mass equivalent mechanical model. Secondly, we analyzed engineering example by using the finite element software, conducted a numerical simulation research on composite model and discrete roadway model based on the theoretical derivation. Finally, we verified the feasibility and applicability of the equivalent method by comparative analysis on two sides and roof-floor displacement of roadway and surrounding stress of rock. Thus, this paper established a simplified equivalent calculation method accord with the stability analysis of bolting and shotcreting support and the overall assess of support parameters.

Abstract: Mechanical properties of sand-pebble layer is very unstable, it is unfavourable for TBM excavation. For the reasons of poor soil conditioning and low plastic flow of muck, EPB TBM tunnel construction in sand-pebble layer of Beijing metro has exposed variety of issues: continuous dynamic earth pressure balance is hard to established, mud cake is formed frequently in earth chamber, key construction parameters such as thrust, torque, advance speed can not be controlled in reasonable scopes, which lead to low efficiency of TBM construction. Taking“Xi-Liu”of line 10 lot 11 as an research object, the mechanical characteristics of sand-pebble layer and construction problems of TBM advancing are analyzed, variety of soil conditioning measures are used for improving plastic flow of muck and minimizing construction influence induced by poor geological conditions, meanwhile contrast studies on key construction parameters before and after soil conditioning are carried out. The results indicate that effect of soil condition plays very significant roles in controlling TBM construction parameters and improving advancing efficiency.

Abstract: The construction schemes of metro station driven with enlarging shield tunnels based on the shield tunnel in the upper and lower step method of artificial were first used in the dongshankou station of Guangzhou Metro Line VI and applied successfully in practice. This paper analyses and studies comprehensively the affection to the ground on the metro station driven with enlarging shield tunnels through numerical simulation. The study in this paper is mainly considered the ground settlement and movement when enlarging shield tunneling in the left tunnel. The ground settlement and movement up to a certain extent will affect the safety of the above adjacent buildings. This paper will provide some guidance to the application of this construction method in the future.

Abstract: On the basis of the three-dimensional,compressible,unsteady-state,viscous N-S Equation and k-ε turbulence model,the simulation calculation is made with the finite volume method on the aerodynamic effect of two high-speed trains passing each other at the same speed through a tunnel,simulating the pressure change,analysising regularity of the pressure,researching comfort in the train.The following conclusions have been drawn from research:The maximum of transient pressure is concerned with the meeting point,when the two high-speed trains meet in tunnel.When the length,the speed and the sealing factor of the train are same,the transient pressure is maximum with the trains meeting at the midpoint of tunnel.When the tunnel length,the speed of the train,the sealing factor and the point of meeting are same,the transient pressure of the longer train is maximum.When the sealing factor is greater than 15s,the standard of permissible pressure (1250Pa\3s) can be satisfied with all circumstances.

Abstract: We derived the relation between surrounding rock displacement of shaft prototype and that of model on its body force condition of self-weight based on the similarity theory. According to the results of discussion of the equation, we derived dimensional expression of surrounding rock displacement of shaft. And we analyzed the relation between displacement and diameter(d) and cross-sectional depth(h) by numerical methods.

Abstract: Considering the high temperature problem, this paper details the process of the heat conduction, builds the differential equations of the heat conduction, discusses the boundary conditions. According to the differential equation of the heat conduction, determined the calculation formula of thermodynamic parameters of the heat conduction and get the calculation formula the temperature and interface between the lining and surrounding rock’s calculation formulas. Builded the model of the thermal stress field of the tunnel lining under the high temperature, compiled the calculation program, analyzed the change of the lining’s stress and the influence by the relevant parameters of lining’s stress field under the high temperature.

Abstract: As a nondestructive testing technology, GPR has been become one of the most important tools in quality inspection of tunnel lining at present. It is widely applied to tunnel disease detection, such as the holes, cracks, voids between tunnel lining and surrounding rock, and it is also used to determine the steel arch distribution and lining thickness of tunnel. Through the application of GPR in a highway tunnel lining detection, response characteristics of reinforced bar and steel arch frame are analyzed on radar maps under different frequencies of radar. Through identifying abnormal reflection in radar maps and interpreting its reason, the number and arrangement of reinforced bar and steel arch frame can be obtained. Comparing with the tunnel design, good results are obtained.

Abstract: For further discussing time variation characteristics of raft foundation on saturated subsoil due to consolidation, parameterized numerical analyses are completed based on Biot consolidation equations by developing elasto-plastic coupled FE model in plane strain state, together with adopting Mohr-Coulomb yield criterion. Computational results show that internal force and deformation of raft foundation display obvious non-monotonic features, which is associated with dissipation of excess pore water pressure. The disequilibrium of dissipation of excess pore water pressure displays more intensive between subsoil areas near raft center and the border due to less Poission’s ratio of subsoil, which leads to more dissipation time and regulation magnitude of distribution of stress and deformation in subsoil. When subsoil is of low permeability coefficients and Poission’s ratios, the non-monotonic features become more clearly and sustain with longer term variation characteristics.

Abstract: The submarine tunnel water-inflow question has many kinds of factor synthesis influences, has highly the complexity and the misalignment, This article used the BP neural network algorithm to establish the submarine tunnel welling up water volume forecast model and to carry on the computation analysis, The result indicated that this model restraining performance is good, the forecast precision is high and simple feasible. This method has provided a new mentality for the submarine tunnel welling up water volume's forecast.

Abstract: Based on soil-structure interaction model, the response analyses of the Menglian tunnel by using viscous-spring artificial boundary and time history analysis method under earthquake accelerations and multiform conditions of surrounding rocks are presented. The seismic responses of the tunnel are calculated by changing parameters of surrounding rocks within certain influencing distances to the linings. The shock absorption effects, applicability, and shock mechanisms of grouting in the surrounding rock are analyzed. The results show that the displacements and stresses of the tunnel linings in karst areas decrease by grouting in the surrounding rock, under the high-intensity seismic load, and the linings are protected when the grouting measure is used. It also shows that the shock absorption effect is better with the increase of the grouting density and range. By calculating analysis, it can achieve the shock absorption effects when the grouting range is 5.5 to 7.0m in the Menglian tunnel. The results provide useful reference for the shock absorption design of tunnel.