Applied Mechanics and Materials Vols. 204-208

Abstract: A particular elastic-plastic-brittle constitutive model, considering the heterogeneity of rock and the features of deep engineering, is presented, in which the multiple yield criteria based on stress space and ductile failure criteria based on strain space are adopted, and the numerical method is FEM. Through the simulation of the compression test of rock samples, the results show that the present model is rational and accurate. The elastoplastic damage mechanism of the surrounding rock mass of deep tunnel is studied and through the display of centralization, extension and transfer of stresses, it is shown that the present model can be used to predict reliably the whole process of formation of broken zone.

Abstract: Double-line cross-river shield tunnels should be set up evacuation routes for disaster prevention, rescue and ventilation at each distance according to the standard requirement, the evacuation passageway generally chooses transverse evacuation passageway, but in the case of complex geological and hydrological conditions, the risk of the construction of horizontal evacuation passages is very big. This paper takes a cross-river tunnel as an example, to set analysis for the risk of setting a horizontal evacuation passages. Used the ANSYS of a 3-d finite element analysis software, selected the number two horizontal channel as the prototype, according to the size and design of shield tunnel line longitudinal cross section of geological structure, establish the finite element calculation model for the interaction of the tunnel, the channel and the surrounding soil, to simulate the process of the excavation of the channel, and the paper studies the risk in the construction process of the channel.

Abstract: The limit displacement was calculated with regard to a large deflection tunnel. The continuum calculation model was established with actual parameters of the surrounding rock of the tunnel as input. In the simulation calculation, the action occasion of the support structure was determined based on the ratio of the measured rock pressure to the geo-stress, and the bearing capacity of the R.C. compressive bending component of the support was expressed with the axial force and bending moment on losing capacity of the support structure in loading; The limit displacement of the tunnel wais determined finally combined with the measured displacement of control points on collapsed or gauge-intrusive sections and cracked primary support or secondary lining sections. Since the deforming rate is more concerned than the displacement in drill and blast tunnel construction, three-level-management of deflection and deforming rate was proposed based on the statistical analysis of measured deforming rate, and the safety requirement for deflection control in construction. The management criterion has reference value to other similar tunnels where difficulty is encountered due to large deflection occurring in construction.

Abstract: The forces on TBM druing tunnelling are analyzed in detail based on the characteristics of mixed face strata. Suitable parameters of TBM are choosed according to the characteristics of the strata ahead. The studies are focused on both the acting posture of TBM and the points of the main forces. A systemic model is consequently set up, which can provide ones with analysis of TBM stability, parameter calculation and tunnelling design in mixed strata. Two cases are finally analyzed of TBM tunnelling in different mixed strata by using this model. Then some of countermeasures is given as reference for TBM tunnelling in such mixed strata in the further.

Abstract: In order to Ganquan tunnel as an example introduced the Loess Tunnel Typical Rocky and appropriate excavation construction technology. Early lining and secondary lining, waterproofing and drainage, and monitoring measurement and advanced geological prediction of key construction processes are described and summarized.

Abstract: It is of great significant to predict the influence of deep excavation in Ju-Zi-Zhou island, so that damage to adjacent ancient tree, and Xiang-jiang Bridge could be prevented. Based on analysis of site condition, geological profile, and strut design, the numerical model was generated in commercial available software package Flac3D, in which Mohr-Coulomb model was introduced. Then, the settlements at several key points on the ground were evaluated in each step of excavation. The calibrated results shows that, the calculated settlement agrees well with the measured. So it can be applied to predict completed state and provide a guidance for next construction.

Abstract: The calculation method for load of multi-arch and extra large cross section tunnels (MELCST) is a new method accounting for the influences caused by the multi-step construction procedure and temporary support on tunnels. The paper analyses the application of the method in the double-side drift construction method, and gives the distribution mode and the value of loose loads in various construction sequence, example analysis is also given through Luohanshan tunnel.

Abstract: Influence mechanisum of lime on the strength and water-resistance properties of phosphogypsum autoclaved brick is exploited for the manufacture of preparing phosphogypsum autoclaved brick. Results of XRD and SEM analysis of phosphogypsum and phosphorous slag powder, influence of lime on the properties of phosphogypsum autoclaved bricks, phase composition, microstructure and thermal analysis of phosphogypsum autoclaved bricks with different lime content, and influence mechanisum of lime on the strength and water-resistance properties development have been discussed. The test results reveal that (a) when the dosage of lime is zero, the major mineral compositions of the autoclaved bricks are CaSO4 and SiO2, thus the strength and water-resistance properties of the bricks are poor, (b) optimum lime to phosphorous slag powder and phosphogypsum ratio yielding maximum strength and Softness coefficient is about 0.03, (c) excess lime beyond the optimum limit (in this case 5%) can remain unreacted and act as weak filler in the phosphogypsum autoclaved bricks leading to reduction in strength and water-resistance properties.

Abstract: Based upon the elastic theory, the gas and oil storage cavern in bedded salt rock formation is generalized as a spatially axisymmetric model. A Love function was built from polynomial and logarithmic functions at first, and then solved, considering the gravity, the internal gas and oil pressure of the cavern, the boundary conditions, as well as the continuity conditions at the interface between salt and non-salt media. Finally, the elastic displacement and stress components are achieved which are satisfied to the main boundary and continuity conditions.

Abstract: Based on the tunnel engineering of Xi’an metro, according to the specific geological conditions, used FLAC3D numerical simulation software, the paper determine the minimum supporting force of the excavation face by two monitoring points’ settlement as the standard. The point at the surface above the excavation face and the other at the top of excavation face. When buried depth of tunnel is greater than 1.5 times the diameter of hole, the surface point cannot effectively reflect the deformation of soil around the tunnel, it should monitor and control the deformation of soil by the top point. The paper determine the maximum supporting force of the excavation face by the analysis of the settlement at the top points in different buried depth of tunnel. Obtain the safety range of supporting force in shield machine excavation face. According to the surface uplift larger phenomenon in shallow tunnel, put forward corresponding countermeasure. It is of great significance to apply reasonable supporting force at excavation face and prevent the surface subsidence and uplift crossing the locations that tunnel depth have large changes.