Applied Mechanics and Materials Vols. 580-583

Abstract: An inversion method based on multi-output support vector regression (MSVR) is proposed for identifying the mechanical parameters of surrounding rock. This method considers the surrounding rock as a multi-output system during excavation, and the surveyed rock deformations of each monitoring section as its output. First, perform numerical experiments based on the principle of orthogonal test to obtain the calculated deformation values corresponding to different rock parameter combinations, and use them as the samples for training the model of MSVR as reflecting the nonlinear mapping relationship between rock and its deformations. Second, use the PSO to seek the optimal rock parameters based on measured deformations of rock mass. An example is employed to test the presented inversion method. The results showed that compared with the inversion method based on single-output support vector regression (SSVR), the proposed one is more inclined to reach the global optimization goals and achieve more reliable inversion results due to its consideration of the inherent correlativity among the measured deformations of each monitoring section.

Abstract: Based on the analysis of movement characteristics of gauge disc cutter in cutterhead of tunneling machine, the motion equation to describe the working behavior of the edge point of gauge disc cutter in tunneling process is deduced by using the method of space coordinate transformation matrix. The motion equation has the advantages of considering more parameters, such as position variables of disc cutter, cutter radius, cutterhead rotating speed and advance speed.

Abstract: By analyzing the typical fire cases and tunnel fire statistics during 2008 to 2013 in Fujian province of China, results shows that the main causes for the fire were vehicle accidents and spontaneous combustion. By the investigation, there are three approaches to prevent the tunnel fire exposed to different combustibles. For flammable solid, an effective method to prevent fires is to decrease the maximum environment temperature and the product concentration. For flammable liquid, adjusting the ambient temperature and enhancing ventilation can prevent or reduce the fire accidents. For flammable gas, the effective method to prevent the fire is to decrease the fuel density and the ambient temperature. So, for long tunnels or busy tunnels, it must strengthen the management of the vehicles. Moreover, in the hot season and rush hour it should control the ambient temperature inside the tunnels.

Abstract: Facing with a variety of risks in the process of the metro construction, the metro construction needs to carry on the risk management. The risk assessment is the main link of the metro project risk management also the foundation of the decision analysis. This paper introduces the basic concept of the subway risk management, as a case study of Changchun No.1 subway construction risk assessment using the fuzzy AHP and the comprehensive evaluation method. The results show that Changchun subway station work sites exist many risk factors and the risk level difference is big. The major attention should be paid to the geological risks, the environment risks and the construction technical risks, while the environment risks and the construction technical risks are the focus of the risk analysis.

Abstract: The monitoring is carried out for deformation of the soil-mixing-wall structures used in Baijihu subway station. The horizontal displacement of deep soil is obtained, as well as the ground subsidence around the edges of the foundation pit. Their variation rules under the influence of some factors, such as soil excavation and support settings etc, is analyzed. The results show that during the process of SMW construction, it is necessary to monitor the horizontal displacement of deep soil and the ground subsidence around the edges of the foundation pit, especially during the early stage of excavation.

Abstract: Small spacing tunnel due to the special structure form and two tubes are only separated by a thin wall. This structure form is likely to cause secondary pollution, pollution gas discharged into the adjacent tunnel. This phenomenon will lead to increased ventilation system energy consumption. This paper analysis gas diffusion path between two adjacent tunnels, using CFD (Ansys Fluent). To relieve the pollution gases secondary pollution of tunnel portal area, using CFD analyzed gas diffusion path under different circumstances, for opening hole on the top of sunshades, extended of the wall between two adjacent tunnels and other programs, and identify more comprehensive disposal program.

Abstract: Taking a foundation pit in Nanjing as the background, a numerical model was established to simulate the dynamic process of foundation excavation by 2D finite element software. The influences of different factors on the displacement of the lateral shield tunnel during the foundation pit excavation are studied. The research indicates: when a foundation pit excavation is needed on the side of a shield tunnel, we should select the area in which the tunnel is buried deeper, control both the excavation volume and the distance between tunnel and pit, and try to avoid the excavation depth close to the buried depth of the tunnel. On the basis of numerical calculation, the protection range of the shield tunnels is determined according to different excavation depth of the foundation pits and different buried depth of the tunnels.

Abstract: In order to effectively predict aspects of tunnel deformation, taking effective and timely measures against the problem to ensure the safety of tunnel ,LS-SVM-MC model is proposed . Namely, Markov chain based on LS-SVM corrects the error, and ultimately improves the accuracy of prediction. By the analysis and calculation of deformation prediction of a tunnel , you can find that the method is more in line with the actual situation, showing predictive superiority and a high prediction accuracy.so the method can serve as a new ways of tunnel deformation prediction,some promotional value can be gained in later work.

Abstract: A mine plans to exploit the low dip thin phosphate deposit by room-and-pillar mining. But a township highway is just above the orebody, and its distance is only 80m, in order to better control the ground pressure in stopes and ensure the operation security, the size of room and pillar must be reasonably designed to maintain the stability of stopes and surrounding rock. The 3D-σ numerical simulation method was applied to analyze the surrounding rock stability in different stope structure parameters. The results show that when holding the size of pointed prop unchanged, the surrounding rock stability would decline with the increase of room width and pillar spacing, for security, the mining plan, the pointed prop is 3×3 m, the stope width and pillar spacing is not more than 9 m, were considered to be one of the optimal. In addition, it is important to emphasize that if the mining depth exceeds 300m, some methods, such as decreasing the spacing of stope and pointed props or increasing the pillar size, need to be taken to avoid the stope instability caused by greater ground pressure.

Abstract: This paper takes a new shield tunnel as the research object, which intends to cross a section of a high speed railway. Based on design specifications and the existing monitoring data to analyze the change rule of track irregularities, this article proposes the control of wavelength and relevant amplitude in the above case, following the design specifications and long-wave irregularity management demands of high-speed highway. And the controlling values of wavelength and amplitude required are presented with the outcome of the range of the settlement trough, drawn out of the under-crossing process. And it also uses large-scale non-linear finite element analysis software to simulate the high speed railway track deformation in actual constructions, to test whether the deformation meet the requirements of the control standards and deformation law. The results can provide reference for the construction measure when shield tunnel under crosses the high speed railway in the future.