Applied Mechanics and Materials Vols. 580-583

Abstract: With the expansion and development of scale of construction on metro engineering, the damage diagnosis and the safety evaluation on underground engineering structure have become vital problems to be solved. This paper raised an idea to distinguish underground engineering structure based on BP neural network: define change rate of curvature of structure, and recognize it as the input scalar of BP neural network, using a reducing unit elastic modulus method to simulate damage location and damage degree, through various set of underground structure extent of damage, recognize the first four order curvature structure change rate as input of BP neural network. The results show that the method using BP neural network can identify the damage degree of underground engineering structure accurately and can solve the damage identification problem of underground engineering structure conveniently and effectively.

Abstract: Taking the free vibration system of a submerged floating tunnel tether as research object, the non-linear free vibration equation was set up. By means of Galerkin method, the partial differential equation was transformed into a set of ordinary ones. The damping ratios of the first four modes were obtained after complex eigenvalue analysis. Subsequently, effects of inclination, sag, initial tension force and length of tether on its modal damping ratios were analyzed. The results show that inclination and sag of tether merely affect the damping ratio of first in-plane mode; they have no effect on the damping ratios of higher order in-plane modes and out of plane modes; the first in-plane modal damping ratio of tether is in direct proportion to its inclination, whereas in inverse proportion to its sag; the first modal damping ratio of tether (both in-plane and out of plane) is in direct proportion to its length, whereas in inverse proportion to its initial tension.

Abstract: Empirical analytic method and theoretical analytic method are usually applied to calculate and predict water gushing yield in the tunnel engineering in the past but have much limitations and errors. Ample water source, hydrodynamic conditions and expedite channels are essential for water-bursting accidents in railroad tunnel engineering. From a lot of study of fractal geometry in rock mass, it is found that the multi-dimension value of fissure network is colligate reflection of the length, the direction, space and the number of fissures, so the value can be used to describe the complicated frameworks in rock mass. But it is a sound tackle to quantities the complicated frameworks. Numerical simulating method is convinced to be applied to calculate and predict water gushing yield of tunnel and underground engineering. It focuses on analyzing texture characteristics of water-containing medium, building hydro-geological conceptual model, and modeling long-term hydrodynamic field development. An experimental application in Paoziling tunnel under-crossing mountain reservoirs in Hunan province was presented in this article, and long-term hydrodynamic field development had been obtained under the condition of drainage from the tunnel, and the gush yield in the tunnel during the process of storing water in the reservoir was also predicted.

Abstract: The article proposed the reliability calculation method for tunnel lining design combining Rock-Mechanics model and Monte Carlo finite element method.The reliability calculation model of tunnel lining structure design was established considering tunnel character. The types of the statistical characteristics and distribution of axial force for the big cross section of the loess tunnel structure had been summarized. The study result stated that the method is feasible. It has important theoretical guiding significance to the practice structure reliability design of tunnel and underground engineering.

Abstract: Two lines intersection is the common transfer manner of the subway. In order to analyze the characteristics and applicability of the two lines transfer manner, this paper analyzes different transfer stations of subways at home and abroad, and evaluate the current use of them, in the views of the form of the intersection of the lines (parallel and intersection), and the relative location between the lines and the stations. Then it summarizes the characteristics and applicability of the transfer manner. Finally, it gives advices of the choices of the two lines transfer stations in different situations.

Abstract: In order to build subway station fire emergency group decision-making system, Aim at the subway station fire characteristics in this paper, analyze the problems of emphasis from emergency decision, and group decision method is proposed to use to solve this problem. The method can avoid failure of the overall decision making mistakes because a single decision maker. Found of decision-making group consist of experts, academics, policy-makers, considering several key factor such as professional, academic, expert ratings, weight, to build group decision model .At the same time, evaluation of the subway station fire emergency group decision effectiveness to build subway station fire emergency response system, Ultimately improve the efficiency of emergency response and level of decision-making for subway station.

Abstract: Tunnel collapse is one of the most common accidents in the tunnel construction of city subway, and risk assessment is a method to measure the magnitude of the collapse risk. In order to effectively identify in advance the risk category of tunnel collapse, an identification method is put forward based on entropy weight method and efficiency coefficient method. On the basis of a comprehensive analysis of factors that affect the collapse, 6 main factors including rock level, tunnel depth, tunnel span, the surrounding conditions, groundwater and construction factors are selected as the evaluation indexes. Through a quantitative description of the evaluation indexes by using the TSP203 geological prediction system, and based on the basic principles of ideal point method, a comprehensive and intelligent evaluation model which can identify the tunnel collapse risk in subway construction is established. Finally, the model is applied to practical engineering, and it shows that the result of risk assessment is consistent with the actual construction conditions, which provides a new perspective on the advancing identification of tunnel collapse risk in subway construction.

Abstract: Due to the special mesh structure, geo-grid material can avoid local subsidence of filling material, reduce uneven settlement of soil mass to the largest degree and improve the whole stability of soil mass, so the reinforced earth-retaining wall with geo-grid is widely used in engineering. Meanwhile, researches on its dynamic characters are not enough and it is hard to judge the whole stability of reinforced earth-retaining wall under seismic condition. When unstable failure happens, the location of failure surface can hardly be identified. These disadvantages have seriously limited the development of this supporting method and cause unsafe potentials for engineering. Based on the FEM strength reduction dynamic analysis and combined with practical engineering, the paper conducts stability analysis on the reinforced earth-retaining wall of geo-grid under seismic condition and the research achievements provide a new thinking for the seismic design of reinforced earth-retaining wall with geo-grid.

Abstract: According to the analysis of the structure, topography, earthquake sequence, and earthquake hazards in September 2012 earthquake of Yiliang County, Yunnan Province, the mechanism of the earthquake damage is given. The low-cycle fatigue, shallow source, topography, population density, seismic capacity of the structure and seismic awareness of the residents is the main damage factor. This research provides a reference to the seismic design of analogous regions.

Abstract: The method of MMCP (modified modal cyclic pushover) which can reflect the dual criterion of deformation and energy was used to make an assessment on seismic performances of the steel reinforced concrete piers and reinforced concrete bridge piers. Then the calculated results were analyzed comparing with the results of dynamic time historical analysis and quasi static test. To some extent, the MMCP analysis may simulate the seismic action. In addition, the MMCP method can also be associated with the design response spectrum, making the evaluation results to be reliable and safe. The results indicate that MMCP applicability analysis also exists in the steel reinforced concrete structure, and the seismic capacity of steel reinforced concrete bridge piers is better than reinforced concrete bridge piers.