Applied Mechanics and Materials Vols. 438-439

Abstract: To enhance the exhaust efficiency during ventilation, three types of air duct outlets were imported. According to the characteristics of velocity distribution simulated by numerical method, the flow field is divided into the mixing zone and the exhaust zone. The gradual contracted air duct outlet can enhance the mixing effect between fresh air and smoke. In the exhaust zone, however, the flow velocity on the upper section of the tunnel is weakened, which is unfavorable for smoke exhaust. Gradual expanded air duct outlet, on the contrary, may weaken the concentration effect of the airflow. The flow velocity on the upper section of the tunnel is increased in the exhaust zone, thus the flow field is more homogenized, which is in favor of smoke exhaust.

Abstract: The compaction stability is of great significant for the quality control and assurance of the continuous compaction measurement in subgrade engineering. Based on the mean-variation method, the exponential function between the roller passes and the roller measurement value was modeled to calculate the compaction stability index Δμ_t^mv. The stabilization process of the compacted soil from loose state to dense state could be well described by the modeled function. Through the results of the roller measurement values in three test field of Shanghai-kunming high-speed rail in Huaihua, Zhijiang and Loudi, different compaction stability index due to the varied construction situations was calculated using the mean-variation method and the exponential function. The result shows that the exponential function is well adaptive to different situations and this method could be developed in controlling the stability of continuous compaction measurement.

Abstract: As an important factor that affects the compaction characteristics of the coarse grained fillers in the high speed railway subgrade, the grain composition is characterized by the application of the fractal theory. Several types of the coarse grained fillers were selected for testing and the results indicated that the relationship actually exists between the compaction characteristics and the fractal dimensions. The variation law of the maximum dry density fluctuating with the quality fractal dimension was analyzed and the results were supposed to estimate the compaction characteristics of the coarse grained fillers.

Abstract: With the development of economy and technology, many high-speed railways have been constructed. However, many of these railway lines have to pass through strong wind areas, and the cross wind in these areas would reduce the operational safety, thus windscreen is an effective facility in many engineering cases to protect the running trains from strong winds. There are two kinds of windscreen, the unilateral windscreen and the enclosed windscreen. By numerical wind tunnel technique, the impacts of the two kinds of windscreen on the lateral force acted on the running trains are analyzed, meanwhile the operational safety could be also evaluated. According to the research results, the moment coefficient has a relatively small variation when the height of the windscreen is more than 3m. The unilateral windscreen with a ventilation rate of 20% is more favorable for the operational safety than the enclosed windscreen.

Abstract: As more and more electric transmission lines have to go through the mining area, if we can fully realize the collapse and deformation characteristics of mined-out area, and master the scientific laws of its occurrence and development, we may take reasonable measures to avoid the happening of accidents, ensure the line to run in a reliable way, and greatly improve the construction quality and economic benefits. For different location conditions of coal mine worked out section to the surface of the power transmission tower, we use finite difference software FLAC3D to analyze mutual influence and interaction between underground worked out section and surface iron tower foundation. The conclusion in this paper can be used as a reference to mining site. The influence range can be estimated before mining, as far as possible avoiding influence within the scope of strata. It is the key to ensure the safety of power transmission tower, people life and property.

Abstract: We obtain response regularity of stress wave in bolt, which regularity can be applied in nondestructive testing of anchoring quality, with establishing longitudinal one-dimensional bolt wave equation, studying longitudinal vibration responses under several boundary conditions by the principle theory of elastokinetics. And it is the principal theory that anchoring quality is deduced by bolt vibration response which is caused by dynamic transient vibration.

Abstract: Take the typical train liquid storage tank as research object, the vibration modes and the fluid-solid coupling dynamic responses of the tank are analyzed under the impulsive excitation using finite element software ANSYS. The research indicates that the difference of the liquid volume in tank has great influence to the structural stress and strain. With the increasing of the liquid volume, the tank natural frequencies gradually reduced, so the liquid sloshing have great effect on the structural vibration modes. And if the tank is full of the liquid, the stress and total deformation of the tank can be obviously reduced.

Abstract: The dynamic characteristics of concrete lining of a circular tunnel was studied combined with the Dahuofang water-conveyance project. The first ten frequencies and modes of vibration were presented. The influence of some factors on the vibration performance of the concrete lining were analyzed, i.e. buried depth, lining thickness, youngs modulus of rock, and water in the tunnel. The results show that the buried depth and the youngs modulus of rock have greater influence on the vibration performance of concrete lining than the lining thickness and the water in the tunnel. Some aseismic measures are given out for the similar engineering.

Abstract: Ventilation shaft is important for the operation of 18 km long Qinling highway tunnel. The main geological problems encountered in the shaft excavation are high geostress and rockburst. Shotcrete can provide effective support in the rockburst conditions during the excavation of shaft in hard rock. According to the classification of rock mass Q system and engineering experience, the parameters of shotcrete support with bolt and mesh are determined, and the numerical simulation is carried out for stability analysis. Finally the dry mix shotcrete technology is applied for the support.

Abstract: A mathematical model for nonlinear constraints is introduced briefly in the paper. Aimed at optimum design of engineering with multivariable and nonlinear constraints, a new method of penalty function applying to GA in combination with the traditional idea of penalty function and Genetic Algorithm is put forward. Optimum design of a certain aqueduct is completed with the method, and good optimum results are given out. Study shows that the function of GA to search for the minimum and pleasing convergence rate is embodied sufficiently by employing the method. The study offers an effective tool for rational design of aqueduct and has certain referenced value for other engineering.