Applied Mechanics and Materials Vols. 170-173

Abstract: The objective of this study is to investigate the water seepage in unsaturated concrete under pressure through theoretical derivation. To establish the theoretical mode of water pressure and seepage velocity various with location and time. Finally, a formula about penetration depth is derived. And it is more practical. Meanwhile, analysis is made about the effect of the water pressure, the strength grade, permeability and relative permeability and other factors on the flow velocity and penetration depth.

Abstract: Deep foundation pit of subway station project are affected by the geological conditions with rich water and sand seriously. So the construction has a greater difficulty. We have to analyze the measured data and study on the deformation law of retaining structure and soil. That can be used as theoretical verification about the design scheme of retaining structure. The results show that this design scheme can be used as the support form in the similar geological conditions.

Abstract: According to geological investigation and monitoring results, this paper analyzed the reasons for large deformation in Baozhen Tunnel, discussed the deformation characteristics and presented the corresponding supporting measures.

Abstract: Abstract. This article based on the underground workshop region of the Shenzhen pumped storage power station, carrying on back-analysis for the initial geostress field of the region of station with method of this article, and then we can obtained the actual initial ground stress.This article based on the measured ground stress data, a 3D non-linear finite element back analysis numerical model for ground stress is set up and the landforms is simulated. This thesis has used ANSYS to do finite element calculation for rocks and soils, the corresponding sample of neural network have been gained. By setting the parameters, the neural network is optimized, then the network is trained with the optimized result. Finally, the initial ground stress field is back-analyzed with in-situ measured stress values. The result is compared with measured value, which meets the requirement for accuracy, showing the reasonabilily of the rock ground stress field obtained.

Abstract: Surrounding rock stress is a one of significant feedback information after tunnel excavation. It is also an important factor influencing the stability of the tunnel, and the premise to determine accurately the tunnel stability. For tunnel surrounding rocks stress determined by many uncertain factors, it is difficult to accurately predict. The BP neural network model for predicting on the stress of the tunnel surrounding rock stress is created. Comparative analyze the results of the surrounding rocks stress prediction on expressway tunnel by momentum gradient algorithm, L-M algorithm and bayesian regularization algorithm. Results show that the use of bayesian regularization algorithm for neural network model has higher forecast accuracy. It can be applied in engineering practice.

Abstract: This paper presents a numerical study on the mechanical behavior of the jointed rocks around the underground opening. By comparing different obliquities and the different locations of the joint, its controlling effect on stability of surrounding rock is evaluated in terms of the shear stress distribution, displacement distribution and the plastic zone pattern, which are induced by underground excavation. The results clearly indicate that, the maximum shear stress occurs mainly near the corner of the opening and the joint plane. When the joint inclination angle is less than 60º, the maximum vertical displacements occur where the joint locates near the skewback. Once the joint inclination angle reaches at 75º, the maximum vertical displacements occur where the joint is through the cross section of the underground opening. The plastic zone reaches minimum at the joint inclination angle of 45º where the joint locates either near the skewback or near spandrel of the opening, while it reaches minimum at the joint inclination angle of 60º where the joint cuts through the cross section of the opening.

Abstract: During the construction of city subway, it often needs to cross under the existing buildings, which will have some influence on these buildings. The article, taking the engineering of subway tunnel in Harbin city for example, uses finite element analysis software to simulate the dynamic excavation of the tunnel, and combines with the measured data of actual monitoring, analyzes the primary support structure stability in the process of tunnel excavation. Finally it draws the conclusion that the stress and displacement near the working face change greatly, the springback displacement of tunnel bottom is big, fracture surface near the entrance of the hole tends to be stable with the excavate of the working face.

Abstract: The fundamental principle for tunnel fire fighting design is to ensure the safety of people’s escape from tunnel fire. Therefore the computer model Tunev (tunnel evacuation) for the people's safe escape was developed. In order to evaluate evacuation safety, Fire risk times Tfire was firstly gotten through simulations of a middle size fire, whose heat release rate (HRR) was 20MW, with a longitudinal velocity of 3m/s suggested in Code for Design of Road Tunnel of 2004, and evacuation times Tevacuate was calculated by an empirical formula in the Togawa evacuation model. Meanwhile, fire spreading to other cars was analyzed by radiation theory. Finally, cross passage spacing was optimized in a method of evacuation safety evaluation. Results are given as follows: Tfire equal to 290s are bigger than Tevacuate equal to 267s, the smallest igniting spacing between cars is 13m, and the optimized cross passage spacing is 290m. All those are shown that: evacuation is safe, and to some extent code is testified correct.

Abstract: The problem of arches selection in primary support of loess tunnel is one of the problems that are now focused on. Based on the two type support of gird and shaped steel, the plastic zone and internal forces are mainly analyzed, by means of numerical simulation, in the loess tunnels with small interval under shallow buried & unsymmetrical pressure. Analysis results indicate that the internal forces in the gird support is slightly smaller than that of the shaped steel support, and the plastic zones are almost the same in the two type support; so it is suggested that the grid support should be adopted in the design of such tunnel from the comprehensive analysis.

Abstract: Based on the turbulence characteristics of spillway, a turbulence model for simulating turbulent flow with free water surface under a body-fitted coordinate is established and a computer program is developed for numerical experiment in this paper. A spillway flow is numerically simulated, and the results are quite fitted with the experimental ones. Thus, the proposed model is also applied to the spillway tunnel optimization.