Applied Mechanics and Materials Vols. 204-208

Abstract: The mixture of water and gas is treated as a homogeneous fluid. Based on Boit’s theory, the influences of water saturation on the dynamic responses of a partially sealed tunnel are investigated in the frequency domain. By utilizing the continuous condition, the analytical solutions of the displacement, stress and pore water pressure of a partially sealed tunnel in the nearly saturated soil are derived subject to the harmonic load. On this basis, the influences of water saturation and permeability coefficient on the system responses are discussed by the numerical example. It is shown that the water saturation has a great influence on the stress and pore water pressure amplitudes. In addition, the permeability in the boundary of the tunnel is reasonably described by the permeability coefficient.

Abstract: The 3D finite element simulation are adopted to study the surrounding rock deformation regularity of main tunnel during the horizontal adit construction stage．The Zhongtiaoshan highway tunnel is taken as an example. The research results are shown as follows：Horizontal adit excavation destroys the original arching effect of the main tunnel, which leads to stress concentration at the intersection of primary supporting structure. The first excavation step plays an important play in the surrounding rock deformation of the intersection. The influence range of the main tunnel which due to the horizontal adit excavation is 1.2D.

Abstract: Based on project in which the existing air defense tunnel was enlarged to build a metro tunnel adjacent to bridge piles in Harbin, the 3-D numerical simulation using FEM was conducted to analyze the internal forces and deformations of piles. The results show that the internal forces and deformations on the right side are larger than those on the left after the enlarged excavation on a single side on sidewalls. The maximum value as well as its position differs according to the distance between the pile and tunnel. After the enlarged excavation on the invert, the increase in the horizontal displacement is smaller than that after the excavation on the sidewall. As to the vertical displacement and axial force, the increase is prominent and the increasing value is larger than the excavation on the sidewall. After the reinforcement measures of advanced pre-supporting and radial grouting are used, According the results, the internal forces and deformations of piles decreases after measures were taken. Compared with measured data on site, the control effect is good.

Abstract: In view of the double-track tunnel on passenger dedicated line with speed 250km/h, finite element programming has been employed to simulate dynamic construction process under shallow-buried and bias conditions with grade IV, including stony and soil, and grade V surrounding rock. Different construction methods under various operation conditions have been compared. Based on stability of surrounding rock and safety of primary and temporary lining, proper construction method under various operation conditions has been presented.

Abstract: Polypropylene fiber reinforced concrete can improve the common concrete flexibility and it is beneficial for interaction between concrete lining structure and rock mass. The use of fiber reinforced concrete with wet sprayed concrete technique can improve the concrete lining structure construction quality and improve the rock mass self-bearing capacity. The wet-sprayed fiber reinforced concrete is first introduced in Jinhuashan railway tunnel early stage lining structure within soft and weak rock mass. The design of Jinhuashan railway tunnel lining structure using fiber reinforced concrete is introduced and the requirement of material used is explained. To evaluate the lining effect using wet-sprayed fiber reinforced concrete, the online monitoring method is used to measure the rock mass pressure and the concrete lining layer stress for both the experimental tunnel sections and comparison tunnel section. The monitoring data result shows that the rock mass pressure in experimental section is even distribution with lower rock mass pressure and lower concrete lining layer stress. The value of rock mass pressure and tunnel lining layer stress in comparison tunnel section is a little higher than that in experimental tunnel section. The experimental tunnel section using fiber reinforced concrete has good lining effect.

Abstract: Structure performance function is established with the consideration of safety factor, taking the primary support structure as a series system and determining the invalidation model of the system, and then the internal forces of primary support are expressed by the limit displacement. The calculating analysis also takes material parameters and geometrical dimension into consideration. Based on a typical tunnel, the reliability degree of the whole system is calculated, which indicates that the reliability degree is rather smaller at a certain section of the primary support, but it can satisfy design requires of the whole system, and the tunnel stays in a safety state.

Abstract: resistance increasing bolt with large deformation has the advantage of both let-pressure bolt and resistance increasing bolt，it makes best use of the advantages and bypass the disadvantages of the two types of bolt，so it can achieve the goal of improving the bearing capacity of surrounding rock and stably bolting the surrounding rock. With more and more retractable anchor are being researched and developed, it is more necessary to research and develop the retractable anchor which can both have the function of let pressure and increasing resistance. Though the way of analysising and summaring the experimental study and application of retractable anchor at home and abroad systematically，the understanding of the retractable bolt is being inhanced，the intact theoretical and practical basis is provided for the extension of this kind of anchor. Finally，the development of retractable anchor in the future is prospected. Resistance increasing bolt with large deformation which both have the function of let pressure and increasing resistance is a kind of retractable anchor，which can apply to deep weak and broken surrounding rock. Therefore，it is worthy of researching and applying.

Abstract: Vibration characteristics of air-entrained concrete was analyzed by vibration slump loss, formwork ability and vibration viscosity coefficient through comparative testing. The results showed that: air-entrained concrete has a characteristic that high slump in vibrating and low after. It was significance to construction with slipform paver. Air-entraining agent improved the concrete structural viscosity under high-frequency vibration was the reason for this characteristics.

Abstract: Disturbance of ground structures by the excavation of underground engineering is a non-linear mechanical behavior process. To find time sequence with the smallest disturbance is important for the safety of mining below railway, river, and building (three-underground mining). A numerical simulation was carried out by 3DEC in mining area. The maximum Lyapunov indices are obtained from the time curves of the maximum unbalanced force. The reasonable time sequence schemes of development project construction under railway in the east ore body of XinQiao Pyrite Mine are compared. The results show that the effect of the data analysis method about the information of unbalanced force-time record based on the chaotic dynamics theory is very positive. It can minimize the risk of scheme with the priority of single mechanical (displacement) index, direct the actual construction effectively and guarantee the safety of ‘three-underground’ complex ore mining by preventive actions in supporting, shortening construction time and other strong measures.

Abstract: The energy-saving slope is an important part in longitudinal design in subway. The paper’s aim is to find the optimal length of energy-saving Slope. So, the paper set a model and calculated method based on dynastic and braking of vehicle. It divides the tunnel into five intervals: accelerated, downhill energy-saving, Traction – idle, uphill energy-saving, braking. To calculate the length of energy-saving slope based on the change theory between Kinetic energy and Potential energy. The result shows that longer of station distance, smaller of max-speed and motor power, greater of angle of slope and carriage quality, needs longer to energy-saving slope. Recommend length of energy-saving slope was [228m, 330m].