Applied Mechanics and Materials Vols. 353-356

Abstract: Difficulties of tunnel construction mainly appear in the entrance and exit stage, some adverse geological problems may occur. In terms of the tunnel at the Changsha-Kunming section of the Shanghai-Kunming passenger line, firstly, adverse geological phenomena at tunnel exits was described. Secondly, major factors leading to disasters were listed, including geology, hydrology and construction procedure. Combined with in-situ conditions, Finite Element Method (FEM) was used to analyze the instability mechanism of surrounding rock after the upper arch gate was excavated by three-bench seven-step exaction method. At last, through comparison between computed result and measuring data, several basic conclusions was obtained. It can make much sense to similar engineering.

Abstract: Based on a subway tunnel construction, the construction method was introduced. The ground subsidence, crown settlement and convergence displacement caused by the cut tunnel are monitored during the tunneling construction and the results of monitoring data for them are analyzed. This technology wells to guide the tunnel-entering construction effectively and avoid the tunnel-entering construction process prone to landslides, thus ensuring the safety of the tunnel construction and will guiding the future construction.

Abstract: Many underground structures have witnessed great damage in recent earthquakes. Thus underground structures in earthquake prone zones should be designed to withstand both static overburden loads and earthquake loads. In this paper, different closed form solutions for the analysis of the tunnel response, are considered as developed on the basis of the theory that the stress increment due to seismic loading can be assessed through a correct estimate of free-field deformation, while the internal forces of tunnel linings subjected to overburden loads can also be estimated through an assumption of far-field stress using the developed solutions. Numerical studies have been performed to validate the available analytical solutions.

Abstract: The southern section of Gouzhigou tunnel, which is in the pipeline project of the natural gas transmission from the western to the eastern region, is located in the medium mountain canyon area in the northern Tianshan fold belt, Xinjiang. The physical geography and geological environment conditions at the tunnel project area are complex. After a field survey, the geological hidden trouble in the project area mainly are unstable rock and collapses at the cave entrance, unstable slopes, abandoned slag slopes and the stability of surrounding rocks. In this paper, the distribution, size and characteristics of the geological hazards are described. The risks of the hazards and the impacts of the tunnel construction safety are analyzed. At last based on the evaluation results of geological security, prevention measures are put forward to remove or weaken the geologic hidden trouble.

Abstract: In the construction process of shield tunneling crossing underneath a intercity railway, it is inevitable to bring a potential safety hazard to the safe operation of the railway. Determing how to evaluate the influence of shield tunneling crossing underneath the railway and how to reduce the influence level are urgent to be solved. Taking a Wuxi subway project cross beneath the intercity railway for example, through numerical simulation and on-site monitoring, the influence level and the best construction parameters for the shield construction have been obtained. Under the action of the most unfavorable load, the settlement of the railway was only 1.9mm after shield tunnel cross through it. Through theoretical analysis and on-site dynamic monitoring methods, it optimized the configuration of shield construction parameters.Adopting the suggested methods, the shield tunnel has crossed through the railway successfully and the results show that the settlement control is perfect.

Abstract: With the development of highway tunnel engineering, the stability of the tunnel become the chief problem in designing and constructing. Tunnel surrounding rock under high stress based on the actual engineering background, model test process of excavation in soft rock tunnels under the distribution factors was finished in triaxial test mechine. Through sensor test, the whole process of tunnel became instable was reflected, and the different conditions of the change rule of surrounding rock stress was budgeted and analysed. the numerical simulation method was used to study dependency of deep tunnel with soft rock in it and the lining deformation time. in which nonlinear Drucker-Prager plastic coupling and creep constitutive model were used to describe the nonlinear viscous-elastic-plastic properties of high stress soft rock. The characteristies of tunnel lining deformation and internal force variation were studied with the above model. Soft rock thickness, soft rock tunnel location effect on inner force and deformation of the structure were discussed. The results have reference value in evaluation of long-term stability of deep tunnel.

Abstract: The civil air defense works are underground protection spaces built in case of war. At present the amount of these works has reached a considerable scale and thorough exploitation and reasonable utilization of these space resources in peacetime is also the key to sustainable development of civil defense. Aiming at the public use planning of Beijings civil air defense works in residential district, the public service suitable for locating in these works and the demand of public service are analyzed. And a suitability evaluation index system for this purpose is established by adopting the method of analytic hierarchy process (AHP). A frame of public use planning of civil air defense works is formed by summarizing the use planning principles of public service and determining the public use planning procedure. The method system can provide technical support and theoretical direction for public use of civil air defense works in residential district of Beijing, and provide reference for other provinces and cities.

Abstract: In this paper, we use ANSYS finite element software to establish calculation model of the underground powerhouse and FLAC3D to calculate the model in different excavation stages. The purpose of calculation is to predict the surrounding rock displacement after excavation for the reference and evaluation of surrounding rock anchoring and rock mass strength on the basis of the computed result of primary stress and displacement.

Abstract: Based on the construction of the New Yangshi Tunnel, a section of the electrified speed-up reconstruction project in Zhe-Gan Railway, the author discusses and studies the construction technology employing annular excavation with core soil reserved method, together with the use of H175 steel frame as initial support in the shallow-buried and long-span railway tunnel in soft rock. Through the technical and economic comparison, it shows that the present method is faster, with the construction progress of 50m per month in average, and is more economical in construction than Center Diaphragm (CD) method with an investment of 4,000,000 Yuan having been saved.

Abstract: According to the triple shear unified yield criterion, the mechanical behavior of the pressure tunnel was put forward. The calculation formulas of the radius of plastic zone were deduced with considerations of the effects of the intermediate principal stress. The results show that the intermediate principal stress effect parameter b has influences on the radius of plastic zone. With the increase of the intermediate principal stress effect parameter b, the radius of plastic zone decreases. The radius of plastic zone is increased, because of the increase of the porous hydraulic pressure.