Applied Mechanics and Materials Vols. 256-259

Abstract: In recent years, as China's national sustained and rapid economic development, the state increased investment to middle-western region, promote the regional development of high grade highway. Therefore, highway tunnel through loess area is getting more and more. Due to the special physical properties of loess, it makes the loess tunnel construction a hot topic. To study on the deformation law of the loess highway tunnel, this paper based on the Shanxi Province Guang Ling to Hun Yuan highway tunnel—East Fu Yao tunnel, we simulate the whole section pre-reinforcement construction technique for three dimensional numerical, and combined with field monitoring measurement to compare and analyze in paper

Abstract: To conduct pro-grouting design and make the prediction of the result of grouting about the chunnel that passes through fractured rock mass, the essay adopts following theoretical formula to calculate the fractured rock mass grouting diffusion radius: Wittke and Wallner Formula、Lombadi Formula and Huang Chunhua Formula. Finally through the analysis of calculation results can conclude: (I) The diffusion radius of the slurry can meet the design requirements under the condition of 3-4 Mpa designed grouting pressure、5 cm grouting holes’ radius and 1800-3600s grouting time. (II) The calculation result of Huang Chunhua Formula is almost the same as Wittke and Wallner Formula and Lombadi Formula, but the margin of grouting diffusion radius’ change as grouting time and grouting pressure growing are different, it’s more close to the real situation.(III) The calculation of these theoretical formula only consider the breadth of fractured rock without considering the variation of its thickness and direction. So all of the calculation results of these formula are generally bigger than the standard.

Abstract: Considering the feature of soil layers and surrounding architectures in line 1 of Ningbo metro, finite element method is used to analyze the impact of displacement of existing shield-tunnel, which comes from the building load on the shallow foundations closed to the metro tunnel. Then, the effect feature of upper load of shallow foundation on metro tunnel is got. It is shown that both the horizontal displacement and the vertical displacement of shallow foundations decrease with increase of the horizontal projection distance between loading position and tunnel, and the reducing magnitude of the vertical displacement is significantly larger than that of the horizontal displacement. Accordingly, it is proposed that both the horizontal displacement and the vertical displacement should be controlled within 10mm when the loading width is approximately 10m, and it can be regarded as the controlling distance of the building load of metro tunnel.

Abstract: The phenomenon of railway and road tunnel passing through the debris flow gully is more and more prevalent, for the rapid development of the construction of railways and highways. At present, the construction experience of tunnels passing through the debris flow gully is not rich enough, so the study on this part is necessary. The engineering geological conditions of Cangyuan Tunnel are complex and the construction of which is difficult. The three-step seven-step method, tunnel surface grouting and tunnel root piles reinforcement basis are used to ensure the stability of the tunnel surrounding rock, based on the characteristics of Cangyuan Tunnel which passes through the debris flow gully. The deformation is controlled within the specification range, which indicates that the construction effect of Cangyuan Tunnel is good. These construction measures solve the construction problems of tunnels which pass through the debris flow gully and ensure project quality and duration, therefore, these construction measures can be used in similar projects.

Abstract: Guandoushan tunnel in the Yibin - Luzhou expressway passes through fault fracture zone at the entrance. Structure internal force are complex during or after the construction. It challenges the safety during construction and operation. Plane finite element model was used to calculate internal force of primary support in the cases of different buried depths and three dimensional finite element model was applied to calculate stress distribution of primary support and secondary lining of the tunnel through fault fracture zone. The results indicate: with the increasing of buried depth, the loads acting on the structure will increase. It leads to uneven stress distribution in longitudinal direction, especially in the border of fault zone. It is suggested to increase the longitudinal reinforcement to improve overall longitudinal shearing resistance capacity and set deformation joint in the intersection to strengthen the longitudinal deformation ability of structure.

Abstract: The enclosure structure of the vertical shaft of subway engineering is generally vertical, and perpendicular to the plane. Due to the effects of the geological condition, the construction condition and the supporting method, the shaft reflects similar deformation characteristics to the enclosure structure of foundation pit. Generally, the enclosure structure deformation can be decomposed into three types, namely the forward rotation, reverse rotation and deflection. When the vertical shaft enclosure structure produces a forward rotation with a lesser degree, it can still be used for positive angle slope processing, which enables us to calculate the safety factor of one side with positive angle enclosure structure in the same way with the slope of foundation pit. Taking the shield-receiving shaft of Dalian Jiaotong university station, Dalian metro No.2, Section 201 as an example, it is the geological conditions and supporting structure that contribute to build the enclosure structure with one-side elevation angle. Based on the above method and taking the geological, construction and supporting conditions into account, FLAC3D is used to build the model, and carry out the solution on safety factor of the enclosure structure with positive angle. The results indicate that under the existing conditions, the enclosure structure safety factor for our example is more than 1.

Abstract: This paper presents the stress and strain distribution and change during the tunnel construction, and the stress and strain are compared with different construction methods. Mathematical model was firstly introduced. Then the stress and the strain during the up tunnel construction from two methods were compared. The historical stress and strain curves of key node of tunnel during the tunnel construction were analyzed. The different stress changes from different construction methods were compared. We can get the conclusion that the construction method affects the stress distribution and change.

Abstract: Based on a large number of surrounding rock stability, it sums up the classification of surrounding rock, nature and failure mechanism in the underground engineering. This paper introduces a underground tunnel hanging assembly support, the supporting structure can effectively solve the problem of insufficient rigidity of the roadway support, and provide a supporting structure with a certain amount of shrinkage.

Abstract: This paper was based on many pre-existing or being successful tunnel projects for study. Through in-depth investigation and analysis of the action mechanism on rock and the construction control under complex geological conditions, the author synthesized the technical advantages of the drilling-blasting method and tunnel boring machine technology into integration as a new drilling-blasting machine method applied in tunnel (lane) excavation. If this method intended by conventional process, it’s difficult to realize mechanized continuous excavating. In this problem, the author put forward two new technologies named helicoid tunnel face and shallow blasthole close blasting to improve. Respectively from the theory, economic, technology and safety, the paper demonstrates the feasibility of drilling-blasting machine method.

Abstract: Underground powerhouse of hydraulic and hydroelectric engineering is a large cavern group structure. Construction process of underground powerhouse is a complex system, whose construction schedule is associated with construction quality. It is necessary to arrange construction schedule adopting construction simulation method and combining with tunnel stability analysis, which can advance the level of construction organization design. By using real-time control theory and methodology, the real-time control model of construction schedule and quality was established, considering construction procedure, geological conditions and resource limitation. The real-time control method of construction schedule and quality was presented, and the practical control procedure was studied. Good effect is obtained through the application of the real-time control method for construction schedule and quality in one real underground powerhouse.