Advanced Materials Research Vols. 838-841

Abstract: The construction method for immerse tube tunnelling varies significantly in sites with different hydrogeological conditions. Using the construction process of the undersea immerse tunnel at Shenjiamen harbour, Zhoushan city, Zhejiang Province as an example, the overall construction process of undocking, float transporting, immerse positioning, locking, grouting and backfilling were introduced in this study, with possible problems at each stage listed in details. The problems occurred when grouting Tube E1, E2 and E3 (floating or settling) and relevant solutions were concluded and the related possible causes were analysed.

Abstract: 2D elasto-plastic finite element method was adopted to analyze the forced state of the surrounding rock and the tunnel lining in every step of the construction project for Fulongping double-decked tunnel. In the analysis,Mohr-Coulombs yield criterion was employed incoporating associated flow law to account for the elasto-plastic characteristics of materials. The tangent stiffness method was adopted to solve the equation of equilibrium, and the stresses which exceeded yielded point were adjusted.

Abstract: Size effect of tunnel excavation in fractured rock mass was analyzed with UDEC in this paper. For simplicity, two series of orthogonal equidistant joints were conceived in the calculation area. Change the excavation size and keep the constitutive model and its parameters of the rock mass around the tunnel to be constant during the solution. The result show, with the increasing of excavation size, vertical displacement of tunnel roof become larger, and the excavation stability turn weaker. So excavation size has great effect on the stability of fractured tunnel. In addition, another key factor, the joint set dip angle, whose effect to the tunnel stability was unearthed by comparing the results of horizontal and 45°joints. The larger the dip angle the weaker the stability at the same tunnel size.

Abstract: The purpose of this study is to find the key factors influencing the tunnel collapse accident, and explore the causal relationships between the causations of the tunnel collapse accident. Based on document surveys and Delphi Method, a system of the causation indicators of the collapse accident is established. In order to make sure that the hierarchy structure of the causation index system of the tunnel collapse accident is illustrative and reasonable, a new method of system structure analysis is proposed based on the integration of Decision making trial and evaluation laboratory (DEMATEL) and Interpretive structure model (ISM). Applying this method, the center degree and the reasoning degree of the causation are obtained firstly, and then the system hierarchy structure of the causation index system of the tunnel collapse accident is actualized. The results showed that the main causes of the tunnel collapse accident are derived from management. This research reveals the interaction relations of the causations of tunnel collapse accident, based on which this research also provides strong theory and methods to support dynamic decision and quantitative risk assessment in tunnel construction.

Abstract: In order to study ground vibration laws of shallow tunnel blasting construction, so in this paper, we put Third Bid of Qingdao Metro Line 3 as the engineering background, selecting the monitoring segment blasting vibration monitoring, studying blasting vibration peak velocity. Basing on the measured data, analyzing the variation regularity resultant velocity vector peak velocity along the tunnel axis direction. The study found that resultant velocity vector peak did not occur just above the tunnel workface, but away from the working face in 1m ~ 1.5m the range. resultant velocity vector peak located in front of the workface is 1.02 to 1.45 times of resultant velocity vector peak located behind of the workface. resultant velocity vector peak located in front of the workface is 2.26 to 2.5 times of resultant velocity vector peak above the workface. resultant velocity vector peak behind the workface is 2.3 to 3 times of resultant velocity vector peak above the workface.

Abstract: In this paper, the background is Qingdao Metro Line 3. Combined with the existing theoretical and on-site construction experience, the defined method of shallow tunnel and the difficulty of construction in the subsurface excavation of urban shallow tunnel are discussed and analyzed. In the subsurface excavation of urban shallow tunnel, it is important to choose appropriate excavation method and right way of tunnel support.

Abstract: In combination with field blasting vibration tests in Daiyuling 2# Tunnel, abundant field monitoring datum have been obtained, in order to predict the strength of blasting vibration and research the control problem about stability of surrounding rock. Through the evaluation on blasting affects of the first excavated tunnel when the last excavated tunnel in the initial stage is into tunnel hole, establish the relationship of blasting vibration disturbing degree both neighborhood tunnels to improve the accuracy. Acoustic testing technology has been adapted to test rock acoustic velocity with blasting from beginning to end. The experimental results show that: (1) rock has a larger effect on attenuation effect in the spread of seismic wave, and blasting is really damage the surrounding rock; (2) regression analysis with the formula reflecting correctly the real situation on the blasting stress wave attenuation; (3) compared with blasting vibration attenuation coefficient both the left tunnel and right tunnel, the blasting vibration damage in soft rock is more than in hard rock; (4) the most dangerous location caused by tunnel blasting excavation is the adjacent tunnel blasting face, and its velocity is 5.8845 cm/s, it is practical and feasible that the clear distance of neighborhood tunnels should keep in 21m.

Abstract: The surrounding rock of Bijia mountain tunnel portal shallow burying segment mostly fractured, the level of these rock are V and VI. Serious collapse accident was happened during the tunnel excavating. Besides, the reason and mechanism of collapse is discussed by analyzing site monitoring displacementtime curves, surrounding rocks, construction method and inclement weather. After the collapse body stability, combined with the actual situation to choose reasonable management plan, after the governance, through analysis the field monitoring curves to inspect the feasibility of the scheme. From the result of operation, the treatment plan had been done well, the construction of tunnel was safety and stability.

Abstract: It is a challenge to deal with karst in the construction of large cross-section tunnel. Under the background of Shuangbei Highway Tunnel, a new kind of grouting technology is introduced. According to hydrogeology, field tests are carried out to select grouting materials and proportion of mixture. Combined with the project practice, grouting construction technology is discussed such as grouting equipments, grouting parameters, operation technique, grouting ending standards. It has been proved that the technology is effective in tunnel construction.

Abstract: GSHP are of strategic and necessary part for the efficient utilization of renewable energy and energy conservation. Vertical ground heat exchanger system is one form of GSHP and it is a way to solve the problem of the imbalance between cooling load and heating load except for some extreme hot or cold climate areas. In the paper, the study of underground heat exchanger heat transfer mode, and the influence law of the borehole diameter, shank spacing, and grout conductivities on thermal resistance of borehole are discussed systematically.