Applied Mechanics and Materials Vols. 744-746

Abstract: Characteristics of the subway project is complex, concealed, lot of potential risks. Aiming these features, in order to reduce the risk of the project and improve the rationality and accuracy of subway risk assessment, the main risk factors in the subway are analyzed and identified by methods of expert investigation and checklists, and the risk index system is established, based on research of the subway construction risk mechanism. Then the membership of each evaluation factor is determined by the expert experience method, and the weight of each risk factor is determined through the method of analytic hierarchy process (AHP). Eventually, the subway engineering risk assessment model is established based on the fuzzy comprehensive evaluation method. Finally, the project example verifies the rationality of the risk assessment model.

Abstract: According to the position and role of borehole, the tunnel face is divided into three regions undercutting area, auxiliary area and surrounding areas and each region have different blasting vibration attenuation law. Using blasting vibration testing instrument TC-4850, the vibration caused by blasting excavation in different region of Chongqing terminal connecting line tunnel was monitored and analyzed, and the vibration characteristics and attenuation law of different region in tunnel face were gained. The results show that: the maximum blasting vibration value was produced in cutting area of tunnel; using the partial excavation and setting large diameter hollow hole in the cut area can effectively reduce the blasting vibration, and the more the number of hollow hole, the damping effect was more significant; vibration attenuation parameters were different in different blasting area in tunnel face and with the increase of excavation area, the vibration attenuation coefficient was gradually decreased. Vibration attenuation index was determined by the geological conditions, basically unchanged, the value of the auxiliary area was 0.5~0.67 times the cutting zone, the value of the surrounding area was 0.25~0.33 times the cutting zone. When adopting sub-steps and sub-regional excavation in small spacing tunnel of Chongqing area, vibration attenuation coefficient can be valued by cutting areas 110~120, auxiliary area 60~80, surrounding region 30~40 and vibration attenuation index can be valued by cutting area 1.5, auxiliary and surrounding region 1.6.

Abstract: Combined with the finite element method (FEM) and the field data of Shenyang Metro NTR engineering for pipe jacking process, the variation of surface deformation and influence factors of NTR construction are systematically analyzed. The result is shown that the curves of the lateral surface subsidence produced by pipe jacking process are accord with the normal distribution curves put forward by Peck .When the top steel pipes are jacked , the surface subsidence develops rapidly and the rate of deformation is larger. In addition , grouting behind the wall and the sequence of the pipe jacking all have a greater impact on the deformation of the layer.

Abstract: This paper is to study the feasibility and mechanical properties of the tunnel trolley in Yangdan mountain. Analyze the internal force and deformation of the trolley and template with the ABAQUS, and the results show that the internal force of the model is much less than yield stress. Therefore, the structure is very safe.

Abstract: The construction of objects of critical infrastructures such as a new roads, utility tunnels, communication networks, underground parks and other structures is associated by the way with generation of vibrations in the vicinity of the underground structures, and not only human lives can be lost but also extensive material damage can be expected due to technological and natural hazards based on vibrations. This paper presents the general governing equations for coupled thermo-hydromechanical process in the tunnel surrounds. Modeling and analysis of laminated composite cylinder applied for the objective analysis of shock wave propagation in the soils and possibilities to estimates of the tunnel structure damage.

Abstract: The top-down bored excavation with cast-in-situ arch method has many advantages, such as forming a complete and stable mechanical structure, reducing construction procedures and the frequency of structure transformation, improving the stability of structure during the construction and so on. According to the specific project of single span top-down bored excavation duct in Changchun Liberation Road station, numerical simulation method is used and finite difference software FLAC 3D is adopted in this paper to analyze and research the applicability of the top-down bored excavation with cast-in-situ arch method to this project. Then optimization analysis for excavation sequence of pilot tunnel is done and the optimum construction scheme is raised to guide the practical project. This research has certain practical significance and also provides references for similar projects.

Abstract: In order to simulate moment distribution on linings of tunnel excavated by shield, FEM-based procedure is proposed. According to geological data of tunnel excavated by shield, FEM model is performed, and the moment, axial force and shear force distributions on linings are computed. The maximum moment on segments decreases while Poisson’s ratio of soil materials touching to segments increases. The moment value and distribution vary with Young’s modulus of soil materials. The maximum positive moment on linings is approximately equal to the maximum negative moment.

Abstract: At present, the complexity of calculation process and expression form of the initial value of iteration for contracted depth in quadratic parabola shaped channels,Seek a new iterative initial value formula for contracted depth in quadratic parabola shaped channels. Through an identical deformation on the basic equation for contracted depth in quadratic parabola shaped channels. Deduce the iterative formula for computing the quadratic parabola section contraction water depth. Introduction the dimensionless contraction water depth concept, plot the dimensionless contraction water depth and the dimensionless parameter relationship curves. Determine the iterative formula of initial value form for quadratic parabolic shaped channels, and based on the theory of optimum fitting, by the minimum residual standard differential and simple form of formula as the goal, the initial iteration value formula for calculation contracted depth in quadratic parabola shaped channels was obtained. It is greatly accelerating the convergence rate iterative calculations. The calculation of a practical case and error analysis of the depth calculations show that in the utility range of , its maximum relative error is less than 0.26% after performing one iteration. This formula has definite physics concept, easy calculation, high precision and wide range compared with the existing formulas. It will bring great convenience for designers.

Abstract: The important flooding drainage phenomenon of the urban regions includes of ground water exchange, sewer water exchange and ground-sewer water exchange. Due to the spread of urban regions development with high economics activities, the distributions and specifications of ditch in urban regions are irregular and un-uniform, equivalent Manhole would be used instead of ditch water exchange and its mechanism to fill ground water and sewer water exchange mode evaluated for urban flooding mode in this study. Sewer’s catchment of Ming-Seng S. Rd 608 Street in Chiayi City as case study applied by SWMM model showing urban flooding phenomenon and the effective drainage mechanism during rainfall similar Typhoon Morakot, thus, providing reliable information and references for engineers.

Abstract: The Fluvial-dominated delta is one of the extremely important deposition systems in oil and gas exploration. In this paper, the three-dimensional numerical simulation of hydrodynamics has been applied to the precise analysis of the formation of fluvial-dominated deltas and the evolution of their distributary channels. The model has been created using the Delft3D program, and the conditions of the numerical model have been set according to the hydrodynamic characteristics of modern rivers and deltas. The calculation field was 20.5 km in length by 10 km in width. With the Mor-Factor set to 60, the simulation time was 45 days. The formation and the avulsion of the mouth bar, as well as the extension, migration and bifurcation of distributary channels, have been observed and studied through analysis of the simulation results. The vertical cross-section shows that the distributary channel was filled multiple times. According to distributary channel evolution characteristics combined with quantitative methods, the terminal distributary channels can be extremely developed under ideal conditions. Due to the cross-cutting and reform effort of distributary channels, sediments were spread widely and continuously. The results show that the numerical model works well in explaining the process of evolution in fluvial-dominated delta distributary channels. This study not only enables us to quantitatively understand the dynamic processes of terminal distributary channels in fluvial-dominated delta systems, but also provides a reference model for numerical simulation of hydrodynamics in sedimentology study.