Applied Mechanics and Materials Vols. 353-356

Abstract: Abstract: During excavation in deep foundation pit, the deformation of soil and earth surface caused by engineering dewatering is an important factor to affect engineering safety. In this paper, according to the data provided by the detailed survey report of route 1 subway in Shenyang, the subsidence laws of the ground and around buildings caused by the dewatering of route 1 subwaywere analyzed by using Coupling System of Flow & Solid in FLAC-3D which is based on poroelasticity theory and consolidation theory, and preliminary results were obtained.

Abstract: Abstract: II type horseshoe with flat–bottom evolved from standard II type horseshoe cross-section. It is composed of a flat-bottom and three arc sections. It is commonly applied in the field of hydroelectric engineering. The critical depth computation equation for II type horseshoe cross-section with flat–bottom tunnel is a transcendental equation and no analytic solution. In this paper, based on the mathematics transformation for the basis equation and the relationship analysis between the dimensionless critical depth and the relative parameters, a direct solution is established for the calculation of critical depth for II type horseshoe cross-section with flat–bottom tunnel according to the fitting principle. This method overcomes the shortage of other iterative trial calculating methods, such as complex calculation step, depend on the special chart and curve, and existed serious error. The formula is simply and the maximum error is less than 0.515% under the general engineering design range (ratio of critical depth and arch radius is located between the 0 - 1.60).

Abstract: Salt cavern storage is usually in bedded salt rock formation except salt dome, in particular in China. The rocks composing a bedded salt rock formation, e.g., mudstone, rock salt, interlayer, etc., often present viscoelastic-plastic behaviors, which is an important influencing factor of the long-term stability of salt caverns in it. Modelling the rheological behavior with the Druck-Prager creep model, an example of stability analysis of four salt caverns at Jintan Salt Mine of China with the finite element method is elaborated in this paper. The results show that besides the inevitable loss of effective storage room with time due to creep deformation, which decreases evidently with internal pressure but decreases slowly at a certain pressure value, the variation of operating internal pressure in each cavern can cause the change of volumes of other nearby caverns and then affect the stability of all the caverns. The internal pressure difference should be as small as possible during the operation of salt caverns.

Abstract: Abstract: II type horseshoe with flat–bottom evolved from standard II type horseshoe cross-section. It is composed of a flat-bottom and three arc sections. It is commonly applied in the field of hydroelectric engineering. The normal water depth computation equation for II type horseshoe cross-section with flat–bottom tunnel is a transcendental equation and no analytic solution. In this paper, based on the mathematics transformation for the basis equation and the relationship analysis between the dimensionless normal water depth and the relative parameters, a simplified calculation formula is established for the calculation of normal water depth for II type horseshoe cross-section with flat–bottom tunnel according to the fitting principle. This method overcomes the shortage of other iterative trial calculating methods, such as complex calculation step, depend on the special chart and curve, and existed serious error. The formula is simply and the maximum error is less than 0.23% under the general engineering design range (ratio of normal water depth and arch radius is between 0.05 - 1.45). it can be used on the engineering designing practice and the edit of the handbook of hydraulic structure design.

Abstract: Based on Nanjing Yangtze River Tunnel project, the selection of segment lining of large profile underwater shield tunnel was analyzed. Considering from structure force, construction and economic, the comparison and selection for assembling modes, joint form, blocking modes, thickness and width of segment lining was carried out, The better segment lining structure was obtained. The study results can offer references for the design of segment lining of similar large profile underwater shield tunnel.

Abstract: Operating safety of adjacent pre-constructed pipeline must be insured when the crude oil and refined oil pipeline is under construction. Applying finite element method, the peak velocities of observed points located at test segment and operating segment of West to East Gas Transmission Pipeline were calculated, and the ratio of the two peak velocities in different relative positions was also obtained. Taking advantage of quantitative relationship between the detonation charge and vibration velocity of particle on the pipeline, the ratio of detonation charge is derived from the peak velocity ratio, thereby the blasting scheme of West to East Gas Transmission Pipeline with different thickness is ascertained. This method is not only economical and convenient, but also has no damage to the pipeline, which also works for other blast schemes of different conditions.

Abstract: To get better understanding of TBM construction risk and avoid it, comprehensive analysis and summary of various factors to TBM construction risk were made in three aspects, such as geological and hydrological conditions, TBM equipment, construction team of TBM. Based on the detailed presentation of hydrological conditions, the corresponding demands of TBM equipment and construction team were put forward. Emphatically from the two aspects of bad geological and countermeasures, design of TBM equipment, corresponding strategies to avoid all kinds of risk were proposed. Using Taiwan Hsuehshan Tunnel as the class project, this paper introduced and analyzed the construction risk and of solutions to it, with the hoping of providing guidance for TBM design, risk analysis and evade of construction and other aspects.

Abstract: Salt rock is now being used widely as storage vault of oil and gas. However, the rheological properties of salt rock have significant influence on the stability of salt caverns and, in particular, induce the reduction of storage volumes. Therefore, the classical Nishihara model is used to describe the rheology of salt rock and incorporated into the finite element simulation firstly. Then the volume shrinkage is calculated for two typical simplified models with single cavern and double caverns. The results show that the storage volume of salt cavern decreases with the internal pressure and increases with service time for either single-cavern model or double-cavern model, which remains unchanged though the volume shrinkage of one cavern is influenced by others.

Abstract: The construction procedure of subsurface excavation method is very complex. In order to obtain the regular pattern that the construction process of pile hole may influence the ground surface subsidence, the author use Lizheng software to analysis the construction parameter of excavation, installation and removal of the support, back building etc. Using the finite element analysis method, the author simulate the surface subsidence. Comparing the simulation results with the measured data, the author get the regular patter of surface subsidence and the envelope diagram of Internal force and displacement of the retaining pile.

Abstract: The long-term deformation behavior for existing underground structures induced by tunneling is a hot problem which engineers designing and practicing in urban subway engineering encounter more frequently than in the past. Based on the Shanghai Railway Transportation project, the long-term deformation of existing tunnels caused by underground excavation is proposed considering soil consolidation by 3D consolidation finite element numerical simulation method. The maximum consolidation deformation values for service Line 4 are obtained within the time span of thirty years after the tunneling excavation is completed. Furthermore, comparisons between numerical simulation results and the field data are conducted according to site investigations. It is concluded that the calculated consolidation displacements are in general consistent with the observed shapes and the soil consolidation has a significant influence on the deformation behavior of existing tunnels during the service process.