Advanced Materials Research Vols. 243-249

Abstract: This paper presents the calculation optimization for two examples of anchored slope, in respect of structural plane involved failures and circular slides by finite element method (FEM). A Goodman contact element subprogram was independently developed and nested in the finite element analysis (FEA) to determine the optimum anchorage parameters such as the length of the rock bolts and the angle at which they are installed.

Abstract: The dynamic consolidation method has been used widely in various engineering domain. With this method, the velocity of reconsolidation settlement was enhanced, the consolidation result was good, and the cost was lower than other methods. However, in the flooded area of Yellow River, the groundwater level is higher, and the shallow saturated silty soil liquefaction will be happened with this single method of dynamic consolidation. It goes against the roadbed stability. According to engineering practice, the vacuum dewatering with lower energy dynamic consolidation method was proposed in this paper. In order to monitor the effect of this consolidation method, the water-level observation hole, pore water pressure gauge, standard guide pile, level gauge have been set up. They could be used to get the groundwater level, the excess pore water pressure, horizontal displacement and land subsidence, respectively. These monitors would last the whole period of the consolidation experiment. Field test results shows that the excess pore water pressure was reduced by 80%-90% during one to three days.

Abstract: Moraine Lake outburst is a common geological disaster in Tibet. Meltwater infiltrates into glacier through the cracks and lubricates it, increasing the instability of glacier. There is a close relationship between glacier landslide and Moraine Lake outburst. In order to explain it, we established the glacier sliding model, and analyzed the sliding characteristics. Then we discussed the link between glacier landslide and Moraine Lake outburst, and then proposed a quantitative expression. Finally we analyzed the glacier stability of Aya Moraine Lake and others, forecasted and evaluated the risk degree of Moraine Lake outburst. Field investigation conclusions are consistent with calculated results, that is to say, the calculated results are accurate and the predictions are reasonable.

Abstract: The cohesion c and friction angle φ are the main strength parameters influencing the stability of slope. Any of them changes, the factor of safety of slope will change, but it has seldom been considered in the literature how the potential slip surface will change at the same time. In the present paper, the analytical deduction and numerical analysis are done to find out the effect of shear strength parameters c and φ to the distribution of potential slip surface. The study shows that, the potential slip surface is affected by the combination of c and φ, whose function is λ=c/(γhtanφ).

Abstract: Black rock strata with special engineering geological characteristics are distributed widely in different geological periods and areas. The scattered sulfide minerals in the rock strata are changed in a short time under the action of the oxygen-rich surface water and oxygen-rich groundwater. And the acidic water with strong erosiveness is formed. Then water--rock interaction between other minerals and the acidic water subsequently occurs with a series of chemical reactions. It can affect the stability of the black rocks themselves and other non-black rocks nearby directly, and cause engineering and environmental geological problems. Through the combination of engineering project and immersion test indoor, the mechanism of water-rock interaction of the black rock strata is researched. Engineering preventions and measures in the black strata region are proposed to avoid the damage to project and the ecological environment around.

Abstract: The dragonmount tailing pond which is taken as the study area has complex hydrogeological condition. It lies in Jingxi county, Guangxi province. In this paper, it gives out the time-concentration curve for the groundwater tracer test, makes use of single-dimensional hydrodynamic dispersion model to figures out the velocity of groundwater, coefficient of dispersion and dispersity. The mechanism of multimodal and double-humped phenomena was also investigated in the tracer test. In this paper, some situations such as leakage path, the trend of groundwater, hydraulic connection were analyzed. The research provides necessary hydrogeological basis for the design of the tailing pond and it’s of great significance to evaluate the pollution of its water source and conduct the construction.

Abstract: Auger drilling is widely employed in pile foundation engineering and sampling test for geological sciences, and is even considered as one of the idealest methods for space sampling. However, in practice, drilling parameters are usually determined by experience which might cause unnecessary accidents as a result of transportation blocking of chips. To achieve smooth chips transportation, the existed critical speed models are firstly analyzed and summarized in this paper followed by the main introduction of the proposed new model of critical drilling parameters. The influence of rotational speed and vertical feeding rate on the actual trajectory of chips transportation as well as the selection of critical models for different applied drilling fields are subsequently investigated and discussed herein. Analyses indicate that the critical models of overall combined chips and chips divided into inner and outer layer are more reliable, vertical feeding rate and rotational speed should be taken into account simultaneously. The analyses on the actual trajectory of chips transportation are helpful to understand the motion state of chips. To achieve safe and efficient drilling production, suggested drilling parameters should be provided by manufacturers according to the solving models mentioned in this paper and the specific drilling fields.

Abstract: Basing on the tunneling of Jiaowu tunnel, combining with finite element program, the continuous excavation by load steps is simulated through the “activation and passivity” method. The mechanics behavior of the half-open and half-hidden structure tunnel and the characteristic of stress and deformation of surrounding rock supporting system are studied and gained. By comparing the analysis results with in-situ testing data, Analysis shows that the calculation is correct and that tunneling surrounding rock deformation is of predictability.

Abstract: The sixth line of Guangzhou Metro Subway is partially located in silty fine sand layer, which is incompact, rich in water, and has high permeability and low bearing capability. When tunnelling in this section, it is easy to bring about gush of water and sand, which will cause the ground surface to settle. Therefore, a two-staged helical conveyer was used to control this phenomenon during tunnelling. First, both the dregs outlets of helical conveyer are turned off to prevent water and sand from rushing forth, then foam material is injected into the earth cabin and the front-end of helical conveyer to keep the cabin pressure from decreasing. Secondly, drain outlet of the second helical conveyer is turned on and the water is drained, then dregs outlet of the second helical conveyer is turned on to discharge the dregs. Finally, dregs outlet of the first helical conveyer is turned on to discharge the dregs in the earth cabin. Such technique was used successfully in tunnelling the section from Datansha to Ruyifang of the sixth line of Guangzhou Metro Subway. It ensured that sinking of the ground surface was avoided while the tunnel shield went through the silty fine sand layer that is rich in water.

Abstract: Due to land scarcity in greater Taipei area, continuously conversion from existing railroad to underground are performed to increase the land utility at different phases and span many years. In addition, integration issues between several transportation systems such as mass transit and high speed rail are also of great concerns. Fourth phase of Nangkang North Tunnel was completed and in full operation in September, 2008. During the construction period, fire codes in Taiwan for special constructions (e.g. ubnderground stations) are also going through various revisions while internationally, new regulations such as AS 4391 in Australia and NFPA130 in USA have been validated and updated. In order to verify the compliance of fire codes nationally and internationally, full scale experiments have been performed before opening to public service with emphasis on various operation modes of mechanical ventilation. This paper aims to numerically investigate and compare the effectiveness of CFD (Computational Fluid Dynamics) with experimental results. As a matter of fact, full scale experiments are implemented in fire codes in Taiwan for the structures which cannot fully comply with normal installation of fire equipments. While computational power and resources are improving tremendously in the past few years, we focus on the potentials to gain insightful information through numerical simulation and provide a repeatable reference for the engineers, designers and fire fighters as well as managerial levels in government before undertaking any full-scale experiment.