Accurate assessment of the stability of natural slopes and earth structures during earthquakes has become a critical aspect of the safe and cost-effective design of several projects in seismically active areas in Taiwan. As an intermediately complicated and accurate approach, Newmark-type displacement method, capable of estimating permanent earthquake-induced displacements as a reliable index of slope performance, is widely adopted to evaluate slope stability under seismic loading. This approach, however, becomes unwieldy when hundreds or thousands of iterations are required for a regional assessment because the yield acceleration (ky), a key parameter of this approach, is estimated by trial and error in conventional slope stability analyses. To cut down the computational effort, we developed a simple procedure to directly evaluate the ky for both shallow and deep slope failures. The factor of safety (FS) of slopes under static condition is first calculated without any iterative procedures, then the ky is determined through the established correlation between FS and ky. The ky calculated by the proposed procedure corresponds well with that obtained by the trial and error approach and, thus, can be applied efficiently to a regional assessment with thousands of slopes.

抄録全体を表示

Geosynthetic reinforced slopes perform reasonably well under earthquake loading conditions as we already know. Consequently, the seismic response of the geosynthetic reinforced slope is worthy to be explored in detail. This study sets earthquake monitoring system for the geosynthetic reinforced slope built in FoGuang University, Ilan, Taiwan. There are totally 3 seismic instruments arranged to record the acceleration time histories of the ground surface, the middle portion and the top portion of the geosynthetic reinforced slope. The recorded acceleration data can be used to understand the seismic response of geosynthetic reinforced slope straightforwardly. The amplification factor for the geosynthetic reinforced slope is discussed in this paper using the recorded data. In addition, this study also simulates the seismic response of geosynthetic reinforced slope, using the acceleration time history recorded at the ground surface from the site, utilizing the finite element computer program PLAXIS. Finally, the predicted results obtained from PLAXIS finite element program are compared with the records from the seismic monitoring system. The agreeable comparison results give us the confidence to explore the seismic response of geosynthetic reinforced slopes by means of numerical technique.

抄録全体を表示

Results of pilot laboratory, field and analytical studies on stability of slopes are presented. The analysis of a condition of slopes is made in connection with construction of the alpine skiing track in the natural boundary the Cook Zhaylau to Alma-Ata, Kazakhstan. Researches are conducted in the conditions of static and seismic impact on slopes. Laboratory researches are executed in a special tray of 200x1500x800(h) mm where natural soil – collapsible loam was modelled by specially picked up composition of soil. The configuration of slopes is picked up on actual by data geodetic measurements и geological researches. Special powder sensors are applied to fixing of destructions in a tray. As a result of researches platforms on which there is a destruction of slopes are visually recorded. Regularities of their formation depending on location and force of static influence, and also for seismic influence with a force of 8 and more than points on a scale MSK 1964. In addition on slopes analytical calculations with use to the Calculation of Stability of Slopes and Plaxis programs are executed. Calculations are executed on static and seismic influences. Data on coefficient of stability and registration of isolines of tension and deformations are obtained. Comparison of experimental and settlement data allowed to increase the accuracy of definition of some boundary conditions put at experimental modeling of slopes and to increase reliability of calculations for determination of coefficients of stability.

抄録全体を表示

In 2011, the Great East Japan Earthquake occurred and it generated a long-period earthquake motion and tsunami. Many coastal structures were damaged with instability of the bearing ground under structure due to earthquake and tsunami. However, the mechanism of the earthquake-tsunami disaster for the coastal structure has not yet been completely revealed. This paper focused on the destabilization of breakwater due to an earthquake and a tsunami. Additionally, destabilization of a breakwater due to earthquake motion and liquefaction were examined using a soil-water coupled finite element analysis based on the elasto-plasticity constitutive equation and tsunami simulation was calculated by using the particle method. In the case of a complex disaster caused by a huge earthquake following by tsunami, when the earthquake includes long-period motion on a breakwater for a long time, the excessive pore water pressure was generated in the sandy ground and consequently liquefaction occurred. As the result, the breakwater was settled. Therefore, tsunami will overflow on the breakwater. Next, we investigated stability of breakwater that received tsunami force after the earthquake acted. The margin of bearing capacity on the breakwater was loss by the decreasing of strength in the sandy ground due to tsunami seepage when tsunami acted on it. Moreover, we discussed on the performance of the breakwater by use numerical simulation result of tsunami flood depth in the land with damage level of the breakwater.

抄録全体を表示

We investigate the collapse mechanism of rectangular cut-and-cover tunnels under seismic loading from inelastic frame analyses. The pattern of propagation of plastic hinges in the reinforced concrete lining is observed. It is shown that the plastic hinge start to form at the bottom corners of the structure. The shear strain at which the tunnel collapses are investigated. Whereas the plastic hinge develops at a shear strain of 1.2 % for soils with a shear velocity of 50 m/s, it is formed at a low shear strain of 0.04 %. The shear strain – moment diagram proposed in this study provide a simple yet robust method to evaluate the seismic performance of cut-and-cover box tunnels under seismic loading.

抄録全体を表示

Landslides trigged by earthquake have leaded to tremendous deaths and injuries and property loss. Therefore, it is an urgent need to make out the flow characteristics, which is fundamental for hazard assessment and risk evaluation. However, the traditional mesh method, which is based on a framework of solid mechanics, has difficulty in simulating the run-out process of landslides considering its deficiency in modelling large deformations. In this paper, the moving particle simulation (MPS) is introduced to simulate landslide run-out. To bypass the pressure fluctuation of the original MPS, this method is modified in three aspects including the kernel function, source term of the Poisson equation and the free surface discrimination. The effectiveness of the pressure stability of the modified MPS is verified and validated by two classical benchmark problems: the dam break problem and the static problem. To preferably describe the dynamic feature of landslide, the Bingham constitutive model with the Mohr-Coulomb yield criterion is introduced into the modified MPS and an equivalent Newtonian viscosity is adapted to bridge the gap between Bingham flow model and Newtonian flow model. Finally, the proposed method is applied to analyze the landslide run-out of the Tangjiashan landslide which is induced by the Ms 8.0 Wenchuan earthquake. The simulated results are compared with the field data to evaluate the effectiveness and the accuracy of the proposed numerical scheme. All calculated results show good agreement with the field data, which indicates that the proposed method is capable to capture the fluidization characteristic of landslide and to reproduce the whole flow process of earthquake-induced landslide. This will ultimately help people assess the hazard to reduce or even avoid this disaster in earthquake-prone zones.

抄録全体を表示

In order to damage of embankments in 2004 Nigatake-ken Chuetsu earthquake and to investigate the influence of the rainfall to the seismic behaviors of embankments, a series of numerical simulations were performed. In this simulation, the three-phase (soil, water, and air) coupled analysis was adopted for taking into account the behavior of unsaturated soil. It is shown that the quantitative reproduction of the deformation of the embankment could be made by applying the rainfall in seepage analysis before dynamic response analysis and that the influence of the heavy rainfall on the dynamic behavior was not small.

抄録全体を表示