Seismic stability evaluation of embankment slope based on catastrophe theory

An evaluation method for the seismic stability of embankment slope was presented based on catastrophe theory. Seven control factors, including internal frictional angle, cohesion force, slope height, slope angle, surface gradients, peak acceleration, and distance to fault were selected for analysis of multi-level objective decomposition. According to the normalization formula and the fuzzy subject function produced by combination of catastrophe theory and fuzzy math, a recursive calculation was carried out to obtain a catastrophic affiliated functional value, which can be used to evaluate the seismic stability of embankment slope. Fifteen samples were used to verify the effectiveness of this method. The results show that compared with the traditional quantitative method, the catastrophe progression owns higher accuracy and good application potential in predicting the seismic stability of embankment slope.

Experimental study on the applicability of Westergaard＇s formula for calculating earthquake-induced hydrodynamic pressure in small lake

Moraine-dammed lake outbursts usually threaten highways, railways, and key facilities in alpine regions. The varying amplitudes and distribution of hydrodynamic pressures significantly affect the stability of the dam. We utilize a shaking table to investigate the development of hydrodynamic pressure caused by different sinusoidal waves and seismic Wolong wave. A series of shaking table tests indicate that the hydrodynamic pressure varia- tion significantly follows seismic acceleration wave motion. The maximum hydrodynamic pressures calculated by Westergaard＇s equation are compared with the experi- mental values under different waves. It is shown that the Westergaard＇s values are lower than the experimental ones under the sinusoidal waves. However, the Westergaard＇s method is able to predict the earthquake-induced hydro- dynamic pressure caused by Wolong wave in small lake with desirable accuracy.

Model tests for surge height of rock avalanche–debris flows based on momentum balance

Rock avalanche–debris flows triggered by earthquakes commonly take place in mountainous areas.When entering a body of water,due to good fluidity they can move for some time instead of halting in water.In this study,we proposed a method for calculating the surge height of rock avalanche–debris flows based on momentum balance and designed a series of model tests to validate this method.The experimental variables include the initial water depth,landslide velocity,and landslide volume.According to the experimental results,we analyzed the maximum wave height in sliding zone based on momentum balance.In addition,we investigated the surge height and proposed the calculation method in propagating zone and running up zone.In this way,we can find out the surge height in different areas when a rock avalanche–debris flow impacts into the water,which could provide a basis for analyzing the burst of barrier lakes.

Snow disaster characteristics in Palongzangbu River Basinand mitigation countermeasures for road engineering

The Palongzangbu River Basin contains the highest number of maritime province glaciers in China. There are 130 glacial lakes, 64 snow avalanche sites and 28 glacial debris flow gullies distributed within the basin. Snow disasters play a controlling role in the Sichuan-Tibet Highway construction, due to the terrain’s special characteristics of high altitude and large height differential. Segmentation mitigation countermeasures for the Sichuan-Tibet Highway are presented based on snow disaster severity level and damage mode of the road. In the Ranwu to Midui section, snow avalanches are regional disasters, so the line should be placed in sunny slopes. In the Midui Gully to Yupu section, the line should be placed in shady slopes and at higher elevations to reduce the risk of glacial lake outburst. In the Yupu to Guxiang section, all three snow disasters are minimal. In the Guxiang to Tongmai section, glacier debris flows are the major threat, thus the road should be placed in shady slopes.

Rapid assessment of seismic landslide zones

In the feasibility stage of the transport route selection, large-scale geological investigations are advised before the route is determined. Therefore, rapid assessment of seismic landslide zones can be completed by the second development of the ArcGIS program. A large amount of geological information can be obtained by this method which is based on existing remote sensing image data. The integrated data can then be used to guide route location selection. This method assesses the angle between the main axis of the slope and the axis of the route and produces a zoning map that identifies slopes that threaten the route by combining with other characteristics including the climate in the study area, and the lithology and seismic structure of the near-field region. A hazard-zone map showing the degree of earthquake-induced landslide can be quickly generated by the comprehensive index method. The seis- mic landslide zone map was verified by comparison with the findings of a geological engineering survey conducted in the study area.

Effects of seismic surge waves and implications for moraine-dammed lake outburst

Moraine dams usually collapse due to over- topping by the surge wave in the dammed lake, and the surge wave is most likely caused by an earthquake. The seismic water wave （SWW） is a major factor causing the dam to break in the earthquake zone. This paper focused on the SWW by model experiments with a shaking water tank under conditions of various water depths, seismic waves, and peak ground accelerations. Two empirical equations were obtained for estimating maximal wave height for the low and high frequency, respectively. Finally, we present the application of the empirical equations on Midui Glacier Lake in Tibet plateau.