|Alternative Title||Rock Landslide Failure Mode and Risk Forecast Induced by Earthquake|
|Place of Conferral||北京|
|Keyword||岩质滑坡 坡体结构 地质强度指标 破坏模式 永久位移预测模型|
Rock slope problem has always been one of the hot spots of geotechnical engineering and geo-hazard in mountain area, especially in southwest China for its special geographical conditions and seismic tectonic activities, which brought the seismic rock slope stability problems to the core. In recent years, with the continuous development of national west economic construction, and the rapid growing emergences of large scale engineering constructions such as hydraulic and hydroelectricity, railway and highway traffic and public work projects, the rock slope has received more and more attention for its stability judgments, failure mode and triggering mechanism, risk prediction in earthquake-prone mountain area.This thesis is focused on the characteristics analysis of slope structure and stability problem of rock slope under seismic effect and take the rock landslides caused by 2008 Sichuan wenchuan earthquake and the subsequent earthquake events as cases study. Combined with the literature data collection, geological data and field survey methods, the geological environment conditions and slope structure conditions are analyzed. The types of slope structure and failure modes of earthquake induced rock landslides are summarized, and based on this basis, the quantitative description method of geological structure index for rock slopes are developed, the rock slope failure mode zones are established. The rock slope stability evaluation method, which based on the non-linear Hoek-Brown rock mass failure criterion and Newmark rigid block theory, based on the inspection index of factor of safety and permanent displacement models are developed for single rock slope and regional slopes, respectively. The effect of the model is verified by the application of the cases study. The main results and conclusions of this thesis are as follows:(1) Rock slope classification and zoning based on slope strcture characterics. In reference to the related researches of slope structure, the slope strcture types and failure modes of rock slope are summarized and conclude. The slope strcture of the rock slope can be divided into six categories: approximate homogeneous slope strcture, layered slope strcture, joint controlled slope strcture, soft- hard alternate slope structure and weak zone controlled slope structure. Based on this division, the typical rock landslides were analyzed for its slope structure index from the quantitative point of view using the field investigation, three dimensional laser scanning and plane projection analysis method.(2) This paper demonstrates the use of a new form of a chart-based slope stability method that satisfies the non-linear Hoek-Brown (HB) criterion. The limit equivalent method is used to assess the stability of rock slopes subjected to seismic inertial force. First, stability charts for calculating the factors of safety (FoS) with a slope angle of β=30° in static and pseudo-static states were proposed by using Slide 6.0 software. Next, scaling factors of the horizontal seismic acceleration coefficient (fKh) and slope angle (fβ) were established to illustrate the influence of the horizontal seismic load and slope angle on the stability of rock slopes, respectively. Using regression analyses of fKh and fβ, a fast calculation model was proposed to solve the slope safety factors based on the stability charts. Finally, the stability charts analysis method (SCAM) was verified against the numerical solutions; the results showed that 70.63% of the data had discrepancies of less than ±10%, and the data with discrepancies greater than ±10% were associated with high values of geological strength index (GSI) and horizontal seismic acceleration coefficient (Kh). The proposed model calculating the FoS of rock slopes is simple and straightforward to use for seismic rock slope design and stability evaluation.(3) Nine kind of permanent displacement models were reviewed and summarized based on the Newmark sliding block theory; based on the strong earthquake station records with magnitude of Ms＞6.0 in from Southwest China region, the Peak ground accelerations (PGA), distance from epicenter (RE), distance from the surface rapture zone (RF), earthquake intensity parameters such as Arisa intensity (Ia) et al. are calculated and counted. The permanent Newmark displacement was calculated under the condition of nine critical acceleration set values :0.05g、0.1g、0.15g、0.2g、0.25g、0.3g、0.4g、0.5ga nd 0.6g for 844 records from strong earthquake stations. Five regression models in terms of the critical acceleration ratio-(ac/amax), the earthquake magnitude (Ms) and Arias intensity et al. are established. The validation is tested by the displacement conversion from the in situ data and the model calculations. The result showed that, the calculation results from models 5, 10 and 13 are in agreement with the measured values. Models 5 and 10 are based on the large quantity of strong earthquake station data, which need complex calculating process and take a long time to get the result, but these two models have a high prediction precision. In model 13, all of the parameters are easy to get with simple calculations, but the prediction precision was a little worse. The proposed models can be applied to earthquake-induced landslide risk assessment and changing trends evaluation, and to provide references for the rapid identification of slope stability and applications of seismic slope reinforce engineering design.
|江兴元. 地震触发岩质滑坡破坏模式与危险性预测[D]. 北京. 中国科学院大学,2016.|
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