RISK ASSESSMENT OF SEISMIC LOESS LANDSLIDE BASED ON NEWMARK MODEL IN BEISHAN, TIANSHUI CITY
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摘要: 本文通过天水市北山野外调查和室内分析相结合的方法，开展基于Newmark累积位移法的地震黄土滑坡危险性分析。分析了研究区的孕灾背景，结合现有滑坡和不稳定斜坡的调查数据，在充分考虑了震源方位角和斜坡坡向角的角度关系基础上，对优势坡向角和劣势坡向角下的斜坡易发性进行分析计算，然后用回归方程求出PGA为0.3 g时斜坡的累积位移，最后计算出斜坡在地震荷载下的失稳概率。在此基础上，对北山进行地震黄土滑坡的危险性评价。分析结果表明：在Newmark模型的地震黄土滑坡危险性评估中引入斜坡坡向角和震源方位角关系，有利于提高小区域（大比例尺）风险评估的准确性。Abstract: Based on the method of field investigation and indoor analysis of Beishan in Tianshui City, Gansu Procince, the analysis of the hazard analysis of the seismic loess landslide is carried out in this article based on the Newmark accumulated displacement method. Through analyzing the disaster-forming environment, combining with the investigation data of the existing landslides and unstable slopes, in fully consideration of the angle relationship between the azimuth angle of the source and the slope angle of the area, the calculation and comparison of the slope prone angle under the dominant slope angle and the inferior slope angle are carried out.Then the accumulation of slope displacementis calculateby using the regression equation when the PGA is 0.3g. Finally, the probability of instability of slope under earthquake load is calculated. On this basis, the risk assessment of the Seismic loess landslide of Beishan area was carried out. The analysis results show that introducing the relationship between the slope angle and the azimuth of seismic source in the risk assessment of the Loess Landslide in the Newmark model is helpful to improve the accuracy of the risk assessment of the small area (large scale).
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Key words:
- Beishan of Tianshui City /
- seismic loess landslide /
- risk assessment /
- Newmark model
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图 2 天水市及周边断裂和历史地震(Ms≥6.0级)分布图
F1—西秦岭北缘断裂；F2—迭部—白龙江断裂；F3—礼县—罗家堡断裂；F4—六盘山断裂；F5—海原断裂
Figure 2. Distribution of faults and historical earthquake sites (Ms≥6.0) in Tianshui City and its vicinity
图 3 Newmark模型滑体静力受力图和地震加速度水平分解图
Figure 3. Static force diagram of Newmark model and diagram of seismic acceleration horizontal decomposition
图 4 考虑斜坡坡向角的Newmark累积位移求解原理图
Figure 4. Principle diagram of Newmark cumulative displacement model in consideration of the slope angle
图 7 优势坡向角下的斜坡临界加速度a′c1
Figure 7. Critical acceleration a′c1 of slope under dominant slope angle
图 8 劣势坡向角下的斜坡临界加速度a′c2
Figure 8. Critical acceleration a′c2 of slope under adverse slope angle
图 9 优势坡向角和劣势坡向角的斜坡累积位移栅格图
(a)优势坡向角(b)劣势坡向角
Figure 9. Grid diagram of accumulative displacement under dominant slope angle & adverse slope angle
图 10 优势坡向角下斜坡失稳概率图
Figure 10. Diagram of instability probability of slope under dominant slope angle
图 11 劣势坡向角下斜坡失稳概率图
Figure 11. Diagram of instability probability of slope under adverse slope angle
表 1 北山岩土体物理力学参数取值表
Table 1. Physical and mechanical parameters of rock and soil in Beishan
岩组 坚硬
(变质岩)较坚硬
(砂砾岩)较软(松散
沉积物，
藉河，
红旗山)软弱(松散
堆积物，距河
流较近，
锻压厂)φ′/° 40 35 24.5 22.2 c′/Pa 220000 140000 90400 59500 γ/(N·m -3) 24500 23000 17800 17500 
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表 2 累积位移Dn的Weibull函数拟合参数表
Table 2. The table of Weibull function fitting parameter of cumulative displacement
Dn P(Dn) 0.005 0.0891 0.05 0.0936 0.5 0.1566 1.5 0.1720 2.0 0.1921
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