917灞桥灾难性黄土滑坡形成因素与运动模拟

持续性强降雨是诱发黄土滑坡的主要因素。 2011年9月份的持续强降雨达到50a来最大值, 在陕西省关中地区诱发了多处滑坡, 造成交通中断, 带来了严重灾难。尤其9月17日发生于白鹿塬的灞桥滑坡(917灞桥滑坡), 共造成32人伤亡的灾难性滑坡事件。为了揭示滑坡成因和运动过程, 通过对917灞桥滑坡灾害的调查和分析, 揭示了灾害的特点和诱发因素, 通过滑坡运动模拟还原了其运动过程和成灾范围。(1)9.17灞桥滑坡体相对高度大约90m, 宽170m, 滑动厚度约10m; 滑动方向为60, 滑动距离约150m, 总方量约15104m3; 滑坡共发生3次滑动, 滑动方量分别为9.5104m3、3.5104m3和2104m3, 平均堆积厚度12m左右; (2)917灞桥滑坡诱发因素主要是长历时的强降雨、开挖后的高陡边坡和特殊的黄土结构性。充足的前期降雨和当日的强降雨是滑坡发生的主要激发因素; 开挖后形成的高陡边坡发育一系列裂隙, 促使滑坡的发生; 裂隙的产生为降雨的优势渗流提供了通道, 加速了滑坡的发生。(3)利用LS_RAPID对917灞桥滑坡进行模拟, 根据模拟结果, 滑坡可以分为3个阶段, 起动加速滑动阶段(0～7.5s), 沿x方向速度从0迅速增加到4.9ms-1, 沿y方向速度从0迅速增加到8.4ms-1; 滑坡体在这一阶段共滑动了65m; 减速滑动极端, 速度开始降低(7.5～14s), x、y方向的平均速度分别降到1.5ms-1和2.5ms-1, 滑坡在这一阶段向前运动了50m; 堆积停止阶段(15～28.6s), 滑坡运动速度持续降低, 堆积厚度逐渐变薄, 滑坡体共向前滑动了175m, 滑坡最大堆积厚度为14m, 与野外调查结果基本一致。结果对认识和研究此类滑坡成因机理具有重要的借鉴意义, 也可为今后该地区防灾和减灾提供参考。

TRIGGERRED FACTORES AND MOTION SIMULATION OF917BAQIAO CATASTROPHIC LANDSLIDE

The continuing heavy precipitation is the most trigger factor for loess landslide. Continued heavy precipitation in the summer of 2011 in Guanzhong region caused the accumulation of rainfall up to the 50-return years, which triggered landslides resulting in many traffic disruptions and bringing a serious disaster. In particular, the Baqiao landslide occurred on the September 17(917Baqiao landslide) at the edge of Bailu highland. It had a total of 32 casualties. In order to reveal the causes and mechanism of the landslide and process motion, investigation and analysis of the917Baqiao landslide were implement to reveal disaster characteristics, triggered factors and formation mechanism. The landslide movement simulation was used to restore the process motion and disaster range. The results show that:(1)The landslide relative height is about 90m. The wide is 170m. Initiation average thickness is about 10m. The sliding direction is 55.The sliding distance is 150m. The total volume is about 15104m3. There is the three sliding cases with the sliding volumes are 9.5104m3, 3.5104m3 and 2104m3, respectively. The average deposit thickness is 12m. (2)It appears that the factors behind the 9.17 landslide in Bailu tableland are numerous and can be classified into three main categories. They are the long periods of heavy precipitation, slope cutting results in steepening of the slopes and the vertical joints in the loess. (3)According to the simulation results, the sliding process can be divided into 3 stages: the first stage is the start and accelerate stage(0～7.5s). The velocity is up to 4.9ms-1 and 8.4ms-1 form 0 in x-direction and y-direction, respectively. The sliding distance is 65m. The second stage is a speed reduction sliding(7.5～14s).The velocity is reduce to 1.5ms-1 and 2.5ms-1 in x-direction and y-direction, respectively. The sliding distance is 50m. The last stage is deposited and stoppage. The velocity is reduced to 0 and the deposited change to thin gradually. The sliding distance is 175m and the maximum deposit thickness is 14m. The simulation results are consistent with the field survey. The results provide important reference for understanding and studying mechanism of this type of landslide and also provide guidance for future disaster prevention and mitigation in this region.