【作者】 余业；

【导师】 黄润秋；

【作者基本信息】 成都理工大学 ， 地质工程， 2011， 硕士

【摘要】 罐滩滑坡位于四川省安县雎水镇团结电站雎水河右岸,受汶川地震及震后暴雨作用,于2008年5月12日晚22:00²3:00发生大规模整体滑移破坏,堵塞河道,形成安县罐滩堰塞湖。滑坡滞后地震8h,属典型地震后效滑坡。天然斜坡发育于存在软弱基座的反倾斜坡中,且坡体岩性上部为白云岩、下部为泥岩,对于这种上“硬”下“软”结构的反倾岩质斜坡发生地震后效型滑坡的成因机制及地震动力响应特征研究有一定的意义。因此通过野外详细地质调查,在阐明滑坡地质环境条件的基础上,描述了滑坡的基本特征及坡体结构特征,结合滑坡变形破坏特征,定性分析滑坡的成因机制演化,最后用3DEC离散元数值模拟软件对滑坡破坏过程进行模拟,得出斜坡在地震作用下的动力响应特征及在降雨作用下的破坏过程,综合定量分析了滑坡的成因机制。具体研究内容及成果如下:（1）罐滩滑坡发育于存在软弱基座的反倾斜坡中,位于龙门山江油-灌县断裂上盘,自然斜坡走向与断裂带近平行,其分支断裂F_3-1滑坡坡体下部通过,上部基岩为T₂j+l弱风化中厚层状白云岩,下部为T1f+t薄层紫红色泥岩和泥质粉砂岩互层,岩体破碎。滑坡前缘高程708m,后缘高程1180m,高差472m,沿河宽400m,纵向长度800m,滑坡总体坡度约45°,前缘由于开挖坡度65°,主滑方向99°,平面面积1.82×10⁵m2,滑坡体积468万m³,形成的安县堰塞湖蓄水量约145×10⁴m³,回水约2km。（2）滑坡变形破坏迹象主要表现为后缘拉裂及前缘压缩-倾倒。后缘分布多条长大拉裂缝,而前缘由于堰塞湖开挖揭露岩层有与基岩相同的层序,但倾角发生明显变化,表明斜坡有向河谷方向倾倒的趋势。（3）滑坡形成机制和发展过程可以定性分为3个阶段:自然斜坡的压缩-倾倒变形、地震作用潜在滑面形成但并未完全贯通,降雨作用滑面贯通斜坡整体破坏阶段。（4）数值模拟显示地震作用下,斜坡动力响应特征表现为对输入地震波存在垂直放大和临空面放大作用,且垂直放大效应较临空面放大效应更为显著。斜坡加速度放大系数总体上水平加速度放大系数大于竖向加速度放大系数,即水平加速度放大效应更为显著,速度放大效应亦有同样规律。（5）数值模拟结果显示地震作用下最小主应力值在坡表可达1.75Mpa,即坡面出现拉应力,拉裂缝出现;从位移特征来看,X向位移最大7.5cm,Y向位移最大21cm,滑坡塑性区并未完全贯通,因此滑坡并未发生;而降雨作用下的数值模拟结果显示滑坡塑性区完全贯通,滑坡发生破坏。因此,调查和分析表明,下软上硬的坡体结构是滑坡产生的基础,强烈的地质构造活动背景是其产生的重要条件,强烈的地面震动和高强度暴雨是导致滑坡产生的主要因素。更多还原

【Abstract】 The Guantan landslide, which is located in the right bank of the Jushui river at Tuanjie hydropower station in Jushui town of Anxian country in Sichuan province. The landslide integrally failed at 22 to 23 in May 12, 2008 and clogged the Jushui river, then formed the Anxian country Guantan quake lakes. The landslide was occurred 8 hours after the earthquake and is a typical landslide that reacted to after-earthquake effect. The landslide is happened in counter-tilt rock slope with weak rock base, which forms the boundary of dolomite rocks in the upper part and the mudstone in the lower part. So for the counter-tilt rock slope with rigid upper layers and weak lower layers, it is significance to research its formation mechanism and dynamic response reacted to after-earthquake effect. Based on the geological conditions, basic characteristics and slope structures characteristics, combined with the formation mechanism qualitative analysis by the characteristics of deformation damage of the slope, this paper simulated the failure process using the 3DEC numerical simulation software and comprehensive- ly and quantitatively analysed the formation mechanism, then obtained the dynamic response to earthquake and failure process under rain. All the research contents and achievements as follows:（1） Guantan landslide is located in counter-tilt slope with weak base and on the upper plate of the Jiangyou-Guanxian Fault. The orientation of the slope is parallel to the fault. Taking the branch of the Jiangyou-Guanxian fault F_3-1 as dividing line, the upper layer is T₂j+l dolomite with weak weathering and medium thickness seam and the lower layer is T1f+t interbed purplish red mudstone and muddy siltstone of which the rock mass is broken. The elevation of the leading edge of the landslide is 708m, and the posterior edge is 1180m. So the lacks is 472 meters. The length along the river is about 400m, and longitudinal length is about 800m. The slope angle is about 45 degree. the leading edge angle is about 65 degree due to excavation. The glide direction is 99 degree, and the area of plane is 18.2 million square meter. Its volume is up to 4.68 million m3, the storage capacity of the lake is about 1.45 million cubic meters, and the backwater is about 2 kilometers.（2） The signs of deformation and failure manifested as tension in the trailing edge and compression-dump in the heading edge. In the trailing edge, several tension cracks distributed. In the heading edge, the rock, exposed by the lake excavation, has the same sequence with bedrock, but the dip has significant change. This showed that the slope has the tendency toward the river valley.（3） The formation mechanism and development process could be separated into 3 phases: compression-dump deformation of the nature slope; potential landslide face formed but not completely transfixed under earthquake, the landslide face completely transfixed and the whole slope failed under rain.（4） The numerical simulation result showed that the dynamic response manifested vertical amplification and free face amplification to the seismic wave, and the vertical amplification effect is magnified more obvious. The amplifying effect of the acceleration is that horizontal acceleration amplification coefficient is greater than vertical acceleration amplification coefficient, it means the horizontal acceleration amplification effect is more obvious, speed amplification effect also have the same law.（5） The numerical simulation showed that, under the earthquake effect, the minimum principal stress appeared and the range is bigger than in nature condition. That means new tension fracture appeared under earthquake and old expanded deeply. Seeing the displacement under earthquake of the slope, the maximum displacement of the X-direction is 7.5cm, the Y-direction is 21cm, but the plastic zone of the slope is not completely transfixed. So the landslide is not happened. Under the rain effect, the simulated result showed that the plastic zone completely transfixed and the slope developed large-scale failure.Based on the research results, the survey and the analysis indicated that the slope structure with rigid upper layers and weak lower layers is the basis of the landslide, the strong tectonic activity is the important condition and the intensity ground shaking and strong rain is the root.更多还原