Deformation mechanism and stability evaluation of Dingjiapo landslide considering the matric suction of unsaturated soil
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摘要:
丁家坡滑坡位于云阳县黄石镇中湾村，对拟建的云阳—开州（云开）高速公路安全具有潜在的威胁。为了查明丁家坡滑坡特征，开展了野外工程地质测绘、钻探与试验测试，采用Geo-studio完全耦合计算模式分析了不同降雨工况下滑坡渗流场、应力场、位移场的变化，考察了基质吸力在滑坡稳定性评价中的作用，并计算了不同降雨历时、降雨强度下滑坡的稳定性系数。结果表明：（1）丁家坡滑坡的斜坡地形、松散的岩性、潜在的临空面等因素决定了滑坡的形成与发育，坡体渗透性较好，降雨作用激励滑坡的变形，目前该滑坡处于蠕滑阶段；（2）降雨入渗后，坡体孔隙水压力增加，基质吸力减小，有效应力和抗剪强度降低，在土-岩界面形成剪应力集中，产生应变和位移，滑坡变形破坏；（3）高强度短历时的降雨使坡体浅层迅速饱和，易形成浅层滑，低强度长历时的降雨使坡体浸润较深，易造成深部滑动，其潜在滑动面主要为土-岩界面；（4）在非饱和状态下土体基质吸力对滑坡的稳定性具有重要影响；（5）目前滑坡处于基本稳定状态，一旦发生降雨，滑坡稳定性将降低，降雨历时越久、降雨强度越大，滑坡越易失稳。相对于滑坡Ⅱ区，滑坡Ⅰ区对云开高速公路安全的影响更大，应该重点对滑坡Ⅰ区进行防护治理。该研究可为工程设计、施工及滑坡的预警预报提供依据。
Abstract:The rainfall-induced Dingjiapo landslide poses a potential threat to the safety of the proposed Yunyang to Kaizhou (Yunkai) expressway. In order to identify the characteristics of Dingjiapo landslide, field engineering geological mapping, drilling and tests are carried out, and a numerical simulation code Geo-studio in a fully coupled computing mode is used to analyze the variations of landslide seepage field, stress field and displacement field under different rainfall conditions. The role of matrix suction in landslide stability evaluation is analyzed and the landslide stability factors under different rainfall duration and rainfall intensity are estimated. The results show that the slope topography, loose soil and rock characteristics and potential free surface of slope determine the landslide formation and development, the permeability of the landslide body is relatively high and the rainfall stimulates the landslide deformation. The landslide is currently in a creep stage with a few fissures in the central and these fissures show signs of widening during the rainy season. Following the rainfall infiltration, pore water pressure rises, matrix suction declines, effective stress and shear strength also decline, and shear stress concentration occurs in the soil-rock interface, which causes strain and displacement of the slope and deformation and damage of the landslide. High-intensity short-term rainfall could rapidly infiltrate the shallow soil and induce a shallow slide in the saturated section. Low-intensity long-term rainfall can saturate the deep soil and cause a deep landslide with the soil-rock interface as a slip surface. The matrix suction has an important influence on the stability of soil landslide. The stability analysis results show that this landslide at present is in a basically stable state and the stability factor would drop in case of rainfall. The longer the rain lasts and the higher the rainfall intensity is, the lower the stability factor will be. The landslide I area has a greater impact on the safety of Yunkai Expressway than the landslide II area and more attention should be paid to the protection and treatment of the landslide I area.
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Key words:
- landslide /
- deformation mechanism /
- rainfall infiltration /
- matrix suction /
- stability evaluation
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表 1 岩土体的物理参数
Table 1. Physical parameters of the rock and soil
岩土介质/参数 滑坡Ⅰ区 滑坡Ⅱ区 滑床 粉质黏土夹碎石块 粉砂质泥岩 中砂岩 天然重度/（kN·m−3） 19.7 19.7 25.1 24.7 饱和重度/（kN·m−3） 20.0 20.0 − − 天然黏聚力/kPa 13.0 15.0 − − 黏聚力（饱和）/kPa 10.5 12.8 − − 天然内摩擦角/（°） 10.5 13.0 − − 内摩擦角（饱和）/（°） 8.6 10.6 − − 弹性模量/MPa 10.0 10.0 4 030 30 000 泊松比 0.30 0.30 0.29 0.20 渗透系数/（m·d−1） 1.35 1.35 0.000 5 0.01 注：“−”表示参数不需要设置，为无。 
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