道路开挖位置对边坡稳定性影响的数值模拟

SIMULATION STUDY OF ROAD-CUT EFFECTS ON SLOPE STABILITY

公路边的滑坡崩塌在中国西南地区是常见的一类地质灾害。道路的开挖一方面改变了边坡原有的地表形态,形成了新的较陡的边坡,如果缺乏保护措施,新的陡坡很容易失稳,从而形成以滚石或浅层滑坡为主的边坡破坏。另一方面,道路开挖有可能会改变原有坡体的结构,降低坡体的安全系数,引起较大规模的滑坡,造成更为严重的灾害。因此,坡体开挖的位置对其稳定程度会产生一定的影响。文中以岩质边坡为例,在建立边坡模型的基础上,采用二维极限平衡数值模拟方法,分析了道路开挖位置对整体边坡稳定性的影响;同时,对加载地震作用的边坡稳定性也进行了模拟分析。研究结果表明,对于有潜在滑动面的坡体,在不同位置进行开挖对坡体稳定性的影响是不同的:在坡脚处或接近滑动面滑出位置开挖道路,将减小阻滑力而导致整体稳定性降低;在接近坡顶处开挖道路则会因卸载坡体物质而提高整体稳定性。合理的开挖位置与坡体坡度有密切关系,在不降低整体安全系数的情况下,坡度较陡的坡体,其开挖位置相应要高一些。无论坡体角度大小,地震作用能够显著降低边坡的稳定性。

Landslides and rock falls along the highway are common geological hazards in Southwest China.As an influencing factor on potential landslides behavior,roads or distance to roads have been successfully used in landslide susceptibility assessments in mountainous area.However,the relationship between the road-cut and the slope stability is not clear.Therefore,we performed two-dimensional slope stability calculation using the general limit equilibrium(GLE)method incorporated in the software SLOPE/W of GeoStudio for stability analysis of slopes.Our studies show that the man-made roads influence on the slope stability mainly exists in two ways:One is to create a new steep slope,which will result in rock falls and shallow landslides along the roads;the other is to influence the stability of the original slope,which will result in comparatively huge landslides.For the latter,our simulation study reveals that the road location,namely at which part of a natural slope to construct a road is important for the slope stability.For a natural slope with a potential slip surface,if a road is constructed at or near the slope toe where the potential slip surface surpasses,it will greatly degrade the slope s factor of safety(Fs)and make the slope unstable;however,if a rode-cut is near the top of the slope,it will increase the slope s Fs and make the slope more stable.The safety location is different for different slope angle,steeper slope needs a higher location for a safety road-cut in comparison with gentle slopes.Moreover,the slope stability decreases when loading a seismic force and it varies with the slope angle.Firstly,the Fs decreases when the slope angle increasing,and when the slope angle reaches 45°,the Fs then becomes greater with the slope angle increasing.