南江县浅层土质滑坡降雨入渗规律与成因机理

Rainfall Infiltration and Formation Mechanism of Shallow Soil Landslides in Nanjiang

为揭示土质滑坡中降雨入渗规律和滑坡成因机理,通过对四川南江县100多个滑坡进行现场调查、统计,选取二潢坪滑坡深入剖析典型滑坡成因机理,对降雨量、GPS累积位移、土体孔隙水压力、土体含水率等综合因素分析后,采用有限元数值法对滑坡的降雨入渗过程进行模拟。结果表明:浅层土质滑坡中孔隙水压力及含水率变化有明显滞后现象,降雨初期以垂直坡面入渗为主,一段时间后则以坡向渗流为主;斜坡中前缘孔隙水压力变化比后缘对降雨更敏感,其原因为前缘黏性堆积体、侧壁陡崖及基岩面共同构成斜坡储水边界;因滑体结构的各向异性,降雨过程中土体中局部孔隙水压力及渗流力瞬时剧增,土体饱水使得软黏土层发生软化,最终导致斜坡整体失稳。

Through field inve stigation an d s ta tis t ics of more th an 100 lan d s l id e sping landslide was selected as a ca se study to reve al th e formation me chanism of an d rain fal l infiltration in soil la n d-slide. Through analyzing mult iple factors in c lu d in g p rec ip i ta t io n , ac cum ulat ive d isp la c em en t of GPS , p ore-wa te r pressure and moisture content of soil , th e proce ss of rain fal l infiltration of E rh u an g p in g finite element analysis. Results showed th a t th e variations of p o re-wa te r p re s su re an d soil moisture the landslide lagged obviously in th e in i t ia l stage of rainfal l p re c ip i ta t io n. The main infiltrationdicular to the surface of slope , an d th en changed to b e along th e slope d ire c t io n. As a wate r -sto rin g boundary wasformed by the cohesive ac cumulat ion body , ste ep s id e cliff an d bed ro ck sur fa ce , pore wate r p re s su re in th e front edge of slope was more sensitive to rain fal l th an th a t in th e r e a r edge d o e s. Due to th e anisotropy of slip mass , local pore water pressure and seepage force r ises sharply d u r in g rain fal l , an d th e soft clay softened , f inal ly resu lt in g inthe global instability of s lope.