洞庭湖区软土质堤防滑坡机理分析

摘要

In order to guide the reinforcement engineerings of the soft soil embankments in Dongting Lake area ,the land-slide mechanism of the embankments is analyzed based on the three-dimensional finite element method .First of all , based on the analysis of regional geology ,the finite element model is established ,and the simulation calculation of the embankments in initial state is carried out .Then ,by using the sensitive analysis for the water levels in flood period ,the stress and deformation of embankment as well as the size and distribution of yielded zones are analyzed .Later on ,the calculation and analysis for the effect of silt migration on the stability of embankment under the action of seepage field are executed .Finally ,the conclusions are got as follows :The penetrative gradient is controlled by the water level difference of Dongting Lake and Caisang Lake and the water level beside Caisang Lake ;All of the silt layers are yielded under the effect of the seepage field ,at the same time ,the upper layer in the embankment is also yielded partly ,and the most severely yielded layer is under the second packway ,which show that it is most prone to damage ;The upstream and down-stream water level difference makes a big difference on the silt ,the greater the water level difference is ,the more severe silt is yielded near the foot of the embankment ,and the most severely yielded zone extends to the inside silt layer of the embankment ;The vehicle loads on the top of the embankment have little influence on its stability ;As long as the full water level difference exists in the both sides of the embankment ,the landslide could be resulted in it ;As the silt in Caisang Lake migrates ,it may aggravate the failure of the embankment .The key to maintain the stability of the embankment is to reduce the influence of the water level difference ,make sure the silt stay in situ and improve the strength of the silt .%为指导洞庭湖区软土质堤防加固工程，基于三维有限元方法，对堤防滑坡机理进行了分析。首先，根据区域地质情况建立了有限元计算模型，并模拟计算了堤防初始状态。然后，对洪水期的水位进行敏感性分析，计算分析了堤防的应力、变形和屈服区大小及分布。之后，计算分析了在渗流场作用下淤泥迁移对堤防稳定性的影响。结果表明：堤脚淤泥中渗透坡降的大小由洞庭湖和采桑湖的水位差及采桑湖侧水位共同决定；在渗流场作用下，淤泥层全部屈服，上部填筑层中也存在屈服，并以采桑湖侧的二级马道下部屈服程度最大，表明该处最容易发生破坏；上下游水位差越大，采桑湖侧堤脚淤泥屈服程度越大，且强屈服区向堤防内部淤泥层中延伸越多；堤防顶部公路上的汽车荷载，对堤防整体的稳定影响不大；只要堤防两侧存在足够的水位差，堤防就有可能发生滑坡；采桑湖湖区淤泥迁移，将加剧堤防的失稳破坏；治理滑坡的关键是降低水位差的影响，防止淤泥迁移，以及提高淤泥强度。