粉质黏土堤防漫溢溃决试验

Experimental study on overflow breaching of embankments constructed with silty clay

为研究粉质黏土堤防漫溢溃决破坏过程及其对水流要素和土体性质的响应规律,以河道流量、筑堤土体含水率和孔隙率为变量,在弯道水槽中开展了9组堤防漫溢溃决概化试验。通过试验发现,粉质黏土堤漫溢溃决溃口发展过程可分为垂向侵蚀和横向扩宽两个阶段,垂向侵蚀阶段以"陡坎"后退为主要形式;筑堤土体含水率与孔隙率不仅影响了溃口垂向侵蚀以及横向扩宽速度,而且决定了溃口最终形态,河道流量主要影响堤防溃口的横向扩宽速度;溃口处流速以及下游水位变化受溃口高度的制约。拟合得到土体黏聚力与土体含水率、孔隙率的相关关系式;通过试验数据提出了由土体黏聚力和水流参数表达的"陡坎"侵蚀后退速度计算公式,证明具有一定合理性。

The purpose of this study is aims to investigate overflow breaching process of embankments constructed with silty clay and their as well as its response to flow and soil characteristics. Nine groups of experiments were conducted on the overflow breaching of cohesive embankments were conducted in a bend flume. Factors considered included inflow discharge, water content, and porosity of the embankment materials. Results showed： It has been found that the breach process can be categorized into a vertical erosion stage and lateral widening stage, with headcut retreat as the main form of erosion form during the vertical erosion stage. The soil water content and porosity not only affected the breach development rate, but also determined the final breach type. The inflow discharge, however, only affected has impact on the breach widening rate. The flow velocities and water level close to the breach were both restricted by the breach height. The relationship between the soil water content, soil porosity, and soil cohesion force was fitted u- sing by the experiment data. A formula expressed by the soil cohesion force and flow parameters for computing the headcut retreat rate was proposed and was proved to be reasonable.