单层和双层堤基管涌砂槽模型试验研究

针对典型的单层和双层堤基进行了管涌机理的砂槽模型试验研究,观察并分析了管涌发生、发展并导致溃堤的机理和过程。试验结果表明,单层和双层堤基管涌发展的机理、通道形状和位置均相似,管涌破坏均发生在透水层的顶面,低于临界水头时,管涌仅在一定范围内发展并最终停止,管涌通道不会与江(河)水连通,一旦超过临界水头,管涌通道持续发展并最终与江(河)水连通,连通管流的强力冲刷最终导致堤基整体破坏和溃堤。但是,单层和双层堤基管涌破坏的水平平均临界水力比降不同,且前者大于后者,对试验用粉细砂,前者为0·278,后者为0·214。

Experimental studies on piping in single-and two-stratum dike foundations

Flume model tests were conducted to simulate piping processes in single-and two-stratum dike foundations. The whole development processes from piping incipit to dike failure are observed and their mechanisms are analysed. The observed phenomenons of the two types of foundations are similar in piping mechanisms, the shape of piping channel and piping positions. Piping occurred at the top of permeabile layer and propagate horizontally towards riverside. Piping extends only to a limited area and will stop when hydraulic head is lower than the critical value. Under this case, dike failures will not happen. Otherwise, if hydraulic head exceeds the critical value, piping will propagate persistently towards riverside and finally cause dike failure. The average critical horizontal seepage gradients of the two foundation types are different. They are 0. 278 and 0. 214 for single-stratum and two-stratum foundations respectively.