Assessment the improvement of soil against piping phenomenon by randomly and conventional reinforcement methods

Piping is internal erosion of the foundation or embankment soils caused by seepage forces. The erosion starts at the downstream toe works toward the reservoir forming pipe or channels under the dam or levee. Piping is considered as the main mechanism of hydraulic failure structures. In this work, the effect of randomly and conventional reinforcement of soil on the critical hydraulic gradient and piping resistance have been investigated through experimental tests. One dimensional piping tests were carried out on unreinforced and reinforced sandy soil samples in a special designed apparatus. Conventional and randomly reinforced samples were made by static compaction method in a special mould. The conventional reinforced samples were made by layer of the geogrid sheets (dimension of mesh 4 mm) in samples but for randomly reinforced, the soil was mixed with different percent of fiber (0.08, 0.15 and 0.23 %) with different length (5, 10 and 15 mm). The results showed that the reinforcement in both methods leads to increasing the critical hydraulic gradient, piping resistance and improving the propertied of soil against piping phenomenon. This improvement is a function of percent of fiber and fiber lengths for randomly reinforced. It is also dependent on the number of layer and arrangement of geogrid sheets in the samples for conventional reinforced samples. On the other hand, the results indicated that at the same condition the effect of conventional reinforcement is more acceptable than randomly reinforcement against piping.