Piping potential of a fibrous peat

The experimental research presented in this paper aims to develop an understanding of the piping mechanisms of a fibrous peat. The organic matter content of the peat is 22.6%. The peat is compacted to 98% of its maximum dry density within a 7.0cm diameter transparent acrylic cylinder. A hole 0.64cm in diameter that penetrates the entire length of the specimen is preformed to simulate an initial piping channel. A constant-head hole-erosion test is performed on the peat specimen. Upon completion of the test, no significantly measurable enlargement of the preformed hole is observed. A comparison is then made with a sandy soil with the same grain size distribution but no organic matter content. The sand is compacted to 100% of its maximum dry density and tested under the same experimental conditions. Erosion of the piping hole progresses quickly toward the perimeter of the mold. To better understand the effect that organic matter may have on erosion resistance, the sand and the peat are mixed to create a composite soil exhibiting similar soil properties. The newly constituted soil is compacted to its maximum dry density and tested under the same experimental conditions. Only a slight increase in the hole size is observed after the test. The preliminary study suggests that (1) the presence of organic matter in soils may cause initial piping erosion rates to decrease toward a stable value; (2) organic matter content appears to play a role in a soil's resistance to piping progression; the presence of a small percentage of organic matter results in a drastic increase in a soils ability to resist this form of erosion.