Reinforcing effects of herbaceous plant root systems under low vertical stresses simulated at the extreme surface layer of a slope with vegetation work

Abstract

In this study, we used a constant pressure direct shear test with low vertical stress simulating overburden pressure of the extremely shallow layer of a slope with plant root systems in order to identify the shear strength characteristics of soil which includes root systems of herbaceous plants. Specimens were prepared by compacting sandy soil where seeds of foreign herbaceous plants were planted. A cross section of the specimen was set to be larger than the Japanese geotechnical society standards to avoid loss of controlling vertical stress by the increase in friction drag at the shear test. The test results show that specimens having more developed root systems have larger shear resistance at large shear displacement. The extreme surface layer of a slope even with small overburden pressure exhibits a reinforcement effect by the root systems of vegetation works.