An experimental investigation on suction influence zone induced by plant transpiration

Extensive research works were conducted in the past utilizing plant roots and stems as slope stabilisation elements by means of mechanical reinforcement. However, hydrological benefits provided by plant-induced suction through transpiration are often overlooked. The objective of this study is to measure and identify any suction influence zone induced by bermudagrass (Cynodon dactylon) in completely decomposed granite (CDG; silty sand) in laboratory. The CDG was compacted in a rectangular test box at a degree of compaction of 80% and the grass was allowed to germinate on the soil surface. The test box was instrumented with heat dissipation marric water potential sensors, which allow marric suction up to 350kPa to be measured indirectly. The setup was placed in a plant room, where atmospheric conditions such as temperature, solar energy and relative humidity were controlled and measured. For comparison purposes, a control experiment (without vegetation), which has an identical experimental setup, was performed. Variations of marric suction between the vegetated and bare specimens were measured and compared. Any grass-induced suction influence zone was identified, in terms of magnitude and distribution.