Model Test of the Reinforcement of Surface Soil by Plant Roots under the Influence of Precipitation

Abstract

We present the results of the reinforcement of plant root systems in surface soil in a model test to simulate actual precipitation conditions. In the test, Eleusine indica was selected as herbage to reinforce the soil. Based on the various moisture contents of plant roots in a pull-out test, a fitting formula describing the interfacial friction strength between the roots and soil and soil moisture content was obtained to explain the amount of slippage of the side slope during the process of rainfall. The experimental results showed that the root systems of plants successfully reinforced soil and stabilized the water content in the surface soil of a slope and that the occurrence time of landslides was delayed significantly in the grass-planting slope model. After the simulated rainfall started, the reinforcement effect of the plant roots changed. As the rainfall increased, the interfacial friction between the roots and the soil exhibited a negative power function relationship with the water content. These conclusions can be used as a reference for the design of plant slope protection and reinforcement.

Root Reinforcement in Slope Stability Models: A Review

“…They suggested that the tensile strength of root systems dynamically changes during a rainstorm, resulting in relevant reduction of the factor of safety. Wang et al (2018) [117] were also interested in the influence of moisture on the root reinforcement, but approached the problem by means of laboratory and numerical experiments. They investigated the changes in the interfacial friction between soil and grass roots during precipitation, finding that grass can delay the time of occurrence of landslide initiation, but that effect diminishes as the soil moisture increases.…”

“…Measures on Roots Roots Modeling Slope or Smaller Scale SSM Basin or Larger Scale SSM Other Abdi et al 2018 [49] x Arnone et al 2016 [87] x x Bordoni et al 2020 [102] x x x Bordoni et al 2016 [100] x x Chiaradia et al 2016 [104] x x x Chok et al 2015 [36] x x Cislaghi et al 2017 [101] x x Cislaghi et al 2017 [85] x x x Cislaghi et al 2018 [86] x Cislaghi et al 2019 [114] x x x Cuomo et al 2020 [91] x Dazio et al 2018 [57] x x Gehring et al 2019 [121] x x Giadrossich et al 2017 [48] x Gonzalez-Ollauri 2017 [99] x x x Hales et al 2018 [82] x x Hales and Miniat 2017 [43] x x x Hwang et al 2015 [81] x x x Kokutse et al 2016 [35] x x Likitlersuang et al 2017 [106] x Masi et al 2020 [70] x Moos et al 2016 [111] x x x Rickli et al 2019 [112] x Rossi et al 2017 [107] x Saadatkhah et al 2016 [93] x x Salvatici et al 2018 [89] x Schmaltz and Mergili 2018 [113] x x Schmaltz et al 2019 [116] x x Switala and Wu 2018 [95] x Switala and Wu 2019 [97] x Vergani et al 2017 [11] x Vergani et al 2017 [118] x x Vergani et al 2015 [21] x x Wang et al 2017 [105] x x x Wang et al 2018 [117] x x Wang et al 2019 [103] x In the last few years, a challenging research trend emerged in the field of slope stability modelling: the progressive widening of application areas from slope to catchment and regional scale-i.e., over dozens or hundreds of squared kilometer-wide areas. Although advances made in the modelling of the mechanica...…”

“…Plants are complex organisms highly interacting with atmosphere, hydrosphere, lithosphere, and biosphere so that the aspects interesting for slope stability are countless and even some potentially very significative ones such as the influence of forest structure, wildfires, and soil moisture gradient have been considered or deepened only recently [43,[111][112][113][114][115][116][117][118][119][120][121]. The research that dealt with the effects of forest structure variables on slope stability such as gap length or distances between trees [111][112][113][114][115] highlighted that these factors are not negligible in order to contain the landslide hazard and that, therefore, should be taken into account by forest management operators.…”

“…The root reinforcement is commonly modelled as a component of the soil cohesion in the slope stability analyses [36,43,91,93,123], so that during the stability simulations it decreases with increasing soil moisture following the same relations adopted for the other components of soil cohesion. Considering that the phenomena affecting the root cohesion decreases with soil moisture increases are different from those affecting the soil particles, further studies on this topic in addition to the Hales and Miniat (2017) [43] and Wang et al, (2018) [117] research would be very helpful to properly consider the root reinforcement in the slope stability modelling.…”

Laboratory model test study of the hydrological effect on granite residual soil slopes considering different vegetation types

“…In various regions, such as the loess region of China, northern Mexico and the Canary Islands of Spain, the relationship between vegetation and slope hydrological effects exhibits different laws 25 , 38 – 40 . Similarly, the hydrological effects of different vegetation types, such as bovine sinew, alfalfa, wood and ginger, are also notably different 14 , 15 , 41 , 42 , 43 . The above research results confirm that vegetation exerts its slope protection impact through hydrological effects, and the effect is strongly influenced by climate, region and vegetation type.…”