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Reinforcement of tree roots in slope stability: A case study from the Ozawa slope in Iwate Prefecture, Japan
| Content Provider | Semantic Scholar |
|---|---|
| Author | Nakamura, Hisashi Nghiem, Quang Minh Iwasa, Naohito |
| Copyright Year | 2007 |
| Abstract | The effect of root reinforcement on slope stability has been well researched through empirical studies, but to date few mechanistic studies have examined the influence of tree roots on slope stability. Furthermore, the previous research has lacked consideration of the effect of landslide displacement on root reinforcement. This paper will analyze the influence of root reinforcement on safety factors (Fs) as a function of slope displacement. A model of a root system as a cluster of straight bars inserted from unstable soil into bedrock is used to reliably estimate increases in the shear resistance of the soil. The relationship between root reinforcement and lateral displacement is analyzed under two conditions: ultimate stress and pullout resistance of root fibers. The species used in the present research was the Japanese cedar (Cryptomeria japonica (L.f.) D. Don.), the most common tree species in Japan. The spatial distribution of root size and root inclination was taken from field experiments performed by Japan Sabo Technical Center in 1998. The reinforcement capacity of root fibers is considered as a function of the horizontal displacement of the landslide and the depth of the slip surface. By combining the data obtained from field experiments with a calculation model of inclined roots, this paper analyzes the Ozawa slope safety factor. Thus, root reinforcement and the slope safety factor were calculated for various displacements in the process of landslide movement. Materials and methods Research site Japan maintains approximately 25 million hectares of forest, 66.4% of the nation’s entire surface area. The forest is concentrated in mountainous areas and hilly terrain, covering about 75% of the nation’s land area (Statistical Handbook of Japan, 2004). The mountains are generally steep with intricately carved ravines. Due to unstable slopes, landslide related natural disasters annually result in serious loss of life and economic damages. Because the mountainous area was mostly forested as mentioned above, research work on landslides needs to consider the influences of root rein∗ E-mail: hnaka@cc.tuat.ac.jp forcement (Abe and Iwamoto, 1990; Endo and Tsuruta, 1969; Gray and Sotir, 1996). The properties and distribution of roots used in this paper are taken from a number of previous field experiments (Abe, 1992; Abe and Iwamoto 1986, Tsukamoto, 1987) in combination with one remarkable experiment (Sabo Technical Center, 1997) performed at the research site location in Ozawa District, Iwate Prefecture, Japan (Figure 1). In our study, the reinforcement of tree roots classified by inclination and diameter (called inclined roots) is considered as a function of both the horizontal displacement and the depth of a landslide (Nghiem et al., 2001). Field experiment and 2-D model of tree roots Two cedar trees (A and B in Figure 1) were cut and carefully excavated to determine the distribution of roots. Stokes et al. (eds), Ecoand Ground Bio-Engineering: The Use of Vegetation to Improve Slope Stability, 81–90. C © 2007. Springer. 81 |
| Starting Page | 81 |
| Ending Page | 90 |
| Page Count | 10 |
| File Format | PDF HTM / HTML |
| DOI | 10.1007/978-1-4020-5593-5_9 |
| Alternate Webpage(s) | https://page-one.springer.com/pdf/preview/10.1007/978-1-4020-5593-5_9 |
| Alternate Webpage(s) | https://doi.org/10.1007/978-1-4020-5593-5_9 |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
