Factors Affecting Slope Instability of the Nhan Co Alumina Red Mud Basin and Economical, Environmentally Friendly Soil Stabilization
Nguyen Van Hoang*,, Hoang Viet Hung**, Nguyen Mai Chi**, Pham Huy Dung**, and Dao Trong Tien**,***
*Institute of Geological Sciences, Vietnam Academy of Science and Technology
No.84 Chua Lang Street, Dong Da District, Hanoi 10000, Vietnam
**Thuyloi University, Hanoi, Vietnam
***Project Management Department 8, Ministry of Agriculture and Rural Development, Daklak, Vietnam
Since 2017, there have been recurring landslides in the red mud basins of the Nhan Co alumina factory, Dak Nong Province, Vietnam, during the rainy seasons. Changes in physical and mechanical soil parameters due to rain water infiltration and the formation of tension cracks have been considered as the main causes of slope instability. The soil cohesion and angle of internal friction decreased nearly thrice and twice, respectively, as the soil became saturated. An economical and environmentally friendly reinforcement using bamboo stem piles in combination with slope regrading is suitable for the site conditions. With a light slope regrading, a bamboo stem pile spacing of 5.3 m ensures that the slope factor of safety (FS) is 1.30, which satisfies the requirements specified by the national technical regulations. The results are helpful and serve as practical fundamentals for a comprehensive control of slope stability of the red mud basins in the Nhan Co alumina factory to avoid possible catastrophic destruction of the local ecology by the spreading of an extremely high pH fluid and mud from the red mud basins due to the landslides into the red mud basins.
-  Dantri, “Chemical fluid spillage at Tan Rai bauxite factory: Small accidence, large loss!,” https://dantri.com.vn/kinh-doanh/boxit-tan-rai-tran-hoa-chat-ra-moi-truong-su-co-nho-thiet-hai-lon-1317152926.htm (in Vietnamese) [accessed March 13, 2019]
-  Tuoitre, “Tan Rai bauxite factory: Soda pipe breakage due to joint aging,” https://tuoitre.vn/nha-may-boxit-tan-rai-ong-chua-xut-vo-do-lao-hoa-khop-noi-1052089.htm (in Vietnamese) [accessed March 13, 2019]
-  Vinacomin, “Environmental impact assessment for the Nhan Co – Dak Nong bauxite mining,” 2013 (in Vietnamese).
-  R. L. Schuster and R. J. Krizek, “Landslides, Analysis and Control,” p. 234, National Academy of Sciences, 1978.
-  M. Fujita, S. Ohshi, and D. Tsutsumi, “A Prediction Method for Slope Failure by Means of Monitoring of Water Content in Slope-Soil Layer,” J. Disaster Res., Vol.5, No.3, pp. 296-305, 2010.
-  H. Goto, Y. Kumahara, S. Uchiyama, Y. Iwasa, T. Yamanaka, R. Motoyoshi, S. Takeuchi, S. Murata, and T. Nakata, “Distribution and Characteristics of Slope Movements in the Southern Part of Hiroshima Prefecture Caused by the Heavy Rain in Western Japan in July 2018,” J. Disaster Res., Vol.1, No.6, pp. 894-901, 2019.
-  Thuy Loi University, http://www.tlu.edu.vn/ (in Vietnamese) [accessed May 31, 2020]
-  Ministry of Construction (MOC), TCVN 4195-1995, 4202-1995: Construction Soil, 1995 (in Vietnamese).
-  BS1377-Part 7:1990, British Standard, “Methods of Test for Soils for Civil Engineering Purposes, Part 7 – Shear Strength Tests (Total Stress),” 1990.
-  ASTM D3080-04, “Standard Test Method for Direct Shear Test of Soils Under Consolidated Drained Conditions.”
-  AS1222.214.171.124-1998, “Methods of testing soils for engineering purposes, Method 6.2.2, Soil strength and consolidation tests – Determination of the shear strength of a soil – Direct shear test using a shear box,” 1998.
-  A. W. Bishop, “The Use of the Slip Circle in the Stability Analysis of Slopes,” Géotechnique, Vol.5, No.1, pp. 7-17, 1955.
-  Dak Nong meteorology station, “2018 and 2019 monitored daily precipitation,” 2020.
-  Y. Rimon, O. Dahan, R. Nativ, and S. Geyer, “Water percolation through the deep vadose zone and groundwater recharge: preliminary results based on a new vadose zone monitoring system,” Water Resour. Res., Vol.43, No.5, W05402, doi: 10.1029/2006WR004855, 2007.
-  T. Turkeltaub, O. Dahan, and D. Kurtzman, “Investigation of groundwater recharge under agricultural fields using transient deep vadose zone data,” Vadose Zone J., Vol.13, pp. 1-13, 2014.
-  Z. Ju, X. Li, and C. Hu, “Water dynamics and groundwater recharge in a deep vadose zone,” Water Supply, Vol.16, No.3, pp. 579-586, doi: 10.2166/ws.2015.165, 2016.
-  R. N. Yong, E. A. Fattah, and N. Skiadas,“Vehicle Traction Mechanics,” p. 307, Elsevier Science, 1984.
-  O. R. Freitag, “A proposed strength classification test for fine grade soils,” J. Terramechanics, Vol.24, No.1, pp. 25-39, 1987.
-  J. S. Panwar and J. C. Siemens, “Shear strength and energy of soil failure related to density and moisture,” Trans. of the ASABE, Vol.15, No.3, pp. 423-427, 1972.
-  K. Terzaghi, R. B. Peck, and G. Mesri, “Soil Mechanics in Engineering Practice,” p. 512, John Wiley & Sons, 1996.
-  H. Zhang, H. Liu, J. Wang, and W. Dong, “Investigation of the effect of water content and degree of compaction on the shear strength of clay soil material,” Functional Materials, Vol.24, No.2, pp. 290-297, 2017.
-  Nhan Co alumina joint stock company, “Environmental impact assessment for the Nhan Co alumina factory in Nhan Co commune, Dak R’lap district, Dak Nong province,” 2009 (in Vietnamese).
-  W. J. M. Rankine, “On the stability of loose earth,” Philosophical Trans. of the Royal Society of London, Vol.147, pp. 9-27, 1857.
-  I. Ishibashi and H. Hazarika, “Soil Mechanics Fundamentals and Applications,” Second edition, p. 392, CRC Press, 2015.
-  J. P. Guyer, “Introduction to Slope Stability and Protection,” Continuing Education and Development, PDHonline Course C547, pp. 1-56. 2012.
-  Vietnamese Academy of Forest Science, “Study of the mechanical, physical and chemical properties of some common wood and bamboo species in Vietnam as a basis for processing, storage and utilization (stage II: 2011-2015),” 2017 (in Vietnamese).
-  Geo-studio, “Seepage modeling with SEEP/W, an engineering methodology,” 2018.
-  Ministry of Agriculture and Rural Development, QCVN 04-05:2012/BNNPTNT, “National technical regulation on hydraulic structures – The basic stipulation for design,” 2012 (in Vietnamese).