Infiltration regulation and stability analysis of soil slope under sustained and small intensity rainfall

Abstract

Rainfall infiltration depth and mode can severely influence slope stability. With the sustained rainfall, the influenced region of slope gradually expands. By using the Green-Ampt model to the soil slope, infiltration regulation was discussed under sustained and small intensity rainfall. And the infiltration rate of unsaturated soil was proposed according to the saturated infiltration theory. Because of the changing of initial moisture content in depth of slope, the saturated or unsaturated infiltration rate and depth could also be changeable with the sustained rainfall infiltration. Based on the principle of strength reduction, the calculation model of slope safety factor was established under different initial moisture contents and infiltration modes. Then, the slope stability was quantitatively analyzed through software FLAC^3D. The calculation results of soil slope engineering show that there is a shorter period for slope stability under different initial moisture contents and unsaturated infiltration ways at the slope wetting front. The stability period of slope is 33.3% according to different initial moisture contents of wetting front less than that of the same initial moisture content of wetting front. And the slope is easier to fail under the unsaturated infiltration. The results agree well with the actual situation under sustained and small intensity rainfall.

Keywords

small intensity rainfall / soil slope / infiltration depth / safety factor

References

[1] FredlundD G, MorgensternN R, WidgerR A. The shear strength of unsaturated soils [J]. Canadian Geotechnical Journal, 1978, 15(3): 313-321

[2] FredlundD G, RahardjoHSoil mechanics for unsaturated soils [M], 1993New YorkJohn Wiley and Sons, Inc.

[3] FredlundD G, XingA Q, FredlundM D, BarbourS L. The relationship of the unsaturated soil shear strength to the soil-water characteristic curve [J]. Canadian Geotechnical Journal, 1996, 33(3): 440-448

[4] FredlundD G. Unsaturated soil mechanics in engineering practice [J]. Journal of Geotechnical and Geoenvironmental Engineering, 2006, 132(3): 286-321

[5] PhilipJ R. Hillslope infiltration: Planar slopes [J]. Water Resour Res, 1991, 27(1): 109-117

[6] ChenL, YoungM H. Green-Ampt infiltration model for sloping surfaces [J]. Water Resources Research, 2006, 42: 1-9

[7] YeL-m, XueC-y, YangH-y, ChenZ-min. Research on the method of calculating penetration depth during a rainfall event [J]. Chinese Journal of Agrometeorology, 2010, 31(supl.1): 66-69

[8] ChenW, MouH-h, ChenL-qiu. Study on rainfall infiltration process and the biggest infiltration depth [J]. Mining and Metallurgical Engineering, 2009, 29(6): 13-17

[9] FangW, EsakiT. Rapid assessment of regional superficial landslide under heavy rainfall [J]. Journal of Central South University, 2012, 19(9): 2663-2673

[10] RichardM. Iverson. Landslide triggering by rain infiltration [J]. Water Resources Research, 2000, 36(7): 1897-1910

[11] ZhouZ, WangH-g, FuH-l, LiuB-chen. Influences of rainfall infiltration on stability of accumulation slope by in-situ monitoring test [J]. Journal of Central South University of Technology, 2009, 16(2): 297-302

[12] ZhangS-lin. The research of infiltrating regulation under rainstorm [J]. Geotechnical Engineering Technique, 2003281-285

[13] GavinK, XueJ-feng. A simple method to analyze infiltration into unsaturated soil slopes [J]. Computers and Geotechnics, 2008, 35(2): 223-230

[14] MohamedT A, AliF H, HashimS, et al. . Relationship between shear strength and soil water characteristic curve of an unsaturated granitic residual soil [J]. American Journal of Environmental Sciences, 2006, 2(4): 142-145

[15] KimB S, ShibuyaS, ParkS, et al. . Application of suction stress for estimating unsaturated shear strength of soils using direct shear testing under low confining pressure [J]. Canadian Geotechnical Journal, 2010, 47(9): 955-970

[16] Chu-agorM L, FoxG A, CancienneR, et al. . Seepage caused tension failures and erosion undercutting of hillslopes [J]. Journal of Hydrology, 2008, 359(3/4): 247-259

[17] LiZ-p, ZhangMi. Effects of rain infiltration on transient safety of unsaturated soil slope [J]. China Civil Engineeringjournal, 2001, 34(5): 57-61

[18] CollinsB D, ZnidarcicD. Stability analyses of rainfall induced landslides [J]. Journal of Geotechnical and Geoenvironmental Engineering, 2004, 130(4): 362-372

[19] LeeS R, KimY K, ChoiJ Y. Application of unsaturated soil parameters to slope design against rainfall infiltration-induced instability [C]. Proceedings of International Conference on Problematic Soils. Famagusta, N, 2005CyprusEastern Mediterranean University25-27

[20] Zhan TonyL, Ng CharlesW W, FredlundD G. Field study of rainfall infiltration into a grassed unsaturated expansive soil slope [J]. Canadian Geotechnical Journal, 2007, 44(4): 392-408

[21] LinH-c, YuY-z, LiG-xin. Influence of rainfall characteristics on soil slope failure [J]. Chinese Journal of Rock Mechanics and Engineering, 2009, 28(1): 198-204

[22] Oh WonT, VanapalliS K. Influence of rain infiltration on the stability of compacted soil slopes [J]. Computers and Geotechnics, 2010, 37(5): 649-657

[23] DawsonE M, RothW H, DrescherA. Slope stability analysis by strength reduction [J]. Geotechnique, 1999, 49(6): 835-840

[24] LiuZ-z, YanZ-x, DuanJian. Couple analysis on strength reduction theory and rheological mechanism for slope stability [J]. Journal of Central South University of Technology, 2008, 15s1: 351-356

[25] HuangM-s, JiaC-qin. Strength reduction FEM in stability analysis of soil slopes subjected to transient unsaturated seepage [J]. Computers and Geotechnics, 2009, 36(1/2): 93-101