Settlement and Prediction of Subgrades in Tidal Flat Areas under Repeated Water Levels
CAI Jun-hua1,2
1. China University of Geosciences(Wuhan), Wuhan Hubei 430074, China;
2. Sanming Transport Construction Investment Co., Ltd, Sanming Fujian 365000, China
Abstract The engineering geological conditions of the Xiapu tidal flat in a subgrade project in Fujian are analyzed. The numerical simulation software Plaxis2D is exploited to study the settlement development of deep and thick grounds in tidal flats under repeated water levels. The growth mechanism of the consolidation degree in each phase is analyzed, and the consolidation degree prediction formula is proposed. The evolution of pore water pressure of subgrades in tidal flats is introduced, and the mechanism of pore water pressure growth under repeated water levels is revealed. The settlement prediction system is developed for deep and thick grounds in tidal flats under the repeated water levels according to the gray prediction method GM(1,1). The correctness is verified by numerical calculation results. Results show that subgrades produce differential settlement under repeated water levels. In the subgrade project in Fujian, the settlement on the top right side of the embankment is larger than that on the left side, and the settlement difference is approximately 36 cm. The settlement rates on the right and left sides of the embankment are 9.43×10-5 and 4.35×10-5 m/day, respectively. The development of the consolidation degree during the loading and consolidation process can be well described by the power function form. The application of the power function expression is recommended. In the phase of repeated water levels, the logistic function expression is recommended for the consolidation degree. In terms of the development of pore water pressure, the pore water pressure of the subgrade on the right side is greater than that on the left side under repeated water levels. The pore water pressure on the right side of the subgrade suddenly increases to 120 kPa, and the pore water pressure is increased to 113 kPa at the center of the subgrade. The pore water pressure of the subgrade on the left side is 10 kPa. The pore pressure is higher than 3 kPa when it is first loaded. On the basis of gray theory, the settlement prediction system for deep tidal flat roadbeds under repeated water levels can control settlement error within 5% and can thus be applied to engineering practice.
CAI Jun-hua. Settlement and Prediction of Subgrades in Tidal Flat Areas under Repeated Water Levels[J]. Journal of Highway and Transportation Research and Development, 2019, 13(3): 22-32.
[1] DONG L, NIU B, HU S, et al. Research on the Influence Law of Bridge Foundation Settlement with Seasonal Underground Water Level Change on High Speed Railway[J]. Japanese Geotechnical Society Special Publication, 2015, 2(39):1407-1411.
[2] GHANI A N A, ROSLAN N I, HAMID A H A. Road Submergence during Flooding and Its Effect on Subgrade Strength[J]. International Journal of Geomate:Geotechnique Construction Materials & Environment, 2016, 10(21/22):1848-1853.
[3] ZHANG Ying-ping, TANG Yi-qun, XU Jie, et al. Deformation Law and Settlement Mechanism of Silt Caused by Cyclic Rise-fall of Water Table[J]. Journal of Tongji University:Natural Science edition, 2017, 45(12):1773-1782.(in Chinese)
[4] ZHANG Wen-jie, ZHAN Liang-tong, LING Dao-sheng, et al. Influence of Reservoir Water Level Fluctuations on Stability of Unsaturated Soil Banks[J].Journal of Zhejiang University:Engineering Edition, 2006,40(8):1365-1370,1428. (in Chinese)
[5] HE Zhong-ming, SHI Zhen-ning, FU Hong-yuan, et al. Influence of Water Decline on Seepage Characteristic and Slope Stability of Embankment along Lake[J]. Journal of Central South University:Science and Technology, 2014,45(9):3227-3233. (in Chinese)
[6] LIU J, GAN, Y, TANG X, et al. Study on the Settlement Prediction Methods of Soft Ground. Boletin Tecnico, 2017,55(14). 562-571.
[7] QIN Ya-qiong. Prediction Method and Engineering Application of Subgrade Settlement Based on Measured Data[D].Changsha:Central South University, 2008. (in Chinese)
[8] ZHANG Tao, CAI Guo-jun, LIU Song-Yu. Settlement Prediction of Soft Ground Based on Weibull Model[J]. Chinese Journal of Geotechnical Engineering,2013,35(S2):212-216. (in Chinese)
[9] QIN Xiao-guang, YANG Long-cai. Application of Grey Prediction in Settlement Prediction of High-speed Railway[J]. Journal of East China Jiaotong University, 2011,28(5):88-92. (in Chinese)
[10] LIU Hong-jun, CHENG Hua-wei, SHAN Wei, et al. Compression and Consolidation Characteristics of Marsh Soft Clay in Different Depths[J]. Journal of Highway and Transportation Research and Development, 2011, 28(8):41-45. (in Chinese)
[11] LIU Zhi-xiang, ZHANG Hai-qing. PLAXIS Advanced Application Tutorial[M].Beijing:Machinery Industry Press, 2015. (in Chinese)
[12] WU Lu-jun, WANG Xiao-yun, LIN Zhong-xi. Several Calculation Methods of Consolidation Degree during Soft Soil Treatment by Preloading Method[J]. Soil Engineering and Foundation, 2009, 23(4):66-68. (in Chinese)
[13] ZHAO Ming-hua, LIU Jian-hua, LIU Yu, et al. Deformation Mechanism and Settlement Forecast of Soft Clay Embankment in Coastal Region[J]. Journal of Highway and Transportation Research and Development, 2006, 23(1):32-35. (in Chinese)
[14] DANG Yao-guo, WANG Zheng-xin.Research on Grey Prediction and Decision Making Model[M]. Beijing:Science Press, 2009:1-15. (in Chinese)
[15] YANG He-ping, ZHAN Wen-tao, ZHAO Wen-jian, et al. Rapid Determination Method of CBR Indices for Expansive Soil Filler Based on GM (1,1) Model[J]. Journal of Highway and Transportation Research and Development, 2012, 29(9):1-7. (in Chinese)
[16] LI Yan. Research and Application of the Grey Forecast Model[D].Zhejiang Sci-Tech University, 2012. (in Chinese)
[17] YANG Hua-long, LIU Jin-Xia, ZHENG Bin. Improvement and Application of Grey Prediction GM (1,1) Model[J]. Mathematics in Practice and Theory, 2011, 41(23):39-46. (in Chinese)
[18] ZHANG Jun-rong, CHEN Bao-guo, YI Xian-long, et al. Analysis on Seepage Characteristics and Stability of Embankment with Water Level Change on Both Sides[J]. Journal of Highway and Transportation Research and Development, 2017, 34(2):35-41. (in Chinese)
[19] LIU Zuo-qiu, ZHOU Cui-ying. One-dimensional Non-linear Large Deformation Consolidation Analysis of Soft Clay Foundation by FDM[J].Acta Scientiarum Naturalium Universitatis Sunyatseni, 2005, 44(3):25-28. (in Chinese)
2019, Vol. 13 
