Abstract:In the upper limit analysis of anti-uplift instability of foundation pit in the past, the soil was usually divided into several rigid bodies, which neglected the shear deformation inside the rigid bodies and the size effect of foundation pit; thus, it was difficult to reflect the actual deformation mechanism of the foundation pit. The displacement increment of Rayleigh distribution function was selected, and the deformation model of narrow foundation pit under Terzaghi mechanism was established. The expression of the shear strength of soil considering soil anisotropy and over-consolidation ratio was adopted. According to the principle of upper bound method, the calculation method of safety coefficients of anti-uplift considering the geometric size of foundation pit was proposed. The influence rule of important parameters, including the geometric size of foundation pit, over-consolidation ratio and anisotropic coefficient of shear strength, on the safety coefficients of anti-uplift was quantitatively analyzed. The comparison between the classic foundation pit failure cases and the results of nonlinear finite element analysis shows that: in the proposed method, the influence of internal bracing erection on the stability of foundation pit is taken into account, and the influence of the width and anisotropy of foundation pit on the safety coefficient of anti-uplift can be considered.
[1] 唐震, 黄茂松, 袁聚云. 基于可变组合机构的黏土基坑抗隆起稳定性上限分析[J]. 岩土工程学报, 2017, 39(增刊2): 180-183.
TANG Zhen, HUANG Maosong, YUAN Juyun. Upper bound analysis of basal stability of excavations in clay based on variable combined mechanism [J]. Chinese Journal of Geotechnical Engineering, 2017, 39(Sup2): 180-183.
[2] 黄茂松, 余生兵. 基坑抗隆起稳定的块体集上限分析[J]. 岩土工程学报, 2012, 34(8): 1440-1447.
HUANG Maosong, YU Shengbing. Upper bound analysis of basal stability in undrained clay based on block set mechanism [J]. Chinese Journal of Geotechnical Engineering, 2012, 34(8): 1440-1447.
[3] HUANG Maosong, TANG Zhen, YUAN Jujun. Basal stability analysis of braced excavations with embedded walls in undrained clay using the upper bound theorem [J ]. Tunnelling and Underground Space Technology, 2018, 79: 231-241.
2006, 132(4): 465-477.
[5] LAM S Y, BOLTON M D. Energy conservation as a principle underlying mobilizable strength design for deep excavations [J]. Journal of Geotechnical and Geoenvironmental Engineering, 2011, 137(11): 1062-1074.
[6] WANG Lizhong, LONG Fan. Base stability analysis of braced deep excavation in undrained anisotropic clay with upper bound theory [J]. Science China Technological Sciences, 2014, 57(9): 1865-1876.
[7] WANG L Z, LIU Y J, HONG Y, et al. Predicting deformation of multipropped excavations in soft clay with a modified mobilizable strength design (MMSD) method [J]. Computers and Geotechnics, 2018, 104: 54-68.
[8] 徐洪钟, 孙鹏鹏, 崔文森, 等. 南京地铁基坑支护结构的MSD综合刚度及变形预估研究[J]. 中国矿业大学学报, 2018, 47(4): 907-912.
XU Hongzhong, SUN Pengpeng, CUI Wensen,et al. MSD synthetic system stiffness and deformation prediction of support structure for deep excavation in Nanjing subway [J]. Journal of China University of Mining & Technology, 2018,47(4): 907-912.
[9] BOLTON M D, LAM S Y, VARDANEGA P J,et al. Ground movements due to deep excavations in Shanghai: Design charts [J]. Frontiers of Structural and Civil Engineering, 2014, 8(3): 201-236.
[10] OROURKE T D. Base stability and ground movement prediction for excavations in soft clay [C]// Retaining Structures. Robinson College, Cambridge: The Institution of Civil Engineers,1993.
[11] JAMIOLKOWSKI M, LADD C C, GERMAINE J T,et al. New developments in field and laboratory testing of soils [C]// Proceedings of the 11th International Conference on Soil Mechanics and Foundation Engineering. Rotterdam, Netherlands: AA Balkema, 1985.
[12] 王洪新. 基坑宽度对围护结构稳定性的影响[J]. 土木工程学报, 2011, 44(6): 120-126.
WANG Hongxin. Influence of excavation width on enclosure-structure stability of foundation pits [J]. China Civil Engineering Journal, 2011, 44(6): 120-126.
[13] CASAGRANDE A, CARILLO N. Shear failure of anisotropic materials [J]. Journal of Boston Society of Civil Engineering, 1944, 31: 74-87.
[14] WHITTLE A J, UKRITCHON B, SU S F,et al. Base stability of deep excavation in anisotropic soft clay [J]. Journal of Geotechnical and Geoenvironmental Engineering, 2000, 126(8): 754-757.
[15] HSIEH P G, OU C Y, LIU H T. Basal heave analysis of excavations with consideration of anisotropic undrained strength of clay [J]. Canadian Geotechnical Journal, 2008, 45(6): 788-799.
[16] MAYNE P W. Determining OCR in clays from laboratory strength[J].Journal of Geotechnical Engineering, 1988, 114(1): 76-92.
[17] CHANG M F. Interpretation of overconsolidation ratio from in situ tests in recent clay deposits in Singapore and Malaysia [J]. Canadian Geotechnical Journal, 1991, 28(2): 210-225.
[18] CHHENG C, LIKITLERSUANG S. Underground excavation behaviour in Bangkok using three-dimensional finite element method [J]. Computers and Geotechnics, 2018, 95: 68-81.
[19] HASHASH Y M A, WHITTLE A J. Ground movement prediction for deep excavations in soft clay [J]. Journal of Geotechnical Engineering, 1996, 122(6): 474-486.