Face Stability of Shield Tunnel in Sandy Cobble Stratum with Continuum-Based Discrete Element Method
XUE Yadong1,2, ZHANG Sen2, LI Xing2, GE Jiacheng2
1. Key Laboratory of Geotechnical and Underground Engineering of Education Ministry, Tongji University, Shanghai 200092, China; 2. College of Civil Engineering, Tongii University, Shanghai 200092, China
Abstract：The instability mechanism of shield tunnel excavation working face in a sandy cobble stratum was explored，and the CDEM (continuum-based discrete element method) was adopted to establish a quasi-continuous numerical model. Triaxial compression tests of sand-cobble soil were carried out numerically to analyse its macro–mesoscopic mechanical characteristics. Based on the features of “particle flow”，“soil arch effect”，and “over-excavation”，a 2D dynamic discrete element model was established to simulate the tunnel working face over-excavation with plane triangular blocks. The progressive instability mechanisms of the tunnel face (such as soil arch effect and cavity zone) were studied. The results show that the macroscopic stress-strain curve of the sandy cobble soil triaxial compression test can be divided into linear elastic，elastoplastic，and ideal plastic stages. The cobble enhances the soil structure as coarse granular particles. The contact surface of the cobble and sand weakens the macroscopic strength. The Hopper flow calibration test with the soil arching effect as the calibration criterion can effectively obtain the friction angle transformation relationships of discrete plane triangles of different scales. The arching effect is notably ahead of the face，develops gradually with over-excavation，and finally dissipates gradually after reaching the limit state. Void regions start from the bottom of the screw conveyor，develop forward and upward gradually with over-excavation and finally cut through the load-bearing arch，reaching the ground surface and forming water-drop shaped void regions. Three types of control standards for over-excavation are proposed based on different strategies.
薛亚东, 张森, 李兴, 葛嘉诚. 基于CDEM的砂卵石地层盾构开挖面稳定性分析[J]. 西南交通大学学报, 2019, 54(3): 499-506,586.
XUE Yadong, ZHANG Sen, LI Xing, GE Jiacheng. Face Stability of Shield Tunnel in Sandy Cobble Stratum with Continuum-Based Discrete Element Method. Journal of SouthWest JiaoTong University, 2019, 54(3): 499-506,586.
范祚文,张子新. 砂卵石地层土压力平衡盾构施工开挖面稳定及邻近建筑物影响模型试验研究[J]. 岩石力学与工程学报,2013,32(12):2506-2512 FAN Zuowen, ZHANG Zixin. Model test of excavation face stability of EPB shield in sandy cobble ground and adjacent building effect[J]. Chinese Journal of Rock Mechanics & Engineering, 2013, 32(12):2506-2512
[3]
CHEN Renpeng, LI Jun, KONG Linggang, et al. Experimental study on face instability of shield tunnel in sand[J]. Tunnelling & Underground Space Technology, 2013, 33(1):12-21
[4]
胡雄玉,晏启祥,何川,等. 土压平衡盾构掘进对散粒体地层扰动和开挖面破坏特性研究[J]. 岩石力学与工程学报,2016,35(8):1618-1627 HU Xiongyu, YAN Qixiang, HE Chuan. Study on the disturbance and excavation face failure feature of granular mixtures stratum due to EPB shield tunneling[J]. Chinese Journal of Rock Mechanics & Engineering, 2016, 35(8):1618-1627
[5]
WANG Yunnian, ZHAO Manhong, LI Shihai, et al. Stochastic structural model of rock and soil aggregates by continuum-based discrete element method[J]. Science in China Ser. E Engineering and Materials Science, 2005, 48(S1):95-106
[6]
白永学,漆泰岳,吴占瑞. 砂卵石地层盾构施工引发的滞后地面塌陷机理[J]. 土木建筑与环境工程,2013,35(1):12-19 BAI Yongxue, QI Taiyue, WU Zhanrui. Lagged surface collapse mechanism of shield construction in sandy pebble stratum[J]. Journal of Civil Architectural & Environmental Engineering, 2013, 35(1):12-19
[7]
江英超,方勇,何川,等. 砂卵石地层盾构施工滞后沉降形成的细观研究[J]. 地下空间与工程学报,2015,11(1):171-177 JIANG Yingchao, FANG Yong, HE Chuan, et al. Study on delayed settlement formation induced by shield tunneling in sandy cobble strata[J]. Chinese Journal of Underground Space & Engineering, 2015, 11(1):171-177
[8]
郑炳旭,冯春,宋锦泉,等. 炸药单耗对赤铁矿爆破块度的影响规律数值模拟研究[J]. 爆破,2015,32(3):62-69 ZHENG Bingxu, FENG Chun, SONG Jinquan, et al. Numerical study on relationship between specific charge and fragmentation distribution of hematite[J]. Blasting, 2015, 32(3):62-69
[9]
徐文杰,胡瑞林,岳中琦,等. 土石混合体细观结构及力学特性数值模拟研究[J]. 岩石力学与工程学报,2007,26(2):300-311 XU Wenjie, HU Ruilin, YUE Zhongqi, et al. Mesostructural character and numerical simulation of mechanical properties of soil-rock mixtures[J]. Chinese Journal of Rock Mechanics & Engineering, 2007, 26(2):300-311
[10]
简鹏,路军富,钟英哲. 基于不同密度与含水率下的砂卵石强度参数研究[J]. 科学技术与工程,2016,16(24):257-261 JIAN Peng, LU Junfu, ZHONG Yingzhe. Study on strength parameter of sandy pebble soil based on different density and moisture content[J]. Science Technology and Engineering, 2016, 16(24):257-261
[11]
薛亚东,刘忠强,吴坚. 崩积混合体直剪试验与PFC2D数值模拟分析[J]. 岩土力学,2014,16(24):257-261 XUE Yadong, LIU Zhongqiang, WU Jian. Direct shear tests and PFC2D numerical simulation of colluvial mixture[J]. Rock and Soil Mechanics, 2014, 16(24):257-261
[12]
XUE Y D,HUANG H W,GRIFFITHS D V. Specimen reconstitution and uniaxial compressive strength testing of rock-soil mixtures[C]//Advances in Ground Technology and Geo-Information. Singapore:Research Publishing,2012:289-299
