Abstract：The EPB shield model of Ф800 mm was used in laboratory test to study the soil disturbance induced by the shield tunneling in the upper-soft and lower-hard ground. The corresponding model of discrete element method (DEM) was established to investigate the over excavation quantitatively and other information about the disturbed ground. When tunneling is in the hard rock, the settlement surface is sector shaped，orienting towards the soft soil. When tunneling is in the soft soil, the settlement surface is funnel shaped. The surface settlement of the upper-soft and lower-hard ground is smaller than that of homogeneous soft soil，while the subsurface settlement is much larger than that of soft soil. The width parameter of subsurface settlement trough K increases exponentially along the gravitational direction，and the width parameter gets larger as the ratio of hard rock to whole tunnel face gets smaller. For the same depth，K of the upper-soft and lower-hard ground is smaller than that of the homogeneous soil. The larger proportion of hard rock the tunnel face has，the proportion of the excavated soft soil contained in the muck differs more from its theoretical value. The maximum horizontal displacement occurs at the point of inflection of vertical settlement trough.
[1] 杨界峰. 复合地层盾构施工技术及其对周围环境影响研究[硕士学位论文][D]. 南京：南京林业大学，2010.(YANG Jiefeng. Shield construction in complex formation and its impact on the surrounding environmental[M. S. Thesis][D]. Nanjing：Nanjing Forestry University，2010.(in Chinese))
[2] 郭 朝. 复合地层Ф7 m盾构的刀盘适应性及施工引起地层变形规律分析[硕士学位论文][D]. 北京：北京交通大学，2014.(GUO Chao. Analysis of adaptability of cutting pan and stratum deformation caused by construction of Ф7 m shield in compound ground[M. S. Thesis][D]. Beijing：Beijing Jiaotong University，2014.(in Chinese))
[3] 王 晖，竺维彬，李大勇. 复合地层中盾构掘进的姿态控制[J]. 施工技术，2011，40(10)：67–69.(WANG Hui，ZHU Weibin，LI Dayong. Posture control of shield tunneling in composite strata[J]. Construction Technology，2011，40(10)：67–69.(in Chinese))
[4] 张明聚，刘晓娟，杜永骁. 复合地层中盾构施工对邻近建筑物群的影响分析[J]. 北京工业大学学报，2013，39(2)：214–219.(ZHANG Mingju，LIU Xiaojuan，DU Yongxiao. Building settlements induced by shield tunneling in close proximity[J]. Journal of Beijing University of Technology，2013，39(2)：214–219.(in Chinese))
[5] 刘 栋. 复合地层中土压盾构隧道开挖面稳定性研究[硕士学位论文][D]. 武汉：华中科技大学，2009.(LIU Dong. Study on stability of tunnel excavation face for EPB shield machine in composite ground [M. S. Thesis][D]. Wuhan：Huazhong University of Science and Technology，2009.(in Chinese))
[6] 竺维彬，王 晖，鞠世健. 复合地层中盾构滚刀磨损原因分析及对策[J]. 现代隧道技术，2006，43(4)：72–75.(ZHU Weibin，WANG Hui，JU Shijian. Analysis of the abrasion of disc cutters of shields in composite ground and countermeasures[J]. Modern Tunnelling Technology，2006，43(4)：72–75.(in Chinese))
[7] 竺维彬，鞠世健. 盾构隧道管片开裂的原因及相应对策[J]. 现代隧道技术，2003，40(1)：21–25.(ZHU Weibin，JU Shijian. Causes and countermeasures for segment cracking in shield-driven tunnel[J]. Modern Tunnelling Technology，2003，40(1)：21–25.(in Chinese))
[8] CHAMPAN D N，AHN S K，HUNT D V L. The use of model tests to investigate the ground displacement associated with multiple tunnel construction in soil[J]. Tunnelling and Underground Space Technology，2006，21(3/4)：413–413.
[9] SHIMADA T. 隧道开挖中的地表下沉模型试验[J]. 隧道译丛，1983，(5)：38–41.(SHIMADA T. Surface subsidence model test during tunnel excavation[J]. Modern Tunnelling Technology，1983，(5)：38–41.(in Chinese)
[10] 朱合华，徐前卫，廖少明，等.土压平衡盾构法施工参数的模型试验研究[J].岩土工程学报，2006，28(5)：553–557.(ZHU Hehua，XU Qianwei，LIAO Shaoming，et al. Experimental study on working parameters of EPB shield machine[J]. Chinese Journal of Geotechnical Engineering，2006，28(5)：553–557.(in Chinese))
[11] 徐前卫，朱合华，廖少明，等. 软土地层土压平衡盾构法施工的模型试验研究[J]. 岩土工程学报，2007，29(12)：1 849–1 857.(XU Qianwei，ZHU Hehua，LIAO Shaoming，et al. Experimental study on EPB shield tunnel construction in soft ground[J]. Chinese Journal of Geotechnical Engineering，2007，29(12)：1 849–1 857.(in Chinese))
[12] 朱合华，徐前卫，郑七振，等. 软土地层土压平衡盾构施工参数的模型试验研究[J]. 土木工程学报，2007，40(9)：87–94.(ZHU Hehua，XU Qianwei，ZHENG Qizhen，et al. Experimental study on the working parameters of EPB shield tunneling in soft ground[J]. China Civil Engineering Journal，2007，40(9)：87–94.(in Chinese))
[13] 何 川，汪 洋，方 勇，等. 土压平衡式盾构掘进过程的相似模型试验[J]. 土木工程学报，2012，45(2)：162–169.(HE Chuan，WANG Yang，FANG Yong，et al. Similarity model test of earth pressure balanced shield tunneling process[J]. China Civil Engineering Journal，2012，45(2)：162–169.(in Chinese))
[14] 方 勇，何 川，江英超，等. 土压平衡式盾构掘进对地层应变场扰动模型试验研究[J]. 铁道学报，2013，35(5)：85–89.(FANG Yong，HE Chuan，JIANG Yinchao，et al. Model test of ground strain disturbance induced by earth-pressure-balanced shield driving[J]. Journal of the China Railway Society，2013，35(5)：85–89.(in Chinese))
[15] 胡雄玉，何 川，方 勇，等. Ф800 mm土压平衡式模型盾构试验系统的研制[J]. 现代隧道技术，2014，51(4)：133–140.(HU Xiongyu，HE Chuan，FANG Yong，et al. Development of the Ф800mm EPB shield model testing system[J]. Modern Tunnelling Technology，2014，51(4)：133–140.(in Chinese))
[16] 江英超，何 川，胡雄玉，等. 砂土地层盾构隧道施工对地层扰动的室内掘进试验研究[J]. 岩石力学与工程学报，2013，35(12)：2 550–2 559.(JIANG Yingchao，HE Chuan，HU Xiongyu，et al. Laboratory test study of soil disturbance caused by shield tunnelling in sandy strata[J]. Chinese Journal of Rock Mechanics and Engineering，2013，35(12)：2 550–2 559.(in Chinese))
[17] 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)：2 506–2 512.(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 and Engineering，2013，32(12)：2 506–2 512.(in Chinese))
[18] 李向红，傅德明. 土压平衡模型盾构掘进试验研究[J]. 岩土工程学报，2006，28(9)：1 101–1 105.(LI Xianghong，FU Deming. Experimental study on excavation behaviour using model EPB shield with a diameter of 1.8 m[J]. Chinese Journal of Geotechnical Engineering，2006，28(9)：1 101–1 105.(in Chinese))
[19] 陈仁朋，李 君，陈云敏，等. 干砂盾构开挖面稳定性模型试验研究[J]. 岩土工程学报，2011，33(1)：117–122.(CHEN Renpen，LI Jun，CHEN Yunmin，et al. Large-scale tests on face stability of shield tunnelling in dry cohesionless soil[J]. Chinese Journal of Geotechnical Engineering，2011，33(1)：117–122.(in Chinese))
[20] Itasca Consulting Group Inc.. Particle flow code in 2 dimensions[M]. Minnesota，USA：[s. n.]，2008：18–38.
[21] 汪成兵. 隧道工程模型试验研究进展[J]. 现代隧道技术，2006，(增)：720–723.(WANG Chengbing. Progress in the research of tunnel engineering model test[J] Modern Tunnelling Technology，2006，(Supp.)：720–723.(in Chinese))
[22] 杜 青，毕 佳，谭跃虎，等.石膏相似材料的模型试验[J]. 施工技术，2005，34(11)：71–73.(DU Qing，BI Jia，TAN Yuehu，et al. Model test of similar material gypsum[J]. Construction Technology，2005，34(11)：71–73.(in Chinese))
[23] MELIS MAYNAR M J，MEDINA RODRIGUEZ L E. Discrete numerical model for analysis of earth pressure balance tunnel excavation[J]. Journal of Geotechnical and Geoenvironmental Engineering，2005，131(10)：1 234–1 242.
[24] O’REILLY M P，NEW B M. Settlements above tunnels in the UK-Their magnitude and prediction[C]// Proceedings of the Tunnelling?82. London：[s. n.]，1982：173–181.
2017, Vol. 36 
