Face Stability Analysis of Shield Tunnel in Sandy Ground Using 3D DEM
-
摘要: 为探明砂土地层盾构隧道掌子面的稳定性，以Chambon和Corté开展的模型试验为基础，采用三维离散元方法研究了隧道埋深对隧道掌子面稳定性的影响规律，并从细观角度解释了开挖面失稳机理.离散元模型引入了三维柔性应力边界，将模型试验中空气或流体压力对掌子面的支撑效应抽象为作用在掌子面颗粒上的指定支护压力，逐步减少该压力，结合地层变形精确得到极限支护压力.通过删除进入隧道轮廓内的砂土颗粒模拟盾构开挖，以考虑该施工力学行为对掌子面稳定性的影响.研究结果表明：隧道埋深与隧道直径之比小于等于1.0时，掌子面极限支护压力随埋深增加而增加，此后趋于稳定，砂土地层中极限支护压力比随埋深增加而减少，地表沉降突增点对应的支护压力小于掌子面极限支护压力，失稳区直接发展到地表，工程中应同时关注地表沉降与仓内支护压力以保证开挖面稳定；隧道埋深与隧道直径之比大于等于2.0时拱顶上方形成了稳定的塌落拱，延伸高度分别约为0.7D（隧道直径）~1.3D与0.9D~2.3D.Abstract: Based on the model test carried out by Chambon and Corte, the three-dimensional discrete element method (3D DEM) was used to study the face stability of shallow shield tunnels in sand, and the face failure mechanism was investigated from microscopic perspectives. A three-dimensional flexible stress boundary was implemented in the numerical model, and the support provided by air or fluid in the chamber for a tunnel face was simplified as specified normal pressure acting on face particles. Pressure was decreased gradually to 0 kPa, and ground deformation was closely recorded. Thus, the limit support pressure could be determined naturally. The tunnel excavation process was incorporated by deleting the particles that flowed into the tunnel, and its effect on tunnel stability was considered. Results show that when C (tunnel buried depth)/D (tunnel diameter) ≤ 1.0, the limit support pressure first increases with buried depth and then tends to be constant. The ratio of the limit support pressure to the initial support pressure decreases with buried depth. The support pressure at which ground settlement accelerates abruptly is smaller than the limit support pressure. The failure zone directly propagates up to the ground surface. In engineering practice, attention should be paid to the ground surface settlement and limit support pressure to keep the tunnel face safe. When C/D ≥ 2.0, a stable soil arch exists above the tunnel crown and extends upwards to approximately 0.7D-1.3D and 0.9D-2.3D.
-
图 8 地中测点沉降与支护压力关系曲线
Figure 8. Relationship between subsurface settlement and support pressure
图 10 典型横断面上地层变形情况
Figure 10. Typical vertical displacement curve at transverse profile
图 12 地表测点沉降与支护压力关系曲线
Figure 12. Relationship between surface settlement and support pressure
图 14 地中沉降槽宽度参数随深度比的变化
Figure 14. Width parameter of subsurface settlement trough versus buried depth ratio
图 15 C/D=2.0掌子面前方应力沿隧道埋深重分布(y=0.5D)
Figure 15. Stress redistribution at C/D=2.0 along buried depth in front of tunnel face (y=0.5D)
图 16 C/D=4.0掌子面前方应力沿隧道埋深重分布(y=0.5D)
Figure 16. Stress redistribution at C/D=4.0 along buried depth in front of tunnel face (y=0.5D)
表 1 PFC3D细观力学参数
Table 1. Calibrated PFC3D microscopic parameters
砂
土粒径
分布/cm法向刚度/
(N·m-1)切向刚度/
(N·m-1)颗粒密度/
(kg·m-3)摩擦
因数1# 8~12 7.0×107 7.0×107 2 400 0.80 2# 15~20 7.5×107 7.5×107 2 500 0.85 
下载: 导出CSV
表 2 不同埋深条件下掌子面极限支护压力
Table 2. Limit support pressure under various C/D
C/D 0.5 1.0 2.0 4.0 pf/kPa 7.5 9.0 10.0 10.5
下载: 导出CSV
表 3 不同埋深条件下地表位移突增时的支护压力
Table 3. pk under various C/D
C/D 0.5 1.0 2.0 4.0 pk/kPa 6.5 6.0 4.5 4.0
下载: 导出CSV
-
MURAYAMA S, ENDO M, HASHIBA T, et al. Geotechnical aspects for the excavating performance of the shield machines[C]//The 21st Annual Lecture in Meeting of Japan Society of Civil Engineers. Tokyo: [s.n.], 1966: 134-140. KRAUSE T. Schildvortrieb mit flüsigkeits-und erdgestüzter ortsbrust[D]. Brunswick: Technical University Carolo Wilhelmina, 1987. HORN N. Horizontal earth pressure on the vertical surfaces of the tunnel tubes[C]//National Conference of the Hungarian Civil Engineering Industry. Budapest: [s.n.], 1961: 7-16. ANAGNOSTOU G, KOVÁI K. Face stability condition with earth pressure balanced shields[J]. Tunnelling and Underground Space Technology, 1996, 11(2):165-73. doi: 10.1016/0886-7798(96)00017-X BROERE W. Tunnel face stability and new CPT application[D]. Delft: Delft University, 2001. ATKINSON J H, POTTS D M. Stability of a shallow circular tunnel in cohesionless soil[J]. Geotechnique, 1977, 27(2):203-215. doi: 10.1680/geot.1977.27.2.203 DAVIS E H, GUNN M J, MAIR F R, et al. The stability of shallow tunnels and underground openings in cohesive material[J]. Geotechnique, 1980, 30(4):397-416. http://www.nrcresearchpress.com/servlet/linkout?suffix=refg6/ref6&dbid=16&doi=10.1139%2Ft11-078&key=10.1680%2Fgeot.1980.30.4.397 LECA E, DORMIEUX L. Upper and lower bound solutions for the face stability of shallow circular tunnels in frictional material[J]. Geotechnique, 1990, 40(4):581-606. doi: 10.1680/geot.1990.40.4.581 MOLLON G, DIAS D, SOUBRA A H. Face stability analysis of circular tunnels driven by a pressurized shield[J]. Journal of Geotechnical and Geoenvironmental Engineering, 2010, 136(1):215-229. doi: 10.1061/(ASCE)GT.1943-5606.0000194 CHAMBON P, CORTÉ J F. Sallow tunnels in cohesionless soil:stability of tunnel face[J]. Journal of Geotechnical Engineering, 1994, 120(7):1148-1164. doi: 10.1061/(ASCE)0733-9410(1994)120:7(1148) KIRSCH A. Experimental investigation of the face stability of shallow tunnels in sand[J]. Acta Geotechnica, 2010, 5(1):43-62. doi: 10.1007/s11440-010-0110-7 IDINGER G, AKLIK P, WU W, et al. Centrifuge model test on the face stability of shallow tunnel[J]. Acta Geotechnica, 2011, 6(2):43-62. http://www.wanfangdata.com.cn/details/detail.do?_type=perio&id=a70c6918dc14459f22917a817382e04d CHEN R P, LI J, KONG L G, et al. Experimental study on face stability of shield tunnel in sand[J]. Tunnelling and Underground Space Technology, 2013, 33(1):12-21. http://www.sciencedirect.com/science/article/pii/S0886779812001447 VERMEER P A, RUSE N M, MARCHER T. Tunnel heading stability in drained ground[J]. Felsbau, 2002, 20(6):8-18. http://www.wanfangdata.com.cn/details/detail.do?_type=perio&id=CC0211513617 LI Y, EMERIAULTB F, KASTNERB R, et al. Stability analysis of large slurry shield-driven tunnel in soft clay[J]. Tunnelling and Underground Space Technology, 2009, 24(4):472-481. doi: 10.1016/j.tust.2008.10.007 CUNDALL P A, STRACK O D. A discrete numerical model for granular assemblies[J]. Géechnique, 1979, 29(1):47-65. http://d.old.wanfangdata.com.cn/OAPaper/oai_arXiv.org_1208.0565 王俊, 何川, 封坤, 等.砂卵石地层中大断面泥水盾构泥膜形态研究[J].现代隧道技术, 2014, 51(6):108-113. http://d.old.wanfangdata.com.cn/Periodical/xdsdjs201406018WANG Jun, HE Chuan, FENG Kun, et al. Research on the dynamic behavior of the slurry membrane of a large-section slurry shield in a sandy cobble stratum[J]. Modern Tunnelling Technology, 2014, 51(6):108-113. http://d.old.wanfangdata.com.cn/Periodical/xdsdjs201406018 缪林昌, 王正兴, 石文博.砂土盾构隧道掘进开挖面稳定理论与颗粒流模拟研究[J].岩土工程学报, 2015, 37(1):98-104. http://d.old.wanfangdata.com.cn/Periodical/ytgcxb201501011MIU Lingchang, WANG Zhengxing, SHI Wenbo. Theoretical and numerical simulations of face stability around shield tunnels in sand[J]. Chinese Journal of Geotechnical Engineering, 2015, 37(1):98-104. http://d.old.wanfangdata.com.cn/Periodical/ytgcxb201501011 CHEN R P, TANG L J, LING D S, et al. Face stability analysis of shallow shield tunnels in dry sandy ground using the discrete element method[J]. Computers and Geotechnics, 2011, 38(2):187-195. doi: 10.1016/j.compgeo.2010.11.003 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):1234-1242. http://www.emeraldinsight.com/servlet/linkout?suffix=b12&dbid=16&doi=10.1108%2F02644400910996862&key=10.1061%2F(ASCE)1090-0241(2005)131%3A10(1234) Itasca Consulting Group Inc. PFC3D (particle flow code in three dimensions) version 4.0 manual[M]. Minneapolis:Itasca Consulting Group Inc, 2001:101-235. MAIR R J, TAYLOR R N, BRACEGIRDLE A. Subsurface settlement profiles above tunnels in clays[J]. Gétechnique, 1993, 43(2):315-320. MAIR R J. Centrifugal modeling of tunnel construction insoft clay[D]. Cambridge: University of Cambridge, 1979. DYER M R, HUTCHINSON M T, EVANS N. Sudden valley sewer: a case history[C]//International Symposium on Geotechnical Aspects of Underground Construction in Soft Ground. London: [s.n.], 1996: 671-676. -
下载:
点击查看大图
图(16) / 表(3)
计量
- 文章访问数: 598
- HTML全文浏览量: 258
- PDF下载量: 218
- 被引次数: 0