| 砂土地层浅埋盾构隧道开挖渗流稳定性的模型试验和计算研究 |
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| 引用本文： | 米博,项彦勇.砂土地层浅埋盾构隧道开挖渗流稳定性的模型试验和计算研究[J].岩土力学,2020(3):837-848. |
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| 作者姓名： | 米博 项彦勇 |
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| 作者单位： | 北京交通大学城市地下工程教育部重点实验室;北京交通大学土木建筑工程学院 |
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| 基金项目： | 国家重点基础研究发展计划(973计划)项目(No.2015CB057800);中央高校基本科研业务费专项资金(No.2017YJS148)。 |
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| 摘 要： | 针对浅埋盾构隧道开挖渗流对开挖面支护压力和地层失稳模式的影响问题,考虑盾构机开挖仓渣土孔隙水压力和面板及开口率的作用,设计制作了水下地层浅埋盾构隧道的开挖渗流模型并建立了附近地层沉降的量测采集系统。在不同的稳态渗流条件下,逐渐加大盾构隧道开挖仓的进土量,量测开挖面水土压力和孔隙水压力以及附近地层沉降,并配合进行了数值模拟和极限平衡计算分析。研究发现:开挖面有效土压力随开挖体积损失的增加而降低,达到极限值后保持不变;维持开挖面稳定的必要支护压力与可以容许的地层失稳范围有关,开挖面的极限有效土压力与地层的极限失稳范围相对应,是最小的必要支护压力。渗流会使开挖面的极限有效土压力增大,与开挖面-地表之间的水头差大致呈线性关系。渗流会使开挖面前方地层的极限失稳范围增大,但对后方地层极限失稳范围的影响不大;对于开挖面-地表相对水头差较小(小于或等于0.33)的情况,渗流主要起到增大地层沉降量的作用,地层的极限失稳范围只是略有增大;对于相对水头差较大(大于0.33并小于1.00)的情况,渗流主要起到增大地层极限失稳范围的作用,而地层最大沉降量有所减小;对于相对水头差很大(大于或等于1.00)的情况,渗流对地层沉降量的影响和对极限失稳范围的影响都基本上已经达到了极限。地层的极限失稳范围可以自下而上地划分成3个部分,开挖面高度范围内的倒棱锥体,地表以下一定深度范围内的(顶部)倒棱台体,以及两者中间一定高度的(中部)倒棱台体,其中,棱锥体的纵向锥角(或纵向破裂角)及横向锥角(或横向破裂角)都随着相对水头差的增大而增大,对地层极限失稳范围的影响最为显著。
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| 关 键 词： | 砂土地层 浅埋盾构隧道开挖-渗流 开挖面稳定性 模型试验 计算分析 |
Model experiment and calculation analysis of excavation-seepage stability for shallow shield tunneling in sandy ground |
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| MI Bo,XIANG Yan-yong.Model experiment and calculation analysis of excavation-seepage stability for shallow shield tunneling in sandy ground[J].Rock and Soil Mechanics,2020(3):837-848. |
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| Authors: | MI Bo XIANG Yan-yong |
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| Institution: | (Key Laboratory of Urban Underground Engineering of Ministry of Education,Beijing Jiaotong University,Beijing 100044,China;School of Civil Engineering,Beijing Jiaotong University,Beijing 100044,China) |
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| Abstract: | Regarding the influence of seepage on face support pressure and ground collapse mode in shallow shield tunnel excavation,an experimental system composed of a shallow shield tunnel excavation-seepage model and a setup of measurement and data acquisition is designed and established,with consideration of pore water pressure in the excavation chamber and face plate opening ratio.The saturated soil pressures and pore water pressures at the face and settlements of surrounding strata are measured under various steady-state seepage conditions,as the soil input into the excavation chamber is gradually increased.Correspondingly,numerical simulations and limit equilibrium calculations are carried out.The major findings are:the effective earth pressure at tunnel face decreases as excavation volume loss increases,but plateaus after reaching a limit value;the necessary support pressure for face stability is related to the allowable collapse range of the stratum,the limit effective earth pressure,i.e.the minimum necessary support pressure at the tunnel face corresponds to the stratum limit collapse range.Seepage increases the limit effective earth pressure of excavation face,which shows roughly linear relationship with the hydraulic head difference between excavation face and ground surface.Seepage may increase the limit collapse range of the soil ahead of the tunnel face,but has little effect on the limit collapse range of the soil behind tunnel face;if the relative hydraulic head difference between tunnel face and ground surface is small(less than or equal to 0.33),seepage will mainly increase soil settlements,while the stratum limit collapse range only increases slightly;if the relative hydraulic head difference is large(greater than 0.33 and less than 1.00),seepage will enlarge the stratum limit collapse range,whereas the maximum settlement of stratum decreases slightly;if the relative hydraulic head difference is very large(greater than or equal to 1.00),the influences of seepage on both the settlement and limit collapse range of stratum have essentially reached their limits.The stratum limit collapse range may be divided into three zones stacking vertically:an inverted pyramid at the bottom within the height of tunnel face,an inverted prismoid at the top within a certain depth range below the ground surface and an inverted prismoid of a certain height in between;out of these three zones,the tapered angles of the inverted pyramid increase in longitudinal and transverse directions when the relative hydraulic head difference increases,and they exert the most significant influence on the limit collapse range of stratum. |
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| Keywords: | sandy soil shallow shield tunnel excavation seepage stability of tunnel face model experiment calculation analysis |
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