Evaluation of the collapsible deformation of surrounding rock of loess hydraulic tunnel considering ground stress variation

IF 3.8 Q2 ENVIRONMENTAL SCIENCES Geoenvironmental Disasters Pub Date : 2023-11-15 DOI:10.1186/s40677-023-00257-2
She Fangtao, Xu Wanying, Liu Lele, Liu Guoping, Li Lei, Duan Changhui
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Abstract

Uneven settlement will occur as a result of the collapsible deformation of the loess strata, and the hydraulic tunnel lining structure will also fail. In this work, laterally confined compression tests were carried out on loess and the double-line method was employed to evaluate the loess collapsibility. The deformation of the surrounding rock of a loess hydraulic tunnel under various ground stresses and its effect on the lining structure was modeled. Three stages were noted in the collapsible deformation of loess. The critical point between the former two stages corresponds to the pre-consolidation pressure of saturated loess and that between the latter two is taken as the structural yield pressure of unsaturated loess. From the relationship between the collapsibility coefficient and vertical stress, the deformation of the tunnel under ground seepage primarily originates from two sources, i.e., the collapsible and compressive deformation. The latter source accounts for the deformation of loess adjacent to the lining when the seepage depth is low, while both sources are included when the bottom of the tunnel invert is infiltrated. The collapsible deformation is lower than that of the original stratum due to the stress relaxation during tunnel excavation. The tensile and compressive stresses of tunnel lining increase linearly with the seepage depth, with the maximum appearing at a position of 20 m away from the midline of the collapse and non-collapse domains. The results will provide a theoretical reference to the design and construction of hydraulic tunnels in collapsible loess stratum.
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考虑地应力变化的黄土水工隧洞围岩湿陷变形评价
黄土地层的湿陷变形会造成不均匀沉降,水工隧道衬砌结构也会发生破坏。本文对黄土进行了侧限压缩试验,并采用双线法对黄土湿陷性进行了评价。模拟了黄土水工隧道围岩在不同地应力作用下的变形及其对衬砌结构的影响。黄土的湿陷变形分为三个阶段。前两个阶段之间的临界点对应于饱和黄土的预固结压力,后两个阶段之间的临界点对应于非饱和黄土的结构屈服压力。从湿陷系数与竖向应力的关系来看,地下渗流作用下隧道的变形主要来源于两个来源,即湿陷变形和压缩变形。渗流深度较低时,后一种源考虑了衬砌附近黄土的变形,而当隧道仰拱底部被渗透时,这两种源都包括在内。隧道开挖过程中,由于应力松弛,围岩的湿陷变形小于原地层的湿陷变形。隧道衬砌的拉压应力随渗流深度的增加呈线性增加,最大应力出现在距离塌落区和非塌落区中线20 m处。研究结果将为湿陷性黄土地层水工隧道的设计和施工提供理论参考。
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来源期刊
Geoenvironmental Disasters
Geoenvironmental Disasters Social Sciences-Geography, Planning and Development
CiteScore
8.90
自引率
6.20%
发文量
22
期刊介绍: Geoenvironmental Disasters is an international journal with a focus on multi-disciplinary applied and fundamental research and the effects and impacts on infrastructure, society and the environment of geoenvironmental disasters triggered by various types of geo-hazards (e.g. earthquakes, volcanic activity, landslides, tsunamis, intensive erosion and hydro-meteorological events). The integrated study of Geoenvironmental Disasters is an emerging and composite field of research interfacing with areas traditionally within civil engineering, earth sciences, atmospheric sciences and the life sciences. It centers on the interactions within and between the Earth''s ground, air and water environments, all of which are affected by climate, geological, morphological and anthropological processes; and biological and ecological cycles. Disasters are dynamic forces which can change the Earth pervasively, rapidly, or abruptly, and which can generate lasting effects on the natural and built environments. The journal publishes research papers, case studies and quick reports of recent geoenvironmental disasters, review papers and technical reports of various geoenvironmental disaster-related case studies. The focus on case studies and quick reports of recent geoenvironmental disasters helps to advance the practical understanding of geoenvironmental disasters and to inform future research priorities; they are a major component of the journal. The journal aims for the rapid publication of research papers at a high scientific level. The journal welcomes proposals for special issues reflecting the trends in geoenvironmental disaster reduction and monothematic issues. Researchers and practitioners are encouraged to submit original, unpublished contributions.
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