V K Kota, A Juneja, R K Bajpai, P Srivastava, G Prabhakar
{"title":"Seismic response of tunnel intersections in jointed rock mass within underground research laboratory: A coupled DEM–DFN approach","authors":"V K Kota, A Juneja, R K Bajpai, P Srivastava, G Prabhakar","doi":"10.1007/s12040-024-02342-y","DOIUrl":null,"url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p>The stability of tunnels in jointed rock masses can be compromised by seismic activity, making it important to understand the characteristics of waves and rock joints. This study investigates the dynamic response of two intersecting tunnels under varying input wavelength and amplitude and the influence of joint density and stiffness on their behaviour using the DEM–DFN approach. A discrete fracture network (DFN) interlay was incorporated into a distinct element method (DEM) model domain to simulate weak zones in rock masses. Analysis shows that higher fracture density reduces shear stress near the DFN interlay, while joint stiffness affects wave transmission, causing a significant drop in shear stress upon wave entry. The increase in joint density and change in interlay thickness intensified the amplification of reflected waves, resulting in wave interference and reduction in transmission waves. For tunnel intersections within the DFN interlay, the larger of the two tunnels, or the main tunnel, experienced substantial deformation when peak ground velocity (PGV) was between 0.05 and 0.25 m/s, while the smaller or access tunnel exhibited maximum displacement only when PGV exceeded this range. Amplification of waves was significant when the ratio of wavelength to tunnel diameter (<i>λ</i>/<i>D</i>) was 10, while <i>λ</i>/<i>D</i> > 75 produced a response similar to uniform quasi-static loading. Tunnel joints with stiffness exceeding 100 GPa/m experienced substantially lower deformations, while those with higher fracture volumetric intensity (<i>P</i><sub>32</sub> = 2 m<sup>2</sup>/m<sup>3</sup>) led to reduced wave propagation. The size of the intersection also influenced the deformation of both tunnels, with larger intersections resulting in greater deformation.</p><h3 data-test=\"abstract-sub-heading\">Research highlights</h3>\n<ul>\n<li>\n<p>The study examines wave propagation through discrete fracture network interlay of varying thickness</p>\n</li>\n<li>\n<p>Dynamic response of intersecting tunnels in jointed rock mass simulated using coupled distinct elements and discrete fracture networks.</p>\n</li>\n<li>\n<p>Investigation of the impact of wavelength, amplitude, joint density, and stiffness on tunnel intersection behaviour.</p>\n</li>\n</ul>","PeriodicalId":15609,"journal":{"name":"Journal of Earth System Science","volume":null,"pages":null},"PeriodicalIF":1.3000,"publicationDate":"2024-07-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Journal of Earth System Science","FirstCategoryId":"89","ListUrlMain":"https://doi.org/10.1007/s12040-024-02342-y","RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q3","JCRName":"GEOSCIENCES, MULTIDISCIPLINARY","Score":null,"Total":0}
引用次数: 0
Abstract
The stability of tunnels in jointed rock masses can be compromised by seismic activity, making it important to understand the characteristics of waves and rock joints. This study investigates the dynamic response of two intersecting tunnels under varying input wavelength and amplitude and the influence of joint density and stiffness on their behaviour using the DEM–DFN approach. A discrete fracture network (DFN) interlay was incorporated into a distinct element method (DEM) model domain to simulate weak zones in rock masses. Analysis shows that higher fracture density reduces shear stress near the DFN interlay, while joint stiffness affects wave transmission, causing a significant drop in shear stress upon wave entry. The increase in joint density and change in interlay thickness intensified the amplification of reflected waves, resulting in wave interference and reduction in transmission waves. For tunnel intersections within the DFN interlay, the larger of the two tunnels, or the main tunnel, experienced substantial deformation when peak ground velocity (PGV) was between 0.05 and 0.25 m/s, while the smaller or access tunnel exhibited maximum displacement only when PGV exceeded this range. Amplification of waves was significant when the ratio of wavelength to tunnel diameter (λ/D) was 10, while λ/D > 75 produced a response similar to uniform quasi-static loading. Tunnel joints with stiffness exceeding 100 GPa/m experienced substantially lower deformations, while those with higher fracture volumetric intensity (P32 = 2 m2/m3) led to reduced wave propagation. The size of the intersection also influenced the deformation of both tunnels, with larger intersections resulting in greater deformation.
Research highlights
The study examines wave propagation through discrete fracture network interlay of varying thickness
Dynamic response of intersecting tunnels in jointed rock mass simulated using coupled distinct elements and discrete fracture networks.
Investigation of the impact of wavelength, amplitude, joint density, and stiffness on tunnel intersection behaviour.
期刊介绍：
The Journal of Earth System Science, an International Journal, was earlier a part of the Proceedings of the Indian Academy of Sciences – Section A begun in 1934, and later split in 1978 into theme journals. This journal was published as Proceedings – Earth and Planetary Sciences since 1978, and in 2005 was renamed ‘Journal of Earth System Science’.
The journal is highly inter-disciplinary and publishes scholarly research – new data, ideas, and conceptual advances – in Earth System Science. The focus is on the evolution of the Earth as a system: manuscripts describing changes of anthropogenic origin in a limited region are not considered unless they go beyond describing the changes to include an analysis of earth-system processes. The journal''s scope includes the solid earth (geosphere), the atmosphere, the hydrosphere (including cryosphere), and the biosphere; it also addresses related aspects of planetary and space sciences. Contributions pertaining to the Indian sub- continent and the surrounding Indian-Ocean region are particularly welcome. Given that a large number of manuscripts report either observations or model results for a limited domain, manuscripts intended for publication in JESS are expected to fulfill at least one of the following three criteria.
The data should be of relevance and should be of statistically significant size and from a region from where such data are sparse. If the data are from a well-sampled region, the data size should be considerable and advance our knowledge of the region.
A model study is carried out to explain observations reported either in the same manuscript or in the literature.
The analysis, whether of data or with models, is novel and the inferences advance the current knowledge.
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