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Time-dependent surrounding soil pressure and mechanical response of tunnel lining induced by surrounding soil viscosity

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Science China(Technological Sciences) 2021年第11期64卷 2453-2468页

作者： MIAO JinBo LU DeChun LIN QingTao KONG FanChao DU XiuLi Institute of Geotechnical and Underground Engineering Beijing University of Technology'Beijing 100124China

A numerical simulation method of shield tunnel excavation is developed to capture the time-dependent deformation behaviour of surrounding soil. The simulation method consists of four parts:(i) an elastic-plastic-viscous constitutive model that can not only reasonably describe the viscous deformation behaviour of soil, but also appropriately calculate the plastic deformation under typical stress paths of excavation;(ii) simulation of main factors related to shield tunnel excavation, including the shield machine, face pressure, lining, grout behavior, and contacts between multiple media;(iii) a simulation procedure for excavation to reflect the process of shield tunnel excavation and achieve reasonable stress and strain fields at the end of the construction stage;(iv) a creep process that is used to investigate the long-term mechanical behaviours of the surrounding soil and tunnel lining. Taking the CK570H tunnel project in Taipei as the background, a numerical simulation is conducted by adopting the developed simulation method. Based on the simulation results, the radial and circumferential stresses acting on the lining, which are induced by the surrounding soil viscosity, are analysed. The rule of the mechanical response of lining, including its deformation, bending moment, and axial force, with time is revealed. On this basis, the long-term safety of the lining is evaluated.

关键词： tunnel surrounding soil pressure soil viscosity shield excavation numerical simulation method time-dependent behaviour

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Effects of red-yellow soil acidification on seed germination of Chinese pine

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Journal of Environmental Sciences 2002年第1期14卷 115-119页

作者： TangHS WangRS ResearchCenterforEco－Environmentalsciences ChineseAcademyofSciencesBeijing100085China.E－mail：tanghs@*** ResearchCenterforEco－Environmentalsciences ChineseAcademyofSciencesBeijing100085

Acid treatments significantly change the physical and chemical properties of red yellow soil by lowering its pH value and leaching out aluminum(Al) ions that are harmful to the growth of plants. The structure of soil will be damaged, resulting in higher viscosity, higher water retention rate and lower air permeability of the soil. The germination rate of Chinese pine( Pinus tabulacformic Carr. ) seeds sowed in soil treated with sulphuric acid(H 2SO 4) decreased compared to that for untreated soil. The direct cause was the large amount of Al ions leached out because of low pH values(≥3.5). The added acid decreased the soil aggregation and increased the number of micro aggregates(under 250 μm in diameter). Such changes increased the soil's viscosity, which tied the pine needles to the soil after the seeds had germinated and prevented the seedlings from fully developing.

关键词： aluminum ion germination of Chinese pine red yellow soil soil aggregates soil viscosity

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