Assessment on tunnel lining to ensure stability in soft ground (original) (raw)
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Journal of Physics: Conference Series
In a shallow tunnel, tunnel construction will triggers a chain of ground movements, resulting in settlements at the ground surface, which become more significant with the decrease in tunnel depth. Therefore, by considering behaviour of the segment tunnel joints (can affect the integrity of tunnel in both circumference and longitudinal directions), the surface settlement trough were investigated. Initial model of dual segmental tunnel lining was model and validated with laboratory test to gain nonlinear response of segment joint. Then, a soil-tunnel simulation model was developed with various segment joint parametric models for Singapore Circle Line Stage 3 (C852) project. Results showed that with the use of flexible segment joints that allow movement (hinge-nonlinear model) in staggered ring tunnel model, the ground deformation depicted higher resemblance of surface settlement pattern to the field data. Steady state settlement was observed after 10m of cutter head distance.
Assessment on Segment Joint to Improve Soil-Tunnel Interaction
MATEC Web of Conferences, 2018
The bending moment of tunnel lining can be influenced by nonuniform ground pressures and joint eccentricities. Influence of joint interaction that induces flexural moment behaviour in segmental tunnel lining was investigated for the project Circle Line Stage 3 (C852), Serangoon Interchange Station. By considering behaviour of segment joint (which can affects the tunnel circumferential and longitudinal safety in overall), the tunnel lining behaviour and displacement of the ground surrounding the tunnel were evaluated. The segment joint modelling in simplified dual-jointed model and in fully soil-tunnel model were developed to assess the effect of segment joint on the overall tunnel response. Ground deformation or settlement trough at the ground surface resulted from the effect of tunnel construction and interaction between soil, tunnel, segment joints and ring joints was predicted. Results showed that with different use of segment joints give different longitudinal settlement. Hinge-nonlinear model together with separated rings model lead to the highest resemblance of surface settlement pattern to the field data when compare to tie model.
Ground Behaviour Around a Tunnel Using Various Soil Models
Electronic Journal of Geotechnical Engineering
Finite Element (FE) analyses are used world widely in geotechnical engineering to obtain the soil displacement caused by tunnelling. The surface settlement induced by tunnelling predicted by FE is known to be wider and shallower than the field measurements particularly for stiff clays with high coefficient of earth pressure at rest, K 0 . It has been recognized that neglecting the non-linearity, anisotropy and three-dimensional effects of the soil model as well as K 0 condition can be the reasons of this discrepancy. Unfortunately, such numerical studies were only limited to the problem in the plane strain condition whereas tunnelling is obviously a three dimensional (3D) problem. This paper compares 3D FE modelling of tunnel constructions in stiff soil of London Clay using non-linear soil model with low and high K 0 regimes. It was found that modelling using isotropic non-linear soil with low value of K 0 gave the best matched-fit data on the observed greenfield surface settlement ...
Liner forces response to very close-proximity tunnelling in soft ground
Japanese Geotechnical Society Special Publication, 2020
Since there are limited literature focused upon the tunnel liner forces response to the very close-proximity tunnelling, a consensus has not yet reached. This study characterised the response of tunnel liner forces to the excavation of soft soil twin tunnels in the very close proximity, with reference to the field measurements and 2D numerical simulations. The "belta" method and the "volume loss" method were to distribute the earth load to the liner and capture the effect of ground loss, respectively, and the "local strain" method was to reproduce the effect of tunnel advance. The predictions were in reasonable agreement with the field measurements except the tunnel invert where the liner might not be in good contact with the surrounding soil. The principle stress change and rotation were analysed. Parametric studies about the joint number and orientation, ground deformability and rotational stiffness of joint were conducted. The critical angles for the distribution of odd number joint were suggested.
IOP Conference Series: Earth and Environmental Science, 2019
Conventional lining design usually considers tunnel lining as a uniform rigid ring model by implying high partial safety factor on the bending moment which is overestimated, due to inaccurate assumptions. To overcome this problem, investigation on the influence of joints on the behaviour of the global lining is significantly important especially when the interaction between segments is included. This paper presents investigation in tunnel segment joint influence on global tunnel lining behaviour especially when the interaction between segments becomes nonlinear, in different type of soil, so that more realistic soil-tunnel lining response can be obtained. The effect of segment joint parameters (linear or nonlinear) and soil parameters was investigated via numerical modelling. The predicted stress and displacement results from the numerical model were verified with the result obtained from field data collection. FEM model of original soil and settlement monitoring data depicted similar pattern of settlement but the FEM model did not captured the sudden settlement at the distance of 40 m from starting point. This was due to the simplification of FEM model and assumption of greenfield. The sand model gave similar result pattern like original case study soil behaviour. Clay model, in opposite, showed heaving at the beginning of construction that caused by the pressure induced by the weight of concrete and moving the water pressure toward the ground. One could conclude that, the elastic settlement profile occurred due to selected parameters of soil and Mohr Coulomb model.
3-D numerical model of jack force interaction to segmental tunnel lining in soft soil
IOP Conference Series: Materials Science and Engineering, 2019
The construction process of a bored tunnel is a complicated process. During tunnelling, loads were acting on tunnel and tunnel lining were installed to support excavation. Simultaneously, soil redistribution induced by tunnel excavation leads to lining to deform. One of the parameters that affect global soil-tunnel behaviour is the jack forces. Jack force is exerted during the tunnel advancement to install the lining and the same time to enhance tunnel face stability. The complexity of jack force application to ensure the overall tunnel stability is not fully studied yet. Hence, the impact of jacking force on segmental tunnel lining and surrounding soil during the tunnel advance is still unclear. This paper presents a numerical simulation by using ABAQUS/Standard 3D FE software to determine and investigate the lining deformations/jacking force relationship. The behaviour of different tunnel lining thickness applied with a variation of jack forces in the tunnel-boring machine (TBM) w...
Acta Geotechnica, 2013
The main purpose of this study was to provide a three-dimensional numerical model, which would allow the tunnel lining behaviour and the displacement field surrounding the tunnel to be evaluated. Most of the processes that occur during mechanized excavation have been simulated in this model. The influence of the lining joint pattern, including segmental lining joints and their connections, has in particular been taken into consideration. The impact of the processes during mechanized excavation, such as the grouting pressure and the jacking forces in the structural forces induced in the tunnel lining, has been presented. These values depend on the tunnel advancement. However, a negligible influence of the joint pattern on the ground displacement field surrounding the tunnel has been observed. Generally, a variation in the structural forces in successive rings along the tunnel axis has been found in a staggered segmental lining, indicating the necessity of simulating the joints in the tunnel lining and using a full three-dimensional numerical model to obtain an accurate estimation. In addition, the considerable influence of the coupling effect between successive rings on the lining behaviour has been highlighted.
Stability Analysis of Different shapes of Tunnel in Cohensionless Soils
IOP conference series, 2023
One of the crucial factors that has gained widespread popularity during the tunnelling construction process is the face stability of tunnel that mainly depends upon the support pressure to be applied at the face of tunnel against the overburden pressure and surcharge loading acting on the earth surface. In this study, stability of different cross sections of tunnels has been investigated in cohesionless soil (loose and medium dense sand) using the Finite Element Analysis software Plaxis 2D V20. Tunnel having cross sectional dimension B as width, D as height positioned at a depth H from the surface of ground. Due to the overburden pressure acting on the face of the tunnel, a suitable uniform compressive pressure is applied at the tunnel periphery in form of lining or anchorage system against the collapse. Variation of deflection at periphery of tunnel is presented for different combinations of H/D and Ф (angle of internal friction of soil), and lining thickness. It is observed that at a particular lining thickness with the increase in H/D, the displacement at the crown in tunnel increases and this could be resisted by increasing the lining thickness. The crown deflection of circular tunnel at particular H/D, lining thickness and Ф was less as compared to semi-circular and square tunnel.
Comparative Study on Different Shape of Tunnel Section
In this paper we have analyzed circular, D-shaped, Horseshoe & rectangular tunnel for a given soil profile. Structural parameters are the main sought information required for designing a tunnel. These parameters mainly depend on the soil parameters and type of section considered. It is a difficult task to select the section of tunnel with wide variation of soil properties. In this study, we have investigated structural performance for different sections of tunnel. A comparative study of displacement, shear force, bending moment at the crown as well as at the side for different section of tunnel has been made. Our study will help us to select a suitable section of tunnel if the soil properties are available and so it will be useful for the tunnel engineering to select the shape for tunnel in the practical application.