Tunnelling-induced Ground Movements Research Articles

Assessment of Building Response Supported on Shallow Foundation Due to Tunnelling in Cohesionless Soil

The depth of foundations significantly influences the building response due to tunnelling-induced ground movement. The present study investigates the responses caused by tunnelling on buildings supported on isolated footings. The response of buildings supported on shallow foundation systems due to progressive tunnelling is investigated through experimental and numerical methods. A three-dimensional finite element analysis (3D FEM) has been developed to evaluate the response of an existing reinforced cement concrete (RCC) building underpasses a circular-shaped tunnel in cohesionless soil. The model includes soil strata, footings, super-structure, and tunnel. Different parametric studies, i.e., C/D ratios, tunnel volume losses, and eccentricity of the building, have been considered in the present study. A scale-down model of the tunnel and building is prepared in the laboratory. The scale-down model simulates the volume loss during tunnelling and evaluates the response on surface and building components due to tunnelling. The surface settlement, total and differential settlement of the foundation, and induced strain on lining and building elementals are estimated. The numerical model is benchmarked with the experimental study conducted in the laboratory. It is observed that the numerical method agrees well with the experimental investigation. The responses of buildings supported on shallow footings are compared with available literature. The findings of the present study will be useful for the hazard estimation of existing buildings situated along/adjacent to a proposed alignment of the tunnel.

Analysis of tunneling-induced ground movements in spatially variable soil under the influence of existing building

Tunnel construction invariably results in ground movement, which is significantly impacted by the spatial variability of soil properties and proximity of existing buildings. However, few studies have examined the coupled effect of these two factors on tunneling-induced ground movement. This study establishes a stochastic finite element model that incorporates both the spatial variability of soil properties and influence of existing buildings. The model is used to perform a series of random analyses, studying the effects of story number, eccentricity, and building length on ground settlements induced by tunneling in soil with spatial variability of Young’s modulus. A probabilistic analysis is conducted to investigate the uncertainties associated with ground settlements. The results of the analysis indicate that the presence of the building enhances the influence of the spatial variability of soil, leading to an increase in the dispersion of ground settlement. For high-rise buildings, the reduction of building eccentricity and length will increase the uncertainty of surface settlement. Neglecting the influence of the existing building in the probability analysis of surface settlement can result in an overestimation of the failure probability.

Twin-tunnelling: Case studies in clay

New developments in the theory and practice of tunnel construction are essential for the industry to progress but it is the relationship between these two areas that is equally as important. Tunnelling practice has greatly benefited from laboratory research; specifically, centrifuge modelling linked with field measurements. The wide body of work on the construction of single tunnels has led to the identification of parameters and techniques that are widely accepted for predicting and assessing the magnitude and extent of tunnelling ground movements. However, the usage of twin tunnels in urban areas for transportation purposes have increased and better understanding on the associated ground displacements are required. This paper firstly provides background to ground displacements due to single tunnel, twin tunnel constructions and common prediction methods used in practice. Then, it introduces recent technological advancements in centrifuge modelling, applied to the complex geotechnical events of twin-tunnelling, that has led to further insight. The tunnelling induced ground displacements obtained from twenty four case studies in clay around the world and eighteen centrifuge tests are presented for further analyses. From that, a comparison between the recent theories of proximity-dependent tunnelling-induced ground movements with case histories has been carried out to establish their validity and limitations. Published field measurements have been reanalysed taking into account newly discovered relationships between the tunnels’ proximity and the magnitude and extent of ground movements, reflected via volume loss and the settlement trough width, respectively. The applicability to field measurements of the additional volume loss prediction method (derived from consideration of the experiment work) for tunnelling in clay is assessed.

An innovative and simple approach for predicting tunnelling-induced ground movements semi-analytically

ABSTRACT A semi-analytical elastic solution for predicting tunnelling-induced ground movements in clayey media is presented in this study. This study modelled the non-uniform ground movements (or non-uniform ground loss) around the tunnel cavity using the Gaussian distribution function. A new approach is proposed to model the tunnel peripheral displacements other than the simplistic trigonometric functions. It is shown that by modelling the ground loss in an elliptical fashion, (i) better prediction of ground surface settlements is obtained compared to the circular ground loss in some cases, while (ii) in other cases, circular ground loss gives better predictions. This indicates that both these approaches should be used to predict the ground surface settlements. Further, the ground displacements observed in East-West Metro, Kolkata, are discussed as a case study. The semi-analytically obtained displacements give good conformity with the observed field measurements in East-West Metro. This solution is much simpler to follow and can be easily employed in a code compared to the complex variable method or airy stress function method.

Prediction of tunnelling induced ground movement in clay using principle of minimum total potential energy

The accurate prediction of tunnelling induced ground movement is of practical and theoretical significance. This paper proposes a mixed empirical-analytical method based on the principle of minimum total potential energy to predict the ground movement due to tunnelling in undrained clay. The proposed method considers the plastic behaviour of the soil. Based on the theory of curvilinear Euler beam, the proposed method considers the soil-lining interaction, which is simplified as a constant force in classical MSD methods. Moreover, the proposed method can deal with the deformation mechanism with multiple undetermined parameters. The tunnelling-induced ground movement can be found by minimizing the total potential energy of the concerned system composed of soil and lining. Four well-documented tunnelling projects are adopted to evaluate the applicability of the proposed method. The results reveal that our method provides better predictions of both surface and subsurface settlements above the tunnel than the other two semi-analytical methods. Moreover, our method excels the other two methods in predicting the tunnelling projects with large gap parameter values as it considers the plastic behaviour of the soil.

Three-dimensional numerical analyses of pile responses to tunneling-induced ground movements in bilayer soil

PurposeThis paper aims to investigate the responses of single piles and pile groups due to tunneling-induced ground movements in a two-layered soil system. The analyses mainly focus on the additional single pile responses in terms of bending moment, lateral deflection, axial force, shaft resistance and pile settlement. Subsequently, a series of parametric studies were carried out to better understand the responses of single piles induced by tunneling. To give further understanding regarding the pile groups, a 2 × 2 pile group with two different pile head conditions, namely, free and capped, was considered.Design/methodology/approachUsing the PLAXIS three-dimensional (3D) software, a full 3D numerical modeling is performed to investigate the effects of ground movements caused by tunneling on adjacent pile foundations. The numerical model was validated using centrifuge test data found in the literature. The relevance of the 3D model is also judged by comparison with the 2D plane strain model using the PLAXIS 2D code.FindingsThe numerical test results reveal that tunneling induces significant displacements and internal forces in nearby piles. The magnitude and distribution of internal forces depend mainly on the position of the pile toe relative to the tunnel depth and the distance between the pile and the vertical axis of the tunnel. As the volume loss increases from 1% to 3%, the apparent loss of pile capacity increases from 11% to 20%. By increasing the pile length from 0.5 to 1.5 times, the tunnel depth, the maximum pile settlement and lateral deflection decrease by about 63% and 18%, respectively. On the other hand, the maximum bending moment and axial load increase by about 7 and 13 times, respectively. When the pile is located at a distance of 2.5 times the tunnel diameter (Dt), the additional pile responses become insignificant. It was found that an increase in tunnel depth from 1.5Dt to 2.5Dt (with a pile length of 3Dt) increases the maximum lateral deflection by about 420%. Regarding the interaction between tunneling and group of piles, a positive group effect was observed with a significant reduction of the internal forces in rear piles. The maximum bending moment of the front piles was found to be higher than that of the rear piles by about 47%.Originality/valueSoil is a complex material that shows differently in primary loading, unloading and reloading with stress-dependent stiffness. This general behavior was not possibly being accounted for in simple elastic perfectly plastic Mohr–Coulomb model which is often used to predict the behavior of soils. Thus, in the present study, the more advanced hardening soil model with small-strain stiffness (HSsmall) is used to model the non-linear stress–strain soil behavior. Moreover, unlike previous studies THAT are usually based on the assumption that the soil is homogeneous and using numerical methods by decoupled loadings under plane strain conditions; in this study, the pile responses have been exhaustively investigated in a two-layered soil system using a fully coupled 3D numerical analysis that takes into account the real interactions between tunneling and pile foundations. The paper presents a distinctive set of findings and insights that provide valuable guidance for the design and construction of shield tunnels passing through pile foundations.

Modified Peck method of evaluating tunnelling-induced ground movements based on measured data

Modified Peck method of evaluating tunnelling-induced ground movements based on measured data

Effects of New Tunnelling on a Buried Pipeline with Joints and Its Detachment

The interactions between the buried pipeline and tunnelling-induced ground movement are studied in this paper, in which the jointed pipeline, Pasternak foundation, and the detachment are considered. A mathematical model using the pulse function is provided to simplify the jointed pipeline to a continuous pipeline with additional local rotations. The determination of detachment is used by the usual iteration method. The finite difference method is utilized to obtain the numerical results. The results calculated by our proposed method agree with the experimental data of centrifuge tests and are close to those obtained by the other methods. The deflection and bending moment of the jointed pipeline can be predicted reasonably, as well as its detachment location. Parametric analyses about the main influencing factors are carried out. The stiffness reduction factor is significant to the discontinuous behavior of the jointed pipeline. During the parametric analyses, the detachment beneath the jointed pipeline sometimes happens and sometimes does not. The responses of the jointed pipeline and its detachment require priority attention.

Behaviours of existing shield tunnels due to tunnelling underneath considering asymmetric ground settlements

New tunnelling underneath could influence existing shield tunnels in underground spaces. The evaluation of the influences of tunnelling-induced ground movements on existing tunnels has been a major concern during urban construction. This paper presents a two-stage analytical method that considers the asymmetric ground settlement for investigating the longitudinal tunnel responses to new tunnelling. An improved semi-analytical solution considering the horizontal movement of the new tunnel is established for evaluating the tunnelling-induced asymmetric greenfield settlement. The proposed method is verified with field measurement data from a case study. A parametric analysis is conducted to study the influences of the input parameters on the tunnel responses. Results indicate that the horizontal movement of the new tunnel due to bias loading or asymmetric construction may lead to asymmetric responses of the existing tunnel. With increasing tunnel horizontal movement, the asymmetry of the tunnel responses becomes more obvious. An increase in the pillar depth and decreases in the tunnel horizontal movement and skew angle lower the internal forces induced by new tunnelling.

Time-dependent analyses for ground movement and stress field induced by tunnelling considering rainfall infiltration mechanics

The evaluation of influence of heavy rainfall on tunnel structural construction is a problem being faced by engineers around the world. Current analytical solutions on the tunnelling-induced ground movements are generally based on the normal sunny weather and provide little attention on the rainfall intensity and duration risk. In this paper, a time-dependent complex variable approach is proposed to estimate the deformation and stress of surrounding soils caused by tunnelling considering the rainfall infiltration mechanisms. The modified Green-Ampt model under the assumption of stratification is used to simulate the rainfall infiltration process and the complex function theory is employed to calculate the subregion mapping for the saturated, transitional, and natural layers. The non-uniform convergence deformation boundary is adopted at the tunnel structure opening so as to consider the displacement controlled excavation effects due to tunnelling. The analytical presented solution is then verified by comparisons with a total of three engineering case records. It is revealed that the presented complex variable solution considering the rainfall infiltration mechanism can provide a prediction of surface settlement, soil subsidence and horizontal displacement in good agreements with the field measurements. Finally, the parameters that affect the ground deformation and stress induced by tunneling in rainy day, including the rainfall intensity, saturated permeability, matric suction, initial water content, are studied. The paper contributes to provides a relatively quick and easy way of accurately evaluating the time-dependent feedback in tunnel-soil interaction system involving heavy rainfall as a potential risk in the preliminary design of tunnel structures considering the adverse weather condition.

A Simplified Method for Predicting Tunneling-Induced Ground Movement considering Nonuniform Deformation Boundary

Stochastic medium (SM) theory is a practical method in ground settlement prediction, while its nonintegrable double integral form makes the solution process complicated. A simplified analytical solution based on the SM theory is developed to predict the ground movement in tunneling excavation. With the simplified solution, the ground movement for single tunnel and twin tunnels could be predicted based on the gap parameter G and influence angle β. A feasible approach is developed to estimate these two parameters using the maximum ground settlement Smax and tunnel design parameters, including tunnel depth H and diameter R. The proposed approach can be used to predict the ground movement curve for both circular and noncircular cross section tunnels. To validate its accuracy, the results predicted by the simplified procedure are compared with those obtained by the SM theory and measured in situ. The comparisons show that the current results agree well with those obtained by the SM theory and measured in situ. The comparison of five tunnels in literature illustrates that the simplified method can provide a more reasonable prediction for the ground movement induced by tunneling.

Method for Probabilistic Assessment of Tunneling-Induced Damage to Surface Structures Considering Soil-Structure Interaction Effects

AbstractA new method is presented to quantify the uncertainty in early-stage assessment of surface structure damage caused by tunneling-induced ground movements. The method employs the Monte Carlo ...

Centrifuge and theoretical study on tunnel-raft interaction in clay

Tunnelling induced ground movement may affect adjacent raft foundations. A series of centrifuge model tests was performed to investigate the settlement and induced strain profiles of rafts of different rigidities due to tunnelling. The results reveal that the theoretical relationship between raft bending strain and deflection ratio derived from a simply supported centrally loaded Timoshenko beam is not able to predict the bending strain and raft settlement in certain situations. An elastic-continuum-based simplified method considering raft weight and soil-raft separation is then presented and first verified against the results of centrifuge tests. Parametric studies were further conducted to investigate the effect of the raft-soil relative location on the relationship between deflection ratio and bending strain. The results reveal the original deflection ratio cannot fully capture the deflection characteristic of the raft settlement due to tunnelling. A modified deflection ratio is proposed to better characterize different raft settlement profiles.

Centrifuge application of fibre Bragg gratings: pile axial loads and wall bending moments

One challenge for geotechnical centrifuge testing of soil–structure interaction problems is the reliable measurement of induced structural strains/forces. This paper presents a novel application of fibre Bragg grating (FBG) sensors for strain measurement within geotechnical centrifuge tests. FBG sensors have several advantages for centrifuge testing, in particular their small size and minimal self-weight. This paper gives an overview of recently developed installation and calibration procedures for FBG sensors within buried centrifuge model structures. The effect of thermal expansion/contraction of the materials (including both the fibre and structures) is considered and assessed. The precision and reliability of the FBG sensors are demonstrated using verification tests. The application of the FBG sensors is considered for two geotechnical problems, namely, pile jacking and a ‘retaining wall’ adjacent to a tunnel (acting as a protective wall to prevent an adjacent structure from tunnelling-induced ground movement). The results demonstrate that the FBG sensors can provide reliable measurements of pile axial strains/forces and protective wall bending moments. The paper provides evidence to support the routine adoption of FBG sensors for strain/force measurement of structures in geotechnical centrifuge modelling.

Cracked Equivalent Beam Models for Assessing Tunneling-Induced Damage in Masonry Buildings

This paper proposes simple numerical models that simulate the influence of tunneling-induced ground movements on masonry buildings founded on shallow strip footings. The focus is on developing an improved understanding of the impact of structural discontinuities due to pre-existing cracks and joints between adjacent buildings. The soil–structure system is idealized with equivalent Timoshenko beams connected to a homogenous elastic half-space with rigid links. The flexibility of the equivalent beam at the location of the crack or building interface is determined using linear-elastic fracture mechanics. The proposed models are first applied to a generic numerical example. Then, they are used to interpret the detailed displacement and strain measurements gathered from a masonry church during nearby tunneling. The results show that pre-existing cracks can have variable influence on the soil–structure interaction depending on their extent and position relative to the building and settlement trough. For the investigated case study, the proposed models illustrate how pre-existing large cracks in the hogging zone localized deformations and how the interaction between adjacent buildings drastically altered response mechanisms.

Analytical prediction of time-dependent behavior for tunneling-induced ground movements and stresses subjected to surcharge loading based on rheological mechanics

Current analytical solutions on the ground movements and stresses induced by shield tunneling in soft soils are generally based on the instantaneous excavation behavior. Furthermore, previous studies seldom took account of the influence of surcharge loading during tunnel excavation process. This paper introduces a complex variable analytical solution to estimate the deformation and stress of surrounding soils caused by shield tunneling subjected to surcharge loading considering the soil rheological mechanisms. The non-uniform convergence deformation boundary is adopted at the tunnel opening and the Boltzmann viscoelastic model is employed in the time-domain solution so as to consider the displacement controlled boundary and the rheological effects. The accuracy of complex variable time-dependent solution is then verified by comparisons with in-situ observed data, and good consistency is obtained. Finally, the parametric analyses are performed to evaluate the influence of correlative coefficients in Boltzmann viscoelastic model and paramount factors of surcharge loading on the feedback around tunneling. The ratios of the peak values of final surface settlements induced by tunneling in viscoelastic soils to those in elastic soils in the initial period vary approximately from 40% to 120%. The soil stresses around the tunnel increase about 50% significantly over time.

Centrifuge modelling of tunnelling induced ground displacements: pressure and displacement control tunnels

Predicting the impact of tunnelling-induced ground movements on existing foundation systems or infrastructure is an important stage during tunnel design or risk assessment processes. Centrifuge modelling has been used extensively as a tool to study soil movements caused by tunnelling and their interactions with existing structures. In 2D plane-strain centrifuge models, tunnel volume loss can be simulated in a variety of ways, but is conventionally done using a fluid-filled flexible membrane or a rigid boundary mechanical model tunnel. The choice of model tunnel has an impact on the imparted tunnel boundary displacements and resulting ground deformations, yet a thorough quantitative evaluation of these effects has not been conducted. This paper aims to address this by contrasting plane-strain centrifuge test results from experiments using a flexible membrane model tunnel with those from a newly developed eccentric rigid boundary mechanical model tunnel. A quantitative assessment of surface and subsurface settlement trough characteristics as well as soil shear and volumetric response is provided. Results from numerical analyses using a hypoplastic constitutive model are also included, focusing on evaluating centrifuge spin-up effects and contrasting numerical outcomes with experimental data relating to settlement trough characteristics and soil shear/volumetric response. The outcomes of this paper should benefit future researchers considering which type of model tunnel to adopt when developing centrifuge tests related to 2D plane-strain tunnel modelling.

Semi-analytical prediction for tunnelling-induced ground movements in multi-layered clayey soils

This paper develops a semi-analytical method to calculate the ground movements due to tunnelling in multi-layered clayey soils which are usually encountered in urban areas. The proposed method is based on the modified Loganathan-Poulos formula combined with the elastic equivalent theory. The key issue disposed in current study is the transformation of the boundary of excavation and the boundary after convergence from multi-layered soil system into single layer soil system. The proposed method is verified through the comparisons with previous associated studies associated with the field measurements from five well-documented cases. A parametric study based on the situation that the interlayer is arranged between the upper and lower soil layer is conducted to explore the effects of the mechanical properties and dimensional variables of the interlayer on ground settlements. The results indicate that the soil stratification has a significant impact on ground movements induced by tunnelling in multi-layered clayey soils.

Effects of Tunneling-Induced Ground Movements on Stability of Piled Raft Foundation: Three-Dimensional Finite-Element Approach

Abstract Across the globe, rapid urbanization demands the construction of tunnels within the vicinity of high-rise buildings supported on piled raft foundations. As a consequence, ground movements ...

A DEM-based study of the disturbance in dry sandy ground caused by EPB shield tunneling

A discrete element method simulation was used to evaluate tunneling-induced ground movement and the parameters of tunnel boring machines. The process of excavation by an Earth Pressure Balance (EPB) shield machine, including soil excavation with a cutter head, soil conditioning in the chamber, and removal of the excavated soil with a screw conveyor, is modeled using the Discrete Element Method (DEM). Deformation of the surface and subsurface of the ground in a sandy soil were studied for different tunnel burial depths and different screw conveyor rotation speeds with a constant advance rate. In addition, machine parameters, such as the cutter head torque, the normal pressure on the cutter head, the screw conveyor torque, and the chamber pressure also were analyzed. The results of the DEM model were found to be in good agreement with results reported in the literature. The method showed great potential for the analysis of both tunneling-induced ground movement and ground-machine interactions. It was determined that the distribution of the pressure of the soil in the chamber was non-linear, especially near the screw conveyor. The pressure of the soil in the chamber, the torque of the machine, and the normal pressure on the cutter head increased with the depth of excavation until a depth was reached at which stress arching occurred in the soil. Changes in the depth of excavation had little effect on the torque of the screw conveyor.