Publications
142 results found
Ruiz Lopez A, Tsiampousi A, Standing J, et al., 2024, A new model for simulating the behaviour of grey cast iron tunnel joints with structural elements in geotechnical analysis, Engineering Structures, Vol: 304, ISSN: 0141-0296
Recent developments have demonstrated that the behaviour of segmental grey cast iron (GCI) tunnel linings can be simulated accurately with sophisticated 3D numerical models where the geometry of the segments and joints is considered explicitly. Such a 3D model is, however, impractical for geotechnical numerical analyses where the tunnel lining is usually simulated with simpler, structural elements. In this paper, a novel tunnel joint model specifically developed for simulating the behaviour of GCI longitudinal joints with beam elements in geotechnical finite element analysis is introduced. Unlike existing models, the model considers the contribution of the bolts to the joint response and the nonlinear decay of the rotational stiffness after joint opening as well as the dependency on the compression level. After calibration of the model parameters, the model was utilised in a series of parametric analyses replicating the elastic continuum model using 2D beam elements. The response of the segmental GCI lining was essentially equivalent to that predicted by an advanced 3D model which validated the new modelling approach. The development of the joint beam model enables the nonlinear behaviour of segmental GCI tunnel linings to be accounted for in routine geotechnical numerical analyses.
Ruiz López A, Tsiampousi A, Standing JR, et al., 2023, The influence of tunnel joints on the present-day condition of a grey cast iron tunnel, Computers and Geotechnics, Vol: 164, Pages: 1-18, ISSN: 0266-352X
The present-day condition of a grey cast iron (GCI) tunnel was investigated numerically by means of a series of plane-strain geotechnical analyses that focused on establishing the influence of the modelling approach adopted to simulate the behaviour of longitudinal tunnel joints. The GCI tunnel lining was simulated in three different ways: (i) as a continuous lining; (ii) as a jointed lining adopting a simple joint model that neglects the presence of the joint bolts and (iii) as a jointed lining adopting a more sophisticated model that considers both the nonlinear response of the joint after opening and the contribution of the bolts to the ultimate capacity. The numerical results demonstrate that accounting for the tunnel joints has a considerable impact on the tunnel response. Significant differences are also observed in the results obtained with the two joint models, hence demonstrating the practical significance of employing an advanced model able to reproduce accurately the rotational behaviour of the joint. The drainage behaviour of the joints was also investigated and the numerical results indicate that drainage even through only the knee joints causes significantly more soil consolidation than that from a watertight tunnel and consequently, larger tunnel deformations and forces.
Foo CF, Le T, Bailie P, et al., 2023, Back-analysis of an embedded retaining wall in stiff clay, Proceedings of the Institution of Civil Engineers - Geotechnical Engineering, Pages: 1-44, ISSN: 1353-2618
The performance of embedded retaining walls during and after excavation is commonly predicted using numerical techniques and assessed by field monitoring. However, subsequent back-analyses of post-construction monitoring data are rarely undertaken. The purpose of this paper is two-fold: (i) to provide a comprehensive post-construction review of site information and monitoring data from a construction site in central London and (ii) to detail results from a parametric study undertaken as part of the back-analyses of five key embedded retaining wall sections. The importance of accounting for the effects of non-linear soil stiffness when predicting wall deflection profiles is highlighted by the parametric study. Good agreement between the numerical model and field monitoring data was achieved through the back-analysis exercise. Differences in the predicted Class C wall deflection profiles are attributed to varying temporary support systems and complex 3D site geometry. Best practice recommendations relating to field monitoring and a new streamlined methodology for performing similar back-analyses are proposed.
Ruiz López A, Tsiampousi A, Standing JR, et al., 2023, Numerical characterisation of the rotational behaviour of grey cast iron tunnel joints, Computers and Geotechnics, Vol: 159, Pages: 1-17, ISSN: 0266-352X
The structural assessment of segmental grey cast iron (GCI) tunnel linings to nearby construction is challenging due to the presence of the joints affecting the stiffness of the tunnel lining. This paper presents an extensive investigation, using 3D finite element (FE) analyses, into the bending moment-rotation (M-θ) behaviour of two GCI tunnel joint geometries. These two geometries correspond to standard running and station tunnels of the London Underground network. The contribution of this study is two-fold. i) The novel characterisation of the M-θ response enables the development of new models for simulating the mechanical response of GCI tunnel joints with structural elements which can be used in simplified, 2D geotechnical analysis for tunnel safety assessments. ii) The analyses provide insight into the behaviour of GCI tunnel linings that would be difficult to achieve through experimental and field observations alone. More specifically, the analyses show that when the bolts are removed from the joints the possibility of tensile failure can be disregarded; that the initial bolt preload influences the rotational stiffness only after some rotation has taken place and does not alter the bending moment of opening; and that the out-of-plane displacement restraint has little influence on the joint response.
Le T, Standing J, Potts D, 2023, Reassessing variations in the small-strain stiffness of London Clay, Géotechnique, Pages: 1-15, ISSN: 0016-8505
High-quality rotary core samples of natural London Clay were taken during installation of subsurface instrumentation to monitor the ground response at Hyde Park, London, to the construction of Crossrail tunnels. An extensive programme of advanced triaxial tests was performed on specimens from London Clay divisions A3 to C. Detailed analysis of their response to undrained shearing in compression from their estimated in situ stress state provides new insights into the magnitude of and changes in stiffness at small- and medium-strain levels. A consistent trend in the variation of small-strain stiffness with depth and lithological division is established for the Hyde Park research site. Differences between the stiffness magnitudes from this investigation and those reported earlier by others are shown to be a result of the conditions before and during undrained shearing, particularly the ratio of shearing axial strain rate to the preceding creep strain rate. This provides an explanation for significant discrepancies in small-strain stiffness values reported in recent years, which have led to uncertainties regarding which values to adopt, particularly for numerical analysis applications. Understanding the relevance of the axial shearing to creep rate ratio allows for improved triaxial testing techniques and the subsequent interpretation of the test data.
Le T, Airey D, Standing JR, 2022, Influence of shearing strain-rate on the mechanical behaviour of three structured clays, Géotechnique, Pages: 1-51, ISSN: 0016-8505
This paper presents the stress–strain behaviour of three structured clays subjected to a number of stepwise changes in strain rate during shearing in a triaxial apparatus. Undrained compression tests were performed on clay specimens in both undisturbed and reconstituted states. As a result, it has been possible to identify the influence of structure on the rate-dependent response of the clays. Step changes in applied shearing strain rates for all tests resulted in predominately isotache-type behaviour within the range of strains from very small strains to large strains at failure. At very small strains, evidence of a limiting elastic modulus was established for both the stiff sedimentary and artificially cemented soil, which is consistent with published literature on other structured geomaterials. The stress–strain behaviour of all three materials was affected by both the degradation of structure with increasing strain and applied strain rate. The influence of structure on the time-dependent behaviour of the clays is discussed by comparing the response of undisturbed and reconstituted specimens and following normalisation by the equivalent pressure. Results indicate that the rate sensitivity evolves with increasing strains and reaches a maximum at strain levels associated with peak shearing resistance.
Farrell S, Standing J, 2022, Monitoring the impact of tunnelling-induced ground movements on a gas main and sewer, 11th International Symposium on Field Monitoring in Geomechanics
Waldron F, Standing J, 2022, Monitoring the response of a piled building to tunnelling using different techniques, 11th International Symposium on Field Monitoring in Geomechanics
Le T, Airey D, Standing J, 2022, Creep behaviour of structured clays in triaxial stress space: theory and experimental investigation, International Journal of Geotechnical Engineering, Vol: 16, Pages: 682-699, ISSN: 1938-6362
This paper investigates the time-dependent behaviour of structured clays in triaxial stress space both theoretically and experimentally. A range of existing theoretical frameworks and phenomenological equations are reviewed and discussed in their ability to interpret the creep behaviour at different states in q:p′ stress space. New experimental results are presented for two structured clays subjected to complex loading conditions. Each test consists of a defined stress path with intermediate stages of creep. Considerable creep deformations were observed at all anisotropic effective stress conditions. Measured viscous deformations were observed to be related to the stress state, approaching stress path and degree of structure present in the soil. The incremental strain ratio, Δεs/Δεvol, measured during constant stress was found to rotate counter-clockwise as a result of drained shearing towards failure for all tests. The experiments also show that for very small stress increments, phenomenological and empirical relations incorrectly predict the development of creep strains with time.
Shire T, Standing J, 2022, Strength and stiffness properties of an unsaturated clayey silt: experimental study at high degrees of saturation, International Journal of Geomechanics (ASCE), Vol: 21, ISSN: 1532-3641
Unsaturated constant water content triaxial compression tests with suction measurement using an Imperial College Tensiometer, and saturated consolidated undrained tests were carried out on reconstituted Brickearth, a naturally unsaturated clayey silt from London. The results show that the saturated effective stress can be applied to the critical state line (CSL) and normalised stiffness for unsaturated Brickearth but that Bishop’s effective stress variable gives a slightly improved CSL. The stiffness derived from local instrumentation demonstrates that Bishop’s effective stress is also beneficial for normalising the stiffness 16modulus over the small strain range (up to axial strainsofabout3%).
Ruiz Lopez A, Tsiampousi A, Standing J, et al., 2022, Numerical investigation of a segmental grey cast iron tunnel ring: validation with laboratory data and application to field conditions, Computers and Geotechnics, Vol: 141, Pages: 1-19, ISSN: 0266-352X
The structural response of a segmental grey cast iron (GCI) tunnel lining ring under distortion was investigated by means of finite element (FE) analysis. Building on previous experimental investigations, a 3D numerical model, capable of reproducing accurately the behaviour observed in the laboratory, was developed with the aim of providing guidelines for the structural assessment of GCI linings in engineering practice. A comprehensive validation of the segmental ring model with the laboratory data was first completed. Subsequently, a parametric study was conducted using a set-up that replicated the widely adopted elastic continuum method, so that differences between the numerical and the analytical solution could be attributed to the presence of the longitudinal joints. In this manner, the influence of the joints on the ring response was quantitatively established and recommendations for routine engineering calculations developed. A set of bending stiffness reduction factors are proposed as a function of the tunnel ovalisation, providing upper and lower limits of the bending stiffness, as well as a global reduction factor which is an average measure of the bending stiffness reduction. These factors can be integrated into the calculation procedure of closed-form solutions in order to account for the segmental nature of GCI linings.
Standing J, vaughan P, charles-jones S, et al., 2021, Observed behaviour of old railway embankments formed of ash and dumped clay fill, Geotechnique: international journal of soil mechanics, Vol: 71, Pages: 938-956, ISSN: 0016-8505
Many old railway embankments were originally formed from loose dumped clay fill on which ash fill was subsequently placed to maintain the track level. These have required considerable maintenance, primarily because of embankment movements. They are mostly covered by trees, and tree roots are present in both fills. As part of a London Underground Limited programme of stabilisation works in the 1990s, two embankments were instrumented to investigate the mechanisms and causes of movement. Lateral deformations, settlements and pore pressures were measured. This paper describes the instrumentation and monitoring techniques that were adopted and presents the findings from the study. It was found that non-recoverable seasonal movements occur in both the ash fill and the clay fill. The former occur in dry weather, particularly in the slopes of the embankments crests, due to ash particle mobility under train loading when the ash is dry. Clay fill deformations are exacerbated by the presence of tree roots. Movements correlate well with climate, as quantified by the soil moisture deficit determined from meteorological data. Establishing the mechanisms of movement within these ash–clay fill embankments helped to guide the design of stabilising measures.
Wan MSP, Standing JR, Potts DM, et al., 2021, Discussion of pore water pressure and total horizontal stress response to EPBM tunnelling in London Clay, Geotechnique: international journal of soil mechanics, Vol: 71, Pages: 368-372, ISSN: 0016-8505
Lopez AR, Tsiampousi A, Taborda DMG, et al., 2021, Numerical investigation into time-dependent effects on short-term tunnelling-induced ground response in London Clay, 10th International Symposium on Geotechnical Aspects of Underground Construction in Soft Ground (IS-Cambridge), Publisher: ROUTLEDGE, Pages: 597-604
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Wan MSP, Standing JR, Potts DM, et al., 2021, Measured post-construction ground response to EPBM tunnelling in London Clay, 10th International Symposium on Geotechnical Aspects of Underground Construction in Soft Ground (IS-Cambridge), Publisher: ROUTLEDGE, Pages: 191-198
Standing JR, 2020, Identification and implications of the London Clay Formation divisions from an engineering perspective, Proceedings of the Geologists' Association, Vol: 131, Pages: 486-499, ISSN: 0016-7878
Historically, engineers frequently viewed the London Clay Formation (LC) as uniform, homogeneous and rather uninteresting. Chris King's seminal work provided a much deeper insight into the characteristics of the LC and how it can be split into divisions, based on the depositional history of the formation and the microfauna present. LC water content profiles were compiled from continuous cores as part of an investigation into variations in tunnelling-induced settlements across St James's Park, allowing distinct zones to be identified. These were found to coincide exactly with the divisions identified by Chris King almost twenty years earlier. Water content profiles can be developed as part of a ground investigation and used to help establish the boundaries between King's divisions. Based on two further water content profiles from Hyde Park and St John's Wood a new methodology for locating the boundaries of the divisions, involving a trend-line for sub-Division A3, is proposed and tested, relevant to conditions in central London. In developing the method, significant differences in the elevation of the divisions between the three sites is observed, suggesting geological processes such as folding or faulting have influenced the LC along the ∼5-km length of the section.Once the boundaries of the LC divisions are known, geotechnical engineers have a greatly improved overall understanding of the ground conditions and how the ground will respond to engineering works such as tunnelling and deep excavations. Broad engineering implications of the divisions are described and discussed, citing case histories where possible.
Standing JR, Buss SR, 2020, Measurement and monitoring, Quarterly Journal of Engineering Geology and Hydrogeology, Vol: 53, Pages: 349-351, ISSN: 1470-9236
Wong LX, Shire T, Standing J, 2020, Effect of depositional water content on the collapsibility of a reconstituted loess, Quarterly Journal of Engineering Geology and Hydrogeology, Vol: 53, Pages: 283-289, ISSN: 1470-9236
Loess, a wind-blown silty soil, can be deposited under a variety of moisture conditions, including dry deposition, wet deposition and gravitational settling of aggregations formed in moist air by capillary forces at grain contacts. This experimental study uses single and double oedometer tests to assess the effect of depositional water content on the collapse potential of reconstituted samples of the Langley Silt Member, known as Brickearth, a natural loessic soil. A freefall sample preparation technique was used to mimic loess formation and environmental scanning electron microscopy was used to relate the observed behaviour to sample fabric. The results show that loess deposited at higher water contents has a greater collapse potential, which is shown to be related to its looser, more granular fabric.
Standing J, 2020, John Burland’s deep-excavation- and tunnelling-related research and industry involvement, Goetechnical Engineering Journal of SEAGS and AGSSEA, ISSN: 0046-5828
During the time that Professor John Burland was an expert witnessforthe Parliamentary hearings for the JubileeLine Extension Project(JLEP), he realised that although tunnels had been constructed in London for more than a century, there were very few well documented case studies describing the response of buildings to tunnelling-induced settlement. Professor Burland had extensive knowledge of the effects of ground movement on buildings, having studied and published his seminal work with Professor Peter Wroth in the 1970swhich he with others developed into a staged process for assessing potential structural damage from excavation-induced ground movements. Construction of the JLEP provided an ideal opportunity to compile a set of exemplary case studies (involvingdifferent structural forms, foundation types,tunnelling methods and geological conditions)and he harnessed this to its full extent. At the start,anumber of ‘gaps in knowledge’ were identified and these were addressed over the following years of monitoring and data analysis. The research culminated in a two-volume book that is still widely referenced almost twenty years later.In this paper a background to ProfessorBurland’s tunnelling-and deep-excavation-related research is given and the gaps in knowledge are summarised along with how they were answered through the JLEP researchfindings. They are reinforced with other more recent tunnelling projects in London that hehas been involved with, in particular the Crossrail project, thus furthering the understanding of ground and structural response to tunnelling, benefittingboth industry and academia.
Avgerinos V, Potts DM, Standing JR, et al., 2019, Predicting tunnelling-induced ground movements and interpreting field measurements using numerical analysis: Crossrail case study at Hyde Park DISCUSSION, Géotechnique, Vol: 69, Pages: 936-939, ISSN: 0016-8505
Ghail R, Standing J, 2019, Development of an engineering geology field trip for civil engineering students, Quarterly Journal of Engineering Geology and Hydrogeology, Vol: 53, Pages: 74-87, ISSN: 1470-9236
This paper describes and discusses the various elements of a one-week Engineering Geology field trip that has been developed for second-year undergraduate students studying Civil Engineering at Imperial College London. It is an essential component of the education of civil engineers and, as such, is a requirement of the accreditation defined by the ICE JBM. The trip is structured to develop the students’ awareness of geological features and their ability to record and sketch key observations in the field. Having described the geological features, the students are prompted to think about consequent potential engineering hazards relating to them and also the influence of human activity, past and present, on the ground and environment. During the course of the week the students develop their observational and logging skills, with constant staff feedback both outdoors and during summary student presentation sessions in the evenings. A marked progressive improvement has been noted as a consequence of this approach. On the final day of the week the students have to map a coastal section, observing and recording the stratigraphy and significant features such as bedding, discontinuities and faulting, with the latter quantified by measuring quantities such as dip, strike and plunge, as appropriate. The students’ work, assessed as part of the field trip, is completed by them and handed in just before final departure at the end of the week, most of it being completed in the field.
Wan MSP, Standing JR, Potts DM, et al., 2019, Pore water pressure and total horizontal stress response to EPBM tunnelling in London Clay, Géotechnique, Vol: 69, Pages: 434-457, ISSN: 0016-8505
The ground response, in terms of surface and subsurface displacements, to twin-bore Crossrail tunnel construction beneath a research monitoring site in Hyde Park, London, using earth-pressure-balance machines (EPBMs) in London Clay, has recently been reported in two companion papers by the authors. This third paper presents and discusses corresponding changes in pore water pressure and total horizontal stress measured using multi-level piezometers and pushed-in spade cells. The three papers together provide a comprehensive and completely unique field monitoring case history of the short-term ground response to EPBM tunnelling in London Clay, making them invaluable for validating future numerical analyses. The fully grouted vibrating-wire piezometers were able to measure the rapid pore water pressure changes around the tunnels as they were constructed. Five distinct immediate pore water pressure responses are identified, induced by different stages of the tunnel drives as the EPBMs approached and passed the instruments. The responses are correlated with tunnel-boring machine operation variables and a postulated arching mechanism, identified for the first time through field measurements. The sense and magnitude of changes in horizontal total stress were reasonable and are correlated with overall pore water pressure changes. Both responses are linked where possible with measured subsurface displacements and generally correlate well, at least qualitatively. Limitations to the measurements and influencing factors are also discussed.
Hendarto H, Standing JR, 2019, Influence of groundwater extraction on land subsidence in Jakarta
Major groundwater extraction in Jakarta, combined with other environmental issues, has caused severe land subsidence in areas of this teeming metropolis. Based on geodetic and PS-InSAR measurements, the current maximum rate of subsidence is more than 20 mm/year which has led to more than 3 m of settlement in northern parts of the city. Potential causes of the land subsidence are excessive groundwater extraction, urban development (e.g. high-rise building and tunnelling) and ongoing natural behaviour of the Jakarta soils. Groundwater pumping is thought to be the primary cause of the land subsidence. Records from groundwater levels, conventional monitoring and remote sensing using PS-InSAR indicate a strong relationship between pumping and land subsidence. Compiled data from more than one century’s measurements indicate that groundwater levels have dropped significantly, by up to 25 m, in central Jakarta. A schematic diagram of historic pore pressure changes resulting from the decreasing groundwater levels has been developed to help explain the situation.
Avgerinos V, Potts DM, Standing JR, 2018, Numerical investigation of the effects of tunnelling on existing tunnels., Géotechnique, Vol: 67, Pages: 808-822, ISSN: 0016-8505
Construction of the Crossrail tunnels just beneath the existing Central line tunnels at the northern side of Hyde Park provided the impetus for this paper. A basic three-dimensional (3D) finite-element (FE) model was developed to study a general case of a new tunnel (NT) crossing perpendicularly below an existing tunnel (ET). A series of 3D FE analyses was carried out and the results presented in this paper reveal some of the interaction effects. Changes in hoop forces, bending moments and lining deformations of the ET due to excavation of the NT are discussed. Conclusions are drawn about how the relative position of the excavation face of the NT in relation to the ET's axis affects the latter's behaviour. Cross-sectional and longitudinal deformations of the ET are discussed, leading to recommendations for field monitoring of similar interaction cases. Two parametric studies were also carried out to quantify the effects of the magnitude of the earth pressure balance machine face pressure and the longitudinal stiffness of the ET on the predicted behaviour of the ET due to construction of the NT.
Mantikos V, Tsiampousi A, Standing JR, 2018, Swelling behaviour of an expansive clay at high suction, 7th International Conference on Unsaturated Soils, Publisher: UNSAT
Deep geological disposal designs for nuclear waste often include an engineered barrier to protect the waste canistersand prevent leakage. The long-term safety of the repository relies on studies of the buffermaterial.Oedometer tests provide values ofdesign parameters fornumerical simulations. Anewly-developed oedometer with automated suction control is presented to assist in the investigation of the coupled hydro-me-chanical-volumetric behaviour of an expansive clay, namely a natural sodium bentonite. The displacement-controlled device was developed to apply suctionover a range of10 MPa to 300 MPausing a divided-flow humidity-generator. The device allows the application of combined stress and suction states, and continuous stress paths of constant volume, stress or suction. The development of the new oedometer is described. Results obtained during the preliminary tests are evaluated through comparison with experimental data from similar tests found in the literature. The current method benefits from continuous control of suction with servo-control of relative humidity using calibrated capacitance hygrometers. The system self-compensates for minor temper-ature changes and therefore the requirement for thermal insulation is not as crucial as in vapour equilibrium methods.
Kimpritis T, Standing JR, Thurner R, 2018, Estimating column diamters in jet-grouting processes, Proceedings of the ICE - Ground Improvement, Vol: 171, Pages: 148-158, ISSN: 1755-0750
Jet grouting is widely used in geotechnical engineering for a variety of applications and is a well-proven technique. As with many techniques developed from a practical perspective, there is still scope for improvements both in construction practice and design. This paper focuses on one of the most crucial elements of quality control required with jet grouting operations, the diameter of the constructed column. First, the jet grouting method is explained and the main issues of the concept highlighted. A description follows of the techniques available for estimating column diameter, discussing their application and evaluation on site. There is a particular emphasis on two methods: inclined core drilling and a newly-developed thermic approach (Meinhard et al., 2010) both of which were implemented on two construction projects. Data from these case studies are reported and analysed extensively, in conjunction with influencing factors such as the ground conditions, to assess their effects on the achieved diameter. An empirical approach for evaluating the diameter of jet-grouted columns is developed based on various factors influencing their size such as monitor lifting speed and soil strength.
Selemetas D, Standing JR, 2018, Response of full-scale piles to EPBM tunnelling in London Clay, Geotechnique: international journal of soil mechanics, Vol: 67, Pages: 823-836, ISSN: 0016-8505
The installation and working test performance of four full-scale instrumented driven piles and their subsequent response to twin tunnels constructed below the pile bases are described. One pair was designed to be largely friction piles and the other pair end-bearing. Their locations relative to the new tunnels were carefully chosen to optimise understanding of pile responses at varying offsets from the centre-lines. The site conditions and the greenfield response to earth pressure balance machine tunnelling at the site were described in a companion paper that reported an expanding displacement field around the tunnels rather than the contracting fields usually observed. The field monitoring results indicated that, during construction, zones of influence existed around tunnels, where the ground and piles were subjected to different degrees and senses of relative vertical displacement. Redistributions of load along the pile lengths occurred as the tunnel boring machines approached, passed beneath and continued beyond the pile bases; lateral pile deflections and bending moments were also induced. Based on the results from this field study, implications for the capacity of existing piles (and design of new piles) subjected to tunnelling-induced movements are assessed for cases of expanding and contracting displacement fields.
Wan MSP, Standing JR, Potts DM, et al., 2018, Measured short-term subsurface ground displacements from EPBM tunnelling in London Clay, Geotechnique: international journal of soil mechanics, Vol: 67, Pages: 748-779, ISSN: 0016-8505
Subsurface ground displacements from the construction of the twin-bore Crossrail tunnels in London Clay by earth pressure balance machines (EPBMs) are presented and discussed, complementing a companion paper by the authors that focused on the surface response. Both papers report vertical and horizontal displacements, in this case measured using comprehensive arrays of instruments installed within boreholes in Hyde Park, London. The Crossrail tunnels are deeper than those cited in most UK case histories concerning tunnelling in stiff clay. Clear insights were gained into subsurface displacement mechanisms: an ‘inward’ displacement field was observed around the Crossrail tunnel construction, in contrast to the ‘outward’ displacement field that developed around the shallower Channel Tunnel Rail Link tunnels constructed east of London using similar EPBMs in London Clay. This has important implications when estimating subsurface displacements using currently available empirical methods. Appraisal of the EPBM operational variables suggests that the relative magnitude of face and tail grout pressures to overburden stress is the key factor contributing to the opposing senses of the observed displacement fields. Earlier tunnelling-induced strain softening of the London Clay is evident from greater subsurface incremental volume losses and settlement trough width parameters relating to subsequent tunnel construction.
Hendarto H, Standing JR, 2018, Ground response to tunnel construction for Jakarta mass rapid transit project, Pages: 335-342
The Jakarta Mass Rapid Transit (MRT) Project, currently under construction, to relieve traffic congestion within the city, has both elevated and underground sections with a transition between them immediately north of Sisingamangaraja station. The tunnel runs from there to Bunderan Hotel Indonesia for 4 km beneath major roads in central Jakarta. Four Earth-Pressure-Balance (EPB) machines with outer diameters of ∼6.7 m are being used to excavate the northbound and southbound tunnels. The tunnels are mostly located in dilluvial strata which comprise stiff to hard silts or clays. Surface settlement predictions have been performed and field measurements analysed to assess the ground response to tunnel construction around the Bunderan Hotel Indonesia. In the early stages of tunnelling, in the northern part of the project (CP106), small degrees of heave, up to about ∼6 mm, occurred directly above the centre-line of the southbound tunnel, reducing with transverse distance to small settlements. Once the Tunnel-Boring Machine (TBM) reached about 320 m southwards, surface movements changed from heave to settlement. The responses suggest that vertical displacements (heave or settlement) depend on TBM variables such as face and tail skin grouting pressures in conjunction with depth of overburden.
Tsiampousi A, Yu JBY, Standing JR, et al., 2017, Behaviour of bolted cast iron joints, Tunnelling and Underground Space Technology, Vol: 68, Pages: 113-129, ISSN: 0886-7798
The structural testing and finite element (FE) analysis described in this paper were part of a major research project undertaken at Imperial College London to investigate the deformation of bolted segmental grey cast iron (GCI) tunnel linings. A key aim was to quantify how joints influence the behaviour of the lining, through a three-path approach comprising physical experiments, finite element modelling, and field instrumentation. The laboratory results have been used to assess the validity of the tunnel assessment methods used by industry.This study examined joint articulation under the serviceability limit state in the absence of hoop force focussing on factors such as applied bolt preload, the loading direction and the freedom of the circumferential flange to deflect. Two half-scale GCI lining segments were bolted together at the longitudinal flanges to form a bolted arch in a similar fashion to the tests performed by Thomas (1977). Modern instrumentation was implemented to gain detailed measurements quantifying changes in global displacements of the two segments, bolt forces and joint opening under applied loading. For the first time, the physical experiments were conducted contemporaneously with the development of a three-dimensional FE model of the joint. The experimental data and the results from the FE analysis indicate a reduction in joint stiffness as the joint articulates under applied load. It is shown that the presence of a joint has far greater influence on the behaviour of the ‘arch’ than the level of preload applied to the bolts in the joint. The FE analysis allowed the deformation behaviour of the joint under positive and negative bending to be investigated: its response under the two modes differs significantly.
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