Centrifuge modelling of tunnelling beneath axially loaded displacement and non-displacement piles in sand

Tunnelling under piled structures is becoming more common in urban areas. However, there is limited guidance available for the prediction of settlements and the loss of bearing capacity of existing piles due to tunnel excavation. This paper aims to provide an improved understanding of the response to tunnelling of axially loaded displacement and non-displacement piles. Data are provided from a series of geotechnical centrifuge tests of tunnel excavation beneath single piles in dry silica sand. The tests evaluate induced settlements of the piles at varying levels of initial safety factor (i.e. the ratio between initial bearing capacity and applied load). Furthermore, a previously published analytical approach, based on cavity expansion theory, is used to investigate the variation of the residual safety factor at constant pile load with tunnel volume loss. The outcomes of both centrifuge and analytical investigations illustrate the importance of pile installation method and initial safety factor and improve understanding of tunnel-pile interaction mechanisms.Engineering and Physical Sciences Research Council (EPSRC) [EP/K023020/1

Centrifuge and real-time hybrid testing of tunnelling beneath piles and piled buildings

Tunnels are constructed increasingly close to existing buried structures, including pile foundations. This poses a serious concern, especially for tunnels built beneath piles. Current understanding of the global tunnel-soil-pile-building interaction effects is lacking, which leads to designs which may be overly conservative or the adoption of expensive measures to protect buildings. This paper presents outcomes from 24 geotechnical centrifuge tests that aim to investigate the salient mechanisms that govern piled building response to tunnelling. Centrifuge test data include greenfield tunnelling, pile loading, and tunnelling beneath single piles and piled frames, all within sand. The global tunnel-piled frame interaction scenario is investigated using a newly developed real-time hybrid testing technique, wherein a numerical model is used to simulate a building frame, a physical (centrifuge) model is used to replicate the tunnel-soil-foundation system and structural loads, and coupling of data between the numerical and physical models is achieved using a real-time load-control interface. The technique enables, for the first time, a realistic redistribution of pile loads (based on the superstructure characteristics) to be modelled in the centrifuge. The unique dataset is used to quantify the effects of several factors which have not previously been well defined, including the pile installation method, initial pile safety factor, and superstructure characteristics. In particular, results illustrate that pile settlement and failure mechanisms are highly dependent on the pre-tunnelling loads and the load redistribution that occurs between piles during tunnel volume loss, which are related to structure weight and stiffness. The paper also provides insight as to how pile capacity should be dealt with in a tunnel-pile interaction context.Engineering and Physical Sciences Research Council [grant number EP/K023020/1, 1296878, EP/N509620/1

Elastoplastic solutions to predict tunnelling-induced load redistribution and deformation of surface structures

In this paper, an elastoplastic two-stage analysis method is proposed to model tunnelling-induced soil-structure interaction and incorporated into a computer program `ASRE'. This solution allows considering both vertical and horizontal greenfield ground movements, gap formation and slippage, continuous or isolated foundations, and a variety of structural configurations and loading conditions. After introducing the proposed formulation, the model predictions are first compared with previously published data for validation. Then, to isolate the effects of various structural characteristics (relative beam-column stiffness, presence of a ground level slab, column height, number of storeys) and foundation types (continuous versus isolated), several example structures are analysed. Results demonstrate the value of the proposed analysis method to study a broad range of building characteristics very quickly, and show how the soil-structure interaction occurring due to underground excavations is altered by both foundation and superstructure configurations. In particular, the difference in behaviour between equivalent simple beams and framed structures on separated footings is clarified.Engineering and Physical Sciences Research Counci

Continuum solutions for tunnel-building interaction and a modified framework for deformation prediction

In this paper, the response of buildings to tunnelling-induced ground movements is studied with elastic and elastoplastic continuum solutions that consider the structure as an equivalent simple beam. A comparison is made between these simple solutions and centrifuge test data to provide insights into flexural and axial building deformations of low-rise bearing wall structures on strip foundations; the influence of wall openings and the foundation scheme on the equivalent beam bending stiffness is also addressed. Subsequently, the effects of structural continuity across greenfield sagging and hogging regions on tunnel-structure interaction are investigated. Finally, the continuum solutions are used to propose a modification factor formulation that accounts for the change in settlement trough shape (compared to the greenfield) due to soil-structure interaction. This formulation, for example, accounts for the change in transverse length of the hogging and sagging regions of a building due to soil- structure interaction, eliminating the need to divide the building at the greenfield inflection points when calculating modification factors. The proposed formulation, which is compared with numerical, experimental and field data from previous research, is shown to better predict flexural building deformations

Structural health monitoring of a masonry viaduct with Fibre Bragg Grating sensors

The Marsh Lane viaduct is a masonry railway bridge constructed during the 19th century nearby Leeds Central Railway Station. The bridge appears significantly damaged due to the increase of the operational train loads over the last decades and due to environmental effects. Due to this degradation, extensive repair was conducted in 2015. After this repair work, an extensive fibre optic sensor network was installed below three spans of the bridge to monitor surface strains at 68 locations on the underside of the arch spans. The paper compares data collected from two monitoring periods, 16 months apart. Combining statistical analysis and signal processing techniques, the results show that local damage, as well as change in the global dynamic behaviour of the structure over time, can be effectively detected with the use of Fibre Bragg Grating sensors.This work is being funded by the Lloyd’s Register Foundation, EPSRC and Innovate UK through the Data-Centric Engineering programme of the Alan Turing Institute and through the Cambridge Centre for Smart Infrastructure and Construction (CSIC). Funding for the monitoring installation was provided by EPSRC under the Ref. EP/N021614/1 grant and by Innovate UK under the Ref. 920035 grant

A multi-sensing monitoring system to study deterioration of a railway bridge

This study presents a multi-sensing monitoring system recently installed in a Victorian railway viaduct in Leeds, UK. The viaduct is in continuous use since its construction during the 19th century and suffers extensive cracking due to the combined action of increased train loads and environmental effects. The bridge was retrofitted in 2015 and there was the need to assess the effectiveness of the intervention and better understand the ongoing deterioration process. For this reason, a multi-sensing system was designed that comprises a fibre Bragg grating network to measure distributed dynamic deformation across three arch spans of the bridge, acoustic emission sensors to detect rates of cracking, and high sensitivity accelerometers to study the dynamic response at critical locations. The system is self-sustaining, self-powered and remotely controlled, and uses an algorithm that combines information from the three different types of sensors to track variations of response parameters of the bridge over time.This work is being funded by the Lloyd’s Register Foundation, EPSRC and Innovate UK through the Data-Centric Engineering programme of the Alan Turing Institute and through the Cambridge Centre for Smart Infrastructure and Construction. Funding for the monitoring installation was provided by EPSRC under the Ref. EP/N021614/1 grant and by Innovate UK under the Ref. 920035 grant

El derecho animal dentro del nuevo paradigma de derecho ambiental

This paper addresses the issue of Animal Law from a double perspective. Firstly, it reflects the legislative inconsistencies within the Argentine law regarding the legal status of the animal, which is mainly considered an object, on the one hand; and it exhibits the national and local jurisprudential development that recognizes the animal as a legal person -not human-, on the other hand. Secondly, this paper describes the characteristics of Animal Law that allows its incorporation as a chapter of the new paradigm of Environmental LawFil: Franza, Jorge A. Universidad de Buenos Aires. Facultad de Derecho. Cátedra Derecho de los Recursos Naturales y Protección del Medio Ambiente. Buenos Aires, ArgentinaDossier "Derecho ambiental y recursos naturales": El presente trabajo aborda el tema del Derecho Animal desde una perspectiva doble. En primer lugar, se reflejan, por un lado, las inconsistencias legislativas dentro del derecho argentino en cuanto al estatus jurídico del animal, al que se lo considera principalmente un objeto, y se muestra, por otro lado, el desarrollo jurisprudencial nacional y local que reconocen al animal como un sujeto de derecho no humano. En segundo lugar, se describen las características del Derecho Animal que permiten su incorporación como un capítulo del nuevo paradigma del Derecho Ambiental

Regulated tissue-specific expression of antagonistic pre-mRNA splicing factors

The SR proteins are essential metazoan pre-mRNA splicing factors that can also influence the selection of alternative 5' splice sites in a concentration-dependent manner. Their activity in alternative splicing in vitro is antagonized by members of the hnRNP A/B family of proteins. The opposite effects of members of these two families of antagonistic splicing factors in vitro and upon overexpression in vivo suggest that changes in their relative levels may be a natural mechanism for the regulation of alternative splicing in vivo. One prediction of this model is that the ratios of these antagonists should vary in different cell types and in other situations in which cellular or viral transcripts are differentially spliced. We raised monoclonal antibodies specific for SFS/ASF and used them to measure the abundance of SFS/ASF protein and its isoforms, its phosphorylation state in vivo and during splicing in vitro, and its association with the spliceosome. SF2/ASF exists predominantly or exclusively in a highly phosphorylated state in vivo in all cell types examined, and unphosphorylated protein was not detectable. Unphosphorylated recombinant SFS/ASF becomes rapidly phosphorylated under splicing conditions in HeLa cell extracts and associates stably with one or more exons of beta-globin pre-mRNA. This interaction appears to persist through the splicing reaction and SF2/ASF remains bound to spliced mRNA. We compared the distribution of SFS/ASF to that of its antagonist, hnRNP Al, in different rat tissues and in immortal and transformed cell lines. We found that the protein levels of these antagonistic splicing factors vary naturally over a very wide range, supporting the notion that changes in the ratio of these proteins can affect alternative splicing of a variety of pre-mRNAs in vivo

The Marsh Lane Railway Viaduct: 2 Years of Monitoring with Combined Sensing and Surveying Technologies

Marsh Lane viaduct is a typical example of a 19th century brick masonry railway arch in the UK. It frequently carries passenger trains to and from Leeds Station. This paper broadly discusses the sensing techniques and associated analysis procedures used to (i) identify the reasons for existing damage, (ii) quantify their impact on the dynamic response of the structure and (iii) measure degradation of the response over a period of one year. To identify existing damage, distortions in geometry of the structure are examined with new point cloud processing techniques. With the aid of limit analyses, these distortions are interpreted, and past support movements which may have caused the distortions are identified. Then, to measure the dynamic response of the bridge, quasi-distributed fibre optic strain sensing and digital image correlation displacement measurement techniques are used. These highlight the increased dynamic response around locations of existing damage, and point out to the global mechanisms of response that could propagate damage. Continuous fibre optic strain measurements between November 2017 and 2018 are then discussed to investigate the ongoing deterioration.This work is being funded by the Lloyd’s Register Foundation, EPSRC and Innovate UK through the Data-Centric Engineering programme of the Alan Turing Institute and through the Cambridge Centre for Smart Infrastructure and Construction. Funding for the monitoring installation was provided by EPSRC under the Ref. EP/N021614/1 grant and by Innovate UK under the Ref. 920035 grant

Real-time data coupling for hybrid testing in a geotechnical centrifuge

Geotechnical centrifuge models necessarily involve simplifications compared to the full-scale scenario under investigation. In particular, structural systems (e.g. buildings or foundations) generally can’t be replicated such that complex full-scale characteristics are obtained. Hybrid testing offers the ability to combine capabilities from physical and numerical modelling to overcome some of the experimental limitations. In this paper, the development of a coupled centrifuge-numerical model (CCNM) pseudo-dynamic hybrid test for the study of tunnel-building interaction is presented. The methodology takes advantage of the relative merits of centrifuge tests (modelling soil behaviour and soil-pile interactions) and numerical simulations (modelling building deformations and load redistribution), with pile load and displacement data being passed in real-time between the two model domains. To appropriately model the full-scale scenario, a challenging force-controlled system was developed (the first of its kind for hybrid testing in a geotechnical centrifuge). The CCNM application can accommodate simple structural frame analyses as well as more rigorous simulations conducted using the finite element analysis software ABAQUS, thereby extending the scope of application to non-linear structural behaviour. A novel data exchange method between ABAQUS and LabVIEW is presented which provides a significant enhancement compared to similar hybrid test developments. Data are provided from preliminary tests which highlight the capabilities of the system to accurately model the global tunnel-building interaction problem