Grand Paris Research Articles

Numerical modelling of a 32 m deep excavation in the suburbs of Paris

As part of the Grand Paris Express project, Fort d’Issy-Vanves-Clamart (FIVC) is one of the 60 new metro stations involving a 32 m deep excavation in layered soils made of limestones and clays. The support system was subject to a comprehensive monitoring program to assess the behavior of the soil and the structure during the works [22]. It comprises wall displacements using inclinometers, bending moments using fiber optic, struts and beams loads using strain gauges and earth pressures at the soil/wall interface using pressure cells. The present paper presents the back analysis done using Finite Elements Models (FEM) in 2D and 3D and, the subgrade reaction method (SRM).The results depict a great consistency between FEM and SRM in terms of reproducing, at the same accuracy level, the wall displacements and bending moments. However, the earth pressure redistribution behind the wall and the props loads are significantly underestimated by SRM (40%) especially for deep excavations. Only FEM can reproduce the measurements since arching effect is allowed within the soil. The present back analysis provides adjustment to the input soil parameters in compliance with their variation range. The resulting set of parameters could be used for an optimization purpose in future designs of deep excavations in similar ground conditions.

Ground improvement by jet grouting and injection to control hydraulic conditions in the frame of Grand Paris Express Project, North-East section: methodology and quality control sequence

The main tunnels of Line 16 Lot1 of the Grand Paris Express project are underway since 2019 using tunnel boring machines (TBM). They are drilled entirely in permeable strata (fine/silty sands, marls, and limestones) at a depth of 20÷30 m below the groundwater level. Groundwater inflow with high pressure is a major issue at the arrival/departure sections of the TBMs as well as during the excavation work of connection galleries between the main tunnels and maintenance or security shafts. Line 16 Lot1 is located under dense urban areas with the requirement of minimizing the drawdown of the groundwater and water inflow in civil engineering works; the purpose is to avoid excessive settlements on existing facilities and dissolution reactivation process of gypsum-rich strata. In order to minimize these risks, different types of ground improvement technics (jet grouting and cement mixture injection) have been applied, where jet grouting is used in fine sandy soil and cement mixture injection used in fissured marly-limestone. In addition, both technics of improvement have been associated on the same site. From a geotechnical point of view, the sands of Beauchamp are classified as coarse-grained soils (60% SM and 40% ML in the Unified soil Classification System ) and Marly-limestone of Saint-Ouen and deep Marls as fissured soft to medium-hard calcareous rock. This paper presents the geotechnical conditions, the ground improvement methodology and quality control during construction. The control sequence is performed by vertical and then horizontal drilling holes. The method of control work after excavation (horizontal control) allows to confirm the quality of the treatment blocks and specifically the bonding between the treatment block and the diaphragm wall.

Acute ambulatory blood pressure response to short-term black carbon exposure: The MobiliSense sensor-based study

Documented relationships between black carbon (BC) exposure and blood pressure (BP) have been inconsistent. Very few studies measured both BC exposure and ambulatory BP across the multiple daily environments visited in the general population, and none adjusted for personal noise exposure, a major confounder. Our study addresses these gaps by considering 245 adults living in the Grand Paris region. Personal exposure to BC was monitored for 2 days using AE51 microaethalometers. Ambulatory BP was measured every 30 min after waking up using Arteriograph 24 monitors (n = 6772). Mixed effect models with a random intercept at the individual level and time-autocorrelation structure adjusted for personal noise exposure were used to evaluate the associations between BC exposure (averaged from 5 min to 1 h before each BP measurement) and BP. To increase the robustness of findings, we eliminated confounding by unmeasured time-invariant personal variables, by modelling the associations with fixed-effect models. All models were adjusted for potential confounders and short-term time trends. Results from mixed models show that a 1-μg/m3 increase in 5-minute averaged BC exposure was associated with an increase of 0.57 mmHg in ambulatory systolic blood pressure (SBP) (95 % CI: 0.30, 0.83) and with an increase of 0.36 mmHg in diastolic blood pressure (DBP) (95 % CI: 0.14, 0.58). The slope of the exposure-response relationship gradually decreased for both SBP and DBP with the increase in the averaging period of BC exposure from 5 min to 1 h preceding each BP measurement. Findings from the fixed-effect models were consistent with these results. There was no effect modification by noise in the associations, across all exposure windows. We found evidence of a relationship between BC exposure and acute increase in ambulatory SBP and DBP after adjustment for personal noise exposure, with potential implications for the development of adverse cardiovascular outcomes.

Full scale study of pile response to EPBS tunnelling on a Grand Paris Express site

This article presents a full-scale experiment on the effect of EPBS tunnelling on pile foundations in the Paris area. Three cast in-situ piles, instrumented with strain gauges and optical fibre cables, were installed at different distances from tunnel axis with various pile base positions to monitor pile strains as the EPBS progresses. This paper investigates pile – soil differential settlements at ground surface, axial load variations, shaft friction mobilization, base load variations, bending moments and pile structural failure possibility. The pile behaviour changed depending on the pile position with respect to the tunnelling machine, with the main changes occurring during the passage of the EPBS beneath or at pile level. Estimation of pile behaviour based on simplified modelling was confirmed by the field monitoring.

The Role of Housing in a Mixed-Asset Portfolio: The Particular Case of Direct Housing within the Greater Paris area

This article explores the role of physical residential real estate within the optimal multi-asset portfolio. Specifically, we consider direct housing within the Grand Paris metropolis between 1996 and 2017 as an asset class together with financial assets. Our findings bring several contributions to the residential market literature. First, directly held housing investment brings diversification benefits to the mixed-asset portfolio. Second, using hierarchical clustering technique, we divide the Greater Paris area into five homogenous groups of communes and compute the optimal weight of each commune as well as each group of communes in the tangency portfolio. Third, we check the weights’ stability through time and confirm that residential real estate always catches the highest weight in the optimal portfolio. Finally, we run additional tests to compare listed real estate performances in a mixed asset portfolio with those obtained by considering physical residential real estate. We conclude that listed real estate is not a substitute for direct housing.

Productivity Benefits of Urban Transportation Megaprojects: A General Equilibrium Analysis of Grand Paris Express

Productivity Benefits of Urban Transportation Megaprojects: A General Equilibrium Analysis of Grand Paris Express

Personal exposure to concentrations and inhalation of black carbon according to transport mode use: The MobiliSense sensor-based study

IntroductionEpidemiological evidence suggests that motorized vehicle users have a higher air pollutant exposure (especially from vehicle exhaust) than active (walking or cycling) transport users. However, studies often relied on insufficiently diverse sample and ignored that minute ventilation has an effect on individuals’ inhaled dose. This study examined commuters’ breathing zone concentration and inhaled doses of black carbon (BC) when travelling by different transport modes in the Grand Paris region. MethodsPersonal exposure to BC was continuously measured with MicroAethalometer (MicroAeth AE51) portable monitors strapped on participants’ shoulder with tube inlet at the level of the neck (breathing zone), and inhaled doses were derived from several methods estimating ventilation [based on metabolic equivalents from accelerometry [METs], heart rate, and breathing rate]. Trip stages and transport modes were assessed from GPS and mobility survey data. Breathing zone concentrations and inhaled doses of BC were compared across transport modes at the trip stage level (n = 7495 for 283 participants) using linear mixed effect models with a random intercept at individual level. ResultsTrip stages involving public transport and private motorized transport were associated with a 2.20 µg/m3 (95% CI: 1.99, 2.41) and 2.29 µg/m3 (95% CI: 2.10, 2.48) higher breathing zone concentration to BC than walking, respectively. Trip stages with other active modes had a 0.41 µg (95% CI: 0.25, 0.57) higher inhaled dose, while those involving public transport and private motorized transport had a 0.25 µg (95% CI: −0.35, −0.15) and 0.19 µg (95 %CI: −0.28, −0.10) lower inhaled dose of BC per 30 min than walking. ConclusionThe ranking of transport modes in terms of personal exposure was markedly different when breathing zone concentrations and inhaled doses were considered. Future studies should take both into account to explore the relationship of air pollutants in transport microenvironments with physiological response.

Experimental study of the performance of a 32 m deep excavation in the suburbs of Paris

Fort d'Issy-Vanves-Clamart metro station is a 32 m deep excavation part of the new subway line 15 of the Grand Paris Express project. The performance of the support system is assessed through a wide monitoring programme covering wall displacements, bending moments, strut loads, ground settlements and earth pressure. Classical instrumentation was set up in redundancy to consolidate field measurements. Advanced devices were used to provide accurate measurement data, in particular fibre optic was installed along the retaining wall with total pressure and pore-water pressure cells placed at the soil–wall interface at four in-depth locations. The aim of the present paper is to provide a full description of deep excavation behaviour through a complete monitoring system. Bending moments captured with fibre optic are more accurate than those derived from inclinometers. An analysis methodology is proposed to address the temperature effect on strut load measurements in order to separate the thermal expansion contribution on the strut loading from the excavation process contribution. The stress redistribution behind the wall was observed with the lateral earth pressure increase of top cells while excavating deep levels. The comprehensive field measurements provided in this paper can supply further back-analysis to improve numerical modelling prediction.

Sprawl Politics: Comparing the City Regions of Paris (France) and Gauteng (South Africa)

What are the politics of ‘sprawl’? We pose this question in two complex city-regions of similar population and scale: one in the south of the world, centred on Johannesburg and Pretoria, South Africa (called Gauteng city-region); and one in the north, centred on Paris, France (variously defined as ‘Paris region’, Île-de-France, Grand Paris, etc). Both cases have experienced redesign of the metropolitan or city-region governance in the recent past; in both, there are constituencies arguing against sprawl but continuing practices that produce sprawl. Both city-regions are subjects of continuing research. Whilst two examples cannot exhaust the complex issues in the field, some light may be shed by bringing cases from the south and north into intersection. The underlying conceptual or theoretical questions include: meanings of ‘sprawl’ in diverse contexts; significance of fragmented city-region government; and differences and similarities in urban processes between southern and northern cities.

Site Reports: Geomechanics and Tunneling 3/2021

AbstractGround control solutions for Grand Paris: Line 15 – Lot T2C / Innovatives Stützmittelkonzept für Grand Paris: Linie 15 – Baulos T2C

Cover Picture: Geomechanics and Tunnelling 3/2021

AbstractRing line no.15 is one of four new metro lines of the Grand Paris Express mega‐project. The construction lot T2C in the southeast of Paris with a length of approx. 7 km is a key part of the new line. It consists of a 4.7 km long tunnel between Noisy‐Champs and Champigny, a 2.2 km long bypass tunnel with a maintenance station, a large‐scale underground junction cavern, and intermediate access shafts. Difficult ground conditions, limited space for construction, and the requirement for minimization of settlements in an urban environment determine the ground control systems for this tunnel project. Among others, the AT – 139 pipe umbrella system with press connection and a wall thickness of 8 mm, foot piles from the DSI hollow bar system as well as GRP face anchors were used. (photo: DSI Underground)

Learning from greater Paris

Following the riots of 2005 that devastated neglected suburbs and the failure of two campaigns for the Olympic Games, Paris has progressively become aware of its lack of metropolitan identity. In order to solve this problem, the French Ministry of Culture has recently set up an international consultation named “Grand Paris” meant to redefine the city’s image and envision its future as a metropolis. This paper retraces a three-year experimentation on Paris’ metropolitan area, carried out by the postgraduate Master of Regional and Urban Planning AMUR, and marked by the emerging public debate on the creation of a Greater Paris. It focuses on the studio’s attempts to develop new means of research and projection, responding to Paris’ metropolitan condition.

Mega-mall, global city and social issues of our times the case of Europacity in Paris

The retail trade fully participates in the international competition between the world's major cities, whether it be by the wealth it generates, or by the ways it reveals city and regional territorial displays. One can argue that city department stores had demonstrated this in the 19th century, while recently mega-shopping malls show that a wide range of public and private actors can be involved in a regional (metropolitan, national …) development project, each playing their own cards, at different scales. The goal of this article is to show how the social, political and economical interests interact regionally (locally) around a commercial project in the context of globalization. It focuses on the Europacity retailtainment mega-mall project, in the town of Gonesse located north of Paris, and framed within the “Métropole du Grand Paris” (Greater Paris Metropolis) urban development project, in itself a government ambition to strengthen the French capital's global position. We will analyse how such a project brings together supporters and opponents at all levels. Indeed, it is common to treat opponents as representatives of localism against globalized entrepreneurs, but this article illustrates a more nuanced reality where each side is part of a multiscalar game of scale.

From Impasse to Improvisation: Grand Paris Express as a Negotiation Agent in a Fragmented Metropolis

This article examines a conflict between two narratives for the future development of Greater Paris – the 'just city' versus the 'global city' – embodied in two competing regional rail proposals, one put forward by the Regional Council and the other by the French State. The first, Arc Express, was developed by Regional Council to reduce existing territorial inequity. A counterproposal, the Grand Huit, was formulated by the French state to serve a network of new economic clusters. A political impasse between these conflicting plans, though a prelude to broader institutional transition, empowered new actors in the negotiation of metropolitan planning. It also engendered experimental tools, such as collective territorial development agreements, with which local stakeholders leveraged the state's agenda to achieve their own objectives and gained greater metropolitan citizenship.

Projecting the Metropolis: Paris 2024 and the (re)scaling of metropolitan governance

Paris' successful bid for the 2024 Summer Olympics arises in the midst of a grand rethinking of the politics of regional and local development in the Île-de-France region. Paris 2024 also emerges at a time when the International Olympic Committee (IOC) is struggling to find cities willing to host the Olympics and has introduced a series of reforms to help recruit and motivate potential bid cities to consider how an Olympic project might be integrated into existing patterns of urban development. This exploratory research examines the blending of the Grand Paris regional development project and the 2024 Olympic ambition. Incorporating results from semi-structured interviews with seven key informants who possess specialized knowledge and are involved with governance mechanisms of the Île-de-France region and urban megaevent development, we explore how the Paris 2024 Olympic Games are being leveraged to facilitate metropolitan transformation. In the highly fragmented institutional setting of the Île-de-France region, negotiating site locations for Olympic facilities and establishing legacy or heritage objectives for the Olympic Games has important implications for the development of an institutional framework for metropolitan governance.

Development of a decision support tool for sustainable urban logistics optimization

Abstract Traffic flows are increasing in cities, partially due to congestions provoked by trucks. These congestions cause many problems such as pollution (gasoil, Carbon, etc.), noise, waste of time. Indeed, cities like Paris, Hamburg, Milan, and “Grand Paris Sud” conurbation are thinking about a sustainable alternative solution to road transportation. Then, a research based on co-creation methodology integrating all stakeholders (local authorities, companies, citizens) for elaborating an alternative solution to road transportation has been defined. This paper presents the architecture and the development of a decision aided tool for simulating and optimizing alternative solutions to road transportation

Urban Poverty, Discrimination, and Fragmented Landscapes: Recasting ‘Le Grand Paris’ Urban Renewal Proposal for Territorial Integration

Urban Poverty, Discrimination, and Fragmented Landscapes: Recasting ‘Le Grand Paris’ Urban Renewal Proposal for Territorial Integration

URBAN STRATEGIES AND COLLECTIVE MEMORY. AN UPPER-MIDDLE CLASS MUNICIPALITY IN THE GRAND PARIS PROJECT

This article proposes a theoretical point of view in order to show the importance of the collective memory and the urban narrative in the strategic approach of the urban project. The capacity of a municipality to build a local narrative joining the past, the memory and the project, is examined in the second part of the article, in a case study of a collectivity confronted with the project of the Grand Paris and strong socio-spatial transformation since 1950. The conclusions of thirty deep interviews, conducted on the people involved in the city organization allow to differentiate legitimated and rejected places in the spaces of remembering, and the difficulties of this kind of municipalities to be pro active in the Grand Paris project.

SPATIAL DETERMINISM AND TERRITORIAL PUBLIC ACTION IN FRANCE: CHALLENGES AND EVOLUTIONS

This article proposes a theoretical point of view in order to show the importance of the collective memory and the urban narrative in the strategic approach of the urban project. The capacity of a municipality to build a local narrative joining the past, the memory and the project, is examined in the second part of the article, in a case study of a collectivity confronted with the project of the Grand Paris and strong socio-spatial transformation since 1950. The conclusions of thirty deep interviews, conducted on the people involved in the city organization allow to differentiate legitimated and rejected places in the spaces of remembering, and the difficulties of this kind of municipalities to be pro active in the Grand Paris project.

Long-term assessment of thermal sustainability of thermoactive geostructures

Thermoactive geostructures represent an original and efficient technique for fulfilling the energy demand of buildings and infrastructure, in terms of both cooling and heating. Thermal and mechanical aspects have to be considered to achieve a proper design of such structures. This paper focuses only on thermal aspects and deals with the development of an original approach based on the analysis of thermal flux and volumetric thermal power to assess the thermal sustainability of a thermoactive geostructure. This approach is firstly applied to a simple three-dimensional geometry to validate some numerical implementation issues. A case study based on a Grand Paris Express metro station is then presented and analysed in terms of temperature variations and heat exchanges. The consideration of the groundwater flow and the thermal exchanges by conduction and advection provides a new and better insight on the thermoactive geostructure energy assessment. Furthermore, the obtained numerical results show the zones of the geostructures where the heat exchanges are the most significant and where the risk of temperature drift is the highest. This analysis can be used to improve the design of the thermoactive metro station.