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The UK Engineering and Physical Science Research Council (EPSRC) and the US National Science Foundation (NSF) supported a Workshop entitled, The Role of Funding, Financing and Emerging Technologies in Delivering and Managing Infrastructure for the 21st Century. The Workshop was held in New York City from the 11th to the 15th of July 2022. It included 30 participants invited by US members of the organizing committee, and 25 invited by UK members as well as online participants. The Workshop assembled a multidisciplinary group of international experts from academia, policy, and practice to explore how to improve infrastructure delivery through innovative funding and financing as well as emerging technologies. This Report captures the discussion and narratives arising from the Workshop and presents recommendations for policy, industry and future research. The Workshop focused on the interconnections between resilience, net-zero carbon and social equity within the context of infrastructure funding and financing. However, each challenge is examined separately in this Report for clarity. The complex interconnections across those issues are acknowledged throughout, with emphasis on the systems and systems-of-systems nature of those challenges. Although this Report addresses challenges related to infrastructure delivery and resilience, and to historical inequities of infrastructure provision and services, challenges related to climate change are considered the most urgent and affect all of the others. Time is running out to address carbon emissions. The window of opportunity to keep an increase in global temperature to 1.5C in reach and to avoid the worst impacts of global warming is closing fast – at best we have less than seven years to halve current global emissions1. The built environment is estimated to contribute from 39% (UN, 2017) to 70% (WRI, 2021) of carbon emissions depending on how emissions are allocated by sector.

This paper investigates the use of InSAR data during shield tunnel construction when short-term settlements occur within a few days. Additionally, the long-term settlement, which occur over several years, in the vicinity of these tunnels are evaluated with inSAR. The North-South Line in Amsterdam is used as a case study for this research. We used the settlement during construction as a-priori information to determine the most likely unwrapping solution for a few selected InSAR points. Then we verified this outcome with the traditional monitoring of the surface levelling points during construction and finally used only the InSAR to evaluate the long-term settlements. We conclude that with prior information InSAR data can be processed correctly and that InSAR can capture the short-term settlement that occur immediately during construction of a shield tunnel. Also, InSAR is a valuable complementary source of information because it provides data outside the area of the levelling points and gives information about settlement patterns prior to and after construction.

In the Observational method Ab Initio approach observational feedback is used to optimize a structural design to field conditions that are found to be uncertain in the design phase. As a deep excavation takes place, the supporting retaining wall deflections can be observed by inclinometers which serve as an extra source of information on the structure’s performance. Although the Observational method can be beneficial for both safety and economic point of view, limited deep excavations have been executed via this design strategy. This is mainly due to the lack of specification on how measurement-processing can be used to support engineers to assess the structure’s safety. This study introduces a methodology for real-time measurement-processing with the use of Bayesian updating. In this methodology retaining wall deflections are used to update the unique field conditions of the construction site. This methodology is applied to a measurement set gathered at the construction of a deep excavation in Groningen, The Netherlands, to demonstrate its potential to supplement the Observational method.

Tunnelling-induced settlement damage to pre-existing buildings is a result of bending and shear deformations, which typically occur simultaneously. However, widely accepted methods to assess building damage caused by tunnelling subsidence focus only on the mode of deformation (i.e. shear or bending) that is assumed to govern the onset of building damage. Furthermore, building damage assessment methods typically relate the dominant mode of deformation to the length to height ratio, L/H, of the structure, while more recent research reported that facade openings significantly affect the dominant deformation mode. This paper presents a series of centrifuge tests that explore bending and shear effects on surface structures that are affected by a shallow tunnel excavation in sand. The tests were performed on3D printed building models with varying L/H ratio and facade openings. The response of these building models to the ground movements caused by the tunnelling operation is monitored using digital image correlation (DIC). Results show that bending deformations increase with the L/H ratio while shearing becomes dominant as the amount of facade openings increases. It is also shown that shearing and bending occur simultaneously and therefore should be combined in future damage assessment methods. The obtained experimental results provide essential benchmark data for computational modelling of tunnelling-induced settlement damage on surface structures, as presented in the companion paper.

Masonry buildings in urban areas can be damaged by differential ground movements caused by underground excavations. Existing procedures for the assessment of building damage due to excavation-induced settlements include the effect of the building on the settlement trough in terms of building stiffness relative to soil stiffness. In these procedures, the relative stiffness is calculated by considering either the bending stiffness or the shear stiffness of the building. In this paper, finite element modelling of buildings subjected to tunneling-induced settlements is used to determine the relative importance of shear and bending deformations in damage predictions. Computational modelling was first validated by simulating centrifuge tests on 3D printed small scale models of masonry buildings subjected to tunneling in sand. Using a similar modelling approach, a sensitivity study was then conducted on the governing effect of shear or bending deformations for different amounts of facade openings. Results indicate the need to include both shear and bending deformation in assessment procedures, and provide essential data towards this objective.

In this article the face stability of slurry shield-driven tunnel in an aquifer is investigated. The influences of slurry infiltration at the face and soil layering are taken into account. The results show that due to the infiltration an additional margin for the support pressure is required. At larger slurry infiltration distance or larger cover depth to tunnel diameter ratio (C/D), a higher margin is required. It also appears that soil layering affects the hydraulic gradient that stabilise the face of cohesionless soil. TBM excavation in a semi-confined aquifer (compared to an unconfined aquifer) leads to higher excess pore water pressures in the soil around the TBM and a reduced infiltration of slurry into the soil in front of the TBM. The excess pore water pressures in a semi-confined aquifer are present over a larger area than in an unconfined aquifer, increasing the risk of a blow-out during excavation.

The feasibility of a tunnel, foundation or excavation project is to some extent dependent on limiting the potential ground movements during construction. To make such an assessment it is important to quantify the stress-path dependent behaviour of the soil undergoing undrained lateral and vertical stress relief. At an early stage in the project, site-specific test data is limited and so predictions must necessarily be based upon expected characteristics of the soil deposit. Analysis of a recently compiled database RFG/TXCU-278 has demonstrated a method of quantifying the variability of stress-strain data from stress-path tests that are more frequently encountered in commercial practice (consolidated-undrained triaxial compression and extension tests) for use in design sensitivity analyses. A soil non-linearity parameter (b) is investigated using the database RFG/TXCU-278 and a series of previously reported tests performed on intact Bothkennar Clay. Evidence from both databases suggests that the variability of b is not strongly linked to the effects of shear mode, OCR, strain rate, or plasticity. It is shown that reasonable predictions of nonlinear behaviour up to a load factor (σmob/σfailure) of 0.8 can be achieved using the MSD-MSF method for a rigid pad test.

The Mobilisable Strength Design (MSD) philosophy has been used in various applications related to underground construction, e.g. for analysis of deep foundation and retaining wall performance. MSD requires simple models for the stress-strain behaviour of soils. The use of a mobilisation factor on undrained strength to limit soil mobilisation was introduced in BS8002 in 1994. To assist with MSD calculations, the mobilisation strain framework (MSF) has been developed to allow geotechnical engineers to account for the non-linear behaviour of fine-grained soils in routine geotechnical design. In this paper, triaxial and pressuremeter test data from the London Clay deposit are analysed, using the MSF, to study the effects of anisotropy on both the mobilisation strains and non-linearity exponent. The implications for design of underground constructions arealso discussed.

This article presents a simple numerical investigation of ground responses to tunnel-boring machine (TBM) tunnelling with active face support. Unlike other numerical modelling in which a flow inward the excavation chamber was assumed, in this modelling a flow inward the ground surrounding the face was assumed. The later flow is caused by the penetration of slurry (for slurry shield) or foam (for EPB). The effect of soil layering (semi-confined and unconfined aquifers) was also taken into account. The numerical results show that the ground response to TBM tunnelling with active face support can be significantly influenced by soil layering. In a semi-confined aquifer, at a distance larger than approximately three times of tunnel diameter from the face, the excess piezometric heads are the same at any depths. This finding is helpful to improve the solution for the excess pore pressure caused by TBM tunnelling in a semi-confined aquifer proposed by Xu et al. (2019). The existing analytical solution of excess pore water pressure distribution for the case of semi-confined aquifer matches well with the numerical result. It appears that for an unconfined aquifer, contour of the excess pore water pressures is like a radial distribution. The steady state model of piezometric head for the homogeneous soil results in excellent matches with the values derived from the numerical modelling. For a semi-confined aquifer, the ground surface heave was observed. Though the face collapse potential was found for the unconfined aquifer, the displacement around the face was very small.

Mechanized tunnelling with EPB-TBMs bases its success on the ability to guarantee a uniform and constant front-face pressure during the excavation, using the excavated soil properly treated with chemical additives. This front-face pressure, measured with pressure sensors inside the working chamber, is kept constant during the excavation phase by balancing the amount of incoming soil, the foam injected, and the amount of soil extracted through the screw conveyor in the working chamber. During the standstill phase, required to install the tunnel lining elements, particularly in the coarse-grained soils, the pressure inside the chamber tends to decrease until the next resumption of the excavation. This effect, mainly linked to the permeability of the soil outside the TBM, tends to increase settlements induced on the surface and, therefore, should be minimized. In this paper, a very simple calculation model proposed by Bezuijen and Gerheim Souza Dias in 2017 for tunnelling in saturated sandy soils, is applied to an Italian tunnelling project. A comparison of model predictions and data recorded real time on the site during the excavation is illustrated and discussed. The predictive ability of the calculation model proposed for saturated sand seems to be useful also for TBM applications in gravelly soil under the phreatic surface, highlighting the weight of the main factors affecting the specific boundary value problem; moreover, it can be a useful tool to address the problem and to individuate technical countermeasures finalized to minimize the phenomenon and its negative effects.