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This document is a closure to a previous paper titled "Effects of Movement Induced by Ground Improvement on the Performance of an Excavation Support System in Underconsolidated Clay." The closure addresses comments and requests for additional information made by a discusser. The closure provides construction information, including the layout of ground improvement works and the installation of deep soil mix columns and jet grout piles. It also discusses the selection of jet grout pressures, undrained shear strength properties of marine clays, and field performance observations. The closure concludes by addressing the limitations of the numerical modeling used in the original paper. [Extracted from the article]

Climate change and sea‐level rise (SLR) are expected to increase the frequency and intensity of coastal flood events, posing risks to coastal communities and infrastructure. While regional climate adaptation investments can provide substantive flood protection, existing plans often neglect uncertainty in future climate conditions and adaptation performance, consequently neglecting the option value of flexibly implementing proposed projects. Addressing this gap, we develop and employ a generalizable real options analysis (ROA) valuation framework that considers how uncertainty in adaptation project costs, SLR, flood severity, and flood losses inform the full range of adaptation performance outcomes. We further propose and apply a novel, computationally efficient flood loss sampling algorithm to estimate the consequences of randomly arriving coastal flood events. We apply this ROA framework to assess the option value of flexibly timing adaptation investments over time, investigating an adaptation pathway proposed by the City of Boston from the perspective of the regional transit system manager. Our results suggest that flexible implementation can provide significant option value in the near‐ to mid‐term (>30 years), with the highest option values under low‐probability, high‐consequence scenarios. Our results also suggest adaptation pathway performance in the latter half of the 21st century is most sensitive to uncertainty in SLR, flood loss estimates, and flood frequency, underscoring the importance of uncertainty quantification in the long‐term valuation of adaptation investments. [ABSTRACT FROM AUTHOR]

The recent construction of an underground mass rapid transit (MRT) station in Singapore involved 21 m deep excavations within underconsolidated marine clay. The lateral earth support system comprised 1 m thick diaphragm walls socketed into the underlying Old Alluvium and 4 levels of preloaded cross-lot struts. Deep soil mixing (DSM) and jet grouting piles (JGP) were used to improve up to 15 m thickness of the marine clay formation. Field monitoring data showed that these ground improvement processes caused large outward deflections of the diaphragm wall panels at some locations prior to the excavation and may have caused yielding within the wall panels. In this paper, the impacts of these prior wall deformations on the subsequent performance of the excavation support system are investigated. The measured performance at two indicative cross sections is compared with results from simplified 2D finite element analyses. The analyses simulate the effects of ground improvement through prescribed boundary pressures and represent the yielding of the diaphragm wall panels through zones of reduced bending stiffness. We show that large outward wall deflections and curvature observed during jet grouting at one section contribute to higher inward wall movements and strut loads measured during excavation, while smaller movements (and curvature) prior to excavation at a second similar cross section cause negligible change in the performance of the temporary earth retaining system. The results highlight (1) the importance of controlling ground movements associated with ground modification processes such as jet grouting, (2) the uncertainties in estimating mechanical properties for the improved soil mass, and (3) the need to improve the representation of non-linear, flexural properties (M-κ) of reinforced concrete diaphragm panels. [ABSTRACT FROM AUTHOR]

The ground response during diaphragm wall panel installation is strongly affected by the support slurry pressure, and by the subsequent lateral pressures during the tremie placement and set-up of wet concrete. The support slurry pressure can be reliably assumed as hydrostatic within the excavated trench, whereas the lateral concreting pressure is much more complex due to the stiffening effect of wet concrete. This paper reviews the measurements of wet concrete pressures from a series of instrumented diaphragm wall panels which show that lateral pressures in the concrete slurry increase as the tremie displaces bentonite slurry and reach a maximum condition about 1 h after placement, while conditions over the longer term closely approximate the hydrostatic pressure of the bentonite-filled trench. The maximum increase of pressure varies at different heights of the same trench, and also varies for two separate panels in the same project, reflecting the varying velocity of concreting. Model tests of concreting pressure on formwork also demonstrate that the lateral pressure reduces from hydrostatic wet concrete pressure a few hours after casting. A time-dependent lateral concreting pressure model is developed to represent these measurements more realistically. This proposed model is implemented into a finite-element program to investigate its effects on the ground response due to the concreting process. Computed results from a reference case can capture the progressive variations of ground movement, earth and pore water pressure in the soil adjacent to the trench during and shortly after the concreting process, which is consistent with the reported measurements. [ABSTRACT FROM AUTHOR]

The selection of an appropriate discount rate is a critical yet often neglected aspect of valuing flood protection and climate adaptation projects. We examine current discounting practices in flood risk management and climate adaptation literature and compare these practices with a proposed fair market value (FMV) discounting approach, in which we discount project cash flows based on their levels of systematic market risk, consistent with practice in the private sector. Using publicly available data, we demonstrate minimal correlation between flood risk–related cash flows and overall market returns, suggesting flooding-related cash flows are most appropriately discounted near the risk-free rate. We consider the example of a proposed storm surge barrier in Boston Harbor and compare prevailing public-sector discounting approaches with this FMV approach. Our results suggest prevailing discounting approaches systematically undervalue flood risk reduction benefits and climate adaptation investments relative to the private-sector valuation implied via the FMV approach. [ABSTRACT FROM AUTHOR]

This paper proposes a multiaxial macroelement for bridge abutments that can be included in the global structural model of a bridge to carry out nonlinear dynamic analyses with very much smaller computational effort than can be achieved using continuum representations of embankment and foundation soil behaviour. The proposed macroelement derives a constitutive force–displacement relationship within a rigorous thermodynamic framework and includes important features of non‐linearity and directional coupling in characterizing the interactions of the abutment with the soil. In a dynamic analysis, the frequency‐dependent response of the system is simulated through the combination of the macroelement with appropriate participating masses. The calibration procedure of the macroelement is based on the assessment of its ultimate capacity and of its response at small displacements, and it is shown that these ingredients can be derived through standardised procedures. In the paper, the macroelement response is validated against the results of fully coupled continuum numerical analyses for a reference soil–abutment system, under both static and seismic loading conditions. We show that the two models achieve similar predictions of maximum and permanent abutment deformations (less than 10–14% difference, respectively) for a suite of three‐axis seismic loading events. [ABSTRACT FROM AUTHOR]

Estimates of flood‐related damages and costs often rely on asset‐specific depth‐damage curves that characterize the fragility of a given asset. To date, there are very few depth‐damage curves that are potentially applicable to rail rapid transit infrastructure, and no studies attempt to construct these relationships specifically these asset classes. Given the lack of empirical performance data or asset‐specific reliability tests, we solicited expert engineering judgment to characterize the fragility of transit assets to saltwater flood exposure. We validate the resulting synthetic depth‐damage relationships via a benchmarking approach and demonstrate consistency with previously published depth‐damage curves for similar asset classes. The solicitation framework presented can easily be extended to other infrastructure assets and systems, potentially serving as a key step toward a more rigorous quantification of the potential risks posed to infrastructure by natural hazards and climate change. [ABSTRACT FROM AUTHOR]

The article presents the discussion on novel elasto-viscoplastic formulation for compression behaviour of clays. Topics include model linearises the limiting compression curve (LCC) by using the logarithm of voids ratio; and immediate elastic strain at the draining boundary of a soil layer after load application producing an infinite spike in elastic strain rate.

Although water quality has extensively improved over the last decade, recreational uses of the canal network in Amsterdam are limited by variations in water quality associated with stormwater runoff and episodic harmful algal blooms. The current systems for monitoring water quality are based on a stationary network of sampling points, offline testing methods, and online measurements of conventional water quality parameters on board a boat that continuously navigates the urban canal network. Here we describe the development and deployment of online algal sensors on board the boat, including a prototype LED-induced fluorescence instrument for algal identification and quantification. We demonstrate that by using only a single patrol vessel, we are able to achieve enough sampling coverage to observe spatiotemporal heterogeneity of algal and chemical water quality within the canal network. The data provide encouraging evidence that opportunistic measurements from a small number of mobile platforms can enable high-resolution mapping and can be used to improve the monitoring of water quality across the city compared to the current network of fixed sampling locations. We also discuss the challenges of operating water quality sensors for long-term autonomous monitoring. [ABSTRACT FROM AUTHOR]

Mudflows from the ongoing eruption of a mud volcano near Sidoarjo (East Java, Indonesia) have continued for more than 15 years and now cover an area of 8.2 km2 to a depth of more than 15 m. The mudflows are contained within a system of perimeter earthen levees/dykes that were constructed as a series of temporary defenses. The levees have marginal stability and limited freeboard due to the low shear strength and high compressibility of the 25-m-deep soft clay foundations, which have already resulted in ground deformations exceeding 7 m. In this paper, we analyze the deformations and stability of the downstream staged construction at a critical reach in order to (1) understand causes of a recent failure (2018); and (2) assess the current state of the levee following completion of a fifth construction stage (2019) that included a 35-m-wide, 4-m-high stabilization berm with an array of prefabricated vertical drains (PVDs) to accelerate consolidation. Our analyses used large-deformation elastoplastic finite-element analyses to simulate consolidation and lateral spreading of the foundation soils due to levee construction and mudflow loads. Levee stability was evaluated using numerical limit analyses for the deformed geometry and simulating changes in undrained strength with the consolidation state and direction of shearing at each stage of construction. The results were consistent with the magnitudes of the observed levee settlements and mechanism of failure; they also show the potential for an additional >2 m settlement over the next 5 years, even without considering creep of the clay or larger-scale processes controlling subsidence around the volcanic caldera. Future construction stages to contain the expected mudflow will require improvement of the mechanical properties of the alluvial clay to ensure adequate long-term freeboard. [ABSTRACT FROM AUTHOR]

In geothermal engineering, the long-term thermomechanical responses of sand and clay are difficult to predict due to the lack of an essential understanding of thermally induced volume change. Recent experimental studies have measured thermal creep of dry sand, glass beads, and clays. However, this universal phenomena of thermal creep has not been properly included in constitutive models of soils. In this paper, the Tsinghua ThermoSoil (TTS) model, previously developed for clay, is extended to describe thermal and mechanical creep of sand. The elemental thermal creep and thermal cyclic behavior of Todi clay and Bangkok sand, reported under hydrostatic stress or oedometric conditions, are reproduced by the proposed formulation. These comparisons show the following key features of behavior described by the extended model (e-TTS): (1) thermal creep of clay can produce either compressive or s1welling behavior depending on the consolidation stress history, (2) the heating rate and temperature range have significant influences on thermal creep, but only small effects on swelling behavior, (3) thermal cycling induces compression of sand, which is dependent on effective stress level and relative density, and (4) the e-TTS model predicts stabilization of thermal creep strains for sands over within 50–100 thermal cycles due to equalization of elastic and locked-in hysteretic strains. [ABSTRACT FROM AUTHOR]

The catastrophic failure of the Córrego do Feijão Dam 1 in January 2019 has raised many questions regarding the safety of tailings storage facilities constructed by upstream methods. The stability of these structures is strongly affected by the internal stratigraphy and properties of the hydraulically deposited, segregated tailings materials (from slimes to coarse sands) and by control of seepage conditions. The authors conducted an independent review of site investigation data reported by an Expert Panel (December 2019) and evaluated the stability for a critical section of the Feijão Dam 1 using 2D numerical limit analyses under various representations of fill stratigraphy and shear strength properties. The results show that the structure has a low factor of safety, FS=1.11–1.16 on average, based on conventional assumptions of drainage conditions for fill strata. The computed failure mechanism is strongly affected by the presence of a layer of normally consolidated, low permeability slimes near the base of the fill, and by the lack of drainage provisions within the starter dam. The analyses show a clearly defined critical mechanism of failure over the full height of the fill and suggest that the dam has smaller margins of safety than previously published limit equilibrium results. The analyses do not resolve or identify causes of the actual dam failure, which occurred more than three years after the end of construction but do suggest that more reliable methods of slope stability are needed in design. [ABSTRACT FROM AUTHOR]

We present experimental observations and a conceptual model for understanding the compression and swelling characteristics of Old Alluvium (OA) from San Juan, Puerto Rico. Prior studies have classified OA as a transported, in situ weathered tropical soil whose intact macrostructure comprises a cemented, pseudo-silt with a mixture of quartz grains and aggregated clay particles. The aggregates include mixtures of kaolinite and smectite coated by Fe-oxides. The Fe-oxides also act as cementing agents between the particles. This study describes results from a series of high-pressure (up to 63 MPa) incremental consolidation tests. Breakdown of the clay aggregates and cemented structure is observed through changes in the compression properties, significant swelling during unloading, and an extraordinary reduction (i.e., by three orders of magnitude) in the coefficient of consolidation. These experimental observations are explained by a combination of mechanical processes, comminution and breakdown of cementing bonds, and physicochemical changes linking pore fluid in the intra- and inter-aggregate pore space. These processes alter the fundamental particle size distribution and macro-porosity of the soil and activate the swelling potential of the smectites concealed by the Fe-oxides coating in the intact material. The experimental observations provide the basis for the formulation of a constitutive model to describe macroscopic compression and swelling behavior of Old Alluvium and offer a framework to understand the response of piedmont transported residual soils found elsewhere. [ABSTRACT FROM AUTHOR]

In recent years, the designers of long girder bridges in seismic areas have frequently opted for a continuous deck. One implication of this choice is that in many instances bridge abutments are called upon to carry large seismic forces, engaging the dynamic response of the soil–abutment system. To deal with this problem, this paper describes the formulation of a novel one-dimensional, inertial macroelement for simulating the dynamic behaviour of bridge abutments. The non-linear force–displacement relationship is characterised by a multi-surface plasticity model using a rigorous thermodynamic approach. The plastic response of the model is bounded by the ultimate capacity of the soil–abutment system that includes dissymmetry of the soil response in active and passive loading directions, while inertial effects transferred by the near-field approach embankment are simulated through appropriate participating masses in the macroelement formulation. The paper describes a straightforward calibration procedure of the proposed macroelement for horizontal, longitudinal loading of the abutment. The macroelement has been incorporated into a simplified, global, finite-element model of a multi-span girder bridge and validated through comparisons with results from a full three-dimensional (3D) dynamic time domain analysis under seismic loading. The inertial macroelement predictions of abutment deformations, axial deck loads and pier reaction forces are in very good agreement with the 3D soil–structure interaction model, and are achieved at much lower computational costs. The proposed inertial macroelement represents a significant improvement over existing simplified models based on linear response of the soil–abutment system. [ABSTRACT FROM AUTHOR]

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This paper presents a generalized, elastoviscoplastic constitutive model, MIT‐SR, that is capable of describing a wide range of time‐dependent characteristics observed in clays from creep to strain‐rate‐dependent shear behavior. The key component of the proposed model is a novel evolution equation that attributes viscoplastic deformations to a state variable, Ra, referred to as internal strain rate, which represents the perturbation of the clay particle assembly due to historical straining. This state variable is driven by external straining actions (under compression or shear), which can be intrinsically linked to the loading step in classical plasticity theory, and decays with time representing a fading memory process. The proposed framework can be used to extend existing time‐independent elastoplastic models. In this case, MIT‐SR is built upon a prior elastoplastic model (MIT‐S1), which uses 3‐D stress‐space surfaces and hardening laws to represent anisotropic effective stress‐strain‐strength properties, and a paraelastic approach to describe nonlinear hysteretic behavior at small strains. The paper highlights the versatility of the proposed MIT‐SR model in representing a wide range of time‐dependent characteristics for normally consolidation behavior and undrained shear behavior. By varying a strain‐rate sensitivity parameter, β, the model can capture a full spectrum from temporary material response to changing strain rate, to isotache‐type behavior where the normal consolidation and critical state lines are functions of the applied steady strain rate. The paper also showcases the model prediction for undrained creep and undrained relaxation behavior, and its promising capability in describing rate‐effects under cyclic direct simple shear. [ABSTRACT FROM AUTHOR]

This paper presents the calibration and validation for a new 3D elastoviscoplastic soil model, MIT‐SR, for Resedimented Boston Blue Clay (RBBC). The calibration procedure requires selection of material constants from standard types of laboratory consolidation and undrained shear tests, and a procedure for initialization of state variables. The formulation includes two key input parameters that describe sensitivity of rate dependence, β, and creep behavior, ρα, for which the calibration requires data including CRS consolidation tests at a range of strain rates and drained creep tests. The calibrated MIT‐SR model is benchmarked through a series of simulations of K0‐consolidated triaxial shear tests and direct simple shear tests on RBBC performed at different rates of shear strain. The calibrated model provides very good predictions of the effects of shear strain rate on key engineering properties such as undrained shear strength, strain to peak shear resistance and critical state conditions as functions of the consolidation stress history. The predictions of multistage, undrained relaxation tests are also in good agreement with unique measured behavior reported for RBBC. The comparisons provide clear evidence of the advances in predictive capabilities achieved using the proposed MIT‐SR formulation compared to preexisting isotache‐type models. [ABSTRACT FROM AUTHOR]

Face-to-face and edge-to-edge free energy interactions of Wyoming Na-montmorillonite platelets were studied by calculating potential of mean force along their center to center reaction coordinate using explicit solvent (i.e., water) molecular dynamics and free energy perturbation methods. Using a series of configurations, the Gay-Berne potential was parametrized and used to examine the mesoscale aggregation and properties of platelets that are initially random oriented under isothermalisobaric conditions. Aggregates of clay were defined by geometrical analysis of face-to-face proximity of platelets with size distribution described by a log-normal function. The isotropy of the microstructure was assessed by computing a scalar order parameter. The number of platelets per aggregate and anisotropy of the microstructure both increases with platelet plan area. The system becomes more ordered and aggregate size increases with increasing pressure until maximum ordered state at confining pressure of 50 atm. Further increase of pressure slides platelets relative to each other leading to smaller aggregate size. The results show aggregate size of (3-8) platelets for sodium-smectite in agreement with experiments (3-10). The geometrical arrangement of aggregates affects mechanical properties of the system. The elastic properties of the meso-scale aggregate assembly are reported and compared with nanoindentation experiments. It is found that the elastic properties at this scale are close to the cubic systems. The elastic stiffness and anisotropy of the assembly increases with the size of the platelets and the level of external pressure. [ABSTRACT FROM AUTHOR]

Smokey the Beaver: Beaver-Dammed Riparian Corridors Stay Green During Wildfire Throughout the Western USA Beaver dams are known to dampen flood waves, enhance groundwater recharge, and keep vegetation green during droughts. Using remote sensing, we found that beaver-dammed riparian corridors had only a 19% reduction in NDVI during wildfires, compared to 58% reduction in NDVI in places without beavers. [Extracted from the article]

Beaver dams are gaining popularity as a low‐tech, low‐cost strategy to build climate resiliency at the landscape scale. They slow and store water that can be accessed by riparian vegetation during dry periods, effectively protecting riparian ecosystems from droughts. Whether or not this protection extends to wildfire has been discussed anecdotally but has not been examined in a scientific context. We used remotely sensed Normalized Difference Vegetation Index (NDVI) data to compare riparian vegetation greenness in areas with and without beaver damming during wildfire. We include data from five large wildfires of varying burn severity and dominant landcover settings in the western United States in our analysis. We found that beaver‐dammed riparian corridors are relatively unaffected by wildfire when compared to similar riparian corridors without beaver damming. On average, the decrease in NDVI during fire in areas without beaver is 3.05 times as large as it is in areas with beaver. However, plant greenness rebounded in the year after wildfire regardless of beaver activity. Thus, we conclude that, while beaver activity does not necessarily play a role in riparian vegetation post‐fire resilience, it does play a significant role in riparian vegetation fire resistance and refugia creation. [ABSTRACT FROM AUTHOR]

It is widely accepted today that most soils exhibit non-linear stress strain properties even at very small strain levels and that improved representation of these stiffness properties is needed to understand and interpret many practical problems involving soil-structure interactions. Much of this understanding relates to research carried out at Imperial College led by John Burland and his colleagues during the 1980’s. This work included the development of devices for routine measurements of local strains in laboratory element tests (Burland & Symes, 1982; Jardine et al. 1984), documentation of small strain stiffness properties for a range of reconstituted and natural soils (Jardine et al. 1984), and representation of these nonlinear stiffness properties in finite element simulations involving a range of soil-structure interactions (Jardine et al. 1986). This information was then synthesized in Burland’s seminal Bjerrum Lecture ‘Small is beautiful’ (Burland, 1989) and linked to the performance of foundations, excavations and tunnels. This paper reviews the importance of small strain non-linearity from the perspectives of i) advancing knowledge of soil behavior, ii) development of more reliable constitutive models, and iii) evaluating impacts in the computed performance for practical geotechnical problems. [ABSTRACT FROM AUTHOR]

Deep mixing methods are widely used for stabilizing soft clayey soils and improving their bearing capacity. However, spatial variability in the shear strength of the cement-treated ground introduces uncertainties in estimating the bearing capacity for design. This paper evaluates the reliability of, block-type, cement-treated foundation under inclined load conditions using random field numerical limit analyses. The undrained shear strength is modelled as a random field which is characterized by a log-normal distribution and a spatial correlation length. Monte Carlo simulations are then used to interpret the stochastic bearing capacity factor and failure mechanisms for inclined concentric loading conditions at selected ratios of the shear strength ratio of cement-treated ground to original clay, the coefficient of variation in undrained shear strength and correlation length of the cement-treated zone. Variability of the undrained shear strength can reduce the expected bearing capacity of the cement-treated ground by 50–70% compared to homogeneously mixed clay. [ABSTRACT FROM AUTHOR]

The aggregation of colloidal clay mineral particles plays an important role in controlling the mechanical and transport properties of soils. Interactions and aggregation of plate-like montmorillonite particles were previously studied with the help of Molecular Dynamics (MD) simulation. This paper investigates the aggregation of cylindrical imogolite-like phyllosilicate nanotubes. Nano-scale MD simulations are carried out to find the potential of mean force between two nanotubes. This PMF is then used in a mesoscale simulation that represents interactions between elemental nanotubes through coarse-graining. We investigate the distribution of water molecules around the curved surfaces, and the effects of the surface charge density and tube length on aggregation. Shorter nanotubes were found to form larger stacks. [ABSTRACT FROM AUTHOR]

The article presents a study discussion on predicting tunnelling-induced ground movements and interpreting field measurements using numerical analysis at Hyde Park. Topics discussed include numerical method to interpret the reported measured surface and subsurface data; modes of displacements around the tunnel cavity; and cavity deformation parameters in order to match measured surface and subsurface displacements.

Nearly one billion people worldwide receive water through piped networks that are not continually pressurized and operate intermittently. The prevalence and persistence of these Intermittent Water Supplies (IWS) is surprising as this mode of operation induces water contamination and customer equity issues. Shortages of source water, customers' water demand, and leaking pipes are frequently cited as necessitating IWS. We propose a framework for understanding the persistence and operation of IWS. The supply system is represented by an average customer and a spatially averaged leakage rate. With this macroscopic hydraulic model, we relate customer demand satisfaction, source water availability, customer demand, and leakage. While this approach ignores the complexities of network topology, we find that the model approximates real systems well (calibrating to four intermittent reference networks achieved R2>0.87). The calibrated model is robust to moderate changes in demand and leakage (maintaining R2>0.81). Using the model, we show that the tipping point between satisfied demand and unsatisfied demand is a local optimum for utilities, which may explain the persistence of IWS. Beyond this point, the volume received by customers does not increase, but utilities must supply more water to the network. The generality of the proposed model enables its use when regulating and upgrading IWS. We demonstrate the latter by critiquing a performance‐based contract that was intended to improve an intermittent supply in India. Demand satisfaction has profound implications for hydraulics and human welfare. We propose the degree of demand satisfaction as a metric for evaluating IWS and for tracking the United Nations Sustainable Development Goal 6.1. Plain Language Summary: While most people get drinking water through underground water pipes, in some areas these pipes only provide water for a few hours each week. Globally, more than one billion people are served by these "intermittent water supply systems". In severely degraded systems, keeping pipes empty most of the time can reduce leakage and conserve source water, but it can also allow mud or sewage to enter through holes or cracks in the pipes, contaminating the water. This paper presents a simple model (an equation) that approximates how intermittent systems behave. The model suggests why intermittent operation is so common and highlights the challenges of improving such systems. The model relates hours of operation to factors such as source water supply, consumer demand, leakage, and if consumer demand is satisfied. The model implies that once consumer demand is satisfied, a system crosses a threshold and behaves differently: leakage, rather than demand, determines most of a system's water requirements. Measuring this threshold could identify systems that leave people thirsty and prioritize such systems for improvements. The model, therefore, provides new tools to support global commitments outlined in the United Nations' Sustainable Development Goal 6.1 and the Human Right to Water. Key Points: Without topology details, our proposed model of intermittent water supplies (IWS) matches closely with more complete network modelsWhile inadvisable, IWS provide utilities traditionally ignored, short‐term benefits (e.g., supply timing will change less due to drought)We propose a new demand satisfaction metric to quantify supply availability and help track Sustainable Development Goal 6.1 in IWS [ABSTRACT FROM AUTHOR]

There is extensive data to show that heating and cooling produces irrecoverable deformations in clays under fully drained conditions. The effects are most pronounced for normally and lightly overconsolidated clays that undergo significant compression. Most constitutive models have key limitations for predicting the thermo-mechanical response of clays through long-term (seasonal) cycles of heating and cooling. The Tsinghua ThermoSoil model (TTS; Zhang and Cheng in Int J Numer Anal Methods Geomech 41(4):527–554, 2017) presents a novel theoretical framework for simulating the coupled thermo-mechanical response of clays. The model uses a double-entropy approach to capture effects of energy dissipation at the microscopic particulate contact level on continuum behavior. This paper proposes a simple procedure for calibrating input parameters and illustrates this process using recent laboratory data for Geneva Clay (Di Donna and Laloui in Eng Geol 190:65–76, 2015). We then investigate capabilities of the TTS model in simulating familiar aspects of thermal consolidation of clays as well as the long-term, progressive accumulation of strains associated with seasonal heating and cooling processes for shallow geothermal systems installed in clays. The model predicts the existence of a long-term steady-state condition where there is no further accumulation of strain. This state depends on the consolidation stress and stress history but is independent of the imposed range of temperature, Tcyc. However, the value of Tcyc does affect the rate of accumulation of strain with thermal cycles. Simulations for normally consolidated Geneva Clay find steady-state strain conditions ranged from 2.0 to 3.7% accumulating within N = 10–50 thermal cycles. [ABSTRACT FROM AUTHOR]

Intermittent water supplies (IWS) deliver piped water to one billion people; this water is often microbially contaminated. Contaminants that accumulate while IWS are depressurized are flushed into customers’ homes when these systems become pressurized. In addition, during the steady-state phase of IWS, contaminants from higher-pressure sources (e.g., sewers) may continue to intrude where pipe pressure is low. To guide the operation and improvement of IWS, this paper proposes an analytic model relating supply pressure, supply duration, leakage, and the volume of intruded, potentially-contaminated, fluids present during flushing and steady-state. The proposed model suggests that increasing the supply duration may improve water quality during the flushing phase, but decrease the subsequent steady-state water quality. As such, regulators and academics should take more care in reporting if water quality samples are taken during flushing or steady-state operational conditions. Pipe leakage increases with increased supply pressure and/or duration. We propose using an equivalent orifice area (EOA) to quantify pipe quality. This provides a more stable metric for regulators and utilities tracking pipe repairs. Finally, we show that the volume of intruded fluid decreases in proportion to reductions in EOA. The proposed relationships are applied to self-reported performance indicators for IWS serving 108 million people described in the IBNET database and in the Benchmarking and Data Book of Water Utilities in India. This application shows that current high-pressure, continuous water supply targets will require extensive EOA reductions. For example, in order to achieve national targets, utilities in India will need to reduce their EOA by a median of at least 90%. [ABSTRACT FROM AUTHOR]

Temporary earth retaining structures help prevent collapse during construction excavation. To ensure that these structures are operating within design specifications, load forces on supports must be monitored. Current monitoring approaches are expensive, sparse, off-line, and thus difficult to integrate into predictive models. This work aims to show that wirelessly connected battery powered sensors are feasible, practical, and have similar accuracy to existing sensor systems. We present the design and validation of ReStructure, an end-to-end prototype wireless sensor network for collection, communication, and aggregation of strain data. ReStructure was validated through a 6-month deployment on a real-life excavation site with all but one node producing valid and accurate strain measurements at higher frequency than existing ones. These results and the lessons learnt provide the basis for future widespread wireless temporary earth retaining structure monitoring that increase measurement density and integrate closely with predictive models to provide timely alerts of damage or potential failure. [ABSTRACT FROM AUTHOR]

The occurrence of pathogenic bacteria in drinking water distribution systems (DWDSs) is a major health concern, and our current understanding is mostly related to pathogenic species such as Legionella pneumophila and Mycobacterium avium but not to bacterial species closely related to them. In this study, genomic-based approaches were used to characterize pathogen-related species in relation to their abundance, diversity, potential pathogenicity, genetic exchange, and distribution across an urban drinking water system. Nine draft genomes recovered from 10 metagenomes were identified as Legionella (4 draft genomes), Mycobacterium (3 draft genomes), Parachlamydia (1 draft genome), and Leptospira (1 draft genome). The pathogenicity potential of these genomes was examined by the presence/absence of virulence machinery, including genes belonging to Type III, IV, and VII secretion systems and their effectors. Several virulence factors known to pathogenic species were detected with these retrieved draft genomes except the Leptospira-related genome. Identical clustered regularly interspaced short palindromic repeats-CRISPR-associated proteins (CRISPR-Cas) genetic signatures were observed in two draft genomes recovered at different stages of the studied system, suggesting that the spacers in CRISPR-Cas could potentially be used as a biomarker in the monitoring of Legionella related strains at an evolutionary scale of several years across different drinking water production and distribution systems. Overall, metagenomics approach was an effective and complementary tool of culturing techniques to gain insights into the pathogenic characteristics and the CRISPR-Cas signatures of pathogen-related species in DWDSs. [ABSTRACT FROM AUTHOR]

This paper summarizes greenfield ground movements caused by the construction of twin 7.1-m-diameter tunnels for London's Crossrail project using earth pressure balance (EPB) tunnel boring machines (TBM). The data include surface deformations from a series of transects in Hyde Park together with subsurface data from one well-instrumented test section. Although far-field ground movements can be well-fitted using established empirical methods or simplified analytical solutions (elastic half-space), nonlinear, inelastic soil behavior is expected to affect measurements close to the tunnel. This paper considers the effects of constitutive behavior on the observed ground movements. Simple [Mohr-Coulomb (M-C)] and more-complex (MIT-S1) soil models are calibrated using results of high-quality laboratory element tests on intact London clay. The models are then used in two-dimensional (2D) numerical simulations in order to optimize three independent cavity-deformation parameters that control the spatial distribution of ground movements associated with the passage of each EPB machine. Simulations using the MIT-S1 model find maximum radial deformations at the crown of the tunnel with very small movements at the soffit, while M-C analyses show minimum deformations closer to the springline. The analyses consistently show that larger volume losses occur for the second, eastbound (EB) tunnel bore [ΔVL/V0 = 0.9-1.0% compared to 0.72-0.79 for prior westbound (WB)]. This result may be attributed in part to differences in EPB control parameters and/or interactions between the two tunnels that are not considered in the current analyses. [ABSTRACT FROM AUTHOR]

This paper describes numerical analyses of laboratory thick-walled cylinder (TWC) tests used to study the stability of vertical wellbores in hard clays. The TWC experiments were designed to simulate the drilling process by reducing the internal cavity pressure although maintaining the external radial stress and measuring internal changes in volume within the model wellbore. Radial deformations of the cavity (borehole squeezing) attributable to plastic deformations of the clay represent a critical condition for the design of wells drilled through ductile formations (i.e., very hard soils and poorly lithified rocks). The current analyses simulate coupled flow and deformation in the TWC soil specimens using a finite element (FE) program and the MIT-E3 model to represent the effective stress-strain-strength properties of the reference clay, resedimented Boston blue clay (RBBC). The model is freshly calibrated using results of laboratory triaxial element tests performed at the same stress levels as the TWC experiments (s'vc = 1-10 MPa). The numerical simulations are compared with data from experiments performed at different levels of confining stress, rates of depressurization, and wall thickness. The numerical model provides good estimates of the instability measured in the TWC tests and provides an accurate estimate of the undrained shear strength controlling cavity deformations. These validations provide confidence in the application of the model for estimating behavior of prototype (i.e., vertical and deviated) wellbores in similar hard clay formations. [ABSTRACT FROM AUTHOR]

• The discussers presented a slip surface that intersects with the downstream slope at the crest of the starter dam. This paper presents a closure to "Stability Analysis of Upstream Tailings Dam Using Numerical Limit Analyses" by Andrew J. Whittle, Hayel M. El-Naggar, Sherif A. Y. Akl, and Abdullah M. Galaa. https://doi.org/10.1061/(ASCE)GT.1943-5606.0002792. The failure surface presented by the discussers is flat and extends horizontally for a long distance upstream, suggesting that the starter dam or the material behind it would not move during the failure process. [Extracted from the article]

Summary We recently identified human N-acetyltransferase 2 ( NAT2 ) as an insulin resistance (IR) gene. Here, we examine the cellular mechanism linking NAT2 to IR and find that Nat1 (mouse ortholog of NAT2 ) is co-regulated with key mitochondrial genes. RNAi-mediated silencing of Nat1 led to mitochondrial dysfunction characterized by increased intracellular reactive oxygen species and mitochondrial fragmentation as well as decreased mitochondrial membrane potential, biogenesis, mass, cellular respiration, and ATP generation. These effects were consistent in 3T3-L1 adipocytes, C2C12 myoblasts, and in tissues from Nat1 -deficient mice, including white adipose tissue, heart, and skeletal muscle. Nat1 -deficient mice had changes in plasma metabolites and lipids consistent with a decreased ability to utilize fats for energy and a decrease in basal metabolic rate and exercise capacity without altered thermogenesis. Collectively, our results suggest that Nat1 deficiency results in mitochondrial dysfunction, which may constitute a mechanistic link between this gene and IR. [ABSTRACT FROM AUTHOR]

Noroviruses (NoVs) are a major cause of acute gastroenteritis worldwide and spread through person-to-person transmission and contaminated food or water. A miniaturised microelectromechanical systems (MEMS)-based electrochemical aptasensor, a biosensor using aptamer as the recognition element for simple, sensitive and rapid detection of NoV has been developed. The novelty of this work is integration of MEMS technology with aptamer to develop a miniaturised and portable electrochemical sensor for environmental pathogen monitoring. An MEMS electrochemical aptasensor device was prepared by immobilising a thiolated DNA aptamer on an on-chip gold (Au) working electrode through the affinity between thiol and Au, and formation of a DNA aptamer monolayer was confirmed by means of cyclic voltammetry as well as visual observation of a fluorescent-labelled aptamer. The MEMS electrochemical aptasensor exhibited rapid and clear square wave voltammetry response against different titres of murine norovirus, an experimental model of human NoV. The possibility of developing a handheld aptasensor platform using a portable electrochemical measurement device is also demonstrated. This research forms initial basis for the development of an electrochemical MEMS-aptasensor platform and its application for virus detection. [ABSTRACT FROM AUTHOR]

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This paper proposes a novel methodology for understanding the meso-scale aggregation of clay platelets in water. We use Molecular Dynamics simulations using the CLAYFF force fields to represent the interactions between two layers of Wyoming montmorillonite (Na-smectite) in bulk water. The analyses are used to establish the potential of mean force at different spacings between the layers for edge-to-edge and face-to-face interactions. This is accomplished by finding the change in free energy as a function of the separation distance between the platelets using thermodynamic perturbation theory with a simple overlap sampling method. These nanoscale results are then used to calibrate the Gay-Berne (GB) potential that represents each platelet as a single-site ellipsoidal body. A coarse-graining upscaling approach then uses the GB potentials and molecular dynamics to represent the meso-scale aggregation of clay platelets (at submicron length scale). Results from meso-scale simulations obtain the equilibrium/jamming configurations for mono-disperse clay platelets. The results show aggregation for a range of clay platelets dimensions and pressures with mean stack size ranging from 3 to 8 platelets. The particle assemblies become more ordered and exhibit more pronounced elastic anisotropy at higher confining pressures. The results are in good agreement with previously measured nano-indentation moduli over a wide range of clay packing densities. [ABSTRACT FROM AUTHOR]

This paper presents a probabilistic approach to evaluating the geotechnical stability problem by incorporating the stochastic spatial variability of soil property within the numerical limit analyses (NLAs). The undrained shear strength and unit weight of soil are treated as a random field which is characterized by a log-normal distribution and a spatial correlation length. The current calculations use a Cholesky Decomposition technique to incorporate these random properties in NLAs. The Random Field Numerical Limit Analyses are applied to evaluate the effects of spatial variability of soil property on the slope stability and failure mechanism of slope. Monte Carlo iterations are then used to interpret the slope reliability and the dimension for collapsed slope for selected ranges of the coefficient of variation in soil property and the ratio of correlation length to slope height. Finally, the variation in the dimension of collapsed slope is examined in terms of the variability of slope reliability. [ABSTRACT FROM PUBLISHER]

The complex mechanical behaviour of granular materials is commonly studied by considering the evolving particle contact network. An often overlooked feature is the influence of micro-scale geometric configuration of pores on the macroscopic response. This paper presents a series of tools to quantify the shape, volume distribution and orientation characteristics of the pore space. The proposed approach is compared against data extracted from physical and numerical experiments with monodisperse assemblies of spheres. Individual pores are represented by polyhedral pore unit cells obtained by combining the Delaunay tessellation with an algorithm for merging Delaunay cells based on the concept of maximal inscribed sphere, after Al-Raoush et al. (Soil Sci Soc Am J 67(6):1687-1700, ). A pore shape parameter is proposed that considers pore volume and surface, and is analytically related to the void ratio and the number of edges forming the polyhedral pore unit cell. The pore volume distribution is shown to be uniquely described by the analytical k-gamma distribution proposed by Aste and Di Matteo (Phys Rev E 77(2):021309, ). A pore orientation tensor is introduced to define the principal orientation of individual pore units. This is subsequently used to define a global orientation tensor that reveals an isotropic pore network for the reference monodisperse assemblies. The global orientation tensor is analytically expressed in terms of the parameters defining the pore volume distribution. [ABSTRACT FROM AUTHOR]

The basement of the Stata Center building on the MIT campus required 12.8 m deep excavations covering a large open-plan site and underlain by more than 25 m of lightly overconsolidated Boston Blue Clay. The excavations were supported by a floating, perimeter diaphragm and braced with a system of internal corner struts, rakers, and tieback anchors. The project involved a complex sequence of berms, access ramps, and phased construction of the concrete mat foundation. One of the key goals of the design was to limit ground movements in order to prevent damage to adjacent structures, including the Alumni Pool building, which was founded on shallow caissons and located less than 1.5 m from the south wall. Lateral wall movements and building settlements were closely monitored throughout construction, while photos from a network of webcams located around the open-plan site provide a detailed time history of the construction processes. This paper describes the development of a comprehensive three-dimensional (3D) finite-element (FE) model for the Stata Center basement excavation, which has been enabled by recent advances made available in a FE software package, including efficient multicore iterative solving capabilities, importing of geometric data from computer-aided design files, and use of embedded pile elements to represent tieback anchors. The analyses highlight the effects of the 3D excavation and support geometry on wall and ground movements. The base case results using a simple elasto-plastic Mohr-Coulomb soil model with undrained conditions in the clay are generally in very good agreement with measured performance. The effects of refined constitutive modeling and partial drainage within the clay have a secondary role in numerical predictions for this project. [ABSTRACT FROM AUTHOR]