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A personal narrative is presented which explores the author's experience of preparing for the offering of the Manufacturing and Product Design (MPD) Diploma in Great Britain.

Introduction: Many men ≥65 years old have histological prostate cancer. Only a small proportion may present clinically with the disease and relatively few will die from prostate cancer. We assessed baseline PSA levels and the risk of clinically detected prostate cancer and prostate specific mortality in this population. Methods: From a regional PSA database, all men aged ≥65 years old who had their first PSA test between 1994 and 1998 were identified. These were followed for prostate cancer diagnosis and mortality until 2003. The absolute risk and hazard ratio for prostate cancer diagnosis and mortality, based on baseline PSA level, were determined. Results: 36003 men were included. Mean age was 74.9 years and mean follow-up 5.4 years. 2153 (6.0%) men were diagnosed with prostate cancer. 13074 (36.3%) died, with prostate cancer the cause of death in 673 men (5.1% of deaths). Within age groups, the absolute risk and hazard ratio of cancer increased incrementally with PSA level (Table). Prostate-specific mortality remained low (<5/1000 person years) at all PSA categories <15.0ng/ml. All-cause mortality was similar in PSA categories <10.0ng/ml, and was much greater than prostate-specific mortality across all PSA categories. Conclusion: The risk of prostate cancer diagnosis and prostate specific mortality is related to baseline PSA level. However, in this age group, death from prostate cancer was infrequent compared to other causes, even when baseline PSA was markedly elevated (up to 20.0ng/ml). A conservative approach to invasive investigation may be appropriate in men older than 65 years. [ABSTRACT FROM AUTHOR]

Objectives To investigate the effect of various genetic and environmental modifiers on left ventricular (LV) wall thickness in a cohort of cats genotyped for the myosin binding protein C3 mutation (MYBPC3). Animals Sixty-four Ragdoll cats. Methods All cats were screened for HCM with echocardiography and genotyping for the HCM-associated MYBPC3:R820W mutation. Cats were also genotyped for previously identified variant polymorphisms of the angiotensin-converting enzyme (ACE) and cardiac beta-adrenergic receptor (ADRB1) genes. Plasma N-terminal pro-B-type natriuretic peptide and cardiac troponin I were also measured. Associations were evaluated between genotype (MYBPC3 negative/positive, and ACE and ADRB1 negative/heterozygous/homozygous), patient factors (body weight, age and sex) and echocardiographic measurements of LV wall thickness. Results Male cats had greater maximum wall thickness (LV max ; 5.8 mm, IQR 5.1–6.4 mm) than females (4.7 mm, IQR 4.4–5.3 mm, p = 0.002). Body weight positively correlated with LV max ( ρ = 0.604, p < 0.001). The MYBPC3:R820W-positive cats had a greater LV max (5.44 mm, IQR 4.83–6.28 mm) than the negative cats (4.76 mm, IQR 4.36–5.32 mm, p = 0.001). Also, the ACE polymorphism genotype was associated with LV max : the homozygous cats (5.37 mm, IQR 5.14–6.4 mm) had greater LV max than the heterozygous cats (4.73 mm, IQR 4.41–5.55 mm, p = 0.014). Only the MYBPC3 genotype and body weight were independently associated with wall thickness in multivariable analysis. Conclusions This study provides evidence that the MYBPC3:R820W mutation is independently associated with LV wall thickness in Ragdoll cats. Body weight is also independently associated with maximum LV wall thickness, but is not currently accounted for in HCM screening. In addition, other genetic modifiers may be associated with variation in LV wall thickness in Ragdolls. [ABSTRACT FROM AUTHOR]

Abstract: Objectives : To determine if natriuretic peptide concentrations are increased in cats with systemic hypertension and/or chronic kidney disease (CKD). Animals : 22 normal cats, 13 normotensive cats with mild-moderate CKD (NT-CKD), 15 hypertensive cats with mild-moderate CKD (HT-CKD) and 8 normotensive cats with severe CKD (NT-CKD-severe). Methods : N-terminal pro-B-type (NT-proBNP) and pro-A-type (NT-proANP) natriuretic peptides were measured in plasma samples from all cats using commercially available assays and concentrations in the normal and diseased groups compared using non-parametric statistical tests. Spearman''s rank correlation was used to test for an association between natriuretic peptide and creatinine concentrations. Results : NT-proANP was significantly higher in the NT-CKD-severe than the normal group of cats (P =0.006) but there were no other differences between groups. NT-proBNP concentrations were significantly higher in the HT-CKD group than both the normal (P <0.001) and the NT-CKD (P <0.001) groups. NT-proBNP concentrations were also higher in the NT-CKD-severe (P <0.001) and the NT-CKD (P =0.005) groups than the normal group. NT-proANP but not NT-proBNP was significantly and positively associated with plasma creatinine concentration. Conclusions : Measurement of NT-proBNP shows promise as a diagnostic marker for systemic hypertension in the cat. Its concentration is not significantly increased in cats with mild-moderate normotensive CKD. [Copyright &y& Elsevier]

Abstract: Objectives: To determine if serum natriuretic peptide (NP) concentrations could distinguish cardiac from non-cardiac causes of respiratory distress (RD) in cats. Animals: Seventy-four cats from 1 university hospital were used. Methods: Serum NP concentrations were measured in 41 cats with non-cardiac respiratory distress (RD-NC) and compared to 33 cats with RD due to congestive heart failure (RD+CHF) using sandwich enzyme immunoassays (ELISA). Results: RD-NC cats had lower (P =0.0001) median NT-proANP and NT-proBNP concentrations (614 and 45fmol/mL, respectively) than RD+CHF cats (1690 and 523fmol/mL, respectively). The area under the curve was 0.88 and 0.96 for the receiver operating curve analysis of the diagnostic accuracy of NT-proANP and NT-proBNP concentrations to discriminate RD+CHF from RD-NC cats (P =0.036). An optimum cut-off concentration of 986fmol/mL for NT-proANP and 220fmol/mL for NT-proBNP accurately discriminated RD-NC from RC+CHF cats with a sensitivity of 93.8% and 93.9% and a specificity of 80.3% and 87.8%, respectively. Conclusions: Serum NP concentrations were different in RD+CHF cats compared to RD-NC cats. Evaluation of circulating NP concentrations may be helpful in the initial approach to cats presenting with respiratory distress, particularly if advances in ELISA technology result in a rapid cage-side test. [Copyright &y& Elsevier]

• An efficient approach for railway ballastless tracks on unsaturated earthworks. • Modelling train-track interaction and unsaturated trackbed-earthwork dynamics. • Numerical stability discussed with the validated model. • New findings into the effect of subgrade saturation on ballastless track dynamics. • Subgrade saturation, train speed and track irregularities affecting pore pressure. Concrete slab tracks help shield the supporting railway earth structure from external water ingress. However, the inevitable cracks that arise during its lifespan provide a pathway for water penetration, leading to changes in the degree of saturation of the underlying support. This can affect the dynamic response of the structure, however is challenging to model due to the computational requirements of three-phase unsaturated soil simulation. To address this, this paper presents two main novelties: 1) an efficient moving frame of reference approach for railway ballastless tracks on unsaturated earthworks subject to train loading, 2) new findings into the effect of degree of subgrade bed saturation on ballastless track dynamics. First the model is presented, including formulations for vehicle-track interaction and unsaturated subgrade dynamics. Considerations for numerical stability are then discussed and the model is validated, before investigating the role of subgrade bed saturation on pore water pressure and displacements. It is shown to have a high impact on pore water pressure generation, but a limited impact on deflections. The effect of train speed is then investigated and it is found that higher train speeds induce higher pore water pressures. Track irregularities are also investigated and it is found that they play an important role in pore water pressures. [ABSTRACT FROM AUTHOR]

The deployment of asphaltic support layers (ASLs) within railway track structures has the potential to increase track bending stiffness, assist moisture runoff and provide a platform for track construction. These merits have increased its usage within the rail industry, however the understanding of asphaltic track dynamics during train loading remains limited. Therefore, the primary aim of this study is the development of new knowledge into the dynamic behavior of concrete slab track systems enhanced with asphaltic underlays. To do so, a numerical simulation approach is used, comprised of two sub-models: 1) a coupled multi-body vehicle−track model, for the purpose of computing wheel/rail forces; and 2) a 3D dynamic finite element track-ground model to simulate stress wave propagation in the sub-structure. The models are validated using both analytical results and field tests, and then used to simulate slab track systems with ASL thicknesses of: 0, 0.05, 0.07, 0.10, and 0.15 m. First the dynamic response at locations both near and far from the track joints are compared to quantify the asphaltic foundation stresses, deflections, accelerations and strains. It is found that stress concentrations occur near the concrete base joints and are an important consideration for ASL design. Next, asphalt concrete durability at 400 km/h line speed is explored considering seasonal temperature variations and it is found that the expected cumulative damage meets serviceability requirements. Finally, the influence of different asphaltic layer thicknesses on reaction modulus is discussed, concluding that the optimal thickness range, considering plastic deformation and construction constraints, is between 0.07 m and 0.10 m. • A hybrid modelling approach is proposed to assess dynamic performance of asphaltic slab tracks. • Effect of asphalt on stresses, deflections, accelerations, and strains is quantified considering slab expansion joints. • Asphalt concrete durability and its implications for asphaltic trackbed design are discussed. • An optimal thickness range for asphaltic support layers is between 0.07 m and 0.10 m [ABSTRACT FROM AUTHOR]

Civil excavation projects frequently yield substantial excess spoil, posing challenges to sustainable construction. This study explores repurposing such spoil for creating controlled low strength material (CLSM), emphasizing the novel use of polycarboxylate superplasticizer (PCE) to reduce the water requirement. The work also distinctively utilizes water film thickness (WFT) theory to elucidate the effects of PCE dosage and WFT on material properties, thereby advancing CLSM mix design. First, using an experimental approach, a series of fresh CLSM samples are prepared, with varying the water-to-solid ratio (W/S) and PCE dosage, to evaluate their packing density, WFT, flowability, and bleeding rate. It is demonstrated that both packing density and WFT experienced a non-linear increase with rising PCE dosage. Regression analysis of the experimental data reveals that the flowability and bleeding rate linearly increase with the rising WFT, and the enhancements are more pronounced at higher PCE dosage. Notably, at a given WFT, the impact of PCE dosage on flowability and bleeding rate reduce as WFT decreases. Additionally, the research identifies specific WFT thresholds correlating with maximum flowability and a 5% bleeding rate. These thresholds mark the critical point at which WFT ceases to influence flowability and delineate the maximum WFT that satisfies the bleeding rate requirements, respectively. These insights are important for optimizing the design of CLSM with PCE in terms of flowability and bleeding rate. • PCE enhances soil-based CLSM flowability at lower W/S, balancing strength. • PCE dosage impacts flowability and bleeding by altering WFT and colloidal attraction. • Combined effects of PCE dosage and WFT on CLSM flowability and bleeding are studied. • WFT thresholds for maximum flowability and 5% bleeding rate decline as PCE dosage increases. [ABSTRACT FROM AUTHOR]

Geotechnical measurements are often limited, leading to the use of interpolation techniques for interpreting spatial variations in geotechnical properties from sparse geo-data. Traditional geostatistical methods suffer from significant computational complexity. On the other hand, data-driven approaches often lack integration with geotechnical domain knowledge, potentially oversimplifying or complicating predictions related to the spatial variability of geotechnical properties. This study introduces a novel framework that combines geotechnical knowledge with data-driven methods to model inherent soil spatial variability incorporating Geotechnical Correlation Field (GCF) that reflects domain knowledge. The GCF, influenced by Autocorrelation Function (ACF) types and Scale of Fluctuation (SOF), provides a flexible basis for accurately representing spatially varying geotechnical properties. Using a large synthetic database comprising known ACF types and SOFs, we constructed a series of specialized neural networks. These networks identify random field parameters at different sites based on sparse data, and the estimated parameters can be directly used to calculate GCFs for a given site. The performance of the proposed method is validated using a set of synthetic data and a real case history in New Zealand. The results demonstrate the model can accurately predict random field parameters for irregularly spaced geo-data, even with limited information. Significantly, the GCFs offer improved physical interpretations and enhance the performance of subsurface modeling. The computational complexity of this method is independent of the number of soil cells, making it highly efficient and scalable. [ABSTRACT FROM AUTHOR]

Transport systems such as highways and railways are constructed on earthworks that experience fluctuating levels of saturation. This can range from dry to fully saturated, however most commonly they are in a state of partial saturation. When numerically modelling such problems, it is important to capture the response of the solid, liquid and gas phases in the material. However, multi-physics solutions are computationally demanding and as a solution this paper presents a finite element approach for the dynamic analysis of unsaturated porous media in a moving coordinate system. The first novelty of the work is the development of a principle of relative motion for a three-phase medium, where the moving load is at rest while the unsaturated porous medium moves relative to the load. This makes it particularly efficient for moving load problems such as transport. The second novelty is a parametric investigation of the three-phase response of a partially saturated medium subject to a moving load. The paper starts by presenting the time domain model in terms of its constitutive relationships and equations for mass and momentum conservation. Next the model is validated using three case studies: the consolidation of a saturated soil column, the dynamics of an unsaturated soil column and finally the response of a saturated foundation to a moving load. It is then used to study a moving 2D plane strain load problem and its performance is compared to that of a standard FEM solution which does not employ a moving coordinate system. Similar accuracy is obtained while computational efficiency is improved by a factor of ten. Finally, the model is used to investigate the effect of degree of saturation and moving load speed on the response of an unsaturated porous medium. It is found that both variables have a significant impact on the dynamic response. [ABSTRACT FROM AUTHOR]

The geotechnical and geodynamic characteristics of railway earthworks under train loading are important quantities for railway and geotechnical engineers, but difficult to quantify. Characterizing the anticipated settlement and dynamic properties of compacted fills after earthwork construction, but before track laying, is advantageous, because modifying construction after laying the track is significantly more expensive. The difficulty in measuring these indices arises from the need to perform cyclic loading that realistically simulates the frequencies and magnitudes induced by trains. To address this issue, this paper introduces a novel shaker designed to apply cyclic loads similar to those of trains. The paper first presents an outline of the design requirements for the shaker, followed by the development of a theoretical dynamics model to aid mechanical design. This model is used for examining various shaker configurations, especially their performance under different potential testing conditions. The shaker's final design includes dual eccentric rotors that excite an adjustable-mass counterweight, complemented by a lateral support frame to counter horizontal movement and ensure vertical excitation. Once the shaker is built, it is used to evaluate newly constructed mudstone earthworks near a railway line. A method for estimating the dynamic stiffness and damping of earthworks is proposed, which uses data from frequency sweep test data from the shaker. Outputs from the dynamics model show close alignment with the field results. Finally, a method for designing the shaker configuration according to the desired loads is proposed. • Large-scale shaker developed for earthworks testing; replicates train-induced stress. • Novel dual-rotor design enhances economic efficiency; no cooling system needed. • Shaker effective in estimating earthworks stiffness and damping coefficients. • Synchronization issues in rotors identified; stable output between 6 and 16 Hz. • Field tests confirm model accuracy; suitable for railway earthworks evaluation. [ABSTRACT FROM AUTHOR]

Expansive soil from civil excavation projects is often considered waste material due to its propensity to swell. This study pioneers a novel approach to sustainable infrastructure by exploring the viability of repurposing expansive soils in the production of controlled low-strength materials (CLSM), incorporating sand and cement into the mix. Laboratory tests were conducted on CLSMs with varying mix proportions to assess their fresh (flowability, bleeding rate, and setting time) and hardened (swelling, unconfined compressive strength, and dry-wet durability) properties. The investigation focuses on three critical parameters: sand-to-soil ratio (S), cement-to-aggregate ratio (C), and water-to-solid ratio (W). Experimental results indicate the problematic swelling behavior of CLSM is mitigated when C surpasses 18%, at an S value of 10%. Adjusting either W or S enhances flowability but also elevates the bleeding rate. An increase in C has a marginal effect on flowability and bleeding rate, but markedly accelerates the setting time. Flowability follows a negative exponential relationship with time. Furthermore, increasing C or decreasing W markedly enhances both residual strength after dry-wet cycles and compressive strength. When S is below 10%, both compressive and residual strengths show a positive correlation with S. Conversely, when S exceeds 10%, a negative correlation is observed with compressive strength. A predictive model for the compressive strength and flowability of CLSM made from expansive soil has been developed, utilizing data normalization techniques. This model assists in determining the optimal mix proportions appropriate for applications in narrow backfills. • Novel CLSM from waste expansive soil mitigates swelling when C > 18% and S = 10%. • Flowability drops 23%− 33% within 90 mins, requiring water adjustment for longer durations. • Optimal S at 10% for peak compressive strength; further increases yield marginal gains. • Study identifies CLSM mixes suitable for low-grade roads and retaining walls. [ABSTRACT FROM AUTHOR]

Geotechnical testing serves to assess the strength and stiffness of in-situ soils, for purposes such as informing foundation design. Despite its importance, time constraints, financial considerations, and site-specific limitations often restrict testing to isolated locations with limited horizontal resolution. Therefore, this paper presents a novel hybrid generative deep learning model designed to approximate soil properties across sites based on sparsely sampled geotechnical data. The model uses geological subsurface samples derived from random field theory as 'a priori' data for a conditional variational auto-encoder (CVAE) model. By doing so, it attempts to map the relationship between in-situ data and the corresponding spatial coordinates, as well as the inherent link between in-situ data and spatial distribution. Then, in the post-processing phase, a Kriging model interpolates minor discrepancies between the measured and predicted values. To demonstrate its practical application, this paper focuses on cone penetration testing (CPT) as the geotechnical test method. The model's development is thoroughly discussed, followed by the validation using in-situ data and an analysis conducted with synthetic data. It is shown that the uncertainty associated with CVAE-Kriging depends upon both the distance from the sample point and the site's inherent complexity. The proposed methodology not only offers refined subsurface modeling but also expands the understanding of uncertainty in geotechnical testing. Practically, it can assist geotechnical engineers with insights during the survey phase. • A hybrid deep generative method for geological subsurface modeling is proposed. • Substantial 'prior' information is incorporated to guide subsurface modeling. • Validation is performed using multiple non-stationary cases and various methods. • The CVAE's uncertainty correlates with the complexity inherent to the site itself. [ABSTRACT FROM AUTHOR]

• Large-scale laboratory tests on railway ballast-subgrade materials under different conditions. • Both conventional and wicking geotextiles can prevent water from infiltrating. • Wicking geotextile offers better performance in reducing moisture content in subgrade soil. • Wicking geotextile decreases fouling degree of ballast under cyclic loading. Geotextiles are used within railways and highways to reduce settlement and improve drainage characteristics. However, the drainage performance of conventional geotextiles under unsaturated conditions can be limited due to capillary barrier effects. Therefore, more recently, wicking geotextiles consisting of woven fibers with deep groves have been developed to improve drainage performance. Despite these potential performance benefits and many related highway studies, there has been minimal study into the performance of wicking geotextiles for railways. Therefore, this study performs large-scale laboratory tests on railway ballast-subgrade materials under three conditions: non-stabilized (NSS), conventional geotextile stabilized (CGSS), and wicking geotextile stabilized (WGSS). Each test sample is subject to 600,000 cyclic loading cycles over 3 phases. The first phase is a stationary phase for consolidation, the second is to simulate loading directly after rainfall, and the third is to simulate loading after flooding. The results are analyzed and four conclusions are drawn: 1) both geotextile types prevent rainfall water from infiltrating into subgrade soils, however the wicking shows elevated performance, 2) the wicking geotextile produces capillary suction, which compared to the conventional geotextile, significantly delays infiltration and helps to reduce the moisture content in subgrade soils, 3) both geotextiles are capable of separation and filtration during rainfall and flooding simulation, however the wicking offers additional performance, 4) the deformation of both geotextiles is similar. [ABSTRACT FROM AUTHOR]

Coarse aggregates are essential for constructing railways and highways, as they affect structural performance through their compacted state and shear strength. Particle geometry influences these properties, but little research has quantitatively investigated how shape indexes impact mechanical indicators. This study addresses this gap by exploring the effect of particle aspect ratio on coarse aggregate compaction and shear behavior using the discrete element method (DEM). The study's key contribution is the development of novel equations that describe the correlation between packing porosity, inter-particle contact state, and aspect ratio control thresholds in a practical format. To do so, first, a point cloud database is compiled from laser scans of 700 natural aggregate particles. Each particle is classified using three aspect-ratio parameters: elongation, flatness, and flatness-elongation index (FEI). They are then digitized as rigid block particle models and compared against actual point clouds. Next, nine aggregates of representative shapes are assessed for their macro and mesoscopic mechanical responses using DEM-based vibro-compaction and direct shear tests. The compaction simulations indicate an exponential relationship between porosity and inter-particle coefficient of friction and show that aggregates with FEI ≈ 0.5 are a good choice. The direct shear simulations consider the same initial porosity, and show that the relationship between peak shear strength and vertical stress follows a power function. Finally, the analysis of contact forces and fabric tensors implies that FEI ≈ 0.5 may also facilitate particle fragmentation control. [ABSTRACT FROM AUTHOR]

• A concept of wedge-shaped self-levelling railway sleeper is introduced. • The type and angle of the wedge sleeper are analysed. • The settlement correction and force behaviour of the wedge sleeper is presented. • The cooperation between 2D and 3D simulations is introduced to increase the feasibility of discrete element simulations. Differential railway track settlement can result in ballast voids, leading to sleepers that hang from the rail and are no longer supported by the ballast. These hanging sleepers are damage for track component. As a solution, this paper proposes and investigates a new concept sleeper with a wedge-shaped geometry, intended to stimulate the migration of ballast into any voids, thus reducing the occurrence of hanging sleepers. A series of scaled laboratory tests and 2D and 3D discrete element simulations are used to investigate different wedge-shaped geometries. The investigations include the wedge type (single long wedge versus multiple mini-wedges) and the wedge angle (30, 45, 60 degrees). First, the scaled laboratory tests are used to study the performance of different wedge geometries. Next, 3D DEM simulations are performed to analyse the contact forces in the ballast due to different wedge designs. Finally, 2D DEM simulations are performed to study the settlement behaviour. The main conclusions are that a single long wedge is preferable compared to multiple smaller wedges. when the wedge sleeper angle is larger than the ballast's angle of repose, particles have the freedom to migrate into the settlement induced voids. Also, an increased wedge sleeper angle stimulates greater particle migration and thus improves the support correction. However the longer wedge also leads to a decrease in effective ballast height under sleeper which may make retrofitting on existing lines challenging. [ABSTRACT FROM AUTHOR]

The structural optimization of basal reinforced piled embankments is usually conducted by examining design alternatives while ignoring the inherent variability of soil properties and studying only a limited number of structural variables. As an alternative, this paper proposes a hybrid modeling framework to introduce soil property uncertainty into embankment settlement calculations. This is important because settlement is critical in the serviceability assessments considered during structural optimization. The proposed framework consists of uncertainty modeling, finite element method, surrogate modeling, and probabilistic analysis. More specifically, a neural network with Monte Carlo dropout that accounts for uncertainty is employed to correlate the soil properties which affect the long-term performance of embankments over soft clay. Next, a coupled finite element analysis is performed using two constitutive soil parameters generated by the neural network to predict post-construction settlements. Combining the finite element (input source) with a surrogate model (data-driven approximation) yields substantial settlement outcomes for structure evaluations. A case study is then used to validate the effectiveness and applicability of this framework. Finally, an exhaustive search approach is used to design a cost-effective improved ground within ultimate and serviceability limit state constraints. Pareto front is computed using a logistic function at different settlement reliability levels. [ABSTRACT FROM AUTHOR]

• Summary and comparison of ballast standards in different countries. • Promising future ballast technologies are discussed. • Ballast qualification considering different material types and local geologies. The properties of railway ballast material are affected by the local geologies and climatic environments from which the parent rock is sourced. These factors can make it challenging to select the most appropriate material for railway applications. To address this issue, this paper first reviews the means of ballast selection in complex environments across the world. The selection criteria for ballast materials are compared and test methods for ballast quality quantification are summarised. Next, ballast parent rock types and the implications of mining approaches are discussed, before analysing ballast morphology with respect to ballast size and shape. Then ballast petrography is reviewed with a focus on the effect of mineral composition on performance. Finally, some promising future ballast technologies are discussed with a focus on environmental performance. These include recycled ballast, asphaltic materials, steel slag and ballast gluing. The review shows that regarding ballast selection means and criteria, the number and type of quantitative indicators varies greatly between countries. In particular there are divergences in test methods and quantitative indicators for ballast quality considering material types and local geologies. Suggested future research directions are proposed, such as the effect of tamping and dynamic track stabilisation on ballast properties. [ABSTRACT FROM AUTHOR]

• The influence of non-linear soil properties on critical speed in railway lines is investigated for both slab and ballasted tracks. • Two models are used: a 3D FEM approach, and a novel dispersion curve technique. • The influence of the Plastic Index (PI), the soft soil thickness and train load magnitude are assessed. • The soil non-linear behaviour plays a very important role in ballasted tracks, while on slab tracks the influence is not so expressive. • For ballasted tracks, the relationship between the critical speed and shallow upper soil layer thickness can be weak. The design of high-speed railway lines involves geotechnical challenges, one of which is the risk of dynamic track amplification, for example on track sections where the train speed approaches the track-ground critical speed. In these cases, soil strains increase significantly with an increase in train speed, far exceeding the limits of linear elastic behaviour. This can result in a non-linear reduction of soil stiffness. To better understand this relationship, this paper studies the influence of soil non-linearity on the critical speed of concrete slab and ballasted tracks. To perform an in-depth analysis into non-linear critical speed, two models are used: a 3D FEM approach, and a novel dispersion curve technique. Using the models, the effect of soil plasticity on non-linearity is studied, with different ranges of plasticity found to play an important role. Secondly, the influence of soil thickness and loading magnitude are evaluated. It is shown that ballasted tracks are deeply affected by the non-linear soil behaviour, compared to a concrete slab track. Further, it is shown that for the ballasted tracks, the relationship between the critical speed and shallow upper soil layer thickness can be weak. [ABSTRACT FROM AUTHOR]

This paper investigates the effect of initial tunnel construction on the future ground vibration levels generated during underground railway line operation. This is important because tunnel construction results in soil disturbance, thus inducing high soil strain levels near the tunnel lining. The resulting soil stiffness degradation impacts the future generation of ground-borne traffic vibration and it's propagation to the foundations of nearby buildings, however has never been investigated. Therefore, to address this, this work develops a novel hybrid modelling approach, consisting of a construction simulation model and an elastodynamics model. First the convergence-confinement method is used to determine the stress state induced during tunnel construction using a tunnel boring machine (TBM). Next a 2.5D FEM-PML model consisting of vehicle-track-tunnel-soil is used to predict the vibration fields induced by underground trains. To link the approaches, the soil stiffness degradation contours computed from the tunnelling simulation act as inputs for the 2.5D underground railway model. This facilitates the assessment of the effect of tunnel construction on vibration levels. It is found that railway ground-borne vibration levels are underestimated if construction effects are ignored, with discrepancies of up to 10 dB found at higher frequencies. Therefore, when estimating future vibration levels during the underground railway design stage (e.g. for subway, metro, high-speed lines ... etc), tunnel construction should be considered as an operational source of uncertainty. • Uncertainties on prediction of vibrations induced by railway traffic due to soil non-homogeneities are investigated. • A hybrid numerical approach is followed: i) simulation of the effects of tunnel construction; ii) simulation of the elastodynamic response due to traffic. • A simple methodology for inclusion of the soil disturbance due to tunneling on the modelling of vibrations induced by railway traffic is proposed. • The soil disturbance due to tunnel construction can play a relevant role as source of uncertainty when predicting vibrations induced by traffic. [ABSTRACT FROM AUTHOR]

The Ethylene Diamine Tetra-acetic Acid (EDTA) titration test is widely used for determining cement content, but its reliability is influenced by the hydration process of cement, which is affected by factors such as water content and hydration time. Despite their importance, these factors have received limited attention in existing research. This study explores the relationships between the volume of titrant required for stabilization, cement content, water content, and hydration time. Using a regression orthogonal test, the primary and secondary relationships, as well as the interdependencies among these factors, are analyzed. Results reveal a negative linear relationship between the titrant volume and both water content and hydration time. Cement content, water content, and hydration time are identified as the most significant factors, with minimal interdependencies observed. Within the test parameters, calculated values exhibit an error margin below 2.4%. Deviations of 2.9% in water content and 86 min in hydration time correspond to an approximate 0.5% change in cement content. These findings offer valuable insights for optimizing cement content detection in Controlled Low-Strength Material (CLSM) mixes, promoting more sustainable construction practices.

Ground-borne noise and vibration from railway lines can cause human distress/annoyance, and also negatively affect real estate property values. Therefore this paper analyses a collection of technical ground-borne noise and vibration reports, detailing commercial vibration assessments undertaken at 1604 railway track sections, in 9 countries across the world. A wide range of rail projects are considered including light rail, tram lines, underground/tunnelled lines, freight, conventional rail and high speed rail. It documents the rise in ground-borne vibration problems and trends in the prediction industry, with the aim of informing the current research area. Firstly, the reports are analysed chronologically and it is found that railway vibration is a growing global concern, and as such, assessments have become more prevalent. International assessment metrics are benchmarked and it is found that velocity decibels (VdB), vibration dose value (VDV) and peak particle velocity (PPV) are the most commonly used methods of assessment. Furthermore, to predict vibration levels, the physical measurement of frequency transfer functions is preferential to numerical modelling. Results from the reports show that ground vibration limits are exceeded in 44% of assessments, and that ground-borne noise limits are exceeded in 31%. Moreover, mitigation measures were required on approximately 50% of projects, revealing that ground-borne noise and vibration is a widespread railroad engineering challenge. To solve these problems, the most commonly used abatement strategy is a modification of the railtrack structure (active mitigation), rather than the implementation of a more passive solution in the far-field., (Copyright © 2015 Elsevier B.V. All rights reserved.)

Railway track support conditions affect ground-borne vibration generation and propagation. Therefore this paper presents a combined experimental and numerical study into high speed rail vibrations for tracks on three types of support: a cutting, an embankment and an at grade section. Firstly, an experimental campaign is undertaken where vibrations and in-situ soil properties are measured at three Belgian rail sites. A finite element model is then developed to recreate the complex ground topology at each site. A validation is performed and it is found that although the at-grade and embankment cases show a correlation with the experimental results, the cutting case is more challenging to replicate. Despite this, each site is then analysed to determine the effect of earthworks profile on ground vibrations, with both the near and far fields being investigated. It is found that different earthwork profiles generate strongly differing ground-borne vibration characteristics, with the embankment profile generating lower vibration levels in comparison to the cutting and at-grade cases. Therefore it is concluded that it is important to consider earthwork profiles when undertaking vibration assessments., (Copyright © 2016 Elsevier B.V. All rights reserved.)