Deflectometer Research Articles

CHANGES IN STRESS-STRAINED SOIL MASS RESULTING FROM THE INSTALLATION OF BORED CAST-IN-SITU PILES AND BARRETTES

Introduction . The paper considers the effect produced by the installation of bored cast-in-situ piles and barrettes on the stress-strain state of the surrounding soil mass for four different types of soil conditions. Aim . To develop a procedure for determining concrete-induced stress acting on walls that enclose a borehole filled with concrete, as well as stress changes during relaxation. Materials and methods . An analysis of experimental studies is performed, both those conducted by the present authors and those available in open sources. By means of back calculations relying on experimental data, the dependence is determined between the maximum concrete-induced stress and the rate of concr eting. The results of post-construction monitoring are used to derive a formula for describing stress relaxation following the completion of concreting works. Results . In this study, the authors proposed a bilinear formula, developed a procedure, and calculated the concrete-induced stress acting on the walls that enclose a borehole filled with concrete, as well as stress changes in the process of relaxation. The effect of the adopted pile installation technique and soil conditions on changes in the stress-strain state of soil mass was studied. A formula was provided for determining the final values of horizontal stresses at the pile-soil interface at the full grade strength of concrete following stress relaxation in the soil, as well as recommendations for numerically calculating changes in the stressstrain state of soil mass during concreting and subsequent concrete hardening in piles and barrettes. Conclusions . The conducted studies into the effect of bored cast in-situ pile installation on the stress-strain state of surrounding soil mass revealed that this stress-strain state depends on the soil conditions of the site, as well as the adopted pile installation technique. Due to the fact that soil is a plastic material, the final value of horizontal stresses is affected by the technique-dependent load dynamics and the soil conditions of the site, which should be taken into account by applying appropriate soil models.

Using Falling Weight Deflectometer (FWD) and Ground Penetrating Radar (GPR) to monitor the effects of seasonal moisture variation on the structural capacity of pavements

Moisture fluctuations in pavement foundation due to environmental conditions (e.g., heavy precipitation, freeze–thaw cycles, groundwater table variation, etc.) can significantly affect pavements’ short- and long-term performance. Moisture variation in the pavement foundation is often monitored as a way to anticipate the structural capacity of pavements. Thus, the ability to monitor moisture variation through a proven non-destructive technology (NDT) such as Ground Penetrating Radar (GPR) would be beneficial for asset management by transportation agencies. This paper summarizes the Minnesota Department of Transportation’s (MnDOT) efforts at validating the use of GPR to monitor moisture in the pavement foundation through comparison with Falling-Weight Deflectometer (FWD) parameters that represent the structural condition of the pavement. The results in this paper are based on GPR, FWD and in-place moisture sensor data collected over 17 months on MnROAD instrumented test sections. The pavement test sections considered in this study included unbound aggregate bases (UAB) with virgin and recycled materials (i.e., RCA and RAP) covering a broad range of geotechnical behavior. Previous efforts established a strong correlation between GPR-based moisture measurements and sensor-based moisture measurements. This correlation is further validated by investigating the relationship between GPR-based moisture measurements and FWD-based indices for structural capacity. The observed correlation is reasonable and in good agreement with the expected correlation between volumetric moisture content (VMC) of the base layer and the structural capacity of a pavement. This agreement validates the use of GPR to monitor moisture in pavement foundation. GPR is not a replacement for FWD, but it can be used in asset management efforts in addition to FWD to assess moisture fluctuation in pavement foundation during and after extreme environmental events (e.g., flooding, freeze-thawing) to determine when and where FWD testing may be necessary.

Laboratory and Field Evaluation of Stabilized Fly Ash as an Alternative Material for Sustainable Pavements

Thermal power plants in India produce a large quantity of fly ash, which is harmful to the environment. Underutilization of fly ash and the scarcity of natural minerals have created the need for an unusual construction strategy to prevent huge waste dumps on valuable land and to preserve fast-depleting resources. A study was conducted to determine the efficacy of lime-stabilized fly ash blended with quarry fines as flexible pavement subbase materials. The laboratory investigations were conducted to determine compaction characteristics, unconfined compressive strength, California bearing ratio (CBR), and durability to obtain the optimal quarry fines, fly ash, and lime (QFL) mix. The durability of QFL mixes was studied using 12 wetting–drying cycles. Using the strength and durability criteria specified by the Indian Road Congress, the optimum mix proportion of 40Q:60F+3L was determined. Pavement analyses were performed using the IITPAVE program. The QFL mix was observed to be superior to conventional granular subbase (GSB) layer material in terms of service life and cost-effectiveness. A field investigation was carried out on trial test sections constructed using the optimum QFL mix and GSB in the subbase layer of pavement. Field dry density and dynamic cone penetrometer (DCP) tests were performed on the compacted subgrade and subbase layers to assess the desired quality assurance in the construction of test sections. The early structural performance assessment of pavement sections using a falling weight deflectometer (FWD) test indicated that QFL could effectively replace conventional GSB.

High-Sensitivity and High-Throughput Quantification of Everolimus in Human Whole Blood Using Ultrahigh-Performance Liquid Chromatography Coupled With Tandem Mass Spectrometry.

Rigorous dose adjustment by therapeutic drug monitoring (TDM) is recommended when everolimus (EVR) is administered for immunosuppression. In this study, the authors developed a highly sensitive ultrahigh-performance liquid chromatography coupled with the tandem mass spectrometry (UHPLC-MS/MS) method for measuring EVR concentrations in whole blood using a high-throughput solid-phase extraction method for sample pretreatment. Furthermore, the blood EVR concentrations in routine TDM samples from patients who underwent renal transplantation measured using the established UHPLC-MS/MS method were compared with those measured using the latex agglutination turbidimetric immunoassay (LTIA). Blood samples were pretreated by solid-phase extraction using a 96-well HLB µElution plate. The clinical application of the newly developed method was evaluated using 87 blood samples from 19 patients who underwent kidney transplant. The calibration curve showed good linearity over a wide range of 0.1-50 ng/mL, with relative error ≤15% obtained from the back calculation of calibrators, and ≤20% for the lower limit of quantification. Within-batch and batch-to-batch accuracies and precisions fulfilled the acceptance criteria of the US Food and Drug Administration guidelines for bioanalytical method validation. The extraction recovery rates were good (≥65.2%), and almost no matrix effects were found in any of the quality control samples. Blood EVR concentrations measured by UHPLC-MS/MS were positively correlated with those measured by LTIA. A Bland-Altman plot indicated that the UHPLC-MS/MS method yielded better measurements than the LTIA method, regardless of the concentration. Therefore, the authors succeeded in developing a novel high-sensitivity and high-throughput method for measuring blood EVR concentration by UHPLC-MS/MS using a µElution plate for sample pretreatment.

Forward calculation of displacement fields with multilayered unsaturated highway system induced by falling weight deflectometer using dynamic response method

A new dynamic forward model of a multilayered highway structure, which considers the unsaturated characteristics of subgrade soil, is established in this paper to assess the dynamic response induced by the falling weight deflectometer (FWD) load. The Laplace-Hankel transform and dynamic stiffness matrix method are employed to solve the governing equations of the unsaturated soil layer. Combined with the global stiffness matrix and boundary conditions, analytical solutions of the entire system can be derived in the transform domain. A numerical integration method is utilized to perform the Laplace-Hankel inverse transform to obtain time-domain solutions. An analysis of the effects of saturation on the stress, displacement, and pore water pressure is presented. It is revealed that the effect of saturation of unsaturated subgrade soil on vertical stress is negligible, whereas vertical displacement and pore water pressure increase significantly with increasing saturation. Additionally, the vertical displacement response on the pavement surface is sensitive to subgrade deterioration and variations in material properties. Moreover, subgrade deterioration can be reflected in the variation in vertical displacement at approximately 1.2 m from the load center for the studied road structure. The proposed model, which is more realistic and reasonable, can provide a theoretical basis for the back-calculation of the elastic modulus of multilayered highway systems.

Management of cavities under flexible pavement road network in metropolitan area: Detection, evaluation, and rehabilitation

This study evaluated a management program of cavities under flexible pavement road network in Seoul Metropolitan City. Consequently, directions for improvement were suggested. The underground cavities beneath the pavement layer were scanned using a vehicle-type multichannel ground penetrating radar (GPR). In addition, the size information including overburden thickness, cavity height, and lengths in longitudinal and transverse directions of the cavities were estimated and compared with the volume of cavities measured via a digital cavity imaging (DCI) system. Moreover, the change in the cavity dimensions with time was monitored. Through field investigation, the cavity volume near the asphalt pavement surface was observed to be smaller than the cavity located in the deep. For certain locations where the cavity existed, pavement cracks on the asphalt surface were identified. Thus, the crack width and depth were measured for the selected 14 locations and compared with the dimensions of the cavities. The results demonstrated that the depth of crack rather than the width exhibited a meaningful correlation with the cavity size. Additionally, the cavities under the flexible pavement layer were repaired using a low-strength filling repair material. Further, the elastic modulus on the pavement surface above a cavity was assessed using a light weight deflectometer (LWD) before and after the rehabilitation process and compared with the value of elastic modulus on the normal surface with no cavity but near the repair work. The results demonstrated that although the rehabilitation process increased the elastic modulus of the pavement layer, it could not be fully recovered owing to the characteristics of the repair material. Furthermore, the rehabilitation process was found to be more effective as the size of cavity was small.

Predicting bedrock depth under asphalt pavement through a data-driven method based on particle swarm optimization-back propagation neural network

Performance evaluations during and after asphalt pavement construction are essential to ensure long-term and safe operations. These evaluations are performed by obtaining each layer’s modulus of the pavement structure by back-calculating the deflection response. However, bedrock under the pavement can seriously affect this analysis. To limit this effect, this paper proposes predicting the bedrock depth by utilizing a data-driven machine learning algorithm based on particle swarm optimization-back propagation neural network (PSO-BPNN) aided by falling weight deflectometer (FWD) tests. Additionally, to provide sufficient data for the PSO-BPNN, a spectral element method with fixed-end boundary conditions (B-SEM) is utilized to calculate the theoretical deflections of multiple pavements at different bedrock depths. After performing a sensitivity analysis, the peak deflections at different measurement points and three time points corresponding to the peak deflection and the two subsequent fluctuation peaks at the load center measurement point are extracted as the input of the PSO-BPNN prediction model. Due to the pervasiveness of measurement errors in field tests, the raw input data are processed by adding random and systematic errors, and the corresponding bedrock depths are taken as the output dataset. The results demonstrate that the PSO-BPNN model is effective and feasible in predicting bedrock depth. Furthermore, in contrast to existing estimation models, the PSO-BPNN prediction model is more accurate and reliable with broad application prospects in road engineering.

Pavement Performance Testing of the Newly Constructed Port Reitz and Moi International Airport, Mombasa Access Road

The 6.4 km long Port Reitz/Moi International Access Road project constructed under the design and build procurement method with an inherent risk of poor quality. A post-construction pavement performance evaluation is thus critical to evaluate the extent to which poor quality occurred. The International Roughness Index was measured using the Hawkeye-2000 Digital Laser Profiler with Pavement Logging Video Camera mounted on a calibrated vehicle and data was analysed using the Hawkeye Processing Toolkit Version 5.0.45, while the road roughness Rating was based on the Australian Road Research Board. The video record was analysed in blocks of equal lengths of 100 m for observation and assessment of the surface defects. The level of defects observed graded together with the IRI measurements gave the Present serviceability Index. Pavement Serviceability Index (PSI) was computed in compliance with ASTM 6433. The falling weight deflectometer equipment meeting the requirement of ASTM D4694 - 09 and ASTM D4695 used to measure pavement deflections under known load simulated the behaviour of the as-built pavement under loading, thus giving the pavement strength and the expected pavement life span. The deflection measurements were conducted on all lanes at intervals of approximately 100 m. The raw deflections (rd) data were converted to normalised deflection (nd) to simulate a standard pressure of 707 KPa from a dual-wheel assembly of 10-ton (100-kN). Back calculation of deflection data done using Rosy Design Software determined the layer strength and residual life. The analysis indicates that the road has residual life ranging from 20-6 years compared to 20-year design life consistent with the assumptions by Ogunsanmi (2019) that Design and Build contracts have an inherent risk of poor quality. In addition to incorporation and monitoring of quality through the design, construction and maintenance stages of the project, identification, evaluation, management, and monitoring of the inherent project risks are recommended for Design and Built Contracts in road projects.

Back-Calculation of the Shear Strength Parameters of Subgrade Soil Based on Lightweight Deflectometer Test Using 3D Numerical Modeling

Back-Calculation of the Shear Strength Parameters of Subgrade Soil Based on Lightweight Deflectometer Test Using 3D Numerical Modeling

Accuracy analysis of modulus results considering the whole process of modulus back-calculation—based on GPR and FWD

• The numerical hypothesis model was corrected by combining GPR and FWD. • The applicability of different regression models for deflection basins was clarified. • The sensitivity of modulus back-calculation results was analyzed. • The accuracy of the modulus back-calculation result has been significantly improved. In this study, based on the consideration of the whole process of modulus back-calculation, the measured deflection basins of asphalt pavements under dynamic loading were obtained by using the falling weight deflectometer (FWD), and the parameters such as thickness, initial modulus range, and Poisson's ratio of each structural layer in the numerical hypothesis model were corrected based on the detection results of the thickness and damage status of each structural layer by the ground-penetrating radar (GPR). At the same time, mathematical regression models such as the Exponential regression model, Parabolic regression model, and Sigmoid regression model were used to fit the theoretical deflection basin, and the accuracy of the relationship model between the deflection basin parameters and the pavement structural parameters constructed after fitting the theoretical deflection basin by different regression models were compared. It is observed that the change in the numerical hypothesis model and the regression model of the theoretical deflection basin can have a significant impact on the modulus back-calculation results. The research results show that when the numerical hypothesis model and the regression model are not corrected and optimized, the absolute value of the relative error between the back-calculation modulus and the dynamic modulus of the asphalt layer obtained in the laboratory test is 64 %. After correcting the numerical hypothesis model and fitting the deflection basin with the Sigmoid regression model, the relative error is within ±4 %. In summary, it is an important method to improve the accuracy of modulus back-calculation by correcting the numerical hypothesis model and optimizing the regression model of the deflection basin.

Long-term evaluation of geotechnical and environmental properties of ash-stabilised road

In 2009, a low-volume gravel road in Sweden was stabilised using fly ash from a local paper mill. The objective was to examine whether fly ash could be used to enhance the stability of the road and how the nearby environment would be affected. The technical and environmental properties of the road have been monitored for two, six, and eleven years. Because the construction costs are higher for ash upgrading than for conventional upgrading, knowing for how long the improved properties will remain is relevant. Strength development was studied using a falling weight deflectometer and compressive strength tests. Environmental properties were studied by chemical analysis of road samples, soil, soil pore water, and vegetation. The results showed that the ash sections had higher stiffness than the reference sections. Leaching tests of road samples showed that the mobility of potassium, sodium, chloride, and sulfate decreased with time. Trace element concentrations in soil samples, except barium, were below the Swedish guideline values for sensitive land use. Chromium, lead, and copper were as high or even higher along the reference section than along the ash section. After 11 years, the pH closest to the ash section was slightly enhanced. Concentrations of zinc and cadmium in the soil pore water were the lowest closest to the ash road, although the total concentrations in the soil were at their highest at the same distance. No toxic levels of trace elements were found in the vegetation close to the road, although a clear difference was observed between plants from the ash section and the reference section, using multivariate data analysis. The positive effects on the geotechnical road properties from ash stabilisation remained after 11 years. The environmental impacts on nearby soil and vegetation can be considered low and acceptable. This study demonstrates that the use of biofuel fly ash in infrastructure projects can contribute to the circular economy and effective use of resources because the demand for pristine materials will be reduced.

Constraints on Earth-Moon dynamical parameters from Eocene cyclostratigraphy

The theoretical prediction of Earth-Moon dynamics in deep geologic time is hampered by limited knowledge of Earth's past tidal dissipation and dynamical ellipticity. Cyclostratigraphy can, however, provide valuable information on the geologic evolution of the Earth-Moon dynamical parameters. Here we investigate Eocene cyclostratigraphy to estimate Earth's precession rate (p), Earth-Moon distance (EMD) and length-of-day (LOD). Two highly-resolved deep sea records are selected from the Atlantic Ocean, with ages centered on 42.5 Ma (40.9–44.3 Ma; IODP Site U1410) and 54.95 Ma (54.1–55.8 Ma; ODP Site 1262). The sedimentary sequences at these sites recorded Milankovitch forcing signals with prominent precession index (Site 1262) and obliquity (Site U1410) frequencies and their amplitude modulations. At Site U1410, amplitude modulation of the main obliquity cycle was tuned to the Earth's 173-kyr orbital inclination (s3-s6) metronome, and at Site 1262, the dominant precession index amplitude modulation to the 405-kyr orbital eccentricity (g2-g5) metronome. This enabled estimation of Earth's precession rate p of 51.486 ± 0.064 arcsec/yr and 51.546 ± 0.168 arcsec/yr for 42.5 Ma and 54.95 Ma, respectively. These p estimates indicate EMD values of 383.710 ± 0.090 × 103 km and 382.625 ± 0.265 × 103 km, and LOD values of 23.679 ± 0.0115 h and 23.667 ± 0.039 h for 42.5 Ma and 54.95 Ma, respectively. These estimates deviate from theoretical predictions based on back calculation assuming present-day tidal dissipation. In particular, a significant discrepancy between the model and observations (cyclostratigraphy) occurs at 54.95 Ma (Site 1262) suggesting contributions from other effects on Earth's rotation, including changes in tidal dissipation and/or Earth's dynamical ellipticity related to mantle convection and the early Eocene global warming.

Effect of support conditions on the performance of B70 sleeper overlying reinforced ballast and sub-ballast layer: Experimental and analytical investigation

It is well known that the moment distribution on the sleepers is very sensitive to deformations of the ballast caused by cyclic axle load over time and other environmental factors. To limit the non-uniform deformations of the ballast, reinforcement of the ballast or sub-ballast with geosynthetics can be a cost-effective solution. In this study, B70 prestressed concrete sleepers were tested under static loading conditions in a special test box developed to simulate the in-situ condition of a railroad track in the laboratory. The main test parameters were the degree of settlement of the ballast and the type of geosynthetics used. Four different settlement levels and two reinforcement types (sub ballast with geonet and ballast with geocells) were considered. The deflections and surface strain maps of the concrete sleepers were measured using the two-dimensional digital image correlation (2D-DIC) method. Following the experimental part, an analytical study was also carried out to investigate the ballast pressure distribution and consequently the moment distribution on the concrete sleeper. Based on the vertical deflection shape of the sleeper, a new algorithm was developed to derive the ballast pressure distribution under the sleeper by back calculation. The experimental results showed that using geocells to reinforce the ballast layer increased the stiffness of the ballast against the vertical deflection of the sleeper. From the analytical results, the magnitude of the negative bending moment increased significantly with increasing settlement level.

Comparing Engineering Properties from Small Diameter Pressuremeter Tests to Nuclear Density Unit Weights and Lightweight Deflectometer Stiffnesses in Cemented Coquina Base and Sandy Subgrades

Abstract Small diameter pressuremeter (SDPMT) equipment was developed and evaluated at four sandy embankment/roadbed sites in east-central Florida. These materials ranged from very loose to very dense. SDPMT tests were developed with the goal of supplementing or even replacing the nuclear density gauge (NDG) tests. SDPMT probes were placed in the pin holes made from NDG testing. Two probe lengths of 15 and 30 cm (6 and 12 in) were used, and two SDPMT testing procedures were used. One was the conventional incremental volume injection method and the second was a continuous injection process. Incremental tests were completed in about 15 min, whereas the continuous tests were completed in less than 1 min. SDPMT elastic moduli and limit pressures were obtained from 156 SDPMT tests. They were compared to dry unit weights from 96 NDG tests and 96 moduli from each of two lightweight deflectometer (LWD) models, one with digital load-deflection output and the other with input load and digital deflection output. One-hundred and twenty statistical models were developed describing the relationships between SDPMT, LWD, and NDG data. Linear, logarithmic, and exponential models were used. Ninety-three of the 120 models produced regression coefficients (R2) greater than 0.7, and 46 of the 120 produced R2 values greater than 0.8. Of the 40 models comparing SDPMT strength and stiffness to NDG dry unit weights, 12 or 30 %, produced R2 values greater than 0.8. Of the 40 models comparing SDPMT strength and stiffness to the Zorn LWD, 23 or 57.5 % produced R2 values greater than 0.8. Of the 40 models comparing SDPMT strength and stiffness to the Dynatest LWD, 11 or 27.5 % produced R2 values greater than 0.8. These models indicate that SDPMT strengths and stiffnesses are strongly correlated to NDG unit weights and LWD stiffnesses.

Identification of Parameters and Fatigue Life Assessment of the Road Pavement Lower Construction Layers under Heavy Construction Traffic.

This article analyzes the results of testing the subgrade and the lower layers of the pavement structure with the light weight deflectometer at a load of 0.1 and 0.15 MPa. It is shown that, with layer systems with an equivalent layer modulus lower than 80 MPa, significant nonlinear phenomena occur at a load of 0.15 MPa. In this situation, the identification of a reliable replacement module, a commonly used test method, at a load of 0.1 MPa, is not appropriate—it significantly overestimates the value of the modules (even by 34%), which in turn translates into a significant overestimation of the fatigue life of the structure. In a situation where intensive exploitation of the lower layers of the pavement structure is planned before the final layer arrangement is made, it is required to apply test loads corresponding to the stress conditions occurring in these layers of the structure. Such a situation takes place under the influence of technological (construction) or temporary traffic (substitute, e.g., by-pass) during construction. In order to verify the above assumptions, numerical calculations (FEM) were carried out in the elastic model for layered structures with replacement modules determined in field tests. It was found that, especially in the case of low-bearing layer systems, it is necessary to use correction factors for modules determined with a dynamic plate at a load of 0.1 MPa. Taking into account the corrected values of the modules will allow to correctly determine the change in the durability of layers at the construction stage and in the subsequent operation of the final pavement structure.

Back to the future: Retrograde alcohol calculations an uncertain science

To respond to Labay and Logan's call for a scientific consensus regarding retrograde extrapolations in alcohol DUI cases by describing the existing practices in England and Wales and outlining changes that need to be made. Retrograde extrapolations, known as back calculations in England and Wales, are widely used in toxicology to estimate the blood alcohol concentration of an individual at some prior time. In 2018, Labay and Logan (Journal of Forensic Sciences, 2018, Vol 63. No 5, 1602–1603) published a call for a scientific consensus regarding back calculations. In the UK guidelines have been issued by the United Kingdom and Ireland Association of Forensic Toxicologists (UKIAFT, 2021, Guidelines for Alcohol Calculations, Version 4.3), while in the US, the Organization of Scientific Area Committees (OSAC) for Forensic Science have issued draft guidelines (2020, Guidelines for Performing Alcohol Calculations in Forensic Toxicology). However, these guidelines are not fully agreed and open for interpretation. Alcohol elimination rates have been discussed in many publications since Widmark's original data were published. The current guidance from UKIAFT, is to report the most likely back calculated result together with a range of results based on the 95% confidence limit elimination rates from Jones's 1996 study of drinking drivers (Journal of Forensic Sciences, 1996, Vol 41, No 5, 922–926). That range of elimination rates being from 9 to 29 mg/100 mL/hour (0.009 to 0.029 g/dL/hour). There is an acceptance of this 95% confidence interval for the reported final result by practitioners. The Divisional Court, upheld by the House of Lords, however ruled that in order to convict someone for being over the prescribed limit on the basis of any back calculation, the case must be proven beyond reasonable doubt. While the 95% confidence interval covers a large portion of the population, 1 in 20 individuals may fall outside the reported values. It is clearly not sufficient to prove a defendant's guilt so clearly that it must be accepted as fact, a common requirement of UK law. A confidence interval increased to 3 standard deviations or 99.73% would provide a greater factual basis for the court and cover a much larger proportion of the population. There is a reluctance within the forensic community to use this larger range as it often renders the calculation ineffective. However, that is simply a consequence of the considerable population variation. Retrograde extrapolations also rely on the subject being post absorptive at the prior time. In the UK, it is considered safe to back calculate if the subject has not eaten or consumed alcohol in the hour prior to the back calculation time. Where the subject has eaten recently prior to the back calculation time, experts are instructed to consider whether the back calculation is valid. In Germany back calculations are not permitted to a time within 2 hours after last drink consumed. The 2 hour limit would better meet the highest standard of ‘beyond reasonable doubt’ burden of proof, and should be used. There is a lot of debate around certain elements of the back calculations and experts have the freedom to interpret variables differently to an extent. Based on the review of many publications the have proposed modifications to the current practice in forensic casework to provide a more robust uncertainty and confidence interval. This will ensure consistency in the testimony given by different experts to the court and provide greater clarity for judges and juries in the assessment of scientific concepts and evidence.

Occurrence of GHB in blood and urine specimens from victims of alleged sexual assault or blackout in Western Switzerland

Although much has been written on the subject of drug facilitated sexual assault (DFSA) or victim of blackout, no epidemiological study has yet been conducted in Switzerland to evaluate the occurrence of GHB and other drugs in this context. GHB is frequently mentioned on social networks and in the media as the most regularly used substance in DFSA, but often without being based on scientific studies. In order to have an assessment of the situation, political authorities asked our laboratory to systematically screen for GHB in samples obtained in case of DSFA or blackout, and driving under the influence of drugs (DUID), with the aim to assess the occurrence of voluntary or involuntary GHB use in Western Switzerland. All DFSA, blackout and DUID cases received in 2021 in our laboratory were routinely tested for the presence of GHB at non-physiological concentrations by enzymatic assay with a urine cut-off of 10 mg equivalent GHB/L. All positive cases were confirmed by gas chromatography coupled to mass spectrometry (GC-MS) using a cut-off of 6 mg/L in urine and 1.5 mg/L in whole blood. All DFSA and blackout cases were also analyzed by GC-MS, to ensure the absence of false negative cases. When requested by the justice, other substances such as ethanol, benzodiazepines, cannabinoids, cocaine, amphetamines, opioids, antidepressant, and other psychoactive substances were screening in urine and/or blood, by immunoassays, head-space gas chromatography coupled to flame ionization detector (HS-GC-FID), GC-MS, and/or liquid chromatography coupled to tandem mass spectrometry or high resolution mass spectrometry (LC-MS/MS; LC-HRMS (orbitrap)). 60 DFSA and blackout cases and 633 DUID cases were included in the study. Women predominated over men in the DFSA and blackout group (77%), while men predominated over women in the DUID group (90%). Median age in the DFSA and blackout group was 23, and median age in the DUID group was 30. The median delay to obtain urine after the event was 12 hours in case of DFSA and blackout, and 2 hours for DUID cases. The median delay to obtain whole blood after the event was 12 hours in case of DFSA and blackout, and 1.5 hours for DUID cases. The presence of GHB at concentration above the cut-off was detected in 1 DFSA and blackout case (130 mg/L in blood and 730 mg/L in urine), and in 3 DUID cases (78 mg/L, not detected, and not detected in blood, and 660 mg/L, 8.6 mg/L, and 25 mg/L in urine, respectively). These cases concerned only men. For these 4 cases, other substances were also detected. Thus, for the DFSA and blackout case, methamphetamine, methylphenidate, zolpidem and pregabaline were detected, and in the DUID cases, methamphetamine was detected in one case, ethanol, cocaine and cannabis were detected in another case, and 3-MMC was detected in the last case. When analyzed, ethanol was detected in 48% of DFSA and blackout cases, cannabinoids in 17%, benzodiazepines and Z-drugs in 10%, antidepressant in 9.8%, cocaine in 6.5%, amphetamines in 6.5%, methylphenidate in 4.8%, and opioids in 2.1%. Median concentration of ethanol after back calculation was 2.07 g/kg in DFSA and blackout cases. The results obtained, showing a very limited voluntary or involuntary use of GHB, are comparable to those obtained in other international studies. For the first time in Switzerland, a study was conducted for the evaluation of the occurrence of GHB in blood and urine specimens from victims of alleged sexual assault or blackout, and DUID cases. The results showed that GHB is very rarely consumed and used in DSFA or blackout cases, in comparison to other psychoactive drugs.

Phase field approach to damage and fracture in asphalt concrete using multiscale finite element modeling of an instrumented pavement section

This study presents a Multiscale Finite Element Model (MsFEM) and Phase Field Fracture (PFF) based approach to study the responses and damage behavior of the viscoelastic Asphalt Concrete (AC) based on the actual traffic loadings. AC is a multiphase heterogeneous material. Understanding the mechanical responses and damage accumulation in different phases of AC has been a challenge for the pavement research community. This study proposes a methodology to overcome this challenge by combining a two-way linked multiscale finite element model with phase-field fracture. A modified PFF degradation function is formulated to quantify the damage and fracture in the AC microstructure. Combining MsFEM with PFF, it is possible to take the material heterogeneity, anisotropic and viscoelastic damage accumulation in the AC microstructure into consideration to identify the overall performance of the macroscale pavement. The developed MsFEM with PFF is validated based on the responses from an instrumented pavement section under Falling Weight Deflectometer (FWD) test load. Model responses are in agreement with field sensor responses, demonstrating that MsFEM with PFF can be used to accurately and efficiently predict AC microstructure performances. The model is also used to perform parametric studies to determine the extent of damage in the microscale AC due to the movement of Super Heavy Loads (SHLs) which is computationally very expensive in a traditional single scale model. The results from the parametric study show that weaker and thinner unbound layers have the highest potential of initiating fatigue damage in the AC microstructure.

Negative Impulse Ground Wire Corona Parameters for Backflash Evaluation of High Voltage Transmission Lines

Ground wires (GW) struck by lightning are often exposed to transient impulse voltages in the MV range. This results in intense negative streamer-type corona, causing a considerable increase in the effective wire capacitance and a corresponding reduction in its surge impedance. Such variables have a significant influence on the tower top potential and on the electromagnetic coupling between the ground wire and phase conductors. Presently there is considerable uncertainty regarding the impulse corona parameters to be used in back flashover calculations. In the present paper a new method is formulated for determination of GW impulse corona parameters. The new approach is compared with two existing methods and with available experimental results. It is found that the method usually used within the IEEE has little physical justification and is excessively conservative. It is also shown that such corona parameters significantly depend on the GW height above ground, which has been totally ignored in the CIGRE method. This and other unjustified simplifying assumptions explain the surprisingly large discrepancy between values of the negative impulse corona constant recommended by CIGRE and IEC.

Experimental Investigation of Moisture Induced Offset Drifts on Plastic Packaged MEMS Sensor Devices

Encapsulated microelectromechanical measurement units are known to be sensitive to ambient humidity conditions, due to various effects caused by moisture diffusing into and out of the plastic packaging components. This paper focuses on investigating the effect that a change of moisture content has on the transient offset behavior of a packaged MEMS sensor by investigating the output signals of several test devices that only differ in their response to deformation of the MEMS core area. This comprises a novel method of experimentally analyzing the transient drift behavior of a MEMS caused by a deformation of the MEMS core area. This approach enables a back calculation of possible deformation shapes of the core area that explain the observed offset drifts in a given package. It was shown that the humidity response of a MEMS sensor is a strongly transient function that is not proportional to the uptake of water and can therefore significantly differ from their humidity performance at or close to a saturated state. Humidity performance tests that take only this state as point of reference for a performance evaluation cannot correctly estimate the humidity induced offset drifts. It was also shown that the moisture induced offset drifts can be traced back to a superposition of several deformation fields leading to several stages of the humidity response of MEMS sensors. Based on the example of the test devices it was shown that MEMS cores can be optimized to minimize the response of moisture effects. [2021-0212]