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Dark Fibre Optic Cables for Shallow Ground Charactrization alongside Railroads
Get PDFWe evaluated the feasibility of existing fibre optic telecommunication cable as a Distributed Acoustic Sensors (DAS) for shallow ground characterization alongside railways and using the running trains as seismic source. We utilized 5 km of fibre optic cable alongside a railway segment localized in the Hanzelijn corridor in the Netherlands. For almost a week, we recorded strain generated by passing trains that was utilized to retrieve coherent and multimodal Rayleigh waves at various soil conditions. The data was recorded in a continuous mode, using a channel spacing of 1.0 m and a sampling frequency of 1,250 Hz. The DAS interrogator was set to a gauge length of 2.0 m to reach the highest possible spatial resolution. We captured at least 60 train passages (running alongside the fibre optic cable) per day. We extracted Rayleigh waves by utilizing seismic interferometry method. The seismic interferometry processing provided virtual broad-band shot-gathers with coherent and clear surface waves trends. The computed phase velocity spectrum at frequencies as high as 30 Hz and wavelength as short as 6 m. The retrieved dispersion curves allowed us to determine S-wave velocity profile at a minimum depth of exploration of 2.0 m. The measured Rayleigh waves and calculated S-wave velocities are comparable to reference values measured with standard Geophone and geotechnical data available at the test segment
Enhanced, statistically-controlled integrated model of geo-data based on CPTu
Get PDFThe paper presents the possibilities of geostatistical analysis of geotechnical data using cluster analysis. As a result of the analysis, geological data from boreholes were replaced by digital data corresponding to parameters measured during CPTU static sounding. A unified database with a depth resolution of 2 cm was obtained, allowing it to be used to build geostatistical geotechnical models, e.g. using kriging. Techniques providing statistical control of the homogeneity of geotechnical separations, based only on measured data and not on interpolated or correlated data, were used to create the model. The technique used makes it possible to create an integrated geo-engineering model of the subsoil even for small sites with limited data
Effect of the fines content on the seismic response of a liquefiable deposit based on dilatometer tests
No full textIn the simplified methods for estimating the cyclic resistance ratio (CRR) based on the flat dilatometer test (DMT), the liquefaction triggering curve is defined as a function of the horizontal stress index. A DMT-based calibration of a simplified pore water pressure model for effective stress analyses has been also recently proposed by Chiaradonna et al. (2023), even though limited to an ideal clean sand. This paper aims to explore the effects of the fines content on the seismic response of a liquefiable site where the cyclic strength of the soils is estimated by dilatometer tests. This evaluation is firstly performed on an ideal one-dimensional soil column, where the percentage of fines content is parametrically changed. Then, the study is verified on a real case, by considering a well-investigated site located in the Emilia-Romagna plain (Italy), where widespread liquefaction occurred in the 2012 seismic sequence. Indeed, a comprehensive site characterization from previous in-situ and laboratory tests carried out by various research groups is available for sand, silty sand, and sandy silt deposits encountered in that area. The nonlinear dynamic analyses accounting for the fines content effect are compared with that obtained by adopting the calibration procedure based on laboratory tests. Guidelines and limitations of the proposed approach obtained from this study are useful in providing awareness to practitioners about the calibration strategies for dynamic analysis based on DMT-tests
The new economic security paradigm
No full textFor decades, the benefits of expanding international trade and foreign direct investment seemed unquestionable. However, the COVID19 pandemic, the Russian invasion of Ukraine (and its economic and energy implications for Europe) and the growing geostrategic rivalry between the US and China have been displacing the "neoliberal" paradigm with one that emphasizes the importance of economic security and warns of the dangers associated to the weaponization of interdependence. This article analyzes the implications of this new paradigm for the future of globalization, trade agreements and multilateral trade governance. It focuses, in particular, on how the European Union is attempting to incorporate elements of economic security without adopting protectionist measures, as part of its drive for strategic autonomy
Use of a portable measurement while drilling system for shallow subsurface characterization
Get PDFThe Portable Measurement While Drilling (PMWD) equipment designed by CEREMA engineers is an innovative and lightweight tool to perform rapid assessment of shallow subsurface conditions. The equipment consists of sensors mounted on a cordless rotary drill that records depth, downforce, rotation, torque, and time. This paper presents results obtained with the portable MWD under laboratory and field conditions, which were directly compared to soil resistance profiles obtained with a lightweight dynamic cone penetrometer (LDCP – PANDA). Results from 66 PMWD profiles and 87 LDCP profiles demonstrated the potential applicability of the portable MWD in shallow subsurface investigations. A linear correlation between the Somerton Index (SD) and the LDCP tip resistance (qd) was obtained in granular soils under controlled conditions, ranging from sand (SP) to sandy gravel (GP). The obtained relationship was applied to MWD results from a 180-m long, 50-m tall grassy slope in New Hampshire, USA. It was observed that the estimated qd values from drilling parameters have a good correspondence with LDCP results at the same testing locations. Shallow subsurface characterization using MWD can potentially be used for shallow foundations, compaction control, pavement subgrade evaluation, and areas prone to geotechnical hazards not easily accessible through usual exploration methods
The Input-Output Framework of Catalonia 2021. Estimation strategy. The Survey on Intermediate Consumption 2021.
No full textTopic 2. Determinants of the macroeconomic context
The Catalan Input Output Framework (MIOC 2021) is drawn up on the basis of the European System of Accounts 2010 and aims to carry out a systematic and detailed description of the totality of an economy, its components and its relationships with other economies European guidelines allow methodological homogeneity and comparability of economic data on an international scale. In Spain, the INE only prepares the Input-Output Framework for the whole of Spain, which gives the MIOC 2021 a strategic character in the knowledge of the Catalan economy and constitutes the basis for the preparation of the economic accounting of Catalonia.
For the construction of the MIOC 2021 it has been necessary to define and implement a new edition of the Intermediate Consumption Survey for 2021 (ECI 2021), a fundamental tool for obtaining detailed information on companies with economic activity in Catalonia, especially in purchases, foreign services and investment and their geographical origin. Also, other sources are used, mainly structural surveys of companies, the INE 2021 Intermediate Consumption and Investment Survey, as well as administrative records and tax sources (form 347 and of the Immediate Supply of Information system). In some branches, such as agriculture, energy and those corresponding to non-market services, a specific treatment has been applied for this purpose.
This work aims to describe the main characteristics of the most relevant source for the construction of the MIOC 2021, that is, the ECI 2021. Specifically, it analyzes the sectorization of economic activity, the target sample, the process survey, the types and characteristics of the questionnaires used. At this point, particular emphasis is placed on the description of the type of information requested according to the type of questionnaire to be applied, taking into account whether the company is mono-sector or multi-sector and whether or not it has establishments outside Catalonia.
In this sense, it should be noted that Idescat has developed a specific application for the management of ECI 2021 fieldwork and the definition of questionnaires in electronic format. This application presents the information requested from the reporting units in a structured way by blocks and differentiated according to the type of questionnaire and the sector of activity, an aspect of particular relevance to facilitate the answer.
The adaptation of the questionnaires according to the company's branch of activity (135 different questionnaires), and the effort to detail the main purchases, adapted to each branch of activity, as well as other survey variables, have been keys for obtaining specific, detailed and quality information.
 
Data-Driven Simulation of Multivariate Cross-Correlated Geotechnical Random Fields from Sparse Measurements
Get PDFIt is widely acknowledged that many geotechnical properties are correlated over space and/or time. Consequently, crosscorrelated random fields play a pivotal role in geotechnical reliability analysis for properly modeling both the auto- and cross-correlation structures of correlated geotechnical properties. Existing methods for simulating cross-correlated random fields typically require precise knowledge of random field parameters as input. However, in a typical site investigation program, engineering constraints such as limited time, budget, and space often lead to sparse measurements of geotechnical properties. Estimating reliable random field parameters, particularly the auto-correlation and crosscorrelation structures of a two-dimensional (2D) cross-correlated random field, from such sparse data is a notorious challenge. To address this issue, this study introduces a 2D cross-correlated random field generator that can directly simulate 2D multivariate cross-correlated geotechnical random field samples (RFSs) from sparsely measured data points. This generator leverages the method developed by Guan and Wang (2023), which employs a joint sparse representation to simultaneously exploit auto- and cross-correlation structures of various spatial/temporal quantities directly from sparse measurements. The effectiveness of the proposed generator is demonstrated using real geotechnical properties data. The results demonstrate that RFSs generated using this method from sparse measurements accurately capture the spatial auto- and cross-correlation structures of different geotechnical properties
Quasi-region-specific model uncertainties of simplified liquefaction triggering analysis
Get PDFIn earthquake-prone regions, assessing soil liquefaction potential is indispensable for contemporary seismic design. Various procedures for liquefaction triggering analysis have emerged over the past decades. However, most of them are derived from generic liquefaction databases, such that the model uncertainties in liquefaction potential assessments applied to a specific region of concern remain unknown, which poses a challenge for engineers to evaluate the liquefaction risks of target sites. This study aims to propose a hierarchical Bayesian model (HBM) to learn the inter-region characteristics of model uncertainties of the traditional simplified liquefaction potential evaluation methods based on a database containing global case histories of liquefaction categorized into several regions where those triggering events occurred. The learning outcomes can yield the model uncertainty of the target region, and the liquefaction probability at the target site under a given ground motion condition. For an illustration of the proposed model, a case history of liquefaction from a specific region is adopted to construct a quasi-region-specific model uncertainty and evaluate the liquefaction probability in the target soil. The illustration shows that the constructed quasi-region-specific model uncertainty with liquefaction histories in the target region can improve liquefaction occurrence prediction in comparison with the prediction without any histories, which is believed to benefit the engineering practice
Determination of rock foundation levels for the expansion of the Cañaveral shopping center from geophysical tests and its correlation with direct exploration
No full textThe Cañaveral shopping center is located on a low slope formed by recent alluvial deposits of low consistency, supported on sedimentary rock of the Girón formation, which is found at depths that change abruptly between one and twelve meters in short distances, influenced by the presence of a geological fault line and processes of erosion and weathering by subway water currents. Considering that the loads on the foundation are of great magnitude, it is necessary to build about 100 deep caisson foundations to reach the rock. However, performing a borehole on each one of them represented a very high cost and long execution times that would generate discomfort in the operation of the warehouse. Therefore, an alternative was proposed to determine the depth levels of the rock through different geophysical tests of seismic lines and electrical tomography and try to calibrate the results through the correlation of some boreholes. During the execution and data processing phase of the geophysical tests, difficulties were encountered due to the level of environmental noise and the obtaining of the wave records, given the variability of the rock levels and even the effect that in some sectors of the study area the rock is very sub-surface. In conclusion, it was possible to identify the strengths and weaknesses of each of the exploration methods and generate a 3D map of the depths of the rock levels that served as input for the design and budget of the foundations, which were verified by constant supervision during construction and thus be able to determine the error percentages, as well as to present recommendations for future works where it is intended to use this type of technique
G-PFEM-aided Derivation of Undrained Shear Strength of Organic Clays from CPT Data
Get PDFAccurate evaluation of undrained shear strength of soils is crucial in geotechnical design and assessment. In the practice, undrained shear strength is obtained most frequently from CPT data, dividing the net cone tip resistance by a cone factor, ð . For organic soils, values between 8.6 and 15.3 are reported, depending on the stress history. The cone factor can be conditioned to the results of laboratory tests, although uncertainties remain on the variety of stress paths followed by the soil elements around the tip of the cone, compared to the ones tested in the laboratory. Non-uniqueness in the definition of the cone factor may lead to either unsafe or over-conservative choices, partly undermining both the reliability and the sustainability of the design. This contribution analyses numerically the inversion technique used to determine the undrained shear strength of organic clays, exploiting data from an extensive in situ and laboratory investigation. The adopted constitutive model was calibrated on the results of laboratory tests. Cone penetration tests were simulated performing coupled hydro-mechanical numerical analyses via G-PFEM, developed in the last decade at CIMNE-UPC. The role played by initial stress state and previous stress history upon stress distribution at failure, cone factor and sleeve friction is discussed. The numerical results suggest how the sleeve friction could be used to condition the cone factor depending on the over-consolidation ratio and demonstrate how combining the different available CPT readings with the aid of numerical results may reduce the uncertainty in the estimation of undrained shear strength