Scipedia
Not a member yet
33380 research outputs found
Sort by
PLENARY LECTURE - Passive seismic methods for site characterization
No full textSite characterization methods to extract the shear-wave velocity (Vs) structure over the first few tens to few hundred of meters or the soil’s resonance frequency using seismic noise recordings have become widespread over the last 40 years. Being cost-effective and easy to implement, especially in urban environment, passive seismic methods have been shown reliable to retrieve the soil resonance frequency and the Vs profile of near-surface geological layers. International efforts over the last 20 years have outlined the capabilities and limitations of passive seismic methods and lead to a series of good-of-practice, state-of-the-art and recommendations on data acquisition and processing. Recent methodological developments using three-component single-station and three-component array methods are promising approaches to better constrain Vs profiles. Also, the very high spatial and temporal resolution offered by the Distributed Acoustic Sensing (DAS) makes this emerging technology one with very high potential for near-surface site characterization, especially in urban environment
Prediction of Future Settlement of Backfill at an Aggregate Mining Quarry Site in Irwindale, CA Using Numerical Method and Settlement Monitoring Data
No full textFuture static settlement of a former aggregate mining quarry site in Irwindale, California is predicted based on the monitoring data and using numerical analyses that consider the total settlement of the deepest portion of the rockfill. The portion of quarry analyzed was backfilled with approximately 61 to 67 meters, has a volume of 2.6 million m3, and covers an area of 114,900 m2. The backfill material ranges from silty sand (SM) to silty gravel (GM) and was compacted to achieve an average relative compaction (RC) of 96%. The deepest fill area is currently being monitored with survey data to predict future 50-year settlement due to secondary compression. Settlement monument data from three different locations has been collected and made available starting from May 2009 up to now. A 3-dimensional model of the rockfill was used to determine an appropriate upper and lower bound of predicted future 50-year settlement from today in 13 stages and scenarios. The modified secondary compression index was estimated along with the modified compression index that was back calculated to match the field monitoring data. We could find good agreement between the field monitoring data and our numerical model when considering total settlement of the rockfill
Development of a 3D Ground Model for an Offshore Wind Farm with Complex Interlayering of Silty Soils
Get PDFThree-dimensional (3D) ground models enable the visualization of complex subsurface conditions in offshore wind farms, which aid engineers in understanding the spatial morphologies and interrelations of different soil layers. Due to the large areas of offshore wind farms, 3D ground models established solely based on limited geotechnical data (e.g., boreholes and cone penetration tests) might lack the required accuracy. Geophysical data, particularly seismic profile data, is capable of revealing stratigraphic information and can be obtained at a relatively low cost. This study presents a case study in which a 3D ground model for an offshore wind farm located off the Southern China coast is developed through the integration of geotechnical and geophysical data. The wind farm features complex interlayering of silty materials below the soft Holocene marine deposits due to repeated sea level changes during the Quaternary period. This created significant challenges for developing a reliable ground model. In this paper, the challenges that were faced and solutions that were applied in this project are presented and discussed
Liquefaction Assessment at Gravel Sites in Croatia Based on Vs and DPT Blow count
Get PDFLiquefaction of loose saturated soil poses a significant threat to civil infrastructure during major earthquake events. Although liquefaction is most common in loose saturated sands, numerous liquefaction events in gravelly soil profiles have been reported. Assessing liquefaction resistance in gravelly soils is challenging because large particle sizes can interfere with the standard penetration test (SPT) and the cone penetration test (CPT). To address this challenge, recent efforts have focused on developing liquefaction triggering curves based on a large diameter (74 mm) dynamic cone penetrometer (DPT) blow count and normalized shear wave velocity, Vs1, which are less affected by gravel-sized particles. While based on field case histories, the curves are poorly constrained in some areas; additional case histories continue to be highly desirable. This paper describes an investigation of six gravel sites that liquefied in the 2020 Mw6.4, Petrinja, Croatia earthquake. At each site, boreholes were completed to define the soil profile, accompanied by DPT soundings and shear wave velocity profiling using the Multi-channel Analysis of Surface Waves (MASW) approach. At some sites, the DPT blow count increased through a silty clay surface layer even though the CPT cone resistance remained constant in this layer. This increase was thus attributed to side friction on the drill rods during penetration. Subsequent DPT tests performed after casing through the silty clay eliminated the rod friction. The measured blow count and shear wave velocities in the critical layers at these sites correctly predicted liquefaction using recent probabilistic DPT- and Vs1-based triggering curve
Finite element analysis of self-boring pressuremeter tests in clay
Get PDFSelf-boring pressuremeter (SBPM) tests are widely used in site investigations, due to their distinct advantage to measure the shear stress-strain-strength properties of the surounding soil with minimum disturbance. The measured pressuremeter curve can be interpreted using analytical solutions based on the long cylindrical cavity expansion theory with relatively simple constitutive models. However, SBPM tests are strongly affected by the soil behavior and details of installation procedure. In addition, the derived parameters for clays (e.g. undrained shear strength, and shear modulus) are affected by a number of state variables such as overconsolidation ratio, and stress level. In this paper, SBPM tests are investigated using finite element analysis and the MIT-S1 model, to consider complex soil behavior more realistically. SBPM tests in K0-consolidated Boston Blue Clay at different OCRs are simulated in axial symmetric and plain strain conditions, consistent with the assumptions used in analytical solutions. The derived undrained shear strength from both contraction and expansion curves are compared with theoretical values from stress-strain curves, to evaluate the reliability of the derived parameters from the SBPM tests
Portable Pressiocone System for Carrying Out CPTU+FDP (Full Displacement Pressumeter) Tests
No full textGeotechnical investigations in the subsoil of existing buildings have always been challenging due to limited space and difficult access. URETEK has developed a portable integrated system for simultaneously carrying out a CPT and a pressumeter test with Full Displacement Pressuremeter (FDP). The 30 kN thrust penetrometer to be used is very small. The reaction is given by two “microanchors”. The cone is a standard 10 cm2 digital memory cone (no cable), capable of measuring qc, fs, u every centimetre. Above the cone there is the FDP equipment with a rubber sheath covered by steel plates and connected, by a tube filled with water, to a device for creating pressure to inflate the sheath and measure pressure-volume curves as in a standard pressumeter test. The pressure-volume device and the depth transducer are connected to a microcomputer that is programmed to carry out CPT+FDP tests in an easy-to-use/user-friendly way
Guidance notes for the production of large FPR OWTP
Get PDFDescription of the technologies and processes developed in the project for the production of the targeted OWTP platforms as well as manufacturing strategies for modular production. Furthermore, it will also contain a brief summary of the two open-door days
and workshops, which will be organize
Improvement of electrical resistivity of cement mortar through nanotechnology
No full textThe diffusion or permeability of ions or gases through the cement matrix is key in the degradation of reinforced concrete for marine applications. The delay in ion diffusion has been an important approach to extend the life of this type of materials. In this work it is detailed how reduce degradation of cement mortar using nanotechnology. The addition of nanoparticles to the cement paste has important implications for the hydration and microstructure, reducing porosity and improving mechanical properties. In this study, different nanoparticles have been used to reduce the porosity of mortars evaluating this improvement by means of electrical resistivity measurements. It is perfectly established the porosity reduction with the increasing of electrical resistivity. Reduction of porosity minimises the intake of aggressive agents into the mortar in a meaningful way, retarding the corrosion of metal reinforcement. Nanoparticles addition (<10%) within cement mortar have allowed to increase the electrical resistivity in up to 112% regarding to control sample, without modifying of mechanical properties.  
Tecnologías de fabricación avanzadas en material compuesto termoplástico dirigidas al sector aeronáutico
No full textLa fabricación avanzada en materiales compuestos termoplásticos es clave para satisfacer los requerimientos del sector aeronáutico. Las ventajas diferenciadoras de los polímeros termoplásticos de alto rendimiento frente a las resinas termoestables, hace que estos materiales sean cada vez más demandados en el sector. Es clave su capacidad de reprocesado que permite 1) la automatización de los procesos, 2) la utilización de la tecnología de unión por soldadura entre sus componentes y 3) aplicar criterios de reciclabilidad y reutilización, imposibles para los materiales termoestables. Su mayor tenacidad y su cumplimiento de los estándares más estrictos de llama, humo y toxicidad aportan un plus importante a sus prestaciones. Polieterimida (PEI), Sulfuro de Polifenileno (PPS), Polieteretercetona (PEEK), Polietercetonacetona (PEKK) y el novedoso poliariletercetona (PAEK) son las matrices empleadas en esta tecnología de materiales compuestos termoplásticos de altas prestaciones. En función de la tipología del componente final, se selecciona la tecnología de procesado más adecuada, dependiendo de aspectos como geometría de pieza, tamaño y número de piezas a fabricar. El objetivo del presente trabajo fue la exploración de tecnologías de procesado de composites termoplásticos, tales como: Termoconformado de láminas compuestas (organosheet), obtención de laminados customizados (tailored sheet consolidation) y moldeo de escamas y/o pellets reforzados mediante compresión (T-BMC, Thermoplastic Bulk Moulding Compound) a través del desarrollo y puesta a punto de la fabricación de prototipos. Los resultados demostraron que estas tecnologías cumplen los requerimientos exigidos por el sector aeronáutico tanto en procesabilidad como en propiedades
Discretization error estimation for flow simulations using general hybrid grids
Get PDFA primary area of the author’s work with his students is outlined in the present article. It regards the estimation of the discretization error with mixed-element and adaptive meshes. Use of general hybrid meshes for computational flow simulations is of importance due to the complexity of both the geometry and the fields. The meshes can consist of a mix of hexahedra, prisms and tetrahedra with pyramids being transitional elements. The discretization error is a primary component of the numerical error in flow simulations. Primary factors affecting it are the local density of the mesh, as well as its “distortions”, namely the variation in local size and orientation (stretching, skewness), the shape of the individual elements (shear, twist), and the local change in their type (grid interfaces). Two distinct approaches have been followed in order to estimate and control the discretization error. The grid-based (“a priori”) approach assesses mesh quality from the analytic expression of the truncation error. The solution-based (“a posteriori”) approach monitors approximations of the variation of flow quantities (“sensors”). Those are then applied to guide adaptation of the grid to the simulated flow fiel