Scipedia
Not a member yet
33380 research outputs found
Sort by
Comparison Between Eggshell Lime and Commercial Lime as a Soil Stabilizing Agent
Get PDFReducing the extraction of natural resources is a current demand in the construction industry. Studies show that eggshells are rich in calcium carbonate and have the potential to replace limestone in lime production. In this context, the objective of this article is to use an eggshell lime produced in the laboratory to stabilize a residual clayey soil and compare the unconfined strength of the admixtures with others using commercial dolomitic lime. Different lime contents and porosities were evaluated and the porosity/lime ratio was studied to understand the unconfined strength behavior of admixtures. In addition to the soil and limes characterization tests, X-ray diffraction tests were carried out to analyze the chemical and mineralogical composition of the materials. The results showed that increasing lime content and decreasing porosity increased unconfined strength. Also, the unconfined strength achieved with the eggshell lime was greater than that achieved with dolomitic lime for the same lime content. The X-ray diffraction tests showed that the eggshell lime is composed almost entirely of calcium hydroxide, and microscopic images demonstrated much stronger bonds in the final product obtained from eggshell lime. The porosity/lime ratio was a good parameter for evaluating unconfined strength. A unique relationship was achieved linking unconfined compressive strength with the porosity/lime ratio for both the eggshell and the dolomitic lime mixtures
Stress History and Effective Shear Strength Parameters Evaluation of a Dilative Stiff Clay
Get PDFThe Cone Penetration Test (CPTu) can be used to evaluate the soil behaviour and properties through correlations (empirical and/or analytical), and the results must be compared to laboratory tests to be validated. This paper presents the evaluation of the effective friction angle (φ’) of a stiff over-consolidated Brazilian clay based on CPTu data and laboratory tests characterization, such as index properties, and the comparison of the effective shear strength parameters obtained by triaxial tests. Based on CPTu data, the soil was classified using the Soil-Behaviour Type Classification System (SBTn) proposed by Robertson (2016), and properties such as over-consolidation ratio (OCR) and the effective friction angle were determined using well-known correlations such as Chen & Mayne (1996) and Ouyang & Mayne (2019). The shear response defined by CPTu was compared to the results of isotropic consolidated triaxial compression tests (CIUC). The results showed mainly a clay-like behaviour based on the CPTu data, in agreement with the laboratory characterization, which indicated high plasticity. Regarding the shear response, both the triaxial test and the CPTu data indicated dilative behaviour under shear. Furthermore, the effective friction angle obtained from the triaxial test and the CPTu data were similar depending on the OCR used in the equation, demonstrating the applicability of the adopted methodologies for the Brazilian stiff over-consolidated clay. Finally, based on CPTu data it is proposed a complement of the SBTn developed by Robertson (2016) with OCR isolines
The stratigraphic reconstruction of longitudinal tunnel based on improved coupled Markov chains
Get PDFThe distribution of natural strata is uncertain due to tectonic movements and sedimentation. Capturing geological uncertainty is a challenge for traditional deterministic models. In this study, an improved three-dimensional coupled Markov chains method for probabilistic stratigraphic reconstruction was developed. This method considers the correlation between the field borehole data. On this basis, an inversion analysis method for horizontal transition probability matrix estimation is proposed. This method makes the predictions more suitable for possible stratigraphic distributions. The accuracy of the method was further verified by different borehole schemes from the Mawan Tunnel in Shenzhen. The results show that the proposed method can still have high accuracy when the number of boreholes is sparse. This method can reflect the asymmetry, continuity and anisotropy of three-dimensional strata
Data-driven Multi-stage Sampling Strategy for Machine Learning of Underground Digital Twins Consdiering Stratigraphic Uncertainty
Get PDFA sound understanding of subsurface geological conditions is crucial for the digitalisation of underground infrastructure. The building and updating of underground digital twins heavily rely on sparse geotechnical measurements (e.g., boreholes) retrieved from the ground, and an efficient sampling strategy can facilitate the interpretation of subsurface heterogeneities. Geotechnical sampling design can be viewed as a constrained optimization process that aims to obtain as much geological information as possible from a limited number of sampling locations within a given site boundary. In this study, a data-driven intelligent sampling strategy is proposed to optimize borehole locations for a multi-stage site investigation of a three-dimensional (3D) geological domain. The initial sampling plan is determined using weighted centroidal Voronoi tessellation, which assigns uniform sampling densities to zones of different importance. Measurements obtained from the initial stage are combined with prior geological knowledge to build underground digital twins using an image-based stochastic modelling method. Multiple realizations of the geological domain can be developed under the framework of Monte Carlo simulation, and stratigraphic uncertainties associated with multiple random realizations can be quantified using information entropy. The location with the maximum entropy is adaptively selected as the next optimal sampling location. The proposed method is the first sampling strategy that can explicitly consider 3D subsurface stratigraphic variations. The performance of the proposed multi-stage sampling strategy is demonstrated using a simulation example. Results indicate that the proposed method can efficiently identify the optimal sampling locations while accounting for irregular site geometries and 3D subsurface stratigraphic uncertainties
Applicability of CPTU to characterize diatomaceous fine-grained soils: a case study in Euganean Hills (Italy)
Get PDFDiatomaceous soils, composed of diatom fossils and clay minerals typically formed in volcanic environments, exhibit characteristics such as low unit weight, high plasticity and liquid limit, significant compressibility, and high friction angles. Despite their presence in various locations globally, knowledge about their geotechnical behavior is limited and primarily based on laboratory tests conducted on artificial samples. This paper presents data obtained from undisturbed samples of natural diatomaceous soils and discusses the interpretation of Cone Penetration Test with Pore Pressure (CPTU) data to classify these complex non-textbook soils and estimate their mechanical properties. The study area is situated in the Po Plain near the thermal anomaly region of the Euganean Hills in Northeast Italy. Three CPTUs and one borehole with the collection of four Osterberg undisturbed samples were conducted. Laboratory tests on the undisturbed samples provided values for Atterberg Limits, soil unit weight, in-situ void ratio, compressibility, and permeability, which were compared with estimations derived from CPTU data analysis. Moreover, Scanning Electron Microscope images provided insight into the distinctive microstructure of diatom microfossils embedded in a clayey matrix. Based on these comparisons, CPTU proves to be effective in estimating relevant parameters of diatomaceous soils, particularly the Soil Behavior Type (SBT) and consolidation coefficient from dissipation tests. However, the agreement in estimating the oedometric modulus is less satisfactory. Therefore, for a precise definition of the geotechnical model, it is recommended to conduct additional laboratory tests, particularly those focused on defining compressibility parameters, given the unique behavior of natural diatomaceous soils
Investigation and monitoring to model the interaction between the Scrovegni’s Chapel in Padova (Italy) and the underlying foundation soil
Get PDFIn Padova's historic centre lies the renowned Scrovegni’s Chapel, painted by Giotto in 1303. The local subsoil primarily consists of silty sand with some layers of silt. The crypt beneath acts as a buffer against soil moisture, preventing damage to the frescoes. However, during heavy rain, groundwater rises flowing across the floor and lateral walls, therefore flooding the pavement. A pumping system is eventually activated to mitigate the pavement inundation. Several investigations including geophysical surveys, piezocone tests, and boreholes with soil sampling have been conducted to provide the subsoil geotechnical model and understand the local hydrogeological behaviour. Monitoring systems, such as piezometers, deep extensometers and optical fiber cables, track groundwater levels and long-term soil displacements. The paper aims to characterize the subsoil's stratigraphy, mechanical properties and permeabilities to model how the environmental conditions affect the ancient Chapel and ensure its long-term stability
A review of 30 years French instrumented and variable energy dynamic cone penetrometer Panda
No full textDynamic penetrometer is a worldwide practice in geotechnical exploration and the French Panda (1) lightweight variable energy is the most developed device nowadays. Widely used in France and other countries, The Panda penetrometer is relatively unknown for characterizing surface soils domain and the possibilities it offers. In this article, the authors offer a brief review of the principle of measurement, its uses, advantages and disadvantages calibration, and interpretation, as well as the different relationships with other in-situ test (CPT, SPT…) and some geotechnical parameters. A summary of the works that can be found and that are based on this technology is also presented. The overall aim is to provide the reader with a basic historical document for a better understanding of the operation and analysis of the results obtained with this device, enabling it to be integrated, as a complement, into in situ investigation campaigns
Empreses, institucions, geopolítica
No full textObjectiu
L’objectiu de la Comunicació es: (1) identificar i sintetitzar les bases actuals de les principals polítiques empresarials i industrials promogudes per la UE, Estats Units, organismes internacionals i governs català i espanyol, i constatar la seva aplicació la realitat del sistema productiu català; i (2) analitzar en quina mesura aquesta acció institucional pot influir en la millora de les dimensions de les empreses del sistema productiu català.
Plantejament
La petita dimensió relativa de les empreses catalanes (com de Espanya, Itàlia i altres països mediterranis) es un dels aspectes que es mencionen com una de les causes del feble creixement de la productivitat del sistema la última dècada. En la mesura que la dimensió recull característiques competitives de les empreses, constitueix un paràmetre d’interès.
Les capacitats empresarials, la seva productivitat i competitivitat, depenen de diversos factors però, en primer lloc, de la qualificació de les persones, i en segon lloc de l’entorn institucional del que aquest treball s’ocupa. Altre factor destacable son les pertorbacions o “shocks” que l’entorn global projecte sobre els sistemes productius.
Alguns shocks recents sobre la economia global provenen de la lluita geoestratègica i militar, en primer lloc, però també d’altres desenvolupaments com: (a) la concentració de poder en les grans plataformes tecnològiques; (b) les transformacions dels sistemes financers; i (c) l’acció dels grans inversors globals de capital privat que influeixen en la gestió de les empreses. L’enfrontament geoestratègic dona lloc a la disrupció de les cadenes de circulació d’inputs, i la resultant recomposició dels sectors productius. Y, sobretot, que els països occidentals volen recuperar el control d’una indústria en bona part transferida a Xina.
Iniciatives internacionals
Front al ampli escenari obert tant la OCDE com la Comissió Europea han intensificat el seu interès i les seves propostes per la millora de la qualitat i potència del conjunt d’empreses que han de operar en l’actual i futur terreny productiu i de relacions internacionals. Tant l’estructura empresarial com la composició sectorial serà afectada d’una manera o altre. Estats Units ha adoptat un conjunt de mesures de política industrial, que fins fa poc descartava i, per tant, els països europeus segueixen la iniciativa. D’altre banda, tant Estats Units com França, Alemanya i altres països europeus apunten la intenció de reforçar l’ indústria militar. Tècnicament seria una bona base de recuperació d’un sector manufacturer intensiu en recerca i coneixements. Socialment significaria el retorn del trade-off “guns or butter”.
Enfoc i resultat esperat
Aquest treball utilitza tres instruments principals d’anàlisi: primer, articles acadèmics; segon, publicacions rellevants de blogs, think tanks, i publicacions econòmiques nacionals i internacionals; i tercer, bases de dades de la OCDE, UE, Eurostat, INE, Idescat, Generalitat i altres publicacions governamentals i organismes internacionals. Finalment s’intenta valorar el grau d’ajust entre els instruments emprats pels governs i l’objectiu de millorar les dimensions empresarials com a element per adquirir competitivitat internacional
El problema de l’assequibilitat de l’habitatge: Descripció, causes i polítiques per combatre-la.
No full textRevealing Structures below Vegetation using UAV-BASED LIDAR
Get PDFLiDAR has been used for the last decade to create digital terrain models using Airborne Laser Scans (ALS) with about 10 points per square metre, mainly depending on flight altitude and speed. The data is used to produce elevation maps or digital surface models, calculate volumes and analyse the Earth's surface or objects above it. However, the resolution and elevation accuracy of about ± 0.3 m means that calculations are only estimates and ground features may not be identified. Unmanned aerial vehicle based LiDAR systems have some advantages over ALS data. Their lower altitude and speed allow the scanner to generate more points per square metre than an ALS. The more laser beams the scanner emits into the same area, the more beams pass through the vegetation and generate more points on the ground or other objects. This increases the level of detail in the digital terrain model. Reference points are another way of increasing the accuracy of the LiDAR scan. These points are placed within the survey area and have known coordinates and elevations to control and fit the result of the LiDAR scan to the coordinate system of the reference points. This data can be used for higher accuracy volume calculations and changes in the terrain structure (e.g. geological changes). Because the terrain is mapped at a high level of detail, it can also be used in explosive ordnance disposal to reveal hidden features such as trenches or bomb craters that may cause a problem for the project