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2D numerical analysis of the seismic response of a karst rock mass: importance of underground caves and geostructural details

Abstract

The present study shows the results of a 2D local seismic response (LSR) analysis, simulated for a geomechanical model consisting of a layered carbonate rock mass with hypogean karst caves and a structural– lithostratigraphic complex setting, in an area within the Municipality of Turi (Apulia, Italy). In this case study a Distinct Element Code (DEM) code (UDEC) was used for the LSR simulations conducted on a model both in the absence and in the presence of two overlapping karst caves. The preliminary stress–strain model analysis show some tensile yielding points clustered on the roof of the upper karst cave, already in static conditions, and the phenomenon becomes even more noticeable in dynamic conditions. This is perfectly in agreement with the real occurrence of a sinkhole that brought to the light the underlying karst cave, in the case study area, in the recent past.

The amplification/deamplification factor (FA) was calculated as the ratio of the top value to the bottom value in the model, both of the max X-acceleration and of the spectral Fourier amplitude in three different ranges of frequencies, in order to estimate the effects of LSR on the X-component of the seismic input. According to the previous studies, the results obtained show a generalised deamplification of the seismic ground motion at the top of the model, both without and with underground karst caves, caused by the presence of the upper karst cave and by the seismic energy absorption because of layers’ discontinuity.

Open access
3D Numerical Modeling of Large Piled-Raft Foundation on Clayey Soils for Different Loadings and Pile-Raft Configurations

Abstract

In a piled-raft foundation, the interaction between structural elements and soil continuum can be simulated very precisely by numerical modeling. In the present study, 3D finite element model has been used to examine the settlement, load-sharing, bending moment, and shear force behavior of piled-raft foundation on different soil profiles for different load configurations and pile-raft configurations (PRCs). The model incorporates the pile-to-soil and raft-to-soil interactions by means of interface elements. The effect of parameters such as pile spacing and raft thickness are also studied. For any soil profile, larger pile spacing is observed to be more efficient in reducing the average settlement and enhancing the load-sharing coefficient. The smaller pile spacing is observed to be efficient in reducing the differential settlement. For any soil profile, the behavior of piledraft foundation is significantly affected by the PRCs and load configurations. Furthermore, the raft thickness has significant effect on settlement, bending moment, and shears force. Thus, the results of the present study can be used as guidelines for analyzing and designing large piled-raft foundation.

Open access
Shear strength of compacted Chlef sand: effect of water content, fines content and others parameters

Abstract

This paper presents a laboratory study of the combined effect of the water content and fines content on the mechanical behaviour of Chlef sand in a medium dense state (RD = 65%) and dense state (RD = 80%). Several mechanical parameters were evaluated such as shear strength, cohesion and friction angle at different water content w = 0, 1, 2 and 3% and different fines content Fc = 0, 10, 20, 30 and 40%. The test results showed that the shear strength of Chlef sand decrease with the increase fines content Fc = 0 to 40%, our tests result also showed that the water content has a significant influence on the shear strength which decreases with the increase in the water content w = 0 to 3%. The fines content and the water content have a significant influence on the mechanical parameters c and φ. Cohesion increases with the percentage of fines and decreases with the increase of the water content while the friction angle decreases with the increase the fines content and the water content.

Open access
Critical state constitutive models and shear loading of overconsolidated clays with deviatoric hardening

Abstract

This paper presents an enhanced constitutive model integrating deviatoric hardening with a modified yield surface for overconsolidated clayey soils in a general framework of Cam-clay type models. Its performance was assessed with the simulation of drained and undrained triaxial tests on three clays at different consolidation states in comparison to two critical state models. The proposed model satisfactorily estimates the shear resistance, while capturing the smooth nonlinearity of the soil response.

Shear triaxial tests at constant mean pressure were performed on an overconsolidated marl to study the shear response. Their simulation attests the importance of deviatoric hardening integration.

Open access
A method for local approximation of a planar deformation field

Abstract

We present a method of approximation of a deformation field based on the local affine transformations constructed based on n nearest neighbors with respect to points of adopted grid. The local affine transformations are weighted by means of inverse distance squared between each grid point and observed points (nearest neighbors). This work uses a deformation gradient, although it is possible to use a displacement gradient instead – the two approaches are equivalent. To decompose the deformation gradient into components related to rigid motions (rotations, translations are excluded from the deformation gradient through differentiation process) and deformations, we used a polar decomposition and decomposition into a sum of symmetric and an anti-symmetric matrices (tensors). We discuss the results from both decompositions. Calibration of a local affine transformations model (i.e., number of nearest neighbors) is performed on observed points and is carried out in a cross-validation procedure. Verification of the method was conducted on simulated data-grids subjected to known (functionally generated) deformations, hence, known in every point of a study area.

Open access
Evaluating map specifications for automated generalization of settlements and road networks in small-scale maps

Abstract

The presented research concerns the methodology for selecting settlements and road networks from 1:250 000 to 1:500 000 and 1:1 000 000 scales. The developed methodology is based on the provisions of the Regulation of the Ministry of Interior from 17 November 2011. The correctness of the generalization principles contained in the Regulation has not yet been verified. Thus this paper aims to fulfil this gap by evaluating map specifications concerning settlement and road network generalizations.

The goal was to automate the selection process by using formalized cartographic knowledge. The selection operators and their parameters were developed and implemented in the form of a generalization model. The input data was the General Geographic Object Database (GGOD), whose detail level corresponds to 1:250 000 scale. The presented research is in line with works on the automation of GGOD generalization performed by the National Mapping Agency (NMA) in Poland (GUGiK). The paper makes the following contributions. First, the selection methodology contained in the Regulation was formalised and presented in the form of a knowledge base. Second, the models for the generalization process were developed. The developed methodology was evaluated by generalizing the settlements and roads in the test area. The results of the settlement and road network generalization for both 1:500 000 and 1:1 000 000 detail levels were compared with the maps designed manually by experienced cartographers.

Open access
Where the geographical expanse ends – Space education in primary school. Implementation of inquiry based science education (IBSE) in geography lessons in Polish school

Abstract

Inquiry based science education has been more and more popular strategy in teaching sciences in recent years. Transregional pressure put by international, standardized knowledge and skills tests (e.g. PISA) to converge curricula (Rundgren 2015) of different European states paradoxically helps to promote the open inquiry method which involves the student in the teaching process. Earlier research done in many countries such as Turkey, Israel, Sweden, The Czech Republic (Heinz et al. 2017), Ireland (Dunne et al. 2013) or The Netherlands (Uum van Martina et al. 2016) shows the increase of interest in IBSE both in Europe and in the world.

Teaching geography in Polish primary schools follows international educational trends. This study analyses several proposals of educational activities connected with Space which support geography teaching. All of them are conducted with using open inquiry method, which is recommended in New National Curriculum of geography (Core Curriculum, 2017, Geography-classes V-VIII).

Open access
Proposal of an Operational Model to Measure Feelings and Emotions in Urban Space

Abstract

People of different cultural backgrounds show different emotional reactions to different urban areas. Finding out how a constructed environment and emotional aspects are related and influence human behavior can be of a great significance in urban planning. Such studies are rooted in environmental psychology and socials sciences; there is a dearth of proper methods and techniques of evaluation with this regard. Moreover, so far there has been no academic study even a review of the relevant practical methods. Thus, there is a need for finding a valid objective evaluation procedure for emotional responses people make to urban space aiming to improve the design of urban areas and urban plan policymaking. In the present research, initially, a review of the research methodologies in environmental psychology, affect and emotions was done. Then, a qualitative content analysis of 30 of the latest projects and research was done in terms of the methodology and tools. Then, the final model was proposed in five stages based on the methods and tools of operationalizing the measurement of feelings and emotions in urban areas. The proposed model combined different research types and different methods applied in different disciplines and thus contribute greatly to solving urban problems.

Open access
A Review of Approaches for Automated Habitat Mapping and their Potential Added Value for Biodiversity Monitoring Projects

Abstract

Habitats are important indicators of biodiversity in their own right, as well as being linked to species, hence their widespread use in reporting on nature conservation planning and policy. For reporting consistent mapping and monitoring habitat extent and change is important. Remote Sensing techniques are becoming an important tool for this. In this paper we describe four examples of methods of semi-automated mapping using Remote Sensing. Because the most effective way of improving the accuracy of the estimation of habitat area is by increasing the sample number, it is important to develop methods for reducing in situ surveys which are expensive. Remote Sensing has the major advantage of comprehensive coverage and the four examples illustrate the potential of extrapolation from semi-automated habitat classifications. The potential for using these methods at national scales is likely to be limited by the need for validation of the automated images and the subsequent calculation of error terms. Existing major national monitoring programs are described, which still use mainly traditional in situ methods. The selection of relatively small numbers of representative samples from environmental classifications to obtain regional estimates reduces the need for large numbers of in situ survey sites and is therefore discussed. The recent development of the use of drones to acquire detailed imagery to support in situ habitat surveys is also covered. Finally, practical problems linked to the methods described in the paper are considered, as in some cases these will override the theoretical benefits of a particular approach. It is concluded that automated methods can enhance existing monitoring systems and should be considered in any biodiversity monitoring system as they represent an opportunity for reducing costs, if integrated with an in situ program.

Open access
Thermal Comfort Characteristic of 5 Patterns of a Persian Garden in a Hot-Arid Climate of Shiraz, Iran

Abstract

Thermal comfort in the open spaces is a significant parameter in public mentally and physically healthy. Increased hot days of cities because of the urban heat island is the common phenomenon in cities. This phenomenon effect cites quality by a different aspect such as air quality, Use of fossil fuels etc. therefore, cooling strategies in the urban and urban park's design is one of the important issues of the designers. Urban parks have a significant effect on heat stress mitigation. Persian garden is known for its microclimate effect on pedestrians, so different patterns of Persian garden is selected to be analyzed in terms of thermal comfort condition on the hottest day of summer so far in the dry hot climate of the Shiraz(12th of July 1998 with the maximum 42°C Ta). In this paper 8 conditions are simulated by Envi-met3.1 to get environment data of these patterns and also the Rayman model is used to calculate the Physiological Equivalent Temperature (PET) as the proper thermal index for outdoor condition. The results demonstrate that alteration of Shortwave radiation both direct and diffuse conditions and mean radiant temperature are affected by both sky view factor and the orientation of the Persian garden. Pavilion location has an important effect in mitigation of the Tmrt by preventing the afternoon powerful sun rays through to the paths in the End.E-W pattern. Therefore, this pattern has a better condition of PET value than the others in Shiraz setting.

Open access