Convergence analysis of fixed stress split iterative scheme for anisotropic poroelasticity with tensor Biot parameter

We perform a convergence analysis of the fixed stress split iterative scheme for the Biot system modeling coupled flow and deformation in anisotropic poroelastic media with tensor Biot parameter. The fixed stress split iterative scheme solves the flow subproblem with all components of the stress tensor frozen using a multipoint flux mixed finite element method, followed by the poromechanics subproblem using a conforming Galerkin method in every coupling iteration at each time step. The coupling iterations are repeated until convergence and Backward Euler is employed for time marching. The convergence analysis is based on studying the equations satisfied by the difference of iterates to show that the fixed stress split iterative scheme for anisotropic poroelasticity with Biot tensor is contractive. We also demonstrate that the scheme is numerically convergent using the classical Mandel’s problem solution for transverse isotropy.     

Prediction of Engineering Properties of Basalt Rock in Jordan Using Ultrasonic Pulse Velocity Test

Basalt is an extrusive igneous rock derived from Lava and spread over different localities in Jordan. It can be used in industrial applications, and as construction materials. Before using basalt, it is essential to determine its dry density, porosity, uniaxial compressive strength, and Brazilian tensile strength. The testing procedure and sample preparation used to determine the engineering properties are time-consuming and need expertise. Hence, the ultrasonic pulse velocity (UPV) test, a quick and non-destructive evaluation method, was used to determine the engineering properties. Empirical relationships for determination of dry density, porosity, uniaxial compressive strength, Brazilian tensile strength, and tangent modulus of elasticity were deduced. Good correlation coefficients (R²?=?0.832–0.929) were obtained between UPV and dry density, porosity, uniaxial compressive strength, Brazilian tensile strength and modulus of elasticity. These correlations were limited to intact basalt with UPV?≥?4000 m/s.     

Emerging grassroots resilience and flood responses in informal settlements in Accra,Ghana

In the last five decades, many informal communities in Accra, Ghana have suffered from annual flood hazards. Residents of these communities appear to have successfully resisted evictions by city authorities; survived flood hazards and poor environmental health conditions. These flood affected households continue to survive with increasing housing and population densities in the face of these annual floods. Are they becoming resilient? Have residents built adaptive capacities through learning experiences from previous flood occurrences and evictions attempts? What has produced and continued to shape their responses to flooding? What can be learned from this supposed grassroots resilience to inform flood management in urban Africa? Using case studies of three informal communities of Glefe, Agbogbloshie and Old Fadama, this paper explores the gradual and evolving adaptive capacities and social resilience to flood hazards among poor urban dwellers. The paper reveals the depth of understanding and embodied nature of flood experiences among affected slum dwellers and how these are gradually being transformed into adaptive capacities and shaping their responses. In the absence of efficient state flood interventions, there are emerging and enduring flood responses and adaptation practices shaped by residents’ social networks, political alliances and sense of place. These responses translates into continuous re-structuring of housing units, construction of communal drains, creation of local evacuation teams and safe havens. Urban policy contributions that can be learned from these emerging grassroots capacities for flood vulnerability management have been proposed.     

The perception of stakeholders on regional transformation on the outskirts of Yogyakarta City,Indonesia

The research was conducted on the outskirts of Yogyakarta City that administratively include three districts of Sleman Regency, namely Depok, Gamping, and Mlati, and three districts of Bantul Regency, namely Kasihan, Sewon, and Banguntapan. It aimed to obtain a deeper understanding on the perceptions of stakeholders on the regional transformation phenomena occurring on the outskirts of Yogyakarta City. This is a qualitative case study research with a single case. The case study research method was selected because the observed phenomenon is contemporary and the analyzed issue is unique. It used a qualitative method with field observations and in-depth interviews to several informants as data acquisition techniques. The informants were stakeholders from state/government, private sector/entrepreneur, academics, and civil society, which were selected using purposive sampling method. The research data processing and analysis included: (1) data reduction, (2) data presentation, and (3) data conclusion. In order to examine the reliability and validity of the data, the research used source triangulation method. The results showed that all stakeholders perceived the regional transformation on the outskirts of Yogyakarta City to have positive and negative consequences on various dimensions. The positive ones were the economic opportunities, generated by the regional transformation process, for both the native people and the migrants. Aside from these positive consequences, the regional transformation on the outskirts of Yogyakarta City also caused negative impacts on the physical, economic, social, and cultural dimensions of the outskirts.     

Impact of irrigated agriculture on groundwater-recharge salinity: a major sustainability concern in semi-arid regions

Intensive irrigated agriculture substantially modifies the hydrological cycle and often has major environmental impacts. The article focuses upon a specific concern—the tendency for progressive long-term increases in the salinity of groundwater recharge derived from irrigated permeable soils and replenishment of unconfined aquifers in more arid regions. This process has received only scant attention in the water-resource literature and has not been considered by agricultural science. This work makes an original contribution by analysing, from scientific principles, how the salinisation of groundwater recharge arises and identifies the factors affecting its severity. If not proactively managed, the process eventually will impact irrigation waterwell salinity, the productivity of agriculture itself, and can even lead to land abandonment. The types of management measure required for mitigation are discussed through three detailed case histories of areas with high-value groundwater-irrigated agriculture (in Spain, Argentina and Pakistan), which provide a long-term perspective on the evolution of the problem over various decades.     

A new GIS-based data mining technique using an adaptive neuro-fuzzy inference system (ANFIS) and k-fold cross-validation approach for land subsidence susceptibility mapping

In this paper, we evaluate the predictive performance of an adaptive neuro-fuzzy inference system (ANFIS) using six different membership functions (MF). In combination with a geographic information system (GIS), ANFIS was used for land subsidence susceptibility mapping (LSSM) in the Marand plain, northwest Iran. This area is prone to droughts and low groundwater levels and subsequent land subsidence damages. Therefore, a land subsidence inventory database was created from an extensive field survey. Areas of land subsidence or areas showing initial signs of subsidence were used for training, while one-third of inventory database were reserved for testing and validation. The inventory database randomly divided into three different folds of the same size. One of the folds was chosen for testing and validation. Other two folds was used for training. This process repeated for every fold in the inventory dataset. Thereafter, land subsidence related factors, such as hydrological and topographical factors, were prepared as GIS layers. Areas susceptible to land subsidence were then analyzed using the ANFIS approach, and land subsidence susceptibility maps were created, whereby six different MFs were applied. Lastly, the results derived from each MF were validated with those areas of the land subsidence database that were not used for training. Receiver operating characteristics (ROC) curves were drawn for all LSSMs, and the areas under the curves were calculated. The ROC analyses for the six LSSMs yielded very high prediction values for two out of the six methods, namely the difference of DsigMF (0.958) and GaussMF (0.951). The integration of ANFIS and GIS generally led to high LSSM prediction accuracies. This study demonstrated that the choice of training dataset and the MF significantly affects the results.     

Use of photo-based 3D photogrammetry in analysing the results of laboratory pressure grouting tests

This paper presents a non-destructive, low-cost, photo-based, 3D reconstruction technique for characterizing geo-materials with irregular shapes of a relatively large size. After being validated against two traditional volume measurement methods, namely the vernier caliper method and the fluid displacement method for regular and irregular shapes, respectively, 3D photogrammetry was used to analyse the grout bulbs formed in laboratory pressure grouting tests. The reconstructed 3D mesh model of the sample provides accurate and detailed 3D vertex data, which allowed the volume, densification efficiency and bleeding behaviour of the grout bulbs to be analysed. Comparing the bulb section views at different grouting pressures also offers an intuitive observation of the grout development and propagation process. Moreover, the 3D vertex data and surface area included in the model are of great importance in validating numerical predictions of the pressure grouting process and analysing the interface shear resistance of grouted soil nails or anchors. Compared to existing approaches, the new 3D photogrammetry method possesses several key advantages: (a) it does not require expensive, specialized equipment; (b) samples are not destroyed or modified during testing; (c) it allows to reconstruct objects of various scales and (d) the software is public domain. Therefore, the adoption of this 3D photogrammetry method will facilitate research in the pressure grouting process and can be extended to other problems in geotechnical engineering.     

Geochemical characteristics of Proterozoic granite magmatism from Southern Granulite Terrain,India: Implications for Gondwana

Granitoid intrusions occur widely in the Southern Granulite Terrain (SGT) of India, particularly within the Cauvery Suture Zone (CSZ), which is considered as the trace of the Neoproterozoic Mozambique ocean closure. Here we present the petrological and geochemical features of 19 granite plutons across the three major tectonic blocks of the terrain. Our data show a wide variation in the compositions of these intrusions from alkali feldspathic syenite to granite. The whole rock geochemistry of these intrusions displays higher concentrations of \(\hbox {SiO}_{2}\), FeO*, \(\hbox {K}_{2}\hbox {O}\), Ba, Zr, Th, LREE and low MgO, \(\hbox {Na}_{2}\hbox {O}\), Ti, P, Nb, Y and HREE’s. The granitoids are metaluminous to slightly peraluminous in nature revealing both I-type and A-type origin. In tectonic discrimination plots, the plutons dominantly show volcanic arc and syn-collisional as well as post-collisional affinity. Based on the available age data together with geochemical constrains, we demonstrate that the granitic magmatism in the centre and south of the terrain is mostly associated with the Neoproterozoic subduction–collision–accretion–orogeny, followed by extensional mechanism of Gondwana tectonics events. Similar widespread granitic activity has also been documented in the Arabian Nubian shield, Madagascar, Sri Lanka and Antarctica, providing similarities for the reconstruction of the crustal fragments of Gondwana supercontinent followed by Pan-African orogeny.     

Using landscape indicators and Analytic Hierarchy Process (AHP) to determine the optimum spatial scale of urban land use patterns in Wuhan,China

Quantifying land use patterns and functions is critical for modeling urban ecological processes, and an emerging challenge is to apply models at multiple spatial scales. Methods of determining the optimum scale of land use patterns are commonly considered using landscape metrics. Landscape metrics are quantitative indicators for analyzing landscape heterogeneity at the landscape level. In this study, due to their widespread use in urban landscape analyses and well-documented effectiveness in quantifying landscape patterns, landscape metrics that represent dominance, shape, fragmentation and connectivity were selected. Five metrics include Patch Density, Contagion, Landscape Shape Index, Aggregation Index and Connectivity. Despite a wide application of landscape metrics for land use studies, the majority mainly focuses on the qualitative analysis of the characteristics of landscape metrics. The previous models are limited in exploring the optimum scale of land use patterns for their lack of quantitation. Therefore, taking the City of Wuhan as an example, the land use unit was treated as a patch, and the landscape pattern metrics at different spatial scales were calculated and compared so as to find the optimum one. Furthermore, a mathematical model of landscape metrics was proposed to quantify the scale effect of urban land use patterns, generating a complementary tool to select the optimum scale. In addition, Analytic Hierarchy Process (AHP) was introduced to determine the respective weights of the chosen landscape metrics in this model. Fractal dimension was ultimately applied to verify the chosen optimum scale of our study region. The results indicated that 60 m is confirmed to be the optimum scale for capturing the spatial variability of land use patterns in this study area.     

Using Simple Dilution Models to Predict New Zealand Estuarine Water Quality

A tool based on simple dilution models is developed to predict potential nutrient concentrations and flushing times for New Zealand estuaries. Potential nutrient concentrations are the concentrations that would occur in the absence of nutrient uptake or losses through biogeochemical processes, and so represent the pressure on a system due to nutrient loading. The dilution modelling approach gives a single time- and space-averaged concentration as a function of flow and nutrient input, with the capability to include seasonal nutrient and flow differences. This tool is intended to be used to identify estuaries likely to be highly sensitive to current nutrient loads based on their physical attributes, or to quickly compare the effects of different land-use scenarios on estuaries. The dilution modelling approach is applied both to a case study of a single New Zealand estuary, and used in a New Zealand-wide assessment of 415 estuaries. For the NZ-wide assessment, annual nutrient loads to each estuary were obtained from a GIS-based land-use model. Comparison with measured data shows that the predicted potential nitrate concentrations are significantly correlated with, but higher than, measured nitrate values from water quality sampling time series. This is consistent with expectations given that the measured concentrations include the effects of nitrogen uptake and loss. The estuary dilution modelling approach is currently incorporated into the GIS-land use model, and is also available as a web-app for assessing eutrophication susceptibility of New Zealand estuaries.