Landslide susceptibility mapping using machine learning algorithms and comparison of their performance at Abha Basin,Asir Region,Saudi Arabia

The current study aimed at evaluating the capabilities of seven advanced machine learning techniques(MLTs),including,Support Vector Machine(SVM),Random Forest(RF),Multivariate Adaptive Regression Spline(MARS),Artificial Neural Network(ANN),Quadratic Discriminant Analysis(QDA),Linear Discriminant Analysis(LDA),and Naive Bayes(NB),for landslide susceptibility modeling and comparison of their performances.Coupling machine learning algorithms with spatial data types for landslide susceptibility mapping is a vitally important issue.This study was carried out using GIS and R open source software at Abha Basin,Asir Region,Saudi Arabia.First,a total of 243 landslide locations were identified at Abha Basin to prepare the landslide inventory map using different data sources.All the landslide areas were randomly separated into two groups with a ratio of 70%for training and 30%for validating purposes.Twelve landslide-variables were generated for landslide susceptibility modeling,which include altitude,lithology,distance to faults,normalized difference vegetation index(NDVI),landuse/landcover(LULC),distance to roads,slope angle,distance to streams,profile curvature,plan curvature,slope length(LS),and slope-aspect.The area under curve(AUC-ROC)approach has been applied to evaluate,validate,and compare the MLTs performance.The results indicated that AUC values for seven MLTs range from 89.0%for QDA to 95.1%for RF.Our findings showed that the RF(AUC=95.1%)and LDA(AUC=941.7%)have produced the best performances in comparison to other MLTs.The outcome of this study and the landslide susceptibility maps would be useful for environmental protection.     

Hybrid Foundation System for Offshore Wind Turbine

The demand on green and clean energy is increasing all over the world. This urge us to try to reduce the obstacles in this field. One of the main obstacles is the high cost of offshore foundation system of wind turbines. A novel offshore hybrid foundation system is proposed for large offshore wind turbines to try to reduce the construction cost. This new system consists of circular precast concrete plate connected on site (i.e. offshore) to a steel monopole that is smaller than the usual pile size used. Parametric study for different foundations systems including monopiles had been done. The displacements at different locations of the foundation and the rotation at the pile head were analyzed and evaluated using a 3D nonlinear finite element model under field-like loading conditions considering different foundation configurations. This work paves the way for the development of design guidelines for this novel foundation system in offshore wind turbine applications.     

Assessment of Reservoir Rock Properties from Rock Physics Modeling and Petrophysical Analysis of Borehole Logging Data to Lessen Uncertainty in Formation Characterization in Ratana Gas Field,Northern Potwar,Pakistan

Petrophysical evaluation and rock physics analysis are the important tools to relate the reservoir properties like porosity, permeability, pore fluids with seismic parameters. Nevertheless, the uncertainties always exist in the quantification of elastic and seismic parameters estimated through wireline logs and rock physics analysis. A workflow based on statistical relationships of rock physics and logs derived elastic and seismic parameters with porosity and the percentage error exist between them is given. The statistical linear regressions are developed for early Eocene Chorgali Formation between various petrophysically factors determined from borehole logging of well Ratana–03 drilled in tectonically disturbed zone and the seismic and elastic parameters estimated through rock physics modeling. The rock physics constraints such as seismic velocities, effective density and elastic moduli calculated from Gassmann fluid substation analysis are in harmony and close agreement to those estimated from borehole logs. The percentage errors between well logs and rock physics computed saturated bulk modulus (K _sat ), effective density (ρ _eff ), compressional and shear wave velocities (V _P and _V S) are 1.31%, 4.23 %, 5.25% and 4.01% respectively. The permeability of reservoir intervals show fairly strong linear relationship with the porosity, indicating that the reservoir interval of the Chorgali Formation is permeable and porous thus having large potential of hydrocarbon accumulation and production.     

Mechanical properties and time-dependent behaviour of sand-granulated rubber mixtures

The use of granulated recycled rubber as a lightweight material in civil engineering applications has been widely growing over the past 20 years. Processed waste tires mixed with soils have been introduced as lightweight fills for slopes, retaining walls, and embankments. It has also been considered as a damping material under foundations in seismic zones. Understanding the properties of sand-rubber mixtures is essential to evaluate its performance in geotechnical applications. Isotopically consolidated drained (CD) triaxial tests were conducted to investigate the effect of rubber size, content and saturation condition on the mechanical properties of sand-rubber mixtures. Moreover, the compressibility of the sand-rubber mixtures under sustained loading was investigated through one dimensional consolidation tests. The unit weight, shear strength and stiffness of sand-rubber mixtures decreased whereas deformability increased at increased rubber content. A non-linear stress-strain response was observed, that changed from brittle to ductile behaviour at increased rubber content. Sand-rubber mixtures, under one dimensional loading, exhibited significant settlement that increased as rubber content increased.     

New <Superscript>40</Superscript>Ar/<Superscript>39</Superscript>Ar age constraints on cooling and unroofing history of the metamorphic host rocks (and igneous intrusion associates) from the Bulfat Complex (Bulfat area), NE-Iraq

The Northern Zagros Suture Zone (NZSZ), formed as a result of the collision between Arabian and Sanandaj-Sirjan microplate, is considered as part of the Zagros orogenic belt. NZSZ is marked by two allochthonous thrust sheets in upward stacking order: lower and upper allochthon. The Bulfat complex is a part of the upper allochthon or “Ophiolite-bearing terrane” of Albian-Cenomenion age (97–105 Ma). Voluminous highly sheared serpentinites associated with ophiolites occur within this upper allochthon. In addition, the Gemo-Qandil Group is characterized by gabbroic to dioritic Bulfat intrusion with a crystallization age spanning from ~45 to ~?40 Ma, as well as extensive metapelites with contact to the Walash-Naupurdam metavolcanic rocks. Due to the deformation in the Sanandaj-Sirjan Zone along the eastern side of the Iraqi segment of NZSZ, the Gemo-Qandil Group was regionally metamorphosed during late Cretaceous (~?80 Ma). This tectono-compressional dynamics ultimately caused an oscillatory deformation against Arabian continental margin deposits as well. During these events, gabbro-diorite intrusion with high-grade contact metamorphic aureoles occurred near Bulfat. Thus, there is an overlap between regional and contact metamorphic conditions in the area. The earlier metamorphic characteristic can be seen only in places where the latter contact influence was insignificant. Generally, this can only observed at a distance of more than 2.5 km from the contact. According to petrographic details and field observations, the thermally metamorphosed metapelitic units of the metasediment have been completely assimilated, with only some streaks of biotite and relicts of initial foliation. They strongly resemble amphibolite-grade slices from the regional metamorphic rocks in the region. Metapelitic samples far from the intrusion give similar biotite cooling ages as the intrusive rocks. Thus, they may be affected by the same thermal event. ⁴⁰Ar/³⁹Ar dating of biotite in metapelite rocks of Bulfat by step-wise heating with laser gave average weighted isotopic ages of 34.78?±?0.06 Ma. This is interpreted as crystallization/recrystallization age of biotite possibly representing the time of cooling and uplift history of the Bulfat intrusion. Cooling and exhumation rates for the Bulfat gabbro-diorite rocks were estimated as ~?400 °C/Ma and ~?3.3 mm/year respectively. According to petrographic details, field observations and Ar/Ar dating concerning the contact metamorphism near Bulfat due to the gabbro-diorite intrusion, no significant deformation is visible during exhumation processes after the Paleogene tectono-thermal event, indicating that isotopic ages of 34.78?±?0.06 Ma could mark the timing of termination of the island arc activity in the Ophiolite-bearing terrane (upper allochthon).     

Skin friction behavior of pile fully embedded in limestone

Pile foundation system in limestone rock layers is commonly used in Riyadh area, Saudi Arabia, for high-rise building, bridges, and other structures. Especially in Riyadh region, bored piles are used for bridges and underpasses not only because of bearing capacity but mainly because of limited spaces for using shallow foundations. In addition, piles are used for bridges over wadis to avoid scouring effects. The loads are transferred by the pile from a superstructure to the rock strata through side friction and end-bearing resistance. However, there are no studies conducted in Riyadh area to quantify the skin friction capacity of pile embedded in limestone rock. Accordingly, this experimental study describes in details the behavior of load transfer mechanism through side friction only on a reinforced concrete pile (75 mm diameter and 150 mm long) constructed on hard limestone rock sample. Soft material (Styrofoam) was placed at the bottom of the pile to eliminate the effect of end-bearing resistance. Unconfined compression test was conducted on intact rock sample to find out the properties of the rock used. The result of the ultimate side friction obtained from the test was compared with values predicted by other researcher methods mentioned in the literature.     

Appraisal of groundwater quality in a crystalline aquifer: a chemometric approach

The purpose of this study is to assess the groundwater quality and identify the processes that control the groundwater chemistry in a crystalline aquifer. A total of 72 groundwater samples were collected during pre- and post-monsoon seasons in the year 2014 in a semi-arid region of Gooty Mandal, Anantapur district, Andhra Pradesh, India. The study utilized chemometric analysis like basic statistics, Pearson’s correlation coefficient (r), principal component analysis (PCA), Gibbs ratio, and index of base exchange to understand the mechanism of controlling the groundwater chemistry in the study area. The results reveal that groundwater in the study area is neutral to slightly alkaline in nature. The order of dominance of cations is Na⁺ > Ca²⁺ > Mg²⁺ > K⁺ while for anions, it is \( {\mathrm{HCO}}_3^{-}>{\mathrm{Cl}}^{-} \)>\( {\mathrm{NO}}_3^{-} \)>\( {\mathrm{SO}}_4^{2-} \)>\( {\mathrm{CO}}_3^{2-}>{\mathrm{F}}^{-} \) in both seasons. Based on the Piper classification, most of the groundwater samples are identified as of sodium bicarbonate (\( {\mathrm{Na}}^{+}-{\mathrm{HCO}}_3^{-}\Big) \) type. According to the results of the principal component analysis (PCA), three factors and two factors were identified pre and post monsoon, respectively. The present study indicates that the groundwater chemistry is mostly controlled by geogenic processes (weathering, dissolution, and ion exchange) and some extent of anthropogenic activities.     

Presence of microporosity in Miocene carbonate platform,Central Luconia,offshore Sarawak,Malaysia

The Luconia Province—offshore Sarawak—is a key hydrocarbon province in Malaysia. However, the gas reservoirs in Central Luconia pose unique problems and challenges as they have partially water-filled microporosity that overprint wireline logs. Microporosity in Central Luconia occurs throughout the Miocene carbonates and is a crucial element that influences fluid flow properties and ultimately the recovery of hydrocarbons. Quantification of macroporosity was achieved using petrographic analysis of thin sections and the FESEM images. The point counting technique was used to estimate the amount of macroporosity from the thin section, which was then subtracted from the total porosity to derive microporosity. The qualitative investigation of the Miocene carbonates indicates the presence of three different types of microporosity namely grain-based microporosity, matrix-based microporosity, and cement-based microporosity. Quantification of microporosity showed that the microporosity varies from sample to sample, ranging from 10 to 60% of the total measured porosity. The depositional texture, mineralogy, and microtexture control this microporosity variation including its abundance and type. The microporosity in Central Luconia is diagenetically controlled based on four major diagenetic mechanisms namely (1) mechanical process/endolithic grains/marine diagenesis; (2) leaching/meteoric diagenesis; (3) cementation/shallow diagenesis; and (4) deeper diagenesis environment.     

A Participatory GIS Approach to Identify Critical Land Degradation Areas and Prioritize Soil Conservation for Mountainous Olive Groves （Case Study）

Climate change scenarios predict an increase in the frequency of heavy rainfall events in some areas. This will increase runoff and soil erosion, and reduce agricultural productivity, particularly on vulnerable mountainous agricultural lands that is already exhibiting high rates of soil erosion. Haphazard implementation of soil and water conservation （SWC） interventions on scattered fields is inefficient in reducing soil erosion. The objective of this study was to identify areas at high risk of erosion to aid the design and implementation of sustainable SWC using GIS analysis and farmers＇ participation approach. A 25 m digital elevation model （DEM） was used to derive layers of flow accumulation, slope steepness and land curvature, which were used to derive an erosion-risk （priority） map for the whole watershed. Boundaries of farmers＇ fields were mapped and verified by the community and each field was classified into high, moderate or low erosion risk. Fields with low flow accumulation （top of hill） and/or steep slope and/or convex slope were assigned high erosion risk and therefore high implementation priority. The study showed that more than 54% of the fields were classified into high erosion risk areas. Accordingly, a community-watershed plan was established, revised and approved by the community.Incentive loans to implement SWC measures were distributed to 100 farmers based on the priorities of their fields. Judged by local farmers and using 16 randomly selected fields, 90% of the targeted areas were correctly identified using the erosion risk map. After two years, the conservation measures had led to marked improvement of soil conservation. The approach is simple and easy to comprehend by the community and provides scientific basis to prioritize the implementation of SWC and to target the most degraded areas, which amplify the impact of these in reducing the vulnerability to land degradation.     

Development of storage capacity and morphology of the Aswan High Dam Reservoir

ABSTRACT

A digital elevation model (DEM), as well as satellite images, was used to detect the changes in the morphology and storage capacity of the Aswan High Dam Reservoir (AHDR) over the past five decades. Study findings indicate that the total storage capacity of the AHDR estimated by the DEM decreased by 12%. This decrease is mainly in the live and the dead storage capacities. The morphology of the reservoir changed in the southern part and at the entrance of the lacustrine part. A gradual conversion of the entrance to the riverine part was observed. The surface area of the AHDR decreased at low water levels because of sedimentation. The average reduction of the surface area between water levels of 140 and 168 m a.s.l. is about 15%, which is equivalent to almost 10 km³.