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The present work compiles results from pullout tests campaigns carried out in recent years. Tests are focused on polyester (PET) strap reinforcement of varied grades (or ultimate tensile strengths and, consequently, stiffness) subjected to different confining pressures and installation conditions. Reinforcements have homogeneous HDPE sheaths with continuous surfaces. Assessments of possible post-pullout damage and the consequences of said deterioration are explored. General conclusions regarding design and construction practices are commented.

Food insecurity is a chronic problem in Africa and is likely to worsen with climate change and population growth. It is largely due to poor yields of the cereal crops caused by factors including stemborer pests, striga weeds and degraded soils. A platform technology, ‘push–pull’, based on locally available companion plants, effectively addresses these constraints resulting in substantial grain yield increases. It involves intercropping cereal crops with a forage legume, desmodium, and planting Napier grass as a border crop. Desmodium repels stemborer moths (push), and attracts their natural enemies, while Napier grass attracts them (pull). Desmodium is very effective in suppressing striga weed while improving soil fertility through nitrogen fixation and improved organic matter content. Both companion plants provide high-value animal fodder, facilitating milk production and diversifying farmers’ income sources. To extend these benefits to drier areas and ensure long-term sustainability of the technology in view of climate change, drought-tolerant trap and intercrop plants are being identified. Studies show that the locally commercial brachiaria cv mulato (trap crop) and greenleaf desmodium (intercrop) can tolerate long droughts. New on-farm field trials show that using these two companion crops in adapted push–pull technology provides effective control of stemborers and striga weeds, resulting in significant grain yield increases. Effective multi-level partnerships have been established with national agricultural research and extension systems, non-governmental organizations and other stakeholders to enhance dissemination of the technology with a goal of reaching one million farm households in the region by 2020. These will be supported by an efficient desmodium seed production and distribution system in eastern Africa, relevant policies and stakeholder training and capacity development.

Pull-out strength tests conducted on screw anchors in uncracked concrete substrates of the C25/30 class are presented in this article. The destructive force for anchor–concrete fasting was tested, and in the next step, the average pull-out strengths of screw anchors in concrete substrates with and without the addition of steel fiber were determined. Currently, the pull-out strengths of anchors in fiber-reinforced concrete substrates are defined as for unreinforced concrete substrates. Therefore, pull-out tests were performed for screw anchors in fiber-reinforced concrete substrates. Fiber contents of 10, 20, 30, and 50 kg/m3 were used. An increase in the load capacity of screw anchors in a fiber-reinforced concrete substrate was demonstrated in a pull-out test compared to base samples without fibers. The coefficient related to the actual fastening behavior of a screw anchor in the fiber-reinforced concrete substrate was determined. It was assumed that a coefficient of 13.10 should be adopted. This was the lowest value obtained for the load capacity in this study for screw anchors in a fiber-reinforced concrete substrate.

An electrophoretic deposition (EPD) process of micro-quartz (MQ) powder is applied to carbon fibers (CFs) with the aim to enhance their interfacial bond to cementitious matrices and to investigate its influence on the microstructural and mechanical properties of the CFs itself. The electrophoretic mobility of the MQ particles with negative charge in aqueous media was confirmed by potential sweep experiments and zeta-potential measurements. High amounts of MQ were successfully deposited onto the fiber surface, as proven by scanning electron microscopy. Single-fiber tension tests and thermogravimetric analysis showed that EPD treatment had little impact on the tensile properties and thermal stability of the modified fibers. However, storing the CFs in cement pore solution impaired temperature stability of untreated and modified fibers. X-ray diffraction and Raman spectroscopy reveal specific changes of CF's microstructure upon EPD treatment and immersion in pore solution. Single-fiber pullout tests showed that the pullout resistance of MQ-modified CFs was enhanced, relative to untreated CFs. This augmentation can be explained by an enhanced interlocking mechanisms between CF and matrix due to the deposited quartz particles on the CF surface.

Soil nailing technique is widely used in stabilizing roadway and tunnel portal cut excavations. The key parameter in the design of soil nail systems is the pull-out capacity. The pull-out capacity of soil nails can be estimated either from the studies involving similar soil conditions or from the empirical formulas available in the literature. Particularly, it has been documented placing nails closer than a certain minimum distance results in a reduction in the pull-out resistance of a nail placed in sand. However, this requirement has not been discussed for the nail groups located within clay formations. In order to investigate the influence of nail spacing on the pull-out resistance of nails, a series of laboratory pull-out experiments were performed in clay of high plasticity. The results of these experiments showed a remarkable trend. Specifically, there was a significant reduction in the pull-out capacity of a nail when the spacing between nails two times the nail diameter (2Ø). In contrast, the pull-out capacity of a nail embedded in clay remained unaffected by neighboring nails, provided the spacing was maintained at six times the nail diameter (6Ø). In addition, during the conducted pull-out tests, it was observed that the failure mode of a single nail and 6Ø spaced group nails near the surface results as heaving around the single nail. However, in the case of closely positioned (2Ø spaced) nails, the affected area following nail failure exhibits distinct characteristics, which operate as a group. This leads to the occurrence of failure in the form of heaving around the group of nails.

Node thickening is a way to strengthen the nodes of a geogrid. Increasing the node thickness in conventional biaxial geogrids enhances the interface frictional strength parameters and improves its three-dimensional reinforcement effect. Based on the triaxial tests of aeolian sand, single-rib strip tests of geogrids, and pull-out tests of geogrid in aeolian sand, a three-dimensional discrete element pull-out model for geogrids with strengthened nodes was developed to investigate the mechanical performance of an aeolian sand–geogrid interface. The influences of increasing node thickness, the number of strengthened nodes, and the spacing between adjacent nodes on the mechanical performance of the geogrid–soil interface were extensively studied used the proposed model. The results demonstrated that strengthened nodes effectively optimize the reinforcing performance of the geogrid. Among the three node-thickening methods, that in which both the upper and lower sides of nodes are thickened showed the most significant improvement in ultimate pull-out resistance and interface friction angle. Moreover, when using the same node-thickening method, the ultimate pull-out resistance increase shows a linear relationship with the node thickness increase and the strengthened node quantity. In comparison with the conventional geogrid, the strengthened nodes in a geogrid lead to a wider shear band and a stronger ability to restrain soil displacement. When multiple strengthened nodes are simultaneously applied, there is a collective effect that is primarily influenced by the spacing between adjacent nodes. The results provide a valuable reference for optimizing the performance of geogrids and determining the spacing for geogrid installation.

With their high storage capacity and energy efficiency as well as the compatibilities with renewable energy sources, high‐temperature aquifer thermal energy storage (HT‐ATES) systems are frequently the target today in the design of temporally and spatially balanced and continuous energy supply systems. The inherent density‐driven buoyancy flow is of greater importance with HT‐ATES, which may lead to a lower thermal recovery efficiency than conventional low‐temperature ATES. In this study, the governing equations for HT‐ATES considering buoyancy flow are nondimensionalized, and four key dimensionless parameters regarding thermal recovery efficiency are determined. Then, using numerical simulations, recovery efficiency for a sweep of the key dimensionless parameters for multiple cycles and storage volumes is examined. Ranges of the key dimensionless parameters for the three displacement regimes, that is, a buoyancy‐dominated regime, a conduction‐dominated regime, and a transition regime, are identified. In the buoyancy‐dominated regime, recovery efficiency is mainly correlated to the ratio between the Rayleigh number and the Peclet number. In the conduction‐dominated regime, recovery efficiency is mainly correlated to the product of a material‐related parameter and the Peclet number. Multivariable regression functions are provided to estimate recovery efficiency using the dimensionless parameters. The recovery efficiency estimated by the regression function shows good agreement with the simulation results. Additionally, well screen designs for optimizing recovery efficiency at various degrees of intensity of buoyancy flow are investigated. The findings of this study can be used for a quick assessment and characterization of the potential HT‐ATES systems based on the geological and operational parameters. Key Points Four key dimensionless parameters for the high‐temperature aquifer thermal energy storage systems are identified The displacement processes are classified into a buoyancy‐dominated regime, a conduction‐dominated regime, and a transition regime Multivariable regression functions are demonstrated for the estimation of thermal recovery efficiency

To diversify the testing of the stone column bearing capacity, this study evaluates the pull-out bearing capacity of stone columns to provide the necessary reaction forces for static load tests. Considering the construction process of stone columns, an anchor cable is embedded in the columns to provide pull-out resistance. The PFC2D discrete element simulation software is used to simulate the pull-out process at different anchor cable depths to obtain the distribution of the ultimate pull-out bearing capacity. The numerical simulation results reveal that when the burial depth of the anchor cable is shallow, the pull-out bearing capacity is linearly related to the burial depth. When the burial depth exceeds 12.0 m, the bearing capacity increases sharply. The error between the onsite anchor cable pull-out test data and the numerical simulation results is less than 10%, demonstrating the accuracy of the numerical simulation presented in this paper. The results are used to propose a formula for the calculation of pull-out bearing capacity. It is found that the embedded anchor cable in the stone column can provide the required reaction forces, demonstrating the feasibility of conducting static load tests using the reaction force on stone columns.

More than 244 million international migrants were estimated to live in a foreign country in 2015, leaving apart the massive number of people that have been relocated in their own country. Furthermore, a substantial proportion of international migrants from southern countries do not reach western nations but resettle in neighbouring low-income countries in the same geographical area. Migration is a complex phenomenon, where 'macro'-, 'meso'- and 'micro'-factors act together to inform the final individual decision to migrate, integrating the simpler previous push-pull theory.Among the 'macro-factors', the political, demographic, socio-economic and environmental situations are major contributors to migration. These are the main drivers of forced migration, either international or internal, and largely out of individuals' control.Among the 'meso-factors', communication technology, land grabbing and diasporic links play an important role. In particular, social media attract people out of their origin countries by raising awareness of living conditions in the affluent world, albeit often grossly exaggerated, with the diaspora link also acting as an attractor. However, 'micro-factors' such as education, religion, marital status and personal attitude to migration also have a key role in making the final decision to migrate an individual choice. The stereotype of the illiterate, poor and rural migrant reaching the borders of affluent countries has to be abandoned. The poorest people simply do not have the means to escape war and poverty and remain trapped in their country or in the neighbouring one.Once in the destination country, migrants have to undergo a difficult and often conflictive integration process in the hosting community. From the health standpoint, newly arrived migrants are mostly healthy (healthy migrant effect), but they may harbour latent infections that need appropriate screening policies. Cultural barriers may sometimes hamper the relation between the migrant patient and the health care provider. The acquisition of western lifestyles is leading to an increase of non-communicable chronic diseases that require attention.Destination countries have to reconsider the positive medium/long-term potential of migration and need to be prepared to receive migrants for the benefit of the migrants themselves and their native population.

At a former uranium mill site where tailings have been removed, prior work has determined several potential ongoing secondary uranium sources. These include locations with uranium sorbed to organic carbon, uranium in the unsaturated zone, and uranium associated with the presence of gypsum. To better understand uranium mobility controls at the site, four single-well push–pull tests (with a drift phase) were completed with the goal of deriving aquifer flow and contaminant transport parameters for inclusion in a future sitewide reactive transport model. This goes beyond the traditional use of a constant sorption distribution coefficient (Kd) and allows for the evaluation of alternative remedial injection fluids, which can produce variable Kd values. Dispersion was first removed from the resulting data to determine possible reactions before conducting reactive transport simulations. These initial analyses indicated the potential need to include cation exchange, uranium sorption, and gypsum dissolution. A reactive transport model using multiple layers to account for partially penetrating wells was completed using the PHT-USG reactive transport modeling code and calibrated using PEST. The model results quantify the hydraulic conductivity and dispersion parameters using the injected tracer concentrations. Uranium sorption, cation exchange, and gypsum dissolution parameters were quantified by comparing the simulated versus observed geochemistry. All simulations required some cation exchange and calcite equilibrium, and one simulation required gypsum dissolution to improve the model fit for calcium and sulfate. Uranium sorption parameters were not strongly influenced by the other parameter values but were highly influenced by uranium concentrations during the drift phase, with possible kinetic rate limitations. Thus, a future recommendation for such push–pull tests is to collect more geochemical data during the drift phase. The final uranium sorption parameters were within the range of values determined from prior column testing. The flow and transport parameters derived from these single-well push–pull tests will provide initial parameters for any future sitewide reactive transport model.