Low Walls Research Articles

Laterally-loaded pile-MSE wall system performance under different design configurations

The need for constructing a shallow or deep foundation (e.g. piles) in a mechanically stabilized earth (MSE) wall for superstructure support has increased. However, the performance of laterally loaded piles within the MSE wall and their interaction with soil and reinforcement are not fully understood. Limited full-scale tests and numerical studies have been conducted to evaluate the behavior of laterally-loaded piles within MSE walls. In this study, thirteen reduced-scale model tests were performed to investigate the effects of changing the wall configuration (wall height, and reinforcement spacing and length) and the pile location on the performance of the pile-MSE wall system under static lateral loads. This experimental study found that the piles in high walls could develop larger maximum compressive and tensile strains. Low walls resulted in larger wall facing deflections and maximum tensile strains in the geogrid reinforcement. Small reinforcement spacing and long reinforcement length resulted in higher pile lateral load capacities, smaller wall facing deflections, and smaller reinforcement tensile strains. The pile offset from the back of the wall facing is a critical factor that affected the pile capacity, the wall facing deflection, the reinforcement tensile strain, and the lateral earth pressure distribution behind the wall facing.

Using Alkali-Activated Dredge Sludge Ash-Bentonite for Low Permeability Cutoff Walls: The Engineering Properties and Micromechanism

Using Alkali-Activated Dredge Sludge Ash-Bentonite for Low Permeability Cutoff Walls: The Engineering Properties and Micromechanism

A Numerical Approach for Natural Convection With Curved Obstacles in an Enclosure Using Lattice Boltzmann Method

Abstract The impact of placing curved obstacles on natural convection in enclosures with differentially heated side walls is analyzed in the current study using the lattice Boltzmann method (LBM). A method to choose characteristic velocity based on Knudsen number is implemented which eradicates the need of arbitrarily guessing characteristic velocities to proceed with simulations. In addition, a less computationally intensive probability distribution function for equilibrium temperature is used. For validation, a standard natural convection problem with left wall at high temperature, right wall at low temperature, and top and bottom adiabatic walls is considered. A grid independence test is conducted and the code is validated with existing results for various Rayleigh numbers, which shows a good agreement. The problem is then modified by including circular and elliptical obstacles of adiabatic, hot, and cold nature. A boundary interpolation technique is used to implement the velocity and temperature boundary conditions at the inner boundaries. The streamline patterns and temperature contours show interesting observations such as dependence of location of vortices on the type of obstacle boundary used, and formation of low or high temperature zones around obstacle at high Rayleigh numbers. Results show that the change in the shape of the obstacle contributes to the Nusselt number variations at the high temperature boundary and low Rayleigh numbers.

Forming Hard Anodic Films on Aluminum by Anodization in Oxalic Acid and Alcohol

Porous anodic films have attracted wide attention because of their potential applications in various industrial fields. Reducing their porosity is expected to improve the hardness. This study focused on evaluating the effect of the electrolyte composition on the hardness of anodic alumina films formed on aluminum by anodization under mild conditions. In particular, the effect of adding alcohol (i.e., ethanol and ethylene glycol) to an oxalic acid–based electrolyte was considered. The voltage–time curve, coating ratio (i.e., film formation efficiency), morphology, and Martens hardness of the resulting anodic alumina films were clearly affected by the type and amount of added alcohol. Adding alcohol effectively suppressed the chemical dissolution of the anodic film during anodization without needing to lower the electrolyte temperature, which formed high-strength films with low porosity and thick pore walls. The Martens hardness of the formed films increased by 18% with the addition of 50 vol% ethanol and increased by 25% with the addition of 50 vol% ethylene glycol.

Benches, fountains and trees: Using mixed-methods with questionnaire and smartphone data to design urban green spaces

Smartphones can help researchers track how people use green spaces and understand how design features impact their behaviors. However, when using this data to evaluate green space designs, researchers should be aware of human perceptions of the features within these environments. We contribute a mixed method approach that allows for comparison between how people report using green space features intended to support wellbeing, with how often they are used in common daily routines. As an illustration of this approach, we present the results of a case study conducted on a university campus that compares how outdoor design features are used by students with how these features are reported as being used. Specifically, we compare perceptions of 362 students about which campus design features create a sense of wellbeing, and which are near locations they report using, with the use of these features recorded by the smartphones of a separate group of 62 students. We found that there were large differences between locations students reported using, and locations tracked students used regularly. Features that were used more often during daily routines (low walls, food retail outlets), did not match features reported as helping create a sense of wellbeing in the questionnaire (benches, trees, and sunshine). Of all the design features we modeled, only water features were positively associated with use in the tracking data and supportive of wellbeing in the questionnaire data. Our findings point to the importance of using tracking data together with response data from questionnaires in mixed-method studies if designers want to locate features that the public consider as supportive to their wellbeing, in locations that will be regularly used.

Perception of French wine buyers regarding environmental issues in wine production

ABSTRACT Increased consumer concern for the environment has motivated winegrowers to adopt more environmentally friendly practices in their vineyards, such as agroecological measures. Thanks to a 2016 French ministerial decree, these measures can now be included in the specifications of wine appellations. However, little is known about consumer perceptions on this topic. The main objective of this research was thus to analyze consumers’ perceptions of environmental issues in wine production, specifically with respect to a selection of agroecological measures in the vineyard. A national survey with 1022 respondents was conducted online in July 2019, and the factors that influenced perceptions were identified using an analysis of variance. The environmental issue of highest concern for consumers was the use of pesticides. However, the majority of the measures selected were perceived as having a positive impact on the environment. Practices aimed at improving biodiversity – such as the preservation of low walls and nest boxes, the establishment of trees, or sodding between parcels – were highly valued by consumers. This research demonstrates that, in order for winemakers to reap the maximum benefit from the implementation of environmentally friendly practices, effective communication of such practices to consumers is crucial.

Structural characteristics of load bearing straw bale walls

Straw bales offer a renewable and affordable construction material suitable for a range of uses as both thermal insulation in walls and roofs, and for low rise loadbearing structural walls. As a co-product of food production, it places no further pressure on land use, and in common with other crop-based materials, straw captures and stores carbon dioxide through photosynthesis, offering the means to construct buildings with a net negative carbon emissions footprint. Straw also further reduces operational carbon emissions by virtue of its excellent thermal resistance. However, despite these benefits, and a successful construction history extending over 100 years in many countries worldwide, straw bale construction has still to make a major commercial impact in the wider construction market. Limited technical understanding of some fundamental performance characteristics (including structural capacity, hygrothermal behaviour, and durability), absence of technical standards, and a lack of certification and product warranty for straw bale, still remain barriers to wider acceptance. In this paper results are presented from a study on full-scale straw bale walls to evaluate the structural performance under vertical loading and lateral loading. The performance of identical straw bale walls, with and without plaster coats, is presented. The study is also unique in presenting on out-of-plane lateral loading and wall performance under eccentric vertical load cases. The research will support structural designers and enable wider uptake of this sustainable form of construction.

Use of a Modal Model in Predicting Propagation from a Point Source Over Grooved Ground

Summary Regularly spaced low walls and rectangular lattices on a hard ground have been investigated as a means for reducing noise levels from surface transport. Predictions of the insertion loss of such surfaces has involved the use of computationally intensive numerical methods such as the Boundary Element Method (BEM) or Finite difference techniques (FDTD and PSTD). By considering point-to-point propagation above regularly spaced acoustically hard grooves with rectangular cross sections, a modal model used hitherto to predict electromagnetic and ultrasonic surface waves is adapted to derive an effective impedance for such a grooved surface. When this effective impedance is used in the classical theory for propagation from a point source above an impedance plane, the modal model enables predictions of excess attenuation spectra that compare closely with those obtained by numerical methods but take a fraction of the time. Also the modal method is extended to predict excess attenuation spectra above phase gradient metasurfaces with porous material in each constituent groove.

КУРГАНЫ СРОСТКИНСКОЙ КУЛЬТУРЫ ЛЕСОСТЕПНОГО АЛТАЯ С ДЕРЕВЯННОЙ РАМОЙ

The article considers a series of seven burial grounds in nine mounds of which around the graves of people, structures of four low walls were installed. They were constructed from single logs, beams or planks forming a square, rectangle or trapezoid. These sites were found on the territory of the Priobsky plateau and the Biysko-Chumysh elevation. The article provides information about the size of the mounds and frames, the location of the frames relative to the graves, the dating and cultural affiliation of the sites in which they were found. Taking into account these data, two types of wooden structures are distinguished: frames-fences and frames-overlap. The fences were used by the Samoyed part of the population of the Srostki culture in the second half of the 9th - first half of the 11th centuries to mark out the sacred site around the central, most significant burial in the mound. Frames with overlaps were a kind of tombstone structure. They were used in the area of the Srostki culture in the second half of the 10th -12th centuries and appeared as a result of contacts with the population of the Middle Irtysh region and Baraba. Keywords: early and advanced Middle Ages, Srostki culture, barrow, burial, frame, fence, overlap

ייעוד ושלבי התפתחות של קירות טרסות-ואדי ושדה בעמק נחל זנוח בשפלת יהודה

This study presents a new methodological approach by which to identify the function, relative age, and field relations between buried walls at two sites in the valley of Nahal (wadi) Zanoah along the morphological contact between the Judean Highland Hills and Foothills. Sedimentology and relative pulsed-photon stimulated luminescence (PPSL)-based chronology of fine-grained sediments beneath, within, above, and abutting the studied walls, reveal the sedimentation phases of the valley and the role of these walls. A wadi-terrace wall was revealed bordering alluvium of a buried and ancient course of Nahal Zanoah, reflecting a more energetic flow regime than that of today. On the palaeosurface of the infilled sediment behind the wadi-terrace wall and up-valley are low field walls, probably marking agricultural boundaries. The upvalley field wall upon colluvium is found to be slightly more mature than the field wall positioned in the wadi-terraceAn overlaying ~0.75 m of sediment originating from the slopes and soils of the drainage basin forms the current valley floor, which appears to have undergone significant deposition due to premodern and modern mechanical activities.

Flexural behavior of low strength masonry wallettes strengthened with welded wire mesh

Due to their low cost and ease of manufacture low strength hollow concrete blocks are extensively used in masonry constructions in rural and semi-urban areas. These unreinforced masonry (URM) walls are typically weak in flexural capacity when subjected to out-of-plane loading caused by heavy wind pressure or earthquakes. Strengthening these URM walls with fiber-reinforced polymer (FRP) composites and textile reinforced matrix (TRM) has shown increased in flexural capacity and ductility though it is of high cost. Hence this study evaluates the feasibility of using cheap materials a welded wire mesh (WWM) as an alternative external strengthening material for improving the out-of-plane behavior of low strength hollow URM walls. A total of six wallettes were constructed using three different mortar mixes i.e strong mortar (1:3), moderately weak mortar (1:4.5) and weak mortar (1:6). Out of these six wallettes, three wallettes were reinforced with WWM and then finish plastered with 1:4 mortar mix. All wallettess were subjected to four point bending test. Results indicated that URM wallettes are not influenced by the mortar strength. Reinforced masonry wallettes however shown remarkable increased in flexural loads and corresponding energy dissipation and displacement ductility.

Irradiance, photosynthesis and elevated pCO2 effects on net calcification in tropical reef macroalgae

Calcifying tropical macroalgae produce sediment, build three-dimensional habitats, and provide substrate for invertebrate larvae on reefs. Thus, lower calcification rates under declining pH and increasing ocean pCO2, or ocean acidification, is a concern. In the present study, calcification rates were examined experimentally under predicted end-of-the-century seawater pCO2 (1116 μatm) and pH (7.67) compared to ambient controls (pCO2 409 μatm; pH 8.04). Nine reef macroalgae with diverse calcification locations, calcium carbonate structure, photophysiology, and site-specific irradiance were examined under light and dark conditions. Species included five from a high light patch reef on the Florida Keys Reef Tract (FKRT) and four species from low light reef walls on Little Cayman Island (LCI). Experiments on FKRT and LCI species were conducted at 500 and 50 μmol photons m−2 s−1 in situ irradiance, respectively. Calcification rates independent of photosystem-II (PSII) were also investigated for FKRT species. The most consistent negative effect of elevated pCO2 on calcification rates in the tropical macroalgae examined occurred in the dark. Most species (89%) had net calcification rates of zero or net dissolution in the dark at low pH. Species from the FKRT that sustained positive net calcification rates in the light at low pH also maintained ~30% of their net calcification rates without PSII at ambient pH. However, calcification rates in the light independent of PSII were not sustained at low pH. Regardless of these low pH effects, most FKRT species daily net calcification rates, integrating light/dark rates over a 24h period, were not significantly different between low and ambient pH. This was due to a 10-fold lower dark, compared to light, calcification rate, and a strong correspondence between calcification and photosynthetic rates. Interestingly, low-light species sustained calcification rates on par with high-light species without high rates of photosynthesis. Low-light species' morphology and physiology that promote high calcification rates at ambient pH, may increase their vulnerability to low pH. Our data indicate that the negative effect of elevated pCO2 and low pH on tropical macroalgae at the organismal level is their impact on dark net calcification, probably enhanced dissolution. However, elevated pCO2 and low pH effects on macroalgae daily calcification rates are greatest in species with lower net calcification rates in the light. Thus, macroalgae able to maintain high calcification rates in the light (high and low irradiance) at low pH, and/or sustain strong biotic control with high [H+] in the bulk seawater, are expected to dominate under global change.

Tailoring twist extrusion process; the better strain behavior at the lower required loads

This study dealt with discovering the optimal conditions of the twist extrusion parameters for producing materials possess enhanced strain behavior with the least amount of extrusion load. It was found that the twist angle has a dominant influence on the strain behavior of the deformed sample with the contribution percentage of 56%, while the effect of friction coefficient would be the most noticeable if the required extrusion load is considered. Based on above, pure copper with the square cross-section was subjected to the process with the large twist angle at the best lubricant state. The results showed that the strength and hardness of the deformed copper were considerably enhanced compared to the initial condition due to the substantial grain refinement. The uniform plastic deformation zone of the deformed sample is limited which causes the reduction of strain-hardening exponent and ductility. Moreover, the lateral region of the sample’s cross-section endures larger plastic strain compared to the central one, leading to owning higher hardness. A combined microstructure consisting of low angle dislocation walls and high angle grain boundaries was also determined for the deformed copper.

Effect of Debonding of Rebars on the Seismic Response of Boundary Elements of Lightly Reinforced Shear Walls

Rebar fracture in boundary elements of lightly reinforced shear walls in recent earthquakes motivated research on the minimum longitudinal reinforcement of shear walls. These researches lead to change in the ACI 318-19 requirement for minimum longitudinal reinforcement of boundary elements. New ACI 318 requirement increases minimum longitudinal reinforcement ratio for boundary elements of shear walls with low demand, that could have economic burden. This study experimentally investigates is it possible to avoid this increase in minimum rebar by debonding rebars in critical region of boundary elements in lightly reinforced shear walls. Tests includes specimens with bonded and debonded rebars, which are tested under monotonic and cyclic loading. Load protocol to account for failure types of low reinforcement shear walls is asymmetric. Test results show that out of plane buckling of specimens with debonded rebars initiates at lower axial strains that could be attributed to reduction in element lateral stiffness due to use of debonding. On the other hand debonding resulted in reduction of local strain demand on rebar. It could be concluded that larger minimum dimension for boundary elements will be required when debonding is employed.

Response assessment and prediction of low yield point steel plate shear walls with curved corrugated web plates and reduced beam sections

In recent years, researchers have been moving increasingly towards new lateral force-resisting systems such as corrugated, low yield point (LYP) steel plate shear walls (SPSWs) fabricated with reduced beam sections. Recent application of curved corrugated web-plates with improved structural performances combined to the merit of LYP steel with superior elongation capacity has motivated the researchers to consider the employment of such elements in unstiffened SPSWs with the aim of developing a high-performing system. Currently, no design code addresses the seismic performance of LYP corrugated steel plate shear walls (CSPSWs). More investigations are required to develop a fundamental understanding of the performance of these seismic systems employing LYP steel material and corrugated infill plates. The present paper investigates the seismic performance of unstiffened, corrugated, and LYP steel walls under monotonic and cyclic loadings. A series of LYP steel plate walls were designed based on the capacity design approach proposed in AISC 341 code. The effectiveness of web plate thickness, corrugation angle, number of corrugations, and the aspect ratio of the plate are evaluated in this study. The results of this research demonstrate how employment of LYP steel material as well as curved corrugated plates is beneficial in improving the strength, hysteresis performance, and stiffness of the system. Increasing the number of corrugation half-waves can adversely affect structural behavior. The behavior of LYP steel plate shear walls with curved corrugated web plates is predicted and examined using a modified plate-frame interaction (M-PFI) method. Analytical predictions are compared with experimental and numerical results.

Analysis of the Wall Geometry with Different Strategies for High Deposition Wire Arc Additive Manufacturing of Mild Steel

Additive manufacturing has gained relevance in recent decades as an alternative to the manufacture of metal parts. Among the additive technologies, those that are classified as Directed Energy Deposition (DED) are characterized by their high deposition rate, noticeably, Wire Arc Additive Manufacturing (WAAM). However, having the inability to produce parts with acceptable final surface quality and high geometric precision is to be considered an important disadvantage in this process. In this paper, different torch trajectory strategies (oscillatory motion and overlap) in the fabrication of low carbon steel walls will be compared using Gas Metal Arc Welding (GMAW)-based WAAM technology. The comparison is done with a study of the mechanical and microstructural characteristics of the produced walls and finally, addressing the productivity obtained utilizing each strategy. The oscillation strategy shows better results, regarding the utilization rate of deposited material and the flatness of the upper surface, this being advantageous for subsequent machining steps.

Postantique Soils as a Source of Land Use Information: A Case Study of an Ancient Greek Agricultural Area on the Northern Black Sea Coast

As an effect of intensive agricultural development of the steppes of the northern Black Sea coast, the finds of postantique agricultural landscapes that preserve relic elements of ancient land-use infrastructure are extremely rare. To these belongs the uniquely preserved ancient Greek land division system on the Tarkhankut Peninsula (north-western Crimea), which was studied using the methods of soil science and biomorphic analysis. This paper explores ancient land-use practices in order to reconstruct the original parameters of the land division system, as well as agricultural techniques employed. For postantique agricultural landscapes, an integrated geoarchaeological approach that includes GIS and remote sensing methodologies, in-field study of microrelief and soil registrograms, pedochronological dating technique, and physicochemical, geochemical, and biomorphic soil analyses has been developed and tested. The soil-geomorphological reconstruction shows that the Hellenistic land division system included a 4.5–4.9 m wide strip of land bordered by a 4.1–4.7 m wide (at the base) and c. 0.2 m high wall and a c. 2 m wide and over 15 cm deep trench, which controlled surface runoff and erosion. Ancient agricultural practices of slope farming resembled the modern ones. Surface runoff and soil erosion were controlled by dividing the catchment area into narrow plots, the borders of which on arable land were marked by simple earthen structures (low walls with shallow trenches). The biomorphic analysis of soil sampled atop these structures indicates that in ancient times, these earthen walls were not cultivated. The study of conservative properties preserved in pedomemory of postagrogenic soils provided valuable evidence of agricultural techniques used in the palaeogeographic conditions of the 4th and 3rd centuries BC.

Assessment of the stability, sorption, and exchangeability of marine dissolved and colloidal metals

The size partitioning of dissolved trace metals is an important factor for determining reactivity and bioavailability of metals in marine environments. This, alongside the advent of more routine shipboard ultrafiltration procedures, has led to increased attention in determining the colloidal phase of metals such as Fe in seawater. While clean and efficient filtration, prompt acidification, and proper storage have long been tenets of trace metal biogeochemistry, few studies aim to quantify the kinetics of colloidal exchange and metal adsorption to bottle walls during storage and acidification. This study evaluates the effect of storage conditions on colloidal size partitioning, the kinetics of colloid exchange over time, and the timescale of bottle wall adsorption and desorption for dissolved Fe, Cu, Ni, Zn, Cd, Pb, Mn and Co. We report that preservation of dissolved size partitioning is possible only for Fe and only under frozen conditions. All metals except Mn and Cd show regeneration of the colloidal phase following its removal in as short as 14 h, validating the importance of prompt ultrafiltration. Adsorption of metals to bottle walls is a well-known sampling artifact often cited for Fe and assumed to be potentially significant for other metals as well. However, only Fe and Co showed significant proclivity to adsorption onto low density polyethylene bottle walls, sorbing a maximum of 91 and 72% over 40 months, respectively. After 20 weeks of acidification neither Fe nor Co desorbed to their original concentrations, leading to an acidified storage recommendation of 30 weeks prior to analyses following storage of unacidified samples for long periods of time. This study provides empirical recommendations for colloidal and dissolved trace metal methodology while also paving the way for much-needed future methods testing.

How did that get there? Understanding sediment transport and accumulation rates in agricultural landscapes using the ESTTraP agent-based model

The 15th–18th century CE site of Engaruka in Tanzania is often described as primarily comprising drystone agricultural terraces, but it is now known that many of these former farming plots are not terraces per se, but are instead sediment traps. Stratigraphic excavations of these traps show that they were built by constructing low drystone walls adjacent to either natural or artificial water courses in order to capture fine alluvial sediments entrained within water flows. In the northern area of the site sediments were accumulated to a depth of up to 700 mm, while in one area in the south of the site over 2 m of deposits were accumulated over at least a 300 year period. The presence of sediment traps on archaeological sites allows investigations of the efficacy and sustainability of these structures over decadal to centennial timescales, since stratigraphic excavations can define the process of construction, and geoarchaeological analyses can explore changes within accumulated sediments over time. Although a combination of stratigraphy and absolute dating can discern the broad sequence and timing of sediment capture they cannot determine sediment-accumulation rates, and these techniques are too time consuming to be used to map the development of over 9 km2 of sediment traps. The ESTTraP agent-based model provides these data by simulating sediment accumulation under different hydrological conditions. Four scenarios were simulated for a period of 100 years: constant water availability (SIM-01), seasonal variability (SIM-02), long-term climate variability (SIM- 03), and vegetation-cover impact (SIM-04). The model results suggest that the fields can be constructed over a short period of time, approximately 1–3 months per 6 × 6 m field, and that to construct a block of 90 fields covering 3,000 m2 it would take between 8 and 13 years in periods of high water availability, and up to 27 years during prolonged dry periods. The results define the amount of time needed to construct individual fields, and suggest that farmers constructed blocks of fields concurrently rather than sequentially expanding across the landscape, and that the c. 10 km2 area of sediment traps at Engaruka could have been constructed by a number of households working independently. The ESTTraP model presents an important resource in the assessment of sediment dynamics and patterns of field development, is relevant to a range of archaeological sites worldwide that include intentional or unintentional alluvial deposition, and has applications for modern landscape management.

The earliest settlement remains at the Ubaid‐related site of Bahra 1 (Kuwait)

The settlement at Bahra 1 lies in the As‐Sabbiya dessert, Kuwait. The site was preliminarily dated to the Ubaid 2/3 period, with four settlement phases distinguished so far. Phases A–C yielded remains of sturdy stone architecture, while the oldest Phase D was represented by a fire‐pit horizon, as well as thin and low walls, perhaps serving as foundations for light and perishable superstructures. Even in the earliest phase, Mesopotamian influence is visible, evidenced by the structures’ orthogonal plan and the high percentage of Ubaid ware. Although the remains of the earliest phase were preserved very fragmentarily and over a limited area, they shed more light on the character of the earliest settlement activity in the region.