Subsoil Material Research Articles

Geotechnologie stosowane w konstrukcjach antropomorficznych: Wykorzystanie georadaru do wykrywania problemów strukturalnych, przyczyn i skutków - studium przypadku w Coimbrze w Portugalii

One of the recurrent problems in civil construction concerns the wear and deterioration of structures due to their use over time. There should be a plan for monitoring the structures to assess and quantify anomalies, which will allow the minimization and rehabilitation measures to be carried out in advance. This study aimed to use geotechnologies, specifically the Ground Probing Radar (GPR), to identify and quantify the damage caused using a swimming pool inserted in a structure built on a residential property. The methodology comprised the use of georradar Sensors & Software PulseEKKO GPR for data acquisition. The data were processed in the software EKKO Project considering the following parameters: 1- Grain/Filter: Dewow + SEC2 Gain (Attenuation:10.00 Start Gain:4.00 Maximum Gain: 950). Seven acquisition profiles were performed: 3 on the East side, 2 on the South side, and 2 on the West side of the pool, with a spacing between 0.8 m. From the visualization of the processed radargrams, and the slices elaborated for each profile with a color palette corresponding to the obtained reflectance values, it was possible to identify the underlying structures of the pavement of the edge of the pool such as beams, beam frames, slope, interior space of the support structure and, most importantly, the degree of subsoil materials alteration, depth, and dispersion of water infiltrations. On the East side, the pool is inserted into the rock formation; it is possible to identify up to 1 m depth of the water infiltration and dispersion. To the West and South, the pool is supported by a built-up structure; underneath there is a hall and the engine room. In these places, the infiltration and dispersion of water were identified until approximately 0.7 m depth, as well as the existing structures and their condition. The 0.7 m corresponds to the thickness of the existing slab and beams. Based on these results, an intervention plan was prepared for the rehabilitation of the deterioration of the materials and the minimization of water percolation through the waterproofing of the pool's surrounding areas.

Influence of Subsoil and Building Material Properties on Mine-Induced Soil–Structure Interaction Effect

Soil–structure interaction (SSI) refers to the dynamic interaction between a structure and the surrounding soil on which it rests. The behavior of the soil can significantly affect the response of the building structure. In the context of civil engineering and structural analysis, SSI becomes particularly important when considering the response of structures to dynamic loads such as earthquakes or so-called paraseismic loads, e.g., mining tremors. Several factors contribute to SSI. Soil and building structure material properties, foundation type, and loading conditions are the most important parameters. The article concerns SSI in the case of mining rock bursts in Poland. The influence of changes in site material conditions and building material properties on the SSI phenomenon was investigated. A few variants of different properties of typical construction materials (brick, reinforced concrete, and cellular concrete) in the case of selected representative building structure were considered. The subsoil material properties from the wide range were also taken into account. Numerical three-dimensional finite element method (FEM) analysis was applied. The adopted models of the soil-structure system were verified by data from in situ experimental vibration measurements. A significant influence of the subgrade material and the building structure material on the SSI was demonstrated.

Importance of the Geological-Geotechnical Investigation Program (GGI) in defining the type of foundation: Case study

This paper presents the importance of a geological-geotechnical survey in order to support the construction of a building in the Samambaia Administrative Region, Federal District, Brazil. The study was carried out in stages. Firstly, a geological-geotechnical study was carried out for the area where the project would be located, based on pre-existing analyses and studies. Next, the analyses carried out in the project area, together with the field investigations (SPT and rotary drilling), added to the topographic survey, helped to define the type of foundation and containment adopted, as well as a greater degree of accuracy of the subsoil material in the excavation area. For the area studied, there was considerable variability in the soils, with a predominance of sand, clayey sand and sandy clay. In addition, there was a considerable presence of rhythmites with quartzites and clayey, silty and sandy laminar intercalations. These surveys and studies were of the utmost importance when it came to choosing the right executive process and making the necessary adjustments during excavations.

Geophysical and geotechnical investigations of the site of a collapsed two-storey building in Modomo, Ile-Ife, Southwestern Nigeria

Geophysical and the geotechnical methods were used to study the site of a collapsed two-storey building in orderto determine the sequence and competence of the subsurface layers and determine the cause of the collapse of the building. The geophysical method employed the electrical resistivity method involving one dimensional (1D) Vertical Electrical Sounding (VES) and the two dimensional (2D) imaging techniques. Three VES stations were occupied using Schlumberger electrode configuration. 2D imaging data were acquired along four traverses using dipole-dipole electrode configuration. The geotechnical method involved Cone Penetration Test (CPT). CPT data was acquired at two points with the aid of 2.5 ton Dutch CPT machine. The results showed four subsurface layers based on the 1D VES results and 2D imaging results namely: topsoil, weathered layer, fractured basement rock and fresh basement rock. The topsoil resistivity varied from 116 Ωm to 191 Ωm and has thickness of about 1.5 m. It was classified as moderately competent. The second layer is weathered rock with resistivity varying between 92 Ωm and 327 Ωm and of about 8 m to 13 m thickness. This layer is also moderately competent. The third layer is fractured basement rock. It underlies the weathered rock and have resistivity varying from 391 Ωm to 405 Ωm. Its thickness varied from about 2 m to 20 m. This layer is competent. The fourth layer is the fresh basement rock having resistivity varying from 1365 Ωm to 12348 Ωm and is highly competent. The subsurface materials in the area are competent and can sustain the foundation of the building. Hence, the study concluded that the building collapse did not result from incompetent subsurface materials. Factors other than incompetent subsoil material that is human factors are believed to be responsible. This study has demonstrated the effectiveness of geophysical and geotechnical investigations in determining the competence of subsurface materials at engineering sites.

Assessment of Morphometric and Hypsometric Analysis of the Ruste Basin Using Remote Sensing and Geographical Information System Techniques

A basin’s characteristics and features need to be comprehended completely by conducting morphometric analysis, such as evaluating the basin’s size, form, and surface features, to estimate floods and erosion rates properly. The main objective of this investigation is to evaluate morphometric measures and hypsometric analysis of Erbil’s Ruste Basin employing remote sensing and geographical information system methods. To investigate the significant tributaries of the selected area, the hydrology tool within the Spatial Analysis Tools of ArcGIS, version 10.7, was utilized to define the basin boundaries, map the drainage networks, and obtain topographic data. The findings of the linear morphometric parameters revealed that the logarithmic relationship between stream orders and stream numbers was negative. The difference in stream order and number seen in the watershed is due to topography and bedrock influence. The results also showed a negative correlation between stream length and stream order, and a coefficient of determination of 0.972, which indicates that the basin is made of low-permeability formation and subsoil materials. Considering the areal morphometric parameters, the circularity ratio, elongation ratio, and form factor are 0.594, 0.853 and 0.572, respectively, suggested a semi-circular shape. A drainage density value of 2.259 km-1 showed that the Ruste Basin is a basin with steeply to very steeply sloping hilly terrain with varying plant covering. Furthermore, the Ruste Basin has high relief and slope with a relief ratio of 0.151 and basin relief of 2.576 km, both of which imply that it has a steep slope with high erosive force, limited infiltration, and a high runoff rate. Ruste Basin’s ruggedness number was 5.819, indicating that it has badlands topography. The average hypsometric integral was 0.467, denoting a mature basin featuring S-shaped hypsometric curves. In conclusion, the results showed that analysis of morphometric parameters and hypsometric integral and curve provides us with a notion to basin characterization and guidance to making appropriate decisions to establish effective actions to sustainable water and soil conservation and natural resources management through applying water harvesting methods, check dams, and bench terraces.

Is the use of a geotextile a necessary rehabilitation strategy to mitigate tailings contamination in soil cover materials? A 7-year field study

The potential pollution risk associated with poor management of mine tailings includes metal pollution of the surrounding environment from dusting and runoff. Thus, the establishment of a vegetation cover (rehabilitation) is viewed as an effective management strategy. Mine tailings can be inhibitory to plant growth due to their physico-chemical characteristics such as extreme pH, high salinity and potential high metal(loid) content, and the provision of a cover soil (≥ 30 cm) is usually recommended. This requires significant volumes of topsoil, which are often in limited supply at mine sites. An alternative may be the use of engineered soil (using organic and/or inorganic additives to improve physico-chemical properties) and placement of a barrier layer to prevent migration of tailings water or fines into the soil cover medium.Metal(loid)s content in soil cover treatments and vegetation uptake were evaluated after 7 years of rehabilitation in 1 m3 plots on a Pb/ Zn TSF. Final 30 cm covers included unamended tailings, subsoil material and subsoil amended with organic wastes (Spent Mushroom Compost (SMC) and Compost like output (CLO)). Treatments were divided into with/without geotextile inclusion. Soil samples were taken at 0–10 cm and 10–20 cm and analysed for pH, salinity (EC), and metal(loid)s/elements (As, Pb, Zn, Ca, Mg, Mn and, K) content. Vegetation was sampled after 1 yrs. growth (2015) and again after 7 years (2021) and analysed for their metal(loid)s/element content.Unamended tailings showed high metal(loid)s content at both depths, but concentrations were much lower in soil treatments. Herbage samples analysed in 2015 showed a higher concentration of metals than for 2021, highlighting the effectiveness and sustainability of amendments over a long period. Vegetation grown in unamended tailings showed the highest content of metal(loid)s, with significantly lower content in soil treatments. No significant difference was found for soil or vegetation metal(loid) content between geotextile inclusion/ exclusion. Results, highlight the relatively shallow soil covers without geotextile provide long term success with no evidence of metal(loid) contamination from underlying tailings.

Fast agricultural topsoil re-formation after complete topsoil loss – Evidence from a unique historical field experiment

Erosion of fertile topsoil means severe land degradation and yield loss. Here, we show that reformation of the fertile topsoil and crop yield increase is possible by good agricultural management within a few decades. Evidence relies on a unique long-term field experiment in NE Germany, where in 1964 the sandy soil (Luvisol) had been excavated to 52 cm and refilled with subsoil material of 52 cm thickness. Undisturbed trials served as controls, these were all combined with either no fertilisation, mineral fertilisation or a combined mineral and organic fertilisation. It took only 26 years until new topsoil had been formed. Its soil organic carbon (SOC) and total N stocks and the aggregate size distributions equalled that of the other treatments; SOC sequestration corresponded to 28 Mg SOC ha−1. The former topsoil buried below the plough layer lost 30–50 percent of its SOC during 5 decades in a non-linear manner. We conclude that our current agricultural tools can restore degraded arable land rather fast and contribute to climate change mitigation through a significant SOC sequestration as well.

Zoogenic soil horizons – termite ecosystem engineers in different agro-ecological regions of Mozambique

Termite nests represent a typical ecosystem engineered to produce a solid and long-lasting home where individuals are protected from predators, rainfall, and sunlight, while maintaining requisite temperatures and humidity. To achieve this, termites translocate and rework soil material as a unique pedogenic force, exposing it to soil genesis factors that may vary temporally. To date, limited information exists on zoogenic soil genesis from termites, with a few reports on the pedomorphological characterization of termite mounds and of the different genetic horizons developed therein. The aims of this work were to report the pedomorphological and physicochemical characterization of termite mounds in two selected sub-tropical agro-ecological zones of Mozambique and to define the genesis of zoogenic soil horizons that form termite mounds. Common soil features like channels and galleries are related to the ability of termites to create a suitable environment for the colony and are created through modification and reworking of soil and subsoil materials. Because of this, termites can be considered as the main pedogenic force, which fosters horizons different in pedomorphological and physicochemical features with respect to the surrounding soil. In view of this, new suffixes or diagnostic horizons may be useful in the characterization of soil horizons affected by bioturbation.

The Geotechnical Investigation of Subsoil Materials in a Typical Basement Terrain, Southwestern Nigeria- A Case study

Geotechnical investigation of the subsurface materials of a proposed Primary Health Center (PHC) in Modeke Oyo East Local Government Area (OELGA). of Oyo State has been conducted. The investigation is aimed to determine the suitability of the site for the proposed Bungalow building by assessing the subsoil strata that underlie the area. Three (3) points were tested to depth of 4.75m using a 2.5-ton DCPT equipment, while three (3) trial pits were dug to a depth of 1.5m with the aid of hand auger, and various lab analysis were conducted on selected samples from the trial pits. The result obtained from the DCPT indicates that subsurface is made up of stiff to very stiff sandy lateritic clay underlain by very stiff to hard sandy lateritic clay with hard pans layers. The allowable bearing pressure was observed to increase with depth to 4.75m further confirmed the subsurface lithologies. The Allowable Bearing Pressure (qa) in kN/m2) with a range of values 81 – 256 kN/m2, 54 – 155 kN/m2 and 162 – 338 kN/m2 for DCPT points 1, 2, and 3 respectively, indicate a Safe Bearing Pressure that can support load up to 45 kN/m with factor of safety of 2.5. Sieve analysis results revealed that the soil is well graded with dominant gravel which show a well-drained soil with good strength characteristics. Liquid limits ranged from 26.7% to 43.3%, plastic limits from 15% to 27% and plasticity index from 9.7% to 27.3%, thus indicating low to medium compressibility. The natural moisture contents values range between 4% and 15%, indicating lateritic clay of low to medium plasticity with low moisture content. Based on the above deductions, it can be concluded that, the factor of safety of 2.5 calculated from the allowable bearing pressure from the CPT, low to medium compressibility from Atterberg limits test and moisture content below 15% show that the investigated site is good and could safely support a bungalow building as proposed.

Reinforcement load in geosynthetic-reinforced pile-supported model embankments

The stress conditions of geosynthetic reinforcements (GRs) are crucial in achieving the accurate serviceability design of geosynthetic-reinforced pile-supported (GRPS) embankments. However, the sensitivity of load distribution to the settlement process has been reported in geosynthetic-reinforced embankment overlying cavities. In this study, a three-dimensional model embankment was used to perform experiments and evaluate the load acting on the GR. A flexible pressure-mapping sensor was introduced to investigate the pressure distribution for two types of supporting conditions: partitioned displacement by multiple movable trapdoors and even trapdoor settlement underneath different subsoil materials. The results showed that the load on the GR was concentrated on the strip areas between adjacent pile heads along with the settlement. The measured load on the GR strip area was related to the settlement process and finally exhibited a U-shaped distribution after detachment from the support underneath. The soil arch height in the subgrade continuously increased with the settlement; meanwhile, the pile head load increased rapidly at first and then decreased slightly or remained stable depending on the foundation support stiffness. For both types of settlement behaviours, soil arching exhibited stress history-related characteristics that influence the load transfer in GRPS embankments.

Forensic Geotechnical Investigation of Cracks in Buildings around Gubi and Environs, Bauchi, North-East Nigeria

The study aims to undertake a geo-forensic investigation of the major causes of cracks in buildings in Gubi and its environs. To achieve this, geophysical and geotechnical approaches were adopted to characterise the soil properties and subsurface rocks. Five (5) Vertical Electrical Soundings (VES) were purposively carried out using Schlumberger configuration to characterize the geoelectrical properties of the soil. In addition, 10 disturbed soil samples were collected for geotechnical laboratory analyses. The indices analyzed are natural moisture content, particle size distribution, Atterberg limits, free swell index, linear shrinkage, and specific gravity. Three geoelectrical layers comprising topsoil, weathered layer, and bedrock basement were delineated within the study area. The resistivity values (10.8 - 42.8 Ωm) suggest that the top and the weathered layers of VES 1and VES 2 are incompetent clay materials. The results of the geotechnical tests however, revealed that the site is underlain by poorly graded clay sand to sand clays (SC) with low to medium plasticity, specific gravity (2.2 - 2.7), liquid limit (25.8 % - 39.0 %), plastic limit (18.8 % - 35.1 %), natural moisture content (7.10 % - 25.0 %) and linear shrinkage limit (2.8 % - 11.3 %). The result generally shows that the soils in the northeastern parts have natural moisture content, linear shrinkage, and free swell value above the permissible limit for a foundation. It was concluded that differential settlement of the incompetent subsoil materials is responsible for the failure of the foundation materials and building walls.

Phosphorus Retention of a Permeable Reactive Barrier Surpassed by an Unvegetated Artificial Pond

An artificial pond bisected by a phosphorus (P) retentive permeable reactive barrier (PRB) alongside Forrest Highway, Coolup, Western Australia was designed to remove P from farmland runoff. The pond bed was made of subsoil and road construction materials likely to have a relatively high P sorption capacity, and there was no vegetation in the bed of the pond. Flow through the pond was intercepted by the PRB, constructed from a mixture of sand, coarse crushed limestone, and bauxite residue (with 10% phospho-gypsum). The effectiveness of P removal and the impact of the PRB was measured by comparing the concentration of contaminants immediately either side of the PRB with established standards, and against background levels in runoff from surrounding farmland. Using coarse limestone to increase flow through the PRB failed where permeability was insufficient to avoid overtopping of the PRB and the wall had to be lowered to allow by-pass and avoid collapse. The PRB was effective in removing total P (TP); however, the influent TP concentration was low (mean 0.19 mg L -1 ) because most P entering from farmland was retained in the shallow pond upstream of the PRB. Despite this, TP removal by the PRB was 53% (2009–2012). Occasionally, in spring when the pond was stagnant and anaerobic, P was released from the PRB. This minor P release coincided with a minor release of iron, consistent with anaerobic conditions found in the PRB. Although not designed to do so, the shallow pond upstream of the PRB reduced the TP concentration from farmland by 85% (mean 1.26 mg L -1 down to 0.19 mg L -1 ), mainly by reducing filterable reactive P concentration. Some elements (arsenic, cobalt, conductivity, fluoride, manganese, molybdenum, pH, selenium, uranium and vanadium) were increased by flow through the PRB, but were low relative to surrounding waters and environmental standards

Supervivencia y crecimiento de Celtis tala Gillies ex Planch en la rehabilitación ecológica de canteras de conchilla abandonadas

In the east of the province of Buenos Aires, the mining of calcareous subsoil materials causes the loss of cover of native forests dominated by Celtis tala, one of the main forest formations in the region. The objective of this study was to evaluate the tala plantation techniques in areas of abandoned quarries, to improve the ecological rehabilitation of such areas. Our hypothesis is that survival and growth are negatively affected by the low availability of fertile soil, the competition with herbaceous plants and high the direct solar radiation incidence. We carried out a field study to estimate survival, diameter at the stem base and height of tala plants as a response to weeding and shelter in a gradient of fertile soil availability. Survival increased with soil depth, and we observed a positive response of growth rate to weeding, which was greater at high fertile soil availability. Only a weak positive effect of shelter on growth was observed at higher fertile soil availability. The loss of forest cover caused by mining cannot be reversed with simple planting techniques. It is necessary to understand the ecophysiological processes that limit the establishment of tala and to plan the management of the remaining fertile soil. Other local tree species should also be assayed.

Effect of Land Reclamation on Soil Properties, Mineralogy and Trace-Element Distribution and Availability: The Example of Technosols Developed on the Tailing Disposal Site of an Abandoned Zn and Pb Mine

Land reclamation is a common practice leading to the restoration of areas affected by industrial activity. Soil studies in reclaimed areas are very useful to determine the effectiveness of reclamation works. The goal of the study was to investigate soil properties, mineral composition, total concentrations of Zn, Pb, Cd and As and chemical forms of these elements in order to assess the success of land reclamation of the abandoned mine tailing disposal site of the “Trzebionka” Zn-Pb mine in Trzebinia, southern Poland. The disposal site was reclaimed by covering tailings with a layer of inert material with a thickness up to 25 cm. The topsoil of the studied soil profiles was comprised of sandy loamy/loamy materials and the subsoil was comprised of sandy tailing materials. The soils were characterized by a neutral or slightly alkaline reaction due to the high content of carbonates. The dominant mineral in the subsoil was dolomite. The studied soils were considerably contaminated with Zn, Pb, Cd and As. A high load of mobile Zn, Pb and Cd was typical of the subsoil material. The reclamation layer does not provide sufficient isolation of toxic tailings from the environment and there is still a high risk of element uptake by plants.

Root-induced fungal growth triggers macroaggregation in forest subsoils

Subsoils are characterized by low concentrations of organic carbon (OC). Nevertheless, they contain more than half of the global soil OC because of their large volume. This discrepancy suggests that subsoils might further sequester carbon (C), thus acting as potential sinks for atmospheric C. Plant roots and associated rhizodeposits are a major OC input source to subsoils. However, whether and how increased OC inputs via plant roots to subsoils affect soil C sequestration mechanisms remains unclear. Here we set up a pot experiment with European Beech (Fagus sylvatica L.) seedlings to investigate the effect of tree roots and associated rhizosphere development on soil aggregation and C allocation in topsoil vs. subsoil material collected from three forest sites of different parent materials. Over a 5-month growth period, the seedlings developed a dense root system transforming the whole soil volume into root-affected (i.e., rhizosphere) soil. We found that roots and the associated rhizosphere development increased the amount of macroaggregates in the two finest-textured subsoils. The most C-poor and fine-textured subsoil had a 15% increase in bulk OC concentration, indicating a potential for C sequestration in subsoils by enhanced macroaggregation. Across subsoils, rooting strongly enhanced microbial abundance and was especially correlated with fungal abundance and a shift in the fungal-to-bacterial- ratio. The strong fungal growth was likely the cause for the enhanced macroaggregation in these subsoils. In topsoils, however, rooting treatment decreased macroaggregate abundance, potentially through the disruption of preexisting aggregates, as indicated by the concomitant increase in microaggregates. Our study supports the growing awareness that OC dynamics may be governed by different mechanisms in top- and subsoils, respectively. It demonstrates that the enhanced addition of OM via plant roots to subsoils boosts fungal growth and thereby increases macroaggregate formation, potentially facilitating C sequestration by occlusion.

Morphometric analysis of Yarehalli micro-watershed, of Davanagere district, Karnataka using remote sensing and GIS techniques

Yarehalli micro-watershed lies between 750 51' 37.58'' to 750 53' 29.93'' East longitudes and 130 58' 59.95'' to 140 1' 3.72'' in Davanagere district of Karnataka. The drainage networks of micro-watershed were delineated from the Survey of India topographical map of 1:50,000 scale. ArcGIS software was used for evaluation of linear, areal and relief as pects of the micro- watershed. The present study reveals that, drainage pattern of the study area is dendritic with trunk order 4th. The watershed area, perimeter, maximum length and width of the watershed was 977 ha, 10.00 km, 4.40 km and 2.20 km respectively. The mean value of bifurcation ratio is 3.23, the micro-watershed have been suffered less structural disturbance and drainage pattern has not been distorted. The value of drainage density is 2.31 km km-2 which indicated that, the region is having permeable subsoil material and good vegetative cover. The value of form factor indicates micro-watershed is approaching towards elongated shape of watershed. The present study reveales that, GIS based approach in evaluation of geo-morphological characteristics is more appropriate than conventional techniques. Over all study suggests that the micro-watershed should be treated with soil and water conservation measures.

Goethite-Bound Phosphorus in an Acidic Subsoil Is Not Available to Beech (Fagus sylvatica L.)

In forests, where supply of bioavailable P from easily weatherable primary minerals is small, plants are thought to recycle P efficiently by uptake of P released from decomposing forest floor material. Yet, a share of the P is leached into subsoil where it is strongly adsorbed onto reactive surfaces of pedogenic Fe and Al oxides. This raised the question whether P leached into subsoil is also recycled. In order to investigate the mobilization of P bound to hydrous Fe oxides, we conducted a mesocosm experiment in a greenhouse. Beech saplings were grown for 14 months in subsoil material (Bw horizon from the P-poor Luss forest) with added goethite-P adsorption complexes, either in inorganic (orthophosphate) or in organic (phytate) form. Four types of control mesocosms were run: soil only and soil mixed with either dissolved orthophosphate or dissolved phytate or goethite. At the end of the experiment, neither total P mass in trees nor P contents in leaves differed between the treatments. According to leaf nutrient contents, plant growth was strongly limited by P in all treatments. Yet, total P mass in trees did not increase over the course of the experiment. Thus, despite of its P demand, beech was not able to acquire P from goethite surfaces within two vegetation periods. Also P added in dissolved form to the soil as well as native soil P were not available. This suggests that once inorganic and organic P is bound to pedogenic metal oxides in mineral soil, it is not recycled, which can be an explanation for field data demonstrating quantitatively significant stocks of P in subsoil of P deficient forests.

Subsoil Characterization for Foundation Stability Using Geophysical and Geotechnical Methods

An Integrated geophysical and geotechnical subsoil characterization of parts of the new stadium complex, Akure, southwestern Nigeria had been carried out with a view to characterize the subsoil materials for stability of proposed engineering foundation. Five (5) magnetic and three (3) dipole-dipole profiling were carried out at station separation of 10 m along the traverses. Twenty one (21) Vertical Electrical Sounding (VES) measurements were made at selected locations along the traverses. A total of five (5) soil samples were collected from a dug pit at a depth of 1.0 m for laboratory analysis. The magnetic profiles delineated characteristic one to two negative peak amplitude anomalies that are typical of thin dipping dyke models (suspected to be fractures, shear zones, faults or geological contacts) along Traverses 1-5. The 2-D geomagnetic section delineated overburden thicknesses ranging from 5 – 15 m along the Traverses. The subsurface geologic units delineated by the geoelectric sections and the 2-D resistivity images consisting of the topsoil, weathered layer, partly weathered/fractured basement and fresh bedrock. Part of the topsoil and the weathered layer are characterized by low resistivity values suggestive of the presence of clay and or weak geomaterials at a depth range of 1 – 4 m within which civil engineering foundation are usually placed. These zones and the fractured/fault zones delineated by the magnetic methods constitute weak geomaterials that are considered to be inimical to civil engineering structures within the study area. Results of geotechnical analysis of soil samples adjudged plasticity indices of samples A, C and D to be of high index and were characterized by high plasticity/compressibility and consequently of low engineering competence. Samples B and E were classified as low-medium plasticity/compressibility, and are rated moderate–high engineering competence. However, it was observed that soil with higher liquid limits or plasticity index have lower electrical resistivity values and hence were adjudged low in engineering foundation competence. Based on the analysis of the results obtained from this study, the engineering foundation suitability of the soil were generally classified as good (B and E), fair (D) and poor (A and C). It can therefore be concluded that the subsoil in the investigated area are generally of low to high civil engineering competence. Keywords: Geophysical; Geotechnical; Subsoil; Competence; Characterization; Foundation, Stability. DOI: 10.7176/JEES/10-6-08 Publication date: June 30 th 2020

Surface and subsurface material selections influence the early outcomes of boreal upland forest restoration

Soil is an essential component supporting the growth and maintenance of forests, providing anchorage, water, and nutrients for a diversity of plants. In Canada's boreal forest, surface soils differ widely in their chemical and physical conditions, ranging from coarse to fine textured mineral soils in the uplands to organic soils in the lowlands. Industrial disturbances in the boreal region require the selective salvage of surface and sub-soils from low- and upland areas during open pit mine operations, which can be used to reconstruct different soil profiles by arranging the materials in variable layers and thicknesses. The type of materials and their configuration in the reconstructed soil profile can have a profound effect on early forest establishment in reclaimed areas. We compared the growth of trembling aspen (Populus tremuloides Michx.), jack pine (Pinus banksiana Lamb.), and white spruce (Picea glauca Moench.) on sites that had different reconstructed soils caps using varying surface soil materials (salvaged lowland peat and upland forest floor material (FFM)), placement depths (10 or 30 cm for peat, 10 or 20 cm for FFM), and subsoil material types determined by salvage depth (Bm, BC, and C). Early seedling establishment and growth and soil and climatic parameters were monitored over a five-year period. Generally, seedling growth was greatest on FFM and appeared to be related to phosphorous availability, while peat as a surface soil reduced growth, likely due to delayed soil warming in the spring and cooler soil conditions that potentially limited resource availability. However, the greater water holding capacity of the organic matter in peat also provided a benefit for seedling growth that was apparent during water limiting climatic conditions. The underlying subsoil material also influenced growth, particularly later in establishment when roots occupied the deeper subsoils. Aspen growth was greatest when the subsoil was shallow salvaged and represented a weathered subsoil (Bm) compared to the more deeply salvaged, less weathered subsoils BC and C. Aspen and pine seedlings, with their larger roots systems, may have benefited from small increases in the silt fraction of the subsoils, likely due to the greater water holding capacity of these otherwise coarse textured sandy soils. Spruce regeneration responded marginally to soil treatments because of its overall slow growth-strategy and tolerance to resource limitations. Our results indicate that different soil capping strategies affect the performance of forest regeneration during post-mining site reconstruction, and boreal forest species may vary in responses according to their ecological life strategies.

Using a nutrient profile index to assess reclamation strategies in the Athabasca oil sands region of northern Alberta

Land reclamation in the Athabasca oil sands region requires construction of entire soil profiles from materials salvaged during mining. Although much attention has been paid to the limited supply of suitable topsoil materials and their impact on ecosystem recovery, suitable clean subsoil materials are also in limited supply, and their efficient and effective use is an important consideration for land managers in the region. Using data from an oil sands reclamation site in northern Alberta, Canada, we compared soil and foliar nutrients to a wildfire-impacted reference ecosystem with a similarity index. Specifically, we evaluated the similarity of forest floor-mineral mix (FFM) and peat-mineral mix (PM) as topsoil, as well as the effect of different depths of salvaged B and C horizon subsoil with PM on top. All reclamation treatments were planted with jack pine (Pinus banksiana Lamb.) and trembling aspen (Populus tremuloides Michx.), which were used to examine foliar nutrient concentrations. Individual macronutrient concentrations were different among treatments in total soil nutrients, but differences decreased in soil bioavailable nutrients and disappeared altogether in foliar nutrients. The similarity index revealed that distinct differences existed between treatments, with FFM being the most similar to the wildfire site. It also revealed a potential deficiency in foliar and soil bioavailable Mn on PM, and that increased water content of deeper subsoils had little to no effect. With use of this nutrient profile similarity index, reclamation practitioners may be able to determine if different soil prescriptions lead to higher levels of similarity to natural ecosystems more quickly.