Clayey Gravel Research Articles

Research on the control of high-fill roadbed with tunnel slag in karst sections

In this study, based on the Kaihua section of the G205 (China) national highway reconstruction project, the construction area of the K4+550–K4+940 section was chosen to conduct settlement control research on the high-fill roadbed of the karst section within the construction area. The viability of using clayey gravel and tunnel slag as roadbed fill was evaluated through laboratory soil tests. The construction technology of grouting was used to manage the substructure of the karst section. After installing prestress anchors on the top of the foundation, a ‘layered’ filling scheme was utilised to fill the tunnel slag and clayey gravel. The Flac3D simulation software was used to contrast the deformation curves of key nodes on unanchored and anchored roadbeds. The test results indicate that the California bearing ratio satisfies the requirements of the specification and that the uniaxial compression strength of the tunnel slag satisfies the requirements of the specification when the clayey gravel is near the optimal moisture content and dry density and when the compaction is controlled within 94%. The use of prestress anchors can strengthen the rock and soil layers of the foundation and reduce the plastic zone distribution. This paper provides a corresponding engineering experience for the treatment of high-fill roadbeds in karst areas.

A Large-Sized Permeameter for Studying Suffusion Characteristics of Anisotropic Soils

Abstract Seepage-induced suffusion involves the migration of fine particles within a soil matrix. Seepage flow is affected by the soil permeability anisotropy of anisotropic soil fabric; however, suffusion anisotropy is unclear because of the limited function of existing permeameters. In recent studies, the effect of seepage direction has been investigated under only low hydraulic gradients because the control of seepage direction relies merely on gravity. In this study, a new, large-sized permeameter is developed with which suffusion tests can be conducted along horizontal or vertical seepage directions under high hydraulic gradients. Correspondingly, the permeameter can accommodate a specimen of 540 × 500 × 470 or 540 × 540 × 440 mm3 (length × width × height). The seepage direction is switched by changing the boundary conditions of the specimen with detachable perforated plates that allow pressurized water originating from different inlets to flow along horizontal or vertical directions. Two repeated pairs of tests were performed on a gap-graded clayey gravel to investigate the suffusion anisotropy of saturated clayey gravel. The results show that the maximum relative deviations of measurements for initial hydraulic conductivity, initiation, and failure hydraulic gradients are less than 3.5 %, demonstrating satisfactory reliability. The ratio of the initial horizontal hydraulic conductivity to vertical hydraulic conductivity for the test soil is 13.87, indicating a significantly anisotropic fabric induced by compaction. The ratios of horizontal initiation and failure hydraulic gradients to vertical initiation and failure hydraulic gradients are 0.52 and 0.59, respectively. This implies that suffusion anisotropy should not be neglected for evaluating the internal instability of anisotropic soils.

Field Investigation of Water Infiltration into a Three-Layer Capillary Barrier Landfill Cover System Using Local Soils and Construction Waste

In response to the rapid urban expansion and the burgeoning number of landfill sites, managing water infiltration in these areas has become a critical challenge, especially in cities like Shenzhen, Hong Kong, and Singapore where traditional cover materials such as silt, clayey gravel, and sand are scarce. A three-layer (silt/gravelly sand/clay) capillary barrier cover system has been proposed to address this issue in humid climates. As an alternative to scarce traditional materials, using local soils and construction waste (CW) for this system presents a viable solution. However, the real-world performance of this adapted three-layer system, constructed with local soils and CW under natural rainfall conditions, remains to be fully evaluated. This paper presents a field test evaluating the water infiltration behavior of a three-layer capillary barrier landfill cover system under natural conditions. The tri-layered system is comprised of a 0.6 m loose local unscreened soil layer, covered by a 0.4 m CW layer and topped by a 0.8 m heavily compacted local screened soil layer. Monitoring findings reveal that, during the wet season, infiltration through the top two layers was staved off until the third rainfall, after which these layers retained moisture until 15 September 2016. The fluctuation in pore water pressure in the topmost layers showed each rainfall was contingent not only on the day’s precipitation but also the hydraulic state. Beyond the hydraulic state’s influence, a deeper tensiometer showed resulted in a diminished correlation between the surge in pore water pressure and daily rainfall. This declining correlation with depth can be attributed to the capillary effect and the reduced permeability of the screened soil layer. Rainfall patterns significantly affect percolation, with the combination of a short-duration, intense rainfall and prolonged weak rainfall resulting in a marked increase in percolation. In the foundational screened soil layer, the pore water pressure remained relatively low, with the cumulative percolation over six months (June to December) registering approximately 10 mm. These findings suggest a promising performance of the three-layer capillary barrier cover system, integrating local soils and CW, in the year of the study conducted in a humid environment.

Geotechnical Suitability of Soils in Road Construction for Sustainable Development in Tropical Africa: Case of Lateritic Graveled Soils of Bandjoun (West, Cameroon)

The environmental impact of the exploitation of geomaterials and their relatively high cost, coupled with the increasingly low financial capital in developing countries, are pushing road actors to turn to inexpensive local ecological materials. The present study is conducted on lateritic graveled soils of Bandjoun (LGSB) in the West Cameroon Region. The aim is to determine whether lateritic gravel soils, particularly those in Bandjoun, can be an ecological and economical alternative to rock aggregates in road construction, considering their geotechnical parameters and environmental impact. These soils were described in the field and were also subjected to complete geotechnical identification in the laboratory. The LGSB presents Californian bearing ratio indices ranging from 26% to 83.3%, a plasticity index of 10.11%, a fines content of 12.05%, an average methylene blue value of 4.25, a water content at the Proctor optimum of 27.6% and a dry density of 1.75 g/cm3. They are silty or clayey gravels and sands of subgroup A-2-7 according to the Highway Research Board classification; sandy and gravelly soils with fines of class B according to the classification of the Road Construction Guide; and silty gravels according to the classification of the Central Laboratory of Bridges and Highways. These soils can be used naturally in pavement layers, in particular in subgrade for all traffic classes and in subbase for low traffic. The tonnage of these soils has been estimated at 18,389 t. The global warming index shows that the use of these soils (18,389 t) in road construction can reduce 31,629–62,706 kg of carbon emissions. The use of lateritic soils in road construction is a very interesting alternative to reduce the environmental impacts associated with the manufacture of rock aggregates. So, lateritic soils should be used instead of rock aggregates for cleaner, more environmentally friendly road construction. The present work presented a specific evaluation of the geotechnical properties and ecological impact of lateritic graveled soils for road construction, as well as their potential for ecological and economic utilization.

Engineering properties of tropical transported soils: case study from the Republic of the Congo

Tropical residual soils are often reported to exhibit highly variable geotechnical characteristics due to their formation by rock weathering under hot, humid conditions. Less is known about the engineering properties of tropical reworked (i.e. transported) soils. The latter soil type is also encountered in tropical regions but can exhibit sorting and include weak structures formed during transport and deposition, causing instability when exposed in road/rail cuttings. We report a case study of geochemical and engineering properties of tropical reworked soils from the slopes of Mt Lekoumou (Republic of the Congo), a banded iron formation ridgeline overlain by loose, unconsolidated clayey gravel. Aside from the uppermost slopes, the area is overlain by colluvium of varying thickness, the target of testing here. Goethite, kaolinite and hematite are dominant minerals, and the colluvium displays moderately high liquid limits but comparatively low plasticity index values. Effective cohesion ( c ′) values were 0 and 31 kPa, and effective friction angles ( ϕ ′) were 26°–39°. Considerable variation in matric suction pressures for the same sample sites, at the same moisture contents, occurs. Thus, as with tropical residual soils, determining test values that are ‘representative’ of site conditions in tropical transported soils can be problematic but remains important.

Evaluation of the stability of terraced slopes in clayey gravel soil using a novel numerical technique

Evaluation of the stability of terraced slopes in clayey gravel soil using a novel numerical technique

The Construction of a Gravity Retaining Wall to Prevent Landslides on the Grogol Kediri Highway

One proof of Kediri's progress is the construction of Doho Kediri International Airport which is expected to improve the economy and tourism in this city. The airport was built with the aim of improving connectivity and suppressing development disparities in southern East Java. The purpose of this study is to plan the construction of an earthquake-resistant which is gravity retaining wall on the Grogol Kediri Highway, Kediri Regency. . Planning is carried out at STA 3.8-4.0. , soil laboratory testing on samples obtained from the studied location. Identification of the soil type, sliding angle, and weight of the soil volume at the site are needed to determine the planning of earthquake-resistant retaining walls. From the soil properties obtained, it can be determined that the land is included in the GC (Clayey Gravel) category With a shear angle of 28° and a weight of 1.463 gr/cm3. These results were used to calculate the dimensions and the stability of the retaining wall using the Coulomb method. The retaining wall should have a peak body width of 1 meter, foundation width of 3.8 meters, foundation thickness of 1 meter, foundation depth of 1.04 meters, foot and heel width of 0.9 meters, height of 6 meters, and bottom body thickness of 2 meters. Based on stability calculations, the retaining wall is safe against overturning, shifting, and subsidence. Therefore, this retaining wall is a viable solution to prevent landslides and mitigate the negative impacts caused by them.

Effect of FTC on the interface between soil materials and asphalt concrete using a direct shear test

The process of freezing and thawing has a great effect on different aspects of materials in cold regions. Due to the complex behavior of materials under the impact of freezing and thawing, several studies conducted on the individual behavior of soil materials or asphalt concrete on this condition. In the present study, the impact of freezing and thawing on the strength characteristics and interaction ratio of soil materials from classes GC (clayey gravel) and GP (poorly graded gravel) at the interface between asphalt and soil materials was assessed. The particle size distribution of the aggregate used in this study was within the grading range recommended by the International Commission on Large Dams (ICOLD) and Fuller's ideal grading curve used in the construction of Mijran Dam, Mazandaran Province, Iran. First, granular materials and asphalt concrete were subjected to weight loss test and durability study, respectively, according to AASHTO-T103 and Iranian Standard 12728. Then, utilizing a large-scale direct shear machine, the contact surface element (interface between granular materials and asphalt concrete) was evaluated under dry and saturated conditions as well as under various freeze-thaw cycling (FTC). The results demonstrate that an increase in the number of FTC let to a decrease in the maximum shear stress under dry and saturated circumstances for both clayey gravels and poorly graded gravels materials at interference with asphalt concrete. In GC materials at the contact surface with asphalt concrete, the interaction ratio reduces by 0.22 % under dry conditions and by 0.54–1.2 % under saturated conditions, relative to its value in the tenth cycle, as the number of FTC increases. In GP materials at the interface with asphalt concrete, as the number of FTC increases, the interaction ratio drops between 9.2 % and 33.61 % in dry conditions and by 20.62 % in saturated situations compared to the value that occurred in 10 cycles.

Variability of Lime-based Lateritic Soil enhanced with Bitumen with varying proportions.

This research investigated the bituminous additive prerequisite of some lateritic soil samples as pavement materials. Both chemical and geotechnical experiment were carried out on untreated (raw) and improved laterite. Bituminous material was utilized in the present research as admixture. The California bearing ratio (CBR), Atterberg limit (Liquid and plastic limit), specific gravity, moisture content, and compaction experiments of the samples were performed with varying percentages or proportions of bitumen; 3, 6, 9 and 12%. The soil categorization test reveals that the lateritic soil is between A-2-7 and A-2-4 which is Silty or clayed clayey gravel and sand based on AASHTO soil categorization. The C.B.R values are 9.87, 4.35% and 7.28% for samples A, B and C correspondently at 0% additive content, while for 12% additives, the result showed maximum C.B.R values for sample A and Bas 41.21% andSample C as 40.04%. Thus, bitumen has been verified to be a good admixture on the enhancement of the properties of lateritic soil as pavement materials.

Effect of Particle Combination Ratio of Soil Rock Mixture on Shear Strength

With the increase of fine-grained soil content, the properties continue to transform to fine-grained soil, which will affect the permeability and strength of the soil. Even if the content of silt and clay in fine-grained soil is not high, it will significantly impact soil properties. When the content of coarse particles is low, the nature of soil depends on the fine particles in the soil. When the content of coarse particles gradually increases, and the coarse particles are overhead, the nature of soil only depends on the coarse-grained soil, and the influence of fine particles on the nature of soil gradually weakens. To reveal the interaction mechanism between coarse and fine particles in high moisture content clayey gravel, this project conducts a systematic experimental study on the high moisture content clayey gravel, takes 0.5mm as the particle size limit, takes the separation of coarse and fine particles in the soil sample as the control test, and systematically tests the shear strength of the separated fine particles; systematic shear strength tests were also carried out on the separated coarse particles. In addition, shear strength tests were carried out on soil samples with different fine particle content.

Comparison between Sediment Material and Natural Subgrade Material for Road Construction

This paper presents the comparison between sediment and natural subgrade material for road construction to check its stability to improve soil properties. Two samples were investigated which are sediment and subgrade construction material which were taken from Wilayat A’seeb, Oman. Sediment was collected from Alkhoud dam, Muscat, and subgrade construction material was collected from Al Mubilah construction site, Muscat. Elemental analyses and mechanical tests were conducted to achieve the purpose of the study. According to the AASHTO classification, the result of the sediment samples shows that it was silty and clayey gravel A-2-4 and clayey sands or sandy clay mixtures according to USCS classification. Also, investigations on the subgrade construction material show that it was silty and clayey gravel and sand A-2-7 according to AASHTO classification and well-graded sands, gravelly sands according to USCS. The result of grain size distribution curves shows that subgrade soil is applicable to be used but sediment is not applicable as pavement construction and. The maximum dry density (MDD) and optimum moisture content (OMC) of the sediment sample are 1.422 g/cm3 and 20.3% respectively. Also, the maximum dry density (MDD) and optimum moisture content (OMC) of the subgrade construction material are 1.634 g/cm3 and 15.5 % respectively. As compared between the two materials, it found that the result of maximum CBR value of subgrade material was 16.13% and the maximum CBR value of sediment material was 16.07% and that means both materials are very close in strength and sediment has the power to be used in road construction with some improvement. According to the experimental results, it shows that the investigated sediment and natural subgrade soil are suitable to be used in the subgrade layer because it is corresponding to the range of Omani standards but it is not suitable to be used as subbase and base layers. Other standards might be compatible with the results to be effective use in subbase and base layers.

Geotechnical soil mapping from electrical and mechanical properties: Case study of the Bafoussam urban area, west Cameroon

Preliminary work in civil engineering works often involves the investigation of soil support in order to secure or predict project safety. The objective of this work is to purpose an urban geotechnical soil map combining physical and mechanical behaviour of the soil and its electrical properties. Field work with auger corer allowed collection of samples for analysis. The results of the Atterberg limits and particle size analysis enabled classification of those soils according to HRB as silty or clayey gravels and sands (class A-2-7) and clayey soils (A-7-5). The Casagrande Plasticity Diagram classifies them as At and Lt (very plastic clays and silts) and the GTR classifies them as sandy and gravelly soils with fines (B6) and fine clay soils (A2 and A3). These classifications show that the study area is mainly covered by sandy-clay, lateritic clay and lateritic gravelly soils. The iso-resistivity maps and resistivity sections made from the results of vertical electrical soundings, allow the identification of three ranges of resistivity: a low resistivity less than 300 Ώ.m, a medium resistivity range between 300 and 500 Ώ.m and a high resistivity greater than 500 Ώ.m. These ranges of resistivity correspond to the different formation disparities that make up the subsurface. Associated penetrograms show these soils are very resistive in the cuirass subsurface zones with very compact formations with permissible stress values between 2.5 and 5.2 bars. At greater depths, these values are moderate in the clayey sands with stresses between 0.8 and 3 bars and low in the clays and lateritic soils (˂1 bar). The application of determination coefficient (R2) and Spearman correlation (rs) between permissible stress and true resistivity gives values of 0.79 and 0.74 respectively. There is a good qualitative and quantitative correlation between these two parameters in the study area. The superimposition and comparison of the different results with the geological formations enables development of a geotechnical soil map. This map enables us to understand the lithological and mechanical heterogeneity of the soils during the construction of structures in the urban perimeter of Bafoussam.

On Random Subspace Optimization-Based Hybrid Computing Models Predicting the California Bearing Ratio of Soils.

The California Bearing Ratio (CBR) is an important index for evaluating the bearing capacity of pavement subgrade materials. In this research, random subspace optimization-based hybrid computing models were trained and developed for the prediction of the CBR of soil. Three models were developed, namely reduced error pruning trees (REPTs), random subsurface-based REPT (RSS-REPT), and RSS-based extra tree (RSS-ET). An experimental database was compiled from a total of 214 soil samples, which were classified according to AASHTO M 145, and included 26 samples of A-2-6 (clayey gravel and sand soil), 3 samples of A-4 (silty soil), 89 samples of A-6 (clayey soil), and 96 samples of A-7-6 (clayey soil). All CBR tests were performed in soaked conditions. The input parameters of the models included the particle size distribution, gravel content (G), coarse sand content (CS), fine sand content (FS), silt clay content (SC), organic content (O), liquid limit (LL), plastic limit (PL), plasticity index (PI), optimum moisture content (OMC), and maximum dry density (MDD). The accuracy of the developed models was assessed using numerous performance indexes, such as the coefficient of determination, relative error, MAE, and RMSE. The results show that the highest prediction accuracy was obtained using the RSS-based extra tree optimization technique.

A levee breach induced by internal erosion in Western Australia

This case study presents a levee breach induced by piping erosion under cyclonic conditions in 2019. The levee is a 2.5 m-high, 500 m-long, mass earth-fill embankment; with no cutoff trench, core or ancillary structures. Located near Port Hedland on the north coast of Western Australia, its purpose is diversionary: to redirect cyclonic surface water away from the nearby Great Northern Highway. The levee was founded directly on alluvium in 1987; it is formed of locally sourced clayey sandy gravel. In 2003, the levee was partially excavated to enable the placement of a buried pipeline through the levee. Following a cyclonic event in 2019, a 27 m length of the levee breached, resulting in significant scour of the foundation and downstream soil. A site visit and investigation were conducted shortly thereafter, where in situ testing and laboratory soil tests on the levee and foundation materials were conducted. Analysis of the site observations and laboratory testing data led to the probable failure mechanism being theorized as having been initiated within the foundation by piping erosion within sand-rich beds of alluvium. The large quantity of water ponding upstream of the levee then caused a progressive washout and breach of the levee. Thematic collection: This article is part of the Role of water in destabilizing slopes collection available at: https://www.lyellcollection.org/cc/Role-of-water-in-destabilizing-slopes

Engineering Geophysical Investigation of Road Failure in a Basement Complex Terrain, Southwestern Nigeria

Geoelectrical and geotechnical investigations were conducted to determine factors responsible for pavement failure in some segments of Adebayo Alao-Akala road in Ibadan, southwestern Nigeria. The geoelectrical investigation employed Schlumberger vertical electrical sounding conducted at fifteen stations occupied along two failed segments and one stable segment of the road, using station spacing of 25 m and maximum electrode spread of 100 m. 2D electrical resistivity survey was also conducted using the dipole-dipole electrode array with electrode spacing, a, of 1 m and expansion factor, n varied from 1 to 5 m. The VES data were interpreted quantitatively by partial curve matching and computer iteration technique and geoelectric sections were generated while 2D resistivity structures of the subsurface were produced from the inverted 2D resistivity data. The geotechnical investigation involved Grain size distribution, Atterberg limits, Compaction and California Bearing Ratio tests conducted on subsoils collected beneath the segment. The failed segments are underlain by low-resistivity clayey subgrade of resistivity mostly less than 100Ωm while the stable segment overlies sandy clay/clayey sand mixture of relatively higher resistivity, ranging from 200Ωm to 530Ωm. The subsoils of the failed segments comprise high-plasticity sandy clay and sandy gravelly clay while those of the stable segment are medium plasticity sandy clayey gravel. The values of maximum dry density are 1.46 Mg/m3-1.73 Mg/m3, 1.71 Mg/m3-1.86 Mg/m3 and 1.75 Mg/m3-1.82 Mg/m3 respectively, with corresponding optimum moisture content of 7%-8%, 11%-20% and 10%-17% and California bearing ratio under soaked condition for 48 hours of 7%-8%, 17%-20% and 11%-17% respectively. The failure of the road pavement is attributable to the clayey nature of the subgrade, and poor drainage. The stable segment is underlain by excellent-to-good subgrade materials. Ingress of surface water into the clayey subgrade occasioned by poor drainage of run-off resulted in deformation of the road pavement in response to vehicular load.

A new approach for stabilization of lateritic soil with Portland cement and sand: strength and durability

The presence of lateritic soils occurs in tropical and subtropical regions. The improvement of lateritic soils that are not suitable for a particular purpose through techniques that combine modification of grain size through the insertion of sand, incorporation of Portland cement and densification through compaction is seen as an alternative. In this context, a dosage method to use a local lateritic soil as construction material in a most rational way reducing the economic and environmental impacts related to this activity is still missing. Therefore, the current research aims to evaluate the performance of a lateritic soil via modification of grain size through the insertion of sand, incorporation of Portland cement and densification through compaction. For this, unconfined compression, and durability (wetting and drying) tests were carried out on specimens of compacted clayey gravel lateritic soil, whose granulometry was modified by the insertion of distinct amounts (from zero to 45%) of weathered sand, treated with distinct Portland cement contents (from 4 to 10%), molded at different dry unit weights (from 16.8 to 20.1 kN/m3) and cured for 7 and 28 days. Results of the mechanical tests have shown the significant influence exerted by cement content and dry unit weight of the blend, followed by curing time and finally sand insertion. Satisfactory correlations between the response variables (qu and ALM) and the adjusted porosity/cement index (η/Cv) were obtained. Furthermore, an innovative approach to replacing the laborious durability test is proposed.

Research on Intelligent Compaction Technology of Subgrade Based on Regression Analysis

A remote monitoring system with the intelligent compaction index CMV as the core is designed and developed to address the shortcomings of traditional subgrade compaction quality evaluation methods. Based on the actual project, the correlation between the CMV and conventional compaction indexes of compaction degree K and dynamic resilient modulus E is investigated by applying the one‐dimensional linear regression equation for three types of subgrade fillers, clayey gravel, pulverized gravel, and soil‐rock mixed fill, and the scheme of fitting CMV to the mean value of conventional indexes is adopted, which is compared with the scheme of fitting CMV to the single point of conventional indexes in the existing specification. The test results show that the correlation between the CMV and conventional indexes of clayey gravel and pulverized gravel is much stronger than that of soil‐rock mixed subgrades, and the correlation coefficient can be significantly improved by fitting CMV to the mean of conventional indexes compared with single‐point fitting, which can be considered as a new method for intelligent rolling correlation verification.

ENGINEERING PROPERTIES OF LATERITIC SOIL IN OTUN AREA, EKITI STATE, NIGERIA

Lateritic soils at Otun Ekiti, Ekiti state, southwestern Nigeria were investigated with respect to their geotechnical properties and their suitability for subgrade and sub – base construction materials. Four disturbed lateritic soil samples (sample A, B, C and D) were selected for the various laboratory techniques. The grain size analyses, the specific gravity tests, the atterberg limit tests, compaction, California bearing ratio and shear box tests were carried out on the samples. The grain size analysis shows that sample A is gravelly silt-clayey sand. Sample B is silt – clayey gravel composition. Sample C is gravelly silt-clayey while Sample D is silt-clayey gravel. Atterberg consistency limit test indicate that sample A has 30.0%, liquid limit 19.5% plastic limit, 10.5% plasticity index, 9.1% shrinkage limit. Sample B has liquid limit of 27.0%, 16.2% plastic limit, 10.8% plasticity index and 7.4% shrinkage limit. Sample C has a liquid limit of 32.4%, plastic limit of 15.6%. It has a plastic index of 16.8%, Shrinkage limit of 9.7% while Sample D has a liquid limit of 36.2%, plastic limit of 17.7%. It has a plastic index of 18.5% and 11.1% as shrinkage limit. Thus, the soil is classified to be intermediate plasticity which can be used for sub – grade and sub – base materials. The soil samples are above the activity (A) line in the zone of intermediate plasticity (CL) which suggests that they are inorganic soils. Based on engineering use chart, the workability as construction engineering is good to fair particularly as erosion resistance in canal construction. However, the high shrinkage limit may also reduce erosion in this area because of cohesion of the plastic clay material. The California Bearing Ratio (CBR) values are within 2 – 3% (mean = 2.75%) and 2 - 4% (mean = 2.75%) in sample A and sample B respectively while California Bearing Ratio (CBR) of 2 - 4% (mean = 2.75%) and 2 – 3% (mean = 2.75%) in sample C and sample D respectively. This implies that the materials can be used as a sub-grade to base course material for support of flexible pavements. The compaction tests for the optimum water content for sample A is 15.0% and 13.0% for standard and modified proctor respectively. The standard and modified proctor for sample B is 15.0% and 14.0% respectively. The compaction tests for the optimum water content for sample C and D is 15.0% and 14.0% for standard and modified proctor respectively. The compaction tests for Sample A indicate a higher fine fraction and thus a higher optimum moisture content while sample B, C and D has higher coarse fraction with lower optimum moisture content. The cohesion falls within 70-90Kpa (mean = 79Kpa) and the angle of internal friction ranges from 260 - 320 with mean of 280 for standard and modified compaction energies respectively. The results obtained from geotechnical analysis suggest that the soil is good to fair as erosion resistance in canal construction because of its high bearing capacity and it can also be used as sub – grade and base course in road construction. Keywords: Lateritic soil, Construction, Erosional and Geotechnical.

Geotechnical characterization of plastic waste materials in pavement subgrade applications

Scarcity of traditional construction materials has motivated researchers to explore alternatives, and besides crushed glass, reclaimed asphalt pavement, and scrap tires, to name a few, plastic waste (unwanted or unusable plastic objects) has also gained attention in recent years. Plastic waste is traditionally re-used or recycled, but it often ends up as trash on curbsides, in landfills, or in our seas and oceans. The substantial amount of plastic waste produced annually worldwide, and its environmental repercussions are the rationale for exploring alternatives in order to recycle plastic waste into construction materials. This exploration can also benefit many industries and would help minimising adverse environmental impacts associated with dumping tones of plastic waste in landfills. Using plastic waste material with soil for soil reinforcement purposes has revealed some improvements in terms of strengths of materials, but nevertheless, this potentiality has not been fully assessed for different types and forms of plastic waste with natural subgrade soil in the road industry. In this paper, ground, flaky, and pelleted shapes of four sorted types of plastic waste from a recycling market were combined with silty or clayey gravel and sand soil of the A-2-7 AASHTO type. These plastic types are: low density polyethylene (LDPE), high density polyethylene (HDPE), polyethylene terephthalate (PETE), and polypropylene (PP) resins. Their various geotechnical properties have been assessed thoroughly. The investigation process entails assessing compaction, Californian Bearing Ratio (CBR), strength, resilient modulus, and permeability properties for both natural sub-grade soil and modified sub-grade soil with the aforementioned types of plastic waste. The results obtained show that the addition of plastic wastes decrease the maximum dry densities of the subgrade soils because of the lower relative density of the plastic material compared to the soil particles. It is also found that the addition of plastic wastes can increase or decrease the CBR and MR values of the subgrade. The nature of change (increase or decrease) and its magnitude are a function of the plastic content, shape and type. Permeability values of many subgrade soil samples increased with the addition of plastic waste, whereas the hydraulic conductivity of some soils modified with plastic remained unchanged. Subgrade soils with plastic had higher friction angle and lower compressive strength than plastic-free soils. The results of this research suggest that partial replacement of subgrade soil material with plastic waste may prove useful in road subgrade applications.

Geotechnical Properties and Stabilization of Well-graded Sand with Clay and Gravel Soils Contaminated with Gasoline

In the search for alternatives to bioremediation of soils, this research aimed to analyze the effects of lime, cement, and asphalt as stabilizers on clayey gravel and sand soil contaminated with gasoline in the laboratory. Concentrations of 10–20% of lime, cement, and asphalt were added to the soil. A standard sample was chosen to compare the results obtained in the modified Proctor compaction, California bearing ratio (CBR), direct shear, and consolidation tests. It was found that the presence of more than 10% liquid low–density hydrocarbon affects plasticity, void ratio, friction angle, moisture content, dry density, and cohesion. According to the tests carried out, soils contaminated with concentrations lower than 10% of gasoline are recommended to construct the subgrade and sub-base layers in pavements. Finally, it was found that cement is the stabilizer that presented overall higher enhancements of the mechanical properties of the clayey gravel and sand soil among the three stabilizers. However, the results also show that depending on the soil use and specific parameter requirements, other stabilizers can be used.