The Effect of Mineral Composition and Quantity of Fines on the Atterberg Limits and Compaction Characteristics of Soils

Because of the various elements that come into play in natural soil formation, the impact of varied proportions of mineral composition and fines amount on Atterberg limits and compaction characteristics of soils is not well known. Three distinct soil samples were used in this investigation. The findings indicated the effect of varied mineral composition proportions and fines amount on the liquid limit, plastic limit, and plasticity index as assessed by the Casagrande test and hand-rolling method. The fluctuation of maximum dry density and optimal moisture content with these three soils has also been studied. Furthermore, correlations were established to indicate the compaction parameters and the amount of minerals and particles in the soil. The data show that the mineral content of the soil has a direct impact on the Atterberg limits and compaction characteristics. Soils containing larger percentages of expansive minerals, such as montmorillonite, have more flexibility and volume change capability. Mineral composition influences compaction parameters such as maximum dry density, ideal water content, axial strain, and axial stress. Soils with a larger proportion of fines, such as Soil 2 and Soil 3, have stronger flexibility and lower compaction qualities, with higher ideal water content and lower maximum dry density. Soil 1 has moderate flexibility and intermediate compaction qualities due to its low fines percentage. The effect of different mineral compositions and fines on the Atterberg limits and compaction characteristics of soils can be used to predict the behavior of compacted soils encountered in engineering practices, reducing the time and effort required to assess soil suitability for engineering use.

Soil Atterberg Limits and Consistency Indices as Influenced by Land Use and Slope Position in Western Iran

Atterberg limits and consistency indices are used for classifications of cohesive(fine-grained) soils in relation with compaction and tillage practices. They also provide information for interpreting several soil mechanical and physical properties such as shear strength, compressibility, shrinkage and swelling potentials. Although, several studies have been conducted regarding the land use effects on various soil mechanical properties, little is known about the effects of land use and slope positions on Atterberg limits and consistency indices. This study was conducted to investigate the effects of land use and slope position on selected soil physical and chemical properties, Atterberg limits and consistency indices in hilly region of western Iran. Three land uses including dryland farming, irrigated farming and pasture and four slope positions(i.e., shoulder, backslope, footslope, and toeslope) were used for soil samplings. One hundred eleven soil samples were collected from the surface soil(0-10 cm). Selected physical and chemical properties, liquid limit(LL), plastic limit(PL) and shrinkage limit(SL) were measured using the standard methods; and consistency indices including plastic index(PI), friability index(FI), shrinkage index(SI) and soil activity(A=PI/clay) were calculated. The results showed that irrigated farming significantly increased organic matter content(OM) and OM/clay ratio, and decreased bulk density(ρb) and relative bulk density(ρb-rel) as a result of higher biomass production and plant residues added to the soil compared to other land uses. Except for sand content, OM, ρb, cation exchange capacity(CEC) and calcium carbonate equivalent(CCE), slope position significantly affected soil physical and chemical properties. The highest values of silt, OM/clay and CEC/clay were found in the toeslope position, predominantly induced by soil redistribution within the landscape. The use of complexed(COC)- noncomplexed organic carbon(NCOC) concept indicated that majority of the studied soils were located below the saturation line and the OM in the soils was mainly in the COC form. The LL, PI, FI and A showed significant differences among the land uses; the highest values belonged to the irrigated farming due to high biomass production and plant residues returned to the soils. Furthermore, slope position significantly affected the Atterberg limits and consistency indices except for SL. The highest values of LL, PI, SI and A were observed in the toeslope position probably because of higher OM and CEC/clay due to greater amount of expandable phyllosilicate clays. Overall, soils on the toeslope under irrigated farming with high LL and SI and low values of FI need careful tillage management to avoid soil compaction.

The geomechanical properties of soils treated with nanosilica particles

This study examines the effect of nanosilica(NS)additive to improve the mechanical properties of clay,clayey sand,and sand.The engineering properties of the soils were investigated through Atterberg limits,compaction,unconfined compression,ultrasonic pulse velocity(UPV),freeze-thaw,and direct shear tests.The NS content varied from 0%to 0.7%and cement content was 5%and 10%by the dry weight of the soil.The curing period varied from 7 d to 150 d.The consistency,compaction,and strength properties of the soils were affected by the presence of NS and cement.The optimum NS contents in clay specimens with 5%and 10%cement were 0.5%and 0.7%,respectively.It was 0.7%in sand specimens with both cement ratios,as well as 0.3%and 0.7%in clayey sand specimens with 5%and 10%cement,respectively.In terms of freeze-thaw resistance,clayey sand specimens containing 0.5%NS and 10%cement had the minimum strength loss.Exponential relationships existed between the ultrasonic pulse velocity(UPV)and the unconfined compressive strength(UCS)of soil specimens having the same curing period.The shear strength parameters of the soils also improved with the addition of NS.Scanning electron microscope(SEM)images demonstrated that cement and NS contributed to the improvement of the soils by producing a denser and more uniform structure.It was concluded that the minor addition of NS could potentially improve the geomechanical properties of the soils.

Application of 2-D and 3-D Geo-electrical Resistivity Tomography and Geotechnical Soil Evaluation for Engineering Site Investigation:A Case Study of Okerenkoko Primary School,Warri-Southwest,Delta State,Nigeria

In the design of building structures,joint efforts must be decided to resolve the depth of competent layers across the intended site to safeguard the durability of civil engineering structures and to avert the disastrous consequences of structural failure and collapse.In this study,an integrated methodology that employed DC resistivity tomography involving 2-D and 3-D techniques and geotechnical-soil analysis was used to evaluate subsoil conditions for engineering site investigation at Okerenkoko primary school,in the Warri-southwest area of Delta State,to adduce the phenomena responsible for the visible cracks/structural failure observed in the buildings.The results obtained brought to light the geological structure beneath the subsurface,which consists of four geoelectric layers identified as topsoil,dry/lithified upper sandy layer,wet sand(water-saturated)and peat/clay/sandy clayey soil(highly water-saturated).The deeply-seated peat/clay materials(ρ≤20Ωm)were delineated in the study area to the depths of 17.1 m and 19.8 m from 2-D and 3-D tomography respectively.3-D images presented as horizontal depth slices revealed the dominance of very low resistivity materials i.e.peat/clay/sandy clay within the fourth,fifth and sixth layers at depths ranging from 8.68-12.5 m,12.5-16.9 m and 16.9-21.9 m respectively.The dominance of mechanically unstable peat/clay/sandy clay layers beneath the subsurface,which are highly mobile in response to volumetric changes,is responsible for the noticeable cracks/failure detected on structures within the study site.These observations were validated by a geotechnical test of soil samples in the study area.Atterberg’s limits of the samples revealed plasticity indices of zero.Thus,the soil samples within the depth analyzed were representatives of sandy soil that does not possess any plasticity.The methods justifiably provided relevant information on the subsurface geology beneath the study site and should be appropriated as major tools for engineering site assessment/geotechnical projects.

Municipal sludge as landfill barrier material

The aim of this research is to find substitute barrier materials for natural clay from two kinds of municipal sludge: waterworks sludge(S_w) and dredging sludge(S_d). Laboratory tests were performed firstly to determine their Atterberg limits and hydraulic conductivity. Based on the results, the use of waterworks sludge was recommended. Then, shear strength tests were performed and it was found the shear resistance property of waterworks sludge is strong enough to maintain slope stability. In order to evaluate the possibility of secondary pollution, the heavy metal contents of waterworks sludge was determined and the results indicated that secondary pollution is unlikely happened. Finally, economic analysis proves that reusing waterworks sludge as barrier will reduce the lost a great for both landfill and waterworks. Based on the results, waterworks sludge was proposed to use and a further long-term simulated landfill test was suggested.

Fall cone tests considering water content, cone penetration index, and plasticity angle of fine-grained soils

This paper analyzed the consistency of some parameters of soils in the literature and experimental results from fall cone test and its application to soil plasticity classification.Over 500 data from both literatures and experiments using fall cone and Casagrande methods were compiled to assess the relationships among specified water content,cone penetration index ebT,and plasticity angle eaT of finegrained soils.The results indicate that no unique correlation exists among b,liquid limit of the fall cone test(LLc)and a.The water content at 1 mm cone penetration eC0T correlates well with b,plasticity ratio eRpT(i.e.the ratio of plastic limit to liquid limit),and a.Finally,the potential of using the btan a diagram to classify soil plasticity was also discussed.

How does organic matter affect the physical and mechanical properties of forest soil?

Determining the physical and mechanical properties of soil and its behavior for engineering projects is essential for road construction operations. One of the most important principles in forest road construction, which is usually neglected, is to avoid mixing organic matter with road materials during excavation and embankment construction. The current study aimed to assess the influence of organic matter on the physical properties and mechanical behaviors of forest soil and to analyze the relation between the amount of organic matter and the behavior of forest soil as road material. A typical soil sample from the study area was collected beside a newly constructed roadbed. The soil was mixed with different percentages of organic matter（control treatment, 5, 10, and 15% by mass） and different tests including Atterberg limits, standard compaction, and California bearing ratio（CBR） tests were conducted on these different soil mixtures. The results showed that soil plasticity increased linearly with increasing organic matter.Increasing the organic matter from 0%（control） to 15%resulted in an increase of 11.64% of the plastic limit and 15.22% of the liquid limit after drying at 110 ℃. Also,increasing the organic matter content reduced the soil maximum dry density and increased the optimum moisture content. Increasing the organic matter from 0 to 15% resulted in an increase of 11.0% of the optimum moisture content and a decrease of 0.29 g/cm;of the maximum dry density. Organic matter decreased the CBR, which is used as the index of road strength. Adding 15% organic matter to the soil resulted in a decrease of the CBR from 15.72 to 4.75%. There was a significant difference between the two drying temperatures（60 and 110 ℃） for the same organic matter mixtures with lower water content values after drying at 60 ℃. The results revealed the adverse influence of organic matter on soil engineering properties and showed the importance of organic matter removal before excavation and fill construction.

Assessment of clay stiffness and strength parameters using index properties

A new approach is developed to determine the shear wave velocity in saturated soft to firm clays using measurements of the liquid limit, plastic limit, and natural water content with depth. The shear wave velocity is assessed using the site-specific variation of the natural water content with the effective mean stress. Subsequently, an iterative process is envisaged to obtain the clay stiffness and strength parameters.The at-rest earth pressure coefficient, as well as bearing capacity factor and rigidity index related to the cone penetration test, is also acquired from the analyses. Comparisons are presented between the measured clay parameters and the results of corresponding analyses in five different case studies. It is demonstrated that the presented approach can provide acceptable estimates of saturated clay stiffness and strength parameters. One of the main privileges of the presented methodology is the site-specific procedure developed based on the relationships between clay strength and stiffness parameters, rather than adopting direct correlations. Despite of the utilized iterative processes, the presented approach can be easily implemented using a simple spreadsheet, benefiting both geotechnical researchers and practitioners.

Determination of the Plasticity Index of Soils with Fine-Grained Soils Using Methylene Blue Test

The amount of fine material available in the soil is significant in Atterberg limits and methylene blue tests. In the context of Atterberg limits, increased amount of clay minerals contained in the soil increases liquid and plastic limit values;however, increasing sand content reduces the moisture content reducing the water retention capacity of the soil which in return reduces the plasticity index (PI) value. In the case of methylene blue test, which is used to specify the quality of the amount of fine material, existence of clay in the medium increases the pollution level of the sand and the amount of methylene solution (V1) used. In this study, soil classes were determined and pollution rates were identified with Atterberg limits, pycnometer, sieve analysis, hydrometer analysis and methylene blue tests conducted on 11 different natural soil samples collected from different regions. From the data obtained, first the relationship between PI and methylene blue (MB) was examined and was evaluated according to the results of the “single regression” method. Furthermore, the other coefficient of uniformity (Cu), coefficient of graduation (Cc), unit weight of soils (γs) parameters obtained from experimental studies were also subjected to “multiple regression analysis” in order to reveal their impact on the MB and this impact was confirmed taking both statistical analyses into account.

Mineralogical and Geochemical Assessment of Clay Properties of Edda, Afikpo Sub Basin Nigeria for Possible Use in the Ceramics Industry

Clay samples from selected part of Edda were analyzed to identify the clay mineral types present,their chemical and physical properties with a view to appraising their industrial suitability as ceramic materials.The mineralogical and geochemical analyses were done using the principles of X-Ray diffraction and X-ray fluorescence respectively.A total of seven clay samples were used for the study,other tests such as plasticity,bulk density,shrinkage,loss on ignition(LOI)and water absorption capacity was carried out to determine the amount of water absorbed under specified conditions.The basic industrial properties assessment showed that more than 70%of the clays are fine-grained.The clays exhibited low to moderate plasticity,moderate shrinkage and bulk density,low to moderate values of both loss on ignition and water absorption capacity.The clays are buff to yellowish in colour.The results of x-ray fluorescence revealed that the mean concentration of major oxide in the clays is shown as follows:SiO_(2)(62.78%),Al_(2)O_(3)(20.25%),total Fe(6.09%),CaO(0.56%),MgO(3.21%),Na_(2)O(0.47%),K_(2)O,(1.44%)and TiO_(2)(0.52%).The samples have high silica content,low alumina and low oxide content.The results of x-ray diffraction revealed that kaolinite is the dominant clay mineral with illite and montmorillonite occurring in subordinate amounts,while quartz and feldspar are the non-clay components present.The characteristics of the clays for each parameter were compared with industrial standards.These properties are appropriate for the Afikpo clays to be useful in the manufacturing of ceramics.However,since the silica content of the clays is high further beneficiation is recommended.

Soil Characteristics in Selected Landfill Sites in the Babylon Governorate, Iraq

The Babylon Governorate is situated in the middle of Iraq. It covers an area of 5,315 km2 and has 2,092,998 inhabitants distributed throughout its five major cities （Qadhaa）. Presently, there is no landfill site in the governorate that meets the environmental criteria for the disposal of municipal and industrial waste. Consequently, GIS （geographic information system） and methods of multi-criteria decision making were used here to select the best sites in each city in the Babylon Governorate that would fulfil the environmental requirements. Two sites were chosen in each city. As the groundwater is very shallow in this area, the design should ensure against groundwater pollution by leachate from these sites. To avoid this problem, soil investigation was conducted at these sites so that the most suitable landfill design could be accomplished. The results of soil investigation in these sites include the soil profile, groundwater depth, chemical properties, allowable bearing capacity, Atterberg limits test results and material characteristics of the soil strata. From the research, it is believed that the best design is one that puts the landfill above ground.

Characterization of the Activity, Mineralogy and Correlations between the Properties of Clayey Soils

The activity is related to the mineralogy and geological history of clays. Soils with the same value of the liquidity limit or plasticity index can have very different characteristics depending on the amount and type of clay minerals. The methylene blue value characterizes the activity of the clays and reflects the surface activity. Ten inactive soils contain minerals (kaolinite, illite), these soils absorb little water. Two swelling soils have normal activity and are composed of minerals (kaolinite, illite, Montmorillonite). The relationships between clayey soils properties, their activities and between the activity and the liquidity limit are defined. The correlations obtained are linear fit and exponential and sigmoidal fits. The correlations obtained with a coefficient of determination of R2 (0.859 - 0.999) can be used to characterize and predict certain parameters of fine-grained soils as a function of clay content.

Evaluating the Stability of Indigenous Akwadum Soil with Cassava Peel Ash and Quarry Dust

Cassava peels are produced as a waste from cassava, which are disposed into landfills. These become an environmental problem;therefore the use of cassava peel ash (CPA) as a soil stabilizer must be encouraged. This study investigates the effects of CPA and quarry dust (QD) on the engineering properties of Akwadum soil behavior, using compaction test, Atterberg limit, and California bearing ratio (CBR). These properties were compared with those of unstabilized soil (original) and soil stabilized with CPA and QD. The natural soil was obtained from a borrowed pit at Akwadum near Koforidua at an average depth of 0.8 m which is meant for road works. This soil sample was stabilized with CPA and QD at 5%, 10% and 20% respectively. The compaction, California bearing ratio and Atterberg limit test were performed on the stabilized soils to thoroughly evaluate them. The results indicate that increasing the percentage of CPA to the natural soil decreases the maximum dry density at increasing optimum water content. The addition of QD at higher percentage increases the maximum dry density at decreasing optimum water content. The results reveal that both QD and CPA improve the engineering properties of the soil with QD providing better results.

Evaluation of rice husk ash and Portland cement reinforced clay for use as road subgrade using the CBR test

The amount of rice husk waste generated in Nigeria is posing serious threat to the environment and the ecosystem.Utilizing these wastes for productive purposes has been of interest to government and researchers.This study evaluated rice hush ash(RHA)reinforced clay for use as road subgrade,using the California Bearing Ratio(CBR)as prescribed in ASTM D1883.The clay was mixed with RHA/Portland cement in the ratios of 0%(control),2.5%,5%,7.5%and 10%.Results showed that the physical properties of the soil in its natural form did not meet the FMW&H guideline specification for subgrade road;thus there was a need to stabilize the soil.As the percentage of RHA increased,the strength of the soil increased,with the maximum strength observed at 5%RHA,beyond which there was decrease in the load bearing capacity of the soil.Optimal CBR ratio of 9.35%was obtained at 5%RHA,5%Portland cement and 90%clay soil.Comparing this result with the soil at natural state(CBR=1.55%),it shows that RHA is a good improvement agent for the soil.This research can be beneficial to highway road construction in areas with similar soil conditions.