Prior Assessment of Variability in the Geotechnical Properties of Soils for Efficient Infrastructure Management

Advance assessments of variations in geotechnical properties of soils are invaluable in making a crucial judgment of geotechnical engineering projects. It could drive to reduce the number of field and laboratory tests so that efficient management design and construction of infrastructure project outputs can be achieved. In this study, we aim at assessing the geotechnical properties of residual, alluvial, marshy, coastal, and compacted soils within the wet and the dry zones of Sri Lanka. Plastic limit (PL), liquid limit (LL), shrinkage limit (SL), plasticity index (PI), liquidity index (LI), compression index (Cc), swell potential (SP), activity, natural moisture content (NMC) and SPT-N values were either extracted from reports or deduced from formulas and graphs. Wet zone marshy soils (My_W) show highest statistical means for PL (~23%), LL (~40%), PI (~16 %), SL (~20 %), LI (~ 1%), Cc (~ 0.200) and NMC (~ 35%), indicating poor engineering properties. Wet zone residual soils (Re_W) represent a wide range of direct correlations to the parent material. CH, OH, CL and SM soil groups for some My_W show high expansive, while, CL, Pt/CL, OL, SC, SM in My_W, CL, and SC in Re_W and CL in Dry Zone Alluvial Soils (Al_D) display medium expansive. The higher SPT-N values were recorded in the upper 6.00m and between 12.00-16.00m for the shell of earth dams (SED_D) in the dry zone, in contrast to Al_D soils representing higher N values for 6.00-12.00m. Except for marshy soils, no vertical variation for plasticity was observed in others. Since high to medium swell potential in the unsaturated zone is encountered within the upper 1.50m, attention should pay to the My_W. LL and PI of My_W were strongly correlated (R2 = 0.83) so that an equation PI% = -1.91 + (0.46*LL%) could be used to calculate PI. The results provide baseline geotechnical property variations for the five soils in Sri Lanka so that during planning, best-calculated assessment could be achieved which could minimize time and cost for crucial geotechnical investigations.

Development of Some Novel Suction-Based Correlations for Swell Behavior of Expansive Soils

Swelling and shrinkage are the two distinctive characteristics of expansive soils, and due to this behavior, these soils are considered a natural hazard for infrastructure. Many structures in different regions have been impaired due to the swell/shrink behavior of the expansive soil. Most of the severe distress is impeded because of the inherent suction (negative pore water pressure) present in expansive soils. Both suction and swelling parameters are greatly affected by the surrounding moisture content. Due to this feature of expansive soil, geotechnical engineers are interested in utilizing the suction-based correlations for the assessment of unsaturated expansive soils. The current investigation was carried out to develop novel correlations incorporating lab testing and field instrumentation. To fulfill the objectives, eight sites of the local expansive soil in Pakistan were selected for samples collection and field testing. Conventional odometer testing was conducted to measure the swell pressure (Sp) and swell potential (S) of the fabricated/remolded specimens. Gypsum block (G-block) sensors were additionally utilized for estimating the matric suction in the field. To expand the database, the previously published data of the same nature was also incorporated. Based on the results, the power form of the novel correlations (suction-based) is highly significant for estimating (Sp), while for swell potential, the logarithmic correlation with R2 = 0.6551 is more significant than other forms of correlations. The proposed suction-based correlation can be equally utilized for the estimation of field suction as well as for swell behavior of expansive soil having a plasticity index (PI) ≥ 22%.

Evaluation of the Curing Time Effect on the Swelling, Unconfined Strength and Resilient Modulus of an Expansive Soil Improved with Hydrated Lime

Soils with high plasticity and high swell potential undergo great volume changes in the presence of unstable water content changes. The resulting expansion leads to damage to pavements and/or lightweight structures with such a subsoil. Expansive soils can be improved by adding chemical stabilizers such as lime, fly ash and micro cement. To construct a highway on an expansive subgrade soil, the subgrade should be stabilized to satisfy the minimum requirements of the highway standards. In this research, expansive clay samples were collected from clay deposits in the Akyurt district of Ankara (Turkey), near Esenboğa Airport. The swelling, strength and resilient modulus properties of the soil samples were determined via laboratory tests. First, reference tests were carried out on natural soil samples. Then, the clay samples were mixed with lime agent at different percentages (1%, 3%, 5%, 7% and 9%) according to the dry weight of the soil. The index, swelling, strength and resilient modulus (Mr) properties of these samples were determined. The soil samples were tested at 7, 28, 56 and 90-day curing times for each percentage of lime agent considered. The changes in the abovementioned properties, especially with regard to the effect of curing time on improvement, were interpreted in this research. Designing for a 7% lime content and a 28-day curing time can be a sound solution for addressing the expansive clay studied in this research, since the criteria of the Turkish Highway Standards are satisfied under these conditions.

Determination of Swell Potential of Soils using Cole in Panyam, North – Central Nigeria

Swell potential of soils from parts of Panyam, North – Central Nigeria were investigated covering 72 square kilometres within latitudes N9021′ and N9026′ and longitudes 9011′E and 9015′30″E. With the increase of civil engineering constructions and the scramble for limited portions of competent soils for such constructions, there is an urgent need in a developing nation to study and characterize such soils based on its geotechnical properties. The geotechnical studies include twenty soil samples taken within the 1.5m depth with the aim of determining the swell potential in order to give appropriate guide to any civil engineering design and construction. The direct method of soil analysis which is the coefficient of linear extensibility (COLE), which ranges from 0.02–0.17 was used for the study. COLE Values greater than 0.06, were considered to be critical for most civil engineering design and constructions. Most of the samples studied were considered not safe for bungalows and some infrastructure without proper safety measures carried out to improve upon it.

An Experimental Study on the Geotechnical, Mineralogical, and Swelling Behavior of KPK Expansive Soils

Expansive soils are found in numerous regions of the world explicitly in arid and semiarid zones. These soils expand when absorbed moisture and shrink when released water. Such soil is viewed as a characteristic risk for infrastructures due to the shrink and swell behavior. These soils become more problematic when lightly or moderately loaded structures are built on them. The swelling and shrinkage in these soils chiefly happen due to the presence of montmorillonite minerals. The mineralogical and swell behavior of foundation soils is playing a vital role in the overall stability of a structure. These parameters are often ignored in the geotechnical report writing stage specifically in small projects, due to which, the durability and service life of the facilities are reduced and the maintenance cost is increased. To mitigate the potential damages in structures constructed on expansive soil, it is necessary to assess the mineralogical and swelling characteristics of expansive soil. The current study aims to determine the geotechnical, mineralogical, and swell behavior of the local expansive soils. Based on the results, the Karak soil has the highest plasticity index (PI) of 37% with a clay fraction of 28%, while the D.I. Khan soil has the least PI of 23% with a clay fraction of 17%. Similarly, Karak’s soil contained a higher percentage of montmorillonite (Rp = 8.9%). The maximum values of swell pressure, swell potential, and 1D deformation are 280 kPa, 12.5%, and 1.92 mm for the Karak soil, 6.45% 150 kPa, and 1.38 mm for D.I. Khan soil, and 10.5%, 245 kPa, and 1.64 mm for Kohat soil, respectively. This concludes that Karak’s soil has high plasticity and swell characteristics than Kohat and D.I. Khan soil. The swell characteristic of expansive soils increases with the increase in the percentage of the fine specifically the clay fraction. Furthermore, the Karak soil is more critical than Kohat and D.I. khan soil for lightly loaded structures.

Undrained Strength Characteristics of Fibre Reinforced Expansive Soils

Expansive soils are those whose volume changes take place while it comes in contact with water. It expands during rainy season due to intake of water and shrinks during summer season. Expansive soils owe their characteristics due to the presence of swelling clay minerals. Expansive soils cover nearly 20% of landmass in India and include almost the entire Deccan plateau, western Madhya Pradesh, parts of Gujarat, Uttar Pradesh, Andhra Pradesh, Karnataka and Maharashtra. The properties that describe the expansive behaviour of soils are free swell index, swell potential and swell pressure. This behaviour has an impounding effect on the bearing capacity and strength of foundation lying on such a soil. Some of the stabilization techniques which are currently being used are physical alternations, sand cushioning, belled piers, under reamed piers, granular pile anchors, chemical stabilization, and fibre reinforcement techniques. This paper focuses on improvement in the strength characteristics of stabilized Chittur soil. The commonly used stabilizer for expansive soils is lime. This paper looks upon alternative materials such as fly ash and polypropylene fibres in order to reduce the lime content. It was concluded from the trials that an optimum combination of 1.5% lime, 10% fly ash and 0.2% polypropylene fibres contribut

Floristics of Difficult Creek Natural Area Preserve: a Piedmont mafic woodland complex in Halifax County, Virginia, U.S.A.

The 331-hectare (819-acre) Difficult Creek Natural Area Preserve (DCNAP) was established in Halifax County, Virginia to protect and manage habitat for rare vascu-lar plant species and animals, and to restore plant communities. Mafic metavolcanic rocks of the Virgilina Formation and felsic metavolcanic and metasedimentary rocks of the Aaron Formation comprise the geologic units on the preserve. The Virgilina-derived soils have high shrink-swell potential, a dense hardpan layer, relatively high base status, and a significant gravelly or stony component; these soil conditions support the highest density of rare plant species known on the preserve. The first noteworthy vascular plant species were documented from the property in 1972 by botanist Alton Harvill of Longwood University, but detailed investigations of the flora did not begin until the site was revisited by the second author in 1993. Rare plant inventory has been the primary focus of botanists since that time. In 2001, the property was acquired by the Virginia Department of Conservation and Recreation, Division of Natural Heritage (DCR) and dedicated as a state Natural Area Preserve, at which point active management for natural communities and associated rare species was initiated. Since the rare plants on site thrive in open woodland or savanna-like conditions, prescribed burns and timber harvests have been used by DCR stewards to restore habitat after decades of fire suppression and conversion of hardwood stands to loblolly pine plantations. In 2018, a thorough floristic study was initiated to highlight the significance of this flora beyond the documentation of rare plants. The two-year inventory documented 653 plant taxa, comprising 326 genera in 106 families. Fourteen of these species are of conservation concern at the global or state level; an additional 12 taxa are considered uncommon and of potential conservation concern (Townsend 2019). These rare or uncommon species are components of two globally rare plant communities. In addition, the globally rare lepidopteran, Erynnis martialis (Mottled Duskywing), occurs on the preserve, the only extant population known in Virginia. Due to agricultural impacts and widespread fire exclusion, few analogs to this flora exist within the southern Piedmont of Virginia.

Reuse of Municipal Solid Waste from Incinerated Ash in the Stabilization of Clayey Soils

A useful method for the disposal of waste from an incineration plant is to reuse it for geotechnical and civil engineering applications. The primary objective of this study concerns the reuse of local incinerated ash from municipal solid wastes in soil stabilization. Municipal Solid Waste Incinerated Ash (MSWIA) is blended with soil in various combinations and tested for its Atterberg limits, unconfined compressive strength (UCS), California Bearing Ratio (CBR), and Free Swell Index (FSI). A 1-D Consolidation Test was conducted, and changes in the soil during the test were examined by a scanning electron microscopic (SEM) analysis. The test results showed that there are increments in the UCS and CBR values with the reductions in the FSI, swell pressure, and swell potential of the treated soils.

Geotechnical and Mineralogical Appraisal of Shale and Claystone Facies of the Maastrichtian Patti Formation, Bida Basin, Nigeria

The need for construction materials in the rapidly developing areas around Federal Capital Territory, Abuja, Nigeria cannot be overemphasized and this study was undertaken in line with this need. The study area, located about 60km from Abuja, is underlain predominantly by shales and claystones of the Patti Formation. These argillaceous rocks may offer locally sourced construction material if they meet certain specifications, however to date, there has not been a geotechnical study of these rocks. The geotechnical properties and the mineralogy of the shale and claystone were investigated to evaluate their suitability for civil engineering works. Particle size distribution, Atterberg limits and X-ray diffraction analyses were performed on fifteen shale and claystone samples collected from three localities (along an approximately 25km transect) for determination of their geotechnical properties and mineralogical composition. Mineralogical data obtained show the samples are dominated by kaolinite with minor amount of montmorillonite. Quartz and minor amounts of microcline, rutile and anatase dominate the non-clay mineral fraction. Particle size data indicate high proportion of fines and they are well graded. The Atterberg limits indicate that the samples have average values of liquid limit of 51%, plastic limit of 23%, plasticity index of 29% and shrinkage limit of 13%. These indicate they are of medium compressibility, low to medium shrink/swell potential, marginal expansive rating and low permeability. High bulk specific gravity (average of 2.61) suggests the samples are inorganic and this is supported by the consistency limits values. Generally, the results indicate the shale and claystone can be useful as stabilizing materials in civil engineering works. In addition, the marginally expansive nature of the shale and claystone, low permeability and intermediate to high plasticity may make them suitable as road subgrade.Keywords— activity, Bida Basin, Gerinya, Kaolinite, plasticity, Patti Formation

Effect of Saline Soils on Durability of Road between Alsamawa and Sawa Lake

Road specialists in the world often suffer the huge challenge in designing a stable road on very soft saline soils, these soils in arid zones have a low bearing capacity with high compressibility and very sensitive to moisture and synchronized with complete collapse. The case study concerned by the deterioration of main road linking between ‎Alsamawa town and Sawa lake approximately 20 km away from Alsamawa town. There are sections of roads affected by converges of nearby local artificial ‎lakes , water drawn from several good drain down to (80) meters depths and causing the deterioration in the road sections , swell-collapse test results represented by a little swell potential values were appeared for zero applied stress, while aggressive collapse were happened with increasing in applied stress, and the increasing in degree of collapsibility corresponding to increasing of applied stress of (50,100,200) KPa, and sodium chloride (NaCl%) in soil layers range between (0.613-16.468) % and slightly to moderately gypseous soils, the case study included several recommendations to treating the deteriorated significantly of road to protect the sub-grade and subbase layer .