Geotechnical Behaviour Research Articles

EVALUATING THE IMPACT OF LIGHT CRUDE OIL CONTAMINATIONS ON GEOTECHNICAL BEHAVIORS OF THE SOIL

Crude oil spills contaminate the soil in many ways including environmental impact and physical and chemical changes of the properties of the host soils. Organic liquids will affect the geotechnical behaviors of the soils. For better understanding of the soil behaviors as a function of oil contaminations a deep experimental investigation was conducted on kaolinite clay and sandy soils. These soils that were polluted by various amounts of crude oils (0%, 3%, 6%, 9%, 12%, and 15% by weight of dry soil). The geotechnical characteristics of the uncontaminated and contaminated soils were determined including the plasticity indices, compaction characteristics, hydraulic conductivity, and linear shrinkage limit. The outputs revealed a decline in dry density and optimum moisture content. The hydraulic conductivity of both soil types decreased due to oil contaminations. Crude oil contamination increased the plasticity indices and raised the linear shrinkage limit of clay soil. Oil-contaminated soil obligates improvements and maintenance prior utilization as construction materials or agricultural purposes

Effect of Curing Temperature on the Geotechnical Behavior of Solidified Sludge in Landfill Temporary Cover Applications

Elevated temperature in municipal solid waste will affect the performance of earthen materials in a landfill cover liner system. Soda residue (SR), ground granulated blast furnace slag, and quicklime were utilized as solidifiers in sewage sludge, and the curing temperature effect on geotechnical behavior of solidified sludge in landfill temporary cove applications was investigated. The unconfined compressive strength, yield stress, coefficient of compressibility, hydraulic conductivity, and microstructural and mineralogical characteristics of solidified sludge at various curing temperatures were measured. Hydration products including ettringite crystals and calcium-silicate-hydrates (C-S-H) were observed in the samples. An increase in temperature from 12 to 40°C improved the solidified sludge strength, but a further increase to 60°C decreased the strength. The lowest coefficient of compressibility and the lowest hydraulic conductivity were observed at 40°C. The pore volume or pore size of the solidified sludge decreased with the increase in temperature. However, the geotechnical performance was improved due to the increase in C-S-H and decrease in ettringite in 40°C sample. 50% SR content was optimum for solidified sludge temporary cover due to its relatively high strength, high yield stress, low compressibility, moderate hydraulic conductivity, and good pollution stabilization capability at different curing temperatures.

Geotechnical behaviour of layered paste tailings in shaking table testing

ABSTRACT Interest in the use of paste tailings technology and understanding of the cyclic behaviour of paste tailings has significantly increased in the past years. However, no studies on geotechnical response of paste tailings to cyclic loading by shaking table testing technique has been performed. Thus, a one-dimensional shaking table testing program was performed to assess the behaviour and liquefaction susceptibility of the layered paste tailings under cyclic loading conditions. The paste tailings were deposited subsequently in three thin layers in a flexible laminar shear box mounted on top of the shaking table, and the response of accelerations, displacements and pore water pressures to seismic loading was measured at the middle depth of each layer of the tailings. Results showed that the acceleration for the bottom and middle layers were similar to that of the base of the shaking table; however, this was not the case for the top layer. The studied paste tailings were resistant to liquefaction during the cyclic loadings, but liquefied after the end of the shaking phase. All layers of paste tailings were subjected to contraction and dilation during the shaking.

Experimental Investigation on the Influence of Oven-Drying on the Geotechnical Properties of Volcanic Ash-Derived Residual Soils

For thousands of years, the volcanic activity present along the Andes Mountain range has generated a large amount of pyroclastic material. As a result, around 60 percent of the soils present in Chile have a volcanic origin, of which, we can find soils derived from volcanic ash. These correspond to soils whose origin is the weathering of volcanic ash, which generates minerals such as allophane, imogolite, and halloysite. The presence of these minerals gives these soils unique geotechnical properties, such as high plasticity, low dry unit weight, and a unique internal structure. Subjecting these soils to extreme temperatures like those needed to perform standard laboratory tests produces changes in their structures, and thus in their geotechnical behavior. These changes are important to be aware of with respect to slope stability problems, embankment conformation, surface foundations, etc. In the present study, a type of soil found in Chile originating from the weathering of volcanic ash and locally named Trumao was studied. Due to its age and formation processes, the main minerals found in the soil are allophane and imogolite, and hence it belongs to the allophanic soil type. The material was studied in its natural state (undisturbed) and, after being oven-dried using common geotechnical tests, the behaviors of both samples were compared. The study shows that some properties are affected significantly by the oven-drying process, and thus it is not recommended to expose the material to high temperatures during geotechnical laboratory testing to avoid misleading results.

The Role of Electrochemistry and Mineralogy in the Geotechnical Behavior of Salinized Soils

The Atterberg limits are essential information and the first step in soil classification for geotechnical purposes. Established laboratoryprocedures use distilled water in the plasticity and liquid limits determination. However, saline solutions frequently interact with soilsin the construction environment through fluid percolation processes. This work aims to understand the variation of the geotechnicalbehavior of two standard materials with different mineralogical compositions (kaolinitic and smectitic) when affected by NaCl ionicsolutions in different concentrations. The purpose is to simulate different soils in environments with the presence of saline solutions.This paper reports an experimental program in which a kaolinite-rich and a smectite-rich material received NaCl solutions in threedifferent concentrations (0.6 %, 3.5 %, and 15.0 %) and had their Atterberg limits determined under these conditions. Additionally,non-contaminated samples of both materials have had their limits measured using distilled water. Physical characterization testsincluded hygroscopic moisture, grain size distribution, grain density, plastic limit (PL), and liquid limit (LL). These data allowed thedetermination of the Skempton activity index (AI), plasticity index (PI), consistency index (CI), classification of soils in the UnifiedSoil Classification System (USCS), and in the Highway Research Board (HRB) with the group index (GI). Mineralogy was determinedby X-ray diffraction and physical chemistry by measuring pH in H2O and KCl, determining the ΔpH, the point of zero-charge (PZC),and the surface electrical potential (Ψo). The results show that the pH values rise with increasing salinity, while ΔpH, PZC, Ψo, LL,AI, PI, GI decrease with increasing salinity. The PL decreases with the increase in salinity for smectite and increases for kaolinite. TheUSCS and HRB demonstrate that the materials start to behave as fewer plastic materials with increased salinity. It is concluded that thevariations in the physicochemical parameters of the environment control and modify the geotechnical behavior of the fine-grained soils.

Evaluating Biosedimentation for Strength Improvement in Acidic Soil

Marine clay soils are problematic soils in the construction industry when they are subjected to construction loads. When these soils are loaded, they lose their structure. This leads to the soil being unable to withstand loads of any magnitude without exhibiting significant, permanent deformations. In order to stabilize the marine soil, new methods for soil improvement were built upon biogrouting by incorporating physical, biological and chemical treatments into the soil. However, the biggest challenge of this method is the bacteria migration through the soil medium. To overcome this issue, the electrokinetic phenomenon can be utilized alongside biogrouting to prevent the bacteria migration. In this regard, the present study applied electrobiogrouting stabilization to investigate the improvement of acidic marine clay soil with a pH of 3.69. To accomplish this, two large-scale physical models with dimensions of 500 × 300 × 1200 mm were fabricated to examine the influence of two different treated distances between the inlet and outlet—450 mm (D45) and 600 mm (D60)—on the stability of the treated soil. It was observed that the shear strength of the treated soil improved significantly. The shear strength at the D45 treated distance increased from 3.65 kPa (untreated soil) to 28.14 kPa (treated soil). However, the strength increased by increasing the treated distance. In addition, compressibility and soil electrical conductivity were reduced significantly, and the Atterberg limits were significantly enhanced from OH to OL. The reasons for the enhancement of treated soil were the formation of CaCO3, which filled the soil voids, and that the water content was reduced. To address issues with marine clay soil, this study aims to minimize the high cost of a special foundation system and the use of non-environmentally friendly materials such as calcium-based binders, aside from the reduction of deformations caused by loading. The findings of this study can be used for acidic soils and the improvement of soil’s geotechnical behavior in general.

Geotechnical Behavior and Physico-Chemical Changes of Lime-Treated and Cement-Treated Silty Soil

Geotechnical Behavior and Physico-Chemical Changes of Lime-Treated and Cement-Treated Silty Soil

Improvement of Pavement Subgrade by Adding Cement and Fly Ash to Natural Desert Sand

Soil characteristics are paramount to design pavements and to assess the economic viability of a road. In the desert, such as that found in southern Libya, the very poor quality of soils leads to important pavement distress such as cracks, rutting, potholes, and lateral shear failure on the edges. To improve the strength of desert sand, an innovative approach is proposed, consisting of adding manufactured sand, ordinary Portland cement (OPC), and fly ash (FA) as a binder. OPC and FA improve the characteristics of mixes of crushed fine aggregate (CFA) and natural desert sand (NDS). These results are based on a gradation of two sand sources to determine the particle distribution and X-ray fluorescence (XRF) to determine their chemical and physical properties, respectively. This research assesses the effect of cement and fly ash on the geotechnical behavior of two mixtures of fine desert and manufactured sands (30:70% and 50:50%). The mix composed of 26% of CFA, 62% of NDS, 5% of OPC, and 7% of FA shows optimal results in terms of strength, compaction, and bearing capacity characteristics.

Preparation and characterization of a specialized lunar regolith simulant for use in lunar low gravity simulation

Lunar in-situ resource utilization (ISRU) has been put on the agenda by many countries. Due to the special material nature and low gravity environment, the lunar regolith demonstrates significantly different behavior from terrestrial geomaterials. However, the systematic understanding of its geotechnical behavior is now seriously restricted by the scarcity of lunar regolith and the difficulty in simulating lunar gravity. A new lunar regolith simulant, termed as China University of Mining and Technology Number One (CUMT-1), has been developed to recover properties of the lunar regolith and simulate the lunar gravity by adopting the recently advanced geotechnical magnetic-similitude-gravity model testing (GMMT) method. The CUMT-1 simulant was prepared by reproducing the in-situ formation and fragmentation of the lunar matrix, which plays a key role in the irregular particle morphology. The mineralogical compositions, particle morphology and gradation, specific gravity, bulk density, void ratio, shear strength, and compressibility were determined. After quantifying the magnetization and magnetic-similitude-gravity characteristics, an application of the cone penetration resistance under low gravity was further given. The obtained results are compared to the values known for lunar regolith samples and other simulants, which demonstrates promising characteristics for use in geotechnical engineering-based and scientific-based applications, especially considering the influence of lunar gravity.

Geotechnical properties of some kaolinite-rich Brazilian Vertisols

Vertisols presenting kaolinite codominance or prevalence were already reported in several countries worldwide. However, the literature has few studies focused on investigating the influence of this clay mineral in soil geotechnical behavior. This study aimed to carry out the characterization of Vertisols in Bahia State, Brazil, to understand the influence of physical, chemical, and mineralogical properties on their geotechnical behavior, as these soils have high natural fertility and have been used for agricultural activity, but with great risk due [...]

Assessment Principles for the Mechanical Behavior of Clay Soils

The factors that determine the geotechnical behavior of soils are mainly their composition, the size of their grains and their moisture content. The design of a soil structure or foundation project must ensure the shear adequacy of the soil in all phases of construction and throughout the life of the project. However, the shear strength, in general, of the soil is not "constant" but depends on key external factors such as the prehistory of loads, the time and succession of load states, the overpressure of the pore water as well as other factors such as relative density, or any preload, the pressure field, the rate of change of the intensive state, etc. The influence of the deformations as well as the change of the intensive state during the sampling should not be ignored. Unlike other materials, in clay materials the determination of shear strength and its interpretation is a very complex problem. The aim of this article is to search for the mechanical behavior of clay soils (lignite, kaolinite, marl) as shown by the laboratory illustration related with the problems on shear strength of materials, based on the results of experimental research

GEOTECHNICAL BEHAVIOUR of REINFORCED SOFT CLAY by MARBLE DUST as A WASTE MATERIAL

Civil engineers around the world are in search of new alternative resources which are required both for cost-effective solutions for ground improvement and conservation of scarce natural resources. The various methods of ground improvement currently in use include lime columns, stone columns, use of chemical stabilizers, and various kinds of inclusions like metal strips, mats, fibres, geosynthetics, etc. The cost of these virgin materials as well as the processes involved is usually high and as such, they are yet to be commonly used in developing foundation performances. This paper illustrates the application of using marble dust stabilization in improving the soft clay soil. Various tests with different marble dust contents were performed to study the effect of using material as a stabilizing technique on main geotechnical soft clay properties. A series of laboratory tests like plasticity and consolidation at a different percentage of marble dust has been done. These experiments showed that the addition of marble dust resulting in composites hardens material which reduced the plasticity and compressibility parameters of the reinforced soft clay. The induction of reinforced composite material successfully decreases and adsorbs the excess water inside the soft clay thus, modifying the soft clay plasticity and significantly increase the soft clay stiffness and decrease the settlement. The used marble dust reducing the volumetric shrinkage and produced isotropic compressible ductile material with less settlement and higher shear strength. This adopted method will be applied to unravel the geotechnical stabilization issues, for instance, road embankments modification and foundation use.

Geotechnical Behaviour of Sandy Sabkha Soils Based on Experimental and Numerical Investigations

Geotechnical Behaviour of Sandy Sabkha Soils Based on Experimental and Numerical Investigations

Geotechnical Evaluation of Diesel Contaminated Clayey Soil

Soil contamination by different hydrocarbons has rapidly expanded worldwide, surpassing the self-purification capacity of soils and increasing the number of contaminated sites. Although much effort has been devoted to study the effects of diesel contamination on the geotechnical properties of soil, there is still limited available information about it. Moreover, there is no available information about the maximum diesel retention that soil can have and its effect on the geotechnical behavior of the soil. Thus, in this paper, we determined the maximum diesel retention by an unsaturated clayey soil and evaluated the impact of diesel contamination on its geotechnical properties. The results showed that the soil could only retain 12.6% of the added diesel and the excess was expulsed. At such a diesel concentration, the saturation rate of the soil was lower than 80%. Diesel contamination increased the plasticity and the internal friction angle of the soil, while its cohesion was considerably decreased. It should be noted that the matric suction of contaminated soil was lower than the one obtained for natural soil. However, its osmotic suction was considerably higher. This indicates that osmotic suction must be considered to evaluate the shear strength of contaminated soils.

Influence of faults on alteration, mineralogy, and geotechnical behavior of granitic residual soils

Influence of faults on alteration, mineralogy, and geotechnical behavior of granitic residual soils

Silt-sized sediments and gypsum on surface formations in the Ebro valley. A disambiguation of the term gypsiferous silts

Since the 60’s, many authors have reported the presence of common silt-sized materials in the Ebro valley, on surface formations and positions that have given rise to several interpretations, sometimes contradictory. According to the references, three main terms are used (gypsiferous silts, loess and flour-like gypsum) applied to silts and fine sands with gypsum accumulations. The two first terms are applied to materials with carbonate contents up to 40-50%, coarse silty to fine sandy textures, and located in different positions. Loess normally appears as thick outcrops on slopes leeward from the main wind direction, with a limited pedogenesis consisting of a partial carbonate mobilisation and gypsum contents between 0 and 30%. The third (gypsum-rich) type has a variable spatial distribution, appearing between limestone layers, along footslopes, outcropping as metric surface formations, or as generalized karstified subsurface accumulations. Their composition is almost 100% silt- to fine sand size lenticular gypsum. While some authors claim for an aeolian origin to all these materials, only part of them (loess) has a clear aeolian origin, while flour-like gypsum derives from on-site weathering of gyprock or by precipitation of calcium- and sulfate saturated watertables as it is reported to occur in many other arid regions; and the rest (gypsiferous silts sensu stricto) are mainly colluvial-alluvial. This distinction is necessary since they differ in their geotechnical behaviour and properties relevant for agricultural land uses, therefore they should be taken into account when carrying out geological mappings or soil surveys in this and similar arid regions.

Silt-sized sediments and gypsum on surface formations in the Ebro valley. A disambiguation of the term gypsiferous silts

Since the 60’s, many authors have reported the presence of common silt-sized materials in the Ebro valley, on surface formations and positions that have given rise to several interpretations, sometimes contradictory. According to the references, three main terms are used (gypsiferous silts, loess and flour-like gypsum) applied to silts and fine sands with gypsum accumulations. The two first terms are applied to materials with carbonate contents up to 40-50%, coarse silty to fine sandy textures, and located in different positions. Loess normally appears as thick outcrops on slopes leeward from the main wind direction, with a limited pedogenesis consisting of a partial carbonate mobilisation and gypsum contents between 0 and 30%. The third (gypsum-rich) type has a variable spatial distribution, appearing between limestone layers, along footslopes, outcropping as metric surface formations, or as generalized karstified subsurface accumulations. Their composition is almost 100% silt- to fine sand size lenticular gypsum. While some authors claim for an aeolian origin to all these materials, only part of them (loess) has a clear aeolian origin, while flour-like gypsum derives from on-site weathering of gyprock or by precipitation of calcium- and sulfate saturated watertables as it is reported to occur in many other arid regions; and the rest (gypsiferous silts sensu stricto) are mainly colluvial-alluvial. This distinction is necessary since they differ in their geotechnical behaviour and properties relevant for agricultural land uses, therefore they should be taken into account when carrying out geological mappings or soil surveys in this and similar arid regions.

Effect of Existing Building Walls on the Geotechnical Behavior of Foundation under Earthquake Loading

— Structure’s systems are subjected to additional loads due to earthquakes that may be produces progressive failures. The building illustrates dissimilar categories of failure mechanism for the minor to major earthquake conditions. These structures categorized to the most susceptible type of building has experienced serious hazard or even full failure for the period of seismic activities, therefore their investigation is a complex thing to do. Consequently, this research aims at studying the behaviour of large-scale model of structures constructed with and without brick walls under seismic conditions. The effect of building walls on the performance of the structure during earthquake loading is investigated numerically using PLAXIS 3D software. An eight story building with basement designed on a mat foundation is simulated as three-dimensional model in case of brick walls existing and without brick walls case. The effect of existence such wall building on the stability of foundation soil system is discussed in the form of lateral, horizontal deformation, and foundation acceleration. The studied showed that the reduction of extreme horizontal displacement and bending moment for building foundation with brick walls reached to 43%, and 68% respectively compared to the building without walls. The consideration of wall as filling for super structure significantly reduce the foundation acceleration by as much as 72% of its initial value, which lead to considerable effect of increasing the foundation stability.

Effect of Existing Building Walls on the Geotechnical Behavior of Foundation under Earthquake Loading

— Structure’s systems are subjected to additional loads due to earthquakes that may be produces progressive failures. The building illustrates dissimilar categories of failure mechanism for the minor to major earthquake conditions. These structures categorized to the most susceptible type of building has experienced serious hazard or even full failure for the period of seismic activities, therefore their investigation is a complex thing to do. Consequently, this research aims at studying the behaviour of large-scale model of structures constructed with and without brick walls under seismic conditions. The effect of building walls on the performance of the structure during earthquake loading is investigated numerically using PLAXIS 3D software. An eight story building with basement designed on a mat foundation is simulated as three-dimensional model in case of brick walls existing and without brick walls case. The effect of existence such wall building on the stability of foundation soil system is discussed in the form of lateral, horizontal deformation, and foundation acceleration. The studied showed that the reduction of extreme horizontal displacement and bending moment for building foundation with brick walls reached to 43%, and 68% respectively compared to the building without walls. The consideration of wall as filling for super structure significantly reduce the foundation acceleration by as much as 72% of its initial value, which lead to considerable effect of increasing the foundation stability.

Effects of contamination with gasoline on engineering properties of fine-grained silty soils with an emphasis on the duration of exposure

Leaking tanks may lead to severe contamination of their surrounding soil. The geotechnical behavior of the soil varies with the physicochemical processes that occur between the contaminant and the soil. In this respect, studying the geochemical properties of gasoline-contaminated soils and sediments seems to be important for engineering and especially environmental purposes. In this paper, laboratory tests were carried out to examine the effects of crude gasoline contamination on some of the geotechnical properties of a silty soil sampled from the Mashhad plain, located in the northeast of Iran. Tests consisted of basic properties, Atterberg limits, compaction, direct shear, and uniaxial compression tests, which were carried out on clean and contaminated soil samples at the same densities. The contaminated samples were prepared by mixing the soils with crude gasoline in the amounts of 3%, 6%, 9%, and 12% of dry weight and curing periods of 0, 7, 15, and 30 days. Results indicated a decrease in the friction angle and an increase in the cohesion of the soil by increasing gasoline content. Besides, a reduction in the maximum dry density and optimum moisture content was observed in the compaction test. The increase in gasoline percentage up to 6% also showed a direct effect on increasing the liquid limit and plastic limit of silty soil, which decreased thereafter. Moreover, any increase in gasoline percentage had a reverse effect on the modulus of elasticity of the soil. The increase in gasoline percentage up to 3% also had a direct impact on the uniaxial compressive strength of the soil, exceeding which it started to decline. Finally, the effects of contamination duration were examined by testing contaminated samples in periods of 7, 15, and 30 days under natural conditions. The results showed a reverse relationship with all geotechnical properties due to aging and a reduction in the gasoline content due to the evaporation of volatile compounds. Also, the numerical analysis of the laboratory results indicated an increase in settling and the percentage of shear strain beneath the foundation with increasing the contamination level, confirming the laboratory results.