Low Plasticity Clay Research Articles

Fractal model for virgin compression of pure clays

The well-known linear relation between the void ratio and the logarithm of pressure for the one-dimensional consolidation has widely incorporated into elastoplastic constitute equation of soils, however, it is not at all straight line for more compressible clays and has several physically unaccepted properties. The compression of clays is explained by fractal theory, and is seen as a balance between the vertical pressure and repulsive force between clay plates. The distance between clay plates depends on the structure formation of the clay flocculation and clay surface. The structure formation of the clay flocculation and clay surface can be modeled by fractal approach. A new formulation of one-dimensional virgin compression of pure clays, expressed by the linear function of ln ν–ln p or ln e–ln p, is proposed based on the fractal model for clay structure. The linear function of ln ν–ln p is suitable to express the virgin compression of the extremely high plasticity clays up to the high pressure of 5000 kPa. For low plasticity clays, the virgin compression satisfies with the linear relationship of ln e–ln p at the pressure higher than 100 kPa. These too are show to be in satisfactory agreement with experimental data. The gradient of the plots of ln ν–ln p and ln e–ln p is related to the fractal dimensions of clay structure, the fundamental material parameters for the first time.

An Improvement Method for Swell Problem in Sulfate Soils that Stabilized by Lime

In this research low plasticity clay (CL) has to be mixed by varying percents of gypsum and after that this mixture would be treated with different amounts of lime, in two methods: regular application and Double application. The swell examinations would be done on these samples; and the influence of sulfates and mixing method on different quantities of swell will be taken into consideration. The results show that the presence of sulfates causes an incredible increase in the swell. This increasing also is at times much more than the thing that is revealed in unimproved samples; but in improved samples from Double process mixing method the quantity of the swell would be decreased in large volume in comparison with regular method.

An oedometer test study on the preconsolidation stress of glaciomarine clays

Stress history is usually determined by interpreting the results of oedometer tests to obtain the preconsolidation stress using traditional methods such as those proposed by Casagrande and Janbu. Both these methods are based on the assumption that the soil experiences a change in stiffness, from a stiff response to a soft response, close to the preconsolidation stress. Disturbed soils, however, especially overconsolidated clays of low plasticity, exhibit a soft response at low stresses, thereby making the interpretation of oedometer tests using traditional methods extremely difficult. Using data mainly from the Haltenbanken area, offshore Norway, a study was undertaken to investigate the various methods and testing procedures available to determining stress history. Oedometer verification tests were also performed on reconstituted specimens to compare interpreted values with the actual applied preconsolidation stress. This paper describes the results of the study by illustrating the variation in the interpretation methods and testing procedures used to determine preconsolidation stress.Key words: preconsolidation stress, yield stress, overconsolidated, low plastic clays, oedometer test, stress history.

The applicability of modified Cam-clay model for low plastic clays under anisotropic loading conditions

The critical state Cam-clay concept gives rational predictions of undrained strength for normally consolidated and over-consolidated clay soils. However, the theory is doubtable to predict the behavior of soil in anisotropic conditions because this critical state theory has been developed by conducting triaxial tests in isotropic condition. Thus, it was considered whether modified cam-clay model(MCCM) could be well applied to predict undrained shear strength and pore water pressure of low plastic clays in anisotropic conditions. As considering test results, the prediction of undrained strength in anisotropic conditions are well coincided with the results of laboratory triaxial compression tests. However, excess pore water presure in anisotropic condition trends to be overestimated at failure, even though the prediction of porewater pressure in isotropic conditions is somewhat coincided with CIU tests. It is thought that the prediction of porewater prediction of stress path during loading of a field such as construction of embankment on soft clays, because a field has been applied to anisotropic condition during loading.

북동태평양 클라리온-클리퍼톤 지역 심해저 표층 퇴적물의 지질공학적 특성 연구

Deep-sea surface sediments were collected using a multiple corer at 20 stations of Clarion-Clipperton fracture zone in the northeast equatorial Pacific to understand latitudinal and longitudinal variations of geotechnical properties. There was a distinct latitudinal variation of geotechnical properties in the study area. The northern sediments showed finer grain size, lower water content and porosity, higher bulk density and specific grain density, lower liquid limits and plastic limits than their southern counterparts. The northern sediments are classified into inorganic clays of low plasticity (fat clays) on plasticity charts and normal to active clay on activity chart, whereas, the southern sediments are classified into fine-grained, highly-plastic, inorganic and biogenic silt or organic clays on plasticity chart and normal to very active clay on activity chart. When shear strength are considered, the northern sediments were found to be in unconsolidated states, while the southern ones to be normal to over-consolidated states. These latitudinal variations in sediment characteristics are likely caused by differences in productivity of surface water that controls sediment compositions, sedimentation rates, and grain solubility.

Time-Dependent Shear Deformation Characteristics of Geomaterials and their Simulation

ABSTRACT The viscous aspects of the stress-strain behaviour of saturated and air-dried clean sands in drained plane strain compression (PSC) and saturated clean sand and soft clays in undrained triaxial compression (TC) are presented. Common as well as different viscous features among the different geomaterials are addressed. The general three-component model is used as the framework for constitutive modelling, in which the total strain rate e is decomposed into elastic and irreversible components ee and eir while the stress σ is decomposed into inviscid (non-viscous) and viscous components σf and σv. In the simplest model (called the new isotach model) among those described in the paper, σf is a nonlinear function of eir, while σv is a non-linear function of eir and always proportional to σf for primary loading. This model is relevant to kaolin for the full pre-peak range and a reconstituted low-plasticity clay (Fujinomori clay) at small strains, both in undrained TC. The model is modified to simulate the viscous effect that decays with eir, as observed with clean sands and a natural soft clay. It is shown that the second type of model (called the viscous evanescent model and the TESRA model) simulates well the above-mentioned behaviour, not only during primary loading, but also at unloaded conditions. The model is further modified to simulate the behaviour of Fujinomori clay whereby the rate at which the viscous effect decays gradually increases with eir (the general TESRA model). The viscous components σv of the three models can be represented by a set of common equations, and the other models are specifically simplified versions of the general TESRA model.

Accelerated Testing Procedures for Evaluating Separation Layer Performance in Open-Graded Base Courses

An accelerated testing procedure was developed to evaluate pumping and deformation performance of separation layers used between open-graded bases and lime-treated and untreated subgrade soils. A pneumatically driven, electronically controlled repeated loading laboratory apparatus was developed. A low plasticity clay and a silty clay till soil were tested. A nonwoven geotextile and a dense-graded base aggregate were evaluated as separation layers. Tests were conducted at various loading levels and durations to develop the testing procedure. Comparisons of specimen pumping and deflection performance for stabilized, separated specimens were made relative to nonseparated and nonstabilized control specimens. Ultimately, loading at levels upwards of five times that expected in the field, for short durations (20,000 cycles or less), was performed to evaluate separation layer performance. Separation layer performance under accelerated loading correlated well to long-term field loading level performance. The testing method was sensitive to the use of geotextiles for separation between soils and open-graded aggregates, though some pumping of fines still occurred. The dense-graded separation level showed a marked drop-off in performance as moisture contents increased above optimum. A distinct breakpoint in subgrade soil performance occurred at a cone index of 200 (California bearing ratio 4). Soils with strengths less than cone index of 200 performed poorly, whereas soils above that strength pumped and deformed minimally regardless of separation layer type. Based upon performance comparisons with nonseparated test cases, the use of a separation layer between lime-stabilized subgrades and open-graded aggregate bases is recommended.

粘性土の圧縮性に関する統計的研究 : その2 大阪平野沖積粘土の体積圧縮係数・有効応力の関係式

The coefficient of volume compressibility m_v is the important index for the building's settlements. So, 12 formulas between m_v and effective stresses are introduced statistically by several methods, using 252 samples of alluvial clay in the Osaka plain. The adaptability of the theoretical values to the test values is studied. Generally, there are high adaptability on the high clastic clays (w≧55% or f_c≧45%) than on the loW plastic clays (w_n<55% or f_c<45%). For high plastic clays there is not much difference on the existence of soil characteristic constants as variables in the formulas

Basics of a new energy-saving technology for manufacturing clay tile

A process for fabricating clay tile by hydrostatic treatment and a device for its production are described. The suggested technology is distinguished from existing ones by an elevated and uniform density of the tile, which improves the quality of the product and makes it possible to decrease its thickness while retaining the requisite service parameters, and it makes the use of all drying equipment unnecessary and reduces the firing temperature. Implementation of the new technology makes it possible to widen the range of products and use lean low-plasticity clays.

Effect of Soil Plasticity on Damping Ratio at Small Cyclic Strains

In soil dynamics, the most common parameter for measuring soil damping is the equivalent viscous damping ratio, which is derived from the theory of a single-degree-of-freedom system with viscous dashpot. The results of a comprehensive literature review on the equivalent viscous damping ratio at small cyclic shear strain amplitudes, yc, between 0.0001% and 0.01% are presented and discussed. On the basis of the published data from different types of laboratory tests two important trends are established. The first is a significant increase of the scatter of the data points as the plasticity index of the soil, PI, decreases. This indicates that damping in low-plasticity clays and sands is more sensitive to factors such as confining stress, overconsolidation ratio and cyclic loading waveform than the damping in high-plasticity clays. The second trend is an increase of the damping ratio with PI. This trend with PI is opposite from the trend at yc > 0.01% established earlier, where damping ratio generally decreases with PI. An explanation is provided that the phenomena responsible for the increase of the damping ratio with PI at small yc are viscous creep and relaxation of the soil.

Influence of volcanic ash as flux on ceramic properties of low plasticity clay and high plasticity clay of Trinidad

AbstractCurrently there is interest in exploring the commercial viability of using ash from the erupting Soufriere Hills volcano on the island of Montserrat in the eastern Caribbean as a flux component in ceramics. Consequently, the fired characteristics (at 1100°C) of model test pieces fabricated from blends of the ash, covering the range 0–30%, with a low plasticity clay and a high plasticity clay (both kaolinitic) of Trinidad have been investigated. The results show that while 5–10% of the ash has little effect on the fired physical and mechanical properties of the low plasticity clay, 15% and above more than doubles the strength and significantly lowers the porosity. At the same time the linear shrinkage is increased by only a few per cent. On the other hand, addition of the ash to the high plasticity clay appears detrimental. In particular, compared with the properties of the clay without ash, increasing amounts of ash progressively and significantly decrease both the green and fired strength and sli...

Comparison of Piezocone and Laboratory Soil Parameters for Bridge Foundation Design on Clays: Case Study in Massachusetts

Results of a case study to demonstrate the use of the piezocone (CPTU) for selection of soil parameters for design of bridge foundations at a clay site in Massachusetts are presented. The test site is the location of several timber-supported bridges that have suffered significant deck and foundation deterioration and need replacement. The soil profile generally consists of 1 to 10 m of fine sand and silt, followed by 45 m of a low-plasticity marine clay that rests on a very dense fine to coarse sand. The site investigation consisted of traditional drilling and sampling techniques, field vane testing, and CPTU profiling. Shelby tube samples were used for laboratory tests, including basic soil characterization and measurements of stress-strain-strength behavior through oedometer and K0 consolidated direct simple shear tests. Results from laboratory tests showed that some of the tube samples had suffered moderate to high levels of sample disturbance, making them unreliable for laboratory stress-strain-strength testing. A comparison of the laboratory results with the CPTU profiles showed that the CPTU provided excellent information on soil stratigraphy and good comparison with the laboratory-determined stress history and undrained shear strength profiles. The CPTU test program involved less time and expense than the laboratory test program and was not susceptible to sample disturbance effects. This case study suggests that state departments of transportation should consider the CPTU as the instrument of first choice in site characterization programs for design of bridges founded on soft clays.

Influence of volcanic ash as flux on ceramic properties of low plasticity clay and high plasticity clay of Trinidad

Influence of volcanic ash as flux on ceramic properties of low plasticity clay and high plasticity clay of Trinidad

Evaluation of Resilient Modulus for Lime- and Cement-Stabilized Synthetic Cohesive Soils

The effects of deviator stress, molding moisture content, stabilizer type and content, curing period, and soil type on the resilient modulus (Mr) of lime- and cement-stabilized cohesive soils were investigated by using Hydrite R (kaolinite) and sodium bentonite (montmorillonite) blends. It was found that Mrincreases with decreasing deviator stress, increasing lime and cement content, and extended curing period. Moisture variations around optimum had little effect on Mrwith higher lime contents. Multiple regression analyses and Student's t-tests indicated that all the factors investigated were significant and could be related to Mrby predictive regression equations. For a given stabilizer type and content, the low-plasticity clay (CL) soil produced the best results. The cement-stabilized CL soil normal cured for 28 days produced the highest Mrvalue. However, cement stabilization was not found to be very effective for the high-plasticity clay (CH) soil. Mineralogical composition has a marked effect on the Mrof lime and cement-stabilized cohesive soils. Kaolinitic CL soils work better than montmorillonitic CH soils with both lime and cement.

The Small Strain Stiffness of a Carbonate Stiff Clay

ABSTRACT Knowledge of the small strain stiffness of the heavily overconsolidated Gault Clay, which has up to 30% calcium carbonate content, is rather limited. This has resulted in some difficulties in the analysis and design of structures constructed in the Gault. In this Technical note, the small strain stiffness of the Gault Clay is examined based on results from triaxial tests with internal small strain measurements, published geophysical data, and values deduced from the back-analysis of full-scale field observations of an excavation at Lion Yard Cambridge, U.K. Comparisons of stiffness values have also been made between the Gault Clay and the non-carbonate heavily overconsolidated London Clay. The results of these examinations have led to the conclusion that the stiffness-strain characteristic of Gault Clay is highly non-linear and exhibits first yield at a threshold shear strain of about 10− 5, beyond which the stiffness deteriorates dramatically from an initially very high value. After modest straining the stiffness reduces to values comparable to those for London Clay. The Gault Clay behaves like a low plasticity clay at small strains but as a high plasticity clay at medium to large strains. This behaviour is probably due to the breakdown of the weakly cemented bonding caused by the calcium carbonate content.

Treatment of Oil-Contaminated Soils for Identification and Classification

Abstract An experimental investigation was performed to evaluate the effects of oil contamination on soils and to establish a methodology to identify and classify contaminated soils. Identification and classification tests were performed before treatment, cleaning, stabilization, or disposal of contaminated soils. There are no standards for identification and classification of contaminated soils. Fine-grained, oil-contaminated soils are often identified and classified as granular soils with large particle sizes and may result in selection of improper treatment techniques. In this study, four uncontaminated soils were first identified and classified; then, all four soils were mixed with 3% motor oil. The oil-contaminated soils were first tested for identification and classification and then treated by (1) heating in ovens at various temperatures (low-temperature desorption), (2) adding solvents (solvent extraction), and (3) adding surfactants (treatment with surfactants). The processed soils were then reidentified and reclassified. Test results showed that treatment with a surfactant produced near-virgin soils for all four soil types. The solvent extraction was adequate only for the silty sand and the silty clay. The low-temperature thermal treatment was inadequate for all four soils. To further confirm the above test results, the low-plastic clay was mixed with 6% motor oil and the above test program repeated. This soil with a higher degree of contamination produced the same results. To provide an explanation for the change in soil behavior due to oil contamination, low-plastic soil was mixed with oil up to 70% by weight and Atterberg limit tests performed. It was concluded that fine-grained soils when contaminated with oil behave as granular soils with particle aggregation. Since soils in this study were artificially contaminated, one should exert caution when applying the results of this study to soils in contact with oil for many years.

Factors Affecting Water Content Determination of Soils by the Microwave Method

Tests were run on sand, silt, clay, and organic soil samples to evaluate the effect of soil type, sample size, water content, and power output on the drying time required for accurate determination of water content by the microwave method. Three different drying methods were used for the evaluation including the American Society for Testing and Materials (ASTM) microwave method (D 4643-87), the ASTM conventional oven method (D 2216-80), and a continuous drying microwave method devised for this study. The conventional oven method was used as the standard method for comparison. The effect of sample size was evaluated by testing samples weighing 20, 40, 60, 80, 100, 150, and 200 gm, all containing 10 percent water by weight. The effect of water content was evaluated using samples weighing 75 gm and containing 5, 10, 15, 20, 30, 40, and 50 percent water by weight. Microwave ovens with power outputs of 450, 600, and 800 watts were used to evaluate the effect of microwave strength. Results indicate that accurate water content determinations can be made using soil samples weighing approximately 150 gm. Sand, silt, low plasticity clay, and slightly organic soil gave very accurate results by the microwave method when compared to the conventional oven method. High plasticity clay and highly organic soil gave erroneously high water content values. Microwave ovens with different power outputs provided consistent drying time estimates, with slightly longer drying times being necessary for the lower output ovens. Based on these results, an equation was developed which can be used to estimate the optimum drying time required for an accurate determination of water content by the microwave method.

A New Method to Measure the Effective Porosity of Clays

Abstract The effective porosity is a required parameter for the mass flow rate calculations in groundwater hydrogeology. It is also a useful parameter in geotechnical engineering. In this paper, a methodology based on the tracer analysis technique is proposed to measure the effective porosity of clays. A test apparatus was developed and operational conditions were optimized to measure the effective porosity in the laboratory. Then the effective porosity of three clays under different chemical environments was measured. The measured effective porosity values showed that there is no unique effective porosity value for a given clay when tested under different chemical environments. The ratio of effective to total porosity values for silty and low plastic clays decreased while those for high plastic clay increased with the increase in degree of contamination.

Behaviour of medium and low plasticity clays under cyclic simple shear conditions : Soil Dynamics and Liquefaction, Proc 4th International Conference on Soil Dynamics and Earthquake Engineering, Mexico City, 23–26 October 1989 P131–141. Publ Southampton: Computational Mechanics Publications, 1989

Behaviour of medium and low plasticity clays under cyclic simple shear conditions : Soil Dynamics and Liquefaction, Proc 4th International Conference on Soil Dynamics and Earthquake Engineering, Mexico City, 23–26 October 1989 P131–141. Publ Southampton: Computational Mechanics Publications, 1989

Determination of undrained shear strength of low plasticity clays : Peters, J F Proc Symposium on Advanced Triaxial Testing of Soil and Rock, Louisville, 19–20 June 1986P460–474. Publ Philadelphia: ASTM, 1988 (ASTM Special Technical Publication 977)

Determination of undrained shear strength of low plasticity clays : Peters, J F Proc Symposium on Advanced Triaxial Testing of Soil and Rock, Louisville, 19–20 June 1986P460–474. Publ Philadelphia: ASTM, 1988 (ASTM Special Technical Publication 977)