Types Of Fine-grained Soils Research Articles

Predictive strength model of cement-treated fine-grained soils using key parameters: Consideration of the total water/cement and soil/cement ratios

Soil stabilization techniques have been widely used to improve the mechanical and engineering properties of soft ground, such as strength, compressibility, and permeability. Recently, dredged soils that have high water content, high compressibility, and low strength have been mixed with cement and used as filling and landfill materials. The water and cement contents and soil types (clay or silt) in these soil–cement mixtures can be determined according to the purpose of use. To this end, the design of these mixtures requires the accurate prediction of the unconfined compressive strength (qu). Therefore, this paper proposes a predictive model for qu of cement-treated fine-grained soils (CTFSs) for ground improvement and stabilization of dredged soils. Ordinary Portland cement and two types of fine-grained soils (clay and silt) were used as the basic materials in the experiment. Unconfined compression tests were performed in a wide range of experiment conditions: water content (wt: 40–170 %), cement content (c: 5–25 %), and curing time (t: 3–90 d), and the results were correlated by two key parameters, wt/c (total water content/cement ratio) and s/c (soil/cement ratio). The results demonstrated that wt/c and s/c were strongly correlated with the qu development of CTFSs depending on the curing period. Therefore, we established a predictive model for qu by combining the power and exponential functions for (s/c)X and (wt/c)Y. The X and Y values of proposed model could equally be applied for different curing periods for soils of different types with different characteristics. In addition, the proposed model could predict long-term qu by using the time coefficient (ct) normalized by the curing period of 7 d. The mean absolute percentage error and coefficient of determination of the proposed model were lower and higher, respectively, than those of the reported data. Overall, the proposed predictive model is a promising tool for predicting the qu of CTFSs, for instance, for ground improvement and cement-treated dredged soils.

Soil-water retention curve model for fine-grained soils accounting for void ratio–dependent capillarity

This paper presents a soil-water retention curve (SWRC) model for fine-grained soils. Compared with existing studies, the proposed model accounts for the distinct roles of the volume change of soils on capillarity and adsorption mechanisms. The capillary water is described by a relation that includes the characteristics of the pore-size distributions as parameters, while the absorbed water is modeled by a novel proposition that both considers the phenomenon of capillary condensation and allows for the decoupling between the degree of capillary and adsorptive saturation. Based on this feature, the void ratio effects are considered in a way in which they only affect capillary water, i.e., consistent with how volume change influences soil microstructures. The relative contributions of void ratio effects and hydraulic hysteresis on the path- and history-dependence of a SWRC in Sr–s–e space, where Sr is degree of saturation, s is matric suction, e is void ratio, for deformable unsaturated soils are examined. The significance of discriminating the effects of volume change on capillary and adsorptive water is illustrated by applying the SWRC model to computing the shear strength of unsaturated soils with different void ratios. The model performance is assessed by comparing against test data reported for four types of fine-grained soils in the literature and those tested for natural loess in this work.

Piecewise strength model for three types of ultra-soft fine-grained soils

Problems of ultra-soft soils, with the characteristics of high water content and very low strength, have been gradually distinguished from those of typical soft soils in recent years to address the new requirements of ocean geotechnical engineering, such as the improvement of dredged fills and hazard assessment of submarine landslides. Focusing on effects of high water content and different shear strain rates on the undrained shear strength of ultra-soft soils, a series of experimental investigations were conducted, using a combination test method, on three types of fine-grained soils with different grain size distributions: kaolin soil, Bohai Sea soil, and South China Sea soil. After preparing ultra-soft soil samples with high water content two to three times the liquid limit, the relationship between the strength and the water content of the soil was analyzed. Then, the changing trend of strength with shear strain rates in a broader range of 0.001–20 s−1 was discussed. Based on the test results and theory of shear thinning behavior, a piecewise model for the ultra-soft soil strength was proposed. The piecewise strength model can adequately reflect the strength characteristics of ultra-soft soils at different shear strain rate ranges, and the parameters in the model can be measured, or simply estimated.

A NEW APPROACH FOR PARTICLE SIZE CHARACTERIZATION OF SOIL BASED ON DYNAMIC IMAGE ANALYSIS (DIA)

Particle size distribution (PSD) affects soil behaviour and plays a main role in geotechnical engineering. In site investiga- tions of large engineering structures, in earthquakes and liquefaction research and before filter material selection, it is necessary to make a number of PSD analyses. There are two popular techniques to determine PSD in the lab: sieving for the coarse-grained samples and hydrometer analysis for fine-grained samples. However, determining the PSD of soil in the lab has some challenges such as time, labour, difficulty and errors related to the analysis. The newly developed dy- namic image analysis (DIA) method based on wavelet transformation (WT) analysis is used as the main approach for determining particle size distribution. The DIA method contains saving the image and processing it with the software for a specified goal. The DIA method holds many advantages over the hydrometer analysis, including automating the test, reducing errors, monitoring and evaluating the particles at any time. In this paper, the PSD of fine-grained soil with a plasticity index (PI(=30 has been determined. The images of soil were prepared with a digital camera at a different time when particles settled through a sedimentation cylinder and were analysed with MATLAB software. The results were compared with the hydrometer analysis. The results showed that at t=15 min, a complete overlapping was seen between the DIA method and hydrometer analysis. The D20, D50 and D80 values by the DIA method were determined respectively, 0.0017, 0.012 and 0.031 mm at t=15 min. The results demonstrated that the DIA technique can be implemented for all types of fine-grained soils, more easily than the hydrometer analysis. The differences between the methods’ results were raised due to the amount of data provided by them.

Study on effect of Microbial Induced Calcite Precipitates on strength of fine grained soils

Summary For construction purposes, it is very essential to provide a strong foundation for the structure. If required, the suitability of soil has to be improved; this process of improving properties of soil is called Soil Stabilisation. This study intends to experimentally analyse the effectiveness of use of an unorthodox liquid soil stabiliser, Microbial Induced Calcite Precipitates (MICP) for improving the shear strength parameters of two different types of fine grained soils. For this process, a species of Bacillus group, B. pastuerii was used to activate and catalyse the calcite precipitation caused by reaction between urea and calcium chloride. Two types of soils, i.e. intermediate compressible clay and highly compressible clay were used for the study. Parameters included concentration of B. pasteurii, concentration of the cementation reagent and duration of treatment. These parameters were applied on both the soils in a specified range in order to optimise their usage. The results proved that with the use of MICP, there was a noticeable improvement (1.5–2.9 times) in the unconfined compressive strength of both type of soils. It was also found that the strength increased with an increase in duration of treatment. Based on this study, optimum quantity and concentration of liquid additive to be added for different soil types for better strength increments were established.

PREDICTION OF COMPACTION CHARECTERISTICS OF SOIL USING PLASTIC LIMIT

In all kinds of earthwork constructions, the laboratory determination of the compaction characteristics of the soils plays an important role. Soil compaction is defined as the method of increasing the density of the soil by application of mechanical energy. The principal reason for the compaction of the soil is to produce a soil mass which can satisfy the three basic criteria. Firstly, the reduction of subsequent settlement of the soil mass, under working loads. Secondly, for the reduction in permeability which will subsequently avoid built up of large water pressures causing liquefaction problems and is also important for retaining water in case of earth dams. Thirdly, it is used for increasing the shear strength of the soils. But the determination of compaction characteristics in laboratory is laborious. It requires significant time and effort. Hence, there is a necessity for prediction of compaction characteristics with the help of correlating it with index properties of soil which can be determined easily. The plastic limit of soil can be found effortlessly and it bears a good correlation with compaction characteristic, namely optimum moisture content (OMC). In this paper, a study is conducted on nine types of fine grained soils like black cotton soil, red clay, china clay, marine clay, silty clay etc. collected from different parts of Telengana and Andhra Pradesh. And a simple equation has been suggested using regression analysis to obtain the optimum moisture content of a soil from the plastic limit, thereby eliminating the dependence of the proctor test for determination of OMC.

Influence of Clay and Silt Proportions on Cement-Treated Fine-Grained Soil

AbstractNatural clay usually contains some silt, which is also a fine-grained soil. The proportion of silt in clay varies depending on the source, and the presence of silt in clay affects the reaction between the soil and cement. The purpose of this research was to study the relationship between the proportions of silt and clay in fine-grained soil and the engineering properties of the fine-grained soil after being stabilized with cement. Six types of fine-grained soils were used in this study: a natural clay and five synthetic clays with various proportions of bentonite and kaolinite. The six clays were mixed with silt in the following silt-to-clay proportions: 0∶100, 15∶85, 30∶70, and 45∶55. Cement was added to the synthetic clays in amounts corresponding to 7.5 and 15% of the dry weight of the soil, and the samples were cured for 28 days. Cement was added to the natural clay in amounts corresponding to 7.5, 15, and 20% of the dry weight of the soil, and samples were cured for 7 and 28 days. The results...

Estimation of the phenolic waste attenuation capacity of some fine-grained soils with the help of ANN modeling

In the present investigation, batch experiments were undertaken in the laboratory for different initial phenol concentration ranging from 10 to 40 mg/L using various types of fine-grained soils namely types A, B, C, D, and E based on physical compositions. The batch kinetic data were statistically analyzed with a three-layered feed-forward artificial neural network (ANN) model for predicting the phenol removal efficiency from the water environment. The input parameters considered were the adsorbent dose, initial phenol concentration, contact time, and percentage of clay and silt content in soils. The response output of the ANN model was considered as the phenol removal efficiency. The predicted results of phenol removal efficiency were compared with the experimental values as obtained from batch tests and also tests for goodness of fitting in ANN model with experimental results. The estimated values of coefficient of correlation (R = 0.99) and mean squared error (MSE = 0.006) reveals a reasonable closeness of experimental and predicted values. Out of five different types of soil, type E exhibited the highest removal efficiency (31.6 %) corresponding to 20 mg/L of initial phenol concentration. A sensitivity analysis was also carried out on the ANN model to ascertain the degree of effectiveness of various input variables.

Laboratory Assessment of Kaolinite and Bentonite under Chemicalelectrokinetic Treatment

Electrokinetic treatment uses low intensity direct electric current or a low electric potential difference, to improve the engineering properties of subsurface soils while having minimum disturbance to the surface. This study aims to investigate the effects of chemical-electrokinetic treatment on properties of two types of clay soils at different intervals under the coupled Chemical, Hydraulic and Electrical (CHE) gradient. “Chemical-electrokinetic treatment” refers to improvement of soil with electrokinetic together with addition of chemical enhancement solution. The enhancement solutions used in this study are hydrated lime and saline solution. The combined effects of these processes together with various electrochemical and geochemical reactions would change the chemical composition of the soil porous medium, hence modifies the properties of the soil. The experiments were conducted in the laboratory using stainless steel electrodes under total applied voltage of 30 V for period of 15 days. Two types of fine-grained soils, kaolinite and bentonite, were used as they possess different mineralogy and geotechnical properties. The cumulative electro-osmotic flow and electric current flow through the soil samples were measured for period of 15 treatment days. Subsequently the specimens were tested for moisture content, pH and Atterberg Limit variations and the results have been reported. Test results revealed that there is a potential of developing this technique to improve engineering properties of finegrained soils, in particular to stabilise and improve soft soils for infrastructure management and constructions.

Experimental Study on Flexural Testing of Compacted Soil Beams

This paper presents an experimental study on flexural testing of three different types of soils molded at three different water contents and two different compaction energies. For this purpose, a custom designed simple beam test setup was developed in the laboratory for inducing the controlled pure bending to the soil under evaluation together with a charged coupled device video camera mounted on to a moving triaxial base plate. Based on the analysis and interpretation of bending moment (BM)-curvature (κ) relationships of tested soil beams, effects of soil type, molding water content, and compaction energy on the flexural behavior could be obtained. For the varied molding water contents and for the range of plasticity indices varied, with an increase in plasticity index of the soil and molding water content, a trend of increasing tensile strain at crack initiation was observed. In comparison, flexural tensile strength at crack initiation was observed to decrease with an increase in molding water content. Further, flexural rigidity at crack initiation was found to be higher for soils having low plasticity index and moist compacted at low-molding water contents. The developed test setup is capable of inducing distortion levels of 0.105 and can be useful in assessing flexural characteristics of different types of fine-grained soils.

Measurement of soil-water characteristic curves for fine-grained soils using a small-scale centrifuge

Considerably long periods of time are required to measure soil-water characteristic curves using conventional equipment such as pressure plate apparatus or a Tempe cell. A commercially available, small-scale medical centrifuge with a swinging type rotor assembly was used to measure the soil-water characteristic curves on statically compacted, fine-grained soil specimens. A specimen holder was specially designed to obtain multiple sets of water content versus suction data for measuring the soil-water characteristic curve at a single speed of rotation of the centrifuge. The soil-water characteristic curves were measured for three different types of fine-grained soils. The three soils used in the study were processed silt (liquid limit, wL = 24%; plasticity index, Ip = 0; and clay = 7%), Indian Head till (wL = 35.5%, Ip = 17%, and clay = 30%), and Regina clay (wL = 75.5%, Ip = 21%, and clay = 70%). The soil-water characteristic curves for the above soils were measured in 0.5, 1, and 2 days, respectively, using the centrifuge technique for suction ranges from 0 to 600 kPa. Time periods of 2, 4–6, and 16 weeks were required for measuring the soil-water characteristic curves for the same soils using a conventional pressure plate apparatus. There is reasonably good agreement between the experimental results obtained by the centrifuge and the pressure plate methods. The results of this study are encouraging as soil-water characteristic curves can be measured in a reduced time period when using a small-scale centrifuge.Key words: unsaturated soils, soil-water characteristic curve, centrifuge technique, soil suction, matric suction, water content.

A reexamination of the permeability index of clays: Discussion

The authors have made a good attempt to generalize the relationship between void ratio and coefficient of permeability for all types of fine-grained soils. An alternate equation for normally consolidated soils has been suggested based on limited data on two Cochin clays. Similarly, for sensitive soils some selected published data were used to obtain a generalized equation. It will be useful for the practicing engineers if such a generalization could be made. Besides the work reported by the authors, there are other correlations which may also be applicable. One such equation is given as follows (observed from data reported by Mesri and Olson 1971): [ l ] l o g e = A + B l o g k where e is void ratio, k is coefficient of permeability, and A and B are empirical constants. The exponential form of the same equation bas been used by Samogyi (1979) and is given by