Study The Consequence of Fly Ash on Some of Physical Soil Characteristics

Study the consequence of adding fly ash (FA) on the Atterberg limit; cohesions and internal friction of angles of the verified soil was the aim of this search. The tested soil according to the system of unified soil classification was (CH) group. Fly ash (FA) was added to the tested soil samples in 1, 3, 6, 9, 12, 15 & 18 % by weight of samples. This study shows that once the tested soil mixed with (FA); the values of cohesion reduced; while the values of the angles of internal frictions increases. The drop in the soil sample cohesion when mixed with 18% of (FA) was 34%, were noteworthy increase in the angles of internal friction. For all soil samples as the percentages of adding (FA) increase, the decrease in the index of plasticity amounts increase also at different rates. The adding of (FA) produced a reduction in the liquid limits; plastic limits and henceforth the plasticity index of the tested soil sample at rate of 43%, 48% and 37% correspondingly. The plasticity index losses took place at the first 3%, at a lesser rate, then the rate increased at 18% of additive and because nearly constant.

Forecasting the Compressibility Parameters of Gypseous Soil using Artificial Neural Networks

To ensure safe design of structures against settlement, it is necessary to determine the compressibility parameters of the underneath soil especially compression and rebound indices. In this paper, an approach to forecast the compressibility parameters of gypseous soils based on index parameters was developed using Artificial Neural Networks technique. Two equations were developed to estimate compression and rebound indices using back propagation algorithm to train multi-layer perceptron, in which good agreements were achieved. The input parameters used were: the depth, gypsum content, liquid limit, plastic limit, plasticity index, passing sieve No.200, dry unit weight, water content and initial void ratio. Two output parameters were determined including compression index and rebound index. A parametric study was also conducted to investigate the generalization and robustness of both models. The findings indicate that both models were reliable within the range of utilized data. It was found that gypsum content has the highest effect on the compressibility index followed by water content, plasticity index, dry unit weight and plastic limit, while other parameters have lower effect. The gypsum content has the highest effect again on the rebound index followed by passing sieve No.200, initial void ratio, plastic limit and plasticity index, while other parameters have lower effect.

Analysis of the current scenario of Compressed Earth Block (CEB) production

The main objective of this study is to identify the parameters that influence the quality of the production of compressed earth blocks (CEB). Thus, an analysis of the performance of the materials that make up the final product was carried out, such as the binders that act as chemical stabilizers and the different types of soils, also the mechanical resistance and durability tests and finally the technical standards for its manufacturing. For this aim, a literature review was carried out in three electronic databases, Scopus, Web of Science and Scielo. The results showed environmental concerns with the use of Portland cement for stabilization, therefore, 18% of the studies used agricultural residues and 25% used mineral by-products, for partial or total replacement of Portland cement. Soils with plasticity indexes between 15% and 30% have a stabilization success rate of 69%, while soils with plasticity index less than 15% have a stabilization greater than 93%, which can be increased to 100% if the soil have a percentage of clay and silt between 21 and 35%. On the other hand, a plasticity index above 30% negatively affects stabilization. The compaction energy applied in the manufacture of CEB is an important parameter, as it influences the density, thermal conductivity and mechanical strength. Among the sustainable construction techniques, CEB is a great option, as it can be done locally and with ease of construction.

Influence of leachates on geotehnical and geochemical properties of termite mound soils

This study investigated the influence of leachate prepared from Telfairia occidentalis on the geotechnical and geochemical properties of termite mound soil obtained from the premises of the federal university of agriculture, Abeokuta, south-western Nigeria. The termite mound soil samples were collected from three different locations and each sample collected was contaminated by mixing with leachates in percentage increments of 0% 10%, 15% and 20% of dry weight of the air-dried soil. The soil samples were subjected to Atterberg limits and hydraulic conductivity tests for geotechnical observation and X-ray fluorescence tests for geochemical tests. The range of values for the geotechnical analyses were obtained as; plastic limit (9.1% – 14.2%), liquid limit (28.6 % – 61%), plasticity index ((18.2% – 49.5%) and hydraulic conductivity (1.85 – 4.1 x 10-8) cm/sec) with a resultant reduction in the plastic limit, liquid limit and plasticity index values but an increase in the hydraulic conductivity of the samples as the leachate concentration increased. The results from X-ray fluorescence analyses after 20% leachate contamination showed that the major elemental chemical composition for the three samples were comprised of SiO2 (56.25 – 56.5%), Al2O3 (28.42 – 28.50%), Fe2O3 (4.46 – 6.5%), TiO2 (1.08 – 1.23%), CaO (1.45 – 1.60%), P2O5 (0 – 0.04%), K2O (0.9 – 6.1%) and MnO (0.02 – 4.7%). There was a marginal alteration of the indices with the values inferring the presence of a minimum composition of feldspar and a major composition of quartz-rich minerals and thus lending more credence to the presence of silicates as shown from the X-ray fluorescence results. It also infers that the termite mounds are predominantly made from sand materials. The termite soil samples obtained from the aforementioned locations may not be suitable for engineering works unless stabilization procedure is adopted.

Analysis of the ratio between the plasticity of clay and the expansion capacity by changes in humidity and temperature

Clay is a cohesive material that varies in volume due to changes in humidity and temperature. Its behavior is studied with physical and geotechnical characterization of the material. The experimental analysis of the expansiveness of clays is related to plasticity, which depends on the expansive minerals it contains. The objective is to analyze the relationship between the plasticity index and the expansion capacity due to changes in humidity and temperature; various types of clay from San José de Cúcuta, Colombia, were studied. Liquid limit and plastic limit were analyzed with which the plasticity index was determined. The test tube free expansion and calcination were carried out at 1000 °C to determine the volumetric change due to humidity and temperature, respectively. The clays with plasticity index of 10% - 20% presented expansion by humidity of 5% - 10% and by calcination of 0% - 10%, which indicates low expansion; while the clay with plasticity index of 20% - 40% presented expansion by moisture of 20% - 50% and by calcination of 25% - 50%, which indicates moderately high expansion. The results show that there is a relationship between plasticity index and the expansion capacity due to changes in humidity and temperature.

Experimental Investigation on the Microstructural Properties of Black Cotton Soil Stabilized with Cinder (Scoria) Fines and Class-C Fly Ash

Black cotton soil is one of the significant problematic soil for any civil or geotechnical engineering application in the whole world. In the past several decades, different experimental studies have been carried out on the stabilization of expansive soil and different types of stabilizers like lime, Portland cement, cement fly ash, and lime fly ash were used and applied in highway and others construction. However, those traditional stabilizers are not environmentally friendly thus further scientific study is needed to minimize the percentage of carbon-based stabilizers. The fact that Ethiopia encountered major engineering problems due to these problematic soils many researchers have been conducted a vital study using traditional stabilizers for several years however there is no significant study on the microstructural properties of stabilized black cotton soil. In this study, a scoria fines and class c fly ash are used at different blended groups, for each group, the stabilizer content ranges from 10 to 30%. The liquid limit and plasticity index of the soil has been decreased with the increasing content of class c fly ash (FA) and cinder fines (CF). Especially after the soil treated with 25% of class c fly ash and 25% of cinder fines, the liquid limit has decreased by 51.61% and, the plasticity index by 78.61%, linear shrinkage by 66.58%, and the free swell index decreased by 78.9%. The CBR and UCS value has increased by 86.2% and 83.9%, respectively, and CBR swell reduced by 61.2% with increasing stabilizer content. The microstructural properties of Raw black cotton soil and samples that are selected based on strength and index properties (BCS+FA3, BCS+CF3, BCS+CF+FA3) were observed by Scanning electron microscopy (SEM) imagining device, and the result clearly shows the alteration in fabric and morphology of the sample. After treatment with class c fly ash and cinder fines, the laminated configuration of black cotton soil has changed to more flocculated and coherent mass. Also, the SEM image proves that cinder fines impart a mechanical bonding that forms well-developed floccules and a more porous nature. These types of particle arrangement and clay aggregation bring the improvement in index and strength properties.

Site Investigations of the Lacustrine Clay in Taihu Lake, China, Using Self-Boring Pressuremeter Test

Site investigations of the soils are considered very important for evaluation of the site conditions, as well as the design and construction for the project built in it. Taihu tunnel is thus far the longest tunnel constructed in the lake in China, with an entire length of over 10 km. However, due to the very insufficient site data obtained for the lacustrine clay in the Taihu lake area, a series of self-boring pressuremeter (SBPM) field tests was therefore carried out. Undrained shear strengths were deduced from the SBPM test, with the results showing generally higher than those obtained from the laboratory tests, which may be attributed to the disturbance to the soil mass during the sampling process. Degradation characteristics of the soil shear modulus (Gs) were mainly investigated, via a thorough comparison between different soil layers, and generally, the shear modulus would cease its decreasing trends and become stable when the shear strain reaches over 1%. Meanwhile, it was found that a linear relationship between the plasticity index and the shear modulus, and between the decay rate of the shear modulus and the plasticity index as well, could be developed. Further statistical analysis over the undrained shear strength and shear modulus distribution of the soils shows that the undrained shear strength of the soils follows a normal distribution, while the shear modulus follows a log-normal distribution. More importantly, the spatial correlation length of the shear modulus is found much smaller than that of the undrained strength.

Effects of Soil Bulk Density and Moisture Content on the Physico-Mechanical Properties of Paddy Soil in Plough Layer

For paddy-upland rotation areas in the middle and lower reaches of the Yangtze River, the paddy soil has undesired physico-mechanical properties of tillage during the dry season. The purpose of this study is to determine the effects of soil bulk density and moisture content on the physico-mechanical properties of paddy soil in the plough layer. The bulk density and moisture content were selected as experimental factors, and the cohesion, tangential adhesion, plasticity index, and soil swelling rate were chosen as experimental indices from physico-mechanical properties of paddy soil in the plough layer. The experimental factors were quantitatively analyzed to explore the change characteristics of the physico-mechanical properties of paddy soil in the plough layer. Conclusions were obtained that show that when the bulk density increased in the range of 1 to 1.6 g·cm−3, the cohesion, tangential adhesion, plasticity index, and swelling rate of paddy soil increased in different degrees. Between 15% and 35% moisture content, the cohesion increased first and then decreased with the increase of moisture content, while the peak cohesion value occurred at the moisture content of 20%. Moisture content was positively correlated with tangential adhesion and negatively correlated with soil swelling rate. This study provides a reference for the regulation of paddy soil tillability in the middle and lower reaches of the Yangtze River Basin.