Some Geotechnical Properties of Clay Soil Enhanced with Silica Fume

Engineering structures found in, or on, some clay soil types may be subject to different damages due to the problematic nature and unfavorited properties of these soils. The unfavorited properties of these soils include shrink and swell changes, high settlement, and low bearing capacity. These soils have high sensitivity to moisture change. The way to reduce or overcome the unfavorited properties of problematic soils is the treatment or enhancement of these soils using different mechanical or chemical methods. In the present paper, silica fume selected as a soil stabilizer material, the effect of different contents of this material on the geotechnical properties of expansive clay soil has been experimentally investigated. Tests included soil specific gravity, soil plasticity, soil compaction, and soil compressibility. It was noted that silica fume, with different contents, decreased the specific gravity, and compaction density, while the compaction water content and Atterberg limits increased. The consolidation parameters of the expansive clay soil were affected by adding the silica fume. The silica fume reduced the consolidation parameters values of the clay soil. At low content silica fume, less than 10%, a very slight reduction can be seen especially for the rebound index value. The final findings of this paper appeared that the high settlement of clay soil can be reduced with the presence of silica fume.

A Review on Effect of Temperature Change on Mechanical Parameters of Fine Soils

Temperature change in soils and its possible effects date back to 20th century where temperature difference between laboratory and field for sampling made researchers interested in this topic. Due to development of technology and industry nowadays, new engineering applications such as nuclear waste disposal, oil extraction and pipelines, geothermal structures etc. have turned temperature change in soils to one of the high trending research topics where suitable knowledge of thermal effects on soils is required. For this purpose, it is tried at first to highlight the importance of temperature effect on geotechnical design by some examples and possible effect of temperature change on mechanical properties of fine soils are reviewed afterward. Investigation on results from literature proved that temperature change could alter some strength and consolidation parameters of fine soils. Different factors are proposed to be responsible for such thermally induced changes in mechanical parameters, however, existing explanations and comments from literature are diverse and not fully understood yet. In order to fill this gap, it is tried to find connections between different mechanical parameters and their behavior toward temperature change and possibly find a unified approach and factor to explain the mechanism responsible for thermally induced changes in mechanical parameters of fine soils. Finally, at the end, it is concluded that effect of temperature on structural rearrangement of solid particles could be a promising factor to connect the responses of different mechanical parameters toward temperature change.

Consolidation parameters in silts from varied rate CPTU tests

<abstract> <p>The interpretation of dissipation tests from cone penetration tests (CPTU) in silt is often considered challenging due to the occurrence of an unknown degree of partial consolidation during penetration which may influence the results significantly. The main objective of the present study is to investigate the influence of penetration rate and hence partial consolidation in silt deposits on the interpretation of consolidation parameters. Rate dependency studies have been carried out so as to give recommendations on how to establish design consolidation parameters in silts and consider the effect of partial consolidation on the development of design parameters. A comprehensive field and laboratory research program has been conducted on a silt deposit in Halsen-Stj?rdal, Norway. Alongside performing various rate penetration CPTU tests with rates varying between 0.5 mm/s and 200 mm/s, dissipation tests were executed to analyze the consolidation behaviour of the soil deposit. Furthermore, a series of soil samples have been taken at the site to carry out high quality laboratory tests. Correction methods developed for non-standard dissipation tests could be successfully applied to the silt deposit indicating partial consolidation. The results revealed an underestimation of the coefficient of consolidation if partial consolidation is neglected in the analysis, emphasizing the importance of considering the drainage conditions at a silt site thoroughly. To study the drainage conditions of a soil deposit a recently proposed approach has been applied introducing a normalized penetration rate to differentiate between drained and undrained behaviour during penetration. It is suggested that a normalized penetration rate of less than 0.1–0.2 indicate drained behaviour while a normalized penetration rate above 40–50 indicate undrained behaviour. Finally, available dissipation test data from a Norwegian Geo-Test Site (NGTS) in Halden, Norway have been used to successfully verify the recommendations made for silts.</p> </abstract>

Unified Evaluation of Consolidation Parameters for Low to High Plastic Range of Cohesive Soils

Knowing the engineering properties of geomaterials is imperative to make the right decision while designing and executing any geotechnical project. For the economical and safe geotechnical design, quick characterization of the compressibility properties of the cohesive soil is often desirable; these properties are indeed tedious to determine through actual tests. Therefore, correlating the consolidation parameters of the soils with its index properties has a great significance in the geotechnical engineering field. Several attempts have been made in the past to develop correlations between the consolidation parameters and index properties of the cohesive soils, within certain limitations. However, there is still a need to develop such correlations based on the extensive database, composing of unified plasticity range of soils, i.e., low to high plasticity. In the current study, 148 undisturbed soil specimens were obtained from different areas of Pakistan. Out of which 120 samples were utilized to develop correlations, and 28 samples were used to check the validity of the developed correlations. In order to enhance the index properties database, 30 more bentonite mixed soil samples were prepared and tested accordingly. Correlations to envisage different consolidation parameters such as compression index, compression ratio and coefficient of volume compressibility were developed using 150 cohesive soil samples of low to high plasticity. In addition, the performance of these developed correlations was verified on a set of 40 soil samples and compared with the performance of different correlations available in the literature. The percentage deviation in the prediction of compressibility characteristics through developed correlations in the present study was found to be very less, which endorsed the excellent reliability of the developed correlations.

Study on the consolidation properties of soft soil distributed in the North Center coastal area of Vietnam

Consolidation parameters of soft soil play an important role in calculating settlement and soft soil improvement by vertical drainage method (distance, quantity, treatment time). In this study, using oedometer tests, consolidation parameters of some soft soils in the North Central coastal region, Vietnam are clarified. The research results show that the compression index Cc has a strong relationship with the natural water content, liquid limit, dry unit weight, and void ratio of the soil. The consolidation coefficient significantly depends on the applied pressure level, at the over-consolidation stage (normal stress is less than pre-consolidation pressure), the consolidation coefficient is high. By contrast, at the normal consolidation stage (normal stress is greater than pre-consolidation pressure), the coefficient of consolidation is small. The pre-consolidation pressure of soil changes with the distribution depth.