Effect of Tea Waste on Cracking of Foundation Soil

Desiccation cracks form on the surface of foundation soils due to matric suction and surface shrinkage with water loss. This paper investigates the effect of tea waste on the change of water content and cracking characteristics of foundation soil during drying. Digital image processing was carried out based on laboratory experiments. The characteristics are monitored with a variation in water content. The effects of different amounts of tea waste on soil drying and cracking were obtained, in order to provide an efficient and new green sustainable material for improving soil evaporation cracking under drought conditions. The results show that the development of cracks of soil samples with tea waste can be categorized into three stages in accordance with the fractal dimension of the desiccation cracks: Stages I, II, and III. The desiccation cracks in Stage III are wider and longer than those in Stages I and II, however, the maximum fractal dimension and stability are also obtained in Stage III. The residual water content of the sample without tea waste is 1.5%. The residual water content of the samples containing 4% and 8% tea waste is 4.6% and 5.4%, respectively, which shows that the tea waste can effectively improve the residual water content of the foundation soil and the water holding capacity of the soil. The fractal dimension of cracks on the soil samples increases gradually with drying. The total length of cracks increases and the development of cracks is more complex. The cracking time of soil samples with different tea waste contents is different. The soil samples with 8% tea waste content crack first. Combined with the variation characteristics of water content, tea waste has water absorption and improves the water holding capacity and stability of foundation soil.

Influence of Clay Fraction and Mineral Composition on Unsaturated Characteristics of Cohesive Foundation Soil in Airports

Taking unsaturated clay foundation soil of an airport project in Hefei as the research object, the effects of particle gradation and mineral composition on the unsaturated soil properties were analyzed through two kinds of tests. The results show that there is a good correlation between the residual water content and the clay fraction or silt fraction content in the grading, and the residual water content has a significant positive linear correlation with the clay fraction content, but a negative linear correlation with the silt fraction content. Residual matric suction has a nonlinear correlation with clay fraction or silt fraction content in gradation, which has a significant nonlinear negative correlation with clay fraction content and a positive nonlinear correlation with silt fraction content. The residual water content and the residual matric suction have obvious linear relationship with the content of montmorillonite but have no obvious correlation with the content of illite. The water-storage coefficient of unsaturated airfield foundation soil decreases exponentially with the increase of clay content and montmorillonite content.

Residual Water Content and Water Saturation of Bazhenov Formation Cores

The article presents a new method of determining the residual water content and water saturation of the Bazhenov rocks formation (unconventional reservoir), which is contingent on the synchronous thermal analysis integrated with gas FT-IR spectroscopy and mass spectroscopy. The studies were executed on extensive factual core material. The combination of thermal and spectrometric methods for the identification of gases which are released during heating of core samples facilitated to analyze the dynamics of water release and proposed methods of its separation accordingly by the degrees of connectivity.

Prediction of Soil-Water Characteristic Curve of Compacted Loess With Different Dry Densities Based on Nuclear Magnetic Resonance

Accurate determination of soil-water characteristic (SWCC) is of great importance for understanding the mechanical properties of unsaturated loess. In this study, the compacted loess columns with different dry densities were prepared. Moisture sensor, water potential sensor and nuclear magnetic resonance (NMR) were used to investigate the SWCC and NMR signals intesity of compacted loess under different dry densities. It has been found that with increasing dry density, the saturated water content and the residual water content gradually decreases, but the decrease in residual water content is smaller, and both can establish a linear relationship with dry density. The NMR results showed that the compacted loess pore volume gradually decreased with increasing dry density. When the dry density increased from 1.45 g/cm3 to 1.55 g/cm3, the pore volume of compacted loess decreased by 14.7%, while when the dry density increased from 1.55 g/cm3 to 1.65 g/cm3, the pore volume of compacted loess decreased by 13.2%. The Van Genuchten (VG) model was used to fit the NMR results and SWCC, and a good corresponding relationship was found between the parameters. Therefore, according to the cumulative NMR intensity parameters, SWCC was predicted under different dry densities and the effect was found very well.

Estimating soil water retention for wide ranges of pressure head and bulk density based on a fractional bulk density concept

Soil water retention determines plant water availability and contaminant transport processes in the subsurface environment. However, it is usually difficult to measure soil water retention characteristics. In this study, an analytical model based on a fractional bulk density (FBD) concept was presented for estimating soil water retention curves. The concept allows partitioning of soil pore space according to the relative contribution of certain size fractions of particles to the change in total pore space. The input parameters of the model are particle size distribution (PSD), bulk density, and residual water content at water pressure head of 15,000 cm. The model was tested on 30 sets of water retention data obtained from various types of soils that cover wide ranges of soil texture from clay to sand and soil bulk density from 0.33 g/cm3 to 1.65 g/cm3. Results showed that the FBD model was effective for all soil textures and bulk densities. The estimation was more sensitive to the changes in soil bulk density and residual water content than PSD parameters. The proposed model provides an easy way to evaluate the impacts of soil bulk density on water conservation in soils that are manipulated by mechanical operation.