Effects of Quartzite on the Desiccation Cracks of Clayey Soils Exposed to Wetting-Drying Cycles

The compacted clayey soils crack on drying because of their high swelling potential, and their hydraulic conductivities increase. To solve this problem, it is essential to stabilize the clayey soils using additive materials. The aim of this study is to examine the suitability of quartzite as a stabilization material to reduce the development of desiccation cracks in compacted clayey liner and cover systems. Experimental study was conducted to investigate the effect of wetting-drying cycles on the initiation and evolution of cracks in compacted clayey soils. For experimental studies, seven samples were prepared stabilized by using 0%, 2.5%, 5%, 7,5%, 10%, 12,5% and 15% quartzite and then they were subjected to four subsequent wetting-drying cycles. The results show that quartzite decreases the development of desiccation cracks on the surface of compacted samples. It is concluded that quartzite as a geological material can be successfully used to reduce the development of desiccation cracks in compacted clayey liner and cover systems exposed wetting-drying cycles.

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.

Desiccation cracks behaviour of leachate in bentonite - zeolite composite liner

This study tested desiccation crack potential and migration of metals through pure bentonite and bentonite-zeolite composites to determine the best composition of the composite liner. Pure bentonite (B) and bentonite-zeolite composites of 2% (B2), 5% (B5), and 8% (B8) were used as controlled variables. The results showed that the addition of zeolite could not minimize the desiccation behavior in the liner. The value of crack intensity factor (CIF) of each sample B, B2, B5, and B8 was 3.44%, 3.51%, 3.58%, and 3.64%, respectively, indicating a moisture content of 29.95%, 34.54%, 30.88%, and 28.21%, respectively.

The Influences of Sand Content and Particle Size on the Desiccation Cracks of Compacted Expansive Soil

The desiccation cracks in expansive soil, which are a common natural phenomenon, have a significant negative impact on the engineering properties of the soil and are the direct cause of many engineering problems and geological disasters. This study aims to investigate the influences of sand content and particle size on desiccation cracks of the compacted expansive soil. First, samples of compacted expansive soil with five sand contents and four sand size groups were prepared. Then, a series of drying tests were performed. The dynamic variation of geometric parameters of the surface crack network during evaporation was quantitatively analyzed by using digital image processing technology and fractal theory. The results demonstrated that the increase of the surface-cracking areas in the early and later stages was manifested by the increase of the crack length and crack width, respectively. In the same size of sand particle group (0.15, 0.3 mm), as the sand content (dry weight ratio of soil sample) increased from 0% to 40%, the surface-cracking ratio (the ratio of the crack area to the total surface area of the soil sample) showed a decreasing trend (13.20%, 11.42%, 10.50%, 8.98%, and 7.71%, respectively). When the sand content (40%) was the same, as the sand size groups increased from [0.15 mm, 0.3 mm) to [1.18 mm, 2.36 mm), the surface-cracking ratio also presented a decreasing trend (7.71%, 7.69%, 4.35%, and 3.73%, respectively). The changing law of the fractal dimension of cracks was the same as that of the surface crack ratio. During the drying process, the deformation of the sample was characterized by centripetal shrinkage or cracking, which were mainly affected by the boundary conditions of the sample. This research’s results verify the effectiveness of sand to improve the dry-shrinkage characteristics of expansive soil, providing a reference for the improvement of roadbeds and the treatment of soil slopes in expansive soil areas.