Abstract
In order to study the influence of the vetiver root system on the swelling characteristics and crack resistance of expansive soil, vetiver grass root growth and its vertical distribution were investigated by the cultivation test and observation. The expansion rate experiment without load and expansive force tests was conducted on planted grass root soil samples, and the effect of the root content on the expansion rate and force of soil mass was analyzed. Finally, the effects of different vetiver contents on the crack resistance of expansive soil were studied by soil cracking experiments in an outdoor natural environment. The results showed that on account of the reinforcement effect of crisscrossing and winding grassroots, the expansion rate and expansive force can be reduced by the grass roots, and the grass roots can significantly increase the anticracking properties of the root‐soil composites. From the surface down, the inhibition effect of the vetiver root on the expansive soil appeared from low to high and then decreased; the effect was optimal in the layer of 10∼15 cm. Compared with the pure expansive soil, the swelling force of the cultivated root expansive soil growing for 180 d decreased by more than 80%, and the unloaded expansive soil reduced by more than 70%. Compared with pure expansive soil, the swelling force and the unloaded expansion rate of cultivated root expansive soil growing for 90 d decreased by more than 50%.
Highlights
Called as “cracked soil,” and cracks have a significant impact on strength index and slope instability [1]. erefore, the instability mechanism and treatment aspects of expansive soil slopes have been widely studied [2,3,4,5,6]. e existing protection methods are roughly divided into two categories [7]: limiting crack development and not limiting crack development
Not limiting crack methods were directly applied to deal with expansive soils, such as the retaining structure method, slope protection method, geotechnical bag method, and physical improvement method. e main methods for restrictive crack development include the geomembrane method, algorithm change, and chemical improvement method and achieve targeted protection from the perspective of water and particles
Zhou et al [28] carried out a confined expansion test and a direct shear test on expansive soils with different initial water contents, and the results have shown that the vetiver root system could reduce the expansive force and increase the shear strength
Summary
Called as “cracked soil,” and cracks have a significant impact on strength index and slope instability [1]. erefore, the instability mechanism and treatment aspects of expansive soil slopes have been widely studied [2,3,4,5,6]. e existing protection methods are roughly divided into two categories [7]: limiting crack development and not limiting crack development. E change in water content is the main reason for the fracture of expansive soil [1] Their findings indicate that vegetation evaporation could slow down the cracking process of the expansive soil. Some scholars have studied the mechanical effects of roots on composite soils and found that the existence of roots could enhance the strength of composites [15,16,17,18,19,20] On this basis, Wang et al [21] show that rice straw can slow the cracking of reinforced soil and declared that the best rate of rice straw is 0.3%. The use of vetiver and other ecological protection methods to treat expansive soil slope disease has been used more and more, the design and construction are mostly based on the experience of engineers, and there is no theoretical support. erefore, the research on the influence of the vetiver root system on the swelling characteristics and crack resistance of expansive soil has an important theoretical significance and engineering application value to inhibit the expansion mechanism of expansive soil and dry shrinkage cracking
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