Strength Characteristics Of Fiber-reinforced Soil

Fiber-reinforced soil is a kind of compound soil which is mixed with a definite proportion of fibers. Fiber belongs to the category of the geosythetic materials, but compared with other geosythetic materials, researching on fiber is less and the corresponding achievements are not yet remarkable. As the result, the theoretical research on fiber reinforcement technique has lagged behind its practical level, which severely hinders a large-scale promotion and application of fiber reinforcement technique. In this paper, shear strength characteristics of fiber-reinforced sand and unconfined compression strength characteristics of fiber-reinforced cemented clay were firstly studied, then the mechanism of fiber reinforcement was discussed. The results showed that:1. Fiber can effectively improve shear strength and ductility of sand. And 0.4% is the critical fiber content of fiber-reinforced sand, which makes the cohesion of fiber-reinforced sand to reach to the peak. However, fiber content has no obvious effect on internal friction angle of reinforced sand.2. The shear strength characteristics of glass fiber reinforced soil can be improved effectively at low water content, the fiber content 0.4% and high relative density conditions.3. Fiber can effectively increase unconfined compression strength of clay, and when fiber content is 0.6%, unconfined compression strength of clay reaches to the peak and then decreases with fiber content increasing. Similarly, unconfined compression strength of fiber-reinforced cemented clay reaches to maximum when the fiber content is 0.6%. Besides, fiber can effectively improve the ductility of cemented clay.4. Cement can significantly increase unconfined compression strength of clay,which increases with cement increasing. But cement weakens the ductility of clay in the same time. Unconfined compression strength of fiber-reinforced cemented clay increases with the curing time increasing, and reach to the peak at 28 th day.5. The increase of shear strength of fiber-reinforced soil is the result of increase of normal stress and decrease of shear stress on the shear surface. Furthermore, the increase of shear strength is relative with orientation of fiber, which can achieve the optimal reinforcing effect when the orientations of fiber and the maximum tensile stress are the same.6. Because the deformations of fiber and soil are coordinative, to maintain this coordination of deformations, fiber restrain the deformation of soil. And the restraint is the equal of lateral pressure △σ3 imposed on soil, which increase the unconfined compression strength of soil.