Effect Of Inclusion Of Basalt And Glass Fibers On Tensile Behaviors Of Clay

With the development of geotechnical and geological engineering,more and more attentions have been paid on the tensile behaviors of clay soils.However,natural clay soil often has low tensile strength and easily causes tensile failure in soil.Due to their excellent mechanical properties and low cost,basalt fiber and glass fiber have been widely used to improve the consolidation and shear properties of soft soils in recent years.However,the current researches have not yet involved whether these fibers can improve the tensile properties of clay soil.Uniaxial direct tension tests were conducted through a strain-controlled tensile apparatus in this thesis.The tensile behaviors of remolded clay,basalt fiber-reinforced clay and glass fiber-reinforced clay were investigated under different dry density and moisture content.The change of tensile strain energy density during tensile test process was also discussed.With the experiments and analyses,the following conclusions can be drawn.(1)Moisture content and dry density has a great influence on tensile strength for both clay and fiber-reinforced clay.The tensile strength first increases and then decreases with the increasing moisture content,and increases linearly with the increasing dry density.Changes in the height and diameter of soil samples have little effect on the tensile strength if the ratio of height to diameter is the same.(2)Basalt fiber and glass fiber can effectively improve the tensile strength of clay.Compared with the tensile strength of the non-fiber clay,the basalt fiber-reinforced clay can increase up to 3 times and the glass fiber-reinforced clay can increase by 2 times at most when the dry density is 1.56g/cm3.When the water content is 16%,the tensile strength of the basalt fiber-reinforced clay can be raised up to 3.3 times and the glass fiber-reinforced clay can increase up to 3.9 times at most.(3)The tensile stress-strain curves of soil samples can be classified into five types.The ascending segment of types ? and ? curve is rapid while the descending section of is slow for type I and first fast then slow for type ?.Type ? curve are slow for both rising and falling segments.The rising section of type IV curve is first fast then slow,and the descending section is fast,slow and fast.The ascending segment of V-type curve rises quickly and when the tensile stress reaches the maximum,it immediately decreases to a low value and even to zero.The types of tensile stress-strain curves have not increased with fiber-reinforced clay.Under the same conditions,however,the stress-strain curves are different between fiber-reinforced clay and non-fiber clay.(4)The peak strain is mainly determined by moisture content and increases with the increasing moisture content.For an identical water content,the peak strain first increases and then decreases with the increase of dry density.When the dry density is small,the peak strain of the fiber-reinforced clay is smaller than that of the non-fiber clay,and it is the opposite when the dry density is larger.When the dry density is fixed,the peak strain increases with the increase of water content,and the peak strain of the non-fiber clay is greater than that of the fiber-reinforced clay.(5)The tensile energy is determined by the stress-strain curve and the tensile strength of the clay.When the water content is given,the strain energy density of the clay increases with the increase of dry density and the strain energy density of the fiber-reinforced clay is greater than that of the non-fiber clay.When the dry density is fixed,the strain energy density of clay first increases and then decreases with the increase of water content,and the difference of the strain energy density between the fiber-reinforced clay and the non-fiber clay is very small.