Experimental Study On The Tensile Strength Of Basalt Fiber Reinforced Soil

Because the tensile strength of the soil is relatively small,there is less relevant research.In fact,the tensile failure of soil is a problem that can not be ignored in geotechnical engineering.Many engineering problems in reality are related to the tensile strength of soil.For example,the tensile fracture around the foundation of the high voltage wire,the stretching fissures on the top of the soil sliding slope,and the uneven settlement of the ground are all manifestations of the tensile damage of the soil.Experts and scholars all over the world have carried out research on the related properties of fiber reinforced soil and found that,as a new type of improved soil material,fiber can effectively enhance the strength and deformation of soil.Fiber reinforced soil is a composite soil in which fibers and soil work together by adding synthetic fibers to the soil.At present,fiber reinforced soil is widely used in subgrade,building foundation,slope retaining wall and river bank engineering.However,since the research on fiber reinforcement mechanism is not consummate,fiber soil synthesis materials have not been widely used and generalized in engineering.Therefore,the study of the tensile properties of fiber reinforced soil not only has theoretical significance for improving the strength theory of soil.It has practical application value for solving complex problems of geotechnical engineering.Loess is a kind of sediment composed of sand and sticky particles.It generally has well developed tubular pores and vertical joint development,and is widely distributed in Shaanxi and other northwest places in China.With the progress of society and the development of economic construction,the study of the characteristics of loess such as pressure resistance,shear resistance,tensile resistance and deformation has gradually been put on the agenda,and the study of the tensile resistance of loess has become more and more.This article mainly focuses on the tensile properties of basalt fiber reinforced loess.The effect of length ratio,tensile rate,fiber content,fiber length,water content and compaction on the tensile properties of fiber reinforced loess is analyzed by uniaxial tensile test.The stress-strain relationship,strength characteristics and failure mechanism are investigated.The test results show that :(1)The tensile strength varies with the length-diameter ratio and tensile rate of the sample for the loess.The larger the length-diameter ratio,the smaller the tensile strength,the faster the tensile rate,and the greater the tensile strength.The laboratory test should select the appropriate length ratio and tensile rate.(2)The tensile strength of the basalt fiber reinforced loess decreases with the increase of the fiber length and the amount of fiber admixture,reaching the maximum value when the fiber admixture is 0.3% and the fiber length is 12 mm.Under the optimal reinforcement condition,the tensile strength increased by 70.5 % over the prime soil.(3)With the increase of water content,the tensile strength of loess and basalt fiber reinforced loess gradually decreases;With the increase of compaction,the tensile strength of loess and basalt fiber reinforced loess gradually increases.The low water content and high pressure reality are more conducive to the development of sample pulling.(4)From the stress-strain relationship curves and failure patterns of loess and basalt fiber reinforced loess it can be seen that the stress of loess and basalt fiber reinforced loess increases with the increase of strain within a certain range.However,after the loess tensile strength reaches its peak,the stress decreases dramatically while the strain stops increasing,and the tensile strength is almost completely lost.At this time,the sample suddenly breaks,the damage process is brief,the fracture develops rapidly,and there are no signs,showing obvious brittle damage.However,after the basalt fiber reinforced loess reaches its peak strength,the tensile strength is reduced but it still has a certain bearing capacity,showing gradually brittle damage.The reinforcement of the fiber increases the peak displacement and strength of the loess and improves the toughness of the soil.And the soil shows the characteristics of cracking and continuous.(5)Loess and basalt fiber reinforced loess sample reachs the tensile strength limit,the tensile section has not broken,and only minor cracks or cracks that are not visible to the naked eye appear on the surface.After reaching the tensile strength limit,the fracture of the tensile section of the loess sample is rapidly developed into a through crack,and the sample is quickly pulled off;Basalt fiber reinforced loess sample fissure development speed is delayed,after the cracking load can continue to withstand the load,the fissure slowly developed into a through crack,and finally showed a "split and continuous" state,the fiber of the fracture surface appeared to be pulled out state,The difference of crack development time and tensile strength of basalt fiber-reinforced soil sample was significantly greater than that of loess sample.