Study On Tensile Strength Characteristics Of Loess

Chinese loess distribution area is the largest in the world, the famous loess plateau is located in the northwest of China,where the buildings were built on the basis of the loess.the Buildings to grassroots, mountain slope, road embankment and the dam were made up of loess as the main filler.for its strength characteristics affect the stabilization of structure foundation and play a decisive role on foundation treatment and design of the engineering structure. In addition, loess, as a kind of special soil,has special properties and its mechanical properties has very big difference with the general soil, therefore, the case for in-depth research has great theoretical and practical significance. The mechanical characteristics of loess is the most important factor that influences the stability of buildings, slopes, tunnels and underground structures et al. The researches on its tensile strength and the related properties are not very abudant compared with the studies on shear strength, collapsibiliy and other properties of loess. The tensile strength of soils are seldom considered in the engineerig exploration, design and stability analysis, which is because its tensile capacity is too weak thus seemes meaningless to common engineering. However, with more and more frastructures in loess areas constructed, such as railway, highway,airport and high earth-rock dams et al, and also due to the frequent burst of natural hazards(e.g. landslide, slope avalanche), the tensile strength and anti-cracking capacity of loess would be much more significant to the stability of earth-structures in loess on the one hand.The paper will lead to Lanzhou Jiuzhoutai remodeling loess, Wang jiagou and Xujiachuan tunnel of Bao-Lan Passenger Transport Line undisturbed loess as the test soil samples, then the tensile properties of loess are studied from two aspects of internal and external influencing factors by axial fracturing method. On the one hand,the research is the effect of soil water content and dry density on the tensile strength.On the other hand, the research is the testing parameters about tensile strength of soil in the process of research, and giving detailed analysis, finally making a comprehensive and systematic explanation in this paper.1. The internal influence factors of test results indicate that the tensile strength of loess is affected mainly by water content and dry density of specimen; moreover, the two factors have a very big impact on tests. The tensile strength of loess decreases with the increasing of water content, however, this relationship has changed near the optimum water content. The tensile strength of loess increases along with the increasing of dry density, meanwhile, it indicates that the curve has a certain range of linear relationship as well as the value of these tensile strengths increases even morerapid along with the dry density near the maximum dry density.2. The external influence factors of test results indicate that tensile strength of remodeled and undisturbed loess is affected by the external factors of axial fracturing test, besides, the influence law within the external factors for remodeling and undisturbed loess is consistent. The destruction of the loess with brittle failure is sudden in the axial fracturing test. The tensile strength also increased gradually with the increasing of the depth of penetration, meanwhile, curve appeared a peak point until the destruction of the loess. The growth of the stress gradient is very uniform in the whole process of fracturing test.(1)The variation of tensile strength from different tests is the smallest if the loading rate was 1.0 mm/min.(2)The tensile strength of specimen with the ratio of height to diameter of 1:1 was the middle one in tensile strength from different tests, the relative value of these tensile strengths was the minimum.(3)The tensile strength of specimens by the static pressing method is higher than that by the compaction method.(4)The tensile strength of the specimens decreases linearly with the increasing of the different diameter of loading cylinders.The test method and study results can be used for valuable reference to the testing of tensile strength of loess and similar soils, and also provide fundamental data and theoretical evidence.