EXPERIMENTAL STUDY ON STRENGTH CHARACTERISTICS OF LOESS AT GROUND FISSURES IN XI'AN UNDER ACTION OF DRY AND WET CYCLE

This paper studies the effect of long-term dry and wet circulation on the strength of ground fissure zone and its nearby loess. It takes the typical loess samples of ground fracture site in Xi'an as the research object. It studies the shear strength parameters and the strength attenuation characteristics of the loess specimens with different moisture content under dry and wet circulation with laboratory test method(mainly for direct shear test). It puts forward a ground fissured loess strength attenuation calculation method. Research results show the follows. (1)Shear strength of ground fissured loess is decreased gradually with the cycle number and water content. One dry-wet cycle or greater than 18%moisture content have affected on the shear strength parameters significantly. (2)The intensity attenuation of the 1 drying and wetting cycles is most obvious. It increases with the increase of dry and wet cycles. (3)Under the action of 1 dry and wet cycle, the attenuation of its strength is most obvious with the moisture content. It gradually decreases with the increase of water content. Its strength attenuates higher when the water content is below 12%, and the strength attenuation is smaller when the water content is greater than 12%.