Experimental Research On Rupture Mechanism Of Loess

The soil would generate all sorts of broken under the function of external force, such as the tensile broken, the shear broken and the plastic rheology. The ground fissure developed in Fen-Wei basin had the complex genesis, and was a kind of soil broken under the coupling function of stress, seepage flow and impairment. The author in this paper researched the mechanism of ground fissures in Fen-Wei basin according to the ground fissures in Sanyuan testing field. Based on a series of mechanical test of loess, such as tensile test, shear test, creep test and numerical test, analyzed the rupture characteristics and behavior related to loess ground fissures. Based on this, discussed the genesis and expansion mechanism of ground fissures developed in loess.The tensile test indicated that the ground fissures developed in loess were concerned to the very small tensile strength and limit strain of loess. When the tensile stress in loess was bigger than tensile strength, the tensile cracks would come into being to release the tensile stress. The creep test indicated that the limit strain in destructive creep stage was related to the confining pressure and water content, and the high water content loess had the more obvious rheological softening character. The Sanyuan ground fissure developed on the ground surface was nearly connected with dump rainstorm, and ground fissure developed in deep layer was related to creep under the function of long-term stress. The test of fissured loess indicated that, the stress state and the original structural plane controlled the rupture of fissures loess, and the fissured loess was easier to produce cracks under low confining pressure. By using the numerical analyzing software RFPA, the initiation, the expansion and the penetrating of fissures in loess were reappeared, and the stress and expansion path of cracks were determined.The broken test of loess showed that the tectonic stress field of Fen-Wei basin was the controlling factor to ground fissures, and other factors were additional factors.