In situ water immersion research on the formation mechanism of collapsible earth fissures

Loess collapse is an important factor in earth fissure formation, and earth fissures resulting from loess collapse are widely distributed in loess areas in China. To explore the basic features and formation mechanism of collapsible earth fissures, we conducted an in situ water immersion test in a loess area. This paper describes the genesis of collapsible earth fissures by monitoring the development processes of collapsible settlement and earth fissure formation. This paper demonstrates that the infiltration process can be divided into three stages, and the subsidence curve of the whole test process can be divided into six stages. During the test, the collapsible deformation gradually developed outward, the collapsible settlement decreased with increasing distance from the test pit, and the horizontal influence distance was approximately 18 m. The collapsible earth fissures were parallel to the test pit, and characterised by horizontal tension and vertical dislocation. With the collapsible deformation expanding outwards, the location of the earth fissure developed outwards. The tensile stress and tensile strain caused by the differential collapsible deformation caused the formation of collapsible earth fissures. When the tensile strain or tensile stress was greater than the ultimate tensile strain or tensile strength, the loess experienced tensile failure and formed an earth fissure.