EXPERIMENTAL STUDY ON SOFTENING CHARACTERISTICS AND MECHANISM OF SOAKING MUDSTONE FROM FENTOU FORMATION IN CHAOHU AREA

Abstract:

To identify the softening characteristics and mechanism of soaking mudstone from Fentou formation in Chaohu area, a series of experiments were carried out on specimens prepared at different soaking time. Utilizing DB-16 ultrasound velocity-measured machine, uniaxial compression machine, the change of wave velocity through mudstone and uniaxial compressive strength were measured. Through X-ray diffractometer (XRD) and fluorescence spectrum analysis system, the mineral & chemical composition of mudstone was made clear. Finally, the microstructures of mudstone were observed by means of scanning electron microscopy (SEM), while the porosity and surface area were calculated by GIS software. The test results show that the uniaxial compressive strength and wave velocity drop obviously, the porosity of mudstone decreases slightly while surface area increases in a little extent after soaking for 90~120d, and the mineral & chemical composition of mudstone changes little. Through analyzing the test results, it is concluded that the fissure caused by the dissolution of soluble salt cementation during the saturation process is the main reason for the softening of mudstone, and the heterogeneity of mudstone is also a key factor leading to the fissure.