巢湖地区坟头组泥岩遇水软化特性与机理试验研究

从物理力学性质、矿物与化学成分、微观结构等方面,对巢湖地区坟头组海相粉砂质泥岩遇水软化的特性与机理进行试验研究.利用DB-16超声测速仪、单轴压力机,测试岩样浸于蒸馏水后不同时间波速、抗压强度的变化;采用电感耦合等离子体法,分析岩样浸泡液化学成分随时间的变化;利用X射线衍射、荧光光谱分析,测试岩样矿物化学成分变化情况;采用电子扫描显微镜观察岩样微观结构,并利用GIS软件对不同浸水时间岩石孔隙率、孔隙表面积进行半定量计算.试验表明,泥岩浸水后,单轴抗压强度和波速明显下降,岩石孔隙率下降,孔隙表面积增加;浸水前后,泥岩化学成分变化不大;水沿微裂隙进入岩石内部,溶解可溶盐胶结,使裂隙向纵深发展,进而使裂隙连通导致岩石软化,其中,岩石微裂隙的产生与岩石内部的不均一性密切有关.

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

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 90~120 d,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.