摘要
红砂岩广泛分布于三峡库区,弄清岸坡消落带红砂岩的抗拉强度在水库运行期周期性"湿干"交替作用下的劣化机制,是科学进行水库运行期红砂岩岸坡稳定性分析与评价的重要前提。以三峡库区马家沟滑坡红砂岩为研究对象,自主研发能模拟水压力和"湿干"交替共同作用的岩石抗拉强度测试系统,进行消落带红砂岩在水压力和"湿干"交替共同作用下的劈裂试验;同时,基于扫描电镜(SEM)、X射线衍射(XRD)及吸水率的测试分析,探讨消落带红砂岩抗拉强度的劣化机制。试验结果表明:在水压力和"湿干"交替的共同作用下,消落带红砂岩的抗拉强度随着"湿干"交替作用次数的增加逐渐劣化,劣化幅度逐渐减小最终趋于0;在"湿干"交替作用前期,红砂岩抗拉强度的劣化幅度较大,第1次"湿干"交替作用后,劣化程度最为明显;2~4次"湿干"交替时,劣化幅度相对较大;4次"湿干"交替作用后,劣化幅度逐渐减小为0;红砂岩抗拉强度的劣化是一个不断累积的过程,是内部黏土矿物湿化过程的水化溶解与膨胀、干燥过程的失水收缩,以及水压力作用下微裂隙的增加、扩展等综合作用的结果,且黏土矿物的水化作用引起的碎屑矿物与胶结物之间的胶结变弱效应在其抗拉强度的劣化过程中起主导作用。研究成果可为合理评价红砂岩岸坡的稳定性提供科学依据。
Red sandstone is widely distributed in the drawdown area of Three Gorges Reservoir,China. Understanding the mechanisms of deterioration of the tensile strength of red sandstone under cyclic wetting-drying during the operation of reservoir is therefore very important for the stability evaluation to the slopes of red sandstone. The red sandstone samples from Majiagou landslide were taken for splitting test to measure the tensile strength under water pressure and cyclic wetting-drying conditions using the test system developed in house. The system can apply the water pressure and wetting-drying cycles. Meanwhile,the tensile strength deterioration of the red sandstone in drawdown area was discussed based on the results of SEM tests,XRD tests and water absorption tests. Experimental studies show that the tensile strength of the red sandstone under water pressure and cyclic wetting-drying conditions decreases gradually with the increasing of the number of wetting-drying cycles. The decreasing rate of the tensile strength after the first wetting-drying cycle is much greater than that after the latter wetting-drying cycle. After the fourth wetting-drying cycle,the decreasing rate of the tensile strength approaches zero,indicating that the tensile strength keeps nearly constant. The tensile strength degradation of the red sandstone is a cumulative process of damages resulting from the expansion of clay minerals due to hydration during wetting process,the shrinkage of clay minerals in the period of drying process,and increasing and propagation of micro pores and cracks under water pressure. The weakening effect of cementation between detrital minerals and cements caused by the hydration of clay minerals under cyclic wetting-drying conditions plays a main role for the degradation of the tensile strength.
出处
《岩石力学与工程学报》
EI
CAS
CSCD
北大核心
2017年第11期2731-2740,共10页
Chinese Journal of Rock Mechanics and Engineering
基金
国家自然科学基金资助项目(51579063
51379106)~~
关键词
岩石力学
红砂岩
湿干交替
强度劣化
rock mechanics
red sandstone
cyclic wetting-drying
strength degradation
