| Since the first first nuclear power station(Qinshan Nuclear Power Station)was built and used,our country has been developing rapidly in the use of nuclear energy.But the disposal of high level radioactive wastes producted in the process of nuclear energy using has become an impediment to further expand the using of nuclear energy.At present,the worldwide recognized methods of high-level radioactive wastes disposal is deep geological disposal.Beishan,Gansu,has been identified as the first choice for the construction of high-level radioactive wastes repository in our country.And the Inner Mongolia Gaomiaozi sodium bentonite has been selected as buffer backfill material for disposal repository in our country.Simulating the real-life situation of strong alkaline ground water and decay heat the buffer backfilling materials situated in and studying the swelling and permeability of bentonite under this environment are relatively rare at home and abroad and has very important practical engineering reference value.Therefore,this paper studied it and the following conclusions were obtained :(1)The free expansion rate and liquid plastic limit of bentonite effected by alkaline-thermal coupling at different lengths are decreased with the increase of temperature and the length of time.And its water holding capacity is gradually declined.The content of montmorillonite in bentonite gradually decreases with the increase of reaction temperature and t he length of time,while the content of pyrophyllite gradually increases.(2)The vertical expansion force of bentonite effected by alkaline-thermal coupling with different length of time is greater than the radial force.That is,the final relative size of the two is not affected by the strong alkali solution,the temperature,and the length of time for both to work together.The swelling force increases rapidly in the early period of the test,and then the growth rate gradually slows until it stabilizes.The ratio of radial and vertical expansion forces is around 0.5 when the force reaches equilibrium.That is,there is no obvious correlation between the ratio of the two and the alkali solution,temperature,and the length of time for both to work together.In addition,when the temperature is same with the increase of the t ime length of alkali thermal coupling and when the time length of alkali thermal coupling is same with the increase of the temperature,the content of montmorillonite in bentonite decreased by 24.9%,the content of pyrophyllite increased by 3.04%,the content of quartz had a certain increase or decrease and the content of albite and zeolite increases with the increase of aging time and temperature.(3)The expansion and permeability properties of soil samples effected by alkaline-thermal coupling after different length of time is worse with the higher of the operating temperature.That is,the expansion performance is negatively related to the operating temperature and duration,and the permeability coefficient is positively.The expansion and permeability performance in the early stage are greatly reduced under the accelerated aging simulation and in the case of a certain amount of alkali solution.But the rate of change gradually slows down as the aging time increases.But in general,it can meet the requirements of deep geological repository for its performance. |
