| As the key component of “Multi-barrier system” in the high-level radioactive waste disposal repository,buffer / backfill material is placed between nuclear waste containers and surrounding rock to block the outward migration of radionuclides.During the running period of the high-level radioactive waste disposal repository,bentonite blcoks-joint system is under a complicated coupled thermo-hudro-mechanical environment,joint of which is the weak area for showing a low performance of blocking the migration of radionuclides.In order to effectively evaluate the buffer/backfill material’s ability of blocking radionuclide migration,it is necessary to study the laws of time evolution and spatial distribution of temperature field,seepage field and stress field interinal the bentonite blocks-joint system under THM coupling condition and their influence on the healing deformation in the joint area.The research contents and achievements of this paper are as follows :(1)Proposing the design scheme and performance requirements of a multi-field coupling test apparats for buffer materials,which is composed of(a)Bentonite blocks-joint system,(b)Experimental box system,(c)Temperature controlling system,(d)Hydrolic controlling system,(e)Data monitoring and collecting system.(2)According to the proposed buffer materials THM coupling experiment scheme.The development plan of the experimental apparatus was worked out in detail and the design drawing of the whole apparatus and each component was drawn.Then the first domestic experimental apparatus for THM coupling characteristics of bentonite blocks-joint system was manufactured(3)A pre-experiment for a period of 7 days,which choosing a self-made loess sample as the experimental material,was carried out.The result showed that each system of the apparatus meets the expected design requirements and can provide controllable and stable thermal,hydrolic and mechanical boundary conditions for the sample,and it can monitor and collect the required test data.(4)According to the apparatus,feasible test methods were put forward and the first THM coupling experiment of bentonite blocks-joint system in China was carried out successfully.By analyzing the test results of the first 100 days,The laws of internal temperature field,seepage field,swelling stress field and joint healing deformation with time evolution and spatial distribution of bentonite blocks-joint system under the coupled thermo-hydro-mechanical conditions are obtained.The effect mechanism of THM coupling on joint healing deformation was preliminarily revealed.This paper is of great importance to evaluate the overall buffering performance of the blocks-joint system and the ability of buffer/backfill materials in the high-level waste disposal repository to block the migration of radionuclides. |
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