Irregular columnar jointed structure is a primary irregular columnar morphological tensile fracture. In order to study the geometric features of irregular columnar joints and the new problems in geotechnical engineering, hydraulic and hydropower engineering caused by columnar jointed basaltic mass, Voronoi graph from geometry was introduced to simulate the irregular columnar jointed basaltic mass at Baihetan hydraulic station. Discrete element software UDEC was used to simulate the whole process of rigid bearing plate test. Anisotropic constitutive of columnar joints was adopted to analyze the stress diffusion of rock mass at dam base of Baihetan. The results show that, the compaction property and hysteresis effect are well simulated based on discrete element simulation of Voronoi joint structure by UDEC. Four stages of cyclic loading and unloading process are imaged clearly. The results from in situ rigid bearing plate tests are explicated and the stress diffusion rule of anisotropic body is affected by structure surface. The elements in the stress state of 4−5 MPa are the most, about more than 35% of the total. Appropriate constitutive must be proposed to columnar jointed rock mass with different styles. It has important significance to realize the nonlinear mechanical behavior of irregular columnar jointed basaltic mass.

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According to the latest medium and long term nuclear power development plan (2005)(2006)(2007)(2008)(2009)(2010)(2011)(2012)(2013)(2014)(2015)(2016)(2017)(2018)(2019)(2020) in China, the revised installed nuclear power capacity would be 86 GW by 2020. Due to the rapid growth of the nuclear power, there will be over 8,000 m 3 A series of laws and regulations on disposal of LILW in China have been issued by the State Council, COSTIND, CAEA, NNSA, SEPA, SBTS, MEP and MOHURD since 1987. The three most important standards for LILW disposal in China are GB9132, HJ/T23 and HAD401/05. GB9132, approved and issued in 1988, is the first national standard for LILW disposal in China (SBTS, 1988). HJ/T23, issued in 1988, is the first industrial standard for nuclear industry in China (SEPA, 1988). HAD401/05, approved and issued in 1998, is the general guide for LILW disposal in China (NNSA, 1998).The current structural forms of repositories for disposal of LILW can be divided into three types: shallow depth facilities, medium depth repository and deep repository. Engineered near surface facilities such as above-grade vault, below-ground vault and earth-mounded concrete bunker are adopted in China. So far, the Beilong Repository is a typical above-grade vault while the Northwest Repository adopts the below-ground vault. CONCLUSIONSThis paper reviews the status of disposal of LILW in China, including the disposal technology, management strategy, laws and regulations, safety guides and technical manual. Secondly, some differences between the standards disposal of LILW in China and IAEA have been studied. Result shows that the near surface disposal facilities in China are depended on the types of LILW, the characteristics of the sites, the structure of disposal unit and so on. There are no regulations for disposal of VLLW yet and a detailed instruction for geotechnical investigation of repositories in China is in great need. This study provides an instruction for siting and construction of near surface disposal facilities in China. REFERENCESState Bureau of Technical Supervision, 1988, Regulations for shallow ground disposal of solid lowl and intermediate level radioactive wastes (GB 9132-88), SBTS, China. State Environmental Protection Administration, 1998, Siting of near surface disposal facilities of low-land-intermediate level radioactive wastes (HJ/T 23-1998), SEPA, China. National Nuclear Safety Administration. 1998, Nuclear safety guide rule (HAD 401), NNSA, China.LILW a year to be disposed by 2020 in China. China will bear more and more financial and environmental pressures in the near future. DISPOSAL OF LILW IN CHINAThe national disposal policy of LILW in China is regional disposal in different area where the LILW is relatively centralized. So far, there are two repositories built, one under construction and two planned for LILW disposal in China. Besides, one repository is planned for VLLW disposal. The Northwest Repository is the first repository for LILW disposal with disposal capacity of 200,000 m³. Its siting process...