核废料地下储库围岩长期水力响应特征

Characterization of the long-term hydro-mechanical response in the host rock of a potential nuclear waste disposal repository

黏土岩由于其低渗透性和损伤自修复等特性,被认为是一种合理的高放废物处置地质屏障。以黏土岩为研究对象,结合相关室内试验和现场监测成果,在总结黏土岩蠕变变形规律的基础上,考虑蠕变过程中的损伤和应变累积,建立黏土岩非线性蠕变损伤本构模型,并将其应用于比利时核废料地下实验室长期水力响应特征分析。研究结果表明:(1)非线性蠕变损伤本构模型能较好地反映黏土岩的非线性蠕变损伤过程;(2)巷道开挖对巷道洞周围岩水力性质影响显著,洞周附近围岩变形增大、孔隙水压力迅速减小;(3)围岩变形与开挖巷道距离和流变时间密切相关:随着与巷道距离的增大,开挖对巷道洞周附近围岩变形、孔隙水压力的影响逐渐减小,而随着时间的增长,巷道洞周附近围岩变形、孔隙水压力逐渐增大;(4)高放废物处置库衬砌的蠕变变形规律与现场监测结果相吻合,验证了模型的可靠性。研究成果将为我国未来黏土岩核废料地下储库的建设和稳定性评估提供重要理论依据。

Clayey rock,in virtue of its properties,such as low permeability,self-sealing,etc.,is considered to be a candidate host rock for underground nuclear disposal facilities.In this paper,we take clayey rock as our study object.Analyzing the related test results of clayey rock both in the laboratory and in situ,a nonlinear creep damage constitutive model has been established.This theoretical model considers the creep damage,as well as the creep strain accumulation effect.Based on the software of ABAQUS,we compiled the corresponding UMAT subroutine.A numerical analysis of the long-term hydro-mechanical response of a nuclear underground repository was carried out.The results indicate that:(1)the nonlinear creep constitutive model can well show the creep process of clayey rock.(2)The deformation,as well as the pore water pressure of the host rock,are significant influenced by the tunnel excavation.The pore water pressure soon decreases with deformation increases after the tunnel excavation.(3)The deformation of the host rock is closely related to the excavation distance and creep time.The excavation effect for both deformation and pore water pressure weakens as the increase of distance between the target location and the excavated tunnel.Meanwhile,due to the time effect,the pore water pressure,as well as the deformation around the tunnel gradually increased.(4)The consensus of the numerical simulation and in situ measurements on the deformation of tunnel linings show the reliability of the theoretical model.The research here will give significant guidance on the long-term stability analysis of the clayey rock nuclear waste repository in China.