地应力对高放废物黏土岩地质处置库洞室群稳定性影响的数值模拟

Numerical Simulation of Influence of Ground Stress on the Stability of High-level Radioactive Waste Geological Repository in Clay Rock

世界上尚无建成投入使用的高放废物(指高水平放射性废物)地质处置库,世界各国的高放废物地质处置库仍是一种概念设计,总体设计思路基本是一致的,主要包括地面设施和地下设施设计两部分。目前主流的高放废物地质处置库地下设施的设计是以“井字形”巷道列阵的形式布置于地下,基于此类洞室群地下结构特征,以我国高放废物黏土岩地质处置库预选区(塔木素预选区)为工程地质背景,结合该预选区地应力场分布特征,针对比利时高放废物黏土岩地质处置库地下设施的概念设计模型,运用ABAQUS数值仿真软件对该高放废物黏土岩地质处置库洞室群主巷道洞轴线方向与最大水平主应力的夹角在0°~90°变化条件下,洞室群周围围岩位移场、应力场和塑性区的分布规律进行了数值模拟研究。结果表明:塔木素预选区受水平、垂直应力作用的影响均较显著,初步认为该预选区地应力分布特征可能具有一定的层控性;为减小地应力对高放废物黏土岩地质处置库稳定性的影响,地质处置库洞室群主巷道洞轴线方向应与地应力方向呈一定的角度;以比利时高放废物黏土岩地质处置库地下设施的概念设计为例,当地质处置库洞室群主巷道洞轴线方向与最大水平主应力夹角a为45°左右时,地质处置库洞室群的稳定性最好。我国目前尚未提出高放废物黏土岩地质处置库的概念设计模型,该研究可为我国高放废物黏土岩地质处置库的设计提供参考。

All over the world there has been no geological repository built in use for high-level radioactive waste so far,and it is still a conceptual design.The general design idea of geological repository is basically the same,mainly including two parts of surface facility and underground facility design.At present,the main stream underground repository facility design is to arrange a“#”-shaped caverns array in the ground.Based on the underground structure characteristics of such caverns,this paper takes the pre-selected area of the clay rock repository in China(the Tamusu pre-selected area)as the engineering geological background.Combined with the distribution characteristics of the pre-stressed area ground stress field and the concept designs of the underground facilities of the geological repository in Belgium,the paper investigates the displacement,stress and plasticity distributions of the cavern group under the changes of the angle between the main axis of the main roadway and the maximum horizontal principal stress of the treatment cavern group from 0 to 90°by the ABAQUS numerical simulation software.It is concluded that the pre-selected area is significantly affected by horizontal and vertical stress effects.It is believed that the characteristics of the stress distribution in the preselected area may be controlled by layers.In order to reduce the influence of the ground stress on the stability of the repository,the direction of the long axis of the main roadway should be at a certain angle with the direction of the ground stress.Taking Belgian conceptual design as an example,the stability of caverns is the best when the angle is about 45°.At present,the conceptual design model of clay rock repository has not been put forward in China.The research can provide reference for the design of high-level radioactive waste repository of clay rock in China.