平面裂隙中膨润土挤出过程的数值模拟

摘要

Bentonite is often used as a buffer and backfill material of high-level nuclear waste repository as a re-sult of its swelling potential , low permeability and other characteristics .When contacted with groundwater , the ben-tonite will swell , and extrude into fractures in the surrounding rock .If the quality of bentonite extrusion exceeds a certain degree , it will in turn degrade the bentonite density in the buffer , and may lead to decline and even loss of the repository performance .To understand this process systematically , a model that decribes the bentonite extrusion in the planar fracture is established , investigating the influence of the electrolyte concentration in groundwater and the bentonite dry density in the buffer .Calculation results show that the bentonite extrusion distance is proportional to the square root of time , and the proportion coefficient raises with decreasing electrolyte concentration and with in-creasing bentonite dry density .%膨润土因其膨胀性、低渗透性等特性常被用作高放核废料处置库的缓冲和回填材料。与地下水接触时，膨润土会发生膨胀，挤入周围岩体的裂隙中。如果进入裂隙中的膨润土的质量超过一定程度的话，会使得缓冲层中的膨润土密度下降，可能会导致处置库性能的降低甚至丧失。为了系统地了解这一过程，建立了膨润土在平面裂隙中的挤出模型，研究了地下水中电解质的浓度和缓冲层内膨润土的干密度的影响。计算结果表明膨润土的挤出距离和时间的平方根成正比关系，比例系数随着电解质浓度的减小而增加，随着膨润土干密度增加而增大。