The design of sealing/backfill elements in high level radioactive waste disposal repository often depends on the laboratory results in terms of swelling pressure and hydraulic conductivity. In this study, a series of swelling pressure test were performed on compacted specimens of MX80 bentonite and Callovo-Oxfordian (COx) claystone mixture with different initial stress state (with and without residual stress relaxation), aiming at investigating the effects of compaction induced residual lateral stress on the swelling pressure. Two methods named “Trimming” and “Transfer” were applied for the residual stress relaxation; whereas specimens were directly compacted in the hydration ring to simulate the case without residual stress relaxation. A higher swelling pressure was obtained on the specimens directly compacted in the testing ring compared to their counterparts with residual stress relaxation. Regarding to the relaxation methods, “Transfer” is more practical for specimen preparation in the laboratory, as it allows the relaxation of the stress without changes in specimens' diameter and mass.

高放废物处置库中密封/回填元件的设计通常取决于膨胀压力和水力传导率方面的实验室结果。本研究对不同初始应力状态（有残余应力松弛和无残余应力松弛）的 MX80 膨润土和 Callovo-Oxfordian (COx) 粘土岩混合物的压实试件进行了一系列膨胀压力试验，旨在研究压实引起残余应力的影响。膨胀压力上的横向应力。残余应力松弛采用“Trimming”和“Transfer”两种方法；而试样直接压实在水化环中以模拟没有残余应力松弛的情况。与具有残余应力松弛的试样相比，在测试环中直接压实的试样获得了更高的膨胀压力。关于松弛方法，“转移”更适用于实验室的试样制备，因为它可以在不改变试样直径和质量的情况下释放应力。