膨润土防水毯水化的膨胀应力

SWELL STRESS OF GEOSYNTHETIC CLAY LINERS UNDER WATER SORBED

采用自制膨胀力测定仪对美国CETCO公司膨润土防水毯(geosyntheticclayliner,GCL)饱和吸水膨胀应力进行了直接测定。结果表明:GCL吸水膨胀应力在测试过程中随时间的变化可明显分出3个阶段,即:应力快速增加,应力缓慢增加和应力平缓波动阶段。3个阶段的膨胀应力值相应为(1.17～4.05)×10–2,(4.05～7.07)×10–2MPa和(7.07～7.19)×10–2MPa。撤销饱和吸水条件后,膨胀应力值以1.53×10–3MPa/h速率降回到初始值。膨胀应力的分阶段变化表明:膨胀应力的增加会阻止水在GCL中扩散,进而抑制水渗透,达到防水效果。此外,饱和吸水状态下,膨润土的持续膨胀应力对其周围工程材料将产生潜在影响,特别是当GCL安置于地下水位附近时,水位变化导致的应力振荡有可能直接破坏周围工程材料。

The swell stresses of a geosynthetic clay liner （GCL）, made by the CETCO Company, USA, were measured directly using a custom-made swell stress instrument under water-sorbed saturation conditions. The results show that in the test process, the variation of the swell stress curve with time can be divided into three segments. In these three segments, the swell stress value increases quickly, increases slowly and fluctuates a little respectively and they correspond to （1.17-4.05）×10^-2 , （4.05-7.07）×10^-2 MPa and （7.07-7.19）×10^-2 MPa. After the water-sorbed saturation condition is removed, the swell stress goes down to its original value at a rate of 1.53×10^-3 MPa/h. The variation of swell stress shows that with the increase of swell stress, the diffusion of water in GCL will be restrained, and water penetration stopped, so GCL has a water-proofing effect. On the other hand, under the water-sorbed saturation condition, persistent swell stress from the GCL may have a potential effect on surrounding engineering materials. For example, when the GCL is installed near the underground water level, water level fluctuation can lead to a change in the swell stress of the GCL, and also may destroy the surrounding engineering materials.