论文部分内容阅读
在高放核废物处置库中,膨润土-砂混合物是一种可选的缓冲回填材料,掌握其在水-力耦合条件下的体变特征对正确评价处置库的长期安全性有重要意义。按照不同的石英砂掺量(0%~50%)配制了6组膨润土/砂混合物,依次进行了单轴侧限压缩、有荷膨胀(轴向应力为0.2 MPa)和饱和再压缩试验,获得了混合物在不同水-力路径下的变形特征,并着重分析了砂掺量的影响。结果表明:(1)膨润土-砂混合物的压缩性与掺砂量、饱和状态和密实度有关。在非饱和及密实度较低(ρ_d<1.7 g/cm~3)的条件下,混合物的压缩指数随砂掺量的增加近似线性减小;当混合物压缩到较高的密实度(ρ_d>1.7 g/cm~3)并且饱和后,压缩指数受掺砂量的影响不明显,但其值远小于非饱和及低密实度状态。(2)混合物的最终膨胀率随着掺砂量的增加呈指数减小,随膨润土有效干密度的增加而呈指数增加。掺砂量达到40%时,膨胀过程伴随有体积回落现象,且体积回落率随砂掺量的增加而加剧。(3)混合物在不同水-力路径中及不同砂掺量条件下呈现的体变差异性与膨润土和砂在试样中的分布状态及二者对土体骨架的主导作用有关,总体上,掺砂量越高或试样密实度越大,砂对体变的主导作用越强。(4)混合物的膨胀力随掺砂量的增加而减小,通过引入膨润土有效干密度参数,建立了混合物膨胀力与该参数间的指数定量关系,可对膨胀力进行预测,并从蒙脱石的体积变化率与质量分布率的角度进一步分析了混合物膨胀力的作用机制。
Bentonite-sand mixture is an optional buffer backfill material in high-level nuclear waste disposal repository. It is of great significance to correctly understand the long-term safety of the repository in order to understand its volume change characteristics under water-power coupling conditions. Six groups of bentonite / sand mixtures were prepared according to different quartz sand dosages (0% ~ 50%), followed by uniaxial lateral compression tests with load expansion (axial stress of 0.2 MPa) and saturation recompression The deformation characteristics of the mixture under different water-power paths were analyzed, and the influence of sand content was analyzed. The results show that: (1) The compressibility of bentonite-sand mixture is related to the amount of sand, saturation and solidity. The compressibility index of the mixture decreases linearly with the increase of sand content under the conditions of low saturation (ρ_d <1.7 g / cm ~ 3) and low compressive strength (ρ_d> 1.7) g / cm ~ 3) and saturated, the compressibility index is not obvious, but its value is far less than the unsaturated and low-density state. (2) The final expansion rate of the mixture decreases exponentially with increasing sand content and increases exponentially with the effective dry density of bentonite. When the sand content is up to 40%, the expansion process is accompanied by volume drop, and the volume drop rate aggravates with the increase of sand content. (3) The heterogeneity of the body deformation exhibited by the mixture under different water-power paths and different sand contents is related to the distribution of bentonite and sand in the sample and the dominant role of the two on the soil skeleton. On the whole, The higher the sand content or the greater the density of the specimen, the stronger the sand’s dominant effect on the bulk. (4) The expansive force of the mixture decreases with the increase of the amount of sand. Through the introduction of the effective dry density parameter of bentonite, the exponential relationship between the expansive force of the mixture and the parameter is established, and the expansive force can be predicted. The mechanism of expansion force of mixture is further analyzed from the perspective of volume change rate and mass distribution rate of stone.