自由膨胀条件下高压实砂-膨润土混合物非饱和渗透特征

Unsaturated permeability of highly compacted sand-bentonite mixtures under unconfined conditions

选择合适的配合比,使得膨润土–石英砂混合物在增加导热性能和强度的同时,又能满足渗透性要求并维持适当的膨胀力,是混合型缓冲/回填材料研究的关键。采用瞬时截面法,通过试验研究了干密度1.9 g/cm3、配合比为7∶3的高庙子膨润土–石英砂混合物的非饱和渗透特性。结果表明,所测非饱和渗透系数主要集中在2.1×10-15～1.0×10-13 m/s,且趋势上随吸力的增大而减小但变化较为平缓;与自由膨胀条件下、纯膨润土试样的非饱和渗透系数相比,混合物渗透系数稍有增大,但变化幅度不太明显。石英砂的加入,改善了混合物的导热性能,且仍然基本符合缓冲/回填材料的低渗透性要求。

Choosing an appropriate content of quartz sand is a key issue for the study of sand-bentonite mixtures used as buffer/backfill materials.It can increase the thermal conductivity and strength of the mixtures while meeting the basic requirements of low permeability and well swelling pressure simultaneously.Based on the instantaneous profile theory,the unsaturated hydraulic permeability of densely compacted sand-Gaomiaozi bentonite（3：7） mixtures with a dry density of 1.9 g/cm3 is tested under unconfined conditions.The results show that the measured unsaturated hydraulic conductivity is between 2.1×10-15 and 1.0×10-12 m/s,and increases with the decrease of the suction but changes gently.Compared with the coefficient of unsaturated hydraulic conductivity of Gaomiaozi bentonite under unconfined conditions,the measured unsaturated hydraulic conductivity of mixtures shows slight increase.Mixing with sand improves the thermal conductivity of the mixture,and keeps the requirement of low permeability for buffer/backfill materials.