冻结土石混合体在单轴压缩下的变形和声发射特征研究

Study on deformation and acoustic emission characteristics of frozen soil-rock mixture in uniaxial compression test

冻结土石混合体具有明显的各向异性和结构效应,相比于冻土,其物理力学行为更加复杂。为了研究冻结土石混合体受压条件下的破坏过程和声发射特征,本文对含石量分别为30%、40%、50%的人工冻结土石混合体试样和不同含水量青藏公路冻结路基砂土石混填物试样进行单轴压缩下的声发射试验。结果表明:(1)与常温土石混合体相比,冻结土石混合体试样受冰晶和冻土的蠕变作用,在单轴压缩过程中表现出轴向应力峰后裂纹发育的变形模式。(2)受冰晶体破裂的影响,冻结土石混合体在加载初始压密阶段就出现一定数量的声发射事件,轴向应力峰后阶段也存在明显的声发射活动,呈现声发射活动的多峰特征。含石量越大,峰后声发射活动越强,且基质土为黏质粉土的土石混合体峰后声发射活动要强于基质土为砂土的冻结土石混合体。(3)冻结黏质粉土的蠕变性质和含石量的大小共同影响试样内部的变形特征。冻结土含量越高,土体越易裹挟块石做整体运动,不利于裂隙的发育,试样多见鼓胀变形,声发射活动较少;当含石量较大时,土石界面数量多,土体与块石差异运动明显,试样以裂隙扩展为主,声发射事件增多,整体变形不明显。

Frozen soil-rock mixtures have the properties of distinct heterogeneity and an obvious structural ef⁃fect,which make their physical and mechanical properties more complex compared with frozen soil.To investi⁃gate the failure model and acoustic emission(AE)properties of frozen soil-rock mixtures,uniaxial compression and AE tests of artificial frozen soil-rock mixture specimens with volumetric rock contents of 30%、40%、50%,and Qinghai-Tibet highway subgrade sandy soil rock mixture specimens with different water contents were car⁃ried.The mechanical properties of the frozen soil-rock mixture and AE parameters were obtained.The results show that:(1)The post-peak ruptures mode of the frozen soil-rock mixture is the main difference from the soilrock mixture in a normal temperature state;(2)ice crystals breakage causes the initial AE signal,obvious multi⁃modal AE signals were observed after post-peak compression stage,and the amount of AE signal of a sample with clayey silt is much more than that of frozen subgrade sandy soil rock mixture;(3)Rock content and creep properties of frozen matrix soil are the main factors affecting the deformation properties and the amount of AE signal.The deformation of the specimens is dominated by overall compression bulging deformation in the low rock content stage,and the amount of AE signals is less than the specimens in a high rock content stage,where deformation is dominated by crack propagation.Specimen with low rock content and strong creep frozen soil in which rocks are wrapped by frozen soils,and motion both as a whole together,the amount of AE signals is less than the specimen with high rock content and weak creep frozen soil that uncoordinated deformation between rocks and soil lead to obvious cracks propagation.