青藏铁路多年冻土场地波速特性分析

Analysis of Wave Velocity Characteristic in Permafrost Site along Qinghai-Tibet Railway

为分析冻土场地波速变化规律,通过现场钻孔波速测试,并结合已有典型场地波速资料,研究了青藏铁路沿线多年冻土场地波速比的经验值及波速变化受控制因素的影响规律。结果表明:多年冻土场地纵横波速比经验参考值可选用1.5左右;冻土层波速传播规律与地温、土层埋深、土质属性、冻结冰晶含量等诸多因素相关;冻结作用使土体的结构性增强从而冻土体强度增强,冻结状态下土体的波速通常大于未冻结场地土体;多年冻土层波速值随土层深度的增加、地温的降低和冻结土体中冰晶含量的增加而增加。

In order to analysis the change law of wave velocity in permafrost site, the empirical value of wave velocity ratio and the influence of wave velocity change by control factors of permafrost site are obtained by using the field drilling wave velocity test and combining with the data of wave velocity in typical site along the Qinghai-Tibet Railway. The results of this study are summarized as follows. The ratio of vertical wave velocity to horizontal wave velocity can be selected by about 1.5 in permafrost site. The spread law of wave velocity of soil layer is related to many factors such as geothermal temperature, buried depth of soil layer, soil properties, freezing ice crystal content, etc . Meanwhile, the freezing effect makes permafrost strength increase due to enhancement of constitutive property, so the wave velocity of soil layer in frozen condition is usually greater than that of unfrozen soil layer. And the wave velocity value of permafrost increases with the increase of soil layer depth, the decrease of geothermal temperature and the increase of ice crystal content in permafrost.