高铁无砟轨道对膨胀变形值要求极为严格,地基的胀缩变形不仅对行车安全性和舒适性产生威胁,而且严重影响高速铁路线路的服役状态和使用寿命.膨胀土地基均为原状膨胀土,为研究原状膨胀土的膨胀规律,以兰新铁路第二双线一处典型原状膨胀土为对象,对3种不同厚度的膨胀土分别进行不同上覆荷载和不同含水率下的膨胀变形试验.研究结果表明:膨胀土的厚度越大,其膨胀量越大;上覆荷载对膨胀量起抑制作用,荷载越大膨胀量越小,荷载越小膨胀量越大;土样的膨胀量随含水率的增加可分为缓慢增长阶段、急速增长阶段和缓慢增长阶段;在厚度一定时,建立含水率增量与上覆荷载耦合情况下原状膨胀土膨胀量计算模型,再依据不同厚度对公式参数进行拟合.建立含水率、上覆荷载和厚度3因素耦合作用下原状膨胀土膨胀量计算模型,模型计算结果与实测数据吻合较好,为今后膨胀土地区高速铁路的修建提供一定的理论支撑.%Swelling deformation value of high speed ballastless track is strictly required. The expansion and contraction deformations of foundation not only threaten the operational safety and comfort, but also adversely affect the serviceability and service life of high-speed railway lines. However, the expansive soil foundation is the undisturbed expansive soil. The deformation of undisturbed expansive soil under the second line of Lanzhou to Xinjiang Railway was studied. Different overloading scenarios were applied to three different thicknesses with different water contents in order to measure the deformation of undisturbed expansive soil. The test results show that the greater the thickness of the expansive soil, the greater the amount of expansion. The overlying load would have a restraining effect for expansion of undisturbed expansive soil. When the load is greater, the amount of expansion is less. When the load is larger, the larger the amount of the load is. The expansion of soil samples can be divided into slow growth stage, rapid growth stage and slow growth stage with the increase of water content. When the thickness is constant, the model of undisturbed expansive soil was established under the water content increment and overburden load. According to the parameters of the formula, the calculation model of expansive soil expansive soil under the coupling effect of water content, overburden load and thickness was established based on the three factors. The calculated results agreed well with the measured data, which provides some theoretical support for the project construction of the high speed railway in the future.
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