低黏土矿物含量泥岩有荷膨胀试验研究

Expansion Test of Mudstone with Low Content of Clay Minerals under Overburden Load

现有铁路规范中判定为无膨胀性的低黏土矿物含量泥岩仍具有膨胀性,其遇水之后产生的微弱膨胀对于变形精度要求只有4 mm的高速铁路具有潜在的破坏作用。以一高速铁路地基中的低黏土矿物含量重塑泥岩为研究对象,通过有荷膨胀率试验研究初始含水率、干密度及上覆荷载对膨胀极限状态的影响规律。研究结果表明:在初始含水率与上覆荷载一定的条件下,泥岩的胀限膨胀率随干密度的增大而增大;在干密度与上覆荷载一定的条件下,初始含水率越大,胀限膨胀率越小;在初始含水率与干密度一定的条件下,胀限膨胀率与胀限含水率均随上覆荷载的增大而减小。同时拟合得到了泥岩胀限膨胀率计算公式,验证结果表明胀限膨胀率实测值与公式预估值误差较小,可以采用拟合出的公式对于实际工程中的膨胀进行预测,为工程提供指导。

Mudstone with low content of clay minerals is determined not expansive by existing railway standards.However,it is still of weak expansion in water,and has potential damage to high-speed railway which is tolerable to a deformation of only 4 mm. In this article,we take the reshaped mudstone with low content of clay minerals in the foundation of a high speed railway as research object,and analyze the effects of initial water content,dry density and overburden load on the bulging limit condition by expansion test under overburden load. Results show that: 1)expansion ratio of mudstone in bulging limit condition increases with the increase of dry density when initial water content and overburden load are stable; 2) the greater the initial water content is,the smaller the expansion rate in bulging limit condition is when dry density and overburden load are stable; 3) expansion rate and water content in bulging limit condition both decrease with the increasing of overburden load when the initial water content and dry density are stable. Furthermore,we obtained the fitting calculation formula of expansion rate in bulging limit condition of mudstone. Verification result shows that the difference between measured value and predicted value by the formula of expansion rate in bulging limit condition is small. The fitted formula could be used to predict expansion in practical engineering to provide guidance for engineering.