酸性环境下黄土湿陷性试验与湿陷敏感性研究

 黄土的胶结连接是黄土湿陷的重要内在因素，对其湿陷敏感性有着直接影响。为了对胶结连接在黄土湿陷敏感性中的作用有更清楚的认识并提出一个能科学的判定黄土湿陷敏感性的评价方法，在黄土湿陷性试验的浸入水溶液里添加不同浓度的硝酸，测试在酸性环境中，不同压力下黄土的湿陷系数、稳定时间、湿陷速率等湿陷敏感性指标。同时用扫描电镜观察试验前后土样的孔隙、结构变化情况。试验结果表明：在酸性溶液中，湿陷性黄土在低压状态下的湿陷系数增大较多，在各级压力下的湿陷稳定时间均有所延长；在水溶液和酸性溶液中，黄土有着不同的湿陷敏感压力区间；湿陷性黄土的结构强度对湿陷性黄土的深度有着重要影响等。在此试验基础上，吸取前人的经验，提出用完成90%湿陷量的用时和湿陷系数这2个指标对黄土及其场地进行湿陷敏感性评价，并以发生过湿陷的场地--抽黄渠为实例对此方法进行验证。验证结果表明，该方法能准确地反映湿陷场地的湿陷敏感性，对湿陷场地上的工程建设具有一定的指导意义。此外，该方法简单、科学，又能与现行规范相结合，因此，易于被业界接受并推广，是对现有少数关于黄土湿陷敏感性研究的有益补充。

Collapsible tests of loess under acid conditions and related sensitivity analysis

Cement connection of loess is an important intrinsic factor of loess collapse，which has the direct impact on the sensitivity of the collapse. In order to have a clearer understanding and to determine the sensitivity of loess collapse，the collapsible tests of loess in acid conditions were carried out to investigate the collapsible coefficient of loess，the stability time，the collapsible deformation rate and other sensitivity indexes of collapse under different pressures. The different concentrations of nitric acid were added to the immersion solution of distilled water. In addition，a scanning electron microscope(SEM) was used to detect the differences of the void space and structure of soil samples before and after the tests. The results show that the collapsible coefficient of the collapsible loess in the acid solution increases greatly under the low pressure，and that the stable time of the collapse is longer under all pressures. Loess collapsing has different ranges of pressure sensitivity in the distilled water and in the acid solution. The structural strength of the collapsible loess has the important influence on its embedded depth，etc. Two indexes that pertain to 90% of the finished time of collapse and the collapsible coefficient are utilized to evaluate the collapsible sensitivity of the loess and loess site. Chou Huang Canal，which collapsed before，is presented as a case study to demonstrate the application of this method. The results indicate that the collapsible sensitivity of the collapsible site is evaluated accurately with the proposed method.