研究目的:软弱地基土是介于正常岩土与软土之间的一种特殊岩土类型。在隧道修建过程中，软弱地基 土普遍存在且对工程影响极大。受隧道施工场地和环境的限制，如何选择隧道软弱地基土承载力检测方法, 确认软弱地基土的性质，快速获得承载力,验证地勘结果，并进一步修正设计，指导施工,确保工程质量达到设 计要求，已经成为建设者们急需解决的一项重要课题。 研究结论:（1）隧道软弱地基土作为天然地基很难满足隧道强度和变形的要求;（2）软弱地基土包括软黏 性土、软粉土、湿陷性黄土、膨胀土、饱和砂土、红层、填土等；（3）软弱地基土承载力的检测一般可采用原位测 试和室内试验，优先推荐采用轻型静力触探或轻型动力触探;（4）该研究成果可应用于隧道施工和监理领域。

Research purposes： Weak foundation soil is a special kind of soil type designated between normal soil and weak soil, there is no clear definition of standards. During tunnel construction, the ubiquity of weak foundation soil has a considerable impact on the construction design. Confined to the tunnel construction site and its engineering environment, how to choose the best method to test the bearing capacity of weak foundation soil, so as to confirm the nature of the soil, arrive at the bearing capacity ASAP, validate the geological exploration results , further modify the design to provide guidances to the construction , ad ensure the project quality to meet design requirements has become a major task for engineers. Research conclusions ： (1) As a natural tunnel foundation , the weak foundation soil can hardly meet the requirements in terms of strength and deformation. (2) The weak foundation soil includes soft clayey soil , powder soil , collapsible loess , expansive soil , saturated sand , red layer , filling , etc. (3) General test methods can be used in in - situ test and laboratory test. Light dynamic penetration test or cone penetration test is recommended. (4) The research result can be applied in the field of tunnel construction and supervision.