Humidity diffusion can stimulate soil deformation. However, evidence for triggering water-induced excessive floor deformation in underground structures remains elusive. This study investigated the issue by solving a case of a loess tunnel affected by floor heave. First, the study tracked the development of field damage during tunnel operation and examined the potential influence of base moistening on inverted arch uplift. Subsequently, a large-scale field tunnel model test was conducted to analyze the moisture distribution, stress, and deformation development at the tunnel base during the humidification process. Finally, the mechanical properties of the base loess at the humidification stages were tested to assess the degradation caused by moistening. Results showed that the moisture distribution at the tunnel base changes from W- to U-shaped during long-term humidification. Moreover, after base humidification, the soil pressure at the arch foot initially decreases sharply and then increases, while the soil pressure at the inverted arch continues to increase. Furthermore, the lining at the arch foot shows an increase in compressive stress, while the inverted arch shows an increase in tensile stress. The differential settlement between the arch foot and inverted arch widens, transitioning to uplift deformation of the inverted arch and ultimately causing floor heave. Laboratory tests showed that the floor heave is primarily caused by the deterioration of the mechanical properties of the loess resulting from humidity diffusion in the tunnel foundation. A time-dependent floor heave model was established by combining the water content, shear strength, compressive strength, and compressibility of the tunnel-base loess, and its feasibility was verified. The model exhibited a sequential decrease in the influence of the internal friction angle, compressive strength, cohesion, and compression coefficient on the floor heave. The findings of this study are considerably important with respect to uncovering the mechanism of floor heave during the operation of loess tunnels and advancing the prediction of damage.

湿度扩散可以刺激土壤变形。然而，引发地下结构中水引起的过度地面变形的证据仍然难以捉摸。本研究通过解决受底鼓影响的黄土隧道案例来研究这个问题。首先，该研究跟踪了隧道运营过程中现场损坏的发展情况，并研究了基底湿润对仰拱隆起的潜在影响。随后，进行了大型野外隧道模型试验，分析了加湿过程中隧道底部的水分分布、应力和变形发展情况。最后，测试了湿润阶段基底黄土的力学性能，以评估湿润引起的退化。结果表明，在长期加湿过程中，隧道底部的湿度分布由W形变为U形。而且，基底加湿后，拱脚处的土压力先急剧减小，然后又增大，而仰拱处的土压力则持续增大。此外，足弓脚处的衬里显示出压应力的增加，而倒拱形则显示出拉应力的增加。拱脚与仰拱之间的差异沉降扩大，转变为仰拱的隆起变形，最终引起底鼓。室内试验表明，底鼓主要是由于隧道基础内湿度扩散导致黄土力学性能恶化而引起的。结合隧道基部黄土的含水量、抗剪强度、抗压强度和压缩性，建立了随时间变化的底鼓模型，并验证了其可行性。该模型表现出内摩擦角、抗压强度、粘聚力和压缩系数对底鼓的影响依次减小。本研究结果对于揭示黄土隧道运营过程中底胀机理、推进损伤预测具有重要意义。