增湿条件下的膨胀土隧道衬砌安全系数分析

Analysis on Tunnel Lining Safety Factor under Humidification Condition in Expansive Soil

膨胀土具有遇水膨胀软化、失水收缩开裂的特性,常引发工程安全问题。目前,关于膨胀土隧道的研究多集中于施工过程,而并未考虑到运营过程中增湿条件对膨胀土隧道衬砌结构受力的影响。针对该问题,以平山膨胀土隧道项目为背景,根据渗流场和温度场控制微分方程的相似性,运用FLAC3D温度模块模拟降雨入渗过程。研究了降雨入渗过程中隧道二次衬砌的弯矩和轴力随膨胀率的变化规律。探讨了增湿过程对衬砌结构受力以及安全系数的影响。结果表明:含水率和膨胀率的增加使得二次衬砌弯矩与轴力产生显著变化。增湿过程使得围岩衬砌安全系数显著降低。建议在膨胀土隧道设计中,充分考虑膨胀率与干湿循环的影响,选用更加保守的安全系数。

The two typical characteristics of the expansive soils,i.e.,the expansive and softening behaviours due to the increase of water,and the shrinkage due to the water loss,are detrimental to the safety of the practical engineering.The current studies concerning the expansive soil tunnel mainly focus on the construction period of tunnelling,whereas they scarcely consider the mechanical response of the liner structure in the operation period of the expansive tunnel.o overcome the deficiency,based on Ping-shan expansive soil tunnel project,the FLAC3 D thermal model used to simulate the process of rainfall infiltration considering the similarity of the differential equation between fluid field and thermal field.The relation between bending moment and axial force of the liner with expansive ration studied and the influence of humidification condition on the structure stress and security coefficient discussed.The results show that the increase of moisture content and expansive ratio has a great impact on the stress of lining.The humidification condition the area of the plastic zone and the security coefficient significantly.The suggestion that the swelling force and humidification condition should be taken into consideration when the expansive soil tunnel is designed,and a larger security coefficient should be adopted.