盾构隧道20m深度以下饱和砂质地层地震液化判别方法探索

Exploration on Seismic Liquefaction Discrimination Method of Saturated Sandy Stratum below 20 m Depth of Shield Tunnel

目前在液化地基条件下盾构隧道抗震设计中,国内外对于20 m深度以下饱和砂质地层的地震液化判别方法较为空白,严重威胁着饱和砂质地层深埋盾构隧道结构的安全。基于典型饱和砂质地层地震液化判别方法,通过大量数据搜集,得到应力折减系数r_(d)与液化深度关系曲线,提出20 m深度以下饱和砂质地层地震液化简化判别方法,填补了现有20 m深度以下地震液化简化判别方法的空白。同时,针对卡纳普里河盾构隧道,利用FLAC 3D中的FINN模块建立土层三维模型对液化区域进行判断,验证了所提出的地震液化简化计算方法的正确性。研究表明:应力折减系数r_(d)随计算深度的增加逐渐减小,当埋深大于20 m时,应力折减系数取值逐渐趋于常数,约为0.5。

At present,in the seismic design of shield tunnel under the condition of liquefied foundation,the seismic liquefaction discrimination method for saturated sandy stratum below 20 m depth is relatively blank at home and abroad,which has become a serious threat to the safety of the deep buried shield tunnel structure in saturated sandy stratum.Based on the typical seismic liquefaction discrimination methods of saturated sand stratum,through a large amount of data collection,the relationship curve between stress reduction factor r_(d)and liquefaction depth is obtained.A simplified discrimination method for seismic liquefaction of saturated sandy stratum below 20 m depth is proposed,which fills the blank of the existing simplified discrimination method for seismic liquefaction below 20 m depth.Meanwhile,for the Kanapuli River shield tunnel,a 3D model of the soil layer was established by the FINN module in FLAC 3D to judge the liquefaction areas,and the correctness of the proposed simplified calculation method for seismic liquefaction is verified.The research shows that the stress reduction factor r_(d)gradually decreases with the increase of the calculation depth.When the buried depth is more than 20 m,the value of r_(d)gradually tends to be constant,about 0.5.