水下盾构隧道地震液化数值分析

砂土地震液化会造成地基失效和结构受损,因此场地液化判别至关重要。国内外规范中的液化判别方法简单实用,但均存在局限性。为更准确、全面地进行场地液化判别,利用三维有限差分程序FLAC^3D,结合孟加拉卡纳普里河底盾构隧道项目,对典型钻孔位置土层的抗震液化特性进行数值分析。利用FLAC^3D中的FINN模块建立土层三维模型,在重力平衡和水压力平衡后施加合理的地震波,进行动力计算,计算模型每个单元在计算过程中的最大超孔压比,若最大超孔压比=1,则该位置土体发生液化;若最大超孔压比<1,则该位置土体不会液化。计算后,部分土体的最大超孔压比=1,其他范围土体的最大超孔压比均<1。研究表明该地区土层会发生地震液化,且不同位置处液化深度不同、液化范围也不同,该数值分析液化判别结果与规范法判别结果一致。

Numerical Analysis of Seismic Liquefaction of Underwater Shield Tunnel

Seismic liquefaction of sand will give rise to the failure of foundation and structural damage. Discriminating liquefaction of the construction site is of vital importance. Liquefaction discrimination methods in specifications in China and abroad are simple and practical, yet still of some limits. In this paper, we performed numerical analysis on the seismic liquefaction characteristics of typical borehole soil layer of a shield tunnel project in Kanapuri River of Bangladesh using the FINN module of FLAC^3D. We applied a reasonable seismic wave after the balance of gravity and water pressure and calculated the maximum excessive pressure ratio of each unit in the calculation process. If the maximum excessive pore pressure ratio is equal to one, the soil is liquefied at this position; if the maximum excessive pore pressure ratio is less than one, the soil is not liquefied. Calculation result revealed that the maximum excessive pore pressure ratio of some parts of soil is equal to one and other parts less than one. The result indicated that seismic liquefaction occurs in the soil layer in this area, and the liquefaction range is different at different locations. The result is consistent with the discriminant results of specification methods.