液化砂土地层加固措施研究与盾构隧道列车振动响应分析

Research on Strengthening Measures of Liquefiable Sandy Ground and Analysis of Train Vibration Response of Shield Tunnel

为研究列车振动荷载对液化砂土地层中盾构隧道下穿路涵的动力响应特性,依托佛山地铁2号线工程,采用室内动三轴试验探明注浆加固对液化砂土动剪切模量、阻尼比等动力学参数的影响规律。通过建立三维有限元模型,系统分析列车振动荷载作用下,液化砂土加固改良前后隧道结构与周围土层的应力与位移动力响应特性及长期沉降规律。研究结果表明:采用注浆加固对地层进行改良,随着超细水泥掺量的增加,土层动剪切模量比增大,土层最大阻尼比减小,隧道结构及地层位移均明显减小;单位体积液化砂土中掺加400 kg超细水泥时改良效果最为明显,管片结构第一主应力、第三主应力分别减小81%、89.9%,周围地层竖直方向、水平方向位移分别减小52.6%、56.3%,隧道结构长期沉降减小67.2%。

According to the dynamic response characteristics of the train vibration load to the shield tunnel passing under the road culvert in the liquefiable sand soil layer and relying on the Foshan Metro Line 2 project,the influences of grouting reinforcement on the dynamic parameters,such as dynamic shear modulus and damping ratio of liquefiable sand soil layer,are investigated by indoor dynamic triaxial test;and a three-dimensional finite element model is established to systematically analyze the reinforcement and improvement of liquefiable sand soil layer under the train vibration load.The dynamic response characteristics and long-term settlement law of the tunnel structure and surrounding soil layer before and after the reinforcement are analyzed.The results show that:the stratum is improved by grouting reinforcement with the increase of additive content of ultra-fine cement,the dynamic shear modulus ratio of soil layer is effectively increased,the maximum damping ratio of soil layer is reduced,and the displacement of tunnel structure and stratum is significantly reduced;the effect is most obvious when the unit volume of liquefiable sand is mixed with 400 kg of ultra-fine cement,and the first principal stress and the third principal stress of segment structure are reduced respectively;the vertical and horizontal displacements of surrounding strata are reduced by 52.6% and 56.3% respectively,and the long-term settlement of tunnel structure is reduced by 67.24%.