基于遗传算法的水下全断面砂岩盾构隧道荷载反演分析

Load Inversion Analysis of Underwater Full-Section Sandstone Shield Tunnel Based on Genetic Algorithm

盾构隧道结构设计中,是否能够较为准确地得到作用在管片衬砌上的荷载十分关键;然而,现场实测实施较为困难,会受到环境和施工因素的影响,而荷载反演是一个较好的得到作用于衬砌上水土荷载的方法。依托佛莞城际铁路狮子洋隧道工程,提出适用于硬岩荷载模式的修正梁-弹簧模型,并结合修正模型对隧道水下全断面处于中风化泥质砂岩时进行荷载反演。比较遗传算法、现场实测和太沙基理论计算的荷载值以及由荷载计算出的内力值,反演得到的中风化泥质砂岩侧压力系数为0.38,基床系数为242.43 MPa/m。结果表明:(1)在该断面下,采用修正模型较为合适,且遗传算法得到的荷载能够较好拟合实测内力值;(2)作用在衬砌上的荷载主要为水压力,荷载计算应采用水土分算;(3)地勘报告中中风化泥质砂岩围岩参数偏小,实际取值可参考遗传算法反演值;(4)采用太沙基理论的荷载计算得到的弯矩值偏大,轴力值偏小,结果偏向保守。

In the design of shield tunnel structures,it is critical to be able to obtain accurately the loads acting on the segment lining.However,the implementation of field measurements is more difficult and will be affected by environmental and construction factors,while,the load inversion is a better way to get the soil and water loads acting on the lining.This paper proposes a modified beam-spring model applicable to the hard rock load pattern based on the Foshan-Dongguan Intercity Railway Shiziyang Tunnel Project.Combined with the modified model,load inversion is carried out for the tunnel section of medium-weathered argillaceous sandstone.The load values calculated by genetic algorithm,field measurements and Terzaghi Theory are compared,as well as the internal force values calculated from these loads.The lateral pressure coefficient of medium-weathered muddy sandstone obtained by inversion is 0.38,and the substrate coefficient is 242.43 MPa/m.The results show that:(1)the use of the modified model is more appropriate under this section,and the loads obtained by the genetic algorithm can better fit the measured internal force values.(2)The load acting on the lining is mainly water pressure,and the load calculation should use water and soil sub-calculation.(3)The parameters of medium-weathered muddy sandstone in the geological survey report are small,and the actual values can refer to the inverse values of the genetic algorithm.(4)The bending moment value obtained from the load calculation using Terzaghi Theory is large and the axial force value is small,and the results tend to be conservative.